{"id": "1108.6266", "title": "Extended Theories of Gravity", "abstract": "Extended Theories of Gravity can be considered a new paradigm to cure shortcomings of General Relativity at infrared and ultraviolet scales. They are an approach that, by preserving the undoubtedly positive results of Einstein's Theory, is aimed to address conceptual and experimental problems recently emerged in Astrophysics, Cosmology and High Energy Physics. In particular, the goal is to encompass, in a self-consistent scheme, problems like Inflation, Dark Energy, Dark Matter, Large Scale Structure and, first of all, to give at least an effective description of Quantum Gravity. We review the basic principles that any gravitational theory has to follow. The geometrical interpretation is discussed in a broad perspective in order to highlight the basic assumptions of General Relativity and its possible extensions in the general framework of gauge theories. Principles of such modifications are presented, focusing on specific classes of theories like f (R)-gravity and scalar-tensor gravity in the metric and Palatini approaches. The special role of torsion is also discussed. The conceptual features of these theories are fully explored and attention is payed to the issues of dynamical and conformal equivalence between them considering also the initial value problem. A number of viability criteria are presented considering the post-Newtonian and the post-Minkowskian limits. In particular, we discuss the problems of neutrino oscillations and gravitational waves in Extended Gravity. Finally, future perspectives of Extended Gravity are considered with possibility to go beyond a trial and error approach.", "keyphrases": ["gravity", "dark energy", "extended theories", "ricci scalar", "extra degree"]}
{"id": "1008.3375", "title": "New models of chaotic inflation in supergravity", "abstract": "We introduce a new class of models of chaotic inflation inspired by the superconformal approach to supergravity. This class of models allows a functional freedom of choice of the inflaton potential V = |f(\u03d5)|^2. The simplest model of this type has a quadratic potential m^2\u03d5^2/2. Another model describes an inflaton field with the standard symmetry breaking potential \u03bb^2 (\u03d5^2-v^2)^2. Depending on the value of v and on initial conditions for inflation, the spectral index n_s may take any value from 0.97 to 0.93, and the tensor-to-scalar ratio r may span the interval form 0.3 to 0.01. A generalized version of this model has a potential \u03bb^2 (\u03d5^\u03b1-v^\u03b1)^2. At large \u03d5and \u03b1> 0, this model describes chaotic inflation with the power law potential \u03d5^2\u03b1. For \u03b1< 0, this potential describes chaotic inflation with a potential which becomes flat in the large field limit. We further generalize these models by introducing a nonminimal coupling of the inflaton field to gravity. The mechanism of moduli stabilization used in these models allows to improve and generalize several previously considered models of chaotic inflation in supergravity.", "keyphrases": ["chaotic inflation", "supergravity", "inflaton potential"]}
{"id": "1607.06077", "title": "Primordial Black Holes as Dark Matter", "abstract": "The possibility that the dark matter comprises primordial black holes (PBHs) is considered, with particular emphasis on the currently allowed mass windows at 10^16 - 10^17g, 10^20 - 10^24g and 1 - 10^3 M_\u2299. The Planck mass relics of smaller evaporating PBHs are also considered. All relevant constraints (lensing, dynamical, large-scale structure and accretion) are reviewed and various effects necessary for a precise calculation of the PBH abundance (non-Gaussianity, non-sphericity, critical collapse and merging) are accounted for. It is difficult to put all the dark matter in PBHs if their mass function is monochromatic but this is still possible if the mass function is extended, as expected in many scenarios. A novel procedure for confronting observational constraints with an extended PBH mass spectrum is therefore introduced. This applies for arbitrary constraints and a wide range of PBH formation models, and allows us to identify which model-independent conclusions can be drawn from constraints over all mass ranges. We focus particularly on PBHs generated by inflation, pointing out which effects in the formation process influence the mapping from the inflationary power spectrum to the PBH mass function. We then apply our scheme to two specific inflationary models in which PBHs provide the dark matter. The possibility that the dark matter is in intermediate-mass PBHs of 1 - 10^3 M_\u2299 is of special interest in view of the recent detection of black-hole mergers by LIGO. The possibility of Planck relics is also intriguing but virtually untestable.", "keyphrases": ["black hole", "dark matter", "planck mass relic", "early universe"]}
{"id": "1602.01765", "title": "Constraints on the Coupling between Dark Energy and Dark Matter from CMB data", "abstract": "We investigate a phenomenological non-gravitational coupling between dark energy and dark matter, where the interaction in the dark sector is parameterized as an energy transfer either from dark matter to dark energy or the opposite. The models are constrained by a whole host of updated cosmological data: cosmic microwave background temperature anisotropies and polarization, high-redshift supernovae, baryon acoustic oscillations, redshift space distortions and gravitational lensing. Both models are found to be compatible with all cosmological observables, but in the case where dark matter decays into dark energy, the tension with the independent determinations of H_0 and \u03c3_8, already present for standard cosmology, increases: this model in fact predicts lower H_0 and higher \u03c3_8, mostly as a consequence of the higher amount of dark matter at early times, leading to a stronger clustering during the evolution. Instead, when dark matter is fed by dark energy, the reconstructed values of H_0 and \u03c3_8 nicely agree with their local determinations, with a full reconciliation between high- and low-redshift observations. A non-zero coupling between dark energy and dark matter, with an energy flow from the former to the latter, appears therefore to be in better agreement with cosmological data.", "keyphrases": ["dark energy", "dark matter", "non-gravitational coupling"]}
{"id": "1309.0605", "title": "Rapidly rotating neutron stars in scalar-tensor theories of gravity", "abstract": "We present the field equations governing the equilibrium of rapidly rotating neutron stars in scalar-tensor theories of gravity, as well as representative numerical solutions. The conditions for the presence of a nontrivial scalar field and the deviations from the general relativistic solutions are studied. Two examples of scalar-tensor theories are examined - one case that is equivalent to the Brans-Dicke theory and a second case, that is perturbatively equivalent to Einstein's General Relativity in the weak field regime, but can differ significantly for strong fields. Our numerical results show that rapidly rotating neutron star models with a nontrivial scalar field exist in both cases and that the effect of the scalar field is stronger for rapid rotation. If we consider values of the coupling parameters in accordance with current observations, only the second example of scalar-tensor theories has significant influence on the neutron star structure. We show that scalarized, rapidly rotating neutron stars exist for a larger range of the parameters than in the static case, since a nontrivial scalar field is present even for values of the coupling constant \u03b2>-4.35, and that these solutions are energetically more favorable than the general relativistic ones. In addition, the deviations of the rapidly rotating scalar-tensor neutron stars from the general-relativistic solutions is significantly larger than in the static case.", "keyphrases": ["neutron star", "scalar-tensor theory", "gravity"]}
{"id": "1701.02544", "title": "Inflationary Primordial Black Holes as All Dark Matter", "abstract": "Following a new microlensing constraint on primordial black holes (PBHs) with \u223c10^20\u201310^28 g [1], we revisit the idea of PBH as all Dark Matter (DM). We have shown that the updated observational constraints suggest the viable mass function for PBHs as all DM to have a peak at \u2243 10^20 g with a small width \u03c3\u2272 0.1, by imposing observational constraints on an extended mass function in a proper way. We have also provided an inflation model that successfully generates PBHs as all DM fulfilling this requirement.", "keyphrases": ["black hole", "dark matter", "early universe"]}
{"id": "0911.3380", "title": "Quasi-Single Field Inflation and Non-Gaussianities", "abstract": "In quasi-single field inflation models, massive isocurvature modes, that are coupled to the inflaton and have mass of order the Hubble parameter, can have nontrivial impacts on density perturbations, especially non-Gaussianities. We study a simple example of quasi-single field inflation in terms of turning inflaton trajectory. Large bispectra with a one-parameter family of novel shapes arise, lying between the well-known local and equilateral shape. The trispectra can also be very large and its magnitude tNL can be much larger than fNL squared.", "keyphrases": ["quasi-single field inflation", "non-gaussianitie", "cosmological collider physics", "scalar field", "inflationary model"]}
{"id": "1009.1782", "title": "Lower limit on the strength and filling factor of extragalactic magnetic fields", "abstract": "High energy photons from blazars can initiate electromagnetic pair cascades interacting with the extragalactic photon background. The charged component of such cascades is deflected and delayed by extragalactic magnetic fields (EGMF), reducing thereby the observed point-like flux and leading potentially to multi degree images in the GeV energy range. We calculate the fluence of 1ES 0229+200 as seen by Fermi-LAT for different EGMF profiles using a Monte Carlo simulation for the cascade development. The non-observation of 1ES 0229+200 by Fermi-LAT suggests that the EGMF fills at least 60 O(10^-16-10^-15)G for life times of TeV activity of O(10^2-10^4)yr. Thus the (non-) observation of GeV extensions around TeV blazars probes the EGMF in voids and puts strong constraints on the origin of EGMFs: Either EGMFs were generated in a space filling manner (e.g. primordially) or EGMFs produced locally (e.g. by galaxies) have to be efficiently transported to fill a significant volume fraction, as e.g. by galactic outflows.", "keyphrases": ["extragalactic magnetic field", "magnetic field", "intergalactic medium"]}
{"id": "1301.7182", "title": "On the Renormalization of the Effective Field Theory of Large Scale Structures", "abstract": "Standard perturbation theory (SPT) for large-scale matter inhomogeneities is unsatisfactory for at least three reasons: there is no clear expansion parameter since the density contrast is not small on all scales; it does not fully account for deviations at large scales from a perfect pressureless fluid induced by short-scale non-linearities; for generic initial conditions, loop corrections are UV-divergent, making predictions cutoff dependent and hence unphysical. The Effective Field Theory of Large Scale Structures successfully addresses all three issues. Here we focus on the third one and show explicitly that the terms induced by integrating out short scales, neglected in SPT, have exactly the right scale dependence to cancel all UV-divergences at one loop, and this should hold at all loops. A particularly clear example is an Einstein deSitter universe with no-scale initial conditions P_in=A k^n. After renormalizing the theory, we use self-similarity to derive a very simple result for the final power spectrum for any n, excluding two-loop corrections and higher. We show how the relative importance of different corrections depend on n. For n=-1.5, relevant for our universe, pressure and dissipative corrections are more important than the two-loop corrections.", "keyphrases": ["effective field theory", "large scale structures", "non-linear regime"]}
{"id": "1211.6269", "title": "The Matter Bounce Scenario in Loop Quantum Cosmology", "abstract": "In the matter bounce scenario, a dust-dominated contracting space-time generates scale-invariant perturbations that, assuming a nonsingular bouncing cosmology, propagate to the expanding branch and set appropriate initial conditions for the radiation-dominated era. Since this scenario depends on the presence of a bounce, it seems appropriate to consider it in the context of loop quantum cosmology where a bouncing universe naturally arises. For a pressureless collapsing universe in loop quantum cosmology, the predicted power spectrum of the scalar perturbations after the bounce is scale-invariant and the tensor to scalar ratio is negligibly small. A slight red tilt can be given to the scale-invariance of the scalar perturbations by a scalar field whose equation of state is P = - \u03f5\u03c1, where \u03f5 is a small positive number. Then, the power spectrum for tensor perturbations is also almost scale-invariant with the same red tilt as the scalar perturbations, and the tensor to scalar ratio is expected to be r \u2248 9 \u00d7 10^-4. Finally, for the predicted amplitude of the scalar perturbations to agree with observations, the critical density in loop quantum cosmology must be of the order \u03c1_c \u223c 10^-9\u03c1_ Pl.", "keyphrases": ["matter bounce scenario", "loop quantum cosmology", "holonomy"]}
{"id": "1001.2308", "title": "Primordial Black Holes as All Dark Matter", "abstract": "We argue that a primordial black hole is a natural and unique candidate for all dark matter. We show that, in a smooth-hybrid new double inflation model, a right amount of the primordial black holes, with a sharply-defined mass, can be produced at the end of the smooth-hybrid regime, through preheating. We first consider masses < 10^(-7)M_sun which are allowed by all the previous constraints. We next discuss much heavier mass 10^5 M_sun hinted at by entropy, and galactic size evolution, arguments. Effects on the running of the scalar spectral index are computed.", "keyphrases": ["black hole", "dark matter", "early universe"]}
{"id": "1307.6090", "title": "An improved upper limit to the CMB circular polarization at large angular scales", "abstract": "Circular polarization of the Cosmic Microwave Background (CMB) offers the possibility of detecting rotations of the universe and magnetic fields in the primeval universe or in distant clusters of galaxies. We used the Milano Polarimeter (MIPOL) installed at the Testa Grigia Observatory, on the italian Alps, to improve the existing upper limits to the CMB circular polarization at large angular scales. We obtain 95 of the CMB circular polarization ranging between 5.0x10^-4 and 0.7x10^-4 at angular scales between 8 and 24 deg, improving by one order of magnitude preexisting upper limits at large angular scales. Our results are still far from the nK region where today expectations place the amplitude of the V Stokes parameter used to characterize circular polarization of the CMB but improve the preexisting limit at similar angular scales. Our observations offered also the opportunity of characterizing the atmospheric emission at 33 GHz at the Testa Grigia Observatory.", "keyphrases": ["upper limit", "polarization", "angular scale"]}
{"id": "1505.04443", "title": "Reconstructing the interaction between dark energy and dark matter using Gaussian Processes", "abstract": "We present a nonparametric approach to reconstruct the interaction between dark energy and dark matter directly from SNIa Union 2.1 data using Gaussian processes, which is a fully Bayesian approach for smoothing data. In this method, once the equation of state (w) of dark energy is specified, the interaction can be reconstructed as a function of redshift. For the decaying vacuum energy case with w=-1, the reconstructed interaction is consistent with the standard \u039bCDM model, namely, there is no evidence for the interaction. This also holds for the constant w cases from -0.9 to -1.1 and for the Chevallier-Polarski-Linder (CPL) parametrization case. If the equation of state deviates obviously from -1, the reconstructed interaction exists at 95% confidence level. This shows the degeneracy between the interaction and the equation of state of dark energy when they get constraints from the observational data.", "keyphrases": ["dark energy", "dark matter", "gaussian process"]}
{"id": "1210.0201", "title": "The Effective Field Theory of Dark Energy", "abstract": "We propose a universal description of dark energy and modified gravity that includes all single-field models. By extending a formalism previously applied to inflation, we consider the metric universally coupled to matter fields and we write in terms of it the most general unitary gauge action consistent with the residual unbroken symmetries of spatial diffeomorphisms. Our action is particularly suited for cosmological perturbation theory: the background evolution depends on only three operators. All other operators start at least at quadratic order in the perturbations and their effects can be studied independently and systematically. In particular, we focus on the properties of a few operators which appear in non-minimally coupled scalar-tensor gravity and galileon theories. In this context, we study the mixing between gravity and the scalar degree of freedom. We assess the quantum and classical stability, derive the speed of sound of fluctuations and the renormalization of the Newton constant. The scalar can always be de-mixed from gravity at quadratic order in the perturbations, but not necessarily through a conformal rescaling of the metric. We show how to express covariant field-operators in our formalism and give several explicit examples of dark energy and modified gravity models in our language. Finally, we discuss the relation with the covariant EFT methods recently appeared in the literature.", "keyphrases": ["effective field theory", "dark energy", "gravity", "non-minimal coupling", "glpv theory"]}
{"id": "0905.4720", "title": "String Axiverse", "abstract": "String theory suggests the simultaneous presence of many ultralight axions possibly populating each decade of mass down to the Hubble scale 10^-33eV. Conversely the presence of such a plenitude of axions (an \"axiverse\") would be evidence for string theory, since it arises due to the topological complexity of the extra-dimensional manifold and is ad hoc in a theory with just the four familiar dimensions. We investigate how upcoming astrophysical experiments will explore the existence of such axions over a vast mass range from 10^-33eV to 10^-10eV. Axions with masses between 10^-33eV to 10^-28eV cause a rotation of the CMB polarization that is constant throughout the sky. The predicted rotation angle is of order \u03b1 1/137. Axions in the mass range 10^-28eV to 10^-18eV give rise to multiple steps in the matter power spectrum, that will be probed by upcoming galaxy surveys. Axions in the mass range 10^-22eV to 10^-10eV affect the dynamics and gravitational wave emission of rapidly rotating astrophysical black holes through the Penrose superradiance process. When the axion Compton wavelength is of order of the black hole size, the axions develop \"superradiant\" atomic bound states around the black hole \"nucleus\". Their occupation number grows exponentially by extracting rotational energy from the ergosphere, culminating in a rotating Bose-Einstein axion condensate emitting gravitational waves. This mechanism creates mass gaps in the spectrum of rapidly rotating black holes that diagnose the presence of axions. The rapidly rotating black hole in the X-ray binary LMC X-1 implies an upper limit on the decay constant of the QCD axion f_a<2*10^17GeV, much below the Planck mass. This reach can be improved down to the grand unification scale f_a<2*10^16GeV, by observing smaller stellar mass black holes.", "keyphrases": ["string axiverse", "particle", "axion-like particle", "boson", "dark matter"]}
{"id": "1403.2757", "title": "Kerr black holes with scalar hair", "abstract": "We present a family of solutions of Einstein's gravity minimally coupled to a complex, massive scalar field, describing asymptotically flat, spinning black holes with scalar hair and a regular horizon. These hairy black holes (HBHs) are supported by rotation and have no static limit. Besides mass M and angular momentum J, they carry a conserved, continuous Noether charge Q measuring the scalar hair. HBHs branch off from the Kerr metric at the threshold of the superradiant instability and reduce to spinning boson stars in the limit of vanishing horizon area. They overlap with Kerr black holes for a set of (M,J) values. A single Killing vector field preserves the solutions, tangent to the null geodesic generators of the event horizon. HBHs can exhibit sharp physical differences when compared to the Kerr solution, such as J/M^2>1, quadrupole moment larger than J^2/M and larger orbital angular velocity at the innermost stable circular orbit. Families of HBHs connected to the Kerr geometry should exist in scalar (and other) models with more general self interactions.", "keyphrases": ["black hole", "scalar hair", "gravity", "kerr", "bosonic field"]}
{"id": "1310.0464", "title": "The Effective Field Theory of Large Scale Structures at Two Loops", "abstract": "Large scale structure surveys promise to be the next leading probe of cosmological information. It is therefore crucial to reliably predict their observables. The Effective Field Theory of Large Scale Structures (EFTofLSS) provides a manifestly convergent perturbation theory for the weakly non-linear regime of dark matter, where correlation functions are computed in an expansion of the wavenumber k of a mode over the wavenumber associated with the non-linear scale k_nl. Since most of the information is contained at high wavenumbers, it is necessary to compute higher order corrections to correlation functions. After the one-loop correction to the matter power spectrum, we estimate that the next leading one is the two-loop contribution, which we compute here. At this order in k/k_nl, there is only one counterterm in the EFTofLSS that must be included, though this term contributes both at tree-level and in several one-loop diagrams. We also discuss correlation functions involving the velocity and momentum fields. We find that the EFTofLSS prediction at two loops matches to percent accuracy the non-linear matter power spectrum at redshift zero up to k 0.6 h/Mpc, requiring just one unknown coefficient that needs to be fit to observations. Given that Standard Perturbation Theory stops converging at redshift zero at k 0.1 h/Mpc, our results demonstrate the possibility of accessing a factor of order 200 more dark matter quasi-linear modes than naively expected. If the remaining observational challenges to accessing these modes can be addressed with similar success, our results show that there is tremendous potential for large scale structure surveys to explore the primordial universe.", "keyphrases": ["effective field theory", "large scale structures", "matter power spectrum", "three-loop order"]}
{"id": "1201.2434", "title": "Observational Probes of Cosmic Acceleration", "abstract": "The accelerating expansion of the universe is the most surprising cosmological discovery in many decades, implying that the universe is dominated by some form of \"dark energy\" with exotic physical properties, or that Einstein's theory of gravity breaks down on cosmological scales. The profound implications of cosmic acceleration have inspired ambitious experimental efforts to measure the history of expansion and growth of structure with percent-level precision or higher. We review in detail the four most well established methods for making such measurements: Type Ia supernovae, baryon acoustic oscillations (BAO), weak gravitational lensing, and galaxy clusters. We pay particular attention to the systematic uncertainties in these techniques and to strategies for controlling them at the level needed to exploit \"Stage IV\" dark energy facilities such as BigBOSS, LSST, Euclid, and WFIRST. We briefly review a number of other approaches including redshift-space distortions, the Alcock-Paczynski test, and direct measurements of H_0. We present extensive forecasts for constraints on the dark energy equation of state and parameterized deviations from GR, achievable with Stage III and Stage IV experimental programs that incorporate supernovae, BAO, weak lensing, and CMB data. We also show the level of precision required for other methods to provide constraints competitive with those of these fiducial programs. We emphasize the value of a balanced program that employs several of the most powerful methods in combination, both to cross-check systematic uncertainties and to take advantage of complementary information. Surveys to probe cosmic acceleration produce data sets with broad applications, and they continue the longstanding astronomical tradition of mapping the universe in ever greater detail over ever larger scales.", "keyphrases": ["cosmic acceleration", "dark energy", "baryon acoustic oscillation", "expansion history", "dark matter"]}
{"id": "0903.0866", "title": "The Physics of Cosmic Acceleration", "abstract": "The discovery that the cosmic expansion is accelerating has been followed by an intense theoretical and experimental response in physics and astronomy. The discovery implies that our most basic notions about how gravity work are violated on cosmological distance scales. One simple fix is the introduction of a cosmological constant into the field equations for general relativity. However, the extremely small value of the cosmological constant, relative to theoretical expectations, has led theorists to explore a wide variety of alternative explanations that involve the introduction of an exotic negative-pressure fluid or a modification of general relativity. Here we briefly review the evidence for cosmic acceleration. We then survey some of the theoretical attempts to account for it, including the cosmological constant, quintessence and its variants, mass-varying neutrinos, and modifications of general relativity, such as scalar-tensor and f(R) theories and braneworld scenarios. We discuss experimental and observational tests that may allow us to distinguish between some of the theoretical ideas that have been put forward.", "keyphrases": ["cosmic acceleration", "relativity", "dark energy", "late time", "cdm model"]}
{"id": "0910.0822", "title": "Thermodynamics of dark energy interacting with dark matter and radiation", "abstract": "We investigate the validity of the generalized second law of thermodynamics, in the cosmological scenario where dark energy interacts with both dark matter and radiation. Calculating separately the entropy variation for each fluid component and for the apparent horizon itself, we show that the generalized second law is always and generally valid, independently of the specific interaction form, of the fluids equation-of-state parameters and of the background geometry.", "keyphrases": ["dark energy", "dark matter", "thermodynamic"]}
{"id": "1109.6571", "title": "Gravitational redshift of galaxies in clusters as predicted by general relativity", "abstract": "The theoretical framework of cosmology is mainly defined by gravity, of which general relativity is the current model. Recent tests of general relativity within the \u039bCold Dark Matter (CDM) model have found a concordance between predictions and the observations of the growth rate and clustering of the cosmic web. General relativity has not hitherto been tested on cosmological scales independent of the assumptions of the \u039bCDM model. Here we report observation of the gravitational redshift of light coming from galaxies in clusters at the 99 per cent confidence level, based upon archival data. The measurement agrees with the predictions of general relativity and its modification created to explain cosmic acceleration without the need for dark energy (f(R) theory), but is inconsistent with alternative models designed to avoid the presence of dark matter.", "keyphrases": ["cluster", "general relativity", "gravitational redshift"]}
{"id": "1906.10218", "title": "Cosmological constraints on post-Newtonian parameters in effectively massless scalar-tensor theories of gravity", "abstract": "We study the cosmological constraints on the variation of the Newton's constant and on post-Newtonian parameters for simple models of scalar-tensor theory of gravity beyond the extended Jordan-Brans-Dicke theory. We restrict ourselves to an effectively massless scalar field with a potential V \u221d F^2, where F(\u03c3)=N_pl^2+\u03be\u03c3^2 is the coupling to the Ricci scalar considered. We derive the theoretical predictions for cosmic microwave background (CMB) anisotropies and matter power spectra by requiring that the effective gravitational strength at present is compatible with the one measured in a Cavendish-like experiment and by assuming adiabatic initial condition for scalar fluctuations. When comparing these models with Planck 2015 and a compilation of baryonic acoustic oscilation (BAO) data, all these models accomodate a marginalized value for H_0 higher than in \u039bCDM. We find no evidence for a statistically significant deviation from Einstein's general relativity. We find \u03be < 0.064 (|\u03be| < 0.011) at 95 (for \u03be < 0, \u03be -1/6). In terms of post-Newtonian parameters, we find 0.995 < \u03b3_ PN < 1 and 0.99987 < \u03b2_ PN < 1 (0.997 < \u03b3_ PN < 1 and 1 < \u03b2_ PN < 1.000011) for \u03be >0 (for \u03be < 0). For the particular case of the conformal coupling, i.e. \u03be=-1/6, we find constraints on the post-Newtonian parameters of similar precision to those within the Solar System.", "keyphrases": ["post-newtonian parameter", "scalar-tensor theory", "gravity"]}
{"id": "1504.02311", "title": "The origin, evolution and signatures of primordial magnetic fields", "abstract": "The universe is magnetized on all scales probed so far. On the largest scales, galaxies and galaxy clusters host magnetic fields at the micro Gauss level coherent on scales up to ten kpc. Recent observational evidence suggests that even the intergalactic medium in voids could host a weak \u223c 10^-16 Gauss magnetic field, coherent on Mpc scales. An intriguing possibility is that these observed magnetic fields are a relic from the early universe, albeit one which has been subsequently amplified and maintained by a dynamo in collapsed objects. We review here the origin, evolution and signatures of primordial magnetic fields. After a brief summary of magnetohydrodynamics in the expanding universe, we turn to magnetic field generation during inflation and other phase transitions. We trace the linear and nonlinear evolution of the generated primordial fields through the radiation era, including viscous effects. Sensitive observational signatures of primordial magnetic fields on the cosmic microwave background, including current constraints from Planck, are discussed. After recombination, primordial magnetic fields could strongly influence structure formation, especially on dwarf galaxy scales. The resulting signatures on reionization, the redshifted 21 cm line, weak lensing and the Lyman-\u03b1 forest are outlined. Constraints from radio and \u03b3-ray astronomy are summarized. Astrophysical batteries and the role of dynamos in reshaping the primordial field are briefly considered. The review ends with some final thoughts on primordial magnetic fields.", "keyphrases": ["primordial magnetic field", "magnetic field", "universe", "galaxy cluster", "astrophysic"]}
{"id": "1307.3220", "title": "On the Velocity in the Effective Field Theory of Large Scale Structures", "abstract": "We compute the renormalized two-point functions of density, divergence and vorticity of the velocity in the Effective Field Theory of Large Scale Structures. Because of momentum and mass conservation, the corrections from short scales to the large-scale power spectra of density, divergence and vorticity must start at order k^4. For the vorticity this constitutes one of the two leading terms. Exact (approximated) self-similarity of an Einstein-de Sitter (\u039bCDM) background fixes the time dependence so that the vorticity power spectrum at leading order is determined by the symmetries of the problem and the power spectrum around the non-linear scale. We show that to cancel all divergences in the velocity correlators one needs new counterterms. These fix the definition of velocity and do not represent new properties of the system. For an Einstein-de Sitter universe, we show that all three renormalized cross- and auto-correlation functions have the same structure but different numerical coefficients, which we compute. We elucidate the differences between using momentum and velocity.", "keyphrases": ["velocity", "effective field theory", "large scale structures", "non-linear regime"]}
{"id": "1109.3350", "title": "Self-consistent evolution of magnetic fields and chiral asymmetry in the early Universe", "abstract": "We show that the evolution of magnetic fields in a primordial plasma, filled with Standard Model particles, at temperatures T > 10 MeV is strongly affected by the quantum chiral anomaly \u2013 an effect that has been neglected previously. Although reactions equilibrating left and right-chiral electrons are in deep thermal equilibrium for T < 80 TeV, an asymmetry between these particle develops in the presence of strong magnetic fields. This results in magnetic helicity transfer from shorter to longer scales. This also leads to an effective generation of lepton asymmetry that may survive in the plasma down to temperatures T 10 MeV, which may strongly affect many processes in the early Universe. Although we report our results for the Standard Model, they are likely to play an important role also in its extensions.", "keyphrases": ["magnetic field", "chiral asymmetry", "early universe", "relativistic plasma", "baryogenesis"]}
{"id": "1402.4090", "title": "Astrophysical and Dark Matter Interpretations of Extended Gamma-Ray Emission from the Galactic Center", "abstract": "We construct empirical models of the diffuse gamma-ray background toward the Galactic Center. Including all known point sources and a template of emission associated with interactions of cosmic rays with molecular gas, we show that the extended emission observed previously in the Fermi Large Area Telescope data toward the Galactic Center is detected at high significance for all permutations of the diffuse model components. However, we find that the fluxes and spectra of the sources in our model change significantly depending on the background model. In particular, the spectrum of the central Sgr A^\u2217 source is less steep than in previous works and the recovered spectrum of the extended emission has large systematic uncertainties, especially at lower energies. If the extended emission is interpreted to be due to dark matter annihilation, we find annihilation into pure b-quark and \u03c4-lepton channels to be statistically equivalent goodness of fits. In the case of the pure b-quark channel, we find a dark matter mass of 39.4(^+3.7_-2.9 stat.)(\u00b1 7.9 sys.)GeV, while a pure \u03c4^+\u03c4^--channel case has an estimated dark matter mass of 9.43(^+0.63_-0.52 stat.)(\u00b1 1.2 sys.)GeV. Alternatively, if the extended emission is interpreted to be astrophysical in origin such as due to unresolved millisecond pulsars, we obtain strong bounds on dark matter annihilation, although systematic uncertainties due to the dependence on the background models are significant.", "keyphrases": ["dark matter", "galactic center", "gamma-ray excess", "astrophysical background"]}
{"id": "1412.2777", "title": "Evidence for interacting dark energy from BOSS", "abstract": "The result presented by the BOSS-SDSS Collaboration measuring the baryon acoustic oscillations of the Lyman-\u03b1 forest from high-redshift quasars indicates a 2.5\u03c3 departure from the standard \u039b-cold-dark-matter model. This is the first time that the evolution of dark energy at high redshifts has been measured, and the current results cannot be explained by simple generalizations of the cosmological constant. We show here that a simple phenomenological interaction in the dark sector provides a good explanation for this deviation, naturally accommodating the Hubble parameter obtained by BOSS, H(z=2.34)=222 \u00b1 7 km s^-1 Mpc^-1. By performing a global fit of the parameters with the inclusion of this new data set together with the Planck data for the interacting model, we are able to show that some interacting models have constraints for H(2.34) and D_A(2.34) that are compatible with the ones obtained by the BOSS Collaboration, showing a better concordance than \u039bCDM. We also show that the interacting models that have a small positive coupling constant, which helps alleviate the coincidence problem, are compatible with the cosmological observations. Adding the likelihood of these new baryon acoustic oscillations data shows an improvement in the global fit, although it is not statistically significant. The coupling constant could not be fully constrained by the data sets used, but the dark energy equation of state shows a slight preference for a value different from a cosmological constant.", "keyphrases": ["dark energy", "boss", "dark matter"]}
{"id": "1810.11855", "title": "An analytic implementation of the IR-resummation for the BAO peak", "abstract": "We develop an analytic method for implementing the IR-resummation of arXiv:1404.5954, which allows one to correctly and consistently describe the imprint of baryon acoustic oscillations (BAO) on statistical observables in large-scale structure. We show that the final IR-resummed correlation function can be computed analytically without relying on numerical integration, thus allowing for an efficient and accurate use of these predictions on real data in cosmological parameter fitting. In this work we focus on the one-loop correlation function and the BAO peak. We show that, compared with the standard numerical integration method of IR-resummation, the new method is accurate to better than 0.2 resummation scheme which is based on using the linear displacements of a fixed fiducial cosmology, which when combined with the method described above, is about six times faster than the standard numerical integration. Finally, we show that this analytic method is generalizable to higher loop computations.", "keyphrases": ["ir-resummation", "bao peak", "baryon acoustic oscillation"]}
{"id": "1912.10437", "title": "Primordial black holes and gravitational waves from parametric amplification of curvature perturbations", "abstract": "We investigate a new mechanism to create large curvature perturbations on small scales due to parameter resonance in a single-field inflationary model with a small periodic structure upon the potential. After reentering the horizon, the amplified curvature perturbations can lead to observable primordial black holes as well as stochastic gravitational waves. The mass of primordial black holes and frequency of the induced gravitational waves depend on the model parameters. The resulted primordial black hole could constitute all dark matter or a fraction of dark matter in the universe, and corresponding stochastic gravitational waves fall in the frequency band measurable for the pulsar timing array and the space-based gravitational wave detectors.", "keyphrases": ["gravitational wave", "curvature perturbation", "primordial black hole"]}
{"id": "0901.0265", "title": "Advances in Inflation in String Theory", "abstract": "We provide a pedagogical overview of inflation in string theory. Our theme is the sensitivity of inflation to Planck-scale physics, which we argue provides both the primary motivation and the central theoretical challenge for the subject. We illustrate these issues through two case studies of inflationary scenarios in string theory: warped D-brane inflation and axion monodromy inflation. Finally, we indicate how future observations can test scenarios of inflation in string theory.", "keyphrases": ["string theory", "inflationary model building", "inflaton candidate"]}
{"id": "1308.4685", "title": "Transforming gravity: from derivative couplings to matter to second-order scalar-tensor theories beyond the Horndeski Lagrangian", "abstract": "We study the structure of scalar-tensor theories of gravity based on derivative couplings between the scalar and the matter degrees of freedom introduced through an effective metric. Such interactions are classified by their tensor structure into conformal (scalar), disformal (vector) and extended disformal (traceless tensor), as well as by the derivative order of the scalar field. Relations limited to first derivatives of the field ensure second order equations of motion in the Einstein frame and hence the absence of Ostrogradski ghost degrees of freedom. The existence of a mapping to the Jordan frame is not trivial in the general case, and can be addressed using the Jacobian of the frame transformation through its eigenvalues and eigentensors. These objects also appear in the study of different aspects of such theories, including the metric and field redefinition transformation of the path integral in the quantum mechanical description. Although sane in the Einstein frame, generic disformally coupled theories are described by higher order equations of motion in the Jordan frame. This apparent contradiction is solved by the use of a hidden constraint: the contraction of the metric equations with a Jacobian eigentensor provides a constraint relation for the higher field derivatives, which allows one to express the dynamical equations in a second order form. This signals a loophole in Horndeski's theorem and allows one to enlarge the set of scalar-tensor theories which are Ostrogradski-stable. The transformed Gauss-Bonnet terms are also discussed for the simplest conformal and disformal relations.", "keyphrases": ["gravity", "derivative coupling", "scalar-tensor theory", "horndeski theory"]}
{"id": "1511.00238", "title": "Quark stars admixed with dark matter", "abstract": "Compact stars consisting of massless quark matter and fermionic dark matter are studied by solving the Tolman-Oppenheimer-Volkoff equations for two fluids separately. Dark matter is further investigated by incorporating inter-fermionic interactions among the dark matter particles. The properties of stars made of quark matter particles and self-interacting and free dark matter particles are explored by obtaining their mass-radius relations. The regions of stability for such a compact star are determined and it is demonstrated that the maximum stable total mass of such a star decreases approximately linearly with increasing dark matter fraction.", "keyphrases": ["star", "dark matter", "significant gravitational effect"]}
{"id": "1404.2601", "title": "Inflation and String Theory", "abstract": "We review cosmological inflation and its realization in quantum field theory and in string theory. This material is a portion of a book, also entitled \"Inflation and String Theory\", to be published by Cambridge University Press.", "keyphrases": ["string theory", "cosmology", "axion", "inflationary model", "large-field inflation"]}
{"id": "1110.6274", "title": "Weakly magnetized black holes as particle accelerators", "abstract": "We study collision of particles in the vicinity of a horizon of a weakly magnetized non-rotating black hole. In the presence of the magnetic field innermost stable circular orbits (ISCO) of charged particles can be located close to the horizon. We demonstrate that for a collision of two particles, one of which is charged and revolving at ISCO and the other is neutral and falling from infinity, the maximal collision energy can be high in the limit of strong magnetic field. This effect has some similarity with the recently discussed effect of high center-of-mass energy for collision of particles in extremely rotating black holes. We also demonstrate that for `realistic' astrophysical black holes their ability to play the role of `accelerators' is in fact quite restricted.", "keyphrases": ["black hole", "particle accelerator", "magnetic field"]}
{"id": "1008.1943", "title": "Properties and uncertainties of scalar field models of dark energy with barotropic equation of state", "abstract": "The dynamics of expansion and large scale structure formation in the multicomponent Universe with dark energy modeled by the minimally coupled scalar field with generalized linear barotropic equation of state (EoS) are analyzed. It is shown that the past dynamics of expansion and future of the Universe \u2013 eternal accelerated expansion or turnaround and collapse \u2013 are completely defined by the current energy density of a scalar field and relation between its current and early EoS parameters. The clustering properties of such models of dark energy and their imprints in the power spectrum of matter density perturbations depend on the same relation and, additionally, on the \"effective sound speed\" of a scalar field, defined by its Lagrangian. It is concluded that such scalar fields with different values of these parameters are distinguishable in principle. This gives the possibility to constrain them by confronting the theoretical predictions with the corresponding observational data. For that we have used the 7-year WMAP data on CMB anisotropies, the Union2 dataset on Supernovae Ia and SDSS DR7 data on luminous red galaxies (LRG) space distribution. Using the Markov Chain Monte Carlo technique the marginalized posterior and mean likelihood distributions are computed for the scalar fields with two different Lagrangians: Klein-Gordon and Dirac-Born-Infeld ones. The properties of such scalar field models of dark energy with best fitting parameters and uncertainties of their determination are also analyzed in the paper.", "keyphrases": ["scalar field model", "dark energy", "barotropic equation"]}
{"id": "1702.02143", "title": "Echo of interactions in the dark sector", "abstract": "We investigate the observational constraints on an interacting vacuum energy scenario with two different neutrino schemes (with and without a sterile neutrino) using the most recent data from CMB temperature and polarization anisotropy, baryon acoustic oscillations (BAO), type Ia supernovae from JLA sample and structure growth inferred from cluster counts. We find that inclusion of the galaxy clusters data with the minimal data combination CMB + BAO + JLA suggests an interaction in the dark sector, implying the decay of dark matter particles into dark energy, since the constraints obtained by including the galaxy clusters data yield a non-null and negative coupling parameter between the dark components at 99% confidence level. We deduce that the current tensions on the parameters H_0 and \u03c3_8 can be alleviated within the framework of the interacting as well as non-interacting vacuum energy models with sterile neutrinos.", "keyphrases": ["dark sector", "dark matter", "non-gravitational coupling"]}
{"id": "1108.0893", "title": "Loop Quantum Cosmology: A Status Report", "abstract": "The goal of this article is to provide an overview of the current state of the art in loop quantum cosmology for three sets of audiences: young researchers interested in entering this area; the quantum gravity community in general; and, cosmologists who wish to apply loop quantum cosmology to probe modifications in the standard paradigm of the early universe. An effort has been made to streamline the material so that, as described at the end of section I, each of these communities can read only the sections they are most interested in, without a loss of continuity.", "keyphrases": ["loop quantum cosmology", "big bang singularity", "cosmological model", "non-perturbative quantization", "scalar field"]}
{"id": "1707.04966", "title": "From hadrons to quarks in neutron stars: a review", "abstract": "We review the equation of state of matter in neutron stars from the solid crust through the liquid nuclear matter interior to the quark regime at higher densities. We focus in detail on the question of how quark matter appears in neutron stars, and how it affects the equation of state. After discussing the crust and liquid nuclear matter in the core we briefly review aspects of microscopic quark physics relevant to neutron stars, and quark models of dense matter based on the Nambu\u2013Jona-Lasinio framework, in which gluonic processes are replaced by effective quark interactions. We turn then to describing equations of state useful for interpretation of both electromagnetic and gravitational observations, reviewing the emerging picture of hadron-quark continuity in which hadronic matter turns relatively smoothly, with at most only a weak first order transition, into quark matter with increasing density. We review construction of unified equations of state that interpolate between the reasonably well understood nuclear matter regime at low densities and the quark matter regime at higher densities. The utility of such interpolations is driven by the present inability to calculate the dense matter equation of state in QCD from first principles. As we review, the parameters of effective quark models \u2013 which have direct relevance to the more general structure of the QCD phase diagram of dense and hot matter \u2013 are constrained by neutron star mass and radii measurements, in particular favoring large repulsive density-density and attractive diquark pairing interactions. We describe the structure of neutron stars constructed from the unified equations of states with crossover. Lastly we present the current equations of state \u2013 called \"QHC18\" for quark-hadron crossover \u2013 in a parametrized form practical for neutron star modeling.", "keyphrases": ["quark", "neutron star", "dense matter"]}
{"id": "1304.1961", "title": "Quintessence: A Review", "abstract": "Quintessence is a canonical scalar field introduced to explain the late-time cosmic acceleration. The cosmological dynamics of quintessence is reviewed, paying particular attention to the evolution of the dark energy equation of state w. For the field potentials having tracking and thawing properties, the evolution of w can be known analytically in terms of a few model parameters. Using the analytic expression of w, we constrain quintessence models from the observations of supernovae type Ia, cosmic microwave background, and baryon acoustic oscillations. The tracking freezing models are hardly distinguishable from the LCDM model, whereas in thawing models the today's field equation of state is constrained to be w_0<-0.7 (95 formula for the growth rate of matter density perturbations in dynamical dark energy models, which allows a possibility to put further bounds on w from the measurement of redshift-space distortions in the galaxy power spectrum. Finally we review particle physics models of quintessence- such as those motivated by supersymmetric theories. The field potentials of thawing models based on a pseudo-Nambu-Goldstone boson or on extended supergravity theories have a nice property that a tiny mass of quintessence can be protected against radiative corrections.", "keyphrases": ["dark energy", "field potential", "quintessence", "alternative", "accelerated expansion"]}
{"id": "1201.6434", "title": "Statistical Anisotropy from Anisotropic Inflation", "abstract": "We review an inflationary scenario with the anisotropic expansion rate. An anisotropic inflationary universe can be realized by a vector field coupled with an inflaton, which can be regarded as a counter example to the cosmic no-hair conjecture. We show generality of anisotropic inflation and derive a universal property. We formulate cosmological perturbation theory in anisotropic inflation. Using the formalism, we show anisotropic inflation gives rise to the statistical anisotropy in primordial fluctuations. We also explain a method to test anisotropic inflation using the cosmic microwave background radiation (CMB).", "keyphrases": ["anisotropic inflation", "primordial fluctuation", "statistical anisotropy", "scalar field"]}
{"id": "1305.4939", "title": "Review of asymmetric dark matter", "abstract": "Asymmetric dark matter models are based on the hypothesis that the present-day abundance of dark matter has the same origin as the abundance of ordinary or visible matter: an asymmetry in the number densities of particles and antiparticles. They are largely motivated by the observed similarity in the mass densities of dark and visible matter, with the former observed to be about five times the latter. This review discusses the construction of asymmetric dark matter models, summarizes cosmological and astrophysical implications and bounds, and touches on direct detection prospects and collider signatures.", "keyphrases": ["dark matter", "dark sector", "matter particle"]}
{"id": "1304.4840", "title": "Essential Building Blocks of Dark Energy", "abstract": "We propose a minimal description of single field dark energy/modified gravity within the effective field theory formalism for cosmological perturbations, which encompasses most existing models. We start from a generic Lagrangian given as an arbitrary function of the lapse and of the extrinsic and intrinsic curvature tensors of the time hypersurfaces in unitary gauge, i.e. choosing as time slicing the uniform scalar field hypersurfaces. Focusing on linear perturbations, we identify seven Lagrangian operators that lead to equations of motion containing at most two (space or time) derivatives, the background evolution being determined by the time dependent coefficients of only three of these operators. We then establish a dictionary that translates any existing or future model whose Lagrangian can be written in the above form into our parametrized framework. As an illustration, we study Horndeski's-or generalized Galileon-theories and show that they can be described, up to linear order, by only six of the seven operators mentioned above. This implies, remarkably, that the dynamics of linear perturbations can be more general than that of Horndeski while remaining second order. Finally, in order to make the link with observations, we provide the entire set of linear perturbation equations in Newtonian gauge, the effective Newton constant in the quasi-static approximation and the ratio of the two gravitational potentials, in terms of the time-dependent coefficients of our Lagrangian.", "keyphrases": ["dark energy", "cosmological perturbation", "lagrangian"]}
{"id": "1204.6135", "title": "Revisit of the Interaction between Holographic Dark Energy and Dark Matter", "abstract": "In this paper we investigate the possible direct, non-gravitational interaction between holographic dark energy (HDE) and dark matter. Firstly, we start with two simple models with the interaction terms Q \u221d\u03c1_dm and Q \u221d\u03c1_de, and then we move on to the general form Q \u221d\u03c1_m^\u03b1\u03c1_de^\u03b2. The cosmological constraints of the models are obtained from the joint analysis of the present Union2.1+BAO+CMB+H_0 data. We find that the data slightly favor an energy flow from dark matter to dark energy, although the original HDE model still lies in the 95.4 level (CL) region. For all models we find c<1 at the 95.4 compared with the cosmic expansion, the effect of interaction on the evolution of \u03c1_dm and \u03c1_de is smaller, and the relative increment (decrement) amount of the energy in the dark matter component is constrained to be less than 9 that even when c<1 the big rip still can be avoided due to the existence of a de Sitter solution at z\u2192-1. We show that this solution can not be accomplished in the two simple models, while for the general model such a solution can be achieved with a large \u03b2, and the big rip may be avoided at the 95.4", "keyphrases": ["holographic dark energy", "dark matter", "non-gravitational coupling"]}
{"id": "0902.4465", "title": "Power-counting and the Validity of the Classical Approximation During Inflation", "abstract": "We use the power-counting formalism of effective field theory to study the size of loop corrections in theories of slow-roll inflation, with the aim of more precisely identifying the limits of validity of the usual classical inflationary treatments. We keep our analysis as general as possible in order to systematically identify the most important corrections to the classical inflaton dynamics. Although most slow-roll models lie within the semiclassical domain, we find the consistency of the Higgs-Inflaton scenario to be more delicate due to the proximity between the Hubble scale during inflation and the upper bound allowed by unitarity on the new-physics scale associated with the breakdown of the semiclassical approximation within the effective theory. Similar remarks apply to curvature-squared inflationary models.", "keyphrases": ["validity", "unitarity", "higgs inflation", "non-minimal coupling", "perturbative unitarity"]}
{"id": "0908.2344", "title": "Composition and thermodynamics of nuclear matter with light clusters", "abstract": "We investigate nuclear matter at finite temperature and density, including the formation of light clusters up to the alpha particle The novel feature of this work is to include the formation of clusters as well as their dissolution due to medium effects in a systematic way using two many-body theories: a microscopic quantum statistical (QS) approach and a generalized relativistic mean field (RMF) model. Nucleons and clusters are modified by medium effects. Both approaches reproduce the limiting cases of nuclear statistical equilibrium (NSE) at low densities and cluster-free nuclear matter at high densities. The treatment of the cluster dissociation is based on the Mott effect due to Pauli blocking, implemented in slightly different ways in the QS and the generalized RMF approaches. We compare the numerical results of these models for cluster abundances and thermodynamics in the region of medium excitation energies with temperatures T <= 20 MeV and baryon number densities from zero to a few times saturation density. The effect of cluster formation on the liquid-gas phase transition and on the density dependence of the symmetry energy is studied. Comparison is made with other theoretical approaches, in particular those, which are commonly used in astrophysical calculations. The results are relevant for heavy-ion collisions and astrophysical applications.", "keyphrases": ["nuclear matter", "light cluster", "nucleon", "supernova matter"]}
{"id": "1110.1049", "title": "Metric-Palatini gravity unifying local constraints and late-time cosmic acceleration", "abstract": "We present a novel approach to modified theories of gravity that consists of adding to the Einstein-Hilbert Lagrangian an f(R) term constructed a la Palatini. Using the respective dynamically equivalent scalar-tensor representation, we show that the theory can pass the Solar System observational constraints even if the scalar field is very light. This implies the existence of a long-range scalar field, which is able to modify the cosmological and galactic dynamics, but leaves the Solar System unaffected. We also verify the absence of instabilities in perturbations and provide explicit models which are consistent with local tests and lead to the late-time cosmic acceleration.", "keyphrases": ["gravity", "late-time cosmic acceleration", "metric einstein-hilbert lagrangian", "hybrid metric-palatini theory"]}
{"id": "0909.0169", "title": "Kerr Black Holes as Particle Accelerators to Arbitrarily High Energy", "abstract": "We show that intermediate mass black holes conjectured to be the early precursors of supermassive black holes and surrounded by relic cold dark matter density spikes can act as particle accelerators with collisions, in principle, at arbitrarily high centre of mass energies in the case of Kerr black holes. While the ejecta from such interactions will be highly redshifted, we may anticipate the possibility of a unique probe of Planck-scale physics.", "keyphrases": ["black hole", "high energy", "mass frame", "extremal kerr", "particle collision"]}
{"id": "1404.5954", "title": "The IR-resummed Effective Field Theory of Large Scale Structures", "abstract": "We present a new method to resum the effect of large scale motions in the Effective Field Theory of Large Scale Structures. Because the linear power spectrum in \u039bCDM is not scale free the effects of the large scale flows are enhanced. Although previous EFT calculations of the equal-time density power spectrum at one and two loops showed a remarkable agreement with numerical results, they also showed a 2 BAO oscillations. We show that this was indeed the case, explain the physical origin and show how a Lagrangian based calculation removes this differences. We propose a simple method to upgrade existing Eulerian calculations to effectively make them Lagrangian and compare the new results with existing fits to numerical simulations. Our new two-loop results agrees with numerical results up to k\u223c 0.6 h/Mpc to within 1 also compute power spectra involving momentum which is significantly more affected by the large scale flows. We show how keeping track of these velocities significantly enhances the UV reach of the momentum power spectrum in addition to removing the BAO related residuals. We compute predictions for the real space correlation function around the BAO scale and investigate its sensitivity to the EFT parameters and the details of the resummation technique.", "keyphrases": ["effective field theory", "large scale structures", "matter power spectrum", "three-loop order", "ir-resummation"]}
{"id": "0912.5297", "title": "New cosmological constraints on primordial black holes", "abstract": "We update the constraints on the fraction of the Universe going into primordial black holes in the mass range 10^9\u201310^17 g associated with the effects of their evaporations on big bang nucleosynthesis and the extragalactic photon background. We include for the first time all the effects of quark and gluon emission by black holes on these constraints and account for the latest observational developments. We then discuss the other constraints in this mass range and show that these are weaker than the nucleosynthesis and photon background limits, apart from a small range 10^13\u201310^14 g, where the damping of cosmic microwave background anisotropies dominates. Finally we review the gravitational and astrophysical effects of nonevaporating primordial black holes, updating constraints over the broader mass range 1\u201310^50 g.", "keyphrases": ["cosmological constraint", "primordial black hole", "extragalactic photon background", "early universe", "certain mass range"]}
{"id": "1311.0029", "title": "Dark Sectors and New, Light, Weakly-Coupled Particles", "abstract": "Dark sectors, consisting of new, light, weakly-coupled particles that do not interact with the known strong, weak, or electromagnetic forces, are a particularly compelling possibility for new physics. Nature may contain numerous dark sectors, each with their own beautiful structure, distinct particles, and forces. This review summarizes the physics motivation for dark sectors and the exciting opportunities for experimental exploration. It is the summary of the Intensity Frontier subgroup \"New, Light, Weakly-coupled Particles\" of the Community Summer Study 2013 (Snowmass). We discuss axions, which solve the strong CP problem and are an excellent dark matter candidate, and their generalization to axion-like particles. We also review dark photons and other dark-sector particles, including sub-GeV dark matter, which are theoretically natural, provide for dark matter candidates or new dark matter interactions, and could resolve outstanding puzzles in particle and astro-particle physics. In many cases, the exploration of dark sectors can proceed with existing facilities and comparatively modest experiments. A rich, diverse, and low-cost experimental program has been identified that has the potential for one or more game-changing discoveries. These physics opportunities should be vigorously pursued in the US and elsewhere.", "keyphrases": ["particle", "dark matter", "axion-like particle", "dark sector", "boson"]}
{"id": "1603.05234", "title": "The clustering of massive Primordial Black Holes as Dark Matter: measuring their mass distribution with Advanced LIGO", "abstract": "The recent detection by Advanced LIGO of gravitational waves (GW) from the merging of a binary black hole system sets new limits on the merging rates of massive primordial black holes (PBH) that could be a significant fraction or even the totality of the dark matter in the Universe. aLIGO opens the way to the determination of the distribution and clustering of such massive PBH. If PBH clusters have a similar density to the one observed in ultra-faint dwarf galaxies, we find merging rates comparable to aLIGO expectations. Massive PBH dark matter predicts the existence of thousands of those dwarf galaxies where star formation is unlikely because of gas accretion onto PBH, which would possibly provide a solution to the missing satellite and too-big-to-fail problems. Finally, we study the possibility of using aLIGO and future GW antennas to measure the abundance and mass distribution of PBH in the range [5 - 200] Msun to 10% accuracy.", "keyphrases": ["black hole", "dark matter", "mass distribution", "universe", "gas accretion"]}
{"id": "1005.3039", "title": "Einstein's Other Gravity and the Acceleration of the Universe", "abstract": "Spacetime curvature plays the primary role in general relativity but Einstein later considered a theory where torsion was the central quantity. Just as the Einstein-Hilbert action in the Ricci curvature scalar R can be generalized to f(R) gravity, we consider extensions of teleparallel, or torsion scalar T, gravity to f(T) theories. The field equations are naturally second order, avoiding pathologies, and can give rise to cosmic acceleration with unique features.", "keyphrases": ["gravity", "einstein", "dark energy", "late-time acceleration", "various cosmological solution"]}
{"id": "1509.08458", "title": "Breaking a Dark Degeneracy with Gravitational Waves", "abstract": "We identify a scalar-tensor model embedded in the Horndeski action whose cosmological background and linear scalar fluctuations are degenerate with the concordance cosmology. The model admits a self-accelerated background expansion at late times that is stable against perturbations with a sound speed attributed to the new field that is equal to the speed of light. While degenerate in scalar fluctuations, self-acceleration of the model implies a present cosmological tensor mode propagation at < 95 with a damping of the wave amplitude that is > 5 general relativity. We show that these discrepancies are endemic to self-accelerated Horndeski theories with degenerate large-scale structure and are tested with measurements of gravitational waves emitted by events at cosmological distances. Hence, gravitational-wave cosmology breaks the dark degeneracy in observations of the large-scale structure between two fundamentally different explanations of cosmic acceleration - a cosmological constant and a scalar-tensor modification of gravity. The gravitational wave event GW150914 recently detected with the aLIGO instruments and its potential association with a weak short gamma-ray burst observed with the Fermi GBM experiment may have provided this crucial measurement.", "keyphrases": ["dark degeneracy", "gravitational wave", "horndeski theory", "scalar-tensor theory", "gws"]}
{"id": "0911.4771", "title": "Magnetic fields in the early universe", "abstract": "We give a pedagogical introduction to two aspects of magnetic fields in the early universe. We first focus on how to formulate electrodynamics in curved space time, defining appropriate magnetic and electric fields and writing Maxwell equations in terms of these fields. We then specialize to the case of magnetohydrodynamics in the expanding universe. We emphasize the usefulness of tetrads in this context. We then review the generation of magnetic fields during the inflationary era, deriving in detail the predicted magnetic and electric spectra for some models. We discuss potential problems arising from back reaction effects and from the large variation of the coupling constants required for such field generation.", "keyphrases": ["universe", "magnetic field", "conformal invariance", "primordial magnetic field"]}
{"id": "1302.0223", "title": "Galilean invariance and the consistency relation for the nonlinear squeezed bispectrum of large scale structure", "abstract": "We discuss the constraints imposed on the nonlinear evolution of the Large Scale Structure (LSS) of the universe by galilean invariance, the symmetry relevant on subhorizon scales. Using Ward identities associated to the invariance, we derive fully nonlinear consistency relations between statistical correlators of the density and velocity perturbations, such as the power spectrum and the bispectrum. These relations are valid up to O (f_NL^2) corrections. We then show that most of the semi-analytic methods proposed so far to resum the perturbative expansion of the LSS dynamics fail to fulfill the constraints imposed by galilean invariance, and are therefore susceptible to non-physical infrared effects. Finally, we identify and discuss a nonperturbative semi-analytical scheme which is manifestly galilean invariant at any order of its expansion.", "keyphrases": ["consistency relation", "galilean invariance", "-correlator function", "soft limit", "dark matter fluid"]}
{"id": "0902.1761", "title": "Detection of Extrasolar Planets by Gravitational Microlensing", "abstract": "Gravitational microlensing provides a unique window on the properties and prevalence of extrasolar planetary systems because of its ability to find low-mass planets at separations of a few AU. The early evidence from microlensing indicates that the most common type of exoplanet yet detected are the so-called \"super-Earth\" planets of 10 Earth-masses at a separation of a few AU from their host stars. The detection of two such planets indicates that roughly one third of stars have such planets in the separation range 1.5-4 AU, which is about an order of magnitude larger than the prevalence of gas-giant planets at these separations. We review the basic physics of the microlensing method, and show why this method allows the detection of Earth-mass planets at separations of 2-3 AU with ground-based observations. We explore the conditions that allow the detection of the planetary host stars and allow measurement of planetary orbital parameters. Finally, we show that a low-cost, space-based microlensing survey can provide a comprehensive statistical census of extrasolar planetary systems with sensitivity down to 0.1 Earth-masses at separations ranging from 0.5 AU to infinity.", "keyphrases": ["extrasolar planet", "planet", "gravitational microlensing"]}
{"id": "1307.4738", "title": "Development of a Relic Neutrino Detection Experiment at PTOLEMY: Princeton Tritium Observatory for Light, Early-Universe, Massive-Neutrino Yield", "abstract": "The PTOLEMY experiment (Princeton Tritium Observatory for Light, Early-Universe, Massive-Neutrino Yield) aims to achieve the sensitivity required to detect the relic neutrino background through a combination of a large area surface-deposition tritium target, MAC-E filter methods, cryogenic calorimetry, and RF tracking and time-of-flight systems. A small-scale prototype is in operation at the Princeton Plasma Physics Laboratory with the goal of validating the technologies that would enable the design of a 100 gram PTOLEMY. With precision calorimetry in the prototype setup, the limitations from quantum mechanical and Doppler broadening of the tritium target for different substrates will be measured, including graphene substrates. Beyond relic neutrino physics, sterile neutrinos contributing to the dark matter in the universe are allowed by current constraints on partial contributions to the number of active neutrino species in thermal equilibrium in the early universe. The current PTOLEMY prototype is expected to have unique sensitivity in the search for sterile neutrinos with electron-flavor content for masses of 0.1\u20131keV, where less stringent, 10eV, energy resolution is required. The search for sterile neutrinos with electron-flavor content with the 100g PTOLEMY is expected to reach the level |U_e4|^2 of 10^-4\u201310^-6, depending on the sterile neutrino mass.", "keyphrases": ["neutrino", "princeton tritium observatory", "massive-neutrino yield"]}
{"id": "1505.06668", "title": "Effective Theory of Large-Scale Structure with Primordial Non-Gaussianity", "abstract": "We develop the effective theory of large-scale structure for non-Gaussian initial conditions. The effective stress tensor in the dark matter equations of motion contains new operators, which originate from the squeezed limit of the primordial bispectrum. Parameterizing the squeezed limit by a scaling and an angular dependence, captures large classes of primordial non-Gaussianity. Within this parameterization, we classify the possible contributions to the effective theory. We show explicitly how all terms consistent with the symmetries arise from coarse graining the dark matter equations of motion and its initial conditions. We also demonstrate that the system is closed under renormalization and that the basis of correction terms is therefore complete. The relevant corrections to the matter power spectrum and bispectrum are computed numerically and their relative importance is discussed.", "keyphrases": ["large-scale structure", "primordial non-gaussianity", "effective theory"]}
{"id": "1705.11098", "title": "Modified Gravity Theories on a Nutshell: Inflation, Bounce and Late-time Evolution", "abstract": "We systematically review some standard issues and also the latest developments of modified gravity in cosmology, emphasizing on inflation, bouncing cosmology and late-time acceleration era. Particularly, we present the formalism of standard modified gravity theory representatives, like F(R), F(\ud835\udca2) and F(T) gravity theories, but also several alternative theoretical proposals which appeared in the literature during the last decade. We emphasize on the formalism developed for these theories and we explain how these theories can be considered as viable descriptions for our Universe. Using these theories, we present how a viable inflationary era can be produced in the context of these theories, with the viability being justified if compatibility with the latest observational data is achieved. Also we demonstrate how bouncing cosmologies can actually be described by these theories. Moreover, we systematically discuss several qualitative features of the dark energy era by using the modified gravity formalism, and also we critically discuss how a unified description of inflation with dark energy era can be described by solely using the modified gravity framework. Finally, we also discuss some astrophysical solutions in the context of modified gravity, and several qualitative features of these solutions. The aim of this review is to gather the different modified gravity techniques and form a virtual modified gravity \"toolbox\", which will contain all the necessary information on inflation, dark energy and bouncing cosmologies in the context of the various forms of modified gravity.", "keyphrases": ["gravity", "late-time evolution", "cosmology", "inflationary era", "dark energy"]}
{"id": "1108.4136", "title": "Sterile neutrinos with eV masses in cosmology \u2013 how disfavoured exactly?", "abstract": "We study cosmological models that contain sterile neutrinos with eV-range masses as suggested by reactor and short-baseline oscillation data. We confront these models with both precision cosmological data (probing the CMB decoupling epoch) and light-element abundances (probing the BBN epoch). In the minimal LambdaCDM model, such sterile neutrinos are strongly disfavoured by current data because they contribute too much hot dark matter. However, if the cosmological framework is extended to include also additional relativistic degrees of freedom \u2013 beyond the three standard neutrinos and the putative sterile neutrinos, then the hot dark matter constraint on the sterile states is considerably relaxed. A further improvement is achieved by allowing a dark energy equation of state parameter w<-1. While BBN strongly disfavours extra radiation beyond the assumed eV-mass sterile neutrino, this constraint can be circumvented by a small nu_e degeneracy. Any model containing eV-mass sterile neutrinos implies also strong modifications of other cosmological parameters. Notably, the inferred cold dark matter density can shift up by 20 to 75 relative to the standard LambdaCDM value.", "keyphrases": ["cosmology", "sterile neutrino", "cosmological observation"]}
{"id": "1903.11584", "title": "The origin of Galactic cosmic rays: challenges to the standard paradigm", "abstract": "A critical review of the standard paradigm for the origin of Galactic cosmic rays is presented. Recent measurements of local and far-away cosmic rays reveal unexpected behaviours, which challenge the commonly accepted scenario. These recent findings are discussed, together with long-standing open issues. Despite the progress made thanks to ever-improving observational techniques and theoretical investigations, at present our understanding of the origin and of the behaviour of cosmic rays remains incomplete. We believe it is still unclear whether a modification of the standard paradigm, or rather a radical change of the paradigm itself is needed in order to interpret all the available data on cosmic rays within a self-consistent scenario.", "keyphrases": ["galactic", "cosmic ray", "diffusive shock acceleration"]}
{"id": "1702.04189", "title": "Weighing neutrinos in the scenario of vacuum energy interacting with cold dark matter: application of the parameterized post-Friedmann approach", "abstract": "We constrain the neutrino mass in the scenario of vacuum energy interacting with cold dark matter by using current cosmological observations. To avoid the large-scale instability problem in interacting dark energy models, we employ the parameterized post-Friedmann (PPF) approach to do the calculation of perturbation evolution, for the Q=\u03b2 H\u03c1_ c and Q=\u03b2 H\u03c1_\u039b models. The current observational data sets used in this work include Planck (cosmic microwave background), BSH (baryon acoustic oscillations, type Ia supernovae, and Hubble constant), and LSS (redshift space distortions and weak lensing). According to the constraint results, we find that \u03b2>0 at more than 1\u03c3 level for the Q=\u03b2 H\u03c1_ c model, which indicates that cold dark matter decays into vacuum energy; while \u03b2=0 is consistent with the current data at 1\u03c3 level for the Q=\u03b2 H\u03c1_\u039b model. Taking the \u039bCDM model as a baseline model, we find that a smaller upper limit, \u2211 m_\u03bd<0.11 eV (2\u03c3), is induced by the latest BAO BOSS DR12 data and the Hubble constant measurement H_0 = 73.00 \u00b1 1.75 km s^-1 Mpc^-1. For the Q=\u03b2 H\u03c1_ c model, we obtain \u2211 m_\u03bd<0.20 eV (2\u03c3) from Planck+BSH. For the Q=\u03b2 H\u03c1_\u039b model, \u2211 m_\u03bd<0.10 eV (2\u03c3) and \u2211 m_\u03bd<0.14 eV (2\u03c3) are derived from Planck+BSH and Planck+BSH+LSS, respectively. We show that these smaller upper limits on \u2211 m_\u03bd are affected more or less by the tension between H_0 and other observational data.", "keyphrases": ["neutrino", "vacuum energy", "dark matter"]}
{"id": "1501.06570", "title": "Superradiance \u2013 the 2020 Edition", "abstract": "Superradiance is a radiation enhancement process that involves dissipative systems. With a 60 year-old history, superradiance has played a prominent role in optics, quantum mechanics and especially in relativity and astrophysics. In General Relativity, black-hole superradiance is permitted by the ergoregion, that allows for energy, charge and angular momentum extraction from the vacuum, even at the classical level. Stability of the spacetime is enforced by the event horizon, where negative energy-states are dumped. Black-hole superradiance is intimately connected to the black-hole area theorem, Penrose process, tidal forces, and even Hawking radiation, which can be interpreted as a quantum version of black-hole superradiance. Various mechanisms (as diverse as massive fields, magnetic fields, anti-de Sitter boundaries, nonlinear interactions, etc...) can confine the amplified radiation and give rise to strong instabilities. These \"black-hole bombs\" have applications in searches of dark matter and of physics beyond the Standard Model, are associated to the threshold of formation of new black hole solutions that evade the no-hair theorems, can be studied in the laboratory by devising analog models of gravity, and might even provide a holographic description of spontaneous symmetry breaking and superfluidity through the gauge-gravity duality. This work is meant to provide a unified picture of this multifaceted subject. We focus on the recent developments in the field, and work out a number of novel examples and applications, ranging from fundamental physics to astrophysics.", "keyphrases": ["angular momentum", "superradiance", "phenomenon", "superradiant instability", "kerr"]}
{"id": "2004.04740", "title": "Dark matter and dark radiation from evaporating primordial black holes", "abstract": "Primordial black holes in the mass range from 10^-5 to 10^9 g might have existed in the early universe. Via their evaporation mechanism (completed before Big Bang Nucleosynthesis), they might have released stable particles beyond the Standard Model. We reconsider the possibility that such particles might constitute the main part or a fraction of the dark matter observed today, updating the impact on this scenario from warm dark matter constraints. If sufficiently light, stable particles from primordial black holes evaporation might also provide a significant contribution to dark radiation. We generalize previous studies on this interesting dark matter and dark radiation production mechanism, by including the effects of accretion and a possible amount of entropy non conservation. We also discuss in some detail specific examples of stable particle candidates beyond the Standard Model.", "keyphrases": ["dark radiation", "black hole", "dark matter"]}
{"id": "0912.0384", "title": "Gravitational waves from neutron stars: Promises and challenges", "abstract": "We discuss different ways that neutron stars can generate gravitational waves, describe recent improvements in modelling the relevant scenarios in the context of improving detector sensitivity, and show how observations are beginning to test our understanding of fundamental physics. The main purpose of the discussion is to establish promising science goals for third-generation ground-based detectors, like the Einstein Telescope, and identify the various challenges that need to be met if we want to use gravitational-wave data to probe neutron star physics.", "keyphrases": ["neutron star", "gravitational wave", "nuclear matter"]}
{"id": "1812.00674", "title": "Gravitational waves induced by scalar perturbations as probes of the small-scale primordial spectrum", "abstract": "Compared to primordial perturbations on large scales, roughly larger than 1 megaparsec, those on smaller scales are not severely constrained. We revisit the issue of probing small-scale primordial perturbations using gravitational waves (GWs), based on the fact that, when large-amplitude primordial perturbations on small scales exist, GWs with relatively large amplitudes are induced at second order in scalar perturbations, and these induced GWs can be probed by both existing and planned gravitational-wave projects. We use accurate methods to calculate these induced GWs and take into account sensitivities of different experiments to induced GWs carefully, to report existing and expected limits on the small-scale primordial spectrum.", "keyphrases": ["scalar perturbation", "small-scale primordial spectrum", "primordial black hole"]}
{"id": "1503.01136", "title": "Combining high-dispersion spectroscopy (HDS) with high contrast imaging (HCI): Probing rocky planets around our nearest neighbors", "abstract": "Aims: In this work, we discuss a way to combine High Dispersion Spectroscopy and High Contrast Imaging (HDS+HCI). For a planet located at a resolvable angular distance from its host star, the starlight can be reduced up to several orders of magnitude using adaptive optics and/or coronography. In addition, the remaining starlight can be filtered out using high-dispersion spectroscopy, utilizing the significantly different (or Doppler shifted) high-dispersion spectra of the planet and star. In this way, HDS+HCI can in principle reach contrast limits of 1e-5 x 1e-5, although in practice this will be limited by photon noise and/or sky-background. Methods: We present simulations of HDS+HCI observations with the E-ELT, both probing thermal emission from a planet at infrared wavelengths, and starlight reflected off a planet atmosphere at optical wavelengths. For the infrared simulations we use the baseline parameters of the E-ELT and METIS instrument, with the latter combining extreme adaptive optics with an R=100,000 IFS. We include realistic models of the adaptive optics performance and atmospheric transmission and emission. For the optical simulation we also assume R=100,000 IFS with adaptive optics capabilities at the E-ELT. Results: One night of HDS+HCI observations with the E-ELT at 4.8 um (d_lambda = 0.07 um) can detect a planet orbiting alpha Cen A with a radius of R=1.5 R_earth and a twin-Earth thermal spectrum of T_eq=300 K at a signal-to-noise (S/N) of 5. In the optical, with a Strehl ratio performance of 0.3, reflected light from an Earth-size planet in the habitable zone of Proxima Centauri can be detected at a S/N of 10 in the same time frame. Recently, first HDS+HCI observations have shown the potential of this technique by determining the spin-rotation of the young massive exoplanet beta Pictoris b. [abridged]", "keyphrases": ["high-dispersion spectroscopy", "high contrast imaging", "planet"]}
{"id": "1206.0267", "title": "The Epoch of Reionization", "abstract": "The Universe's dark ages end with the formation of the first generation of galaxies. These objects start emitting ultraviolet radiation that carves out ionized regions around them. After a sufficient number of ionizing sources have formed, the ionized fraction of the gas in the Universe rapidly increases until hydrogen becomes fully ionized. This period, during which the cosmic gas went from neutral to ionized, is known as the Universe's Epoch of Reionization . The Epoch of Reionization is related to many fundamental questions in cosmology, such as properties of the first galaxies, physics of (mini-)quasars, formation of very metal-poor stars and a slew of other important research topics in astrophysics. Hence uncovering it will have far reaching implications on the study of structure formation in the early Universe. This chapter reviews the current observational evidence for the occurrence of this epoch, its key theoretical aspects and main characteristics, and finally the various observational probes that promise to uncover it. A special emphasis is put on the redshifted 21 cm probe, the various experiments that are currently being either built or designed, and what we can learn from them about the Epoch of Reionization.", "keyphrases": ["epoch", "reionization", "neutral hydrogen"]}
{"id": "2010.00593", "title": "Static response and Love numbers of Schwarzschild black holes", "abstract": "We derive the quadratic action for the physical degrees of freedom of massless spin-0, spin-1, and spin-2 perturbations on a Schwarzschild\u2013(A)dS background in arbitrary dimensions. We then use these results to compute the static response of asymptotically flat Schwarzschild black holes to external fields. Our analysis reproduces known facts about black hole Love numbers, in particular that they vanish for all types of perturbation in four spacetime dimensions, but also leads to new results. For instance, we find that neutral Schwarzschild black holes polarize in the presence of an electromagnetic background in any number of spacetime dimensions except four. Moreover, we calculate for the first time black hole Love numbers for vector-type gravitational perturbations in higher dimensions and find that they generically do not vanish. Along the way, we shed some light on an apparent discrepancy between previous results in the literature, and clarify some aspects of the matching between perturbative calculations of static response on a Schwarzschild background and the point-particle effective theory", "keyphrases": ["response", "schwarzschild", "black hole"]}
{"id": "1110.0462", "title": "The Cosmic Origins Spectrograph", "abstract": "The Cosmic Origins Spectrograph (COS) is a moderate-resolution spectrograph with unprecedented sensitivity that was installed into the Hubble Space Telescope (HST) in May 2009, during HST Servicing Mission 4 (STS-125). We present the design philosophy and summarize the key characteristics of the instrument that will be of interest to potential observers. For faint targets, with flux F_lambda 1.0E10-14 ergs/s/cm2/Angstrom, COS can achieve comparable signal to noise (when compared to STIS echelle modes) in 1-2 time. This has led to a significant increase in the total data volume and data quality available to the community. For example, in the first 20 months of science operation (September 2009 - June 2011) the cumulative redshift pathlength of extragalactic sight lines sampled by COS is 9 times that sampled at moderate resolution in 19 previous years of Hubble observations. COS programs have observed 214 distinct lines of sight suitable for study of the intergalactic medium as of June 2011. COS has measured, for the first time with high reliability, broad Lya absorbers and Ne VIII in the intergalactic medium, and observed the HeII reionization epoch along multiple sightlines. COS has detected the first CO emission and absorption in the UV spectra of low-mass circumstellar disks at the epoch of giant planet formation, and detected multiple ionization states of metals in extra-solar planetary atmospheres. In the coming years, COS will continue its census of intergalactic gas, probe galactic and cosmic structure, and explore physics in our solar system and Galaxy.", "keyphrases": ["cosmic origins spectrograph", "hst", "instrument"]}
{"id": "1006.1769", "title": "Eddington's theory of gravity and its progeny", "abstract": "We resurrect Eddington's proposal for the gravitational action in the presence of a cosmological constant and extend it to include matter fields. We show that the Newton-Poisson equation is modified in the presence of sources and that charged black holes show great similarities with those arising in Born-Infeld electrodynamics coupled to gravity. When we consider homogeneous and isotropic space-times we find that there is a minimum length (and maximum density) at early times, clearly pointing to an alternative theory of the Big Bang. We thus argue that the modern formulation of Eddington's theory, Born-Infeld gravity, presents us with a novel, non-singular description of the Universe.", "keyphrases": ["gravity", "cosmology", "space-time", "eddington", "big bang singularity"]}
{"id": "1109.6324", "title": "Black holes in scalar-tensor gravity", "abstract": "Hawking has proven that black holes which are stationary as the endpoint of gravitational collapse in Brans\u2013Dicke theory (without a potential) are no different than in general relativity. We extend this proof to the much more general class of scalar-tensor and f(R) gravity theories, without assuming any symmetries apart from stationarity.", "keyphrases": ["gravity", "black hole", "scalar-tensor theory", "no-hair theorem", "minimal coupling"]}
{"id": "0904.2835", "title": "Matter Bounce in Horava-Lifshitz Cosmology", "abstract": "Horava-Lifshitz gravity, a recent proposal for a UV-complete renormalizable gravity theory, may lead to a bouncing cosmology. In this note we argue that Horava-Lifshitz cosmology may yield a concrete realization of the matter bounce scenario, and thus give rise to an alternative to inflation for producing a scale-invariant spectrum of cosmological perturbations. In this scenario, quantum vacuum fluctuations exit the Hubble radius in the pre-bounce phase and the spectrum is transformed into a scale-invariant one on super-Hubble scales before the bounce because the long wavelength modes undergo squeezing of their wave-functions for a longer period of time than shorter wavelength modes. The scale-invariance of the spectrum of curvature fluctuations is preserved during and after the bounce. A distinctive prediction of this scenario is the amplitude and shape of the bispectrum.", "keyphrases": ["cosmology", "horava-lifshitz gravity", "matter bounce scenario"]}
{"id": "1308.2911", "title": "Test of consistency between Planck and WMAP", "abstract": "Within the context of the concordance model of cosmology we test the consistency of the angular power spectrum data from WMAP and Planck looking for possible systematics. The best fit concordance model to each observation is used as a mean function along with a Crossing function with an orthogonal basis to fit the data from the other observation searching for any possible deviation. We report that allowing an overall amplitude shift in the observed angular power spectra of the two observations, the best fit mean function from Planck data is consistent with WMAP 9 year data but the best fit mean function generated from WMAP-9 data is not consistent with Planck data at the 3\u03c3 level. This is an expected result when there is no clear systematic/tension between two observations and one of them has a considerably higher precision. We conclude that there is no clear tension between Planck and WMAP 9 year angular power spectrum data from a statistical point of view (allowing the overall amplitude shift). Our result highlights the fact that while the angular power spectrum from cosmic microwave background observations is a function of various cosmological parameters, comparing individual parameters might be misleading in the presence of cosmographic degeneracies. Another main result of our analysis is the importance of the overall amplitudes of the observed spectra from Planck and WMAP observations. Fixing the amplitudes at their reported values results in an unresolvable tension between the two observations at more than 3\u03c3 level which can be a hint towards a serious systematic.", "keyphrases": ["consistency", "planck", "wmap"]}
{"id": "2101.11735", "title": "Wave Dark Matter", "abstract": "We review the physics and phenomenology of wave dark matter: a bosonic dark matter candidate lighter than about 30 eV. Such particles have a de Broglie wavelength exceeding the average inter-particle separation in a galaxy like the Milky Way, and are well described as classical waves. We outline the particle physics motivations for them, including the QCD axion and ultra-light axion-like-particles such as fuzzy dark matter. The wave nature of the dark matter implies a rich phenomenology: (1) Wave interference leads to order unity density fluctuations on de Broglie scale. A manifestation is vortices where the density vanishes and around which the velocity circulates. There is one vortex ring per de Broglie volume on average. (2) For sufficiently low masses, soliton condensation occurs at centers of halos. The soliton oscillates and random walks, another manifestation of wave interference. The halo/subhalo abundance is suppressed at small masses, but the precise prediction from numerical wave simulations remains to be determined. (3) For ultra-light 10^-22 eV dark matter, the wave interference substructures can be probed by tidal streams/gravitational lensing. The signal can be distinguished from that due to subhalos by the dependence on stream orbital radius/image separation. (4) Axion detection experiments are sensitive to interference substructures for moderately light masses. The stochastic nature of the waves affects the interpretation of experiments and motivates the measurement of correlation functions. Current constraints and open questions, covering detection experiments and cosmological/galactic/black-hole observations, are discussed.", "keyphrases": ["dark matter", "axion", "fuzzy dark matter", "wave nature"]}
{"id": "1004.3294", "title": "Cosmological Tests of Gravity", "abstract": "Modifications of general relativity provide an alternative explanation to dark energy for the observed acceleration of the universe. We review recent developments in modified gravity theories, focusing on higher dimensional approaches and chameleon/f(R) theories. We classify these models in terms of the screening mechanisms that enable such theories to approach general relativity on small scales (and thus satisfy solar system constraints). We describe general features of the modified Friedman equation in such theories. The second half of this review describes experimental tests of gravity in light of the new theoretical approaches. We summarize the high precision tests of gravity on laboratory and solar system scales. We describe in some detail tests on astrophysical scales ranging from kpc (galaxy scales) to Gpc (large-scale structure). These tests rely on the growth and inter-relationship of perturbations in the metric potentials, density and velocity fields which can be measured using gravitational lensing, galaxy cluster abundances, galaxy clustering and the Integrated Sachs-Wolfe effect. A robust way to interpret observations is by constraining effective parameters, such as the ratio of the two metric potentials. Currently tests of gravity on astrophysical scales are in the early stages \u2014 we summarize these tests and discuss the interesting prospects for new tests in the coming decade.", "keyphrases": ["gravity", "dark energy", "dark matter", "large scale", "cosmology"]}
{"id": "1707.09578", "title": "Primordial black holes and second order gravitational waves from ultra-slow-roll inflation", "abstract": "The next generation of space-borne gravitational wave detectors may detect gravitational waves from extreme mass-ratio inspirals with primordial black holes. To produce primordial black holes which contribute a non-negligible abundance of dark matter and are consistent with the observations, a large enhancement in the primordial curvature power spectrum is needed. For a single field slow-roll inflation, the enhancement requires a very flat potential for the inflaton, and this will increase the number of e-folds. To avoid the problem, an ultra-slow-roll inflation at the near inflection point is required. We elaborate the conditions to successfully produce primordial black hole dark matter from single field inflation and propose a toy model with polynomial potential to realize the big enhancement of the curvature power spectrum at small scales while maintaining the consistency with the observations at large scales. The power spectrum for the second order gravitational waves generated by the large density perturbations at small scales is consistent with the current pulsar timing array observations.", "keyphrases": ["gravitational wave", "ultra-slow-roll inflation", "primordial black hole"]}
{"id": "1709.09066", "title": "Line-Intensity Mapping: 2017 Status Report", "abstract": "Following the first two annual intensity mapping workshops at Stanford in March 2016 and Johns Hopkins in June 2017, we report on the recent advances in theory, instrumentation and observation that were presented in these meetings and some of the opportunities and challenges that were identified looking forward. With preliminary detections of CO, [CII], Lya and low-redshift 21cm, and a host of experiments set to go online in the next few years, the field is rapidly progressing on all fronts, with great anticipation for a flood of new exciting results. This current snapshot provides an efficient reference for experts in related fields and a useful resource for nonspecialists. We begin by introducing the concept of line-intensity mapping and then discuss the broad array of science goals that will be enabled, ranging from the history of star formation, reionization and galaxy evolution to measuring baryon acoustic oscillations at high redshift and constraining theories of dark matter, modified gravity and dark energy. After reviewing the first detections reported to date, we survey the experimental landscape, presenting the parameters and capabilities of relevant instruments such as COMAP, mmIMe, AIM-CO, CCAT-p, TIME, CONCERTO, CHIME, HIRAX, HERA, STARFIRE, MeerKAT/SKA and SPHEREx. Finally, we describe recent theoretical advances: different approaches to modeling line luminosity functions, several techniques to separate the desired signal from foregrounds, statistical methods to analyze the data, and frameworks to generate realistic intensity map simulations.", "keyphrases": ["galaxy", "line-intensity mapping", "volume", "spectral line", "spatial fluctuation"]}
{"id": "1104.2669", "title": "f(R,T) gravity", "abstract": "We consider f(R,T) modified theories of gravity, where the gravitational Lagrangian is given by an arbitrary function of the Ricci scalar R and of the trace of the stress-energy tensor T. We obtain the gravitational field equations in the metric formalism, as well as the equations of motion for test particles, which follow from the covariant divergence of the stress-energy tensor. Generally, the gravitational field equations depend on the nature of the matter source. The field equations of several particular models, corresponding to some explicit forms of the function f(R,T), are also presented. An important case, which is analyzed in detail, is represented by scalar field models. We write down the action and briefly consider the cosmological implications of the f(R,T^\u03d5) models, where T^\u03d5 is the trace of the stress-energy tensor of a self-interacting scalar field. The equations of motion of the test particles are also obtained from a variational principle. The motion of massive test particles is non-geodesic, and takes place in the presence of an extra force orthogonal to the four-velocity. The Newtonian limit of the equation of motion is further analyzed. Finally, we provide a constraint on the magnitude of the extra-acceleration by analyzing the perihelion precession of the planet Mercury in the framework of the present model.", "keyphrases": ["gravity", "trace", "tensor", "generalization", "geometry-matter coupling"]}
{"id": "1205.3365", "title": "Everything You Always Wanted To Know About The Cosmological Constant Problem (But Were Afraid To Ask)", "abstract": "This article aims at discussing the cosmological constant problem at a pedagogical but fully technical level. We review how the vacuum energy can be regularized in flat and curved space-time and how it can be understood in terms of Feynman bubble diagrams. In particular, we show that the properly renormalized value of the zero-point energy density today (for a free theory) is in fact far from being 122 orders of magnitude larger than the critical energy density, as often quoted in the literature. We mainly consider the case of scalar fields but also treat the cases of fermions and gauge bosons which allows us to discuss the question of vacuum energy in super-symmetry. Then, we discuss how the cosmological constant can be measured in cosmology and constrained with experiments such as measurements of planet orbits in our solar system or atomic spectra. We also review why the Lamb shift and the Casimir effect seem to indicate that the quantum zero-point fluctuations are not an artifact of the quantum field theory formalism. We investigate how experiments on the universality of free fall can constrain the gravitational properties of vacuum energy and we discuss the status of the weak equivalence principle in quantum mechanics, in particular the Collela, Overhausser and Werner experiment and the quantum Galileo experiment performed with a Salecker-Wigner-Peres clock. Finally, we briefly conclude with a discussion on the solutions to the cosmological constant problem that have been proposed so far.", "keyphrases": ["cosmological constant problem", "quantum field theory", "universe", "vacuum energy density", "supersymmetry"]}
{"id": "1106.3312", "title": "Cosmology of the Galileon from Massive Gravity", "abstract": "We covariantize the decoupling limit of massive gravity proposed in arXiv:1011.1232 and study the cosmology of this theory as a proxy, which embodies key features of the fully non-linear covariant theory. We first confirm that it exhibits a self-accelerating solution, similar to what has been found in arXiv:1010.1780, where the Hubble parameter corresponds to the graviton mass. For a certain range of parameters fluctuations relative to the self-accelerating background are stable and form an attractor solution. We also show that a degravitating solution can not be constructed in this covariantized proxy theory in a meaningful way. As for cosmic structure formation, we find that the helicity-0 mode of the graviton causes an enhancement relative to LCDM. For consistency we also compare proxy theories obtained starting from different frames in the decoupling limit and discuss the possibility of obtaining a non-representative proxy theory by choosing the wrong starting frame.", "keyphrases": ["massive gravity", "scalar-tensor theory", "galileon theory"]}
{"id": "1204.2832", "title": "Reconstruction of dark energy and expansion dynamics using Gaussian processes", "abstract": "An important issue in cosmology is reconstructing the effective dark energy equation of state directly from observations. With few physically motivated models, future dark energy studies cannot only be based on constraining a dark energy parameter space, as the errors found depend strongly on the parameterisation considered. We present a new non-parametric approach to reconstructing the history of the expansion rate and dark energy using Gaussian Processes, which is a fully Bayesian approach for smoothing data. We present a pedagogical introduction to Gaussian Processes, and discuss how it can be used to robustly differentiate data in a suitable way. Using this method we show that the Dark Energy Survey - Supernova Survey (DES) can accurately recover a slowly evolving equation of state to sigma_w = +-0.04 (95 at z=0.7, with a minimum error of +-0.015 at the sweet-spot at z 0.14, provided the other parameters of the model are known. Errors on the expansion history are an order of magnitude smaller, yet make no assumptions about dark energy whatsoever. A code for calculating functions and their first three derivatives using Gaussian processes has been developed and is available for download at http://www.acgc.uct.ac.za/ seikel/GAPP/index.html .", "keyphrases": ["dark energy", "expansion dynamic", "gaussian process", "cosmology", "gapp"]}
{"id": "1509.03884", "title": "Testing black hole candidates with electromagnetic radiation", "abstract": "Astrophysical black hole candidates are thought to be the Kerr black holes of general relativity, but there is not yet direct observational evidence that the spacetime geometry around these objects is described by the Kerr solution. The study of the properties of the electromagnetic radiation emitted by gas or stars orbiting these objects can potentially test the Kerr black hole hypothesis. In this paper, I review the state of the art of this research field, describing the possible approaches to test the Kerr metric with current and future observational facilities and discussing current constraints.", "keyphrases": ["black hole candidate", "radiation", "gravity", "accretion disk", "astrophysical data"]}
{"id": "1007.0443", "title": "Generalization of the Fierz-Pauli Action", "abstract": "We consider the Lagrangian of gravity covariantly amended by the mass and polynomial interaction terms with arbitrary coefficients, and reinvestigate the consistency of such a theory in the decoupling limit, up to the fifth order in the nonlinearities. We calculate explicitly the self-interactions of the helicity-0 mode, as well as the nonlinear mixing between the helicity-0 and -2 modes. We show that ghost-like pathologies in these interactions disappear for special choices of the polynomial interactions, and argue that this result remains true to all orders in the decoupling limit. Moreover, we show that the linear, and some of the nonlinear mixing terms between the helicity-0 and -2 modes can be absorbed by a local change of variables, which then naturally generates the cubic, quartic, and quintic Galileon interactions, introduced in a different context. We also point out that the mixing between the helicity-0 and 2 modes can be at most quartic in the decoupling limit. Finally, we discuss the implications of our findings for the consistency of the effective field theory away from the decoupling limit, and for the Boulware-Deser problem.", "keyphrases": ["fierz-pauli action", "gravity", "generalization", "gabadadze", "tolley"]}
{"id": "1003.5751", "title": "Dust of Dark Energy", "abstract": "We introduce a novel class of field theories where energy always flows along timelike geodesics, mimicking in that respect dust, yet which possess non-zero pressure. This theory comprises two scalar fields, one of which is a Lagrange multiplier enforcing a constraint between the other's field value and derivative. We show that this system possesses no wave-like modes but retains a single dynamical degree of freedom. Thus, the sound speed is always identically zero on all backgrounds. In particular, cosmological perturbations reproduce the standard behaviour for hydrodynamics with vanishing sound speed. Using all these properties we propose a model unifying Dark Matter and Dark Energy in a single degree of freedom. In a certain limit this model exactly reproduces the evolution history of Lambda-CDM, while deviations away from the standard expansion history produce a potentially measurable difference in the evolution of structure.", "keyphrases": ["dark energy", "scalar field", "dark matter"]}
{"id": "1610.08981", "title": "One Law To Rule Them All: The Radial Acceleration Relation of Galaxies", "abstract": "We study the link between baryons and dark matter in 240 galaxies with spatially resolved kinematic data. Our sample spans 9 dex in stellar mass and includes all morphological types. We consider (i) 153 late-type galaxies (LTGs; spirals and irregulars) with gas rotation curves from the SPARC database; (ii) 25 early-type galaxies (ETGs; ellipticals and lenticulars) with stellar and HI data from ATLAS^3D or X-ray data from Chandra; and (iii) 62 dwarf spheroidals (dSphs) with individual-star spectroscopy. We find that LTGs, ETGs, and \"classical\" dSphs follow the same radial acceleration relation: the observed acceleration (gobs) correlates with that expected from the distribution of baryons (gbar) over 4 dex. The relation coincides with the 1:1 line (no dark matter) at high accelerations but systematically deviates from unity below a critical scale of 10^-10 m/s^2. The observed scatter is remarkably small (<0.13 dex) and largely driven by observational uncertainties. The residuals do not correlate with any global or local galaxy property (baryonic mass, gas fraction, radius, etc.). The radial acceleration relation is tantamount to a Natural Law: when the baryonic contribution is measured, the rotation curve follows, and vice versa. Including ultrafaint dSphs, the relation may extend by another 2 dex and possibly flatten at gbar<10^-12 m/s^2, but these data are significantly more uncertain. The radial acceleration relation subsumes and generalizes several well-known dynamical properties of galaxies, like the Tully-Fisher and Faber-Jackson relations, the \"baryon-halo\" conspiracies, and Renzo's rule.", "keyphrases": ["radial acceleration relation", "galaxy", "tight correlation"]}
{"id": "1012.5313", "title": "Determination of intergalactic magnetic fields from gamma ray data", "abstract": "We report a measurement of intergalactic magnetic fields using combined data from Atmospheric Cherenkov Telescopes and Fermi Gamma-Ray Space Telescope, based on the spectral data alone. If blazars are assumed to produce both gamma rays and cosmic rays, the observed spectra are not sensitive to the intrinsic spectrum of the source, because, for a distant blazar, secondary photons produced in line-of-sight cosmic-ray interactions dominate the signal. In this case, we find 0.01 fG < B < 30 fG. If one excludes the cosmic-ray component, the 0.01 fG lower limit remains, but the upper limit depends on the spectral properties of the source. We present the allowed ranges for a variety of model parameters.", "keyphrases": ["intergalactic magnetic field", "magnetic field", "cosmic ray", "multi-frequency blazar observation"]}
{"id": "1611.06130", "title": "Inflationary primordial black holes for the LIGO gravitational wave events and pulsar timing array experiments", "abstract": "Primordial black holes (PBHs) are one of the candidates to explain the gravitational wave (GW) signals observed by the LIGO detectors. Among several phenomena in the early Universe, cosmic inflation is a major example to generate PBHs from large primordial density perturbations. In this paper, we discuss the possibility to interpret the observed GW events as mergers of PBHs which are produced by cosmic inflation. The primordial curvature perturbation should be large enough to produce a sizable amount of PBHs and thus we have several other probes to test this scenario. We point out that the current pulsar timing array (PTA) experiments already put severe constraints on GWs generated via the second-order effects, and that the observation of the cosmic microwave background (CMB) puts severe restriction on its \u03bc distortion. In particular, it is found that the scalar power spectrum should have a very sharp peak at k \u223c 10^6 Mpc^-1 to fulfill the required abundance of PBHs while evading constraints from the PTA experiments together with the \u03bc distortion. We propose a mechanism which can realize such a sharp peak. In the future, simple inflation models that generate PBHs via almost Gaussian fluctuations could be probed/excluded.", "keyphrases": ["primordial black hole", "gravitational wave", "pulsar timing array", "early universe"]}
{"id": "0901.1986", "title": "The WMAP cold spot", "abstract": "The WMAP cold spot was found by applying spherical wavelets to the first year WMAP data. An excess of kurtosis of the wavelet coefficient was observed at angular scales of around 5 degrees. This excess was shown to be inconsistent with Gaussian simulations with a p-value of around 1 (b = -57, l = 209) was shown to be the main cause of this deviation. Several hypotheses were raised to explain the origin of the cold spot. After performing a Bayesian template fit a collapsing cosmic texture was found to be the most probable hypothesis explaining the spot. Here we review the properties of the cold spot and the possible explanations.", "keyphrases": ["wmap", "cold spot", "several statistical estimator"]}
{"id": "1507.00744", "title": "Hypermagnetic Fields and Baryon Asymmetry from Pseudoscalar Inflation", "abstract": "We show that maximally helical hypermagnetic fields produced during pseudoscalar inflation can generate the observed baryon asymmetry of the universe via the B+L anomaly in the Standard Model. We find that most of the parameter space of pseudoscalar inflation that explains the cosmological data leads to baryon overproduction, hence the models of natural inflation are severely constrained. We also point out a connection between the baryon number and topology of the relic magnetic fields. Both the magnitude and sign of magnetic helicity can be detected in future diffuse gamma ray data. This will be a smoking gun evidence for a link between inflation and the baryon asymmetry of the Universe.", "keyphrases": ["baryon asymmetry", "pseudoscalar inflation", "gauge field"]}
{"id": "1703.05448", "title": "Lectures on the Infrared Structure of Gravity and Gauge Theory", "abstract": "This is a redacted transcript of a course given by the author at Harvard in spring semester 2016. It contains a pedagogical overview of recent developments connecting the subjects of soft theorems, the memory effect and asymptotic symmetries in four-dimensional QED, nonabelian gauge theory and gravity with applications to black holes. The lectures may be viewed online at https://goo.gl/3DJdOr. Please send typos or corrections to strominger@physics.harvard.edu.", "keyphrases": ["gravity", "gauge theory", "flat space"]}
{"id": "1209.4661", "title": "The Extragalactic Background Light and the Gamma-ray Opacity of the Universe", "abstract": "The extragalactic background light (EBL) is one of the fundamental observational quantities in cosmology. All energy releases from resolved and unresolved extragalactic sources, and the light from any truly diffuse background, excluding the cosmic microwave background (CMB), contribute to its intensity and spectral energy distribution. It therefore plays a crucial role in cosmological tests for the formation and evolution of stellar objects and galaxies, and for setting limits on exotic energy releases in the universe. The EBL also plays an important role in the propagation of very high energy gamma-rays which are attenuated en route to Earth by pair producing gamma-gamma interactions with the EBL and CMB. The EBL affects the spectrum of the sources, predominantly blazars, in the 10 GeV to 10 TeV energy regime. Knowledge of the EBL intensity and spectrum will allow the determination of the intrinsic blazar spectrum in a crucial energy regime that can be used to test particle acceleration mechanisms and VHE gamma-ray production models. Conversely, knowledge of the intrinsic gamma-ray spectrum and the detection of blazars at increasingly higher redshifts will set strong limits on the EBL and its evolution. This paper reviews the latest developments in the determination of the EBL and its impact on the current understanding of the origin and production mechanisms of gamma-rays in blazars, and on energy releases in the universe. The review concludes with a summary and future directions in Cherenkov Telescope Array techniques and in infrared ground-based and space observatories that will greatly improve our knowledge of the EBL and the origin and production of very high energy gamma-rays.", "keyphrases": ["extragalactic background light", "universe", "redshift", "dust"]}
{"id": "2102.08252", "title": "Fanaroff-Riley classification of radio galaxies using group-equivariant convolutional neural networks", "abstract": "Weight sharing in convolutional neural networks (CNNs) ensures that their feature maps will be translation-equivariant. However, although conventional convolutions are equivariant to translation, they are not equivariant to other isometries of the input image data, such as rotation and reflection. For the classification of astronomical objects such as radio galaxies, which are expected statistically to be globally orientation invariant, this lack of dihedral equivariance means that a conventional CNN must learn explicitly to classify all rotated versions of a particular type of object individually. In this work we present the first application of group-equivariant convolutional neural networks to radio galaxy classification and explore their potential for reducing intra-class variability by preserving equivariance for the Euclidean group E(2), containing translations, rotations and reflections. For the radio galaxy classification problem considered here, we find that classification performance is modestly improved by the use of both cyclic and dihedral models without additional hyper-parameter tuning, and that a D16 equivariant model provides the best test performance. We use the Monte Carlo Dropout method as a Bayesian approximation to recover epistemic uncertainty as a function of image orientation and show that E(2)-equivariant models are able to reduce variations in model confidence as a function of rotation.", "keyphrases": ["classification", "radio galaxy", "convolutional neural network"]}
{"id": "1403.3358", "title": "Gravitational collapse of Bose-Einstein condensate dark matter halos", "abstract": "We study the mechanisms of the gravitational collapse of the Bose-Einstein condensate dark matter halos, described by the zero temperature time-dependent nonlinear Schr\u00f6dinger equation (the Gross-Pitaevskii equation), with repulsive inter-particle interactions. By using a variational approach, and by choosing an appropriate trial wave function, we reformulate the Gross-Pitaevskii equation with spherical symmetry as Newton's equation of motion for a particle in an effective potential, which is determined by the zero point kinetic energy, the gravitational energy, and the particles interaction energy, respectively. The velocity of the condensate is proportional to the radial distance, with a time dependent proportionality function. The equation of motion of the collapsing dark matter condensate is studied by using both analytical and numerical methods. The collapse of the condensate ends with the formation of a stable configuration, corresponding to the minimum of the effective potential. The radius and the mass of the resulting dark matter object are obtained, as well as the collapse time of the condensate. The numerical values of these global astrophysical quantities, characterizing condensed dark matter systems, strongly depend on the two parameters describing the condensate, the mass of the dark matter particle, and of the scattering length, respectively. The stability of the condensate under small perturbations is also studied, and the oscillations frequency of the halo is obtained. Hence these results show that the gravitational collapse of the condensed dark matter halos can lead to the formation of stable astrophysical systems with both galactic and stellar sizes.", "keyphrases": ["dark matter halo", "gravitational collapse", "einstein condensate"]}
{"id": "1506.08575", "title": "The two faces of mimetic Horndeski gravity: disformal transformations and Lagrange multiplier", "abstract": "We show that very general scalar-tensor theories of gravity (including, e.g., Horndeski models) are generically invariant under disformal transformations. However there is a special subset, when the transformation is not invertible, that yields new equations of motion which are a generalization of the so-called \"mimetic\" dark matter theory recently introduced by Chamsedinne and Mukhanov. These conclusions hold true irrespective of whether the scalar field in the action of the assumed scalar-tensor theory of gravity is the same or different than the scalar field involved in the transformation. The new equations of motion for our general mimetic theory can also be derived from an action containing an additional Lagrange multiplier field. The general mimetic scalar-tensor theory has the same number of derivatives in the equations of motion as the original scalar-tensor theory. As an application we show that the simplest mimetic scalar-tensor model is able to mimic the cosmological background of a flat FLRW model with a barotropic perfect fluid with any constant equation of state.", "keyphrases": ["gravity", "disformal transformation", "lagrange"]}
{"id": "1507.05326", "title": "Precision Comparison of the Power Spectrum in the EFTofLSS with Simulations", "abstract": "We study the prediction of the dark matter power spectrum at two-loop order in the Effective Field Theory of Large Scale Structures (EFTofLSS) using high precision numerical simulations. In our universe, short distance non-linear perturbations, not under perturbative control, affect long distance fluctuations through an effective stress tensor that needs to be parametrized in terms of counterterms that are functions of the long distance fluctuating fields. We find that at two-loop order it is necessary to include three counterterms: a linear term in the over density, \u03b4, a quadratic term, \u03b4^2, and a higher derivative term, \u2202^2\u03b4. After the inclusion of these three terms, the EFTofLSS at two-loop order matches simulation data up to k\u2243 0.34 h Mpc^-1 at redshift z=0, up to k\u2243 0.55 h Mpc^-1 at z=1, and up to k\u2243 1.1 h Mpc^-1 at z=2. At these wavenumbers, the cosmic variance of the simulation is at least as small as 10^-3, providing a high precision comparison between theory and data. The actual reach of the theory is affected by theoretical uncertainties associated to not having included higher order terms in perturbation theory, for which we provide an estimate, and by potentially overfitting the data, which we also try to address. Since in the EFTofLSS the coupling constants associated with the counterterms are unknown functions of time, we show how a simple parametrization gives a sensible description of their time-dependence. Overall, the k-reach of the EFTofLSS is much larger than previous analytical techniques, showing that the amount of cosmological information amenable to high-precision analytical control might be much larger than previously believed.", "keyphrases": ["eftoflss", "simulation", "matter power spectrum", "precision comparison", "three-loop order"]}
{"id": "1203.4595", "title": "Conformal consistency relations for single-field inflation", "abstract": "We generalize the single-field consistency relations to capture not only the leading term in the squeezed limit\u2014going as 1/q^3, where q is the small wavevector\u2014but also the subleading one, going as 1/q^2. This term, for an (n+1)-point function, is fixed in terms of the variation of the n-point function under a special conformal transformation; this parallels the fact that the 1/q^3 term is related with the scale dependence of the n-point function. For the squeezed limit of the 3-point function, this conformal consistency relation implies that there are no terms going as 1/q^2. We verify that the squeezed limit of the 4-point function is related to the conformal variation of the 3-point function both in the case of canonical slow-roll inflation and in models with reduced speed of sound. In the second case the conformal consistency conditions capture, at the level of observables, the relation among operators induced by the non-linear realization of Lorentz invariance in the Lagrangian. These results mean that, in any single-field model, primordial correlation functions of \u03b6are endowed with an SO(4,1) symmetry, with dilations and special conformal transformations non-linearly realized by \u03b6. We also verify the conformal consistency relations for any n-point function in models with a modulation of the inflaton potential, where the scale dependence is not negligible. Finally, we generalize (some of) the consistency relations involving tensors and soft internal momenta.", "keyphrases": ["single-field inflation", "single-field model", "conformal consistency relation", "inflationary correlator", "goldstone boson"]}
{"id": "1011.4374", "title": "Relativistic effects and primordial non-Gaussianity in the galaxy bias", "abstract": "When dealing with observables, one needs to generalize the bias relation between the observed galaxy fluctuation field to the underlying matter distribution in a gauge-invariant way. We provide such relation at second-order in perturbation theory adopting the local Eulerian bias model and starting from the observationally motivated uniform-redshift gauge. Our computation includes the presence of primordial non-Gaussianity. We show that large scale-dependent relativistic effects in the Eulerian bias arise independently from the presence of some primordial non-Gaussianity. Furthermore, the Eulerian bias inherits from the primordial non-Gaussianity not only a scale-dependence, but also a modulation with the angle of observation when sources with different biases are correlated.", "keyphrases": ["primordial non-gaussianity", "bias", "relativistic effect"]}
{"id": "1204.2797", "title": "A Tentative Gamma-Ray Line from Dark Matter Annihilation at the Fermi Large Area Telescope", "abstract": "The observation of a gamma-ray line in the cosmic-ray fluxes would be a smoking-gun signature for dark matter annihilation or decay in the Universe. We present an improved search for such signatures in the data of the Fermi Large Area Telescope (LAT), concentrating on energies between 20 and 300 GeV. Besides updating to 43 months of data, we use a new data-driven technique to select optimized target regions depending on the profile of the Galactic dark matter halo. In regions close to the Galactic center, we find a 4.6 sigma indication for a gamma-ray line at 130 GeV. When taking into account the look-elsewhere effect the significance of the observed excess is 3.2 sigma. If interpreted in terms of dark matter particles annihilating into a photon pair, the observations imply a dark matter mass of 129.8\u00b12.4^+7_-13 GeV and a partial annihilation cross-section of <\u03c3v> = 1.27\u00b10.32^+0.18_-0.28 x 10^-27 cm^3 s^-1 when using the Einasto dark matter profile. The evidence for the signal is based on about 50 photons; it will take a few years of additional data to clarify its existence.", "keyphrases": ["gamma-ray line", "dark matter annihilation", "line emission"]}
{"id": "1407.2809", "title": "Adding helicity to inflationary magnetogenesis", "abstract": "The most studied mechanism of inflationary magnetogenesis relies on the time-dependence of the coefficient of the gauge kinetic term F_\u03bc\u03bd F^\u03bc\u03bd. Unfortunately, only extremely finely tuned versions of the model can consistently generate the cosmological magnetic fields required by observations. We propose a generalization of this model, where also the pseudoscalar invariant F_\u03bc\u03bd F\u0303^\u03bc\u03bd is multiplied by a time dependent function. The new parity violating term allows more freedom in tuning the amplitude of the field at the end of inflation. Moreover, it leads to a helical magnetic field that is amplified at large scales by magnetohydrodynamical processes during the radiation dominated epoch. As a consequence, our model can satisfy the observational lower bounds on fields in the intergalactic medium, while providing a seed for the galactic dynamo, if inflation occurs at an energy scale ranging from 10^5 to 10^10 GeV. Such energy scale is well below that suggested by the recent BICEP2 result, if the latter is due to primordial tensor modes. However, the gauge field is a source of tensors during inflation and generates a spectrum of gravitational waves that can give a sizable tensor to scalar ratio r= O(0.2) even if inflation occurs at low energies. This system therefore evades the Lyth bound. For smaller values of r, lower values of the inflationary energy scale are required. The model predicts fully helical cosmological magnetic fields and a chiral spectrum of primordial gravitational waves.", "keyphrases": ["inflationary magnetogenesis", "magnetogenesis", "axion"]}
{"id": "1912.02934", "title": "Surveying the reach and maturity of machine learning and artificial intelligence in astronomy", "abstract": "Machine learning (automated processes that learn by example in order to classify, predict, discover or generate new data) and artificial intelligence (methods by which a computer makes decisions or discoveries that would usually require human intelligence) are now firmly established in astronomy. Every week, new applications of machine learning and artificial intelligence are added to a growing corpus of work. Random forests, support vector machines, and neural networks (artificial, deep, and convolutional) are now having a genuine impact for applications as diverse as discovering extrasolar planets, transient objects, quasars, and gravitationally-lensed systems, forecasting solar activity, and distinguishing between signals and instrumental effects in gravitational wave astronomy. This review surveys contemporary, published literature on machine learning and artificial intelligence in astronomy and astrophysics. Applications span seven main categories of activity: classification, regression, clustering, forecasting, generation, discovery, and the development of new scientific insight. These categories form the basis of a hierarchy of maturity, as the use of machine learning and artificial intelligence emerges, progresses or becomes established.", "keyphrases": ["machine learning", "astronomy", "next generation survey"]}
{"id": "1006.3504", "title": "Evidence for strong extragalactic magnetic fields from Fermi observations of TeV blazars", "abstract": "Magnetic fields in galaxies are produced via the amplification of seed magnetic fields of unknown nature. The seed fields, which might exist in their initial form in the intergalactic medium, were never detected. We report a lower bound B\u2265 3\u00d7 10^-16 gauss on the strength of intergalactic magnetic fields, which stems from the nonobservation of GeV gamma-ray emission from electromagnetic cascade initiated by tera-electron volt gamma-ray in intergalactic medium. The bound improves as \u03bb_B^-1/2 if magnetic field correlation length, \u03bb_B, is much smaller than a megaparsec. This lower bound constrains models for the origin of cosmic magnetic fields.", "keyphrases": ["extragalactic magnetic field", "intergalactic medium", "galaxy cluster"]}
{"id": "1109.3845", "title": "Open FRW universes and self-acceleration from nonlinear massive gravity", "abstract": "In the context of a recently proposed nonlinear massive gravity with Lorentz-invariant mass terms, we investigate open Friedmann-Robertson-Walker (FRW) universes driven by arbitrary matter source. While the flat FRW solutions were recently shown to be absent, the proof does not extend to the open universes. We find three independent branches of solutions to the equations of motion for the St\u00fcckelberg scalars. One of the branches does not allow any nontrivial FRW cosmologies, as in the previous no-go result. On the other hand, both of the other two branches allow general open FRW universes governed by the Friedmann equation with the matter source, the standard curvature term and an effective cosmological constant \u039b_\u00b1=c_\u00b1m_g^2. Here, m_g is the graviton mass, +and - represent the two branches, and c_\u00b1 are constants determined by the two dimensionless parameters of the theory. Since an open FRW universe with a sufficiently small curvature constant can approximate a flat FRW universe but there is no exactly flat FRW solution, the theory exhibits a discontinuity at the flat FRW limit.", "keyphrases": ["self-acceleration", "massive gravity", "open frw universe", "fiducial metric"]}
{"id": "2103.13825", "title": "Dark matter and dark radiation from evaporating Kerr primordial black holes", "abstract": "The mechanism of the generation of dark matter and dark radiation from the evaporation of primordial black holes is very interesting. We consider the case of Kerr black holes to generalize previous results obtained in the Schwarzschild case. For dark matter, the results do not change dramatically and the bounds on warm dark matter apply similarly: in particular, the Kerr case cannot save the scenario of black hole domination for light dark matter. For dark radiation, the expectations for \u0394 N_eff do not change significantly with respect to the Schwarzschild case, but for an enhancement in the case of spin 2 particles: in the massless case, however, the projected experimental sensitivity would be reached only for extremal black holes.", "keyphrases": ["dark radiation", "black hole", "dark matter"]}
{"id": "1603.05806", "title": "Cosmology in generalized Proca theories", "abstract": "We consider a massive vector field with derivative interactions that propagates only the 3 desired polarizations (besides two tensor polarizations from gravity) with second-order equations of motion in curved space-time. The cosmological implications of such generalized Proca theories are investigated for both the background and the linear perturbation by taking into account the Lagrangian up to quintic order. In the presence of a matter fluid with a temporal component of the vector field, we derive the background equations of motion and show the existence of de Sitter solutions relevant to the late-time cosmic acceleration. We also obtain conditions for the absence of ghosts and Laplacian instabilities of tensor, vector, and scalar perturbations in the small-scale limit. Our results are applied to concrete examples of the general functions in the theory, which encompass vector Galileons as a specific case. In such examples, we show that the de Sitter fixed point is always a stable attractor and study viable parameter spaces in which the no-ghost and stability conditions are satisfied during the cosmic expansion history.", "keyphrases": ["proca theory", "gravity", "late-time cosmic acceleration", "cosmology", "dark energy model"]}
{"id": "1003.5912", "title": "Semi-annihilation of Dark Matter", "abstract": "We show that the thermal relic abundance of dark matter can be affected by a new type of reaction: semi-annihilation. Semi-annihilation takes the schematic form X_i X_j -> X_k phi, where X_i are stable dark matter particles and phi is an unstable state. Such reactions are generically present when dark matter is composed of more than one species with \"flavor\" and/or \"baryon\" symmetries. We give a complete set of coupled Boltzmann equations in the presence of semi-annihilations, and study two toy models featuring this process. Semi-annihilation leads to non-trivial dark matter dynamics in the early universe, often dominating over ordinary annihilation in determining the relic abundance. This process also has important implications for indirect detection experiments, by enriching the final state spectrum from dark matter (semi-)annihilation in the Milky Way.", "keyphrases": ["dark matter", "matter particle", "semi-annihilation"]}
{"id": "1108.0874", "title": "Conformal invariance of scalar perturbations in inflation", "abstract": "In inflationary models where the source of scalar perturbations is not the inflaton, but one or more scalars with negligible coupling with the inflaton, the resulting perturbations are not only scale invariant, but fully conformally invariant with conformal dimension close to zero. This is closely related to the fact that correlation functions can only depend on the de Sitter invariant distances. These properties follow from the isometries of the inflationary de Sitter space and are thus completely independent of the dynamics. The 3-point function is fixed in terms of two constants, while the 4-point function is a function of two parameters (instead of five as in the absence of conformal invariance). The conformal invariance of correlators can be directly checked in Fourier space, as we show in an explicit example. A detection of a non-conformal correlation function, for example an equilateral 3-point function, would imply that the source of perturbations is not decoupled from the inflaton.", "keyphrases": ["conformal invariance", "sitter spacetime", "slow-roll inflation"]}
{"id": "1211.1624", "title": "Effective field theory approach to quasi-single field inflation and effects of heavy fields", "abstract": "We apply the effective field theory approach to quasi-single field inflation, which contains an additional scalar field with Hubble scale mass other than inflaton. Based on the time-dependent spatial diffeomorphism, which is not broken by the time-dependent background evolution, the most generic action of quasi-single field inflation is constructed up to third order fluctuations. Using the obtained action, the effects of the additional massive scalar field on the primordial curvature perturbations are discussed. In particular, we calculate the power spectrum and discuss the momentum-dependence of three point functions in the squeezed limit for general settings of quasi-single field inflation. Our framework can be also applied to inflation models with heavy particles. We make a qualitative discussion on the effects of heavy particles during inflation and that of sudden turning trajectory in our framework.", "keyphrases": ["quasi-single field inflation", "heavy field", "cosmological observable"]}
{"id": "1212.6701", "title": "Escape of superheavy and highly energetic particles produced by particle collisions near maximally charged black holes", "abstract": "For particle collision near rapidly rotating Kerr black holes, the center-of-mass energy can be arbitrarily high if the angular momentum of either of the colliding particles is fine-tuned. Recently, it has been shown that particles which are produced by such a particle collision and escape to infinity cannot be very massive nor very energetic. For electrically charged black holes there is a similar phenomenon, where the center-of-mass energy for the collision of charged particles near the horizon can be arbitrarily high. One might expect that there would exist a similar bound on the energy and mass of particles that are produced by such a particle collision and escape to infinity. In this paper, however, we see that this expectation is not the case. We explicitly show that superheavy and highly energetic charged particles produced by the collision near maximally charged black holes can escape to infinity at least within classical theory if the backreaction and self-force of the particle can be neglected.", "keyphrases": ["superheavy", "particle collision", "black hole"]}
{"id": "1402.2161", "title": "Probing cosmic opacity at high redshifts with gamma-ray bursts", "abstract": "Probing the evolution of the universe at high redshifts with standard candles is a powerful way to discriminate dark energy models, where an open question nowadays is whether this component is constant or evolves with time. One possible source of ambiguity in this kind of analyses comes from cosmic opacity, which can mimick a dark enery behaviour. However, most tests of cosmic opacity have been restricted to the redshift range z<2. In this work, by using luminosity distances of gamma-ray bursts (GRBs), given the validity of the Amati relation, and the latest H(z) data we determine constraints on the cosmic opacity at high redshifts (z>2) for a flat \u039bCDM model. A possible degenerescence of the results with the adopted cosmological model is also investigated by considering a flat XCDM model. The limits on cosmic opacity in the redshift range 0<z<2 are updated with type Ia supernovae (SNe Ia) from the Union2.1 sample, where we added the most distant (z=1.713) spectroscopically confirmed SNe Ia. From the analyses performed, we find that both SNe Ia and GRBs samples are compatible with a transparent universe at 1\u03c3 level and the results are independent of the dark energy equation of state parameter w.", "keyphrases": ["cosmic opacity", "high redshift", "gamma-ray burst", "cosmological model"]}
{"id": "1406.7843", "title": "Bias in the Effective Field Theory of Large Scale Structures", "abstract": "We study how to describe collapsed objects, such as galaxies, in the context of the Effective Field Theory of Large Scale Structures. The overdensity of galaxies at a given location and time is determined by the initial tidal tensor, velocity gradients and spatial derivatives of the regions of dark matter that, during the evolution of the universe, ended up at that given location. Similarly to what recently done for dark matter, we show how this Lagrangian space description can be recovered by upgrading simpler Eulerian calculations. We describe the Eulerian theory. We show that it is perturbatively local in space, but non-local in time, and we explain the observational consequences of this fact. We give an argument for why to a certain degree of accuracy the theory can be considered as quasi time-local and explain what the operator structure is in this case. We describe renormalization of the bias coefficients so that, after this and after upgrading the Eulerian calculation to a Lagrangian one, the perturbative series for galaxies correlation functions results in a manifestly convergent expansion in powers of k/k_ NL and k/k_ M, where k is the wavenumber of interest, k_ NL is the wavenumber associated to the non-linear scale, and k_ M is the comoving wavenumber enclosing the mass of a galaxy.", "keyphrases": ["effective field theory", "large scale structures", "biased tracer", "non-linear regime", "analytic understanding"]}
{"id": "1008.0048", "title": "Imperfect Dark Energy from Kinetic Gravity Braiding", "abstract": "We introduce a large class of scalar-tensor models with interactions containing the second derivatives of the scalar field but not leading to additional degrees of freedom. These models exhibit peculiar features, such as an essential mixing of scalar and tensor kinetic terms, which we have named kinetic braiding. This braiding causes the scalar stress tensor to deviate from the perfect-fluid form. Cosmology in these models possesses a rich phenomenology, even in the limit where the scalar is an exact Goldstone boson. Generically, there are attractor solutions where the scalar monitors the behaviour of external matter. Because of the kinetic braiding, the position of the attractor depends both on the form of the Lagrangian and on the external energy density. The late-time asymptotic of these cosmologies is a de Sitter state. The scalar can exhibit phantom behaviour and is able to cross the phantom divide with neither ghosts nor gradient instabilities. These features provide a new class of models for Dark Energy. As an example, we study in detail a simple one-parameter model. The possible observational signatures of this model include a sizeable Early Dark Energy and a specific equation of state evolving into the final de-Sitter state from a healthy phantom regime.", "keyphrases": ["dark energy", "kinetic gravity braiding", "derivative", "cosmology", "field theory"]}
{"id": "1007.1421", "title": "Dark matter, neutron stars and strange quark matter", "abstract": "We show that self-annihilating neutralino WIMP dark matter accreted onto neutron stars may provide a mechanism to seed compact objects with long-lived lumps of strange quark matter, or strangelets, for WIMP masses above a few GeV. This effect may trigger a conversion of most of the star into a strange star. We use an energy estimate for the long-lived strangelet based on the Fermi gas model combined with the MIT bag model to set a new limit on the possible values of the WIMP mass that can be especially relevant for subdominant species of massive neutralinos.", "keyphrases": ["neutron star", "strange quark matter", "dark matter"]}
{"id": "1003.5020", "title": "Primordial non-Gaussianity from the large scale structure", "abstract": "Primordial non-Gaussianity is a potentially powerful discriminant of the physical mechanisms that generated the cosmological fluctuations observed today. Any detection of non-Gaussianity would have profound implications for our understanding of cosmic structure formation. In this paper, we review past and current efforts in the search for primordial non-Gaussianity in the large scale structure of the Universe.", "keyphrases": ["large scale structure", "primordial non-gaussianity", "topic"]}
{"id": "1411.3712", "title": "A unifying description of dark energy", "abstract": "We review and extend a novel approach that we introduced recently, to describe general dark energy or scalar-tensor models. Our approach relies on an ADM formulation based on the hypersurfaces where the underlying scalar field is uniform. The advantage of this approach is that it can describe in the same language and in a minimal way a vast number of existing models, such as quintessence models, F(R) theories, scalar tensor theories, their Horndeski extensions and beyond. It also naturally includes Horava-Lifshitz theories. As summarized in this review, our approach provides a unified treatment of the linear cosmological perturbations about a FLRW universe, obtained by a systematic expansion of our general action up to quadratic order. This shows that the behaviour of these linear perturbations is generically characterized by five time-dependent functions. We derive the full equations of motion in the Newtonian gauge, and obtain in particular the equation of state for dark energy perturbations, in the Horndeski case, in terms of these functions. Our unifying description thus provides the simplest and most systematic way to confront theoretical models with current and future cosmological observations.", "keyphrases": ["unifying description", "dark energy", "treatment", "effective field theory", "gravity"]}
{"id": "1910.09811", "title": "A data-driven model of nucleosynthesis with chemical tagging in a lower-dimensional latent space", "abstract": "Chemical tagging seeks to identify unique star formation sites from present-day stellar abundances. Previous techniques have treated each abundance dimension as being statistically independent, despite theoretical expectations that many elements can be produced by more than one nucleosynthetic process. In this work we introduce a data-driven model of nucleosynthesis where a set of latent factors (e.g., nucleosynthetic yields) contribute to all stars with different scores, and clustering (e.g., chemical tagging) is modelled by a mixture of multivariate Gaussians in a lower-dimensional latent space. We use an exact method to simultaneously estimate the factor scores for each star, the partial assignment of each star to each cluster, and the latent factors common to all stars, even in the presence of missing data entries. We use an information-theoretic Bayesian principle to estimate the number of latent factors and clusters. Using the second Galah data release we find that six latent factors are preferred to explain N = 2,566 stars with 17 chemical abundances. We identify the rapid- and slow-neutron capture processes, as well as latent factors consistent with Fe-peak and \u03b1-element production, and another where K and Zn dominate. When we consider N 160,000 stars with missing abundances we find another 7 factors, as well as 16 components in latent space. Despite these components showing separation in chemistry that is explained through different yield contributions, none show significant structure in their positions or motions. We argue that more data, and joint priors on cluster membership that are constrained by dynamical models, are necessary to realise chemical tagging at a galactic-scale. We release software that allows for model parameters to be optimised in seconds given a fixed number of latent factors, components, and 10^7 abundance measurements.", "keyphrases": ["data-driven model", "nucleosynthesis", "lower-dimensional latent space"]}
{"id": "2202.02695", "title": "Towards a smooth unification from an ekpyrotic bounce to the dark energy era", "abstract": "In the context of a ghost free f(R,\ud835\udca2) model, we present a non-singular cosmological scenario in which the universe initially contracts through an ekpyrotic phase having a bouncing like behaviour, and following the bounce, it smoothly transits to a matter or radiation like deceleration era which is further smoothly connected to the dark energy era at present epoch. We consider the Gauss-Bonnet (GB) coupling function in such a way that it gets compatible with the event GW170817. Using suitable reconstruction technique, we obtain the non-trivial scalar field potential as well as the GB coupling function. Such scalar potential and GB coupling function source a smooth unified scenario from an ekpyrotic bounce to the dark energy era with an intermediate deceleration era. The occurrence of ekpyrotic contraction phase justifies the resolution of the anisotropic problem (also known as BKL instability) in the background evolution. The Hubble radius shows an asymmetric behaviour around the bounce, in particular, the evolution of the Hubble radius leads to the generation era of the primordial perturbation modes far before the bounce in the deep sub-Hubble regime. Accordingly we perform the scalar and tensor perturbation evolution in the present context, and as a result, the scalar power spectrum at large scale modes is found to be problematic. Thus an extended scenario is proposed where we consider a pre-ekpyrotic phase having the equation of state parameter is less than unity, and re-examine the scalar and tensor power spectra, on large scales that cross the Hubble radius during the pre-ekpyrotic stage. In this regard, the GB coupling function shows considerable effects in reducing the tensor to scalar ratio compared to the case where the GB coupling is absent. Furthermore the dark energy epoch is consistent with the Planck+SNe+BAO data.", "keyphrases": ["ekpyrotic bounce", "dark energy era", "unified scenario"]}
{"id": "2005.10324", "title": "A bright millisecond-duration radio burst from a Galactic magnetar", "abstract": "Magnetars are highly magnetized young neutron stars that occasionally produce enormous bursts and flares of X-rays and gamma-rays. Of the approximately thirty magnetars currently known in our Galaxy and Magellanic Clouds, five have exhibited transient radio pulsations. Fast radio bursts (FRBs) are millisecond-duration bursts of radio waves arriving from cosmological distances. Some have been seen to repeat. A leading model for repeating FRBs is that they are extragalactic magnetars, powered by their intense magnetic fields. However, a challenge to this model has been that FRBs must have radio luminosities many orders of magnitude larger than those seen from known Galactic magnetars. Here we report the detection of an extremely intense radio burst from the Galactic magnetar SGR 1935+2154 using the Canadian Hydrogen Intensity Mapping Experiment (CHIME) FRB project. The fluence of this two-component bright radio burst and the estimated distance to SGR 1935+2154 together imply a 400-800 MHz burst energy of \u223c 3 \u00d7 10^34 erg, which is three orders of magnitude brighter than those of any radio-emitting magnetar detected thus far. Such a burst coming from a nearby galaxy would be indistinguishable from a typical FRB. This event thus bridges a large fraction of the radio energy gap between the population of Galactic magnetars and FRBs, strongly supporting the notion that magnetars are the origin of at least some FRBs.", "keyphrases": ["radio burst", "galactic magnetar", "hard x-ray burst"]}
{"id": "1608.02454", "title": "Probing the interaction between dark matter and dark energy in the presence of massive neutrinos", "abstract": "We consider the possibility of an interaction in the dark sector in the presence of massive neutrinos, and study the observational constraints on three different scenarios of massive neutrinos using the most recent CMB anisotropy data in combination with type Ia supernovae, baryon acoustic oscillations, and Hubble parameter measurements. When a sterile neutrino is introduced in the interacting dark sector scenario in addition to the standard model prediction of neutrinos, we find that the coupling parameter, characterizing the interaction between dark matter and dark energy, is non-zero at 2\u03c3 confidence level. The interaction model with sterile neutrino is also found to be a promising one to alleviate the current tension on Hubble constant. We do not find the evidence for a coupling in the dark sector when the possibility of a sterile neutrino is discarded.", "keyphrases": ["dark matter", "neutrino", "dark sector", "gravitational theory"]}
{"id": "0910.5224", "title": "Baryon Acoustic Oscillations", "abstract": "Baryon Acoustic Oscillations (BAO) are frozen relics left over from the pre-decoupling universe. They are the standard rulers of choice for 21st century cosmology, providing distance estimates that are, for the first time, firmly rooted in well-understood, linear physics. This review synthesises current understanding regarding all aspects of BAO cosmology, from the theoretical and statistical to the observational, and includes a map of the future landscape of BAO surveys, both spectroscopic and photometric.", "keyphrases": ["acoustic oscillation", "universe", "baryon acoustic oscillations"]}
{"id": "1806.09531", "title": "Probing Radio Intensity at high-Z from Marion: 2017 Instrument", "abstract": "We introduce Probing Radio Intensity at high-Z from Marion (PRIZM), a new experiment designed to measure the globally averaged sky brightness, including the expected redshifted 21 cm neutral hydrogen absorption feature arising from the formation of the first stars. PRIZM consists of two dual-polarization antennas operating at central frequencies of 70 and 100 MHz, and the experiment is located on Marion Island in the sub-Antarctic. We describe the initial design and configuration of the PRIZM instrument that was installed in 2017, and we present preliminary data that demonstrate that Marion Island offers an exceptionally clean observing environment, with essentially no visible contamination within the FM band.", "keyphrases": ["high-z", "marion", "probing radio intensity"]}
{"id": "1308.4935", "title": "An exact Jacobi map in the geodesic light-cone gauge", "abstract": "The remarkable properties of the recently proposed geodesic light-cone (GLC) gauge allow to explicitly solve the geodetic-deviation equation, and thus to derive an exact expression for the Jacobi map J^A_B(s,o) connecting a generic source s to a geodesic observer o in a generic space time. In this gauge J^A_B factorizes into the product of a local quantity at s times one at o, implying similarly factorized expressions for the area and luminosity distance. In any other coordinate system J^A_B is simply given by expressing the GLC quantities in terms of the corresponding ones in the new coordinates. This is explicitly done, at first and second order, respectively, for the synchronous and Poisson gauge-fixing of a perturbed, spatially-flat cosmological background, and the consistency of the two outcomes is checked. Our results slightly amend previous calculations of the luminosity-redshift relation and suggest a possible non-perturbative way for computing the effects of inhomogeneities on observations based on light-like signals.", "keyphrases": ["jacobi map", "geodesic light-cone gauge", "gauge"]}
{"id": "2109.06200", "title": "From large-scale environment to CGM angular momentum to star forming activities \u2013 I: star-forming galaxies", "abstract": "The connection between halo gas acquisition through the circumgalactic medium (CGM) and galaxy star formation has long been studied. In this series of two papers, we put this interplay within the context of the galaxy environment on large scales (several hundreds of kpc), which, to a certain degree, maps out various paths for galaxy interactions. We use the IllustrisTNG-100 simulation to demonstrate that the large-scale environment modulates the circumgalactic gas angular momentum, resulting in either enhanced (Paper I) or suppressed (Paper II) star formation inside a galaxy. In this paper (Paper I), we show that the large-scale environment around a star-forming galaxy is often responsible for triggering new episodes of star formation. Such an episodic star formation pattern is well synced with a pulsating motion of the circumgalactic gas, which, on the one hand receives angular momentum modulations from the large-scale environment, yielding in-spiralling gas to fuel the star-forming reservoir, while, on the other hand, is affected by the feedback activities from the galaxy centre. As a result, a present-day star-forming galaxy may have gone through several cycles of star-forming and quiescent phases during its evolutionary history, with the circumgalactic gas carrying out a synchronized cadence of \"breathing in and out\" motions out to \u223c 100 kpc.", "keyphrases": ["large-scale environment", "angular momentum", "galaxy"]}
{"id": "1006.0064", "title": "The Galactic Center Massive Black Hole and Nuclear Star Cluster", "abstract": "The Galactic Center is an excellent laboratory for studying phenomena and physical processes that may be occurring in many other galactic nuclei. The Center of our Milky Way is by far the closest galactic nucleus, and observations with exquisite resolution and sensitivity cover 18 orders of magnitude in energy of electromagnetic radiation. Theoretical simulations have become increasingly more powerful in explaining these measurements. This review summarizes the recent progress in observational and theoretical work on the central parsec, with a strong emphasis on the current empirical evidence for a central massive black hole and on the processes in the surrounding dense nuclear star cluster. We present the current evidence, from the analysis of the orbits of more than two dozen stars and from the measurements of the size and motion of the central compact radio source, Sgr A*, that this radio source must be a massive black hole of about 4.4 \u00d71e6 Msun, beyond any reasonable doubt. We report what is known about the structure and evolution of the dense nuclear star cluster surrounding this black hole, including the astounding fact that stars have been forming in the vicinity of Sgr A* recently, apparently with a top-heavy stellar mass function. We discuss a dense concentration of fainter stars centered in the immediate vicinity of the massive black hole, three of which have orbital peri-bothroi of less than one light day. This 'S-star cluster' appears to consist mainly of young early-type stars, in contrast to the predicted properties of an equilibrium 'stellar cusp' around a black hole. This constitutes a remarkable and presently not fully understood 'paradox of youth'. We also summarize what is known about the emission properties of the accreting gas onto Sgr A* and how this emission is beginning to delineate the physical properties in the hot accretion zone around the event horizon.", "keyphrases": ["black hole", "nuclear star cluster", "galaxy"]}
{"id": "1411.2980", "title": "Millisecond pulsars and the Galactic Center gamma-ray excess: the importance of luminosity function and secondary emission", "abstract": "Several groups of authors have analyzed Fermi LAT data in a region around the Galactic Center finding an unaccounted gamma-ray excess over diffuse backgrounds in the GeV energy range. It has been argued that it is difficult or even impossible to explain this diffuse emission by the leading astrophysical candidates - millisecond pulsars (MSPs). Here we provide a new estimate of the contribution to the excess by a population of yet unresolved MSP located in the bulge of the Milky Way. We simulate this population with the GALPLOT package by adopting a parametric approach, with the range of free parameters gauged on the MSP characteristics reported by the second pulsar catalogue (2PC). We find that the conclusions strongly depend on the details of the MSP luminosity function (in particular, its high luminosity end) and other explicit or tacit assumptions on the MSP statistical properties, which we discuss. Notably, for the first time we study the importance of the possible secondary emission of the MSPs in the Galactic Center, i.e. the emission via inverse Compton losses of electrons injected in the interstellar medium. Differently from a majority of other authors, we find that within current uncertainties a large if not dominant contribution of MSPs to the excess cannot be excluded. We also show that the sensitivities of future instruments or possibly already of the latest LAT data analysis (Pass 8) provide good perspectives to test this scenario by resolving a significant number of MSPs.", "keyphrases": ["pulsar", "gamma-ray excess", "luminosity function"]}
{"id": "1403.6768", "title": "Can primordial magnetic fields be the origin of the BICEP2 data?", "abstract": "If the B-mode signal in the CMB polarization seen by the BICEP2 experiment is confirmed, it has dramatic implications for models of inflation. The result is also in tension with Planck limits on standard inflationary models. It is therefore important to investigate whether this signal can arise from alternative sources. If so, this could lessen the pressure on inflationary models and the tension with Planck data. We investigate whether vector and tensor modes from primordial magnetic fields can explain the signal. We find that in principle, magnetic fields generated during inflation can indeed produce the required B-mode, for a suitable range of energy scales of inflation. In this case, the primordial gravitational wave amplitude is negligible, so that there is no tension with Planck and no problems posed for current inflationary models. However, the simplest magnetic model is in tension with Planck limits on non-Gaussianity in the trispectrum. It may be possible to fine-tune the magnetogenesis model so that this non-Gaussianity is suppressed. Alternatively, a weaker magnetic field can pass the non-Gaussianity constraints and allow the primordial tensor mode to be reduced to r 0.09, thus removing the tension with Planck data and alleviating the problems with simple inflationary models.", "keyphrases": ["primordial magnetic field", "magnetic field", "gravitational wave", "observed b-mode polarization"]}
{"id": "2001.08220", "title": "Primordial black holes as dark matter and gravitational waves from single-field polynomial inflation", "abstract": "We consider the possibility that the majority of dark matter in our Universe consists of black holes of primordial origin. We determine the conditions under which such black holes may have originated from a single-field model of inflation characterized by a quartic polynomial potential. We also explore the effect of higher-dimensional operators. The large power spectrum of curvature perturbations that is needed for a large black hole abundance sources sizable second order tensor perturbations. The resulting stochastic background of primordial gravitational waves could be detected by the future space-based observatories LISA and DECIGO or \u2013as long as we give up on the dark matter connection\u2013by the ground-based Advanced LIGO-Virgo detector network.", "keyphrases": ["black hole", "dark matter", "gravitational wave"]}
{"id": "0901.2262", "title": "Holographic Ricci dark energy: Current observational constraints, quintom feature, and the reconstruction of scalar-field dark energy", "abstract": "In this work, we consider the cosmological constraints on the holographic Ricci dark energy proposed by Gao et al. [Phys. Rev. D 79, 043511 (2009)], by using the observational data currently available. The main characteristic of holographic Ricci dark energy is governed by a positive numerical parameter \u03b1 in the model. When \u03b1<1/2, the holographic Ricci dark energy will exhibit a quintomlike behavior; i.e., its equation of state will evolve across the cosmological-constant boundary w=-1. The parameter \u03b1 can be determined only by observations. Thus, in order to characterize the evolving feature of dark energy and to predict the fate of the universe, it is of extraordinary importance to constrain the parameter \u03b1 by using the observational data. In this paper, we derive constraints on the holographic Ricci dark energy model from the latest observational data including the Union sample of 307 type Ia supernovae, the shift parameter of the cosmic microwave background given by the five-year Wilkinson Microwave Anisotropy Probe observations, and the baryon acoustic oscillation measurement from the Sloan Digital Sky Survey. The joint analysis gives the best-fit results (with 1\u03c3 uncertainty): \u03b1=0.359^+0.024_-0.025 and \u03a9_ m0=0.318^+0.026_-0.024. That is to say, according to the observations, the holographic Ricci dark energy takes on the quintom feature. Finally, in light of the results of the cosmological constraints, we discuss the issue of the scalar-field dark energy reconstruction, based on the scenario of the holographic Ricci vacuum energy.", "keyphrases": ["dark energy", "observational constraint", "cosmology", "holographic ricci"]}
{"id": "1601.04424", "title": "Asymmetry between galaxies with clockwise handedness and counterclockwise handedness", "abstract": "While it is clear that spiral galaxies can have different handedness, galaxies with clockwise patterns are assumed to be symmetric in all of their other characteristics to galaxies with counterclockwise patterns. Here we use data from SDSS DR7 to show that photometric data can distinguish between clockwise and counterclockwise galaxies. Pattern recognition algorithms trained and tested using the photometric data of a clean manually crafted dataset of 13,440 spiral galaxies with z<0.25 can predict the handedness of a spiral galaxy in 64 50 classified galaxies showed similar results of 65 suggesting that the observed asymmetry is consistent also in datasets annotated in a fully automatic process, and without human intervention. That shows that the photometric data collected by SDSS is sensitive to the handedness of the galaxy. Also, analysis of the number of galaxies classified as clockwise and counterclockwise by crowdsourcing shows that manual classification between spiral and elliptical galaxies can be affected by the handedness of the galaxy, and therefore galaxy morphology analyzed by citizen science campaigns might be biased by the galaxy handedness. Code and data used in the experiment are publicly available, and the experiment can be easily replicated.", "keyphrases": ["galaxy", "handedness", "asymmetry", "clockwise spin pattern"]}
{"id": "2109.06197", "title": "From large-scale environment to CGM angular momentum to star forming activities \u2013 II: quenched galaxies", "abstract": "The gas needed to sustain star formation in galaxies is supplied by the circumgalactic medium (CGM), which in turn is affected by accretion from large scales. In a series of two papers, we examine the interplay between a galaxy's ambient CGM and central star formation within the context of the large-scale environment. We use the IllustrisTNG-100 simulation to show that the influence exerted by the large-scale galaxy environment on the CGM gas angular momentum results in either enhanced (Paper I) or suppressed (Paper II, this paper) star formation inside a galaxy. We find that for present-day quenched galaxies, both the large-scale environments and the ambient CGM have always had higher angular momenta throughout their evolutionary history since at least z=2, in comparison to those around present-day star-forming disk galaxies, resulting in less efficient gas inflow into the central star-forming gas reservoirs. A sufficiently high CGM angular momentum, as inherited from the larger-scale environment, is thus an important factor in keeping a galaxy quenched, once it is quenched. The process above naturally renders two key observational signatures: (1) a coherent rotation pattern existing across multiple distances from the large-scale galaxy environment, to the circumgalactic gas, to the central stellar disk; and (2) an anti-correlation between galaxy star-formation rates and orbital angular momenta of interacting galaxy pairs or groups.", "keyphrases": ["large-scale environment", "angular momentum", "galaxy"]}
{"id": "1311.7380", "title": "Testing the Interaction between Dark Energy and Dark Matter with Planck Data", "abstract": "Interacting Dark Energy and Dark Matter is used to go beyond the standard cosmology. We base our arguments on Planck data and conclude that an interaction is compatible with the observations and can provide a strong argument towards consistency of different values of cosmological parameters.", "keyphrases": ["dark energy", "dark matter", "cosmology"]}
{"id": "1410.1527", "title": "What Does The PAMELA Antiproton Spectrum Tell Us About Dark Matter?", "abstract": "Measurements of the cosmic ray antiproton spectrum can be used to search for contributions from annihilating dark matter and to constrain the dark matter annihilation cross section. Depending on the assumptions made regarding cosmic ray propagation in the Galaxy, such constraints can be quite stringent. We revisit this topic, utilizing a set of propagation models fit to the cosmic ray boron, carbon, oxygen and beryllium data. We derive upper limits on the dark matter annihilation cross section and find that when the cosmic ray propagation parameters are treated as nuisance parameters (as we argue is appropriate), the resulting limits are significantly less stringent than have been previously reported. We also note (as have several previous groups) that simple GALPROP-like diffusion-reacceleration models predict a spectrum of cosmic ray antiprotons that is in good agreement with PAMELA's observations above 5 GeV, but that significantly underpredict the flux at lower energies. Although the complexity of modeling cosmic ray propagation at GeV-scale energies makes it difficult to determine the origin of this discrepancy, we consider the possibility that the excess antiprotons are the result of annihilating dark matter. Suggestively, we find that this excess is best fit for a dark matter mass of approximately 35 GeV and annihilation cross section of approximately 1e-26 cm^3/s (to b-bbar), in good agreement with the mass and cross section previously shown to be required to generate the gamma-ray excess observed from the Galactic Center.", "keyphrases": ["antiproton", "dark matter", "annihilation cross section"]}
{"id": "1909.05271", "title": "The Cosmological Analysis of the SDSS/BOSS data from the Effective Field Theory of Large-Scale Structure", "abstract": "The Effective Field Theory of Large-Scale Structure (EFTofLSS) is a formalism that allows us to predict the clustering of Cosmological Large-Scale Structure in the mildly non-linear regime in an accurate and reliable way. After validating our technique against several sets of numerical simulations, we perform the analysis for the cosmological parameters of the DR12 BOSS data. We assume \u039bCDM, a fixed value of the baryon/dark-matter ratio, \u03a9_b/\u03a9_c, and of the tilt of the primordial power spectrum, n_s, and no significant input from numerical simulations. By using the one-loop power spectrum multipoles, we measure the primordial amplitude of the power spectrum, A_s, the abundance of matter, \u03a9_m, and the Hubble parameter, H_0, to about 13%, 3.2% and 3.2% respectively, obtaining ln(10^10As)=2.72\u00b1 0.13, \u03a9_m=0.309\u00b1 0.010, H_0=68.5\u00b1 2.2 km/(s Mpc) at 68% confidence level. If we then add a CMB prior on the sound horizon, the error bar on H_0 is reduced to 1.6%. These results are a substantial qualitative and quantitative improvement with respect to former analyses, and suggest that the EFTofLSS is a powerful instrument to extract cosmological information from Large-Scale Structure.", "keyphrases": ["cosmological analysis", "boss", "effective field theory", "large-scale structure", "baryon"]}
{"id": "1203.0209", "title": "Observing the Earth as an exoplanet with LOUPE, the Lunar Observatory for Unresolved Polarimetry of Earth", "abstract": "The detections of small, rocky exoplanets have surged in recent years and will likely continue to do so. To know whether a rocky exoplanet is habitable, we have to characterise its atmosphere and surface. A promising characterisation method for rocky exoplanets is direct detection using spectropolarimetry. This method will be based on single pixel signals, because spatially resolving exoplanets is impossible with current and near-future instruments. Well-tested retrieval algorithms are essential to interpret these single pixel signals in terms of atmospheric composition, cloud and surface coverage. Observations of Earth itself provide the obvious benchmark data for testing such algorithms. The observations should provide signals that are integrated over the Earth's disk, that capture day and night variations, and all phase angles. The Moon is a unique platform from where the Earth can be observed as an exoplanet, undisturbed, all of the time. Here, we present LOUPE, the Lunar Observatory for Unresolved Polarimetry of Earth, a small and robust spectropolarimeter to observe our Earth as an exoplanet.", "keyphrases": ["earth", "lunar observatory", "unresolved polarimetry"]}
{"id": "1702.03901", "title": "Primordial black holes from single field models of inflation", "abstract": "Primordial black holes (PBH) have been shown to arise from high peaks in the matter power spectra of multi-field models of inflation. Here we show, with a simple toy model, that it is also possible to generate a peak in the curvature power spectrum of single-field inflation. We assume that the effective dynamics of the inflaton field presents a near-inflection point which slows down the field right before the end of inflation and gives rise to a prominent spike in the fluctuation power spectrum at scales much smaller than those probed by Cosmic Microwave Background (CMB) and Large Scale Structure (LSS) observations. This peak will give rise, upon reentry during the radiation era, to PBH via gravitational collapse. The mass and abundance of these PBH is such that they could constitute the totality of the Dark Matter today. We satisfy all CMB and LSS constraints and predict a very broad range of PBH masses. Some of these PBH are light enough that they will evaporate before structure formation, leaving behind a large curvature fluctuation on small scales. This broad mass distribution of PBH as Dark Matter will be tested in the future by AdvLIGO and LISA interferometers.", "keyphrases": ["primordial black hole", "single field inflation", "primordial power spectrum"]}
{"id": "0904.3515", "title": "The Rotation of Janus and Epimetheus", "abstract": "Epimetheus, a small moon of Saturn, has a rotational libration (an oscillation about synchronous rotation) of 5.9 +- 1.2 degrees, placing Epimetheus in the company of Earth's Moon and Mars' Phobos as the only natural satellites for which forced rotational libration has been detected. The forced libration is caused by the satellite's slightly eccentric orbit and non-spherical shape. Detection of a moon's forced libration allows us to probe its interior by comparing the measured amplitude to that predicted by a shape model assuming constant density. A discrepancy between the two would indicate internal density asymmetries. For Epimetheus, the uncertainties in the shape model are large enough to account for the measured libration amplitude. For Janus, on the other hand, although we cannot rule out synchronous rotation, a permanent offset of several degrees between Janus' minimum moment of inertia (long axis) and the equilibrium sub-Saturn point may indicate that Janus does have modest internal density asymmetries. The rotation states of Janus and Epimetheus experience a perturbation every four years, as the two moons \"swap\" orbits. The sudden change in the orbital periods produces a free libration about synchronous rotation that is subsequently damped by internal friction. We calculate that this free libration is small in amplitude (<0.1 degree) and decays quickly (a few weeks, at most), and is thus below the current limits for detection using Cassini images.", "keyphrases": ["rotation", "janus", "epimetheus", "libration", "oscillation"]}
{"id": "1702.03284", "title": "The ALP miracle: unified inflaton and dark matter", "abstract": "We propose a scenario where both inflation and dark matter are described by a single axion-like particle (ALP) in a unified manner. In a class of the minimal axion hilltop inflation, the effective masses at the maximum and mimimum of the potential have equal magnitude but opposite sign, so that the ALP inflaton is light both during inflation and in the true vacuum. After inflation, most of the ALPs decay and evaporate into plasma through a coupling to photons, and the remaining ones become dark matter. We find that the observed CMB and matter power spectrum as well as the dark matter abundance point to an ALP of mass m_\u03d5 = O(0.01) eV and the axion-photon coupling g_\u03d5\u03b3\u03b3 = O(10^-11)GeV^-1: the ALP miracle. The suggested parameter region is within the reach of the next generation axion helioscope, IAXO. Furthermore, thermalized ALPs contribute to hot dark matter and its abundance is given in terms of the effective number of extra neutrino species, \u0394 N_ eff\u2243 0.03, which can be tested by the future CMB experiments. We also discuss a case with multiple ALPs, where the coupling to photons can be enhanced in the early Universe by an order of magnitude or more, which enlarges the parameter space for the ALP miracle. The heavy ALP plays a role of the waterfall field in hybrid inflation, and reheats the Universe, and it can be searched for in various experiments such as SHiP.", "keyphrases": ["dark matter", "axion-like particle", "alp inflaton"]}
{"id": "1003.2422", "title": "The effect of neutrinos on the matter distribution as probed by the Intergalactic Medium", "abstract": "We present a suite of full hydrodynamical cosmological simulations that quantitatively address the impact of neutrinos on the (mildly non-linear) spatial distribution of matter and in particular on the neutral hydrogen distribution in the Intergalactic Medium (IGM), which is responsible for the intervening Lyman-alpha absorption in quasar spectra. The free-streaming of neutrinos results in a (non-linear) scale-dependent suppression of power spectrum of the total matter distribution at scales probed by Lyman-alpha forest data which is larger than the linear theory prediction by about 25 strongly redshift dependent. By extracting a set of realistic mock quasar spectra, we quantify the effect of neutrinos on the flux probability distribution function and flux power spectrum. The differences in the matter power spectra translate into a 2.5 for neutrino masses with Sigma m_\u03bd = 0.3 eV (0.6 eV). This rather small effect is difficult to detect from present Lyman-alpha forest data and nearly perfectly degenerate with the overall amplitude of the matter power spectrum as characterised by sigma_8. If the results of the numerical simulations are normalized to have the same sigma_8 in the initial conditions, then neutrinos produce a smaller suppression in the flux power of about 3 m_\u03bd = 0.6eV (1.2 eV) when compared to a simulation without neutrinos. We present constraints on neutrino masses using the Sloan Digital Sky Survey flux power spectrum alone and find an upper limit of Sigma m_\u03bd < 0.9 eV (2 sigma C.L.), comparable to constraints obtained from the cosmic microwave background data or other large scale structure probes.", "keyphrases": ["neutrino", "matter distribution", "intergalactic medium"]}
{"id": "1008.5157", "title": "Higgs inflation: consistency and generalisations", "abstract": "We analyse the self-consistency of inflation in the Standard Model, where the Higgs field has a large non-minimal coupling to gravity. We determine the domain of energies in which this model represents a valid effective field theory as a function of the background Higgs field. This domain is bounded above by the cutoff scale which is found to be higher than the relevant dynamical scales throughout the whole history of the Universe, including the inflationary epoch and reheating. We present a systematic scheme to take into account quantum loop corrections to the inflationary calculations within the framework of effective field theory. We discuss the additional assumptions that must be satisfied by the ultra-violet completion of the theory to allow connection between the parameters of the inflationary effective theory and those describing the low-energy physics relevant for the collider experiments. A class of generalisations of inflationary theories with similar properties is constructed.", "keyphrases": ["gravity", "field theory", "higgs inflation", "unitarity violation", "higgs boson"]}
{"id": "1008.1783", "title": "Constraints on Dark Matter from Colliders", "abstract": "We show that colliders can impose strong constraints on models of dark matter, in particular when the dark matter is light. We analyze models where the dark matter is a fermion or scalar interacting with quarks and/or gluons through an effective theory containing higher dimensional operators which represent heavier states that have been integrated out of the effective field theory. We determine bounds from existing Tevatron searches for monojets as well as expected LHC reaches for a discovery. We find that colliders can provide information which is complementary or in some cases even superior to experiments searching for direct detection of dark matter through its scattering with nuclei. In particular, both the Tevatron and the LHC can outperform spin dependent searches by an order of magnitude or better over much of parameter space, and if the dark matter couples mainly to gluons, the LHC can place bounds superior to any spin independent search.", "keyphrases": ["dark matter", "collider", "gluon", "effective field theory", "heavy state"]}
{"id": "1308.3255", "title": "A new life for sterile neutrinos: resolving inconsistencies using hot dark matter", "abstract": "Within the standard LCDM model of cosmology, the recent Planck measurements have shown discrepancies with other observations, e.g., measurements of the current expansion rate H_0, the galaxy shear power spectrum and counts of galaxy clusters. We show that if LCDM is extended by a hot dark matter component, which could be interpreted as a sterile neutrino, the data sets can be combined consistently. A combination of Planck data, WMAP-9 polarisation data, measurements of the BAO scale, the HST measurement of H_0, Planck galaxy cluster counts and galaxy shear data from the CFHTLens survey yields Delta N_eff = 0.61 pm 0.30 and m_s^eff = (0.41 pm 0.13) eV at 1 sigma. The former is driven mainly by the large H_0 of the HST measurement, while the latter is driven by cluster data. CFHTLens galaxy shear data prefer Delta N_eff >0 and a non-zero mass. Taken together, we find hints for the presence of a hot dark matter component at 3 sigma. A sterile neutrino motivated by the reactor and gallium anomalies appears rejected at even higher significance and an accelerator anomaly sterile neutrino is found in tension at 2 sigma.", "keyphrases": ["sterile neutrino", "hot dark matter", "cosmology"]}
{"id": "1608.08008", "title": "Estimating cosmological parameters by the simulated data of gravitational waves from the Einstein Telescope", "abstract": "We investigate the constraint ability of the gravitational wave (GW) as the standard siren on the cosmological parameters by using the third-generation gravitational wave detector: the Einstein Telescope. We simulate the luminosity distances and redshift measurements from 100 to 1000 GW events. We use two different algorithms to constrain the cosmological parameters. For the Hubble constant H_0 and dark matter density parameter \u03a9_m, we adopt the Markov chain Monte Carlo approach. We find that with about 500-600 GW events we can constrain the Hubble constant with an accuracy comparable to Planck temperature data and Planck lensing combined results, while for the dark matter density, GWs alone seem not able to provide the constraints as good as for the Hubble constant; the sensitivity of 1000 GW events is a little lower than that of Planck data. It should require more than 1000 events to match the Planck sensitivity. Yet, for analyzing the more complex dynamical property of dark energy, i.e., the equation of state w, we adopt a new powerful nonparametric method: the Gaussian process. We can reconstruct w directly from the observational luminosity distance at every redshift. In the low redshift region, we find that about 700 GW events can give the constraints of w(z) comparable to the constraints of a constant w by Planck data with type Ia supernovae. Those results show that GWs as the standard sirens to probe the cosmological parameters can provide an independent and complementary alternative to current experiments.", "keyphrases": ["cosmological parameter", "gravitational wave", "black hole"]}
{"id": "0910.5236", "title": "Signature of the interaction between dark energy and dark matter in observations", "abstract": "We investigate the effect of an interaction between dark energy and dark matter upon the dynamics of galaxy clusters. This effect is computed through the Layser-Irvine equation, which describes how an astrophysical system reaches virial equilibrium and was modified to include the dark interactions. Using observational data from almost 100 purportedly relaxed galaxy clusters we put constraints on the strength of the couplings in the dark sector. We compare our results with those from other observations and find that a positive (in the sense of energy flow from dark energy to dark matter) non vanishing interaction is consistent with the data within several standard deviations.", "keyphrases": ["dark energy", "dark matter", "relaxed galaxy cluster"]}
{"id": "1012.5068", "title": "Nationalism and internationalism in science: the case of the discovery of cosmic rays", "abstract": "The discovery of cosmic rays, a milestone in science, comprised scientists in Europe and the US and took place during a period characterised by nationalism and lack of communication. Many scientists that took part in this research a century ago were intrigued by the penetrating radiation and tried to understand the origin of it. Several important contributions to the discovery of the origin of cosmic rays have been forgotten and in particular that of Domenico Pacini, who in June 1911 demonstrated by studying the decrease of radioactivity with an electroscope immersed in water that cosmic rays could not come from the crust of the Earth. Several historical, political and personal facts might have contributed to the substantial disappearance of Pacini from the history of science.", "keyphrases": ["science", "cosmic ray", "nationalism"]}
{"id": "1011.3988", "title": "Running Spectral Index from Inflation with Modulations", "abstract": "We argue that a large negative running spectral index, if confirmed, might suggest that there are abundant structures in the inflaton potential, which result in a fairly large (both positive and negative) running of the spectral index at all scales. It is shown that the center value of the running spectral index suggested by the recent CMB data can be easily explained by an inflaton potential with superimposed periodic oscillations. In contrast to cases with constant running, the perturbation spectrum is enhanced at small scales, due to the repeated modulations. We mention that such features at small scales may be seen by 21 cm observations in the future.", "keyphrases": ["spectral index", "inflaton potential", "small modulation"]}
{"id": "1203.4166", "title": "The neutron star inner crust and symmetry energy", "abstract": "The cell structure of clusters in the inner crust of a cold \u03b2-equilibrium neutron star is studied within a Thomas Fermi approach and compared with other approaches which include shell effects. Relativistic nuclear models are considered. We conclude that the symmetry energy slope L may have quite dramatic effects on the cell structure if it is very large or small. Rod-like and slab-like pasta clusters have been obtained in all models except one with a large slope L.", "keyphrases": ["neutron star", "inner crust", "symmetry energy", "astrophysical observation"]}
{"id": "1101.3910", "title": "Latent solitons, black strings, black branes, and equations of state in Kaluza-Klein models", "abstract": "In Kaluza-Klein models with an arbitrary number of toroidal internal spaces, we investigate soliton solutions which describe the gravitational field of a massive compact object. We single out the physically interesting solution corresponding to a point-like mass. For the general solution we obtain equations of state in the external and internal spaces. These equations demonstrate that the point-like mass soliton has dust-like equations of state in all spaces. We also obtain the PPN parameters, which give the possibility to obtain the formulas for perihelion shift, deflection of light and time delay of radar echoes. Additionally, the gravitational experiments lead to a strong restriction on the parameter of the model: \u03c4 = -(2.1\u00b1 2.3)\u00d7 10^-5. The point-like mass solution contradicts this restriction. The condition \u03c4=0 satisfies the experimental limitation and defines a new class of solutions which are indistinguishable from general relativity. We call such solutions latent solitons. Black strings and black branes belong to this class. Moreover, the condition of stability of the internal spaces singles out black strings/branes from the latent solitons and leads uniquely to the black string/brane equations of state p_i=-\u03f5/2, in the internal spaces and to the number of the external dimensions d_0=3. The investigation of multidimensional static spherically symmetric perfect fluid with dust-like equation of state in the external space confirms the above results.", "keyphrases": ["soliton", "black string", "brane", "point-like mass", "toroidal compactification"]}
{"id": "1401.4819", "title": "Observational Tests of Nonlocal Gravity: Galaxy Rotation Curves and Clusters of Galaxies", "abstract": "A classical nonlocal generalization of Einstein's theory of gravitation has recently been developed via the introduction of a scalar causal \"constitutive\" kernel that must ultimately be determined from observational data. It turns out that the nonlocal aspect of gravity in this theory can simulate dark matter; indeed, in the Newtonian regime of nonlocal gravity, we recover the phenomenological Tohline-Kuhn approach to modified gravity. A simple generalization of the Kuhn kernel in the context of nonlocal general relativity leads to a two-parameter modified Newtonian force law that involves an additional repulsive Yukawa-type interaction. We determine the parameters of our nonlocal kernel by comparing the predictions of the theory with observational data regarding the rotation curves of spiral galaxies. The best-fitting stellar mass-to-light ratio turns out to be in agreement with astrophysical models; moreover, our results are consistent with the Tully-Fisher relation for spiral galaxies. Light deflection in nonlocal gravity is consistent with general relativity at Solar System scales, while beyond galactic scales an enhanced deflection angle is predicted that is compatible with lensing by the effective \"dark matter\". Furthermore, we extend our results to the internal dynamics of rich clusters of galaxies and show that the dynamical mass of the cluster obtained from nonlocal gravity is consistent with the measured baryonic mass.", "keyphrases": ["nonlocal gravity", "galaxy", "dark matter"]}
{"id": "0901.2702", "title": "VFISV: Very Fast Inversion of the Stokes Vector for the Helioseismic and Magnetic Imager", "abstract": "In this paper we describe in detail the implementation and main properties of a new inversion code for the polarized radiative transfer equation (VFISV: Very Fast inversion of the Stokes vector). VFISV will routinely analyze pipeline data from the Helioseismic and Magnetic Imager (HMI) on-board of the Solar Dynamics Observatory (SDO). It will provide full-disk maps (4096\u00d74096 pixels) of the magnetic field vector on the Solar Photosphere every 10 minutes. For this reason VFISV is optimized to achieve an inversion speed that will allow it to invert 16 million pixels every 10 minutes with a modest number (approx. 50) of CPUs. Here we focus on describing a number of important details, simplifications and tweaks that have allowed us to significantly speed up the inversion process. We also give details on tests performed with data from the spectropolarimeter on-board of the Hinode spacecraft.", "keyphrases": ["fast inversion", "helioseismic", "magnetic imager"]}
{"id": "1802.04313", "title": "Debris Disks: Structure, Composition, and Variability", "abstract": "Debris disks are tenuous, dust-dominated disks commonly observed around stars over a wide range of ages. Those around main sequence stars are analogous to the Solar System's Kuiper Belt and Zodiacal light. The dust in debris disks is believed to be continuously regenerated, originating primarily with collisions of planetesimals. Observations of debris disks provide insight into the evolution of planetary systems; the composition of dust, comets, and planetesimals outside the Solar System; as well as placing constraints on the orbital architecture and potentially the masses of exoplanets that are not otherwise detectable. This review highlights recent advances in multiwavelength, high-resolution scattered light and thermal imaging that have revealed a complex and intricate diversity of structures in debris disks, and discusses how modeling methods are evolving with the breadth and depth of the available observations. Two rapidly advancing subfields highlighted in this review include observations of atomic and molecular gas around main sequence stars, and variations in emission from debris disks on very short (days to years) timescales, providing evidence of non-steady state collisional evolution particularly in young debris disks.", "keyphrases": ["composition", "planetary system", "debris disk"]}
{"id": "1008.1250", "title": "Cosmological perturbations in f(T) gravity", "abstract": "We investigate the cosmological perturbations in f(T) gravity. Examining the pure gravitational perturbations in the scalar sector using a diagonal vierbien, we extract the corresponding dispersion relation, which provides a constraint on the f(T) ansatzes that lead to a theory free of instabilities. Additionally, upon inclusion of the matter perturbations, we derive the fully perturbed equations of motion, and we study the growth of matter overdensities. We show that f(T) gravity with f(T) constant coincides with General Relativity, both at the background as well as at the first-order perturbation level. Applying our formalism to the power-law model we find that on large subhorizon scales (O(100 Mpc) or larger), the evolution of matter overdensity will differ from LCDM cosmology. Finally, examining the linear perturbations of the vector and tensor sectors, we find that (for the standard choice of vierbein) f(T) gravity is free of massive gravitons.", "keyphrases": ["gravity", "cosmology", "cosmological implication"]}
{"id": "0909.2776", "title": "Quintom Cosmology: Theoretical implications and observations", "abstract": "We review the paradigm of quintom cosmology. This scenario is motivated by the observational indications that the equation of state of dark energy across the cosmological constant boundary is mildly favored, although the data are still far from being conclusive. As a theoretical setup we introduce a no-go theorem existing in quintom cosmology, and based on it we discuss the conditions for the equation of state of dark energy realizing the quintom scenario. The simplest quintom model can be achieved by introducing two scalar fields with one being quintessence and the other phantom. Based on the double-field quintom model we perform a detailed analysis of dark energy perturbations and we discuss their effects on current observations. This type of scenarios usually suffer from a manifest problem due to the existence of a ghost degree of freedom, and thus we review various alternative realizations of the quintom paradigm. The developments in particle physics and string theory provide potential clues indicating that a quintom scenario may be obtained from scalar systems with higher derivative terms, as well as from non-scalar systems. Additionally, we construct a quintom realization in the framework of braneworld cosmology, where the cosmic acceleration and the phantom divide crossing result from the combined effects of the field evolution on the brane and the competition between four and five dimensional gravity. Finally, we study the outsets and fates of a universe in quintom cosmology. In a scenario with null energy condition violation one may obtain a bouncing solution at early times and therefore avoid the Big Bang singularity. Furthermore, if this occurs periodically, we obtain a realization of an oscillating universe. Lastly, we comment on several open issues in quintom cosmology and their connection to future investigations.", "keyphrases": ["dark energy", "quintom model", "quintom cosmology", "general relativity", "field theory"]}
{"id": "1002.2995", "title": "On Inflation with Non-minimal Coupling", "abstract": "A simple realization of inflation consists of adding the following operators to the Einstein-Hilbert action: (partial phi)^2, lambda phi^4, and xi phi^2 R, with xi a large non-minimal coupling. Recently there has been much discussion as to whether such theories make sense quantum mechanically and if the inflaton phi can also be the Standard Model Higgs. In this note we answer these questions. Firstly, for a single scalar phi, we show that the quantum field theory is well behaved in the pure gravity and kinetic sectors, since the quantum generated corrections are small. However, the theory likely breaks down at m_pl / xi due to scattering provided by the self-interacting potential lambda phi^4. Secondly, we show that the theory changes for multiple scalars phi with non-minimal coupling xi phi dot phi R, since this introduces qualitatively new interactions which manifestly generate large quantum corrections even in the gravity and kinetic sectors, spoiling the theory for energies > m_pl / xi. Since the Higgs doublet of the Standard Model includes the Higgs boson and 3 Goldstone bosons, it falls into the latter category and therefore its validity is manifestly spoiled. We show that these conclusions hold in both the Jordan and Einstein frames and describe an intuitive analogy in the form of the pion Lagrangian. We also examine the recent claim that curvature-squared inflation models fail quantum mechanically. Our work appears to go beyond the recent discussions.", "keyphrases": ["non-minimal coupling", "higgs inflation", "perturbative unitarity"]}
{"id": "1301.1123", "title": "Axions : Theory and Cosmological Role", "abstract": "We review recent developments on axion cosmology. Topics include : axion cold dark matter, axions from topological defects, axion isocurvature perturbation and its non-Gaussianity and axino/saxion cosmology in supersymmetric axion model.", "keyphrases": ["dark matter", "axion", "universe", "phenomenology"]}
{"id": "1504.04623", "title": "Cosmological Tests of Modified Gravity", "abstract": "We review recent progress in the construction of modified gravity models as alternatives to dark energy as well as the development of cosmological tests of gravity. Einstein's theory of General Relativity (GR) has been tested accurately within the local universe i.e. the Solar System, but this leaves the possibility open that it is not a good description of gravity at the largest scales in the Universe. This being said, the standard model of cosmology assumes GR on all scales. In 1998, astronomers made the surprising discovery that the expansion of the Universe is accelerating, not slowing down. This late-time acceleration of the Universe has become the most challenging problem in theoretical physics. Within the framework of GR, the acceleration would originate from an unknown dark energy. Alternatively, it could be that there is no dark energy and GR itself is in error on cosmological scales. In this review, we first give an overview of recent developments in modified gravity theories including f(R) gravity, braneworld gravity, Horndeski theory and massive/bigravity theory. We then focus on common properties these models share, such as screening mechanisms they use to evade the stringent Solar System tests. Once armed with a theoretical knowledge of modified gravity models, we move on to discuss how we can test modifications of gravity on cosmological scales. We present tests of gravity using linear cosmological perturbations and review the latest constraints on deviations from the standard \u039bCDM model. Since screening mechanisms leave distinct signatures in the non-linear structure formation, we also review novel astrophysical tests of gravity using clusters, dwarf galaxies and stars.", "keyphrases": ["modified gravity", "cosmological scale", "scalar-tensor theory"]}
{"id": "0904.0829", "title": "Cosmology of the Lifshitz universe", "abstract": "We study the ultraviolet complete non-relativistic theory recently proposed by Horava. After introducing a Lifshitz scalar for a general background, we analyze the cosmology of the model in Lorentzian and Euclidean signature. Vacuum solutions are found and it is argued the existence of non-singular bouncing profiles. We find a general qualitative agreement with both the picture of Causal Dynamical Triangulations and Quantum Einstein Gravity. However, inflation driven by a Lifshitz scalar field on a classical background might not produce a scale-invariant spectrum when the principle of detailed balance is assumed.", "keyphrases": ["scalar field", "cosmology", "ho\u0159ava-lifshitz gravity", "flatness problem", "higher-order curvature term"]}
{"id": "1402.3553", "title": "Jets and Outflows From Star to Cloud: Observations Confront Theory", "abstract": "In this review we focus on the role jets and outflows play in the star and planet formation process. Our essential question can be posed as follows: are jets/outflows merely an epiphenomenon associated with star formation or do they play an important role in mediating the physics of assembling stars both individually and globally? We address this question by reviewing the current state of observations and their key points of contact with theory. Our review of jet/outflow phenomena is organized into three length-scale domains: Source and Disk Scales (0.1-10^2 au) where the connection with protostellar and disk evolution theories is paramount; Envelope Scales (10^2-10^5 au) where the chemistry and propagation shed further light on the jet launching process, its variability and its impact on the infalling envelope; Parent Cloud Scales (10^5-10^6 au) where global momentum injection into cluster/cloud environments become relevant. Issues of feedback are of particular importance on the smallest scales where planet formation regions in a disk may be impacted by the presence of disk winds, irradiation by jet shocks or shielding by the winds. Feedback on envelope scales may determine the final stellar mass (core-to-star efficiency) and envelope dissipation. Feedback also plays an important role on the larger scales with outflows contributing to turbulent support within clusters including alteration of cluster star formation efficiencies (feedback on larger scales currently appears unlikely). A particularly novel dimension of our review is that we consider results on jet dynamics from the emerging field of High Energy Density Laboratory Astrophysics (HEDLA). HEDLA is now providing direct insights into the 3-D dynamics of fully magnetized, hypersonic, radiative outflows.", "keyphrases": ["star formation", "jet", "protostellar jet"]}
{"id": "0901.1106", "title": "Bose-Einstein Condensation of Dark Matter Axions", "abstract": "We show that cold dark matter axions thermalize and form a Bose-Einstein condensate. We obtain the axion state in a homogeneous and isotropic universe, and derive the equations governing small axion perturbations. Because they form a BEC, axions differ from ordinary cold dark matter in the non-linear regime of structure formation and upon entering the horizon. Axion BEC provides a mechanism for the production of net overall rotation in dark matter halos, and for the alignment of cosmic microwave anisotropy multipoles.", "keyphrases": ["dark matter", "bose-einstein condensation", "axion field"]}
{"id": "0905.3746", "title": "Non-Gaussianities in Single Field Inflation and their Optimal Limits from the WMAP 5-year Data", "abstract": "Using the recently developed effective field theory of inflation, we argue that the size and the shape of the non-Gaussianities generated by single-field inflation are generically well described by two parameters: f_NL^equil, which characterizes the size of the signal that is peaked on equilateral configurations, and f_NL^orthog, which instead characterizes the size of the signal which is peaked both on equilateral configurations and flat-triangle configurations (with opposite signs). The shape of non-Gaussianities associated with f_NL^orthog is orthogonal to the one associated to f_NL^equil, and former analysis have been mostly blind to it. We perform the optimal analysis of the WMAP 5-year data for both of these parameters. We find no evidence of non-Gaussianity, and we have the following constraints: -125 < f_NL^equil < 435, -369 < f_NL^orthog < 71 at 95 can be translated into limits on parameters of the Lagrangian of single-field inflation. For one of them, the speed of sound of the inflaton fluctuations, we find that it is either bounded to be c_s > 0.011 at 95 be so small that the higher-derivative kinetic term dominate at horizon crossing. We are able to put similar constraints on the other operators of the inflaton Lagrangian.", "keyphrases": ["field theory", "single-field inflation", "non-gaussianitie"]}
{"id": "1802.03394", "title": "Mimetic gravity as DHOST theories", "abstract": "We show that theories of mimetic gravity can be viewed as degenerate higher-order scalar-tensor (DHOST) theories that admit an extra local (gauge) symmetry in addition to the usual diffeomorphism invariance. We reformulate and classify mimetic theories in this perspective. Using the effective theory of dark energy, recently extended to include DHOST theories, we then investigate the linear perturbations about a homogeneous and isotropic background for all mimetic theories. We also include matter, in the form of a k-essence scalar field, and we derive the quadratic action for linear perturbations in this case.", "keyphrases": ["dhost theory", "mimetic gravity", "other theoretic development"]}
{"id": "1505.03644", "title": "Reconciling Planck results with low redshift astronomical measurements", "abstract": "We show that emerging tension between the direct astronomical measurements at low redshifts and cosmological parameters deduced from the Planck measurements of the CMB anisotropies can be alleviated if the dark matter consists of two fractions, stable part being dominant and a smaller unstable fraction. The latter constitutes \u223c 10 per cent at the recombination epoch if decays by now.", "keyphrases": ["redshift", "astronomical measurement", "dark matter"]}
{"id": "1401.3965", "title": "Mirror dark matter: Cosmology, galaxy structure and direct detection", "abstract": "A simple way to accommodate dark matter is to postulate the existence of a hidden sector. That is, a set of new particles and forces interacting with the known particles predominantly via gravity. In general this leads to a large set of unknown parameters, however if the hidden sector is an exact copy of the standard model sector, then an enhanced symmetry arises. This symmetry, which can be interpreted as space-time parity, connects each ordinary particle (e, \u03bd, p, n, \u03b3, ....) with a mirror partner (e', \u03bd', p', n', \u03b3', ...). If this symmetry is completely unbroken, then the mirror particles are degenerate with their ordinary particle counterparts, and would interact amongst themselves with exactly the same dynamics that govern ordinary particle interactions. The only new interaction postulated is photon - mirror photon kinetic mixing, whose strength \u03f5, is the sole new fundamental (Lagrangian) parameter relevant for astrophysics and cosmology. It turns out that such a theory, with suitably chosen initial conditions effective in the very early Universe, can provide an adequate description of dark matter phenomena provided that \u03f5\u223c 10^-9. This review focuses on three main developments of this mirror dark matter theory during the last decade: Early universe cosmology, galaxy structure and the application to direct detection experiments.", "keyphrases": ["dark matter", "cosmology", "galaxy structure"]}
{"id": "1306.1289", "title": "Revisiting the interacting model of new agegraphic dark energy", "abstract": "In this paper, a new version of the interacting model of new agegraphic dark energy (INADE) is proposed and analyzed in detail. The interaction between dark energy and dark matter is reconsidered. The interaction term Q=bH_0\u03c1_ de^\u03b1\u03c1_ dm^1-\u03b1 is adopted, which abandons the Hubble expansion rate H and involves both \u03c1_ de and \u03c1_ dm. Moreover, the new initial condition for the agegraphic dark energy is used, which solves the problem of accommodating baryon matter and radiation in the model. The solution of the model can be given using an iterative algorithm. A concrete example for the calculation of the model is given. Furthermore, the model is constrained by using the combined Planck data (Planck+BAO+SNIa+H_0) and the combined WMAP-9 data (WMAP+BAO+SNIa+H_0). Three typical cases are considered: (A) Q=bH_0\u03c1_ de, (B) Q=bH_0\u221a(\u03c1_ de\u03c1_ dm), and (C) Q=bH_0\u03c1_ dm, which correspond to \u03b1=1, 1/2, and 0, respectively. The departures of the models from the \u039bCDM model are measured by the \u0394BIC and \u0394AIC values. It is shown that the INADE model is better than the NADE model in the fit, and the INADE(A) model is the best in fitting data among the three cases.", "keyphrases": ["dark energy", "dark matter", "non-gravitational coupling"]}
{"id": "1603.06814", "title": "Galaxy bispectrum, primordial non-Gaussianity and redshift space distortions", "abstract": "Measurements of the non-Gaussianity of the primordial density field have the power to considerably improve our understanding of the physics of inflation. Indeed, if we can increase the precision of current measurements by an order of magnitude, a null-detection would rule out many classes of scenarios for generating primordial fluctuations. Large-scale galaxy redshift surveys represent experiments that hold the promise to realise this goal. Thus, we model the galaxy bispectrum and forecast the accuracy with which it will probe the parameter f_ NL, which represents the degree of primordial local-type non Gaussianity. Specifically, we address the problem of modelling redshift space distortions (RSD) in the tree-level galaxy bispectrum including f_ NL. We find novel contributions associated with RSD, with the characteristic large scale amplification induced by local-type non-Gaussianity. These RSD effects must be properly accounted for in order to obtain un-biased measurements of f_ NL from the galaxy bispectrum. We propose an analytic template for the monopole which can be used to fit against data on large scales, extending models used in the recent measurements. Finally, we perform idealised forecasts on \u03c3_f_ NL \u2013 the accuracy of the determination of local non-linear parameter f_ NL \u2013 from measurements of the galaxy bispectrum. Our findings suggest that current surveys can in principle provide f_ NL constraints competitive with Planck, and future surveys could improve them further.", "keyphrases": ["primordial non-gaussianity", "galaxy bispectrum", "primordial matter bispectrum"]}
{"id": "1901.10947", "title": "Galaxy clusters and a possible variation of the fine structure constant", "abstract": "Galaxy clusters have been used as a cosmic laboratory to verify a possible time variation of fundamental constants. Particularly, it has been shown that the ratio Y_SZD_A^2/C_XZSY_X, which is expected to be constant with redshift, can be used to probe a variation of the fine structure constant, \u03b1. In this ratio, Y_SZD_A^2 is the integrated comptonization parameter of a galaxy cluster obtained via Sunyaev-Zel'dovich (SZ) effect observations multiplied by its angular diameter distance, D_A, Y_X is the X-ray counterpart and C_XSZ is an arbitrary constant. Using a combination of SZ and X-ray data, a recent analysis found Y_SZD_A^2/C_XZSY_X = C\u03b1(z)^3.5, where C is a constant. In this paper, following previous results that suggest that a variation of \u03b1 necessarily leads to a violation of the cosmic distance duality relation, D_L/D_A(1+z)^2 = 1, where D_L is the luminosity distance of a given source, we derive a new expression, Y_SZD_A^2/C_XSZY_X = C\u03b1^3.5\u03b7^-1(z), where \u03b7(z) = D_L/D_A(1+z)^2. In particular, considering the direct relation \u03b7(z) \u221d\u03b1(z)^1/2, derived from a class of dilaton runaway models, measurements of the ratio Y_SZD_A^2/C_XSZY_X provided by the Planck collaboration, we discuss bounds on a possible variation of \u03b1. We also estimate the value of the constant C, which is compatible with the unity at 2\u03c3 level, indicating that the assumption of isothermality for the temperature profile of the galaxy clusters used in the analysis holds.", "keyphrases": ["possible variation", "fine structure constant", "galaxy cluster"]}
{"id": "1406.2209", "title": "Model independent evidence for dark energy evolution from Baryon Acoustic Oscillations", "abstract": "Baryon Acoustic Oscillations (BAO) allow us to determine the expansion history of the Universe, thereby shedding light on the nature of dark energy. Recent observations of BAO's in the SDSS DR9 and DR11 have provided us with statistically independent measurements of H(z) at redshifts of 0.57 and 2.34, respectively. We show that these measurements can be used to test the cosmological constant hypothesis in a model independent manner by means of an improved version of the Om diagnostic. Our results indicate that the SDSS DR11 measurement of H(z) = 222 \u00b1 7 km/sec/Mpc at z = 2.34, when taken in tandem with measurements of H(z) at lower redshifts, imply considerable tension with the standard \u039bCDM model. Our estimation of the new diagnostic Omh^2 from SDSS DR9 and DR11 data, namely Omh^2 \u2248 0.122 \u00b1 0.01, which is equivalent to \u03a9_0mh^2 for the spatially flat \u039bCDM model, is in tension with the value \u03a9_0mh^2 = 0.1426 \u00b1 0.0025 determined for \u039bCDM from Planck+WP. This tension is alleviated in models in which the cosmological constant was dynamically screened (compensated) in the past. Such evolving dark energy models display a pole in the effective equation of state of dark energy at high redshifts, which emerges as a smoking gun test for these theories.", "keyphrases": ["dark energy", "baryon acoustic oscillations", "high redshift"]}
{"id": "1208.3562", "title": "Dark Radiation in LARGE Volume Models", "abstract": "We consider reheating driven by volume modulus decays in the LARGE Volume Scenario. Such reheating always generates non-zero dark radiation through the decays to the axion partner, while the only competitive visible sector decays are Higgs pairs via the Giudice-Masiero term. In the framework of sequestered models where the cosmological moduli problem is absent, the simplest model with a shift-symmetric Higgs sector generates 1.56 < N_eff - N_eff,SM < 1.74. For more general cases, the known experimental bounds on N_eff strongly constrain the parameters and matter content of the models.", "keyphrases": ["dark radiation", "axionic dark radiation", "extra-radiation"]}
{"id": "1001.2600", "title": "Reheating in Inflationary Cosmology: Theory and Applications", "abstract": "Reheating is an important part of inflationary cosmology. It describes the production of Standard Matter particles after the phase of accelerated expansion. We give a review of the reheating process, focusing on an in-depth discussion of the preheating stage which is characterized by exponential particle production due to a parametric resonance or tachyonic instability. We give a brief overview of the thermalization process after preheating and end with a survey of some applications to supersymmetric theories and to other issues in cosmology such as baryogenesis, dark matter and metric preheating.", "keyphrases": ["inflationary cosmology", "inflaton field", "reheating"]}
{"id": "1802.02093", "title": "Constraint on energy-momentum squared gravity from neutron stars and its cosmological implications", "abstract": "Deviations from the predictions of general relativity due to energy-momentum squared gravity (EMSG) are expected to become pronounced in the high density cores of neutron stars. We derive the hydrostatic equilibrium equations in EMSG and solve them numerically to obtain the neutron star mass-radius relations for four different realistic equations of state. We use the existing observational measurements of the masses and radii of neutron stars to constrain the free parameter, \u03b1 , that characterizes the coupling between matter and spacetime in EMSG. We show that -10^-38 cm^3/erg<\u03b1 <+10^-37 cm^3/erg. Under this constraint, we discuss what contributions EMSG can provide to the physics of neutron stars, in particular, their relevance to the so called hyperon puzzle in neutron stars. We also discuss how EMSG alters the dynamics of the early universe from the predictions of the standard cosmological model. We show that EMSG leaves the standard cosmology safely unaltered back to t\u223c 10^-4 seconds at which the energy density of the universe is \u223c 10^34 erg cm^-3.", "keyphrases": ["gravity", "neutron star", "cosmological model"]}
{"id": "1004.1856", "title": "The Hubble Constant", "abstract": "Considerable progress has been made in determining the Hubble constant over the past two decades. We discuss the cosmological context and importance of an accurate measurement of the Hubble constant, and focus on six high-precision distance-determination methods: Cepheids, tip of the red giant branch, maser galaxies, surface brightness fluctuations, the Tully-Fisher relation and Type Ia supernovae. We discuss in detail known systematic errors in the measurement of galaxy distances and how to minimize them. Our best current estimate of the Hubble constant is 73 +/-2 (random) +/-4 (systematic) km/s/Mpc. The importance of improved accuracy in the Hubble constant will increase over the next decade with new missions and experiments designed to increase the precision in other cosmological parameters. We outline the steps that will be required to deliver a value of the Hubble constant to 2 constraints on other cosmological parameters that will then be possible with such accuracy.", "keyphrases": ["hubble constant", "progress", "universe"]}
{"id": "2008.01074", "title": "Neutrino decoupling including flavour oscillations and primordial nucleosynthesis", "abstract": "We revisit the decoupling of neutrinos in the early universe with flavour oscillations. We rederive the quantum kinetic equations which determine the neutrino evolution based on a BBGKY-like hierarchy, and include for the first time the full collision term, with both on- and off-diagonal terms for all relevant reactions. We focus on the case of zero chemical potential and solve these equations numerically. We also develop an approximate scheme based on the adiabatic evolution in the matter basis. In fact, the large difference between the oscillations and cosmological time scales allows to consider averaged flavour oscillations which can speed up the numerical integration by two orders of magnitude, when combined with a direct computation of the differential system Jacobian. The approximate numerical scheme is also useful to gain more insight into the physics of neutrino decoupling. Including the most recent results on plasma thermodynamics QED corrections, we update the effective number of neutrinos to N_eff = 3.0440. Finally we study the impact of flavour oscillations during neutrino decoupling on the subsequent primordial nucleosynthesis.", "keyphrases": ["flavour oscillation", "primordial nucleosynthesis", "neutrino"]}
{"id": "1603.02687", "title": "Kerr black holes with Proca hair", "abstract": "Bekenstein proved that in Einstein's gravity minimally coupled to one (or many) real, Abelian, Proca field, stationary black holes (BHs) cannot have Proca hair. Dropping Bekenstein's assumption that matter inherits spacetime symmetries, we show this model admits asymptotically flat, stationary, axi-symmetric, regular on and outside an event horizon BHs with Proca hair, for an even number of real (or an arbitrary number of complex) Proca fields. To establish it, we start by showing that a test, complex Proca field can form bound states, with real frequency, around Kerr BHs: stationary Proca clouds. These states exist at the threshold of superradiance. It was conjectured in arXiv:1403.2757, that the existence of such clouds at the linear level implies the existence of a new family of BH solutions at the non-linear level. We confirm this expectation and explicitly construct examples of such Kerr black holes with Proca hair (KBHsPH). For a single complex Proca field, these BHs form a countable number of families with three continuous parameters (ADM mass, ADM angular momentum and Noether charge). They branch off from the Kerr solutions that can support stationary Proca clouds and reduce to Proca stars when the horizon size vanishes. We present the domain of existence of one family of KBHsPH, as well as its phase space in terms of ADM quantities. Some physical properties of the solutions are discussed; in particular, and in contrast with Kerr BHs with scalar hair, some spacetime regions can be counter-rotating with respect to the horizon. We further establish a no-Proca-hair theorem for static, spherically symmetric BHs but allowing the complex Proca field to have a harmonic time dependence, which shows BHs with Proca hair in this model require rotation and have no static limit. KBHsPH are also disconnected from Kerr-Newman BHs with a real, massless vector field.", "keyphrases": ["black hole", "proca hair", "kerr"]}
{"id": "0904.1382", "title": "Relativistic stars in f(R) gravity", "abstract": "We study the strong gravity regime in viable models of so-called f(R) gravity that account for the observed cosmic acceleration. In contrast with recent works suggesting that very relativistic stars might not exist in these models, we find numerical solutions corresponding to static star configurations with a strong gravitational field. The choice of the equation of state for the star is crucial for the existence of solutions. Indeed, if the pressure exceeds one third of the energy density in a large part of the star, static configurations do not exist. In our analysis, we use a polytropic equation of state, which is not plagued with this problem and, moreover, provides a better approximation for a realistic neutron star.", "keyphrases": ["gravity", "star configuration", "relativistic star", "scalaron"]}
{"id": "1404.7852", "title": "Aligned Natural Inflation in String Theory", "abstract": "We propose a scenario for realizing super-Planckian axion decay constants in Calabi-Yau orientifolds of type IIB string theory, leading to large-field inflation. Our construction is a simple embedding in string theory of the mechanism of Kim, Nilles, and Peloso, in which a large effective decay constant arises from alignment of two smaller decay constants. The key ingredient is gaugino condensation on magnetized or multiply-wound D7-branes. We argue that, under very mild assumptions about the topology of the Calabi-Yau, there are controllable points in moduli space with large effective decay constants.", "keyphrases": ["natural inflation", "string theory", "axion", "decay"]}
{"id": "1104.0730", "title": "Corrections to the apparent value of the cosmological constant due to local inhomogeneities", "abstract": "Supernovae observations strongly support the presence of a cosmological constant, but its value, which we will call apparent, is normally determined assuming that the Universe can be accurately described by a homogeneous model. Even in the presence of a cosmological constant we cannot exclude nevertheless the presence of a small local inhomogeneity which could affect the apparent value of the cosmological constant. Neglecting the presence of the inhomogeneity can in fact introduce a systematic misinterpretation of cosmological data, leading to the distinction between an apparent and true value of the cosmological constant. We establish the theoretical framework to calculate the corrections to the apparent value of the cosmological constant by modeling the local inhomogeneity with a \u039b LTB solution. Our assumption to be at the center of a spherically symmetric inhomogeneous matter distribution correspond to effectively calculate the monopole contribution of the large scale inhomogeneities surrounding us, which we expect to be the dominant one, because of other observations supporting a high level of isotropy of the Universe around us. By performing a local Taylor expansion we analyze the number of independent degrees of freedom which determine the local shape of the inhomogeneity, and consider the issue of central smoothness, showing how the same correction can correspond to different inhomogeneity profiles. Contrary to previous attempts to fit data using large void models our approach is quite general. The correction to the apparent value of the cosmological constant is in fact present for local inhomogeneities of any size, and should always be taken appropriately into account both theoretically and observationally.", "keyphrases": ["cosmological constant", "inhomogeneity", "dark energy component"]}
{"id": "1603.02356", "title": "Measuring the distance-redshift relation with the cross-correlation of gravitational wave standard sirens and galaxies", "abstract": "Gravitational waves from inspiraling compact binaries are known to be an excellent absolute distance indicator, yet it is unclear whether electromagnetic counterparts of these events are securely identified for measuring their redshifts, especially in the case of black hole-black hole mergers such as the one recently observed with the Advanced LIGO. We propose to use the cross-correlation between spatial distributions of gravitational wave sources and galaxies with known redshifts as an alternative means of constraining the distance-redshift relation from gravitational waves. In our analysis, we explicitly include the modulation of the distribution of gravitational wave sources due to weak gravitational lensing. We show that the cross-correlation analysis in next-generation observations will be able to tightly constrain the relation between the absolute distance and the redshift, and therefore constrain the Hubble constant as well as dark energy parameters.", "keyphrases": ["distance-redshift relation", "cross-correlation", "galaxy", "gravitational wave source"]}
{"id": "0907.2562", "title": "Chern-Simons Modified General Relativity", "abstract": "Chern-Simons modified gravity is an effective extension of general relativity that captures leading-order, gravitational parity violation. Such an effective theory is motivated by anomaly cancelation in particle physics and string theory. In this review, we begin by providing a pedagogical derivation of the three distinct ways such an extension arises: (1) in particle physics, (2) from string theory and (3) geometrically. We then review many exact and approximate, vacuum solutions of the modified theory, and discuss possible matter couplings. Following this, we review the myriad astrophysical, solar system, gravitational wave and cosmological probes that bound Chern-Simons modified gravity, including discussions of cosmic baryon asymmetry and inflation. The review closes with a discussion of possible future directions in which to test and study gravitational parity violation.", "keyphrases": ["gravity", "string theory", "chern-simon", "riemann tensor", "levi-civita connection"]}
{"id": "0905.3750", "title": "Building the Terrestrial Planets: Constrained Accretion in the Inner Solar System", "abstract": "To date, no accretion model has succeeded in reproducing all observed constraints in the inner Solar System. These constraints include 1) the orbits, in particular the small eccentricities, and 2) the masses of the terrestrial planets \u2013 Mars' relatively small mass in particular has not been adequately reproduced in previous simulations; 3) the formation timescales of Earth and Mars, as interpreted from Hf/W isotopes; 4) the bulk structure of the asteroid belt, in particular the lack of an imprint of planetary embryo-sized objects; and 5) Earth's relatively large water content, assuming that it was delivered in the form of water-rich primitive asteroidal material. Here we present results of 40 high-resolution (N=1000-2000) dynamical simulations of late-stage planetary accretion with the goal of reproducing these constraints, although neglecting the planet Mercury. We assume that Jupiter and Saturn are fully-formed at the start of each simulation, and test orbital configurations that are both consistent with and contrary to the \"Nice model.\" We find that a configuration with Jupiter and Saturn on circular orbits forms low-eccentricity terrestrial planets and a water-rich Earth on the correct timescale, but Mars' mass is too large by a factor of 5-10 and embryos are often stranded in the asteroid belt. A configuration with Jupiter and Saturn in their current locations but with slightly higher initial eccentricities (e = 0.07-0.1) produces a small Mars, an embryo-free asteroid belt, and a reasonable Earth analog but rarely allows water delivery to Earth. None of the configurations we tested reproduced all the observed constraints. (abridged)", "keyphrases": ["planet", "accretion", "inner solar system", "asteroid belt"]}
{"id": "2005.05992", "title": "Black holes with scalar hair in light of the Event Horizon Telescope", "abstract": "Searching for violations of the no-hair theorem (NHT) is a powerful way to test gravity, and more generally fundamental physics, particularly with regards to the existence of additional scalar fields. The first observation of a black hole (BH) shadow by the Event Horizon Telescope (EHT) has opened a new direct window onto tests of gravity in the strong-field regime, including probes of violations of the NHT. We consider two scenarios described by the Einstein-Maxwell equations of General Relativity and electromagnetism, to which we add a scalar field. In the first case we consider a minimally-coupled scalar field with a potential, whereas in the second case the field is conformally-coupled to curvature. In both scenarios we construct charged BH solutions, which are found to carry primary scalar hair. We then compute the shadows cast by these two BHs as a function of their electric charge and scalar hair parameter. Comparing these shadows to the shadow of M87* recently imaged by the EHT collaboration, we set constraints on the amount of scalar hair carried by these two BHs. The conformally-coupled case admits a regime for the hair parameter, compatible with EHT constraints, describing a so-called mutated Reissner-Nordstr\u00f6m BH: this solution was recently found to effectively mimic a wormhole. Our work provides novel constraints on fundamental physics, and in particular on violations of the no-hair theorem and the existence of additional scalar fields, from the shadow of M87*.", "keyphrases": ["event horizon telescope", "scalar field", "black hole"]}
{"id": "1912.07064", "title": "Small-scale structure of fuzzy and axion-like dark matter", "abstract": "Axion-like particle (ALP) dark matter shows distinctive behavior on scales where wavelike effects dominate over self-gravity. Ultralight axions are candidates for fuzzy dark matter (FDM) whose de Broglie wavelength in virialized halos reaches scales of kiloparsecs. Important features of FDM scenarios are the formation of solitonic halo cores, suppressed small-scale perturbations, and enhanced gravitational relaxation. More massive ALPs, including the QCD axion, behave like CDM on galactic scales but may be clumped into axion miniclusters if they were produced after inflation. Just as FDM halos, axion miniclusters may host the formation of coherent bound objects (axion stars) by Bose-Einstein condensation. This article presents a selection of topics in this field that are currently under active investigation.", "keyphrases": ["dark matter", "fuzzy dark matter", "axion minicluster"]}
{"id": "1510.07633", "title": "Axion Cosmology", "abstract": "1. Introduction 2. Models: the QCD axion; the strong CP problem; PQWW, KSVZ, DFSZ; anomalies, instantons and the potential; couplings; axions in string theory 3. Production and I.C.'s: SSB and non-perturbative physics; the axion field during inflation and PQ SSB; cosmological populations - decay of parent, topological defects, thermal production, vacuum realignment 4. The Cosmological Field: action; background evolution; misalignment for QCD axion and ALPs; cosmological perturbation theory - i.c.'s, early time treatment, axion sound speed and Jeans scale, transfer functions and WDM; the Schrodinger picture; simualting axions; BEC 5. CMB and LSS: Primary anisotropies; matter power; combined constraints; Isocurvature and inflation 6. Galaxy Formation; halo mass function; high-z and the EOR; density profiles; the CDM small-scale crises 7. Accelerated expansion: the c.c. problem; axion inflation (natural and monodromy) 8. Gravitational interactions with black holes and pulsars 9. Non-gravitational interactions: stellar astrophysics; LSW; vacuum birefringence; axion forces; direct detection with ADMX and CASPEr; Axion decays; dark radiation; astrophysical magnetic fields; cosmological birefringence 10. Conclusions A Theta vacua of gauge theories B EFT for cosmologists C Friedmann equations D Cosmological fluids E Bayes Theorem and priors F Degeneracies and sampling G Sheth-Tormen HMF", "keyphrases": ["string theory", "axion cosmology", "dark matter", "ultra-light axion"]}
{"id": "1412.5049", "title": "Analytic Prediction of Baryonic Effects from the EFT of Large Scale Structures", "abstract": "The large scale structures of the universe will likely be the next leading source of cosmological information. It is therefore crucial to understand their behavior. The Effective Field Theory of Large Scale Structures provides a consistent way to perturbatively predict the clustering of dark matter at large distances. The fact that baryons move distances comparable to dark matter allows us to infer that baryons at large distances can be described in a similar formalism: the backreaction of short-distance non-linearities and of star-formation physics at long distances can be encapsulated in an effective stress tensor, characterized by a few parameters. The functional form of baryonic effects can therefore be predicted. In the power spectrum the leading contribution goes as \u221d k^2 P(k), with P(k) being the linear power spectrum and with the numerical prefactor depending on the details of the star-formation physics. We also perform the resummation of the contribution of the long-wavelength displacements, allowing us to consistently predict the effect of the relative motion of baryons and dark matter. We compare our predictions with simulations that contain several implementations of baryonic physics, finding percent agreement up to relatively high wavenumbers such as k\u2243 0.3 h Mpc^-1 or k\u2243 0.6 h Mpc^-1, depending on the order of the calculation. Our results open a novel way to understand baryonic effects analytically, as well as to interface with simulations.", "keyphrases": ["baryonic effect", "large scale structures", "effective field theory", "non-linear regime"]}
{"id": "1211.1095", "title": "CMB constraint on non-Gaussianity in isocurvature perturbations", "abstract": "We study the CMB constraint on non-Gaussianity in CDM isocurvature perturbations. Non-Gaussian isocurvature perturbations can be produced in various models at the very early stage of the Universe. Since the isocurvature perturbations little affect the structure formation at late times, CMB is the best probe of isocurvature non-Gaussianity at least in the near future. In this paper, we focus on uncorrelated isocurvature perturbations and constrain their non-Gaussianity. For this purpose, we employ several state-of-art techniques for the analysis of CMB data and simulation. We use the WMAP 7 year data of temperature anisotropy. When the adiabatic perturbations are assumed to be Gaussian, we obtained a constraint on the isocurvature non-Gaussianity alpha^2 f_NL^(ISO)=40+-66 for the scale invariant isocurvature power spectrum, where alpha is the ratio of the power spectrum of isocurvature perturbations to that of the adiabatic ones. When we assume that the adiabatic perturbations can also be non-Gaussian, we obtain f_NL=38+-24 and alpha^2 f_NL^(ISO)=-8+-72. We also discuss implications our results for the axion CDM isocurvature model.", "keyphrases": ["non-gaussianity", "isocurvature perturbation", "cmb constraint"]}
{"id": "1903.03836", "title": "Holographic dark energy from nonadditive entropy: cosmological perturbations and observational constraints", "abstract": "We apply the holographic principle in the cosmological context through the nonadditive Tsallis entropy, used to describe the thermodynamic properties of nonstandard statistical systems such as the gravitational ones. Assuming the future event horizon as the infrared cutoff, we build a dark energy model free from cosmological inconsistencies, which includes standard thermodynamics and standard holographic dark energy as a limiting case. We thus describe the dynamics of Tsallis holographic dark energy in a flat FLRW background. Hence, we investigate cosmological perturbations in the linear regime on sub-horizon scales. We study the growth of matter fluctuations in the case of clustering dark matter and a homogeneous dark energy component. Furthermore, we employ the most recent late-time cosmic data to test the observational viability of our theoretical scenario. We thus obtain constraints on the free parameters of the model by means of Monte Carlo numerical method. We also used Bayesian selection criteria to estimate the statistical preference for Tsallis holographic dark energy compared to the concordance \u039bCDM paradigm. Our results show deviations from standard holographic dark energy within the 2\u03c3 confidence level. Finally, the analysis of the dark energy equation of state indicates a quintessence-like behaviour with no evidence for phantom-divide crossing at the 1\u03c3 level.", "keyphrases": ["dark energy", "cosmological perturbation", "holographic dark energy"]}
{"id": "1003.6074", "title": "The Ages of Stars", "abstract": "The age of an individual star cannot be measured, only estimated through mostly model-dependent or empirical methods, and no single method works well for a broad range of stellar types or for a full range in age. This review presents a summary of the available techniques for age-dating stars and ensembles of stars, their realms of applicability, and their strengths and weaknesses. My emphasis is on low-mass stars because they are present from all epochs of star formation in the Galaxy and because they present both special opportunities and problems. The ages of open clusters are important for understanding the limitations of stellar models and for calibrating empirical age indicators. For individual stars, a hierarchy of quality for the available age-dating methods is described. Although our present ability to determine the ages of even the nearest stars is mediocre, the next few years hold great promise as asteroseismology probes beyond stellar surfaces and starts to provide precise interior properties of stars and as models continue to improve when stressed by better observations.", "keyphrases": ["age", "star", "low-mass star", "cluster", "rotational evolution"]}
{"id": "2106.03150", "title": "Asymptotic behavior of null geodesics near future null infinity: Significance of gravitational waves", "abstract": "We investigate the behavior of null geodesics near future null infinity in asymptotically flat spacetimes. In particular, we focus on the asymptotic behavior of null geodesics that correspond to worldlines of photons initially emitted in the directions tangential to the constant radial surfaces in the Bondi coordinates. The analysis is performed for general dimensions, and the difference between the four-dimensional cases and the higher-dimensional cases is stressed. In four dimensions, some assumptions are required to guarantee the null geodesics to reach future null infinity, in addition to the conditions of asymptotic flatness. Without these assumptions, gravitational waves may prevent photons from reaching null infinity. In higher dimensions, by contrast, such assumptions are not necessary, and gravitational waves do not affect the asymptotic behavior of null geodesics.", "keyphrases": ["null geodesic", "flat spacetime", "asymptotic behavior"]}
{"id": "1402.5031", "title": "Modified gravity and coupled quintessence", "abstract": "The distinction between modified gravity and quintessence or dynamical dark energy is difficult. Many models of modified gravity are equivalent to models of coupled quintessence by virtue of variable transformations. This makes an observational differentiation between modified gravity and dark energy very hard. For example, the additional scalar degree of freedom in f(R)-gravity or non-local gravity can be interpreted as the cosmon of quintessence. Nevertheless, modified gravity can shed light on questions of interpretation, naturalness and simplicity. We present a simple model where gravity is modified by a field dependent Planck mass. It leads to a universe with a cold and slow beginning. This cosmology can be continued to the infinite past such that no big bang singularity occurs. All observables can be described equivalently in a hot big bang picture with inflation and early dark energy.", "keyphrases": ["gravity", "coupled quintessence", "dark energy"]}
{"id": "1608.03839", "title": "Mimicking dark matter in Horndeski gravity", "abstract": "Since the rediscovery of Horndeski gravity, a lot of work has been devoted to the exploration of its properties, especially in the context of dark energy. However, one sector of this theory, namely the one containing the coupling of the Einstein tensor to the kinetic term of the scalar field, shows some surprising features in the construction of black holes and neutron stars. Motivated by these new results, I explore the possibility that this sector of Horndeski gravity can mimic cold dark matter at cosmological level and also explain the flattening of galactic rotation curves. I will show that, in principle, it is possible to achieve both goals with at least two scalar fields and a minimal set of assumptions.", "keyphrases": ["dark matter", "horndeski gravity", "scalar field"]}
{"id": "1602.00682", "title": "Perfect fluid in Lagrangian formulation due to generalized three-form field", "abstract": "A Lagrangian formulation of perfect fluid due to a noncanonical three-form field is investigated. The thermodynamic quantities such as energy density, pressure and the four velocity are obtained and then analyzed by comparing with the k-essence scalar field. The nonrelativistic matter due to the generalized three-form field with the equation of state parameter being zero is realized while it might not be possible for the k-essence scalar field. We also found that nonadiabatic pressure perturbations can be possibly generated. The fluid dynamics of the perfect fluid due to the three-form field corresponds to the system in which the number of particles is not conserved. We argue that it is interesting to use this three-form field to represent the dark matter for the classical interaction theory between dark matter and dark energy.", "keyphrases": ["fluid", "lagrangian formulation", "three-form field"]}
{"id": "1612.00345", "title": "Holographic Dark Energy", "abstract": "We review the paradigm of holographic dark energy (HDE), which arises from a theoretical attempt of applying the holographic principle (HP) to the dark energy (DE) problem. Making use of the HP and the dimensional analysis, we derive the general formula of the energy density of HDE. Then, we describe the properties of HDE model, in which the future event horizon is chosen as the characteristic length scale. We also introduce the theoretical explorations and the observational constraints for this model. Next, in the framework of HDE, we discuss various topics, such as spatial curvature, neutrino, instability of perturbation, time-varying gravitational constant, inflation, black hole and big rip singularity. In addition, from both the theoretical and the observational aspects, we introduce the interacting holographic dark energy scenario, where the interaction between dark matter and HDE is taken into account. Furthermore, we discuss the HDE scenario in various modified gravity (MG) theories, such as Brans-Dicke theory, braneworld theory, scalar-tensor theory, Horava-Lifshitz theory, and so on. Besides, we introduce the attempts of reconstructing various scalar-field DE and MG models from HDE. Moreover, we introduce other DE models inspired by the HP, in which different characteristic length scales are chosen. Finally, we make comparisons among various HP-inspired DE models, by using cosmological observations and diagnostic tools.", "keyphrases": ["gravity", "cosmology", "holographic dark energy"]}
{"id": "1406.2402", "title": "Effective field theory of modified gravity on the spherically symmetric background: leading order dynamics and the odd-type perturbations", "abstract": "We consider perturbations of a static and spherically symmetric background endowed with a metric tensor and a scalar field in the framework of the effective field theory of modified gravity. We employ the previously developed 2+1+1 canonical formalism of a double Arnowitt-Deser-Misner (ADM) decomposition of space-time, which singles out both time and radial directions. Our building block is a general gravitational action that depends on scalar quantities constructed from the 2+1+1 canonical variables and the lapse. Variation of the action up to first-order in perturbations gives rise to three independent background equations of motion, as expected from spherical symmetry. The dynamical equations of linear perturbations follow from the second-order Lagrangian after a suitable gauge fixing. We derive conditions for the avoidance of ghosts and Laplacian instabilities for the odd-type perturbations. We show that our results not only incorporates those derived in the most general scalar-tensor theories with second-order equations of motion (the Horndeski theories) but they can be applied to more generic theories beyond Horndeski.", "keyphrases": ["gravity", "odd-type perturbation", "effective field theory"]}
{"id": "1712.08623", "title": "Direct detection of gravitational waves can measure the time variation of the Planck mass", "abstract": "The recent discovery of a \u03b3-ray counterpart to a gravitational wave event has put extremely stringent constraints on the speed of gravitational waves at the present epoch. In turn, these constraints place strong theoretical pressure on potential modifications of gravity, essentially allowing only a conformally-coupled scalar to be active in the present Universe. In this paper, we show that direct detection of gravitational waves from optically identified sources can also measure or constrain the strength of the conformal coupling in scalar\u2013tensor models through the time variation of the Planck mass. As a first rough estimate, we find that the LISA satellite can measure the dimensionless time variation of the Planck mass (the so-called parameter \u03b1_M) at redshift around 1.5 with an error of about 0.03 to 0.13, depending on the assumptions concerning future observations. Stronger constraints can be achieved once reliable distance indicators at z>2 are developed, or with GW detectors that extend the capabilities of LISA, like the proposed Big Bang Observer. We emphasize that, just like the constraints on the gravitational speed, the bound on \u03b1_M is independent of the cosmological model.", "keyphrases": ["gravitational wave", "time variation", "direct detection"]}
{"id": "1406.4135", "title": "The Bispectrum in the Effective Field Theory of Large Scale Structure", "abstract": "We study the bispectrum in the Effective Field Theory of Large Scale Structure, consistently accounting for the effects of short-scale dynamics. We begin by proving that, as long as the theory is perturbative, it can be formulated to arbitrary order using only operators that are local in time. We then derive all the new operators required to cancel the UV-divergences and obtain a physically meaningful prediction for the one-loop bispectrum. In addition to new, subleading stochastic noises and the viscosity term needed for the one-loop power spectrum, we find three new effective operators. The three new parameters can be constrained by comparing with N-body simulations. The best fit is precisely what is suggested by the structure of UV-divergences, hence justifying a formula for the EFTofLSS bispectrum whose only fitting parameter is already fixed by the power spectrum. This result predicts the bispectrum of N-body simulations up to k \u2248 0.22 h Mpc^-1 at z=0, an improvement by nearly a factor of two as compared to one-loop standard perturbation theory.", "keyphrases": ["bispectrum", "effective field theory", "one-loop bispectrum", "dark matter", "non-linear regime"]}
{"id": "1407.1885", "title": "PAINTER: a spatio-spectral image reconstruction algorithm for optical interferometry", "abstract": "Astronomical optical interferometers sample the Fourier transform of the intensity distribution of a source at the observation wavelength. Because of rapid perturbations caused by atmospheric turbulence, the phases of the complex Fourier samples (visibilities) cannot be directly exploited. Consequently, specific image reconstruction methods have been devised in the last few decades. Modern polychromatic optical interferometric instruments are now paving the way to multiwavelength imaging. This paper is devoted to the derivation of a spatio-spectral (3D) image reconstruction algorithm, coined PAINTER (Polychromatic opticAl INTErferometric Reconstruction software). The algorithm relies on an iterative process, which alternates estimation of polychromatic images and of complex visibilities. The complex visibilities are not only estimated from squared moduli and closure phases, but also differential phases, which helps to better constrain the polychromatic reconstruction. Simulations on synthetic data illustrate the efficiency of the algorithm and in particular the relevance of injecting a differential phases model in the reconstruction.", "keyphrases": ["image reconstruction algorithm", "interferometry", "painter"]}
{"id": "1803.05716", "title": "Magnetars: a short review and some sparse considerations", "abstract": "We currently know about 30 magnetars: seemingly isolated neutron stars whose properties can be (in part) comprehended only acknowledging that they are endowed with magnetic fields of complex morphology and exceptional intensity-at least in some components of the field structure. Although magnetars represent only a small percentage of the known isolated neutron stars, there are almost certainly many more of them, since most magnetars were discovered in transitory phases called outbursts, during which they are particularly noticeable. In outburst, in fact, a magnetar can be brighter in X-rays by orders of magnitude and usually emit powerful bursts of hard-X/soft-gamma-ray photons that can be detected almost everywhere in the Galaxy with all-sky monitors such as those on board the Fermi satellite or the Neil Gehrels Swift Observatory. Magnetars command great attention because the large progress that has been made in their understanding is proving fundamental to fathom the whole population of isolated neutron stars, and because, due to their extreme properties, they are relevant for a vast range of different astrophysical topics, from the study of gamma-ray bursts and superluminous supernovae, to ultraluminous X-ray sources, fast radio bursts, and even to sources of gravitational waves. Several excellent reviews with different focuses were published on magnetars in the last few years: among others, Israel and Dall'Osso (2011); Rea and Esposito (2011); Turolla and Esposito (2013); Mereghetti et al. (2015); Turolla et al. (2015); Kaspi and Beloborodov (2017). Here, we quickly recall the history of these sources and travel through the main observational facts, trying to touch some recent and sometimes little-discussed ramifications of magnetars.", "keyphrases": ["neutron star", "outburst", "magnetar"]}
{"id": "1406.4143", "title": "The One-Loop Matter Bispectrum in the Effective Field Theory of Large Scale Structures", "abstract": "Given the importance of future large scale structure surveys for delivering new cosmological information, it is crucial to reliably predict their observables. The Effective Field Theory of Large Scale Structures (EFTofLSS) provides a manifestly convergent perturbative scheme to compute the clustering of dark matter in the weakly nonlinear regime in an expansion in k/k_ NL, where k is the wavenumber of interest and k_ NL is the wavenumber associated to the nonlinear scale. It has been recently shown that the EFTofLSS matches to 1% level the dark matter power spectrum at redshift zero up to k\u2243 0.3 hMpc^-1 and k\u2243 0.6 hMpc^-1 at one and two loops respectively, using only one counterterm that is fit to data. Similar results have been obtained for the momentum power spectrum at one loop. This is a remarkable improvement with respect to former analytical techniques. Here we study the prediction for the equal-time dark matter bispectrum at one loop. We find that at this order it is sufficient to consider the same counterterm that was measured in the power spectrum. Without any remaining free parameter, and in a cosmology for which k_ NL is smaller than in the previously considered cases (\u03c3_8=0.9), we find that the prediction from the EFTofLSS agrees very well with N-body simulations up to k\u2243 0.25 hMpc^-1, given the accuracy of the measurements, which is of order a few percent at the highest k's of interest. While the fit is very good on average up to k\u2243 0.25 hMpc^-1, the fit performs slightly worse on equilateral configurations, in agreement with expectations that for a given maximum k, equilateral triangles are the most nonlinear.", "keyphrases": ["effective field theory", "dark matter", "one-loop bispectrum"]}
{"id": "1401.0385", "title": "Super-Sample Covariance in Simulations", "abstract": "Using separate universe simulations, we accurately quantify super-sample covariance (SSC), the typically dominant sampling error for matter power spectrum estimators in a finite volume, which arises from the presence of super survey modes. By quantifying the power spectrum response to a background mode, this approach automatically captures the separate effects of beat coupling in the quasilinear regime, halo sample variance in the nonlinear regime and a new dilation effect which changes scales in the power spectrum coherently across the survey volume, including the baryon acoustic oscillation scale. It models these effects at typically the few percent level or better with a handful of small volume simulations for any survey geometry compared with directly using many thousands of survey volumes in a suite of large volume simulations. The stochasticity of the response is sufficiently small that in the quasilinear regime, SSC can be alternately included by fitting the mean density in the volume with these fixed templates in parameter estimation. We also test the halo model prescription and find agreement typically at better than the 10 level for the response.", "keyphrases": ["covariance", "simulation", "response", "super-sample mode", "overdensity"]}
{"id": "1205.0311", "title": "Dark Matter in the Milky Way's Dwarf Spheroidal Satellites", "abstract": "The Milky Way's dwarf spheroidal satellites include the nearest, smallest and least luminous galaxies known. They also exhibit the largest discrepancies between dynamical and luminous masses. This article reviews the development of empirical constraints on the structure and kinematics of dSph stellar populations and discusses how this phenomenology translates into constraints on the amount and distribution of dark matter within dSphs. Some implications for cosmology and the particle nature of dark matter are discussed, and some topics/questions for future study are identified.", "keyphrases": ["dwarf spheroidal satellite", "dark matter", "mass-to-light ratio"]}
{"id": "1511.07587", "title": "Testing the no-hair theorem with the continuum-fitting and the iron line methods: a short review", "abstract": "The continuum-fitting and the iron line methods are leading techniques capable of probing the spacetime geometry around astrophysical black hole candidates and testing the no-hair theorem. In the present paper, we review the two approaches, from the astrophysical models and their assumptions, to the constraining power with present and future facilities.", "keyphrases": ["no-hair", "continuum-fitting", "iron line method", "astrophysical black hole", "gravity"]}
{"id": "1207.4187", "title": "Consistency relation for cosmic magnetic fields", "abstract": "If cosmic magnetic fields are indeed produced during inflation, they are likely to be correlated with the scalar metric perturbations that are responsible for the Cosmic Microwave Background anisotropies and Large Scale Structure. Within an archetypical model of inflationary magnetogenesis, we show that there exists a new simple consistency relation for the non-Gaussian cross correlation function of the scalar metric perturbation with two powers of the magnetic field in the squeezed limit where the momentum of the metric perturbation vanishes. We emphasize that such a consistency relation turns out to be extremely useful to test some recent calculations in the literature. Apart from primordial non-Gaussianity induced by the curvature perturbations, such a cross correlation might provide a new observational probe of inflation and can in principle reveal the primordial nature of cosmic magnetic fields.", "keyphrases": ["magnetic field", "curvature perturbation", "gauge field"]}
{"id": "1502.07418", "title": "An ultra-luminous quasar with a twelve-billion-solar-mass black hole at redshift 6.30", "abstract": "So far, roughly 40 quasars with redshifts greater than z=6 have been discovered. Each quasar contains a black hole with a mass of about one billion solar masses (10^9 M_\u2299). The existence of such black holes when the Universe was less than 1 billion years old presents substantial challenges to theories of the formation and growth of black holes and the coevolution of black holes and galaxies. Here we report the discovery of an ultra-luminous quasar, SDSS J010013.02+280225.8, at redshift z=6.30. It has an optical and near-infrared luminosity a few times greater than those of previously known z>6 quasars. On the basis of the deep absorption trough on the blue side of the Ly \u03b1 emission line in the spectrum, we estimate the proper size of the ionized proximity zone associated with the quasar to be 26 million light years, larger than found with other z>6.1 quasars with lower luminosities. We estimate (on the basis of a near-infrared spectrum) that the black hole has a mass of \u223c 1.2 \u00d7 10^10 M_\u2299, which is consistent with the 1.3 \u00d7 10^10 M_\u2299 derived by assuming an Eddington-limited accretion rate.", "keyphrases": ["ultra-luminous quasar", "black hole", "redshift", "solar mass"]}
{"id": "1412.4976", "title": "New test of the FLRW metric using the distance sum rule", "abstract": "We present a new test of the validity of the Friedmann-Lemaitre-Robertson-Walker (FLRW) metric, based on comparing the distance from redshift 0 to z_1 and from z_1 to z_2 to the distance from 0 to z_2. If the universe is described by the FLRW metric, the comparison provides a model-independent measurement of spatial curvature. The test relies on geometrical optics, it is independent of the matter content of the universe and the applicability of the Einstein equation on cosmological scales. We apply the test to observations, using the Union2.1 compilation of supernova distances and Sloan Lens ACS Survey galaxy strong lensing data. The FLRW metric is consistent with the data, and the spatial curvature parameter is constrained to be -1.22<\u03a9_K0<0.63, or -0.08<\u03a9_K0<0.97 with a prior from the cosmic microwave background and the local Hubble constant, though modelling of the lenses is a source of significant systematic uncertainty.", "keyphrases": ["flrw metric", "spatial curvature", "new test"]}
{"id": "1206.3077", "title": "Can strong gravitational lensing distinguish naked singularities from black holes?", "abstract": "In this paper we study gravitational lensing in the strong field limit from the perspective of cosmic censorship, to investigate whether or not naked singularities, if at all they exist in nature, can be distinguished from black holes. We study the gravitational lensing in the strong field regime in the JMN spacetime, a spherically symmetric geometry that contains a naked singularity and which matches smoothly with Schwarzschild metric beyond a finite radius. This metric is a toy model which was shown recently to be the end state of gravitational collapse. In the presence of the photon sphere gravitational lensing signature of this spacetime is identical to that of Schwarzschild black hole with infinitely many relativistic images and Einstein rings, all of them located beyond a certain critical angle from optic axis and the inner relativistic images all clumped together. However, in the absence of the photon sphere, which is the case for a wide range of parameter values in this spacetime, we show that we get finitely many relativistic images and Einstein rings spaced reasonably apart from one another, some of which can be formed inside the critical angle for the corresponding Schwarzschild black hole. This study suggests that the observation of relativistic images and rings might, in principle, allow us to unravel the existence of the naked singularity in the absence of the photon sphere. The results obtained here are in contrast with the earlier investigation on JNW naked singularities radial caustic was always present in the absence of photon sphere, while it is absent in JMN geometry. We also point out the practical difficulties that might be encountered in the observation of the relativistic images and suggest that new dedicated experiments and techniques must be developed in future for this purpose.", "keyphrases": ["naked singularity", "black hole", "relativistic image"]}
{"id": "1103.4164", "title": "Conformal Invariance, Dark Energy, and CMB Non-Gaussianity", "abstract": "In addition to simple scale invariance, a universe dominated by dark energy naturally gives rise to correlation functions possessing full conformal invariance. This is due to the mathematical isomorphism between the conformal group of certain 3 dimensional slices of de Sitter space and the de Sitter isometry group SO(4,1). In the standard homogeneous isotropic cosmological model in which primordial density perturbations are generated during a long vacuum energy dominated de Sitter phase, the embedding of flat spatial sections in de Sitter space induces a conformal invariant perturbation spectrum and definite prediction for the shape of the non-Gaussian CMB bispectrum. In the case in which the density fluctuations are generated instead on the de Sitter horizon, conformal invariance of the horizon embedding implies a different but also quite definite prediction for the angular correlations of CMB non-Gaussianity on the sky. Each of these forms for the bispectrum is intrinsic to the symmetries of de Sitter space and in that sense, independent of specific model assumptions. Each is different from the predictions of single field slow roll inflation models which rely on the breaking of de Sitter invariance. We propose a quantum origin for the CMB fluctuations in the scalar gravitational sector from the conformal anomaly that could give rise to these non-Gaussianities without a slow roll inflaton field, and argue that conformal invariance also leads to the expectation for the relation n_S-1=n_T between the spectral indices of the scalar and tensor power spectrum. Confirmation of this prediction or detection of non-Gaussian correlations in the CMB of one of the bispectral shape functions predicted by conformal invariance can be used both to establish the physical origins of primordial density fluctuations and distinguish between different dynamical models of cosmological vacuum dark energy.", "keyphrases": ["dark energy", "cmb non-gaussianity", "conformal invariance", "slow-roll inflation"]}
{"id": "1904.10298", "title": "Primordial black hole tower: Dark matter, earth-mass, and LIGO black holes", "abstract": "We investigate a possibility of primordial black hole (PBH) formation with a hierarchical mass spectrum in multiple phases of inflation. As an example, we find that one can simultaneously realize a mass spectrum which has recently attracted a lot of attention: stellar-mass PBHs (\u223c\ud835\udcaa(10)M_\u2299) as a possible source of binary black holes detected by LIGO/Virgo collaboration, asteroid-mass (\u223c\ud835\udcaa(10^-12)M_\u2299) as a main component of dark matter, and earth-mass (\u223c\ud835\udcaa(10^-5)M_\u2299) as a source of ultrashort-timescale events in Optical Gravitational Lensing Experiment microlensing data. The recent refined de Sitter swampland conjecture may support such a multi-phase inflationary scenario with hierarchical mass PBHs as a transition signal of each inflationary phase.", "keyphrases": ["black hole", "dark matter", "earth-mass", "gravitational wave"]}
{"id": "1207.1492", "title": "Interacting dark matter and modified holographic Ricci dark energy plus a noninteracting cosmic component", "abstract": "We investigate a spatially flat Friedmann-Robertson-Walker universe that has an interacting dark matter, a modified holographic Ricci dark energy (MHRDE), plus a third, decoupled component that behaves as a radiation term. We consider a nonlinear interaction in the dark component densities and their derivatives up to second order. We apply the \u03c7^2 method to the observational Hubble data for constraining the cosmological parameters and analyze the amount of dark energy in the radiation era for both MHRDE and holographic Ricci dark energy models. The former is consistent with the bound \u03a9_x(z\u2243 1100)<0.1 reported for the behavior of dark energy at early times while the latter does not fulfill it.", "keyphrases": ["dark matter", "big-bang nucleosynthesis epoch", "dark sector"]}
{"id": "1710.05877", "title": "Dark Energy after GW170817 and GRB170817A", "abstract": "The observation of GW170817 and its electromagnetic counterpart implies that gravitational waves travel at the speed of light, with deviations smaller than a few \u00d7 10^-15. We discuss the consequences of this experimental result for models of dark energy and modified gravity characterized by a single scalar degree of freedom. To avoid tuning, the speed of gravitational waves must be unaffected not only for our particular cosmological solution, but also for nearby solutions obtained by slightly changing the matter abundance. For this to happen the coefficients of various operators must satisfy precise relations that we discuss both in the language of the Effective Field Theory of Dark Energy and in the covariant one, for Horndeski, beyond Horndeski and degenerate higher-order theories. The simplification is dramatic: of the three functions describing quartic and quintic beyond Horndeski theories, only one remains and reduces to a standard conformal coupling to the Ricci scalar for Horndeski theories. We show that the deduced relations among operators do not introduce further tuning of the models, since they are stable under quantum corrections.", "keyphrases": ["gravity", "horndeski", "dark energy", "gw170817 event", "glpv theory"]}
{"id": "0902.3163", "title": "Does Bulk Viscosity Create a Viable Unified Dark Matter Model?", "abstract": "We investigate in detail the possibility that a single imperfect fluid with bulk viscosity can replace the need for separate dark matter and dark energy in cosmological models. With suitable choices of model parameters, we show that the background cosmology in this model can mimic that of a LCDM Universe to high precision. However, as the cosmic expansion goes through the decelerating-accelerating transition, the density perturbations in this fluid are rapidly damped out. We show that,although this does not significantly affect structure formation in baryonic matter, it makes the gravitational potential decay rapidly at late times, leading to modifications in predictions of cosmological observables such as the CMB power spectrum and weak lensing. This model of unified dark matter is thus difficult to reconcile with astronomical observations. We also clarify the differences with respect to other unified dark matter models where the fluid is barotropic, i.e., p=p(rho), such as the (generalized) Chaplygin gas model, and point out their observational difficulties. We also summarize the status of dark sector models with no new dynamical degrees of freedom introduced and discuss the problems with them.", "keyphrases": ["bulk viscosity", "dark matter", "dark energy", "gravitational potential"]}
{"id": "1207.3706", "title": "Spectral breaks as a signature of cosmic ray induced turbulence in the Galaxy", "abstract": "We show that the complex shape of the cosmic ray (CR) spectrum, as recently measured by PAMELA and inferred from Fermi-LAT gamma-ray observations of molecular clouds in the Gould belt, can be naturally understood in terms of basic plasma astrophysics phenomena. A break from a harder to a softer spectrum at blue rigidity R\u224310 GV follows from a transition from transport dominated by advection of particles with Alfven waves to a regime where diffusion in the turbulence generated by the same CRs is dominant. A second break at R\u2243200 GV happens when the diffusive propagation is no longer determined by the self-generated turbulence, but rather by the cascading of externally generated turbulence (for instance due to supernova (SN) bubbles) from large spatial scales to smaller scales where CRs can resonate. Implications of this scenario for the cosmic ray spectrum, grammage and anisotropy are discussed.", "keyphrases": ["cosmic ray", "turbulence", "spectral hardening"]}
{"id": "1709.01091", "title": "Dark energy two decades after: Observables, probes, consistency tests", "abstract": "The discovery of the accelerating universe in the late 1990s was a watershed moment in modern cosmology, as it indicated the presence of a fundamentally new, dominant contribution to the energy budget of the universe. Evidence for dark energy, the new component that causes the acceleration, has since become extremely strong, owing to an impressive variety of increasingly precise measurements of the expansion history and the growth of structure in the universe. Still, one of the central challenges of modern cosmology is to shed light on the physical mechanism behind the accelerating universe. In this review, we briefly summarize the developments that led to the discovery of dark energy. Next, we discuss the parametric descriptions of dark energy and the cosmological tests that allow us to better understand its nature. We then review the cosmological probes of dark energy. For each probe, we briefly discuss the physics behind it and its prospects for measuring dark energy properties. We end with a summary of the current status of dark energy research.", "keyphrases": ["cosmology", "dark energy", "late time", "alternative", "available data"]}
{"id": "2003.04800", "title": "Observational detection of correlation between galaxy spins and initial conditions", "abstract": "Galaxy spins can be predicted from the initial conditions in the early Universe through the tidal tensor twist. In simulations, their directions are well preserved through cosmic time, consistent with expectations of angular momentum conservation. We report a \u223c 3 \u03c3 detection of correlation between observed oriented directions of galaxy angular momenta and their predictions based on the initial density field reconstructed from the positions of SDSS galaxies. The detection is driven by a group of spiral galaxies classified by the Galaxy Zoo as (anti-)clockwise, with a modest improvement from adding galaxies from MaNGA and SAMI surveys. This is the first such detection of the oriented galaxy spin direction, which opens a way to use measurements of galaxy spins to probe fundamental physics in the early Universe.", "keyphrases": ["galaxy spin", "initial condition", "early universe"]}
{"id": "1403.2049", "title": "Cosmology of the proxy theory to massive gravity", "abstract": "In this paper, we scrutinize very closely the cosmology in the proxy theory to massive gravity obtained in Phys. Rev. D84 (2011) 043503. This proxy theory was constructed by covariantizing the decoupling limit Lagrangian of massive gravity and represents a subclass of Horndeski scalar-tensor theory. Thus, this covariantization unifies two important classes of modified gravity theories, namely massive gravity and Horndeski theories. We go beyond the regime which was studied in Phys. Rev. D84 (2011) 043503 and show that the theory does not admit any homogeneous and isotropic self-accelerated solutions. We illustrate that the only attractor solution is flat Minkowski solution, hence this theory is less appealing as a dark energy model. We also show that the absence of de Sitter solutions is tightly related to the presence of shift symmetry breaking interactions.", "keyphrases": ["gravity", "scalar-tensor theory", "horndeski theory", "cosmology"]}
{"id": "1509.02120", "title": "Perturbation theory, effective field theory, and oscillations in the power spectrum", "abstract": "We explore the relationship between the nonlinear matter power spectrum and the various Lagrangian and Standard Perturbation Theories (LPT and SPT). We first look at it in the context of one dimensional (1-d) dynamics, where 1LPT is exact at the perturbative level and one can exactly resum the SPT series into the 1LPT power spectrum. Shell crossings lead to non-perturbative effects, and the PT ignorance can be quantified in terms of their ratio, which is also the transfer function squared in the absence of stochasticity. At the order of PT we work, this parametrization is equivalent to the results of effective field theory (EFT), and can thus be expanded in terms of the same parameters. We find that its radius of convergence is larger than the SPT loop expansion. The same EFT parametrization applies to all SPT loop terms and, if stochasticity can be ignored, to all N-point correlators. In 3-d, the LPT structure is considerably more complicated, and we find that LPT models with parametrization motivated by the EFT exhibit running with k and that SPT is generally a better choice. Since these transfer function expansions contain free parameters that change with cosmological model their usefulness for broadband power is unclear. For this reason we test the predictions of these models on baryonic acoustic oscillations (BAO) and other primordial oscillations, including string monodromy models, for which we ran a series of simulations with and without oscillations. Most models are successful in predicting oscillations beyond their corresponding PT versions, confirming the basic validity of the model.", "keyphrases": ["oscillation", "power spectrum", "eft", "perturbation theory"]}
{"id": "0901.0011", "title": "The role of sterile neutrinos in cosmology and astrophysics", "abstract": "We present a comprehensive overview of an extension of the Standard Model that contains three right-handed (sterile) neutrinos with masses below the electroweak scale [the Neutrino Minimal Standard Model, (nuMSM)]. We consider the history of the Universe from the inflationary era through today and demonstrate that most of the observed phenomena beyond the Standard Model can be explained within the framework of this model. We review the mechanism of baryon asymmetry of the Universe in the nuMSM and discuss a dark matter candidate that can be warm or cold and satisfies all existing constraints. From the viewpoint of particle physics the model provides an explanation for neutrino flavor oscillations. Verification of the nuMSM is possible with existing experimental techniques.", "keyphrases": ["neutrino", "electroweak scale", "dark matter", "early universe", "lepton asymmetry"]}
{"id": "1306.4160", "title": "Anisotropy in solid inflation", "abstract": "In the model of solid / elastic inflation, inflation is driven by a source that has the field theoretical description of a solid. To allow for prolonged slow roll inflation, the solid needs to be extremely insensitive to the spatial expansion. We point out that, because of this property, the solid is also rather inefficient in erasing anisotropic deformations of the geometry. This allows for a prolonged inflationary anisotropic solution, providing the first example with standard gravity and scalar fields only which evades the conditions of the so called cosmic no-hair conjecture. We compute the curvature perturbations on the anisotropic solution, and the corresponding phenomenological bound on the anisotropy. Finally, we discuss the analogy between this model and the f (phi) F^2 model, which also allows for anisotropic inflation thanks to a suitable coupling between the inflaton phi and a vector field. We remark that the bispectrum of the curvature perturbations in solid inflation is enhanced in the squeezed limit and presents a nontrivial angular dependence, as had previously been found for the f (phi) F^2 model.", "keyphrases": ["solid inflation", "curvature perturbation", "bispectrum"]}
{"id": "1601.06133", "title": "Dark Energy vs. Modified Gravity", "abstract": "Understanding the reason for the observed accelerated expansion of the Universe represents one of the fundamental open questions in physics. In cosmology, a classification has emerged among physical models for the acceleration, distinguishing between Dark Energy and Modified Gravity. In this review, we give a brief overview of models in both categories as well as their phenomenology and characteristic observable signatures in cosmology. We also introduce a rigorous distinction between Dark Energy and Modified Gravity based on the strong and weak equivalence principles.", "keyphrases": ["modified gravity", "cosmology", "dark energy"]}
{"id": "2106.13793", "title": "Teleparallel Gravity: From Theory to Cosmology", "abstract": "Teleparallel gravity has significantly increased in popularity in recent decades, bringing attention to Einstein's other theory of gravity. In this Review, we relate this form of geometry to the broader metric-affine approach to forming gravitational theories where we describe a systematic way of constructing consistent teleparallel theories that respect certain physical conditions such as local Lorentz invariance. We first use teleparallel gravity to formulate a teleparallel equivalent of general relativity which is dynamically equivalent to general relativity but which may have different behaviors for other scenarios, such as quantum gravity. After setting this foundation, we describe the plethora of modified teleparallel theories of gravity that have been proposed in the literature. In the second part of the Review, we first survey works in teleparallel astrophysics literature where we focus on the open questions in this regime of physics. We then discuss the cosmological consequences for the various formulations of teleparallel gravity. We do this at background level by exploring works using various approaches ranging from dynamical systems to Noether symmetries, and more. Naturally, we then discuss perturbation theory, firstly by giving a concise approach in which this can be applied in teleparallel gravity theories and then apply it to a number of important theories in the literature. Finally, we examine works in observational and precision cosmology across the plethora of proposal theories. This is done using some of the latest observations and is used to tackle cosmological tensions which may be alleviated in teleparallel cosmology. We also introduce a number of recent works in the application of machine learning to gravity, we do this through deep learning and Gaussian processes, together with discussions about other approaches in the literature.", "keyphrases": ["teleparallel gravity", "curvature", "non-metricity"]}
{"id": "1512.04543", "title": "The small scatter of the baryonic Tully-Fisher relation", "abstract": "In a LCDM cosmology, the baryonic Tully-Fisher relation (BTFR) is expected to show significant intrinsic scatter resulting from the mass-concentration relation of dark matter halos and the baryonic-to-halo mass ratio. We study the BTFR using a sample of 118 disc galaxies (spirals and irregulars) with data of the highest quality: extended HI rotation curves (tracing the outer velocity) and Spitzer photometry at 3.6 \u03bcm (tracing the stellar mass). Assuming that the stellar mass-to-light ratio (M*/L) is nearly constant at 3.6 \u03bcm, we find that the scatter, slope, and normalization of the BTFR systematically vary with the adopted M*/L. The observed scatter is minimized for M*/L > 0.5, corresponding to nearly maximal discs in high-surface-brightness galaxies and BTFR slopes close to 4. For any reasonable value of M*/L, the intrinsic scatter is 0.1 dex, below general LCDM expectations. The residuals show no correlations with galaxy structural parameters (radius or surface brightness), contrary to the predictions from some semi-analytic models of galaxy formation. These are fundamental issues for LCDM cosmology.", "keyphrases": ["baryonic tully-fisher relation", "galaxy formation", "baryonic mass"]}
{"id": "1901.07803", "title": "Primordial black holes as dark matter and generators of cosmic structure", "abstract": "Primordial black holes (PBHs) could provide the dark matter but a variety of constraints restrict the possible mass windows to 10^16 - 10^17g, 10^20 - 10^24g and 10 - 10^3M_\u2299. The last possibility is of special interest in view of the recent detection of black-hole mergers by LIGO. PBHs larger than 10^3 M_\u2299 might have important cosmological consequences even if they have only a small fraction of the dark matter density. In particular, they could generate cosmological structures either individually through the \"seed\" effect or collectively through the \"Poisson\" effect, thereby alleviating some problems associated with the standard cold dark matter scenario.", "keyphrases": ["black hole", "dark matter", "cosmological consequence"]}
{"id": "1007.0027", "title": "Galilean Genesis: an alternative to inflation", "abstract": "We propose a novel cosmological scenario, in which standard inflation is replaced by an expanding phase with a drastic violation of the Null Energy Condition (NEC): \u1e22 >> H^2. The model is based on the recently introduced Galileon theories, that allow NEC violating solutions without instabilities. The unperturbed solution describes a Universe that is asymptotically Minkowski in the past, expands with increasing energy density until it exits the regime of validity of the effective field theory and reheats. This solution is a dynamical attractor and the Universe is driven to it, even if it is initially contracting. The study of perturbations of the Galileon field reveals some subtleties, related to the gross violation of the NEC and it shows that adiabatic perturbations are cosmologically irrelevant. The model, however, suggests a new way to produce a scale invariant spectrum of isocurvature perturbations, which can later be converted to adiabatic: the Galileon is forced by symmetry to couple to the other fields as a dilaton; the effective metric it yields on the NEC violating solution is that of de Sitter space, so that all light scalars will automatically acquire a nearly scale-invariant spectrum of perturbations.", "keyphrases": ["alternative", "universe", "field theory", "galilean genesis", "inflationary scenario"]}
{"id": "0909.1960", "title": "Kinks and small-scale structure on cosmic strings", "abstract": "We discuss some hitherto puzzling features of the small-scale structure of cosmic strings. We argue that kinks play a key role, and that an important quantity to study is their sharpness distribution. In particular we suggest that for very small scales the two-point correlation function of the string tangent vector varies linearly with the separation and not as a fractional power, as proposed by Polchinski and Rocha [Phys. Rev. D 74, 083504 (2006)]. However, our results are consistent with theirs, because the range of scales to which this linearity applies shrinks as evolution proceeds.", "keyphrases": ["cosmic string", "string", "kink"]}
{"id": "1410.7770", "title": "Measuring angular diameter distances of strong gravitational lenses", "abstract": "The distance-redshift relation plays a fundamental role in constraining cosmological models. In this paper, we show that measurements of positions and time delays of strongly lensed images of a background galaxy, as well as those of the velocity dispersion and mass profile of a lens galaxy, can be combined to extract the angular diameter distance of the lens galaxy. Physically, as the velocity dispersion and the time delay give a gravitational potential (GM/r) and a mass (GM) of the lens, respectively, dividing them gives a physical size (r) of the lens. Comparing the physical size with the image positions of a lensed galaxy gives the angular diameter distance to the lens. A mismatch between the exact locations at which these measurements are made can be corrected by measuring a local slope of the mass profile. We expand on the original idea put forward by Paraficz and Hjorth, who analyzed singular isothermal lenses, by allowing for an arbitrary slope of a power-law spherical mass density profile, an external convergence, and an anisotropic velocity dispersion. We find that the effect of external convergence cancels out when dividing the time delays and velocity dispersion measurements. We derive a formula for the uncertainty in the angular diameter distance in terms of the uncertainties in the observables. As an application, we use two existing strong lens systems, B1608+656 (z_ L=0.6304) and RXJ1131-1231 (z_ L=0.295), to show that the uncertainty in the inferred angular diameter distances is dominated by that in the velocity dispersion, \u03c3^2, and its anisotropy. We find that the current data on these systems should yield about 16 \u03c3^2 at the so-called sweet-spot radius. Achieving 7 can determine \u03c3^2 with 5", "keyphrases": ["angular diameter distance", "lense", "lens galaxy"]}
{"id": "1605.01712", "title": "New constraints on interacting dark energy from cosmic chronometers", "abstract": "We use the latest compilation of observational Hubble parameter measurements estimated with the differential evolution of cosmic chronometers, in combination with the local value of the Hubble constant recently measured with 2.4 interacts directly with the dark matter sector. To diminish the degeneracy between the parameters we additionally consider standard probes, such as Supernovae Type Ia from joint light curves (JLA) sample, Baryon Acoustic Oscillation distance measurements (BAO), and cosmic microwave background data from Planck 2015 estimations. Our analysis shows that the direct interaction between dark energy and dark matter is mildly flavored, while the dark energy equation-of-state parameter is w < - 1 at 3\u03c3 confidence level.", "keyphrases": ["dark energy", "cosmic chronometer", "dark matter", "cosmology"]}
{"id": "1803.02771", "title": "Testing the equivalence principle on cosmological scales", "abstract": "The equivalence principle, that is one of the main pillars of general relativity, is very well tested in the Solar system; however, its validity is more uncertain on cosmological scales, or when dark matter is concerned. This article shows that relativistic effects in the large-scale structure can be used to directly test whether dark matter satisfies Euler's equation, i.e. whether its free fall is characterised by geodesic motion, just like baryons and light. After having proposed a general parametrisation for deviations from Euler's equation, we perform Fisher-matrix forecasts for future surveys like DESI and the SKA, and show that such deviations can be constrained with a precision of order 10 directly with standard methods like redshift-space distortions and gravitational lensing, since these observables are not sensitive to the time component of the metric. Our analysis shows therefore that relativistic effects bring new and complementary constraints to alternative theories of gravity.", "keyphrases": ["equivalence principle", "cosmological scale", "relativistic effect"]}
{"id": "1202.4013", "title": "Theory of magnetic reconnection in solar and astrophysical plasmas", "abstract": "Magnetic reconnection is a fundamental process in a plasma that facilitates the release of energy stored in the magnetic field by permitting a change in the magnetic topology. In this article we present a review of the current state of understanding of magnetic reconnection. We discuss theoretical results regarding the formation of current sheets in complex 3D magnetic fields, and describe the fundamental differences between reconnection in two and three dimensions. We go on to outline recent developments in modelling of reconnection with kinetic theory, as well as in the MHD framework where a number of new 3D reconnection regimes have been identified. We discuss evidence from observations and simulations of solar system plasmas that support this theory, and summarise some prominent locations in which this new reconnection theory is relevant in astrophysical plasmas.", "keyphrases": ["magnetic reconnection", "astrophysical plasma", "magnetosphere"]}
{"id": "1007.5498", "title": "General treatment of isocurvature perturbations and non-Gaussianities", "abstract": "We present a general formalism that provides a systematic computation of the linear and non-linear perturbations for an arbitrary number of cosmological fluids in the early Universe going through various transitions, in particular the decay of some species (such as a curvaton or a modulus). Using this formalism, we revisit the question of isocurvature non-Gaussianities in the mixed inflaton-curvaton scenario and show that one can obtain significant non-Gaussianities dominated by the isocurvature mode while satisfying the present constraints on the isocurvature contribution in the observed power spectrum. We also study two-curvaton scenarios, taking into account the production of dark matter, and investigate in which cases significant non-Gaussianities can be produced.", "keyphrases": ["treatment", "isocurvature perturbation", "non-gaussianitie"]}
{"id": "2112.10779", "title": "Quintessence and the Swampland: The parametrically controlled regime of moduli space", "abstract": "We provide evidence that slow roll is not possible in any parametrically controlled regime of the moduli space of string theory. This is proven in full generality in the asymptotic limit of the moduli space of type II and heterotic Calabi-Yau compactifications for the dilaton and any number of K\u00e4hler moduli. Our results suggest that in order to build quintessence into string theory one must work in the interior of moduli space where numerical, even if not parametric, control could still be achieved.", "keyphrases": ["string theory", "modulus space", "quintessence"]}
{"id": "1411.5021", "title": "Inflation with a constant rate of roll", "abstract": "We consider an inflationary scenario where the rate of inflaton roll defined by \u03d5\u0308/H\u03d5\u0307 remains constant. The rate of roll is small for slow-roll inflation, while a generic rate of roll leads to the interesting case of `constant-roll' inflation. We find a general exact solution for the inflaton potential required for such inflaton behaviour. In this model, due to non-slow evolution of background, the would-be decaying mode of linear scalar (curvature) perturbations may not be neglected. It can even grow for some values of the model parameter, while the other mode always remains constant. However, this always occurs for unstable solutions which are not attractors for the given potential. The most interesting particular cases of constant-roll inflation remaining viable with the most recent observational data are quadratic hilltop inflation (with cutoff) and natural inflation (with an additional negative cosmological constant). In these cases even-order slow-roll parameters approach non-negligible constants while the odd ones are asymptotically vanishing in the quasi-de Sitter regime.", "keyphrases": ["roll", "constant-roll inflation", "curvature perturbation"]}
{"id": "1908.09139", "title": "Curvature tension: evidence for a closed universe", "abstract": "The curvature parameter tension between Planck 2018, cosmic microwave background lensing, and baryon acoustic oscillation data is measured using the suspiciousness statistic to be 2.5 to 3\u03c3. Conclusions regarding the spatial curvature of the universe which stem from the combination of these data should therefore be viewed with suspicion. Without CMB lensing or BAO, Planck 2018 has a moderate preference for closed universes, with Bayesian betting odds of over 50:1 against a flat universe, and over 2000:1 against an open universe.", "keyphrases": ["universe", "spatial curvature", "standard deviation", "cdm model", "debate"]}
{"id": "1101.3655", "title": "Evolution of cosmological perturbations in Bose-Einstein condensate dark matter", "abstract": "We consider the global cosmological evolution and the evolution of the density contrast in the Bose-Einstein condensate dark matter model, in the framework of a Post-Newtonian cosmological approach. In the Bose-Einstein model, dark matter can be described as a non-relativistic, Newtonian gravitational condensate, whose density and pressure are related by a barotropic equation of state. For a condensate with quartic non-linearity, the equation of state is polytropic with index n=1. The basic equation describing the evolution of the perturbations of the Bose-Einstein condensate is obtained, and its solution is studied by using both analytical and numerical methods. The global cosmological evolution as well as the evolution of the perturbations of the condensate dark matter shows significant differences with respect to the pressureless dark matter model, considered in the framework of standard cosmology. Therefore the presence of condensate dark matter could have modified drastically the cosmological evolution of the early universe, as well as the large scale structure formation process.", "keyphrases": ["bose-einstein condensate", "dark matter", "post-newtonian cosmological approach"]}
{"id": "1306.5725", "title": "Dark Matter and Pulsar Model Constraints from Galactic Center Fermi-LAT Gamma Ray Observations", "abstract": "Employing Fermi-LAT gamma ray observations, several independent groups have found excess extended gamma ray emission at the Galactic center (GC). Both, annihilating dark matter (DM) or a population of \u223c 10^3 unresolved millisecond pulsars (MSPs) are regarded as well motivated possible explanations. However, there is significant uncertainties in the diffuse galactic background at the GC. We have performed a revaluation of these two models for the extended gamma ray source at the GC by accounting for the systematic uncertainties of the Galactic diffuse emission model. We also marginalize over point source and diffuse background parameters in the region of interest. We show that the excess emission is significantly more extended than a point source. We find that the DM (or pulsars population) signal is larger than the systematic errors and therefore proceed to determine the sectors of parameter space that provide an acceptable fit to the data. We found that a population of order a 1000 MSPs with parameters consistent with the average spectral shape of Fermi-LAT measured MSPs was able to fit the GC excess emission. For DM, we found that a pure \u03c4^+\u03c4^- annihilation channel is not a good fit to the data. But a mixture of \u03c4^+\u03c4^- and bb\u0305 with a <\u03c3 v> of order the thermal relic value and a DM mass of around 20 to 60 GeV provides an adequate fit.", "keyphrases": ["unresolved millisecond pulsar", "dark matter", "inner galaxy"]}
{"id": "1103.3690", "title": "Investigation of the field-induced ferromagnetic phase transition in spin polarized neutron matter: a lowest order constrained variational approach", "abstract": "In this paper, the lowest order constrained variational (LOCV) method has been used to investigate the magnetic properties of spin polarized neutron matter in the presence of strong magnetic field at zero temperature employing AV_18 potential. Our results indicate that a ferromagnetic phase transition is induced by a strong magnetic field with strength greater than 10^18 G, leading to a partial spin polarization of the neutron matter. It is also shown that the equation of state of neutron matter in the presence of magnetic field is stiffer than the case in absence of magnetic field.", "keyphrases": ["ferromagnetic phase transition", "spin", "neutron matter"]}
{"id": "1103.4829", "title": "Cosmological Parameters from Observations of Galaxy Clusters", "abstract": "Studies of galaxy clusters have proved crucial in helping to establish the standard model of cosmology, with a universe dominated by dark matter and dark energy. A theoretical basis that describes clusters as massive, multi-component, quasi-equilibrium systems is growing in its capability to interpret multi-wavelength observations of expanding scope and sensitivity. We review current cosmological results, including contributions to fundamental physics, obtained from observations of galaxy clusters. These results are consistent with and complementary to those from other methods. We highlight several areas of opportunity for the next few years, and emphasize the need for accurate modeling of survey selection and sources of systematic error. Capitalizing on these opportunities will require a multi-wavelength approach and the application of rigorous statistical frameworks, utilizing the combined strengths of observers, simulators and theorists.", "keyphrases": ["galaxy cluster", "dark matter", "cosmology"]}
{"id": "1311.0290", "title": "Single-Field Consistency Relations of Large Scale Structure. Part II: Resummation and Redshift Space", "abstract": "We generalize the recently derived single-field consistency relations of Large Scale Structure in two directions. First, we treat the effect of the long modes (with momentum q) on the short ones (with momentum k) non-perturbatively, by writing resummed consistency relations which do not require k/q \u03b4_q << 1. These relations do not make any assumptions on the short-scales physics and are extended to include (an arbitrary number of) multiple long modes, internal lines with soft momenta and soft loops. We do several checks of these relations in perturbation theory and we verify that the effect of soft modes always cancels out in equal-time correlators. Second, we write the relations directly in redshift space, without assuming the single-stream approximation: not only the long mode affects the short scales as a homogeneous gravitational field, but it also displaces them by its velocity along the line-of-sight. Redshift space consistency relations still vanish when short modes are taken at equal time: an observation of a signal in the squeezed limit would point towards multifield inflation or a violation of the equivalence principle.", "keyphrases": ["large scale structure", "redshift space", "long mode"]}
{"id": "1403.1129", "title": "Epicyclic frequencies for rotating strange quark stars: the importance of stellar oblateness", "abstract": "Kilohertz QPOs can be used as a probe of the inner regions of accretion disks in compact stars and hence also of the properties of the central object. Most models of kHz QPOs involve epicyclic frequencies to explain their origin. We compute the epicyclic frequencies of nearly circular orbits around rotating strange quark stars. The MIT bag model is used to model the equation of state of quark matter and the uniformly rotating stellar configurations are computed in full general relativity. The vertical epicyclic frequency and the related nodal precession rate of inclined orbits are very sensitive to the oblateness of the rotating star. For slowly rotating stellar models of moderate and high mass strange stars, the sense of the nodal precession changes at a certain rotation rate. At lower stellar rotation rates the orbital nodal precession is prograde, as it is in the Kerr metric, while at higher rotation rates the precession is retrograde, as it is for Maclaurin spheroids. Thus, qualitatively, the orbits around rapidly rotating strange quark stars are affected more strongly by the effects of stellar oblateness than by the effects of general relativity. We show that epicyclic and orbital frequencies calculated numerically for small mass strange stars are in very good agreement with analytical formulae for Maclaurin spheroids.", "keyphrases": ["strange quark star", "star", "stellar oblateness"]}
{"id": "1201.4848", "title": "On the importance of heavy fields during inflation", "abstract": "We study the dynamics of two-field models of inflation characterized by a hierarchy of masses between curvature and isocurvature modes. When the hierarchy is large, a low energy effective field theory (EFT) exists in which only curvature modes participate in the dynamics of perturbations. In this EFT heavy fields continue to have a significant role in the low energy dynamics, as their interaction with curvature modes reduces their speed of sound whenever the multi-field trajectory is subject to a sharp turn in target space. Here we analyze under which general conditions this EFT remains a reliable description for the linear evolution of curvature modes. We find that the main condition consists on demanding that the rate of change of the turn's angular velocity stays suppressed with respect to the masses of heavy modes. This adiabaticity condition allows the EFT to accurately describe a large variety of situations in which the multi-field trajectory is subject to sharp turns. To test this, we analyze several models with turns and show that, indeed, the power spectra obtained for both the original two-field theory and its single-field EFT are identical when the adiabaticity condition is satisfied. In particular, when turns are sharp and sudden, they are found to generate large features in the power spectrum, accurately reproduced by the EFT.", "keyphrases": ["heavy field", "field theory", "curvature perturbation", "expansion rate"]}
{"id": "1511.02651", "title": "Impacts of dark energy on weighing neutrinos after Planck 2015", "abstract": "We investigate how dark energy properties impact the cosmological limits on the total mass of active neutrinos. We consider two typical, simple dark energy models (that have only one more additional parameter than \u039bCDM), i.e., the wCDM model and the holographic dark energy (HDE) model, as examples, to make an analysis. In the cosmological fits, we use the Planck 2015 temperature and polarization data, in combination with other low-redshift observations, including the baryon acoustic oscillations, type Ia supernovae, and Hubble constant measurement, as well as the Planck lensing measurements. We find that, once dynamical dark energy is considered, the degeneracy between \u2211 m_\u03bd and H_0 will be changed, i.e., in the \u039bCDM model, \u2211 m_\u03bd is anti-correlated with H_0, but in the wCDM and HDE models, \u2211 m_\u03bd becomes positively correlated with H_0. Compared to \u039bCDM, in the wCDM model the limit on \u2211 m_\u03bd becomes much looser, but in the HDE model the limit becomes much tighter. In the HDE model, we obtain \u2211 m_\u03bd<0.113 eV (95% CL) with the combined data sets, which is perhaps the most stringent upper limit by far on neutrino mass. Thus, our result in the HDE model is nearly ready to diagnose the neutrino mass hierarchy with the current cosmological observations.", "keyphrases": ["dark energy", "neutrino", "cosmology", "holographic dark energy"]}
{"id": "1103.3219", "title": "BEC dark matter, Zeldovich approximation and generalized Burgers equation", "abstract": "If the dark matter in the universe is a self-gravitating Bose-Einstein condensate (BEC) with quartic self-interaction described by the Gross-Pitaevskii-Poisson system, the adhesion model, the Burgers equation and the cosmological Kardar-Parisi-Zhang (KPZ) equation that have been introduced heuristically to solve the problems inherent to cold dark matter (CDM) models find a natural justification and an interesting generalization.", "keyphrases": ["dark matter", "einstein condensate", "astrophysical scale"]}
{"id": "2104.06295", "title": "LyST: a Scalar-Tensor Theory of Gravity on Lyra Manifold", "abstract": "We present a scalar-tensor theory of gravity on a torsion-free and metric compatible Lyra manifold. This is obtained by generalizing the concept of physical reference frame by considering a scale function defined over the manifold. The choice of a specific frame induces a local base, naturally non-holonomic, whose structure constants give rise to extra terms in the expression of the connection coefficients and in the expression for the covariant derivative. In the Lyra manifold, transformations between reference frames involving both coordinates and scale change the transformation law of tensor fields, when compared to those of the Riemann manifold. From a direct generalization of the Einstein-Hilbert minimal action coupled with a matter term, it was possible to build a Lyra invariant action, which gives rise to the associated Lyra Scalar-Tensor theory of gravity (LyST), with field equations for g_\u03bc\u03bd and \u03d5. These equations have a well-defined Newtonian limit, from which it can be seen that both metric and scale play a role in the description gravitational interaction. We present a spherically symmetric solution for the LyST gravity field equations. It dependent on two parameters m and r_L, whose physical meaning is carefully investigated. We highlight the properties of LyST spherically symmetric line element and compare it to Schwarzchild solution.", "keyphrases": ["scalar-tensor theory", "gravity", "lyra manifold"]}
{"id": "1402.7114", "title": "Universe acceleration in modified gravities: F(R) and F(T) cases", "abstract": "We review recent progress on cosmological issues and theoretical properties of modified gravity theories. In particular, we explicitly explore the conformal transformation, the Starobinsky inflation, and a unified scenario of inflation and late time acceleration in F(R) gravity and F(T) gravity (extended teleparallel gravity). Furthermore, we examine neutron stars and the hyperon problem in F(R) gravity. Moreover, for loop quantum cosmology (LQC), the natures of finite-time future singularities in F(T) gravity are presented. In addition, we investigate F(T) gravity theories from the Kaluza-Klein (KK) and Randall-Sundrum (RS) theories.", "keyphrases": ["gravity", "dark energy problem", "late-time cosmic acceleration"]}
{"id": "1606.03843", "title": "Pulsars as probes of gravity and fundamental physics", "abstract": "Radio-loud neutron stars known as pulsars allow a wide range of experimental tests for fundamental physics, ranging from the study of super-dense matter to tests of general relativity and its alternatives. As a result, pulsars provide strong-field tests of gravity, they allow for the direct detection of gravitational waves in a 'pulsar timing array', and they promise the future study of black hole properties. This contribution gives an overview of the on-going experiments and recent results.", "keyphrases": ["gravity", "neutron star", "pulsar"]}
{"id": "1111.1436", "title": "Neutrino mass in cosmology: status and prospects", "abstract": "I give an overview of the effects of neutrino masses in cosmology, focussing on the role they play in the evolution of cosmological perturbations. I discuss how recent observations of the cosmic microwave background anisotropies and the large-scale matter distribution can probe neutrino masses with greater precision than current laboratory experiments. I describe several new techniques that will be used to probe cosmology in the future, as well as recent advances in the computation of the nonlinear matter power spectrum and related observables.", "keyphrases": ["cosmology", "neutrino mass", "dark matter"]}
{"id": "1004.2535", "title": "Role of Galactic sources and magnetic fields in forming the observed energy-dependent composition of ultrahigh-energy cosmic rays", "abstract": "Recent results from Pierre Auger Observatory, showing energy dependent chemical composition of ultrahigh-energy cosmic rays (UHECRs) with a growing fraction of heavy elements at high energies, suggest a possible non-negligible contribution of the Galactic sources. We show that, in the case of UHECRs produced by gamma-ray bursts (GRBs) or rare types of supernova explosions that took place in Milky Way in the past, the change in UHECR composition can result from the difference in diffusion times for different species. The anisotropy in the direction of the Galactic Center is expected to be a few per cent on average, but the locations of the most recent/closest bursts can be associated with observed clusters of UHECRs.", "keyphrases": ["galactic source", "magnetic field", "cosmic ray"]}
{"id": "1506.05976", "title": "Neutrino masses and cosmology with Lyman-alpha forest power spectrum", "abstract": "We present constraints on neutrino masses, the primordial fluctuation spectrum from inflation, and other parameters of the \u039bCDM model, using the one-dimensional Ly\u03b1-forest power spectrum measured by Palanque-Delabrouille et al. (2013) from SDSS-III/BOSS, complemented by Planck 2015 cosmic microwave background (CMB) data and other cosmological probes. This paper improves on the previous analysis by Palanque-Delabrouille et al. (2015) by using a more powerful set of calibrating hydrodynamical simulations that reduces uncertainties associated with resolution and box size, by adopting a more flexible set of nuisance parameters for describing the evolution of the intergalactic medium, by including additional freedom to account for systematic uncertainties, and by using Planck 2015 constraints in place of Planck 2013. Fitting Ly\u03b1 data alone leads to cosmological parameters in excellent agreement with the values derived independently from CMB data, except for a weak tension on the scalar index n_s. Combining BOSS Ly\u03b1 with Planck CMB constrains the sum of neutrino masses to \u2211 m_\u03bd < 0.12 eV (95% C.L.) including all identified systematic uncertainties, tighter than our previous limit (0.15 eV) and more robust. Adding Ly\u03b1 data to CMB data reduces the uncertainties on the optical depth to reionization \u03c4, through the correlation of \u03c4 with \u03c3_8. Similarly, correlations between cosmological parameters help in constraining the tensor-to-scalar ratio of primordial fluctuations r. The tension on n_s can be accommodated by allowing for a running dn_s/dln k. Allowing running as a free parameter in the fits does not change the limit on \u2211 m_\u03bd. We discuss possible interpretations of these results in the context of slow-roll inflation.", "keyphrases": ["cosmology", "cosmic microwave background", "neutrino masse", "dark matter"]}
{"id": "1907.03150", "title": "Effective Field Theory of Dark Energy: a Review", "abstract": "The discovery of cosmic acceleration has triggered a consistent body of theoretical work aimed at modeling its phenomenology and understanding its fundamental physical nature. In recent years, a powerful formalism that accomplishes both these goals has been developed, the so-called effective field theory of dark energy. It can capture the behavior of a wide class of modified gravity theories and classify them according to the imprints they leave on the smooth background expansion history of the Universe and on the evolution of linear perturbations. The effective field theory of dark energy is based on a Lagrangian description of cosmological perturbations which depends on a number of functions of time, some of which are non-minimal couplings representing genuine deviations from General Relativity. Such a formalism is thus particularly convenient to fit and interpret the wealth of new data that will be provided by future galaxy surveys. Despite its recent appearance, this formalism has already allowed a systematic investigation of what lies beyond the General Relativity landscape and provided a conspicuous amount of theoretical predictions and observational results. In this review, we report on these achievements.", "keyphrases": ["dark energy", "general relativity", "effective field theory"]}
{"id": "1212.5018", "title": "A novel approach in the WIMP quest: Cross-Correlation of Gamma-Ray Anisotropies and Cosmic Shear", "abstract": "Both cosmic shear and cosmological gamma-ray emission stem from the presence of Dark Matter (DM) in the Universe: DM structures are responsible for the bending of light in the weak lensing regime and those same objects can emit gamma-rays, either because they host astrophysical sources (active galactic nuclei or star-forming galaxies) or directly by DM annihilations (or decays, depending on the properties of the DM particle). Such gamma-rays should therefore exhibit strong correlation with the cosmic shear signal. In this Letter, we compute the cross-correlation angular power spectrum of cosmic shear and gamma-rays produced by the annihilation/decay of Weakly Interacting Massive Particle (WIMP) DM, as well as from astrophysical sources. We show that this observable provides novel information on the composition of the Extra-galactic Gamma-ray Background (EGB), since the amplitude and shape of the cross-correlation signal strongly depends on which class of source is responsible for the gamma-ray emission. If the DM contribution to the EGB is significant (at least in a definite energy range), although compatible with current observational bounds, its strong correlation with the cosmic shear makes such signal potentially detectable by combining Fermi-LAT data with forthcoming galaxy surveys, like Dark Energy Survey and Euclid. At the same time, the same signal would demonstrate that the weak lensing observables are indeed due to particle DM matter and not to possible modifications of General Relativity.", "keyphrases": ["cross-correlation", "cosmic shear", "dark matter"]}
{"id": "0904.3739", "title": "The Atacama Large Millimeter/submillimeter Array", "abstract": "The Atacama Large Millimeter/submillimeter Array (ALMA) is an international radio telescope under construction in the Atacama Desert of northern Chile. ALMA is situated on a dry site at 5000 m elevation, allowing excellent atmospheric transmission over the instrument wavelength range of 0.3 to 10 mm. ALMA will consist of two arrays of high-precision antennas. One, of up to 64 12-m diameter antennas, is reconfigurable in multiple patterns ranging in size from 150 meters up to 15 km. A second array is comprised of a set of four 12-m and twelve 7-m antennas operating in one of two closely packed configurations 50 m in diameter. The instrument will provide both interferometric and total-power astronomical information on atomic, molecular and ionized gas and dust in the solar system, our Galaxy, and the nearby to high-redshift universe. In this paper we outline the scientific drivers, technical challenges and planned progress of ALMA.", "keyphrases": ["atacama large millimeter", "submillimeter array", "alma"]}
{"id": "1507.05390", "title": "Derivative-dependent metric transformation and physical degrees of freedom", "abstract": "We study metric transformations which depend on a scalar field \u03d5 and its first derivatives and confirm that the number of physical degrees of freedom does not change under such transformations, as long as they are not singular. We perform a Hamiltonian analysis of a simple model in the gauge \u03d5 = t. In addition, we explicitly show that the transformation and the gauge fixing do commute in transforming the action. We then extend the analysis to more general gravitational theories and transformations in general gauges. We verify that the set of all constraints and the constraint algebra are left unchanged by such transformations and conclude that the number of degrees of freedom is not modified by a regular and invertible generic transformation among two metrics. We also discuss the implications on the recently called \"hidden\" constraints and on the case of a singular transformation, a.k.a. mimetic gravity.", "keyphrases": ["transformation", "physical degree", "gravity", "singular limit", "setup"]}
{"id": "1302.6717", "title": "Back-Reaction in Relativistic Cosmology", "abstract": "We introduce the concept of back-reaction in relativistic cosmological modeling. Roughly speaking, this can be thought of as the difference between the large-scale behaviour of an inhomogeneous cosmological solution of Einstein's equations, and a homogeneous and isotropic solution that is a best-fit to either the average of observables or dynamics in the inhomogeneous solution. This is sometimes paraphrased as `the effect that structure has of the large-scale evolution of the universe'. Various different approaches have been taken in the literature in order to try and understand back-reaction in cosmology. We provide a brief and critical summary of some of them, highlighting recent progress that has been made in each case.", "keyphrases": ["cosmology", "einstein", "back-reaction"]}
{"id": "1309.4924", "title": "Remarks on mechanical approach to observable Universe", "abstract": "We consider the Universe deep inside the cell of uniformity. At these scales, the Universe is filled with inhomogeneously distributed discrete structures (galaxies, groups and clusters of galaxies), which perturb the background Friedmann model. Here, the mechanical approach (Eingorn Zhuk, 2012) is the most appropriate to describe the dynamics of the inhomogeneities which is defined, on the one hand, by gravitational potentials of inhomogeneities and, on the other hand, by the cosmological expansion of the Universe. In this paper, we present additional arguments in favor of this approach. First, we estimate the size of the cell of uniformity. With the help of the standard methods of statistical physics and for the galaxies of the type of the Milky Way and Andromeda, we get that it is of the order of 190 Mpc which is rather close to observations. Then, we show that the nonrelativistic approximation (with respect to the peculiar velocities) is valid for z \u2272 10, i.e. approximately for 13 billion years from the present moment. We consider scalar perturbations and, within the \u039bCDM model, justify the main equations. Moreover, we demonstrate that radiation can be naturally incorporated into our scheme. This emphasizes the viability of our approach. This approach gives a possibility to analyze different cosmological models and compare them with the observable Universe. For example, we indicate some problematic aspects of the spatially flat models. Such models require a rather specific distribution of the inhomogeneities to get a finite potential at any points outside gravitating masses. We also criticize the application of the Schwarzschild-de Sitter solution to the description of the motion of test bodies on the cosmological background.", "keyphrases": ["mechanical approach", "universe", "inhomogeneity", "cosmological model"]}
{"id": "1107.3145", "title": "The relation between metallicity, stellar mass and star formation in galaxies: an analysis of observational and model data", "abstract": "We study relations between stellar mass, star formation and gas-phase metallicity in a sample of 177,071 unique emission line galaxies from the SDSS-DR7, as well as in a sample of 43,767 star forming galaxies at z=0 from the cosmological semi-analytic model L-GALAXIES. We demonstrate that metallicity is dependent on star formation rate at fixed mass, but that the trend is opposite for low and for high mass galaxies. Low-mass galaxies that are actively forming stars are more metal-poor than quiescent low-mass galaxies. High-mass galaxies, on the other hand, have lower gas-phase metallicities if their star formation rates are small. Remarkably, the same trends are found for our sample of model galaxies. We find that massive model galaxies with low gas-phase metallicities have undergone a gas-rich merger in the past, inducing a starburst which exhausted their cold gas reservoirs and shut down star formation. This led to a gradual dilution in the gas-phase metallicities of these systems via accretion of gas. These model galaxies have lower-than-average gas-to-stellar mass ratios and higher-than-average central black hole masses. We confirm that massive galaxies with low gas-phase metallicities in our observational sample also have very massive black holes. We propose that accretion may therefore play a significant role in regulating the gas-phase metallicities of present-day massive galaxies.", "keyphrases": ["metallicity", "stellar mass", "galaxy"]}
{"id": "1808.02877", "title": "Dark Energy in the Swampland", "abstract": "In this Letter, we study the implications of string Swampland criteria for dark energy in view of ongoing and future cosmological observations. If string theory should be the ultimate quantum gravity theory, there is evidence that exact de Sitter solutions with a positive cosmological constant cannot describe the fate of the late-time universe. Even though cosmological models with dark energy given by a scalar field \u03c0 evolving in time are not in direct tension with string theory, they have to satisfy the Swampland criteria |\u0394\u03c0|<d\u223c\ud835\udcaa(1) and |V'|/V>c\u223c\ud835\udcaa(1), where V is the scalar field potential. In view of the restrictive implications that the Swampland criteria have on dark energy, we investigate the accuracy needed for future observations to tightly constrain standard dark-energy models. We find that current 3-\u03c3 constraints with c \u2272 1.35 are still well in agreement with the string Swampland criteria. However, Stage-4 surveys such as Euclid, LSST and DESI, tightly constraining the equation of state w(z), will start putting surviving quintessence models into tensions with the string Swampland criteria by demanding c<0.4. We further investigate whether any idealised futuristic survey will ever be able to give a decisive answer to the question whether the cosmological constant would be preferred over a time-evolving dark-energy model within the Swampland criteria. Hypothetical surveys with a reduction in the uncertainties by a factor of \u223c20 compared to Euclid would be necessary to reveal strong tension between quintessence models obeying the string Swampland criteria and observations by pushing the allowed values down to c<0.1. In view of such perspectives, there will be fundamental observational limitations with future surveys.", "keyphrases": ["swampland", "sitter solution", "cosmological constant", "dark energy"]}
{"id": "1611.00036", "title": "The DESI Experiment Part I: Science,Targeting, and Survey Design", "abstract": "DESI (Dark Energy Spectroscopic Instrument) is a Stage IV ground-based dark energy experiment that will study baryon acoustic oscillations (BAO) and the growth of structure through redshift-space distortions with a wide-area galaxy and quasar redshift survey. To trace the underlying dark matter distribution, spectroscopic targets will be selected in four classes from imaging data. We will measure luminous red galaxies up to z=1.0. To probe the Universe out to even higher redshift, DESI will target bright [O II] emission line galaxies up to z=1.7. Quasars will be targeted both as direct tracers of the underlying dark matter distribution and, at higher redshifts (2.1 < z < 3.5), for the Ly-\u03b1 forest absorption features in their spectra, which will be used to trace the distribution of neutral hydrogen. When moonlight prevents efficient observations of the faint targets of the baseline survey, DESI will conduct a magnitude-limited Bright Galaxy Survey comprising approximately 10 million galaxies with a median z\u2248 0.2. In total, more than 30 million galaxy and quasar redshifts will be obtained to measure the BAO feature and determine the matter power spectrum, including redshift space distortions.", "keyphrases": ["desi", "galaxy", "precision", "large-scale structure", "generation"]}
{"id": "2002.12778", "title": "Constraints on Primordial Black Holes", "abstract": "We update the constraints on the fraction of the Universe that may have gone into primordial black holes (PBHs) over the mass range 10^-5\u201310^50 g. Those smaller than \u223c 10^15 g would have evaporated by now due to Hawking radiation, so their abundance at formation is constrained by the effects of evaporated particles on big bang nucleosynthesis, the cosmic microwave background (CMB), the Galactic and extragalactic \u03b3-ray and cosmic ray backgrounds and the possible generation of stable Planck mass relics. PBHs larger than \u223c 10^15 g are subject to a variety of constraints associated with gravitational lensing, dynamical effects, influence on large-scale structure, accretion and gravitational waves. We discuss the constraints on both the initial collapse fraction and the current fraction of the CDM in PBHs at each mass scale but stress that many of the constraints are associated with observational or theoretical uncertainties. We also consider indirect constraints associated with the amplitude of the primordial density fluctuations, such as second-order tensor perturbations and \u03bc-distortions arising from the effect of acoustic reheating on the CMB, if PBHs are created from the high-\u03c3 peaks of nearly Gaussian fluctuations. Finally we discuss how the constraints are modified if the PBHs have an extended mass function, this being relevant if PBHs provide some combination of the dark matter, the LIGO/Virgo coalescences and the seeds for cosmic structure. Even if PBHs make a small contribution to the dark matter, they could play an important cosmological role and provide a unique probe of the early Universe.", "keyphrases": ["black hole", "universe", "primordial density fluctuation", "dark matter", "observational constraint"]}
{"id": "1808.04493", "title": "The Simons Observatory: Instrument Overview", "abstract": "The Simons Observatory (SO) will make precise temperature and polarization measurements of the cosmic microwave background (CMB) using a set of telescopes which will cover angular scales between 1 arcminute and tens of degrees, contain over 60,000 detectors, and observe at frequencies between 27 and 270 GHz. SO will consist of a 6 m aperture telescope coupled to over 30,000 transition-edge sensor bolometers along with three 42 cm aperture refractive telescopes, coupled to an additional 30,000+ detectors, all of which will be located in the Atacama Desert at an altitude of 5190 m. The powerful combination of large and small apertures in a CMB observatory will allow us to sample a wide range of angular scales over a common survey area. SO will measure fundamental cosmological parameters of our universe, constrain primordial fluctuations, find high redshift clusters via the Sunyaev-Zel`dovich effect, constrain properties of neutrinos, and trace the density and velocity of the matter in the universe over cosmic time. The complex set of technical and science requirements for this experiment has led to innovative instrumentation solutions which we will discuss. The large aperture telescope will couple to a cryogenic receiver that is 2.4 m in diameter and nearly 3 m long, creating a number of technical challenges. Concurrently, we are designing the array of cryogenic receivers housing the 42 cm aperture telescopes. We will discuss the sensor technology SO will use and we will give an overview of the drivers for and designs of the SO telescopes and receivers, with their cold optical components and detector arrays.", "keyphrases": ["simons observatory", "telescope", "small aperture", "series"]}
{"id": "2008.04323", "title": "IceCube-Gen2: The Window to the Extreme Universe", "abstract": "The observation of electromagnetic radiation from radio to \u03b3-ray wavelengths has provided a wealth of information about the universe. However, at PeV (10^15 eV) energies and above, most of the universe is impenetrable to photons. New messengers, namely cosmic neutrinos, are needed to explore the most extreme environments of the universe where black holes, neutron stars, and stellar explosions transform gravitational energy into non-thermal cosmic rays. The discovery of cosmic neutrinos with IceCube has opened this new window on the universe. In this white paper, we present an overview of a next-generation instrument, IceCube-Gen2, which will sharpen our understanding of the processes and environments that govern the universe at the highest energies. IceCube-Gen2 is designed to: 1) Resolve the high-energy neutrino sky from TeV to EeV energies; 2) Investigate cosmic particle acceleration through multi-messenger observations; 3) Reveal the sources and propagation of the highest energy particles in the universe; 4) Probe fundamental physics with high-energy neutrinos. IceCube-Gen2 will increase the annual rate of observed cosmic neutrinos by a factor of ten compared to IceCube, and will be able to detect sources five times fainter than its predecessor. Furthermore, through the addition of a radio array, IceCube-Gen2 will extend the energy range by several orders of magnitude compared to IceCube. Construction will take 8 years and cost about $350M. The goal is to have IceCube-Gen2 fully operational by 2033. IceCube-Gen2 will play an essential role in shaping the new era of multi-messenger astronomy, fundamentally advancing our knowledge of the high-energy universe. This challenging mission can be fully addressed only in concert with the new survey instruments across the electromagnetic spectrum and gravitational wave detectors which will be available in the coming years.", "keyphrases": ["window", "pev", "neutrino", "icecube-gen2"]}
{"id": "1703.04793", "title": "When the Universe Expands Too Fast: Relentless Dark Matter", "abstract": "We consider a modification to the standard cosmological history consisting of introducing a new species \u03d5 whose energy density red-shifts with the scale factor a like \u03c1_\u03d5\u221d a^-(4+n). For n>0, such a red-shift is faster than radiation, hence the new species dominates the energy budget of the universe at early times while it is completely negligible at late times. If equality with the radiation energy density is achieved at low enough temperatures, dark matter can be produced as a thermal relic during the new cosmological phase. Dark matter freeze-out then occurs at higher temperatures compared to the standard case, implying that reproducing the observed abundance requires significantly larger annihilation rates. Here, we point out a completely new phenomenon, which we refer to as relentless dark matter: for large enough n, unlike the standard case where annihilation ends shortly after the departure from thermal equilibrium, dark matter particles keep annihilating long after leaving chemical equilibrium, with a significant depletion of the final relic abundance. Relentless annihilation occurs for n \u2265 2 and n \u2265 4 for s-wave and p-wave annihilation, respectively, and it thus occurs in well motivated scenarios such as a quintessence with a kination phase. We discuss a few microscopic realizations for the new cosmological component and highlight the phenomenological consequences of our calculations for dark matter searches.", "keyphrases": ["universe", "dark matter", "non-standard cosmology"]}
{"id": "1511.04277", "title": "Indirect (source-free) integration method. II. Self-force consistent radial fall", "abstract": "We apply our method of indirect integration, described in Part I, at fourth order, to the radial fall affected by the self-force. The Mode-Sum regularisation is performed in the Regge-Wheeler gauge using the equivalence with the harmonic gauge for this orbit. We consider also the motion subjected to a self-consistent and iterative correction determined by the self-force through osculating stretches of geodesics. The convergence of the results confirms the validity of the integration method. This work complements and justifies the analysis and the results appeared in Int. J. Geom. Meth. Mod. Phys., 11, 1450090 (2014).", "keyphrases": ["integration method", "self-force", "radial fall"]}
{"id": "1409.0540", "title": "The Landscape of the Neutrino Mechanism of Core-Collapse Supernovae: Neutron Star and Black Hole Mass Functions, Explosion Energies and Nickel Yields", "abstract": "If the neutrino luminosity from the proto-neutron star formed during a massive star core collapse exceeds a critical threshold, a supernova (SN) results. Using spherical quasi-static evolutionary sequences for hundreds of progenitors over a range of metallicities, we study how the explosion threshold maps onto observables, including the fraction of successful explosions, the neutron star (NS) and black hole (BH) mass functions, the explosion energies (E_SN) and nickel yields (M_Ni), and their mutual correlations. Successful explosions are intertwined with failures in a complex pattern that is not simply related to initial progenitor mass or compactness. We predict that progenitors with initial masses of 15 +/- 1, 19 +/- 1, and 21-26 M_Sun are most likely to form BHs, that the BH formation probability is non-zero at solar-metallicity and increases significantly at low metallicity, and that low luminosity, low Ni-yield SNe come from progenitors close to success/failure interfaces. We qualitatively reproduce the observed E_SN-M_Ni correlation, we predict a correlation between the mean and width of the NS mass and E_SN distributions, and that the means of the NS and BH mass distributions are correlated. We show that the observed mean NS mass of 1.33 M_Sun implies that the successful explosion fraction is higher than 0.35. Overall, we show that the neutrino mechanism can in principle explain the observed properties of SNe and their compact objects. We argue that the rugged landscape of progenitors and outcomes mandates that SN theory should focus on reproducing the wide ranging distributions of observed SN properties.", "keyphrases": ["neutrino mechanism", "neutron star", "black hole"]}
{"id": "1003.3459", "title": "Quantum Radiation of Oscillons", "abstract": "Many classical scalar field theories possess remarkable solutions: coherently oscillating, localized clumps, known as oscillons. In many cases, the decay rate of classical small amplitude oscillons is known to be exponentially suppressed and so they are extremely long lived. In this work we compute the decay rate of quantized oscillons. We find it to be a power law in the amplitude and couplings of the theory. Therefore, the quantum decay rate is very different to the classical decay rate and is often dominant. We show that essentially all oscillons eventually decay by producing outgoing radiation. In single field theories the outgoing radiation has typically linear growth, while if the oscillon is coupled to other bosons the outgoing radiation can have exponential growth. The latter is a form of parametric resonance: explosive energy transfer from a localized clump into daughter fields. This may lead to interesting phenomenology in the early universe. Our results are obtained from a perturbative analysis, a non-perturbative Floquet analysis, and numerics.", "keyphrases": ["radiation", "oscillon", "field theory", "lifetime"]}
{"id": "1108.0403", "title": "Production of dust by massive stars at high redshift", "abstract": "The large amounts of dust detected in sub-millimeter galaxies and quasars at high redshift pose a challenge to galaxy formation models and theories of cosmic dust formation. At z > 6 only stars of relatively high mass (> 3 Msun) are sufficiently short-lived to be potential stellar sources of dust. This review is devoted to identifying and quantifying the most important stellar channels of rapid dust formation. We ascertain the dust production efficiency of stars in the mass range 3-40 Msun using both observed and theoretical dust yields of evolved massive stars and supernovae (SNe) and provide analytical expressions for the dust production efficiencies in various scenarios. We also address the strong sensitivity of the total dust productivity to the initial mass function. From simple considerations, we find that, in the early Universe, high-mass (> 3 Msun) asymptotic giant branch stars can only be dominant dust producers if SNe generate < 3 x 10^-3 Msun of dust whereas SNe prevail if they are more efficient. We address the challenges in inferring dust masses and star-formation rates from observations of high-redshift galaxies. We conclude that significant SN dust production at high redshift is likely required to reproduce current dust mass estimates, possibly coupled with rapid dust grain growth in the interstellar medium.", "keyphrases": ["dust", "massive star", "high redshift"]}
{"id": "1606.08474", "title": "Magnetogenesis from axion inflation", "abstract": "In this work we compute the production of magnetic fields in models of axion inflation coupled to the hypercharge sector of the Standard Model through a Chern-Simons interaction term. We make the simplest choice of a quadratic inflationary potential and use lattice simulations to calculate the magnetic field strength, helicity and correlation length at the end of inflation. For small values of the axion-gauge field coupling strength the results agree with no-backreaction calculations and estimates found in the literature. For larger couplings the helicity of the magnetic field differs from the no-backreaction estimate and depends strongly on the comoving wavenumber. We estimate the post-inflationary evolution of the magnetic field based on known results for the evolution of helical and non-helical magnetic fields. The magnetic fields produced by axion inflation with large couplings to U(1)_Y can reach B_ eff\u2273 10^-16 G, exhibiting a field strength B_ phys\u2248 10^-13 G and a correlation length \u03bb_ phys\u224810 pc. This result is insensitive to the exact value of the coupling, as long as the coupling is large enough to allow for instantaneous preheating. Depending on the assumptions for the physical processes that determine blazar properties, these fields can be found consistent with blazar observations based on the value of B_ eff. Finally, the intensity of the magnetic field for large coupling can be enough to satisfy the requirements for a recently proposed baryogenesis mechanism, which utilizes the chiral anomaly of the Standard Model.", "keyphrases": ["axion inflation", "magnetogenesis", "gauge field"]}
{"id": "1603.05834", "title": "Bouncing Cosmologies: Progress and Problems", "abstract": "We review the status of bouncing cosmologies as alternatives to cosmological inflation for providing a description of the very early universe, and a source for the cosmological perturbations which are observed today. We focus on the motivation for considering bouncing cosmologies, the origin of fluctuations in these models, and the challenges which various implementations face.", "keyphrases": ["cosmology", "bounce", "primordial perturbation", "string gas cosmology", "gravity"]}
{"id": "0904.1938", "title": "Magnetic fields of non-degenerate stars", "abstract": "Magnetic fields are present in a wide variety of stars throughout the HR diagram and play a role at basically all evolutionary stages, from very-low-mass dwarfs to very massive stars, and from young star-forming molecular clouds and protostellar accretion discs to evolved giants/supergiants and magnetic white dwarfs/neutron stars. These fields range from a few microG (e.g., in molecular clouds) to TeraG and more (e.g., in magnetic neutron stars); in non-degenerate stars in particular, they feature large-scale topologies varying from simple nearly-axisymmetric dipoles to complex non-axsymmetric structures, and from mainly poloidal to mainly toroidal topology. After recalling the main techniques of detecting and modelling stellar magnetic fields, we review the existing properties of magnetic fields reported in cool, hot and young non-degenerate stars and protostars, and discuss our understanding of the origin of these fields and their impact on the birth and life of stars.", "keyphrases": ["star", "stellar magnetic field", "magnetic field"]}
{"id": "0908.4089", "title": "Naturally inflating on steep potentials through electromagnetic dissipation", "abstract": "In models of natural inflation, the inflaton is an axion-like particle. Unfortunately, axion potentials in UV-complete theories appear to be too steep to drive inflation. We show that, even for a steep potential, natural inflation can occur if the coupling between axion and gauge fields is taken into account. Due to this coupling, quanta of the gauge field are produced by the rolling of the axion. If the coupling is large enough, such a dissipative effect slows down the axion, leading to inflation even for a steep potential. The spectrum of perturbations is quasi-scale invariant, but in the simplest construction its amplitude is larger than 10^-5. We discuss a possible way out of this problem.", "keyphrases": ["steep potential", "dissipation", "gauge field", "axionic coupling", "steep inflation"]}
{"id": "1604.00246", "title": "Gravitational-wave signal from binary neutron stars: a systematic analysis of the spectral properties", "abstract": "A number of works have shown that important information on the equation of state of matter at nuclear density can be extracted from the gravitational waves emitted by merging neutron-star binaries. We present a comprehensive analysis of the gravitational-wave signal emitted during the inspiral, merger and post-merger of 56 neutron-star binaries. This sample of binaries, arguably the largest studied to date with realistic equations of state, spans across six different nuclear-physics equations of state and ten masses, allowing us to sharpen a number of results recently obtained on the spectral properties of the gravitational-wave signal. Overall we find that: (i) for binaries with masses differing no more than 20%, the frequency at gravitational-wave amplitude's maximum is related quasi-universally with the tidal deformability of the two stars; (ii) the spectral properties vary during the post-merger phase, with a transient phase lasting a few millisecond after the merger and followed by a quasi-stationary phase; (iii) when distinguishing the spectral peaks between these two phases, a number of ambiguities in the identification of the peaks disappear, leaving a simple and robust picture; (iv) using properly identified frequencies, quasi-universal relations are found between the spectral features and the properties of the neutron stars; (v) for the most salient peaks analytic fitting functions can be obtained in terms of the stellar tidal deformability or compactness. Altogether, these results support the idea that the equation of state of nuclear matter can be constrained tightly when a signal in gravitational waves from binary neutron stars is detected.", "keyphrases": ["neutron star", "spectral property", "gravitational-wave signal"]}
{"id": "1404.2249", "title": "Teleparallel equivalent of Gauss-Bonnet gravity and its modifications", "abstract": "Inspired by the teleparallel formulation of General Relativity, whose Lagrangian is the torsion invariant T, we have constructed the teleparallel equivalent of Gauss-Bonnet gravity in arbitrary dimensions. Without imposing the Weitzenbock connection, we have extracted the torsion invariant T_G, equivalent (up to boundary terms) to the Gauss-Bonnet term G. T_G is constructed by the vielbein and the connection, it contains quartic powers of the torsion tensor, it is diffeomorphism and Lorentz invariant, and in four dimensions it reduces to a topological invariant as expected. Imposing the Weitzenbock connection, T_G depends only on the vielbein, and this allows us to consider a novel class of modified gravity theories based on F(T,T_G), which is not spanned by the class of F(T) theories, nor by the F(R,G) class of curvature modified gravity. Finally, varying the action we extract the equations of motion for F(T,T_G) gravity.", "keyphrases": ["gravity", "teleparallel equivalent", "higher-curvature modification"]}
{"id": "1704.03351", "title": "Born-Infeld inspired modifications of gravity", "abstract": "General Relativity has shown an outstanding observational success in the scales where it has been directly tested. However, modifications have been intensively explored in the regimes where it seems either incomplete or signals its own limit of validity. In particular, the breakdown of unitarity near the Planck scale strongly suggests that General Relativity needs to be modified at high energies and quantum gravity effects are expected to be important. This is related to the existence of spacetime singularities when the solutions of General Relativity are extrapolated to regimes where curvatures are large. In this sense, Born-Infeld inspired modifications of gravity have shown an extraordinary ability to regularise the gravitational dynamics, leading to non-singular cosmologies and regular black hole spacetimes in a very robust manner and without resorting to quantum gravity effects. This has boosted the interest in these theories in applications to stellar structure, compact objects, inflationary scenarios, cosmological singularities, and black hole and wormhole physics, among others. We review the motivations, various formulations, and main results achieved within these theories, including their observational viability, and provide an overview of current open problems and future research opportunities.", "keyphrases": ["gravity", "non-singular cosmology", "manner", "born-infeld"]}
{"id": "1401.0586", "title": "Hot Accretion Flows Around Black Holes", "abstract": "Black hole accretion flows can be divided into two broad classes: cold and hot. Cold accretion flows, which consist of cool optically thick gas, are found at relatively high mass accretion rates. Prominent examples are the standard thin disk, which occurs at a fraction of the Eddington mass accretion rate, and the slim disk at super-Eddington rates. These accretion flows are responsible for luminous systems such as active galactic nuclei radiating at or close to the Eddington luminosity and black hole X-ray binaries in the soft state. Hot accretion flows, the topic of this review, are virially hot and optically thin. They occur at lower mass accretion rates, and are described by models such as the advection-dominated accretion flow and luminous hot accretion flow. Because of energy advection, the radiative efficiency of these flows is in general lower than that of a standard thin accretion disk. Moreover, the efficiency decreases with decreasing mass accretion rate. Observations show that hot accretion flows are associated with jets. In addition, theoretical arguments suggest that hot flows should produce strong winds. Hot accretion flows are believed to be present in low-luminosity active galactic nuclei and in black hole X-ray binaries in the hard and quiescent states. The prototype is Sgr A*, the ultra-low-luminosity supermassive black hole at our Galactic center. The jet, wind and radiation from a supermassive black hole with a hot accretion flow can interact with the external interstellar medium and modify the evolution of the host galaxy. Details of this \"maintenance-mode feedback\" could, in principle, be worked out through theoretical studies and numerical simulations of hot accretion flows.", "keyphrases": ["accretion", "black hole", "astrophysic"]}
{"id": "1610.03763", "title": "Gravitational waves at interferometer scales and primordial black holes in axion inflation", "abstract": "We study the prospects of detection at terrestrial and space interferometers, as well as at pulsar timing array experiments, of a stochastic gravitational wave background which can be produced in models of axion inflation. This potential signal, and the development of these experiments, open a new window on inflation on scales much smaller than those currently probed with Cosmic Microwave Background and Large Scale Structure measurements. The sourced signal generated in axion inflation is an ideal candidate for such searches, since it naturally grows at small scales, and it has specific properties (chirality and non-gaussianity) that can distinguish it from an astrophysical background. We study under which conditions such a signal can be produced at an observable level, without the simultaneous overproduction of scalar perturbations in excess of what is allowed by the primordial black hole limits. We also explore the possibility that scalar perturbations generated in a modified version of this model may provide a distribution of primordial black holes compatible with the current bounds, that can act as a seeds of the present black holes in the universe.", "keyphrases": ["primordial black hole", "axion inflation", "gravitational wave"]}
{"id": "1012.4697", "title": "Constraints on the induced gravitational wave background from primordial black holes", "abstract": "We perform a consistent calculation of primordial black hole (PBH) mass spectrum and second-order induced gravitational wave (GW) background produced from primordial scalar perturbations in radiation era of the early Universe. It is shown that the maximal amplitudes of the second order GW spectrum that can be approached without conflicting with the PBH data do not depend significantly on the shape of primordial perturbation spectrum. The constraints on the GW background obtained in previous works are extended to a wider GW frequency range. We discuss the applicability of the currently available pulsar timing limits for obtaining the constraints on scalar power spectrum and PBH abundance and show that they can be used for strongly constraining the PBH number density in the PBH mass range \u223c (0.03 - 10) M_\u2299.", "keyphrases": ["primordial black hole", "scalar perturbation", "early universe"]}
{"id": "1108.5600", "title": "Cosmological parameter estimation using Particle Swarm Optimization (PSO)", "abstract": "Obtaining the set of cosmological parameters consistent with observational data is an important exercise in current cosmological research. It involves finding the global maximum of the likelihood function in the multi-dimensional parameter space. Currently sampling based methods, which are in general stochastic in nature, like Markov-Chain Monte Carlo(MCMC), are being commonly used for parameter estimation. The beauty of stochastic methods is that the computational cost grows, at the most, linearly in place of exponentially (as in grid based approaches) with the dimensionality of the search space. MCMC methods sample the full joint probability distribution (posterior) from which one and two dimensional probability distributions, best fit (average) values of parameters and then error bars can be computed. In the present work we demonstrate the application of another stochastic method, named Particle Swarm Optimization (PSO), that is widely used in the field of engineering and artificial intelligence, for cosmological parameter estimation from WMAP seven years data. We find that there is a good agreement between the values of the best fit parameters obtained from PSO and publicly available code COSMOMC. However, there is a slight disagreement between error bars mainly due to the fact that errors are computed differently in PSO. Apart from presenting the results of our exercise, we also discuss the merits of PSO and explain its usefulness in more extensive search in higher dimensional parameter space.", "keyphrases": ["particle swarm optimization", "pso", "cosmological parameter estimation"]}
{"id": "2007.06481", "title": "GW190425, GW190521 and GW190814: Three candidate mergers of primordial black holes from the QCD epoch", "abstract": "The two recent gravitational-wave events GW190425 and GW190814 from the third observing run of LIGO/Virgo have both a companion which is unexpected if originated from a neutron star or a stellar black hole, with masses [1.6-2.5] M_\u2299 and [2.5-2.7] M_\u2299 and merging rates 460^+1050_-360 and 7^+16_-6 events/yr/Gpc^3 respectively, at 90% c.l.. Moreover, the recent event GW190521 has black hole components with masses 67 and 91 M_\u2299, and therefore lies in the so-called pair-instability mass gap, where there should not be direct formation of stellar black holes. The possibility that all of these compact objects are Primordial Black Holes (PBHs) is investigated. The known thermal history of the Universe predicts that PBH formation is boosted at the time of the QCD transition, inducing a peak in their distribution at this particular mass scale, and a bump around 30-50 M_\u2299. We find that the merging rates inferred from GW190425, GW190521 and GW190814 are consistent with PBH binaries formed by capture in dense halos in the matter era or in the early universe. At the same time, the rate of black hole mergers around 30 M_\u2299 and of sub-solar PBH mergers do not exceed the LIGO/Virgo limits. Such PBHs could explain a significant fraction, or even the totality of the Dark Matter, but they must be sufficiently strongly clustered in order to be consistent with current astrophysical limits.", "keyphrases": ["black hole", "early universe", "dark matter"]}
{"id": "2001.03624", "title": "The Expansion of the Universe is Faster than Expected", "abstract": "The present rate of the expansion of our Universe, the Hubble constant, can be predicted from the cosmological model using measurements of the early Universe, or more directly measured from the late Universe. But as these measurements improved, a surprising disagreement between the two appeared. In 2019, a number of independent measurements of the late Universe using different methods and data provided consistent results making the discrepancy with the early Universe predictions increasingly hard to ignore. We review key advances realized by 2019: \u2013 The local or late Universe measurement of the Hubble constant improved from 10 \u2013 In 2019, multiple independent teams presented measurements with different methods and different calibrations to produce consistent results. \u2013 These late Universe estimations disagree at 4\u03c3 to 6\u03c3 with predictions made from the Cosmic Microwave Background in conjunction with the standard cosmological model, a disagreement that is hard to explain or ignore.", "keyphrases": ["universe", "hubble constant", "cosmological observation"]}
{"id": "0909.0259", "title": "Particle Clumping and Planetesimal Formation Depend Strongly on Metallicity", "abstract": "We present three-dimensional numerical simulations of particle clumping and planetesimal formation in protoplanetary disks with varying amounts of solid material. As centimeter-size pebbles settle to the mid-plane, turbulence develops through vertical shearing and streaming instabilities. We find that when the pebble-to-gas column density ratio is 0.01, corresponding roughly to solar metallicity, clumping is weak, so the pebble density rarely exceeds the gas density. Doubling the column density ratio leads to a dramatic increase in clumping, with characteristic particle densities more than ten times the gas density and maximum densities reaching several thousand times the gas density. This is consistent with unstratified simulations of the streaming instability that show strong clumping in particle dominated flows. The clumps readily contract gravitationally into interacting planetesimals of order 100 km in radius. Our results suggest that the correlation between host star metallicity and exoplanets may reflect the early stages of planet formation. We further speculate that initially low metallicity disks can be particle enriched during the gas dispersal phase, leading to a late burst of planetesimal formation.", "keyphrases": ["planetesimal formation", "metallicity", "particle clumping"]}
{"id": "1701.08165", "title": "Dynamical dark energy in light of the latest observations", "abstract": "A flat Friedman-Roberson-Walker universe dominated by a cosmological constant (\u039b) and cold dark matter (CDM) has been the working model preferred by cosmologists since the discovery of cosmic acceleration. However, tensions of various degrees of significance are known to be present among existing datasets within the \u039bCDM framework. In particular, the Lyman-\u03b1 forest measurement of the Baryon Acoustic Oscillations (BAO) by the Baryon Oscillation Spectroscopic Survey (BOSS) prefers a smaller value of the matter density fraction \u03a9_ M compared to the value preferred by cosmic microwave background (CMB). Also, the recently measured value of the Hubble constant, H_0=73.24\u00b11.74 km s^-1 Mpc^-1, is 3.4\u03c3 higher than 66.93\u00b10.62 km s^-1 Mpc^-1 inferred from the Planck CMB data. In this work, we investigate if these tensions can be interpreted as evidence for a non-constant dynamical dark energy (DE). Using the Kullback-Leibler (KL) divergence to quantify the tension between datasets, we find that the tensions are relieved by an evolving DE, with the dynamical DE model preferred at a 3.5\u03c3 significance level based on the improvement in the fit alone. While, at present, the Bayesian evidence for the dynamical DE is insufficient to favour it over \u039bCDM, we show that, if the current best fit DE happened to be the true model, it would be decisively detected by the upcoming DESI survey.", "keyphrases": ["dark energy", "cosmology", "new physics", "expansion history", "dark matter effect"]}
{"id": "1105.3182", "title": "A Measurement of the Damping Tail of the Cosmic Microwave Background Power Spectrum with the South Pole Telescope", "abstract": "We present a measurement of the angular power spectrum of the cosmic microwave background (CMB) using data from the South Pole Telescope (SPT). The data consist of 790 square degrees of sky observed at 150 GHz during 2008 and 2009. Here we present the power spectrum over the multipole range 650 < ell < 3000, where it is dominated by primary CMB anisotropy. We combine this power spectrum with the power spectra from the seven-year Wilkinson Microwave Anisotropy Probe (WMAP) data release to constrain cosmological models. We find that the SPT and WMAP data are consistent with each other and, when combined, are well fit by a spatially flat, LCDM cosmological model. The SPT+WMAP constraint on the spectral index of scalar fluctuations is ns = 0.9663 +/- 0.0112. We detect, at 5-sigma significance, the effect of gravitational lensing on the CMB power spectrum, and find its amplitude to be consistent with the LCDM cosmological model. We explore a number of extensions beyond the LCDM model. Each extension is tested independently, although there are degeneracies between some of the extension parameters. We constrain the tensor-to-scalar ratio to be r < 0.21 (95 index to be dns/dlnk = -0.024 +/- 0.013. We strongly detect the effects of primordial helium and neutrinos on the CMB; a model without helium is rejected at 7.7-sigma, while a model without neutrinos is rejected at 7.5-sigma. The primordial helium abundance is measured to be Yp = 0.296 +/- 0.030, and the effective number of relativistic species is measured to be Neff = 3.85 +/- 0.62. The constraints on these models are strengthened when the CMB data are combined with measurements of the Hubble constant and the baryon acoustic oscillation feature. Notable improvements include ns = 0.9668 +/- 0.0093, r < 0.17 (95", "keyphrases": ["cosmic microwave background", "power spectrum", "south pole telescope", "neutrino"]}
{"id": "1607.08781", "title": "Radio detection of Cosmic-Ray Air Showers and High-Energy Neutrinos", "abstract": "This review provides an introduction to the radio emission by particle cascades, an overview on the various experiments, and explains methods for the radio measurement of air-shower properties. Furthermore, potential applications of the radio technique in high-energy astroparticle physics are discussed. Due to the successful operation of digital radio experiments and due to the improved quantitative understanding of the emission, radio detection is back on the list of promising techniques for extensive air showers. With a threshold of about 100 PeV radio detectors are particularly useful to study the highest-energy galactic cosmic rays and ultra-high-energy extragalactic particles of all types. Various antenna arrays like LOPES, CODALEMA, AERA, LOFAR, and Tunka-Rex have shown that radio measurements can compete in precision with other techniques, in particular for the arrival direction, the energy, and the position of the shower maximum. The scientific potential of the radio technique seems to be maximum in combination with particle detectors, which increases the total accuracy for air-shower measurements. This is crucial for a better separation of different primary particles, like gamma-ray photons, neutrinos, or different types of nuclei. In addition to air-showers the radio technique can be used for particle cascades in dense media. Several pioneering experiments like ARA, ARIANNA, and ANITA are currently searching for cascades induced by ultra-high-energy neutrinos in ice. Moreover, several future projects aim at both, high-energy cosmic-rays and neutrinos. SKA will search for neutrino and cosmic-ray initiated cascades in the lunar regolith and provide unprecedented detail for air-shower measurements. Finally, radio detectors with huge exposure like GRAND, SWORD, or EVA are being considered to study the highest energy cosmic rays and neutrinos.", "keyphrases": ["air shower", "cosmic ray", "radio detection", "ultra-high energy"]}
{"id": "2202.03381", "title": "High-Energy Neutrinos from Active Galactic Nuclei", "abstract": "Active Galactic Nuclei (AGN) are sources of high-energy gamma-rays and are considered to be promising candidates to be sources of high-energy cosmic rays and neutrinos as well. We present and discuss various models for ion acceleration and their interactions with matter and radiation leading to high-energy neutrino production. We consider neutrino production mechanisms in both jet-loud and jet-quiet AGN, focusing on disks and coronae in the vicinity of the central black hole, jet regions, and magnetized environments surrounding the AGN. The IceCube Collaboration has reported high-energy neutrino events that may come from both the jet-loud AGN TXS 0506+056 and the jet-quiet AGN NGC 1068. We discuss the implications of these observations themselves as well as the the origins of the all-sky neutrino intensity.", "keyphrases": ["neutrino", "active galactic nuclei", "high-energy proton"]}
{"id": "2207.12338", "title": "Revealing Galaxy Candidates out to z \u223c 16 with JWST Observations of the Lensing Cluster SMACS0723", "abstract": "One of the main goals of the JWST is to study the first galaxies in the Universe. We present a systematic photometric analysis of very distant galaxies in the first JWST deep field towards the massive lensing cluster SMACS0723. As a result, we report the discovery of two galaxy candidates at z\u223c16, only 250 million years after the Big Bang. We also identify two candidates at z\u223c 12 and 6 candidates at z\u223c 9-11. Our search extended out to z\u227221 by combining color information across seven NIRCam and NIRISS filters. By modelling the Spectral Energy Distributions (SEDs) with and , we test the robustness of the photometric redshift estimates. While their intrinsic (un-lensed) luminosity is typical of the characteristic luminosity L^* at z>10, our high-redshift galaxies typically show small sizes and their morphologies are consistent with disks in some cases. The highest-redshift candidates have extremely blue UV-continuum slopes -3 < \u03b2 <-2.4, young ages \u223c 10-100 Myr, and stellar masses around log(M_\u22c6/M_\u2299)=8.8 inferred from their SED modeling, which indicate a rapid build-up of their stellar mass. Our search clearly demonstrates the capabilities of JWST to uncover robust photometric candidates up to very high redshifts, and peer into the formation epoch of the first galaxies.", "keyphrases": ["galaxy candidate", "cluster smacs0723", "photometric redshift"]}
{"id": "2010.00040", "title": "Bridging the gap: spectral distortions meet gravitational waves", "abstract": "Gravitational waves (GWs) have the potential to probe the entirety of cosmological history due to their nearly perfect decoupling from the thermal bath and any intervening matter after emission. In recent years, GW cosmology has evolved from merely being an exciting prospect to an actively pursued avenue for discovery, and the early results are very promising. As we highlight in this paper, spectral distortions (SDs) of the cosmic microwave background (CMB) uniquely probe GWs over six decades in frequency, bridging the gap between astrophysical high- and cosmological low-frequency measurements. This means SDs will not only complement other GW observations, but will be the sole probe of physical processes at certain scales. To illustrate this point, we explore the constraining power of various proposed SD missions on a number of phenomenological scenarios: early-universe phase transitions (PTs), GW production via the dynamics of SU(2) and ultra-light U(1) axions, and cosmic string (CS) network collapse. We highlight how some regions of parameter space were already excluded with data from COBE/FIRAS, taken over two decades ago. To facilitate the implementation of SD constraints in arbitrary models we provide GW2SD. This tool calculates the window function, which easily maps a GW spectrum to a SD amplitude, thus opening another portal for GW cosmology with SDs, with wide reaching implications for particle physics phenomenology.", "keyphrases": ["gap", "spectral distortion", "gravitational wave"]}
{"id": "1712.09804", "title": "A Global ILC Approach in Pixel Space over Large Angular Scales of the Sky using CMB Covariance Matrix", "abstract": "We propose a new internal linear combination (ILC) method in the pixel space, applicable on large angular scales of the sky, to estimate a foreground minimized Cosmic Microwave Background (CMB) temperature anisotropy map by incorporating prior knowledge about the theoretical CMB covariance matrix. Usual ILC method in pixel space, on the contrary, does not use any information about the underlying CMB covariance matrix. The new approach complements the usual pixel space ILC technique specifically at low multipole region, using global information available from theoretical CMB covariance matrix as well as from the data. Since we apply our method over the large scale on the sky containing low multipoles we perform foreground minimization globally. We apply our methods on low resolution Planck and WMAP foreground contaminated CMB maps and validate the methodology by performing detailed Monte-Carlo simulations. Our cleaned CMB map and its power spectrum have significantly less error than those obtained following usual ILC technique at low resolution that does not use CMB covariance information. Another very important advantage of our method is that the cleaned power spectrum does not have any negative bias at the low multipoles because of effective suppression of CMB-foreground chance correlations on large angular scales of the sky. Our cleaned CMB map and its power spectrum match well with those estimated by other research groups.", "keyphrases": ["pixel space", "large angular scale", "cmb covariance matrix", "sky"]}
{"id": "0907.0707", "title": "New Perspective on Galaxy Clustering as a Cosmological Probe: General Relativistic Effects", "abstract": "We present a general relativistic description of galaxy clustering in a FLRW universe. The observed redshift and position of galaxies are affected by the matter fluctuations and the gravity waves between the source galaxies and the observer, and the volume element constructed by using the observables differs from the physical volume occupied by the observed galaxies. Therefore, the observed galaxy fluctuation field contains additional contributions arising from the distortion in observable quantities and these include tensor contributions as well as numerous scalar contributions. We generalize the linear bias approximation to relate the observed galaxy fluctuation field to the underlying matter distribution in a gauge-invariant way. Our full formalism is essential for the consistency of theoretical predictions. As our first application, we compute the angular auto correlation of large-scale structure and its cross correlation with CMB temperature anisotropies. We comment on the possibility of detecting primordial gravity waves using galaxy clustering and discuss further applications of our formalism.", "keyphrases": ["galaxy clustering", "relativistic effect", "large scale", "non-primordial phenomenon", "non-gaussianity"]}
{"id": "1407.0376", "title": "Galaxy number counts to second order and their bispectrum", "abstract": "We determine the number counts to second order in cosmological perturbation theory in the Poisson gauge and allowing for anisotropic stress. The calculation is performed using an innovative approach based on the recently proposed \"geodesic light-cone\" gauge. This allows us to determine the number counts in a purely geometric way, without using Einstein's equation. The result is valid for general dark energy models and (most) modified gravity models. We then evaluate numerically the relevant contributions to the number counts bispectrum. In particular we consider the terms involving the density, redshift space distortion and lensing.", "keyphrases": ["bispectrum", "perturbation theory", "redshift"]}
{"id": "1407.1342", "title": "A coarse grained perturbation theory for the Large Scale Structure, with cosmology and time independence in the UV", "abstract": "Standard cosmological perturbation theory (SPT) for the Large Scale Structure (LSS) of the Universe fails at small scales (UV) due to strong nonlinearities and to multistreaming effects. In Pietroni et al. 2011 a new framework was proposed in which the large scales (IR) are treated perturbatively while the information on the UV, mainly small scale velocity dispersion, is obtained by nonlinear methods like N-body simulations. Here we develop this approach, showing that it is possible to reproduce the fully nonlinear power spectrum (PS) by combining a simple (and fast) 1-loop computation for the IR scales and the measurement of a single, dominant, correlator from N-body simulations for the UV ones. We measure this correlator for a suite of seven different cosmologies, and we show that its inclusion in our perturbation scheme reproduces the fully non-linear PS with percent level accuracy, for wave numbers up to k\u223c 0.4 h Mpc^-1 down to z=0. We then show that, once this correlator has been measured in a given cosmology, there is no need to run a new simulation for a different cosmology in the suite. Indeed, by rescaling this correlator by a proper function computable in SPT, the reconstruction procedure works also for the other cosmologies and for all redshifts, with comparable accuracy. Finally, we clarify the relation of this approach to the Effective Field Theory methods recently proposed in the LSS context.", "keyphrases": ["perturbation theory", "large scale structure", "cosmology"]}
{"id": "1211.0008", "title": "Turbulence, Magnetic Reconnection in Turbulent Fluids and Energetic Particle Acceleration", "abstract": "Turbulence is ubiquitous in astrophysics. It radically changes many astrophysical phenomena, in particular, the propagation and acceleration of cosmic rays. We present the modern understanding of compressible magnetohydrodynamic (MHD) turbulence, in particular its decomposition into Alfv\u00e9n, slow and fast modes, discuss the density structure of turbulent subsonic and supersonic media, as well as other relevant regimes of astrophysical turbulence. All this information is essential for understanding the energetic particle acceleration that we discuss further in the review. For instance, we show how fast and slow modes accelerate energetic particles through the second order Fermi acceleration, while density fluctuations generate magnetic fields in pre-shock regions enabling the first order Fermi acceleration of high energy cosmic rays. Very importantly, however, the first order Fermi cosmic ray acceleration is also possible in sites of magnetic reconnection. In the presence of turbulence this reconnection gets fast and we present numerical evidence supporting the predictions of the Lazarian Vishniac (1999) model of fast reconnection. The efficiency of this process suggests that magnetic reconnection can release substantial amounts of energy in short periods of time. As the particle tracing numerical simulations show that the particles can be efficiently accelerated during the reconnection, we argue that the process of magnetic reconnection may be much more important for particle acceleration than it is currently accepted. In particular, we discuss the acceleration arising from reconnection as a possible origin of the anomalous cosmic rays measured by Voyagers as well as the origin cosmic ray excess in the direction of Heliotail.", "keyphrases": ["magnetic reconnection", "energetic particle acceleration", "turbulence"]}
{"id": "1310.1513", "title": "Gravitational self-force from radiation-gauge metric perturbations", "abstract": "Calculations of the gravitational self-force (GSF) in curved spacetime require as input the metric perturbation in a sufficiently regular gauge. A basic challenge in the program to compute the GSF for orbits around a Kerr black hole is that the standard procedure for reconstructing the perturbation is formulated in a class of radiation gauges, in which the particle singularity is non-isotropic and extends away from the particle's location. Here we present two practical schemes for calculating the GSF using a radiation-gauge reconstructed metric as input. The schemes are based on a detailed analysis of the local structure of the particle singularity in the radiation gauges. We identify 3 types of radiation gauges: two containing a radial string-like singularity emanating from the particle, either in one direction (\"half-string\" gauges) or both directions (\"full-string\" gauges); and a third type containing no strings but with a jump discontinuity across a surface intersecting the particle. Based on a flat-space example, we argue that the standard mode-by-mode reconstruction procedure yields the \"regular half\" of a half-string solution, or (equivalently) either of the regular halves of a no-string solution. For the half-string case, we formulate the GSF in a locally deformed radiation gauge that removes the string singularity near the particle. We derive a mode-sum formula for the GSF in this gauge, analogous to the standard Lorenz-gauge formula but with modified regularization parameters. For the no-string case, we formulate the GSF directly, without a local deformation, and we derive a mode-sum formula that requires no correction to the parameters but involves a certain averaging procedure. We explain the consistency of our results with Gralla's invariance theorem, and discuss the correspondence between our method and a related approach by Friedman et al.", "keyphrases": ["metric perturbation", "black hole", "radiation gauge", "gravitational self-force"]}
{"id": "1201.1934", "title": "Radiation and Relaxation of Oscillons", "abstract": "We study oscillons, extremely long-lived localized oscillations of a scalar field, with three different potentials: quartic, sine-Gordon model and in a new class of convex potentials. We use an absorbing boundary at the end of the lattice to remove emitted radiation. The energy and the frequency of an oscillon evolve in time and are well fitted by a constant component and a decaying, radiative part obeying a power law as a function time. The power spectra of the emitted radiation show several distinct frequency peaks where oscillons release energy. In two dimensions, and with suitable initial conditions, oscillons do not decay within the range of the simulations, which in quartic theory reach 10^8 time units. While it is known that oscillons in three-dimensional quartic theory and sine-Gordon model decay relatively quickly, we observe a surprising persistence of the oscillons in the convex potential with no sign of demise up to 10^7 time units. This leads us to speculate that an oscillon in such a potential could actually live infinitely long both in two and three dimensions.", "keyphrases": ["oscillon", "radiation", "lifetime", "field theory", "i-balls"]}
{"id": "1909.05966", "title": "Learning Bayesian posteriors with neural networks for gravitational-wave inference", "abstract": "We seek to achieve the Holy Grail of Bayesian inference for gravitational-wave astronomy: using deep-learning techniques to instantly produce the posterior p(\u03b8|D) for the source parameters \u03b8, given the detector data D. To do so, we train a deep neural network to take as input a signal + noise data set (drawn from the astrophysical source-parameter prior and the sampling distribution of detector noise), and to output a parametrized approximation of the corresponding posterior. We rely on a compact representation of the data based on reduced-order modeling, which we generate efficiently using a separate neural-network waveform interpolant [A. J. K. Chua, C. R. Galley M. Vallisneri, Phys. Rev. Lett. 122, 211101 (2019)]. Our scheme has broad relevance to gravitational-wave applications such as low-latency parameter estimation and characterizing the science returns of future experiments. Source code and trained networks are available online at https://github.com/vallis/truebayes.", "keyphrases": ["neural network", "inference", "learning"]}
{"id": "1602.03186", "title": "Doppler term in the galaxy two-point correlation function: wide-angle, velocity, Doppler lensing and cosmic acceleration effects", "abstract": "We study the parity-odd part (that we shall call Doppler term) of the linear galaxy two-point correlation function that arises from wide-angle, velocity, Doppler lensing and cosmic acceleration effects. As it is important at low redshift and at large angular separations, the Doppler term is usually neglected in the current generation of galaxy surveys. For future wide-angle galaxy surveys such as Euclid, SPHEREx and SKA, however, we show that the Doppler term must be included. The effect of these terms is dominated by the magnification due to relativistic aberration effects and the slope of the galaxy redshift distribution and it generally mimics the effect of the local type primordial non-Gaussianity with the effective nonlinearity parameter f_ NL^ eff of a few, we show that this would affect forecasts on measurements of f_ NL at low-redshift. Our results show that a survey at low redshift with large number density over a wide area of the sky could detect the Doppler term with a signal-to-noise ratio of \u223c 1-20, depending on survey specifications.", "keyphrases": ["galaxy", "two-point correlation function", "cosmic acceleration effect"]}
{"id": "2007.07288", "title": "The Atacama Cosmology Telescope: DR4 Maps and Cosmological Parameters", "abstract": "We present new arcminute-resolution maps of the Cosmic Microwave Background temperature and polarization anisotropy from the Atacama Cosmology Telescope, using data taken from 2013-2016 at 98 and 150 GHz. The maps cover more than 17,000 deg^2, the deepest 600 deg^2 with noise levels below 10 \u03bcK-arcmin. We use the power spectrum derived from almost 6,000 deg^2 of these maps to constrain cosmology. The ACT data enable a measurement of the angular scale of features in both the divergence-like polarization and the temperature anisotropy, tracing both the velocity and density at last-scattering. From these one can derive the distance to the last-scattering surface and thus infer the local expansion rate, H_0. By combining ACT data with large-scale information from WMAP we measure H_0 = 67.6 \u00b1 1.1 km/s/Mpc, at 68 independently-measured Planck satellite estimate (from ACT alone we find H_0 = 67.9 \u00b1 1.5 km/s/Mpc). The \u039bCDM model provides a good fit to the ACT data, and we find no evidence for deviations: both the spatial curvature, and the departure from the standard lensing signal in the spectrum, are zero to within 1\u03c3; the number of relativistic species, the primordial Helium fraction, and the running of the spectral index are consistent with \u039bCDM predictions to within 1.5 - 2.2\u03c3. We compare ACT, WMAP, and Planck at the parameter level and find good consistency; we investigate how the constraints on the correlated spectral index and baryon density parameters readjust when adding CMB large-scale information that ACT does not measure. The DR4 products presented here will be publicly released on the NASA Legacy Archive for Microwave Background Data Analysis.", "keyphrases": ["atacama cosmology telescope", "cosmic microwave background", "universe", "cosmological model", "large-scale structure"]}
{"id": "1007.3891", "title": "Primordial magnetogenesis", "abstract": "Magnetic fields appear everywhere in the universe. From stars and galaxies, all the way to galaxy clusters and remote protogalactic clouds magnetic fields of considerable strength and size have been repeatedly observed. Despite their widespread presence, however, the origin of cosmic magnetic fields is still a mystery. The galactic dynamo is believed capable of amplifying weak magnetic seeds to strengths like those measured in ours and other galaxies, but the question is where do these seed fields come from? Are they a product of late, post-recombination, physics or are they truly cosmological in origin? The idea of primordial magnetism is attractive because it makes the large-scale magnetic fields, especially those found in early protogalactic systems, easier to explain. As a result, a host of different scenarios have appeared in the literature. Nevertheless, early magnetogenesis is not problem free, with a number of issues remaining open and a matter of debate. We review the question of primordial magnetic fields and consider the limits set on their strength by the current observational data. The various mechanisms of pre-recombination magnetogenesis are presented and their advantages and shortcomings are debated. We consider both classical and quantum scenarios, that operate within as well as outside the standard model, and also discuss how future observations could be used to decide whether the large-scale magnetic fields we see in the universe today are truly primordial or not.", "keyphrases": ["magnetogenesis", "galaxy", "cosmology", "primordial magnetic field"]}
{"id": "1806.10488", "title": "Wormhole geometries supported by three-form fields", "abstract": "In this work, we find novel static and spherically symmetric wormhole geometries using a three-form field. By solving the gravitational field equations, we find a variety of analytical and numerical solutions and show that it is possible for the matter fields threading the wormhole to satisfy the null and weak energy conditions throughout the spacetime, when the three-form field is present. In these cases, the form field is responsible for supporting the wormhole and all the exoticity is confined to it. Thus, the three-form curvature terms, which may be interpreted as a gravitational fluid, sustain these non-standard wormhole geometries, fundamentally different from their counterparts in General Relativity. We also show that in the case of a vanishing redshift function the field can display a cosmological constant behavior.", "keyphrases": ["three-form field", "spacetime", "wormhole geometry"]}
{"id": "1401.1286", "title": "Cosmological constraints on interacting dark energy with redshift-space distortion after Planck data", "abstract": "The interacting dark energy model could propose a effective way to avoid the coincidence problem. In this paper, dark energy is taken as a fluid with a constant equation of state parameter w_x. In a general gauge, we could obtain two sets of different perturbation equations when the momentum transfer potential is vanished in the rest frame of dark matter or dark energy. There are many kinds of interacting forms from the phenomenological considerations, here, we choose Q=3H\u03be_x\u03c1_x which owns the stable perturbations in most cases. Then, according to the Markov Chain Monte Carlo method, we constrain the model by currently available cosmic observations which include cosmic microwave background radiation, baryon acoustic oscillation, type Ia supernovae, and f\u03c3_8(z) data points from redshift-space distortion. Jointing the geometry tests with the large scale structure information, the results show a tighter constraint on the interacting model than the case without f\u03c3_8(z) data. We find the interaction rate in 3\u03c3 regions: \u03be_x=0.00372_-0.00372- 0.00372-0.00372^+0.000768+0.00655+0.0102. It means that the recently cosmic observations favor a small interaction rate between the dark sectors, at the same time, the measurement of redshift-space distortion could rule out a large interaction rate in the 1\u03c3 region.", "keyphrases": ["dark energy", "redshift-space distortion", "dark matter", "cosmic observation", "cosmology"]}
{"id": "1701.06992", "title": "Reconstructing CMB fluctuations and the mean reionization optical depth", "abstract": "The Thomson optical depth from reionization is a limiting factor in measuring the amplitude of primordial fluctuations, and hence in measuring physics that affects the low-redshift amplitude, such as the neutrino masses. Current constraints on the optical depth, based on directly measuring large-scale cosmic microwave background (CMB) polarization, are challenging due to foregrounds and systematic effects. Here, we consider an indirect measurement of large-scale polarization, using observed maps of small-scale polarization together with maps of fields that distort the CMB, such as CMB lensing and patchy reionization. We find that very futuristic CMB surveys will be able to reconstruct large-scale polarization, and thus the mean optical depth, using only measurements on small scales.", "keyphrases": ["reionization", "optical depth", "large-scale polarization"]}
{"id": "1511.06532", "title": "On the theory and applications of modern cosmography", "abstract": "Cosmography represents an important branch of cosmology which aims to describe the universe without the need of postulating a priori any particular cosmological model. All quantities of interest are expanded as a Taylor series around here and now, providing in principle, a way of directly matching with cosmological data. In this way, cosmography can be regarded a model-independent technique, able to fix cosmic bounds, although several issues limit its use in various model reconstructions. The main purpose of this review is to focus on the key features of cosmography, emphasising both the strategy for obtaining the observable cosmographic series and pointing out any drawbacks which might plague the standard cosmographic treatment. In doing so, we relate cosmography to the most relevant cosmological quantities and to several dark energy models. We also investigate whether cosmography is able to provide information about the form of the cosmological expansion history, discussing how to reproduce the dark fluid from the cosmographic sound speed. Following this, we discuss limits on cosmographic priors and focus on how to experimentally treat cosmographic expansions. Finally, we present some of the latest developments of the cosmographic method, reviewing the use of rational approximations, based on cosmographic Pad\u00e9 polynomials. Future prospects leading to more accurate cosmographic results, able to better reproduce the expansion history of the universe are also discussed in detail.", "keyphrases": ["cosmography", "model-independent approach", "degeneracy"]}
{"id": "1107.4973", "title": "A kinetic theory of diffusion in general relativity with cosmological scalar field", "abstract": "A new model to describe the dynamics of particles undergoing diffusion in general relativity is proposed. The evolution of the particle system is described by a Fokker-Planck equation without friction on the tangent bundle of spacetime. It is shown that the energy-momentum tensor for this matter model is not divergence-free, which makes it inconsistent to couple the Fokker-Planck equation to the Einstein equations. This problem can be solved by postulating the existence of additional matter fields in spacetime or by modifying the Einstein equations. The case of a cosmological scalar field term added to the left hand side of the Einstein equations is studied in some details. For the simplest cosmological model, namely the flat Robertson-Walker spacetime, it is shown that, depending on the initial value of the cosmological scalar field, which can be identified with the present observed value of the cosmological constant, either unlimited expansion or the formation of a singularity in finite time will occur in the future. Future collapse into a singularity also takes place for a suitable small but positive present value of the cosmological constant, in contrast to the standard diffusion-free scenario.", "keyphrases": ["relativity", "scalar field", "cosmological model"]}
{"id": "1004.2868", "title": "Inference with minimal Gibbs free energy in information field theory", "abstract": "Non-linear and non-Gaussian signal inference problems are difficult to tackle. Renormalization techniques permit us to construct good estimators for the posterior signal mean within information field theory (IFT), but the approximations and assumptions made are not very obvious. Here we introduce the simple concept of minimal Gibbs free energy to IFT, and show that previous renormalization results emerge naturally. They can be understood as being the Gaussian approximation to the full posterior probability, which has maximal cross information with it. We derive optimized estimators for three applications, to illustrate the usage of the framework: (i) reconstruction of a log-normal signal from Poissonian data with background counts and point spread function, as it is needed for gamma ray astronomy and for cosmography using photometric galaxy redshifts, (ii) inference of a Gaussian signal with unknown spectrum and (iii) inference of a Poissonian log-normal signal with unknown spectrum, the combination of (i) and (ii). Finally we explain how Gaussian knowledge states constructed by the minimal Gibbs free energy principle at different temperatures can be combined into a more accurate surrogate of the non-Gaussian posterior.", "keyphrases": ["gibbs", "free energy", "inference"]}
{"id": "1306.1446", "title": "PlanetPack: a radial-velocity time-series analysis tool facilitating exoplanets detection, characterization, and dynamical simulations", "abstract": "We present PlanetPack, a new software tool that we developed to facilitate and standardize the advanced analysis of radial velocity (RV) data for the goal of exoplanets detection, characterization, and basic dynamical N-body simulations. PlanetPack is a command-line interpreter, that can run either in an interactive mode or in a batch mode of automatic script interpretation. Its major abilities include: (i) Advanced RV curve fitting with the proper maximum-likelihood treatment of unknown RV jitter; (ii) User-friendly multi-Keplerian as well as Newtonian N-body RV fits; (iii) Use of more efficient maximum-likelihood periodograms that involve the full multi-planet fitting (sometimes called as \u201cresidual\u201d or \u201crecursive\u201d periodograms); (iv) Easily calculatable parametric 2D likelihood function level contours, reflecting the asymptotic confidence regions; (v) Fitting under some useful functional constraints is user-friendly; (vi) Basic tasks of short- and long-term planetary dynamical simulation using a fast Everhart-type integrator based on Gauss\u2013Legendre spacings; (vii) Fitting the data with red noise (auto-correlated errors); (viii) Various analytical and numerical methods for the tasks of determining the statistical significance. It is planned that further functionality may be added to PlanetPack in the future. During the development of this software, a lot of effort was made to improve the calculational speed, especially for CPU-demanding tasks. PlanetPack was written in pure C++ (standard of 1998/2003), and is expected to be compilable and usable on a wide range of platforms.", "keyphrases": ["exoplanet detection", "dynamical simulation", "planetpack"]}
{"id": "1208.3722", "title": "Too massive neutron stars: The role of dark matter?", "abstract": "The maximum mass of a neutron star is generally determined by the equation of state of the star material. In this study, we take into account dark matter particles, assumed to behave like fermions with a free parameter to account for the interaction strength among the particles, as a possible constituent of neutron stars. We find dark matter inside the star would soften the equation of state more strongly than that of hyperons, and reduce largely the maximum mass of the star. However, the neutron star maximum mass is sensitive to the particle mass of dark matter, and a very high neutron star mass larger than 2 times solar mass could be achieved when the particle mass is small enough. Such kind of dark-matter- admixed neutron stars could explain the recent measurement of the Shapiro delay in the radio pulsar PSR J1614-2230, which yielded a neutron star mass of 2 times solar mass that may be hardly reached when hyperons are considered only, as in the case of the microscopic Brueckner theory. Furthermore, in this particular case, we point out that the dark matter around a neutron star should also contribute to the mass measurement due to its pure gravitational effect. However, our numerically calculation illustrates that such contribution could be safely ignored because of the usual diluted dark matter environment assumed. We conclude that a very high mass measurement of about 2 times solar mass requires a really stiff equation of state in neutron stars, and find a strong upper limit (<= 0.64 GeV) for the particle mass of non-self- annihilating dark matter based on the present model.", "keyphrases": ["neutron star", "dark matter", "gravitational effect"]}
{"id": "1710.05901", "title": "Dark Energy after GW170817: dead ends and the road ahead", "abstract": "Multi-messenger gravitational wave (GW) astronomy has commenced with the detection of the binary neutron star merger GW170817 and its associated electromagnetic counterparts. The almost coincident observation of both signals places an exquisite bound on the GW speed |c_g/c-1|\u22645\u00b710^-16. We use this result to probe the nature of dark energy (DE), showing that a large class of scalar-tensor theories and DE models are highly disfavored. As an example we consider the covariant Galileon, a cosmologically viable, well motivated gravity theory which predicts a variable GW speed at low redshift. Our results eliminate any late-universe application of these models, as well as their Horndeski and most of their beyond Horndeski generalizations. Three alternatives (and their combinations) emerge as the only possible scalar-tensor DE models: 1) restricting Horndeski's action to its simplest terms, 2) applying a conformal transformation which preserves the causal structure and 3) compensating the different terms that modify the GW speed (to be robust, the compensation has to be independent on the background on which GWs propagate). Our conclusions extend to any other gravity theory predicting varying c_g such as Einstein-Aether, Ho\u0159ava gravity, Generalized Proca, TeVeS and other MOND-like gravities.", "keyphrases": ["horndeski", "dark energy", "gravitational wave observation", "cosmological time"]}
{"id": "1010.5307", "title": "Anisotropic Power-law Inflation", "abstract": "We study an inflationary scenario in supergravity model with a gauge kinetic function. We find exact anisotropic power-law inflationary solutions when both the potential function for an inflaton and the gauge kinetic function are exponential type. The dynamical system analysis tells us that the anisotropic power-law inflation is an attractor for a large parameter region.", "keyphrases": ["anisotropic inflation", "cosmic no-hair conjecture", "vector field", "watanabe", "motivated model"]}
{"id": "1512.03918", "title": "Measurement of the dipole in the cross-correlation function of galaxies", "abstract": "It is usually assumed that in the linear regime the two-point correlation function of galaxies contains only a monopole, quadrupole and hexadecapole. Looking at cross-correlations between different populations of galaxies, this turns out not to be the case. In particular, the cross-correlations between a bright and a faint population of galaxies contain also a dipole. In this paper we present the first attempt to measure this dipole. We discuss the four types of effects that contribute to the dipole: relativistic distortions, evolution effect, wide-angle effect and large-angle effect. We show that the first three contributions are intrinsic anti-symmetric contributions that do not depend on the choice of angle used to measure the dipole. On the other hand the large-angle effect appears only if the angle chosen to extract the dipole breaks the symmetry of the problem. We show that the relativistic distortions, the evolution effect and the wide-angle effect are too small to be detected in the LOWz and CMASS sample of the BOSS survey. On the other hand with a specific combination of angles we are able to measure the large-angle effect with high significance. We emphasise that this large-angle dipole does not contain new physical information, since it is just a geometrical combination of the monopole and the quadrupole. However this measurement, which is in excellent agreement with theoretical predictions, validates our method for extracting the dipole from the two-point correlation function and it opens the way to the detection of relativistic effects in future surveys like e.g. DESI.", "keyphrases": ["dipole", "galaxy", "wide-angle effect", "relativistic effect"]}
{"id": "1105.2303", "title": "Relic gravitational waves from light primordial black holes", "abstract": "The energy density of relic gravitational waves (GWs) emitted by primordial black holes (PBHs) is calculated. We estimate the intensity of GWs produced at quantum and classical scattering of PBHs, the classical graviton emission from the PBH binaries in the early Universe, and the graviton emission due to PBH evaporation. If nonrelativistic PBHs dominated the cosmological energy density prior to their evaporation, the probability of formation of dense clusters of PBHs and their binaries in such clusters would be significant and the energy density of the generated gravitational waves in the present day universe could exceed that produced by other known mechanisms. The intensity of these gravitational waves would be maximal in the GHz frequency band of the spectrum or higher and makes their observation very difficult by present detectors but also gives a rather good possibility to investigate it by present and future high frequency gravitational waves electromagnetic detectors. However, the low frequency part of the spectrum in the range f\u223c 0.1-10 Hz may be detectable by the planned space interferometers DECIGO/BBO. For sufficiently long duration of the PBH matter dominated stage the cosmological energy fraction of GWs from inflation would be noticeably diluted.", "keyphrases": ["gravitational wave", "primordial black hole", "early universe"]}
{"id": "1007.4277", "title": "Scale-dependent non-Gaussianity probes inflationary physics", "abstract": "We calculate the scale dependence of the bispectrum and trispectrum in (quasi) local models of non-Gaussian primordial density perturbations, and characterize this scale dependence in terms of new observable parameters. They can help to discriminate between models of inflation, since they are sensitive to properties of the inflationary physics that are not probed by the standard observables. We find consistency relations between these parameters in certain classes of models. We apply our results to a scenario of modulated reheating, showing that the scale dependence of non-Gaussianity can be significant. We also discuss the scale dependence of the bispectrum and trispectrum, in cases where one varies the shape as well as the overall scale of the figure under consideration. We conclude providing a formulation of the curvature perturbation in real space, which generalises the standard local form by dropping the assumption that f_NL and g_NL are constants.", "keyphrases": ["non-gaussianity", "inflationary physics", "scale dependence"]}
{"id": "1211.3618", "title": "Bondi accretion onto cosmological black holes", "abstract": "In this paper we investigate a steady accretion within the Einstein-Straus vacuole, in the presence of the cosmological constant. The dark energy damps the mass accretion rate and \u2014 above certain limit \u2014 completely stops the steady accretion onto black holes, which in particular is prohibited in the inflation era and after (roughly) 10^12 years from Big Bang (assuming the presently known value of the cosmological constant). Steady accretion would not exist in the late phases of the Penrose's scenario - known as the Weyl curvature hypothesis - of the evolution of the Universe.", "keyphrases": ["accretion", "black hole", "cosmological constant"]}
{"id": "1401.7519", "title": "Cosmic rays in galaxy clusters and their non-thermal emission", "abstract": "Radio observations prove the existence of relativistic particles and magnetic field associated with the intra-cluster-medium (ICM) through the presence of extended synchrotron emission in the form of radio halos and peripheral relics. This observational evidence has fundamental implications on the physics of the ICM. Non-thermal components in galaxy clusters are indeed unique probes of very energetic processes operating within clusters that drain gravitational and electromagnetic energy into cosmic rays and magnetic fields. These components strongly affect the (micro-)physical properties of the ICM, including viscosity and electrical conductivities, and have also potential consequences on the evolution of clusters themselves. The nature and properties of cosmic rays in galaxy clusters, including the origin of the observed radio emission on cluster-scales, have triggered an active theoretical debate in the last decade. Only recently we can start addressing some of the most important questions in this field, thanks to recent observational advances, both in the radio and at high energies. The properties of cosmic rays and of cluster non-thermal emissions depend on the dynamical state of the ICM, the efficiency of particle acceleration mechanisms in the ICM and on the dynamics of these cosmic rays. In this review we discuss in some detail the acceleration and transport of cosmic rays in galaxy clusters and the most relevant observational milestones that have provided important steps on our understanding of this physics. Finally, looking forward to the possibilities from new generations of observational tools, we focus on what appear to be the most important prospects for the near future from radio and high-energy observations.", "keyphrases": ["galaxy cluster", "non-thermal emission", "cosmic ray", "relativistic electron", "diffusive shock acceleration"]}
{"id": "1305.6936", "title": "Matter around Kerr black holes in scalar-tensor theories: scalarization and superradiant instability", "abstract": "In electrovacuum stationary, asymptotically flat black holes in scalar-tensor theories of gravity are described by the Kerr-Newman family of solutions, just as in general relativity. We show that there exist two mechanisms which can render Kerr black holes unstable when matter is present in the vicinity of the black hole, as this induces an effective mass for the scalar. The first mechanism is a tachyonic instability that appears when the effective mass squared is negative, triggering the development of scalar hair \u2014 a black hole version of \"spontaneous scalarization\". The second instability is associated with superradiance and is present when the effective mass squared is positive and when the black hole spin exceeds a certain threshold. The second mechanism is also responsible for a resonant effect in the superradiant scattering of scalar waves, with amplification factors as large as 10^5 or more.", "keyphrases": ["black hole", "scalar-tensor theory", "superradiant instability"]}
{"id": "1411.0115", "title": "Cosmology with cosmic shear observations: a review", "abstract": "Cosmic shear is the distortion of images of distant galaxies due to weak gravitational lensing by the large-scale structure in the Universe. Such images are coherently deformed by the tidal field of matter inhomogeneities along the line of sight. By measuring galaxy shape correlations, we can study the properties and evolution of structure on large scales as well as the geometry of the Universe. Thus, cosmic shear has become a powerful probe into the nature of dark matter and the origin of the current accelerated expansion of the Universe. Over the last years, cosmic shear has evolved into a reliable and robust cosmological probe, providing measurements of the expansion history of the Universe and the growth of its structure. We review here the principles of weak gravitational lensing and show how cosmic shear is interpreted in a cosmological context. Then we give an overview of weak-lensing measurements, and present the main observational cosmic-shear results since it was discovered 15 years ago, as well as the implications for cosmology. We then conclude with an outlook on the various future surveys and missions, for which cosmic shear is one of the main science drivers, and discuss promising new weak cosmological lensing techniques for future observations.", "keyphrases": ["galaxy", "dark matter", "cosmology"]}
{"id": "1704.06184", "title": "Anisotropy of the astrophysical gravitational wave background: analytic expression of the angular power spectrum and correlation with cosmological observations", "abstract": "Unresolved and resolved sources of gravitational waves are at the origin of a stochastic gravitational wave background. While the computation of its mean density as a function of frequency in a homogeneous and isotropic universe is standard lore, the computation of its anisotropies requires to understand the coarse graining from local systems, to galactic scales and then to cosmology. An expression of the gravitational wave energy density valid in any general spacetime is derived. It is then specialized to a perturbed Friedmann-Lema\u00eetre spacetime in order to determine the angular power spectrum of this stochastic background as well as its correlation with other cosmological probes, such as the galaxy number counts and weak lensing. Our result for the angular power spectrum also provides an expression for the variance of the gravitational wave background.", "keyphrases": ["gravitational wave background", "angular power spectrum", "anisotropy"]}
{"id": "1801.08857", "title": "The dynamical connection between Phaethon and Pallas", "abstract": "Phaethon (3200) is an active Near Earth Asteroid classified as a B-type object and a suspected former member of the Pallas family. In this article, we search for sources of Phaethon-like orbits originating from the two strongest resonances in the region of the Pallas family; namely, the 5:2 and 8:3 mean motion resonances with Jupiter, located at a\u223c 2.82 AU and a \u223c 2.70 AU, respectively. The probability for this dynamical connection observed in <cit.> was close to 2 per cent. Using sophisticated numerical methods, we found a highly efficient dynamical flow between Pallas and Phaethon. As many as 43.6 per cent of test particles placed in the 5:2 resonance were able to reach the orbit of Phaethon; whereas, for the 8:3 resonance, this percentage was 46.9 per cent.", "keyphrases": ["dynamical connection", "phaethon", "pallas", "motion resonance"]}
{"id": "1810.08220", "title": "Polarization of gravitational waves in symmetric teleparallel theories of gravity and their modifications", "abstract": "Symmetric teleparallel gravity (STG) offers an interesting avenue to formulate a theory of gravitation that relies neither on curvature nor torsion but only on non-metricity Q. Given the growing number of observations of gravitational waves (GWs) and their use to explore gravitational theories, in this work we investigate the GWs in various extensions of STG, focusing on their speed and polarization. For the simple STG, for theories that arise from the generalized irreducible decomposition of STG, and for f(Q) gravity, we obtain the same speed and polarizations with general relativity. For scalar - non-metricity theories, where a scalar field is nonminimally coupled to f(Q), we find that GWs propagate in general with a speed different than the one of light. Finally, for the case of f(Q,B) gravity we find that new polarizations do appear.", "keyphrases": ["gravitational wave", "symmetric teleparallel gravity", "polarization"]}
{"id": "1607.02035", "title": "Secular resonances with Ceres and Vesta", "abstract": "In this work we explore dynamical perturbations induced by the massive asteroids Ceres and Vesta on main-belt asteroids through secular resonances. First we determine the location of the linear secular resonances with Ceres and Vesta in the main belt, using a purely numerical technique. Then we use a set of numerical simulations of fictitious asteroids to investigate the importance of these secular resonances in the orbital evolution of main-belt asteroids. We found, evaluating the magnitude of the perturbations in the proper elements of the test particles, that in some cases the strength of these secular resonances is comparable to that of known non-linear secular resonances with the giant planets. Finally we explore the asteroid families that are crossed by the secular resonances we studied, and identified several cases where the latter seem to play an important role in their post-impact evolution.", "keyphrases": ["ceres", "vesta", "secular resonance"]}
{"id": "1205.0710", "title": "Heavy fields, reduced speeds of sound and decoupling during inflation", "abstract": "We discuss and clarify the validity of effective single field theories of inflation obtained by integrating out heavy degrees of freedom in the regime where adiabatic perturbations propagate with a suppressed speed of sound. We show by construction that it is indeed possible to have inflationary backgrounds where the speed of sound remains suppressed and slow-roll persists for long enough. In this class of models, heavy fields influence the evolution of adiabatic modes in a manner that is consistent with decoupling of physical low and high energy degrees of freedom. We emphasize the distinction between the effective masses of the isocurvature modes and the eigenfrequencies of the propagating high energy modes. Crucially, we find that the mass gap that defines the high frequency modes increases with the strength of the turn, even as the naive heavy (isocurvature) and light (curvature) modes become more strongly coupled. Adiabaticity is preserved throughout, and the derived effective field theory remains in the weakly coupled regime, satisfying all current observational constraints on the resulting primordial power spectrum. In addition, these models allow for an observably large equilateral non-Gaussianity.", "keyphrases": ["adiabatic mode", "heavy field", "curvature perturbation"]}
{"id": "1909.10322", "title": "Can we distinguish black holes from naked singularities by the images of their accretion disks?", "abstract": "We study here images of thin accretion disks around black holes and two classes of naked singularity spacetimes and compare these scenarios. The naked singularity models which have photon spheres have single accretion disk with its inner edge lying outside the photon sphere. The images and shadows created by these models mimic those of black holes. It follows, therefore, that further and more detailed analysis of the images and shadows structure in such case is needed to confirm or otherwise the existence of an event horizon for the compact objects such as the galactic centers. However, naked singularity models which do not have any photon spheres can have either double disks or a single disk extending up to the singularity. The images obtained from such models significantly differ from those of black holes. Moreover, the images of the two classes of naked singularities in this latter case, differ also from one another, thereby allowing them to be distinguish from one another through the observation of the images.", "keyphrases": ["black hole", "naked singularity", "accretion disk"]}
{"id": "2111.04966", "title": "Gravitational axial perturbations of Schwarzschild-like black holes in dark matter halos", "abstract": "Gravitational waves emitted by distorted black holes, such as those arising from the coalescence of binary black holes, or a falling compact star into a supermassive black hole, carry not only information about the corresponding spacetime but also information about the environment surrounding the black holes. In this paper, we study the effects of the dark matter halos with three different density profiles on the gravitational axial perturbations of a Schwarzschild-like black hole. For this purpose, we first consider modified Schwarzschild black holes with three different dark matter profiles and derive the equation of motion of the axial perturbations of the modified Schwarzschild metric. It is shown that by ignoring the dark matter perturbations, a Regge-Wheeler-like master equation with a modified potential for the axial perturbation can be obtained explicitly. Then we calculate the complex frequencies of the quasi-normal modes of the Schwarzschild-like black hole in the dark matter halos by applying the sixth-order WKB method. The corresponding gravitational wave spectra with the effects of the dark matter halos have also been discussed.", "keyphrases": ["black hole", "dark matter halo", "gravitational axial perturbation"]}
{"id": "1310.4988", "title": "Single-field inflation \u00e0 la generalized Chaplygin gas", "abstract": "In the simplest scenario for inflation, i. e. in the single-field inflation, it is presented an inflaton field with properties equivalent to a generalized Chaplygin gas. Their study is performed using the Hamilton-Jacobi approach to cosmology. The main results are contrasted with the measurements recently released by the Planck data, combined with the WMAP large-angle polarization. If the measurements released by Planck for the scalar spectral index together with its running are taken into account it is found a value for the \u03b1-parameter associated to the generalized Chaplygin gas given by \u03b1 = 0.2578 \u00b1 0.0009.", "keyphrases": ["chaplygin gas", "inflaton field", "single-field inflation"]}
{"id": "1211.6752", "title": "Bars and secular evolution in disk galaxies: Theoretical input", "abstract": "Bars play a major role in driving the evolution of disk galaxies and in shaping their present properties. They cause angular momentum to be redistributed within the galaxy, emitted mainly from (near-)resonant material at the inner Lindblad resonance of the bar, and absorbed mainly by (near-)resonant material in the spheroid (i.e., the halo and, whenever relevant, the bulge) and in the outer disk. Spheroids delay and slow down the initial growth of the bar they host, but, at the later stages of the evolution, they strengthen the bar by absorbing angular momentum. Increased velocity dispersion in the (near-)resonant regions delays bar formation and leads to less strong bars. When bars form they are vertically thin, but soon their inner parts puff up and form what is commonly known as the boxy/peanut bulge. This gives a complex and interesting shape to the bar which explains a number of observations and also argues that the COBE/DIRBE bar and the Long bar in our Galaxy are, respectively, the thin and the thick part of a single bar. The value of the bar pattern speed may be set by optimising the balance between emitters and absorbers, so that a maximum amount of angular momentum is redistributed. As they evolve, bars grow stronger and rotate slower. Bars also redistribute matter within the galaxy, create a disky bulge (pseudo-bulge), increase the disk scale-length and extent and drive substructures such as spirals and rings. They also affect the shape of the inner part of the spheroid, which can evolve from spherical to triaxial.", "keyphrases": ["secular evolution", "disk galaxy", "star"]}
{"id": "1406.1609", "title": "Examining the consistency relations describing the three-point functions involving tensors", "abstract": "It is well known that the non-Gaussianity parameter f__ NL characterizing the scalar bi-spectrum can be expressed in terms of the scalar spectral index in the squeezed limit, a property that is referred to as the consistency relation. In this work, we consider the consistency relations associated with the three-point cross-correlations involving scalars and tensors as well as the tensor bi-spectrum in inflationary models driven by a single, canonical, scalar field. Characterizing the cross-correlations in terms of the dimensionless non-Gaussianity parameters C__ NL^\u211b and C__ NL^\u03b3 that we had introduced earlier, we express the consistency relations governing the cross-correlations as relations between these non-Gaussianity parameters and the scalar or tensor spectral indices, in a fashion similar to that of the purely scalar case. We also discuss the corresponding relation for the non-Gaussianity parameter h__ NL used to describe the tensor bi-spectrum. We analytically establish these consistency relations explicitly in the following two situations: a simple example involving a specific case of power law inflation and a non-trivial scenario in the so-called Starobinsky model that is governed by a linear potential with a sharp change in its slope. We also numerically verify the consistency relations in three types of inflationary models that permit deviations from slow roll and lead to scalar power spectra with features which typically result in an improved fit to the data than the more conventional, nearly scale invariant, spectra. We close with a summary of the results we have obtained. (Abridged)", "keyphrases": ["consistency relation", "three-point function", "tensor", "conformal symmetry", "single field model"]}
{"id": "1503.08826", "title": "On the Statistics of Biased Tracers in the Effective Field Theory of Large Scale Structures", "abstract": "With the completion of the Planck mission, in order to continue to gather cosmological information it has become crucial to understand the Large Scale Structures (LSS) of the universe to percent accuracy. The Effective Field Theory of LSS (EFTofLSS) is a novel theoretical framework that aims to develop an analytic understanding of LSS at long distances, where inhomogeneities are small. We further develop the description of biased tracers in the EFTofLSS to account for the effect of baryonic physics and primordial non-Gaussianities, finding that new bias coefficients are required. Then, restricting to dark matter with Gaussian initial conditions, we describe the prediction of the EFTofLSS for the one-loop halo-halo and halo-matter two-point functions, and for the tree-level halo-halo-halo, matter-halo-halo and matter-matter-halo three-point functions. Several new bias coefficients are needed in the EFTofLSS, even though their contribution at a given order can be degenerate and the same parameters contribute to multiple observables. We develop a method to reduce the number of biases to an irreducible basis, and find that, at the order at which we work, seven bias parameters are enough to describe this extremely rich set of statistics. We then compare with the output of N-body simulations. For the lowest mass bin, we find percent level agreement up to k\u2243 0.3 h Mpc^-1 for the one-loop two-point functions, and up to k\u2243 0.15 h Mpc^-1 for the tree-level three-point functions, with the k-reach decreasing with higher mass bins. This is consistent with the theoretical estimates, and suggests that the cosmological information in LSS amenable to analytical control is much more than previously believed.", "keyphrases": ["tracer", "effective field theory", "large scale structures", "non-linear regime"]}
{"id": "1210.0569", "title": "Solid Inflation", "abstract": "We develop a cosmological model where primordial inflation is driven by a 'solid', defined as a system of three derivatively coupled scalar fields obeying certain symmetries and spontaneously breaking a certain subgroup of these. The symmetry breaking pattern differs drastically from that of standard inflationary models: time translations are unbroken. This prevents our model from fitting into the standard effective field theory description of adiabatic perturbations, with crucial consequences for the dynamics of cosmological perturbations. Most notably, non-gaussianities in the curvature perturbations are unusually large, with f_NL 1/(\u03f5.c_s^2), and have a novel shape: peaked in the squeezed limit, with anisotropic dependence on how the limit is approached. Other unusual features include the absence of adiabatic fluctuation modes during inflation\u2014which does not impair their presence and near scale-invariance after inflation\u2014and a slightly blue tilt for the tensor modes.", "keyphrases": ["primordial inflation", "curvature perturbation", "solid inflation", "bispectrum", "reason"]}
{"id": "1104.3585", "title": "Fermi gamma-ray `bubbles' from stochastic acceleration of electrons", "abstract": "Gamma-ray data from Fermi-LAT reveal a bi-lobular structure extending up to 50 degrees above and below the galactic centre, which presumably originated in some form of energy release there less than a few million years ago. It has been argued that the gamma-rays arise from hadronic interactions of high energy cosmic rays which are advected out by a strong wind, or from inverse-Compton scattering of relativistic electrons accelerated at plasma shocks present in the bubbles. We explore the alternative possibility that the relativistic electrons are undergoing stochastic 2nd-order Fermi acceleration by plasma wave turbulence through the entire volume of the bubbles. The observed gamma-ray spectral shape is then explained naturally by the resulting hard electron spectrum and inverse Compton losses. Rather than a constant volume emissivity as in other models, we predict a nearly constant surface brightness, and reproduce the observed sharp edges of the bubbles.", "keyphrases": ["bubble", "electron", "inverse compton scattering"]}
{"id": "1712.04002", "title": "Cosmic structures and gravitational waves in ghost-free scalar-tensor theories of gravity", "abstract": "We study cosmic structures in the quadratic Degenerate Higher Order Scalar Tensor (qDHOST) model, which has been proposed as the most general scalar-tensor theory (up to quadratic dependence on the covariant derivatives of the scalar field), which is not plagued by the presence of ghost instabilities. We then study a static, spherically symmetric object embedded in de Sitter space-time for the qDHOST model. This model exhibits breaking of the Vainshtein mechanism inside the cosmic structure and Schwarzschild-de Sitter space-time outside, where General Relativity (GR) can be recovered within the Vainshtein radius. We then look for the conditions on the parameters on the considered qDHOST scenario which ensure the validity of the Vainshtein screening mechanism inside the object and the fulfilment of the recent GW170817/GRB170817A constraint on the speed of propagation of gravitational waves. We find that these two constraints rule out the same set of parameters, corresponding to the Lagrangians that are quadratic in second-order derivatives of the scalar field, for the shift symmetric qDHOST.", "keyphrases": ["gravitational wave", "scalar-tensor theory", "cosmic structure"]}
{"id": "0910.0241", "title": "Generalized Swiss-cheese cosmologies: Mass scales", "abstract": "We generalize the Swiss-cheese cosmologies so as to include nonzero linear momenta of the associated boundary surfaces. The evolution of mass scales in these generalized cosmologies is studied for a variety of models for the background without having to specify any details within the local inhomogeneities. We find that the final effective gravitational mass and size of the evolving inhomogeneities depends on their linear momenta but these properties are essentially unaffected by the details of the background model.", "keyphrases": ["swiss-cheese cosmology", "cosmology", "mass scale"]}
{"id": "2112.06861", "title": "Tests of General Relativity with GWTC-3", "abstract": "The ever-increasing number of detections of gravitational waves (GWs) from compact binaries by the Advanced LIGO and Advanced Virgo detectors allows us to perform ever-more sensitive tests of general relativity (GR) in the dynamical and strong-field regime of gravity. We perform a suite of tests of GR using the compact binary signals observed during the second half of the third observing run of those detectors. We restrict our analysis to the 15 confident signals that have false alarm rates \u2264 10^-3 yr^-1. In addition to signals consistent with binary black hole (BH) mergers, the new events include GW200115_042309, a signal consistent with a neutron star\u2013BH merger. We find the residual power, after subtracting the best fit waveform from the data for each event, to be consistent with the detector noise. Additionally, we find all the post-Newtonian deformation coefficients to be consistent with the predictions from GR, with an improvement by a factor of 2 in the -1PN parameter. We also find that the spin-induced quadrupole moments of the binary BH constituents are consistent with those of Kerr BHs in GR. We find no evidence for dispersion of GWs, non-GR modes of polarization, or post-merger echoes in the events that were analyzed. We update the bound on the mass of the graviton, at 90 eV/c^2. The final mass and final spin as inferred from the pre-merger and post-merger parts of the waveform are consistent with each other. The studies of the properties of the remnant BHs, including deviations of the quasi-normal mode frequencies and damping times, show consistency with the predictions of GR. In addition to considering signals individually, we also combine results from the catalog of GW signals to calculate more precise population constraints. We find no evidence in support of physics beyond GR.", "keyphrases": ["general relativity", "gwtc-3", "black hole", "fundamental physics", "cosmology"]}
{"id": "1204.4207", "title": "On Soft Limits of Inflationary Correlation Functions", "abstract": "Soft limits of inflationary correlation functions are both observationally relevant and theoretically robust. Various theorems can be proven about them that are insensitive to detailed model-building assumptions. In this paper, we re-derive several of these theorems in a universal way. Our method makes manifest why soft limits are such an interesting probe of the spectrum of additional light fields during inflation. We illustrate these abstract results with a detailed case study of the soft limits of quasi-single-field inflation.", "keyphrases": ["inflationary correlator", "consistency relation", "conformal consistency relation", "cosmological collider", "non-gaussianitie"]}
{"id": "1307.1628", "title": "A Population of Fast Radio Bursts at Cosmological Distances", "abstract": "Searches for transient astrophysical sources often reveal unexpected classes of objects that are useful physical laboratories. In a recent survey for pulsars and fast transients we have uncovered four millisecond-duration radio transients all more than 40 from the Galactic plane. The bursts' properties indicate that they are of celestial rather than terrestrial origin. Host galaxy and intergalactic medium models suggest that they have cosmological redshifts of 0.5 to 1, and distances of up to 3 gigaparsecs. No temporally coincident x- or gamma-ray signature was identified in association with the bursts. Characterization of the source population and identification of host galaxies offers an opportunity to determine the baryonic content of the Universe.", "keyphrases": ["fast radio bursts", "pulsar", "frbs", "dispersion measure", "cosmological origin"]}
{"id": "1101.0191", "title": "Modified gravity models of dark energy", "abstract": "We review recent progress of modified gravity models of dark energy\u2013based on f(R) gravity, scalar-tensor theories, braneworld gravity, Galileon gravity, and other theories. In f(R) gravity and Brans-Dicke theory it is possible to design viable models consistent with local gravity constraints under a chameleon mechanism, while satisfying conditions for the cosmological viability. The Dvali-Gabadazde-Porrati braneworld model can be compatible with local gravity constraints through a nonlinear field self-interaction arising from a brane-bending mode, but the self-accelerating solution contains a ghost mode in addition to the tension with observational data about the cosmic expansion history. The extension of the field self-interaction to more general forms satisfying a Galilean symmetry in the flat space-time allows a possibility to avoid the appearance of ghosts and Laplacian instabilities, while the late-time cosmic acceleration can be realized by the field kinetic energy. We study the evolution of cosmological perturbations in those models to place constraints on model parameters from the observations of large-scale structure, cosmic microwave background, and weak lensing. We also briefly review other modified gravitational models of dark energy\u2013 such as those based on Gauss-Bonnet gravity and Lorentz-violating theories.", "keyphrases": ["gravity model", "general relativity", "cosmological scale"]}
{"id": "1206.2503", "title": "Explosion Mechanisms of Core-Collapse Supernovae", "abstract": "Supernova theory, numerical and analytic, has made remarkable progress in the past decade. This progress was made possible by more sophisticated simulation tools, especially for neutrino transport, improved microphysics, and deeper insights into the role of hydrodynamic instabilities. Violent, large-scale nonradial mass motions are generic in supernova cores. The neutrino-heating mechanism, aided by nonradial flows, drives explosions, albeit low-energy ones, of ONeMg-core and some Fe-core progenitors. The characteristics of the neutrino emission from new-born neutron stars were revised, new features of the gravitational-wave signals were discovered, our notion of supernova nucleosynthesis was shattered, and our understanding of pulsar kicks and explosion asymmetries was significantly improved. But simulations also suggest that neutrino-powered explosions might not explain the most energetic supernovae and hypernovae, which seem to demand magnetorotational driving. Now that modeling is being advanced from two to three dimensions, more realism, new perspectives, and hopefully answers to long-standing questions are coming into reach.", "keyphrases": ["core-collapse supernovae", "nucleosynthesis", "explosion"]}
{"id": "1009.0866", "title": "The Atacama Cosmology Telescope: Cosmological Parameters from the 2008 Power Spectra", "abstract": "We present cosmological parameters derived from the angular power spectrum of the cosmic microwave background (CMB) radiation observed at 148 GHz and 218 GHz over 296 deg^2 with the Atacama Cosmology Telescope (ACT) during its 2008 season. ACT measures fluctuations at scales 500<l<10000. We fit a model for the lensed CMB, Sunyaev-Zel'dovich (SZ), and foreground contribution to the 148 GHz and 218 GHz power spectra, including thermal and kinetic SZ, Poisson power from radio and infrared point sources, and clustered power from infrared point sources. The power from thermal and kinetic SZ at 148 GHz is estimated to be B_3000 = 6.8+-2.9 uK^2, where B_l=l(l+1)C_l/2pi. We estimate primary cosmological parameters from the 148 GHz spectrum, marginalizing over SZ and source power. The LCDM cosmological model is a good fit to the data, and LCDM parameters estimated from ACT+WMAP are consistent with the 7-year WMAP limits, with scale invariant n_s = 1 excluded at 99.7 lensing is disfavored at 2.8sigma. By measuring the third to seventh acoustic peaks, and probing the Silk damping regime, the ACT data improve limits on cosmological parameters that affect the small-scale CMB power. The ACT data combined with WMAP give a 6sigma detection of primordial helium, with Y_P = 0.313+-0.044, and a 4sigma detection of relativistic species, assumed to be neutrinos, with Neff = 5.3+-1.3 (4.6+-0.8 with BAO+H0 data). From the CMB alone the running of the spectral index is constrained to be dn/dlnk = -0.034 +- 0.018, the limit on the tensor-to-scalar ratio is r<0.25 (95 possible contribution of Nambu cosmic strings to the power spectrum is constrained to string tension Gmu<1.6 \u00d710^-7 (95", "keyphrases": ["atacama cosmology telescope", "cosmological parameter", "angular power spectrum", "cosmic microwave background", "helium abundance"]}
{"id": "1007.2410", "title": "General Covariance in Quantum Gravity at a Lifshitz Point", "abstract": "In the minimal formulation of gravity with Lifshitz-type anisotropic scaling, the gauge symmetries of the system are foliation-preserving diffeomorphisms of spacetime. Consequently, compared to general relativity, the spectrum contains an extra scalar graviton polarization. Here we investigate the possibility of extending the gauge group by a local U(1) symmetry to \"nonrelativistic general covariance.\" This extended gauge symmetry eliminates the scalar graviton, and forces the coupling constant \u03bb in the kinetic term of the minimal formulation to take its relativistic value, \u03bb=1. The resulting theory exhibits anisotropic scaling at short distances, and reproduces many features of general relativity at long distances.", "keyphrases": ["quantum gravity", "foliation-preserving diffeomorphism", "general covariance", "newtonian pre-potential"]}
{"id": "1205.1056", "title": "A two measure model of dark energy and dark matter", "abstract": "In this work we construct a unified model of dark energy and dark matter. This is done with the following three elements: a gravitating scalar field, phi with a non-conventional kinetic term, as in the string theory tachyon; an arbitrary potential, V(phi); two measures \u2013 a metric measure (sqrt-g) and a non-metric measure (Phi). The model has two interesting features: (i) For potentials which are unstable and would give rise to tachyonic scalar field, this model can stabilize the scalar field. (ii) The form of the dark energy and dark matter that results from this model is fairly insensitive to the exact form of the scalar field potential.", "keyphrases": ["dark energy", "dark matter", "scalar field"]}
{"id": "1509.00590", "title": "Interdependence between integrable cosmological models with minimal and non-minimal coupling", "abstract": "We consider the relation between exact solutions of cosmological models having minimally and non-minimally coupled scalar fields. This is done for a particular class of solvable models which, in the Einstein frame, have potentials depending on hyperbolic functions and in the Jordan frame, where the non-minimal coupling is conformal, possess a relatively simple dynamics. We show that a particular model in this class can be generalized to the cases of closed and open Friedmann universes and still exhibits a simple dynamics. Further we illustrate the conditions for the existences of bounces in some sub-classes of the set of integrable models we have considered.", "keyphrases": ["cosmological model", "non-minimal coupling", "scalar field", "integrable model"]}
{"id": "1701.00836", "title": "Adaptive optics in high-contrast imaging", "abstract": "The development of adaptive optics (AO) played a major role in modern astronomy over the last three decades. By compensating for the atmospheric turbulence, these systems enable to reach the diffraction limit on large telescopes. In this review, we will focus on high contrast applications of adaptive optics, namely, imaging the close vicinity of bright stellar objects and revealing regions otherwise hidden within the turbulent halo of the atmosphere to look for objects with a contrast ratio lower than 10^-4 with respect to the central star. Such high-contrast AO-corrected observations have led to fundamental results in our current understanding of planetary formation and evolution as well as stellar evolution. AO systems equipped three generations of instruments, from the first pioneering experiments in the nineties, to the first wave of instruments on 8m-class telescopes in the years 2000, and finally to the extreme AO systems that have recently started operations. Along with high-contrast techniques, AO enables to reveal the circumstellar environment: massive protoplanetary disks featuring spiral arms, gaps or other asymmetries hinting at on-going planet formation, young giant planets shining in thermal emission, or tenuous debris disks and micron-sized dust leftover from collisions in massive asteroid-belt analogs. After introducing the science case and technical requirements, we will review the architecture of standard and extreme AO systems, before presenting a few selected science highlights obtained with recent AO instruments.", "keyphrases": ["high-contrast imaging", "adaptive optic", "performance"]}
{"id": "1105.3621", "title": "A generalized lens equation for light deflection in weak gravitational fields", "abstract": "A generalized lens equation for weak gravitational fields in Schwarzschild metric and valid for finite distances of source and observer from the light deflecting body is suggested. The magnitude of neglected terms in the generalized lens equation is estimated to be smaller than or equal to 15 Pi/4 (m/d')^2, where m is the Schwarzschild radius of massive body and d' is Chandrasekhar's impact parameter. The main applications of this generalized lens equation are extreme astrometrical configurations, where 'Standard post-Newtonian approach' as well as 'Classical lens equation' cannot be applied. It is shown that in the appropriate limits the proposed lens equation yields the known post-Newtonian terms, 'enhanced' post-post-Newtonian terms and the Classical lens equation, thus provides a link between these both essential approaches for determining the light deflection.", "keyphrases": ["lens equation", "light deflection", "weak gravitational field"]}
{"id": "2009.14048", "title": "Magnetic reconnection and thermal equilibration", "abstract": "When a magnetic field is forced to evolve on a time scale \u03c4_ev, as by footpoint motions driving the solar corona or non-axisymmetric instabilities in tokamaks, the magnetic field lines undergo large-scale changes in topology on a time scale approximately an order of magnitude longer than \u03c4_ev. But, the physics that allows such changes operates on a time scale eight or more orders of magnitude slower. An analogous phenomenon occurs in air. Temperature equilibration occurs on a time scale approximately an order of magnitude longer than it takes air to cross a room, \u03c4_ev, although the physical mechanism that allows temperature equilibration is approximately four orders of magnitude slower than \u03c4_ev. The use of Lagrangian coordinates allows the fundamental equations to be solved and both phenomena explained. The paradigms and presumptions of traditional theories of magnetic reconnection are so ingrained that the understanding gained from analyses using Lagrangian coordinates has been largely ignored. The theories of thermal equilibration and magnetic reconnection are developed in parallel to help readers obtain an understanding of the importance and implications of analyses using Lagrangian coordinates.", "keyphrases": ["thermal equilibration", "solar corona", "magnetic reconnection"]}
{"id": "1511.07659", "title": "Detection Efficiency of Asteroid Surveys", "abstract": "A comprehensive characterization of the detection efficiency of nine of the major asteroid surveys that have been active over the past two decades is presented. The detection efficiency is estimated on a nightly basis by comparing the detected asteroids with the complete catalog of known asteroids propagated to the same observing epoch. Results include a nightly estimate of the detection efficiency curves as a function of apparent magnitude and apparent velocity of the asteroids, as well as a cumulative analysis to estimate the overall performance of each survey. The limiting magnitude distribution is estimated for each survey, and it is then modeled as a function of telescope aperture to obtain an estimate over a wide range of apertures.", "keyphrases": ["asteroid survey", "apparent magnitude", "detection efficiency"]}
{"id": "1210.3245", "title": "Anelastic dynamo models with variable electrical conductivity: an application to gas giants", "abstract": "The observed surface dynamics of Jupiter and Saturn is dominated by a banded system of zonal winds. Their depth remains unclear but they are thought to be confined to the very outer envelopes where hydrogen remains molecular and the electrical conductivity is small. The dynamo maintaining the dipole-dominated magnetic fields of both gas giants likely operates in the deeper interior where hydrogen assumes a metallic state. Here, we present numerical simulations that attempt to model both the zonal winds and the interior dynamo action in an integrated approach. Using the anelastic version of the MHD code MagIC, we explore the effects of density stratification and radial electrical conductivity variation. The electrical conductivity is mostly assumed to remain constant in the thicker inner metallic region and it decays exponentially towards the outer boundary throughout the molecular envelope. Our results show that the combination of stronger density stratification and weaker conducting outer layer is essential for reconciling dipole dominated dynamo action and a fierce equatorial zonal jet. Previous simulations with homogeneous electrical conductivity show that both are merely exclusive, with solutions either having strong zonal winds and multipolar magnetic fields or weak zonal winds and dipole-dominated magnetic fields. All jets tend to be geostrophic and therefore reach right through the convective shell in our simulations. The particular setup explored here allows a strong equatorial jet to remain confined to the weaker conducting outer region where it does not interfere with the deeper seated dynamo action. The flanking mid to high latitude jets, on the other hand, have to remain faint to yield a strongly dipolar magnetic field. The fiercer jets on Jupiter and Saturn only seem compatible with the observed dipolar fields when they remain confined to a weaker conducting outer layer.", "keyphrases": ["dynamo model", "electrical conductivity", "gas giant"]}
{"id": "1502.01249", "title": "The Yarkovsky and YORP Effects", "abstract": "The Yarkovsky effect describes a small but significant force that affects the orbital motion of meteoroids and asteroids smaller than 30-40 kilometers in diameter. It is caused by sunlight; when these bodies heat up in the Sun, they eventually re-radiate the energy away in the thermal waveband, which in turn creates a tiny thrust. This recoil acceleration is much weaker than solar and planetary gravitational forces, but it can produce measurable orbital changes over decades and substantial orbital effects over millions to billions of years. The same physical phenomenon also creates a thermal torque that, complemented by a torque produced by scattered sunlight, can modify the rotation rates and obliquities of small bodies as well. This rotational variant has been coined the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect. During the past decade or so, the Yarkovsky and YORP effects have been used to explore and potentially resolve a number of unsolved mysteries in planetary science dealing with small bodies. Here we review the main results to date, and preview the goals for future work.", "keyphrases": ["yarkovsky", "yorp effect", "physical phenomenon", "rotation rate", "gravitational perturbation"]}
{"id": "1003.1745", "title": "Cosmology of the Very Early Universe", "abstract": "In these lectures I focus on early universe models which can explain the currently observed structure on large scales. I begin with a survey of inflationary cosmology, the current paradigm for understanding the origin of the universe as we observe it today. I will discuss some progress and problems in inflationary cosmology before moving on to a description of two alternative scenarios - the Matter Bounce and String Gas Cosmology. All early universe models connect to observations via the evolution of cosmological perturbations - a topic which will be discussed in detail in these lectures.", "keyphrases": ["matter bounce", "cosmology", "universe scenario"]}
{"id": "1202.1247", "title": "Backreaction on the luminosity-redshift relation from gauge invariant light-cone averaging", "abstract": "Using a recently proposed gauge invariant formulation of light-cone averaging, together with adapted \"geodesic light-cone\" coordinates, we show how an \"induced backreaction\" effect emerges, in general, from correlated fluctuations in the luminosity distance and covariant integration measure. Considering a realistic stochastic spectrum of inhomogeneities of primordial (inflationary) origin we find that both the induced backreaction on the luminosity-redshift relation and the dispersion are larger than naively expected. On the other hand the former, at least to leading order and in the linear perturbative regime, cannot account by itself for the observed effects of dark energy at large-redshifts. A full second-order calculation, or even better a reliable estimate of contributions from the non-linear regime, appears to be necessary before firm conclusions on the correct interpretation of the data can be drawn.", "keyphrases": ["luminosity-redshift relation", "gauge", "light-cone averaging"]}
{"id": "1105.5280", "title": "What galaxy surveys really measure", "abstract": "In this paper we compute the quantity which is truly measured in a large galaxy survey. We take into account the effects coming from the fact that we actually observe galaxy redshifts and sky positions and not true spatial positions. Our calculations are done within linear perturbation theory for both the metric and the observer velocities but they can be used for non-linear matter power spectra. We shall see that the complications due to the fact that we only observe on our background lightcone and that we do not truly know the distance of the observed galaxy, but only its redshift is not only an additional difficulty, but even more a new opportunity for future galaxy surveys.", "keyphrases": ["galaxy survey", "relativistic effect", "large scale", "matter density fluctuation", "telescope"]}
{"id": "0904.3542", "title": "Multiple Spectral Splits of Supernova Neutrinos", "abstract": "Collective oscillations of supernova neutrinos swap the electron neutrino and antineutrino spectra with those of another flavor in certain energy intervals bounded by sharp spectral splits. This phenomenon is far more general than previously appreciated: typically one finds one or more swaps and accompanying splits in the neutrino and antineutrino channels for both inverted and normal neutrino mass hierarchies. Depending on an instability condition, swaps develop around spectral crossings (energies where the electron neutrino or antineutrino fluxes are equal to that of another flavor, as well as infinite E where all fluxes vanish), and the widths of swaps are determined by the spectra and fluxes. Wash-out by multi-angle decoherence varies across the spectrum and splits can survive as sharp spectral features.", "keyphrases": ["supernova neutrinos", "neutrino", "flavor transition"]}
{"id": "1106.3228", "title": "Parity Violation in Graviton Non-gaussianity", "abstract": "We study parity violation in graviton non-gaussianity generated during inflation. We develop a useful formalism to calculate graviton non-gaussianity. Using this formalism, we explicitly calculate the parity violating part of the bispectrum for primordial gravitational waves in the exact de Sitter spacetime and prove that no parity violation appears in the non-gaussianity. We also extend the analysis to slow-roll inflation and find that the parity violation of the bispectrum is proportional to the slow-roll parameter. We argue that parity violating non-gaussianity can be tested by the CMB. Our results are also useful for calculating three-point function of the stress tensor in the non-conformal field theory through the gravity/field theory correspondence.", "keyphrases": ["graviton non-gaussianity", "primordial gravitational wave", "parity violation"]}
{"id": "1203.2984", "title": "Cosmological evolution of finite temperature Bose-Einstein Condensate dark matter", "abstract": "Once the temperature of a bosonic gas is smaller than the critical, density dependent, transition temperature, a Bose - Einstein Condensation process can take place during the cosmological evolution of the Universe. Bose - Einstein Condensates are very strong candidates for dark matter, since they can solve some major issues in observational astrophysics, like, for example, the galactic core/cusp problem. The presence of the dark matter condensates also drastically affects the cosmic history of the Universe. In the present paper we analyze the effects of the finite dark matter temperature on the cosmological evolution of the Bose-Einstein Condensate dark matter systems. We formulate the basic equations describing the finite temperature condensate, representing a generalized Gross-Pitaevskii equation that takes into account the presence of the thermal cloud in thermodynamic equilibrium with the condensate. The temperature dependent equations of state of the thermal cloud and of the condensate are explicitly obtained in an analytical form. By assuming a flat Friedmann-Robertson-Walker (FRW) geometry, the cosmological evolution of the finite temperature dark matter filled Universe is considered in detail in the framework of a two interacting fluid dark matter model, describing the transition from the initial thermal cloud to the low temperature condensate state. The dynamics of the cosmological parameters during the finite temperature dominated phase of the dark matter evolution are investigated in detail, and it is shown that the presence of the thermal excitations leads to an overall increase in the expansion rate of the Universe.", "keyphrases": ["dark matter", "einstein condensate", "cosmological implication"]}
{"id": "1409.3627", "title": "Parity-odd correlators of diffuse gamma rays and intergalactic magnetic fields", "abstract": "We develop the connection between intergalactic helical magnetic fields and parity odd signatures in the diffuse gamma ray sky. We find that the location and the amplitude of a peak in a parity odd correlator, Q(R), can be used to infer the normal and helical power spectra of the intergalactic magnetic field. When applied to Fermi-LAT data, the amplitude of the observed peak in Q(R) gives \u223c 10^-14 G intergalactic magnetic field strength, which is consistent with an earlier independent estimate that only used the peak location (Tashiro et al. 2014). We discuss features in the observed Q(R) that further support the intergalactic magnetic field hypothesis and make predictions for future tests.", "keyphrases": ["correlator", "intergalactic magnetic field", "magnetic field", "helicity", "fermi-lat"]}
{"id": "2111.00013", "title": "Magnetohydrodynamic simulations of self-consistent rotating neutron stars with mixed poloidal and toroidal magnetic fields", "abstract": "We perform the first magnetohydrodynamic simulations in full general relativity of self-consistent rotating neutron stars (NSs) with ultrastrong mixed poloidal and toroidal magnetic fields. The initial uniformly rotating NS models are computed assuming perfect conductivity, stationarity, and axisymmetry. Although the specific geometry of the mixed field configuration can delay or accelerate the development of various instabilities known from analytic perturbative studies, all our models finally succumb to them. Differential rotation is developed spontaneously in the cores of our magnetars which, after sufficient time, is converted back to uniform rotation. The rapidly rotating magnetars show a significant amount of ejecta, which can be responsible for transient kilonova signatures. However no highly collimated, helical magnetic fields or incipient jets, which are necessary for gamma-ray bursts, arise at the poles of these magnetars by the time our simulations are terminated.", "keyphrases": ["neutron star", "toroidal magnetic field", "magnetohydrodynamic simulation"]}
{"id": "1112.3365", "title": "Contact Term, its Holographic Description in QCD and Dark Energy", "abstract": "In this work we study the well known contact term, which is the key element in resolving the so-called U(1)_A problem in QCD. We study this term using the dual Holographic Description. We argue that in the dual picture the contact term is saturated by the D2 branes which can be interpreted as the tunnelling events in Minkowski space-time. We quote a number of direct lattice results supporting this identification. We also argue that the contact term receives a Casimir -like correction \u223c ( R)^-1 rather than naively expected exp(- R) when the Minkowski space-time R_3,1 is replaced by a large but finite manifold with a size R. Such a behaviour is consistent with other QFT-based computations when power like corrections are due to nontrivial properties of topological sectors of the theory. In holographic description such a behaviour is due to massless Ramond-Ramond (RR) field living in the bulk of multidimensional space when power like corrections is a natural outcome of massless RR field. In many respects the phenomenon is similar to the Aharonov -Casher effect when the \"modular electric field\" can penetrate into a superconductor where the electric field is exponentially screened. The role of \"modular operator\" from Aharonov -Casher effect is played by large gauge transformation operator T in 4d QCD, resulting the transparency of the system to topologically nontrivial pure gauge configurations. We discuss some profound consequences of our findings. In particular, we speculate that a slow variation of the contact term in expanding universe might be the main source of the observed Dark Energy.", "keyphrases": ["holographic description", "dark energy", "quantum field theory"]}
{"id": "0902.4399", "title": "Optimal Binning of the Primordial Power Spectrum", "abstract": "The primordial power spectrum describes the initial perturbations in the Universe which eventually grew into the large-scale structure we observe today, and thereby provides an indirect probe of inflation or other structure-formation mechanisms. In this paper we will investigate the best scales the primordial power spectrum can be probed, in accordance with the knowledge about other cosmological parameters such as \u03a9_b, \u03a9_c, \u03a9_\u039b, h and \u03c4. The aim is to find the most informative way of measuring the primordial power spectrum at different length scales, using different types of surveys and the information they provide for the desired cosmological parameters. We will find the optimal binning of the primordial power spectrum for this purpose, by making use of the Fisher matrix formalism. We will then find a statistically orthogonal basis for a set of cosmological parameters, mentioned above, and a set of bins of the primordial power spectrum to investigate the correlation between the two sets. For this purpose we make use of principal component analysis and Hermitian square root of the Fisher matrix. The surveys used in this project are Planck and SDSS(BRG), but the formalism can easily be extended to any windowed measurements of the perturbation spectrum.", "keyphrases": ["binning", "primordial power spectrum", "fisher matrix formalism"]}
{"id": "1702.08825", "title": "Neutrino-driven Explosions", "abstract": "The question why and how core-collapse supernovae (SNe) explode is one of the central and most long-standing riddles of stellar astrophysics. A solution is crucial for deciphering the SN phenomenon, for predicting observable signals such as light curves and spectra, nucleosynthesis, neutrinos, and gravitational waves, for defining the role of SNe in the evolution of galaxies, and for explaining the birth conditions and properties of neutron stars (NSs) and stellar-mass black holes. Since the formation of such compact remnants releases over hundred times more energy in neutrinos than the SN in the explosion, neutrinos can be the decisive agents for powering the SN outburst. According to the standard paradigm of the neutrino-driven mechanism, the energy transfer by the intense neutrino flux to the medium behind the stagnating core-bounce shock, assisted by violent hydrodynamic mass motions (sometimes subsumed by the term \"turbulence\"), revives the outward shock motion and thus initiates the SN blast. Because of the weak coupling of neutrinos in the region of this energy deposition, detailed, multidimensional hydrodynamic models including neutrino transport and a wide variety of physics are needed to assess the viability of the mechanism. Owing to advanced numerical codes and increasing supercomputer power, considerable progress has been achieved in our understanding of the physical processes that have to act in concert for the success of neutrino-driven explosions. First studies begin to reveal observational implications and avenues to test the theoretical picture by data from individual SNe and SN remnants but also from population-integrated observables. While models will be further refined, a real breakthrough is expected through the next Galactic core-collapse SN, when neutrinos and gravitational waves can be used to probe the conditions deep inside the dying star. (abridged)", "keyphrases": ["explosion", "core-collapse supernovae", "neutrino", "neutrino-driven explosion"]}
{"id": "1208.3399", "title": "Dynamics of oscillating scalar field in thermal environment", "abstract": "There often appear coherently oscillating scalar fields in particle physics motivated cosmological scenarios, which may have rich phenomenological consequences. Scalar fields should somehow interact with background thermal bath in order to decay into radiation at an appropriate epoch, but introducing some couplings to the scalar field makes the dynamics complicated. We investigate in detail the dynamics of a coherently oscillating scalar field, which has renormalizable couplings to another field interacting with thermal background. The scalar field dynamics and its resultant abundance are significantly modified by taking account of following effects : (1) thermal correction to the effective potential, (2) dissipation effect on the scalar field in thermal bath, (3) non-perturbative particle production events and (4) formation of non-topological solitons. There appear many time scales depending on the scalar mass, amplitude, couplings and the background temperature, which make the efficiencies of these effects non-trivial.", "keyphrases": ["scalar field", "dissipation effect", "soliton"]}
{"id": "1112.0524", "title": "Astrophysical uncertainties on direct detection experiments", "abstract": "Direct detection experiments are poised to detect dark matter in the form of weakly interacting massive particles (WIMPs). The signals expected in these experiments depend on the ultra-local WIMP density and velocity distribution. Firstly we review methods for modelling the dark matter distribution. We then discuss observational determinations of the local dark matter density, circular speed and escape speed and the results of numerical simulations of Milky Way-like dark matter halos. In each case we highlight the uncertainties and assumptions made. We then overview the resulting uncertainties in the signals expected in direct detection experiments, specifically the energy, time and direction dependence of the event rate. Finally we conclude by discussing techniques for handling the astrophysical uncertainties when interpreting data from direct detection experiments.", "keyphrases": ["direct detection experiment", "particle", "astrophysical uncertainty"]}
{"id": "1305.5259", "title": "Two Field Matter Bounce Cosmology", "abstract": "We re-examine the non-singular Matter Bounce scenario first developed in [arXiv:1206.2382], which starts with a matter-dominated period of contraction and transitions into an Ekpyrotic phase of contraction. We consider both matter fields, the first of which plays the role of regular matter, and the second of which is responsible for the non-singular bounce. Since the dominant matter field is massive, the induced curvature fluctuations are initially not scale-invariant, whereas the fluctuations of the second scalar field (which are initially entropy fluctuations) are scale-invariant. We study the transfer of the initial entropy perturbations into curvature fluctuations in the matter-dominated phase of contraction and show that the latter become nearly scale invariant on large scales but are blue tilted on small scales. We study the evolution of both curvature and entropy fluctuations through the bounce, and show that both have a scale-invariant spectrum which is blue-tilted on small scales. However, we find that the entropy fluctuations have an amplitude that is much smaller than that of the curvature perturbations, due to gravitational amplification of curvature perturbations during the bounce phase.", "keyphrases": ["cosmology", "matter bounce scenario", "scalar field"]}
{"id": "1009.2068", "title": "Probing dark matter models with neutrinos from the Galactic center", "abstract": "We calculate the contained and upward muon and shower fluxes due to neutrinos produced via dark matter annihilation or decay in the Galactic center. We consider dark matter models in which the dark matter particle is a gravitino, a Kaluza-Klein particle and a particle in leptophilic models. The Navarro-Frenk-White profile for the dark matter density distribution in the Galaxy is used. We incorporate neutrino oscillations by assuming maximal mixing and parametrize our results for muon and shower distributions. The muon and shower event rates and the minimum observation times in order to reach 2\u03c3 detection significance are evaluated. We illustrate how observation times vary with the cone half angle chosen about the Galactic center, with the result that the optimum angles are about 10^\u2218 and 50^\u2218 for the muon events and shower events, respectively. We find that for the annihilating dark matter models such as the leptophilic and Kaluza-Klein models, upward and contained muon as well as showers are promising signals for dark matter detection in just a few years of observation, whereas for decaying dark matter models, the same observation times can only be reached with showers. We also illustrate for each model the parameter space probed with the 2\u03c3 signal detection in five years. We discuss how the shape of the parameter space probed change with significance and the observation time.", "keyphrases": ["dark matter model", "neutrino", "galactic center"]}
{"id": "1409.0042", "title": "Background model systematics for the Fermi GeV excess", "abstract": "The possible gamma-ray excess in the inner Galaxy and the Galactic center (GC) suggested by Fermi-LAT observations has triggered a large number of studies. It has been interpreted as a variety of different phenomena such as a signal from WIMP dark matter annihilation, gamma-ray emission from a population of millisecond pulsars, or emission from cosmic rays injected in a sequence of burst-like events or continuously at the GC. We present the first comprehensive study of model systematics coming from the Galactic diffuse emission in the inner part of our Galaxy and their impact on the inferred properties of the excess emission at Galactic latitudes 2^\u2218<|b|<20^\u2218 and 300 MeV to 500 GeV. We study both theoretical and empirical model systematics, which we deduce from a large range of Galactic diffuse emission models and a principal component analysis of residuals in numerous test regions along the Galactic plane. We show that the hypothesis of an extended spherical excess emission with a uniform energy spectrum is compatible with the Fermi-LAT data in our region of interest at 95% CL. Assuming that this excess is the extended counterpart of the one seen in the inner few degrees of the Galaxy, we derive a lower limit of 10.0^\u2218 (95% CL) on its extension away from the GC. We show that, in light of the large correlated uncertainties that affect the subtraction of the Galactic diffuse emission in the relevant regions, the energy spectrum of the excess is equally compatible with both a simple broken power-law of break energy 2.1\u00b10.2 GeV, and with spectra predicted by the self-annihilation of dark matter, implying in the case of b\u0305b final states a dark matter mass of 49^+6.4_-5.4 GeV.", "keyphrases": ["gamma-ray excess", "fermi-lat", "dark matter", "galactic center excess", "annihilation cross section"]}
{"id": "1201.0068", "title": "The fastest way to circle a black hole", "abstract": "Black-hole spacetimes with a \"photonsphere\", a hypersurface on which massless particles can orbit the black hole on circular null geodesics, are studied. We prove that among all possible trajectories (both geodesic and non-geodesic) which circle the central black hole, the null circular geodesic is characterized by the shortest possible orbital period as measured by asymptotic observers. Thus, null circular geodesics provide the fastest way to circle black holes. In addition, we conjecture the existence of a universal lower bound for orbital periods around compact objects (as measured by flat-space asymptotic observers): T_\u221e\u2265 4\u03c0 M, where M is the mass of the central object. This bound is saturated by the null circular geodesic of the maximally rotating Kerr black hole.", "keyphrases": ["black hole", "circular null geodesic", "fast way"]}
{"id": "1104.1174", "title": "The effects of galaxy formation on the matter power spectrum: A challenge for precision cosmology", "abstract": "Upcoming weak lensing surveys, such as LSST, EUCLID, and WFIRST, aim to measure the matter power spectrum with unprecedented accuracy. In order to fully exploit these observations, models are needed that, given a set of cosmological parameters, can predict the non-linear matter power spectrum at the level of 1 0.1<k<10 h/Mpc. We have employed the large suite of simulations from the OWLS project to investigate the effects of various baryonic processes on the matter power spectrum. In addition, we have examined the distribution of power over different mass components, the back-reaction of the baryons on the CDM, and the evolution of the dominant effects on the matter power spectrum. We find that single baryonic processes are capable of changing the power spectrum by up to several tens of per cent. Our simulation that includes AGN feedback, which we consider to be our most realistic simulation as, unlike those used in previous studies, it has been shown to solve the overcooling problem and to reproduce optical and X-ray observations of groups of galaxies, predicts a decrease in power relative to a dark matter only simulation ranging, at z=0, from 1 k 0.3 h/Mpc to 10 naive view that baryons raise the power through cooling, which is the dominant effect only for k>70 h/Mpc. Therefore, baryons, and particularly AGN feedback, cannot be ignored in theoretical power spectra for k>0.3 h/Mpc. It will thus be necessary to improve our understanding of feedback processes in galaxy formation, or at least to constrain them through auxiliary observations, before we can fulfil the goals of upcoming weak lensing surveys.", "keyphrases": ["galaxy formation", "matter power spectrum", "cosmology", "baryon"]}
{"id": "1404.3713", "title": "Maximal freedom at minimum cost: linear large-scale structure in general modifications of gravity", "abstract": "We present a turnkey solution, ready for implementation in numerical codes, for the study of linear structure formation in general scalar-tensor models involving a single universally coupled scalar field. We show that the totality of cosmological information on the gravitational sector can be compressed - without any redundancy - into five independent and arbitrary functions of time only and one constant. These describe physical properties of the universe: the observable background expansion history, fractional matter density today, and four functions of time describing the properties of the dark energy. We show that two of those dark-energy property functions control the existence of anisotropic stress, the other two - dark-energy clustering, both of which are can be scale-dependent. All these properties can in principle be measured, but no information on the underlying theory of acceleration beyond this can be obtained. We present a translation between popular models of late-time acceleration (e.g. perfect fluids, f (R), kinetic gravity braiding, galileons), as well as the effective field theory framework, and our formulation. In this way, implementing this formulation numerically would give a single tool which could consistently test the majority of models of late-time acceleration heretofore proposed.", "keyphrases": ["gravity", "dark energy", "property function", "effective field theory", "horndeski theory"]}
{"id": "1308.6587", "title": "Black holes with surrounding matter in scalar-tensor theories", "abstract": "We uncover two mechanisms that can render Kerr black holes unstable in scalar-tensor gravity, both associated to the presence of matter in the vicinity of the black hole and the fact that this introduces an effective mass for the scalar. Our results highlight the importance of understanding the structure of spacetime in realistic, astrophysical black holes in scalar-tensor theories.", "keyphrases": ["scalar-tensor theory", "gravity", "black hole"]}
{"id": "1408.3856", "title": "Extreme neutron stars from Extended Theories of Gravity", "abstract": "We discuss neutron stars with strong magnetic mean fields in the framework of Extended Theories of Gravity. In particular, we take into account models derived from f(R) and f( G) extensions of General Relativity where functions of the Ricci curvature invariant R and the Gauss-Bonnet invariant G are respectively considered. Dense matter in magnetic mean field, generated by magnetic properties of particles, is described by assuming a model with three meson fields and baryons octet. As result, the considerable increasing of maximal mass of neutron stars can be achieved by cubic corrections in f(R) gravity. In principle, massive stars with M> 4 M_\u2299 can be obtained. On the other hand, stable stars with high strangeness fraction (with central densities \u03c1_c\u223c 1.5-2.0 GeV/fm^3) are possible considering quadratic corrections of f(G) gravity. The magnetic field strength in the star center is of order 6-8\u00d7 10^18 G. In general, we can say that other branches of massive neutron stars are possible considering the extra pressure contributions coming from gravity extensions. Such a feature can constitute both a probe for alternative theories and a way out to address anomalous self-gravitating compact systems.", "keyphrases": ["neutron star", "gravity", "astrophysical level"]}
{"id": "1906.11549", "title": "Probing Primordial-Black-Hole Dark Matter with Scalar Induced Gravitational Waves", "abstract": "The possibility that primordial black holes (PBHs) represent all of the dark matter (DM) in the Universe and explain the coalescences of binary black holes detected by LIGO/Virgo has attracted a lot of attention. PBHs are generated by the enhancement of scalar perturbations which inevitably produce the induced gravitational waves (GWs). We calculate the induced GWs up to the third-order correction which not only enhances the amplitude of induced GWs, but also extends the cutoff frequency from 2k_* to 3k_*. Such effects of the third-order correction lead to an around 10% increase of the signal-to-noise ratio (SNR) for both LISA and pulsar timing array (PTA) observations, and significantly widen the mass range of PBHs in the stellar mass window accompanying detectable induced GWs for PTA observations including IPTA, FAST and SKA. On the other hand, the null detections of the induced GWs by LISA and PTA experiments will exclude the possibility that all of the DM is comprised of PBHs and the GW events detected by LIGO/Virgo are generated by PBHs.", "keyphrases": ["dark matter", "gravitational wave", "black hole"]}
{"id": "1111.4124", "title": "Nuclear matter fourth-order symmetry energy in the relativistic mean field models", "abstract": "Within the nonlinear relativistic mean field model, we derive the analytical expression of the nuclear matter fourth-order symmetry energy E_sym,4(\u03c1). Based on two accurately calibrated interactions FSUGold and IU-FSU, our results show that the value of E_sym,4(\u03c1) at normal nuclear matter density \u03c1_0 is generally less than 1 MeV, confirming the empirical parabolic approximation to the equation of state for asymmetric nuclear matter at \u03c1_0. On the other hand, we find that the E_sym,4(\u03c1) may become nonnegligible at high densities. Furthermore, the analytical form of the E_sym,4(\u03c1) provides the possibility to study the higher-order effects on the isobaric incompressibility of asymmetric nuclear matter, i.e., K_sat(\u03b4)=K_0+K_sat,2\u03b4 ^2+K_sat,4\u03b4 ^4+\ud835\udcaa(\u03b4 ^6) where \u03b4 =(\u03c1_n-\u03c1_p)/\u03c1 is the isospin asymmetry, and we find that the value of K_sat,4 is generally small compared with that of the K_sat,2. In addition, we study the effects of the E_sym,4(\u03c1) on the proton fraction x_p and the core-crust transition density \u03c1_t and pressure P_t in neutron stars. Interestingly, we find that, compared with the results from the empirical parabolic approximation, including the E_sym,4(\u03c1) contribution can significantly enhance the x_p at high densities and strongly reduce the \u03c1_t and P_t in neutron stars, demonstrating that the widely used empirical parabolic approximation may cause large errors in determining the x_p at high densities as well as the \u03c1_t and P_t in neutron stars within the nonlinear relativistic mean field model, consistent with previous nonrelativistic calculations.", "keyphrases": ["symmetry energy", "neutron star", "nuclear matter"]}
{"id": "1004.0818", "title": "Local non-Gaussianity from inflation", "abstract": "The non-Gaussian distribution of primordial perturbations has the potential to reveal the physical processes at work in the very early Universe. Local models provide a well-defined class of non-Gaussian distributions that arise naturally from the non-linear evolution of density perturbations on super-Hubble scales starting from Gaussian field fluctuations during inflation. I describe the delta-N formalism used to calculate the primordial density perturbation on large scales and then review several models for the origin of local primordial non-Gaussianity, including the cuvaton, modulated reheating and ekpyrotic scenarios. I include an appendix with a table of sign conventions used in specific papers.", "keyphrases": ["non-gaussianity", "early universe", "fluctuation", "hubble scale"]}
{"id": "1008.5159", "title": "Test bodies and naked singularities: is the self-force the cosmic censor?", "abstract": "Jacobson and Sotiriou showed that rotating black holes could be spun-up past the extremal limit by the capture of non-spinning test bodies, if one neglects radiative and self-force effects. This would represent a violation of the Cosmic Censorship Conjecture in four-dimensional, asymptotically flat spacetimes. We show that for some of the trajectories giving rise to naked singularities, radiative effects can be neglected. However, for these orbits the conservative self-force is important, and seems to have the right sign to prevent the formation of naked singularities.", "keyphrases": ["naked singularity", "self-force", "black hole", "test body", "stability"]}
{"id": "2101.03179", "title": "A Luminous Quasar at Redshift 7.642", "abstract": "Distant quasars are unique tracers to study the formation of the earliest supermassive black holes (SMBHs) and the history of cosmic reionization. Despite extensive efforts, only two quasars have been found at z\u22657.5, due to a combination of their low spatial density and the high contamination rate in quasar selection. We report the discovery of a luminous quasar at z=7.642, J0313-1806, the most distant quasar yet known. This quasar has a bolometric luminosity of 3.6\u00d710^13 L_\u2299. Deep spectroscopic observations reveal a SMBH with a mass of (1.6\u00b10.4) \u00d710^9M_\u2299 in this quasar. The existence of such a massive SMBH just \u223c670 million years after the Big Bang challenges significantly theoretical models of SMBH growth. In addition, the quasar spectrum exhibits strong broad absorption line (BAL) features in CIV and SiIV, with a maximum velocity close to 20 relativistic BAL features, combined with a strongly blueshifted CIV emission line, indicate that there is a strong active galactic nucleus (AGN) driven outflow in this system. ALMA observations detect the dust continuum and [CII] emission from the quasar host galaxy, yielding an accurate redshift of 7.6423 \u00b1 0.0013 and suggesting that the quasar is hosted by an intensely star-forming galaxy, with a star formation rate of \u223c 200 M_\u2299 yr^-1 and a dust mass of \u223c7\u00d710^7 M_\u2299. Followup observations of this reionization-era BAL quasar will provide a powerful probe of the effects of AGN feedback on the growth of the earliest massive galaxies.", "keyphrases": ["quasar", "host galaxy", "universe"]}
{"id": "1007.0414", "title": "A Survey of Stellar Families: Multiplicity of Solar-Type Stars", "abstract": "We present the results of a comprehensive assessment of companions to solar-type stars. A sample of 454 stars, including the Sun, was selected from the Hipparcos catalog with \u03c0 > 40 mas, \u03c3_\u03c0/\u03c0 < 0.05, 0.5 < B - V < 1.0 ( F6-K3), and constrained by absolute magnitude and color to exclude evolved stars. New observational aspects of this work include surveys for (1) very close companions with long-baseline interferometry at the CHARA Array, (2) close companions with speckle interferometry, and (3) wide proper motion companions identified by blinking multi-epoch archival images. In addition, we include the results from extensive radial-velocity monitoring programs and evaluate companion information from various catalogs. The overall observed fractions of single, double, triple, and higher order systems are 56 counting all confirmed stellar and brown dwarf companions. Our completeness analysis indicates that only a few undiscovered companions remain in this well-studied sample, implying that the majority (54 stars are single, in contrast to the results of prior multiplicity studies. The orbital-period distribution of companions is unimodal and roughly log-normal with a peak of about 300 years. The period-eccentricity relation shows a roughly flat distribution beyond the expected circularization for periods below 12 days. The mass-ratio distribution shows a preference for like-mass pairs, which occur more frequently in relatively close pairs. The fraction of planet hosts among single, binary, and multiple systems are statistically indistinguishable, suggesting that planets are as likely to form around single stars as they are around components of binary or multiple systems with sufficiently wide separations.", "keyphrases": ["solar-type star", "majority", "planet"]}
{"id": "1009.2770", "title": "Formation of asteroid pairs by rotational fission", "abstract": "Asteroid pairs sharing similar heliocentric orbits were found recently. Backward integrations of their orbits indicated that they separated gently with low relative velocities, but did not provide additional insight into their formation mechanism. A previously hypothesized rotational fission process4 may explain their formation - critical predictions are that the mass ratios are less than about 0.2 and, as the mass ratio approaches this upper limit, the spin period of the larger body becomes long. Here we report photometric observations of a sample of asteroid pairs revealing that primaries of pairs with mass ratios much less than 0.2 rotate rapidly, near their critical fission frequency. As the mass ratio approaches 0.2, the primary period grows long. This occurs as the total energy of the system approaches zero requiring the asteroid pair to extract an increasing fraction of energy from the primary's spin in order to escape. We do not find asteroid pairs with mass ratios larger than 0.2. Rotationally fissioned systems beyond this limit have insufficient energy to disrupt. We conclude that asteroid pairs are formed by the rotational fission of a parent asteroid into a proto-binary system which subsequently disrupts under its own internal system dynamics soon after formation.", "keyphrases": ["asteroid pair", "fission", "heliocentric orbit", "formation mechanism", "rotational property"]}
{"id": "1503.08948", "title": "A closer look at interacting dark energy with statefinder hierarchy and growth rate of structure", "abstract": "We investigate the interacting dark energy models by using the diagnostics of statefinder hierarchy and growth rate of structure. We wish to explore the deviations from \u039bCDM and to differentiate possible degeneracies in the interacting dark energy models with the geometrical and structure growth diagnostics. We consider two interacting forms for the models, i.e., Q_1=\u03b2 H\u03c1_c and Q_2=\u03b2 H\u03c1_de, with \u03b2 being the dimensionless coupling parameter. Our focus is the I\u039bCDM model that is a one-parameter extension to \u039bCDM by considering a direct coupling between the vacuum energy (\u039b) and cold dark matter (CDM), with the only additional parameter \u03b2. But we begin with a more general case by considering the IwCDM model in which dark energy has a constant w (equation-of-state parameter). For calculating the growth rate of structure, we employ the \"parametrized post-Friedmann\" theoretical framework for interacting dark energy to numerically obtain the \u03f5(z) values for the models. We show that in both geometrical and structural diagnostics the impact of w is much stronger than that of \u03b2 in the IwCDM model. We thus wish to have a closer look at the I\u039bCDM model by combining the geometrical and structural diagnostics. We find that the evolutionary trajectories in the S^(1)_3\u2013\u03f5 plane exhibit distinctive features and the departures from \u039bCDM could be well evaluated, theoretically, indicating that the composite null diagnostic {S^(1)_3, \u03f5} is a promising tool for investigating the interacting dark energy models.", "keyphrases": ["dark energy", "statefinder hierarchy", "growth rate", "dark matter", "non-gravitational coupling"]}
{"id": "1712.02334", "title": "DEMNUni: Massive neutrinos and the bispectrum of large scale structures", "abstract": "The main effect of massive neutrinos on the large-scale structure consists in a few percent suppression of matter perturbations on all scales below their free-streaming scale. Such effect is of particular importance as it allows to constraint the value of the sum of neutrino masses from measurements of the galaxy power spectrum. In this work, we present the first measurements of the next higher-order correlation function, the bispectrum, from N-body simulations that include massive neutrinos as particles. This is the simplest statistics characterising the non-Gaussian properties of the matter and dark matter halos distributions. We investigate, in the first place, the suppression due to massive neutrinos on the matter bispectrum, comparing our measurements with the simplest perturbation theory predictions, finding the approximation of neutrinos contributing at quadratic order in perturbation theory to provide a good fit to the measurements in the simulations. On the other hand, as expected, a linear approximation for neutrino perturbations would lead to O(f_\u03bd) errors on the total matter bispectrum at large scales. We then attempt an extension of previous results on the universality of linear halo bias in neutrino cosmologies, to non-linear and non-local corrections finding consistent results with the power spectrum analysis.", "keyphrases": ["massive neutrino", "bispectrum", "n-body simulation"]}
{"id": "0912.3142", "title": "Fractal universe and quantum gravity", "abstract": "We propose a field theory which lives in fractal spacetime and is argued to be Lorentz invariant, power-counting renormalizable, ultraviolet finite, and causal. The system flows from an ultraviolet fixed point, where spacetime has Hausdorff dimension 2, to an infrared limit coinciding with a standard four-dimensional field theory. Classically, the fractal world where fields live exchanges energy momentum with the bulk with integer topological dimension. However, the total energy momentum is conserved. We consider the dynamics and the propagator of a scalar field. Implications for quantum gravity, cosmology, and the cosmological constant are discussed.", "keyphrases": ["quantum gravity", "fractal universe", "causal dynamical triangulation", "asymptotic safety"]}
{"id": "1610.04231", "title": "ZOMG-I. How the cosmic web inhibits halo growth and generates assembly bias", "abstract": "The clustering of dark matter haloes with fixed mass depends on their formation history, an effect known as assembly bias. We use zoom N -body simulations to investigate the origin of this phenomenon. For each halo at redshift z=0, we determine the time in which the physical volume containing its final mass becomes stable. We consider five examples for which this happens at z 1.5 and two that do not stabilize by z=0. The zoom simulations show that early-collapsing haloes do not grow in mass at z=0 while late-forming ones show a net inflow. The reason is that 'accreting' haloes are located at the nodes of a network of thin filaments feeding them. Conversely, each 'stalled' halo lies within a prominent filament that is thicker than the halo size. Infalling material from the surroundings becomes part of the filament while matter within it recedes from the halo. We conclude that assembly bias originates from quenching halo growth due to tidal forces following the formation of non-linear structures in the cosmic web, as previously conjectured in the literature. Also the internal dynamics of the haloes change: the velocity anisotropy profile is biased towards radial (tangential) orbits in accreting (stalled) haloes. Our findings reveal the cause of the yet unexplained dependence of halo clustering on the anisotropy. Finally, we extend the excursion-set theory to account for these effects. A simple criterion based on the ellipticity of the linear tidal field combined with the spherical collapse model provides excellent predictions for both classes of haloes.", "keyphrases": ["cosmic web", "halo growth", "assembly bias"]}
{"id": "1806.03681", "title": "CAMELOT: Cubesats Applied for MEasuring and LOcalising Transients - Mission Overview", "abstract": "We propose a fleet of nanosatellites to perform an all-sky monitoring and timing based localisation of gamma-ray transients. The fleet of at least nine 3U cubesats shall be equipped with large and thin CsI(Tl) scintillator based soft gamma-ray detectors read out by multi-pixel photon counters. For bright short gamma-ray bursts (GRBs), by cross-correlating their light curves, the fleet shall be able to determine the time difference of the arriving GRB signal between the satellites and thus determine the source position with an accuracy of \u223c10^'. This requirement demands precise time synchronization and accurate time stamping of the detected gamma-ray photons, which will be achieved by using on-board GPS receivers. Rapid follow up observations at other wavelengths require the capability for fast, nearly simultaneous downlink of data using a global inter-satellite communication network. In terms of all-sky coverage, the proposed fleet will outperform all GRB monitoring missions.", "keyphrases": ["cubesat", "localising transients", "camelot"]}
{"id": "1211.6112", "title": "High Contrast Imaging with an Arbitrary Aperture: Active Correction of Aperture Discontinuities", "abstract": "We present a new method to achieve high-contrast images using segmented and/or on-axis telescopes. Our approach relies on using two sequential Deformable Mirrors to compensate for the large amplitude excursions in the telescope aperture due to secondary support structures and/or segment gaps. In this configuration the parameter landscape of Deformable Mirror Surfaces that yield high contrast Point Spread Functions is not linear, and non-linear methods are needed to find the true minimum in the optimization topology. We solve the highly non-linear Monge-Ampere equation that is the fundamental equation describing the physics of phase induced amplitude modulation. We determine the optimum configuration for our two sequential Deformable Mirror system and show that high-throughput and high contrast solutions can be achieved using realistic surface deformations that are accessible using existing technologies. We name this process Active Compensation of Aperture Discontinuities (ACAD). We show that for geometries similar to JWST, ACAD can attain at least 10^-7 in contrast and an order of magnitude higher for both the future Extremely Large Telescopes and on-axis architectures reminiscent of HST. We show that the converging non-linear mappings resulting from our Deformable Mirror shapes actually damp near-field diffraction artifacts in the vicinity of the discontinuities. Consequently, ACAD is a true broadband solution to the problem of high-contrast imaging with segmented and/or on-axis apertures. We finally show that once the non-linear solution is found, fine tuning with linear methods used in wavefront control can be applied to further contrast by another order of magnitude. Generally speaking, the ACAD technique can be used to significantly improve a broad class of telescope designs for a variety of problems.", "keyphrases": ["active correction", "aperture discontinuities", "deformable mirror"]}
{"id": "1504.03790", "title": "Magnetic field spectrum at cosmological recombination revisited", "abstract": "If vector type perturbations are present in the primordial plasma before recombination, the generation of magnetic fields is known to be inevitable through the Harrison mechanism. In the context of the standard cosmological perturbation theory, non-linear couplings of first-order scalar perturbations create second-order vector perturbations, which generate magnetic fields. Here we reinvestigate the generation of magnetic fields at second-order in cosmological perturbations on the basis of our previous study, and extend it by newly taking into account the time evolution of purely second-order vector perturbations with a newly developed second-order Boltzmann code. We confirm that the amplitude of magnetic fields from the product-terms of the first-order scalar modes is consistent with the result in our previous study. However, we find, both numerically and analytically, that the magnetic fields from the purely second-order vector perturbations partially cancel out the magnetic fields from one of the product-terms of the first-order scalar modes, in the tight coupling regime in the radiation dominated era. Therefore, the amplitude of the magnetic fields on small scales, k \u2273 10 h Mpc^-1, is smaller than the previous estimates. The amplitude of the generated magnetic fields at cosmological recombination is about B_ rec =5.0\u00d7 10^-24 Gauss on k = 5.0 \u00d7 10^-1 h Mpc^-1. Finally, we discuss the reason of the discrepancies that exist in estimates of the amplitude of magnetic fields among other authors.", "keyphrases": ["cosmological recombination", "perturbation theory", "magnetic field"]}
{"id": "0912.2164", "title": "Neutrino emission from triplet pairing of neutrons in neutron stars", "abstract": "Neutrino emission due to the pair breaking and formation processes in the bulk triplet superfluid in neutron stars is investigated with taking into account of anomalous weak interactions. We consider the problem in the BCS approximation discarding Fermi-liquid effects. In this approach we derive self-consistent equations for anomalous vector and axial-vector vertices of weak interactions taking into account the ^3P_2- ^3F_2 mixing. Further we simplify the problem and consider the pure ^3P_2 pairing with m_j=0, as is adopted in the minimal cooling paradigm. As was expected because of current conservation we have obtained a large suppression of the neutrino emissivity in the vector channel. More exactly, the neutrino emission through the vector channel vanishes in the nonrelativistic limit V_F=0. The axial channel is also found to be moderately suppressed. The total neutrino emissivity is suppressed by a factor of 1.9\u00d710^-1 relative to original estimates using bare weak vertices.", "keyphrases": ["neutron star", "neutrino emission", "neutral weak current"]}
{"id": "1208.2701", "title": "Revising the Halofit Model for the Nonlinear Matter Power Spectrum", "abstract": "Based on a suite of state-of-the-art high-resolution N-body simulations, we revisit the so-called halofit model (Smith et al. 2003) as an accurate fitting formula for the nonlinear matter power spectrum. While the halofit model has been frequently used as a standard cosmological tool to predict the nonlinear matter power spectrum in a universe dominated by cold dark matter, its precision has been limited by the low-resolution of N-body simulations used to determine the fitting parameters, suggesting the necessity of improved fitting formula at small scales for future cosmological studies. We run high-resolution N-body simulations for 16 cosmological models around the Wilkinson Microwave Anisotropy Probe (WMAP) best-fit cosmological parameters (1, 3, 5, and 7 year results), including dark energy models with a constant equation of state. The simulation results are used to re-calibrate the fitting parameters of the halofit model so as to reproduce small-scale power spectra of the N-body simulations, while keeping the precision at large scales. The revised fitting formula provides an accurate prediction of the nonlinear matter power spectrum in a wide range of wavenumber (k \u2264 30h Mpc^-1) at redshifts 0 \u2264 z \u2264 10, with 5 \u2264z \u226410and 10 3. We discuss the impact of the improved halofit model on weak lensing power spectra and correlation functions, and show that the improved model better reproduces ray-tracing simulation results.", "keyphrases": ["halofit model", "matter power", "non-linear growth"]}
{"id": "1302.5663", "title": "Magnetic Fields in the Milky Way and in Galaxies (revised version of September 2023)", "abstract": "Most of the visible matter in the Universe is ionized, so that cosmic magnetic fields are quite easy to generate and due to the lack of magnetic monopoles hard to destroy. Magnetic fields have been measured in or around practically all celestial objects, either by in-situ measurements of spacecrafts or by the electromagnetic radiation of embedded cosmic rays, gas, or dust. The Earth, the Sun, solar planets, stars, pulsars, the Milky Way, nearby galaxies, distant radio galaxies, quasars, and even intergalactic space in clusters of galaxies have significant magnetic fields. Even larger volumes of the Universe may be permeated by so-far invisble magnetic fields. Information on cosmic magnetic fields has increased enormously as the result of the rapid development of observational methods, especially in radio astronomy. In the Milky Way, a wealth of magnetic phenomena was discovered that are only partly related to objects visible in other spectral ranges. The large-scale structure of the Milky Way's magnetic field is still under debate. The available data for external spiral galaxies can well be explained by field amplification and ordering via the dynamo mechanism. The measured field strengths and the similarity of field patterns and flow patterns of the diffuse ionized gas give strong indication that galactic magnetic fields are dynamically important. They may affect the formation of spiral arms, outflows, and the general evolution of galaxies. In spite of our increasing knowledge on magnetic fields, many important questions on the origin and evolution of magnetic fields, like their first occurrence in young galaxies or the existence of large-scale intergalactic fields, remain unanswered. Progress can be expected from new-generation radio telescopes like LOFAR and the SKA, for which \"cosmic magnetism\" is a key science project.", "keyphrases": ["milky way", "galaxy", "magnetic field"]}
{"id": "0912.0998", "title": "Power-law solutions and accelerated expansion in scalar-tensor theories", "abstract": "We find exact power-law solutions for scalar-tensor theories and clarify the conditions under which they can account for an accelerated expansion of the Universe. These solutions have the property that the signs of both the Hubble rate and the deceleration parameter in the Jordan frame may be different from the signs of their Einstein-frame counterparts. For special parameter combinations we identify these solutions with asymptotic attractors that have been obtained in the literature through dynamical-system analysis. We establish an effective general-relativistic description for which the geometrical equivalent of dark energy is associated with a time dependent equation of state. The present value of the latter is consistent with the observed cosmological \u201cconstant\". We demonstrate that this type of power-law solutions for accelerated expansion cannot be realized in f(R) theories.", "keyphrases": ["scalar-tensor theory", "power-law solution", "different aspect"]}
{"id": "1912.08751", "title": "Graduated dark energy: Observational hints of a spontaneous sign switch in the cosmological constant", "abstract": "We study the cosmological constant (\u039b) in the standard \u039bCDM model by introducing the graduated dark energy (gDE) characterised by a minimal dynamical deviation from the null inertial mass density of the \u039b in the form \u03c1_ inert\u221d\u03c1^\u03bb<0 with \u03bb<1 being a ratio of two odd integers, for which its energy density \u03c1 dynamically takes negative values in the finite past. For large negative values of \u03bb, it creates a phenomenological model described by a smooth function that approximately describes the \u039b spontaneously switching sign in the late universe to become positive today. We confront the model with the latest combined observational data sets of PLK+BAO+SN+H. It is striking that the data predict bimodal posterior probability distributions for the parameters of the model along with large negative \u03bb values; the new maximum significantly excludes the \u039b, and the old maximum contains the \u039b. The improvement in the goodness of fit for the \u039b reaches highly significant levels, \u0394\u03c7_ min^2=6.4 for the new maxima, while it remains at insignificant levels, \u0394\u03c7_ min^2\u22720.02, for the old maxima. We show that, in contrast to the old maxima, which do not distinguish from the \u039b, the new maxima agree with the model-independent H_0 measurements, high-precision Ly-\u03b1 data, and model-independent Omh^2 diagnostic estimates. Our results provide strong hints of a spontaneous sign switch in the cosmological constant and lead us to conjecture that the universe has transitioned from AdS vacua to dS vacua, at a redshift z\u2248 2.32 and triggered the late-time acceleration, and suggests looking for such mechanisms in string theory constructions.", "keyphrases": ["dark energy", "cosmological constant", "low-redshift"]}
{"id": "1001.0995", "title": "General class of vacuum Brans-Dicke wormholes", "abstract": "Recently, traversable wormhole geometries were constructed in the context of f(R) gravity. The latter is equivalent to a Brans-Dicke theory with a coupling parameter w=0, which is apparently excluded from the narrow interval, -3/2<w<-4/3, extensively considered in the literature of static wormhole solutions in vacuum Brans-Dicke theory. However, this latter interval is only valid for a specific choice of an integration constant of the field equations derived on the basis of a post-Newtonian weak field approximation, and there is no reason for it to hold in the presence of compact objects with strong gravitational fields. In this context, we construct a general class of vacuum Brans-Dicke wormholes that include the value of w=0. Furthermore, we present the general condition for the existence of vacuum Brans-Dicke wormhole geometries, and show that the presence of effective negative energy densities is a generic feature of these vacuum solutions.", "keyphrases": ["vacuum", "brans-dicke wormhole", "wormhole geometry"]}
{"id": "1606.04691", "title": "Cosmology and the neutrino mass ordering", "abstract": "We propose a simple method to quantify a possible exclusion of the inverted neutrino mass ordering from cosmological bounds on the sum of the neutrino masses. The method is based on Bayesian inference and allows for a calculation of the posterior odds of normal versus inverted ordering. We apply the method for a specific set of current data from Planck CMB data and large-scale structure surveys, providing an upper bound on the sum of neutrino masses of 0.14 eV at 95 versus inverted ordering of about 2:1. If cosmological data is combined with data from oscillation experiments the odds reduce to about 3:2. For an exclusion of the inverted ordering from cosmology at more than 95 accuracy of better than 0.02 eV is needed for the sum. We demonstrate that such a value could be reached with planned observations of large scale structure by analysing artificial mock data for a EUCLID-like survey.", "keyphrases": ["neutrino masse", "mass ordering", "cosmology"]}
{"id": "1311.1819", "title": "The Dispersal of Protoplanetary Disks", "abstract": "Protoplanetary disks are the sites of planet formation, and the evolution and eventual dispersal of these disks strongly influences the formation of planetary systems. Disk evolution during the planet-forming epoch is driven by accretion and mass-loss due to winds, and in typical environments photoevaporation by high-energy radiation from the central star is likely to dominate final gas disk dispersal. We present a critical review of current theoretical models, and discuss the observations that are used to test these models and inform our understanding of the underlying physics. We also discuss the role disk dispersal plays in shaping planetary systems, considering its influence on both the process(es) of planet formation and the architectures of planetary systems. We conclude by presenting a schematic picture of protoplanetary disk evolution and dispersal, and discussing prospects for future work.", "keyphrases": ["dispersal", "protoplanetary disk", "star"]}
{"id": "1002.0834", "title": "Circles-in-the-sky searches and observable cosmic topology in a flat Universe", "abstract": "[Abridged] In a Universe with a detectable nontrivial spatial topology the last scattering surface contains pairs of matching circles with the same distribution of temperature fluctuations - the so-called circles-in-the-sky. Searches for nearly antipodal circles in maps of cosmic microwave background have so far been unsuccessful. This negative outcome along with recent theoretical results concerning the detectability of nearly flat compact topologies is sufficient to exclude a detectable nontrivial topology for most observers in very nearly flat positively and negatively curved Universes (0<|\u03a9_tot-1| \u2272 10^-5). Here we investigate the consequences of these searches for observable nontrivial topologies if the Universe turns out to be exactly flat (\u03a9_tot=1). We demonstrate that in this case the conclusions deduced from such searches can be radically different. We show that for all multiply-connected orientable flat manifolds it is possible to directly study the action of the holonomies in order to obtain a general upper bound on the angle that characterizes the deviation from antipodicity of pairs of matching circles associated with the shortest closed geodesic. This bound is valid for all observers and all possible values of the compactification length parameters. We also show that in a flat Universe there are observers for whom the circles-in-the-sky searches already undertaken are insufficient to exclude the possibility of a detectable nontrivial spatial topology. It is remarkable how such small variations in the spatial curvature of the Universe, which are effectively indistinguishable geometrically, can have such a drastic effect on the detectability of cosmic topology.", "keyphrases": ["cosmic topology", "flat universe", "circle", "flat manifold", "circles-in-the-sky search"]}
{"id": "1301.0824", "title": "The Atacama Cosmology Telescope: Cosmological parameters from three seasons of data", "abstract": "We present constraints on cosmological and astrophysical parameters from high-resolution microwave background maps at 148 GHz and 218 GHz made by the Atacama Cosmology Telescope (ACT) in three seasons of observations from 2008 to 2010. A model of primary cosmological and secondary foreground parameters is fit to the map power spectra and lensing deflection power spectrum, including contributions from both the thermal Sunyaev-Zeldovich (tSZ) effect and the kinematic Sunyaev-Zeldovich (kSZ) effect, Poisson and correlated anisotropy from unresolved infrared sources, radio sources, and the correlation between the tSZ effect and infrared sources. The power ell^2 C_ell/2pi of the thermal SZ power spectrum at 148 GHz is measured to be 3.4 +\u00ad 1.4 muK^2 at ell=3000, while the corresponding amplitude of the kinematic SZ power spectrum has a 95 confidence level upper limit of 8.6 muK^2. Combining ACT power spectra with the WMAP 7-year temperature and polarization power spectra, we find excellent consistency with the LCDM model. We constrain the number of effective relativistic degrees of freedom in the early universe to be Neff=2.79 +\u00ad 0.56, in agreement with the canonical value of Neff=3.046 for three massless neutrinos. We constrain the sum of the neutrino masses to be Sigma m_nu < 0.39 eV at 95 Hubble constant measurements. We constrain the amount of primordial helium to be Yp = 0.225 +\u00ad 0.034, and measure no variation in the fine structure constant alpha since recombination, with alpha/alpha0 = 1.004 +/- 0.005. We also find no evidence for any running of the scalar spectral index, dns/dlnk = -0.004 +\u00ad 0.012.", "keyphrases": ["atacama cosmology telescope", "universe", "cosmic microwave background", "dark matter", "sub-orbital experiment"]}
{"id": "1501.04090", "title": "Singular Inflation", "abstract": "We prove that a homogeneous and isotropic universe containing a scalar field with a power-law potential, V(\u03d5 )=A\u03d5 ^n, with 0<n<1 and A>0 always develops a finite-time singularity at which the Hubble rate and its first derivative are finite, but its second derivative diverges. These are the first examples of cosmological models with realistic matter sources that possess weak singularities of 'sudden' type. We also show that a large class of models with even weaker singularities exist for non-integer n>1. More precisely, if k<n<k+1 where k is a positive integer then the first divergence of the Hubble rate occurs with its (k+2)th derivative. At early times these models behave like standard large-field inflation models but they encounter a singular end-state when inflation ends. We term this singular inflation.", "keyphrases": ["scalar field", "power-law potential", "cosmology", "singular inflation", "singularity"]}
{"id": "1605.04482", "title": "Primordial black holes as a novel probe of primordial gravitational waves. II: Detailed analysis", "abstract": "Recently we have proposed a novel method to probe primordial gravitational waves from upper bounds on the abundance of primordial black holes (PBHs). When the amplitude of primordial tensor perturbations generated in the early Universe is fairly large, they induce substantial scalar perturbations due to their second-order effects. If these induced scalar perturbations are too large when they reenter the horizon, then PBHs are overproduced, their abundance exceeding observational upper limits. That is, primordial tensor perturbations on superhorizon scales can be constrained from the absence of PBHs. In our recent paper we have only shown simple estimations of these new constraints, and hence in this paper, we present detailed derivations, solving the Einstein equations for scalar perturbations induced at second order in tensor perturbations. We also derive an approximate formula for the probability density function of induced density perturbations, necessary to relate the abundance of PBHs to the primordial tensor power spectrum, assuming primordial tensor perturbations follow Gaussian distributions. Our new upper bounds from PBHs are compared with other existing bounds obtained from big bang nucleosynthesis, cosmic microwave background, LIGO/Virgo and pulsar timing arrays.", "keyphrases": ["gravitational wave", "primordial tensor perturbation", "primordial black hole"]}
{"id": "1404.7661", "title": "MOND theory", "abstract": "A general account of MOND theory is given. I start with the basic tenets of MOND, which posit departure from standard dynamics in the limit of low acceleration \u2013 below an acceleration constant a0 \u2013 where dynamics become scale invariant. I list some of the salient predictions of these tenets. The special role of a0 and its significance are then discussed. In particular, I stress its coincidence with cosmologically relevant accelerations. The deep-MOND limit and the consequences of its scale invariance are considered in some detail. General aspects of MOND theories are then described, after which I list briefly presently known theories, both nonrelativistic and relativistic. Most full-fledged theories modify the gravitational action, hinge on a0, introduce an interpolating function between the low and high accelerations, and obey MOND requirements in the opposite limits. These theories have much heuristic value as proofs of various concepts (e.g., that covariant MOND theories can be written with correct gravitational lensing). But, probably, they are, at best, effective theories of limited applicability. I then outline several other promising approaches to constructing MOND theories that strive to obtain MOND as an effective theory from deeper concepts, for example, by modifying inertia and/or gravity as a result of interactions with some omnipresent agent. Some theories do enjoy a natural appearance of a cosmological-constant-like contribution that, furthermore, exhibits the observed connection with a0. However, none were shown to address fully the mass discrepancies in cosmology and structure formation that are otherwise explained by cosmological dark matter. We have no clues as to whether and how MOND aspects enter non-gravitational phenomena, but I discuss briefly some possibilities.", "keyphrases": ["coincidence", "gravity", "mond theory"]}
{"id": "1503.06313", "title": "Magnetars: Properties, Origin and Evolution", "abstract": "Magnetars are neutron stars in which a strong magnetic field is the main energy source. About two dozens of magnetars, plus several candidates, are currently known in our Galaxy and in the Magellanic Clouds. They appear as highly variable X-ray sources and, in some cases, also as radio and/or optical pulsars. Their spin periods (2-12 s) and spin-down rates ( 10^-13-10^-10 s/s) indicate external dipole fields of 10^13-15 G, and there is evidence that even stronger magnetic fields are present inside the star and in non-dipolar magnetospheric components. Here we review the observed properties of the persistent emission from magnetars, discuss the main models proposed to explain the origin of their magnetic field and present recent developments in the study of their evolution and connection with other classes of neutron stars.", "keyphrases": ["neutron star", "magnetar", "anomalous x-ray pulsar"]}
{"id": "1909.12630", "title": "White dwarfs as a probe of dark energy", "abstract": "We investigate the radial density distribution of the dynamical dark energy inside the white dwarfs (WDs) and its possible impact on their intrinsic structure. The minimally-coupled dark energy with barotropic equation of state which has three free parameters (density, equation of state and effective sound speed) is used. We analyse how such dark energy affects the mass-radius relation for the WDs because of its contribution to the joint gravitational potential of the system. For this we use Chandrasekhar model of the WDs, where model parameters are the parameter of the chemical composition and the relativistic parameter. To evaluate the dark energy distribution inside a WD we solve the conservation equation in the spherical static metric. Obtained distribution is used to find the parameters of dark energy for which the deviation from the Chandrasekhar model mass-radius relation become non-negligible. We conclude also, that the absence of observational evidence for existence of WDs with untypical intrinsic structure (mass-radius relation) gives us lower limit for the value of effective sound speed of dark energy c_s^2 \u2273 10^-4 (in units of speed of light).", "keyphrases": ["dark energy", "mass-radius relation", "white dwarf"]}
{"id": "1004.2488", "title": "Cosmological Non-Linearities as an Effective Fluid", "abstract": "The universe is smooth on large scales but very inhomogeneous on small scales. Why is the spacetime on large scales modeled to a good approximation by the Friedmann equations? Are we sure that small-scale non-linearities do not induce a large backreaction? Related to this, what is the effective theory that describes the universe on large scales? In this paper we make progress in addressing these questions. We show that the effective theory for the long-wavelength universe behaves as a viscous fluid coupled to gravity: integrating out short-wavelength perturbations renormalizes the homogeneous background and introduces dissipative dynamics into the evolution of long-wavelength perturbations. The effective fluid has small perturbations and is characterized by a few parameters like an equation of state, a sound speed and a viscosity parameter. These parameters can be matched to numerical simulations or fitted from observations. We find that the backreaction of small-scale non-linearities is very small, being suppressed by the large hierarchy between the scale of non-linearities and the horizon scale. The effective pressure of the fluid is always positive and much too small to significantly affect the background evolution. Moreover, we prove that virialized scales decouple completely from the large-scale dynamics, at all orders in the post-Newtonian expansion. We propose that our effective theory be used to formulate a well-defined and controlled alternative to conventional perturbation theory, and we discuss possible observational applications. Finally, our way of reformulating results in second-order perturbation theory in terms of a long-wavelength effective fluid provides the opportunity to understand non-linear effects in a simple and physically intuitive way.", "keyphrases": ["universe", "viscous fluid", "effective field theory", "large-scale structure", "dark matter"]}
{"id": "1801.08559", "title": "The impact of baryons on the matter power spectrum from the Horizon-AGN cosmological hydrodynamical simulation", "abstract": "Accurate cosmology from upcoming weak lensing surveys relies on knowledge of the total matter power spectrum at percent level at scales k < 10 h/Mpc, for which modelling the impact of baryonic physics is crucial. We compare measurements of the total matter power spectrum from the Horizon cosmological hydrodynamical simulations: a dark matter-only run, one with full baryonic physics, and another lacking Active Galactic Nuclei (AGN) feedback. Baryons cause a suppression of power at k\u2243 10 h/Mpc of <15% at z=0, and an enhancement of a factor of a few at smaller scales due to the more efficient cooling and star formation. The results are sensitive to the presence of the highest mass haloes in the simulation and the distribution of dark matter is also impacted up to a few percent. The redshift evolution of the effect is non-monotonic throughout z=0-5 due to an interplay between AGN feedback and gas pressure, and the growth of structure. We investigate the effectiveness of an analytic `baryonic correction model' in describing our results. We require a different redshift evolution and propose an alternative fitting function with 4 free parameters that reproduces our results within 5%. Compared to other simulations, we find the impact of baryonic processes on the total matter power spectrum to be smaller at z=0. Correspondingly, our results suggest that AGN feedback is not strong enough in the simulation. Total matter power spectra from the Horizon simulations are made publicly available at https://www.horizon-simulation.org/catalogues.html", "keyphrases": ["baryon", "cosmological hydrodynamical simulation", "active galactic nucleus"]}
{"id": "1911.02087", "title": "Planck evidence for a closed Universe and a possible crisis for cosmology", "abstract": "The recent Planck Legacy 2018 release has confirmed the presence of an enhanced lensing amplitude in CMB power spectra compared to that predicted in the standard \u039bCDM model. A closed universe can provide a physical explanation for this effect, with the Planck CMB spectra now preferring a positive curvature at more than 99 % C.L. Here we further investigate the evidence for a closed universe from Planck, showing that positive curvature naturally explains the anomalous lensing amplitude and demonstrating that it also removes a well-known tension within the Planck data set concerning the values of cosmological parameters derived at different angular scales. We show that since the Planck power spectra prefer a closed universe, discordances higher than generally estimated arise for most of the local cosmological observables, including BAO. The assumption of a flat universe could, therefore, mask a cosmological crisis where disparate observed properties of the Universe appear to be mutually inconsistent. Future measurements are needed to clarify whether the observed discordances are due to undetected systematics, or to new physics, or simply are a statistical fluctuation.", "keyphrases": ["universe", "cosmological parameter", "different angular scale", "non-zero spatial curvature"]}
{"id": "0902.0660", "title": "Effects of dark sectors' mutual interaction on the growth of structures", "abstract": "We present a general formalism to study the growth of dark matter perturbations when dark energy perturbations and interactions between dark sectors are present. We show that dynamical stability of the growth of structure depends on the type of coupling between dark sectors. By taking the appropriate coupling to ensure the stable growth of structure, we observe that the effect of the dark sectors' interaction overwhelms that of dark energy perturbation on the growth function of dark matter perturbation. Due to the influence of the interaction, the growth index can differ from the value without interaction by an amount within the observational sensibility, which provides a possibility to disclose the interaction between dark sectors through future observations on the growth of large structure.", "keyphrases": ["dark sector", "non-gravitational coupling", "cosmic structure"]}
{"id": "1903.00007", "title": "Fast likelihood-free cosmology with neural density estimators and active learning", "abstract": "Likelihood-free inference provides a framework for performing rigorous Bayesian inference using only forward simulations, properly accounting for all physical and observational effects that can be successfully included in the simulations. The key challenge for likelihood-free applications in cosmology, where simulation is typically expensive, is developing methods that can achieve high-fidelity posterior inference with as few simulations as possible. Density-estimation likelihood-free inference (DELFI) methods turn inference into a density estimation task on a set of simulated data-parameter pairs, and give orders of magnitude improvements over traditional Approximate Bayesian Computation approaches to likelihood-free inference. In this paper we use neural density estimators (NDEs) to learn the likelihood function from a set of simulated datasets, with active learning to adaptively acquire simulations in the most relevant regions of parameter space on-the-fly. We demonstrate the approach on a number of cosmological case studies, showing that for typical problems high-fidelity posterior inference can be achieved with just \ud835\udcaa(10^3) simulations or fewer. In addition to enabling efficient simulation-based inference, for simple problems where the form of the likelihood is known, DELFI offers a fast alternative to MCMC sampling, giving orders of magnitude speed-up in some cases. Finally, we introduce pydelfi \u2013 a flexible public implementation of DELFI with NDEs and active learning \u2013 available at <https://github.com/justinalsing/pydelfi>.", "keyphrases": ["cosmology", "neural density estimator", "learning"]}
{"id": "1301.0322", "title": "Solving Large Scale Structure in Ten Easy Steps with COLA", "abstract": "We present the COmoving Lagrangian Acceleration (COLA) method: an N-body method for solving for Large Scale Structure (LSS) in a frame that is comoving with observers following trajectories calculated in Lagrangian Perturbation Theory (LPT). Unlike standard N-body methods, the COLA method can straightforwardly trade accuracy at small-scales in order to gain computational speed without sacrificing accuracy at large scales. This is especially useful for cheaply generating large ensembles of accurate mock halo catalogs required to study galaxy clustering and weak lensing, as those catalogs are essential for performing detailed error analysis for ongoing and future surveys of LSS. As an illustration, we ran a COLA-based N-body code on a box of size 100Mpc/h with particles of mass 5*10^9Msolar/h. Running the code with only 10 timesteps was sufficient to obtain an accurate description of halo statistics down to halo masses of at least 10^11Msolar/h. This is only at a modest speed penalty when compared to mocks obtained with LPT. A standard detailed N-body run is orders of magnitude slower than our COLA-based code. The speed-up we obtain with COLA is due to the fact that we calculate the large-scale dynamics exactly using LPT, while letting the N-body code solve for the small scales, without requiring it to capture exactly the internal dynamics of halos. Achieving a similar level of accuracy in halo statistics without the COLA method requires at least 3 times more timesteps than when COLA is employed.", "keyphrases": ["large scale structure", "cola", "comoving", "lagrangian acceleration", "n-body code"]}
{"id": "1302.0130", "title": "Symmetries and Consistency Relations in the Large Scale Structure of the Universe", "abstract": "We study the symmetries enjoyed by the Newtonian equations of motion of the non-relativistic dark matter fluid coupled to gravity which give rise to the phenomenon of gravitational instability. We also discuss some consistency relations involving the soft limit of the (n + 1)-correlator functions of matter and galaxy overdensities.", "keyphrases": ["large scale structure", "dark matter fluid", "gravity", "soft limit", "-correlator function"]}
{"id": "1507.07756", "title": "Magnetic reconnection: from the Sweet-Parker model to stochastic plasmoid chains", "abstract": "(abridged) Magnetic reconnection is the topological reconfiguration of the magnetic field in a plasma, accompanied by the violent release of energy and particle acceleration. Reconnection is as ubiquitous as plasmas themselves, with solar flares perhaps the most popular example. Over the last few years, the theoretical understanding of magnetic reconnection in large-scale fluid systems has undergone a major paradigm shift. The steady-state model of reconnection described by the famous Sweet-Parker (SP) theory, which dominated the field for 50 years, has been replaced with an essentially time-dependent, bursty picture of the reconnection layer, dominated by the continuous formation and ejection of multiple secondary islands (plasmoids). Whereas in the SP model reconnection was predicted to be slow, a major implication of this new paradigm is that reconnection in fluid systems is fast (i.e., independent of the Lundquist number), provided that the system is large enough. This conceptual shift hinges on the realization that SP-like current layers are violently unstable to the plasmoid instability - implying, therefore, that such current sheets are super-critically unstable and thus can never form in the first place. This suggests that the formation of a current sheet and the subsequent reconnection process cannot be decoupled, as is commonly assumed. This paper provides an introductory-level overview of the recent developments in reconnection theory and simulations that led to this essentially new framework. We briefly discuss the role played by the plasmoid instability in selected applications, and describe some of the outstanding challenges that remain at the frontier of this subject. Amongst these are the analytical and numerical extension of the plasmoid instability to (i) 3D and (ii) non-MHD regimes. New results are reported in both cases.", "keyphrases": ["reconnection", "plasmoid instability", "current sheet", "magnetic reconnection", "plasma process"]}
{"id": "1610.03665", "title": "An analytic halo approach to the bispectrum of galaxies in redshift space", "abstract": "We present an analytic formula for the galaxy bispectrum in redshift space on the basis of the halo approach description with the halo occupation distribution of central galaxies and satellite galaxies. This work is an extension of a previous work on the galaxy power spectrum, which illuminated the significant contribution of satellite galaxies to the higher multipole spectrum through the non-linear redshift space distortions of their random motions. Behaviors of the multipoles of the bispectrum are compared with results of numerical simulations assuming a halo occupation distribution of the LOWZ sample of the SDSS-III BOSS survey. Also presented are analytic approximate formulas for the multipoles of the bispectrum, which is useful to understanding their characteristic properties. We demonstrate that the Fingers of God effect is quite important for the higher multipoles of the bispectrum in redshift space, depending on the halo occupation distribution parameters.", "keyphrases": ["bispectrum", "redshift space", "high multipole"]}
{"id": "1210.5169", "title": "Low-energy collective excitations in the neutron star inner crust", "abstract": "We study the low-energy collective excitations of the neutron star inner crust, where a neutron superfluid coexists with a Coulomb lattice of nuclei. The dispersion relation of the modes is calculated systematically from a microscopic theory including neutron band structure effects. These effects are shown to lead to a strong mixing between the Bogoliubov-Anderson bosons of the neutron superfluid and the longitudinal crystal lattice phonons. In addition, the speed of the transverse shear mode is greatly reduced as a large fraction of superfluid neutrons are entrained by nuclei. Not only does the much smaller velocity of the transverse mode increase the specific heat of the inner crust, but it also decreases its electron thermal conductivity. These results may impact our interpretation of the thermal relaxation in accreting neutron stars. Due to strong mixing, the mean free path of the superfluid mode is found to be greatly reduced. Our results for the collective mode dispersion relations and their damping may also have implications for neutron star seismology.", "keyphrases": ["collective excitation", "neutron star", "inner crust"]}
{"id": "1211.0083", "title": "Ultra Slow-Roll Inflation and the non-Gaussianity Consistency Relation", "abstract": "Ultra slow-roll inflation has recently been used to challenge the non-Gaussianity consistency relation. We show that this inflationary scenario belongs to a one parameter class of models and we study its properties and observational predictions. We demonstrate that the power spectrum remains scale-invariant and that the bi-spectrum is of the local type with fnl=5(3-ns)/4 which, indeed, represents a modification of the consistency relation. However, we also show that the system is unstable and suffers from many physical problems among which is the difficulty to correctly WMAP normalize the model. We conclude that ultra slow-roll inflation remains a very peculiar case, the physical relevance of which is probably not sufficient to call into question the validity of the consistency relation.", "keyphrases": ["non-gaussianity consistency relation", "ultra slow-roll inflation", "inflationary model", "constant-roll condition", "scalar field model"]}
{"id": "1908.05625", "title": "An Improved Distance to NGC 4258 and its Implications for the Hubble Constant", "abstract": "NGC 4258 is a critical galaxy for establishing the extragalactic distance scale and estimating the Hubble constant (Ho). Water masers in the nucleus of the galaxy orbit about its supermassive black hole, and very long baseline interferometric observations of their positions, velocities, and accelerations can be modeled to give a geometric estimate of the angular-diameter distance to the galaxy. We have improved the technique to obtain model parameter values, reducing both statistical and systematic uncertainties compared to previous analyses. We find the distance to NGC 4258 to be 7.576 +/- 0.082 (stat.) +/- 0.076 (sys.) Mpc. Using this as the sole source of calibration of the Cepheid-SN Ia distance ladder results in Ho = 72.0 +/- 1.9 km/s/Mpc, and in concert with geometric distances from Milky Way parallaxes and detached eclipsing binaries in the LMC we find Ho = 73.5 +/- 1.4 km/s/Mpc. The improved distance to NGC 4258 also provides a new calibration of the tip of the red giant branch of M_F814W = -4.01 +/- 0.04mag, with reduced systematic errors for the determination of Ho compared to the LMC-based calibration, because it is measured on the same Hubble Space Telescope photometric system and through similarly low extinction as SN Ia host halos. The result is Ho = 71.1 +/- 1.9 km/s/Mpc, in good agreement with the result from the Cepheid route, and there is no difference in Ho when using the same calibration from NGC 4258 and the same SN Ia Hubble diagram intercept to start and end both distance ladders.", "keyphrases": ["improved distance", "ngc", "hubble constant", "today"]}
{"id": "1807.04672", "title": "Bias due to neutrinos must not uncorrect'd go", "abstract": "In cosmologies with massive neutrinos, the galaxy bias defined with respect to the total matter field (cold dark matter, baryons, and non-relativistic neutrinos) depends on the sum of the neutrino masses M_\u03bd, and becomes scale-dependent even on large scales. This effect has been usually neglected given the sensitivity of current surveys, but becomes a severe systematic for future surveys aiming to provide the first detection of non-zero M_\u03bd. The effect can be corrected for by defining the bias with respect to the density field of cold dark matter and baryons instead of the total matter field. In this work, we provide a simple prescription for correctly mitigating the neutrino-induced scale-dependent bias effect in a practical way. We clarify a number of subtleties regarding how to properly implement this correction in the presence of redshift-space distortions and non-linear evolution of perturbations. We perform a MCMC analysis on simulated galaxy clustering data that match the expected sensitivity of the Euclid survey. We find that the neutrino-induced scale-dependent bias can lead to important shifts in both the inferred mean value of M_\u03bd, as well as its uncertainty. We show how these shifts propagate to other cosmological parameters correlated with M_\u03bd, such as the cold dark matter physical density \u03a9_cdm h^2 and the scalar spectral index n_s. In conclusion, we find that correctly accounting for the neutrino-induced scale-dependent bias will be of crucial importance for future galaxy clustering analyses. We encourage the cosmology community to correctly account for this effect using the simple prescription we present in our work. The tools necessary to easily correct for the neutrino-induced scale-dependent bias will be made publicly available in an upcoming release of the Boltzmann solver .", "keyphrases": ["neutrino", "cosmological parameter", "bias"]}
{"id": "1811.10929", "title": "Constraining twin stars with GW170817", "abstract": "If a phase transition is allowed to take place in the core of a compact star, a new stable branch of equilibrium configurations can appear, providing solutions with the same mass as the purely hadronic branch and hence giving rise to twin-star configurations. We perform an extensive analysis of the features of the phase transition leading twin-star configurations and, at the same time, fulfilling the constraints coming from the maximum mass of 2M_\u2299 and the information following gravitational-wave event GW170817. In particular, we use a general equation of state for the neutron-star matter that parametrizes the hadron-quark phase transition between the model describing the hadronic phase and a constant speed of sound for the quark phase. We find that the largest number of twin-star solutions has masses in the neutron-star branch in the range 1-2M_\u2299 and twin-branch masses \u2273 2M_\u2299. The analysis of the masses, radii and tidal deformabilities also reveals that when twin stars appear, the tidal deformability shows two distinct branches with the same mass, thus differing considerably from the behaviour expected for neutron stars. In addition, we find that the data from GW170817 is compatible with the existence of hybrid stars and could also be interpreted as produced by the merger of a binary system of hybrid stars or of a hybrid star with a neutron star. The presence of a hybrid star in the inspiral phase can be established clearly if future gravitational-wave detections measure chirp masses \u2133\u2272 1.2M_\u2299 and tidal deformabilities of \u039b_1.4\u2272 400 for 1.4M_\u2299 stars. Finally, combining all observational information available, we set constraints on the parameters that characterise the phase transition, the maximum masses, and the radii of 1.4M_\u2299 stars described by equations of state leading to twin-star configurations.", "keyphrases": ["star", "compact neutron star", "event gw170817 point"]}
{"id": "2012.12983", "title": "Probing planetary-mass primordial black holes with continuous gravitational waves", "abstract": "Gravitational waves can probe the existence of planetary-mass primordial black holes. Considering a mass range of [10^-7-10^-2]M_\u2299, inspiraling primordial black holes could emit either continuous gravitational waves, quasi-monochromatic signals that last for many years, or transient continuous waves, signals whose frequency evolution follows a power law and last for \ud835\udcaa(hours-months). We show that primordial black hole binaries in our galaxy may produce detectable gravitational waves for different mass functions and formation mechanisms. In order to detect these inspirals, we adapt methods originally designed to search for gravitational waves from asymmetrically rotating neutron stars. The first method, the Frequency-Hough, exploits the continuous, quasi-monochromatic nature of inspiraling black holes that are sufficiently light and far apart such that their orbital frequencies can be approximated as linear with a small spin-up. The second method, the Generalized Frequency-Hough, drops the assumption of linearity and allows the signal frequency to follow a power-law evolution. We explore the parameter space to which each method is sensitive, derive a theoretical sensitivity estimate, determine optimal search parameters and calculate the computational cost of all-sky and directed searches. We forecast limits on the abundance of primordial black holes within our galaxy, showing that we can constrain the fraction of dark matter that primordial black holes compose, f_ PBH, to be f_ PBH\u2272 1 for chirp masses between [4\u00d7 10^-5-10^-3]M_\u2299 for current detectors. For the Einstein Telescope, we expect the constraints to improve to f_ PBH\u2272 10^-2 for chirp masses between [10^-4-10^-3]M_\u2299.", "keyphrases": ["black hole", "gravitational wave", "dark matter"]}
{"id": "1402.2301", "title": "Detection of An Unidentified Emission Line in the Stacked X-ray spectrum of Galaxy Clusters", "abstract": "We detect a weak unidentified emission line at E=(3.55-3.57)+/-0.03 keV in a stacked XMM spectrum of 73 galaxy clusters spanning a redshift range 0.01-0.35. MOS and PN observations independently show the presence of the line at consistent energies. When the full sample is divided into three subsamples (Perseus, Centaurus+Ophiuchus+Coma, and all others), the line is significantly detected in all three independent MOS spectra and the PN \"all others\" spectrum. It is also detected in the Chandra spectra of Perseus with the flux consistent with XMM (though it is not seen in Virgo). However, it is very weak and located within 50-110eV of several known faint lines, and so is subject to significant modeling uncertainties. On the origin of this line, we argue that there should be no atomic transitions in thermal plasma at this energy. An intriguing possibility is the decay of sterile neutrino, a long-sought dark matter particle candidate. Assuming that all dark matter is in sterile neutrinos with m_s=2E=7.1 keV, our detection in the full sample corresponds to a neutrino decay mixing angle sin^2(2theta)=7e-11, below the previous upper limits. However, based on the cluster masses and distances, the line in Perseus is much brighter than expected in this model. This appears to be because of an anomalously bright line at E=3.62 keV in Perseus, possibly an Ar XVII dielectronic recombination line, although its flux would be 30 times the expected value and physically difficult to understand. In principle, such an anomaly might explain our line detection in other subsamples as well, though it would stretch the line energy uncertainties. Another alternative is the above anomaly in the Ar line combined with the nearby 3.51 keV K line also exceeding expectation by factor 10-20. Confirmation with Chandra and Suzaku, and eventually Astro-H, are required to determine the nature of this new line.(ABRIDGED)", "keyphrases": ["unidentified emission line", "stacked x-ray spectrum", "galaxy cluster"]}
{"id": "1311.3856", "title": "Cosmological evidence for leptonic asymmetry after Planck", "abstract": "Recently, the Planck satellite found a larger and most precise value of the matter energy density, that impacts on the present values of other cosmological parameters such as the Hubble constant, the present cluster abundances and the age of the Universe. The existing tension between Planck determination of these parameters in the frame of the base LambdaCDM model and their direct measurements generated lively discussions and several interpretations. In this paper we quantify this tension by exploring several extensions of the base LambdaCDM model that include the leptonic asymmetry. We set bounds on the radiation content of the Universe and neutrino properties by using the latest cosmological measurements, imposing also self-consistent BBN constraints on the primordial helium abundance. For all cosmological asymmetric models we find the preference of cosmological data for smaller values of active and sterile neutrino masses. This increases the tension between cosmological and short baseline neutrino oscillation data that favor a sterile neutrino with the mass of around 1 eV. For the case of degenerate massive neutrinos, we find that the discrepancies with direct determinations of the Hubble constant, the present cluster abundances and the age of the Universe are alleviated at 1.3 sigma for all leptonic asymmetric models. We also find 2 sigma statistical evidence of the preference of cosmological data for the normal neutrino hierarchy. This is more evident for the case of cosmological models involving leptonic asymmetry and three massive neutrino species. We conclude that the current cosmological data favor the leptonic asymmetric extension of the base LambdaCDM model and normal neutrino mass hierarchy over the models with additional sterile neutrino species and/or inverted neutrino mass hierarchy.", "keyphrases": ["leptonic asymmetry", "cosmological data", "massive neutrino"]}
{"id": "1701.09062", "title": "Galactic Winds and the Role Played by Massive Stars", "abstract": "Galactic winds from star-forming galaxies play at key role in the evolution of galaxies and the inter-galactic medium. They transport metals out of galaxies, chemically-enriching the inter-galactic medium and modifying the chemical evolution of galaxies. They affect the surrounding inter-stellar and circum-galactic media, thereby influencing the growth of galaxies through gas accretion and star-formation. In this contribution we first summarize the physical mechanisms by which the momentum and energy output from a population of massive stars and associated supernovae can drive galactic winds. We use the proto-typical example of M82 to illustrate the multiphase nature of galactic winds. We then describe how the basic properties of galactic winds are derived from the data, and summarize how the properties of galactic winds vary systematically with the properties of the galaxies that launch them. We conclude with a brief discussion of the broad implications of galactic winds.", "keyphrases": ["wind", "massive star", "galaxy", "inter-galactic medium"]}
{"id": "1703.00068", "title": "Magnetars", "abstract": "Magnetars are young and highly magnetized neutron stars which display a wide array of X-ray activity including short bursts, large outbursts, giant flares and quasi-periodic oscillations, often coupled with interesting timing behavior including enhanced spin-down, glitches and anti-glitches. The bulk of this activity is explained by the evolution and decay of an ultrastrong magnetic field, stressing and breaking the neutron star crust, which in turn drives twists of the external magnetosphere and powerful magnetospheric currents. The population of detected magnetars has grown to about 30 objects and shows unambiguous phenomenological connection with very highly magnetized radio pulsars. Recent progress in magnetar theory includes explanation of the hard X-ray component in the magnetar spectrum and development of surface heating models, explaining the sources' remarkable radiative output.", "keyphrases": ["neutron star", "flare", "magnetar", "astrophysic", "generation"]}
{"id": "0911.4411", "title": "Constraints on neutrino \u2013 dark matter interactions from cosmic microwave background and large scale structure data", "abstract": "We update a previous investigation of cosmological effects of a non-standard interaction between neutrinos and dark matter. Parameterizing the elastic-scattering cross section between the two species as a function of the temperature of the universe, the resulting neutrino-dark matter fluid has a non-zero pressure, which determines diffusion-damped oscillations in the matter power spectrum similar to the acoustic oscillations generated by the photon-baryon fluid. Using cosmic microwave background data in combination with large scale structure experiment results, we then put constraints on the fraction of the interacting dark matter component as well as on the corresponding opacity.", "keyphrases": ["neutrino", "dark matter interaction", "cosmic microwave background"]}
{"id": "1210.4218", "title": "Extended f(R,L_m) gravity with generalized scalar field and kinetic term dependences", "abstract": "We generalize previous work by considering a novel gravitational model with an action given by an arbitrary function of the Ricci scalar, the matter Lagrangian density, a scalar field and a kinetic term constructed from the gradients of the scalar field, respectively. The gravitational field equations in the metric formalism are obtained, as well as the equations of motion for test particles, which follow from the covariant divergence of the stress-energy tensor. Specific models with a nonminimal coupling between the scalar field and the matter Lagrangian are further explored. We emphasize that these models are extremely useful for describing an interaction between dark energy and dark matter, and for explaining the late-time cosmic acceleration.", "keyphrases": ["scalar field", "kinetic term", "geometry-matter coupling"]}
{"id": "1109.4769", "title": "GYOTO: a new general relativistic ray-tracing code", "abstract": "GYOTO, a general relativistic ray-tracing code, is presented. It aims at computing images of astronomical bodies in the vicinity of compact objects, as well as trajectories of massive bodies in relativistic environments. This code is capable of integrating the null and timelike geodesic equations not only in the Kerr metric, but also in any metric computed numerically within the 3+1 formalism of general relativity. Simulated images and spectra have been computed for a variety of astronomical targets, such as a moving star or a toroidal accretion structure. The underlying code is open source and freely available. It is user-friendly, quickly handled and very modular so that extensions are easy to integrate. Custom analytical metrics and astronomical targets can be implemented in C++ plug-in extensions independent from the main code.", "keyphrases": ["ray-tracing code", "kerr metric", "gyoto"]}
{"id": "2012.08151", "title": "Gravitational wave constraints on the primordial black hole dominated early universe", "abstract": "We calculate the gravitational waves (GWs) induced by the density fluctuations due to inhomogeneous distribution of primordial black holes (PBHs) in the case where PBHs eventually dominate and reheat the universe by Hawking evaporation. The initial PBH density fluctuations are isocurvature in nature. We find that most of the induced GWs are generated right after evaporation, when the universe transits from the PBH dominated era to the radiation dominated era and the curvature perturbation starts to oscillate wildly. The strongest constraint on the amount of the produced GWs comes from the big bang nucleosynthesis (BBN). We improve previous constraints on the PBH fraction and find that it cannot exceed 10^-3. Furthermore, this maximum fraction decreases as the mass increases and reaches 10^-9 for M_ PBH\u223c 5\u00d710^8 g, which is the largest mass allowed by the BBN constraint on the reheating temperature. Considering that PBH may cluster above a given clustering scale, we also derive a lower bound on the scale of clustering. Interestingly, the GW spectrum for M_ PBH\u223c 10^4 -10^8 g enters the observational window of LIGO and DECIGO and could be tested in the future. Although we focus on the PBH dominated early universe in this paper, our methodology is applicable to any model with early isocurvature perturbation.", "keyphrases": ["primordial black hole", "early universe", "gravitational wave"]}
{"id": "1707.00957", "title": "General bounds in Hybrid Natural Inflation", "abstract": "Recently we have studied in great detail a model of Hybrid Natural Inflation (HNI) by constructing two simple effective field theories. These two versions of the model allow inflationary energy scales as small as the electroweak scale in one of them or as large as the Grand Unification scale in the other, therefore covering the whole range of possible energy scales. In any case the inflationary sector of the model is of the form V(\u03d5)=V_0 (1+a cos(\u03d5/f)) where 0\u2264 a<1 and the end of inflation is triggered by an independent waterfall field. One interesting characteristic of this model is that the slow-roll parameter \u03f5(\u03d5) is a non-monotonic function of \u03d5 presenting a maximum close to the inflection point of the potential. Because the scalar spectrum \ud835\udcab_s(k) of density fluctuations when written in terms of the potential is inversely proportional to \u03f5(\u03d5) we find that \ud835\udcab_s(k) presents a minimum at \u03d5_min. The origin of the HNI potential can be traced to a symmetry breaking phenomenon occurring at some energy scale f which gives rise to a (massless) Goldstone boson. Non-perturbative physics at some temperature T<f might occur which provides a potential (and a small mass) to the originally massless boson to become the inflaton (a pseudo-Nambu-Goldstone boson). Thus the inflaton energy scale \u0394 is bounded by the symmetry breaking scale, \u0394\u2261 V_H^1/4 <f. To have such a well defined origin and hierarchy of scales in inflationary models is not common. We use this property of HNI to determine bounds for the inflationary energy scale \u0394 and for the tensor-to-scalar ratio r.", "keyphrases": ["bound", "hybrid natural inflation", "energy scale"]}
{"id": "1103.3185", "title": "Running coupling: Does the coupling between dark energy and dark matter change sign during the cosmological evolution?", "abstract": "In this paper we put forward a running coupling scenario for describing the interaction between dark energy and dark matter. The dark sector interaction in our scenario is free of the assumption that the interaction term Q is proportional to the Hubble expansion rate and the energy densities of dark sectors. We only use a time-variable coupling b(a) (with a the scale factor of the universe) to characterize the interaction Q. We propose a parametrization form for the running coupling b(a)=b_0a+b_e(1-a) in which the early-time coupling is given by a constant b_e, while today the coupling is given by another constant, b_0. For investigating the feature of the running coupling, we employ three dark energy models, namely, the cosmological constant model (w=-1), the constant w model (w=w_0), and the time-dependent w model (w(a)=w_0+w_1(1-a)). We constrain the models with the current observational data, including the type Ia supernova, the baryon acoustic oscillation, the cosmic microwave background, the Hubble expansion rate, and the X-ray gas mass fraction data. The fitting results indicate that a time-varying vacuum scenario is favored, in which the coupling b(z) crosses the noninteracting line (b=0) during the cosmological evolution and the sign changes from negative to positive. The crossing of the noninteracting line happens at around z=0.2-0.3, and the crossing behavior is favored at about 1\u03c3 confidence level. Our work implies that we should pay more attention to the time-varying vacuum model and seriously consider the phenomenological construction of a sign-changeable or oscillatory interaction between dark sectors.", "keyphrases": ["dark energy", "cosmological evolution", "baryon", "vacuum scenario", "non-gravitational coupling"]}
{"id": "1202.6242", "title": "Probing the Equation of State of Nuclear Matter via Neutron Star Asteroseismology", "abstract": "We general relativistically calculate the frequency of fundamental torsional oscillations of neutron star crusts, where we focus on the crystalline properties obtained from macroscopic nuclear models in a way depending on the equation of state of nuclear matter. We find that the calculated frequency is sensitive to the density dependence of the symmetry energy, but almost independent of the incompressibility of symmetric nuclear matter. By identifying the lowest-frequency quasi-periodic oscillation in giant flares observed from soft gamma-ray repeaters as the fundamental torsional mode and allowing for the dependence of the calculated frequency on stellar models, we provide a lower limit of the density derivative of the symmetry energy as L\u2243 50 MeV.", "keyphrases": ["nuclear matter", "neutron star", "magnetar giant flare"]}
{"id": "1402.6661", "title": "Variable gravity: A suitable framework for quintessential inflation", "abstract": "In this paper, we investigate a scenario of variable gravity and apply it to the unified description of inflation and late time cosmic acceleration dubbed quintessential inflation. The scalar field called \"cosmon\" which in this model unifies both the concepts reduces to inflaton at early epochs. We calculate the slow-roll parameters, the Hubble parameter at the end of inflation, the reheating temperature,the tensor-to-scalar ration and demonstrate the agreement of the model with observations and the Planck data.As for the post inflationary dynamics, cosmon tracks the background before it exits the scaling regime at late times. The scenario gives rise to correct epoch sequence of standard cosmology, namely, radiative regime, matter phase and dark-energy. We show that the long kinetic regime after inflation gives rise to enhancement of relic gravity wave amplitude resulting into violation of nucleosynthesis constraint at the commencement of radiative regime in case of an inefficient reheating mechanism such as gravitational particle production. Instant preheating is implemented to successfully circumvent the problem. As a generic feature, the scenario gives rise to a blue spectrum for gravity waves on scales smaller than the comoving horizon scale at the commencement of the radiative regime.", "keyphrases": ["quintessential inflation", "scalar field", "cosmology", "variable gravity"]}
{"id": "0907.5220", "title": "Gravitational redshift and other redshift-space distortions of the imaginary part of the power spectrum", "abstract": "I extend the usual linear-theory formula for large-scale clustering in redshift-space to include gravitational redshift. The extra contribution to the standard galaxy power spectrum is suppressed by k_c^-2, where k_c=c k/a H (k is the wavevector, a the expansion factor, and H=\u0227/a), and is thus effectively limited to the few largest-scale modes and very difficult to detect; however, a correlation, \u221dk_c^-1, is generated between the real and imaginary parts of the Fourier space density fields of two different types of galaxy, which would otherwise be zero, i.e., the cross-power spectrum has an imaginary part: P_ab(k,\u03bc)/P(k)=(b_a+f\u03bc^2)(b_b+f\u03bc^2) -i(3\u03a9_m/2)(\u03bc/k_c)(b_a-b_b)+\ud835\udcaa(k_c^-2), where P(k) is the real-space mass-density power spectrum, b_i are the galaxy biases, \u03bcis the cosine of the angle between the wavevector and line of sight, and f=dlnD/dlna (D is the linear growth factor). The total signal-to-noise of measurements of this effect is not dominated by the largest scales \u2013 it converges at k 0.05 h/Mpc. This gravitational redshift result is pedagogically interesting, but naive in that it is gauge dependent and there are other effects of similar form and size, related to the transformation between observable and proper coordinates. I include these effects, which add other contributions to the coefficient of \u03bc/k_c, and add a \u03bc^3/k_c term, but don't qualitatively change the picture. The leading source of noise in the measurement is galaxy shot-noise, not sample variance, so developments that allow higher S/N surveys can make this measurement powerful, although it would otherwise be only marginally detectable in a JDEM-scale survey.", "keyphrases": ["imaginary part", "power spectrum", "gravitational redshift", "galaxy bias"]}
{"id": "1411.0686", "title": "Black holes as particle detectors: evolution of superradiant instabilities", "abstract": "Superradiant instabilities of spinning black holes can be used to impose strong constraints on ultralight bosons, thus turning black holes into effective particle detectors. However, very little is known about the development of the instability and whether its nonlinear time evolution accords to the linear intuition. For the first time, we attack this problem by studying the impact of gravitational-wave emission and gas accretion on the evolution of the instability. Our quasi-adiabatic, fully-relativistic analysis shows that: (i) gravitational-wave emission does not have a significant effect on the evolution of the black hole, (ii) accretion plays an important role and (iii) although the mass of the scalar cloud developed through superradiance can be a sizeable fraction of the black-hole mass, its energy-density is very low and backreaction is negligible. Thus, massive black holes are well described by the Kerr geometry even if they develop bosonic clouds through superradiance. Using Monte Carlo methods and very conservative assumptions, we provide strong support to the validity of the linearized analysis and to the bounds of previous studies.", "keyphrases": ["particle detector", "superradiant instability", "ultralight boson", "black hole"]}
{"id": "1102.4619", "title": "Nonlinear Perturbation Theory Integrated with Nonlocal Bias, Redshift-space Distortions, and Primordial Non-Gaussianity", "abstract": "The standard nonlinear perturbation theory of the gravitational instability is extended to incorporate the nonlocal bias, redshift-space distortions, and primordial non-Gaussianity. We show that local Eulerian bias is not generally compatible to local Lagrangian bias in nonlinear regime. The Eulerian and Lagrangian biases are nonlocally related order by order in the general perturbation theory. The relation between Eulerian and Lagrangian kernels of density perturbations with biasing are derived. The effects of primordial non-Gaussianity and redshift-space distortions are also incorporated in our general formalism, and diagrammatic methods are introduced. Vertex resummations of higher-order perturbations in the presence of bias are considered. Resummations of Lagrangian bias are shown to be essential to handle biasing schemes in a general framework.", "keyphrases": ["perturbation theory", "nonlocal bias", "primordial non-gaussianity", "ipt"]}
{"id": "1806.06803", "title": "Absence of a fundamental acceleration scale in galaxies", "abstract": "The Radial Acceleration Relation confirms that a nontrivial acceleration scale can be found in the average internal dynamics of galaxies. The existence of such a scale is not obvious as far as the standard cosmological model is concerned, and it has been interpreted as a possible sign of modified gravity. The implications could be profound: it could in principle explain galactic dynamics without large amounts of yet-undetected dark matter and address issues that the standard cosmological model faces at galactic scales. Here, we consider 193 disk galaxies from the SPARC and THINGS databases and, using Bayesian inference, we show that the probability of existence of a fundamental acceleration that is common to all the galaxies is essentially zero: the p-value is smaller than 10^-20 or, equivalently, the null hypothesis is rejected at more than 10\u03c3. We conclude that the acceleration scale unveiled by the Radial Acceleration Relation is of emergent nature, possibly caused by a complex interplay between baryons and dark matter. In particular, the MOND theory, or any other theory that behaves like it at galactic scales, is ruled out as a fundamental theory for galaxies at more than 10\u03c3.", "keyphrases": ["acceleration scale", "galaxy", "debate"]}
{"id": "1412.3455", "title": "Linking Tests of Gravity On All Scales: from the Strong-Field Regime to Cosmology", "abstract": "The current effort to test General Relativity employs multiple disparate formalisms for different observables, obscuring the relations between laboratory, astrophysical and cosmological constraints. To remedy this situation, we develop a parameter space for comparing tests of gravity on all scales in the universe. In particular, we present new methods for linking cosmological large-scale structure, the Cosmic Microwave Background and gravitational waves with classic PPN tests of gravity. Diagrams of this gravitational parameter space reveal a noticeable untested regime. The untested window, which separates small-scale systems from the troubled cosmological regime, could potentially hide the onset of corrections to General Relativity.", "keyphrases": ["gravity", "cosmology", "length scale"]}
{"id": "1703.00013", "title": "How Dark Matter Came to Matter", "abstract": "The history of the dark matter problem can be traced back to at least the 1930s, but it was not until the early 1970s that the issue of 'missing matter' was widely recognized as problematic. In the latter period, previously separate issues involving missing mass were brought together in a single anomaly. We argue that reference to a straightforward 'accumulation of evidence' alone is inadequate to comprehend this episode. Rather, the rise of cosmological research, the accompanying renewed interest in the theory of relativity and changes in the manpower division of astronomy in the 1960s are key to understanding how dark matter came to matter. At the same time, this story may also enlighten us on the methodological dimensions of past practices of physics and cosmology.", "keyphrases": ["dark matter", "cosmology", "non-gravitational nature"]}
{"id": "0909.0753", "title": "Atomic Dark Matter", "abstract": "We propose that dark matter is dominantly comprised of atomic bound states. We build a simple model and map the parameter space that results in the early universe formation of hydrogen-like dark atoms. We find that atomic dark matter has interesting implications for cosmology as well as direct detection: Protohalo formation can be suppressed below M_proto\u223c 10^3 - 10^6 M_\u2299 for weak scale dark matter due to Ion-Radiation interactions in the dark sector. Moreover, weak-scale dark atoms can accommodate hyperfine splittings of order 100, consistent with the inelastic dark matter interpretation of the DAMA data while naturally evading direct detection bounds.", "keyphrases": ["cosmology", "atomic dark matter", "atom"]}
{"id": "1008.3907", "title": "Indications of a spatial variation of the fine structure constant", "abstract": "We previously reported Keck telescope observations suggesting a smaller value of the fine structure constant, alpha, at high redshift. New Very Large Telescope (VLT) data, probing a different direction in the universe, shows an inverse evolution; alpha increases at high redshift. Although the pattern could be due to as yet undetected systematic effects, with the systematics as presently understood the combined dataset fits a spatial dipole, significant at the 4.2-sigma level, in the direction right ascension 17.5 +/- 0.9 hours, declination -58 +/- 9 degrees. The independent VLT and Keck samples give consistent dipole directions and amplitudes, as do high and low redshift samples. A search for systematics, using observations duplicated at both telescopes, reveals none so far which emulate this result.", "keyphrases": ["spatial variation", "fine structure constant", "sky", "visual echelle spectrograph", "hawaii"]}
{"id": "1403.3401", "title": "Coy Dark Matter and the anomalous magnetic moment", "abstract": "Coy Dark Matter removes the tension between the traditional WIMP paradigm of Dark Matter and the latest exclusion bounds from direct detection experiments. In this paper we present a leptophilic Coy Dark Matter model that, on top of explaining the spatially extended 1-5 GeV \u03b3-ray excess detected at the Galactic Center, reconciles the measured anomalous magnetic moment of muon with the corresponding Standard Model prediction. The annihilation channel of DM is \u03c7\u03c7\u2192\u03c4\u03c4\u0305 with the DM mass m_\u03c7 = 9.43 (^+.063_-0.52 stat.) (\u00b1 1.2 sys.) GeV given by best-fit of the \u03b3-ray excess. Fitting the measured anomalous magnetic moment of the muon requires instead a pseudoscalar mediator with a minimal mass m_a = 12^+7_-3 GeV.", "keyphrases": ["dark matter", "anomalous magnetic moment", "pseudoscalar mediator"]}
{"id": "1507.02924", "title": "Magnetars: the physics behind observations", "abstract": "Magnetars are the strongest magnets in the present universe and the combination of extreme magnetic field, gravity and density makes them unique laboratories to probe current physical theories (from quantum electrodynamics to general relativity) in the strong field limit. Magnetars are observed as peculiar, burst\u2013active X-ray pulsars, the Anomalous X-ray Pulsars (AXPs) and the Soft Gamma Repeaters (SGRs); the latter emitted also three \"giant flares,\" extremely powerful events during which luminosities can reach up to 10^47 erg/s for about one second. The last five years have witnessed an explosion in magnetar research which has led, among other things, to the discovery of transient, or \"outbursting,\" and \"low-field\" magnetars. Substantial progress has been made also on the theoretical side. Quite detailed models for explaining the magnetars' persistent X-ray emission, the properties of the bursts, the flux evolution in transient sources have been developed and confronted with observations. New insight on neutron star asteroseismology has been gained through improved models of magnetar oscillations. The long-debated issue of magnetic field decay in neutron stars has been addressed, and its importance recognized in relation to the evolution of magnetars and to the links among magnetars and other families of isolated neutron stars. The aim of this paper is to present a comprehensive overview in which the observational results are discussed in the light of the most up-to-date theoretical models and their implications. This addresses not only the particular case of magnetar sources, but the more fundamental issue of how physics in strong magnetic fields can be constrained by the observations of these unique sources.", "keyphrases": ["neutron star", "magnetar", "surface"]}
{"id": "1511.01465", "title": "Linear response to long wavelength fluctuations using curvature simulations", "abstract": "We study the local response to long wavelength fluctuations in cosmological N-body simulations, focusing on the matter and halo power spectra, halo abundance and non-linear transformations of the density field. The long wavelength mode is implemented using an effective curved cosmology and a mapping of time and distances. The method provides an alternative, most probably more precise, way to measure the isotropic halo biases. Limiting ourselves to the linear case, we find generally good agreement between the biases obtained from the curvature method and the traditional power spectrum method at the level of a few percent. We also study the response of halo counts to changes in the variance of the field and find that the slope of the relation between the responses to density and variance differs from the naive derivation assuming a universal mass function by 18 measurements of the amplitude of local non-Gaussianity using scale dependent bias. We also analyze the halo power spectrum and halo-dark matter cross-spectrum response to long wavelength fluctuations and derive second order halo bias from it, as well as the super-sample variance contribution to the galaxy power spectrum covariance matrix.", "keyphrases": ["response", "long wavelength fluctuation", "simulation"]}
{"id": "1007.1462", "title": "Trispectrum estimator in equilateral type non-Gaussian models", "abstract": "We investigate an estimator to measure the primordial trispectrum in equilateral type non-Gaussian models such as k-inflation, single field DBI inflation and multi-field DBI inflation models from Cosmic Microwave Background (CMB) anisotropies. The shape of the trispectrum whose amplitude is not constrained by the bispectrum in the context of effective theory of inflation and k-inflation is known to admit a separable form of the estimator for CMB anisotropies. We show that this shape is 87 % correlated with the full quantum trispectrum in single field DBI inflation, while it is 33 % correlated with the one in multi-field DBI inflation when curvature perturbation is originated from purely entropic contribution. This suggests that g_ NL ^equil, the amplitude of this particular shape, provides a reasonable measure of the non-Gaussianity from the trispectrum in equilateral non-Gaussian models. We relate model parameters such as the sound speed, c_s and the transfer coefficient from entropy perturbations to the curvature perturbation, T_\u211b S with g_ NL ^equil, which enables us to constrain model parameters in these models once g_ NL^equil is measured in WMAP and Planck.", "keyphrases": ["equilateral type", "non-gaussian model", "trispectrum"]}
{"id": "1411.4359", "title": "Homogeneous cosmology with aggressively expanding civilizations", "abstract": "In the context of a homogeneous universe, we note that the appearance of aggressively expanding advanced life is geometrically similar to the process of nucleation and bubble growth in a first-order cosmological phase transition. We exploit this similarity to describe the dynamics of life saturating the universe on a cosmic scale, adapting the phase transition model to incorporate probability distributions of expansion and resource consumption strategies. Through a series of numerical solutions spanning several orders of magnitude in the input assumption parameters, the resulting cosmological model is used to address basic questions related to the intergalactic spreading of life, dealing with issues such as timescales, observability, competition between strategies, and first-mover advantage. Finally, we examine physical effects on the universe itself, such as reheating and the backreaction on the evolution of the scale factor, if such life is able to control and convert a significant fraction of the available pressureless matter into radiation. We conclude that the existence of life, if certain advanced technologies are practical, could have a significant influence on the future large-scale evolution of the universe.", "keyphrases": ["cosmology", "civilization", "life", "expansion speed"]}
{"id": "1003.1327", "title": "Stochastic growth of quantum fluctuations during slow-roll inflation", "abstract": "We compute the growth of the mean square of quantum fluctuations of test fields with small effective mass during a slowly changing, nearly de Sitter stage which took place in different inflationary models. We consider a minimally coupled scalar with a small mass, a modulus with an effective mass \u221d H^2 (with H as the Hubble parameter) and a massless non-minimally coupled scalar in the test field approximation and compare the growth of their relative mean square with the one of gauge-invariant inflaton fluctuations. We find that in most of the single field inflationary models the mean square gauge invariant inflaton fluctuation grows faster than any test field with a non-negative effective mass. Hybrid inflationary models can be an exception: the mean square of a test field can dominate over the gauge invariant inflaton fluctuation one on suitably choosing parameters. We also compute the stochastic growth of quantum fluctuation of a second field, relaxing the assumption of its zero homogeneous value, in a generic inflationary model; as a main result, we obtain that the equation of motion of a gauge invariant variable associated, order by order, with a generic quantum scalar fluctuation during inflation can be obtained only if we use the number of e-folds as the time variable in the corresponding Langevin and Fokker-Planck equations for the stochastic approach. We employ this approach to derive some bounds in the case of a model with two massive fields.", "keyphrases": ["quantum fluctuation", "slow-roll inflation", "scalar field"]}
{"id": "1004.0629", "title": "Neutron Stars as Dark Matter Probes", "abstract": "We examine whether the accretion of dark matter onto neutron stars could ever have any visible external effects. Captured dark matter which subsequently annihilates will heat the neutron stars, although it seems the effect will be too small to heat close neutron stars at an observable rate whilst those at the galactic centre are obscured by dust. Non-annihilating dark matter would accumulate at the centre of the neutron star. In a very dense region of dark matter such as that which may be found at the centre of the galaxy, a neutron star might accrete enough to cause it to collapse within a period of time less than the age of the Universe. We calculate what value of the stable dark matter-nucleon cross section would cause this to occur for a large range of masses.", "keyphrases": ["dark matter", "neutron star", "black hole"]}
{"id": "1710.03054", "title": "Strongly Coupled Quasi-Single Field Inflation", "abstract": "We study the power spectrum of quasi-single field inflation where strong coupling is considered. The contribution from the massive propagator can be divided into local and non-local contributions. The local one is the leading contribution and is power-law suppressed as a function of mass, while the non-local contribution is exponentially suppressed in the large mass limit. For the local contribution, it is possible to use the effective field theory approach to study the power spectrum in the strongly coupled region of the parameter space. For the non-local contribution, we developed a partial effective field theory method to simplify the calculation: When there are multiple massive propagators, one can fully compute it after integrating out all but one massive propagator by effective field theory. The result retains the \"standard clock\" signal, which is interesting for probing the expansion history of the primordial universe and the physics of a \"cosmological collider\". The error involved compared to the full calculation is power law suppressed by the effective mass of the heavy field.", "keyphrases": ["quasi-single field inflation", "cosmological collider physics", "particle physics"]}
{"id": "1409.4801", "title": "Catalog of observed tangents to the spiral arms in the Milky Way galaxy", "abstract": "From the sun's location in the Galactic disk, one can use different arm tracers (CO, HII, thermal or ionized or relativistic electrons, masers, cold or hot dust, etc) to locate a tangent to each spiral arm in the disk of the Milky Way galaxy. We present a Master catalog of the astronomically observed tangents to the Galaxy's spiral arms, using different arm tracers from the literature. Some arm tracers can have slightly divergent results from several papers, so a mean is taken - see Appendix for CO, HII, and masers. The Master catalog of means currently consists of 63 mean tracer entries, spread over many arms (Carina, Crux-Centaurus, Norma, Perseus origin, near 3-kpc, Scutum, Sagittarius), stemming from 107 original arm tracer entries. Additionally, we updated and revised a previous a previous statistical analysis of the angular offset and linear separation from the mid-arm, for each different mean arm tracer. Given enough arm tracers, and summing and averaging over all spiral arms, one could determine if arm tracers have separate and parallel lanes in the Milky Way. This statistical analysis allows a cross-cut of a galactic spiral arm to be made, confirming a recent discovery of a linear separation between arm tracers. Here, from the mid-arm's CO to the inner edge's hot dust, the arm half-width is about 340 parsecs; doubling would yield a full arm width of 680 parsecs. We briefly compare these observations with the predictions of many spiral arm theories, notably the density wave theory.", "keyphrases": ["spiral arm", "milky way", "galaxy"]}
{"id": "0901.0989", "title": "Gravitational waves from an early matter era", "abstract": "We investigate the generation of gravitational waves due to the gravitational instability of primordial density perturbations in an early matter-dominated era which could be detectable by experiments such as LIGO and LISA. We use relativistic perturbation theory to give analytic estimates of the tensor perturbations generated at second order by linear density perturbations. We find that large enhancement factors with respect to the naive second-order estimate are possible due to the growth of density perturbations on sub-Hubble scales. However very large enhancement factors coincide with a breakdown of linear theory for density perturbations on small scales. To produce a primordial gravitational wave background that would be detectable with LIGO or LISA from density perturbations in the linear regime requires primordial comoving curvature perturbations on small scales of order 0.02 for Advanced LIGO or 0.005 for LISA, otherwise numerical calculations of the non-linear evolution on sub-Hubble scales are required.", "keyphrases": ["perturbation theory", "gravitational wave", "gws"]}
{"id": "1710.02758", "title": "Resurrecting Quadratic Inflation with a non-minimal coupling to gravity", "abstract": "We study Quadratic Inflation with the inflaton field \u03d5 coupled non-minimally to the curvature scalar R, so that the potential during inflation is of the form V\u221d m^2\u03d5^2+\u03be R\u03d5^2. We show that with a suitable choice of the non-minimal coupling strength, \u03be=\ud835\udcaa(10^-3), one can resurrect the success of the scenario when compared against the Planck and BICEP2/Keck Array data, and that in the region of the parameter space which is still allowed the model predicts values of the tensor-to-scalar ratio in the range 0.01\u2264 r < 0.12, making it possible to either confirm the scenario or rule it out already by the current or near-future experiments, such as BICEP3 or LiteBIRD. However, we show that in this case the near-future observations are unlikely to be able to distinguish between the metric and Palatini formulations of gravity.", "keyphrases": ["quadratic inflation", "non-minimal coupling", "gravity"]}
{"id": "2102.03152", "title": "Superradiance in Kerr-like black holes", "abstract": "Recent strong-field regime tests of gravity are so far in agreement with general relativity. In particular, astrophysical black holes appear all to be consistent with the Kerr spacetime, but the statistical error on current observations allows for small yet detectable deviations from this description. Here we study superradiance of scalar and electromagnetic test fields around the Kerr-like Konoplya\u2013Zhidenko black hole and we observe that for large values of the deformation parameter superradiance is highly suppressed with respect to the Kerr case. Surprisingly, there exists a range of small values of the deformation parameter for which the maximum amplification factor is larger than the Kerr one. We also provide a first result about the superradiant instability of these non-Kerr spacetimes against massive scalar fields.", "keyphrases": ["black hole", "superradiant instability", "superradiance"]}
{"id": "1208.2496", "title": "Dark radiation and small-scale structure problems with decaying particles", "abstract": "Although the standard \u039bCDM model describes the cosmic microwave background radiation and the large scale structure of the Universe with great success, it has some tensions with observations in the effective number of neutrino species (dark radiation) and the number of small scale structures (overabundance problem). Here we propose a scenario which can relax these tensions by producing both dark matter and dark radiation by late decays of heavy particle. Thanks to the generation mechanism, dark matters are rather warm so that the small-scale structure problem is resolved. This scenario can be naturally realized in supersymmetric axion model, in which axions produced by saxion decays provide dark radiation, while axinos from saxion decays form warm dark matter. We identify a parameter region of supersymmetric axion model satisfying all known cosmological constraints.", "keyphrases": ["particle", "dark matter", "axion", "dark radiation"]}
{"id": "1211.7054", "title": "Dark Energy or Modified Gravity? An Effective Field Theory Approach", "abstract": "We take an Effective Field Theory (EFT) approach to unifying existing proposals for the origin of cosmic acceleration and its connection to cosmological observations. Building on earlier work where EFT methods were used with observations to constrain the background evolution, we extend this program to the level of the EFT of the cosmological perturbations - following the example from the EFT of Inflation. Within this framework, we construct the general theory around an assumed background which will typically be chosen to mimic Lambda-CDM, and identify the parameters of interest for constraining dark energy and modified gravity models with observations. We discuss the similarities to the EFT of Inflation, but we also identify a number of subtleties including the relationship between the scalar perturbations and the Goldstone boson of the spontaneously broken time translations. We present formulae that relate the parameters of the fundamental Lagrangian to the speed of sound, anisotropic shear stress, effective Newtonian constant, and Caldwell's varpi parameter emphasizing the connection to observations. It is anticipated that this framework will be of use in constraining individual models, as well as for placing model-independent constraints on dark energy and modified gravity model building.", "keyphrases": ["gravity", "effective field theory", "cosmological observation"]}
{"id": "1204.6318", "title": "Effects and Detectability of Quasi-Single Field Inflation in the Large-Scale Structure and Cosmic Microwave Background", "abstract": "Quasi-single field inflation predicts a peculiar momentum dependence in the squeezed limit of the primordial bispectrum which smoothly interpolates between the local and equilateral models. This dependence is directly related to the mass of the isocurvatons in the theory which is determined by the supersymmetry. Therefore, in the event of detection of a non-zero primordial bispectrum, additional constraints on the parameter controlling the momentum-dependence in the squeezed limit becomes an important question. We explore the effects of these non-Gaussian initial conditions on large-scale structure and the cosmic microwave background, with particular attention to the galaxy power spectrum at large scales and scale-dependence corrections to galaxy bias. We determine the simultaneous constraints on the two parameters describing the QSF bispectrum that we can expect from upcoming large-scale structure and cosmic microwave background observations. We find that for relatively large values of the non-Gaussian amplitude parameters, but still well within current uncertainties, galaxy power spectrum measurements will be able to distinguish the QSF scenario from the predictions of the local model. A CMB likelihood analysis, as well as Fisher matrix analysis, shows that there is also a range of parameter values for which Planck data may be able distinguish between QSF models and the related local and equilateral shapes. Given the different observational weightings of the CMB and LSS results, degeneracies can be significantly reduced in a joint analysis.", "keyphrases": ["quasi-single field inflation", "cosmic microwave background", "primordial bispectrum", "cosmological collider physics"]}
{"id": "1803.02620", "title": "Mimicking dark matter and dark energy in a mimetic model compatible with GW170817", "abstract": "The recent observation of the the gravitational wave event GW170817 and of its electromagnetic counterpart GRB170817A, from a binary neutron star merger, has established that the speed of gravitational waves deviates from the speed of light by less than one part in 10^15. As a consequence, many extensions of General Relativity are inevitably ruled out. Among these we find the most relevant sectors of Horndeski gravity. In its original formulation, mimetic gravity is able to mimic cosmological dark matter, has tensorial perturbations that travel exactly at the speed of light but has vanishing scalar perturbations and this fact persists if we combine mimetic with Horndeski gravity. In this work, we show that implementing the mimetic gravity action with higher-order terms that break the Horndeski structure yields a cosmological model that satisfies the constraint on the speed of gravitational waves and mimics both dark energy and dark matter with a non-vanishing speed of sound. In this way, we are able to reproduce the \u039bCDM cosmological model without introducing particle cold dark matter.", "keyphrases": ["dark matter", "dark energy", "gravity theory"]}
{"id": "1407.2446", "title": "The little sibling of the big rip singularity", "abstract": "We present a new cosmological event, which we named the little sibling of the big rip. This event is much smoother than the big rip singularity. When the little sibling of the big rip is reached, the Hubble rate and the scale factor blow up but the cosmic derivative of the Hubble rate does not. This abrupt event takes place at an infinite cosmic time where the scalar curvature explodes. We show that a doomsday \u00e1 la little sibling of the big rip is compatible with an accelerating universe, indeed at present it would mimic perfectly a LCDM scenario. It turns out that eventhough the event seems to be harmless as it takes place in the infinite future, the bound structures in the universe would be unavoidably destroyed on a finite cosmic time from now. The model can be motivated by considering that the weak energy condition should not be abusibely violated in our Universe, and it could give us some hints about the status of recently formulated nonlinear energy conditions.", "keyphrases": ["sibling", "singularity", "scale factor", "abrupt event", "cosmic time"]}
{"id": "1811.00605", "title": "The nature of fast radio bursts", "abstract": "Physical constraints on the sources of fast radio bursts are few, and therefore viable theoretical models are many. However, no one model can match all the available observational characteristics, meaning that these radio bursts remain one of the most mysterious phenomena in astrophysics.", "keyphrases": ["fast radio burst", "frbs", "astronomy", "millisecond duration"]}
{"id": "1808.08967", "title": "De Sitter vs Quintessence in String Theory", "abstract": "De Sitter solutions have been recently conjectured to be incompatible with quantum gravity. In this paper we critically assess the progress and challenges of different mechanisms to obtain de Sitter vacua in string compactifications and compare them to quintessence models. We argue that, despite recent criticisms, de Sitter models reached a level of concreteness and calculational control which has been improving over time. On the other hand, building string models of quintessence appears to be more challenging and requires additional fine-tuning. We discuss the tension between the swampland conjecture and the Higgs potential and find examples which can evade fifth-force bounds even if they seem very hard to realise in string theory. We also comment on the tension with low-redshift data and explore ultra-light axions from string theory as dark energy candidates.", "keyphrases": ["string theory", "swampland conjecture", "vacuum"]}
{"id": "1011.3727", "title": "Kinematic dynamo in spherical Couette flow", "abstract": "We investigate numerically kinematic dynamos driven by flow of electrically conducting fluid in the shell between two concentric differentially rotating spheres, a configuration normally referred to as spherical Couette flow. We compare between axisymmetric (2D) and fully three dimensional flows, between low and high global rotation rates, between prograde and retrograde differential rotations, between weak and strong nonlinear inertial forces, between insulating and conducting boundaries, and between two aspect ratios. The main results are as follows. Azimuthally drifting Rossby waves arising from the destabilisation of the Stewartson shear layer are crucial to dynamo action. Differential rotation and helical Rossby waves combine to contribute to the spherical Couette dynamo. At a slow global rotation rate, the direction of differential rotation plays an important role in the dynamo because of different patterns of Rossby waves in prograde and retrograde flows. At a rapid global rotation rate, stronger flow supercriticality (namely the difference between the differential rotation rate of the flow and its critical value for the onset of nonaxisymmetric instability) facilitates the onset of dynamo action. A conducting magnetic boundary condition and a larger aspect ratio both favour dynamo action.", "keyphrases": ["dynamo", "couette flow", "force"]}
{"id": "1312.3540", "title": "Integrable cosmological models with non-minimally coupled scalar fields", "abstract": "We obtain general solutions for some flat Friedmann universes filled with a scalar field in induced gravity models and models including the Hilbert-Einstein curvature term plus a scalar field conformally coupled to gravity. As is well known, these models are connected to minimally coupled models through the combination of a conformal transformation and a transformation of the scalar field. The explicit forms of the self-interaction potentials for six exactly solvable models are presented here. We obtain the general solution for one of the integrable models, namely, the induced gravity model with a power-law potential for the self-interaction of the scalar field. We argue that although being mathematically in a one-to-one correspondence with the solutions in the minimally coupled models, the solutions in the corresponding non-minimally coupled models are physically different. This is because the cosmological evolutions seen by an internal observer connected with the cosmic time can be quite different. The study of a few induced gravity models with particular potentials gives us an explicit example of such a difference.", "keyphrases": ["scalar field", "friedmann universe", "hilbert-einstein curvature term", "integrable cosmological model"]}
{"id": "1305.2930", "title": "Perturbations in Chromo-Natural Inflation", "abstract": "Chromo-Natural Inflation is the first worked example of a model of inflation in which slow-roll inflation is achieved by \"magnetic drift\" as opposed to Hubble friction. In this work, we give an account of the perturbations at linear order in this model. Our analysis uncovers two novel phenomena. First, the amplitude of scalar curvature perturbations is not directly tied to the shape of the inflationary potential. This allows the theory to violate na\u00efve formulations of the Lyth bound. Second, the tensor sector of the theory is significantly altered from the usual case: the non-Abelian gauge field perturbations have a tensor degree of freedom. One chirality of the this tensor can be exponentially enhanced by a temporary instability near horizon crossing; this chiral instability exists because of the classical gauge field background, which violates parity. These tensor fluctuations of the gauge field also couple to gravitational waves at linear order in perturbation theory and source a chiral spectrum of gravitational waves. This spectrum can be exponentially enhanced over the usual inflationary spectrum due to the instability in the gauge sector. These new features cause the theory in its present form to be in significant tension with current observational data. This is because the new scalar physics leads to a significant reddening of the spectral tilt in the same region of parameter space where the exponential enhancement of the gravitational wave amplitude is small enough to satisfy current constraints on the tensor-to-scalar index. Hence, the model either predicts a spectral tilt that is too red, or it overproduces gravitational waves, or both.", "keyphrases": ["chromo-natural inflation", "curvature perturbation", "gauge field", "gravitational wave"]}
{"id": "1105.0909", "title": "Linear kinetic Sunyaev-Zel'dovich effect and void models for acceleration", "abstract": "There has been considerable recent interest in cosmological models in which the current apparent acceleration is due to a very large local underdensity, or void, instead of some form of dark energy. Here we examine a new proposal to constrain such models using the linear kinetic Sunyaev-Zel'dovich (kSZ) effect due to structure within the void. The simplified \"Hubble bubble\" models previously studied appeared to predict far more kSZ power than is actually observed, independently of the details of the initial conditions and evolution of perturbations in such models. We show that the constraining power of the kSZ effect is considerably weakened (though still impressive) under a fully relativistic treatment of the problem, and point out several theoretical ambiguities and observational shortcomings which further qualify the results. Nevertheless, we conclude that a very large class of void models is ruled out by the combination of kSZ and other methods.", "keyphrases": ["sunyaev-zel'dovich effect", "void model", "cosmological model"]}
{"id": "1902.10503", "title": "Cosmological Tests of Gravity", "abstract": "Cosmological observations are beginning to reach a level of precision that allow us to test some of the most fundamental assumptions in our working model of the Universe. One such an assumption is that gravity is governed by the General Theory of Relativity. In this review we discuss how one might go about extending General Relativity and how such extensions can be described in a unified way on large scales. This allows us to describe the impact of modified gravity on the growth and morphology of the large scale structure of the Universe. On smaller scales we explore the physics of gravitational screening and how it might manifest itself in galaxies, clusters and, more generally, in the cosmic web. We then analyze the current constraints from large scale structure and conclude by discussing the future prospects of the field in light of the plethora of surveys currently being planned.", "keyphrases": ["gravity", "large scale", "plethora", "dark energy", "cosmological test"]}
{"id": "1306.3691", "title": "Equilateral non-Gaussianity from heavy fields", "abstract": "The effect of self-interactions of heavy scalar fields during inflation on the primordial non-Gaussianity is studied. We take a specific constant-turn quasi-single field inflation as an example. We derive an effective theory with emphasis on non-linear self-interactions of heavy fields and calculate the corresponding non-Gaussianity, which is of equilateral type and can be as relevant as those computed previously in the literature. We also derive the non-Gaussianity by directly using the in-in formalism, and verify the equivalence of these two approaches.", "keyphrases": ["non-gaussianity", "heavy field", "quasi-single field inflation", "collider", "particle"]}
{"id": "1106.5508", "title": "ELMAG: A Monte Carlo simulation of electromagnetic cascades on the extragalactic background light and in magnetic fields", "abstract": "A Monte Carlo program for the simulation of electromagnetic cascades initiated by high-energy photons and electrons interacting with extragalactic background light (EBL) is presented. Pair production and inverse Compton scattering on EBL photons as well as synchrotron losses and deflections of the charged component in extragalactic magnetic fields (EGMF) are included in the simulation. Weighted sampling of the cascade development is applied to reduce the number of secondary particles and to speed up computations. As final result, the simulation procedure provides the energy, the observation angle, and the time delay of secondary cascade particles at the present epoch. Possible applications are the study of TeV blazars and the influence of the EGMF on their spectra or the calculation of the contribution from ultrahigh energy cosmic rays or dark matter to the diffuse extragalactic gamma-ray background. As an illustration, we present results for deflections and time-delays relevant for the derivation of limits on the EGMF.", "keyphrases": ["electromagnetic cascade", "extragalactic background light", "high-energy photon"]}
{"id": "1810.11000", "title": "Gravitational Waves Induced by non-Gaussian Scalar Perturbations", "abstract": "We study gravitational waves (GWs) induced by non-Gaussian curvature perturbations. We calculate the density parameter per logarithmic frequency interval, \u03a9_GW(k), given that the power spectrum of the curvature perturbation \ud835\udcab_\u211b(k) has a narrow peak at some small scale k_*, with a local-type non-Gaussianity, and constrain the nonlinear parameter f_NL with the future LISA sensitivity curve as well as with constraints from the abundance of the primordial black holes (PBHs). We find that the non-Gaussian contribution to \u03a9_GW increases as k^3, peaks at k/k_*=4/\u221a(3), and has a sharp cutoff at k=4k_*. The non-Gaussian part can exceed the Gaussian part if \ud835\udcab_\u211b(k)f_NL^2\u22731. If both a slope \u03a9_GW(k)\u221d k^\u03b2 with \u03b2\u223c3 and the multiple-peak structure around a cutoff are observed, it can be recognized as a smoking gun of the primordial non-Gaussianity. We also find that if PBHs with masses of 10^20g to 10^22g are identified as cold dark matter of the Universe, the corresponding GWs must be detectable by LISA-like detectors, irrespective of the value of \ud835\udcab_\u211b or f_NL.", "keyphrases": ["curvature perturbation", "black hole", "primordial non-gaussianity", "gravitational wave", "primordial scalar perturbation"]}
{"id": "1801.04268", "title": "Cosmological Backgrounds of Gravitational Waves", "abstract": "Gravitational waves (GWs) have a great potential to probe cosmology. We review early universe sources that can lead to cosmological backgrounds of GWs. We begin by presenting definitions of GWs in flat space-time and in a cosmological setting, and discussing the reasons why GW backgrounds from the early universe are of a stochastic nature. We recap current observational constraints on stochastic backgrounds, and discuss some of the characteristics of present and future GW detectors including advanced LIGO, advanced Virgo, the Einstein Telescope, KAGRA, LISA. We then review in detail early universe GW generation mechanisms proposed in the literature, as well as the properties of the GW backgrounds they give rise to. We classify the backgrounds in five categories: GWs from quantum vacuum fluctuations during standard slow-roll inflation, GWs from processes that operate within extensions of the standard inflationary paradigm, GWs from post-inflationary preheating and related non-perturbative phenomena, GWs from first order phase transitions (related or not to the electroweak symmetry breaking), and GWs from topological defects, in particular from cosmic strings. The phenomenology of early universe processes that can generate a stochastic background of GWs is extremely rich, and some backgrounds are within the reach of near-future GW detectors. A future detection of any of these backgrounds will provide crucial information on the underlying high energy theory describing the early universe, probing energy scales well beyond the reach of particle accelerators.", "keyphrases": ["gravitational wave", "early universe", "stochastic background", "black hole", "non-perturbative phenomenon"]}
{"id": "1204.3669", "title": "The Search for a Primordial Magnetic Field", "abstract": "Magnetic fields appear wherever plasma and currents can be found. As such, they thread through all scales in Nature. It is natural, therefore, to suppose that magnetic fields might have been formed within the high temperature environments of the big bang. Such a primordial magnetic field (PMF) would be expected to arise from and/or influence a variety of cosmological phenomena such as inflation, cosmic phase transitions, big bang nucleosynthesis, the cosmic microwave background (CMB) temperature and polarization anisotropies, the cosmic gravity wave background, and the formation of large-scale structure. In this review, we summarize the development of theoretical models for analyzing the observational consequences of a PMF. We also summarize the current state of the art in the search for observational evidence of a PMF. In particular we review the framework needed to calculate the effects of a PMF power spectrum on the CMB and the development of large scale structure. We summarize the current constraints on the PMF amplitude B_\u03bb and the power spectral index n_B and discuss prospects for better determining these quantities in the near future.", "keyphrases": ["primordial magnetic field", "cosmic microwave background", "early universe"]}
{"id": "1001.5349", "title": "The matter Lagrangian and the energy-momentum tensor in modified gravity with non-minimal coupling between matter and geometry", "abstract": "We show that in modified f(R) type gravity models with non-minimal coupling between matter and geometry, both the matter Lagrangian, and the energy-momentum tensor, are completely and uniquely determined by the form of the coupling. This result is obtained by using the variational formulation for the derivation of the equations of motion in the modified gravity models with geometry-matter coupling, and the Newtonian limit for a fluid obeying a barotropic equation of state. The corresponding energy-momentum tensor of the matter in modified gravity models with non-minimal coupling is more general than the usual general-relativistic energy-momentum tensor for perfect fluids, and it contains a supplementary, equation of state dependent term, which could be related to the elastic stresses in the body, or to other forms of internal energy. Therefore, the extra-force induced by the coupling between matter and geometry never vanishes as a consequence of the thermodynamic properties of the system, or for a specific choice of the matter Lagrangian, and it is non-zero in the case of a fluid of dust particles.", "keyphrases": ["matter lagrangian", "gravity", "non-minimal coupling"]}
{"id": "1303.3628", "title": "Shear and rotation in Chaplygin cosmology", "abstract": "We study the effect of shear and rotation on results previously obtained dealing with the application of the spherical collapse model (SCM) to generalized Chaplygin gas (gCg) dominated universes. The system is composed of baryons and gCg and the collapse is studied for different values of the parameter \u03b1 of the gCg. We show that the joint effect of shear and rotation is that of slowing down the collapse with respect to the simple SCM. This result is of utmost importance for the so-called unified dark matter models, since the described slow down in the growth of density perturbation can solve one of the main problems of the quoted models, namely the instability described in previous papers [e.g., H. B. Sandvik et al., Phys. Rev. D 69, 123524 (2004)] at the linear perturbation level.", "keyphrases": ["rotation", "joint effect", "shear"]}
{"id": "1302.4831", "title": "Modified gravity: walk through accelerating cosmology", "abstract": "We review the accelerating (mainly, dark energy) cosmologies in modified gravity. Special attention is paid to cosmologies leading to finite-time future singularities in F(R), F(G) and \u2131(R,G) modified gravities. The removal of the finite-time future singularities via addition of R^2-term which simultaneously unifies the early-time inflation with late-time acceleration is also briefly mentioned. Accelerating cosmology including the scenario unifying inflation with dark energy is considered in F(R) gravity with Lagrange multipliers. In addition, we examine domain wall solutions in F(R) gravity. Furthermore, covariant higher derivative gravity with scalar projectors is explored.", "keyphrases": ["gravity", "cosmology", "dark energy problem", "late-time cosmic acceleration"]}
{"id": "1201.6526", "title": "Multiple populations in globular clusters. Lessons learned from the Milky Way globular clusters", "abstract": "Recent progress in studies of globular clusters has shown that they are not simple stellar populations, being rather made of multiple generations. Evidence stems both from photometry and spectroscopy. A new paradigm is then arising for the formation of massive star clusters, which includes several episodes of star formation. While this provides an explanation for several features of globular clusters, including the second parameter problem, it also opens new perspectives about the relation between globular clusters and the halo of our Galaxy, and by extension of all populations with a high specific frequency of globular clusters, such as, e.g., giant elliptical galaxies. We review progress in this area, focusing on the most recent studies. Several points remain to be properly understood, in particular those concerning the nature of the polluters producing the abundance pattern in the clusters and the typical timescale, the range of cluster masses where this phenomenon is active, and the relation between globular clusters and other satellites of our Galaxy.", "keyphrases": ["cluster", "star formation", "lifetime"]}
{"id": "1009.2094", "title": "Primordial magnetic field limits from cosmological data", "abstract": "We study limits on a primordial magnetic field arising from cosmological data, including that from big bang nucleosynthesis, cosmic microwave background polarization plane Faraday rotation limits, and large-scale structure formation. We show that the physically-relevant quantity is the value of the effective magnetic field, and limits on it are independent of how the magnetic field was generated.", "keyphrases": ["magnetic field", "cosmological data", "nucleosynthesis", "primordial magnetic field"]}
{"id": "1001.4088", "title": "Scalar-Scalar, Scalar-Tensor, and Tensor-Tensor Correlators from Anisotropic Inflation", "abstract": "We compute the phenomenological signatures of a model (Watanabe et al' 09) of anisotropic inflation driven by a scalar and a vector field. The action for the vector is U(1) invariant, and the model is free of ghost instabilities. A suitable coupling of the scalar to the kinetic term of the vector allows for a slow roll evolution of the vector vev, and hence for a prolonged anisotropic expansion; this provides a counter example to the cosmic no hair conjecture. We compute the nonvanishing two point correlation functions between physical modes of the system, and express them in terms of power spectra with angular dependence. The anisotropy parameter g_* for the scalar-scalar spectrum (defined as in the Ackerman et al '07 parametrization) turns out to be negative in the simplest realization of the model, which, therefore, cannot account for the angular dependence emerged in some analyses of the WMAP data. A g_* of order -0.1 is achieved when the energy of the vector is about 6-7 orders of magnitude smaller than that of the scalar during inflation. For such values of the parameters, the scalar-tensor correlation (which is in principle a distinctive signature of anisotropic spaces) is smaller than the tensor-tensor correlation.", "keyphrases": ["anisotropic inflation", "curvature perturbation", "gauge field", "broken rotational invariance"]}
{"id": "1203.4352", "title": "Measurability of the tidal polarizability of neutron stars in late-inspiral gravitational-wave signals", "abstract": "The gravitational wave signal from a binary neutron star inspiral contains information on the nuclear equation of state. This information is contained in a combination of the tidal polarizability parameters of the two neutron stars and is clearest in the late inspiral, just before merger. We use the recently defined tidal extension of the effective one-body formalism to construct a controlled analytical description of the frequency-domain phasing of neutron star inspirals up to merger. Exploiting this analytical description we find that the tidal polarizability parameters of neutron stars can be measured by the advanced LIGO-Virgo detector network from gravitational wave signals having a reasonable signal-to-noise ratio of \u03c1=16. This measurability result seems to hold for all the nuclear equations of state leading to a maximum mass larger than 1.97M_\u2299. We also propose a promising new way of extracting information on the nuclear equation of state from a coherent analysis of an ensemble of gravitational wave observations of separate binary merger events.", "keyphrases": ["neutron star", "tidal deformability", "gravitational-wave detector"]}
{"id": "1201.5390", "title": "Signatures of photon-axion conversion in the thermal spectra and polarization of neutron stars", "abstract": "Conversion of photons into axions under the presence of a strong magnetic field can dim the radiation from magnetized astrophysical objects. Here we perform a detailed calculation aimed at quantifying the signatures of photon-axion conversion in the spectra, light curves, and polarization of neutron stars (NSs). We take into account the energy and angle-dependence of the conversion probability and the surface thermal emission from NSs. The latter is computed from magnetized atmosphere models that include the effect of photon polarization mode conversion due to vacuum polarization. The resulting spectral models, inclusive of the general-relativistic effects of gravitational redshift and light deflection, allow us to make realistic predictions for the effects of photon to axion conversion on observed NS spectra, light curves, and polarization signals. We identify unique signatures of the conversion, such as an increase of the effective area of a hot spot as it rotates away from the observer line of sight. For a star emitting from the entire surface, the conversion produces apparent radii that are either larger or smaller (depending on axion mass and coupling strength) than the limits set by NS equations of state. For an emission region that is observed phase-on, photon-axion conversion results in an inversion of the plane of polarization with respect to the no-conversion case. While the quantitative details of the features that we identify depend on NS properties (magnetic field strength, temperature) and axion parameters, the spectral and polarization signatures induced by photon-axion conversion are distinctive enough to make NSs very interesting and promising probes of axion physics.", "keyphrases": ["photon-axion conversion", "neutron star", "photon"]}
{"id": "1811.02590", "title": "Cosmological constraints from the Hubble diagram of quasars at high redshifts", "abstract": "The concordance (LambdaCDM) model reproduces the main current cosmological observations assuming the validity of general relativity at all scales and epochs, the presence of cold dark matter, and of a cosmological constant, equivalent to a dark energy with constant density in space and time. However, the LambdaCDM model is poorly tested in the redshift interval between the farthest observed Type Ia supernovae5 and that of the Cosmic Microwave background (CMB). We present new measurements of the expansion rate of the Universe in the range 0.5<z<5.5 based on a Hubble diagram of quasars. The quasar distances are estimated from their X-ray and ultraviolet emission, following a method developed by our group. The distance modulus-redshift relation of quasars at z<1.4 is in agreement with that of supernovae and with the concordance model. Yet, a deviation from the LambdaCDM model emerges at higher redshift, with a statistical significance of 4 sigma. If an evolution of the dark energy equation of state is allowed, the data suggest a dark energy density increasing with time.", "keyphrases": ["quasar", "dark energy density", "gamma-ray burst"]}
{"id": "1512.00086", "title": "The Evolution of the Intergalactic Medium", "abstract": "The bulk of cosmic matter resides in a dilute reservoir that fills the space between galaxies, the intergalactic medium (IGM). The history of this reservoir is intimately tied to the cosmic histories of structure formation, star formation, and supermassive black hole accretion. Our models for the IGM at intermediate redshifts (2<z<5) are a tremendous success, quantitatively explaining the statistics of Lyman-alpha absorption of intergalactic hydrogen. However, at both lower and higher redshifts (and around galaxies) much is still unknown about the IGM. We review the theoretical models and measurements that form the basis for the modern understanding of the IGM, and we discuss unsolved puzzles (ranging from the largely unconstrained process of reionization at high-z to the missing baryon problem at low-z), highlighting the efforts that have the potential to solve them.", "keyphrases": ["intergalactic medium", "igm", "redshift", "hydrogen", "reionization"]}
{"id": "1209.2117", "title": "The Parameterized Post-Friedmann Framework for Theories of Modified Gravity: Concepts, Formalism and Examples", "abstract": "A unified framework for theories of modified gravity will be an essential tool for interpreting the forthcoming deluge of cosmological data. We present such a formalism, the Parameterized Post-Friedmann framework (PPF), which parameterizes the cosmological perturbation theory of a wide variety of modified gravity models. PPF is able to handle spin-0 degrees of freedom from new scalar, vector and tensor fields, meaning that it is not restricted to simple models based solely on cosmological scalar fields. A direct correspondence is maintained between the parameterization and the underlying space of theories, which allows us to build up a `dictionary' of modified gravity theories and their PPF correspondences. In this paper we describe the construction of the parameterization and demonstrate its use through a number of worked examples relevant to the current literature. We indicate how the formalism will be implemented numerically, so that the dictionary of modified gravity can be pitted against forthcoming observations.", "keyphrases": ["parameterized post-friedmann framework", "formalism", "gravity model"]}
{"id": "1111.2838", "title": "Physics of Dark Matter in the Light of Dark Atoms", "abstract": "Direct searches for dark matter lead to serious problems for simple models with stable neutral Weakly Interacting Massive Particles (WIMPs) as candidates for dark matter. A possibility is discussed that new stable quarks and charged leptons exist and are hidden from detection, being bound in neutral dark atoms of composite dark matter. Stable -2 charged particles O^\u2013 are bound with primordial helium in O-helium (OHe) atoms, being specific nuclear interacting form of composite Warmer than Cold dark matter. Slowed down in the terrestrial matter, OHe is elusive for direct methods of underground dark matter detection based on the search for effects of nuclear recoil in WIMP-nucleus collisions. The positive results of DAMA experiments can be explained as annual modulation of radiative capture of O-helium by nuclei. In the framework of this approach test of DAMA results in detectors with other chemical content becomes a nontrivial task, while the experimental search of stable charged particles at LHC or in cosmic rays acquires a meaning of direct test for composite dark matter scenario.", "keyphrases": ["dark matter", "dark atoms", "early universe"]}
{"id": "1007.5148", "title": "Scale-dependence of Non-Gaussianity in the Curvaton Model", "abstract": "We investigate the scale-dependence of f_NL in the self-interacting curvaton model. We show that the scale-dependence, encoded in the spectral index n_f_NL, can be observable by future cosmic microwave background observations, such as CMBpol, in a significant part of the parameter space of the model. We point out that together with information about the trispectrum g_NL, the self-interacting curvaton model parameters could be completely fixed by observations. We also discuss the scale-dependence of g_NL and its implications for the curvaton model, arguing that it could provide a complementary probe in cases where the theoretical value of n_f_NL is below observational sensitivity.", "keyphrases": ["non-gaussianity", "curvaton model", "scale-dependence"]}
{"id": "1410.4239", "title": "Quantum corrections in massive bigravity and new effective composite metrics", "abstract": "We compute the one-loop quantum corrections to the interactions between the two metrics of the ghost-free massive bigravity. When considering gravitons running in the loops, we show how the structure of the interactions gets destabilized at the quantum level, exactly in the same way as in its massive gravity limit. A priori one might have expected a better quantum behavior, however the broken diffeomorphism invariance out of the two initial diffeomorphisms in bigravity has similar consequences at the quantum level as the broken diffeomorphism in massive gravity. From lessons of the generated quantum corrections through matter loops we propose yet other types of effective composite metrics to which the matter fields can couple. Among these new effective metrics there might be one or more that could provide interesting phenomenology and important cosmological implications.", "keyphrases": ["massive bigravity", "matter field", "quantum correction"]}
{"id": "0903.4395", "title": "Some Uncomfortable Thoughts on the Nature of Gravity, Cosmology, and the Early Universe", "abstract": "A specific theoretical framework is important for designing and conducting an experiment, and for interpretation of its results. The field of gravitational physics is expanding, and more clarity is needed. It appears that some popular notions, such as `inflation' and `gravity is geometry', have become more like liabilities than assets. A critical analysis is presented and the ways out of the difficulties are proposed.", "keyphrases": ["gravity", "total energy", "stage"]}
{"id": "1505.07556", "title": "Scalar-Fluid theories: cosmological perturbations and large-scale structure", "abstract": "Recently a new Lagrangian framework was introduced to describe interactions between scalar fields and relativistic perfect fluids. This allows two consistent generalizations of coupled quintessence models: non-vanishing pressures and a new type of derivative interaction. Here the implications of these to the formation of cosmological large-scale structure are uncovered at the linear order. The full perturbation equations in the two cases are derived in a unified formalism and their Newtonian, quasi-static limit is studied analytically. Requiring the absence of an effective sound speed for the coupled dark matter fluid restricts the Lagrangian to be a linear function of the matter number density. This still leaves new potentially viable classes of both algebraically and derivatively interacting models wherein the coupling may impact the background expansion dynamics and imprint signatures into the large-scale structure.", "keyphrases": ["cosmological perturbation", "large-scale structure", "fluid", "scalar-fluid theory"]}
{"id": "1502.06424", "title": "Probing the imprint of interacting dark energy on very large scales", "abstract": "The observed galaxy power spectrum acquires relativistic corrections from lightcone effects, and these corrections grow on very large scales. Future galaxy surveys in optical, infrared and radio bands will probe increasingly large wavelength modes and reach higher redshifts. In order to exploit the new data on large scales, an accurate analysis requires inclusion of the relativistic effects. This is especially the case for primordial non-Gaussianity and for extending tests of dark energy models to horizon scales. Here we investigate the latter, focusing on models where the dark energy interacts non-gravitationally with dark matter. Interaction in the dark sector can also lead to large-scale deviations in the power spectrum. If the relativistic effects are ignored, the imprint of interacting dark energy will be incorrectly identified and thus lead to a bias in constraints on interacting dark energy on very large scales.", "keyphrases": ["dark energy", "large scale", "galaxy survey", "dark matter"]}
{"id": "1602.04766", "title": "Slowly rotating neutron stars in scalar-tensor theories with a massive scalar field", "abstract": "In the scalar-tensor theories with a massive scalar field the coupling constants, and the coupling functions in general, which are observationally allowed, can differ significantly from those in the massless case. This fact naturally implies that the scalar-tensor neutron stars with a massive scalar field can have rather different structure and properties in comparison with their counterparts in the massless case and in general relativity. In the present paper we study slowly rotating neutron stars in scalar-tensor theories with a massive gravitational scalar. Two examples of scalar-tensor theories are examined - the first example is the massive Brans-Dicke theory and the second one is a massive scalar-tensor theory indistinguishable from general relativity in the weak field limit. In the later case we study the effect of the scalar field mass on the spontaneous scalarization of neutron stars. Our numerical results show that the inclusion of a mass term for the scalar field indeed changes the picture drastically compared to the massless case. It turns out that mass, radius and moment of inertia for neutron stars in massive scalar-tensor theories can differ drastically from the pure general relativistic solutions if sufficiently large masses of the scalar field are considered.", "keyphrases": ["neutron star", "scalar-tensor theory", "field mass"]}
{"id": "1912.02622", "title": "Science Case for the Einstein Telescope", "abstract": "The Einstein Telescope (ET), a proposed European ground-based gravitational-wave detector of third-generation, is an evolution of second-generation detectors such as Advanced LIGO, Advanced Virgo, and KAGRA which could be operating in the mid 2030s. ET will explore the universe with gravitational waves up to cosmological distances. We discuss its main scientific objectives and its potential for discoveries in astrophysics, cosmology and fundamental physics.", "keyphrases": ["einstein telescope", "gravitational-wave detector", "astrophysic", "future", "cosmic explorer"]}
{"id": "1804.07732", "title": "A Cosmological Signature of the SM Higgs Instability: Gravitational Waves", "abstract": "A fundamental property of the Standard Model is that the Higgs potential becomes unstable at large values of the Higgs field. For the current central values of the Higgs and top masses, the instability scale is about 10^11 GeV and therefore not accessible by colliders. We show that a possible signature of the Standard Model Higgs instability is the production of gravitational waves sourced by Higgs fluctuations generated during inflation. We fully characterise the two-point correlator of such gravitational waves by computing its amplitude, the frequency at peak, the spectral index, as well as their three-point correlators for various polarisations. We show that, depending on the Higgs and top masses, either LISA or the Einstein Telescope and Advanced-Ligo, could detect such stochastic background of gravitational waves. In this sense, collider and gravitational wave physics can provide fundamental and complementary informations. Furthermore, the consistency relation among the three- and the two-point correlators could provide an efficient tool to ascribe the detected gravitational waves to the Standard Model itself. Since the mechanism described in this paper might also be responsible for the generation of dark matter under the form of primordial black holes, this latter hypothesis may find its confirmation through the detection of gravitational waves.", "keyphrases": ["gravitational wave", "primordial black hole", "curvature perturbation"]}
{"id": "1302.6075", "title": "Rotating regular black holes", "abstract": "The formation of spacetime singularities is a quite common phenomenon in General Relativity and it is regulated by specific theorems. It is widely believed that spacetime singularities do not exist in Nature, but that they represent a limitation of the classical theory. While we do not yet have any solid theory of quantum gravity, toy models of black hole solutions without singularities have been proposed. So far, there are only non-rotating regular black holes in the literature. These metrics can be hardly tested by astrophysical observations, as the black hole spin plays a fundamental role in any astrophysical process. In this letter, we apply the Newman-Janis algorithm to the Hayward and to the Bardeen black hole metrics. In both cases, we obtain a family of rotating solutions. Every solution corresponds to a different matter configuration. Each family has one solution with special properties, which can be written in Kerr-like form in Boyer-Lindquist coordinates. These special solutions are of Petrov type D, they are singularity free, but they violate the weak energy condition for a non-vanishing spin and their curvature invariants have different values at r=0 depending on the way one approaches the origin. We propose a natural prescription to have rotating solutions with a minimal violation of the weak energy condition and without the questionable property of the curvature invariants at the origin.", "keyphrases": ["black hole", "singularity", "axial symmetry"]}
{"id": "1205.3089", "title": "Radio Searches of Fermi LAT Sources and Blind Search Pulsars: The Fermi Pulsar Search Consortium", "abstract": "We present a summary of the Fermi Pulsar Search Consortium (PSC), an international collaboration of radio astronomers and members of the Large Area Telescope (LAT) collaboration, whose goal is to organize radio follow-up observations of Fermi pulsars and pulsar candidates among the LAT gamma-ray source population. The PSC includes pulsar observers with expertise using the world's largest radio telescopes that together cover the full sky. We have performed very deep observations of all 35 pulsars discovered in blind frequency searches of the LAT data, resulting in the discovery of radio pulsations from four of them. We have also searched over 300 LAT gamma-ray sources that do not have strong associations with known gamma-ray emitting source classes and have pulsar-like spectra and variability characteristics. These searches have led to the discovery of a total of 43 new radio millisecond pulsars (MSPs) and four normal pulsars. These discoveries greatly increase the known population of MSPs in the Galactic disk, more than double the known population of so-called `black widow' pulsars, and contain many promising candidates for inclusion in pulsar timing arrays.", "keyphrases": ["fermi", "pulsar", "radio telescope", "radio search"]}
{"id": "1807.05449", "title": "Differentially rotating neutron stars in scalar-tensor theories of gravity", "abstract": "We present the first numerical models of differentially rotating stars in alternative theories of gravity. We chose a particular class of scalar-tensor theories of gravity that is indistinguishable from GR in the weak field regime but can lead to significant deviations when strong fields are considered. We show that the maximum mass that a differentially rotating neutron star can sustain increases significantly for scalarized solutions and such stars can reach larger angular momenta. In addition, the presence of a nontrivial scalar field has the effect of increasing the required axis ratio for reaching a given value of angular momentum, when compared to a corresponding model of same rest mass in general relativity. We find that the scalar field also makes rapidly rotating models less quasi-toroidal than their general-relativistic counterparts. For large values of the angular momentum and values of the coupling parameter that are in agreement with the observations, we find a second turning point for scalarized models along constant angular momentum sequences, which could have interesting implications for the stability of remnants created in a binary neutron star merger.", "keyphrases": ["neutron star", "scalar-tensor theory", "large angular momenta"]}
{"id": "1106.1334", "title": "Neutrino-less Double Beta Decay and Particle Physics", "abstract": "We review the particle physics aspects of neutrino-less double beta decay. This process can be mediated by light massive Majorana neutrinos (standard interpretation) or by something else (non-standard interpretations). The physics potential of both interpretations is summarized and the consequences of future measurements or improved limits on the half-life of neutrino-less double beta decay are discussed. We try to cover all proposed alternative realizations of the decay, including light sterile neutrinos, supersymmetric or left-right symmetric theories, Majorons, and other exotic possibilities. Ways to distinguish the mechanisms from one another are discussed. Experimental and nuclear physics aspects are also briefly touched, alternative processes to double beta decay are discussed, and an extensive list of references is provided.", "keyphrases": ["double beta decay", "majorana neutrinos", "neutrino"]}
{"id": "0906.1813", "title": "Primordial perturbations and non-Gaussianities from modulated trapping", "abstract": "We propose a new mechanism to generate primordial curvature perturbations, based on the resonant production of particles during inflation. It is known that this phenomenon can trap the inflaton for a fraction of e-fold. This effect is governed by the mass of the produced particles and by their coupling to the inflaton, parameters which can depend on the expectation value of other fields. If one of such additional fields - a 'modulaton' - is light, then its fluctuations, acquired during the earlier stages of inflation, will induce a spatial modulation of the trapping, and thus of the end of inflation, corresponding to a curvature perturbation. We calculate the power spectrum, bispectrum and trispectrum of the curvature perturbations generated by this mechanism, taking into account the perturbations due to the inflaton fluctuations as well. We find that modulated trapping could provide the main contribution to the observed power spectrum and lead to detectable primordial non-gaussianities.", "keyphrases": ["trapping", "curvature perturbation", "non-gaussianitie"]}
{"id": "1312.6328", "title": "Large-scale stable interacting dark energy model: Cosmological perturbations and observational constraints", "abstract": "Dark energy might interact with cold dark matter in a direct, nongravitational way. However, the usual interacting dark energy models (with constant w) suffer from some catastrophic difficulties. For example, the Q\u221d\u03c1_ c model leads to an early-time large-scale instability, and the Q\u221d\u03c1_ de model gives rise to the future unphysical result for cold dark matter density (in the case of a positive coupling). In order to overcome these fatal flaws, we propose in this paper an interacting dark energy model (with constant w) in which the interaction term is carefully designed to realize that Q\u221d\u03c1_ de at the early times and Q\u221d\u03c1_ c in the future, simultaneously solving the early-time superhorizon instability and future unphysical \u03c1_ c problems. The concrete form of the interaction term in this model is Q=3\u03b2 H \u03c1_de\u03c1_c/\u03c1_de+\u03c1_c, where \u03b2 is the dimensionless coupling constant. We show that this model is actually equivalent to the decomposed new generalized Chaplygin gas (NGCG) model, with the relation \u03b2=-\u03b1 w. We calculate the cosmological perturbations in this model in a gauge-invariant way and show that the cosmological perturbations are stable during the whole expansion history provided that \u03b2>0. Furthermore, we use the Planck data in conjunction with other astrophysical data to place stringent constraints on this model (with eight parameters), and we find that indeed \u03b2>0 is supported by the joint constraint at more than 1\u03c3 level. The excellent theoretical features and the support from observations all indicate that the decomposed NGCG model deserves more attention and further investigation.", "keyphrases": ["dark energy model", "cosmological perturbation", "non-gravitational interaction"]}
{"id": "1803.06910", "title": "Exploring neutrino mass and mass hierarchy in the scenario of vacuum energy interacting with cold dark matter", "abstract": "We investigate the constraints on total neutrino mass in the scenario of vacuum energy interacting with cold dark matter. We focus on two typical interaction forms, i.e., Q=\u03b2 H\u03c1_ c and Q=\u03b2 H\u03c1_\u039b. To avoid the occurrence of large-scale instability in interacting dark energy cosmology, we adopt the parameterized post-Friedmann approach to calculate the perturbation evolution of dark energy. We employ observational data, including the Planck cosmic microwave background temperature and polarization data, baryon acoustic oscillation data, a JLA sample of type Ia supernovae observation, direct measurement of the Hubble constant, and redshift space distortion data. We find that, compared with those in the \u039bCDM model, much looser constraints on \u2211 m_\u03bd are obtained in the Q=\u03b2 H\u03c1_ c model, whereas slightly tighter constraints are obtained in the Q=\u03b2 H\u03c1_\u039b model. Consideration of the possible mass hierarchies of neutrinos reveals that the smallest upper limit of \u2211 m_\u03bd appears in the degenerate hierarchy case. By comparing the values of \u03c7^2_ min, we find that the normal hierarchy case is favored over the inverted one. In particular, we find that the difference \u0394\u03c7^2_ min\u2261\u03c7^2_ IH; min-\u03c7^2_ NH; min> 2 in the Q=\u03b2 H\u03c1_ c model. In addition, we find that \u03b2=0 is consistent with the current observations in the Q=\u03b2 H\u03c1_ c model, and \u03b2 < 0 is favored at more than the 1\u03c3 level in the Q=\u03b2 H\u03c1_\u039b model.", "keyphrases": ["neutrino mass", "vacuum energy", "dark matter"]}
{"id": "1606.09199", "title": "Inflation Model Selection meets Dark Radiation", "abstract": "We investigate how inflation model selection is affected by the presence of additional free-streaming relativistic degrees of freedom, i.e. dark radiation. We perform a full Bayesian analysis of both inflation parameters and cosmological parameters taking reheating into account self-consistently. We compute the Bayesian evidence for a few representative inflation scenarios in both the standard \u039bCDM model and an extension including dark radiation parametrised by its effective number of relativistic species N_eff. Using a minimal dataset (Planck low-\u2113 polarisation, temperature power spectrum and lensing reconstruction), we find that the observational status of most inflationary models is unchanged. The exceptions are potentials such as power-law inflation that predict large values for the scalar spectral index that can only be realised when N_eff is allowed to vary. Adding baryon acoustic oscillations data and the B-mode data from BICEP2/Keck makes power-law inflation disfavoured, while adding local measurements of the Hubble constant H_0 makes power-law inflation slightly favoured compared to the best single-field plateau potentials. This illustrates how the dark radiation solution to the H_0 tension would have deep consequences for inflation model selection.", "keyphrases": ["dark radiation", "inflation model selection", "massive neutrino"]}
{"id": "1712.10014", "title": "On the common nature of dark matter and dark energy: galaxy groups", "abstract": "It is shown that the cosmological constant links the roots both of General Relativity and Newtonian gravity via the general function satisfying Newton's theorem according to which the gravitating sphere acts as a point mass situated in its center. The quantitative evidence for this link is given via the correspondence of the current value of the cosmological constant with the value of the cosmological term in the modified Newtonian gravity to explain the dark matter in the galaxies. This approach reveals: (a) the nature of dark matter as gravity's signature, (b) the common nature of dark matter and of cosmological constant (dark energy), (c) that the dark matter as a consequence of repulsive gravity increasing with the distance ensures the observed higher mass-to-luminosity M/L ratio while moving from the scales of galaxies to galaxy clusters. The galactic halos via non-force-free interaction due to the repulsive \u039b-term of gravity determine the features of galactic disks as is supported by observations. The data of galaxy groups of the Hercules-Bootes region are also shown to support the \u039b-gravity nature of the dark matter i.e. the value of the cosmological constant is derived not from cosmological data. Among the consequences of such modified General Relativity is the natural link to AdS/CFT correspondence.", "keyphrases": ["dark matter", "dark energy", "galaxy group", "gravity"]}
{"id": "1009.3021", "title": "General Relativistic Description of the Observed Galaxy Power Spectrum: Do We Understand What We Measure?", "abstract": "We extend the general relativistic description of galaxy clustering developed in Yoo, Fitzpatrick, and Zaldarriaga (2009). For the first time we provide a fully general relativistic description of the observed matter power spectrum and the observed galaxy power spectrum with the linear bias ansatz. It is significantly different from the standard Newtonian description on large scales and especially its measurements on large scales can be misinterpreted as the detection of the primordial non-Gaussianity even in the absence thereof. The key difference in the observed galaxy power spectrum arises from the real-space matter fluctuation defined as the matter fluctuation at the hypersurface of the observed redshift. As opposed to the standard description, the shape of the observed galaxy power spectrum evolves in redshift, providing additional cosmological information. While the systematic errors in the standard Newtonian description are negligible in the current galaxy surveys at low redshift, correct general relativistic description is essential for understanding the galaxy power spectrum measurements on large scales in future surveys with redshift depth z>3. We discuss ways to improve the detection significance in the current galaxy surveys and comment on applications of our general relativistic formalism in future surveys.", "keyphrases": ["galaxy", "general relativistic description", "ultra-large scale", "photon"]}
{"id": "0909.0948", "title": "The chemical composition of the Sun", "abstract": "The solar chemical composition is an important ingredient in our understanding of the formation, structure and evolution of both the Sun and our solar system. Furthermore, it is an essential reference standard against which the elemental contents of other astronomical objects are compared. In this review we evaluate the current understanding of the solar photospheric composition. In particular, we present a re-determination of the abundances of nearly all available elements, using a realistic new 3-dimensional (3D), time-dependent hydrodynamical model of the solar atmosphere. We have carefully considered the atomic input data and selection of spectral lines, and accounted for departures from LTE whenever possible. The end result is a comprehensive and homogeneous compilation of the solar elemental abundances. Particularly noteworthy findings are significantly lower abundances of carbon, nitrogen, oxygen and neon compared with the widely-used values of a decade ago. The new solar chemical composition is supported by a high degree of internal consistency between available abundance indicators, and by agreement with values obtained in the solar neighborhood and from the most pristine meteorites. There is, however, a stark conflict with standard models of the solar interior according to helioseismology, a discrepancy that has yet to find a satisfactory resolution.", "keyphrases": ["chemical composition", "sun", "astronomical object", "solar photospheric abundance"]}
{"id": "1212.4726", "title": "Theoretical Models of Dark Energy", "abstract": "Mounting observational data confirm that about 73 consists of dark energy which is responsible for the current accelerated expansion of the Universe. We present observational evidences and dark energy projects. We then review various theoretical ideas that have been proposed to explain the origin of dark energy; they contain the cosmological constant, modified matter models, modified gravity models and the inhomogeneous model. The cosmological constant suffers from two major problems: one regarding fine-tuning and the other regarding coincidence. To solve them there arose modified matter models such as quintessence, k-essence, coupled dark energy, and unified dark energy. We compare those models by presenting attractive aspects, new rising problems and possible solutions. Furthermore we review modified gravity models that lead to late-time accelerated expansion without invoking a new form of dark energy; they contain f(R) gravity and the Dvali-Gabadadze-Porrati model. We also discuss observational constraints on those models and on future modified gravity theories. Finally we review the inhomogeneous Lemaitre-Tolman-Bondi model that drops an assumption of the spatial homogeneity of the Universe. We also present basics of cosmology and scalar field theory, which are useful especially for students and novices to understand dark energy models.", "keyphrases": ["dark energy", "accelerated expansion", "cosmological constant"]}
{"id": "1207.3804", "title": "Examining the evidence for dynamical dark energy", "abstract": "We apply a new non-parametric Bayesian method for reconstructing the evolution history of the equation-of-state w of dark energy, based on applying a correlated prior for w(z), to a collection of cosmological data. We combine the latest supernova (SNLS 3-year or Union2.1), cosmic microwave background, redshift space distortion and the baryonic acoustic oscillation measurements (including BOSS, WiggleZ and 6dF) and find that the cosmological constant appears consistent with current data, but that a dynamical dark energy model which evolves from w<-1 at z\u223c0.25 to w > -1 at higher redshift is mildly favored. Estimates of the Bayesian evidences show little preference between the cosmological constant model and the dynamical model for a range of correlated prior choices. Looking towards future data, we find that the best fit models for current data could be well distinguished from the \u039bCDM model by observations such as Planck and Euclid-like surveys.", "keyphrases": ["dark energy", "cosmological data", "redshift"]}
{"id": "1304.6474", "title": "No-bomb theorem for charged Reissner-Nordstrom black holes", "abstract": "The fundamental role played by black holes in many areas of physics makes it highly important to explore the nature of their stability. The stability of charged Reissner-Nordstr\u00f6m black holes to neutral (gravitational and electromagnetic) perturbations was established almost four decades ago. However, the stability of these charged black holes under charged perturbations has remained an open question due to the complexity introduced by the well-known phenomena of superradiant scattering: A charged scalar field impinging on a charged Reissner-Nordstr\u00f6m black hole can be amplified as it scatters off the hole. If the incident field has a non-zero rest mass, then the mass term effectively works as a mirror, preventing the energy extracted from the hole from escaping to infinity. One may suspect that the superradiant amplification of charged fields by the charged black hole may lead to an instability of the Reissner-Nordstr\u00f6m spacetime (in as much the same way that rotating Kerr black holes are unstable under rotating scalar perturbations). However, in this Letter we show that, for charged Reissner-Nordstr\u00f6m black holes in the regime (Q/M)^2\u2264 8/9, the two conditions which are required in order to trigger a possible superradiant instability [namely: (1) the existence of a trapping potential well outside the black hole, and (2) superradiant amplification of the trapped modes] cannot be satisfied simultaneously. Our results thus support the stability of charged Reissner-Nordstr\u00f6m black holes under charged scalar perturbations in the regime (Q/M)^2\u2264 8/9.", "keyphrases": ["black hole", "spacetime", "superradiant instability"]}
{"id": "0908.0920", "title": "Inflation and dark energy from three-forms", "abstract": "Three-forms can give rise to viable cosmological scenarios of inflation and dark energy with potentially observable signatures distinct from standard single scalar field models. In this study, the background dynamics and linear perturbations of self-interacting three-form cosmology are investigated. The phase space of cosmological solutions possesses (super)-inflating attractors and saddle points which can describe three-form driven inflation or dark energy. The quantum generation and the classical evolution of perturbations is considered. The scalar and tensor spectra from a three-form inflation and the impact from the presence of a three-form on matter perturbations are computed. Stability properties and equivalence of the model with alternative formulations are discussed.", "keyphrases": ["dark energy", "three-form", "cosmology"]}
{"id": "1311.2609", "title": "Secular Evolution in Disk Galaxies", "abstract": "Self-gravitating systems evolve toward the most tightly bound configuration that is reachable via available evolution processes. The inner parts shrink and the outer parts expand, provided that some physical process transports energy or angular momentum outward. The evolution of stars, star clusters, protostellar and protoplanetary disks, black hole accretion disks, and galaxy disks are all fundamentally similar. These processes for galaxy disks are the subjects of my lectures and of this Canary Islands Winter School. Part 1 discusses formation, growth, and death of bars. Part 2 details the slow (\"secular\") rearrangement of angular momentum that results from interactions between stars or gas and nonaxisymmetries such as bars. We have a heuristic understanding of how this forms outer rings, inner rings, and stuff dumped into the center. Observations show that barred galaxies have central concentrations of gas and star formation. Timescales imply that they grow central \"pseudobulges\" that get mistaken for elliptical-galaxy-like classical bulges but that formed gently out of disks. Part 3 shows how we distinguish between classical and pseudo bulges. Part 4 reviews how environmental secular evolution transforms gas-rich, star-forming spirals and irregulars into gas-poor, red and dead S0 and spheroidal (\"Sph\") galaxies. Sphs are not ellipticals; they have structural parameters like those of low-luminosity S+Im galaxies. So Sphs are bulgeless S0s. Part 5 combines hierarchical clustering and secular evolution into a comprehensive picture.", "keyphrases": ["disk galaxy", "angular momentum", "star", "secular evolution", "bar formation"]}
{"id": "1406.6049", "title": "Matter creation in a nonsingular bouncing cosmology", "abstract": "We examine reheating in the two-field matter bounce cosmology. In this model, the universe evolves from a matter-dominated phase of contraction to an Ekpyrotic phase of contraction before the nonsingular bounce. The Ekpyrotic phase frees the model from unwanted anisotropies, but leaves the universe cold and empty of particles after the bounce. For this reason, we explore two particle production mechanisms which take place during the course of the cosmological evolution: Parker particle production where the matter field couples only to gravity and particle creation via interactions between the matter field and the bounce field. Although we show that both mechanisms can produce particles in this model, we find that Parker particle production is sufficient to reheat the universe to high temperatures. Thus there is a priori no need to add an interaction term to the Lagrangian of the model. Still, particle creation via interactions can contribute to the formation of matter and radiation, but only if the coupling between the fields is tuned to be large.", "keyphrases": ["cosmology", "matter bounce scenario", "primordial curvature perturbation"]}
{"id": "1203.6625", "title": "Local non-Gaussianity from rapidly varying sound speeds", "abstract": "We study the effect of non-trivial sound speeds on local-type non-Gaussianity during multiple-field inflation. To this end, we consider a model of multiple-field DBI and use the deltaN formalism to track the super-horizon evolution of perturbations. By adopting a sum separable Hubble parameter we derive analytic expressions for the relevant quantities in the two-field case, valid beyond slow variation. We find that non-trivial sound speeds can, in principle, curve the trajectory in such a way that significant local-type non-Gaussianity is produced. Deviations from slow variation, such as rapidly varying sound speeds, enhance this effect. To illustrate our results we consider two-field inflation in the tip regions of two warped throats and find large local-type non-Gaussianity produced towards the end of the inflationary process.", "keyphrases": ["non-gaussianity", "sound speed", "sum", "local feature"]}
{"id": "1304.6404", "title": "The spectral evolution of the first galaxies. II. Spectral signatures of Lyman continuum leakage from galaxies in the reionization epoch", "abstract": "The fraction of ionizing photons (fesc) that escape from z>6 galaxies is an important parameter when assessing the role of these objects in the reionization of the Universe, but the opacity of the intergalactic medium precludes a direct measurement of fesc for individual galaxies at these epochs. We argue, that since fesc regulates the impact of nebular emission on the spectra of galaxies, it should nonetheless be possible to indirectly probe fesc well into the reionization epoch. As a first step, we demonstrate that by combining measurements of the rest-frame UV slope beta with the equivalent width of the Hb emission line, galaxies with very high Lyman continuum escape fractions (fesc>0.5) should be identifiable up to z 9 through spectroscopy with the upcoming James Webb Space Telescope (JWST). By targeting strongly lensed galaxies behind low-redshift galaxy clusters, JWST spectra of sufficiently good quality can be obtained for M(1500)<-16.0 galaxies at z 7 and for M(1500)<-17.5 galaxies at z 9. Dust-obscured star formation may complicate the analysis, but supporting observations with ALMA or the planned SPICA mission may provide useful constraints on the dust properties of these galaxies.", "keyphrases": ["galaxy", "reionization epoch", "nebular emission"]}
{"id": "0903.4682", "title": "Constraints on the relationship between stellar mass and halo mass at low and high redshift", "abstract": "We use a statistical approach to determine the relationship between the stellar masses of galaxies and the masses of the dark matter halos in which they reside. We obtain a parameterized stellar-to-halo mass (SHM) relation by populating halos and subhalos in an N-body simulation with galaxies and requiring that the observed stellar mass function be reproduced. We find good agreement with constraints from galaxy-galaxy lensing and predictions of semi-analytic models. Using this mapping, and the positions of the halos and subhalos obtained from the simulation, we find that our model predictions for the galaxy two-point correlation function (CF) as a function of stellar mass are in excellent agreement with the observed clustering properties in the SDSS at z=0. We show that the clustering data do not provide additional strong constraints on the SHM function and conclude that our model can therefore predict clustering as a function of stellar mass. We compute the conditional mass function, which yields the average number of galaxies with stellar masses in the range [m, m+dm] that reside in a halo of mass M. We study the redshift dependence of the SHM relation and show that, for low mass halos, the SHM ratio is lower at higher redshift. The derived SHM relation is used to predict the stellar mass dependent galaxy CF and bias at high redshift. Our model predicts that not only are massive galaxies more biased than low mass ones at all redshifts, but the bias increases more rapidly with increasing redshift for massive galaxies than for low mass ones. We present convenient fitting functions for the SHM relation as a function of redshift, the conditional mass function, and the bias as a function of stellar mass and redshift.", "keyphrases": ["stellar mass", "redshift", "mass function"]}
{"id": "1109.2314", "title": "Does the growth of structure affect our dynamical models of the universe? The averaging, backreaction and fitting problems in cosmology", "abstract": "Structure occurs over a vast range of scales in the universe. Our large-scale cosmological models are coarse-grained representations of what exists, which have much less structure than there really is. An important problem for cosmology is determining the influence the small-scale structure in the universe has on its large-scale dynamics and observations. Is there a significant, general relativistic, backreaction effect from averaging over structure? One issue is whether the process of smoothing over structure can contribute to an acceleration term and so alter the apparent value of the cosmological constant. If this is not the case, are there other aspects of concordance cosmology that are affected by backreaction effects? Despite much progress, this 'averaging problem' is still unanswered, but it cannot be ignored in an era of precision cosmology.", "keyphrases": ["universe", "averaging", "cosmic backreaction", "large-scale structure", "einstein equation"]}
{"id": "1110.0673", "title": "Thermodynamical universality of the Lovelock black holes", "abstract": "The necessary and sufficient condition for the thermodynamical universality of the static spherically symmetric Lovelock black hole is that it is the pure Lovelock \u039b-vacuum solution. By universality we mean the thermodynamical parameters: temperature and entropy always bear the same relationship to the horizon radius irrespective of the Lovelock order and the spacetime dimension. For instance, the entropy always goes in terms of the horizon radius as rh and r^2 respectively for h odd and even dimensions. This universality uniquely identifies the pure Lovelock black hole with \u039b.", "keyphrases": ["black hole", "horizon radius", "thermodynamical universality"]}
{"id": "2106.07118", "title": "Large-scale asymmetry in galaxy spin directions: evidence from the Southern hemisphere", "abstract": "Recent observations using several different telescopes and sky surveys showed patterns of asymmetry in the distribution of galaxies by their spin directions as observed from Earth. These studies were done with data imaged from the Northern hemisphere, showing excellent agreement between different telescopes and different analysis methods. Here, data from the DESI Legacy Survey was used. The initial dataset contains \u223c2.2\u00b710^7 galaxy images, reduced to \u223c8.1\u00b710^5 galaxies annotated by their spin direction using a symmetric algorithm. That makes it not just the first analysis of its kind in which the majority of the galaxies are in the Southern hemisphere, but also by far the largest dataset used for this purpose to date. The results show strong agreement between opposite parts of the sky, such that the asymmetry in one part of the sky is similar to the inverse asymmetry in the corresponding part of the sky in the opposite hemisphere. Fitting the distribution of galaxy spin directions to cosine dependence shows a dipole axis with probability of 4.66\u03c3. Interestingly, the location of the most likely axis is within close proximity to the CMB Cold Spot. The profile of the distribution is nearly identical to the asymmetry profile of the distribution identified in Pan-STARRS, and it is within 1\u03c3 difference from the distribution profile in SDSS and HST. All four telescopes show similar large-scale profile of asymmetry.", "keyphrases": ["asymmetry", "galaxy spin direction", "southern hemisphere", "non-random distribution"]}
{"id": "1011.4743", "title": "Discussing direct search of dark matter particles in the Minimal Supersymmetric extension of the Standard Model with light neutralinos", "abstract": "We examine the status of light neutralinos in an effective Minimal Supersymmetric extension of the Standard Model (MSSM) at the electroweak scale which was considered in the past and discussed in terms of the available data of direct searches for dark matter (DM) particles. Our reanalysis is prompted by new measurements at the Tevatron and B-factories which might potentially provide significant constraints on the MSSM model. Here we examine in detail all these new data and show that the present published results from the Tevatron and B-factories have only a mild effect on the original light neutralino population. This population, which fits quite well the DAMA/LIBRA annual modulation data, would also agree with the preliminary results of CDMS, CoGeNT and CRESST, should these data, which are at present only hints or excesses of events over the expected backgrounds, be interpreted as authentic signals of DM. For the neutralino mass we find a lower bound of 7-8 GeV. Our results differ from some recent conclusions by other authors because of a few crucial points which we try to single out and elucidate.", "keyphrases": ["dark matter particle", "minimal supersymmetric extension", "light neutralino", "electroweak scale"]}
{"id": "1205.3421", "title": "Dark energy cosmology: the equivalent description via different theoretical models and cosmography tests", "abstract": "We review different dark energy cosmologies. In particular, we present the \u039bCDM cosmology, Little Rip and Pseudo-Rip universes, the phantom and quintessence cosmologies with Type I, II, III and IV finite-time future singularities and non-singular dark energy universes. In the first part, we explain the \u039bCDM model and well-established observational tests which constrain the current cosmic acceleration. After that, we investigate the dark fluid universe where a fluid has quite general equation of state (EoS) [including inhomogeneous or imperfect EoS]. All the above dark energy cosmologies for different fluids are explicitly realized, and their properties are also explored. It is shown that all the above dark energy universes may mimic the \u039bCDM model currently, consistent with the recent observational data. Furthermore, special attention is paid to the equivalence of different dark energy models. We consider single and multiple scalar field theories, tachyon scalar theory and holographic dark energy as models for current acceleration with the features of quintessence/phantom cosmology, and demonstrate their equivalence to the corresponding fluid descriptions. In the second part, we study another equivalent class of dark energy models which includes F(R) gravity as well as F(R) Ho\u0159ava-Lifshitz gravity and the teleparallel f(T) gravity. The cosmology of such models representing the \u039bCDM-like universe or the accelerating expansion with the quintessence/phantom nature is described. Finally, we approach the problem of testing dark energy and alternative gravity models to general relativity by cosmography. We show that degeneration among parameters can be removed by accurate data analysis of large data samples and also present the examples.", "keyphrases": ["dark energy model", "gravity", "dark energy cosmology", "late-time cosmic acceleration", "exotic form"]}
{"id": "0906.4520", "title": "A little inflation in the early universe at the QCD phase transition", "abstract": "We explore a scenario that allows for a strong first order phase-transition of QCD at non-negligible baryon number in the early universe and its possible cosmological observable consequences. The main assumption is a quasi-stable QCD-vacuum state that leads to a short period of inflation, consequently diluting the net baryon to photon ratio to it's today observed value. A strong mechanism for baryogenesis is needed to start out with a baryon asymmetry of order unity, e.g. as provided by Affleck-Dine baryogenesis. The cosmological implications are direct effects on primordial density fluctuations up to dark matter mass scales of 1 - 10 solar masses, change in the spectral slope up to mass scales of 10^6 - 10^8 solar masses, production of primordial magnetic fields with initial strength up to 10^12 Gauss and a gravitational wave spectrum with present day peak strain amplitude of at most h_c = 5 * 10^-15 around a frequency of 4*10^-8 Hz. The little QCD inflation scenario could be probed with the upcoming heavy ion research facility FAIR at GSI, Darmstadt.", "keyphrases": ["little inflation", "early universe", "qcd phase transition"]}
{"id": "1610.06559", "title": "Prospects for Cosmological Collider Physics", "abstract": "It is generally expected that heavy fields are present during inflation, which can leave their imprint in late-time cosmological observables. The main signature of these fields is a small amount of distinctly shaped non-Gaussianity, which if detected, would provide a wealth of information about the particle spectrum of the inflationary Universe. Here we investigate to what extent these signatures can be detected or constrained using futuristic 21-cm surveys. We construct model-independent templates that extract the squeezed-limit behavior of the bispectrum, and examine their overlap with standard inflationary shapes and secondary non-Gaussianities. We then use these templates to forecast detection thresholds for different masses and couplings using a 3D reconstruction of modes during the dark ages (z\u223c 30-100). We consider interactions of several broad classes of models and quantify their detectability as a function of the baseline of a dark ages interferometer. Our analysis shows that there exists the tantalizing possibility of discovering new particles with different masses and interactions with future 21-cm surveys.", "keyphrases": ["cosmological collider physics", "particle physics", "quasi-single field inflation"]}
{"id": "1507.06186", "title": "Neutron stars - cooling and transport", "abstract": "Observations of thermal radiation from neutron stars can potentially provide information about the states of supranuclear matter in the interiors of these stars with the aid of the theory of neutron-star thermal evolution. We review the basics of this theory for isolated neutron stars with strong magnetic fields, including most relevant thermodynamic and kinetic properties in the stellar core, crust, and blanketing envelopes.", "keyphrases": ["cooling", "neutron star", "neutrino emission"]}
{"id": "1806.04253", "title": "Analytical template for gravitational-wave echoes: signal characterization and prospects of detection with current and future interferometers", "abstract": "Gravitational-wave echoes in the post-merger ringdown phase are under intense scrutiny as probes of near-horizon quantum structures and as signatures of exotic states of matter in ultracompact stars. We present an analytical template that describes the ringdown and the echo signal for nonspinning objects in terms of two physical parameters: the reflectivity and the redshift at the surface of the object. We characterize the properties of the template and adopt it in a preliminary parameter estimation with current (aLIGO) and future (Cosmic Explorer, Einstein Telescope, LISA) gravitational-wave detectors. For fixed signal-to-noise ratio in the post-merger phase, the constraints on the model parameters depend only mildly on the details of the detector sensitivity curve, but depend strongly on the reflectivity. Our analysis suggests that it might be possible to detect or rule out Planckian corrections at the horizon scale for perfectly-reflecting ultracompact objects at 5\u03c3 confidence level with Advanced LIGO/Virgo. On the other hand, signal-to-noise ratios in the ringdown phase equal to \u2248 100 (as achievable with future interferometers) might allow us to probe near-horizon quantum structures with reflectivity \u227330% (\u227385%) at 2\u03c3 (3\u03c3) level.", "keyphrases": ["gravitational-wave echo", "echo", "future interferometer"]}
{"id": "1203.3542", "title": "The Effective Field Theory of Dark Matter Direct Detection", "abstract": "We extend and explore the general non-relativistic effective theory of dark matter (DM) direct detection. We describe the basic non-relativistic building blocks of operators and discuss their symmetry properties, writing down all Galilean-invariant operators up to quadratic order in momentum transfer arising from exchange of particles of spin 1 or less. Any DM particle theory can be translated into the coefficients of an effective operator and any effective operator can be simply related to most general description of the nuclear response. We find several operators which lead to novel nuclear responses. These responses differ significantly from the standard minimal WIMP cases in their relative coupling strengths to various elements, changing how the results from different experiments should be compared against each other. Response functions are evaluated for common DM targets - F, Na, Ge, I, and Xe - using standard shell model techniques. We point out that each of the nuclear responses is familiar from past studies of semi-leptonic electroweak interactions, and thus potentially testable in weak interaction studies. We provide tables of the full set of required matrix elements at finite momentum transfer for a range of common elements, making a careful and fully model-independent analysis possible. Finally, we discuss embedding non-relativistic effective theory operators into UV models of dark matter.", "keyphrases": ["effective field theory", "dark matter", "direct detection", "effective operator", "matter-nucleon interaction"]}
{"id": "1807.09800", "title": "New scaling solutions in cubic Horndeski theories", "abstract": "We propose a viable dark energy scenario in the presence of cubic Horndeski interactions and a standard scalar-field kinetic term with two exponential potentials. We show the existence of new scaling solutions along which the cubic coupling G_3 provides an important contribution to the field density that scales in the same way as the background fluid density. The solutions finally exit to the epoch of cosmic acceleration driven by a scalar-field dominated fixed point arising from the second exponential potential. We clarify the viable parameter space in which all the theoretically consistent conditions including those for the absence of ghost and Laplacian instabilities are satisfied on scaling and scalar-field dominated critical points. In comparison to Quintessence with the same scalar potential, we find that the cubic coupling gives rise to some novel features: (i) the allowed model parameter space is wider in that a steeper potential can drive the cosmic acceleration; (ii) the dark energy equation of state w_\u03d5 today can be closer to -1 relative to Quintessence; (iii) even if the density associated with the cubic coupling dominates over the standard field density in the scaling era, the former contribution tends to be suppressed at low redshifts. We also compute quantities associated with the growth of matter perturbations and weak lensing potentials under the quasi-static approximation in the sub-horizon limit and show that the cubic coupling leads to the modified evolution of perturbations which can be distinguished from Quintessence.", "keyphrases": ["scaling solution", "horndeski theory", "cosmic acceleration"]}
{"id": "1205.2384", "title": "Hubble flows and gravitational potentials in observable Universe", "abstract": "In this paper, we consider the Universe deep inside of the cell of uniformity. At these scales, the Universe is filled with inhomogeneously distributed discrete structures (galaxies, groups and clusters of galaxies), which disturb the background Friedmann model. We propose mathematical models with conformally flat, hyperbolic and spherical spaces. For these models, we obtain the gravitational potential for an arbitrary number of randomly distributed inhomogeneities. In the cases of flat and hyperbolic spaces, the potential is finite at any point, including spatial infinity, and valid for an arbitrary number of gravitating sources. For both of these models, we investigate the motion of test masses (e.g., dwarf galaxies) in the vicinity of one of the inhomogeneities. We show that there is a distance from the inhomogeneity, at which the cosmological expansion prevails over the gravitational attraction and where test masses form the Hubble flow. For our group of galaxies, it happens at a few Mpc and the radius of the zero-acceleration sphere is of the order of 1 Mpc, which is very close to observations. Outside of this sphere, the dragging effect of the gravitational attraction goes very fast to zero.", "keyphrases": ["universe", "inhomogeneity", "hyperbolic space", "hubble flow", "mechanical approach"]}
{"id": "1310.1093", "title": "PRIMUS: Galaxy Clustering as a Function of Luminosity and Color at 0.2<z<1", "abstract": "We present measurements of the luminosity and color-dependence of galaxy clustering at 0.2<z<1.0 in the PRIsm MUlti-object Survey (PRIMUS). We quantify the clustering with the redshift-space and projected two-point correlation functions, xi(rp,pi) and wp(rp), using volume-limited samples constructed from a parent sample of over 130,000 galaxies with robust redshifts in seven independent fields covering 9 sq. deg. of sky. We quantify how the scale-dependent clustering amplitude increases with increasing luminosity and redder color, with relatively small errors over large volumes. We find that red galaxies have stronger small-scale (0.1<rp<1 Mpc/h) clustering and steeper correlation functions compared to blue galaxies, as well as a strong color dependent clustering within the red sequence alone. We interpret our measured clustering trends in terms of galaxy bias and obtain values between b_gal=0.9-2.5, quantifying how galaxies are biased tracers of dark matter depending on their luminosity and color. We also interpret the color dependence with mock catalogs, and find that the clustering of blue galaxies is nearly constant with color, while redder galaxies have stronger clustering in the one-halo term due to a higher satellite galaxy fraction. In addition, we measure the evolution of the clustering strength and bias, and we do not detect statistically significant departures from passive evolution. We argue that the luminosity- and color-environment (or halo mass) relations of galaxies have not significantly evolved since z=1. Finally, using jackknife subsampling methods, we find that sampling fluctuations are important and that the COSMOS field is generally an outlier, due to having more overdense structures than other fields; we find that 'cosmic variance' can be a significant source of uncertainty for high-redshift clustering measurements.", "keyphrases": ["galaxy", "color", "primus"]}
{"id": "1806.05874", "title": "Momentum space sampling of neutrinos in N-body simulations", "abstract": "Including massive neutrinos in N-body simulations is a challenging task due to the large thermal velocities of the neutrinos. In particle based codes this leads to problems of shot-noise due to insufficient sampling of the neutrino momentum distribution function. In this paper we investigate the benefits and drawbacks of a scheme first suggested in a paper by Banerjee et al. in which the initial neutrino distribution is symmetrised in momentum space. We confirm that this method reduce shot-noise significantly, but we also find that it generates some spurious power in the neutrino power spectrum at intermediate and small scales. We speculate that this happens because many neutrinos in the simulation sample the same underlying dark matter structures while moving through the simulation. By carefully tuning the number of directions in momentum space of the initial neutrino distribution we show that some improvements can be made over the case where initial neutrino directions are purely random. At redshifts z\u2273 3 the method works very well, but at smaller redshifts significant improvements are not possible due to the spurious power generation.", "keyphrases": ["neutrino", "n-body simulation", "large thermal velocity"]}
{"id": "1404.2604", "title": "Matter creation and cosmic acceleration", "abstract": "We investigate the creation of cold dark matter (CCDM) cosmology as an alternative to explain the cosmic acceleration. Particular attention is given to the evolution of density perturbations and constraints coming from recent observations. By assuming negligible effective sound speed we compare CCDM predictions with redshift-space-distortion based f(z) sigma_8(z) measurements. We identify a subtle issue associated with which contribution in the density contrast should be used in this test and then show that the CCDM results are the same as those obtained with LambdaCDM. These results are then contrasted with the ones obtained at the background level. For the background tests we have used type Ia supernovae data (Union 2.1 compilation) in combination with baryonic acoustic oscillations and cosmic microwave background observations and also measurements of the Hubble parameter at different redshifts. As a consequence of the studies we have performed at both the background and perturbation levels, we explicitly show that CCDM is observationally degenerate with respect to LambdaCDM (dark degeneracy). The need to overcome the lack of a fundamental microscopic basis for the CCDM is the major challenge for this kind of model.", "keyphrases": ["creation", "cosmic acceleration", "dark matter", "cosmology"]}
{"id": "2003.05784", "title": "Newtonian Fractional-Dimension Gravity and MOND", "abstract": "This paper introduces a possible alternative model of gravity based on the theory of fractional-dimension spaces and its applications to Newtonian gravity. In particular, Gauss's law for gravity as well as other fundamental classical laws are extended to a D-dimensional metric space, where D can be a non-integer dimension. We show a possible connection between this Newtonian Fractional-Dimension Gravity (NFDG) and Modified Newtonian Dynamics (MOND), a leading alternative gravity model which accounts for the observed properties of galaxies and other astrophysical structures without requiring the dark matter hypothesis. The MOND acceleration constant a_0\u2243 1.2 \u00d7 10^ -10^ -2 can be related to a natural scale length l_0 in NFDG, i.e., a_0\u2248 GM/l_0^2, for astrophysical structures of mass M, and the deep-MOND regime is present in regions of space where the dimension is reduced to D \u2248 2. For several fundamental spherically-symmetric structures, we compare MOND results, such as the empirical Radial Acceleration Relation (RAR), circular speed plots, and logarithmic plots of the observed radial acceleration g_obs vs. the baryonic radial acceleration g_bar, with NFDG results. We show that our model is capable of reproducing these results using a variable local dimension D (w ), where w =r/l_0 is a dimensionless radial coordinate. At the moment, we are unable to derive explicitly this dimension function D (w ) from first principles, but it can be obtained empirically in each case from the general RAR. Additional work on the subject, including studies of axially-symmetric structures, detailed galactic rotation curves fitting, and a possible relativistic extension, will be needed to establish NFDG as a viable alternative model of gravity.", "keyphrases": ["dimension", "gravity model", "newtonian fractional-dimension gravity", "alternative gravitational model"]}
{"id": "1206.2382", "title": "Towards a Nonsingular Bouncing Cosmology", "abstract": "We present a nonsingular bouncing cosmology using single scalar field matter with non-trivial potential and non-standard kinetic term. The potential sources a dynamical attractor solution with Ekpyrotic contraction which washes out small amplitude anisotropies. At high energy densities the field evolves into a ghost condensate, leading to a nonsingular bounce. Following the bounce there is a smooth transition to standard expanding radiation and matter dominated phases. Using linear cosmological perturbation theory we track each Fourier mode of the curvature fluctuation throughout the entire cosmic evolution. Using standard matching conditions for nonsingular bouncing cosmologies we verify that the spectral index does not change during the bounce. We show there is a controlled period of exponential growth of the fluctuation amplitude for the perturbations (but not for gravitational waves) around the bounce point which does not invalidate the perturbative treatment. This growth induces a natural suppression mechanism for the tensor to scalar ratio of fluctuations. Moreover, we study the generation of the primordial power spectrum of curvature fluctuations for various types of initial conditions. For the pure vacuum initial condition, on scales which exit the Hubble radius in the phase of Ekpyrotic contraction, the spectrum is deeply blue. For thermal particle initial condition, one possibility for generating a scale-invariant spectrum makes use of a special value of the background equation of state during the contracting Ekpyrotic phase. If the Ekpyrotic phase is preceded by a period of matter-dominated contraction, the primordial power spectrum is nearly scale-invariant on large scales (scales which exit the Hubble radius in the matter-dominated phase) but acquires a large blue tilt on small scales.", "keyphrases": ["cosmology", "scalar field", "ghost condensate"]}
{"id": "1107.2934", "title": "The Baryonic Tully-Fisher Relation of Gas Rich Galaxies as a Test of LCDM and MOND", "abstract": "The Baryonic Tully-Fisher Relation (BTFR) is an empirical relation between baryonic mass and rotation velocity in disk galaxies. It provides tests of galaxy formation models in LCDM and of alternative theories like MOND. Observations of gas rich galaxies provide a measure of the slope and normalization of the BTFR that is more accurate (if less precise) than that provided by star dominated spirals, as their masses are insensitive to the details of stellar population modeling. Recent independent data for such galaxies are consistent with Mb = AVf^4 with A = 47+/-6 Msun (km/s)^-4. This is equivalent to MOND with a_0 = 1.3 +/- 0.3 A/s/s. The scatter in the data is consistent with being due entirely to observational uncertainties. It is unclear why the physics of galaxy formation in LCDM happens to pick out the relation predicted by MOND. We introduce a feedback efficacy parameter E to relate halo properties to those of the galaxies they host. E correlates with star formation rate and gas fraction in the sense that galaxies that have experienced the least star formation have been most impacted by feedback.", "keyphrases": ["baryonic tully-fisher relation", "baryonic mass", "disk galaxy", "star formation rate"]}
{"id": "1103.0768", "title": "Gravitational power from cosmic string loops with many kinks", "abstract": "We investigate the effect of a large number of kinks on the gravitational power radiated by cosmic string loops. We show that the total power radiated by a loop with N left-moving and right-moving kinks is proportional to N and increases with the typical kink angle. We then apply these results to loops containing junctions which give rise to a proliferation of the number of sharp kinks. We show that the time of gravitational decay of these loops is smaller than previously assumed. In light of this we revisit the gravitational wave burst predictions from a network containing such loops. We find there is no parameter regime in which the rate of individual kink bursts is enhanced with respect to standard networks. By contrast, there remains a region of parameter space for which the kink-kink bursts dominate the stochastic background. Finally, we discuss the order of magnitude of the typical number of sharp kinks resulting from kink proliferation on loops with junctions.", "keyphrases": ["cosmic string loop", "kink", "gravitational power"]}
{"id": "0905.0173", "title": "Stagflation \u2013 Bose-Einstein condensation in the early universe", "abstract": "Our universe experienced the accelerated expansion at least twice; an extreme inflationary acceleration in the early universe and the recent mild acceleration. By introducing the Bose-Einstein condensation (BEC) phase of a boson field, we have been developing a unified model of dark energy (DE) and dark matter (DM) for the later mild acceleration. In this scenario, two phases of BEC (=DE) and normal gas (=DM) transform with each other through BEC phase transition. This unified model has successfully explained the mild acceleration as an attractor. We extend this BEC cosmology to the early universe without introducing new ingredients. In this scenario, the inflation is naturally initiated by the condensation of the bosons in the huge vacuum energy. This inflation and even the cosmic expansion eventually terminates exactly at zero energy density. We call this stage as stagflation. At this stagflation era, particle production and the decay of BEC take place. The former makes the universe turn into the standard hot big bang stage and the latter makes the cosmological constant vanishingly small after the inflation. Furthermore, we calculate the density fluctuations produced in this model, which turns out to be in the range allowed by the present observational data. We also show that the stagflation is quite robust and easily appears when one allows negative region of the potential. Further, we comment on the possibility that BEC generation/decay series might have continued all the time in the cosmic history from the inflation to present.", "keyphrases": ["bose-einstein condensation", "early universe", "dark matter", "condensate state physic"]}
{"id": "0908.1274", "title": "Magnetic fluctuation power near proton temperature anisotropy instability thresholds in the solar wind", "abstract": "The proton temperature anisotropy in the solar wind is known to be constrained by the theoretical thresholds for pressure anisotropy-driven instabilities. Here we use approximately 1 million independent measurements of gyroscale magnetic fluctuations in the solar wind to show for the first time that these fluctuations are enhanced along the temperature anisotropy thresholds of the mirror, proton oblique firehose, and ion cyclotron instabilities. In addition, the measured magnetic compressibility is enhanced at high plasma beta (\u03b2_\u2225\u2273 1) along the mirror instability threshold but small elsewhere, consistent with expectations of the mirror mode. The power in this frequency (the 'dissipation') range is often considered to be driven by the solar wind turbulent cascade, an interpretation which should be qualified in light of the present results. In particular, we show that the short wavelength magnetic fluctuation power is a strong function of collisionality, which relaxes the temperature anisotropy away from the instability conditions and reduces correspondingly the fluctuation power.", "keyphrases": ["temperature anisotropy", "solar wind", "ion cyclotron instability", "magnetic fluctuation power"]}
{"id": "1003.6097", "title": "Hunting for Primordial Non-Gaussianity in the Cosmic Microwave Background", "abstract": "Since the first limit on the (local) primordial non-Gaussianity parameter, fNL, was obtained from COBE data in 2002, observations of the CMB have been playing a central role in constraining the amplitudes of various forms of non-Gaussianity in primordial fluctuations. The current 68 7-year WMAP data is fNL=32+/-21, and the Planck satellite is expected to reduce the uncertainty by a factor of four in a few years from now. If fNL>>1 is found by Planck with high statistical significance, all single-field models of inflation would be ruled out. Moreover, if the Planck satellite finds fNL=30, then it would be able to test a broad class of multi-field models using the four-point function (trispectrum) test of tauNL>=(6fNL/5)^2. In this article, we review the methods (optimal estimator), results (WMAP 7-year), and challenges (secondary anisotropy, second-order effect, and foreground) of measuring primordial non-Gaussianity from the CMB data, present a science case for the trispectrum, and conclude with future prospects.", "keyphrases": ["primordial non-gaussianity", "cosmic microwave background", "universe", "powerful observational tool", "gaussian statistic"]}
{"id": "1502.03597", "title": "Quintessential inflation with canonical and noncanonical scalar fields and Planck 2015 results", "abstract": "We investigate two classes of models of quintessential inflation, based upon canonical as well as noncanonical scalar fields. In particular, introducing potentials steeper than the standard exponential, we construct models that can give rise to a successful inflationary phase, with signatures consistent with Planck 2015 results. Additionally, using nonminimal coupling of the scalar field with massive neutrino matter, we obtain the standard thermal history of the Universe, with late-time cosmic acceleration as the last stage of evolution. In both cases, inflation and late-time acceleration are connected by a tracker solution.", "keyphrases": ["noncanonical scalar field", "scalar field", "cosmic acceleration", "quintessential inflation"]}
{"id": "1105.4529", "title": "Diffusive propagation of cosmic rays from supernova remnants in the Galaxy. II: anisotropy", "abstract": "We investigate the effects of stochasticity in the spatial and temporal distribution of supernova remnants on the anisotropy of cosmic rays observed at Earth. The calculations are carried out for different choices of the diffusion coefficient D(E) for propagation in the Galaxy. The propagation and spallation of nuclei are taken into account. At high energies we assume that D(E)\u223c(E/Z)^\u03b4, with \u03b4=1/3 and \u03b4=0.6 being the reference scenarios. The large scale distribution of supernova remnants in the Galaxy is modeled following the distribution of pulsars with and without accounting for the spiral structure of the Galaxy. Our calculations allow us to determine the contribution to anisotropy resulting from both the large scale distribution of SNRs in the Galaxy and the random distribution of the nearest remnants. The naive expectation that the anisotropy amplitude scales as D(E) is shown to be an oversimplification which does not reflect in the predicted anisotropy for any realistic distribution of the sources. The fluctuations in the anisotropy pattern are dominated by nearby sources, so that predicting or explaining the observed anisotropy amplitude and phase becomes close to impossible. We find however that the very weak energy dependence of the anisotropy amplitude below 10^5 GeV and the rise at higher energies, can best be explained if the diffusion coefficient is D(E)\u223c E^1/3. Faster diffusion, for instance with \u03b4=0.6, leads in general to an exceedingly large anisotropy amplitude. The spiral structure introduces interesting trends in the energy dependence of the anisotropy pattern, which qualitatively reflect the trend seen in the data. For large values of the halo size we find that the anisotropy becomes dominated by the large scale regular structure of the source distribution, leading indeed to a monotonic increase of \u03b4_A with energy.", "keyphrases": ["cosmic ray", "supernova remnant", "diffusive propagation"]}
{"id": "1304.5957", "title": "Further matters in space-time geometry: f(R,T,R_\u03bc\u03bdT^\u03bc\u03bd) gravity", "abstract": "We consider a gravitational model in which matter is non-minimally coupled to geometry, with the effective Lagrangian of the gravitational field being given by an arbitrary function of the Ricci scalar, the trace of the matter energy-momentum tensor, and the contraction of the Ricci tensor with the matter energy-momentum tensor. The field equations of the model are obtained in the metric formalism, and the equation of motion of a massive test particle is derived. In this type of models the matter energy-momentum tensor is generally not conserved, and this non-conservation determines the appearance of an extra-force acting on the particles in motion in the gravitational field. The Newtonian limit of the model is also considered, and an explicit expression for the extra-acceleration which depends on the matter density is obtained in the small velocity limit for dust particles. We also analyze in detail the so-called Dolgov-Kawasaki instability, and obtain the stability conditions of the model with respect to local perturbations. A particular class of gravitational field equations can be obtained by imposing the conservation of the energy-momentum tensor. We derive the corresponding field equations for the conservative case by using a Lagrange multiplier method, from a gravitational action that explicitly contains an independent parameter multiplying the divergence of the energy-momentum tensor. The cosmological implications of the model are investigated for both the conservative and non-conservative cases, and several classes of analytical solutions are obtained.", "keyphrases": ["geometry", "gravity model", "einstein quantum gravity"]}
{"id": "1204.3662", "title": "A New Model of the Galactic Magnetic Field", "abstract": "A new, much improved model of the Galactic Magnetic Field (GMF) is presented. We use the WMAP7 Galactic Synchrotron Emission map and more than forty thousand extragalactic rotation measures to constrain the parameters of the GMF model, which is substantially generalized compared to earlier work to now include an out-of-plane component (as suggested by observations of external galaxies) and striated-random fields (motivated by theoretical considerations). The new model provides a greatly improved fit to observations. Consistent with our earlier analyses, the best-fit model has a disk field and an extended halo field. Our new analysis reveals the presence of a large, out-of-plane component of the GMF; as a result, the polarized synchrotron emission of our Galaxy seen by an edge-on observer is predicted to look intriguingly similar to what has been observed in external edge-on galaxies. We find evidence that the cosmic ray electron density is significantly larger than given by GALPROP, or else that there is a widespread striated component to the GMF.", "keyphrases": ["galactic magnetic field", "synchrotron emission", "galaxy"]}
{"id": "1701.01116", "title": "Testing strong-field gravity with tidal Love numbers", "abstract": "The tidal Love numbers (TLNs) encode the deformability of a self-gravitating object immersed in a tidal environment and depend significantly both on the object's internal structure and on the dynamics of the gravitational field. An intriguing result in classical general relativity is the vanishing of the TLNs of black holes. We extend this result in three ways, aiming at testing the nature of compact objects: (i) we compute the TLNs of exotic compact objects, including different families of boson stars, gravastars, wormholes, and other toy models for quantum corrections at the horizon scale. In the black-hole limit, we find a universal logarithmic dependence of the TLNs on the location of the surface; (ii) we compute the TLNs of black holes beyond vacuum general relativity, including Einstein-Maxwell, Brans-Dicke and Chern-Simons gravity; (iii) We assess the ability of present and future gravitational-wave detectors to measure the TLNs of these objects, including the first analysis of TLNs with LISA. Both LIGO, ET and LISA can impose interesting constraints on boson stars, while LISA is able to probe even extremely compact objects. We argue that the TLNs provide a smoking gun of new physics at the horizon scale, and that future gravitational-wave measurements of the TLNs in a binary inspiral provide a novel way to test black holes and general relativity in the strong-field regime.", "keyphrases": ["gravity", "love number", "black hole", "compact object", "boson star"]}
{"id": "1303.3069", "title": "Lower Bounds on Magnetic Fields in Intergalactic Voids from Long-Term GeV-TeV Light Curves of the Blazar Mrk 421", "abstract": "Lower bounds are derived on the amplitude B of intergalactic magnetic fields (IGMFs) in the region between Galaxy and the blazar Mrk 421, from constraints on the delayed GeV pair-echo flux that are emitted by secondary e^-e^+ produced in \u03b3\u03b3interactions between primary TeV gamma-rays and the cosmic infrared background. The distribution of galaxies mapped by the Sloan Digital Sky Survey shows that this region is dominated by a large intergalactic void. We utilize data from long-term, simultaneous GeV-TeV observations by the Fermi Large Area Telescope and the ARGO-YBJ experiment extending over 850 days. For an assumed value of B, we evaluate the daily GeV pair-echo flux expected from the TeV data, select the dates where this exceeds the Fermi 2-\u03c3sensitivity, compute the probability that this flux is excluded by the Fermi data for each date, and then combine the probabilities using the inverse normal method. Consequently, we exclude B < 10^-20.5 G for a field coherence length of 1 kpc at 4- \u03c3level, as long as plasma instabilities are unimportant for cooling of the pair beam. This is much more significant than the 2-\u03c3bounds we obtained previously from observations of Mrk 501, by virtue of more extensive data from the ARGO-YBJ, as well as improved statistical analysis. Compared with most other studies of IGMF bounds, the evidence we present here for a non-zero IGMF is more robust as it does not rely on unproven assumptions on the primary TeV emission during unobserved periods.", "keyphrases": ["magnetic field", "intergalactic voids", "blazar observation"]}
{"id": "1806.11472", "title": "Two-field disformal transformation and mimetic cosmology", "abstract": "We extend the disformal transformation to models with two scalar fields and look at its singular limit. Solving the eigentensor equation for the Jacobian of the transformation of the metrics we find the two-field extension of the mimetic scenario in the singular conformal limit. At the background level the setup mimics the roles of dark matter cosmology. We decompose the perturbations into the adiabatic and entropy modes in which the adiabatic perturbation is tangential to the classical trajectory while the entropy mode is perpendicular to it. We show that the adiabatic mode is frozen while the entropy mode propagates with the sound speed equal to unity with no instabilities.", "keyphrases": ["disformal transformation", "two-field extension", "mimetic gravity", "conformal transformation"]}
{"id": "1803.00541", "title": "White dwarfs and revelations", "abstract": "We use the most recent, complete and independent measurements of masses and radii of white dwarfs in binaries to bound the class of non-trivial modified gravity theories, viable after GW170817/GRB170817, using its effect on the mass-radius relation of the stars. We show that the uncertainty in the latest data is sufficiently small that residual evolutionary effects, most notably the effect of core composition, finite temperature and envelope structure, must now accounted for if correct conclusions about the nature of gravity are to be made. We model corrections resulting from finite temperature and envelopes to a base Hamada-Salpeter cold equation of state and derive consistent bounds on the possible modifications of gravity in the stars' interiors, finding that Y< 0.14 at 95% confidence, an improvement of a factor of three with respect to previous bounds. Finally, our analysis reveals some fundamental degeneracies between the theory of gravity and the precise chemical makeup of white dwarfs.", "keyphrases": ["dwarf", "gravity", "possible modification"]}
{"id": "1010.3769", "title": "Chameleon dark energy models with characteristic signatures", "abstract": "In chameleon dark energy models, local gravity constraints tend to rule out parameters in which observable cosmological signatures can be found. We study viable chameleon potentials consistent with a number of recent observational and experimental bounds. A novel chameleon field potential, motivated by f(R) gravity, is constructed where observable cosmological signatures are present both at the background evolution and in the growth-rate of the perturbations. We study the evolution of matter density perturbations on low redshifts for this potential and show that the growth index today gamma_0 can have significant dispersion on scales relevant for large scale structures. The values of gamma_0 can be even smaller than 0.2 with large variations of gamma on very low redshifts for the model parameters constrained by local gravity tests. This gives a possibility to clearly distinguish these chameleon models from the Lambda-Cold-Dark-Matter model in future high-precision observations.", "keyphrases": ["dark energy model", "chameleon", "scalar potential"]}
{"id": "0909.0007", "title": "Fingerprinting dark energy", "abstract": "Dark energy perturbations are normally either neglected or else included in a purely numerical way, obscuring their dependence on underlying parameters like the equation of state or the sound speed. However, while many different explanations for the dark energy can have the same equation of state, they usually differ in their perturbations so that these provide a fingerprint for distinguishing between different models with the same equation of state. In this paper we derive simple yet accurate approximations that are able to characterize a specific class of models (encompassing most scalar-field models) which is often generically called \"dark energy\". We then use the approximate solutions to look at the impact of the dark energy perturbations on the dark matter power spectrum and on the integrated Sachs-Wolfe effect in the cosmic microwave background radiation.", "keyphrases": ["dark energy", "anisotropic stress", "pressure"]}
{"id": "1704.03464", "title": "PBH dark matter from axion inflation", "abstract": "Protected by an approximate shift symmetry, axions are well motivated candidates for driving cosmic inflation. Their generic coupling to the Chern-Simons term of any gauge theory gives rise to a wide range of potentially observable signatures, including equilateral non-Gaussianites in the CMB, chiral gravitational waves in the range of direct gravitational wave detectors and primordial black holes (PBHs). In this paper we revisit these predictions for axion inflation models non-minimally coupled to gravity. Contrary to the case of minimally coupled models which typically predict scale-invariant mass distributions for the generated PBHs at small scales, we demonstrate how broadly peaked PBH spectra naturally arises in this setup. For specific parameter values, all of dark matter can be accounted for by PBHs.", "keyphrases": ["dark matter", "axion", "black hole"]}
{"id": "1102.4638", "title": "The First Galaxies", "abstract": "We review our current understanding of how the first galaxies formed at the end of the cosmic dark ages, a few 100 million years after the Big Bang. Modern large telescopes discovered galaxies at redshifts greater than seven, whereas theoretical studies have just reached the degree of sophistication necessary to make meaningful predictions. A crucial ingredient is the feedback exerted by the first generation of stars, through UV radiation, supernova blast waves, and chemical enrichment. The key goal is to derive the signature of the first galaxies to be observed with upcoming or planned next-generation facilities, such as the James Webb Space Telescope or Atacama Large Millimeter Array. From the observational side, ongoing deep-field searches for very high-redshift galaxies begin to provide us with empirical constraints on the nature of the first galaxies.", "keyphrases": ["first galaxy", "dark age", "cosmology", "hydrogen", "pop iii"]}
{"id": "1606.09307", "title": "The rotation curve of a point particle in stringy gravity", "abstract": "Double Field Theory suggests to view the whole massless sector of closed strings as the gravitational unity. The fundamental symmetries therein, including the \ud835\udc0e(D,D) covariance, can determine unambiguously how the Standard Model as well as a relativistic point particle should couple to the closed string massless sector. The theory also refines the notion of singularity. We consider the most general, spherically symmetric, asymptotically flat, static vacuum solution to D=4 Double Field Theory, which contains three free parameters and consequently generalizes the Schwarzschild geometry. Analyzing the circular geodesic of a point particle in string frame, we obtain the orbital velocity as a function of R/(M_\u221eG) which is the dimensionless radial variable normalized by mass. The rotation curve generically features a maximum and thus non-Keplerian over a finite range, while becoming asymptotically Keplerian at infinity, R/(M_\u221eG)\u2192\u221e. The adoption of the string frame rather than Einstein frame is the consequence of the fundamental symmetry principle. Our result opens up a new scheme to solve the dark matter/energy problems by modifying General Relativity at `short' range of R/(M_\u221eG).", "keyphrases": ["rotation curve", "point particle", "string frame"]}
{"id": "1210.7792", "title": "Symmetries and Loops in Inflation", "abstract": "In this paper, we prove that the superhorizon conservation of the curvature perturbation zeta in single-field inflation holds as an operator statement. This implies that all zeta-correlators are time independent at all orders in the loop expansion. Our result follows directly from locality and diffeomorphism invariance of the underlying theory. We also explore the relationship between the conservation of zeta, the single-field consistency relation and the renormalization of composite operators.", "keyphrases": ["single-field inflation", "inflationary correlator", "conformal consistency relation"]}
{"id": "0908.2624", "title": "Accurate masses and radii of normal stars: modern results and applications", "abstract": "This paper presents and discusses a critical compilation of accurate, fundamental determinations of stellar masses and radii. We have identified 95 detached binary systems containing 190 stars (94 eclipsing systems, and alpha Centauri) that satisfy our criterion that the mass and radius of both stars be known to 3 temperature, metal abundance, rotational velocity and apsidal motion determinations when available, and we compute a number of other physical parameters, notably luminosity and distance. We discuss the use of this information for testing models of stellar evolution. The amount and quality of the data also allow us to analyse the tidal evolution of the systems in considerable depth, testing prescriptions of rotational synchronisation and orbital circularisation in greater detail than possible before. The new data also enable us to derive empirical calibrations of M and R for single (post-) main-sequence stars above 0.6 M(Sun). Simple, polynomial functions of T(eff), log g and [Fe/H] yield M and R with errors of 6 Excellent agreement is found with independent determinations for host stars of transiting extrasolar planets, and good agreement with determinations of M and R from stellar models as constrained by trigonometric parallaxes and spectroscopic values of T(eff) and [Fe/H]. Finally, we list a set of 23 interferometric binaries with masses known to better than 3 fundamental radius determinations (except alpha Aur). We discuss the prospects for improving these and other stellar parameters in the near future.", "keyphrases": ["star", "stellar model", "accurate masse"]}
{"id": "0910.3375", "title": "Casimir Energy, Holographic Dark Energy and Electromagnetic Metamaterial Mimicking de Sitter", "abstract": "We compute the Casimir energy of the photon field in a de Sitter space and find it to be proportional to the size of the horizon, the same form of the holographic dark energy. We suggest to make metamaterials to mimic de Sitter space in laboratory and measure the predicted Casimir energy.", "keyphrases": ["holographic dark energy", "photon field", "casimir energy"]}
{"id": "1004.5509", "title": "Dark energy with non-adiabatic sound speed: initial conditions and detectability", "abstract": "Assuming that the universe contains a dark energy fluid with a constant linear equation of state and a constant sound speed, we study the prospects of detecting dark energy perturbations using CMB data from Planck, cross-correlated with galaxy distribution maps from a survey like LSST. We update previous estimates by carrying a full exploration of the mock data likelihood for key fiducial models. We find that it will only be possible to exclude values of the sound speed very close to zero, while Planck data alone is not powerful enough for achieving any detection, even with lensing extraction. We also discuss the issue of initial conditions for dark energy perturbations in the radiation and matter epochs, generalizing the usual adiabatic conditions to include the sound speed effect. However, for most purposes, the existence of attractor solutions renders the perturbation evolution nearly independent of these initial conditions.", "keyphrases": ["sound speed", "initial condition", "dark energy"]}
{"id": "1709.09501", "title": "Cosmological Models in Energy-Momentum-Squared Gravity", "abstract": "We study the cosmological effects of adding terms of higher-order in the usual energy-momentum tensor to the matter lagrangian of general relativity. This is in contrast to most studies of higher-order gravity which focus on generalising the Einstein-Hilbert curvature contribution to the lagrangian. The resulting cosmological theories include many particular theories, like bulk viscous cosmologies, loop quantum gravity, K-essence, and brane-world cosmologies. We find a range of exact solutions for isotropic universes, discuss their behaviours with reference to the early and late-time evolution, accelerated expansion, and the occurrence or avoidance of singularities. We briefly discuss extensions to anisotropic cosmologies and delineate the situations where the higher-order matter terms will dominate over anisotropies on approach to cosmological singularities.", "keyphrases": ["gravity", "energy-momentum tensor", "matter lagrangian"]}
{"id": "1203.2286", "title": "Elliptical galaxies kinematics within general relativity with renormalization group effects", "abstract": "The renormalization group framework can be applied to Quantum Field Theory on curved space-time, but there is no proof whether the beta-function of the gravitational coupling indeed goes to zero in the far infrared or not. In a recent paper we have shown that the amount of dark matter inside spiral galaxies may be negligible if a small running of the General Relativity coupling G is present. Here we extend the proposed model to elliptical galaxies and present a detailed analysis on the modeling of NGC 4494 (an ordinary elliptical) and NGC 4374 (a giant elliptical). In order to compare our results to a well known alternative model to the standard dark matter picture, we also evaluate NGC 4374 with MOND. In this galaxy MOND leads to a significative discrepancy with the observed velocity dispersion curve and has a significative tendency towards tangential anisotropy. On the other hand, the approach based on the renormalization group and general relativity (RGGR) could be applied with good results to these elliptical galaxies and is compatible with lower mass-to-light ratios (of about the Kroupa IMF type).", "keyphrases": ["galaxy", "general relativity", "dark matter-like effect"]}
{"id": "1105.1265", "title": "GRIPS - Gamma-Ray Imaging, Polarimetry and Spectroscopy", "abstract": "We propose to perform a continuously scanning all-sky survey from 200 keV to 80 MeV achieving a sensitivity which is better by a factor of 40 or more compared to the previous missions in this energy range. The Gamma-Ray Imaging, Polarimetry and Spectroscopy (GRIPS) mission addresses fundamental questions in ESA's Cosmic Vision plan. Among the major themes of the strategic plan, GRIPS has its focus on the evolving, violent Universe, exploring a unique energy window. We propose to investigate \u03b3-ray bursts and blazars, the mechanisms behind supernova explosions, nucleosynthesis and spallation, the enigmatic origin of positrons in our Galaxy, and the nature of radiation processes and particle acceleration in extreme cosmic sources including pulsars and magnetars. The natural energy scale for these non-thermal processes is of the order of MeV. Although they can be partially and indirectly studied using other methods, only the proposed GRIPS measurements will provide direct access to their primary photons. GRIPS will be a driver for the study of transient sources in the era of neutrino and gravitational wave observatories such as IceCUBE and LISA, establishing a new type of diagnostics in relativistic and nuclear astrophysics. This will support extrapolations to investigate star formation, galaxy evolution, and black hole formation at high redshifts.", "keyphrases": ["gamma-ray imaging", "polarimetry", "energy range", "mev.", "grips"]}
{"id": "1306.2770", "title": "Solar Irradiance Variability and Climate", "abstract": "The brightness of the Sun varies on all time scales on which it has been observed, and there is increasing evidence that it has an influence on climate. The amplitudes of such variations depend on the wavelength and possibly on the time scale. Although many aspects of this variability are well established, the exact magnitude of secular variations (going beyond a solar cycle) and the spectral dependence of variations are under discussion. The main drivers of solar variability are thought to be magnetic features at the solar surface. The climate reponse can be, on a global scale, largely accounted for by simple energetic considerations, but understanding the regional climate effects is more difficult. Promising mechanisms for such a driving have been identified, including through the influence of UV irradiance on the stratosphere and dynamical coupling to the surface. Here we provide an overview of the current state of our knowledge, as well as of the main open questions.", "keyphrases": ["climate", "spectral dependence", "solar irradiance variability"]}
{"id": "2001.09213", "title": "The Megamaser Cosmology Project. XIII. Combined Hubble constant constraints", "abstract": "We present a measurement of the Hubble constant made using geometric distance measurements to megamaser-hosting galaxies. We have applied an improved approach for fitting maser data and obtained better distance estimates for four galaxies previously published by the Megamaser Cosmology Project: UGC 3789, NGC 6264, NGC 6323, and NGC 5765b. Combining these updated distance measurements with those for the maser galaxies CGCG 074-064 and NGC 4258, and assuming a fixed velocity uncertainty of 250 km s^-1 associated with peculiar motions, we constrain the Hubble constant to be H_0 = 73.9 \u00b1 3.0 km s^-1 Mpc^-1 independent of distance ladders and the cosmic microwave background. This best value relies solely on maser-based distance and velocity measurements, and it does not use any peculiar velocity corrections. Different approaches for correcting peculiar velocities do not modify H_0 by more than \u00b11\u03c3, with the full range of best-fit Hubble constant values spanning 71.8-76.9 km s^-1 Mpc^-1. We corroborate prior indications that the local value of H_0 exceeds the early-Universe value, with a confidence level varying from 95-99 velocities.", "keyphrases": ["megamaser cosmology project", "hubble constant", "late-universe measurement"]}
{"id": "1809.03484", "title": "Gravitational Wave Decay into Dark Energy", "abstract": "We study the decay of gravitational waves into dark energy fluctuations \u03c0, through the processes \u03b3\u2192\u03c0\u03c0 and \u03b3\u2192\u03b3\u03c0, made possible by the spontaneous breaking of Lorentz invariance. Within the EFT of Dark Energy (or Horndeski/beyond Horndeski theories) the first process is large for the operator 1/2m\u0303_4^2(t) \u03b4 g^00 ( ^(3) R + \u03b4 K_\u03bc^\u03bd\u03b4 K^\u03bc_\u03bd -\u03b4 K^2 ), so that the recent observations force m\u0303_4 =0 (or equivalently \u03b1_ H=0). This constraint, together with the requirement that gravitational waves travel at the speed of light, rules out all quartic and quintic GLPV theories. Additionally, we study how the same couplings affect the propagation of gravitons at loop order. The operator proportional to m\u0303_4^2 generates a calculable, non-Lorentz invariant higher-derivative correction to the graviton propagation. The modification of the dispersion relation provides a bound on m\u0303_4^2 comparable to the one of the decay. Conversely, operators up to cubic Horndeski do not generate sizeable higher-derivative corrections.", "keyphrases": ["decay", "dark energy", "spontaneous breaking", "graviton"]}
{"id": "1106.3569", "title": "Compact stars in Eddington inspired gravity", "abstract": "A new, Eddington inspired theory of gravity was recently proposed by Banados and Ferreira. It is equivalent to General Relativity in vacuum, but differs from it inside matter. This viable, one parameter theory was shown to avoid cosmological singularities and turns out to lead to many other exciting new features that we report here. First, for a positive coupling parameter, the field equations have a dramatic impact on the collapse of dust, and do not lead to singularities. We further find that the theory supports stable, compact pressureless stars made of perfect fluid, which provide interesting models of self-gravitating dark matter. Finally, we show that the mere existence of relativistic stars imposes a strong, near optimal constraint on the coupling parameter, which can even be improved by observations of the moment of inertia of the double pulsar.", "keyphrases": ["star", "general relativity", "cosmology", "dark matter"]}
{"id": "1010.3693", "title": "Features of heavy physics in the CMB power spectrum", "abstract": "The computation of the primordial power spectrum in multi-field inflation models requires us to correctly account for all relevant interactions between adiabatic and non-adiabatic modes around and after horizon crossing. One specific complication arises from derivative interactions induced by the curvilinear trajectory of the inflaton in a multi-dimensional field space. In this work we compute the power spectrum in general multi-field models and show that certain inflaton trajectories may lead to observationally significant imprints of `heavy' physics in the primordial power spectrum if the inflaton trajectory turns, that is, traverses a bend, sufficiently fast (without interrupting slow roll), even in cases where the normal modes have masses approaching the cutoff of our theory. We emphasise that turning is defined with respect to the geodesics of the sigma model metric, irrespective of whether this is canonical or non-trivial. The imprints generically take the form of damped superimposed oscillations on the power spectrum. In the particular case of two-field models, if one of the fields is sufficiently massive compared to the scale of inflation, we are able to compute an effective low energy theory for the adiabatic mode encapsulating certain relevant operators of the full multi-field dynamics. As expected, a particular characteristic of this effective theory is a modified speed of sound for the adiabatic mode which is a functional of the background inflaton trajectory and the turns traversed during inflation. Hence in addition, we expect non-Gaussian signatures directly related to the features imprinted in the power spectrum.", "keyphrases": ["power spectrum", "heavy field", "single-field description"]}
{"id": "1910.09557", "title": "Gravitational waves and higher dimensions: Love numbers and Kaluza-Klein excitations", "abstract": "Gravitational-wave (GW) observations provide a wealth of information on the nature and properties of black holes. Among these, tidal Love numbers or the multipole moments of the inspiralling and final objects are key to a number of constraints. Here, we consider these observations in the context of higher-dimensional scenarios, with flat large extra dimensions. We show that \u2013 as might be anticipated, but not always appreciated in the literature \u2013 physically motivated set-ups are unconstrained by gravitational-wave data. Dynamical processes that do not excite the Kaluza-Klein (KK) modes lead to a signal identical to that in four-dimensional general relativity in vacuum . In addition, any possible excitation of the KK modes is highly suppressed relative to the dominant quadrupolar term; given existing constraints on the extra dimensions and the masses of the objects seen in gravitational-wave observations, KK modes appear at post-Newtonian order \u223c 10^11. Finally, we re-compute the tidal Love numbers of spherical black holes in higher dimensions. We confirm that these are different from zero, but comparing with previous computations we find a different magnitude and sign.", "keyphrases": ["dimension", "love number", "gravitational wave"]}
{"id": "1310.7915", "title": "Ward identities and consistency relations for the large scale structure with multiple species", "abstract": "We present fully nonlinear consistency relations for the squeezed bispectrum of Large Scale Structure. These relations hold when the matter component of the Universe is composed of one or more species, and generalize those obtained in Peloso, Pietroni '13 and Kehagias, Riotto '13 in the single species case. The multi-species relations apply to the standard dark matter + baryons scenario, as well as to the case in which some of the fields are auxiliary quantities describing a particular population, such as dark matter halos or a specific galaxy class. If a large scale velocity bias exists between the different populations new terms appear in the consistency relations with respect to the single species case. As an illustration, we discuss two physical cases in which such a velocity bias can exist: (1) a new long range scalar force in the dark matter sector (resulting in a violation of the equivalence principle in the dark matter-baryon system), and (2) the distribution of dark matter halos relative to that of the underlying dark matter field.", "keyphrases": ["consistency relation", "specie", "violation", "ward identity"]}
{"id": "1101.1525", "title": "Parity violation in the Cosmic Microwave Background from a pseudoscalar inflaton", "abstract": "If the inflaton is a pseudoscalar, then it naturally interacts with gauge fields via an axion-like coupling to F_\u03bc\u03bdF\u0303^\u03bc\u03bd. Through this coupling, the rolling inflaton produces quanta of the gauge field, that in their turn source the tensor components of the metric perturbations. Due to the parity-violating nature of the system, the right- and the left-handed tensor modes have different amplitudes. Such an asymmetry manifests itself in the form of non-vanishing TB and EB correlation functions in the Cosmic Microwave Background (CMB). We compute the amplitude of the parity-violating tensor modes and we discuss two scenarios, consistent with the current data, where parity-violating CMB correlation functions will be detectable in future experiments.", "keyphrases": ["cosmic microwave background", "gauge field", "vacuum"]}
{"id": "1111.2183", "title": "Contributions from the Cherenkov Telescope Array (CTA) Consortium to the ICRC 2011", "abstract": "The Cherenkov Telescope Array (CTA) is a project for the construction of a next generation VHE gamma ray observatory with full sky coverage. Its aim is improving by about one order of magnitude the sensitivity of the existing installations, covering about 5 decades in energy (from few tens of GeV to above a hundred TeV) and having enhanced angular and energy resolutions. During 2010 the project became a truly global endeavour carried out by a consortium of about 750 collaborators from Europe, Asia, Africa and the North and South Americas. Also during 2010 the CTA project completed its Design Study phase and started a Preparatory Phase that is expected to extend for three years and should lead to the starting of the construction of CTA. An overview of the CTA Consortium activities project will be given.", "keyphrases": ["cherenkov telescope array", "consortium", "observatory"]}
{"id": "1510.04191", "title": "Circular geodesics and thick tori around rotating boson stars", "abstract": "Accretion disks play an important role in the evolution of their relativistic inner compact objects. The emergence of a new generation of interferometers will allow to resolve these accretion disks and provide more information about the properties of the central gravitating object. Due to this instrumental leap forward it is crucial to investigate the accretion disk physics near various types of inner compact objects now to deduce later constraints on the central objects from observations. A possible candidate for the inner object is the boson star. Here, we will try to analyze the differences between accretion structures surrounding boson stars and black holes. We aim at analysing the physics of circular geodesics around boson stars and study simple thick accretion tori (so-called Polish doughnuts) in the vicinity of these stars. We realize a detailed study of the properties of circular geodesics around boson stars. We then perform a parameter study of thick tori with constant angular momentum surrounding boson stars. This is done using the boson star models computed by a code constructed with the spectral solver library KADATH. We demonstrate that all the circular stable orbits are bound. In the case of a constant angular momentum torus, a cusp in the torus surface exists only for boson stars with a strong gravitational scalar field. Moreover, for each inner radius of the disk, the allowed specific angular momentum values lie within a constrained range which depends on the boson star considered. We show that the accretion tori around boson stars have different characteristics than in the vicinity of a black hole. With future instruments it could be possible to use these differences to constrain the nature of compact objects.", "keyphrases": ["thick tori", "boson star", "circular geodesic"]}
{"id": "2011.04911", "title": "Newtonian Fractional-Dimension Gravity and Rotationally Supported Galaxies", "abstract": "We continue our analysis of Newtonian Fractional-Dimension Gravity, an extension of the standard laws of Newtonian gravity to lower dimensional spaces including those with fractional (i.e., non-integer) dimension. We apply our model to three rotationally supported galaxies: NGC 7814 (Bulge-Dominated Spiral), NGC 6503 (Disk-Dominated Spiral), and NGC 3741 (Gas-Dominated Dwarf). As was done in the general cases of spherically-symmetric and axially-symmetric structures, which were studied in previous work on the subject, we examine a possible connection between our model and Modified Newtonian Dynamics, a leading alternative gravity model which explains the observed properties of these galaxies without requiring the Dark Matter hypothesis. In our model, the MOND acceleration constant a_0\u2243 1.2 \u00d7 10^-10^ -2 can be related to a natural scale length l_0, namely a_0\u2248 GM/l_0^2 for a galaxy of mass M. Also, the empirical Radial Acceleration Relation, connecting the observed radial acceleration g_obs with the baryonic one g_bar, can be explained in terms of a variable local dimension D. As an example of this methodology, we provide detailed rotation curve fits for the three galaxies mentioned above.", "keyphrases": ["galaxy", "gas-dominated dwarf", "gravity model", "newtonian fractional-dimension gravity", "alternative gravitational model"]}
{"id": "1105.0207", "title": "Seeking String Theory in the Cosmos", "abstract": "We review the existence, formation and properties of cosmic strings in string theory, the wide variety of observational techniques that are being employed to detect them, and the constraints that current observations impose on string theory models.", "keyphrases": ["string theory", "topological defect", "early universe"]}
{"id": "1711.04819", "title": "Uncertainty quantification for radio interferometric imaging: II. MAP estimation", "abstract": "Uncertainty quantification is a critical missing component in radio interferometric imaging that will only become increasingly important as the big-data era of radio interferometry emerges. Statistical sampling approaches to perform Bayesian inference, like Markov Chain Monte Carlo (MCMC) sampling, can in principle recover the full posterior distribution of the image, from which uncertainties can then be quantified. However, for massive data sizes, like those anticipated from the Square Kilometre Array (SKA), it will be difficult if not impossible to apply any MCMC technique due to its inherent computational cost. We formulate Bayesian inference problems with sparsity-promoting priors (motivated by compressive sensing), for which we recover maximum a posteriori (MAP) point estimators of radio interferometric images by convex optimisation. Exploiting recent developments in the theory of probability concentration, we quantify uncertainties by post-processing the recovered MAP estimate. Three strategies to quantify uncertainties are developed: (i) highest posterior density credible regions; (ii) local credible intervals (cf. error bars) for individual pixels and superpixels; and (iii) hypothesis testing of image structure. These forms of uncertainty quantification provide rich information for analysing radio interferometric observations in a statistically robust manner. Our MAP-based methods are approximately 10^5 times faster computationally than state-of-the-art MCMC methods and, in addition, support highly distributed and parallelised algorithmic structures. For the first time, our MAP-based techniques provide a means of quantifying uncertainties for radio interferometric imaging for realistic data volumes and practical use, and scale to the emerging big-data era of radio astronomy.", "keyphrases": ["radio", "interferometric imaging", "uncertainty quantification"]}
{"id": "1909.13489", "title": "Another look at redshift drift and the backreaction conjecture", "abstract": "Earlier studies have conjectured that redshift drift is described by spatially averaged quantities and thus becomes positive if the average expansion of the Universe accelerates. This conclusion is reevaluated here by considering exact light propagation in a simple toy-model with average accelerated expansion. The toy-model and light propagation setup is explicitly designed for concordance between spatial averages and averages along light rays. While it is verified that redshift-distance relations are well described by average quantities in this setup, it is found that the redshift drift is not. Specifically, the redshift drift is negative despite the on-average late-time accelerated expansion of the model. This result implies that measuring redshift drift signals at low redshifts gives the potential for directly falsifying the backreaction conjecture. However, the results are based on a toy-model so it is in principle possible that the result is an artifact and that redshift drift is in reality well described by spatially averaged quantities. The result therefore highlights the importance of developing exact solutions to the Einstein equations which exhibit average accelerated expansion without local expansion so that the relation between spatial averages and observations can be firmly established.", "keyphrases": ["redshift drift", "backreaction conjecture", "redshift-distance relation"]}
{"id": "1002.0600", "title": "Non-Gaussianity of quantum fields during inflation", "abstract": "In this review, we discuss how non-Gaussianity of cosmological perturbations arises from inflation. After introducing the in-in formalism to calculate the n-point correlation function of quantum fields, we present the computation of the bispectrum of the curvature perturbation generated in general single field inflation models. The shapes of the bispectrum are compared with the local-type non-Gaussianity that arises from non-linear dynamics on super-horizon scales.", "keyphrases": ["quantum field", "in-in formalism", "non-gaussianity", "universe"]}
{"id": "1008.1183", "title": "Measuring our peculiar velocity on the CMB with high-multipole off-diagonal correlations", "abstract": "Our peculiar velocity with respect to the CMB rest frame is known to induce a large dipole in the CMB. However, the motion of an observer has also the effect of distorting the anisotropies at all scales, as shown by Challinor and Van Leeuwen (2002), due to aberration and Doppler effects. We propose to measure independently our local motion by using off-diagonal two-point correlation functions for high multipoles. We study the observability of the signal for temperature and polarization anisotropies. We point out that Planck can measure the velocity \u03b2 with an error of about 30 of about 20 degrees. This method constitutes a cross-check, which can be useful to verify that our CMB dipole is due mainly to our velocity or to disentangle the velocity from other possible intrinsic sources. Although in this paper we focus on our peculiar velocity, a similar effect would result also from other intrinsic vectorial distortion of the CMB which would induce a dipolar lensing. Measuring the off-diagonal correlation terms is therefore a test for a preferred direction on the CMB sky.", "keyphrases": ["velocity", "off-diagonal correlation", "cmb multipole"]}
{"id": "1706.01705", "title": "Improved constraints on lepton asymmetry from the cosmic microwave background", "abstract": "A cosmic lepton asymmetry \u03b7_l=(n_l-n_l\u0305)/n_\u03b3 affects the primordial helium abundance and the expansion rate of the early Universe. Both of these effects have an impact on the anisotropies of the cosmic microwave background (CMB). We derive constraints on the neutrino chemical potentials from the Planck 2015 data, assuming equal lepton flavour asymmetries and negligible neutrino masses. We find \u03be=-0.002 ^+0.114_-0.111 (95% CL) for the chemical potentials, which corresponds to -0.085 \u2264\u03b7_l\u2264 0.084. Our constraints on the lepton asymmetry are significantly stronger than previous constraints from CMB data analysis and we argue that they are more robust than those from primordial light element abundances. The resulting constraints on the primordial helium and deuterium abundances are consistent with those from direct measurements.", "keyphrases": ["lepton asymmetry", "cosmic microwave background", "neutrino"]}
{"id": "1007.2700", "title": "Cosmology of a covariant Galileon field", "abstract": "We study the cosmology of a covariant scalar field respecting a Galilean symmetry in flat space-time. We show the existence of a tracker solution that finally approaches a de Sitter fixed point responsible for cosmic acceleration today. The viable region of model parameters is clarified by deriving conditions under which ghosts and Laplacian instabilities of scalar and tensor perturbations are absent. The field equation of state exhibits a peculiar phantom-like behavior along the tracker, which allows a possibility to observationally distinguish the Galileon gravity from the Lambda-CDM model.", "keyphrases": ["covariant galileon field", "cosmology", "galileon gravity model", "cosmological application"]}
{"id": "1311.1212", "title": "Cosmology with massive neutrinos II: on the universality of the halo mass function and bias", "abstract": "We use a large suite of N-body simulations to study departures from universality in halo abundances and clustering in cosmologies with non-vanishing neutrino masses. To this end, we study how the halo mass function and halo bias factors depend on the scaling variable \u03c3^2(M,z), the variance of the initial matter fluctuation field, rather than on halo mass M and redshift z themselves. We show that using the variance of the cold dark matter rather than the total mass field, i.e., \u03c3^2_cdm(M,z) rather than \u03c3^2_m(M,z), yields more universal results. Analysis of halo bias yields similar conclusions: When large-scale halo bias is defined with respect to the cold dark matter power spectrum, the result is both more universal, and less scale- or k-dependent. These results are used extensively in Papers I and III of this series.", "keyphrases": ["neutrino", "halo mass function", "dark matter", "cosmology", "galaxy"]}
{"id": "1311.0866", "title": "Cosmology with massive neutrinos I: towards a realistic modeling of the relation between matter, haloes and galaxies", "abstract": "By using a suite of large box-size N-body simulations that incorporate massive neutrinos as an extra set of particles, we investigate the impact of neutrino masses on the spatial distribution of dark matter haloes and galaxies. We compute the bias between the spatial distribution of dark matter haloes and the overall matter and cold dark matter distributions using statistical tools such as the power spectrum and the two-point correlation function. Overall we find a scale-dependent bias on large scales for the cosmologies with massive neutrinos. However, our results indicate that the scale-dependence in the bias is reduced if the latter is computed with respect to the cold dark matter distribution only. We find that the value of the bias on large scales is reasonably well reproduced by the Tinker fitting formula once the linear cold dark matter power spectrum is used, instead of the total matter power spectrum. We investigate whether scale-dependent bias really comes from purely neutrino's effect or from nonlinear gravitational collapse of haloes. For this purpose, we address the \u03a9_\u03bd-\u03c3_8 degeneracy and find that such degeneracy is not perfect, implying that neutrinos imprint a slight scale dependence on the large-scale bias. Finally, by using a simple halo occupation distribution (HOD) model, we investigate the impact of massive neutrinos on the distribution of galaxies within dark matter haloes. We use the main galaxy sample in the Sloan Digital Sky Survey II Data Release 7 to investigate if the small-scale galaxy clustering alone can be used to discriminate among different cosmological models with different neutrino masses. Our results suggest that different choices of the HOD parameters can reproduce the observational measurements relatively well, and we quantify the difference between the values of the HOD parameters between massless and massive neutrino cosmologies.", "keyphrases": ["neutrino", "massive neutrino cosmology", "cosmology"]}
{"id": "1508.04141", "title": "Evolution of cosmological perturbations and the production of non-Gaussianities through a nonsingular bounce: Indications for a no-go theorem in single field matter bounce cosmologies", "abstract": "Assuming that curvature perturbations and gravitational waves originally arise from vacuum fluctuations in a matter-dominated phase of contraction, we study the dynamics of the cosmological perturbations evolving through a nonsingular bouncing phase described by a generic single scalar field Lagrangian minimally coupled to Einstein gravity. In order for such a model to be consistent with the current upper limits on the tensor-to-scalar ratio, there must be an enhancement of the curvature fluctuations during the bounce phase. We show that, while it remains possible to enlarge the amplitude of curvature perturbations due to the nontrivial background evolution, this growth is very limited because of the conservation of curvature perturbations on super-Hubble scales. We further perform a general analysis of the evolution of primordial non-Gaussianities through the bounce phase. By studying the general form of the bispectrum we show that the non-Gaussianity parameter f_NL (which is of order unity before the bounce phase) is enhanced during the bounce phase if the curvature fluctuations grow. Hence, in such nonsingular bounce models with matter given by a single scalar field, there appears to be a tension between obtaining a small enough tensor-to-scalar ratio and not obtaining a value of f_NL in excess of the current upper bounds. This conclusion may be considered as a \"no-go\" theorem that rules out any single field matter bounce cosmology starting with vacuum initial conditions for the fluctuations.", "keyphrases": ["cosmological perturbation", "gravitational wave", "tensor-to-scalar ratio"]}
{"id": "1307.7696", "title": "Minimal Supergravity Models of Inflation", "abstract": "We present a superconformal master action for a class of supergravity models with one arbitrary function defining the Jordan frame. It leads to a gauge-invariant action for a real vector multiplet, which upon gauge fixing describes a massive vector multiplet, or to a dual formulation with a linear multiplet and a massive tensor field. In both cases the models have one real scalar, the inflaton, naturally suited for single-field inflation. Vectors and tensors required by supersymmetry to complement a single real scalar do not acquire vev's during inflation, so there is no need to stabilize the extra scalars which are always present in the theories with chiral matter multiplets. The new class of models can describe any inflaton potential which vanishes at its minimum and grows monotonically away from the minimum. In this class of supergravity models one can fit any desirable choice of inflationary parameters n_s and r.", "keyphrases": ["inflaton potential", "minimal supergravity models", "cosmological attractor"]}
{"id": "1602.07192", "title": "Transformations between Jordan and Einstein frames: Bounces, antigravity, and crossing singularities", "abstract": "We study the relation between the Jordan-Einstein frame transition and the possible description of the crossing of singularities in flat Friedmann universes, using the fact that the regular evolution in one frame can correspond to crossing singularities in the other frame. We show that some interesting effects arise in simple models such as one with a massless scalar field or another wherein the potential is constant in the Einstein frame. The dynamics in these models and in their conformally coupled counterparts are described in detail, and a method for the continuation of such cosmological evolutions beyond the singularity is developed. We compare our approach with some other, recently developed, approaches to the problem of the crossing of singularities.", "keyphrases": ["einstein frame", "singularity", "friedmann universe", "scalar field", "jordan frame"]}
{"id": "0911.4820", "title": "Constraint on Coupled Dark Energy Models from Observations", "abstract": "The coupled dark energy models, in which the quintessence scalar field nontrivially couples to the cold dark matter, have been proposed to explain the coincidence problem. In this paper we study the perturbations of coupled dark energy models and the effects of this interaction on the current observations. Here, we pay particular attention to its imprint on the late-time Integrated Sachs-Wolfe (ISW) effect. We perform a global analysis of the constraints on this interaction from the current observational data. Considering the typical exponential form as the interaction form, we obtain that the strength of interaction between dark sectors is constrained as \u03b2<0.085 at 95 confidence level. Furthermore, we find that future measurements with smaller error bars could improve the constraint on the strength of coupling by a factor two, when compared to the present constraints.", "keyphrases": ["dark energy", "dark matter", "non-gravitational coupling"]}
{"id": "1205.2158", "title": "Massive gravity from bimetric gravity", "abstract": "We discuss the subtle relationship between massive gravity and bimetric gravity, focusing particularly on the manner in which massive gravity may be viewed as a suitable limit of bimetric gravity. The limiting procedure is more delicate than currently appreciated. Specifically, this limiting procedure should not unnecessarily constrain the background metric, which must be externally specified by the theory of massive gravity itself. The fact that in bimetric theories one always has two sets of metric equations of motion continues to have an effect even in the massive gravity limit, leading to additional constraints besides the one set of equations of motion naively expected. Thus, since solutions of bimetric gravity in the limit of vanishing kinetic term are also solutions of massive gravity, but the contrary statement is not necessarily true, there is not complete continuity in the parameter space of the theory. In particular, we study the massive cosmological solutions which are continuous in the parameter space, showing that many interesting cosmologies belong to this class.", "keyphrases": ["gravity", "bimetric theory", "kinetic term", "cosmology", "phenomenological advantage"]}
{"id": "1304.5795", "title": "Tests of Lorentz invariance: a 2013 update", "abstract": "We present an updated review of Lorentz invariance tests in Effective field theories (EFT) in the matter as well as in the gravity sector. After a general discussion of the role of Lorentz invariance and a derivation of its transformations along the so called von Ignatovski theorem, we present the dynamical frameworks developed within local EFT and the available constraints on the parameters governing the Lorentz breaking effects. In the end, we discuss two specific examples, the OPERA \"affaire\" and the case of Ho\u0159ava-Lifshitz gravity. The first case will serve as an example, and a caveat, of the practical application of the general techniques developed for constraining Lorentz invariance violation (LIV) to a direct observation potentially showing these effects. The second case will show how the application of the same techniques to a specific quantum gravity scenario has far fetching implications not foreseeable in a purely phenomenological EFT approach.", "keyphrases": ["lorentz invariance", "gravity", "violation", "liv", "planck scale"]}
{"id": "1305.0813", "title": "Hemispherical Asymmetry and Local non-Gaussianity: a Consistency Condition", "abstract": "In this paper we provide a consistency relation between the amplitude of the hemispherical bipolar asymmetry, A, and the amplitude of the primordial non-Gaussianity in the squeezed limit, f_NL, as |A| \u2272 10^-1 f_NL. We demonstrate that this consistency condition is at work for any model of inflation in which the curvature perturbations is sourced by a single light field with the Bunch-Davies initial condition, irrespective of the number of inflation fields which contribute to the background inflationary expansion. As a non-trivial example, we show that observable hemispherical asymmetry can be generated in single field non-attractor inflationary models. We also study hemispherical asymmetry generated in the models of multiple fields inflation. We show that A is controlled by the weighted sum of non-Gaussianity contribution from each field. In particular, we show that observable hemispherical asymmetry can be generated in models where inhomogeneities are generated from a light scalar field modulating the surface of end of inflation.", "keyphrases": ["non-gaussianity", "consistency condition", "hemispherical asymmetry", "formalism"]}
{"id": "1010.5546", "title": "Interior Models of Uranus and Neptune", "abstract": "'Empirical' models (pressure vs. density) of Uranus and Neptune interiors constrained by the gravitational coefficients J_2, J_4, the planetary radii and masses, and Voyager solid-body rotation periods are presented. The empirical pressure-density profiles are then interpreted in terms of physical equations of state of hydrogen, helium, ice (H_2O), and rock (SiO_2) to test the physical plausibility of the models. The compositions of Uranus and Neptune are found to be similar with somewhat different distributions of the high-Z material. The big difference between the two planets is that Neptune requires a non-solar envelope while Uranus is best matched with a solar composition envelope. Our analysis suggests that the heavier elements in both Uranus' and Neptune's interior might increase gradually towards the planetary centers. Indeed it is possible to fit the gravitational moments without sharp compositional transitions.", "keyphrases": ["uranus", "planet", "interior"]}
{"id": "1307.1883", "title": "Wormhole geometries in Eddington-inspired Born-Infeld gravity", "abstract": "Eddington-inspired Born-Infeld gravity (EiBI) gravity is a recently proposed modified theory of gravity, based on the classic work of Eddington and on Born-Infeld nonlinear electrodynamics. In this paper, we consider the possibility that wormhole geometries are sustained in EiBI gravity. We present the gravitational field equations for an anisotropic stress-energy tensor and consider the generic conditions, for the auxiliary metric, at the wormhole throat. In addition to this, we obtain an exact solution for an asymptotically flat wormhole.", "keyphrases": ["born-infeld gravity", "wormhole geometry", "gravitational fluid"]}
{"id": "1701.02754", "title": "Circular polarisation: a new probe of dark matter and neutrinos in the sky", "abstract": "The study of anomalous electromagnetic emission in the sky is the basis of indirect searches for dark matter. It is also a powerful tool to constrain the radiative decay of active neutrinos. Until now, quantitative analyses have focused on the flux and energy spectrum of such an emission; polarisation has never been considered. Here we show that we could be missing out on an essential piece of information. The radiative decay of neutrinos, as well as the interactions of dark matter and neutrinos with Standard Model particles can generate a circular polarisation signal in X-rays or \u03b3-rays. If observed, this could reveal important information about their spatial distribution and particle-antiparticle ratio, and could even reveal the nature of the high-energy particle physics processes taking place in astrophysical sites. The question of the observability of these polarised signatures and their separation from background astrophysical sources is left for future work.", "keyphrases": ["polarisation", "dark matter", "neutrino"]}
{"id": "1212.4160", "title": "Dark radiation from particle decay: cosmological constraints and opportunities", "abstract": "We study particle decay as the origin of dark radiation. After elaborating general properties and useful parametrisations we provide model-independent and easy-to-use constraints from nucleosynthesis, the cosmic microwave background and structure formation. Bounds on branching ratios and mass hierarchies depend in a unique way on the time of decay. We demonstrate their power to exclude well-motivated scenarios taking the example of the lightest ordinary sparticle decaying into the gravitino. We point out signatures and opportunities in cosmological observations and structure formation. For example, if there are two dark decay modes, dark radiation and the observed dark matter with adjustable free-streaming can originate from the same decaying particle, solving small-scale problems of structure formation. Hot dark matter mimicking a neutrino mass scale as deduced from cosmological observations can arise and possibly be distinguished after a discovery. Our results can be used as a guideline for model building.", "keyphrases": ["particle decay", "gravitino", "dark radiation"]}
{"id": "1403.1780", "title": "Transit Search from Antarctica and Chile - Comparison and Combination", "abstract": "Observing sites at the East-Antarctic plateau are considered to provide exceptional conditions for astronomy. The aim of this work is to assess its potential for detecting transiting extrasolar planets through a comparison and combination of photometric data from Antarctica with time series from a midlatitude site. During 2010, the two small aperture telescopes ASTEP 400 (Dome C) and BEST II (Chile) together performed an observing campaign of two target fields and the transiting planet WASP-18b. For the latter, a bright star, Dome C appears to yield an advantageous signal-to-noise ratio. For field surveys, both Dome C and Chile appear to be of comparable photometric quality. However, within two weeks, observations at Dome C yield a transit detection efficiency that typically requires a whole observing season in Chile. For the first time, data from Antarctica and Chile have been combined to extent the observational duty cycle. This approach is both feasible in practice and favorable for transit search, as it increases the detection yield by 12-18", "keyphrases": ["antarctica", "chile", "site", "transit search"]}
{"id": "1004.1637", "title": "Non-Gaussian halo assembly bias", "abstract": "The strong dependence of the large-scale dark matter halo bias on the (local) non-Gaussianity parameter, f_NL, offers a promising avenue towards constraining primordial non-Gaussianity with large-scale structure surveys. In this paper, we present the first detection of the dependence of the non-Gaussian halo bias on halo formation history using N-body simulations. We also present an analytic derivation of the expected signal based on the extended Press-Schechter formalism. In excellent agreement with our analytic prediction, we find that the halo formation history-dependent contribution to the non-Gaussian halo bias (which we call non-Gaussian halo assembly bias) can be factorized in a form approximately independent of redshift and halo mass. The correction to the non-Gaussian halo bias due to the halo formation history can be as large as 100 enhancement for old halos. This could in principle be a problem for realistic galaxy surveys if observational selection effects were to pick galaxies occupying only recently formed halos. Current semi-analytic galaxy formation models, for example, imply an enhancement in the expected signal of 23 48 respectively.", "keyphrases": ["halo assembly bias", "simulation", "-body simulation"]}
{"id": "1110.2484", "title": "Improved constraints on the primordial power spectrum at small scales from ultracompact minihalos", "abstract": "For a Gaussian spectrum of primordial density fluctuations, ultracompact minihalos (UCMHs) of dark matter are expected to be produced in much greater abundance than, e.g., primordial black holes. Forming shortly after matter-radiation equality, these objects would develop very dense and spiky dark matter profiles. In the standard scenario where dark matter consists of thermally-produced, weakly-interacting massive particles, UCMHs could thus appear as highly luminous gamma-ray sources, or leave an imprint in the cosmic microwave background by changing the reionisation history of the Universe. We derive corresponding limits on the cosmic abundance of UCMHs at different epochs, and translate them into constraints on the primordial power spectrum. We find the resulting constraints to be quite severe, especially at length scales much smaller than what can be directly probed by the cosmic microwave background or large-scale structure observations. We use our results to provide an updated compilation of the best available constraints on the power of density fluctuations on all scales, ranging from the present-day horizon to scales more than 20 orders of magnitude smaller.", "keyphrases": ["primordial power spectrum", "dark matter", "black hole", "matter particle"]}
{"id": "1801.01503", "title": "No Slip Gravity", "abstract": "A subclass of the Horndeski modified gravity theory we call No Slip Gravity has particularly interesting properties: 1) a speed of gravitational wave propagation equal to the speed of light, 2) equality between the effective gravitational coupling strengths to matter and light, G_ matter and G_ light, hence no slip between the metric potentials, yet difference from Newton's constant, and 3) suppressed growth to give better agreement with galaxy clustering observations. We explore the characteristics and implications of this theory, and project observational constraints. We also give a simple expression for the ratio of the gravitational wave standard siren distance to the photon standard candle distance, in this theory and others, and enable a direct comparison of modified gravity in structure growth and in gravitational waves, an important crosscheck.", "keyphrases": ["slip gravity", "photon", "structure growth"]}
{"id": "1605.04023", "title": "LIGO gravitational wave detection, primordial black holes and the near-IR cosmic infrared background anisotropies", "abstract": "LIGO's discovery of a gravitational wave from two merging black holes (BHs) of similar masses rekindled suggestions that primordial BHs (PBHs) make up the dark matter (DM). If so, PBHs would add a Poissonian isocurvature density fluctuation component to the inflation-produced adiabatic density fluctuations. For LIGO's BH parameters, this extra component would dominate the small-scale power responsible for collapse of early DM halos at z>10, where first luminous sources formed. We quantify the resultant increase in high-z abundances of collapsed halos that are suitable for producing the first generation of stars and luminous sources. The significantly increased abundance of the early halos would naturally explain the observed source-subtracted near-IR cosmic infrared background (CIB) fluctuations, which cannot be accounted for by known galaxy populations. For LIGO's BH parameters this increase is such that the observed CIB fluctuation levels at 2 to 5 micron can be produced if only a tiny fraction of baryons in the collapsed DM halos forms luminous sources. Gas accretion onto these PBHs in collapsed halos, where first stars should also form, would straightforwardly account for the observed high coherence between the CIB and unresolved cosmic X-ray background in soft X-rays. We discuss modifications possibly required in the processes of first star formation if LIGO-type BHs indeed make up the bulk or all of DM. The arguments are valid only if the PBHs make up all, or at least most, of DM, but at the same time the mechanism appears inevitable if DM is made of PBHs.", "keyphrases": ["black hole", "dark matter", "x-ray background", "universe"]}
{"id": "1408.4805", "title": "Observation of Small-scale Anisotropy in the Arrival Direction Distribution of TeV Cosmic Rays with HAWC", "abstract": "The High-Altitude Water Cherenkov (HAWC) Observatory is sensitive to gamma rays and charged cosmic rays at TeV energies. The detector is still under construction, but data acquisition with the partially deployed detector started in 2013. An analysis of the cosmic-ray arrival direction distribution based on 4.9\u00d7 10^10 events recorded between June 2013 and February 2014 shows anisotropy at the 10^-4 level on angular scales of about 10^\u2218. The HAWC cosmic-ray sky map exhibits three regions of significantly enhanced cosmic-ray flux; two of these regions were first reported by the Milagro experiment. A third region coincides with an excess recently reported by the ARGO-YBJ experiment. An angular power spectrum analysis of the sky shows that all terms up to \u2113=15 contribute significantly to the excesses.", "keyphrases": ["small-scale anisotropy", "arrival direction distribution", "cosmic ray"]}
{"id": "1407.5625", "title": "Challenges in Explaining the Galactic Center Gamma-Ray Excess with Millisecond Pulsars", "abstract": "Millisecond pulsars have been discussed as a possible source of the gamma-ray excess observed from the region surrounding the Galactic Center. With this in mind, we use the observed population of bright low-mass X-ray binaries to estimate the number of millisecond pulsars in the Inner Galaxy. This calculation suggests that only 1-5 pulsars. We also use the luminosity function derived from local measurements of millisecond pulsars, along with the number of point sources resolved by Fermi, to calculate an upper limit for the diffuse emission from such a population. While this limit is compatible with the millisecond pulsar population implied by the number of low-mass X-ray binaries, it strongly excludes the possibility that most of the excess originates from such objects.", "keyphrases": ["pulsar", "low-mass x-ray binary", "inner galaxy"]}
{"id": "1007.3204", "title": "Cyclic cosmology from Lagrange-multiplier modified gravity", "abstract": "We investigate cyclic and singularity-free evolutions in a universe governed by Lagrange-multiplier modified gravity, either in scalar-field cosmology, as well as in f(R) one. In the scalar case, cyclicity can be induced by a suitably reconstructed simple potential, and the matter content of the universe can be successfully incorporated. In the case of f(R)-gravity, cyclicity can be induced by a suitable reconstructed second function f_2(R) of a very simple form, however the matter evolution cannot be analytically handled. Furthermore, we study the evolution of cosmological perturbations for the two scenarios. For the scalar case the system possesses no wavelike modes due to a dust-like sound speed, while for the f(R) case there exist an oscillation mode of perturbations which indicates a dynamical degree of freedom. Both scenarios allow for stable parameter spaces of cosmological perturbations through the bouncing point.", "keyphrases": ["cosmology", "lagrange-multiplier", "gravity", "alternative theory"]}
{"id": "2007.10340", "title": "HInet: Generating neutral hydrogen from dark matter with neural networks", "abstract": "Upcoming 21cm surveys will map the spatial distribution of cosmic neutral hydrogen (HI) over very large cosmological volumes. In order to maximize the scientific return of these surveys, accurate theoretical predictions are needed. Hydrodynamic simulations currently are the most accurate tool to provide those predictions in the mildly to non-linear regime. Unfortunately, their computational cost is very high: tens of millions of CPU hours. We use convolutional neural networks to find the mapping between the spatial distribution of matter from N-body simulations and HI from the state-of-the-art hydrodynamic simulation IllustrisTNG. Our model performs better than the widely used theoretical model: Halo Occupation Distribution (HOD) for all statistical properties up to the non-linear scales k\u22721 h/Mpc. Our method allows the generation of 21cm mocks over very big cosmological volumes with similar properties as hydrodynamic simulations.", "keyphrases": ["neutral hydrogen", "dark matter", "neural network"]}
{"id": "1101.0811", "title": "Measuring the Spins of Accreting Black Holes", "abstract": "A typical galaxy is thought to contain tens of millions of stellar-mass black holes, the collapsed remnants of once massive stars, and a single nuclear supermassive black hole. Both classes of black holes accrete gas from their environments. The accreting gas forms a flattened orbiting structure known as an accretion disk. During the past several years, it has become possible to obtain measurements of the spins of the two classes of black holes by modeling the X-ray emission from their accretion disks. Two methods are employed, both of which depend upon identifying the inner radius of the accretion disk with the innermost stable circular orbit (ISCO), whose radius depends only on the mass and spin of the black hole. In the Fe K method, which applies to both classes of black holes, one models the profile of the relativistically-broadened iron line with a special focus on the gravitationally redshifted red wing of the line. In the continuum-fitting method, which has so far only been applied to stellar-mass black holes, one models the thermal X-ray continuum spectrum of the accretion disk. We discuss both methods, with a strong emphasis on the continuum-fitting method and its application to stellar-mass black holes. Spin results for eight stellar-mass black holes are summarized. These data are used to argue that the high spins of at least some of these black holes are natal, and that the presence or absence of relativistic jets in accreting black holes is not entirely determined by the spin of the black hole.", "keyphrases": ["spin", "black hole", "continuum-fitting method"]}
{"id": "1302.6247", "title": "Simulations of particle acceleration beyond the classical synchrotron burnoff limit in magnetic reconnection: An explanation of the Crab flares", "abstract": "It is generally accepted that astrophysical sources cannot emit synchrotron radiation above 160 MeV in their rest frame. This limit is given by the balance between the accelerating electric force and the radiation reaction force acting on the electrons. The discovery of synchrotron gamma-ray flares in the Crab Nebula, well above this limit, challenges this classical picture of particle acceleration. To overcome this limit, particles must accelerate in a region of high electric field and low magnetic field. This is possible only with a non-ideal magnetohydrodynamic process, like magnetic reconnection. We present the first numerical evidence of particle acceleration beyond the synchrotron burnoff limit, using a set of 2D particle-in-cell simulations of ultra-relativistic pair plasma reconnection. We use a new code, Zeltron, that includes self-consistently the radiation reaction force in the equation of motion of the particles. We demonstrate that the most energetic particles move back and forth across the reconnection layer, following relativistic Speiser orbits. These particles then radiate >160 MeV synchrotron radiation rapidly, within a fraction of a full gyration, after they exit the layer. Our analysis shows that the high-energy synchrotron flux is highly variable in time because of the strong anisotropy and inhomogeneity of the energetic particles. We discover a robust positive correlation between the flux and the cut-off energy of the emitted radiation, mimicking the effect of relativistic Doppler amplification. A strong guide field quenches the emission of >160 MeV synchrotron radiation. Our results are consistent with the observed properties of the Crab flares, supporting the reconnection scenario.", "keyphrases": ["particle acceleration", "synchrotron burnoff limit", "magnetic reconnection"]}
{"id": "1305.1337", "title": "Limits on the dependence of the fine-structure constant on gravitational potential from white-dwarf spectra", "abstract": "We propose a new probe of the dependence of the fine structure constant, alpha, on a strong gravitational field using metal lines in the spectra of white dwarf stars. Comparison of laboratory spectra with far-UV astronomical spectra from the white dwarf star G191-B2B recorded by the Hubble Space Telescope Imaging Spectrograph gives limits on the fractional variation of alpha of (Delta alpha/alpha)=(4.2 +- 1.6)x10^(-5) and (-6.1 +- 5.8)x10^(-5) from Fe V and Ni V spectra, respectively, at a dimensionless gravitational potential relative to Earth of (Delta phi) 5x10^(-5). With better determinations of the laboratory wavelengths of the lines employed these results could be improved by up to two orders of magnitude.", "keyphrases": ["fine-structure constant", "gravitational field", "white dwarf"]}
{"id": "1510.06930", "title": "Degenerate higher derivative theories beyond Horndeski: evading the Ostrogradski instability", "abstract": "Theories with higher order time derivatives generically suffer from ghost-like instabilities, known as Ostrogradski instabilities. This fate can be avoided by considering \"degenerate\" Lagrangians, whose kinetic matrix cannot be inverted, thus leading to constraints between canonical variables and a reduced number of physical degrees of freedom. In this work, we derive in a systematic way the degeneracy conditions for scalar-tensor theories that depend quadratically on second order derivatives of a scalar field. We thus obtain a classification of all degenerate theories within this class of scalar-tensor theories. The quartic Horndeski Lagrangian and its extension beyond Horndeski belong to these degenerate cases. We also identify new families of scalar-tensor theories with the intriguing property that they are degenerate despite the nondegeneracy of the purely scalar part of their Lagrangian.", "keyphrases": ["ostrogradsky instability", "lagrangians", "scalar-tensor theory", "horndeski theory"]}
{"id": "1807.11495", "title": "Femtolensing by Dark Matter Revisited", "abstract": "Femtolensing of gamma ray bursts (GRBs) has been put forward as an exciting possibility to probe exotic astrophysical objects with masses below 10^-13 solar masses such as small primordial black holes or ultra-compact dark matter minihalos, made up for instance of QCD axions. In this paper we critically review this idea, properly taking into account the extended nature of the source as well as wave optics effects. We demonstrate that most GRBs are inappropriate for femtolensing searches due to their large sizes. This removes the previous femtolensing bounds on primordial black holes, implying that vast regions of parameter space for primordial black hole dark matter are not robustly constrained. Still, we entertain the possibility that a small fraction of GRBs, characterized by fast variability can have smaller sizes and be useful. However, a large number of such bursts would need to be observed to achieve meaningful constraints. We study the sensitivity of future observations as a function of the number of detected GRBs and of the size of the emission region.", "keyphrases": ["dark matter", "black hole", "femtolensing", "mass range", "gravitational wave"]}
{"id": "1409.4472", "title": "Nonlocal Gravity: The General Linear Approximation", "abstract": "The recent classical nonlocal generalization of Einstein's theory of gravitation is presented within the framework of general relativity via the introduction of a preferred frame field. The nonlocal generalization of Einstein's field equations is derived. The linear approximation of nonlocal gravity (NLG) is thoroughly examined and the solutions of the corresponding field equations are discussed. It is shown that nonlocality, with a characteristic length scale of order 1 kpc, simulates dark matter in the linear regime while preserving causality. Light deflection in linearized nonlocal gravity is studied in connection with gravitational lensing; in particular, the propagation of light in the weak gravitational field of a uniformly moving source is investigated. The astrophysical implications of the results are briefly mentioned.", "keyphrases": ["general linear approximation", "einstein", "nonlocal gravity"]}
{"id": "1204.4114", "title": "Observational Evidence of AGN Feedback", "abstract": "Radiation, winds and jets from the active nucleus of a massive galaxy can interact with its interstellar medium leading to ejection or heating of the gas. This can terminate star formation in the galaxy and stifle accretion onto the black hole. Such Active Galactic Nucleus (AGN) feedback can account for the observed proportionality between central black hole and host galaxy mass. Direct observational evidence for the radiative or quasar mode of feedback, which occurs when the AGN is very luminous, has been difficult to obtain but is accumulating from a few exceptional objects. Feedback from the kinetic or radio mode, which uses the mechanical energy of radio-emitting jets often seen when the AGN is operating at a lower level, is common in massive elliptical galaxies. This mode is well observed directly through X-ray observations of the central galaxies of cool core clusters in the form of bubbles in the hot surrounding medium. The energy flow, which is roughly continuous, heats the hot intracluster gas and reduces radiative cooling and subsequent star formation by an order of magnitude. Feedback appears to maintain a long-lived heating/cooling balance. Powerful, jetted radio outbursts may represent a further mode of energy feedback which affect the cores of groups and subclusters. New telescopes and instruments from the radio to X-ray bands will come into operation over the next few years and lead to a rapid expansion in observational data on all modes of AGN feedback.", "keyphrases": ["agn feedback", "group", "observational evidence"]}
{"id": "1901.11181", "title": "Large-scale inhomogeneity of dark energy produced in the ancestor vacuum", "abstract": "We investigate large-scale inhomogeneity of dark energy in the bubble nucleation scenario of the universe. In this scenario, the present universe was created by a bubble nucleation due to quantum tunneling from a metastable ancestor vacuum, followed by a primordial inflationary era. During the bubble nucleation, supercurvature modes of some kind of a scalar field are produced, and remain until present without decaying; thus they can play a role of the dark energy, if the mass of the scalar field is sufficiently light in the present universe. The supercurvature modes fluctuate at a very large spatial scale, much longer than the Hubble length in the present universe. Thus they create large-scale inhomogeneities of the dark energy, and generate large-scale anisotropies in the cosmic microwave background (CMB) fluctuations. This is a notable feature of this scenario, where quantum fluctuations of a scalar field are responsible for the dark energy. In this paper, we calculate imprints of the scenario on the CMB anisotropies through the integrated Sachs-Wolfe (ISW) effect, and give observational constraints on the curvature parameter \u03a9_K and on an additional parameter \u03f5 describing some properties of the ancestor vacuum.", "keyphrases": ["dark energy", "ancestor vacuum", "large-scale inhomogeneity"]}
{"id": "1008.3902", "title": "Testing the No-Hair Theorem with Observations of Black Holes in the Electromagnetic Spectrum", "abstract": "According to the no-hair theorem, astrophysical black holes are uniquely described by their mass and spin. In this paper, we review a new framework for testing the no-hair hypothesis with observations in the electromagnetic spectrum. The approach is formulated in terms of a Kerr-like spacetime containing a quadrupole moment that is independent of both mass and spin. If the no-hair theorem is correct, then any deviation from the Kerr metric quadrupole has to be zero. We show how upcoming VLBI imaging observations of Sgr A* as well as spectroscopic observations of iron lines from accreting black holes with IXO may lead to the first astrophysical test of the no-hair theorem.", "keyphrases": ["no-hair theorem", "black hole", "electromagnetic spectrum"]}
{"id": "1203.6776", "title": "Inhomogeneous vacuum energy", "abstract": "Vacuum energy remains the simplest model of dark energy which could drive the accelerated expansion of the Universe without necessarily introducing any new degrees of freedom. Inhomogeneous vacuum energy is necessarily interacting in general relativity. Although the four-velocity of vacuum energy is undefined, an interacting vacuum has an energy transfer and the vacuum energy defines a particular foliation of spacetime with spatially homogeneous vacuum energy in cosmological solutions. It is possible to give a consistent description of vacuum dynamics and in particular the relativistic equations of motion for inhomogeneous perturbations given a covariant prescription for the vacuum energy, or equivalently the energy transfer four-vector, and we construct gauge-invariant vacuum perturbations. We show that any dark energy cosmology can be decomposed into an interacting vacuum+matter cosmology whose inhomogeneous perturbations obey simple first-order equations.", "keyphrases": ["vacuum energy", "dark energy", "four-velocity", "inhomogeneous perturbation", "dark matter"]}
{"id": "1108.2789", "title": "Cosmography in f(T)-gravity", "abstract": "Being based on the only assumption that the universe is homogenous and isotropic on large scales, cosmography is an ideal tool to investigate the cosmic expansion history in a almost model-independent way. Fitting the data on the luminosity distance and Baryon Acoustic Oscillations allows to determine the confidence ranges for the cosmographic parameters hence giving some quantitative constraints that a whatever theory has to fulfill. As an application, we consider here the case of teleparallel gravity (TEGR) also referred to as f(T)-gravity. To this end, we first work out analytical expressions to express the present day values of f(T)-derivatives as a function of the cosmographic parameters which hold under quite general and physically motivated conditions. We then use the constraints coming from cosmography to find out the confidence ranges for f(T)-derivatives up to the fifth order and show how these can be used to check the viability of given TEGR models without the need to explicitly solve the second order dynamic equations.", "keyphrases": ["f(t)-gravity", "cosmography", "general relativity"]}
{"id": "1502.03458", "title": "Consistently violating the non-Gaussian consistency relation", "abstract": "Non-attractor models of inflation are characterized by the super-horizon evolution of curvature perturbations, introducing a violation of the non-Gaussian consistency relation between the bispectrum's squeezed limit and the power spectrum's spectral index. In this work we show that the bispectrum's squeezed limit of non-attractor models continues to respect a relation dictated by the evolution of the background. We show how to derive this relation using only symmetry arguments, without ever needing to solve the equations of motion for the perturbations.", "keyphrases": ["violation", "consistency relation", "non-attractor model", "curvature perturbation", "slow-roll"]}
{"id": "0905.1552", "title": "Non-Gaussianity from Isocurvature Perturbations : Analysis of Trispectrum", "abstract": "Non-Gaussianity may exist in the CDM isocurvature perturbation. We provide general expressions for the bispectrum and trispectrum of both adiabatic and isocurvature pertubations. We apply our result to the QCD axion case, and found a consistency relation between the coefficients of the bispectrum and trispectrum : tau_NL^(iso) 10^3 [f_NL^(iso)]^4/3, if the axion is dominantly produced by quantum fluctuation. Thus future observations of the trispectrum, as well as the bispectrum, will be important for understanding the origin of the CDM and baryon asymmetry.", "keyphrases": ["trispectrum", "non-gaussianity", "isocurvature mode"]}
{"id": "1304.4723", "title": "Magnetic field amplification by the small-scale dynamo in the early Universe", "abstract": "In this paper we show that the Universe is already strongly magnetized at very early epochs during cosmic evolution. Our calculations are based on the efficient amplification of weak magnetic seed fields, which are unavoidably present in the early Universe, by the turbulent small-scale dynamo. We identify two mechanisms for the generation of turbulence in the radiation dominated epoch where velocity fluctuations are produced by the primordial density perturbation and by possible first-order phase transitions at the electroweak or QCD scales. We show that all the necessities for the small-scale dynamo to work are fulfilled. Hence, this mechanism, operating due to primordial density perturbations, guarantees fields with comoving field strength B_0\u223c10^-6\u03b5^1/2 nG on scales up to \u03bb_c\u223c0.1 pc, where \u03b5 is the saturation efficiency. The amplification of magnetic seed fields could be even larger if there are first-order phase transitions in the early Universe. Where, on scales up to \u03bb_c\u223c100 pc, the comoving field strength due to this mechanism will be B_0\u223c10^-3\u03b5^1/2 nG at the present time. Such fields, albeit on small scales, can play an important role in structure formation and could provide an explanation to the apparently observed magnetic fields in the voids of the large-scale structure.", "keyphrases": ["small-scale dynamo", "early universe", "density perturbation", "magnetic field amplification"]}
{"id": "1103.5974", "title": "Inhomogeneities in the universe", "abstract": "Standard models of galaxy formation predict that matter distribution is statistically homogeneous and isotropic and characterized by (i) spatial homogeneity for r<10 Mpc/h, (ii) small-amplitude structures of relatively limited size (i.e., r<100) Mpc/h and (iii) anti-correlations for r > r_c 150 Mpc/h (i.e., no structures of size larger than r_c). Whether or not the observed galaxy distribution is interpreted to be compatible with these predictions depend on the a-priori assumptions encoded in the statistical methods employed to characterize the data and on the a-posteriori hypotheses made to interpret the results. We present strategies to test the most common assumptions and we find evidences that, in the available samples, galaxy distribution is spatially inhomogeneous for r<100 Mpc/h but statistically homogeneous and isotropic. We conclude that the observed inhomogeneities pose a fundamental challenge to the standard picture of cosmology but they also represent an important opportunity which may open new directions for many cosmological puzzles.", "keyphrases": ["universe", "galaxy distribution", "inhomogeneity"]}
{"id": "1705.09667", "title": "Observational evidence for intermediate-mass black holes", "abstract": "Intermediate-mass black holes (IMBHs), with masses in the range 100-10^6 M_\u2299, are the link between stellar-mass BHs and supermassive BHs (SMBHs). They are thought to be the seeds from which SMBHs grow, which would explain the existence of quasars with BH masses of up to 10^10 M_\u2299 when the Universe was only 0.8 Gyr old. The detection and study of IMBHs has thus strong implications for understanding how SMBHs form and grow, which is ultimately linked to galaxy formation and growth, as well as for studies of the universality of BH accretion or the epoch of reionisation. Proving the existence of seed BHs in the early Universe is not yet feasible with the current instrumentation; however, those seeds that did not grow into SMBHs can be found as IMBHs in the nearby Universe. In this review I summarize the different scenarios proposed for the formation of IMBHs and gather all the observational evidence for the few hundreds of nearby IMBH candidates found in dwarf galaxies, globular clusters, and ultraluminous X-ray sources, as well as the possible discovery of a few seed BHs at high redshift. I discuss some of their properties, such as X-ray weakness and location in the BH mass scaling relations, and the possibility to discover IMBHs through high velocity clouds, tidal disruption events, gravitational waves, or accretion disks in active galactic nuclei. I finalize with the prospects for the detection of IMBHs with up-coming observatories.", "keyphrases": ["intermediate-mass black hole", "dwarf galaxy", "globular cluster"]}
{"id": "1511.03696", "title": "Grain Alignment: Role of Radiative Torques and Paramagnetic Relaxation", "abstract": "Polarization arising from aligned dust grains presents a unique opportunity to study magnetic fields in the diffuse interstellar medium and molecular clouds. Polarization from circumstellar regions, accretion disks and comet atmospheres can also be related to aligned dust.To reliably trace magnetic fields quantitative theory of grain alignment is required. Formulating the theory that would correspond to observations was one of the longstanding problems in astrophysics. Lately this problem has been successfully addressed, and in this review we summarize some of the most important theoretical advances in the theory of grain alignment by radiative torques (RATs) that act on realistic irregular dust grains. We discuss an analytical model of RATs and the ways to make RAT alignment more efficient, e.g. through paramagnetic relaxation when grains have inclusions with strong magnetic response. For very small grains for which RAT alignment is inefficient, we also discuss paramagnetic relaxation and a process termed resonance relaxation. We provide an extensive analysis of the observational tests of grain alignment theory.", "keyphrases": ["paramagnetic relaxation", "dust grain", "magnetic field", "grain alignment"]}
{"id": "1006.1731", "title": "Dark Matter from Split Seesaw", "abstract": "The seesaw mechanism in models with extra dimensions is shown to be generically consistent with a broad range of Majorana masses. The resulting democracy of scales implies that the seesaw mechanism can naturally explain the smallness of neutrino masses for an arbitrarily small right-handed neutrino mass. If the scales of the seesaw parameters are split, with two right-handed neutrinos at a high scale and one at a keV scale, one can explain the matter-antimatter asymmetry of the universe, as well as dark matter. The dark matter candidate, a sterile right-handed neutrino with mass of several keV, can account for the observed pulsar velocities and for the recent data from Chandra X-ray Observatory, which suggest the existence of a 5 keV sterile right-handed neutrino.", "keyphrases": ["seesaw mechanism", "neutrino", "dark matter"]}
{"id": "0912.3592", "title": "Results from the Final Exposure of the CDMS II Experiment", "abstract": "We report results from a blind analysis of the final data taken with the Cryogenic Dark Matter Search experiment (CDMS II) at the Soudan Underground Laboratory, Minnesota, USA. A total raw exposure of 612 kg-days was analyzed for this work. We observed two events in the signal region; based on our background estimate, the probability of observing two or more background events is 23 Particle (WIMP)-nucleon elastic-scattering spin-independent cross-section of 7.0x10^-44 cm^2 for a WIMP of mass 70 GeV/c^2 at the 90 Combining this result with all previous CDMS II data gives an upper limit on the WIMP-nucleon spin-independent cross-section of 3.8x10^-44 cm^2 for a WIMP of mass 70 GeV/c^2. We also exclude new parameter space in recently proposed inelastic dark matter models.", "keyphrases": ["cdms", "candidate event", "cross section", "matter particle", "cdms collaboration"]}
{"id": "0912.0269", "title": "Non-gaussianity in the foreground-reduced CMB maps", "abstract": "[Abridged]: A detection or nondetection of primordial non-Gaussianity by using the CMB data is crucial not only to discriminate inflationary models but also to test alternative scenarios. Non-Gaussianity offers, therefore, a powerful probe of the physics of the primordial universe. The extraction of primordial non-Gaussianity is a difficult enterprise since several effects of non-primordial nature can produce non-Gaussianity. Most of the Gaussianity analyses of CMB data have been performed by using part-sky frequency, where masks are used to deal with the galactic diffuse foreground emission. However, full-sky map seems to be potentially more appropriate to test for Gaussianity of the CMB data. On the other hand, masks can induce bias in some non-Gaussianity analyses. Here we use two recent large-angle non-Gaussianity indicators, based on skewness and kurtosis of large-angle patches of CMB maps, to examine the question of non-Gaussianity in the available full-sky five-year and seven-year WMAP maps. We show that these full-sky foreground-reduced maps present a significant deviation from Gaussianity of different levels, which vary with the foreground-reducing procedures. We also make a Gaussianity analysis of the foreground-reduced five-year and seven-year WMAP maps with a KQ75 mask, and compare with the similar analysis performed with the full-sky foreground-reduced maps. This comparison shows a significant reduction in the levels of non-Gaussianity when the mask is employed, which provides indications on the suitability of the foreground-reduced maps as Gaussian reconstructions of the full-sky CMB.", "keyphrases": ["cmb map", "foreground-reduced map", "non-gaussianity", "large-angle deviation"]}
{"id": "0912.0397", "title": "Constraints on the anisotropy of dark energy", "abstract": "If the equation of state of dark energy is anisotropic there will be additional quadrupole anisotropy in the cosmic microwave background induced by the time dependent anisotropic stress quantified in terms of \u0394 w. Assuming that the entire amplitude of the observed quadrupole is due to this anisotropy, we conservatively impose a limit of |\u0394 w| < 2.1\u00d7 10^-4 for any value of w\u2265 -1 assuming that \u03a9_ m<0.5. This is considerably tighter than that which comes from SNe. Stronger limits, upto a factor of 10, are possible for specific values of \u03a9_ m and w. Since we assume this component is uncorrelated with the stochastic component from inflation, we find that both the expectation value and the sample variance are increased. There no improvement in the likelihood of an anomalously low quadrupole as suggested by previous work on an elliptical universe.", "keyphrases": ["anisotropy", "dark energy", "cosmic microwave background"]}
{"id": "1606.03747", "title": "Probing primordial features with future galaxy surveys", "abstract": "We study the capability of future measurements of the galaxy clustering power spectrum to probe departures from a power-law spectrum for primordial fluctuations. On considering the information from the galaxy clustering power spectrum up to quasi-linear scales, i.e. k<0.1 h Mpc^-1, we present forecasts for DESI, Euclid and SPHEREx in combination with CMB measurements. As examples of departures in the primordial power spectrum from a simple power-law, we consider four Planck 2015 best-fits motivated by inflationary models with different breaking of the slow-roll approximation. These four representative models provide an improved fit to CMB temperature anisotropies, although not at statistical significant level. As for other extensions in the matter content of the simplest \u039bCDM model, the complementarity of the information in the resulting matter power spectrum expected from these galaxy surveys and in the primordial power spectrum from CMB anisotropies can be effective in constraining cosmological models. We find that the three galaxy surveys can add significant information to CMB to better constrain the extra parameters of the four models considered.", "keyphrases": ["primordial feature", "galaxy survey", "matter power spectrum"]}
{"id": "1901.10152", "title": "Resonant multiple peaks in the induced gravitational waves", "abstract": "We identify analytically a multiple-peak structure in the energy-density spectrum of induced gravitational waves (GWs) generated at second-order from a primordial scalar perturbations also with multiple(n) peaks at small scales k_*i. The energy-density spectrum of induced GWs exhibits at most C_n+1^2 and at least n peaks at wave-vectors k_ij\u2261(k_*i+k_*j)/\u221a(3) due to resonant amplification, and, under the narrow-width approximation, it contains an universal factor that can be interpreted as a result of momentum conservation. We also extend these discussions to the case of non-Gaussian perturbations.", "keyphrases": ["peak", "gravitational wave", "curvature perturbation"]}
{"id": "1906.11476", "title": "A single fast radio burst localized to a massive galaxy at cosmological distance", "abstract": "Fast Radio Bursts (FRBs) are brief radio emissions from distant astronomical sources. Some are known to repeat, but most are single bursts. Non-repeating FRB observations have had insufficient positional accuracy to localize them to an individual host galaxy. We report the interferometric localization of the single pulse FRB 180924 to a position 4 kpc from the center of a luminous galaxy at redshift 0.3214. The burst has not been observed to repeat. The properties of the burst and its host are markedly different from the only other accurately localized FRB source. The integrated electron column density along the line of sight closely matches models of the intergalactic medium, indicating that some FRBs are clean probes of the baryonic component of the cosmic web.", "keyphrases": ["fast radio burst", "galaxy", "cosmological distance"]}
{"id": "1306.2307", "title": "The Hot and Energetic Universe: A White Paper presenting the science theme motivating the Athena+ mission", "abstract": "This White Paper, submitted to the recent ESA call for science themes to define its future large missions, advocates the need for a transformational leap in our understanding of two key questions in astrophysics: 1) How does ordinary matter assemble into the large scale structures that we see today? 2) How do black holes grow and shape the Universe? Hot gas in clusters, groups and the intergalactic medium dominates the baryonic content of the local Universe. To understand the astrophysical processes responsible for the formation and assembly of these large structures, it is necessary to measure their physical properties and evolution. This requires spatially resolved X-ray spectroscopy with a factor 10 increase in both telescope throughput and spatial resolving power compared to currently planned facilities. Feedback from supermassive black holes is an essential ingredient in this process and in most galaxy evolution models, but it is not well understood. X-ray observations can uniquely reveal the mechanisms launching winds close to black holes and determine the coupling of the energy and matter flows on larger scales. Due to the effects of feedback, a complete understanding of galaxy evolution requires knowledge of the obscured growth of supermassive black holes through cosmic time, out to the redshifts where the first galaxies form. X-ray emission is the most reliable way to reveal accreting black holes, but deep survey speed must improve by a factor 100 over current facilities to perform a full census into the early Universe. The Advanced Telescope for High Energy Astrophysics (Athena+) mission provides the necessary performance (e.g. angular resolution, spectral resolution, survey grasp) to address these questions and revolutionize our understanding of the Hot and Energetic Universe. These capabilities will also provide a powerful observatory to be used in all areas of astrophysics.", "keyphrases": ["energetic universe", "science theme", "high-energy astrophysics", "second large mission"]}
{"id": "1306.0004", "title": "Bimetric gravity doubly coupled to matter: theory and cosmological implications", "abstract": "A ghost-free theory of gravity with two dynamical metrics both coupled to matter is shown to be consistent and viable. Its cosmological implications are studied, and the models, in particular in the context of partially massless gravity, are found to explain the cosmic acceleration without resorting to dark energy.", "keyphrases": ["gravity", "cosmological implication", "spin-2 field"]}
{"id": "1411.2349", "title": "Models of the Primordial Standard Clock", "abstract": "Oscillating massive fields in the primordial universe can be used as Standard Clocks. The ticks of these oscillations induce features in the density perturbations, which directly record the time evolution of the scale factor of the primordial universe, thus if detected, provide a direct evidence for the inflation scenario or the alternatives. In this paper, we construct a full inflationary model of primordial Standard Clock and study its predictions on the density perturbations. This model provides a full realization of several key features proposed previously. We compare the theoretical predictions from inflation and alternative scenarios with the Planck 2013 temperature data on Cosmic Microwave Background (CMB), and identify a statistically marginal but interesting candidate. We discuss how future CMB temperature and polarization data, non-Gaussianity analysis and Large Scale Structure data may be used to further test or constrain the Standard Clock signals.", "keyphrases": ["primordial standard clock", "oscillation", "universe", "standard clock signal", "cpsc model"]}
{"id": "1407.7293", "title": "Generalized energy conditions in Extended Theories of Gravity", "abstract": "Theories of physics can be considered viable if the initial value problem and the energy conditions are formulated self-consistently. The former allow a uniquely determined dynamical evolution of the system, and the latter guarantee that causality is preserved and that \"plausible\" physical sources have been considered. In this work, we consider the further degrees of freedom related to curvature invariants and scalar fields in Extended Theories of Gravity (ETG). These new degrees of freedom can be recast as effective perfect fluids that carry different meanings with respect to the standard matter fluids generally adopted as sources of the field equations. It is thus somewhat misleading to apply the standard general relativistic energy conditions to this effective energy-momentum, as the latter contains the matter content and a geometrical quantity, which arises from the ETG considered. Here, we explore this subtlety, extending on previous work, in particular, to cases with the contracted Bianchi identities with diffeomorphism invariance and to cases with generalized explicit curvature-matter couplings, which imply the non-conservation of the energy-momentum tensor. Furthermore, we apply the analysis to specific ETGs, such as scalar-tensor gravity, f(R) gravity and modified Gauss-Bonnet gravity. Interesting results appear such as matter that may exhibit unusual thermodynamical features, for instance, and gravity that retains its attractive character in the presence of negative pressures; or alternatively, we verify that repulsive gravity may occur for standard matter.", "keyphrases": ["energy condition", "extended theories", "gravity", "tensor"]}
{"id": "0902.0548", "title": "Universality of electron-positron distributions in extensive air showers", "abstract": "Using a large set of simulated extensive air showers, we investigate universality features of electron and positron distributions in very-high-energy cosmic-ray air showers. Most particle distributions depend only on the depth of the shower maximum and the number of particles in the cascade at this depth. We provide multi-dimensional parameterizations for the electron-positron distributions in terms of particle energy, vertical and horizontal momentum angle, lateral distance, and time distribution of the shower front. These parameterizations can be used to obtain realistic electron-positron distributions in extensive air showers for data analysis and simulations of Cherenkov radiation, fluorescence signal, and radio emission.", "keyphrases": ["electron-positron distribution", "air shower", "particle energy"]}
{"id": "1901.07183", "title": "Horndeski theory and beyond: a review", "abstract": "This article is intended to review the recent developments in the Horndeski theory and its generalization, which provide us with a systematic understanding of scalar-tensor theories of gravity as well as a powerful tool to explore astrophysics and cosmology beyond general relativity. This review covers the generalized Galileons, (the rediscovery of) the Horndeski theory, cosmological perturbations in the Horndeski theory, cosmology with a violation of the null energy condition, degenerate higher-order scalar-tensor theories and their status after GW170817, the Vainshtein mechanism in the Horndeski theory and beyond, and hairy black hole solutions.", "keyphrases": ["gravity", "null energy condition", "horndeski theory", "dofs", "additional degree"]}
{"id": "2008.04737", "title": "Newtonian Fractional-Dimension Gravity and Disk Galaxies", "abstract": "This paper continues previous work on a novel alternative model of gravity, based on the theory of fractional-dimension spaces applied to Newton's law of gravitation. In particular, our Newtonian Fractional-Dimension Gravity is now applied to axially-symmetric structures, such as thin/thick disk galaxies described by exponential, Kuzmin, or other similar mass distributions. As in the case of spherically-symmetric structures, which was studied in previous work on the subject, we examine a possible connection between our model and Modified Newtonian Dynamics, a leading alternative gravity model, which accounts for the observed properties of galaxies and other astrophysical structures without requiring the dark matter hypothesis. By relating the MOND acceleration constant a_0\u2243 1.2 \u00d7 10^ -10^ -2 to a natural scale length l_0 of our model, namely a_0\u2248 GM/l_0^2 for a galaxy of mass M, and by using the empirical Radial Acceleration Relation, we are able to explain the connection between the observed radial acceleration g_obs and the baryonic radial acceleration g_bar in terms of a variable local dimension D. As an example of this methodology, we provide a detailed rotation curve fitting for the case of the field dwarf spiral galaxy NGC 6503.", "keyphrases": ["disk galaxy", "gravity model", "newtonian fractional-dimension gravity", "alternative gravitational model"]}
{"id": "1503.01775", "title": "The EFT of Large Scale Structures at All Redshifts: Analytical Predictions for Lensing", "abstract": "We study the prediction of the Effective Field Theory of Large Scale Structures (EFTofLSS) for the matter power spectrum at different redshifts. In previous work, we found that the two-loop prediction can match the nonlinear power spectrum measured from N-body simulations at redshift zero within approximately 2 free parameter, the so-called \"speed of sound\". We determine the time evolution of this parameter by matching the EFTofLSS prediction to simulation output at different redshifts, and find that it is well-described by a fitting function that only includes one additional parameter. After the two free parameters are fixed, the prediction agrees with nonlinear data within approximately 2 at least k\u223c 1 h Mpc^-1 at z\u2265 1, and also within approximately 5 2.3 h Mpc^-1atz=3, a major improvement with respect to other perturbative techniques. We also develop an accurate way to estimate where the EFTofLSS predictions at different loop orders should fail, based on the sizes of the next-order terms that are neglected, and find agreement with the actual comparisons to data. Finally, we use our matter power spectrum results to perform analytical calculations of lensing potential power spectra corresponding to both CMB and galaxy lensing. This opens the door to future direct applications of the EFTofLSS to observations of gravitational clustering on cosmic scales.", "keyphrases": ["large scale structures", "redshift", "effective field theory", "dark matter dynamic", "non-linear regime"]}
{"id": "1310.7482", "title": "Primordial non-Gaussianity in the bispectra of large-scale structure", "abstract": "The statistics of large-scale structure in the Universe can be used to probe non-Gaussianity of the primordial density field, complementary to existing constraints from the cosmic microwave background. In particular, the scale dependence of halo bias, which affects the halo distribution at large scales, represents a promising tool for analyzing primordial non-Gaussianity of local form. Future observations, for example, may be able to constrain the trispectrum parameter gNL that is difficult to study and constrain using the CMB alone. We investigate how galaxy and matter bispectra can distinguish between the two non-Gaussian parameters fNL and gNL, whose effects give nearly degenerate contributions to the power spectra. We use a generalization of the univariate bias approach, making the hypothesis that the number density of halos forming at a given position is a function of the local matter density contrast and of its local higher-order statistics. Using this approach, we calculate the halo-matter bispectra and analyze their properties. We determine a connection between the sign of the halo bispectrum on large scales and the parameter gNL. We also construct a combination of halo and matter bispectra that is sensitive to fNL, with little contamination from gNL. We study both the case of single and multiple sources to the primordial gravitational potential, discussing how to extend the concept of stochastic halo bias to the case of bispectra. We use a specific halo mass-function to calculate numerically the bispectra in appropriate squeezed limits, confirming our theoretical findings.", "keyphrases": ["bispectra", "large-scale structure", "primordial non-gaussianity"]}
{"id": "1302.2151", "title": "Lanczos-Lovelock models of gravity", "abstract": "Lanczos-Lovelock models of gravity represent a natural and elegant generalization of Einstein's theory of gravity to higher dimensions. They are characterized by the fact that the field equations only contain up to second derivatives of the metric even though the action functional can be a quadratic or higher degree polynomial in the curvature tensor. Because these models share several key properties of Einstein's theory they serve as a useful set of candidate models for testing the emergent paradigm for gravity. This review highlights several geometrical and thermodynamical aspects of Lanczos-Lovelock models which have attracted recent attention.", "keyphrases": ["gravity", "dimension", "lanczos-lovelock model"]}
{"id": "1205.0792", "title": "Exact Wavelets on the Ball", "abstract": "We develop an exact wavelet transform on the three-dimensional ball (i.e. on the solid sphere), which we name the flaglet transform. For this purpose we first construct an exact transform on the radial half-line using damped Laguerre polynomials and develop a corresponding quadrature rule. Combined with the spherical harmonic transform, this approach leads to a sampling theorem on the ball and a novel three-dimensional decomposition which we call the Fourier-Laguerre transform. We relate this new transform to the well-known Fourier-Bessel decomposition and show that band-limitedness in the Fourier-Laguerre basis is a sufficient condition to compute the Fourier-Bessel decomposition exactly. We then construct the flaglet transform on the ball through a harmonic tiling, which is exact thanks to the exactness of the Fourier-Laguerre transform (from which the name flaglets is coined). The corresponding wavelet kernels are well localised in real and Fourier-Laguerre spaces and their angular aperture is invariant under radial translation. We introduce a multiresolution algorithm to perform the flaglet transform rapidly, while capturing all information at each wavelet scale in the minimal number of samples on the ball. Our implementation of these new tools achieves floating-point precision and is made publicly available. We perform numerical experiments demonstrating the speed and accuracy of these libraries and illustrate their capabilities on a simple denoising example.", "keyphrases": ["ball", "transform", "quadrature rule", "fourier-laguerre basis", "tiling"]}
{"id": "1408.1678", "title": "On couplings to matter in massive (bi-)gravity", "abstract": "We investigate the coupling to matter in ghost-free massive (bi-)gravity. When species in the matter sector couple covariantly to only one metric, we show that at one\u2013loop these couplings do not spoil the special structure of the graviton potential. When the same species couples directly to both metrics we show that a ghost is present at the classical level and that loops destroy the special structure of the potential at an unacceptably low scale. We then propose a new `composite' effective metric built out of both metrics. When matter fields couple covariantly to this effective metric, the would be Boulware\u2013Deser ghost is absent in different representative limits. At one\u2013loop such couplings do not detune the special structure of the potential. We conjecture that matter can couple covariantly to that effective metric in all generality without introducing any Boulware\u2013Deser ghost below a cut-off scale parametrically larger than the strong coupling scale. We also discuss alternative couplings to matter where the kinetic and potential terms of the matter field couple to different metrics. In both cases we discuss preliminary implications for cosmology.", "keyphrases": ["bi-)gravity", "matter field", "ghost-free potential structure"]}
{"id": "1107.0741", "title": "DAMA and CoGeNT without astrophysical uncertainties", "abstract": "The CoGeNT collaboration has reported evidence of an annual modulation in its first fifteen months of data. Here we compare the amplitude and phase of this signal to the modulation observed by the DAMA collaboration, assuming that both arise due to elastically scattering dark matter (DM). We directly map the CoGeNT signal to the DAMA detector without specifying any astrophysical parameters and compare this with the signal measured by DAMA. We also compare with constraints from CDMS II and XENON10. We find that DM of mass 5-14 GeV that couples equally to protons and neutrons is strongly disfavoured. Isospin-violating DM fares better but requires a boosted modulation fraction.", "keyphrases": ["cogent", "astrophysical uncertainty", "dama", "velocity distribution", "detection data"]}
{"id": "1505.03813", "title": "The Nitrogen Budget of Earth", "abstract": "We comprehensively compile and review N content in geologic materials to calculate a new N budget for Earth. Using analyses of rocks and minerals in conjunction with N-Ar geochemistry demonstrates that the Bulk Silicate Earth (BSE) contains \u223c7\u00b14 times present atmospheric N (4\u00d710^18 kg N, PAN), with 27\u00b116\u00d710^18 kg N. Comparison to chondritic composition, after subtracting N sequestered into the core, yields a consistent result, with BSE N between 17\u00b113\u00d710^18 kg to 31\u00b124\u00d710^18 kg N. In the chondritic comparison we calculate a N mass in Earth's core (180\u00b1110 to 300\u00b1180\u00d710^18 kg) and discuss the Moon as a proxy for the early mantle. Significantly, we find the majority of the planetary budget of N is in the solid Earth. The N estimate herein precludes the need for a \"missing N\" reservoir. Nitrogen-Ar systematics in mantle rocks and basalts identify two mantle reservoirs: MORB-source like (MSL) and high-N. High-N mantle is composed of young, N-rich material subducted from the surface and is identified in OIB and some xenoliths. In contrast, MSL appears to be made of old material, though a component of subducted material is evident in this reservoir as well. Using our new budget, we calculate a \u03b415N value for BSE plus atmosphere of \u223c2. This value should be used when discussing bulk Earth N isotope evolution. Additionally, our work indicates that all surface N could pass through the mantle over Earth history, and the mantle may act as a long-term sink for N. Since N acts as a tracer of exchange between the atmosphere, oceans, and mantle over time, clarifying its distribution in the Earth is critical for evolutionary models concerned with Earth system evolution. We suggest that N be viewed in the same vein as carbon: it has a fast, biologically mediated cycle which connects it to a slow, tectonically-controlled geologic cycle.", "keyphrases": ["earth", "bulk silicate earth", "reservoir"]}
{"id": "1304.0484", "title": "On the cosmology of massive gravity", "abstract": "We present a review of cosmological solutions in non-linear massive gravity, focusing on the stability of perturbations. Although homogeneous and isotropic solutions have been found, these are now known to suffer from either Higuchi ghost or a new non-linear ghost instability. We discuss two approaches to alleviate this issue. By relaxing the symmetry of the background by e.g. breaking isotropy in the hidden sector, it is possible to accommodate a stable cosmological solution. Alternatively, extending the theory to allow for new dynamical degrees of freedom can also remove the conditions which lead to the instability. As examples for this case, we study the stability of self-accelerating solutions in the quasi-dilatonic extension and generic cosmological solutions in the varying mass extension. While the quasi-dilaton case turns out to be unstable, the varying mass case allows stable regimes of parameters. Viable self-accelerating solutions in the varying mass theory yet remain to be found.", "keyphrases": ["cosmology", "gravity", "ghost instability"]}
{"id": "1606.00513", "title": "Productive Interactions: heavy particles and non-Gaussianity", "abstract": "We analyze the shape and amplitude of oscillatory features in the primordial power spectrum and non-Gaussianity induced by periodic production of heavy degrees of freedom coupled to the inflaton \u03d5. We find that non-adiabatic production of particles can contribute effects which are detectable or constrainable using cosmological data even if their time-dependent masses are always heavier than the scale \u03d5\u0307^1/2, much larger than the Hubble scale. This provides a new role for UV completion, consistent with the criteria from effective field theory for when heavy fields cannot be integrated out. This analysis is motivated in part by the structure of axion monodromy, and leads to an additional oscillatory signature in a subset of its parameter space. At the level of a quantum field theory model that we analyze in detail, the effect arises consistently with radiative stability for an interesting window of couplings up to of order \u2272 1. The amplitude of the bispectrum and higher-point functions can be larger than that for Resonant Non-Gaussianity, and its signal/noise may be comparable to that of the corresponding oscillations in the power spectrum (and even somewhat larger within a controlled regime of parameters). Its shape is distinct from previously analyzed templates, but was partly motivated by the oscillatory equilateral searches performed recently by the Planck collaboration. We also make some general comments about the challenges involved in making a systematic study of primordial non-Gaussianity.", "keyphrases": ["particle", "non-gaussianity", "heavy field", "collider", "reason"]}
{"id": "2002.03603", "title": "The LISA-Taiji network", "abstract": "Both LISA and Taiji, planned space-based gravitational-wave detectors in orbit around the Sun, are expected to launch in 2030-2035. Assuming a one-year overlap, we explore a potential LISA-Taiji network to fast and accurately localize the gravitational-wave sources.", "keyphrases": ["network", "lisa", "taiji", "mission"]}
{"id": "1211.3202", "title": "Stationary Scalar Clouds Around Rotating Black Holes", "abstract": "Motivated by novel results in the theory of wave dynamics in black-hole spacetimes, we analyze the dynamics of a massive scalar field surrounding a rapidly rotating Kerr black hole. In particular, we report on the existence of stationary (infinitely long-lived) regular field configurations in the background of maximally rotating black holes. The effective height of these scalar \"clouds\" above the central black hole is determined analytically. Our results support the possible existence of stationary scalar field dark matter distributions surrounding rapidly rotating black holes.", "keyphrases": ["scalar cloud", "black hole", "spacetime", "field configuration", "bound-state scalar configuration"]}
{"id": "1801.05235", "title": "Primordial Black Holes - Perspectives in Gravitational Wave Astronomy -", "abstract": "This is a review article on the primordial black holes (PBHs), with particular focus on the massive ones (\u2273 10^15 g) which have not evaporated by the present epoch by the Hawking radiation. By the detections of gravitational waves by LIGO, we have gained a completely novel tool to observationally search for PBHs complementary to the electromagnetic waves. Based on the perspective that gravitational-wave astronomy will make a significant progress in the next decades, a purpose of this article is to give a comprehensive review covering a wide range of topics on PBHs. After discussing PBH formation as well as several inflation models leading to PBH production, we summarize various existing and future observational constraints. We then present topics on formation of PBH binaries, gravitational waves from PBH binaries, various observational tests of PBHs by using gravitational waves.", "keyphrases": ["gravitational wave", "primordial black holes", "early universe", "baryonic matter"]}
{"id": "1907.09484", "title": "Limit on the LMC mass from a census of its satellites", "abstract": "We study the orbits of ultra-faint dwarf galaxies in the combined presence of the Milky Way and LMC and we find 6 dwarfs which were likely accreted with the LMC (Car 2, Car 3, Hor 1, Hyi 1, Phe 2, Ret 2), in addition to the SMC, representing strong evidence of dwarf galaxy group infall. This procedure depends on the gravitational pull of the LMC, thus allowing us to place a lower bound on the Cloud's mass of M_ LMC > 1.24\u00d710^11 M_\u2299. This mass estimate is validated by applying the technique to a cosmological zoom-in simulation of a Milky Way-like galaxy with an LMC analogue where we find that while this lower bound may be overestimated, it will improve in the future with smaller observational errors. We apply this technique to dwarf galaxies lacking radial velocities and find that Eri 3 has a broad range of radial velocities for which it has a significant chance (> 0.4) of having being bound to the Cloud. We study the non-Magellanic classical satellites and find that Fornax has an appreciable probability of being an LMC satellite if the LMC is sufficiently massive. In addition, we explore how the orbits of the Milky Way satellites change in the presence of the LMC and find a significant change for several objects. Finally, we find that the LMC satellites are slightly smaller than the Milky Way satellites at a fixed luminosity, possibly due to the different tidal environments they have experienced.", "keyphrases": ["lmc", "satellite", "dwarf galaxy"]}
{"id": "0911.3363", "title": "Spinning Black Holes as Particle Accelerators", "abstract": "It has recently been pointed out that particles falling freely from rest at infinity outside a Kerr black hole can in principle collide with arbitrarily high center of mass energy in the limiting case of maximal black hole spin. Here we aim to elucidate the mechanism for this fascinating result, and to point out its practical limitations, which imply that ultra-energetic collisions cannot occur near black holes in nature.", "keyphrases": ["black hole", "particle", "ultra-energetic collision", "gravitational radiation"]}
{"id": "1708.07769", "title": "General relativistic weak-field limit and Newtonian N-body simulations", "abstract": "We show how standard Newtonian N-body simulations can be interpreted in terms of the weak-field limit of general relativity by employing the recently developed Newtonian motion gauge. Our framework allows the inclusion of radiation perturbations and the non-linear evolution of matter. We show how to construct the weak-field metric by combining Newtonian simulations with results from Einstein-Boltzmann codes. We discuss observational effects on weak lensing and ray tracing, identifying important relativistic corrections.", "keyphrases": ["weak-field limit", "newtonian n-body simulation", "general relativity"]}
{"id": "0906.0767", "title": "Non-Gaussianity beyond slow roll in multi-field inflation", "abstract": "We study the non-Gaussianity generated during multiple-field inflation. We provide an exact expression for the bispectrum parameter f_NL which is valid beyond the slow-roll regime, valid for certain classes of inflationary models. We then study a new, exact multi-field inflationary model considering a case where the bispectrum grows to observable values at the end of inflation. We show that in this case the trispectrum is also large and may even provide the dominant signal of non-Gaussianity.", "keyphrases": ["multi-field inflation", "inflationary model", "non-gaussianity", "two-field model"]}
{"id": "1408.1952", "title": "Exploring gravitational theories beyond Horndeski", "abstract": "We have recently proposed a new class of gravitational scalar-tensor theories free from Ostrogradski instabilities, in arXiv:1404.6495. As they generalize Horndeski theories, or \"generalized\" galileons, we call them G^3. These theories possess a simple formulation when the time hypersurfaces are chosen to coincide with the uniform scalar field hypersurfaces. We confirm that they contain only three propagating degrees of freedom by presenting the details of the Hamiltonian formulation. We examine the coupling between these theories and matter. Moreover, we investigate how they transform under a disformal redefinition of the metric. Remarkably, these theories are preserved by disformal transformations that depend on the scalar field gradient, which also allow to map subfamilies of G^3 into Horndeski theories.", "keyphrases": ["gravitational theory", "horndeski", "glpv theory", "ghost-like ostrogradski instability", "space-time"]}
{"id": "1403.0007", "title": "Cosmic Star Formation History", "abstract": "Over the past two decades, an avalanche of data from multiwavelength imaging and spectroscopic surveys has revolutionized our view of galaxy formation and evolution. Here we review the range of complementary techniques and theoretical tools that allow astronomers to map the cosmic history of star formation, heavy element production, and reionization of the Universe from the cosmic \"dark ages\" to the present epoch. A consistent picture is emerging, whereby the star-formation rate density peaked approximately 3.5 Gyr after the Big Bang, at z 1.9, and declined exponentially at later times, with an e-folding timescale of 3.9 Gyr. Half of the stellar mass observed today was formed before a redshift z = 1.3. About 25 rate density, and another 25 stars formed during the epoch of reionization. Under the assumption of a universal initial mass function, the global stellar mass density inferred at any epoch matches reasonably well the time integral of all the preceding star-formation activity. The comoving rates of star formation and central black hole accretion follow a similar rise and fall, offering evidence for co-evolution of black holes and their host galaxies. The rise of the mean metallicity of the Universe to about 0.001 solar by z = 6, one Gyr after the Big Bang, appears to have been accompanied by the production of fewer than ten hydrogen Lyman-continuum photons per baryon, a rather tight budget for cosmological reionization.", "keyphrases": ["star formation", "universe", "redshift", "mass density", "cosmological reionization"]}
{"id": "1406.4140", "title": "Beyond the Linear-Order Relativistic Effect in Galaxy Clustering: Second-Order Gauge-Invariant Formalism", "abstract": "We present the second-order general relativistic description of the observed galaxy number density in a cosmological framework. The observed galaxy number density is affected by the volume and the source effects, both of which arise due to the mismatch between physical and observationally inferred quantities such as the redshift, the angular position, the volume, and the luminosity of the observed galaxies. These effects are computed to the second order in metric perturbations without choosing a gauge condition or adopting any restrictions on vector and tensor perturbations, extending the previous linear-order calculations. Paying particular attention to the second-order gauge transformation, we explicitly isolate unphysical gauge modes and construct second-order gauge-invariant variables. Moreover, by constructing second-order tetrads in the observer's rest frame, we clarify the relation between the physical and the parametrized photon wavevectors. Our second-order relativistic description will provide an essential tool for going beyond the power spectrum in the era of precision measurements of galaxy clustering. We discuss potential applications and extensions of the second-order relativistic description of galaxy clustering.", "keyphrases": ["relativistic effect", "galaxy clustering", "several group"]}
{"id": "1302.0093", "title": "Gauss-Bonnet dark energy by Lagrange multipliers", "abstract": "A string-inspired effective theory of gravity, containing Gauss-Bonnet invariant interacting with a scalar field, is considered in view of obtaining cosmological dark energy solutions. A Lagrange multiplier is inserted into the action in order to achieve the cosmological reconstruction by selecting suitable forms of couplings and potentials. Several cosmological exact solutions (including dark energy of quintessence, phantom or Little Rip type) are derived in presence and in absence of the Lagrange multiplier showing the difference in the two dynamical approaches. In the models that we consider, the Lagrange multiplier behaves as a sort of dust fluid that realizes the transitions between matter dominated and dark energy epochs. The relation between Lagrange multipliers and Noether symmetries is discussed.", "keyphrases": ["dark energy", "lagrange multiplier", "scalar field"]}
{"id": "0903.2658", "title": "Weibel, Two-Stream, Filamentation, Oblique, Bell, Buneman... which one grows faster ?", "abstract": "Many competing linear instabilities are likely to occur in astrophysical settings, and it is important to assess which one grows faster for a given situation. An analytical model including the main beam plasma instabilities is developed. The full 3D dielectric tensor is thus explained for a cold relativistic electron beam passing through a cold plasma, accounting for a guiding magnetic field, a return electronic current and moving protons. Considering any orientations of the wave vector allows to retrieve the most unstable mode for any parameters set. An unified description of the Filamentation (Weibel), Two-Stream, Buneman, Bell instabilities (and more) is thus provided, allowing for the exact determination of their hierarchy in terms of the system parameters. For relevance to both real situations and PIC simulations, the electron-to-proton mass ratio is treated as a parameter, and numerical calculations are conducted with two different values, namely 1/1836 and 1/100. In the system parameters phase space, the shape of the domains governed by each kind of instability is far from being trivial. For low density beams, the ultra-magnetized regime tends to be governed by either the Two-Stream or the Buneman instabilities. For beam densities equalling the plasma one, up to four kinds of modes are likely to play a role, depending of the beam Lorentz factor. In some regions of the system parameters phase space, the dominant mode may vary with the electron-to-proton mass ratio. Application is made to Solar Flares, Intergalactic Streams and Relativistic shocks physics.", "keyphrases": ["two-stream", "filamentation", "buneman"]}
{"id": "1210.2194", "title": "Neutrino masses and cosmological parameters from a Euclid-like survey: Markov Chain Monte Carlo forecasts including theoretical errors", "abstract": "We present forecasts for the accuracy of determining the parameters of a minimal cosmological model and the total neutrino mass based on combined mock data for a future Euclid-like galaxy survey and Planck. We consider two different galaxy surveys: a spectroscopic redshift survey and a cosmic shear survey. We make use of the Monte Carlo Markov Chains (MCMC) technique and assume two sets of theoretical errors. The first error is meant to account for uncertainties in the modelling of the effect of neutrinos on the non-linear galaxy power spectrum and we assume this error to be fully correlated in Fourier space. The second error is meant to parametrize the overall residual uncertainties in modelling the non-linear galaxy power spectrum at small scales, and is conservatively assumed to be uncorrelated and to increase with the ratio of a given scale to the scale of non-linearity. It hence increases with wavenumber and decreases with redshift. With these two assumptions for the errors and assuming further conservatively that the uncorrelated error rises above 2 shear/galaxy survey achieves a 1-sigma error on Mnu close to 32 meV/25 meV, sufficient for detecting the total neutrino mass with good significance. If the residual uncorrelated errors indeed rises rapidly towards smaller scales in the non-linear regime as we have assumed here then the data on non-linear scales does not increase the sensitivity to the total neutrino mass. Assuming instead a ten times smaller theoretical error with the same scale dependence, the error on the total neutrino mass decreases moderately from sigma(Mnu) = 18 meV to 14 meV when mildly non-linear scales with 0.1 h/Mpc < k < 0.6 h/Mpc are included in the analysis of the galaxy survey data.", "keyphrases": ["forecast", "neutrino masse", "euclid satellite"]}
{"id": "1808.09955", "title": "QuasarNET: Human-level spectral classification and redshifting with Deep Neural Networks", "abstract": "We introduce QuasarNET, a deep convolutional neural network that performs classification and redshift estimation of astrophysical spectra with human-expert accuracy. We pose these two tasks as a feature detection problem: presence or absence of spectral features determines the class, and their wavelength determines the redshift, very much like human-experts proceed. When ran on BOSS data to identify quasars through their emission lines, QuasarNET defines a sample 99.51\u00b10.03% pure and 99.52\u00b10.03% complete, well above the requirements of many analyses using these data. QuasarNET significantly reduces the problem of line-confusion that induces catastrophic redshift failures to below 0.2%. We also extend QuasarNET to classify spectra with broad absorption line (BAL) features, achieving an accuracy of 98.0\u00b10.4% for recognizing BAL and 97.0\u00b10.2% for rejecting non-BAL quasars. QuasarNET is trained on data of low signal-to-noise and medium resolution, typical of current and future astrophysical surveys, and could be easily applied to classify spectra from current and upcoming surveys such as eBOSS, DESI and 4MOST.", "keyphrases": ["redshift", "bal", "quasarnet"]}
{"id": "1304.7762", "title": "Coevolution (Or Not) of Supermassive Black Holes and Host Galaxies", "abstract": "We review the observed demographics and inferred evolution of supermassive black holes (BHs) found by dynamical modeling of spatially resolved kinematics. Most influential was the discovery of a tight correlation between BH mass and the velocity dispersion of the host-galaxy bulge. It and other correlations led to the belief that BHs and bulges coevolve by regulating each other's growth. New results are now replacing this simple story with a richer and more plausible picture in which BHs correlate differently with different galaxy components. BHs are found in pure-disk galaxies, so classical (elliptical-galaxy-like) bulges are not necessary to grow BHs. But BHs do not correlate with galaxy disks. And any correlations with disk-grown pseudobulges or halo dark matter are so weak as to imply no close coevolution. We suggest that there are four regimes of BH feedback. 1- Local, stochastic feeding of small BHs in mainly bulgeless galaxies involves too little energy to result in coevolution. 2- Global feeding in major, wet galaxy mergers grows giant BHs in short, quasar-like \"AGN\" events whose feedback does affect galaxies. This makes classical bulges and coreless-rotating ellipticals. 3- At the highest BH masses, maintenance-mode feedback into X-ray gas has the negative effect of helping to keep baryons locked up in hot gas. This happens in giant, core-nonrotating ellipticals. They inherit coevolution magic from smaller progenitors. 4- Independent of any feedback physics, the averaging that results from successive mergers helps to engineer tight BH correlations.", "keyphrases": ["black hole", "host galaxy", "coevolution", "stellar velocity dispersion", "star"]}
{"id": "0911.1955", "title": "The Temperature of the Cosmic Microwave Background", "abstract": "The FIRAS data are independently recalibrated using the WMAP data to obtain a CMB temperature of 2.7260 +/- 0.0013. Measurements of the temperature of the cosmic microwave background are reviewed. The determination from the measurements from the literature is cosmic microwave background temperature of 2.72548 +/- 0.00057 K.", "keyphrases": ["cosmic microwave background", "cmb temperature", "perfect blackbody spectrum", "radiation"]}
{"id": "1412.5182", "title": "Physical Processes in the Interstellar Medium", "abstract": "Interstellar space is filled with a dilute mixture of charged particles, atoms, molecules and dust grains, called the interstellar medium (ISM). Understanding its physical properties and dynamical behavior is of pivotal importance to many areas of astronomy and astrophysics. Galaxy formation and evolution, the formation of stars, cosmic nucleosynthesis, the origin of large complex, prebiotic molecules and the abundance, structure and growth of dust grains which constitute the fundamental building blocks of planets, all these processes are intimately coupled to the physics of the interstellar medium. However, despite its importance, its structure and evolution is still not fully understood. Observations reveal that the interstellar medium is highly turbulent, consists of different chemical phases, and is characterized by complex structure on all resolvable spatial and temporal scales. Our current numerical and theoretical models describe it as a strongly coupled system that is far from equilibrium and where the different components are intricately linked together by complex feedback loops. Describing the interstellar medium is truly a multi-scale and multi-physics problem. In these lecture notes we introduce the microphysics necessary to better understand the interstellar medium. We review the relations between large-scale and small-scale dynamics, we consider turbulence as one of the key drivers of galactic evolution, and we review the physical processes that lead to the formation of dense molecular clouds and that govern stellar birth in their interior.", "keyphrases": ["interstellar medium", "molecular cloud", "star formation", "radiation pressure"]}
{"id": "1204.1109", "title": "Crossing Statistic: Reconstructing the Expansion History of the Universe", "abstract": "We present that by combining Crossing Statistic and Smoothing method one can reconstruct the expansion history of the universe with a very high precision without considering any prior on the cosmological quantities such as the equation of state of dark energy. We show that the presented method performs very well in reconstruction of the expansion history of the universe independent of the underlying models and it works well even for non-trivial dark energy models with fast or slow changes in the equation of state of dark energy. Accuracy of the reconstructed quantities along with independence of the method to any prior or assumption gives the proposed method advantages to the other non-parametric methods proposed before in the literature. Applying on the Union 2.1 supernovae combined with WiggleZ BAO data we present the reconstructed results and test the consistency of the two data sets in a model independent manner. Results show that latest available supernovae and BAO data are in good agreement with each other and spatially flat LCDM model is in concordance with the current data.", "keyphrases": ["expansion history", "smoothing method", "cosmological quantity", "dark energy", "crossing statistic"]}
{"id": "1909.05277", "title": "Cosmological Parameters from the BOSS Galaxy Power Spectrum", "abstract": "We present cosmological parameter measurements from the publicly available Baryon Oscillation Spectroscopic Survey (BOSS) data on anisotropic galaxy clustering in Fourier space. Compared to previous studies, our analysis has two main novel features. First, we use a complete perturbation theory model that properly takes into account the non-linear effects of dark matter clustering, short-scale physics, galaxy bias, redshift-space distortions, and large-scale bulk flows. Second, we employ a Markov-Chain Monte-Carlo technique and consistently reevaluate the full power spectrum likelihood as we scan over different cosmologies. Our baseline analysis assumes minimal \u039bCDM, varies the neutrino masses within a reasonably tight range, fixes the primordial power spectrum tilt, and uses the big bang nucleosynthesis prior on the physical baryon density \u03c9_b. In this setup, we find the following late-Universe parameters: Hubble constant H_0=(67.9\u00b1 1.1) kms^-1Mpc^-1, matter density fraction \u03a9_m=0.295\u00b1 0.010, and the mass fluctuation amplitude \u03c3_8=0.721\u00b1 0.043. These parameters were measured directly from the BOSS data and independently of the Planck cosmic microwave background observations. Scanning over the power spectrum tilt or relaxing the other priors do not significantly alter our main conclusions. Finally, we discuss the information content of the BOSS power spectrum and show that it is dominated by the location of the baryon acoustic oscillations and the power spectrum shape. We argue that the contribution of the Alcock-Paczynski effect is marginal in \u039bCDM, but becomes important for non-minimal cosmological models.", "keyphrases": ["galaxy", "power spectrum", "cosmological parameter", "large-scale structure", "effective field theory"]}
{"id": "1302.2625", "title": "keV Neutrino Model Building", "abstract": "We review the model building aspects for keV sterile neutrinos as Dark Matter candidates. After giving a brief discussion of some cosmological and astrophysical aspects, we first discuss the currently known neutrino data and observables. We then explain the purpose and goal of neutrino model building, and review some generic methods used. Afterwards certain aspects specific for keV neutrino model building are discussed, before reviewing the bulk of models in the literature. We try to keep the discussion on a pedagogical level, while nevertheless pointing out some finer details where necessary and useful. Ideally, this review should enable a grad student or an interested colleague from cosmology or astrophysics with some prior experience to start working on the field.", "keyphrases": ["sterile neutrino", "dark matter candidate", "electroweak scale"]}
{"id": "1002.0833", "title": "Resonant Non-Gaussianity", "abstract": "We provide a derivation from first principles of the primordial bispectrum of scalar perturbations produced during inflation driven by a canonically normalized scalar field whose potential exhibits small sinusoidal modulations. A potential of this type has been derived in a class of string theory models of inflation based on axion monodromy. We use this model as a concrete example, but we present our derivations and results for a general slow-roll potential with superimposed modulations. We show analytically that a resonance between the oscillations of the background and the oscillations of the fluctuations is responsible for the production of an observably large non-Gaussian signal. We provide an explicit expression for the shape of this resonant non-Gaussianity. We show that there is essentially no overlap between this shape and the local, equilateral, and orthogonal shapes, and we stress that resonant non-Gaussianity is not captured by the simplest version of the effective field theory of inflation. We hope our analytic expression will be useful to further observationally constrain this class of models.", "keyphrases": ["bispectrum", "resonant non-gaussianity", "resonance", "high energy physic"]}
{"id": "1805.11104", "title": "The Self-gravitating Gas Fraction and The Critical Density for Star Formation", "abstract": "We analytically calculate the star formation efficiency and dense self-gravitating gas fraction in the presence of magneto-gravo-turbulence using the model of Burkhart (2018), which employs a piecewise lognormal and powerlaw density Probability Distribution Function (PDF). We show that the PDF transition density from lognormal to powerlaw forms is a mathematically motivated critical density for star formation and can be physically related to the density where the Jeans length is comparable to the sonic length, i.e. the post-shock critical density for collapse. When the PDF transition density is taken as the critical density, the instantaneous star formation efficiency (\u03f5_ inst) and depletion time (\u03c4_ depl) can be calculated from the dense self-gravitating gas fraction represented as the fraction of gas in the PDF powerlaw tail. We minimize the number of free parameters in the analytic expressions for \u03f5_ inst and \u03c4_ depl by using the PDF transition density instead of a parameterized critical density for collapse and thus provide a more direct pathway for comparison with observations. We test the analytic predictions for the transition density and self-gravitating gas fraction against AREPO moving mesh gravoturbulent simulations and find good agreement. We predict that, when gravity dominates the density distribution in the star-forming gas, the star formation efficiency should be weakly anti-correlated with the sonic Mach number while the depletion time should increase with increasing sonic Mach number. The star formation efficiency and depletion time depend primarily on the dense self-gravitating gas fraction, which in turn depends on the interplay of gravity, turbulence and stellar feedback. Our model prediction is in agreement with recent observations, such as the M51 PdBI Arcsecond Whirlpool Survey (PAWS).", "keyphrases": ["self-gravitating gas fraction", "critical density", "star formation"]}
{"id": "1305.3756", "title": "Hybrid modified gravity unifying local tests, galactic dynamics and late-time cosmic acceleration", "abstract": "The non-equivalence between the metric and Palatini formalisms of f(R) gravity is an intriguing feature of these theories. However, in the recently proposed hybrid metric-Palatini gravity, consisting of the superposition of the metric Einstein-Hilbert Lagrangian with an f( R) term constructed \u00e0 la Palatini, the \"true\" gravitational field is described by the interpolation of these two non-equivalent approaches. The theory predicts the existence of a light long-range scalar field, which passes the local constraints and affects the galactic and cosmological dynamics. Thus, the theory opens new possibilities for a unified approach, in the same theoretical framework, to the problems of dark energy and dark matter, without distinguishing a priori matter and geometric sources, but taking their dynamics into account under the same standard.", "keyphrases": ["gravity", "late-time cosmic acceleration", "dark matter"]}
{"id": "1405.0346", "title": "Blue Tensor Spectrum from Particle Production during Inflation", "abstract": "We discuss a mechanism of particle production during inflation that can result in a blue gravitational wave (GW) spectrum, compatible with the BICEP2 result and with the r < 0.11 limit on the tensor-to-scalar ratio at the Planck pivot scale. The mechanism is based on the production of vector quanta from a rolling pseudo-scalar field. Both the vector and the pseudo-scalar are only gravitationally coupled to the inflaton, to keep the production of inflaton quanta at an unobservable level (the overproduction of non-gaussian scalar perturbations is a generic difficulty for mechanisms that aim to generate a visible GW signal from particle production during inflation). This mechanism can produce a detectable amount of GWs for any inflationary energy scale. The produced GWs are chiral and non-gaussian; both these aspects can be tested with large-scale polarization data (starting from Planck). We study how to reconstruct the pseudo-scalar potential from the GW spectrum.", "keyphrases": ["particle production", "gravitational wave", "gauge field", "tensor mode"]}
{"id": "1603.09073", "title": "Curvature constraints from Large Scale Structure", "abstract": "We modified the CLASS code in order to include relativistic galaxy number counts in spatially curved geometries; we present the formalism and study the effect of relativistic corrections on spatial curvature. The new version of the code is now publicly available. Using a Fisher matrix analysis, we investigate how measurements of the spatial curvature parameter \u03a9_K with future galaxy surveys are affected by relativistic effects, which influence observations of the large scale galaxy distribution. These effects include contributions from cosmic magnification, Doppler terms and terms involving the gravitational potential. As an application, we consider angle and redshift dependent power spectra, which are especially well suited for model independent cosmological constraints. We compute our results for a representative deep, wide and spectroscopic survey, and our results show the impact of relativistic corrections on the spatial curvature parameter estimation. We show that constraints on the curvature parameter may be strongly biased if, in particular, cosmic magnification is not included in the analysis. Other relativistic effects turn out to be subdominant in the studied configuration. We analyze how the shift in the estimated best-fit value for the curvature and other cosmological parameters depends on the magnification bias parameter, and find that significant biases are to be expected if this term is not properly considered in the analysis.", "keyphrases": ["large scale structure", "correction", "relativistic effect", "cosmological parameter", "curvature"]}
{"id": "1403.6344", "title": "Neutrino electromagnetic interactions: a window to new physics", "abstract": "We review the theory and phenomenology of neutrino electromagnetic interactions, which give us powerful tools to probe the physics beyond the Standard Model. After a derivation of the general structure of the electromagnetic interactions of Dirac and Majorana neutrinos in the one-photon approximation, we discuss the effects of neutrino electromagnetic interactions in terrestrial experiments and in astrophysical environments. We present the experimental bounds on neutrino electromagnetic properties and we confront them with the predictions of theories beyond the Standard Model.", "keyphrases": ["electromagnetic interaction", "new physics", "neutrino", "helicity state"]}
{"id": "2004.12579", "title": "Power spectrum of halo intrinsic alignments in simulations", "abstract": "We use a suite of N-body simulations to study intrinsic alignments (IA) of halo shapes with the surrounding large-scale structure in the \u039bCDM model. For this purpose, we develop a novel method to measure multipole moments of the three-dimensional power spectrum of the E-mode field of halo shapes with the matter/halo distribution, P_\u03b4 E^(\u2113)(k) (or P^(\u2113)_ hE), and those of the auto-power spectrum of the E mode, P^(\u2113)_EE(k), based on the E/B-mode decomposition. The IA power spectra have non-vanishing amplitudes over the linear to nonlinear scales, and the large-scale amplitudes at k\u2272 0.1 h Mpc^-1 are related to the matter power spectrum via a constant coefficient (A_ IA), similar to the linear bias parameter of galaxy or halo density field. We find that the cross- and auto-power spectra P_\u03b4 E and P_EE at nonlinear scales, k\u2273 0.1 h Mpc^-1, show different k-dependences relative to the matter power spectrum, suggesting a violation of the nonlinear alignment model commonly used to model contaminations of cosmic shear signals. The IA power spectra exhibit baryon acoustic oscillations, and vary with halo samples of different masses, redshifts and cosmological parameters (\u03a9_ m, S_8). The cumulative signal-to-noise ratio for the IA power spectra is about 60 covariance is found to give a significant contribution to the total covariance. Thus our results demonstrate that the IA power spectra of galaxy shapes, measured from imaging and spectroscopic surveys for an overlapping area of the sky, can be used to probe the underlying matter power spectrum, the primordial curvature perturbations, and cosmological parameters, in addition to the standard galaxy density power spectrum.", "keyphrases": ["intrinsic alignment", "simulation", "galaxy shape", "power spectrum"]}
{"id": "1702.05847", "title": "Constant-roll inflation: confrontation with recent observational data", "abstract": "The previously proposed class of phenomenological inflationary models in which the assumption of inflaton slow-roll is replaced by the more general, constant-roll condition is compared with the most recent cosmological observational data, mainly the Planck ones. Models in this two-parametric class which remain viable appear to be close to the slow-roll ones, and their inflaton potentials are close to (but still different from) that of the natural inflation model. Permitted regions for the two model parameters are presented.", "keyphrases": ["phenomenological inflationary model", "constant-roll condition", "constant-roll inflation"]}
{"id": "1609.05870", "title": "Generalized SU(2) Proca Theory", "abstract": "Following previous works on generalized Abelian Proca theory, also called vector Galileon, we investigate the massive extension of an SU(2) gauge theory, i.e., the generalized SU(2) Proca model, which could be dubbed non-Abelian vector Galileon. This particular symmetry group permits fruitful applications in cosmology such as inflation driven by gauge fields. Our approach consists in building, in an exhaustive way, all the Lagrangians containing up to six contracted Lorentz indices. For this purpose, and after identifying by group theoretical considerations all the independent Lagrangians which can be written at these orders, we consider the only linear combinations propagating three degrees of freedom and having healthy dynamics for their longitudinal mode, i.e., whose pure St\u00fcckelberg contribution turns into the SU(2) multi-Galileon dynamics. Finally, and after having considered the curved space-time expansion of these Lagrangians, we discuss the form of the theory at all subsequent orders.", "keyphrases": ["proca theory", "massive extension", "gauge field", "generalized su(2"]}
{"id": "2007.15345", "title": "Beyond Einstein's General Relativity: Hybrid metric-Palatini gravity and curvature-matter couplings", "abstract": "Einstein's General Relativity (GR) is possibly one of the greatest intellectual achievements ever conceived by the human mind. In fact, over the last century, GR has proven to be an extremely successful theory, with a well established experimental footing. However, the discovery of the late-time cosmic acceleration, which represents a new imbalance in the governing gravitational field equations, has forced theorists and experimentalists to question whether GR is the correct relativistic theory of gravitation, and has spurred much research in modified gravity, where extensions of the Hilbert-Einstein action describe the gravitational field. In this review, we perform a detailed theoretical and phenomenological analysis of two largely explored extensions of f(R) gravity, namely: (i) the hybrid metric-Palatini theory; (ii) and modified gravity with curvature-matter couplings. Relative to the former, it has been established that both metric and Palatini versions of f(R) gravity possess interesting features but also manifest severe drawbacks. A hybrid combination, containing elements from both of these formalisms, turns out to be very successful in accounting for the observed phenomenology and avoids some drawbacks of the original approaches. Relative to the curvature-matter coupling theories, these offer interesting extensions of f(R) gravity, where the explicit nonminimal couplings between an arbitrary function of the scalar curvature R and the Lagrangian density of matter, induces a non-vanishing covariant derivative of the energy-momentum tensor. We extensively explore both theories in a plethora of applications, namely, the weak-field limit, galactic and extragalactic dynamics, cosmology, stellar-type compact objects, irreversible matter creation processes and the quantum cosmology of a specific curvature-matter coupling theory.", "keyphrases": ["gravity", "curvature-matter coupling", "explicit nonminimal coupling", "cosmology"]}
{"id": "1803.01961", "title": "Bouncing Cosmology made simple", "abstract": "We introduce the \"wedge diagram,\" an intuitive way to illustrate how cosmological models with a classical (non-singular) bounce generically resolve fundamental problems in cosmology. These include the well-known horizon, flatness, and inhomogeneity problems; the small tensor-to-scalar ratio observed in the cosmic microwave background; the low entropy at the beginning of a hot, expanding phase; and the avoidance of quantum runaway. The same diagrammatic approach can be used to compare with other cosmological scenarios.", "keyphrases": ["cosmology", "bounce", "inflationary scenario"]}
{"id": "1011.5550", "title": "Naked singularities as particle accelerators", "abstract": "We investigate here the particle acceleration by naked singularities to arbitrarily high center of mass energies. Recently it has been suggested that black holes could be used as particle accelerators to probe the Planck scale physics. We show that the naked singularities serve the same purpose and probably would do better than their black hole counterparts. We focus on the scenario of a self-similar gravitational collapse starting from a regular initial data, leading to the formation of a globally naked singularity. It is seen that when particles moving along timelike geodesics interact and collide near the Cauchy horizon, the energy of collision in the center of mass frame will be arbitrarily high, thus offering a window to Planck scale physics.", "keyphrases": ["singularity", "particle accelerator", "gravitational collapse"]}
{"id": "1804.02275", "title": "On the propagation of gravitational waves in strong magnetic fields", "abstract": "The propagation of gravitational waves is explored in the cosmological context. It is explicitly demonstrated that the propagation of gravitational waves could be influenced by the medium. It is shown that in the thermal radiation, the propagation of gravitational waves in general relativity is different from that in the scalar-tensor theory. The propagation of gravitational waves is investigated in the uniform magnetic field. As a result, it is found that cosmic magnetic fields could influence on the propagation of gravitational waves to non-negligible extent. The corresponding estimation for the spiral galaxy NGC 6946 effect is made.", "keyphrases": ["propagation", "gravitational wave", "magnetic field"]}
{"id": "1707.06277", "title": "WIMP dark matter candidates and searches - current status and future prospects", "abstract": "We review several current aspects of dark matter theory and experiment. We overview the present experimental status, which includes current bounds and recent claims and hints of a possible signal in a wide range of experiments: direct detection in underground laboratories, gamma-ray, cosmic ray, X-ray, neutrino telescopes, and the LHC. We briefly review several possible particle candidates for a Weakly Interactive Massive Particle (WIMP) and dark matter that have recently been considered in the literature. We pay particular attention to the lightest neutralino of supersymmetry as it remains the best motivated candidate for dark matter and also shows excellent detection prospects. Finally we briefly review some alternative scenarios that can considerably alter properties and prospects for the detection of dark matter obtained within the standard thermal WIMP paradigm.", "keyphrases": ["dark matter candidate", "massive particle", "electroweak scale"]}
{"id": "1908.10972", "title": "Mysterious Coherence in Several-Megaparsec Scales Between Galaxy Rotation and Neighbor Motion", "abstract": "In our recent report, observational evidence supports that the rotational direction of a galaxy tends to be coherent with the average motion of its nearby neighbors within 1 Mpc. We extend the investigation to neighbors at farther distances, in order to examine if such dynamical coherence is found even in large scales. The Calar Alto Legacy Integral Field Area (CALIFA) survey data and the NASA-Sloan Atlas (NSA) catalog are used. From the composite map of velocity distribution of 'neighbor' galaxies within 15 Mpc from the CALIFA galaxies, the composite radial profiles of the luminosity-weighted mean velocity of neighbors are derived. These profiles show unexpectedly strong evidence of the dynamical coherence between the rotation of the CALIFA galaxies and the average line-of-sight motion of their neighbors within several Mpc distances. Such a signal is particularly strong when the neighbors are limited to red ones: the luminosity-weighted mean velocity at 1 < D <= 6 Mpc is as large as 30.6+/-10.9 km/s (2.8-sigma significance to random spin-axis uncertainty) for central rotation (R <= Re). In the comparison of several subsamples, the dynamical coherence tends to be marginally stronger for the diffuse or kinematically-well-aligned CALIFA galaxies. For this mysterious coherence in large scales, we cautiously suggest a scenario that it results from a possible relationship between the long-term motion of a large-scale structure and the rotations of galaxies in it.", "keyphrases": ["galaxy", "mysterious coherence", "spin direction", "non-random distribution", "cosmological scale"]}
{"id": "1409.7174", "title": "Dissipative hidden sector dark matter", "abstract": "A simple way of explaining dark matter without modifying known Standard Model physics is to require the existence of a hidden (dark) sector, which interacts with the visible one predominantly via gravity. We consider a hidden sector containing two stable particles charged under an unbroken U(1)^' gauge symmetry, hence featuring dissipative interactions. The massless gauge field associated with this symmetry, the dark photon, can interact via kinetic mixing with the ordinary photon. In fact, such an interaction of strength \u03f5\u223c 10 ^-9 appears to be necessary in order to explain galactic structure. We calculate the effect of this new physics on Big Bang Nucleosynthesis and its contribution to the relativistic energy density at Hydrogen recombination. We then examine the process of dark recombination, during which neutral dark states are formed, which is important for large-scale structure formation. Galactic structure is considered next, focussing on spiral and irregular galaxies. For these galaxies we modelled the dark matter halo (at the current epoch) as a dissipative plasma of dark matter particles, where the energy lost due to dissipation is compensated by the energy produced from ordinary supernovae (the core-collapse energy is transferred to the hidden sector via kinetic mixing induced processes in the supernova core). We find that such a dynamical halo model can reproduce several observed features of disk galaxies, including the cored density profile and the Tully-Fisher relation. We also discuss how elliptical and dwarf spheroidal galaxies could fit into this picture. Finally, these analyses are combined to set bounds on the parameter space of our model, which can serve as a guideline for future experimental searches.", "keyphrases": ["dark matter", "massless", "dark sector"]}
{"id": "1711.03929", "title": "Isotropic vs. Anisotropic components of BAO data: a tool for model selection", "abstract": "We conduct a selective analysis of the isotropic (D_V) and anisotropic (AP) components of the most recent Baryon Acoustic Oscillations (BAO) data. We find that these components provide significantly different constraints and could provide strong diagnostics for model selection, also in view of more precise data to arrive. For instance, in the \u039bCDM model, we find a mild tension of \u223c 2 \u03c3 for the \u03a9_m estimates obtained using D_V and AP separately. Considering both \u03a9_k and w as free parameters, we find that the concordance model is in tension with the best-fit values provided by the BAO data alone at 2.2\u03c3. We complemented the BAO data with the Supernova Ia (SNIa) and Observational Hubble datasets to perform a joint analysis on the \u039bCDM model and its standard extensions. By assuming \u039bCDM scenario, we find that these data provide H_0 = 69.4 \u00b1 1.7 km/s Mpc^-1 as the best-fit value for the present expansion rate. In the k\u039bCDM scenario we find that the evidence for acceleration using the BAO data alone is more than \u223c 5.8\u03c3, which increases to 8.4 \u03c3 in our joint analysis.", "keyphrases": ["anisotropic component", "bao data", "model selection"]}
{"id": "1801.04834", "title": "Cobalt: A GPU-based correlator and beamformer for LOFAR", "abstract": "For low-frequency radio astronomy, software correlation and beamforming on general purpose hardware is a viable alternative to custom designed hardware. LOFAR, a new-generation radio telescope centered in the Netherlands with international stations in Germany, France, Ireland, Latvia, Poland, Sweden and the UK, has successfully used software real-time processors based on IBM Blue Gene technology since 2004. Since then, developments in technology have allowed us to build a system based on commercial off-the-shelf components that combines the same capabilities with lower operational cost. In this paper we describe the design and implementation of a GPU-based correlator and beamformer with the same capabilities as the Blue Gene based systems. We focus on the design approach taken, and show the challenges faced in selecting an appropriate system. The design, implementation and verification of the software system shows the value of a modern test-driven development approach. Operational experience, based on three years of operations, demonstrates that a general purpose system is a good alternative to the previous supercomputer-based system or custom-designed hardware.", "keyphrases": ["gpu-based correlator", "beamformer", "lofar"]}
{"id": "1002.1754", "title": "Baryon and Lepton Number as Local Gauge Symmetries", "abstract": "We investigate a simple theory where Baryon number (B) and Lepton number (L) are local gauge symmetries. In this theory B and L are on the same footing and the anomalies are cancelled by adding a single new fermionic generation. There is an interesting realization of the seesaw mechanism for neutrino masses. Furthermore, there is a natural suppression of flavour violation in the quark and leptonic sectors since the gauge symmetries and particle content forbid tree level flavor changing neutral currents involving the quarks or charged leptons. Also one finds that the stability of a dark matter candidate is an automatic consequence of the gauge symmetry. Some constraints and signals at the Large Hadron Collider are briefly discussed.", "keyphrases": ["lepton number", "local gauge symmetry", "baryon"]}
{"id": "1304.7317", "title": "Cosmic opacity: cosmological-model-independent tests and their impacts on cosmic acceleration", "abstract": "With assumptions that the violation of the distance-duality (DD) relation entirely arises from non-conservation of the photon number and the absorption is frequency independent in the observed frequency range, we perform cosmological-model-independent tests for the cosmic opacity. The observational data include the largest Union2.1 SN Ia sample, which is taken for observed D_L, and galaxy cluster samples compiled by De Filippis et al. and Bonamente et al., which are responsible for providing observed D_A. Two parameterizations, \u03c4(z)=2\u03f5 z and \u03c4(z)=(1+z)^2\u03f5-1 are adopted for the optical depth associated to the cosmic absorption. We find that, an almost transparent universe is favored by Filippis et al. sample but it is only marginally accommodated by Bonomente et al. samples at 95.4 C. L. when the r<100 kpc-cut spherical \u03b2 model is considered). Taking the possible cosmic absorption (in 68.3 the model-independent tests into consideration, we correct the distance modulus of SNe Ia and then use them to study their cosmological implications. The constraints on the \u039bCDM show that a decelerating expanding universe with \u03a9_\u039b=0 is only allowed at 99.7 Bonamente et al. sample is considered. Therefore, our analysis suggests that an accelerated cosmic expansion is still needed to account for the dimming of SNe and the standard cosmological scenario remains to be supported by current observations.", "keyphrases": ["cosmological-model-independent test", "cosmic opacity", "old passive galaxy", "gas mass fraction"]}
{"id": "1006.5694", "title": "Dark Energy in Practice", "abstract": "In this paper we review a part of the approaches that have been considered to explain the extraordinary discovery of the late time acceleration of the Universe. We discuss the arguments that have led physicists and astronomers to accept dark energy as the current preferable candidate to explain the acceleration. We highlight the problems and the attempts to overcome the difficulties related to such a component. We also consider alternative theories capable of explaining the acceleration of the Universe, such as modification of gravity. We compare the two approaches and point out the observational consequences, reaching the sad but foresightful conclusion that we will not be able to distinguish between a Universe filled by dark energy or a Universe where gravity is different from General Relativity. We review the present observations and discuss the future experiments that will help us to learn more about our Universe. This is not intended to be a complete list of all the dark energy models but this paper should be seen as a review on the phenomena responsible for the acceleration. Moreover, in a landscape of hardly compelling theories, it is an important task to build simple measurable parameters useful for future experiments that will help us to understand more about the evolution of the Universe.", "keyphrases": ["task", "dark energy", "accelerated expansion"]}
{"id": "1305.0279", "title": "Effective theory for the Vainshtein mechanism from the Horndeski action", "abstract": "Starting from the general Horndeski action, we derive the most general effective theory for scalar perturbations around flat space that allows us to screen fifth forces via the Vainshtein mechanism. The effective theory is described by a generalization of the Galileon Lagrangian, which we use to study the stability of spherically symmetric configurations exhibiting the Vainshtein effect. In particular, we discuss the phenomenological consequences of a scalar-tensor coupling that is absent in the standard Galileon Lagrangian. This coupling controls the superluminality and stability of fluctuations inside the Vainshtein radius in a way that depends on the density profile of a matter source. Particularly we find that the vacuum solution is unstable due to this coupling.", "keyphrases": ["vainshtein mechanism", "fifth force", "symmetric background"]}
{"id": "0909.3924", "title": "Assisted dark energy", "abstract": "Cosmological scaling solutions, which give rise to a scalar-field density proportional to a background fluid density during radiation and matter eras, are attractive to alleviate the energy scale problem of dark energy. In the presence of multiple scalar fields the scaling solution can exit to the epoch of cosmic acceleration through the so-called assisted inflation mechanism. We study cosmological dynamics of a multi-field system in details with a general Lagrangian density p=sum_i=1^n X_i g(X_i e^lambda_i phi_i), where X_i=-(nabla phi_i)^2/2 is the kinetic energy of the i-th field phi_i, lambda_i is a constant, and g is an arbitrary function in terms of Y_i=X_i e^lambda_i phi_i. This covers most of the scalar-field models of dark energy proposed in literature that possess scaling solutions. Using the bound coming from Big-Bang-Nucleosynthesis and the condition under which the each field cannot drive inflation as a single component of the universe, we find the following features: (i) a transient or eternal cosmic acceleration can be realized after the scaling matter era, (ii) a \"thawing\" property of assisting scalar fields is crucial to determine the evolution of the field equation of state w_phi, and (iii) the field equation of state today can be consistent with the observational bound w_phi<-0.8 in the presence of multiple scalar fields.", "keyphrases": ["dark energy", "rise", "multiple scalar field", "arbitrary function"]}
{"id": "1008.1786", "title": "Galacticus: A Semi-Analytic Model of Galaxy Formation", "abstract": "We describe a new, free and open source semi-analytic model of galaxy formation, Galacticus. The Galacticus model was designed to be highly modular to facilitate expansion and the exploration of alternative descriptions of key physical ingredients. We detail the Galacticus engine for evolving galaxies through a merging hierarchy of dark matter halos and give details of the specific implementations of physics currently available in Galacticus. Finally, we show results from an example model that is in reasonably good agreement with several observational datasets. We use this model to explore numerical convergence and to demonstrate the types of information which can be extracted from Galacticus.", "keyphrases": ["semi-analytic model", "galaxy formation", "galacticus"]}
{"id": "1209.4562", "title": "Is the 130 GeV Line Real? A Search for Systematics in the Fermi-LAT Data", "abstract": "Our recent claims of a Galactic center feature in Fermi-LAT data at approximately 130 GeV have prompted an avalanche of papers proposing explanations ranging from dark matter annihilation to exotic pulsar winds. Because of the importance of such interpretations for physics and astrophysics, a discovery will require not only additional data, but a thorough investigation of possible LAT systematics. While we do not have access to the details of each event reconstruction, we do have information about each event from the public event lists and spacecraft parameter files. These data allow us to search for suspicious trends that could indicate a spurious signal. We consider several hypotheses that might make an instrumental artifact more apparent at the Galactic center, and find them implausible. We also search for an instrumental signature in the Earth limb photons, which provide a smooth reference spectrum for null tests. We find no significant 130 GeV feature in the Earth limb sample. However, we do find a marginally significant 130 GeV feature in Earth limb photons with a limited range of detector incidence angles. This raises concerns about the 130 GeV Galactic center feature, even though we can think of no plausible model of instrumental behavior that connects the two. A modest amount of additional limb data would tell us if the limb feature is a statistical fluke. If the limb feature persists, it would raise doubts about the Pass 7 processing of E > 100 GeV events. At present we find no instrumental systematics that could plausibly explain the excess Galactic center emission at 130 GeV.", "keyphrases": ["gev", "systematic", "fermi-lat data", "galactic center", "gamma-ray line"]}
{"id": "1003.2719", "title": "A thermally stable heating mechanism for the intracluster medium: turbulence, magnetic fields and plasma instabilities", "abstract": "We consider the problem of self-regulated heating and cooling in galaxy clusters and the implications for cluster magnetic fields and turbulence. Viscous heating of a weakly collisional magnetised plasma is regulated by the pressure anisotropy with respect to the local direction of the magnetic field. The intracluster medium is a high-beta plasma, where pressure anisotropies caused by the turbulent stresses and the consequent local changes in the magnetic field will trigger very fast microscale instabilities. We argue that the net effect of these instabilities will be to pin the pressure anisotropies at a marginal level, controlled by the plasma beta parameter. This gives rise to local heating rates that turn out to be comparable to the radiative cooling rates. Furthermore, we show that a balance between this heating and Bremsstrahlung cooling is thermally stable, unlike the often conjectured balance between cooling and thermal conduction. Given a sufficient (and probably self-regulating) supply of turbulent power, this provides a physical mechanism for mitigating cooling flows and preventing cluster core collapse. For observed density and temperature profiles, the assumed balance of viscous heating and radiative cooling allows us to predict magnetic-field strengths, turbulent velocities and turbulence scales as functions of distance from the centre. Specific predictions and comparisons with observations are given for several different clusters. Our predictions can be further tested by future observations of cluster magnetic fields and turbulent velocities.", "keyphrases": ["turbulence", "magnetic field", "plasma instability", "local heating rate"]}
{"id": "1909.11816", "title": "Determination of properties of protoneutron stars toward black hole formation via gravitational wave observations", "abstract": "We examine the frequencies of the fundamental (f-) and the gravity (g_i-) mode in gravitational waves from accreting protoneutron stars (PNSs) toward black hole formation. For this purpose, we analyze numerical results of gravitational collapse of massive stars for two different progenitors with three equations of state. We adopt profiles of central objects obtained from the numerical simulations by solving general relativistic neutrino-radiation hydrodynamics under the spherical symmetry. Using a series of snapshots as a static configuration at each time step, we solve the eigenvalue problem to determine the specific frequencies of gravitational waves from the evolving PNSs with accretion from core bounce to black hole formation by the relativistic Cowling approximation. We find that the frequency of the f-mode gravitational waves can be expressed as a function of the average density of the PNS at each time step almost independently of the progenitor models in accord with the previous studies on ordinary PNSs. We also find that the ratio of the g_1-mode frequency to the f-mode frequency is insensitive to the progenitor, but strongly depends on the compactness of the PNSs. Having a simultaneous observation of the f- and g_1-mode gravitational waves, it would provide the information of the average density and compactness of PNS, which can reconstruct the evolution of mass and radius of the PNSs as a constraint on the equation of state at high densities. Furthermore, we show that the highest average density of the PNS with the maximum mass can be estimated with the detection of the f-mode gravitational waves together with the help of the neutrino observations.", "keyphrases": ["protoneutron star", "black hole formation", "gravitational wave signal", "asteroseismology", "supernovae"]}
{"id": "2201.00882", "title": "The dynamics and outcome of star formation with jets, radiation, winds, and supernovae in concert", "abstract": "We analyze the first giant molecular cloud (GMC) simulation to follow the formation of individual stars and their feedback from jets, radiation, winds, and supernovae, using the STARFORGE framework in the GIZMO code. We evolve the GMC for \u223c 9 Myr, from initial turbulent collapse to dispersal by feedback. Protostellar jets dominate feedback momentum initially, but radiation and winds cause cloud disruption at \u223c 8% star formation efficiency (SFE), and the first supernova at 8.3 Myr comes too late to influence star formation significantly. The per-freefall SFE is dynamic, accelerating from 0 to \u223c 18% before dropping quickly to <1 compresses it to a narrower range. The primary cluster forms hierarchically and condenses to a brief (\u223c 1 Myr) compact (\u223c 1 pc) phase, but does not virialize before the cloud disperses, and the stars end as an unbound expanding association. The initial mass function resembles the Chabrier (2005) form with a high-mass slope \u03b1=-2 and a maximum mass of 55 M_\u2299. Stellar accretion takes \u223c 400 kyr on average, but \u2273 1 Myr for >10 M_\u2299 stars, so massive stars finish growing latest. The fraction of stars in multiples increases as a function of primary mass, as observed. Overall, the simulation much more closely resembles reality, compared to variations which neglect different feedback physics entirely. But more detailed comparison with synthetic observations is necessary to constrain the theoretical uncertainties.", "keyphrases": ["star formation", "jet", "molecular cloud"]}
{"id": "1712.01396", "title": "Gravitational-Wave Fringes at LIGO: Detecting Compact Dark Matter by Gravitational Lensing", "abstract": "Utilizing gravitational-wave (GW) lensing opens a new way to understand the small-scale structure of the universe. We show that, in spite of its coarse angular resolution and short duration of observation, LIGO can detect the GW lensing induced by compact structures, in particular by compact dark matter (DM) or primordial black holes of 10 - 10^5 M_\u2299, which remain interesting DM candidates. The lensing is detected through GW frequency chirping, creating the natural and rapid change of lensing patterns: frequency-dependent amplification and modulation of GW waveforms. As a highest-frequency GW detector, LIGO is a unique GW lab to probe such light compact DM. With the design sensitivity of Advanced LIGO, one-year observation by three detectors can optimistically constrain the compact DM density fraction f_ DM to the level of a few percent.", "keyphrases": ["compact dark matter", "gravitational lensing", "black hole"]}
{"id": "1208.0002", "title": "Making Galaxies in a Cosmological Context: The Need for Early Stellar Feedback", "abstract": "We introduce the Making Galaxies in a Cosmological Context (MaGICC) program of smoothed particle hydrodynamics (SPH) simulations. We describe a parameter study of galaxy formation simulations of an L* galaxy that uses early stellar feedback combined with supernova feedback to match the stellar mass\u2013halo mass relationship. While supernova feedback alone can reduce star formation enough to match the stellar mass\u2013halo mass relationship, the galaxy forms too many stars before z=2 to match the evolution seen using abundance matching. Our early stellar feedback is purely thermal and thus operates like a UV ionization source as well as providing some additional pressure from the radiation of massive, young stars. The early feedback heats gas to >10^6 K before cooling to 10^4 K. The pressure from this hot gas creates a more extended disk and prevents more star formation prior to z=1 than supernovae feedback alone. The resulting disk galaxy has a flat rotation curve, an exponential surface brightness profile, and matches a wide range of disk scaling relationships. The disk forms from the inside-out with an increasing exponential scale length as the galaxy evolves. Overall, early stellar feedback helps to simulate galaxies that match observational results at low and high redshifts.", "keyphrases": ["galaxy", "cosmological context", "early stellar feedback"]}
{"id": "1304.4825", "title": "Pulsars and magnetars", "abstract": "The high-energy sources known as anomalous X-ray pulsars (AXPs) and soft gamma-ray repeaters (SGRs) are well explained as magnetars: isolated neutron stars powered by their own magnetic energy. After explaining why it is generally believed that the traditional energy sources at work in other neutron stars (accretion, rotation, residual heat) cannot power the emission of AXPs/SGRs, I review the observational properties of the twenty AXPs/SGRs currently known and describe the main features of the magnetar model. In the last part of this review I discuss the recent discovery of magnetars with low external dipole field and some of the relations between AXPs/SGRs and other classes of isolated neutron stars.", "keyphrases": ["magnetar", "anomalous x-ray pulsar", "neutron star"]}
{"id": "1501.06921", "title": "Near-Field Cosmology with Metal-Poor Stars", "abstract": "The oldest, most metal-poor stars in the Galactic halo and satellite dwarf galaxies present an opportunity to explore the chemical and physical conditions of the earliest star forming environments in the Universe. We review the fields of stellar archaeology and dwarf galaxy archaeology by examining the chemical abundance measurements of various elements in extremely metal-poor stars. Focus on the carbon-rich and carbon-normal halo star populations illustrates how these provide insight into the Population III star progenitors responsible for the first metal enrichment events. We extend the discussion to near-field cosmology, which is concerned with the formation of the first stars and galaxies and how metal-poor stars can be used to constrain these processes. Complementary abundance measurements in high-redshift gas clouds further help to establish the early chemical evolution of the Universe. The data appear consistent with the existence of two distinct channels of star formation at the earliest times.", "keyphrases": ["metal-poor star", "star", "near-field cosmology"]}
{"id": "1606.06971", "title": "Multi-field inflation and cosmological perturbations", "abstract": "We provide a concise review on multi-field inflation and cosmological perturbations. We discuss convenient and physically meaningful bases in terms of which perturbations can be systematically studied. We give formal accounts on the gauge fixing conditions and present the perturbation action in two gauges. We also briefly review non-linear perturbations.", "keyphrases": ["multi-field inflation", "scalar field", "high-energy particle physics"]}
{"id": "1205.5556", "title": "Formation of Galaxy Clusters", "abstract": "In this review, we describe our current understanding of cluster formation: from the general picture of collapse from initial density fluctuations in an expanding Universe to detailed simulations of cluster formation including the effects of galaxy formation. We outline both the areas in which highly accurate predictions of theoretical models can be obtained and areas where predictions are uncertain due to uncertain physics of galaxy formation and feedback. The former includes the description of the structural properties of the dark matter halos hosting cluster, their mass function and clustering properties. Their study provides a foundation for cosmological applications of clusters and for testing the fundamental assumptions of the standard model of structure formation. The latter includes the description of the total gas and stellar fractions, the thermodynamical and non-thermal processes in the intracluster plasma. Their study serves as a testing ground for galaxy formation models and plasma physics. In this context, we identify a suitable radial range where the observed thermal properties of the intra-cluster plasma exhibit the most regular behavior and thus can be used to define robust observational proxies for the total cluster mass. We put particular emphasis on examining assumptions and limitations of the widely used self-similar model of clusters. Finally, we discuss the formation of clusters in non-standard cosmological models, such as non-Gaussian models for the initial density field and models with modified gravity, along with prospects for testing these alternative scenarios with large cluster surveys in the near future.", "keyphrases": ["galaxy cluster", "universe", "matter density field", "high peak"]}
{"id": "1711.08759", "title": "Revival of the Deser-Woodard nonlocal gravity model: Comparison of the original nonlocal form and a localized formulation", "abstract": "We examine the origin of two opposite results for the growth of perturbations in the Deser-Woodard (DW) nonlocal gravity model. One group previously analyzed the model in its original nonlocal form and showed that the growth of structure in the DW model is enhanced compared to general relativity (GR) and thus concluded that the model was ruled out. Recently, however, another group has reanalyzed it by localizing the model and found that the growth in their localized version is suppressed even compared to the one in GR. The question was whether the discrepancy originates from an intrinsic difference between the nonlocal and localized formulations or is due to their different implementations of the sub-horizon limit. We show that the nonlocal and local formulations give the same solutions for the linear perturbations as long as the initial conditions are set the same. The different implementations of the sub-horizon limit lead to different transient behaviors of some perturbation variables; however, they do not affect the growth of matter perturbations at the sub-horizon scale much. In the meantime, we also report an error in the numerical calculation code of the former group and verify that after fixing the error the nonlocal version also gives the suppressed growth. Finally, we discuss two alternative definitions of the effective gravitational constant taken by the two groups and some open problems.", "keyphrases": ["gravity model", "original nonlocal form", "formulation", "initial condition"]}
{"id": "1706.06109", "title": "Very massive stars, pair-instability supernovae and intermediate-mass black holes with the SEVN code", "abstract": "Understanding the link between massive (\u2273 30 M_\u2299) stellar black holes (BHs) and their progenitor stars is a crucial step to interpret observations of gravitational-wave events. In this paper, we discuss the final fate of very massive stars (VMSs), with zero-age main sequence (ZAMS) mass >150 M_\u2299, accounting for pulsational pair-instability supernovae (PPISNe) and for pair-instability supernovae (PISNe). We describe an updated version of our population synthesis code SEVN, in which we added stellar evolution tracks for VMSs with ZAMS mass up to 350M_\u2299 and we included analytical prescriptions for PPISNe and PISNe. We use the new version of SEVN to study the BH mass spectrum at different metallicity Z, ranging from Z=2.0\u00d7 10^-4 to Z=2.0\u00d7 10^-2. The main effect of PPISNe and PISNe is to favour the formation of BHs in the mass range of the first gravitational-wave event (GW150914), while they prevent the formation of remnants with mass 60 - 120 M_\u2299. In particular, we find that PPISNe significantly enhance mass loss of metal-poor (Z\u2264 2.0\u00d7 10^-3) stars with ZAMS mass 60\u2264M_ZAMS/M_\u2299\u2264 125. In contrast, PISNe become effective only for moderately metal-poor (Z<8.0\u00d7 10^-3) VMSs. VMSs with M_ ZAMS\u2273220 M_\u2299 and Z<10^-3 do not undergo PISNe and form intermediate-mass BHs (IMBHs, with mass \u2273 200M_\u2299) via direct collapse.", "keyphrases": ["massive star", "pair-instability supernovae", "black hole"]}
{"id": "1106.4319", "title": "Asymmetric Dark Matter via Spontaneous Co-Genesis", "abstract": "We investigate, in the context of asymmetric dark matter (DM), a new mechanism of spontaneous co-genesis of linked DM and baryon asymmetries, explaining the observed relation between the baryon and DM densities, Omega_DM/Omega_B 5. The co-genesis mechanism requires a light scalar field, phi, with mass below 5 eV which couples derivatively to DM, much like a `dark axion'. The field phi can itself provide a final state into which the residual symmetric DM component can annihilate away.", "keyphrases": ["spontaneous co-genesis", "baryon", "asymmetric dark matter"]}
{"id": "1111.1404", "title": "Testing coupled dark energy with next-generation large-scale observations", "abstract": "Coupling dark energy to dark matter provides one of the simplest way to effectively modify gravity at large scales without strong constraints from local (i.e. solar system) observations. Models of coupled dark energy have been studied several times in the past and are already significantly constrained by cosmic microwave background experiments. In this paper we estimate the constraints that future large-scale observations will be able to put on the coupling and in general on all the parameters of the model. We combine cosmic microwave background, tomographic weak lensing, redshift distortions and power spectrum probes. We show that next-generation observations can improve the current constraint on the coupling to dark matter by two orders of magnitude; this constraint is complementary to the current solar-system bounds on a coupling to baryons.", "keyphrases": ["dark energy", "large-scale observation", "dark matter"]}
{"id": "1401.5177", "title": "Testing coupled dark energy with large scale structure observation", "abstract": "The coupling between the dark components provides a new approach to mitigate the coincidence problem of cosmological standard model. In this paper, dark energy is treated as a fluid with a constant equation of state, whose coupling with dark matter is Q\u0305=3H\u03be_x\u03c1\u0305_x. In the frame of dark energy, we derive the evolution equations for the density and velocity perturbations. According to the Markov Chain Monte Carlo method, we constrain the model by currently available cosmic observations which include cosmic microwave background radiation, baryon acoustic oscillation, type Ia supernovae, and f\u03c3_8(z) data points from redshift-space distortion. The results show the interaction rate in 3\u03c3 regions: \u03be_x=0.00328_-0.00328-0.00328-0.00328^+0.000736+0.00549+0.00816, which means that the recently cosmic observations favor a small interaction rate which is up to the order of 10^-2, meanwhile, the measurement of redshift-space distortion could rule out the large interaction rate in the 1\u03c3 region.", "keyphrases": ["dark energy", "dark matter", "cosmic observation", "large number", "current observational data"]}
{"id": "1012.0185", "title": "A SAURON study of dwarf elliptical galaxies in the Virgo Cluster: kinematics and stellar populations", "abstract": "Dwarf elliptical galaxies (dEs) are the most common galaxy type in nearby galaxy clusters; even so, many of their basic properties have yet to be quantified. Here we present the results of our study of 4 Virgo dwarf ellipticals obtained with the SAURON integral field unit on the William Herschel Telescope (La Palma, Spain). While traditional long-slit observations are likely to miss more complicated kinematic features, with SAURON we are able to study both kinematics and stellar populations in two dimensions, obtaining a much more detailed view of the mass distribution and star formation histories. What is visible even in such a small sample is that dEs are not a uniform group, not only morphologically, but also as far as their kinematic and stellar population properties are concerned. We find the presence of substructures, varying degrees of flattening and of rotation, as well as differences in age and metallicity gradients. We confirm that two of our galaxies are significantly flattened, yet non-rotating objects, which makes them likely triaxial systems. The comparison between the dwarf and the giant groups shows that dEs could be a low-mass extension of Es in the sense that they do seem to follow the same trends with mass. However, dEs as progenitors of Es seem less likely as we have seen that dEs have much lower abundance ratios.", "keyphrases": ["dwarf", "elliptical galaxy", "stellar population"]}
{"id": "1002.2717", "title": "The median recoil direction as a WIMP directional detection signal", "abstract": "Direct detection experiments have reached the sensitivity required to detect dark matter WIMPs. Demonstrating that a putative signal is due to WIMPs, and not backgrounds, is a major challenge however. The direction dependence of the WIMP scattering rate provides a potential WIMP `smoking gun'. If the WIMP distribution is predominantly smooth, the Galactic recoil distribution is peaked in the direction opposite to the direction of Solar motion. Previous studies have found that, for an ideal detector, of order 10 WIMP events would be sufficient to reject isotropy, and rule out an isotropic background. We examine how the median recoil direction could be used to confirm the WIMP origin of an anisotropic recoil signal. Specifically we determine the number of events required to reject the null hypothesis that the median direction is random (corresponding to an isotropic Galactic recoil distribution) at 95 confidence. We find that for zero background 31 events are required, a factor of roughly 2 more than are required to simply reject isotropy. We also investigate the effect of a non-zero isotropic background. As the background rate is increased the number of events required increases, initially fairly gradually and then more rapidly, once the signal becomes subdominant. We also discuss the effect of features in the speed distribution at large speeds, as found in recent high resolution simulations, on the median recoil direction.", "keyphrases": ["median recoil direction", "wimp", "directional detection"]}
{"id": "1011.3477", "title": "Cosmic Jets", "abstract": "We discuss time-dependent gravitational fields that \"accelerate\" free test particles to the speed of light resulting in cosmic double-jet configurations. It turns out that complete gravitational collapse along a spatial axis together with corresponding expansion along the other two axes leads to the accelerated motion of free test particles up and down parallel to the collapse axis such that a double-jet pattern is asymptotically formed with respect to the collapsed configuration.", "keyphrases": ["test particle", "collapse", "pattern", "cosmic jet"]}
{"id": "1301.4543", "title": "The large scale magnetic fields of thin accretion disks", "abstract": "Large scale magnetic field threading an accretion disk is a key ingredient in the jet formation model. The most attractive scenario for the origin of such a large scale field is the advection of the field by the gas in the accretion disk from the interstellar medium or a companion star. However, it is realized that outward diffusion of the accreted field is fast compared to the inward accretion velocity in a geometrically thin accretion disk if the value of the Prandtl number Pm is around unity. In this work, we revisit this problem considering the angular momentum of the disk is removed predominantly by the magnetically driven outflows. The radial velocity of the disk is significantly increased due to the presence of the outflows. Using a simplified model for the vertical disk structure, we find that even moderately weak fields can cause sufficient angular momentum loss via a magnetic wind to balance outward diffusion. There are two equilibrium points, one at low field strengths corresponding to a plasma-beta at the midplane of order several hundred, and one for strong accreted fields, beta 1. We surmise that the first is relevant for the accretion of weak, possibly external, fields through the outer parts of the disk, while the latter one could explain the tendency, observed in full 3D numerical simulations, of strong flux bundles at the centers of disk to stay confined in spite of strong MRI turbulence surrounding them.", "keyphrases": ["large scale", "magnetic field", "accretion disk"]}
{"id": "1506.04048", "title": "Inflationary Imprints on Dark Matter", "abstract": "We show that dark matter abundance and the inflationary scale H could be intimately related. Standard Model extensions with Higgs mediated couplings to new physics typically contain extra scalars displaced from vacuum during inflation. If their coupling to Standard Model is weak, they will not thermalize and may easily constitute too much dark matter reminiscent to the moduli problem. As an example we consider Standard Model extended by a Z_2 symmetric singlet s coupled to the Standard Model Higgs \u03a6 via \u03bb\u03a6^\u2020\u03a6 s^2. Dark matter relic density is generated non-thermally for \u03bb\u2272 10^-7. We show that the dark matter yield crucially depends on the inflationary scale. For H\u223c 10^10 GeV we find that the singlet self-coupling and mass should lie in the regime \u03bb_ s\u2273 10^-9 and m_ s\u2272 50 GeV to avoid dark matter overproduction.", "keyphrases": ["dark matter", "primordial condensate", "universe"]}
{"id": "1402.0867", "title": "The Big Problems in Star Formation: the Star Formation Rate, Stellar Clustering, and the Initial Mass Function", "abstract": "Star formation lies at the center of a web of processes that drive cosmic evolution: generation of radiant energy, synthesis of elements, formation of planets, and development of life. Decades of observations have yielded a variety of empirical rules about how it operates, but at present we have no comprehensive, quantitative theory. In this review I discuss the current state of the field of star formation, focusing on three central questions: what controls the rate at which gas in a galaxy converts to stars? What determines how those stars are clustered, and what fraction of the stellar population ends up in gravitationally-bound structures? What determines the stellar initial mass function, and does it vary with star-forming environment? I use these three question as a lens to introduce the basics of star formation, beginning with a review of the observational phenomenology and the basic physical processes. I then review the status of current theories that attempt to solve each of the three problems, pointing out links between them and opportunities for theoretical and numerical work that crosses the scale between them. I conclude with a discussion of prospects for theoretical progress in the coming years.", "keyphrases": ["star formation", "initial mass function", "generation", "turbulence"]}
{"id": "1203.0395", "title": "Cosmological Hysteresis and the Cyclic Universe", "abstract": "A Universe filled with a homogeneous scalar field exhibits `Cosmological hysteresis'. Cosmological hysteresis is caused by the asymmetry in the equation of state during expansion and contraction. This asymmetry results in the formation of a hysteresis loop: \u222e pdV, whose value can be non-vanishing during each oscillatory cycle. For flat potentials, a negative value of the hysteresis loop leads to the increase in amplitude of consecutive cycles and to a universe with older and larger successive cycles. Such a universe appears to possess an arrow of time even though entropy production is absent and all of the equations respect time-reversal symmetry ! Cosmological hysteresis appears to be widespread and exists for a large class of scalar field potentials and mechanisms for making the universe bounce. For steep potentials, the value of the hysteresis loop can be positive as well as negative. The expansion factor in this case displays quasi-periodic behaviour in which successive cycles can be both larger as well as smaller than previous ones. This quasi-regular pattern resembles the phenomenon of BEATS displayed by acoustic systems. Remarkably, the expression relating the increase/decrease in oscillatory cycles to the quantum of hysteresis appears to be model independent. The cyclic scenario is extended to spatially anisotropic models and it is shown that the anisotropy density decreases during successive cycles if the hysteresis loop is negative.", "keyphrases": ["cyclic universe", "scalar field potential", "phenomenon", "cosmological hysteresis"]}
{"id": "2005.05534", "title": "Gravitational baryogenesis in extended teleparallel theories of gravity", "abstract": "The article communicates gravitational baryogenesis in non-minimal f(T) gravity and f(T,B) teleparallel gravity where T denote the torsion scalar and B a boundary term. These extended teleparallel theories of gravity differ from the usual f(T) gravity and therefore could provide key insights in expounding the baryon asymmetry of the universe. Furthermore, such a study also put constraints on the model parameters of these extended teleparallel theory of gravity. I present different baryogenesis interactions proportional to \u2202_iT, \u2202_if(T), \u2202_i(T+B) and \u2202_if(T+B) and find that both of these teleparallel theories of gravity yield viable estimates of the baron-to-entropy ratio compatible with observations except for the baryogenesis interaction proportional to \u2202_i(T+B). It is therefore encouraging to exercise these extended theories of gravity in other cosmological areas to under their efficiency and applicability in characterizing the current state of the universe.", "keyphrases": ["extended teleparallel theory", "gravity", "gravitational baryogenesis"]}
{"id": "1408.3465", "title": "Thermodynamic interpretation of the generalized gravity models with geometry - matter coupling", "abstract": "Modified gravity theories with geometry - matter coupling, in which the action is an arbitrary function of the Ricci scalar and the matter Lagrangian (f(R,L_m) gravity), and of the Ricci scalar and of the trace of the matter energy-momentum tensor (f(R,T) gravity), respectively, have the intriguing property that the divergence of the matter energy - momentum tensor is nonzero. In the present paper, by using the formalism of open thermodynamic systems, we interpret the generalized conservation equations in these gravitational theories from a thermodynamic point of view as describing irreversible matter creation processes, which could be validated by fundamental particle physics. Thus particle creation corresponds to an irreversible energy flow from the gravitational field to the created matter constituents, with the second law of thermodynamics requiring that space-time transforms into matter. The equivalent particle number creation rates, the creation pressure and the entropy production rates are obtained for both f(R,L_m) and f(R,T) gravity theories. The temperature evolution laws of the newly created particles are also obtained. In the case of the f(R,T) gravity theory the open irreversible thermodynamic interpretation of a simple cosmological model is presented in detail. It is also shown that due to the geometry\u2013matter coupling, during the cosmological evolution a large amount of comoving entropy could be produced.", "keyphrases": ["gravity model", "matter coupling", "cosmological model", "thermodynamic interpretation"]}
{"id": "1012.5411", "title": "Circular motion of neutral test particles in Reissner-Nordstr\u00f6m spacetime", "abstract": "We investigate the motion of neutral test particles in the gravitational field of a mass M with charge Q described by the Reissner-Nordstr\u00f6m (RN) spacetime. We focus on the study of circular stable and unstable orbits around configurations describing either black holes or naked singularities. We show that at the classical radius, defined as Q^2/M, there exist orbits with zero angular momentum due to the presence of repulsive gravity. The analysis of the stability of circular orbits indicates that black holes are characterized by a continuous region of stability. In the case of naked singularities, the region of stability can split into two non-connected regions inside which test particles move along stable circular orbits.", "keyphrases": ["neutral test particle", "spacetime", "circular orbit"]}
{"id": "2111.08541", "title": "The homogeneity scale and the growth rate of cosmic structures", "abstract": "We propose a novel approach to obtain the growth rate of cosmic structures, f(z), from the evolution of the cosmic homogeneity scale, R_H(z). Our methodology needs two ingredients in a specific functional form: R_H(z) data and the matter two-point correlation function today, i.e., \u03be(r, z=0). We use a Gaussian Process approach to reconstruct the function R_H. In the absence of suitable observational information of the matter correlation function in the local Universe, z \u2243 0, we assume a fiducial cosmology to obtain \u03be(r, z=0). For this reason, our final result turns out to be a consistency test of the cosmological model assumed. Our results show a good agreement between: (i) the growth rate f^R_H(z) obtained through our approach, (ii) the f^\u039bCDM(z) expected in the fiducial model, and (iii) the best-fit f(z) from data compiled in the literature. Moreover, using this data compilation, we perform a Gaussian Process to reconstruct the growth rate function f^data(z) and compare it with the function f^R_H(z) finding a concordance of < 2 \u03c3, a good result considering the few data available for both reconstruction processes. With more accurate R_H(z) data, from forthcoming surveys, the homogeneity scale function might be better determined and would have the potential to discriminate between \u039bCDM and alternative scenarios as a new cosmological observable.", "keyphrases": ["homogeneity scale", "growth rate", "cosmic structure"]}
{"id": "1612.00451", "title": "Gas Accretion in Star-Forming Galaxies", "abstract": "Cold-mode gas accretion onto galaxies is a direct prediction of LCDM simulations and provides galaxies with fuel that allows them to continue to form stars over the lifetime of the Universe. Given its dramatic influence on a galaxy's gas reservoir, gas accretion has to be largely responsible for how galaxies form and evolve. Therefore, given the importance of gas accretion, it is necessary to observe and quantify how these gas flows affect galaxy evolution. However, observational data have yet to conclusively show that gas accretion ubiquitously occurs at any epoch. Directly detecting gas accretion is a challenging endeavor and we now have obtained a significant amount of observational evidence to support it. This chapter reviews the current observational evidence of gas accretion onto star-forming galaxies.", "keyphrases": ["star-forming galaxy", "star", "gas accretion"]}
{"id": "1702.08338", "title": "Collective neutrino oscillations and neutrino wave packets", "abstract": "Effects of decoherence by wave packet separation on collective neutrino oscillations in dense neutrino gases are considered. We estimate the length of the wave packets of neutrinos produced in core collapse supernovae and the expected neutrino coherence length, and then proceed to consider the decoherence effects within the density matrix formalism of neutrino flavour transitions. First, we demonstrate that for neutrino oscillations in vacuum the decoherence effects are described by a damping term in the equation of motion of the density matrix of a neutrino as a whole (as contrasted to that of the fixed-momentum components of the neutrino density matrix). Next, we consider neutrino oscillations in ordinary matter and dense neutrino backgrounds, both in the adiabatic and non-adiabatic regimes. In the latter case we study two specific models of adiabaticity violation \u2013 one with short-term and another with extended non-adiabaticity. It is demonstrated that, while in the adiabatic case a damping term is present in the equation of motion of the neutrino density matrix (just like in the vacuum oscillation case), no such term in general appears in the non-adiabatic regime.", "keyphrases": ["wave packet", "decoherence", "collective neutrino oscillation"]}
{"id": "1505.07148", "title": "DEMNUni: The clustering of large-scale structures in the presence of massive neutrinos", "abstract": "(abridged) We analyse the clustering features of Large Scale Structures (LSS) in the presence of massive neutrinos, employing a set of large-volume, high-resolution cosmological N-body simulations, where neutrinos are treated as a separate collisionless fluid. The volume of 8, combined with a resolution of about 8\u00d7 10^10 for the cold dark matter (CDM) component, represents a significant improvement over previous N-body simulations in massive neutrino cosmologies. We show that most of the nonlinear evolution is generated exclusively by the CDM component. We find that accounting only for the nonlinear evolution of the CDM power spectrum allows to recover the total matter power spectrum with the same accuracy as the massless case. Indeed, we show that, the most recent version of the formula calibrated on \u039bCDM simulations can be applied directly to the linear CDM power spectrum without requiring additional fitting parameters in the massive case. As a second step, we study the abundance and clustering properties of CDM halos, confirming that, in massive neutrino cosmologies, the proper definition of the halo bias should be made with respect to the cold rather than the total matter distribution, as recently shown in the literature. Here we extend these results to the redshift space, finding that, when accounting for massive neutrinos, an improper definition of the linear bias can lead to a systematic error of about 1-2 % in the determination of the linear growth rate from anisotropic clustering. This result is quite important if we consider that future spectroscopic galaxy surveys, as Euclid, are expected to measure the linear growth-rate with statistical errors less than about 3 % at z\u22721.", "keyphrases": ["neutrino", "dark matter", "abundance", "structure formation", "particle representation"]}
{"id": "1003.3415", "title": "Testing the No-Hair Theorem with Observations in the Electromagnetic Spectrum: I. Properties of a Quasi-Kerr Spacetime", "abstract": "According to the no-hair theorem, an astrophysical black hole is uniquely described by only two quantities, the mass and the spin. In this series of papers, we investigate a framework for testing the no-hair theorem with observations of black holes in the electromagnetic spectrum. We formulate our approach in terms of a parametric spacetime which contains a quadrupole moment that is independent of both mass and spin. If the no-hair theorem is correct, then any deviation of the black-hole quadrupole moment from its Kerr value has to be zero. We analyze in detail the properties of this quasi-Kerr spacetime that are critical to interpreting observations of black holes and demonstrate their dependence on the spin and quadrupole moment. In particular, we show that the location of the innermost stable circular orbit and the gravitational lensing experienced by photons are affected significantly at even modest deviations of the quadrupole moment from the value predicted by the no-hair theorem. We argue that observations of black-hole images, of relativistically broadened iron lines, as well as of thermal X-ray spectra from accreting black holes will lead in the near future to an experimental test of the no-hair theorem.", "keyphrases": ["no-hair theorem", "spacetime", "black hole"]}
{"id": "0911.0483", "title": "Chiral three-nucleon forces and neutron matter", "abstract": "We calculate the properties of neutron matter and highlight the physics of chiral three-nucleon forces. For neutrons, only the long-range 2 pi-exchange interactions of the leading chiral three-nucleon forces contribute, and we derive density-dependent two-body interactions by summing the third particle over occupied states in the Fermi sea. Our results for the energy suggest that neutron matter is perturbative at nuclear densities. We study in detail the theoretical uncertainties of the neutron matter energy, provide constraints for the symmetry energy and its density dependence, and explore the impact of chiral three-nucleon forces on the S-wave superfluid pairing gap.", "keyphrases": ["three-nucleon force", "neutron matter", "symmetry energy", "chiral", "momentum space"]}
{"id": "2012.14981", "title": "Baryogenesis from ultralight primordial black holes and strong gravitational waves from cosmic strings", "abstract": "Ultralight primordial black holes (PBHs)(\u227210^9g) completely evaporate via Hawking radiation (HR) and produce all the particles in a given theory regardless of their other interactions. If the right handed (RH) neutrinos are produced from PBH evaporation, successful baryogenesis via leptogenesis predicts mass scale of RH neutrinos as well as black holes. We show that, given the lepton number violation (generation of RH neutrino masses) in the theory is a consequence of a gauged U(1) breaking which is then followed by the formation of PBHs, a network of cosmic strings naturally gives rise to strong stochastic gravitational wave (GW) signal at the sensitivity level of pulsar timing arrays (PTA) and LIGO5. Besides, due to a transient period of black hole domination in the early universe, for which baryon asymmetry is independent of initial PBH density, a break in the GW spectra occurs around MHz frequency. Therefore, to observe the break along with the usual GW signal by the emission of gravitons via HR, GW detectors at higher frequencies are called for. The recent finding by the NANOGrav PTA of a stochastic common spectrum process (interpreted as GWs) across many pulsars is in tension with PBH baryogenesis for large cosmic string loops (\u03b1\u2243 0.1).", "keyphrases": ["primordial black hole", "gravitational wave", "baryogenesis"]}
{"id": "1304.4514", "title": "Distance Priors from Planck and Dark Energy Constraints from Current Data", "abstract": "We derive distance priors from Planck first data release, and examine their impact on dark energy constraints from current observational data. We give the mean values and covariance matrix of R, l_a, \u03a9_b h^2, n_s, which give an efficient summary of Planck data. The CMB shift parameters are R=\u221a(\u03a9_m H_0^2) r(z_*), and l_a=\u03c0r(z_*)/r_s(z_*), where z_* is the redshift at the last scattering surface, and r(z_*) and r_s(z_*) denote our comoving distance to z_* and sound horizon at z_* respectively. We find that Planck distance priors are significantly tighter than those from WMAP9. However, adding Planck distance priors does not lead to significantly improved dark energy constraints using current data, compared to adding WMAP9 distance priors. This is because Planck data appear to favor a higher matter density and lower Hubble constant, in tension with most of the other current cosmological data sets. Adding Planck distance priors to current data leads to a marginal inconsistency with a cosmological constant in a flat universe.", "keyphrases": ["dark energy constraint", "current data", "distance prior"]}
{"id": "1001.4580", "title": "Quasar variability limits on cosmological density of cosmic strings", "abstract": "We put robust upper limits on the average cosmological density \u03a9_s of cosmic strings based on the variability properties of a large homogeneous sample of SDSS quasars. We search for an excess of characteristic variations of quasar brightness that are associated with string lensing and use the observed distribution of this variation to constrain the density of strings. The limits obtained do not invoke any clustering of strings, apply to both open segments and closed loops of strings, usefully extend over a wide range of tensions 10^-13 < G\u03bc/c^2 < 10^-9 and reach down the level of \u03a9_s=0.01 and below. Further progress in this direction will depend on better understanding of quasar intrinsic variability rather than a mere increase in the volume of data.", "keyphrases": ["variability", "cosmic string", "quasar"]}
{"id": "1304.6884", "title": "Combustion of a neutron star into a strange quark star: The neutrino signal", "abstract": "There are strong indications that the process of conversion of a neutron star into a strange quark star proceeds as a strong deflagration implying that in a few milliseconds almost the whole star is converted. Starting from the three-dimensional hydrodynamic simulations of the combustion process which provide the temperature profiles inside the newly born strange star, we calculate for the first time the neutrino signal that is to be expected if such a conversion process takes place. The neutrino emission is characterized by a luminosity and a duration that is typical for the signal expected from protoneutron stars and represents therefore a powerful source of neutrinos which could be possibly directly detected in case of events occurring close to our Galaxy. We discuss moreover possible connections between the birth of strange stars and explosive phenomena such as supernovae and gamma-ray-bursts.", "keyphrases": ["neutron star", "quark star", "neutrino signal"]}
{"id": "1212.4812", "title": "Near Earth Asteroids with measurable Yarkovsky effect", "abstract": "We seek evidence of the Yarkovsky effect among Near Earth Asteroids (NEAs) by measuring the Yarkovsky-related orbital drift from the orbital fit. To prevent the occurrence of unreliable detections we employ a high precision dynamical model, including the Newtonian attraction of 16 massive asteroids and the planetary relativistic terms, and a suitable astrometric data treatment. We find 21 NEAs whose orbital fits show a measurable orbital drift with a signal to noise ratio (SNR) greater than 3. The best determination is for asteroid (101955) 1999 RQ36, resulting in the recovery of one radar apparition and an orbit improvement by two orders of magnitude. In addition, we find 16 cases with a lower SNR that, despite being less reliable, are good candidates for becoming stronger detections in the future. In some cases it is possible to constrain physical quantities otherwise unknown by means of the detected orbital drift. Furthermore, the distribution of the detected orbital drifts shows an excess of retrograde rotators that can be connected to the delivery mechanism from the most important NEA feeding resonances and allows us to infer the distribution for NEAs obliquity. We discuss the implications of the Yarkovsky effect for impact predictions. In particular, for asteroid (29075) 1950 DA our results favor a retrograde rotation that would rule out an impact in 2880.", "keyphrases": ["asteroid", "yarkovsky effect", "orbital drift", "orbital fit", "near-earth asteroid"]}
{"id": "1303.3121", "title": "Cosmic variance and the measurement of the local Hubble parameter", "abstract": "There is an approximately 9 two independent constraints on the expansion rate of the universe: one indirectly arising from the cosmic microwave background and baryon acoustic oscillations, and one more directly obtained from local measurements of the relation between redshifts and distances to sources. We argue that by taking into account the local gravitational potential at the position of the observer this tension - strengthened by the recent Planck results - is partially relieved and the concordance of the standard model of cosmology increased. We estimate that measurements of the local Hubble constant are subject to a cosmic variance of about 2.4 (limiting it to z>0.023), a more significant correction than that taken into account already. Nonetheless, we show that one would need a very rare fluctuation to fully explain the offset in the Hubble rates. If this tension is further strengthened, a cosmology beyond the standard model may prove necessary.", "keyphrases": ["variance", "hubble parameter", "expansion rate", "cosmic microwave background"]}
{"id": "1306.6283", "title": "KASCADE-Grande measurements of energy spectra for elemental groups of cosmic rays", "abstract": "The KASCADE-Grande air shower experiment [W. Apel, et al. (KASCADE-Grande collaboration), Nucl. Instrum. Methods A 620 (2010) 202] consists of, among others, a large scintillator array for measurements of charged particles, Nch, and of an array of shielded scintillation counters used for muon counting, Nmu. KASCADE-Grande is optimized for cosmic ray measurements in the energy range 10 PeV to about 2000 PeV, where exploring the composition is of fundamental importance for understanding the transition from galactic to extragalactic origin of cosmic rays. Following earlier studies of the all-particle and the elemental spectra reconstructed in the knee energy range from KASCADE data [T. Antoni, et al. (KASCADE collaboration), Astropart. Phys. 24 (2005) 1], we have now extended these measurements to beyond 200 PeV. By analysing the two-dimensional shower size spectrum Nch vs. Nmu for nearly vertical events, we reconstruct the energy spectra of different mass groups by means of unfolding methods over an energy range where the detector is fully efficient. The procedure and its results, which are derived based on the hadronic interaction model QGSJET-II-02 and which yield a strong indication for a dominance of heavy mass groups in the covered energy range and for a knee-like structure in the iron spectrum at around 80 PeV, are presented. This confirms and further refines the results obtained by other analyses of KASCADE-Grande data, which already gave evidence for a knee-like structure in the heavy component of cosmic rays at about 80 PeV [W. Apel, et al. (KASCADE-Grande collaboration), Phys. Rev. Lett. 107 (2011) 171104].", "keyphrases": ["energy spectra", "group", "cosmic ray"]}
{"id": "1202.4808", "title": "Crossing Statistic: Bayesian interpretation, model selection and resolving dark energy parametrization problem", "abstract": "By introducing Crossing functions and hyper-parameters I show that the Bayesian interpretation of the Crossing Statistics [1] can be used trivially for the purpose of model selection among cosmological models. In this approach to falsify a cosmological model there is no need to compare it with other models or assume any particular form of parametrization for the cosmological quantities like luminosity distance, Hubble parameter or equation of state of dark energy. Instead, hyper-parameters of Crossing functions perform as discriminators between correct and wrong models. Using this approach one can falsify any assumed cosmological model without putting priors on the underlying actual model of the universe and its parameters, hence the issue of dark energy parametrization is resolved. It will be also shown that the sensitivity of the method to the intrinsic dispersion of the data is small that is another important characteristic of the method in testing cosmological models dealing with data with high uncertainties.", "keyphrases": ["bayesian interpretation", "crossing statistic", "complicated correlation"]}
{"id": "1011.0372", "title": "Measuring the escape velocity and mass profiles of galaxy clusters beyond their virial radius", "abstract": "The caustic technique uses galaxy redshifts alone to measure the escape velocity and mass profiles of galaxy clusters to clustrocentric distances well beyond the virial radius, where dynamical equilibrium does not necessarily hold. We provide a detailed description of this technique and analyse its possible systematic errors. We apply the caustic technique to clusters with mass M_200>=10^14h^-1 M_sun extracted from a cosmological hydrodynamic simulation of a LambdaCDM universe. With a few tens of redshifts per squared comoving megaparsec within the cluster, the caustic technique, on average, recovers the profile of the escape velocity from the cluster with better than 10 percent accuracy up to r 4 r_200. The caustic technique also recovers the mass profile with better than 10 percent accuracy in the range (0.6-4) r_200, but it overestimates the mass up to 70 percent at smaller radii. This overestimate is a consequence of neglecting the radial dependence of the filling function F_beta(r). The 1-sigma uncertainty on individual escape velocity profiles increases from 20 to 50 percent when the radius increases from r 0.1 r_200 to 4 r_200. Individual mass profiles have 1-sigma uncertainty between 40 and 80 percent within the radial range (0.6-4) r_200. We show that the amplitude of these uncertainties is completely due to the assumption of spherical symmetry, which is difficult to drop. Alternatively, we can apply the technique to synthetic clusters obtained by stacking individual clusters: in this case, the 1-sigma uncertainty on the escape velocity profile is smaller than 20 percent out to 4 r_200. The caustic technique thus provides reliable average profiles which extend to regions difficult or impossible to probe with other techniques.", "keyphrases": ["mass profile", "galaxy cluster", "virial radius"]}
{"id": "1504.00324", "title": "Non-local bias in the halo bispectrum with primordial non-Gaussianity", "abstract": "Primordial non-Gaussianity can lead to a scale-dependent bias in the density of collapsed halos relative to the underlying matter density. The galaxy power spectrum already provides constraints on local-type primordial non-Gaussianity complementary those from the cosmic microwave background (CMB), while the bispectrum contains additional shape information and has the potential to outperform CMB constraints in future. We develop the bias model for the halo density contrast in the presence of local-type primordial non-Gaussianity, deriving a bivariate expansion up to second order in terms of the local linear matter density contrast and the local gravitational potential in Lagrangian coordinates. Non-linear evolution of the matter density introduces a non-local tidal term in the halo model. Furthermore, the presence of local-type non-Gaussianity in the Lagrangian frame leads to a novel non-local convective term in the Eulerian frame, that is proportional to the displacement field when going beyond the spherical collapse approximation. We use an extended Press-Schechter approach to evaluate the halo mass function and thus the halo bispectrum. We show that including these non-local terms in the halo bispectra can lead to corrections of up to 25% for some configurations, on large scales or at high redshift.", "keyphrases": ["bias", "primordial non-gaussianity", "galaxy bispectrum"]}
{"id": "1203.6222", "title": "Determining the Hubble constant using Giant extragalactic HII regions and HII galaxies", "abstract": "We report the first results of a long term program aiming to provide accurate independent estimates of the Hubble constant (H0) using the L-sigma distance estimator for Giant extragalactic HII regions (GEHR) and HII galaxies. We have used VLT and Subaru high dispersion spectroscopic observations of a local sample of HII galaxies, identified in the SDSS DR7 catalogue in order to re-define and improve the L(Hbeta)-sigma distance indicator and to determine the Hubble constant. To this end we utilized as local calibration or `anchor' of this correlation, GEHR in nearby galaxies which have accurate distance measurements determined via primary indicators. Using our best sample of 69 nearby HII galaxies and 23 GEHR in 9 galaxies we obtain H0=74.3 +- 3.1 (statistical) +- 2.9 (systematic) km /s Mpc, in excellent agreement with, and independently confirming, the most recent SNe Ia based results.", "keyphrases": ["hubble constant", "hii region", "hii galaxy"]}
{"id": "1810.08629", "title": "Quantifying baryon effects on the matter power spectrum and the weak lensing shear correlation", "abstract": "Feedback processes from baryons are expected to strongly affect weak-lensing observables of current and future cosmological surveys. In this paper we present a new parametrisation of halo profiles based on gas, stellar, and dark matter density components. This parametrisation is used to modify outputs of gravity-only N-body simulations (following the prescription of Schneider and Teyssier [1]) in order to mimic baryonic effects on the matter density field. The resulting baryonic correction model relies on a few well motivated physical parameters and is able to reproduce the redshift zero clustering signal of hydrodynamical simulations at two percent accuracy below k\u223c10 h/Mpc. A detailed study of the baryon suppression effects on the matter power spectrum and the weak lensing shear correlation reveals that the signal is dominated by two parameters describing the slope of the gas profile in haloes and the maximum radius of gas ejection. We show that these parameters can be constrained with the observed gas fraction of galaxy groups and clusters from X-ray data. Based on these observations we predict a beyond percent effect on the power spectrum above k=0.2-1.0 h/Mpc with a maximum suppression of 15-25 percent around k\u223c 10 h/Mpc. As a result, the weak lensing angular shear power spectrum is suppressed by 15-25 percent at scales beyond \u2113\u223c 100-600 and the shear correlations \u03be_+ and \u03be_- are affected at the 10-25 percent level below 5 and 50 arc-minutes, respectively. The relatively large uncertainties of these predictions are a result of the poorly known hydrostatic mass bias of current X-ray observations as well as the generic difficulty to observe the low density gas outside of haloes.", "keyphrases": ["baryon", "matter power spectrum", "lensing shear correlation"]}
{"id": "1112.1922", "title": "Tides in colliding galaxies", "abstract": "Long tails and streams of stars are the most noticeable upshots of galaxy collisions. Their origin as gravitational, tidal, disturbances has however been recognized only less than fifty years ago and more than ten years after their first observations. This Review describes how the idea of galactic tides emerged, in particular thanks to the advances in numerical simulations, from the first ones that included tens of particles to the most sophisticated ones with tens of millions of them and state-of-the-art hydrodynamical prescriptions. Theoretical aspects pertaining to the formation of tidal tails are then presented. The third part of the review turns to observations and underlines the need for collecting deep multi-wavelength data to tackle the variety of physical processes exhibited by collisional debris. Tidal tails are not just stellar structures, but turn out to contain all the components usually found in galactic disks, in particular atomic / molecular gas and dust. They host star-forming complexes and are able to form star-clusters or even second-generation dwarf galaxies. The final part of the review discusses what tidal tails can tell us (or not) about the structure and content of present-day galaxies, including their dark components, and explains how tidal tails may be used to probe the past evolution of galaxies and their mass assembly history. On-going deep wide-field surveys disclose many new low-surface brightness structures in the nearby Universe, offering great opportunities for attempting galactic archeology with tidal tails.", "keyphrases": ["galaxy", "collisional debris", "content"]}
{"id": "1610.06463", "title": "Tracing water vapor and ice during dust growth", "abstract": "The processes that govern the evolution of dust and water (in the form of vapor or ice) in protoplanetary disks are intimately connected. We have developed a model that simulates dust coagulation, dust dynamics (settling, turbulent mixing), vapor diffusion, and condensation/sublimation of volatiles onto grains in a vertical column of a protoplanetary disk. We employ the model to study how dust growth and dynamics influence the vertical distribution of water vapor and water ice in the region just outside the radial snowline. Our main finding is that coagulation (boosted by the enhanced stickiness of icy grains) and the ensuing vertical settling of solids results in water vapor being depleted, but not totally removed, from the region above the snowline on a timescale commensurate with the vertical turbulent mixing timescale. Depending on the strength of the turbulence and the temperature, the depletion can reach factors of up to \u223c50 in the disk atmosphere. In our isothermal column, this vapor depletion results in the vertical snowline moving closer to the midplane (by up to 2 gas scale heights) and the gas-phase C/O ratio above the vertical snowline increasing. Our findings illustrate the importance of dynamical effects and the need for understanding coevolutionary dynamics of gas and solids in planet-forming environments.", "keyphrases": ["water vapor", "ice", "dust growth"]}
{"id": "1606.08448", "title": "Relative Likelihood for Life as a Function of Cosmic Time", "abstract": "Is life most likely to emerge at the present cosmic time near a star like the Sun? We address this question by calculating the relative formation probability per unit time of habitable Earth-like planets within a fixed comoving volume of the Universe, dP(t)/dt, starting from the first stars and continuing to the distant cosmic future. We conservatively restrict our attention to the context of \"life as we know it\" and the standard cosmological model, LCDM. We find that unless habitability around low mass stars is suppressed, life is most likely to exist near 0.1 solar-mass stars ten trillion years from now. Spectroscopic searches for biosignatures in the atmospheres of transiting Earth-mass planets around low mass stars will determine whether present-day life is indeed premature or typical from a cosmic perspective.", "keyphrases": ["likelihood", "life", "cosmic time"]}
{"id": "2111.03606", "title": "GWTC-3: Compact Binary Coalescences Observed by LIGO and Virgo During the Second Part of the Third Observing Run", "abstract": "The third Gravitational-Wave Transient Catalog (GWTC-3) describes signals detected with Advanced LIGO and Advanced Virgo up to the end of their third observing run. Updating the previous GWTC-2.1, we present candidate gravitational waves from compact binary coalescences during the second half of the third observing run (O3b) between 1 November 2019, 15:00 UTC and 27 March 2020, 17:00 UTC. There are 35 compact binary coalescence candidates identified by at least one of our search algorithms with a probability of astrophysical origin p_astro > 0.5. Of these, 18 were previously reported as low-latency public alerts, and 17 are reported here for the first time. Based upon estimates for the component masses, our O3b candidates with p_astro > 0.5 are consistent with gravitational-wave signals from binary black holes or neutron star-black hole binaries, and we identify none from binary neutron stars. However, from the gravitational-wave data alone, we are not able to measure matter effects that distinguish whether the binary components are neutron stars or black holes. The range of inferred component masses is similar to that found with previous catalogs, but the O3b candidates include the first confident observations of neutron star-black hole binaries. Including the 35 candidates from O3b in addition to those from GWTC-2.1, GWTC-3 contains 90 candidates found by our analysis with p_astro > 0.5 across the first three observing runs. These observations of compact binary coalescences present an unprecedented view of the properties of black holes and neutron stars.", "keyphrases": ["gravitational-wave transient catalog", "binary black hole", "neutron star merger"]}
{"id": "1707.01042", "title": "Perturbation theory for cosmologies with non-linear structure", "abstract": "The next generation of cosmological surveys will operate over unprecedented scales, and will therefore provide exciting new opportunities for testing general relativity. The standard method for modelling the structures that these surveys will observe is to use cosmological perturbation theory for linear structures on horizon-sized scales, and Newtonian gravity for non-linear structures on much smaller scales. We propose a two-parameter formalism that generalizes this approach, thereby allowing interactions between large and small scales to be studied in a self-consistent and well-defined way. This uses both post-Newtonian gravity and cosmological perturbation theory, and can be used to model realistic cosmological scenarios including matter, radiation and a cosmological constant. We find that the resulting field equations can be written as a hierarchical set of perturbation equations. At leading-order, these equations allow us to recover a standard set of Friedmann equations, as well as a Newton-Poisson equation for the inhomogeneous part of the Newtonian energy density in an expanding background. For the perturbations in the large-scale cosmology, however, we find that the field equations are sourced by both non-linear and mode-mixing terms, due to the existence of small-scale structures. These extra terms should be expected to give rise to new gravitational effects, through the mixing of gravitational modes on small and large scales - effects that are beyond the scope of standard linear cosmological perturbation theory. We expect our formalism to be useful for accurately modelling gravitational physics in universes that contain non-linear structures, and for investigating the effects of non-linear gravity in the era of ultra-large-scale surveys.", "keyphrases": ["cosmology", "non-linear structure", "perturbation theory"]}
{"id": "1210.3859", "title": "Observational Constraints on Quintessence: Thawing, Tracker, and Scaling models", "abstract": "For two types of quintessence models having thawing and tracking properties, there exist analytic solutions for the dark energy equation of state w expressed in terms of several free parameters. We put observational bounds on the parameters in such scenarios by using the recent data of Supernovae type Ia, Cosmic Microwave Background, and Baryon Acoustic Oscillations. The observational constraints are quite different depending on whether or not the recent BAO data from BOSS are taken into account. With the BOSS data the upper bounds of today's values of w (=w_0) in thawing models is very close to -1, whereas without this data the values of w_0 away from -1 can be still allowed. The tracker equation of state w_(0) during the matter era is constrained to be w_(0)<-0.949 at 95 the tracker models with w away from -1 are severely disfavored. We also study observational constraints on scaling models in which w starts to evolve from 0 in the deep matter era and show that the transition to the equation of state close to w=-1 needs to occur at an early cosmological epoch. In the three classes of quintessence models studied in this paper, the past evolution of the Hubble parameters in the best-fit models shows only less than the 2.5 difference compared to the LCDM.", "keyphrases": ["quintessence", "scaling model", "dark energy", "baryon acoustic oscillations", "observational constraint"]}
{"id": "1108.1317", "title": "Inference of the cosmological parameters from gravitational waves: application to second generation interferometers", "abstract": "The advanced world-wide network of gravitational waves (GW) observatories is scheduled to begin operations within the current decade. Thanks to their improved sensitivity, they promise to yield a number of detections and thus to open a new observational windows for astronomy and astrophysics. Among the scientific goals that should be achieved, there is the independent measurement of the value of the cosmological parameters, hence an independent test of the current cosmological paradigm. Due to the importance of such task, a number of studies have evaluated the capabilities of GW telescopes in this respect. However, since GW do not yield information about the source redshift, different groups have made different assumptions regarding the means through which the GW redshift can be obtained. These different assumptions imply also different methodologies to solve this inference problem. This work presents a formalism based on Bayesian inference developed to facilitate the inclusion of all assumptions and prior information about a GW source within a single data analysis framework. This approach guarantees the minimisation of information loss and the possibility of including naturally event-specific knowledge (such as the sky position for a Gamma Ray Burst - GW coincident observation) in the analysis. The workings of the method are applied to a specific example, loosely designed along the lines of the method proposed by Schutz in 1986, in which one uses information from wide-field galaxy surveys as prior information for the location of a GW source. I show that combining the results from few tens of observations from a network of advanced interferometers will constrain the Hubble constant H_0 to an accuracy of \u223c 4 - 5", "keyphrases": ["cosmological parameter", "gravitational wave", "inference"]}
{"id": "1103.0031", "title": "Ultrahigh Energy Cosmic Rays", "abstract": "This is a review of the most resent results from the investigation of the Ultrahigh Energy Cosmic Rays, particles of energy exceeding 10^18 eV. After a general introduction to the topic and a brief review of the lower energy cosmic rays and the detection methods, the two most recent experiments, the High Resolution Fly's Eye (HiRes) and the Southern Auger Observatory are described. We then concentrate on the results from these two experiments on the cosmic ray energy spectrum, the chemical composition of these cosmic rays and on the searches for their sources. We conclude with a brief analysis of the controversies in these results and the projects in development and construction that can help solve the remaining problems with these particles.", "keyphrases": ["cosmic ray", "particle", "ultra-high energy"]}
{"id": "2009.10424", "title": "Small scale induced gravitational waves from primordial black holes, a stringent lower mass bound, and the imprints of an early matter to radiation transition", "abstract": "In all inflationary scenarios of primordial black holes (PBH) formation, amplified scalar perturbations inevitably accompany an induced stochastic gravitational waves background (ISGWB) at smaller scales. In this paper, we study the ISGWB originating from the inflationary model, introduced in our previous paper [1] wherein PBHs can be produced with a nearly monochromatic mass fraction in the asteroid mass window accounting for the total dark matter in the universe. We numerically calculate the ISGWB in our scenario for frequencies ranging from nanoHz to KHz that covers the observational scales corresponding to future space based GW observatories such as IPTA, LISA, DECIGO and ET. Interestingly, we find that ultralight PBHs (M_ PBH\u223c 10^-20 M_\u2299) which shall completely evaporate by today with exceedingly small contribution to dark matter, would still generate an ISGWB that may be detected by a future design of the ground based Advanced LIGO detector. Using a model independent approach, we obtain a stringent lower mass limit for ultralight PBHs which would be valid for a large class of ultra slow roll inflationary models. Further, we extend our formalism to study the imprints of a reheating epoch on both the ISGWB and the derived lower mass bound. We find that any non-instantaneous reheating leads to an even stronger lower bound on PBHs mass and an epoch of a prolonged matter dominated reheating shifts the ISGWB spectrum to smaller frequencies. In particular, we show that an epoch of an early matter dominated phase leads to a secondary amplification of ISGWB at much smaller scales corresponding to the smallest comoving scale leaving the horizon during inflation or the end of inflation scale. Finally, we discuss the prospects of the ISGWB detection by the proposed and upcoming GW observatories.", "keyphrases": ["gravitational wave", "primordial black hole", "early matter"]}
{"id": "1206.0732", "title": "Relativistic corrections and non-Gaussianity in radio continuum surveys", "abstract": "Forthcoming radio continuum surveys will cover large volumes of the observable Universe and will reach to high redshifts, making them potentially powerful probes of dark energy, modified gravity and non-Gaussianity. Here we extend recent works by analyzing the general relativistic (GR) corrections to the angular power spectrum. These GR corrections to the standard Newtonian analysis of the power spectrum become significant on scales near and beyond the Hubble scale at each redshift. We consider the continuum surveys with LOFAR, WSRT and ASKAP, and examples of continuum surveys with the SKA. We find that the GR corrections are at most percent-level in LOFAR, WODAN and EMU surveys, but they can produce O(10 surveys. The signal is however dominated by cosmic variance, and multiple-tracer observations will be needed to overcome this problem. The GR corrections are suppressed in continuum surveys because of the integration over redshift \u2013 we expect that GR corrections will be enhanced for future SKA HI surveys in which the source redshifts will be known. We also provide predictions for the angular power spectra in the case where the primordial perturbations have local non-Gaussianity. We find that non-Gaussianity dominates over GR corrections, and rises above cosmic variance whenf_NL\u22735for SKA continuum surveys.", "keyphrases": ["non-gaussianity", "radio", "relativistic effect", "galaxy distribution"]}
{"id": "1604.00469", "title": "Fluctuations of electrical conductivity: a new source for astrophysical magnetic fields", "abstract": "We consider the generation of magnetic field by the flow of a fluid for which the electrical conductivity is nonuniform. A new amplification mechanism is found which leads to dynamo action for flows much simpler than those considered so far. In particular, the fluctuations of the electrical conductivity provide a way to bypass anti-dynamo theorems. For astrophysical objects, we show through three-dimensional global numerical simulations that the temperature-driven fluctuations of the electrical conductivity can amplify an otherwise decaying large scale equatorial dipolar field. This effect could play a role for the generation of the unusually tilted magnetic field of the iced giants Neptune and Uranus.", "keyphrases": ["electrical conductivity", "magnetic field", "fluctuation"]}
{"id": "1901.05465", "title": "The Faintest Dwarf Galaxies", "abstract": "The lowest luminosity (L < 10^5 L_sun) Milky Way satellite galaxies represent the extreme lower limit of the galaxy luminosity function. These ultra-faint dwarfs are the oldest, most dark matter-dominated, most metal-poor, and least chemically evolved stellar systems known. They therefore provide unique windows into the formation of the first galaxies and the behavior of dark matter on small scales. In this review, we summarize the discovery of ultra-faint dwarfs in the Sloan Digital Sky Survey in 2005, and the subsequent observational and theoretical progress in understanding their nature and origin. We describe their stellar kinematics, chemical abundance patterns, structural properties, stellar populations, orbits, and luminosity function, and what can be learned from each type of measurement. We conclude that: (1) in most cases, the stellar velocity dispersions of ultra-faint dwarfs are robust against systematic uncertainties such as binary stars and foreground contamination; (2) the chemical abundance patterns of stars in ultra-faint dwarfs require two sources of r-process elements, one of which can likely be attributed to neutron star mergers; (3) even under conservative assumptions, only a small fraction of ultra-faint dwarfs may have suffered significant tidal stripping of their stellar components; (4) determining the properties of the faintest dwarfs out to the virial radius of the Milky Way will require very large investments of observing time with future telescopes. Finally, we offer a look forward at the observations that will be possible with future facilities as the push toward a complete census of the Local Group dwarf galaxy population continues.", "keyphrases": ["dwarf", "ultra-faint dwarf", "dark matter"]}
{"id": "1007.0185", "title": "Model Independent Signatures of New Physics in the Inflationary Power Spectrum", "abstract": "We compute the universal generic corrections to the inflationary power spectrum due to unknown high-energy physics. We arrive at this result via a careful integrating out of massive fields in the \"in-in\" formalism yielding a consistent and predictive low-energy effective description in time-dependent backgrounds. We find that the power spectrum is universally modified at order H/M, where H is the scale of inflation. This is qualitatively different from the universal corrections in time-independent backgrounds, and it suggests that such effects may be present in upcoming cosmological observations.", "keyphrases": ["new physics", "inflationary power spectrum", "massive field"]}
{"id": "1403.0371", "title": "Constraining the spin and the deformation parameters from the black hole shadow", "abstract": "Within 5-10 years, very-long baseline interferometry (VLBI) facilities will be able to directly image the accretion flow around SgrA^*, the super-massive black hole candidate at the center of the Galaxy, and observe the black hole \"shadow\". In 4-dimensional general relativity, the no-hair theorem asserts that uncharged black holes are described by the Kerr solution and are completely specified by their mass M and by their spin parameter a. In this paper, we explore the possibility of distinguishing Kerr and Bardeen black holes from their shadow. In Hioki Maeda (2009), under the assumption that the background geometry is described by the Kerr solution, the authors proposed an algorithm to estimate the value of a/M by measuring the distortion parameter \u03b4, an observable quantity that characterizes the shape of the shadow. Here, we try to extend their approach. Since the Hioki-Maeda distortion parameter is degenerate with respect to the spin and possible deviations from the Kerr solution, one has to measure another quantity to test the Kerr black hole hypothesis. We study a few possibilities. We find that it is extremely difficult to distinguish Kerr and Bardeen black holes from the sole observation of the shadow, and out of reach for the near future. The combination of the measurement of the shadow with possible accurate radio observations of a pulsar in a compact orbit around SgrA^* could be a more promising strategy to verify the Kerr black hole paradigm.", "keyphrases": ["spin", "black hole", "general relativity"]}
{"id": "1106.0152", "title": "Vesta and Ceres: crossing the history of the Solar System", "abstract": "The evolution of the Solar System can be schematically divided into three different phases: the Solar Nebula, the Primordial Solar System and the Modern Solar System. These three periods were characterized by very different conditions, both from the point of view of the physical conditions and from that of the processes there were acting through them. Across the Solar Nebula phase, planetesimals and planetary embryos were forming and differentiating due to the decay of short-lived radionuclides. At the same time, giant planets formed their cores and accreted the nebular gas to reach their present masses. After the gas dispersal, the Primordial Solar System began its evolution. In the inner Solar System, planetary embryos formed the terrestrial planets and, in combination with the gravitational perturbations of the giant planets, depleted the residual population of planetesimals. In the outer Solar System, giant planets underwent a violent, chaotic phase of orbital rearrangement which caused the Late Heavy Bombardment. Then the rapid and fierce evolution of the young Solar System left place to the more regular secular evolution of the Modern Solar System. Vesta, through its connection with HED meteorites, and plausibly Ceres too were between the first bodies to form in the history of the Solar System. Here we discuss the timescale of their formation and evolution and how they would have been affected by their passage through the different phases of the history of the Solar System, in order to draw a reference framework to interpret the data that Dawn mission will supply on them.", "keyphrases": ["ceres", "solar system", "giant planet", "vesta"]}
{"id": "1904.11991", "title": "Building the Evryscope: Hardware Design and Performance", "abstract": "The Evryscope is a telescope array designed to open a new parameter space in optical astronomy, detecting short timescale events across extremely large sky areas simultaneously. The system consists of a 780 MPix 22-camera array with an 8150 sq. deg. field of view, 13\" per pixel sampling, and the ability to detect objects down to Mg=16 in each 2 minute dark-sky exposure. The Evryscope, covering 18,400 sq.deg. with hours of high-cadence exposure time each night, is designed to find the rare events that require all-sky monitoring, including transiting exoplanets around exotic stars like white dwarfs and hot subdwarfs, stellar activity of all types within our galaxy, nearby supernovae, and other transient events such as gamma ray bursts and gravitational-wave electromagnetic counterparts. The system averages 5000 images per night with 300,000 sources per image, and to date has taken over 3.0M images, totaling 250TB of raw data. The resulting light curve database has light curves for 9.3M targets, averaging 32,600 epochs per target through 2018. This paper summarizes the hardware and performance of the Evryscope, including the lessons learned during telescope design, electronics design, a procedure for the precision polar alignment of mounts for Evryscope-like systems, robotic control and operations, and safety and performance-optimization systems. We measure the on-sky performance of the Evryscope, discuss its data-analysis pipelines, and present some example variable star and eclipsing binary discoveries from the telescope. We also discuss new discoveries of very rare objects including 2 hot subdwarf eclipsing binaries with late M-dwarf secondaries (HW Vir systems), 2 white dwarf / hot subdwarf short-period binaries, and 4 hot subdwarf reflection binaries. We conclude with the status of our transit surveys, M-dwarf flare survey, and transient detection.", "keyphrases": ["evryscope", "performance", "telescope array", "sky"]}
{"id": "1903.01183", "title": "Dark compact objects: an extensive overview", "abstract": "We study the structure of compact objects that contain non-self annihilating, self-interacting dark matter admixed with ordinary matter made of neutron star and white dwarf materials. We extend the previous work Phys. Rev. D 92 123002 (2015) on these dark compact objects by analyzing the effect of weak and strongly interacting dark matter with particle masses in the range of 1-500 GeV, so as to set some constraints in the strength of the interaction and the mass of the dark matter particle. We find that the total mass of the compact objects increases with decreasing dark matter particle mass. In the strong interacting case and for dark matter particle masses in the range 1-10 GeV, the total mass of the compact objects largely exceeds the 2M_\u2299 constraint for neutron star masses and the nominal 1M_\u2299for white dwarfs, while for larger dark matter particle masses or in the weakly interacting case the compact objects show masses in agreement or smaller than these constraints, thus hinting at the exclusion of strongly self-interacting dark matter of masses 1-10 GeV in the interior of these compact objects. Moreover, we observe that the smaller the dark matter particle mass, the larger the quantity of dark matter captured is, putting constraints on the dark matter mass trapped in the compact objects so as to fullfill \u2243 2M_\u2299 observations. Finally, the inhomogeneity of distribution of dark matter in the Galaxy implies a mass dependence of compact objects from the environment which can be used to put constraints on the characteristics of the Galaxy halo DM profile and on particle mass. In view of the these results, we discuss the formation of the dark compact objects in an homogeneous and non-homogeneous dark matter environment.", "keyphrases": ["compact object", "dark matter", "neutron star", "white dwarf material", "element"]}
{"id": "1302.6587", "title": "Naturalness and the Status of Supersymmetry", "abstract": "For decades, the unnaturalness of the weak scale has been the dominant problem motivating new particle physics, and weak-scale supersymmetry has been the dominant proposed solution. This paradigm is now being challenged by a wealth of experimental data. In this review, we begin by recalling the theoretical motivations for weak-scale supersymmetry, including the gauge hierarchy problem, grand unification, and WIMP dark matter, and their implications for superpartner masses. These are set against the leading constraints on supersymmetry from collider searches, the Higgs boson mass, and low-energy constraints on flavor and CP violation. We then critically examine attempts to quantify naturalness in supersymmetry, stressing the many subjective choices that impact the results both quantitatively and qualitatively. Finally, we survey various proposals for natural supersymmetric models, including effective supersymmetry, focus point supersymmetry, compressed supersymmetry, and R-parity-violating supersymmetry, and summarize their key features, current status, and implications for future experiments.", "keyphrases": ["status", "supersymmetry", "dark matter", "naturalness", "susy"]}
{"id": "2004.14773", "title": "Non-Cold Dark Matter from Primordial Black Hole Evaporation", "abstract": "Dark matter coupled solely gravitationally can be produced through the decay of primordial black holes in the early universe. If the dark matter is lighter than the initial black hole temperature, it could be warm enough to be subject to structure formation constraints. In this paper we perform a more precise determination of these constraints. We first evaluate the dark matter phase-space distribution, without relying on the instantaneous decay approximation. We then interface this phase-space distribution with the Boltzmann code CLASS to extract the corresponding matter power spectrum, which we find to match closely those of warm dark matter models, albeit with a different dark matter mass. This mapping allows us to extract constraints from Lyman-\u03b1 data without the need to perform hydrodynamical simulations. We robustly rule out the possibility, consistent with previous analytic estimates, of primordial black holes having come to dominate the energy density of the universe and simultaneously given rise to all the DM through their decay. Consequences and implications for dark radiation and leptogenesis are also briefly discussed.", "keyphrases": ["dark matter", "black hole", "dark radiation"]}
{"id": "1604.00378", "title": "Oscillating Filaments: I - Oscillation and Geometrical Fragmentation", "abstract": "We study the stability of filaments in equilibrium between gravity and internal as well as external pressure using the grid based AMR-code RAMSES. A homogeneous, straight cylinder below a critical line mass is marginally stable. However, if the cylinder is bent, e.g. with a slight sinusoidal perturbation, an otherwise stable configuration starts to oscillate, is triggered into fragmentation and collapses. This previously unstudied behavior allows a filament to fragment at any given scale, as long as it has slight bends. We call this process `geometrical fragmentation'. In our realization the spacing between the cores matches the wavelength of the sinusoidal perturbation, whereas up to now, filaments were thought to be only fragmenting on the characteristical scale set by the mass-to-line ratio. Using first principles, we derive the oscillation period as well as the collapse timescale analytically. To enable a direct comparison with observations, we study the line-of-sight velocity for different inclinations. We show that the overall oscillation pattern can hide the infall signature of cores.", "keyphrases": ["filament", "geometrical fragmentation", "oscillation"]}
{"id": "0907.5199", "title": "Massive Galaxies in COSMOS: Evolution of Black hole versus bulge mass but not versus total stellar mass over the last 9 Gyrs?", "abstract": "We constrain the ratio of black hole (BH) mass to total stellar mass of type-1 AGN in the COSMOS survey at 1<z<2. For 10 AGN at mean redshift z 1.4 with both HST/ACS and HST/NICMOS imaging data we are able to compute total stellar mass M_(*,total), based on restframe UV-to-optical host galaxy colors which constrain mass-to-light ratios. All objects have virial BH mass-estimates available from the COSMOS Magellan/IMACS and zCOSMOS surveys. We find zero difference between the M_BH\u2013M_(*,total)-relation at z 1.4 and the M_BH\u2013M_(*,bulge)-relation in the local Universe. Our interpretation is: (a) If our objects were purely bulge-dominated, the M_BH\u2013M_(*,bulge)-relation has not evolved since z 1.4. However, (b) since we have evidence for substantial disk components, the bulges of massive galaxies (logM_(*,total)=11.1+-0.25 or logM_BH 8.3+-0.2) must have grown over the last 9 Gyrs predominantly by redistribution of disk- into bulge-mass. Since all necessary stellar mass exists in the galaxy at z=1.4, no star-formation or addition of external stellar material is required, only a redistribution e.g. induced by minor and major merging or through disk instabilities. Merging, in addition to redistributing mass in the galaxy, will add both BH and stellar/bulge mass, but does not change the overall final M_BH/M_(*,bulge) ratio. Since the overall cosmic stellar and BH mass buildup trace each other tightly over time, our scenario of bulge-formation in massive galaxies is independent of any strong BH-feedback and means that the mechanism coupling BH and bulge mass until the present is very indirect.", "keyphrases": ["galaxy", "black hole", "stellar mass"]}
{"id": "1106.2642", "title": "Two-fluid dark matter models", "abstract": "We investigate the possibility that dark matter is a mixture of two non-interacting perfect fluids, with different four-velocities and thermodynamic parameters. The two-fluid model can be described as an effective single anisotropic fluid, with distinct radial and tangential pressures. The basic equations describing the equilibrium structure of the two-fluid dark matter model, and of the tangential velocity of test particles in stable circular orbits, are obtained for the case of a spherically symmetric static geometry. By assuming a non-relativistic kinetic model for the dark matter particles, the density profile and the tangential velocity of the dark matter mixture are obtained by numerically integrating the gravitational field equations. The cosmological implications of the model are also briefly considered, and it is shown that the anisotropic two-fluid model isotropizes in the large time limit.", "keyphrases": ["dark matter model", "two-fluid model", "single anisotropic fluid"]}
{"id": "1510.07704", "title": "The Pluto system: Initial results from its exploration by New Horizons", "abstract": "The Pluto system was recently explored by NASA's New Horizons spacecraft, making closest approach on 14 July 2015. Pluto's surface displays diverse landforms, terrain ages, albedos, colors, and composition gradients. Evidence is found for a water-ice crust, geologically young surface units, surface ice convection, wind streaks, volatile transport, and glacial flow. Pluto's atmosphere is highly extended, with trace hydrocarbons, a global haze layer, and a surface pressure near 10 microbars. Pluto's diverse surface geology and long-term activity raise fundamental questions about how small planets remain active many billions of years after formation. Pluto's large moon Charon displays tectonics and evidence for a heterogeneous crustal composition, its north pole displays puzzling dark terrain. Small satellites Hydra and Nix have higher albedos than expected.", "keyphrases": ["pluto system", "new horizons", "july", "surface", "planet"]}
{"id": "1304.7277", "title": "First observational constraints on tensor non-Gaussianity sourced by primordial magnetic fields from cosmic microwave background", "abstract": "Primordial magnetic fields (PMFs) create a large squeezed-type non-Gaussianity in tensor perturbation, which generates non-Gaussian temperature fluctuations in the cosmic microwave background (CMB). We for the first time derive an observational constraint on such a tensor non-Gaussianity from observed CMB maps. Analyzing temperature maps of the WMAP 7-year data, we find that such a tensor non-Gaussianity is consistent with zero. This gives an upper bound on PMF strength smoothed on 1 Mpc as B_1 Mpc < 3.1 nG at 95", "keyphrases": ["tensor non-gaussianity", "primordial magnetic field", "cosmic microwave background"]}
{"id": "1306.3512", "title": "String Inflation After Planck 2013", "abstract": "We briefly summarize the impact of the recent Planck measurements for string inflationary models, and outline what might be expected to be learned in the near future from the expected improvement in sensitivity to the primordial tensor-to-scalar ratio. We comment on whether these models provide sufficient added value to compensate for their complexity, and ask how they fare in the face of the new constraints on non-gaussianity and dark radiation. We argue that as a group the predictions made before Planck agree well with what has been seen, and draw conclusions from this about what is likely to mean as sensitivity to primordial gravitational waves improves.", "keyphrases": ["planck", "string theory", "inflationary model building", "bicep2 result"]}
{"id": "0912.0015", "title": "Axion cold dark matter in non-standard cosmologies", "abstract": "We study the parameter space of cold dark matter axions in two cosmological scenarios with non-standard thermal histories before Big Bang nucleosynthesis: the Low Temperature Reheating (LTR) cosmology and the kination cosmology. If the Peccei-Quinn symmetry breaks during inflation, we find more allowed parameter space in the LTR cosmology than in the standard cosmology and less in the kination cosmology. On the contrary, if the Peccei-Quinn symmetry breaks after inflation, the Peccei-Quinn scale is orders of magnitude higher than standard in the LTR cosmology and lower in the kination cosmology. We show that the axion velocity dispersion may be used to distinguish some of these non-standard cosmologies. Thus, axion cold dark matter may be a good probe of the history of the Universe before Big Bang nucleosynthesis.", "keyphrases": ["dark matter", "non-standard cosmology", "axion"]}
{"id": "0902.4066", "title": "CMB bispectrum from primordial magnetic fields on large angular scales", "abstract": "Primordial magnetic fields lead to non-Gaussian signals in the Cosmic Microwave Background (CMB) even at the lowest order, as magnetic stresses, and the temperature anisotropy they induce, depend quadratically on the magnetic field. In contrast, CMB non-Gaussianity due to inflationary scalar perturbations arise only as a higher order effect. We propose here a novel probe of stochastic primordial magnetic fields that exploits the characteristic CMB non-Gaussianity that they induce. In particular, we compute the CMB bispectrum (b_l__1l__2l__3) induced by stochastic primordial fields on large angular scales. We find a typical value of l_1(l_1+1)l_3(l_3+1) b_l__1l__2l__3\u223c 10^-22, for magnetic fields of strength B_0 \u223c 3 nano Gauss and with a nearly scale invariant magnetic spectrum. Current observational limits on the bispectrum allow us to set upper limits on B_0 \u223c 35 nano Gauss, which can be improved by including other magnetically induced contributions to the bispectrum.", "keyphrases": ["primordial magnetic field", "large angular scale", "cmb bispectrum"]}
{"id": "2004.04009", "title": "Constraining extra dimensions on cosmological scales with LISA future gravitational wave siren data", "abstract": "We investigate the idea that current cosmic acceleration could be the consequence of gravitational leakage into extra dimensions on cosmological scales rather than the result of a non-zero cosmological constant, and consider the ability of future gravitational-wave siren observations to probe this phenomenon and constrain the parameters of phenomenological models of this gravitational leakage. In theories that include additional non-compact spacetime dimensions, the gravitational leakage intro extra dimensions leads to a reduction in the amplitude of observed gravitational waves and thereby a systematic discrepancy between the distance inferred to such sources from GW and EM observations. We investigate the capability of a gravitational space interferometer such as LISA to probe this modified gravity on large scales. We find that the extent to which LISA will be able to place limits on the number of spacetime dimensions and other cosmological parameters characterising modified gravity will strongly depend on the actual number and redshift distribution of sources, together with the uncertainty on the GW measurements. A relatively small number of sources (\u223c 1) and high measurement uncertainties would strongly restrict the ability of LISA to place meaningful constraints on the parameters in cosmological scenarios where gravity is only five-dimensional and modified at scales larger than about \u223c 4 times the Hubble radius. Conversely, if the number of sources observed amounts to a four-year average of \u223c 27, then in the most favourable cosmological scenarios LISA has the potential to place meaningful constraints on the cosmological parameters with a precision of \u223c 1% on the number of dimensions and \u223c 7.5% on the scale beyond which gravity is modified, thereby probing the late expansion of the universe up to a redshift of \u223c 8.", "keyphrases": ["extra dimension", "cosmological scale", "gravitational wave"]}
{"id": "1102.4658", "title": "Cosmological constraints on dark matter models with velocity-dependent annihilation cross section", "abstract": "We derive cosmological constraints on the annihilation cross section of dark matter with velocity-dependent structure, motivated by annihilating dark matter models through Sommerfeld or Breit-Wigner enhancement mechanisms. In models with annihilation cross section increasing with decreasing dark matter velocity, big-bang nucleosynthesis and cosmic microwave background give stringent constraints.", "keyphrases": ["dark matter model", "annihilation cross section", "matter velocity distribution"]}
{"id": "1612.09365", "title": "Searching for deviations from the General Relativity Theory with gas mass fraction of galaxy clusters and complementary probes", "abstract": "Nowadays, thanks to the improved precision of cosmological data, it has been possible to search for deviation from the general relativity theory with tests on large cosmic scales. Particularly, there is a class of modified gravity theories that breaks the Einstein equivalence principle (EEP) in the electromagnetic sector, generating variations of the fine structure constant, violations of the cosmic distance duality relation and the evolution law of the cosmic microwave background (CMB) radiation. In recent papers, this class of theories has been tested with angular diameter distances from galaxy clusters, type Ia supernovae and CMB temperature. In this work we propose a new test by considering the most recent X-ray surface brightness observations of galaxy clusters jointly with type Ia supernovae and CMB temperature. The crucial point here is that we take into account the dependence of the X-ray gas mass fraction of galaxy clusters on possible variations of the fine structure constant and violations of the cosmic distance duality relation. Our basic result is that this new approach is competitive with the previous one and it also does not show significant deviations from the general relativity.", "keyphrases": ["general relativity theory", "gas mass fraction", "galaxy cluster"]}
{"id": "2110.12620", "title": "Constraints on small-scale primordial density fluctuation from cosmic microwave background through dark matter annihilation", "abstract": "The cosmic microwave background (CMB) observation by the Planck satellite precisely determines primordial curvature fluctuations on larger scales than \ud835\udcaa(1) Mpc, while the small-scale curvature fluctuation is still less constrained. The constraint on small-scale fluctuations is highly improved if we assume the standard thermal relic dark matter scenario. When small-scale fluctuations are large enough, dense regions collapse to form small halos even in a redshift z\u227310^3, which is called ultracompact minihalos. These minihalos enhance the annihilation of the dark matter and it is constrained by observations such as extragalactic gamma rays and the CMB. We revisit the effect of minihalos formed by the small-scale density fluctuations and calculate the ionization history modified by the dark matter annihilation. We perform the Markov Chain Monte Carlo method to constrain the size of small-scale curvature fluctuations by the CMB power spectrum. It is found that the constraint from the CMB power spectrum is comparable to that from the extragalactic gamma rays. We confirm that our constraint mainly comes from the energy injection in early time (z\u2273 100) and hence it is independent of the uncertainty of minihalo properties in the late time.", "keyphrases": ["density fluctuation", "cosmic microwave background", "dark matter annihilation"]}
{"id": "1206.5537", "title": "Leptogenesis from a GeV Seesaw without Mass Degeneracy", "abstract": "For Leptogenesis based on the type-I seesaw mechanism, we present a systematic calculation of lepton-number violating and purely flavoured asymmetries within nonequilibrium Quantum Field Theory. We show that sterile neutrinos with non-degenerate masses in the GeV range can explain the baryon asymmetry of the Universe via flavoured Leptogenesis. This is possible due to the interplay of thermal and flavour effects. Our approach clarifies the relation between Leptogenesis from the oscillations of sterile neutrinos and the more commonly studied scenarios from decays and inverse decays. We explain why lower mass bounds for non-degenerate sterile neutrinos derived for Leptogenesis from out-of-equilibrium decays do not apply to flavoured Leptogenesis with GeV-scale neutrinos.", "keyphrases": ["neutrino", "baryon asymmetry", "leptogenesis"]}
{"id": "1404.4083", "title": "The TT, TB, EB and BB correlations in anisotropic inflation", "abstract": "The ongoing and future experiments will measure the B-mode from different sky coverage and frequency bands, with the potential to reveal non-trivial features in polarization map. In this work we study the TT, TB, EB and BB correlations associated with the B-mode polarization of CMB map in models of charged anisotropic inflation. The model contains a chaotic-type large field complex inflaton which is charged under the U(1) gauge field. We calculate the statistical anisotropies generated in the power spectra of the curvature perturbation, the tensor perturbation and their cross-correlation. It is shown that the asymmetry in tensor power spectrum is a very sensitive probe of the gauge coupling. While the level of statistical anisotropy in temperature power spectrum can be small and satisfy the observational bounds, the interactions from the gauge coupling can induce large directional dependence in tensor modes. This will leave interesting anisotropic fingerprints in various correlations involving the B-mode polarization such as the TB cross-correlation which may be detected in upcoming Planck polarization data. In addition, the TT correlation receives an anisotropic contribution from the tensor sector which naturally decays after l \u2273 100. We expect that the mechanism of using tensor sector to induce asymmetry at low l to be generic which can also be applied to address other low l CMB anomalies.", "keyphrases": ["anisotropic inflation", "tensor perturbation", "primordial gravitational wave"]}
{"id": "1608.08038", "title": "Numerical integration of dynamical systems with Lie series: Relativistic acceleration and non-gravitational forces", "abstract": "The integration of the equations of motion in gravitational dynamical systems \u2013 either in our Solar System or for extra-solar planetary system \u2013 being non integrable in the global case, is usually performed by means of numerical integration. Among the different numerical techniques available for solving ordinary differential equations, the numerical integration using Lie series has shown some advantages. In its original form (Hanslmeier 1984), it was limited to the N-body problem where only gravitational interactions are taken into account. We present in this paper a generalisation of the method by deriving an expression of the Lie-terms when other major forces are considered. As a matter of fact, previous studies had been made but only for objects moving under gravitational attraction. If other perturbations are added, the Lie integrator has to be re-built. In the present work we consider two cases involving position and position-velocity dependent perturbations: relativistic acceleration in the framework of General Relativity and a simplified force for the Yarkovsky effect. A general iteration procedure is applied to derive the Lie series to any order and precision. We then give an application to the integration of the equation of motions for typical Near-Earth objects and planet Mercury.", "keyphrases": ["relativistic acceleration", "force", "numerical integration"]}
{"id": "1110.0669", "title": "Shear viscosity due to phonons in superfluid neutron stars", "abstract": "We compute the contribution of phonons to the shear viscosity \u03b7 in superfluid neutron stars, assuming neutron pairing in a ^1S_0 channel. We use a Boltzmann equation amended by a collision term that takes into account the binary collisions of phonons. We use effective field theory techniques to extract the phonon scattering rates, written as a function of the equation of state (EoS) of the system. Our formulation is rather general, and can be used to extract the shear viscosity due to binary collisions of phonons for other superfluids, such as the cold Fermi gas in the unitarity limit. We find that \u03b7\u221d 1/T^5, the proportionality factor depending on the EoS of the system. Our results indicate that the phonon contribution to \u03b7 cannot be ignored and might have relevant effects in the dynamics of the different oscillation modes of the star.", "keyphrases": ["superfluid neutron star", "phonon contribution", "shear viscosity"]}
{"id": "2203.02793", "title": "Hundreds of new satellites of figure-eight orbit computed with high precision", "abstract": "Satellites (topological powers) of the famous figure-eight orbit are special periodic solutions of the planar three-body problem. In this paper we use a modified Newton's method based on the Continuous analog of Newton's method and high precision arithmetic for a purposeful numerical search of new satellites of the figure-eight orbit. Over 700 new satellites are found, including 76 new linearly stable ones. 7 of the newly found linearly stable satellites are choreographies. The linear stability is checked by a high precision computing of the eigenvalues of the monodromy matrices. The initial conditions of all found solutions are given with 150 correct decimal digits.", "keyphrases": ["satellite", "figure-eight orbit", "high precision"]}
{"id": "1006.1342", "title": "Eddington-limited accretion and the black hole mass function at redshift 6", "abstract": "We present discovery observations of a quasar in the Canada-France High-z Quasar Survey (CFHQS) at redshift z=6.44. We also use near-IR spectroscopy of nine CFHQS quasars at z 6 to determine black hole masses. These are compared with similar estimates for more luminous Sloan Digital Sky Survey (SDSS) quasars to investigate the relationship between black hole mass and quasar luminosity. We find a strong correlation between MgII FWHM and UV luminosity and that most quasars at this early epoch are accreting close to the Eddington limit. Thus these quasars appear to be in an early stage of their life cycle where they are building up their black hole mass exponentially. Combining these results with the quasar luminosity function, we derive the black hole mass function at z=6. Our black hole mass function is 10^4 times lower than at z=0 and substantially below estimates from previous studies. The main uncertainties which could increase the black hole mass function are a larger population of obscured quasars at high-redshift than is observed at low-redshift and/or a low quasar duty cycle at z=6. In comparison, the global stellar mass function is only 10^2 times lower at z=6 than at z=0. The difference between the black hole and stellar mass function evolution is due to either rapid early star formation which is not limited by radiation pressure as is the case for black hole growth or inefficient black hole seeding. Our work predicts that the black hole mass - stellar mass relation for a volume-limited sample of galaxies declines rapidly at very high redshift. This is in contrast to the observed increase at 4<z<6 from the local relation if one just studies the most massive black holes.", "keyphrases": ["hole mass function", "redshift", "eddington-limited accretion"]}
{"id": "2104.14496", "title": "Low scale leptogenesis and dark matter in the presence of primordial black holes", "abstract": "We study the possibility of low scale leptogenesis along with dark matter (DM) in the presence of primordial black holes (PBH). For a common setup to study both leptogenesis and DM we consider the minimal scotogenic model which also explains light neutrino mass at radiative level. While PBH in the mass range of 0.1-10^5 g can, in principle, affect leptogenesis, the required initial PBH fraction usually leads to overproduction of scalar doublet DM whose thermal freeze-out occurs before PBH evaporation. PBH can lead to non-thermal source of leptogenesis as well as dilution of thermally generated lepton asymmetry via entropy injection, with the latter being dominant. The parameter space of scotogenic model which leads to overproduction of baryon or lepton asymmetry in standard cosmology can be made consistent in the presence of PBH with appropriate initial mass and energy fraction. On the other hand, for such PBH parameters, the scalar DM is constrained to be in light mass regime where its freeze-out occurs after PBH evaporation. We then discuss the possibility of fermion singlet DM with N_2 leptogenesis in the same model where due to singlet nature of DM, its connection with PBH parameters and hence leptogenesis becomes stronger compared to the previous case.", "keyphrases": ["dark matter", "black hole", "low scale leptogenesis"]}
{"id": "1301.6878", "title": "Modified-gravity wormholes without exotic matter", "abstract": "A fundamental ingredient in wormhole physics is the flaring-out condition at the throat which, in classical general relativity, entails the violation of the null energy condition. In this work, we present the most general conditions in the context of modified gravity, in which the matter threading the wormhole throat satisfies all of the energy conditions, and it is the higher order curvature terms, which may be interpreted as a gravitational fluid, that support these nonstandard wormhole geometries. Thus, we explicitly show that wormhole geometries can be theoretically constructed without the presence of exotic matter, but are sustained in the context of modified gravity.", "keyphrases": ["wormhole", "exotic matter", "gravity"]}
{"id": "0905.3500", "title": "Density fluctuations from warm inflation", "abstract": "Thermal fluctuations provide the main source of large scale density perturbations in warm inflationary models of the early universe. For the first time, general results are obtained for the power spectrum in the case when the friction coefficient in the inflaton equation of motion depends on temperature. A large increase in the amplitude of perturbations occurs when the friction coefficient increases with temperature. This has to be taken into account when constructing models of warm inflation. New results are also given for the thermal fluctuations in the weak regime of warm inflation when the friction coefficient is relatively small.", "keyphrases": ["warm inflation", "coefficient", "density fluctuation", "inflaton field", "dissipative coefficient"]}
{"id": "1204.2007", "title": "Cosmography and constraints on the equation of state of the Universe in various parametrizations", "abstract": "We use cosmography to present constraints on the kinematics of the Universe, without postulating any underlying theoretical model. To this end, we use a Monte Carlo Markov Chain analysis to perform comparisons to the supernova Ia Union 2 compilation, combined with the Hubble Space Telescope measurements of the Hubble constant, and the Hubble parameter datasets. We introduce a sixth order cosmographic parameter and show that it does not enlarge considerably the posterior distribution when comparing to the fifth order results. We also propose a way to construct viable parameter variables to be used as alternatives of the redshift z. These can overcome both the problems of divergence and lack of accuracy associated with the use of z. Moreover, we show that it is possible to improve the numerical fits by re-parameterizing the cosmological distances. In addition, we constrain the equation of state of the Universe as a whole by the use of cosmography. Thus, we derive expressions which can be directly used to fit the equation of state and the pressure derivatives up to fourth order. To this end, it is necessary to depart from a pure cosmographic analysis and to assume the Friedmann equations as valid. All our results are consistent with the \u039bCDM model, although alternative fluid models, with nearly constant pressure and no cosmological constant, match the results accurately as well.", "keyphrases": ["redshift", "cosmography", "gravity", "cosmic fluid", "extended theories"]}
{"id": "1902.01485", "title": "Conversion Measure of Faraday Rotation-Conversion with application to Fast Radio Bursts", "abstract": "Faraday Rotation-Conversion is the simultaneous rotation of all three Stokes polarization parameters Q, U, V as an electromagnetic wave propagates through a magnetized plasma. In this regime the Faraday plasma screen is characterized by more than just a Rotation Measure. We define the Conversion Measure that characterizes the wavelength-dependent conversion between the linear and circular polarization. In a cold plasma, the conversion occurs at the localized regions along the wave's path, where the large-scale magnetic field is perpendicular to the propagation direction. The number of these regions along the line of sight through the screen, and their individual contributions to the conversion measure, can be inferred from the polarization measurements. We argue that the simultaneous measurement of wavelength-dependent linear and circular polarization might give an important insight into the magnetic-field geometry of the Faraday screen in FRB121102 and other repeating Fast Radio Bursts.", "keyphrases": ["faraday rotation-conversion", "fast radio bursts", "conversion measure"]}
{"id": "1311.0282", "title": "Sterile neutrino dark matter bounds from galaxies of the Local Group", "abstract": "We show that the canonical oscillation-based (non-resonant) production of sterile neutrino dark matter is inconsistent at >99 observations of galaxies in the Local Group. We set lower limits on the non-resonant sterile neutrino mass of 2.5 keV (equivalent to 0.7 keV thermal mass) using phase-space densities derived for dwarf satellite galaxies of the Milky Way, as well as limits of 8.8 keV (equivalent to 1.8 keV thermal mass) based on subhalo counts of N-body simulations of M 31 analogues. Combined with improved upper mass limits derived from significantly deeper X-ray data of M 31 with full consideration for background variations, we show that there remains little room for non-resonant production if sterile neutrinos are to explain 100 non-oscillation sterile neutrino production remain viable mechanisms for generating sufficient dark matter sterile neutrinos.", "keyphrases": ["neutrino", "dark matter", "dwarf satellite galaxy"]}
{"id": "1707.06938", "title": "Relativistic N-body simulations with massive neutrinos", "abstract": "Some of the dark matter in the Universe is made up of massive neutrinos. Their impact on the formation of large scale structure can be used to determine their absolute mass scale from cosmology, but to this end accurate numerical simulations have to be developed. Due to their relativistic nature, neutrinos pose additional challenges when one tries to include them in N-body simulations that are traditionally based on Newtonian physics. Here we present the first numerical study of massive neutrinos that uses a fully relativistic approach. Our N-body code, gevolution, is based on a weak-field formulation of general relativity that naturally provides a self-consistent framework for relativistic particle species. This allows us to model neutrinos from first principles, without invoking any ad-hoc recipes. Our simulation suite comprises some of the largest neutrino simulations performed to date. We study the effect of massive neutrinos on the nonlinear power spectra and the halo mass function, focusing on the interesting mass range between 0.06 eV and 0.3 eV and including a case for an inverted mass hierarchy.", "keyphrases": ["massive neutrino", "n-body code", "general relativity"]}
{"id": "2201.00697", "title": "All-sky search for continuous gravitational waves from isolated neutron stars using Advanced LIGO and Advanced Virgo O3 data", "abstract": "We present results of an all-sky search for continuous gravitational waves which can be produced by spinning neutron stars with an asymmetry around their rotation axis, using data from the third observing run of the Advanced LIGO and Advanced Virgo detectors. Four different analysis methods are used to search in a gravitational-wave frequency band from 10 to 2048 Hz and a first frequency derivative from -10^-8 to 10^-9 Hz/s. No statistically-significant periodic gravitational-wave signal is observed by any of the four searches. As a result, upper limits on the gravitational-wave strain amplitude h_0 are calculated. The best upper limits are obtained in the frequency range of 100 to 200 Hz and they are \u223c1.1\u00d710^-25 at 95% confidence-level. The minimum upper limit of 1.10\u00d710^-25 is achieved at a frequency 111.5 Hz. We also place constraints on the rates and abundances of nearby planetary- and asteroid-mass primordial black holes that could give rise to continuous gravitational-wave signals.", "keyphrases": ["gravitational wave", "neutron star", "all-sky search"]}
{"id": "1307.2158", "title": "PeV neutrinos from interactions of cosmic rays with the interstellar medium in the Galaxy", "abstract": "We present a self-consistent interpretation of the of very-high-energy neutrino signal from the direction of the inner Galaxy, which is a part of the astronomical neutrino signal reported by IceCube. We demonstrate that an estimate of the neutrino flux in the E>100 TeV energy range lies at the high-energy power-law extrapolation of the spectrum of diffuse gamma-ray emission from the Galactic Ridge, as observed by Fermi telescope. This suggests that IceCube neutrino and Fermi/LAT gamma-ray fluxes are both produced in interactions of cosmic rays with the interstellar medium in the Norma arm and/or in the Galactic Bar. Cosmic rays responsible for the gamma-ray and neutrino flux are characterised by hard spectrum with the slope harder than -2.4 and cut-off energy higher than 10 PeV.", "keyphrases": ["interstellar medium", "galaxy", "neutrino flux", "fermi telescope", "gamma-ray flux"]}
{"id": "1009.0591", "title": "Is there further evidence for spatial variation of fundamental constants?", "abstract": "The detection of a spatial variation of the fine-structure constant, alpha, based on study of quasar absorption systems has recently been reported. The physics that causes this alpha-variation should have other observable manifestations, and this motivates us to look for complementary astrophysical effects. In this paper we propose a method to test whether spatial variation of fundamental constants existed during the epoch of big bang nucleosynthesis. Using existing measurements of primordial deuterium abundance we find very weak indications that such a signature might exist, but the paucity of measurements precludes any firm conclusion. We also examine existing quasar absorption spectra data that are sensitive to variation of the electron-to-proton mass ratio, mu, and x = (alpha^2 mu g_p) for spatial variation.", "keyphrases": ["spatial variation", "fundamental constant", "fine structure"]}
{"id": "1102.5343", "title": "Equilateral Non-Gaussianity and New Physics on the Horizon", "abstract": "We examine the effective theory of single-field inflation in the limit where the scalar perturbations propagate with a small speed of sound. In this case the non-linearly realized time-translation symmetry of the Lagrangian implies large interactions, giving rise to primordial non-Gaussianities. When the non-Gaussianities are measurable, these interactions will become strongly coupled unless new physics appears close to the Hubble scale. Due to its proximity to the Hubble scale, the new physics is not necessarily decoupled from inflationary observables and can potentially affect the predictions of the model. To understand the types of corrections that may arise, we construct weakly-coupled completions of the theory and study their observational signatures.", "keyphrases": ["new physics", "effective theory", "slow-roll", "coupling scale"]}
{"id": "1210.4026", "title": "Covariant multi-galileons and their generalisation", "abstract": "We find a covariant completion of the flat-space multi-galileon theory, preserving second-order field equations. We then generalise this to arrive at an enlarged class of second order theories describing multiple scalars and a single tensor, and conjecture that these are a multi-scalar version of Horndeski's most general scalar-tensor theory.", "keyphrases": ["multi-galileon", "second-order field equation", "scalar-tensor theory"]}
{"id": "1402.1933", "title": "Nonlinear relativistic corrections to cosmological distances, redshift and gravitational lensing magnification. II - Derivation", "abstract": "We present a derivation of the cosmological distance-redshift relation up to second order in perturbation theory. In addition, we find the observed redshift and the lensing magnification to second order. We do not require that the density contrast is small, we only that the metric potentials and peculiar velocities are small. Thus our results apply into the nonlinear regime, and can be used for most dark energy models. We present the results in a form which can be readily computed in an N-body simulation. This paper accompanies arXiv:1207.2109, where the key results are summarised in a physically transparent form and applications are discussed.", "keyphrases": ["redshift", "magnification", "perturbation theory"]}
{"id": "1307.2229", "title": "Weyl-Cartan-Weitzenb\u00f6ck gravity through Lagrange multiplier", "abstract": "We consider an extension of the Weyl-Cartan-Weitzenb\u00f6ck (WCW) and teleparallel gravity, in which the Weitzenb\u00f6ck condition of the exact cancellation of curvature and torsion in a Weyl-Cartan geometry is inserted into the gravitational action via a Lagrange multiplier. In the standard metric formulation of the WCW model, the flatness of the space-time is removed by imposing the Weitzenb\u00f6ck condition in the Weyl-Cartan geometry, where the dynamical variables are the space-time metric, the Weyl vector and the torsion tensor, respectively. However, once the Weitzenb\u00f6ck condition is imposed on the Weyl-Cartan space-time, the metric is not dynamical, and the gravitational dynamics and evolution is completely determined by the torsion tensor. We show how to resolve this difficulty, and generalize the WCW model, by imposing the Weitzenb\u00f6ck condition on the action of the gravitational field through a Lagrange multiplier. The gravitational field equations are obtained from the variational principle, and they explicitly depend on the Lagrange multiplier. As a particular model we consider the case of the Riemann-Cartan space-times with zero non-metricity, which mimics the teleparallel theory of gravity. The Newtonian limit of the model is investigated, and a generalized Poisson equation is obtained, with the weak field gravitational potential explicitly depending on the Lagrange multiplier and on the Weyl vector. The cosmological implications of the theory are also studied, and three classes of exact cosmological models are considered.", "keyphrases": ["gravity", "lagrange", "weitzenb\u00f6ck condition", "weyl-cartan geometry", "weyl-cartan-weitzenb\u00f6ck"]}
{"id": "1406.5510", "title": "Light rings as observational evidence for event horizons: long-lived modes, ergoregions and nonlinear instabilities of ultracompact objects", "abstract": "Ultracompact objects are self-gravitating systems with a light ring. It was recently suggested that fluctuations in the background of these objects are extremely long-lived and might turn unstable at the nonlinear level, if the object is not endowed with a horizon. If correct, this result has important consequences: objects with a light ring are black holes. In other words, the nonlinear instability of ultracompact stars would provide a strong argument in favor of the \"black hole hypothesis,\" once electromagnetic or gravitational-wave observations confirm the existence of light rings. Here we explore in some depth the mode structure of ultracompact stars, in particular constant-density stars and gravastars. We show that the existence of very long-lived modes \u2013 localized near a second, stable null geodesic \u2013 is a generic feature of gravitational perturbations of such configurations. Already at the linear level, such modes become unstable if the object rotates sufficiently fast to develop an ergoregion. Finally, we conjecture that the long-lived modes become unstable under fragmentation via a Dyson-Chandrasekhar-Fermi mechanism at the nonlinear level. Depending on the structure of the star, it is also possible that nonlinearities lead to the formation of small black holes close to the stable light ring. Our results suggest that the mere observation of a light ring is a strong evidence for the existence of black holes.", "keyphrases": ["long-lived mode", "nonlinear instability", "black hole", "light ring", "ultra-compact object"]}
{"id": "1110.4169", "title": "Prospects for determination of thermal history after inflation with future gravitational wave detectors", "abstract": "Thermal history of the Universe between inflation and big-bang nucleosynthesis has not yet been revealed observationally. It will be probed by the detection of primordial gravitational waves generated during inflation, which contain information on the reheating temperature as well as the equation of state of the Universe after inflation. Based on Fisher information formalism, we examine how accurately the tensor-to-scalar ratio and reheating temperature after inflation can be simultaneously determined with space-based gravitational wave detectors such as the DECI-hertz Interferometer Gravitational-wave Observatory (DECIGO) and the Big-Bang Observer (BBO). We show that the reheating temperature is best determined if it is around 10^7 GeV for tensor-to-scalar ratio of around 0.1, and explore the detectable parameter space. We also find that equation of state of the early Universe can be also determined accurately enough to distinguish different equation-of-state parameters if the inflationary gravitational waves are successfully detected. Thus future gravitational wave detectors provide a unique and promising opportunity to reveal the thermal history of the Universe around 10^7 GeV.", "keyphrases": ["thermal history", "gravitational wave detector", "universe"]}
{"id": "2107.10291", "title": "The H_0 Olympics: A fair ranking of proposed models", "abstract": "Despite the remarkable success of the \u039bCold Dark Matter (\u039bCDM) cosmological model, a growing discrepancy has emerged (currently measured at the level of \u223c 4-6 \u03c3) between the value of the Hubble constant H_0 measured using the local distance ladder and the value inferred using the cosmic microwave background and galaxy surveys. While a vast array of \u039bCDM extensions have been proposed to explain these discordant observations, understanding the (relative) success of these models in resolving the tension has proven difficult \u2013 this is a direct consequence of the fact that each model has been subjected to differing, and typically incomplete, compilations of cosmological data. In this review, we attempt to make a systematic comparison of sixteen different models which have been proposed to resolve the H_0 tension (spanning both early- and late-Universe solutions), and quantify the relative success of each using a series of metrics and a vast array of data combinations. Owing to the timely appearance of this article, we refer to this contest as the \u201dH_0 Olympics\u201d; the goal being to identify which of the proposed solutions, and more broadly which underlying mechanisms, are most likely to be responsible for explaining the observed discrepancy (should unaccounted for systematics not be the culprit). This work also establishes a foundation of tests which will allow the success of novel proposals to be meaningful \u201dbenchmarked\u201d.", "keyphrases": ["h_0 olympics", "discrepancy", "hubble tension", "cmb data", "universe"]}
{"id": "1305.4790", "title": "Non-singular quantum-inspired gravitational collapse", "abstract": "We consider general relativistic homogeneous gravitational collapses for dust and radiation. We show that replacing the density profile with an effective density justified by some quantum gravity framework leads to the avoidance of the final singularity. The effective density acts on the collapsing cloud by introducing an isotropic pressure, which is negligible at the beginning of the collapse and becomes negative and dominant in the strong field regime. Event horizons never form and therefore the outcome of the collapse is not a black hole, in the sense that there are no regions causally disconnected from future null infinity. Apparent horizons form when the mass of the object exceeds a critical value, disappear when the matter density approaches an upper bound and gravity becomes very weak (asymptotic freedom regime), form again after the bounce as a consequence of the decrease in the matter density, and eventually disappear when the density becomes too low and the matter is radiated away. The possibility of detecting radiation coming from the high density region of a collapsing astrophysical object in which classically there would be the creation of a singularity could open a new window to experimentally test theories of quantum gravity.", "keyphrases": ["collapse", "gravity", "strong field regime", "black hole"]}
{"id": "2011.08385", "title": "First constraints on the intrinsic CMB dipole and our velocity with Doppler and aberration", "abstract": "We test the usual hypothesis that the Cosmic Microwave Background (CMB) dipole, its largest anisotropy, is due to our peculiar velocity with respect to the Hubble flow by measuring independently the Doppler and aberration effects on the CMB using Planck 2018 data. We remove the spurious contributions from the conversion of intensity into temperature and arrive at measurements which are independent from the CMB dipole itself for both temperature and polarization maps and both SMICA and NILC component-separation methods. Combining these new measurements with the dipole one we get the first constraints on the intrinsic CMB dipole. Assuming a standard dipolar lensing contribution we can put an upper limit on the intrinsic amplitude: 3.7 mK (95 CI). We estimate the peculiar velocity of the solar system without assuming a negligible intrinsic dipole contribution: v = (300^+111_-93) km/s with (l,b) = (276 \u00b1 33, 51 \u00b1 19)^\u2218 [SMICA], and v = (296^+111_-88) km/s with (l,b) = (280 \u00b1 33, 50 \u00b1 20)^\u2218 [NILC] with negligible systematic contributions. These values are consistent with the peculiar velocity hypothesis of the dipole.", "keyphrases": ["cmb dipole", "doppler", "aberration"]}
{"id": "0901.2750", "title": "Are loop quantum cosmos never singular?", "abstract": "A unified treatment of all known types of singularities for flat, isotropic and homogeneous spacetimes in the framework of loop quantum cosmology (LQC) is presented. These include bangs, crunches and all future singularities. Using effective spacetime description we perform a model independent general analysis of the properties of curvature, behavior of geodesics and strength of singularities. For illustration purposes a phenomenological model based analysis is also performed. We show that all values of the scale factor at which a strong singularity may occur are excluded from the effective loop quantum spacetime. Further, if the evolution leads to either a vanishing or divergent scale factor then the loop quantum universe is asymptotically deSitter in that regime. We also show that there exist a class of sudden extremal events, which includes a recently discussed possibility, for which the curvature or its derivatives will always diverge. Such events however turn out to be harmless weak curvature singularities beyond which geodesics can be extended. Our results point towards a generic resolution of physical singularities in LQC.", "keyphrases": ["loop quantum cosmology", "curvature singularity", "matter bounce scenario"]}
{"id": "1003.4404", "title": "Formation of Supermassive Black Holes", "abstract": "Evidence shows that massive black holes reside in most local galaxies. Studies have also established a number of relations between the MBH mass and properties of the host galaxy such as bulge mass and velocity dispersion. These results suggest that central MBHs, while much less massive than the host ( 0.1 cosmologies, a single big galaxy today can be traced back to the stage when it was split up in hundreds of smaller components. Did MBH seeds form with the same efficiency in small proto-galaxies, or did their formation had to await the buildup of substantial galaxies with deeper potential wells? I briefly review here some of the physical processes that are conducive to the evolution of the massive black hole population. I will discuss black hole formation processes for `seed' black holes that are likely to place at early cosmic epochs, and possible observational tests of these scenarios.", "keyphrases": ["black hole", "cosmology", "accretion", "galactic nucleus"]}
{"id": "1608.07066", "title": "Extended vector-tensor theories", "abstract": "Recently, several extensions of massive vector theory in curved space-time have been proposed in many literatures. In this paper, we consider the most general vector-tensor theories that contain up to two derivatives with respect to metric and vector field. By imposing a degeneracy condition of the Lagrangian in the context of ADM decomposition of space-time to eliminate an unwanted mode, we construct a new class of massive vector theories where five degrees of freedom can propagate, corresponding to three for massive vector modes and two for massless tensor modes. We find that the generalized Proca and the beyond generalized Proca theories up to the quartic Lagrangian, which should be included in this formulation, are degenerate theories even in curved space-time. Finally, introducing new metric and vector field transformations, we investigate the properties of thus obtained theories under such transformations.", "keyphrases": ["vector-tensor theory", "generalized proca theory", "second-order domain"]}
{"id": "1312.3529", "title": "The Best Inflationary Models After Planck", "abstract": "We compute the Bayesian evidence and complexity of 193 slow-roll single-field models of inflation using the Planck 2013 Cosmic Microwave Background data, with the aim of establishing which models are favoured from a Bayesian perspective. Our calculations employ a new numerical pipeline interfacing an inflationary effective likelihood with the slow-roll library ASPIC and the nested sampling algorithm MULTINEST. The models considered represent a complete and systematic scan of the entire landscape of inflationary scenarios proposed so far. Our analysis singles out the most probable models (from an Occam's razor point of view) that are compatible with Planck data, while ruling out with very strong evidence 34 models that are favoured by the Bayesian evidence, corresponding to 15 different potential shapes. If the Bayesian complexity is included in the analysis, only 9 different potential shapes. These shapes are all of the plateau type.", "keyphrases": ["inflationary model", "simple model", "cosmic inflation"]}
{"id": "1101.4387", "title": "WIMPless dark matter and the excess gamma rays from the Galactic center", "abstract": "In this paper we discuss the excess gamma rays from the Galactic center, the WMAP haze and the CoGeNT and DAMA results in WIMPless models. At the same time we also investigate the low energy constraints from the anomalous magnetic moment of leptons and from some lepton flavor violating decays. It is found that, for scalar or vector WIMPless dark matter, neither the WMAP haze nor the CoGeNT and DAMA observations could be explained simultaneously with the excess gamma rays from the Galactic center. As to fermion WIMPless dark matter, it is only marginally possible to accommodate the CoGeNT and DAMA results with the excess gamma rays from the Galactic center with vector connector fields. On the other hand, only scalar connector fields could interpret the WMAP haze concerning the constraints of anomalous magnetic moment of leptons. Furthermore, if there is only one connector field for all the charged leptons, some lepton flavor violating decays could happen with too large branching ratios severely violating the experimental bounds.", "keyphrases": ["dark matter", "excess gamma ray", "galactic center", "thermal relic density"]}
{"id": "1003.1142", "title": "Annihilation vs. Decay: Constraining dark matter properties from a gamma-ray detection", "abstract": "Most proposed dark matter candidates are stable and are produced thermally in the early Universe. However, there is also the possibility of unstable (but long-lived) dark matter, produced thermally or otherwise. We propose a strategy to distinguish between dark matter annihilation and/or decay in the case that a clear signal is detected in gamma-ray observations of Milky Way dwarf spheroidal galaxies with gamma-ray experiments. The sole measurement of the energy spectrum of an indirect signal would render the discrimination between these cases impossible. We show that by examining the dependence of the intensity and energy spectrum on the angular distribution of the emission, the origin could be identified as decay, annihilation, or both. In addition, once the type of signal is established, we show how these measurements could help to extract information about the dark matter properties, including mass, annihilation cross section, lifetime, dominant annihilation and decay channels, and the presence of substructure. Although an application of the approach presented here would likely be feasible with current experiments only for very optimistic dark matter scenarios, the improved sensitivity of upcoming experiments could enable this technique to be used to study a wider range of dark matter models.", "keyphrases": ["dark matter property", "gamma-ray experiment", "annihilation"]}
{"id": "1502.01250", "title": "A loophole to the universal photon spectrum in electromagnetic cascades: application to the \"cosmological lithium problem\"", "abstract": "The standard theory of electromagnetic cascades onto a photon background predicts a quasi-universal shape for the resulting non-thermal photon spectrum. This has been applied to very disparate fields, including non-thermal big bang nucleosynthesis (BBN). However, once the energy of the injected photons falls below the pair-production threshold the spectral shape is very different, a fact that has been overlooked in past literature. This loophole may have important phenomenological consequences, since it generically alters the BBN bounds on non-thermal relics: for instance it allows to re-open the possibility of purely electromagnetic solutions to the so-called \"cosmological lithium problem\", which were thought to be excluded by other cosmological constraints. We show this with a proof-of-principle example and a simple particle physics model, compared with previous literature.", "keyphrases": ["photon", "cosmological lithium problem", "physics solution"]}
{"id": "1601.07426", "title": "Radio detection of cosmic ray air showers in the digital era", "abstract": "In 1965 it was discovered that cosmic ray air showers emit impulsive radio signals at frequencies below 100 MHz. After a period of intense research in the 1960s and 1970s, however, interest in the detection technique faded almost completely. With the availability of powerful digital signal processing techniques, new attempts at measuring cosmic ray air showers via their radio emission were started at the beginning of the new millennium. Starting with modest, small-scale digital prototype setups, the field has evolved, matured and grown very significantly in the past decade. Today's second-generation digital radio detection experiments consist of up to hundreds of radio antennas or cover areas of up to 17 km^2. We understand the physics of the radio emission in extensive air showers in detail and have developed analysis strategies to accurately derive from radio signals parameters which are related to the astrophysics of the primary cosmic ray particles, in particular their energy, arrival direction and estimators for their mass. In parallel to these successes, limitations inherent in the physics of the radio signals have also become increasingly clear. In this article, we review the progress of the past decade and the current state of the field, discuss the current paradigm of the radio emission physics and present the experimental evidence supporting it. Finally, we discuss the potential for future applications of the radio detection technique to advance the field of cosmic ray physics.", "keyphrases": ["ray air shower", "radio detection", "air-shower"]}
{"id": "1504.01970", "title": "Testing the Kerr Nature of Black Hole Candidates using Iron Line Spectra in the CPR Framework", "abstract": "The iron K\u03b1 line commonly observed in the X-ray spectrum of both stellar-mass and supermassive black hole candidates originates from X-ray fluorescence of the inner accretion disk. Accordingly, it can be used to map the spacetime geometry around these objects. In this paper, we extend previous work using the iron K\u03b1 line to test the Kerr black hole hypothesis. We adopt the Cardoso-Pani-Rico parametrization and we test the possibility of constraining possible deviations from the Kerr solution that can be obtained from observations across the range of black hole spins and inclination angles. We confirm previous claims that the iron K\u03b1 line is potentially a quite powerful probe for testing the Kerr metric given sufficiently high quality data and with systematics under control, especially in the case of fast-rotating black holes and high inclination angles since both conditions serve to maximize relativistic effects. We find that some geometric perturbations from Kerr geometry manifest more strongly in the iron line profile than others. While the perturbation parameter \u03f5^t_3 can be well constrained by the iron line profile, an orthogonal data set is necessary to constrain departures from Kerr geometry in \u03f5^r_3.", "keyphrases": ["black hole", "accretion disk", "astrophysical model"]}
{"id": "0907.4238", "title": "How Far Are We from the Quantum Theory of Gravity?", "abstract": "I give a pedagogical explanation of what it is about quantization that makes general relativity go from being a nearly perfect classical theory to a very problematic quantum one. I also explain why some quantization of gravity is unavoidable, why quantum field theories have divergences, why the divergences of quantum general relativity are worse than those of the other forces, what physicists think this means and what they might do with a consistent theory of quantum gravity if they had one. Finally, I discuss the quantum gravitational data that have recently become available from cosmology.", "keyphrases": ["gravity", "consistent theory", "phenomenon"]}
{"id": "1306.6518", "title": "Cosmological constraints on axionic dark radiation from axion-photon conversion in the early Universe", "abstract": "Axions seem ubiquitous in string theories and some of them may be produced non-thermally by heavy scalar decays, contributing to dark radiation. We study various cosmological effects of photons produced from the axionic dark radiation through axion-photon conversion in the presence of primordial magnetic fields, and derive tight constraints on the combination of the axion-photon coupling and the primordial magnetic field.", "keyphrases": ["axionic dark radiation", "dark radiation", "early universe", "primordial magnetic field"]}
{"id": "1605.02149", "title": "Time-Sliced Perturbation Theory II: Baryon Acoustic Oscillations and Infrared Resummation", "abstract": "We use time-sliced perturbation theory (TSPT) to give an accurate description of the infrared non-linear effects affecting the baryonic acoustic oscillations (BAO) present in the distribution of matter at very large scales. In TSPT this can be done via a systematic resummation that has a simple diagrammatic representation and does not involve uncontrollable approximations. We discuss the power counting rules and derive explicit expressions for the resummed matter power spectrum up to next-to leading order and the bispectrum at the leading order. The two-point correlation function agrees well with N-body data at BAO scales. The systematic approach also allows to reliably assess the shift of the baryon acoustic peak due to non-linear effects.", "keyphrases": ["perturbation theory", "baryon", "ir-resummation"]}
{"id": "1903.00083", "title": "Host galaxies of merging compact objects: mass, star formation rate, metallicity and colours", "abstract": "Characterizing the properties of the host galaxies of merging compact objects provides essential clues to interpret current and future gravitational-wave detections. Here, we investigate the stellar mass, star formation rate (SFR), metallicity and colours of the host galaxies of merging compact objects in the local Universe, by combining the results of MOBSE population-synthesis models together with galaxy catalogs from the EAGLE simulation. We predict that the stellar mass of the host galaxy is an excellent tracer of the merger rate per galaxy n_ GW of double neutron stars (DNSs), double black holes (DBHs) and black hole-neutron star binaries (BHNSs). We find a significant correlation also between n_ GW and SFR. As a consequence, n_ GW correlates also with the r-band luminosity and with the g-r colour of the host galaxies. Interestingly, \u227360 and \u227373 Universe lie in early-type galaxies, such as NGC 4993. We predict a local DNS merger rate density of \u223c238 Gpc^-3 yr ^-1 and a DNS merger rate \u223c16-121 Myr^-1 for Milky Way-like galaxies. Thus, our results are consistent with both the DNS merger rate inferred from GW170817 and the one inferred from Galactic DNSs.", "keyphrases": ["star formation rate", "metallicity", "host galaxy"]}
{"id": "0903.5137", "title": "A new chronology for the Moon and Mercury", "abstract": "In this paper we present a new method for dating the surface of the Moon, obtained by modeling the incoming flux of impactors and converting it into a size distribution of resulting craters. We compare the results from this model with the standard chronology for the Moon showing their similarities and discrepancies. In particular, we find indications of a non-constant impactor flux in the last 500 Myr and also discuss the implications of our findings for the Late Heavy Bombardment hypothesis. We also show the potential of our model for accurate dating of other inner Solar System bodies, by applying it to Mercury.", "keyphrases": ["chronology", "moon", "mercury"]}
{"id": "1304.6737", "title": "Frame independent cosmological perturbations", "abstract": "We compute the third order gauge invariant action for scalar-graviton interactions in the Jordan frame. We demonstrate that the gauge invariant action for scalar and tensor perturbations on one physical hypersurface only differs from that on another physical hypersurface via terms proportional to the equation of motion and boundary terms, such that the evolution of non-Gaussianity may be called unique. Moreover, we demonstrate that the gauge invariant curvature perturbation and graviton on uniform field hypersurfaces in the Jordan frame are equal to their counterparts in the Einstein frame. These frame independent perturbations are therefore particularly useful in relating results in different frames at the perturbative level. On the other hand, the field perturbation and graviton on uniform curvature hypersurfaces in the Jordan and Einstein frame are non-linearly related, as are their corresponding actions and n-point functions.", "keyphrases": ["cosmological perturbation", "gauge", "frame"]}
{"id": "1705.02358", "title": "Dark Matter Self-interactions and Small Scale Structure", "abstract": "We review theories of dark matter (DM) beyond the collisionless paradigm, known as self-interacting dark matter (SIDM), and their observable implications for astrophysical structure in the Universe. Self-interactions are motivated, in part, due to the potential to explain long-standing (and more recent) small scale structure observations that are in tension with collisionless cold DM (CDM) predictions. Simple particle physics models for SIDM can provide a universal explanation for these observations across a wide range of mass scales spanning dwarf galaxies, low and high surface brightness spiral galaxies, and clusters of galaxies. At the same time, SIDM leaves intact the success of \u039bCDM cosmology on large scales. This report covers the following topics: (1) small scale structure issues, including the core-cusp problem, the diversity problem for rotation curves, the missing satellites problem, and the too-big-to-fail problem, as well as recent progress in hydrodynamical simulations of galaxy formation; (2) N-body simulations for SIDM, including implications for density profiles, halo shapes, substructure, and the interplay between baryons and self-interactions; (3) semi-analytic Jeans-based methods that provide a complementary approach for connecting particle models with observations; (4) merging systems, such as cluster mergers (e.g., the Bullet Cluster) and minor infalls, along with recent simulation results for mergers; (5) particle physics models, including light mediator models and composite DM models; and (6) complementary probes for SIDM, including indirect and direct detection experiments, particle collider searches, and cosmological observations. We provide a summary and critical look for all current constraints on DM self-interactions and an outline for future directions.", "keyphrases": ["small scale structure", "dwarf galaxy", "cosmology", "dark matter", "dark sector"]}
{"id": "1807.01714", "title": "The trouble with Hubble: Local versus global expansion rates in inhomogeneous cosmological simulations with numerical relativity", "abstract": "In a fully inhomogeneous, anisotropic cosmological simulation performed by solving Einstein's equations with numerical relativity, we find a local measurement of the effective Hubble parameter differs by less than 1% compared to the global value. This variance is consistent with predictions from Newtonian gravity. We analyse the averaged local expansion rate on scales comparable to Type 1a supernova surveys, and find that local variance cannot resolve the tension between the <cit.> and <cit.> measurements.", "keyphrases": ["expansion rate", "cosmological simulation", "numerical relativity"]}
{"id": "1005.0380", "title": "First Dark Matter Results from the XENON100 Experiment", "abstract": "The XENON100 experiment, in operation at the Laboratori Nazionali del Gran Sasso in Italy, is designed to search for dark matter WIMPs scattering off 62 kg of liquid xenon in an ultra-low background dual-phase time projection chamber. In this letter, we present first dark matter results from the analysis of 11.17 live days of non-blind data, acquired in October and November 2009. In the selected fiducial target of 40 kg, and within the pre-defined signal region, we observe no events and hence exclude spin-independent WIMP-nucleon elastic scattering cross-sections above 3.4 x 10^-44 cm^2 for 55 GeV/c^2 WIMPs at 90 interpretation of the CoGeNT and DAMA signals as being due to spin-independent, elastic, light mass WIMP interactions.", "keyphrases": ["dark matter", "matter result", "xenon100 experiment", "massive particle"]}
{"id": "0912.1249", "title": "The Lagrangian description of perfect fluids and modified gravity with an extra force", "abstract": "We revisit the issue of the correct Lagrangian description of a perfect fluid (pressure versus minus energy density) in relation with modified gravity theories in which galactic luminous matter couples nonminimally to the Ricci scalar. These Lagrangians are only equivalent when the fluid couples minimally to gravity and not otherwise; in the presence of nonminimal coupling they give rise to two distinct theories with different predictions.", "keyphrases": ["lagrangian description", "perfect fluid", "gravity"]}
{"id": "1310.3509", "title": "Bounds on self-interacting fermion dark matter from observations of old neutron stars", "abstract": "The existence of old neutron stars deeply constrains self-interacting fermion dark matter, which can form star-killing black holes. We quantify this constraint on dark matter-nucleon scattering, considering collapse scenarios that broaden bounds over intermediate masses. We then find the self- and co-annihilation rates necessary to lift these dark matter-nucleon scattering bounds. For Yukawa-coupled dark matter that fits dwarf galaxy halo profiles with a coupling \u03b1 = 10^-1-10^-4, a scalar mediator mass m_\u03d5 = 1-500 MeV, and DM mass m_X = 0.1-10^7 GeV, we show that fermion dark matter is unconstrained if it self-annihilates at a rate greater than 10^-40 cm^3/s or co-annihilates with baryons at a rate greater than 10^-50 cm^3/s.", "keyphrases": ["fermion", "dark matter", "neutron star", "black hole"]}
{"id": "1910.05670", "title": "Band-limited Features in the Primordial Power Spectrum Do Not Resolve the Hubble Tension", "abstract": "For a standard \u039bCDM universe with a power-law primordial power spectrum, the discrepancy between early- and late-universe measurements of the Hubble constant continued to grow and recently reached 5.3\u03c3. During inflation, local features in the inflationary potential often lead to band-limited features in the primordial power spectrum, hence breaking the power-law assumption in the derivation of the Hubble tension. We investigate whether such inflationary \"glitches\" can ease the Hubble tension. The recently released Planck temperature and polarization data and the 2019 SH0ES+H0LiCOW joint constraint on the Hubble constant are combined to drive a blind Daubechies wavelet signal search in the primordial power spectrum, up to a resolution \u0394ln k\u223c 0.1. We find no significant detection of any features beyond power law. With 64 more degrees of freedom injected in the primordial power spectrum, the Hubble tension persists at a 4.9\u03c3 level.", "keyphrases": ["primordial power spectrum", "hubble tension", "band-limited feature"]}
{"id": "1204.3178", "title": "Galactic Dark Matter in the Phantom Field", "abstract": "We investigate the possibility that the galactic dark matter exists in an scenario where the phantom field is responsible for the dark energy. We obtain the statically and spherically approximate solution for this kind of the galaxy system with a supermassive black hole at its center. The solution of the metric functions is satisfied with g_tt = - g_rr^-1. Constrained by the observation of the rotational stars moving in circular orbits with nearly constant tangential speed in a spiral galaxy, the background of the phantom field which is spatially inhomogeneous has an exponential potential. To avoid the well-known quantum instability of the vacuum at high frequencies, the phantom field defined in an effective theory is valid only at low energies. Under this assumption, we further investigate the following properties. The absorption cross section of the low-energy S-wave excitations of the phantom field into the central black hole is shown to be the horizontal area of the central black hole. Because the infalling phantom particles have a total negative energy, the accretion of the phantom energy is related to the decrease of the black hole mass which is estimated to be much less than a solar mass in the lifetime of the Universe. Using a simple model with the cold dark matter very weakly coupled to the \"low-frequency\" phantom particles which are generated from the background, we show that these two densities can be quasi-stable in the galaxy.", "keyphrases": ["phantom field", "dark energy", "black hole", "galactic dark matter"]}
{"id": "1709.07049", "title": "Gravitational waves from single neutron stars: an advanced detector era survey", "abstract": "With the doors beginning to swing open on the new gravitational wave astronomy, this review provides an up-to-date survey of the most important physical mechanisms that could lead to emission of potentially detectable gravitational radiation from isolated and accreting neutron stars. In particular we discuss the gravitational wave-driven instability and asteroseismology formalism of the f- and r-modes, the different ways that a neutron star could form and sustain a non-axisymmetric quadrupolar \"mountain\" deformation, the excitation of oscillations during magnetar flares and the possible gravitational wave signature of pulsar glitches. We focus on progress made in the recent years in each topic, make a fresh assessment of the gravitational wave detectability of each mechanism and, finally, highlight key problems and desiderata for future work.", "keyphrases": ["neutron star", "radiation", "r-mode", "oscillation", "gravitational wave"]}
{"id": "0906.4370", "title": "Cosmological simulations of galaxy clusters", "abstract": "We review recent progress in the description of the formation and evolution of galaxy clusters in a cosmological context by using numerical simulations. We focus our presentation on the comparison between simulated and observed X-ray properties, while we will also discuss numerical predictions on properties of the galaxy population in clusters. Many of the salient observed properties of clusters, such as X-ray scaling relations, radial profiles of entropy and density of the intracluster gas, and radial distribution of galaxies are reproduced quite well. In particular, the outer regions of cluster at radii beyond about 10 per cent of the virial radius are quite regular and exhibit scaling with mass remarkably close to that expected in the simplest case in which only the action of gravity determines the evolution of the intra-cluster gas. However, simulations generally fail at reproducing the observed cool-core structure of clusters: simulated clusters generally exhibit a significant excess of gas cooling in their central regions, which causes an overestimate of the star formation and incorrect temperature and entropy profiles. The total baryon fraction in clusters is below the mean universal value, by an amount which depends on the cluster-centric distance and the physics included in the simulations, with interesting tensions between observed stellar and gas fractions in clusters and predictions of simulations. Besides their important implications for the cosmological application of clusters, these puzzles also point towards the important role played by additional physical processes, beyond those already included in the simulations. We review the role played by these processes, along with the difficulty for their implementation, and discuss the outlook for the future progress in numerical modeling of clusters.", "keyphrases": ["galaxy cluster", "baryon fraction", "cosmological simulation"]}
{"id": "2005.12041", "title": "Constraints on neutrino mass in the scenario of vacuum energy interacting with cold dark matter after Planck 2018", "abstract": "In this work, we investigate the constraints on the total neutrino mass in the scenario of vacuum energy interacting with cold dark matter (abbreviated as I\u039bCDM) by using the latest cosmological observations. We consider four typical interaction forms, i.e., Q=\u03b2 H \u03c1_ de, Q=\u03b2 H \u03c1_ c, Q=\u03b2 H_0\u03c1_ de, and Q=\u03b2 H_0\u03c1_ c, in the I\u039bCDM scenario. To avoid the large-scale instability problem in interacting dark energy models, we employ the extended parameterized post-Friedmann method for interacting dark energy to calculate the perturbation evolution of dark energy in these models. The observational data used in this work include the cosmic microwave background (CMB) measurements from the Planck 2018 data release, the baryon acoustic oscillation (BAO) data, the type Ia supernovae (SN) observation (Pantheon compilation), and the 2019 local distance ladder measurement of the Hubble constant H_0 from the Hubble Space Telescope. We find that, compared with those in the \u039bCDM+\u2211 m_\u03bd model, the constrains on \u2211 m_\u03bd are looser in the four I\u039bCDM+\u2211 m_\u03bd models. When considering the three mass hierarchies of neutrinos, the constraints on \u2211 m_\u03bd are tightest in the degenerate hierarchy case and loosest in the inverted hierarchy case. In addition, in the four I\u039bCDM+\u2211 m_\u03bd models, the values of coupling parameter \u03b2 are larger using the CMB+BAO+SN+H_0 data combination than that using the CMB+BAO+SN data combination, and \u03b2>0 is favored at more than 1\u03c3 level when using CMB+BAO+SN+H_0 data combination. The issue of the H_0 tension is also discussed in this paper. We find that, compared with the \u039bCDM+\u2211 m_\u03bd model, the H_0 tension can be alleviated in the I\u039bCDM+\u2211 m_\u03bd model to some extent.", "keyphrases": ["neutrino mass", "vacuum energy", "dark matter"]}
{"id": "1810.05225", "title": "Inherently stable effective field theory for dark energy and modified gravity", "abstract": "The growing wealth of cosmological observations places increasingly more stringent constraints on dark energy and alternative gravity models. Particularly successful in efficiently probing the vast model space has been the effective field theory of dark energy and modified gravity, providing a unified framework for generalised cosmological predictions. However, the optimal parametrisation of the free time-dependent functions inherent to the formalism is still unresolved. It should respect a multitude of requirements, ranging from simplicity, generality, and representativity of known theories to computational efficiency. But in particular, for theoretical soundness, the parameter space should adhere to strict stability requirements. We have recently proposed an inherently stable effective field theory with physical basis of Planck mass evolution, sound speed of the scalar field fluctuation, kinetic coefficient, and background expansion, which covers Horndeski models with luminal speed of gravity. Here we devise a parametrisation of these basis functions that can straightforwardly be configured to evade theoretical pathologies such as ghost or gradient instabilities or to accommodate further theoretical priors such as (sub)luminal scalar sound speed. The parametrisation is simple yet general, conveniently represents a broad range of known dark energy and gravitational theories, and with a simple additional approximation can be rendered numerically highly efficient. Finally, by operating in our new basis, we show that there are no general limitations from stability requirements on the current values that can be assumed by the phenomenological modification of the Poisson equation and the gravitational slip besides the exclusion of anti-gravity. The inherently stable effective field theory is ready for implementation in parameter estimation analyses employing linear cosmological observations.", "keyphrases": ["effective field theory", "dark energy", "gravity"]}
{"id": "1504.00351", "title": "On Separate Universes", "abstract": "(abridged version) The separate universe conjecture states that in General Relativity a density perturbation behaves locally (i.e. on scales much smaller than the wavelength of the mode) as a separate universe with different background density and curvature. We prove this conjecture for a spherical compensated tophat density perturbation of arbitrary amplitude and radius in \u039bCDM. We then use Conformal Fermi Coordinates to generalize this result to scalar perturbations of arbitrary configuration and scale. In this case, the separate universe conjecture holds for the isotropic part of the perturbations. The anisotropic part on the other hand is exactly captured by a tidal field in the Newtonian form. We show that the separate universe picture is restricted to scales larger than the sound horizons of all fluid components. We then derive an expression for the locally measured matter bispectrum induced by a long-wavelength mode of arbitrary wavelength. We show that nonlinear gravitational dynamics does not generate observable contributions that scale like local-type non-Gaussianity f_ NL^ loc, and hence does not contribute to a scale-dependent galaxy bias \u0394 b \u221d k^-2 on large scales; rather, the locally measurable long-short mode coupling assumes a form essentially identical to subhorizon perturbation theory results, once the long-mode density perturbation is replaced by the synchronous-comoving gauge density perturbation. Apparent f_ NL^ loc-type contributions arise through projection effects on photon propagation, which depend on the specific large-scale structure tracer and observable considered, and are in principle distinguishable from the local mode coupling induced by gravity. We conclude that any observation of f_ NL^ loc beyond these projection effects signals a departure from standard single-clock inflation.", "keyphrases": ["universe", "non-gaussianity", "projection effect", "single-field model", "consistency relation"]}
{"id": "1005.3270", "title": "Off-equatorial orbits in strong gravitational fields near compact objects \u2013 II: halo motion around magnetic compact stars and magnetized black holes", "abstract": "Off-equatorial circular orbits with constant latitudes (halo orbits) of electrically charged particles exist near compact objects. In the previous paper, we discussed this kind of motion and demonstrated the existence of minima of the two-dimensional effective potential which correspond to the stable halo orbits. Here, we relax previous assumptions of the pseudo-Newtonian approach for the gravitational field of the central body and study properties of the halo orbits in detail. Within the general relativistic approach, we carry out our calculations in two cases. Firstly, we examine the case of a rotating magnetic compact star. Assuming that the magnetic field axis and the rotation axis are aligned with each other, we study the orientation of motion along the stable halo orbits. In the poloidal plane, we also discuss shapes of the related effective potential halo lobes where the general off-equatorial motion can be bound. Then we focus on the halo orbits near a Kerr black hole immersed in an asymptotically uniform magnetic field of external origin. We demonstrate that, in both the cases considered, the lobes exhibit two different regimes, namely, one where completely disjoint lobes occur symmetrically above and below the equatorial plane, and another where the lobes are joined across the plane. A possible application of the model concerns the structure of putative circumpulsar discs consisting of dust particles. We suggest that the particles can acquire a small (but non-zero) net electric charge, and this drives them to form the halo lobes.", "keyphrases": ["gravitational field", "magnetic compact star", "off-equatorial orbit"]}
{"id": "1312.0613", "title": "The Habitable Epoch of the Early Universe", "abstract": "In the redshift range 100<(1+z)<137, the cosmic microwave background (CMB) had a temperature of 273-373K (0-100 degrees Celsius), allowing early rocky planets (if any existed) to have liquid water chemistry on their surface and be habitable, irrespective of their distance from a star. In the standard LCDM cosmology, the first star-forming halos within our Hubble volume started collapsing at these redshifts, allowing the chemistry of life to possibly begin when the Universe was merely 10-17 million years old. The possibility of life starting when the average matter density was a million times bigger than it is today argues against the anthropic explanation for the low value of the cosmological constant.", "keyphrases": ["universe", "redshift", "rocky planet"]}
{"id": "1009.5443", "title": "Nonparametric Reconstruction of the Dark Energy Equation of State", "abstract": "A basic aim of ongoing and upcoming cosmological surveys is to unravel the mystery of dark energy. In the absence of a compelling theory to test, a natural approach is to better characterize the properties of dark energy in search of clues that can lead to a more fundamental understanding. One way to view this characterization is the improved determination of the redshift-dependence of the dark energy equation of state parameter, w(z). To do this requires a robust and bias-free method for reconstructing w(z) from data that does not rely on restrictive expansion schemes or assumed functional forms for w(z). We present a new nonparametric reconstruction method that solves for w(z) as a statistical inverse problem, based on a Gaussian Process representation. This method reliably captures nontrivial behavior of w(z) and provides controlled error bounds. We demonstrate the power of the method on different sets of simulated supernova data; the approach can be easily extended to include diverse cosmological probes.", "keyphrases": ["reconstruction", "dark energy equation", "cosmology", "state parameter"]}
{"id": "1402.3755", "title": "Evolution of the universe in entropic cosmologies via different formulations", "abstract": "We study two types of entropic-force models in a homogeneous, isotropic, spatially flat, matter-dominated universe. The first type is a `\u039b(t) type' similar to \u039b(t)CDM (varying-lambda cold dark matter) models in which both the Friedmann equation and the acceleration equation include an extra driving term. The second type is a `BV type' similar to bulk viscous models in which the acceleration equation includes an extra driving term whereas the Friedmann equation does not. In order to examine the two types systematically, we consider an extended entropic-force model that includes a Hubble parameter (H) term and a constant term in entropic-force terms. The H term is derived from a volume entropy whereas the constant term is derived from an entropy proportional to the square of an area entropy. Based on the extended entropic-force model, we examine four models obtained from combining the H and constant terms with the \u039b(t) and BV types. The four models agree well with the observed supernova data and describe the background evolution of the late universe properly. However, the evolution of first-order density perturbations is different in each of the four models, especially for low redshift, assuming that an effective sound speed is negligible. The \u039b(t) type is found to be consistent with the observed growth rate of clustering, in contrast with the BV type examined in this study. A unified formulation is proposed as well, in order to examine density perturbations of the two types systematically.", "keyphrases": ["universe", "entropic-force model", "bulk viscous model"]}
{"id": "1203.6698", "title": "Unconventional Cosmology", "abstract": "I review two cosmological paradigms which are alternative to the current inflationary scenario. The first alternative is the \"matter bounce\", a non-singular bouncing cosmology with a matter-dominated phase of contraction. The second is an \"emergent\" scenario, which can be implemented in the context of \"string gas cosmology\". I will compare these scenarios with the inflationary one and demonstrate that all three lead to an approximately scale-invariant spectrum of cosmological perturbations.", "keyphrases": ["cosmology", "alternative", "inflationary cosmology see"]}
{"id": "2202.06969", "title": "Public data release of the FIRE-2 cosmological zoom-in simulations of galaxy formation", "abstract": "We describe a public data release of the FIRE-2 cosmological zoom-in simulations of galaxy formation, available at http://flathub.flatironinstitute.org/fire, from the Feedback In Realistic Environments (FIRE) project. FIRE-2 simulations achieve parsec-scale resolution to explicitly model the multi-phase interstellar medium while implementing direct models for stellar evolution and feedback, including stellar winds, core-collapse and Ia supernovae, radiation pressure, photoionization, and photoelectric heating. We release complete snapshots from 3 suites of simulations. The first comprises 20 simulations that zoom in on 14 Milky Way-mass galaxies, 5 SMC/LMC-mass galaxies, and 4 lower-mass galaxies including 1 ultra-faint; we release 39 snapshots across z = 0 - 10. The second comprises 4 massive galaxies, with 19 snapshots across z = 1 - 10. Finally, a high-redshift suite comprises 22 simulations, with 11 snapshots across z = 5 - 10. Each simulation also includes dozens of resolved lower-mass (satellite) galaxies in its zoom-in region. Snapshots include all stored properties for all dark matter, gas, and star particles, including 11 elemental abundances for stars and gas, and formation times (ages) of star particles. We also release accompanying (sub)halo catalogs, which include galaxy properties and member star particles. For the simulations to z = 0, including all Milky Way-mass galaxies, we release the formation coordinates and an \"ex-situ\" flag for all star particles, pointers to track particles across snapshots, catalogs of stellar streams, and multipole basis expansions for the halo mass distributions. We describe publicly available python packages for reading and analyzing these simulations.", "keyphrases": ["cosmological zoom-in simulation", "galaxy formation", "star"]}
{"id": "1709.08414", "title": "Molecular gas in debris disks around young A-type stars", "abstract": "According to the current paradigm of circumstellar disk evolution, gas-rich primordial disks evolve into gas-poor debris disks compose of second-generation dust. To explore the transition between these phases, we searched for ^12CO, ^13CO, and C^18O emission in seven dust-rich debris disks around young A-type stars, using ALMA in Band 6. We discovered molecular gas in three debris disks. In all these disks, the ^12CO line was optically thick, highlighting the importance of less abundant molecules in reliable mass estimates. Supplementing our target list by literature data, we compiled a volume-limited sample of dust-rich debris disks around young A-type stars within 150 pc. We obtained a CO detection rate of 11/16 above a ^12CO J=2-1 line luminosity threshold of \u223c 1.4 \u00d7 10 ^4 Jykms^-1pc^2 in the sample. This high incidence implies that the presence of CO gas in bright debris disks around young A-type stars is likely more the rule than the exception. Interestingly, dust-rich debris disks around young FG-type stars exhibit, with the same detectability threshold as for A-type stars, significantly lower gas incidence. While the transition from protoplanetary to debris phase is associated with a drop of dust content, our results exhibit a large spread in the CO mass in our debris sample, with peak values comparable to those in protoplanetary Herbig Ae disks. In the particularly CO-rich debris systems the gas may have primordial origin, characteristic of a hybrid disk.", "keyphrases": ["debris disk", "young a-type star", "molecular gas"]}
{"id": "1107.1143", "title": "Constraints on dissipative unified dark matter", "abstract": "Modern cosmology suggests that the Universe contains two dark components \u2013 dark matter and dark energy \u2013 both unkown in laboratory physics and both lacking direct evidence. Alternatively, a unified dark sector, described by a single fluid, has been proposed. Dissipation is a common phenomenon in nature and it thus seems natural to consider models dominated by a viscous dark fluid. We focus on the study of bulk viscosity, as isotropy and homogeneity at large scales implies the suppression of shear viscosity, heat flow and diffusion. The generic ansatz \u03be\u221d\u03c1^\u03bd for the coefficient of bulk viscosity (\u03c1 denotes the mass/energy density), which for \u03bd = - 1/2 mimics the \u039bCDM background evolution, offers excellent fits to supernova and H(z) data. We show that viscous dark fluids suffer from large contributions to the integrated Sachs-Wolfe effect (generalising a previous study by Li Barrow) and a suppression of structure growth at small-scales (as seen from a generalized Meszaros equation). Based on recent observations, we conclude that viscous dark fluid models (with \u03be\u221d\u03c1^\u03bd and neglecting baryons) are strongly challenged.", "keyphrases": ["dark matter", "dark energy", "gravitational potential"]}
{"id": "2001.02451", "title": "Is the Hubble tension a hint of AdS phase around recombination?", "abstract": "Anti-de Sitter (AdS) vacua, being theoretically important, might have an unexpected impact on the observable universe. We find that in early dark energy (EDE) scenarios the existence of AdS vacua around recombination can effectively lift the CMB-inferred H_0 value. As an example, we study a phenomenological EDE model with an AdS phase starting at the redshift z\u223c2000 and ending shortly after recombination (hereafter the universe will settle down in a \u039b>0 phase until now), and obtain a best-fit H_0=72.74 km/s/Mpc without degrading the CMB fit compared with the standard \u039bCDM model.", "keyphrases": ["recombination", "low-redshift", "dynamical dark energy"]}
{"id": "1512.09139", "title": "Probing circular polarization in stochastic gravitational wave background with pulsar timing arrays", "abstract": "We study the detectability of circular polarization in a stochastic gravitational wave background from various sources such as supermassive black hole binaries, cosmic strings, and inflation in the early universe with pulsar timing arrays. We calculate generalized overlap reduction functions for the circularly polarized stochastic gravitational wave background. We find that the circular polarization can not be detected for an isotropic background. However, there is a chance to observe the circular polarization for an anisotropic gravitational wave background. We also show how to separate polarized gravitational waves from unpolarized gravitational waves.", "keyphrases": ["circular polarization", "gravitational wave background", "pulsar timing array"]}
{"id": "1909.07395", "title": "Cusp-to-core transition in low-mass dwarf galaxies induced by dynamical heating of cold dark matter by primordial black holes", "abstract": "We performed a series of high-resolution N-body simulations to examine whether dark matter candidates in the form of primordial black holes (PBHs) can solve the cusp-core problem in low-mass dwarf galaxies. If some fraction of the dark matter in low-mass dwarf galaxies consists of PBHs and the rest is cold dark matter, dynamical heating of the cold dark matter by the PBHs induces a cusp-to-core transition in the total dark matter profile. The mechanism works for PBHs in the 25-100 M_ mass window, consistent with the LIGO detections, but requires a lower limit on the PBH mass fraction of 1% of the total dwarf galaxy dark matter content. The cusp-to-core transition time-scale is between 1 and 8 Gyr. This time-scale is also a constant multiple of the relaxation time between cold dark matter particles and PBHs, which depends on the mass, the mass fraction and the scale radius of the initial density profile of PBHs. We conclude that dark matter cores occur naturally in halos comprised of cold dark matter and PBHs, without the need to invoke baryonic processes.", "keyphrases": ["low-mass dwarf galaxy", "cold dark matter", "primordial black hole"]}
{"id": "1708.01709", "title": "On the Effective Field Theory for Quasi-Single Field Inflation", "abstract": "We study the effective field theory (EFT) description of the virtual particle effects in quasi-single field inflation, which unifies the previous results on large mass and large mixing cases. By using a horizon crossing approximation and matching with known limits, approximate expressions for the power spectrum and the spectral index are obtained. The error of the approximate solution is within 10 less-than-0.1 corrections on the n_s-r diagram are plotted for a few inflation models. Especially, the quasi-single field correction drives m^2\u03d5^2 inflation to the best fit region on the n_s-r diagram, with an amount of equilateral non-Gaussianity which can be tested in future experiments.", "keyphrases": ["effective field theory", "quasi-single field inflation", "cosmological collider physics"]}
{"id": "1304.6183", "title": "Halo-independent analysis of direct detection data for light WIMPs", "abstract": "We present a halo-independent analysis of direct detection data on \"light WIMPs,\" i.e. weakly interacting massive particles with mass close to or below 10 GeV/c^2. We include new results from silicon CDMS detectors (bounds and excess events), the latest CoGeNT acceptances, and recent measurements of low sodium quenching factors in NaI crystals. We focus on light WIMPs with spin-independent isospin-conserving and isospin-violating interactions with nucleons. For these dark matter candidates we find that a low quenching factor would make the DAMA modulation incompatible with a reasonable escape velocity for the dark matter halo, and that the tension among experimental data tightens in both the isospin-conserving and isospin-violating scenarios. We also find that a new although milder tension appears between the CoGeNT and DAMA annual modulations on one side and the silicon excess events on the other, in that it seems difficult to interpret them as the modulated and unmodulated aspects of the same WIMP dark matter signal.", "keyphrases": ["detection data", "light wimp", "halo-independent analysis"]}
{"id": "2006.13525", "title": "The Flat Sky Approximation to Galaxy Number Counts", "abstract": "We derive and test an approximation for the angular power spectrum of galaxy number counts in the flat sky limit. The standard density and redshift space distortion (RSD) terms in the resulting approximation are distinct to the Limber approximation, providing an accurate result for multipoles as low as \u2113\u224310, where the corresponding Limber approximation is completely inaccurate. At equal redshift the accuracy of the density and RSD (standard) terms is around 0.2 redshifts, if we consider the total power spectrum, the precision is better than 5 3.6\u00d710^-4(1+z)^2.14)where the standard terms are well-approximated, or for large enough redshift differences\u03b4>\u03b4_1 (\u22430.33(r(z)H(z))/(z+1))where the lensing terms dominate. The flat sky expressions for the pure lensing and the lensing-density cross-correlation terms are equivalent to the Limber approximation. For arbitrary redshift differences, the Limber approximation achieves an accuracy of 0.5\u2113\u224340for pure lensing and\u2113\u224380for density-lensing). Besides being very accurate, the flat sky approximation is computationally much simpler and can therefore be very useful for data analysis and forecasts with MCMC methods. This will be particularly crucial for upcoming galaxy surveys that will measure the power spectrum of galaxy number counts.", "keyphrases": ["galaxy number count", "limber approximation", "flat sky approximation"]}
{"id": "1011.0916", "title": "Constraining the cosmic radiation density due to lepton number with Big Bang Nucleosynthesis", "abstract": "The cosmic energy density in the form of radiation before and during Big Bang Nucleosynthesis (BBN) is typically parameterized in terms of the effective number of neutrinos N_eff. This quantity, in case of no extra degrees of freedom, depends upon the chemical potential and the temperature characterizing the three active neutrino distributions, as well as by their possible non-thermal features. In the present analysis we determine the upper bounds that BBN places on N_eff from primordial neutrino\u2013antineutrino asymmetries, with a careful treatment of the dynamics of neutrino oscillations. We consider quite a wide range for the total lepton number in the neutrino sector, eta_nu= eta_nu_e+eta_nu_mu+eta_nu_tau and the initial electron neutrino asymmetry eta_nu_e^in, solving the corresponding kinetic equations which rule the dynamics of neutrino (antineutrino) distributions in phase space due to collisions, pair processes and flavor oscillations. New bounds on both the total lepton number in the neutrino sector and the nu_e -barnu_e asymmetry at the onset of BBN are obtained fully exploiting the time evolution of neutrino distributions, as well as the most recent determinations of primordial 2H/H density ratio and 4He mass fraction. Note that taking the baryon fraction as measured by WMAP, the 2H/H abundance plays a relevant role in constraining the allowed regions in the eta_nu -eta_nu_e^in plane. These bounds fix the maximum contribution of neutrinos with primordial asymmetries to N_eff as a function of the mixing parameter theta_13, and point out the upper bound N_eff < 3.4. Comparing these results with the forthcoming measurement of N_eff by the Planck satellite will likely provide insight on the nature of the radiation content of the universe.", "keyphrases": ["lepton number", "big bang nucleosynthesis", "neutrino"]}
{"id": "1704.06657", "title": "A tale of two modes: Neutrino free-streaming in the early universe", "abstract": "We present updated constraints on the free-streaming nature of cosmological neutrinos from cosmic microwave background (CMB) power spectra, baryonic acoustic oscillation data, and local measurements of the Hubble constant. Specifically, we consider a Fermi-like four-fermion interaction between massless neutrinos, characterized by an effective coupling constant G_ eff, and resulting in a neutrino opacity \u03c4\u0307_\u03bd\u221d G_ eff^2 T_\u03bd^5. Using a conservative prior on the parameter log_10(G_ eff MeV^2), we find a bimodal posterior distribution. The first of these modes is consistent with the standard \u039bCDM cosmology and corresponds to neutrinos decoupling at redshift z_\u03bd, dec > 1.3\u00d710^5. The other mode of the posterior, dubbed the \"interacting neutrino mode\", corresponds to neutrino decoupling occurring within a narrow redshift window centered around z_\u03bd, dec\u223c8300. This mode is characterized by a high value of the effective neutrino coupling constant, together with a lower value of the scalar spectral index and amplitude of fluctuations, and a higher value of the Hubble parameter. Using both a maximum likelihood analysis and the ratio of the two mode's Bayesian evidence, we find the interacting neutrino mode to be statistically disfavored compared to the standard \u039bCDM cosmology. Interestingly, the addition of CMB polarization and direct Hubble constant measurements significantly raises the statistical significance of this secondary mode, indicating that new physics in the neutrino sector could help explain the difference between local measurements of H_0, and those inferred from CMB data. A robust consequence of our results is that neutrinos must be free streaming long before the epoch of matter-radiation equality.", "keyphrases": ["neutrino", "early universe", "cosmic microwave background", "hidden dark sector"]}
{"id": "1212.6001", "title": "Extended analysis of CMB constraints on non-Gaussianity in isocurvature perturbations", "abstract": "We study CMB constraints on non-Gaussianity from isocurvature perturbations of general types. Specifically, we study CDM/neutrino isocurvature perturbations which are uncorrelated or totally correlated with adiabatic ones. Using the data from the WMAP 7-year observation at V and W bands, we obtained optimal constraints on the nonlinearity parameters of adiabatic and isocurvature perturbations. Our result shows that primordial perturbations are consistent with Gaussian ones at around 2 sigma level for above mentioned isocurvature modes.", "keyphrases": ["cmb constraint", "non-gaussianity", "isocurvature perturbation"]}
{"id": "1901.05966", "title": "The baryonic Tully-Fisher relation for different velocity definitions and implications for galaxy angular momentum", "abstract": "We study the baryonic Tully-Fisher relation (BTFR) at z=0 using 153 galaxies from the SPARC sample. We consider different definitions of the characteristic velocity from HI and H-alpha rotation curves, as well as HI line-widths from single-dish observations. We reach the following results: (1) The tightest BTFR is given by the mean velocity along the flat part of the rotation curve. The orthogonal intrinsic scatter is extremely small (6 3.85+/-0.09, but systematic uncertainties may drive the slope from 3.5 to 4.0. Other velocity definitions lead to BTFRs with systematically higher scatters and shallower slopes. (2) We provide statistical relations to infer the flat rotation velocity from HI line-widths or less extended rotation curves (like H-alpha and CO data). These can be useful to study the BTFR from large HI surveys or the BTFR at high redshifts. (3) The BTFR is more fundamental than the relation between angular momentum and galaxy mass (the Fall relation). The Fall relation has about 7 times more scatter than the BTFR, which is merely driven by the scatter in the mass-size relation of galaxies. The BTFR is already the \"fundamental plane\" of galaxy discs: no value is added with a radial variable as a third parameter.", "keyphrases": ["baryonic tully-fisher relation", "velocity definition", "galaxy"]}
{"id": "2010.02929", "title": "Baryonic effects in the Effective Field Theory of Large-Scale Structure and an analytic recipe for lensing in CMB-S4", "abstract": "Upcoming Large-Scale Structure surveys will likely become the next leading sources of cosmological information, making it crucial to have a precise understanding of the influence of baryons on cosmological observables. The Effective Field Theory of Large-Scale Structure (EFTofLSS) provides a consistent way to predict the clustering of dark matter and baryons on large scales, where their leading corrections in perturbation theory are given by a simple and calculable functional form even after the onset of baryonic processes. In this paper, we extend the two-fluid-like system up to two-loop order in perturbation theory. Along the way, we show that a new linear counterterm proportional to the relative velocity of the fluids could generically be present, but we show that its effects are expected to be small in our universe. Regardless, we show how to consistently perform perturbation theory in the presence of this new term. We find that the EFTofLSS at two-loop order can accurately account for the details of baryonic processes on large scales. We compare our results to a hydrodynamical N-body simulation at many redshifts and find that the counterterms associated with the leading corrections to dark matter and baryons start to differ between redshifts z \u2248 3 and z \u2248 2, signaling the onset of star-formation physics. We then use these fits to compute the lensing power spectrum, show that the understanding of baryonic processes will be important for analyzing CMB-S4 data, and show that the two-loop EFTofLSS accurately captures these effects for \u2113\u2272 2000. Our results are also potentially of interest for current and future weak lensing surveys.", "keyphrases": ["effective field theory", "large-scale structure", "baryonic effect"]}
{"id": "1412.1836", "title": "CMB anisotropies generated by a stochastic background of primordial magnetic fields with non-zero helicity", "abstract": "We consider the impact of a stochastic background of primordial magnetic fields with non-vanishing helicity on CMB anisotropies in temperature and polarization. We compute the exact expressions for the scalar, vector and tensor part of the energy-momentum tensor including the helical contribution, by assuming a power-law dependence for the spectra and a comoving cutoff which mimics the damping due to viscosity. We also compute the parity-odd correlator between the helical and non-helical contribution which generate the TB and EB cross-correlation in the CMB pattern. We finally show the impact of including the helical term on the power spectra of CMB anisotropies up to multipoles with ell O(10^3).", "keyphrases": ["primordial magnetic field", "magnetic field", "cmb anisotropy"]}
{"id": "0909.1063", "title": "Scintillation efficiency and ionization yield of liquid xenon for mono-energetic nuclear recoils down to 4 keV", "abstract": "Liquid Xenon (LXe) is an excellent material for experiments designed to detect dark matter in the form of Weakly Interacting Massive Particles (WIMPs). A low energy detection threshold is essential for a sensitive WIMP search. The understanding of the relative scintillation efficiency (Leff) and ionization yield of low energy nuclear recoils in LXe is limited for energies below 10 keV. In this paper, we present new measurements that extend the energy down to 4 keV, finding that Leff decreases with decreasing energy. We also measure the quenching of scintillation efficiency due to the electric field in LXe, finding no significant field dependence.", "keyphrases": ["xenon", "nuclear recoil", "scintillation efficiency"]}
{"id": "2203.04634", "title": "Systematic bias on parameterized tests of general relativity due to neglect of orbital eccentricity", "abstract": "Gravitational-wave observations provide a unique opportunity to test general relativity (GR) in the strong-field and highly dynamical regime of the theory. Parametrized tests of GR are one well-known approach for quantifying violations of GR. This approach constrains deviations in the coefficients of the post-Newtonian phasing formula, which describes the gravitational-wave phase evolution of a compact binary as it inspirals. Current bounds from this test using LIGO/Virgo observations assume that binaries are circularized by the time they enter the detector frequency band. Here, we investigate the impact of residual binary eccentricity on the parametrized tests. We study the systematic biases in the parameter bounds when a phasing based on the circular orbit assumption is employed for a system that has some small residual eccentricity. We find that a systematic bias (for example, on the leading Newtonian deformation parameter) becomes comparable to the statistical errors for even moderate eccentricities of \u223c 0.04 at 10 Hz in LIGO/Virgo band for binary black holes, and \u223c 0.008 for binary neutron stars. This happens at even lower values of orbital eccentricity in the frequency band of third-generation (3G) detectors like Cosmic Explorer (\u223c 0.005 at 10 Hz for binary black holes and \u223c 0.002 for binary neutron stars). These results demonstrate that incorporating physical effects like eccentricity in waveform models is important for accurately extracting science results from future detectors.", "keyphrases": ["parameterized test", "general relativity", "orbital eccentricity"]}
{"id": "1506.00148", "title": "Near-horizon circular orbits and extremal limit for dirty rotating black holes", "abstract": "We consider generic rotating axially symmetric \"dirty\" (surrounded by matter) black holes. Near-horizon circular equatorial orbits are examined in two different cases of near-extremal (small surface gravity \u03ba) and exactly extremal black holes. This has a number of qualitative distinctions. In the first case, it is shown that such orbits can lie as close to the horizon as one wishes on suitably chosen slices of space-time when \u03ba\u2192 0. This generalizes observation of T. Jacobson Class. Quantum Grav. 28 187001 (2011) made for the Kerr metric. If a black hole is extremal (\u03ba =0), circular on-horizon orbits are impossible for massive particles but, in general, are possible in its vicinity. The corresponding black hole parameters determine also the rate with which a fine-tuned particle on the noncircular near-horizon orbit asymptotically approaches the horizon. Properties of orbits under discussion are also related to the Ba energy collisions near black holes. Impossibility of the on-horizon orbits in question is manifestation of kinematic censorship that forbids infinite energies in collisions.", "keyphrases": ["circular orbit", "black hole", "near-horizon"]}
{"id": "1403.3961", "title": "Cosmology with Mimetic Matter", "abstract": "We consider minimal extensions of the recently proposed Mimetic Dark Matter and show that by introducing a potential for the mimetic non-dynamical scalar field we can mimic nearly any gravitational properties of the normal matter. In particular, the mimetic matter can provide us with inflaton, quintessence and even can lead to a bouncing nonsingular universe. We also investigate the behaviour of cosmological perturbations due to a mimetic matter. We demonstrate that simple mimetic inflation can produce red-tilted scalar perturbations which are largely enhanced over gravity waves.", "keyphrases": ["mimetic matter", "quintessence", "gravity", "matter model"]}
{"id": "1712.02783", "title": "Dark Energy and Modified Gravity in the Effective Field Theory of Large-Scale Structure", "abstract": "We develop an approach to compute observables beyond the linear regime of dark matter perturbations for general dark energy and modified gravity models. We do so by combining the Effective Field Theory of Dark Energy and Effective Field Theory of Large-Scale Structure approaches. In particular, we parametrize the linear and nonlinear effects of dark energy on dark matter clustering in terms of the Lagrangian terms introduced in a companion paper, focusing on Horndeski theories and assuming the quasi-static approximation. The Euler equation for dark matter is sourced, via the Newtonian potential, by new nonlinear vertices due to modified gravity and, as in the pure dark matter case, by the effects of short-scale physics in the form of the divergence of an effective stress tensor. The effective fluid introduces a counterterm in the solution to the matter continuity and Euler equations, which allows a controlled expansion of clustering statistics on mildly nonlinear scales. We use this setup to compute the one-loop dark-matter power spectrum.", "keyphrases": ["modified gravity", "effective field theory", "dark energy"]}
{"id": "1204.0189", "title": "Reconstruction of a Nonminimal Coupling Theory with Scale-invariant Power Spectrum", "abstract": "A nonminimal coupling single scalar field theory, when transformed from Jordan frame to Einstein frame, can act like a minimal coupling one. Making use of this property, we investigate how a nonminimal coupling theory with scale-invariant power spectrum could be reconstructed from its minimal coupling counterpart, which can be applied in the early universe. Thanks to the coupling to gravity, the equation of state of our universe for a scale-invariant power spectrum can be relaxed, and the relation between the parameters in the action can be obtained. This approach also provides a means to address the Big-Bang puzzles and anisotropy problem in the nonminimal coupling model within Jordan frame. Due to the equivalence between the two frames, one may be able to find models that are free of the horizon, flatness, singularity as well as anisotropy problems.", "keyphrases": ["nonminimal coupling theory", "scale-invariant power spectrum", "gravity"]}
{"id": "2008.11338", "title": "Curvature-slope correlation of nuclear symmetry energy and its imprints on the crust-core transition, radius and tidal deformability of canonical neutron stars", "abstract": "Background: The nuclear symmetry energy E_sym(\u03c1) encodes information about the energy necessary to make nuclear systems more neutron-rich. While its slope parameter L at the saturation density \u03c1_0 of nuclear matter has been relatively well constrained by recent astrophysical observations and terrestrial nuclear experiments, its curvature K_sym characterizing the E_sym(\u03c1) around 2\u03c1_0 remains largely unconstrained. Over 520 calculations for E_sym(\u03c1) using various nuclear theories and interactions in the literature have predicted several significantly different K_sym-L correlations. Purpose: If a unique K_sym-L correlation of E_sym(\u03c1) can be firmly established, it will enable us to progressively better constrain the high-density behavior of E_sym(\u03c1) using the available constraints on its slope parameter L. We investigate if and by how much the different K_sym-L correlations may affect neutron star observables. Method: A meta-model of nuclear Equation of States (EOSs) with three representative K_sym-L correlation functions is used to generate multiple EOSs for neutron stars. We then examine effects of the K_sym-L correlation on the crust-core transition density and pressure as well as the radius and tidal deformation of canonical neutron stars. Results:The K_sym-L correlation affects significantly both the crust-core transition density and pressure. It also has strong imprints on the radius and tidal deformability of canonical neutron stars especially at small L values. The available data from LIGO/VIRGO and NICER set some useful limits for the slope L but can not distinguish the three representative K_sym-L correlations considered.", "keyphrases": ["symmetry energy", "neutron star", "crust-core transition density"]}
{"id": "1810.09994", "title": "The Giant Radio Array for Neutrino Detection (GRAND): Science and Design", "abstract": "The Giant Radio Array for Neutrino Detection (GRAND) is a planned large-scale observatory of ultra-high-energy (UHE) cosmic particles, with energies exceeding 10^8 GeV. Its goal is to solve the long-standing mystery of the origin of UHE cosmic rays. To do this, GRAND will detect an unprecedented number of UHE cosmic rays and search for the undiscovered UHE neutrinos and gamma rays associated to them with unmatched sensitivity. GRAND will use large arrays of antennas to detect the radio emission coming from extensive air showers initiated by UHE particles in the atmosphere. Its design is modular: 20 separate, independent sub-arrays, each of 10 000 radio antennas deployed over 10 000 km^2. A staged construction plan will validate key detection techniques while achieving important science goals early. Here we present the science goals, detection strategy, preliminary design, performance goals, and construction plans for GRAND.", "keyphrases": ["giant radio array", "neutrino detection", "grand"]}
{"id": "1306.3214", "title": "Superconformal generalizations of the Starobinsky model", "abstract": "We find a way to represent the Starobinsky model in terms of a simple conformally invariant theory with spontaneous symmetry breaking. We also present a superconformal theory, which, upon spontaneous breaking of the superconformal symmetry, provides a consistent supergravity generalization of the Starobinsky model.", "keyphrases": ["starobinsky model", "superconformal generalization", "supergravity model", "su(2,1)/su(2"]}
{"id": "1804.10607", "title": "Gaia DR2 in 6D: Searching for the fastest stars in the Galaxy", "abstract": "We search for the fastest stars in the subset of stars with radial velocity measurements of the second data release (DR2) of the European Space Agency mission Gaia. Starting from the observed positions, parallaxes, proper motions, and radial velocities, we construct the distance and total velocity distribution of more than 7 million stars in our Milky Way, deriving the full 6D phase space information in Galactocentric coordinates. These information are shared in a catalogue, publicly available at http://home.strw.leidenuniv.nl/ marchetti/research.html. To search for unbound stars, we then focus on stars with a probability greater than 50 % of being unbound from the Milky Way. This cut results in a clean sample of 125 sources with reliable astrometric parameters and radial velocities. Of these, 20 stars have probabilities greater than 80 % of being unbound from the Galaxy. On this latter sub-sample, we perform orbit integration to characterize the stars' orbital parameter distributions. As expected given the relatively small sample size of bright stars, we find no hypervelocity star candidates, stars that are moving on orbits consistent with coming from the Galactic Centre. Instead, we find 7 hyper-runaway star candidates, coming from the Galactic disk. Surprisingly, the remaining 13 unbound stars cannot be traced back to the Galaxy, including two of the fastest stars (around 700 km/s). If conformed, these may constitute the tip of the iceberg of a large extragalactic population or the extreme velocity tail of stellar streams.", "keyphrases": ["star", "radial velocity", "proper motion", "orbit integration", "gaia dr2"]}
{"id": "1004.3558", "title": "Exploring the String Axiverse with Precision Black Hole Physics", "abstract": "It has recently been suggested that the presence of a plenitude of light axions, an Axiverse, is evidence for the extra dimensions of string theory. We discuss the observational consequences of these axions on astrophysical black holes through the Penrose superradiance process. When an axion Compton wavelength is comparable to the size of a black hole, the axion binds to the black hole \"nucleus\" forming a gravitational atom in the sky. The occupation number of superradiant atomic levels, fed by the energy and angular momentum of the black hole, grows exponentially. The black hole spins down and an axion Bose-Einstein condensate cloud forms around it. When the attractive axion self-interactions become stronger than the gravitational binding energy, the axion cloud collapses, a phenomenon known in condensed matter physics as \"Bosenova\". The existence of axions is first diagnosed by gaps in the mass vs spin plot of astrophysical black holes. For young black holes the allowed values of spin are quantized, giving rise to \"Regge trajectories\" inside the gap region. The axion cloud can also be observed directly either through precision mapping of the near horizon geometry or through gravitational waves coming from the Bosenova explosion, as well as axion transitions and annihilations in the gravitational atom. Our estimates suggest that these signals are detectable in upcoming experiments, such as Advanced LIGO, AGIS, and LISA. Current black hole spin measurements imply an upper bound on the QCD axion decay constant of 2 x 10^17 GeV, while Advanced LIGO can detect signals from a QCD axion cloud with a decay constant as low as the GUT scale. We finally discuss the possibility of observing the gamma-rays associated with the Bosenova explosion and, perhaps, the radio waves from axion-to-photon conversion for the QCD axion.", "keyphrases": ["string axiverse", "black hole", "boson", "superradiant instability", "hole superradiance"]}
{"id": "1606.01520", "title": "Circular polarizations of gravitational waves from core-collapse supernovae: a clear indication of rapid rotation", "abstract": "We propose to employ the circular polarization of gravitational waves emitted by core-collapse supernovae as an unequivocal indication of rapid rotation deep in their cores. It has been demonstrated by three dimensional simulations that non-axisymmetric accretion flows may develop spontaneously via hydrodynamical instabilities in the post-bounce cores. It is not surprising then that the gravitational waves emitted by such fluid motions are circularly polarized. We show in this letter that a network of the second generation detectors of gravitational waves worldwide may be able to detect such polarizations up to the opposite side of Galaxy as long as the rotation period is shorter than a few seconds prior to collapse.", "keyphrases": ["gravitational wave", "core-collapse supernovae", "circular polarization"]}
{"id": "1101.3436", "title": "The Statefinder hierarchy: An extended null diagnostic for concordance cosmology", "abstract": "We show how higher derivatives of the expansion factor can be developed into a null diagnostic for concordance cosmology (LCDM). It is well known that the Statefinder \u2013 the third derivative of the expansion factor written in dimensionless form, a^(3)/aH^3, equals unity for LCDM. We generalize this result to higher derivatives of the expansion factor and demonstrate that the hierarchy, a^(n)/aH^n, can be converted to a form that stays pegged at unity in concordance cosmology. This remarkable property of the Statefinder hierarchy enables it to be used as an extended null diagnostic for the cosmological constant. The Statefinder hierarchy combined with the growth rate of matter perturbations defines a composite null diagnostic which can distinguish evolving dark energy from LCDM.", "keyphrases": ["statefinder hierarchy", "extended null", "concordance cosmology"]}
{"id": "1201.5741", "title": "Adaptive Optics for Astronomy", "abstract": "Adaptive Optics is a prime example of how progress in observational astronomy can be driven by technological developments. At many observatories it is now considered to be part of a standard instrumentation suite, enabling ground-based telescopes to reach the diffraction limit and thus providing spatial resolution superior to that achievable from space with current or planned satellites. In this review we consider adaptive optics from the astrophysical perspective. We show that adaptive optics has led to important advances in our understanding of a multitude of astrophysical processes, and describe how the requirements from science applications are now driving the development of the next generation of novel adaptive optics techniques.", "keyphrases": ["astronomy", "diffraction limit", "adaptive optics"]}
{"id": "1804.05860", "title": "A Complete Census of Luminous Stellar Variability on Day to Decade Timescales", "abstract": "Stellar photometric variability offers a novel probe of the interior structure and evolutionary state of stars. Here we present a census of stellar variability on day to decade timescales across the color-magnitude diagram for 73,000 stars brighter than M_I=-5 in the Whirlpool Galaxy (M51). Our Cycle 24 HST program acquired V and I-band images over 34 epochs spanning one year with pseudo-random cadences enabling sensitivity to periods from days to months. We supplement these data with archival V and I-band HST data obtained in 1995 and 2005 providing sensitivity to variability on decade timescales. At least 50 stars brighter than M_I=-7 show strong evidence for variability within our Cycle 24 data; among stars with V-I>2 the variability fraction rises to 100 Large amplitude variability (>0.3 mag) on decade timescales is restricted to red supergiants and very luminous blue stars. Both populations display fairly smooth variability on month-year timescales. The Cepheid instability strip is clearly visible in our data, although the variability fraction within this region never exceeds 10 magnitude diagram broadly agrees with theoretical sources of variability, including the instability strip, red supergiant pulsational instabilities, long-period fundamental mode pulsations, and radiation-dominated envelopes in massive stars. Our data can be used to place stringent constraints on the precise onset of these various instabilities and their lifetimes and growth rates.", "keyphrases": ["stellar variability", "decade timescale", "star"]}
{"id": "2006.10462", "title": "Quasinormal modes and Hawking radiation of black holes in cubic gravity", "abstract": "We consider quasinormal modes and Hawking radiation of four-dimensional asymptotically flat black holes in the most general up to-cubic-order-in-curvature dimension-independent Einsteinian theory of gravity that shares its graviton spectrum with the Einstein theory on constant curvature backgrounds. We show that damping rate and real oscillation frequencies of quasinormal modes for scalar, electromagnetic and Dirac fields are suppressed once the coupling with the cubic term is on. The intensity of Hawking radiation is suppressed as well, leading to, roughly, one order longer lifetime at a sufficiently large coupling constant.", "keyphrases": ["black hole", "gravity", "quasinormal mode"]}
{"id": "2201.01716", "title": "Analytical study of higher-order ring images of accretion disk around black hole", "abstract": "Gravitational lensing of a light source by a black hole leads to appearance of higher-order images produced by photons that loop around the black hole before reaching the observer. Higher-order images were widely investigated numerically and analytically, in particular using so-called strong deflection limit of gravitational deflection. After recent observations of the black hole image, attention has been drawn to higher-order rings, which are lensed images of the accreting matter of the black hole environment and can appear near the boundary of the black hole shadow. In this article, we use strong deflection limit technique to investigate higher-order ring images of luminous accretion disc around a Schwarzschild black hole. We consider thin disk given by the inner and outer radii and an observer located far from the black hole on the axis of symmetry. For this configuration, it becomes possible to find the angular radii, thicknesses, and solid angles of higher-order rings in the form of compact analytical expressions. We show that the size of the rings is mainly determined by the position of the inner boundary of the accretion disk, which makes it possible to use them to distinguish between different accretion models. Possible generalizations of our model to non-symmetric images can help to make the estimation of black hole angular momentum. We also present the analytical estimation of fluxes from higher-order images. Our method makes it easy to investigate n=2 and n=3 higher-order rings, the possible observation of which in future projects is currently being discussed.", "keyphrases": ["higher-order ring image", "accretion disk", "black hole"]}
{"id": "2011.02483", "title": "Starburst galaxies strike back: a multi-messenger analysis with Fermi-LAT and IceCube data", "abstract": "Starburst galaxies, which are known as \"reservoirs\" of high-energy cosmic-rays, can represent an important high-energy neutrino \"factory\" contributing to the diffuse neutrino flux observed by IceCube. In this paper, we revisit the constraints affecting the neutrino and gamma-ray hadronuclear emissions from this class of astrophysical objects. In particular, we go beyond the standard prototype-based approach leading to a simple power-law neutrino flux, and investigate a more realistic model based on a data-driven blending of spectral indexes, thereby capturing the observed changes in the properties of individual emitters. We then perform a multi-messenger analysis considering the extragalactic gamma-ray background (EGB) measured by Fermi-LAT and different IceCube data samples: the 7.5-year High-Energy Starting Events (HESE) and the 6-year high-energy cascade data. Along with starburst galaxies, we take into account the contributions from blazars and radio galaxies as well as the secondary gamma-rays from electromagnetic cascades. Remarkably, we find that, differently from the highly-constrained prototype scenario, the spectral index blending allows starburst galaxies to account for up to 40% of the HESE events at 95.4% CL, while satisfying the limit on the non-blazar EGB component. Moreover, values of \ud835\udcaa(100 PeV) for the maximal energy of accelerated cosmic-rays by supernovae remnants inside the starburst are disfavoured in our scenario. In broad terms, our analysis points out that a better modeling of astrophysical sources could alleviate the tension between neutrino and gamma-ray data interpretation.", "keyphrases": ["multi-messenger analysis", "fermi-lat", "starburst galaxy"]}
{"id": "2004.00650", "title": "The mass gap, the spin gap, and the origin of merging binary black holes", "abstract": "Two of the dominant channels to produce the black-hole binary mergers observed by LIGO and Virgo are believed to be the isolated evolution of stellar binaries in the field and dynamical formation in star clusters. Their relative efficiency can be characterized by a \"mixing fraction.\" Pair instabilities prevent stellar collapse from generating black holes more massive than about 45 M_\u2299. This \"mass gap\" only applies to the field formation scenario, and it can be filled by repeated mergers in clusters. A similar reasoning applies to the binary's effective spin. If black holes are born slowly rotating, the high-spin portion of the parameter space (the \"spin gap\") can only be populated by black hole binaries that were assembled dynamically. Using a semianalytical cluster model, we show that future gravitational-wave events in either the mass gap, the spin gap, or both can be leveraged to infer the mixing fraction between the field and cluster formation channels.", "keyphrases": ["mass gap", "spin gap", "black hole"]}
{"id": "1503.07660", "title": "Bulge growth through disk instabilities in high-redshift galaxies", "abstract": "The role of disk instabilities, such as bars and spiral arms, and the associated resonances, in growing bulges in the inner regions of disk galaxies have long been studied in the low-redshift nearby Universe. There it has long been probed observationally, in particular through peanut-shaped bulges. This secular growth of bulges in modern disk galaxies is driven by weak, non-axisymmetric instabilities: it mostly produces pseudo-bulges at slow rates and with long star-formation timescales. Disk instabilities at high redshift (z>1) in moderate-mass to massive galaxies (10^10 to a few 10^11 Msun of stars) are very different from those found in modern spiral galaxies. High-redshift disks are globally unstable and fragment into giant clumps containing 10^8-10^9 Msun of gas and stars each, which results in highly irregular galaxy morphologies. The clumps and other features associated to the violent instability drive disk evolution and bulge growth through various mechanisms, on short timescales. The giant clumps can migrate inward and coalesce into the bulge in a few 10^8 yr. The instability in the very turbulent media drives intense gas inflows toward the bulge and nuclear region. Thick disks and supermassive black holes can grow concurrently as a result of the violent instability. This chapter reviews the properties of high-redshift disk instabilities, the evolution of giant clumps and other features associated to the instability, and the resulting growth of bulges and associated sub-galactic components.", "keyphrases": ["disk instability", "galaxy", "bulge growth"]}
{"id": "2010.04500", "title": "On the relationship between mean observations, spatial averages and the Dyer-Roeder approximation in Einstein-Straus models", "abstract": "The redshift and redshift-distance relation in different Einstein-Straus models are considered. Specifically, the mean of these observables along 1000 light rays in different specific models are compared with predictions based on the Dyer-Roeder approximation and relations based on spatial averaging. It is shown that in certain limits, including those studied earlier in the literature, the Dyer-Roeder approximation and relations based on spatial averages agree with each other to a good precision regarding the redshift and redshift-distance relation and make good predictions of the mean of the exact relations. In limits where the two methods disagree, the Dyer-Roeder approximation clearly yields the better approximation of the true mean. This is explained by demonstrating the effect of boundary terms and integrated Sachs-Wolfe contributions but it is pointed out that the result seems to be valid for other Swiss-cheese models as well. Lastly, an expression for the redshift drift in Einstein-Straus models is presented and used for studying the behavior of this quantity in particular Einstein-Straus models.", "keyphrases": ["spatial average", "dyer-roeder approximation", "einstein-straus model"]}
{"id": "1605.03053", "title": "Constraining spatial variations of the fine structure constant using clusters of galaxies and Planck data", "abstract": "We propose an improved methodology to constrain spatial variations of the fine structure constant using clusters of galaxies. We use the Planck 2013 data to measure the thermal Sunyaev-Zeldovich effect at the location of 618 X-ray selected clusters. We then use a Monte Carlo Markov Chain algorithm to obtain the temperature of the Cosmic Microwave Background at the location of each galaxy cluster. When fitting three different phenomenological parameterizations allowing for monopole and dipole amplitudes in the value of the fine structure constant we improve the results of earlier analysis involving clusters and the CMB power spectrum, and we also found that the best-fit direction of a hypothetical dipole is compatible with the direction of other known anomalies. Although the constraining power of our current datasets do not allow us to test the indications of a fine-structure constant dipole obtained though high-resolution optical/UV spectroscopy, our results do highlight that clusters of galaxies will be a very powerful tool to probe fundamental physics at low redshift.", "keyphrases": ["spatial variation", "fine structure", "galaxy"]}
{"id": "1605.01938", "title": "The final spin from binary black holes in quasi-circular orbits", "abstract": "We revisit the problem of predicting the spin magnitude and direction of the black hole resulting from the merger of two black holes with arbitrary masses and spins inspiralling in quasi-circular orbits. We do this by analyzing a catalog of 619 recent numerical-relativity simulations collected from the literature and spanning a large variety of initial conditions. By combining information from the post-Newtonian approximation, the extreme mass-ratio limit and perturbative calculations, we improve our previously proposed phenomenological formulae for the final remnant spin. In contrast with alternative suggestions in the literature, and in analogy with our previous expressions, the new formula is a simple algebraic function of the initial system parameters and is not restricted to binaries with spins aligned/anti-aligned with the orbital angular momentum, but can be employed for fully generic binaries. The accuracy of the new expression is significantly improved, especially for almost extremal progenitor spins and for small mass ratios, yielding a root-mean-square error \u03c3\u22480.002 for aligned/anti-aligned binaries and \u03c3\u22480.006 for generic binaries. Our new formula is suitable for cosmological applications and can be employed robustly in the analysis of the gravitational waveforms from advanced interferometric detectors.", "keyphrases": ["final spin", "black hole", "quasi-circular orbit"]}
{"id": "1411.5843", "title": "Magnetic fields of neutron stars in X-ray binaries", "abstract": "A substantial fraction of the known neutron stars resides in X-ray binaries \u2013 systems in which one compact object accretes matter from a companion star. Neutron stars in X-ray binaries have magnetic fields among the highest found in the Universe, spanning at least the range from \u223c10^8 to several 10^13 G. The magnetospheres around these neutron stars have a strong influence on the accretion process, which powers most of their emission. The magnetic field intensity and geometry, are among the main factors responsible for the large variety of spectral and timing properties observed in the X-ray energy range, making these objects unique laboratories to study the matter behavior and the radiation processes in magnetic fields unaccessible on Earth. In this paper we review the main observational aspects related to the presence of magnetic fields in neutron star X-ray binaries and some methods that are used to estimate their strength.", "keyphrases": ["neutron star", "x-ray binary", "magnetic field"]}
{"id": "2008.08084", "title": "Determining the Hubble Constant without the Sound Horizon: Measurements from Galaxy Surveys", "abstract": "Two sources of geometric information are encoded in the galaxy power spectrum: the sound horizon at recombination and the horizon at matter-radiation equality. Analyzing the BOSS DR12 galaxy power spectra using perturbation theory with \u03a9_m priors from Pantheon supernovae but no priors on \u03a9_b, we obtain constraints on H_0 from the second scale, finding H_0 = 65.1^+3.0_-5.4 km s^-1Mpc^-1; this differs from the best-fit of SH0ES at 95% confidence. Similar results are obtained if \u03a9_m is constrained from uncalibrated BAO: H_0 = 65.6^+3.4_-5.5 km s^-1Mpc^-1. Adding the analogous lensing results from Baxter & Sherwin 2020, the posterior shifts to 70.6^+3.7_-5.0 km s^-1Mpc^-1. Using mock data, Fisher analyses, and scale-cuts, we demonstrate that our constraints do not receive significant information from the sound horizon scale. Since many models resolve the H_0 controversy by adding new physics to alter the sound horizon, our measurements are a consistency test for standard cosmology before recombination. A simple forecast indicates that such constraints could reach \u03c3_H_0\u2243 1.6 km s^-1Mpc^-1 in the era of Euclid.", "keyphrases": ["hubble constant", "sound horizon", "galaxy power spectrum", "equality"]}
{"id": "0911.2243", "title": "Comment on \"Kerr Black Holes as Particle Accelerators to Arbitrarily High Energy\"", "abstract": "It has been suggested that rotating black holes could serve as particle colliders with arbitrarily high center-of-mass energy. Astrophysical limitations on the maximal spin, back-reaction effects and sensitivity to the initial conditions impose severe limits on the likelihood of such collisions.", "keyphrases": ["black hole", "high energy", "maximal spin", "gravitational radiation"]}
{"id": "1009.0677", "title": "Primordial non-Gaussianity from the DBI Galileons", "abstract": "We study primordial fluctuations generated during inflation in a class of models motivated by the DBI Galileons, which are extensions of the DBI action that yield second order field equations. This class of models generalises the DBI Galileons in a similar way with K-inflation. We calculate the primordial non-Gaussianity from the bispectrum of the curvature perturbations at leading order in the slow-varying approximations. We show that the estimator for the equilateral-type non-Gaussianity, f_ NL ^equil, can be applied to measure the amplitude of the primordial bispectrum even in the presence of the Galileon-like term although it gives a slightly different momentum dependence from K-inflation models. For the DBI Galileons, we find -0.32 /c_s^2 < f_ NL ^equil < -0.16/c_s^2 and large primordial non-Gaussianities can be obtained when c_s is much smaller than 1 as in the usual DBI inflation. In G-inflation models, where a de Sitter solution is obtained without any potentials, the non-linear parameter is given by f_ NL^equil = 4.62 r^-2/3 where r is the tensor to scalar ratio, giving a stringent constraint on the model.", "keyphrases": ["non-gaussianity", "dbi galileons", "primordial fluctuation", "galileon theory"]}
{"id": "2001.10000", "title": "Turbulence Regulates the Rate of Planetesimal Formation via Gravitational Collapse", "abstract": "We study how the interaction between the streaming instability and intrinsic gas-phase turbulence affects planetesimal formation via gravitational collapse in protoplanetary disks. Turbulence impedes the formation of particle clumps by acting as an effective turbulent diffusivity, but it can also promote planetesimal formation by concentrating solids, for example in zonal flows. We quantify the effect of turbulent diffusivity using numerical simulations of the streaming instability in small local domains, forced with velocity perturbations that establish approximately Kolmogorov-like turbulence. We find that planetesimal formation is suppressed by turbulence once velocity fluctuations exceed \u27e8\u03b4 v^2 \u27e9\u2243 10^-3.5 - 10^-3 c_s^2. Turbulence whose strength is just below the threshold reduces the rate at which solids are bound into clumps. Our results suggest that the well-established turbulent thickening of the mid-plane solid layer is the primary mechanism by which turbulence influences planetesimal formation and that planetesimal formation requires a mid-plane solid-to-gas ratio \u03f5\u2273 0.5. We also quantify the initial planetesimal mass function using a new clump-tracking method to determine each planetesimal mass shortly after collapse. For models in which planetesimals form, we show that the mass function is well-described by a broken power law, whose parameters are robust to the inclusion and strength of imposed turbulence. Turbulence in protoplanetary disks is likely to substantially exceed the threshold for planetesimal formation at radii where temperatures T \u2273 10^3 K lead to thermal ionization. Planetesimal formation may therefore be unviable in the inner disk out to 2-3 times the dust sublimation radius.", "keyphrases": ["planetesimal formation", "gravitational collapse", "turbulence"]}
{"id": "1503.00056", "title": "Detailed Shape and Evolutionary Behavior of the X-ray Luminosity Function of Active Galactic Nuclei", "abstract": "We construct the rest-frame 2\u201310 keV intrinsic X-ray luminosity function of Active Galactic Nuclei (AGNs) from a combination of X-ray surveys from the all-sky Swift BAT survey to the Chandra Deep Field-South. We use 3200 AGNs in our analysis, which covers six orders of magnitude in flux. The inclusion of the XMM and Chandra COSMOS data has allowed us to investigate the detailed behavior of the XLF and evolution. In deriving our XLF, we take into account realistic AGN spectrum templates, absorption corrections, and probability density distributions in photometric redshift. We present an analytical expression for the overall behavior of the XLF in terms of the luminosity-dependent density evolution, smoothed two power-law expressions in 11 redshift shells, three-segment power-law expression of the number density evolution in four luminosity classes, and binned XLF. We observe a sudden flattening of the low luminosity end slope of the XLF slope at z> 0.6. Detailed structures of the AGN downsizing have been also revealed, where the number density curves have two clear breaks at all luminosity classes above log LX>43. The two break structure is suggestive of two-phase AGN evolution, consisting of major merger triggering and secular processes.", "keyphrases": ["x-ray luminosity function", "active galactic nuclei", "redshift"]}
{"id": "1706.01277", "title": "Dark Matter Limits From Dwarf Spheroidal Galaxies with The HAWC Gamma-Ray Observatory", "abstract": "The High Altitude Water Cherenkov (HAWC) gamma-ray observatory is a wide field of view observatory sensitive to 500 GeV - 100 TeV gamma rays and cosmic rays. It can also perform diverse indirect searches for dark matter (DM) annihilation and decay. Among the most promising targets for the indirect detection of dark matter are dwarf spheroidal galaxies. These objects are expected to have few astrophysical sources of gamma rays but high dark matter content, making them ideal candidates for an indirect dark matter detection with gamma rays. Here we present individual limits on the annihilation cross section and decay lifetime for 15 dwarf spheroidal galaxies within the HAWC field-of-view, as well as their combined limit. These are the first limits on the annihilation cross section and decay lifetime using data collected with HAWC.", "keyphrases": ["dwarf spheroidal galaxy", "astrophysical source", "dark matter"]}
{"id": "1106.1616", "title": "Measuring neutron-star properties via gravitational waves from binary mergers", "abstract": "We demonstrate by a large set of merger simulations for symmetric binary neutron stars (NSs) that there is a tight correlation between the frequency peak of the postmerger gravitational-wave (GW) emission and the physical properties of the nuclear equation of state (EoS), e.g. expressed by the radius of the maximum-mass Tolman-Oppenheimer-Volkhoff configuration. Therefore, a single measurement of the peak frequency of the postmerger GW signal will constrain the NS EoS significantly. For plausible optimistic merger-rate estimates a corresponding detection with Advanced LIGO is likely to happen within an operation time of roughly a year.", "keyphrases": ["gravitational wave", "neutron star", "merger remnant"]}
{"id": "1705.08945", "title": "Does information entropy play a role in the expansion and acceleration of the Universe?", "abstract": "We propose an interpretation of the expansion and acceleration of the Universe from an information theoretic viewpoint. We obtain the time evolution of the configuration entropy of the mass distribution in a static Universe and show that the process of gravitational instability leads to a rapid dissipation of configuration entropy during the growth of the density fluctuations making such a Universe entropically unfavourable. We find that in an expanding Universe, the configuration entropy rate is governed by the expansion rate of the Universe and the growth rate of density fluctuations. The configuration entropy rate becomes smaller but still remains negative in a matter dominated Universe and eventually becomes zero at some future time in a \u039b dominated Universe. The configuration entropy may have a connection to the dark energy and possibly plays a driving role in the current accelerating expansion of the Universe leading the Universe to its maximum entropy configuration.", "keyphrases": ["universe", "configuration entropy", "dissipation", "non-linear state"]}
{"id": "2003.01252", "title": "Quasi-periodic oscillations from the accretion disk around distorted black holes", "abstract": "We study the quasi-periodic oscillations from the accretion disk around the distorted Schwarzschild black hole in the framework of the resonant models. We confine ourselves to the case of a quadrupole distortion which can be caused for example by the accreting matter flow in the vicinity of the compact object. For the purpose we examine the linear stability of the circular geodesic orbits in the equatorial plane and derive analytical expressions for the radial and vertical epicyclic frequencies. We investigate their properties in comparison with the isolated Schwarzschild black hole. Due to the influence of the external matter the vertical epicyclic frequency is not always positive anymore, and the stability of the circular orbits is determined by the interplay between both of the frequencies. As a result, the stable circular orbits do not extend to infinity, but are confined to a finite annular region between an inner and an outer marginally stable orbit. In addition, the degeneracy between the vertical epicyclic and the orbital frequency, which is characteristic for the Schwarzschild solution, is broken, and there are regions in the parametric space where the radial epicyclic frequency is larger than the vertical one. All these properties allow for much more diverse types of non-linear resonances to be excited than for the isolated Schwarzschild black hole, which can provide an explanation for the observed 3:2 ratio between the twin-peak frequencies of the quasi-periodic oscillations from the accretion disk.", "keyphrases": ["accretion disk", "black hole", "quasi-periodic oscillation"]}
{"id": "1505.02874", "title": "Origin of nonlinearity and plausible turbulence by hydromagnetic transient growth in accretion disks: Faster growth rate than magnetorotational instability", "abstract": "We investigate the evolution of hydromagnetic perturbations in a small section of accretion disks. It is known that molecular viscosity is negligible in accretion disks. Hence, it has been argued that a mechanism, known as Magnetorotational Instability (MRI), is responsible for transporting matter in the presence of weak magnetic field. However, there are some shortcomings, which question effectiveness of MRI. Now the question arises, whether other hydromagnetic effects, e.g. transient growth (TG), can play important role to bring nonlinearity in the system, even at weak magnetic fields. Otherwise, whether MRI or TG, which is primarily responsible to reveal nonlinearity to make the flow turbulent? Our results prove explicitly that the flows with high Reynolds number (Re), which is the case of realistic astrophysical accretion disks, exhibit nonlinearity by TG of perturbation modes faster than that by modes producing MRI. For a fixed wave vector, MRI dominates over transient effects, only at low Re, lower than its value expected to be in astrophysical accretion disks, and low magnetic fields. This seriously questions (overall) persuasiveness of MRI in astrophysical accretion disks.", "keyphrases": ["plausible turbulence", "accretion disk", "magnetorotational instability"]}
{"id": "1510.03723", "title": "Galaxy Bias and Primordial Non-Gaussianity", "abstract": "We present a systematic study of galaxy biasing in the presence of primordial non-Gaussianity. For a large class of non-Gaussian initial conditions, we define a general bias expansion and prove that it is closed under renormalization, thereby showing that the basis of operators in the expansion is complete. We then study the effects of primordial non-Gaussianity on the statistics of galaxies. We show that the equivalence principle enforces a relation between the scale-dependent bias in the galaxy power spectrum and that in the dipolar part of the bispectrum. This provides a powerful consistency check to confirm the primordial origin of any observed scale-dependent bias. Finally, we also discuss the imprints of anisotropic non-Gaussianity as motivated by recent studies of higher-spin fields during inflation.", "keyphrases": ["primordial non-gaussianity", "imprint", "galaxy bias"]}
{"id": "1711.04818", "title": "Uncertainty quantification for radio interferometric imaging: I. proximal MCMC methods", "abstract": "Uncertainty quantification is a critical missing component in radio interferometric imaging that will only become increasingly important as the big-data era of radio interferometry emerges. Since radio interferometric imaging requires solving a high-dimensional, ill-posed inverse problem, uncertainty quantification is difficult but also critical to the accurate scientific interpretation of radio observations. Statistical sampling approaches to perform Bayesian inference, like Markov Chain Monte Carlo (MCMC) sampling, can in principle recover the full posterior distribution of the image, from which uncertainties can then be quantified. However, traditional high-dimensional sampling methods are generally limited to smooth (e.g. Gaussian) priors and cannot be used with sparsity-promoting priors. Sparse priors, motivated by the theory of compressive sensing, have been shown to be highly effective for radio interferometric imaging. In this article proximal MCMC methods are developed for radio interferometric imaging, leveraging proximal calculus to support non-differential priors, such as sparse priors, in a Bayesian framework. Furthermore, three strategies to quantify uncertainties using the recovered posterior distribution are developed: (i) local (pixel-wise) credible intervals to provide error bars for each individual pixel; (ii) highest posterior density credible regions; and (iii) hypothesis testing of image structure. These forms of uncertainty quantification provide rich information for analysing radio interferometric observations in a statistically robust manner.", "keyphrases": ["interferometric imaging", "proximal mcmc method", "uncertainty quantification"]}
{"id": "1409.0425", "title": "Magnetic catalysis in nuclear matter", "abstract": "A strong magnetic field enhances the chiral condensate at low temperatures. This so-called magnetic catalysis thus seeks to increase the vacuum mass of nucleons. We employ two relativistic field-theoretical models for nuclear matter, the Walecka model and an extended linear sigma model, to discuss the resulting effect on the transition between vacuum and nuclear matter at zero temperature. In both models we find that the creation of nuclear matter in a sufficiently strong magnetic field becomes energetically more costly due to the heaviness of magnetized nucleons, even though it is also found that nuclear matter is more strongly bound in a magnetic field. Our results are potentially important for dense nuclear matter in compact stars, especially since previous studies in the astrophysical context have always ignored the contribution of the magnetized Dirac sea and thus the effect of magnetic catalysis.", "keyphrases": ["nuclear matter", "strong magnetic field", "magnetized nucleon", "magnetic catalysis"]}
{"id": "1704.02744", "title": "Finding strong lenses in CFHTLS using convolutional neural networks", "abstract": "We train and apply convolutional neural networks, a machine learning technique developed to learn from and classify image data, to Canada-France-Hawaii Telescope Legacy Survey (CFHTLS) imaging for the identification of potential strong lensing systems. An ensemble of four convolutional neural networks was trained on images of simulated galaxy-galaxy lenses. The training sets consisted of a total of 62,406 simulated lenses and 64,673 non-lens negative examples generated with two different methodologies. The networks were able to learn the features of simulated lenses with accuracy of up to 99.8 simulations. An ensemble of trained networks was applied to all of the 171 square degrees of the CFHTLS wide field image data, identifying 18,861 candidates including 63 known and 139 other potential lens candidates. A second search of 1.4 million early type galaxies selected from the survey catalog as potential deflectors, identified 2,465 candidates including 117 previously known lens candidates, 29 confirmed lenses/high-quality lens candidates, 266 novel probable or potential lenses and 2097 candidates we classify as false positives. For the catalog-based search we estimate a completeness of 21-28 with respect to detectable lenses and a purity of 15 rate of 1 in 671 images tested. We predict a human astronomer reviewing candidates produced by the system would identify 20 probable lenses and 100 possible lenses per hour in a sample selected by the robot. Convolutional neural networks are therefore a promising tool for use in the search for lenses in current and forthcoming surveys such as the Dark Energy Survey and the Large Synoptic Survey Telescope.", "keyphrases": ["lense", "cfhtls", "convolutional neural network"]}
{"id": "0905.2721", "title": "Effect of large-scale coherent structures on turbulent convection", "abstract": "We study an effect of large-scale coherent structures on global properties of turbulent convection in laboratory experiments in air flow in a rectangular chamber with aspect ratios A \u2248 2 and A\u2248 4 (with the Rayleigh numbers varying in the range from 5 \u00d7 10^6 to 10^8). The large-scale coherent structures comprise the one-cell and two-cell flow patterns. We found that a main contribution to the turbulence kinetic energy production in turbulent convection with large-scale coherent structures is due to the non-uniform large-scale motions. Turbulence in large Rayleigh number convection with coherent structures is produced by shear, rather than by buoyancy. We determined the scalings of global parameters (e.g., the production and dissipation of turbulent kinetic energy, the turbulent velocity and integral turbulent scale, the large-scale shear, etc.) of turbulent convection versus the temperature difference between the bottom and the top walls of the chamber. These scalings are in an agreement with our theoretical predictions. We demonstrated that the degree of inhomogeneity of the turbulent convection with large-scale coherent structures is small.", "keyphrases": ["large-scale coherent structure", "turbulent convection", "buoyancy"]}
{"id": "0902.0362", "title": "Dark Matter Annihilation Rates with Velocity-Dependent Annihilation Cross Sections", "abstract": "The detection of byproducts from particle annihilations in galactic halos would provide important information about the nature of the dark matter. Observational evidence for a local excess of high-energy positrons has motivated recent models with an additional interaction between dark matter particles that can result in a Sommerfeld enhancement to the cross section for annihilation. In such models, the cross section becomes velocity-dependent and may enhance the dark matter annihilation rate in the solar neighborhood relative to the rate in the early universe sufficiently to source observed fluxes of high-energy positrons. We demonstrate that, for particle interaction cross sections that increase with decreasing velocity, the kinematical structures of dark matter halos with interior density profiles shallower than isothermal, such as Navarro-Frenk-White or Einasto halos, may induce a further enhancement owing to the position-dependent velocity distribution. We provide specific examples for the increase in the annihilation rate with a cross section enhanced by the Sommerfeld effect. In dark matter halos like that of the Milky Way and Local Group dwarf galaxies, the effective cross section at the halo center can be significantly larger than its local value. The additional enhancement owing to halo kinematics depends upon the parameters of any model, but is a prediction of certain models aimed at explaining measured positron fluxes and can exceed an order of magnitude.", "keyphrases": ["velocity-dependence", "annihilation cross section", "dark matter particle", "matter velocity distribution"]}
{"id": "2001.03181", "title": "The Dust Attenuation Law in Galaxies", "abstract": "Understanding the properties and physical mechanisms that shape dust attenuation curves in galaxies is one of the fundamental questions of extragalactic astrophysics, with a great practical significance for deriving the physical properties of galaxies, such as the star formation rate and stellar mass. Attenuation curves result from a combination of dust grain properties, dust content, and the spatial arrangement of dust and different populations of stars. In this review we assess the current state of the field, paying particular attention to the importance of extinction curves as the building blocks of attenuation laws. We introduce a quantitative framework to characterize and compare extinction and attenuation curves, present a theoretical foundation for interpreting empirical results, overview an array of observational methods, and review the observational state of the field at both low and high redshift. Our main conclusions are: Attenuation curves exhibit a large range of slopes, from curves with shallow (Milky Way-like) slopes to those exceeding the slope of the SMC extinction curve. The slopes of the curves correlate strongly with the effective optical opacities, in the sense that galaxies with low dust column density (lower visual attenuation) tend to have steeper slopes, whereas the galaxies with high dust column density have shallower (grey) slopes. Galaxies appear to exhibit a diverse range of 2175A UV bump strengths, but on average have suppressed bumps compared to the average Milky Way extinction curve. Theoretical studies indicate that variations in bump strength may result from similar geometric and radiative transfer effects that drive the correlation between the slope and the dust column.", "keyphrases": ["attenuation", "galaxy", "dust grain property", "extinction curve"]}
{"id": "1505.03143", "title": "Strangulation as the primary mechanism for shutting down star formation in galaxies", "abstract": "Local galaxies are broadly divided into two main classes, star-forming (gas-rich) and quiescent (passive and gas-poor). The primary mechanism responsible for quenching star formation in galaxies and transforming them into quiescent and passive systems is still unclear. Sudden removal of gas through outflows or stripping is one of the mechanisms often proposed. An alternative mechanism is so-called \"strangulation\", in which the supply of cold gas to the galaxy is halted. Here we report that the difference between quiescent and star forming galaxies in terms of stellar metallicity (i.e. the fraction of metals heavier than helium in stellar atmospheres) can be used to discriminate efficiently between the two mechanisms. The analysis of the stellar metallicity in local galaxies, from 26,000 spectra, clearly reveals that strangulation is the primary mechanism responsible for quenching star formation, with a typical timescale of 4 billion years, at least for local galaxies with a stellar mass less than 10^11 solar masses. This result is further supported independently by the stellar age difference between quiescent and star-forming galaxies, which indicates that quiescent galaxies of less than 10^11 solar masses are on average observed four billion years after quenching due to strangulation.", "keyphrases": ["primary mechanism", "galaxy", "strangulation"]}
{"id": "1801.07260", "title": "Does the Hubble constant tension call for new physics?", "abstract": "The \u039b Cold Dark Matter model (\u039bCDM) represents the current standard model in cosmology. Within this, there is a tension between the value of the Hubble constant, H_0, inferred from local distance indicators and the angular scale of fluctuations in the Cosmic Microwave Background (CMB). We investigate whether the tension is significant enough to warrant new physics in the form of modifying or adding energy components to the standard cosmological model. We find that late time dark energy explanations are slightly disfavoured whereas a pre-CMB decoupling extra dark energy component has a marginally positive Bayesian evidence. A constant equation of state of the additional early energy density is constrained to 0.086^+0.04_-0.03. Although this value deviates significantly from 1/3, valid for dark radiation, the latter is not disfavoured based on the Bayesian evidence. If the tension persists, future estimates of H_0 at the 1% level will be able to decisively determine which of the proposed explanations is favoured.", "keyphrases": ["hubble constant", "new physic", "dark energy", "low red-shift data", "tension\u2014as"]}
{"id": "1105.2425", "title": "The Generalized Uncertainty Principle and the Friedmann equations", "abstract": "The Generalized Uncertainty Principle (or GUP) affects the dynamics in Plank scale. So the known equations of physics are expected to get modified at that very high energy regime. Very recently authors in (Ali et al. 2009) proposed a new Generalized Uncertainty Principle (or GUP) with a linear term in Plank length. In this article, the proposed GUP is expressed in a more general form and the effect is studied for the modification of the Friedmann equations of the FRW universe. In the midway the known entropy-area relation get some new correction terms, the leading order term being proportional to square root of area.", "keyphrases": ["generalized uncertainty principle", "friedmann equation", "gup"]}
{"id": "1909.01420", "title": "The interplay of magnetically-dominated turbulence and magnetic reconnection in producing nonthermal particles", "abstract": "Magnetized turbulence and magnetic reconnection are often invoked to explain the nonthermal emission observed from a wide variety of astrophysical sources. By means of fully-kinetic 2D and 3D PIC simulations, we investigate the interplay between turbulence and reconnection in generating nonthermal particles in magnetically-dominated pair plasmas. A generic by-product of the turbulence evolution is the generation of a nonthermal particle spectrum with a power-law energy range. The power-law slope p is harder for larger magnetizations and stronger turbulence fluctuations, and it can be as hard as p < 2. The Larmor radius of particles at the high-energy cutoff is comparable to the size l of the largest eddies. Plasmoid-mediated reconnection, which self-consistently occurs in the turbulent plasma, controls the physics of particle injection. Then, particles are further accelerated by stochastic scattering off turbulent fluctuations. The work done by parallel electric fields - naturally expected in reconnection layers - is responsible for most of the initial energy increase, and is proportional to the magnetization \u03c3 of the system, while the subsequent energy gain, which dominates the overall energization of high-energy particles, is powered by the perpendicular electric fields of turbulent fluctuations. The two-stage acceleration process leaves an imprint in the particle pitch-angle distribution: low-energy particles are aligned with the field, while the highest energy particles move preferentially orthogonal to it. The energy diffusion coefficient of stochastic acceleration scales as D_\u03b3\u223c 0.1\u03c3(c/l)\u03b3^2, where \u03b3 is the particle Lorentz factor. This results in fast acceleration timescales t_acc\u223c (3/\u03c3) l/c. Our findings have important implications for understanding the generation of nonthermal particles in high-energy astrophysical sources.", "keyphrases": ["turbulence", "magnetic reconnection", "nonthermal particle"]}
{"id": "1806.02580", "title": "The internal rotation of globular clusters revealed by Gaia DR2", "abstract": "Line-of-sight kinematic studies indicate that many Galactic globular clusters have a significant degree of internal rotation. However, three-dimensional kinematics from a combination of proper motions and line-of-sight velocities are needed to unveil the role of angular momentum in the formation and evolution of these old stellar systems. Here we present the first quantitative study of internal rotation on the plane-of-the-sky for a large sample of globular clusters using proper motions from Gaia DR2. We detect signatures of rotation in the tangential component of proper motions for 11 out of 51 clusters at a >3-sigma confidence level, confirming the detection reported in Gaia collaboration et al. (2018) for 8 clusters, and additionally identify 11 GCs with a 2-sigma rotation detection. For the clusters with a detected global rotation, we construct the two-dimensional rotation maps and proper motion rotation curves, and we assess the relevance of rotation with respect to random motions (V/\u03c3\u223c0.08-0.51). We find evidence of a correlation between the degree of internal rotation and relaxation time, highlighting the importance of long-term dynamical evolution in shaping the clusters current properties. This is a strong indication that angular momentum must have played a fundamental role in the earliest phases of cluster formation. Finally, exploiting the spatial information of the rotation maps and a comparison with line-of-sight data, we provide an estimate of the inclination of the rotation axis for a subset of 8 clusters. Our work demonstrates the potential of Gaia data for internal kinematic studies of globular clusters and provides the first step to reconstruct their intrinsic three-dimensional structure.", "keyphrases": ["rotation", "cluster", "gaia dr2"]}
{"id": "1512.01203", "title": "A brief history of the multiverse", "abstract": "The theory of the inflationary multiverse changes the way we think about our place in the world. According to its most popular version, our world may consist of infinitely many exponentially large parts, exhibiting different sets of low-energy laws of physics. Since these parts are extremely large, the interior of each of them behaves as if it were a separate universe, practically unaffected by the rest of the world. This picture, combined with the theory of eternal inflation and anthropic considerations, may help to solve many difficult problems of modern physics, including the cosmological constant problem. In this article I will briefly describe this theory and provide links to the some hard to find papers written during the first few years of the development of the inflationary multiverse scenario.", "keyphrases": ["history", "multiverse", "cosmology"]}
{"id": "2105.03439", "title": "Hierarchical mergers of stellar-mass black holes and their gravitational-wave signatures", "abstract": "We review theoretical findings, astrophysical modeling, and current gravitational-wave evidence of hierarchical stellar-mass black-hole mergers. While most of the compact binary mergers detected by LIGO and Virgo are expected to consist of first-generation black holes formed from the collapse of stars, others might instead be of second (or higher) generation, containing the remnants of previous black-hole mergers. Such a subpopulation of hierarchically assembled black holes presents distinctive gravitational-wave signatures, namely higher masses, possibly within the pair-instability mass gap, and dimensionless spins clustered at the characteristic value of \u223c0.7. In order to produce hierarchical mergers, astrophysical environments need to overcome the relativistic recoils imparted to black-hole merger remnants, a condition which prefers hosts with escape speeds \u2273 100 km/s. Promising locations for efficient production of hierarchical mergers include nuclear star clusters and accretion disks surrounding active galactic nuclei, though environments that are less efficient at retaining merger products such as globular clusters may still contribute significantly to the detectable population of repeated mergers. While GW190521 is the single most promising hierarchical-merger candidate to date, constraints coming from large population analyses are becoming increasingly more powerful.", "keyphrases": ["black hole", "gravitational-wave signature", "hierarchical merger"]}
{"id": "1705.05567", "title": "Primordial black hole constraints for extended mass functions", "abstract": "We revisit the cosmological and astrophysical constraints on the fraction of the dark matter in primordial black holes (PBHs) with an extended mass function. We consider a variety of mass functions, all of which are described by three parameters: a characteristic mass and width and a dark matter fraction. Various observations then impose constraints on the dark matter fraction as a function of the first two parameters. We show how these constraints relate to those for a monochromatic mass function, demonstrating that they usually become more stringent in the extended case than the monochromatic one. Considering only the well-established bounds, and neglecting the ones that depend on additional astrophysical assumptions, we find that there are three mass windows, around 4\u00d7 10^-17M_\u2299, 2\u00d7 10^-14M_\u2299 and 25-100M_\u2299, where PBHs can constitute all dark matter. However, if one includes all the bounds, PBHs can only constitute of order 10% of the dark matter.", "keyphrases": ["black hole", "astrophysical constraint", "dark matter", "early universe", "pbh masse"]}
{"id": "1307.2450", "title": "A formal introduction to Horndeski and Galileon theories and their generalizations", "abstract": "We review different constructions of Galileon theories in both flat and curved space, and for both single scalar field models as well as multi-field models. Our main emphasis is on the formal mathematical properties of these theories and their construction.", "keyphrases": ["horndeski", "galileon theory", "scalar field"]}
{"id": "1512.09291", "title": "The case for cases B and C: intrinsic hydrogen line ratios of the broad-line region of active galactic nuclei, reddenings, and accretion disc sizes", "abstract": "Low-redshift active galactic nuclei (AGNs) with extremely blue optical spectral indices are shown to have a mean, velocity-averaged, broad-line H\u03b1/H\u03b2 ratio of 2.72 \u00b1 0.04, consistent with a Baker-Menzel Case B value. Comparison of a wide range of properties of the very bluest AGNs with those of a luminosity-matched subset of the Dong et al. blue AGN sample indicates that the only difference is the internal reddening. Ultraviolet fluxes are brighter for the bluest AGNs by an amount consistent with the flat AGN reddening curve of Gaskell et al.(2004). The lack of a significant difference in the GALEX (FUV\u2013NUV) colour index strongly rules out a steep SMC-like reddening curve and also argues against an intrinsically harder spectrum for the bluest AGNs. For very blue AGNs the Ly\u03b1/H\u03b2 ratio is also consistent with being the Case B value. The Case B ratios provide strong support for the self-shielded broad-line model of Gaskell, Klimek Nazarova. It is proposed that the greatly enhanced Ly\u03b1/H\u03b2 ratio at very high velocities is a consequence of continuum fluorescence in the Lyman lines (Case C). Reddenings of AGNs mean that the far-UV luminosity is often underestimated by up to an order of magnitude. This is a major factor causing the discrepancies between measured accretion disc sizes and the predictions of simple accretion disc theory. Dust covering fractions for most AGNs are lower than has been estimated. The total mass in lower mass supermassive black holes must be greater than hitherto estimated.", "keyphrases": ["reddening", "accretion disc size", "active galactic nucleus"]}
{"id": "1107.4642", "title": "Viscous Little Rip Cosmology", "abstract": "Dark energy of phantom or quintessence nature with an equation of state parameter w almost equal to -1 often leads the universe evolution to a finite-time future singularity. An elegant solution to this problem has been recently proposed <cit.> under the form of the so-called Little Rip cosmology which appears to be a realistic alternative to the \u039bCDM model. A viscous Little Rip cosmology is here proposed. Whereas generically bulk viscosity tends to promote the Big Rip, we find that there are a number of situations where this is not the case and where the formalism nicely adjusts itself to the Little Rip scenario. We prove, in particular, that a viscous fluid (or, equivalently, one with an inhomogeneous (imperfect) equation of state) is perfectly able to produce a Little Rip cosmology as a purely viscosity effect. The possibility of its induction as a combined result of viscosity and a general (power-like) equation of state is also investigated in detail. To finish, a physical, inertial force interpretation of the dissolution of bound structures in the Little Rip cosmology is presented.", "keyphrases": ["little rip", "future singularity", "cosmic time", "hubble parameter"]}
{"id": "1310.5728", "title": "High-Resolution Three-Dimensional Simulations of Core-Collapse Supernovae in Multiple Progenitors", "abstract": "Three-dimensional simulations of core-collapse supernovae are granting new insight into the as-yet uncertain mechanism that drives successful explosions. While there is still debate about whether explosions are obtained more easily in 3D than in 2D, it is undeniable that there exist qualitative and quantitative differences between the results of 3D and 2D simulations. We present an extensive set of high-resolution one-, two-, and three-dimensional core-collapse supernova simulations with multispecies neutrino leakage carried out in two different progenitors. Our simulations confirm the results of Couch (2013) indicating that 2D explodes more readily than 3D. We argue that this is due to the inadequacies of 2D to accurately capture important aspects of the three-dimensional dynamics. We find that without artificially enhancing the neutrino heating rate we do not obtain explosions in 3D. We examine the development of neutrino-driven convection and the standing accretion shock instability and find that, in separate regimes, either instability can dominate. We find evidence for growth of the standing accretion shock instability for both 15-M_\u2299 and 27-M_\u2299 progenitors, however, it is weaker in 3D exploding models. The growth rate of both instabilities is artificially enhanced along the symmetry axis in 2D as compared with our axis-free 3D Cartesian simulations. Our work highlights the growing consensus that core-collapse supernovae must be studied in 3D if we hope to solve the mystery of how the explosions are powered.", "keyphrases": ["three-dimensional simulation", "core-collapse supernovae", "accretion shock instability"]}
{"id": "1209.1106", "title": "Absolute calibration of a wideband antenna and spectrometer for sky noise spectral index measurements", "abstract": "A new method of absolute calibration of sky noise temperature using a three-position switched spectrometer, measurements of antenna and low noise amplifier impedance with a vector network analyzer, and ancillary measurements of the amplifier noise waves is described. The details of the method and its application to accurate wideband measurements of the spectral index of the sky noise are described and compared with other methods.", "keyphrases": ["calibration", "antenna", "sky noise"]}
{"id": "1303.6912", "title": "The Phenomenology of Right Handed Neutrinos", "abstract": "Neutrinos are the only particles in the Standard Model of particle physics that have only been observed with left handed chirality to date. If right handed neutrinos exist, they could be responsible for several phenomena that have no explanation within the Standard Model, including neutrino oscillations, the baryon asymmetry of the universe, dark matter and dark radiation. After a pedagogical introduction, we review recent progress in the phenomenology of right handed neutrinos. We in particular discuss the mass ranges suggested by hints for neutrino oscillation anomalies and dark radiation (eV), sterile neutrino dark matter scenarios (keV) and experimentally testable theories of baryogenesis (GeV to TeV). We summarize constraints from theoretical considerations, laboratory experiments, astrophysics and cosmology for each of these.", "keyphrases": ["neutrinos", "dark matter", "cosmology"]}
{"id": "1109.6234", "title": "Interacting Dark Energy \u2013 constraints and degeneracies", "abstract": "In standard cosmologies, dark energy interacts only gravitationally with dark matter. There could be a non-gravitational interaction in the dark sector, leading to changes in the effective DE equation of state, in the redshift dependence of the DM density and in structure formation. We use CMB, BAO and SNIa data to constrain a model where the energy transfer in the dark sector is proportional to the DE density. There are two subclasses, defined by the vanishing of momentum transfer either in the DM or the DE frame. We conduct a Markov-Chain Monte-Carlo analysis to obtain best-fit parameters. The background evolution allows large interaction strengths, and the constraints from CMB anisotropies are weak. The growth of DM density perturbations is much more sensitive to the interaction, and can deviate strongly from the standard case. However, the deviations are degenerate with galaxy bias and thus more difficult to constrain. Interestingly, the ISW signature is suppressed since the non-standard background evolution can compensate for high growth rates. We also discuss the partial degeneracy between interacting DE and modified gravity, and how this can be broken.", "keyphrases": ["dark energy", "degeneracy", "dark matter", "non-gravitational interaction", "coupled model"]}
{"id": "1810.04581", "title": "The spin alignment of galaxies with the large-scale tidal field in hydrodynamic simulations", "abstract": "The correlation between the spins of dark matter halos and the large-scale structure (LSS) has been studied in great detail over a large redshift range, while investigations of galaxies are still incomplete. Motivated by this point, we use the state-of-the-art hydrodynamic simulation, Illustris-1, to investigate mainly the spin\u2013LSS correlation of galaxies at redshift of z=0. We mainly find that the spins of low-mass, blue, oblate galaxies are preferentially aligned with the slowest collapsing direction (e_3) of the large-scale tidal field, while massive, red, prolate galaxy spins tend to be perpendicular to e_3. The transition from a parallel to a perpendicular trend occurs at \u223c10^9.4 M_\u2299/h in the stellar mass, \u223c0.62 in the g-r color, and \u223c0.4 in triaxiality. The transition stellar mass decreases with increasing redshifts. The alignment was found to be primarily correlated with the galaxy stellar mass. Our results are consistent with previous studies both in N-body simulations and observations. Our study also fills the vacancy in the study of the galaxy spin\u2013LSS correlation at z=0 using hydrodynamical simulations and also provides important insight to understand the formation and evolution of galaxy angular momentum.", "keyphrases": ["galaxy", "large-scale tidal field", "hydrodynamic simulation", "matter halo", "stellar mass"]}
{"id": "1901.00567", "title": "The atmospheric circulation and climate of terrestrial planets orbiting Sun-like and M-dwarf stars over a broad range of planetary parameters", "abstract": "The recent detections of temperate terrestrial planets orbiting nearby stars and the promise of characterizing their atmospheres motivates a need to understand how the diversity of possible planetary parameters affects the climate of terrestrial planets. In this work, we investigate the atmospheric circulation and climate of terrestrial exoplanets orbiting both Sun-like and M-dwarf stars over a wide swath of possible planetary parameters, including the planetary rotation period, surface pressure, incident stellar flux, surface gravity, planetary radius, and cloud particle size. We do so using a general circulation model (GCM) that includes non-grey radiative transfer and the effects of clouds. The results from this suite of simulations generally show qualitatively similar dependencies of circulation and climate on planetary parameters as idealized GCMs, with quantitative differences due to the inclusion of additional model physics. Notably, we find that the effective cloud particle size is a key unknown parameter that can greatly affect the climate of terrestrial exoplanets. We confirm a transition between low and high dayside cloud coverage of synchronously rotating terrestrial planets with increasing rotation period. We determine that this cloud transition is due to eddy-driven convergence near the substellar point and should not be parameterization-dependent. Finally, we compute full-phase light curves from our simulations of planets orbiting M-dwarf stars, finding that changing incident stellar flux and rotation period affect observable properties of terrestrial exoplanets. Our GCM results can guide expectations for planetary climate over the broad range of possible terrestrial exoplanets that will be observed with future space telescopes.", "keyphrases": ["atmospheric circulation", "terrestrial planet", "m-dwarf"]}
{"id": "0901.0546", "title": "The ARCADE 2 Instrument", "abstract": "The second generation Absolute Radiometer for Cosmology, Astrophysics, and Diffuse Emission (ARCADE 2) instrument is a balloon-borne experiment to measure the radiometric temperature of the cosmic microwave background and Galactic and extra-Galactic emission at six frequencies from 3 to 90 GHz. ARCADE 2 utilizes a double-nulled design where emission from the sky is compared to that from an external cryogenic full-aperture blackbody calibrator by cryogenic switching radiometers containing internal blackbody reference loads. In order to further minimize sources of systematic error, ARCADE 2 features a cold fully open aperture with all radiometrically active components maintained at near 2.7 K without windows or other warm objects, achieved through a novel thermal design. We discuss the design and performance of the ARCADE 2 instrument in its 2005 and 2006 flights.", "keyphrases": ["arcade", "instrument", "cosmology", "astrophysics", "radio source"]}
{"id": "1803.01998", "title": "Dwarf irregular galaxies with extended HI gas disks: Suppression of small-scale spiral structure by dark matter halo", "abstract": "Dwarf irregular galaxies with extended HI disk distributions, such as DDO 154, allow measurement of rotation curves, hence deduction of dark matter halo properties to large radial distances, up to several times the optical radius. These galaxies contain a huge reservoir of dark matter halo, which dominates over most of disk. We study the effect of the dark matter halo on small-scale spiral features by carrying out the local, non-axisymmetric perturbation analysis in the disks of five such late-type, gas-rich dwarf irregular galaxies, namely, DDO 154, NGC 3741, DDO 43, NGC 2366, and DDO 168 which host a dense and compact dark matter halo. We show that when the gas disk is treated alone, it allows a finite swing amplification; which would result in small-scale spiral structure in the outer gas disk, but the addition of dark matter halo in the analysis results in a higher Toomre Q parameter which prevents the amplification almost completely. This trend is also seen to be true in regions inside the optical radius. This implies absence of strong small-scale spiral arms in these galaxies, which is in agreement with observations. Hence despite being gas-rich, and in fact having gas as the main baryonic component, these galaxies cannot support small-scale spiral structure which would otherwise have been expected in normal gas-rich galaxies.", "keyphrases": ["galaxy", "small-scale spiral structure", "dark matter halo"]}
{"id": "0909.0751", "title": "Particle Production During Inflation: Observational Constraints and Signatures", "abstract": "In a variety of inflation models the motion of the inflaton may trigger the production of some non-inflaton particles during inflation, for example via parametric resonance or a phase transition. Particle production during inflation leads to observables in the cosmological fluctuations, such as features in the primordial power spectrum and also nongaussianities. Here we focus on a prototype scenario with inflaton, \u03d5, and iso-inflaton, \u03c7, fields interacting during inflation via the coupling g^2 (\u03d5-\u03d5_0)^2\u03c7^2. Since several previous investigations have hinted at the presence of localized \"glitches\" in the observed primordial power spectrum, which are inconsistent with the simplest power-law model, it is interesting to determine the extent to which such anomalies can be explained by this simple and well-motivated model. Our prototype scenario predicts a bump-like feature in the primordial power spectrum, rather than an oscillatory \"ringing\" pattern as has previously been assumed. We discuss the observational constraints on such features. We find that bumps with amplitude as large as 10 fluctuations from inflation are allowed on scales relevant for Cosmic Microwave Background experiments. Our results imply an upper limit on the coupling g^2 which is crucial for assessing the detectability of the nongaussianity produced by inflationary particle production. We also discuss more complicated features that result from superposing multiple instances of particle production. Finally, we point to a number of microscopic realizations of this scenario in string theory and supersymmetry and discuss the implications of our constraints for the popular brane/axion monodromy inflation models.", "keyphrases": ["primordial power spectrum", "particle production", "field annihilation", "high energy physic"]}
{"id": "1104.3106", "title": "Chern-Simons anomaly as polarization effect", "abstract": "The parity violating Chern-Simons term in the epoch before the electroweak phase transition can be interpreted as a polarization effect associated to massless right-handed electrons (positrons) in the presence of a large-scale seed hypermagnetic field. We reconfirm the viability of a unified seed field scenario relating the cosmological baryon asymmetry and the origin of the protogalactic large-scale magnetic fields observed in astronomy.", "keyphrases": ["polarization effect", "positron", "chern-simon anomaly"]}
{"id": "1612.01102", "title": "Globally coherent short duration magnetic field transients and their effect on ground based gravitational-wave detectors", "abstract": "It has been recognized that the magnetic fields from the Schumann resonances could affect the search for a stochastic gravitational-wave background by LIGO and Virgo. Presented here are the observations of short duration magnetic field transients that are coincident in the magnetometers at the LIGO and Virgo sites. Data from low-noise magnetometers in Poland and Colorado, USA, are also used and show short duration magnetic transients of global extent. We measure at least 2.3 coincident (between Poland and Colorado) magnetic transient events per day where one of the pulses exceeds 200 pT. Given the recently measured values of the magnetic coupling to differential arm motion for Advanced LIGO, there would be a few events per day that would appear simultaneously at the gravitational-wave detector sites and could move the test masses of order 10^-18 m. We confirm that in the advanced detector era short duration transient gravitational-wave searches must account for correlated magnetic field noise in the global detector network.", "keyphrases": ["magnetic field transient", "low-noise magnetometer", "gravitational-wave detector site"]}
{"id": "1811.10997", "title": "Constraining the photon coupling of ultra-light dark-matter axion-like particles by polarization variations of parsec-scale jets in active galaxies", "abstract": "Ultra-light dark matter may consist of axion-like particles with masses below 10^(-19) eV. Two-photon interactions of these particles affect the polarization of radiation propagating through the dark matter. Coherent oscillations of the Bose condensate of the particles induce periodic changes in the plane of polarisation of emission passing through the condensate. We estimate this effect and analyze MOJAVE VLBA polarization observations of bright downstream features in the parsec-scale jets of active galaxies. Through the non-observation of periodic polarization changes, we are able to constrain the photon coupling of the ultra-light dark-matter axion-like particles at the level of < 10^(-12)/GeV for masses between 5*10^(-23) eV and 1.2*10^(-21) eV.", "keyphrases": ["ultra-light dark-matter", "axion-like particle", "parsec-scale jet"]}
{"id": "1910.02914", "title": "Galaxy Power Spectrum Multipoles Covariance in Perturbation Theory", "abstract": "We compute the covariance of the galaxy power spectrum multipoles in perturbation theory, including the effects of nonlinear evolution, nonlinear and nonlocal bias, radial redshift-space distortions, arbitrary survey window and shot noise. We rewrite the power spectrum FKP estimator in terms of the usual windowed galaxy fluctuations and the fluctuations in the number of galaxies inside the survey volume. We show that this leads to a stronger super-sample covariance than assumed in the literature and causes a substantial leakage of Gaussian information. We decompose the covariance matrix into several contributions that provide an insight into its behavior for different biased tracers. We show that for realistic surveys, the covariance of power spectrum multipoles is already dominated by shot noise and super survey mode coupling in the weakly non-linear regime. Both these effects can be accurately modeled analytically, making a perturbative treatment of the covariance very compelling. Our method allows for the covariance to be varied as a function of cosmology and bias parameters very efficiently, with survey geometry entering as fixed kernels that can be computed separately using fast fourier transforms (FFTs). We find excellent agreement between our analytic covariance and that estimated from BOSS DR12 Patchy mock catalogs in the whole range we tested, up to k=0.6 h/Mpc. This bodes well for application to future surveys such as DESI and Euclid. The CovaPT code that accompanies this paper is available at https://github.com/JayWadekar/CovaPT", "keyphrases": ["covariance", "perturbation theory", "mock catalog"]}
{"id": "1703.06889", "title": "Impact of supermassive black hole growth on star formation", "abstract": "Supermassive black holes are found at the centre of massive galaxies. During the growth of these black holes they light up to become visible as active galactic nuclei (AGN) and release extraordinary amounts of energy across the electromagnetic spectrum. This energy is widely believed to regulate the rate of star formation in the black holes' host galaxies via so-called \"AGN feedback\". However, the details of how and when this occurs remains uncertain from both an observational and theoretical perspective. I review some of the observational results and discuss possible observational signatures of the impact of super-massive black hole growth on star formation.", "keyphrases": ["black hole growth", "star formation", "active galactic nucleus"]}
{"id": "1608.05206", "title": "Detecting Dynamical States from Noisy Time Series using Bicoherence", "abstract": "Deriving meaningful information from observational data is often restricted by many limiting factors, the most important of which is the presence of noise. In this work, we present the use of the bicoherence function to extract information about the underlying nonlinearity from noisy time series. We show that a system evolving in the presence of noise which has its dynamical state concealed from quantifiers like the power spectrum and correlation dimension D2, can be revealed using the bicoherence function. We define an index called main peak bicoherence function as the bicoherence associated with the maximal power spectral peak. We show that this index is extremely useful while dealing with quasi-periodic data as it can distinguish strange non chaos from quasi periodicity even with added noise. We demonstrate this in a real world scenario, by taking the bicoherence of variable stars showing period doubling and strange non-chaotic behavior. Our results indicate that bicoherence analysis can also bypass the method of surrogate analysis using Fourier phase randomization, used to differentiate linear stochastic processes from non linear ones, in conventional methods involving measures like D2.", "keyphrases": ["noisy time series", "bicoherence", "quantifier"]}
{"id": "1907.06666", "title": "Measuring neutrino masses with large-scale structure: Euclid forecast with controlled theoretical error", "abstract": "We present a Markov-Chain Monte-Carlo (MCMC) forecast for the precision of neutrino mass and cosmological parameter measurements with a Euclid-like galaxy clustering survey. We use a complete perturbation theory model for the galaxy one-loop power spectrum and tree-level bispectrum, which includes bias, redshift space distortions, IR resummation for baryon acoustic oscillations and UV counterterms. The latter encapsulate various effects of short-scale dynamics which cannot be modeled within perturbation theory. Our MCMC procedure consistently computes the non-linear power spectra and bispectra as we scan over different cosmologies. The second ingredient of our approach is the theoretical error covariance which captures uncertainties due to higher-order non-linear corrections omitted in our model. Having specified characteristics of a Euclid-like spectroscopic survey, we generate and fit mock galaxy power spectrum and bispectrum likelihoods. Our results suggest that even under very agnostic assumptions about non-linearities and short-scale physics a future Euclid-like survey will be able to measure the sum of neutrino masses with a standard deviation of 28 meV. When combined with the Planck cosmic microwave background likelihood, this uncertainty decreases to 13 meV. Over-optimistically reducing the theoretical error on the bispectrum down to the two-loop level marginally tightens this bound to 11 meV. Moreover, we show that the future large-scale structure (LSS) spectroscopic data will greatly improve constraints on the other cosmological parameters, e.g. reaching a percent (per mille) error on the Hubble constant with LSS alone (LSS + Planck).", "keyphrases": ["neutrino masse", "forecast", "theoretical error"]}
{"id": "1505.00174", "title": "Cosmological disformal invariance", "abstract": "The invariance of physical observables under disformal transformations is considered. It is known that conformal transformations leave physical observables invariant. However, whether it is true for disformal transformations is still an open question. In this paper, it is shown that a pure disformal transformation without any conformal factor is equivalent to rescaling the time coordinate. Since this rescaling applies equally to all the physical quantities, physics must be invariant under a disformal transformation, that is, neither causal structure, propagation speed nor any other property of the fields are affected by a disformal transformation itself. This fact is presented at the action level for gravitational and matter fields and it is illustrated with some examples of observable quantities. We also find the physical invariance for cosmological perturbations at linear and high orders in perturbation, extending previous studies. Finally, a comparison with Horndeski and beyond Horndeski theories under a disformal transformation is made.", "keyphrases": ["invariance", "cosmological perturbation", "horndeski theory"]}
{"id": "1512.06180", "title": "Is the Effective Field Theory of Dark Energy Effective?", "abstract": "The effective field theory of cosmic acceleration systematizes possible contributions to the action, accounting for both dark energy and modifications of gravity. Rather than making model dependent assumptions, it includes all terms, subject to the required symmetries, with four (seven) functions of time for the coefficients. These correspond respectively to the Horndeski and general beyond Horndeski class of theories. We address the question of whether this general systematization is actually effective, i.e. useful in revealing the nature of cosmic acceleration when compared with cosmological data. The answer is no and yes: there is no simple time dependence of the free functions \u2013 assumed forms in the literature are poor fits, but one can derive some general characteristics in early and late time limits. For example, we prove that the gravitational slip must restore to general relativity in the de Sitter limit of Horndeski theories, and why it doesn't more generally. We also clarify the relation between the tensor and scalar sectors, and its important relation to observations; in a real sense the expansion history H(z) or dark energy equation of state w(z) is 1/5 or less of the functional information! In addition we discuss the de Sitter, Horndeski, and decoupling limits of the theory utilizing Goldstone techniques.", "keyphrases": ["effective field theory", "dark energy", "cosmological data"]}
{"id": "1512.02291", "title": "Testing modified gravity and no-hair relations for the Kerr-Newman metric through quasi-periodic oscillations of galactic microquasars", "abstract": "We construct multipole moments for stationary, asymptotically flat, spacetime solutions to higher-order curvature theories of gravity. The moments are defined using 3+1 techniques involving timelike Killing vector constructions as in the classic papers by Geroch and Hansen. Using the fact that the Kerr-Newman metric is a vacuum solution to a particular class of f(R) theories of gravity, we compute all its moments, and find that they admit recurrence relations similar to those for the Kerr solution in general relativity. It has been proposed previously that modelling the measured frequencies of quasi-periodic oscillations from galactic microquasars enables experimental tests of the no-hair theorem. We explore the possibility that, even if the no-hair relation is found to break down in the context of general relativity, there may be an f(R) counterpart that is preserved. We apply the results to the microquasars GRS 1915+105 and GRO J1655-40 using the diskoseismology and kinematic resonance models, and constrain the spins and `charges' [which are not really electric charges in the f(R) context] of their black holes.", "keyphrases": ["gravity", "quasi-periodic oscillation", "galactic microquasar"]}
{"id": "2010.00008", "title": "Black hole binaries and light fields: Gravitational molecules", "abstract": "We show that light scalars can form quasibound states around binaries. In the nonrelativistic regime, these states are formally described by the quantum-mechanical Schrodinger equation for a one-electron heteronuclear diatomic molecule. We performed extensive numerical simulations of scalar fields around black hole binaries showing that a scalar structure condenses around the binary \u2013 we dub these states \"gravitational molecules\". We further show that these are well described by the perturbative, nonrelativistic description.", "keyphrases": ["gravitational molecule", "scalar field", "black hole binary"]}
{"id": "1912.08209", "title": "Tomographic galaxy clustering with the Subaru Hyper Suprime-Cam first year public data release", "abstract": "We analyze the clustering of galaxies in the first public data release of the HSC Subaru Strategic Program. Despite the relatively small footprints of the observed fields, the data are an excellent proxy for the deep photometric datasets that will be acquired by LSST, and are therefore an ideal test bed for the analysis methods being implemented by the LSST DESC. We select a magnitude limited sample with i<24.5 and analyze it in four redshift bins covering 0.15\u2272 z \u22721.5. We carry out a Fourier-space analysis of the two-point clustering of this sample, including all auto- and cross-correlations. We demonstrate the use of map-level deprojection methods to account for fluctuations in the galaxy number density caused by observational systematics. Through an HOD analysis, we place constraints on the characteristic halo masses of this sample, finding a good fit up to scales k_ max=1 Mpc^-1, including both auto- and cross-correlations. Our results show monotonically decreasing average halo masses, which can be interpreted in terms of the drop-out of red galaxies at high redshifts for a flux-limited sample. In terms of photometric redshift systematics, we show that additional care is needed in order to marginalize over uncertainties in the redshift distribution in galaxy clustering, and that these uncertainties can be constrained by including cross-correlations. We are able to make a \u223c3\u03c3 detection of lensing magnification in the HSC data. Our results are stable to variations in \u03c3_8 and \u03a9_c and we find constraints that agree well with measurements from Planck and low-redshift probes. Finally, we use our pipeline to study the clustering of galaxies as a function of limiting flux, and provide a simple fitting function for the linear galaxy bias for magnitude limited samples as a function of limiting magnitude and redshift. [abridged]", "keyphrases": ["galaxy", "public data release", "flux-limited sample"]}
{"id": "2006.12420", "title": "The Hubble Tension in Light of the Full-Shape Analysis of Large-Scale Structure Data", "abstract": "The disagreement between direct late-time measurements of the Hubble constant from the SH0ES collaboration, and early-universe measurements based on the \u039bCDM model from the Planck collaboration might, at least in principle, be explained by new physics in the early universe. Recently, the application of the Effective Field Theory of Large-Scale Structure to the full shape of the power spectrum of the SDSS/BOSS data has revealed a new, rather powerful, way to measure the Hubble constant and the other cosmological parameters from Large-Scale Structure surveys. In light of this, we analyze two models for early universe physics, Early Dark Energy and Rock 'n' Roll, that were designed to significantly ameliorate the Hubble tension. Upon including the information from the full shape to the Planck, BAO, and Supernovae measurements, we find that the degeneracies in the cosmological parameters that were introduced by these models are well broken by the data, so that these two models do not significantly ameliorate the tension.", "keyphrases": ["hubble tension", "full-shape analysis", "power spectrum", "lss data", "local distance ladder"]}
{"id": "1207.2048", "title": "The initial conditions of star formation: cosmic rays as the fundamental regulators", "abstract": "Cosmic rays (CRs) control the thermal, ionization and chemical state of the dense H_2 gas regions that otherwise remain shielded from far-UV and optical stellar radiation propagating through the dusty ISM of galaxies. It is in such CR-dominated regions (CRDRs) rather than Photon-dominated regions (PDRs) of H_2 clouds where the star formation initial conditions are set, making CRs the ultimate star-formation feedback factor in galaxies, able to operate even in their most deeply dust-enshrouded environments. CR-controlled star formation initial conditions naturally set the stage for a near-invariant stellar Initial Mass Function (IMF) in galaxies as long as their average CR energy density U_CR permeating their molecular ISM remains within a factor of 10 of its Galactic value. Nevertheless, in the extreme environments of the compact starbursts found in merging galaxies, where U_CR\u223c(few)x10^3U_CR,Gal, CRs dramatically alter the initial conditions of star formation. In the resulting extreme CRDRs H_2 cloud fragmentation will produce far fewer low mass (<8 M_sol) stars, yielding a top-heavy stellar IMF. This will be a generic feature of CR-controlled star-formation initial conditions, lending a physical base for a bimodal IMF during galaxy formation, with a top-heavy one for compact merger-induced starbursts, and an ordinary IMF preserved for star formation in isolated gas-rich disks. In this scheme the integrated galactic IMFs (IGIMF) are expected to be strong functions of the star formation history of galaxies.", "keyphrases": ["star formation", "cosmic ray", "initial mass function"]}
{"id": "1905.01250", "title": "Combined Rastall and Rainbow theories of gravity with applications to neutron stars", "abstract": "The possibility of modifications on general relativity is investigated. We propose an alternative theory of gravity constructed with the combination of Rastall and Rainbow theories. The hydrostatic equilibrium equations are obtained in order to test the new theory in neutron stars, whose mass-radius diagrams are obtained using modern equations of state of nuclear matter derived from relativistic mean field models and compared with the ones computed by the Tolman-Oppenheimer-Volkoff equations. We conclude that substantial modifications are obtained even for very small alterations on the two free parameters, making the reproduction of astrophysical observations an easy task.", "keyphrases": ["rainbow theory", "gravity", "neutron star"]}
{"id": "1507.05102", "title": "Weighing neutrinos with cosmic neutral hydrogen", "abstract": "We investigate the signatures left by massive neutrinos on the spatial distribution of neutral hydrogen (HI) in the post-reionization era by running hydrodynamic simulations that include massive neutrinos as additional collisionless particles. We find that halos in massive/massless neutrino cosmologies host a similar amount of neutral hydrogen, although for a fixed halo mass, on average, the HI mass increases with the sum of the neutrino masses. Our results show that HI is more strongly clustered in cosmologies with massive neutrinos, while its abundance, \u03a9_ HI(z), is lower. These effects arise mainly from the impact of massive neutrinos on cosmology: they suppress both the amplitude of the matter power spectrum on small scales and the abundance of dark matter halos. Modelling the HI distribution with hydrodynamic simulations at z > 3, and a simple analytic model at z<3, we use the Fisher matrix formalism to conservatively forecast the constraints that Phase 1 of the Square Kilometre Array (SKA) will place on the sum of neutrino masses, M_\u03bd\u2261\u03a3 m_\u03bd. We find that with 10,000 hours of interferometric observations at 3 \u2272 z \u2272 6 from a deep and narrow survey with SKA1-LOW, the sum of the neutrino masses can be measured with an error \u03c3(M_\u03bd)\u22720.3 eV (95 be obtained with a wide and deep SKA1-MID survey at z \u2272 3, using the single-dish mode. By combining data from MID, LOW, and Planck, plus priors on cosmological parameters from a Stage IV spectroscopic galaxy survey, the sum of the neutrino masses can be determined with an error \u03c3(M_\u03bd)\u22430.06 eV (95", "keyphrases": ["neutrino", "neutral hydrogen", "cosmological parameter"]}
{"id": "2112.01264", "title": "Thermodynamics of galaxy clusters in modified Newtonian potential", "abstract": "We study the thermodynamics of galaxy clusters in a modified Newtonian potential motivated by a general solution to Newton's \"sphere-point\" equivalence theorem. We obtain the N particle partition function by evaluating the configurational integral while accounting for the extended nature of galaxies (via the inclusion of the softening parameter \u03f5 into the potential energy function). This softening parameter takes care of the galaxy-halos whose effect on structuring the shape of the galactic disc has been found recently. The spatial distribution of the particles (galaxies) is also studied in this framework. A comparison of the new clustering parameter b_+ to the original clustering parameters is presented in order to visualize the effect of the modified gravity. We also discuss the possibility of system symmetry breaking via the behavior of the specific heat as a function of temperature.", "keyphrases": ["galaxy cluster", "newtonian potential", "thermodynamic"]}
{"id": "1504.01676", "title": "Cosmological ensemble and directional averages of observables", "abstract": "We show that at second order, ensemble averages of observables and directional averages do not commute due to gravitational lensing \u2013 observing the same thing in many directions over the sky is not the same as taking an ensemble average. In principle this non-commutativity is significant for a variety of quantities that we often use as observables and can lead to a bias in parameter estimation. We derive the relation between the ensemble average and the directional average of an observable, at second order in perturbation theory. We discuss the relevance of these two types of averages for making predictions of cosmological observables, focusing on observables related to distances and magnitudes. In particular, we show that the ensemble average of the distance in a given observed direction is increased by gravitational lensing, whereas the directional average of the distance is decreased. For a generic observable, there exists a particular function of the observable that is not affected by second-order lensing perturbations. We also show that standard areas have an advantage over standard rulers, and we discuss the subtleties involved in averaging in the case of supernova observations.", "keyphrases": ["average", "second order", "perturbation theory", "redshift"]}
{"id": "1002.1425", "title": "Nonlocal Modification of Newtonian Gravity", "abstract": "The Newtonian regime of a recent nonlocal extension of general relativity (GR) is investigated. Nonlocality is introduced via a scalar \"constitutive\" kernel in a special case of the translational gauge theory of gravitation, namely, the teleparallel equivalent of GR. In this theory, the nonlocal aspect of gravity simulates dark matter. A nonlocal and nonlinear generalization of Poisson's equation of Newtonian gravitation is presented. The implications of nonlocality for the gravitational physics in the solar system are briefly studied.", "keyphrases": ["gravitation", "dark matter", "nonlocality", "newtonian limit"]}
{"id": "1609.05476", "title": "Cosmological constraints from the redshift dependence of the Alcock-Paczynski effect: application to the SDSS-III BOSS DR12 galaxies", "abstract": "We apply the methodology developed in <cit.> to BOSS DR12 galaxies and derive cosmological constraints from the redshift dependence of the Alcock-Paczynski (AP) effect. The apparent anisotropy in the distribution of observed galaxies arise from two main sources, the redshift-space distortion (RSD) effect due to the galaxy peculiar velocities, and the geometric distortion when incorrect cosmological models are assumed for transforming redshift to comoving distance, known as the AP effect. Anisotropies produced by the RSD effect are, although large, maintaining a nearly uniform magnitude over a large range of redshift, while the degree of anisotropies from the AP effect varies with redshift by much larger magnitude. We split the DR12 galaxies into six redshift bins, measure the 2-point correlation function in each bin, and assess the redshift evolution of anisotropies. We obtain constraints of \u03a9_m=0.290 \u00b1 0.053, w = -1.07 \u00b1 0.15, which are comparable with the current constraints from other cosmological probes such as type Ia supernovae, cosmic microwave background, and baryon acoustic oscillation (BAO). Combining these cosmological probes with our method yield tight constraints of \u03a9_m = 0.301 \u00b1 0.006, w=-1.054 \u00b1 0.025. Our method is complementary to the other large scale structure probes like BAO and topology. We expect this technique will play an important role in deriving cosmological constraints from large scale structure surveys.", "keyphrases": ["redshift dependence", "dr12 galaxy", "cosmological constraint"]}
{"id": "1310.0870", "title": "Nonparametric reconstruction of dynamical dark energy via observational Hubble parameter data", "abstract": "We study the power of current and future observational Hubble parameter data (OHD) on non-parametric estimations of the dark energy equation of state, w(z). We propose a new method by conjunction of principal component analysis (PCA) and the criterion of goodness of fit (GoF) criterion to reconstruct w(z), ensuring the sensitivity and reliability of the extraction of features in the EoS. We also give an new error model to simulate future OHD data, to forecast the power of future OHD on the EoS reconstruction. The result shows that current OHD, despite in less quantity, give not only a similar power of reconstruction of dark energy compared to the result given by type Ia supernovae, but also extend the constraint on w(z) up to redshift z\u22432. Additionally, a reasonable forecast of future data in more quantity and better quality greatly enhances the reconstruction of dark energy.", "keyphrases": ["dark energy", "hubble parameter data", "nonparametric reconstruction"]}
{"id": "1004.0695", "title": "Neutrino and axion hot dark matter bounds after WMAP-7", "abstract": "We update cosmological hot dark matter constraints on neutrinos and hadronic axions. Our most restrictive limits use 7-year data from the Wilkinson Microwave Anisotropy Probe for the cosmic microwave background anisotropies, the halo power spectrum (HPS) from the 7th data release of the Sloan Digital Sky Survey, and the Hubble constant from Hubble Space Telescope observations. We find 95 (assuming \u2211m_\u03bd=0), and \u2211m_\u03bd<0.41 eV and m_a<0.72 eV for two hot dark matter components after marginalising over the respective other mass. CMB data alone yield \u2211m_\u03bd<1.19 eV (no axions), while for axions the HPS is crucial for deriving m_a constraints. This difference can be traced to the fact that for a given hot dark matter fraction axions are much more massive than neutrinos.", "keyphrases": ["axion", "dark matter abundance", "cosmological data"]}
{"id": "0808.1786", "title": "Generation of fluctuations during inflation: comparison of stochastic and field-theoretic approaches", "abstract": "We prove that the stochastic and standard field-theoretical approaches produce exactly the same results for the amount of light massive scalar field fluctuations generated during inflation in the leading order of the slow-roll approximation. This is true both in the case for which this field is a test one and inflation is driven by another field, and the case for which the field plays the role of inflaton itself. In the latter case, in order to calculate the average of the mean square of the gauge-invariant inflaton fluctuation, the logarithm of the scale factor a has to be used as the time variable in the Fokker-Planck equation in the stochastic approach. The implications of particle production during inflation for the second stage of inflation and for the moduli problem are also discussed. The case of a massless self-interacting test scalar field in a de Sitter background with a zero initial renormalized mean square is also considered in order to show how the stochastic approach can easily produce results corresponding to diagrams with an arbitrary number of scalar field loops in the field-theoretical approach (explicit results up to 4 loops inclusive are presented).", "keyphrases": ["fluctuation", "scalar field", "quantum effect"]}
{"id": "1307.5083", "title": "Cosmic Variance of the Spectral Index from Mode Coupling", "abstract": "We demonstrate that local, scale-dependent non-Gaussianity can generate cosmic variance uncertainty in the observed spectral index of primordial curvature perturbations. In a universe much larger than our current Hubble volume, locally unobservable long wavelength modes can induce a scale-dependence in the power spectrum of typical subvolumes, so that the observed spectral index varies at a cosmologically significant level (|\u0394ns | O(0.04)). Similarly, we show that the observed bispectrum can have an induced scale dependence that varies about the global shape. If tensor modes are coupled to long wavelength modes of a second field, the locally observed tensor power and spectral index can also vary. All of these effects, which can be introduced in models where the observed non-Gaussianity is consistent with bounds from the Planck satellite, loosen the constraints that observations place on the parameters of theories of inflation with mode coupling. We suggest observational constraints that future measurements could aim for to close this window of cosmic variance uncertainty.", "keyphrases": ["spectral index", "mode coupling", "non-gaussianity", "cosmic variance"]}
{"id": "1206.0738", "title": "From Disks to Planets", "abstract": "This pedagogical chapter covers the theory of planet formation, with an emphasis on the physical processes relevant to current research. After summarizing empirical constraints from astronomical and geophysical data, we describe the structure and evolution of protoplanetary disks. We consider the growth of planetesimals and of larger solid protoplanets, followed by the accretion of planetary atmospheres, including the core accretion instability. We also examine the possibility that gas disks fragment directly into giant planets and/or brown dwarfs. We defer a detailed description of planet migration and dynamical evolution to other work, such as the complementary chapter in this series by Morbidelli (available at arXiv:1106.4114).", "keyphrases": ["planet", "physical process", "dust", "gas drag"]}
{"id": "1308.1896", "title": "Dynamical compactification in Einstein-Gauss-Bonnet gravity from geometric frustration", "abstract": "In this paper we study dynamical compactification in Einstein-Gauss-Bonnet gravity from arbitrary dimension for generic values of the coupling constants. We showed that, when the curvature of the extra dimensional space is negative, for any value of the spatial curvature of the four dimensional space-time one obtains a realistic behavior in which for asymptotic time both the volume of the extra dimension and expansion rate of the four dimensional space-time tend to a constant. Remarkably, this scenario appears within the open region of parameters space for which the theory does not admit any maximally symmetric (4+D)- dimensional solution, which gives to the dynamical compactification an interpretation as geometric frustration. In particular there is no need to fine-tune the coupling constants of the theory so that the present scenario does not violate \"naturalness hypothesis\". Moreover we showed that with increase of the number of extra dimensions the stability properties of the solution are increased.", "keyphrases": ["compactification", "einstein-gauss-bonnet gravity", "geometric frustration"]}
{"id": "2012.12132", "title": "MOVES IV. Modelling the influence of stellar XUV-flux, cosmic rays, and stellar energetic particles on the atmospheric composition of the hot Jupiter HD 189733b", "abstract": "Hot Jupiters provide valuable natural laboratories for studying potential contributions of high-energy radiation to prebiotic synthesis in the atmospheres of exoplanets. In this fourth paper of the MOVES (Multiwavelength Observations of an eVaporating Exoplanet and its Star) programme, we study the effect of different types of high-energy radiation on the production of organic and prebiotic molecules in the atmosphere of the hot Jupiter HD 189733b. Our model combines X-ray and UV observations from the MOVES programme and 3D climate simulations from the 3D Met Office Unified Model to simulate the atmospheric composition and kinetic chemistry with the STAND2019 network. Also, the effects of galactic cosmic rays and stellar energetic particles are included. We find that the differences in the radiation field between the irradiated dayside and the shadowed nightside lead to stronger changes in the chemical abundances than the variability of the host star's XUV emission. We identify ammonium (NH4+) and oxonium (H3O+) as fingerprint ions for the ionization of the atmosphere by both galactic cosmic rays and stellar particles. All considered types of high-energy radiation have an enhancing effect on the abundance of key organic molecules such as hydrogen cyanide (HCN), formaldehyde (CH2O), and ethylene (C2H4). The latter two are intermediates in the production pathway of the amino acid glycine (C2H5NO2) and abundant enough to be potentially detectable by JWST.", "keyphrases": ["cosmic ray", "stellar energetic particle", "atmospheric composition", "exoplanetary atmosphere"]}
{"id": "1608.01048", "title": "Gravitational wave asteroseismology with protoneutron stars", "abstract": "We examine the time evolution of the frequencies of the gravitational wave after the bounce within the framework of relativistic linear perturbation theory using the results of one dimensional numerical simulations of core-collapse supernovae. Protoneutron star models are constructed in such a way that the mass and radius of protoneutron star become equivalent to the results obtained from the numerical simulations. Then, we find that the frequencies of gravitational waves radiating from protoneutron stars strongly depend on the mass and radius of protoneutron stars, but almost independently of the profiles of electron fraction and entropy per baryon inside the star. Additionally, we find that the frequencies of gravitational waves can be characterized by the square root of the average density of protoneutron star irrespectively the progenitor models, which are completely different from the empirical formula for cold neutron stars. The dependence of the spectra on the mass and radius is different from that of the g-mode: the oscillations around the surface of protoneutron stars due to the convection and the standing accretion-shock instability. Careful observations of the these modes of gravitational waves can determine the evolution of the mass and radius of protoneutron stars after core-bounce. Furthermore, the expected frequencies of gravitational waves are around a few hundred hertz in the early stage after bounce, which must be a good candidate for the ground-based gravitational wave detectors.", "keyphrases": ["protoneutron star", "core-collapse supernovae", "gravitational wave asteroseismology", "gravitational wave signal"]}
{"id": "2109.09606", "title": "Higher mass limits of neutron stars from the equation of states in curved spacetime", "abstract": "In order to solve the Tolman-Oppenheimer-Volkoff equations for neutron stars, one routinely uses the equation of states which are computed in the Minkowski spacetime. Using a first-principle approach, it is shown that the equation of states which are computed within the curved spacetime of the neutron stars include the effect of gravitational time dilation. It arises due to the radially varying interior metric over the length scale of the star and consequently it leads to a much higher mass limit. As an example, for a given set of parameters in a \u03c3-\u03c9 model of nuclear matter, the maximum mass limit is shown to increase from 1.61 M_\u2299 to 2.24 M_\u2299 due to the inclusion of gravitational time dilation.", "keyphrases": ["neutron star", "spacetime", "high mass limit"]}
{"id": "1101.4256", "title": "The Astrophysics of Ultrahigh Energy Cosmic Rays", "abstract": "The origin of the highest energy cosmic rays is still unknown. The discovery of their sources will reveal the workings of the most energetic astrophysical accelerators in the universe. Current observations show a spectrum consistent with an origin in extragalactic astrophysical sources. Candidate sources range from the birth of compact objects to explosions related to gamma-ray bursts or to events in active galaxies. We discuss the main effects of propagation from cosmologically distant sources including interactions with cosmic background radiation and magnetic fields. We examine possible acceleration mechanisms leading to a survey of candidate sources and their signatures. New questions arise from an observed hint of sky anisotropies and an unexpected evolution of composition indicators. Future observations may reach the necessary sensitivity to achieve charged particle astronomy and to observe ultrahigh energy photons and neutrinos, which will further illuminate the workings of the universe at these extreme energies. In addition to fostering a new understanding of high-energy astrophysical phenomena, the study of ultrahigh energy cosmic rays can constrain the structure of the Galactic and extragalactic magnetic fields as well as probe particle interactions at energies orders of magnitude higher than achieved in terrestrial accelerators.", "keyphrases": ["cosmic ray", "high energy", "pulsar", "active galactic nucleus", "telescope array experiment"]}
{"id": "2012.12682", "title": "Final design and development status of the acquisition and guiding system for SOXS", "abstract": "SOXS (Son Of X-Shooter) will be the new medium resolution (R 4500 for 1\u201d slit), high-efficiency, wide band spectrograph for the ESO NTT at La Silla, optimized for classification and follow-up of transient events. SOXS will simultaneously cover UV optical and NIR bands (0.35-2.00 micron) using two different arms and a pre-slit Common Path feeding system. The instrument will be also equipped by a Calibration Unit and an Acquisition Camera (AC) System. In this paper we present the final opto-mechanical design for the AC System and we describe its development status. The project is currently in manufacturing and integration phases.", "keyphrases": ["design", "development status", "soxs"]}
{"id": "1402.7103", "title": "An Observational Perspective of Transitional Disks", "abstract": "Transitional disks are objects whose inner disk regions have undergone substantial clearing. The Spitzer Space Telescope produced detailed spectral energy distributions (SEDs) of transitional disks that allowed us to infer their radial dust disk structure in some detail, revealing the diversity of this class of disks. The growing sample of transitional disks also opened up the possibility of demographic studies, which provided unique insights. There now exist (sub)millimeter and infrared images that confirm the presence of large clearings of dust in transitional disks. In addition, protoplanet candidates have been detected within some of these clearings. Transitional disks are thought to be a strong link to planet formation around young stars and are a key area to study if further progress is to be made on understanding the initial stages of planet formation. Here we provide a review and synthesis of transitional disk observations to date with the aim of providing timely direction to the field, which is about to undergo its next burst of growth as ALMA reaches its full potential. We discuss what we have learned about transitional disks from SEDs, color-color diagrams, and imaging in the (sub)mm and infrared. We then distill the observations into constraints for the main disk clearing mechanisms proposed to date (i.e., photoevaporation, grain growth, and companions) and explore how the expected observational signatures from these mechanisms, particularly planet-induced disk clearing, compare to actual observations. Lastly, we discuss future avenues of inquiry to be pursued with ALMA, JWST, and next generation of ground-based telescopes.", "keyphrases": ["transitional disk", "dust", "planet formation", "star", "gap"]}
{"id": "1806.01301", "title": "Holographic dark energy through Tsallis entropy", "abstract": "In order to apply holography and entropy relations to the whole universe, which is a gravitational and thus nonextensive system, for consistency one should use the generalized definition for the universe horizon entropy, namely Tsallis nonextensive entropy. We formulate Tsallis holographic dark energy, which is a generalization of standard holographic dark energy quantified by a new dimensionless parameter \u03b4, possessing the latter as a particular sub-case. We provide a simple differential equation for the dark energy density parameter, as well as an analytical expression for its equation-of-state parameter. In this scenario the universe exhibits the usual thermal history, namely the successive sequence of matter and dark-energy epochs, before resulting in a complete dark energy domination in the far future. Additionally, the dark energy equation-of-state parameter presents a rich behavior and, according to the value of \u03b4, it can be quintessence-like, phantom-like, or experience the phantom-divide crossing before or after the present time. Finally, we confront the scenario with Supernovae type Ia and Hubble parameter observational data, and we show that the agreement is very good, with \u03b4 preferring a value slightly larger than its standard value 1.", "keyphrases": ["dark energy", "entropy relation", "holographic dark energy"]}
{"id": "1403.5610", "title": "Bayesian Reconstruction of the Velocity Distribution of Weakly Interacting Massive Particles from Direct Dark Matter Detection Data", "abstract": "In this paper, we extended our earlier work on the reconstruction of the (time-averaged) one-dimensional velocity distribution of Galactic Weakly Interacting Massive Particles (WIMPs) and introduce the Bayesian fitting procedure to the theoretically predicted velocity distribution functions. In this reconstruction process, the (rough) velocity distribution reconstructed by using raw data from direct Dark Matter detection experiments directly, i.e. measured recoil energies, with one or more different target materials, has been used as \"reconstructed-input\" information. By assuming a fitting velocity distribution function and scanning the parameter space based on the Bayesian analysis, the astronomical characteristic parameters, e.g. the Solar and Earth's Galactic velocities, will be pinned down as the output results. Our Monte-Carlo simulations show that this Bayesian scanning procedure could reconstruct the true (input) WIMP velocity distribution function pretty precisely with negligible systematic deviations of the reconstructed characteristic Solar and Earth's velocities and 1 sigma statistical uncertainties of < 20 km/s. Moreover, for the use of an improper fitting velocity distribution function, our reconstruction process could still offer useful information about the shape of the velocity distribution. In addition, by comparing these estimates to theoretical predictions, one could distinguish different (basic) functional forms of the theoretically predicted one-dimensional WIMP velocity distribution function with 2 sigma to 4 sigma confidence levels.", "keyphrases": ["velocity distribution", "bayesian analysis", "galactic velocity"]}
{"id": "1806.10653", "title": "A three-dimensional map of the Milky Way using classical Cepheid variable stars", "abstract": "The Milky Way is a barred spiral galaxy, with physical properties inferred from various tracers informed by the extrapolation of structures seen in other galaxies. However, the distances of these tracers are measured indirectly and are model-dependent. We constructed a map of the Milky Way in three-dimensions based on the positions and distances of thousands of classical Cepheid variable stars. This map shows the structure of our Galaxy's young stellar population, and allows us to constrain the warped shape of the Milky Way's disk. A simple model of star formation in the spiral arms reproduces the observed distribution of Cepheids.", "keyphrases": ["map", "milky way", "cepheid"]}
{"id": "1108.3068", "title": "Can decaying modes save void models for acceleration?", "abstract": "The unexpected dimness of Type Ia supernovae (SNe), apparently due to accelerated expansion driven by some form of dark energy or modified gravity, has led to attempts to explain the observations using only general relativity with baryonic and cold dark matter, but by dropping the standard assumption of homogeneity on Hubble scales. In particular, the SN data can be explained if we live near the centre of a Hubble-scale void. However, such void models have been shown to be inconsistent with various observations, assuming the void consists of a pure growing mode. Here it is shown that models with significant decaying mode contribution today can be ruled out on the basis of the expected cosmic microwave background spectral distortion. This essentially closes one of the very few remaining loopholes in attempts to rule out void models, and strengthens the evidence for Hubble-scale homogeneity.", "keyphrases": ["void model", "metric", "ltb"]}
{"id": "1611.06133", "title": "Effects of variable eccentricity on the climate of an Earth-like world", "abstract": "The Kepler era of exoplanetary discovery has presented the Astronomical community with a cornucopia of planetary systems very different from the one which we inhabit. It has long been known that Jupiter plays a major role in the orbital parameters of Mars and it's climate, but there is also a long-standing belief that Jupiter would play a similar role for Earth if not for its large moon. Using a three dimensional general circulation model (3-D GCM) with a fully-coupled ocean we simulate what would happen to the climate of an Earth-like world if Mars did not exist, but a Jupiter-like planet was much closer to Earth's orbit. We investigate two scenarios that involve evolution of the Earth-like planet's orbital eccentricity from 0\u20130.283 over 6500 years, and from 0\u20130.066 on a time scale of 4500 years. In both cases we discover that they would maintain relatively temperate climates over the time-scales simulated. More Earth-like planets in multi-planet systems will be discovered as we continue to survey the skies and the results herein show that the proximity of large gas giant planets may play an important role in the habitability of these worlds. These are the first such 3-D GCM simulations using a fully-coupled ocean with a planetary orbit that evolves over time due to the presence of a giant planet.", "keyphrases": ["eccentricity", "climate", "earth-like world"]}
{"id": "2204.02061", "title": "Effect of nucleon effective mass and symmetry energy on the neutrino mean free path in a neutron star", "abstract": "The Korea-IBS-Daegu-SKKU energy density functional (KIDS-EDF) models, constructed from the perturbative expansion of the energy density in nuclear matter, have been successfully and widely applied in describing the properties of finite nuclei and infinite nuclear matter. In the present work, we extend the applications of the KIDS-EDF models to investigate the implications of the nucleon effective mass and nuclear symmetry energy for the properties of neutron stars (NSs) and neutrino interaction with the NS constituent matter in the linear response approximation (LRA). At fixed neutrino energy and momentum transfer, we analyze the total differential cross section of neutrino, the neutrino mean free path (NMFP), and the NS mass-radius (M-R) relations. Remarkable results are given by the KIDS0-m*87 and SLy4 models, in which M_n^* /M \u2272 1, and their NMFPs are quite higher in comparison with those obtained from the KIDS0, KIDS-A, and KIDS-B models, which result in M_n^*/M \u2273 1. For the KIDS0, KIDS-A, and KIDS-B models, we obtain \u03bb\u2272 R_NS, indicating that these models could predict the slow NS cooling and neutrino trapping in NSs. In contrast, the KIDS0-m*87 and SLy4 models yield \u03bb\u2273 R_NS and thus we expect faster NS cooling and a small possibility of neutrino trapping within NSs. We also calculate the NMFP as a function of the neutrino energy and the nuclear matter density and find that the NMFP decreases as the density and neutrino energy increase, which is consistent with the result obtained in the Brussels-Montreal Skyrme (BSk17 and BSk18) models at saturation density.", "keyphrases": ["nucleon", "effective mass", "neutron star"]}
{"id": "1108.3065", "title": "A new code for equilibriums and quasiequilibrium initial data of compact objects", "abstract": "We present a new code, named COCAL - Compact Object CALculator, for the computation of equilibriums and quasiequilibrium initial data sets of single or binary compact objects of all kinds. In the cocal code, those solutions are calculated on one or multiple spherical coordinate patches covering the initial hypersurface up to the asymptotic region. The numerical method used to solve field equations written in elliptic form is an adaptation of self-consistent field iterations in which Green's integral formula is computed using multipole expansions and standard finite difference schemes. We extended the method so that it can be used on a computational domain with excised regions for a black hole and a binary companion. Green's functions are constructed for various types of boundary conditions imposed at the surface of the excised regions for black holes. The numerical methods used in cocal are chosen to make the code simpler than any other recent initial data codes, accepting the second order accuracy for the finite difference schemes. We perform convergence tests for time symmetric single black hole data on a single coordinate patch, and binary black hole data on multiple patches. Then, we apply the code to obtain spatially conformally flat binary black hole initial data using boundary conditions including the one based on the existence of equilibrium apparent horizons.", "keyphrases": ["new code", "quasiequilibrium", "compact object"]}
{"id": "1702.08644", "title": "A flaring magnetar in FRB 121102?", "abstract": "The persistent radio counterpart of FRB 121102 is estimated to have N\u223c 10^52 particles, energy E_N\u223c 10^48 erg, and size R\u223c 10^17 cm. The source can be a nebula inflated and heated by an intermittent outflow from a magnetar \u2014 a neutron star powered by its magnetic (rather than rotational) energy. The object is young and frequently liberating energy in magnetic flares driven by accelerated ambipolar diffusion in the neutron star core, feeding the nebula and producing bright millisecond bursts. The particle number in the nebula is consistent with ion ejecta from giant flares. The nebula may also contain the freeze-out of electron-positron pairs N_\u00b1\u223c 10^51 created months after the neutron star birth; the same mechanism offers an explanation for N_\u00b1 in the Crab nebula. The persistent source around FRB 121102 is likely heated by magnetic dissipation and internal waves excited by the magnetar ejecta. The volumetric heating by waves explains the nebula's enormous efficiency in producing radio emission. The repeating radio bursts are suggested to occur much closer to the magnetar, whose flaring magnetosphere drives ultrarelativistic internal shocks into the magnetar wind. The shocks are mediated by Larmor rotation that forms a GHz maser with the observed ms duration. Furthermore, the flare ejecta can become charge-starved and then convert to electromagnetic waves.", "keyphrases": ["flare", "magnetar", "neutron star", "internal shock"]}
{"id": "1604.06065", "title": "gevolution: a cosmological N-body code based on General Relativity", "abstract": "We present a new N-body code, gevolution, for the evolution of large scale structure in the Universe. Our code is based on a weak field expansion of General Relativity and calculates all six metric degrees of freedom in Poisson gauge. N-body particles are evolved by solving the geodesic equation which we write in terms of a canonical momentum such that it remains valid also for relativistic particles. We validate the code by considering the Schwarzschild solution and, in the Newtonian limit, by comparing with the Newtonian N-body codes Gadget-2 and RAMSES. We then proceed with a simulation of large scale structure in a Universe with massive neutrinos where we study the gravitational slip induced by the neutrino shear stress. The code can be extended to include different kinds of dark energy or modified gravity models and going beyond the usually adopted quasi-static approximation. Our code is publicly available.", "keyphrases": ["n-body code", "general relativity", "dark energy", "gevolution", "mean evolution"]}
{"id": "1905.00446", "title": "Echoes from Quantum Black Holes", "abstract": "One of the most triumphant predictions of the theory if general relativity was the recent LIGO-Virgo detection of gravitational wave (GW) signals produced in binary black hole (BH) mergers. However, it is suggested that exotic compact objects, proposed in quantum gravity models of BHs, may produce similar classical GW waveforms, followed by delayed repeating \"echoes\". In a companion paper [1], we have presented different arguments for a universal Boltzmann reflectivity of quantum BH horizons. Here, we investigate the resulting echoes from this prescription. We derive corresponding quasi-normal modes (QNMs) for quantum BHs analytically, and show how their initial conditions can be related to the QNMs of classical BHs. Ergoregion instability is suppressed by the imperfect reflectivity. We then compare the analytic and numerical predictions for echoes in real time, verifying their consistency. In particular, we find that the amplitudes of the first 20 echoes decay inversely with time, while the subsequent echoes decay exponentially. Finally, we present predictions for the signal-to-noise ratio of echoes for spinning BHs, which should be imminently detectable for massive remnants, subject to the uncertainty in the nonlinear initial conditions of the BH merger.", "keyphrases": ["black hole", "horizon", "echo"]}
{"id": "1607.03203", "title": "Light speed variation from gamma-ray bursts", "abstract": "The effect of quantum gravity can bring a tiny light speed variation which is detectable through energetic photons propagating from gamma ray bursts (GRBs) to an observer such as the space observatory. Through an analysis of the energetic photon data of the GRBs observed by the Fermi Gamma-ray Space Telescope (FGST), we reveal a surprising regularity of the observed time lags between photons of different energies with respect to the Lorentz violation factor due to the light speed energy dependence. Such regularity suggests a linear form correction of the light speed v(E)=c(1-E/E_ LV), where E is the photon energy and E_ LV=(3.60 \u00b1 0.26) \u00d7 10^17 GeV is the Lorentz violation scale measured by the energetic photon data of GRBs. The results support an energy dependence of the light speed in cosmological space.", "keyphrases": ["photon", "grb", "time lag", "light speed variation"]}
{"id": "1612.06535", "title": "Weak gravitational lensing", "abstract": "According to the theory of general relativity, masses deflect light in a way similar to convex glass lenses. This gravitational lensing effect is astigmatic, giving rise to image distortions. These distortions allow to quantify cosmic structures statistically on a broad range of scales, and to map the spatial distribution of dark and visible matter. We summarise the theory of weak gravitational lensing and review applications to galaxies, galaxy clusters and larger-scale structures in the Universe.", "keyphrases": ["lensing", "universe", "dark matter distribution", "background galaxy", "dark energy equation"]}
{"id": "1404.6704", "title": "Reheating constraints to inflationary models", "abstract": "Evidence from the BICEP2 experiment for a significant gravitational-wave background has focussed attention on inflaton potentials V(\u03d5) \u221d\u03d5^\u03b1 with \u03b1=2 (\"chaotic\" or \"m^2\u03d5^2\" inflation) or with smaller values of \u03b1, as may arise in axion-monodromy models. Here we show that reheating considerations may provide additional constraints to these models. The reheating phase preceding the radiation era is modeled by an effective equation-of-state parameter w_ re. The canonical reheating scenario is then described by w_ re=0. The simplest \u03b1=2 models are consistent with w_ re = 0 for values of n_s well within the current 1\u03c3 range. Models with \u03b1=1 or \u03b1=2/3 require a more exotic reheating phase, with -1/3<w_ re<0, unless n_s falls above the current 1\u03c3 range. Likewise, models with \u03b1=4 require a physically implausible w_ re>1/3, unless n_s is close to the lower limit of the 2\u03c3 range. For m^2\u03d5^2 inflation and canonical reheating as a benchmark, we derive a relation log_10(T_ re/10^6 GeV) \u2243 2000 (n_s-0.96) between the reheat temperature T_ re and the scalar spectral index n_s. Thus, if n_s is close to its central value, then T_ re\u2272 10^6 GeV, just above the electroweak scale. If the reheat temperature is higher, as many theorists may prefer, then the scalar spectral index should be closer to n_s\u22430.965 (at the pivot scale k=0.05 Mpc^-1), near the upper limit of the 1\u03c3 error range. Improved precision in the measurement of n_s should allow m^2\u03d5^2, axion-monodromy, and \u03d5^4 models to be distinguished, even without precise measurement of r, and to test the m^2\u03d5^2 expectation of n_s\u22430.965.", "keyphrases": ["inflationary model", "electroweak scale", "universe", "reheating", "primordial fluctuation"]}
{"id": "1112.3340", "title": "The stellar and sub-stellar IMF of simple and composite populations", "abstract": "The current knowledge on the stellar IMF is documented. It appears to become top-heavy when the star-formation rate density surpasses about 0.1Msun/(yr pc^3) on a pc scale and it may become increasingly bottom-heavy with increasing metallicity and in increasingly massive early-type galaxies. It declines quite steeply below about 0.07Msun with brown dwarfs (BDs) and very low mass stars having their own IMF. The most massive star of mass mmax formed in an embedded cluster with stellar mass Mecl correlates strongly with Mecl being a result of gravitation-driven but resource-limited growth and fragmentation induced starvation. There is no convincing evidence whatsoever that massive stars do form in isolation. Various methods of discretising a stellar population are introduced: optimal sampling leads to a mass distribution that perfectly represents the exact form of the desired IMF and the mmax-to-Mecl relation, while random sampling results in statistical variations of the shape of the IMF. The observed mmax-to-Mecl correlation and the small spread of IMF power-law indices together suggest that optimally sampling the IMF may be the more realistic description of star formation than random sampling from a universal IMF with a constant upper mass limit. Composite populations on galaxy scales, which are formed from many pc scale star formation events, need to be described by the integrated galactic IMF. This IGIMF varies systematically from top-light to top-heavy in dependence of galaxy type and star formation rate, with dramatic implications for theories of galaxy formation and evolution.", "keyphrases": ["composite population", "stellar imf", "galaxy", "massive star", "initial mass function"]}
{"id": "2109.08145", "title": "Universal relations between the quasinormal modes of neutron star and tidal deformability", "abstract": "Universal relations independently of the equation of state (EOS) for neutron star matter are valuable, if they exist, for extracting the neutron star properties, which generally depend on the EOS. In this study, we newly derive the universal relations predicting the gravitational wave frequencies for the fundamental (f), the 1st pressure (p_1), and the 1st spacetime (w_1) modes and the damping rate for the f- and w_1-modes as a function of the dimensionless tidal deformability. In particular, with the universal relations for the f-modes one can predict the frequencies and damping rate with less than 1% accuracy for canonical neutron stars.", "keyphrases": ["quasinormal mode", "neutron star", "tidal deformability"]}
{"id": "2005.12287", "title": "Gravitational Decoherence of Dark Matter", "abstract": "Decoherence describes the tendency of quantum sub-systems to dynamically lose their quantum character. This happens when the quantum sub-system of interest interacts and becomes entangled with an environment that is traced out. For ordinary macroscopic systems, electromagnetic and other interactions cause rapid decoherence. However, dark matter (DM) may have the unique possibility of exhibiting naturally prolonged macroscopic quantum properties due to its weak coupling to its environment, particularly if it only interacts gravitationally. In this work, we compute the rate of decoherence for light DM in the galaxy, where a local density has its mass, size, and location in a quantum superposition. The decoherence is via the gravitational interaction of the DM overdensity with its environment, provided by ordinary matter. We focus on relatively robust configurations: DM perturbations that involve an overdensity followed by an underdensity, with no monopole, such that it is only observable at relatively close distances. We use non-relativistic scattering theory with a Newtonian potential generated by the overdensity to determine how a probe particle scatters off of it and thereby becomes entangled. As an application, we consider light scalar DM, including axions. In the galactic halo, we use diffuse hydrogen as the environment, while near the earth, we use air as the environment. For an overdensity whose size is the typical DM de Broglie wavelength, we find that the decoherence rate in the halo is higher than the present Hubble rate for DM masses m_a \u2272 5 \u00d7 10^-7eV and in earth based experiments it is higher than the classical field coherence rate for m_a \u2272 10^-6eV. When spreading of the states occurs, the rates can become much faster, as we quantify. Also, we establish that DM BECs decohere very rapidly and so are very well described by classical field theory.", "keyphrases": ["decoherence", "dark matter", "gravitational interaction"]}
{"id": "1709.07503", "title": "Can the graviton have a large mass near black holes?", "abstract": "The mass of the graviton, if nonzero, is usually considered to be very small, e.g. of the Hubble scale, from several observational constraints. In this paper, we propose a gravity model where the graviton mass is very small in the usual weak gravity environments, below all the current graviton mass bounds, but becomes much larger in the strong gravity regime such as a black hole's vicinity. For black holes in this model, significant deviations from general relativity emerge very close to the black hole horizon and alter the black hole quasi-normal modes, which can be extracted from the ringdown waveform of black hole binary mergers. Also, the enhancement of the graviton mass near the horizon can result in echoes in the late time ringdown, which can be verified in the upcoming gravitational wave observations of higher sensitivity.", "keyphrases": ["graviton", "black hole", "weak gravity environment"]}
{"id": "1010.2177", "title": "Chemically homogeneous evolution in massive binaries", "abstract": "Rotation can have severe consequences for the evolution of massive stars. It is now considered as one of the main parameters, alongside mass and metallicity that determine the final fate of single stars. In massive, fast rotating stars mixing processes induced by rotation may be so efficient that helium produced in the center is mixed throughout the envelope. Such stars evolve almost chemically homogeneously. At low metallicity they remain blue and compact, while they gradually evolve into Wolf-Rayet stars and possibly into progenitors of long gamma-ray bursts. In binaries this type of evolution may occur because of (I) tides in very close binaries, as a result of (II) spin up by mass transfer, as result of (III) a merger of the two stars and (IV) when one of the components in the binary was born with a very high initial rotation rate. As these stars stay compact, the evolutionary channels are very different from what classical binary evolutionary models predict. In this contribution we discuss examples of nearly chemically homogeneous evolution in very close tidally-locked binaries. Even in such very close massive binaries, the stars may remain compact and avoid mass transfer, while Roche lobe overflow and a merger would be inevitable in the classical picture. This type of evolution may provide an alternative path to form tight Wolf-Rayet binaries and massive black hole binaries.", "keyphrases": ["homogeneous evolution", "massive binary", "helium"]}
{"id": "1705.07858", "title": "The structure of terrestrial bodies: Impact heating, corotation limits and synestias", "abstract": "During accretion, terrestrial bodies attain a wide range of thermal and rotational states, which are accompanied by significant changes in physical structure (size, shape, pressure and temperature profile, etc.). However, variations in structure have been neglected in most studies of rocky planet formation and evolution. Here, we present a new code, HERCULES, that solves for the equilibrium structure of planets as a series of overlapping constant-density spheroids. Using HERCULES and a smoothed particle hydrodynamics code, we show that Earth-like bodies display a dramatic range of morphologies. For any rotating planetary body, there is a thermal limit beyond which the rotational velocity at the equator intersects the Keplerian orbital velocity. Beyond this corotation limit (CoRoL), a hot planetary body forms a structure, which we name a synestia, with a corotating inner region connected to a disk-like outer region. By analyzing calculations of giant impacts and models of planet formation, we show that typical rocky planets are substantially vaporized multiple times during accretion. For the expected angular momentum of growing planets, a large fraction of post-impact bodies will exceed the CoRoL and form synestias. The common occurrence of hot, rotating states during accretion has major implications for planet formation and the properties of the final planets. In particular, the structure of post-impact bodies influences the physical processes that control accretion, core formation and internal evolution. Synestias also lead to new mechanisms for satellite formation. Finally, the wide variety of possible structures for terrestrial bodies also expands the mass-radius range for rocky exoplanets.", "keyphrases": ["terrestrial body", "corotation limit", "planet formation", "post-impact body"]}
{"id": "1303.0863", "title": "Do SGRs/AXPs and radio AXPs have the same nature?", "abstract": "SGRs/AXPs are assumed to be a class of neutron stars (NS) powered by magnetic energy and not by rotation, as normal radio pulsars. However, the recent discovery of radio-pulsed emission in four of this class of sources, where the spin-down rotational energy lost \u0116_ rot is larger than the X-ray luminosity L_X during the quiescent state - as in normal pulsars - opens the question of the nature of these radio AXPs in comparison to the others of this class. In this work, we show that the radio AXPs obey a linear log-log relation between L_X and \u0116_ rot, very similar to the one of normal X-ray pulsars, a correlation not seen for the others SGRs/AXPs. This result suggests a different nature between the radio AXPs comparing to the others SGRs/AXPs.", "keyphrases": ["sgr", "axp", "radio axp", "recent discovery", "radio-pulsed emission"]}
{"id": "1212.0541", "title": "Hot X-ray coronae around massive spiral galaxies: a unique probe of structure formation models", "abstract": "Luminous X-ray gas coronae in the dark matter halos of massive spiral galaxies are a fundamental prediction of structure formation models, yet only a few such coronae have been detected so far. In this paper, we study the hot X-ray coronae beyond the optical disks of two normal massive spirals, NGC1961 and NGC6753. Based on XMM-Newton X-ray observations, hot gaseous emission is detected to 60 kpc - well beyond their optical radii. The hot gas has a best-fit temperature of kT 0.6 keV and an abundance of 0.1 Solar, and exhibits a fairly uniform distribution, suggesting that the quasi-static gas resides in hydrostatic equilibrium in the potential well of the galaxies. The bolometric luminosity of the gas in the (0.05-0.15)r_200 region (r_200 is the virial radius) is 6e40 erg/s for both galaxies. The baryon mass fractions of NGC1961 and NGC6753 are f_b 0.1, which fall short of the cosmic baryon fraction. The hot coronae around NGC1961 and NGC6753 offer an excellent basis to probe structure formation simulations. To this end, the observations are confronted with the moving mesh code Arepo and the smoothed particle hydrodynamics code Gadget. Although neither model gives a perfect description, the observed luminosities, gas masses, and abundances favor the Arepo code. Moreover, the shape and the normalization of the observed density profiles are better reproduced by Arepo within 0.5r_200. However, neither model incorporates efficient feedback from supermassive black holes or supernovae, which could alter the simulated properties of the X-ray coronae. With the further advance of numerical models, the present observations will be essential in constraining the feedback effects in structure formation simulations.", "keyphrases": ["spiral galaxy", "hot x-ray coronae", "optical radius"]}
{"id": "1005.3923", "title": "Giant Rings in the CMB Sky", "abstract": "We find a unique direction in the CMB sky around which giant rings have an anomalous mean temperature profile. This direction is in very close alignment with the afore measured anomalously large bulk flow direction. Using Monte Carlo simulations, we estimate the significance of the giant rings at the 3\u03c3 level and the alignment with the bulk flow at 2.5\u03c3. We argue that a cosmic defect seeded by a pre-inflationary particle could explain the giant rings, the large bulk flow and their alignment.", "keyphrases": ["ring", "cmb sky", "particle"]}
{"id": "1607.05567", "title": "Revisit of the interacting holographic dark energy model after Planck 2015", "abstract": "We investigate the observational constraints on the interacting holographic dark energy model. We consider five typical interacting models with the interaction terms Q=3\u03b2 H\u03c1_de, Q=3\u03b2 H\u03c1_c, Q=3\u03b2 H(\u03c1_de+\u03c1_ c), Q=3\u03b2 H\u221a(\u03c1_de\u03c1_ c), and Q=3\u03b2 H\u03c1_de\u03c1_c/\u03c1_de+\u03c1_ c, respectively, where \u03b2 is a dimensionless coupling constant. The observational data we use in this paper include the JLA compilation of type Ia supernovae data, the Planck 2015 distance priors data of cosmic microwave background observation, the baryon acoustic oscillations measurements, and the Hubble constant direct measurement. We make a comparison for these five interacting holographic dark energy models by employing the information criteria, and we find that, within the framework of holographic dark energy, the Q=3\u03b2 H\u03c1_de\u03c1_ c/\u03c1_ de+\u03c1_ c model is most favored by current data, and the Q=3\u03b2 H\u03c1_ c model is relatively not favored by current data. For the Q=3\u03b2 H\u03c1_de and Q=3\u03b2 H\u03c1_de\u03c1_ c/\u03c1_ de+\u03c1_ c models, a positive coupling \u03b2 can be detected at more than 2\u03c3 significance.", "keyphrases": ["holographic dark energy", "dark energy model", "non-gravitational coupling"]}
{"id": "1409.1595", "title": "Advances in exoplanet science from Kepler", "abstract": "Numerous telescopes and techniques have been used to find and study extrasolar planets, but none has been more successful than NASA's Kepler Space Telescope. Kepler has discovered the majority of known exoplanets, the smallest planets to orbit normal stars, and the worlds most likely to be similar to our home planet. Most importantly, Kepler has provided our first look at typical characteristics of planets and planetary systems for planets with sizes as small as and orbits as large as those of the Earth.", "keyphrases": ["exoplanet science", "kepler", "kepler space telescope"]}
{"id": "1806.10832", "title": "Updated Bounds on Sum of Neutrino Masses in Various Cosmological Scenarios", "abstract": "We present strong bounds on the sum of three active neutrino masses (\u2211 m_\u03bd) in various cosmological models. We use the following baseline datasets: CMB temperature data from Planck 2015, BAO measurements from SDSS-III BOSS DR12, the newly released SNe Ia dataset from Pantheon Sample, and a prior on the optical depth to reionization from 2016 Planck Intermediate results. We constrain cosmological parameters in \u039b CDM model with 3 massive active neutrinos. For this \u039b CDM+\u2211 m_\u03bd model we find a upper bound of \u2211 m_\u03bd < 0.152 eV at 95% C.L. Adding the high-l polarization data from Planck strengthens this bound to \u2211 m_\u03bd < 0.118 eV, which is very close to the minimum required mass of \u2211 m_\u03bd\u2243 0.1 eV for inverted hierarchy. This bound is reduced to \u2211 m_\u03bd < 0.110 eV when we also vary r, the tensor to scalar ratio (\u039b CDM+r+\u2211 m_\u03bd model), and add an additional dataset, BK14, the latest data released from the Bicep-Keck collaboration. This bound is further reduced to \u2211 m_\u03bd < 0.101 eV in a cosmology with non-phantom dynamical dark energy (w_0 w_a CDM+\u2211 m_\u03bd model with w(z)\u2265 -1 for all z). Considering the w_0 w_a CDM+r+\u2211 m_\u03bd model and adding the BK14 data again, the bound can be even further reduced to \u2211 m_\u03bd < 0.093 eV. For the w_0 w_a CDM+\u2211 m_\u03bd model without any constraint on w(z), the bounds however relax to \u2211 m_\u03bd < 0.276 eV. Adding a prior on the Hubble constant (H_0 = 73.24\u00b1 1.74 km/sec/Mpc) from Hubble Space Telescope (HST), the above mentioned bounds further improve to \u2211 m_\u03bd < 0.117 eV, 0.091 eV, 0.085 eV, 0.082 eV, 0.078 eV and 0.247 eV respectively. This substantial improvement is mostly driven by a more than 3\u03c3 tension between Planck 2015 and HST measurements of H_0 and should be taken cautiously. (abstract abridged)", "keyphrases": ["neutrino masse", "cosmology", "dark energy"]}
{"id": "1111.3556", "title": "The local dark matter phase-space density and impact on WIMP direct detection", "abstract": "We present a new determination of the local dark matter phase-space density. This result is obtained implementing, in the limit of isotropic velocity distribution and spherical symmetry, Eddington's inversion formula, which links univocally the dark matter distribution function to the density profile, and applying, within a Bayesian framework, a Markov Chain Monte Carlo algorithm to sample mass models for the Milky Way against a broad and variegated sample of dynamical constraints. We consider three possible choices for the dark matter density profile, namely the Einasto, NFW and Burkert profiles, finding that the velocity dispersion, which characterizes the width in the distribution, tends to be larger for the Burkert case, while the escape velocity depends very weakly on the profile, with the mean value we obtain being in very good agreement with estimates from stellar kinematics. The derived dark matter phase-space densities differ significantly\u2013most dramatically in the high velocity tails\u2013from the model usually taken as a reference in dark matter detection studies, a Maxwell-Boltzmann distribution with velocity dispersion fixed in terms of the local circular velocity and with a sharp truncation at a given value of the escape velocity. We discuss the impact of astrophysical uncertainties on dark matter scattering rates and direct detection exclusion limits, considering a few sample cases and showing that the most sensitive ones are those for light dark matter particles and for particles scattering inelastically. As a general trend, when adopting a self-consistent phase-space density, we find that rates are larger, and hence exclusion limits stronger, than with the standard Maxwell-Boltzmann approximation. Tools for applying our result on the local dark matter phase-space density to other dark matter candidates or experimental setups are provided.", "keyphrases": ["dark matter", "phase-space density", "direct detection"]}
{"id": "1712.06227", "title": "Thermonuclear X-ray bursts", "abstract": "Type-I X-ray bursts arise from unstable thermonuclear burning of accreted fuel on the surface of neutron stars. In this chapter we review the fundamental physics of the burning processes, and summarise the observational, numerical, and nuclear experimental progress over the preceding decade. We describe the current understanding of the conditions that lead to burst ignition, and the influence of the burst fuel on the observational characteristics. We provide an overview of the processes which shape the burst X-ray spectrum, including the observationally elusive discrete spectral features. We report on the studies of timing behaviour related to nuclear burning, including burst oscillations and mHz quasi-periodic oscillations. We describe the increasing role of nuclear experimental physics in the interpretation of astrophysical data and models. We survey the simulation projects that have taken place to date, and chart the increasing dialogue between modellers, observers, and nuclear experimentalists. Finally, we identify some open problems with prospects of a resolution within the timescale of the next such review.", "keyphrases": ["x-ray burst", "neutron star", "thermonuclear", "material", "such burst"]}
{"id": "2005.11325", "title": "Thermalization of large energy release in the early Universe", "abstract": "Spectral distortions of the cosmic microwave background (CMB) provide a unique tool for learning about the early phases of cosmic history, reaching deep into the primordial Universe. At redshifts z<10^6, thermalization processes become inefficient and existing limits from COBE/FIRAS imply that no more than \u0394\u03c1/\u03c1<6\u00d7 10^-5 (95 been injected into the CMB. However, at higher redshifts, when thermalization is efficient, the constraint weakens and \u0394\u03c1/\u03c1\u2243 0.01-0.1 could in principle have occurred. Existing computations for the evolution of distortions commonly assume \u0394\u03c1/\u03c1\u226a 1 and thus become inaccurate in this case. Similarly, relativistic temperature corrections become relevant for large energy release, but have previously not been modeled as carefully. Here we study the evolution of distortions and the thermalization process after single large energy release at z>10^5. We show that for large distortions the thermalization efficiency is significantly reduced and that the distortion visibility is sizeable to much earlier times. This tightens spectral distortions constraints on low-mass primordial black holes with masses M_ PBH < 6\u00d7 10^11 g. Similarly, distortion limits on the amplitude of the small-scale curvature power spectrum at wavenumbers k>10^4 Mpc^-1 and short-lived decaying particles with lifetimes t_X< 10^7 s are tightened, however, these still require a more detailed time-dependent treatment. We also briefly discuss the constraints from measurements of the effective number of relativistic degrees of freedom and light element abundances and how these complement spectral distortion limits.", "keyphrases": ["large energy release", "universe", "thermalization"]}
{"id": "2107.11552", "title": "The Regulated NiCu Cycles with the new ^57Cu(p,\u03b3)^58Zn reaction rate and the Influence on Type-I X-Ray Bursts: GS 1826-24 Clocked Burster", "abstract": "During the X-ray bursts of GS 1826-24, \"clocked burster\", the nuclear reaction flow that surges through the rapid-proton capture process path has to pass through the NiCu cycles before reaching the ZnGa cycles that moderate the further extent of hydrogen burning in the region above germanium and selenium isotopes. The ^57Cu(p,\u03b3)^58Zn reaction located in the NiCu cycles plays an important role in influencing the burst light curves as found by Cyburt et al. (2016). We deduce the ^57Cu(p,\u03b3)^58Zn reaction rate based on the experimentally determined important nuclear structure information, isobaric-multiplet-mass equation, and large-scale shell model calculations. Based on the isobaric-multiplet-mass equation, we propose a possible order of 1^+_1 and 2^+_3 dominant resonance states and constrain the resonance energy of the 1^+_2 state. The latter reduces the contribution of the 1^+_2 dominant resonance state. The new reaction rate is up to a factor of four lower than the Forstner et al. (2001) rate recommended by JINA REACLIB v2.2 at the temperature regime sensitive to clocked bursts of GS 1826-24. Using the simulation from the one-dimensional implicit hydrodynamic code, KEPLER, to model the thermonuclear X-ray bursts of GS 1826-24 clocked burster, we find that the new ^57Cu(p,\u03b3)^58Zn coupled with the latest ^56Ni(p,\u03b3)^57Cu and ^55Ni(p,\u03b3)^56Cu reaction rates redistributes the reaction flow in the NiCu cycles and strongly influences the burst ash composition, whereas the ^59Cu(p,\u03b1)^56Ni and ^59Cu(p,\u03b3)^60Zn reactions suppress the influence of the ^57Cu(p,\u03b3)^58Zn reaction and diminish the impact of nuclear reaction flow that by-passes the important ^56Ni waiting point induced by the ^55Ni(p,\u03b3)^56Cu reaction on burst light curve.", "keyphrases": ["new ^57cu(p", "reaction rate", "clocked burster"]}
{"id": "1409.5266", "title": "Instrumentation for the detection and characterization of exoplanets", "abstract": "In no other field of astrophysics has the impact of new instrumentation been as substantial as in the domain of exoplanets. Before 1995 our knowledge about exoplanets was mainly based on philosophical and theoretical considerations. The following years have been marked, instead, by surprising discoveries made possible by high-precision instruments. More recently the availability of new techniques moved the focus from detection to the characterization of exoplanets. Next-generation facilities will produce even more complementary data that will lead to a comprehensive view of exoplanet characteristics and, by comparison with theoretical models, to a better understanding of planet formation.", "keyphrases": ["characterization", "exoplanet", "instrumentation"]}
{"id": "1805.05985", "title": "Probability of Warm Inflation in Loop Quantum Cosmology", "abstract": "Warm inflation is analyzed in the context of Loop Quantum Cosmology (LQC). The bounce in LQC provides a mean through which a Liouville measure can be defined, which has been used previously to characterize the a priori probability for inflation in LQC. Here we take advantage of the tools provided by LQC to study instead the a priori probability for warm inflation dynamics in the context of a monomial quartic inflaton potential. We study not only the question of how a general warm inflation dynamics can be realized in LQC with an appropriate number of e-folds, but also how such dynamics is constrained to be in agreement with the latest cosmic microwave background radiation from Planck. The fraction of warm inflation trajectories in LQC that gives both the required minimum amount e-folds of expansion and also passes through the observational window of allowed values for the tensor-to-scalar ratio and the spectral tilt is explicitly obtained. We find that the probability of warm inflation with a monomial quartic potential in LQC is higher than that of cold inflation in the same context. Furthermore, we also obtain that the a priori probability gets higher as the inherent dissipation of the warm inflation dynamics increases.", "keyphrases": ["warm inflation", "loop quantum cosmology", "inflaton potential"]}
{"id": "1310.8134", "title": "Statistics of cosmic density profiles from perturbation theory", "abstract": "The joint probability distribution function (PDF) of the density within multiple concentric spherical cells is considered. It is shown how its cumulant generating function can be obtained at tree order in perturbation theory as the Legendre transform of a function directly built in terms of the initial moments. In the context of the upcoming generation of large-scale structure surveys, it is conjectured that this result correctly models such a function for finite values of the variance. Detailed consequences of this assumption are explored. In particular the corresponding one-cell density probability distribution at finite variance is computed for realistic power spectra, taking into account its scale variation. It is found to be in agreement with \u039b-CDM simulations at the few percent level for a wide range of density values and parameters. Related explicit analytic expansions at the low and high density tails are given. The conditional (at fixed density) and marginal probability of the slope \u2013 the density difference between adjacent cells \u2013 and its fluctuations is also computed from the two-cells joint PDF; it also compares very well to simulations, in particular in under-dense regions, with a significant reduced cosmic scatter compared to over-dense regions. It is emphasized that this could prove useful when studying the statistical properties of voids as it can serve as a statistical indicator to test gravity models and/or probe key cosmological parameters.", "keyphrases": ["density profile", "perturbation theory", "finite variance"]}
{"id": "1206.5549", "title": "Chiral Effects and Cosmic Magnetic Fields", "abstract": "In the presence of cosmic chiral asymmetry, chiral-vorticity and chiral-magnetic effects can play an important role in the generation and evolution of magnetic fields in the early universe. We include these chiral effects in the magnetic field equations and find solutions under simplifying assumptions. Our numerical and analytical results show the presence of an attractor solution in which chiral effects produce a strong, narrow, Gaussian peak in the magnetic spectrum and the magnetic field becomes maximally helical. The peak in the spectrum shifts to longer length scales and becomes sharper with evolution. We also find that the dynamics may become non-linear for certain parameters, pointing to the necessity of a more complete analysis.", "keyphrases": ["magnetic field", "early universe", "chiral anomaly", "baryogenesis", "electroweak"]}
{"id": "1108.4688", "title": "The impact of massive neutrinos on the abundance of massive clusters", "abstract": "We study the spherical, top-hat collapse model for a mixed dark matter model including cold dark matter (CDM) and massive neutrinos of mass scales ranging from m_nu= 0.05 to a few 0.1eV, the range of lower- and upper-bounds implied from the neutrino oscillation experiments and the cosmological constraints. To develop this model, we properly take into account relative differences between the density perturbation amplitudes of different components (radiation, baryon, CDM and neutrinos) around the top-hat CDM overdensity region assuming the adiabatic initial conditions. Furthermore, we solve the linearized Boltzmann hierarchy equations to obtain time evolution of the lineariezed neutrino perturbations, yet including the effect of nonlinear gravitational potential due to the nonlinear CDM and baryon overdensities in the late stage. We find that the presence of massive neutrinos slows down the collapse of CDM (plus baryon) overdensity, however, that the neutrinos cannot fully catch up with the the nonlinear CDM perturbation due to its large free-streaming velocity for the ranges of neutrino masses and halo masses we consider. We find that, just like CDM models, the collapse time of CDM overdensity is well monitored by the linear-theory extrapolated overdensity of CDM plus baryon perturbation, smoothed with a given halo mass scale, if taking into account the suppression effect of the massive neutrinos on the linear growth rate. Using these findings, we argue that the presence of massive neutrinos of mass scales 0.05 or 0.1eV may cause a significant decrease in the abundance of massive halos compared to the model without the massive neutrinos; e.g., by 25 respectively, for halos with 10^15Ms and at z=1.", "keyphrases": ["massive neutrino", "cold dark matter", "baryon"]}
{"id": "1811.00197", "title": "Probing the Universe's baryons with fast radio bursts", "abstract": "Fast radio bursts were discovered just over a decade ago, and their origin remains a mystery. Despite this, astronomers have been using them to investigate the matter through which their bright, impulsive radiation travels.", "keyphrases": ["universe", "baryon", "fast radio burst", "astronomy"]}
{"id": "1109.0710", "title": "Super-massive binary black holes and emission lines in active galactic nuclei", "abstract": "The broad emission spectral lines emitted from AGNs are our main probe of the geometry and physics of the broad line region (BLR) close to the SMBH. There is a group of AGNs that emits very broad and complex line profiles, showing two displaced peaks, one blueshifted and one redshifted from the systemic velocity defined by the narrow lines, or a single such peak. It has been proposed that such line shapes could indicate a supermassive binary black hole (SMB) system. We discuss here how the presence of an SMB will affect the BLRs of AGNs and what the observational consequences might be. We review previous claims of SMBs based on broad line profiles and find that they may have non-SMB explanations as a consequence of a complex BLR structure. Because of these effects it is very hard to put limits on the number of SMBs from broad line profiles. It is still possible, however, that unusual broad line profiles in combination with other observational effects (line ratios, quasi-periodical oscillations, spectropolarimetry, etc.) could be used for SMBs detection. Some narrow lines (e.g., [O III]) in some AGNs show a double-peaked profile. Such profiles can be caused by streams in the Narrow Line Region (NLR), but may also indicate the presence of a kilo-parsec scale mergers. A few objects indicated as double-peaked narrow line emitters are confirmed as kpc-scale margers, but double-peaked narrow line profiles are mostly caused by the complex NLR geometry. We briefly discuss the expected line profile of broad Fe K\u03b1 that probably originated in the accretion disk(s) around SMBs. Finally we consider rare configurations where a SMB system might be gravitationally lensed by a foreground galaxy, and discuss the expected line profiles in these systems.", "keyphrases": ["black hole", "emission line", "galactic nucleus"]}
{"id": "1010.0407", "title": "Observational constraints on Galileon cosmology", "abstract": "We study the cosmology of a covariant Galileon field with five covariant Lagrangians and confront this theory with the most recent cosmological probes: the type Ia supernovae data (Constitution and Union2 sets), cosmic microwave background (WMAP7) and the baryon acoustic oscillations (SDSS7). In the Galileon cosmology with a late-time de Sitter attractor, there is a tracker that attracts solutions with different initial conditions to a common trajectory. Including the cosmic curvature K, we place observational constraints on two distinct cases: (i) the tracker, and (ii) the generic solutions to the equations of motion. We find that the tracker solution can be consistent with the individual observational data, but it is disfavored by the combined data analysis. The generic solutions fare quite well when a non-zero curvature parameter is taken into account, but the Akaike and Bayesian information criteria show that they are not particularly favored over the LCDM model.", "keyphrases": ["galileon cosmology", "baryon acoustic oscillation", "observational constraint"]}
{"id": "1011.2646", "title": "Real-time Cosmology", "abstract": "In recent years the possibility of measuring the temporal change of radial and transverse position of sources in the sky in real time have become conceivable thanks to the thoroughly improved technique applied to new astrometric and spectroscopic experiments, leading to the research domain we call Real-time cosmology. We review for the first time great part of the work done in this field, analysing both the theoretical framework and some endeavor to foresee the observational strategies and their capability to constrain models. We firstly focus on real time measurements of the overall redshift drift and angular separation shift in distant source, able to trace background cosmic expansion and large scale anisotropy, respectively. We then examine the possibility of employing the same kind of observations to probe peculiar and proper acceleration in clustered systems and therefore the gravitational potential. The last two sections are devoted to the short time future change of the cosmic microwave background, as well as to the temporal shift of the temperature anisotropy power spectrum and maps. We conclude revisiting in this context the effort made to forecast the power of upcoming experiments like CODEX, GAIA and PLANCK in providing these new observational tools.", "keyphrases": ["redshift", "real-time cosmology", "universe", "e-elt", "timescale"]}
{"id": "1208.2669", "title": "Multiscale magnetic underdense regions on the solar surface: Granular and Mesogranular scales", "abstract": "The Sun is a non-equilibrium dissipative system subjected to an energy flow which originates in its core. Convective overshooting motions create temperature and velocity structures which show a temporal and spatial evolution. As a result, photospheric structures are generally considered to be the direct manifestation of convective plasma motions. The plasma flows on the photosphere govern the motion of single magnetic elements. These elements are arranged in typical patterns which are observed as a variety of multiscale magnetic patterns. High resolution magnetograms of quiet solar surface revealed the presence of magnetic underdense regions in the solar photosphere, commonly called voids, which may be considered a signature of the underlying convective structure. The analysis of such patterns paves the way for the investigation of all turbulent convective scales from granular to global. In order to address the question of magnetic structures driven by turbulent convection at granular and mesogranular scales we used a \"voids\" detection method. The computed voids distribution shows an exponential behavior at scales between 2 and 10 Mm and the absence of features at 5-10 Mm mesogranular scales. The absence of preferred scales of organization in the 2-10 Mm range supports the multiscale nature of flows on the solar surface and the absence of a mesogranular convective scale.", "keyphrases": ["magnetic underdense region", "solar surface", "mesogranular scale"]}
{"id": "1707.01950", "title": "Mufasa:The strength and evolution of galaxy conformity in various tracers", "abstract": "We investigate galaxy conformity using the Mufasa cosmological hydrodynamical simulation. We show a bimodal distribution in galaxy colour with radius, albeit with too many low-mass quenched satellite galaxies compared to observations. Mufasa produces conformity in observed properties such as colour, sSFR, and HI content; i.e neighbouring galaxies have similar properties. We see analogous trends in other properties such as in environment, stellar age, H_2 content, and metallicity. We introduce quantifying conformity using S(R), measuring the relative difference in upper and lower quartile properties of the neighbours. We show that low-mass and non-quenched haloes have weak conformity (S(R)\u2264 0.5) extending to large projected radii R in all properties, while high-mass and quenched haloes have strong conformity (S(R)\u223c 1) that diminishes rapidly with R and disappears at R\u2265 1 Mpc. S(R) is strongest for environment in low-mass haloes, and sSFR (or colour) in high-mass haloes, and is dominated by one-halo conformity with the exception of HI in small haloes. Metallicity shows a curious anti-conformity in massive haloes. Tracking the evolution of conformity for z=0 galaxies back in time shows that conformity broadly emerges as a late-time (z\u2264 1) phenomenon. However, for fixed halo mass bins, conformity is fairly constant with redshift out to z\u2265 2. These trends are consistent with the idea that strong conformity only emerges once haloes grow above Mufasa's quenching mass scale of \u223c 10^12M_\u2299. A quantitative measure of conformity in various properties, along with its evolution, thus represents a new and stringent test of the impact of quenching on environment within current galaxy formation models.", "keyphrases": ["galaxy conformity", "tracer", "hydrodynamical simulation"]}
{"id": "1410.2511", "title": "Torsional oscillations of neutron stars in scalar-tensor theory of gravity", "abstract": "We study torsional oscillations of neutron stars in the scalar-tensor theory of gravity using the relativistic Cowling approximation. We compute unperturbed neutron star models adopting realistic equations of state for the neutron star's core and crust. For scalar-tensor theories that allow for spontaneous scalarization, the crust thickness can be significantly smaller than in general relativity. We derive the perturbation equation describing torsional oscillations in scalar-tensor theory, and we solve the corresponding eigenvalue problem to find the oscillation frequencies. The fundamental mode (overtone) frequencies become smaller (larger) than in general relativity for scalarized stellar models. Torsional oscillation frequencies may yield information on the crust microphysics if microphysics effects are not degenerate with strong-gravity effects, such as those due to scalarization. To address this issue, we consider two different models for the equation of state of the crust and we look at the effects of electron screening. The effect of scalarization on torsional oscillation frequencies turns out to be smaller than uncertainties in the microphysics for all spontaneous scalarization models allowed by binary pulsar observations. Our study shows that the observation of quasi-periodic oscillations (QPOs) following giant flares can be used to constrain the microphysics of neutron star crusts, whether spontaneous scalarization occurs or not.", "keyphrases": ["neutron star", "scalar-tensor theory", "torsional oscillation"]}
{"id": "1112.2018", "title": "The nuclear symmetry energy, the inner crust, and global neutron star modeling", "abstract": "The structure and composition of the inner crust of neutron stars, as well as global stellar properties such as radius and moment of inertia, have been shown to correlate with parameters characterizing the symmetry energy of nuclear matter such as its magnitude J and density dependence L at saturation density. It is thus mutually beneficial to nuclear physicists and astrophysicists to examine the combined effects of such correlations on potential neutron star observables in the light of recent experimental and theoretical constraints on J, L, and relationships between them. We review some basic correlations between these nuclear and astrophysical observables, and illustrate the impact of recent progress in constraining the J-L parameter space on the composition of the inner crust, crust-core transition density and pressure, and extent of the hypothesized pasta region. We use a simple compressible liquid drop model in conjunction with a simple model of nuclear matter which allows for independent, smooth, variation of the J and L. We extend the model into the core using the same nuclear matter model to explore the effects on global crust and core properties, and on potential observables such as crust oscillation frequencies and mechanically supported crust deformation. Throughout we illustrate the importance of the relationship between J and L implicit in a particular model of nuclear matter to the predictions of neutron star properties.", "keyphrases": ["symmetry energy", "inner crust", "nuclear matter", "heavy-ion collision"]}
{"id": "1509.08767", "title": "Dark matter direct-detection experiments", "abstract": "In the past decades, several detector technologies have been developed with the quest to directly detect dark matter interactions and to test one of the most important unsolved questions in modern physics. The sensitivity of these experiments has improved with a tremendous speed due to a constant development of the detectors and analysis methods, proving uniquely suited devices to solve the dark matter puzzle, as all other discovery strategies can only indirectly infer its existence. Despite the overwhelming evidence for dark matter from cosmological indications at small and large scales, a clear evidence for a particle explaining these observations remains absent. This review summarises the status of direct dark matter searches, focussing on the detector technologies used to directly detect a dark matter particle producing recoil energies in the keV energy scale. The phenomenological signal expectations, main background sources, statistical treatment of data and calibration strategies are discussed.", "keyphrases": ["matter particle", "recoil energy", "dark matter", "direct detection", "scattering"]}
{"id": "0911.4718", "title": "Testing Properties of the Galactic Center Black Hole Using Stellar Orbits", "abstract": "The spin and quadrupole moment of the supermassive black hole at the Galactic center can in principle be measured via astrometric monitoring of stars orbiting at milliparsec (mpc) distances, allowing tests of general relativistic \"no-hair\" theorems (Will 2008). One complicating factor is the presence of perturbations from other stars, which may induce orbital precession of the same order of magnitude as that due to general relativistic effects. The expected number of stars in this region is small enough that full N-body simulations can be carried out. We present the results of a comprehensive set of such simulations, which include a post-Newtonian treatment of spin-orbit effects. A number of possible models for the distribution of stars and stellar remnants are considered. We find that stellar perturbations are likely to obscure the signal due to frame-dragging for stars beyond 0.5 mpc from the black hole, while measurement of the quadrupole moment is likely to require observation of stars inside 0.2 mpc. A high fraction of stellar remnants, e.g. 10-Solar-mass black holes, in this region would make tests of GR problematic at all radii. We discuss the possibility of separating the effects of stellar perturbations from those due to GR.", "keyphrases": ["galactic center", "black hole", "star"]}
{"id": "1005.0141", "title": "Relativistic Radiation Mediated Shocks", "abstract": "The structure of relativistic radiation mediated shocks (RRMS) propagating into a cold electron-proton plasma is calculated and analyzed. A qualitative discussion of the physics of relativistic and non relativistic shocks, including order of magnitude estimates for the relevant temperature and length scales, is presented. Detailed numerical solutions are derived for shock Lorentz factors \u0393_u in the range 6\u2264\u0393_u\u226430, using a novel iteration technique solving the hydrodynamics and radiation transport equations (the protons, electrons and positrons are argued to be coupled by collective plasma processes and are treated as a fluid). The shock transition (deceleration) region, where the Lorentz factor \u0393 drops from \u0393_u to \u223c 1, is characterized by high plasma temperatures T\u223c\u0393 m_ec^2 and highly anisotropic radiation, with characteristic shock-frame energy of upstream and downstream going photons of a few \u00d7 m_ec^2 and \u223c\u0393^2 m_ec^2, respectively.Photon scattering is dominated by e^\u00b1 pairs, with pair to proton density ratio reaching \u224810^2\u0393_u. The width of the deceleration region, in terms of Thomson optical depths for upstream going photons, is large, \u0394\u03c4\u223c\u0393_u^2 (\u0394\u03c4\u223c1 neglecting the contribution of pairs) due to Klein Nishina suppression of the scattering cross section. A high energy photon component, narrowly beamed in the downstream direction, with a nearly flat power-law like spectrum, \u03bd I_\u03bd\u221d\u03bd^0, and an energy cutoff at \u223c\u0393_u^2 m_ec^2 carries a fair fraction of the energy flux at the end of the deceleration region. An approximate analytic model of RRMS, reproducing the main features of the numerical results, is provided.", "keyphrases": ["shock", "cold electron-proton plasma", "relativistic radiation"]}
{"id": "1111.1787", "title": "Dark-Matter Admixed Neutron Stars", "abstract": "We study the hydrostatic equilibrium configuration of an admixture of degenerate dark matter and normal nuclear matter by using a general relativistic two-fluid formalism. We consider non- self-annihilating dark matter particles of mass 1 GeV. The mass-radius relations and moments of inertia of these dark-matter admixed neutron stars are investigated and the stability of these stars is demonstrated by performing a radial perturbation analysis. We find a new class of compact stars which consists of a small normal matter core with radius of a few km embedded in a ten-kilometer- sized dark matter halo. These stellar objects may be observed as extraordinarily small neutron stars that are incompatible with realistic nuclear matter models.", "keyphrases": ["star", "dark matter", "relativistic two-fluid formalism", "compact object"]}
{"id": "1608.04403", "title": "Observable Deviations from Homogeneity in an Inhomogeneous Universe", "abstract": "How does inhomogeneity affect our interpretation of cosmological observations? It has long been wondered to what extent the observable properties of an inhomogeneous universe differ from those of a corresponding Friedman-Lemaitre-Robertson-Walker (FLRW) model, and how the inhomogeneities affect that correspondence. Here, we use numerical relativity to study the behavior of light beams traversing an inhomogeneous universe and construct the resulting Hubble diagrams. The universe that emerges exhibits an average FLRW behavior, but inhomogeneous structures contribute to deviations in observables across the observer's sky. We also investigate the relationship between angular diameter distance and the angular extent of a source, finding deviations that grow with source redshift. These departures from FLRW are important path-dependent effects with implications for using real observables in an inhomogeneous universe such as our own.", "keyphrases": ["universe", "numerical relativity", "einstein equation"]}
{"id": "1004.5349", "title": "The most massive objects in the Universe", "abstract": "We calculate the most massive object in the Universe, finding it to be a cluster of galaxies with total mass M_200=3.8e15 Msun at z=0.22, with the 1 sigma marginalized regions being 3.3e15 Msun<M<4.4e15 Msun and 0.12<z<0.36. We restrict ourselves to self-gravitating bound objects, and base our results on halo mass functions derived from N-body simulations. Since we consider the very highest mass objects, the number of candidates is expected to be small, and therefore each candidate can be extensively observed and characterized. If objects are found with excessively large masses, or insufficient objects are found near the maximum expected mass, this would be a strong indication of the failure of LambdaCDM. The expected range of the highest masses is very sensitive to redshift, providing an additional evolutionary probe of LambdaCDM. We find that the three most massive clusters in the recent SPT 178 deg^2 catalog match predictions, while XMMU J2235.3\u20132557 is roughly 3 sigma inconsistent with LambdaCDM. We discuss Abell 2163 and Abell 370 as candidates for the most massive cluster in the Universe, although uncertainties in their masses preclude definitive comparisons with theory. Our findings motivate further observations of the highest mass end of the mass function. Future surveys will explore larger volumes, and the most massive object in the Universe may be identified within the next decade. The mass distribution of the largest objects in the Universe is a potentially powerful test of LambdaCDM, probing non-Gaussianity and the behavior of gravity on large scales.", "keyphrases": ["massive object", "universe", "non-gaussianity"]}
{"id": "1509.03483", "title": "Efficient, uninformative sampling of limb-darkening coefficients for a three-parameter law", "abstract": "Stellar limb-darkening impacts a wide range of astronomical measurements. The accuracy to which it is modelled limits the accuracy in any covariant parameters of interest, such as the radius of a transiting planet. With the ever growing availability of precise observations and the importance of robust estimates of astrophysical parameters, an emerging trend has been to freely fit the limb-darkening coefficients (LDCs) describing a limb-darkening law of choice, in order to propagate our ignorance of the true intensity profile. In practice, this approach has been limited to two-parameter limb-darkening laws, such as the quadratic law, due to the relative ease of sampling the physically allowed range of LDCs. Here, we provide a highly efficient method for sampling LDCs describing a more accurate three-parameter non-linear law. We first derive analytic criteria which can quickly test if a set of LDCs are physical, although naive sampling with these criteria leads to an acceptance rate less than 1 cone-like volume, from which we are able to draw uniform samples. We show that samples drawn uniformly from the conal region are physically valid in 97.3 realizations and encompass 94.4 provide Python and Fortran code (LDC3) to sample from this region (and perform the reverse calculation) at https://github.com/davidkipping/LDC3, which also includes a subroutine to efficiently test whether a sample is physically valid or not.", "keyphrases": ["sampling", "limb-darkening coefficient", "intensity profile"]}
{"id": "1711.10256", "title": "Astrophysical Black Holes: A Compact Pedagogical Review", "abstract": "Black holes are among the most extreme objects that can be found in the Universe and an ideal laboratory for testing fundamental physics. This article will briefly review the basic properties of black holes as expected from general relativity, the main astronomical observations, and the leading astrophysical techniques to probe the strong gravity region of these objects. It is mainly intended to provide a compact introductory overview on astrophysical black holes to new students entering this research field, as well as to senior researchers working in general relativity and alternative theories of gravity and wishing to quickly learn the state of the art of astronomical observations of black holes.", "keyphrases": ["black hole", "general relativity", "astronomical observation", "accretion disk"]}
{"id": "1606.04180", "title": "From order to chaos in Earth satellite orbits", "abstract": "We consider Earth satellite orbits in the range of semi-major axes where the perturbing effects of Earth's oblateness and lunisolar gravity are of comparable order. This range covers the medium-Earth orbits (MEO) of the Global Navigation Satellite Systems and the geosynchronous orbits (GEO) of the communication satellites. We recall a secular and quadrupolar model, based on the Milankovitch vector formulation of perturbation theory, which governs the long-term orbital evolution subject to the predominant gravitational interactions. We study the global dynamics of this two-and-a-half degrees-of-freedom Hamiltonian system by means of the fast Lyapunov indicator (FLI), used in a statistical sense. Specifically, we characterize the degree of chaoticity of the action space using angle-averaged normalized FLI maps, thereby overcoming the angle dependencies of the conventional stability maps. Emphasis is placed upon the phase-space structures near secular resonances, which are of first importance to the space debris community. We confirm and quantify the transition from order to chaos in MEO, stemming from the critical inclinations, and find that highly inclined GEO orbits are particularly unstable. Despite their reputed normality, Earth satellite orbits can possess an extraordinarily rich spectrum of dynamical behaviors, and, from a mathematical perspective, have all the complications that make them very interesting candidates for testing the modern tools of chaos theory.", "keyphrases": ["chaos", "earth satellite orbit", "meo"]}
{"id": "1311.2724", "title": "The evolution of the large-scale structure of the universe: beyond the linear regime", "abstract": "These lecture notes introduce analytical tools, methods and results describing the growth of cosmological structure beyond the linear regime. The presentation is focused on the single flow regime of the Vlasov-Poisson equation describing the development of gravitational instabilities in a pressureless fluid. These notes include the introduction of diagrammatic representations of the standard perturbation theory with applications to the calculation of the so-called loop contributions to the power spectra. A large part of these notes is devoted to the exploration of the convergence properties of these terms from the contribution of both the long-wave modes and the short-wave modes. The resulting performances of the two-loop corrections of the power spectra are then presented. Finally other avenues that use different methods are explored. In particular it is shown how joint density and profile probability distribution functions can be constructed out of the multiple-variable cumulant generating functions computed at tree order.", "keyphrases": ["universe", "linear regime", "perturbation theory"]}
{"id": "1301.5315", "title": "Cosmological constraints on a decomposed Chaplygin gas", "abstract": "Any unified dark matter cosmology can be decomposed into dark matter interacting with vacuum energy, without introducing any additional degrees of freedom. We present observational constraints on an interacting vacuum plus dark energy corresponding to a generalised Chaplygin gas cosmology. We consider two distinct models for the interaction leading to either a barotropic equation of state or dark matter that follows geodesics, corresponding to a rest-frame sound speed equal to the adiabatic sound speed or zero sound speed, respectively. For the barotropic model, the most stringent constraint on \u03b1 comes from the combination of CMB+SNIa+LSS(m) gives \u03b1<5.66\u00d710^-6 at the 95 the barotropic model must be extremely close to the \u039bCDM cosmology. For the case where the dark matter follows geodesics, perturbations have zero sound speed, and CMB+SNIa+gISW then gives the much weaker constraint -0.15<\u03b1<0.26 at the 95", "keyphrases": ["chaplygin gas", "dark matter", "vacuum energy", "dark energy", "barotropic model"]}
{"id": "1205.0160", "title": "Quasi-Single Field Inflation with Large Mass", "abstract": "We study the effect of massive isocurvaton on density perturbations in quasi-single field inflation models, when the mass of the isocurvaton M becomes larger than the order of the Hubble parameter H. We analytically compute the correction to the power spectrum, leading order in coupling but exact for all values of mass. This verifies the previous numerical results for the range 0<M<3H/2 and shows that, in the large mass limit, the correction is of order H^2/M^2.", "keyphrases": ["quasi-single field inflation", "cosmological collider physics", "scalar field", "early universe", "new physics"]}
{"id": "2101.08092", "title": "An effective field theory of holographic dark energy", "abstract": "A general covariant local field theory of the holographic dark energy model is presented. It turns out the low energy effective theory of the holographic dark energy is the massive gravity theory whose graviton has 3 polarisations, including one scalar mode and two tensor modes. The Compton wavelength is the size of the future event horizon of the universe. The UV-IR correspondence in the holographic dark energy model stems from the scalar graviton's strong coupling at the energy scale that marks the breaking down of the effective field theory.", "keyphrases": ["effective field theory", "holographic dark energy", "graviton"]}
{"id": "1701.06168", "title": "Direct N-body simulations of globular clusters \u2013 III. Palomar 4 on an eccentric orbit", "abstract": "Palomar 4 is a low-density globular cluster with a current mass \u224830000 M_\u2299 in the outer halo of the Milky Way with a two-body relaxation time of the order of a Hubble time. Yet, it is strongly mass segregated and contains a stellar mass function depleted of low-mass stars. Pal 4 was either born this way or it is a result of extraordinary dynamical evolution. Since two-body relaxation cannot explain these signatures alone, enhanced mass loss through tidal shocking may have had a strong influence on Pal 4. Here, we compute a grid of direct N-body simulations to model Pal 4 on various eccentric orbits within the Milky Way potential to find likely initial conditions that reproduce its observed mass, half-light radius, stellar MF-slope and line-of-sight velocity dispersion. We find that Pal 4 is most likely orbiting on an eccentric orbit with an eccentricity of e\u2248 0.9 and pericentric distance of R_p\u22485 kpc. In this scenario, the required 3D half-mass radius at birth is similar to the average sizes of typical GCs (R_h\u22484-5 pc), while its birth mass is about M_0\u224810^5 M_\u2299. We also find a high degree of primordial mass segregation among the cluster stars, which seems to be necessary in every scenario we considered. Thus, using the tidal effect to constrain the perigalactic distance of the orbit of Pal 4, we predict that the proper motion of Pal 4 should be in the range -0.52\u2264\u03bc_\u03b4\u2264-0.38 mas yr^-1 and -0.30\u2264\u03bc_\u03b1cos\u03b4\u2264-0.15 mas yr^-1.", "keyphrases": ["globular cluster", "eccentric orbit", "direct n-body simulation"]}
{"id": "1403.5053", "title": "Neutrino masses, leptogenesis, and sterile neutrino dark matter", "abstract": "We analyze a scenario in which the lightest heavy neutrino N_1 is a dark matter candidate and the second- heaviest neutrino N_2 decays producing a lepton number. If N_1 were in thermal equilibrium, its energy density today would be much larger than that of the observed dark matter, so we consider energy injection by the decay of N_2. In this paper, we show the parameters of this scenario that give the correct abundances of dark matter and baryonic matter and also induce the observed neutrino masses. This model can explain a possible sterile neutrino dark matter signal of M_1=7 keV in the x-ray observation of x-ray multi-mirror mission.", "keyphrases": ["leptogenesis", "sterile neutrino", "dark matter candidate", "thermal equilibrium"]}
{"id": "1209.2972", "title": "Surface singularities in Eddington-inspired Born-Infeld gravity", "abstract": "Eddington-inspired Born-Infeld gravity was recently proposed as an alternative to general relativity that offers a resolution of spacetime singularities. The theory differs from Einstein's gravity only inside matter due to nondynamical degrees of freedom, and it is compatible with all current observations. We show that the theory is reminiscent of Palatini f(R) gravity and that it shares the same pathologies, such as curvature singularities at the surface of polytropic stars and unacceptable Newtonian limit. This casts serious doubts on its viability.", "keyphrases": ["eddington-inspired born-infeld gravity", "curvature singularity", "surface"]}
{"id": "0909.2644", "title": "The Runts of the Litter: Why planets formed through gravitational instability can only be failed binary stars", "abstract": "Recent direct imaging discoveries suggest a new class of massive, distant planets around A stars. These widely separated giants have been interpreted as signs of planet formation driven by gravitational instability, but the viability of this mechanism is not clear cut. In this paper, we first discuss the local requirements for fragmentation and the initial fragment mass scales. We then consider whether the fragment's subsequent growth can be terminated within the planetary mass regime. Finally, we place disks in the larger context of star formation and disk evolution models. We find that in order for gravitational instability to produce planets, disks must be atypically cold in order to reduce the initial fragment mass. In addition, fragmentation must occur during a narrow window of disk evolution, after infall has mostly ceased, but while the disk is still sufficiently massive to undergo gravitational instability. Under more typical conditions, disk-born objects will likely grow well above the deuterium burning planetary mass limit. We conclude that if planets are formed by gravitational instability, they must be the low mass tail of the distribution of disk-born companions. To validate this theory, on-going direct imaging surveys must find a greater abundance of brown dwarf and M-star companions to A-stars. Their absence would suggest planet formation by a different mechanism such as core accretion, which is consistent with the debris disks detected in these systems.", "keyphrases": ["star", "brown dwarf", "circumstellar disk"]}
{"id": "1910.07525", "title": "Minimal Warm Inflation", "abstract": "Slow-roll inflation is a successful paradigm. However we find that even a small coupling of the inflaton to other light fields can dramatically alter the dynamics and predictions of inflation. As an example, the inflaton can generically have an axion-like coupling to gauge bosons. Even relatively small couplings will automatically induce a thermal bath during inflation. The thermal friction from this bath can easily be stronger than Hubble friction, significantly altering the usual predictions of any particular inflaton potential. Thermal effects suppress the tensor-to-scalar ratio r significantly, and predict unique non-gaussianities. This axion-like coupling provides a minimal model of warm inflation which avoids the usual problem of thermal backreaction on the inflaton potential. As a specific example, we find that hybrid inflation with this axion-like coupling can easily fit the current cosmological data.", "keyphrases": ["bath", "minimal warm inflation", "mwi", "dissipative regime"]}
{"id": "1809.08735", "title": "Dark energy in Horndeski theories after GW170817: A review", "abstract": "The gravitational-wave event GW170817 from a binary neutron star merger together with the electromagnetic counterpart showed that the speed of gravitational waves c_t is very close to that of light for the redshift z<0.009. This places tight constraints on dark energy models constructed in the framework of modified gravitational theories. We review models of the late-time cosmic acceleration in scalar-tensor theories with second-order equations of motion (dubbed Horndeski theories) by paying particular attention to the evolution of dark energy equation of state and observables relevant to the cosmic growth history. We provide a gauge-ready formulation of scalar perturbations in full Horndeski theories and estimate observables associated with the evolution of large-scale structures, cosmic microwave background, and weak lensing by employing a so-called quasi-static approximation for the modes deep inside the sound horizon. In light of the recent observational bound of c_t, we also classify surviving dark energy models into four classes depending on different structure-formation patterns and discuss how they can be observationally distinguished from each other. In particular, the nonminimally coupled theories in which the scalar field \u03d5 has a coupling with the Ricci scalar R of the form G_4(\u03d5) R, including f(R) gravity, can be tightly constrained not only from the cosmic expansion and growth histories but also from the variation of screened gravitational couplings. The cross correlation of integrated Sachs-Wolfe signal with galaxy distributions can be a key observable for placing bounds on the relative ratio of cubic Galileon density to total dark energy density. The dawn of gravitational-wave astronomy will open up a new window to constrain nonminimally coupled theories further by the modified luminosity distance of tensor perturbations.", "keyphrases": ["horndeski theory", "late-time cosmic acceleration", "gravitational coupling", "dark energy", "cosmology"]}
{"id": "2110.13508", "title": "Gauge-invariant perturbation theory on the Schwarzschild background spacetime Part I : \u2013 Formulation and odd-mode perturbations", "abstract": "This is the Part I paper of our series of full papers on a gauge-invariant linear perturbation theory on the Schwarzschild background spacetime which was briefly reported in our short papers [K. Nakamura, Class. Quantum Grav. 38 (2021), 145010; K. Nakamura, Letters in High Energy Physics 2021 (2021), 215.]. We first review our general framework of the gauge-invariant perturbation theory, which can be easily extended to the higher-order perturbation theory. When we apply this general framework to perturbations on the Schwarzschild background spacetime, a gauge-invariant treatments of l=0,1 mode perturbations are required. On the other hand, in the current consensus on the perturbations of the Schwarzschild spacetime, gauge-invariant treatments for l=0,1 modes are difficult if we keep the reconstruction of the original metric perturbations in our mind. Based on this situation, we propose a strategy of a gauge-invariant treatments of l=0,1 mode perturbations through the decomposition of the metric perturbations by singular harmonic functions at once and the regularization of this singularity through the imposition of the boundary conditions to the Einstein equations. Following this proposal, we derive the linearized Einstein equations for any modes of l\u2265 0 in a gauge-invariant manner. We discuss the solutions to the odd-mode perturbation equations in the linearized Einstein equations and show that these perturbations include the Kerr parameter perturbation in these odd-mode perturbation, which is physically reasonable.", "keyphrases": ["odd-mode perturbation", "einstein equation", "gravitation"]}
{"id": "1303.1349", "title": "Improved Primordial Non-Gaussianity Constraints from Measurements of Galaxy Clustering and the Integrated Sachs-Wolfe Effect", "abstract": "We present the strongest robust constraints on primordial non-Gaussianity (PNG) from currently available galaxy surveys, combining large-scale clustering measurements and their cross-correlations with the cosmic microwave background. We update the data sets used by Giannantonio et al. (2012), and broaden that analysis to include the full set of two-point correlation functions between all surveys. In order to obtain the most reliable constraints on PNG, we advocate the use of the cross-correlations between the catalogs as a robust estimator and we perform an extended analysis of the possible systematics to reduce their impact on the results. To minimize the impact of stellar contamination in our luminous red galaxy (LRG) sample, we use the recent Baryon Oscillations Spectroscopic Survey catalog of Ross et al. (2011). We also find evidence for a new systematic in the NVSS radio galaxy survey similar to, but smaller than, the known declination-dependent issue; this is difficult to remove without affecting the inferred PNG signal, and thus we do not include the NVSS auto-correlation function in our analyses. We find no evidence of primordial non-Gaussianity; for the local-type configuration we obtain for the skewness parameter -36 < f_NL < 45 at 95 when using the most conservative part of our data set, improving previous results; we also find no evidence for significant kurtosis, parameterized by g_NL. In addition to PNG, we simultaneously constrain dark energy and find that it is required with a form consistent with a cosmological constant.", "keyphrases": ["non-gaussianity", "galaxy survey", "bias"]}
{"id": "1605.04915", "title": "Maximized ExoEarth Candidate Yields for Starshades", "abstract": "The design and scale of a future mission to directly image and characterize potentially Earth-like planets will be impacted, to some degree, by the expected yield of such planets. Recent efforts to increase the estimated yields, by creating observation plans optimized for the detection and characterization of Earth-twins, have focused solely on coronagraphic instruments; starshade-based missions could benefit from a similar analysis. Here we explore how to prioritize observations for a starshade given the limiting resources of both fuel and time, present analytic expressions to estimate fuel use, and provide efficient numerical techniques for maximizing the yield of starshades. We implemented these techniques to create an approximate design reference mission code for starshades and used this code to investigate how exoEarth candidate yield responds to changes in mission, instrument, and astrophysical parameters for missions with a single starshade. We find that a starshade mission operates most efficiently somewhere between the fuel- and exposure-time limited regimes, and as a result, is less sensitive to photometric noise sources as well as parameters controlling the photon collection rate in comparison to a coronagraph. We produced optimistic yield curves for starshades, assuming our optimized observation plans are schedulable and future starshades are not thrust-limited. Given these yield curves, detecting and characterizing several dozen exoEarth candidates requires either multiple starshades or an eta_Earth > 0.3.", "keyphrases": ["exoearth candidate yield", "starshade", "design"]}
{"id": "1004.3426", "title": "Terzan 5: an alternative interpretation for the split horizontal branch", "abstract": "We consider the horizontal branch (HB) of the Globular Cluster Terzan 5, recently shown to be split into two parts, the fainter one (delta M_K 0.3mag) having a lower metallicity than the more luminous. Both features show that it contains at least two stellar populations. The separation in magnitude has been ascribed to an age difference of 6 Gyr and interpreted as the result of an atypical evolutionary history for this cluster. We show that the observed HB morphology is also consistent with a model in which the bright HB is composed of second generation stars that are metal enriched and with a helium mass fraction larger (by delta Y 0.07) than that of first generation stars populating the fainter part of the HB. Terzan 5 would therefore be anomalous, compared to most \"normal\" clusters hosting multiple populations, only because its second generation is strongly contaminated by supernova ejecta; the previously proposed prolonged period of star formation, however, is not required. The iron enrichment of the bright HB can be ascribed either to contamination from Type Ia supernova ejecta of the low-iron, helium rich, ejecta of the massive asympotic giant branch stars of the cluster, or to its mixing with gas, accreting on the cluster from the environment, that has been subject to fast metal enrichment due to its proximity with the galactic bulge. The model here proposed requires only a small age difference, of 100Myr.", "keyphrases": ["horizontal branch", "evolutionary history", "terzan"]}
{"id": "1703.05139", "title": "Strongly Coupled Dark Energy with Warm dark matter vs. LCDM", "abstract": "Cosmologies including strongly Coupled (SC) Dark Energy (DE) and Warm dark matter (SCDEW) are based on a conformally invariant (CI) attractor solution modifying the early radiative expansion. Then, aside of radiation, a kinetic field \u03a6 and a DM component account for a stationary fraction, \u223c 1 %, of the total energy. Most SCDEW predictions are hardly distinguishable from LCDM, while SCDEW alleviates quite a few LCDM conceptual problems, as well as its difficulties to meet data below the average galaxy scale. The CI expansion begins at the inflation end, when \u03a6 (future DE) possibly plays a role in reheating, and ends at the Higgs' scale. Afterwards, a number of viable options is open, allowing for the transition from the CI expansion to the present Universe. In this paper: (i) We show how the attractor is recovered when the spin degrees of freedom decreases. (ii) We perform a detailed comparison of CMB anisotropy and polarization spectra for SCDEW and LCDM, including tensor components, finding negligible discrepancies. (iii) Linear spectra exhibit a greater parameter dependence at large k's, but are still consistent with data for suitable parameter choices. (iv) We also compare previous simulation results with fresh data on galaxy concentration. Finally, (v) we outline numerical difficulties at high k. This motivates a second related paper, where such problems are treated in a quantitative way.", "keyphrases": ["dark energy", "dark matter", "cosmology"]}
{"id": "1102.3812", "title": "On the relative abundance of LiH and LiH+ molecules in the early universe: new results from quantum reactions", "abstract": "The relative efficiencies of the chemical pathways that can lead to the destruction of LiH and LiH+ molecules, conjectured to be present in the primordial gas and to control molecular cooling processes in the gravitational collapse of the post-recombination era, are revisited by using accurate quantum calculations for the several reactions involved. The new rates are employed to survey the behavior of the relative abundance of these molecules at redshifts of interest for early universe conditions. We find significant differences with respect to previous calculations, the present ones yielding LIH abundances higher than LiH+ at all redshifts.", "keyphrases": ["relative abundance", "lih", "lih+ molecule"]}
{"id": "1610.09852", "title": "Physical effects involved in the measurements of neutrino masses with future cosmological data", "abstract": "Future Cosmic Microwave Background experiments together with upcoming galaxy and 21-cm surveys will provide extremely accurate measurements of different cosmological observables located at different epochs of the cosmic history. The new data will be able to constrain the neutrino mass sum with the best precision ever. In order to exploit the complementarity of the different redshift probes, a deep understanding of the physical effects driving the impact of massive neutrinos on CMB and large scale structures is required. The goal of this work is to describe these effects, assuming a summed neutrino mass close to its minimum allowed value. We find that parameter degeneracies can be removed by appropriate combinations, leading to robust and model independent constraints. A joint forecast of the sensitivity of Euclid and DESI surveys together with a CORE-like CMB experiment leads to a 1\u03c3 uncertainty of 14 meV on the summed neutrino mass. However this particular combination gives rise to a peculiar degeneracy between M_\u03bd and the optical depth at reionization. Independent constraints from 21-cm surveys can break this degeneracy and decrease the 1\u03c3 uncertainty down to 12 meV.", "keyphrases": ["neutrino masse", "future cosmological data", "cosmology", "cosmic microwave background"]}
{"id": "2005.10543", "title": "Neutron stars with large quark cores", "abstract": "We describe charge-neutral neutron star matter in \u03b2-equilibrium using hybrid equations of state, where a first-order phase transition from hadronic to quark matter is realized. The hadronic matter is described in a model-independent way by a Taylor expansion around saturation density n_0, while the three-flavor NJL model is used for the quark matter. Exploring the present uncertainty on the empirical parameters of nuclear matter and the parameter space of the NJL model, we construct two datasets of thermodynamically consistent and causal hybrid EoSs, compatible with astrophysical observations. We conclude that, to sustain a considerable quark core size, the intensity of the phase transition from hadron to quark matter cannot be strong, having a energy density gap below 200 MeV/fm^3, and must occur at baryon densities not above four times the saturation density. A non zero but not too strong quark vector-isoscalar term and a weak vector isovector quark term are required. Large quark cores carrying almost half of the star mass are possible inside neutron stars with a maximum mass \u2248 2.2 M_\u2299. To get a considerable number of hybrid EoS predicting quark matter already inside neutron stars with a mass \u223c 1.4 M_\u2299, we require that the onset of quarks occurs in the range 1.3n_0 and 2.5n_0. Neutron stars with large quark cores corresponding to more than one fourth of the total star mass, are possible if the energy density gap and the pressure at transition are below 100 MeV/fm^3. However, under these constraints, the maximum neutron star mass is limited to \u2272 2.06 M_\u2299. No strong signatures from quark matter were found on the radius and the tidal deformability for neutron star masses below 1.8 M_\u2299.", "keyphrases": ["quark core", "three-flavor njl model", "neutron"]}
{"id": "1405.6575", "title": "X-ray reverberation around accreting black holes", "abstract": "Luminous accreting stellar mass and supermassive black holes produce power-law continuum X-ray emission from a compact central corona. Reverberation time lags occur due to light travel time-delays between changes in the direct coronal emission and corresponding variations in its reflection from the accretion flow. Reverberation is detectable using light curves made in different X-ray energy bands, since the direct and reflected components have different spectral shapes. Larger, lower frequency, lags are also seen and are identified with propagation of fluctuations through the accretion flow and associated corona. We review the evidence for X-ray reverberation in active galactic nuclei and black hole X-ray binaries, showing how it can be best measured and how it may be modelled. The timescales and energy-dependence of the high frequency reverberation lags show that much of the signal is originating from very close to the black hole in some objects, within a few gravitational radii of the event horizon. We consider how these signals can be studied in the future to carry out X-ray reverberation mapping of the regions closest to black holes.", "keyphrases": ["black hole", "accretion flow", "x-ray reverberation"]}
{"id": "1503.04162", "title": "Generation of the magnetic helicity in a neutron star driven by the electroweak electron-nucleon interaction", "abstract": "We study the instability of magnetic fields in a neutron star core driven by the parity violating part of the electron-nucleon interaction in the Standard Model. Assuming a seed field of the order 10^12G, that is a common value for pulsars, one obtains its amplification due to such a novel mechanism by about five orders of magnitude, up to 10^17G, at time scales \u223c (10^3 - 10^5)yr. This effect is suggested to be a possible explanation of the origin of the strongest magnetic fields observed in magnetars. The growth of a seed magnetic field energy density is stipulated by the corresponding growth of the magnetic helicity density due to the presence of the anomalous electric current in the Maxwell equation. Such an anomaly is the sum of the two competitive effects: (i) the chiral magnetic effect driven by the difference of chemical potentials for the right and left handed massless electrons and (ii) constant chiral electroweak electron-nucleon interaction term, which has the polarization origin and depends on the constant neutron density in a neutron star core. The remarkable issue for the decisive role of the magnetic helicity evolution in the suggested mechanism is the arbitrariness of an initial magnetic helicity including the case of non-helical fields from the beginning. The tendency of the magnetic helicity density to the maximal helicity case at large evolution times provides the growth of a seed magnetic field to the strongest magnetic fields in astrophysics.", "keyphrases": ["magnetic helicity", "neutron star", "electron-nucleon interaction", "magnetic field instability", "electroweak interaction"]}
{"id": "2011.10288", "title": "Retrograde Polish Doughnuts around Boson Stars", "abstract": "We investigate Polish doughnuts with a uniform constant specific angular momentum distribution in the space-times of rotating boson stars. In such space-times thick tori can exhibit unique features not present in Kerr space-times. For instance, in the context of retrograde tori, they may possess two centers connected or not by a cusp. Rotating boson stars also feature a static ring, neither present in Kerr space-times. This static ring consists of static orbits, where particles are at rest with respect to a zero angular momentum observer at infinity. Here we show that the presence of a static ring allows for an associated static surface of a retrograde thick torus, where inside the static surface the fluid moves in prograde direction. We classify the retrograde Polish doughnuts and present several specific examples.", "keyphrases": ["boson star", "static ring", "orbit"]}
{"id": "1709.08482", "title": "On magnetic field amplification and particle acceleration near non-relativistic astrophysical shocks: Particles in MHD Cells simulations", "abstract": "We present simulations of magnetized astrophysical shocks taking into account the interplay between the thermal plasma of the shock and supra-thermal particles. Such interaction is depicted by combining a grid-based magneto-hydrodynamics description of the thermal fluid with particle in cell techniques devoted to the dynamics of supra-thermal particles. This approach, which incorporates the use of adaptive mesh refinement features, is potentially a key to simulate astrophysical systems on spatial scales that are beyond the reach of pure particle-in-cell simulations. We consider in this study non-relativistic shocks with various Alfvenic Mach numbers and magnetic field obliquity. We recover all the features of both magnetic field amplification and particle acceleration from previous studies when the magnetic field is parallel to the normal to the shock. In contrast with previous particle-in-cell-hybrid simulations, we find that particle acceleration and magnetic field amplification also occur when the magnetic field is oblique to the normal to the shock but on larger timescales than in the parallel case. We show that in our simulations, the supra-thermal particles are experiencing acceleration thanks to a pre-heating process of the particle similar to a shock drift acceleration leading to the corrugation of the shock front. Such oscillations of the shock front and the magnetic field locally help the particles to enter the upstream region and to initiate a non-resonant streaming instability and finally to induce diffuse particle acceleration.", "keyphrases": ["magnetic field amplification", "particle acceleration", "astrophysical shock"]}
{"id": "2010.02230", "title": "The galaxy power spectrum take on spatial curvature and cosmic concordance", "abstract": "The concordance of the \u039bCDM cosmological model in light of current observations has been the subject of an intense debate in recent months. The 2018 Planck Cosmic Microwave Background (CMB) temperature anisotropy power spectrum measurements appear at face value to favour a spatially closed Universe with curvature parameter \u03a9_K<0. This preference disappears if Baryon Acoustic Oscillation (BAO) measurements are combined with Planck data to break the geometrical degeneracy, although the reliability of this combination has been questioned due to the strong tension present between the two datasets when assuming a curved Universe. Here, we approach this issue from yet another point of view, using measurements of the full-shape (FS) galaxy power spectrum, P(k), from the Baryon Oscillation Spectroscopic Survey DR12 CMASS sample. By combining Planck data with FS measurements, we break the geometrical degeneracy and find \u03a9_K=0.0023 \u00b1 0.0028. This constrains the Universe to be spatially flat to sub-percent precision, in excellent agreement with results obtained using BAO measurements. However, as with BAO, the overall increase in the best-fit \u03c7^2 suggests a similar level of tension between Planck and P(k) under the assumption of a curved Universe. While the debate on spatial curvature and the concordance between cosmological datasets remains open, our results provide new perspectives on the issue, highlighting the crucial role of FS measurements in the era of precision cosmology.", "keyphrases": ["spatial curvature", "concordance", "cosmological model", "closed universe"]}
{"id": "1106.4341", "title": "Mantle Convection, Plate Tectonics, and Volcanism on Hot Exo-Earths", "abstract": "Recently discovered exoplanets on close-in orbits should have surface temperatures of 100's to 1000's of K. They are likely tidally locked and synchronously rotating around their parent stars and, if an atmosphere is absent, have surface temperature contrasts of many 100's to 1000's K between permanent day and night sides. We investigated the effect of elevated surface temperature and strong surface temperature contrasts for Earth-mass planets on the (i) pattern of mantle convection, (ii) tectonic regime, and (iii) rate and distribution of partial melting, using numerical simulations of mantle convection with a composite viscous/pseudo-plastic rheology. Our simulations indicate that, if a close-in rocky exoplanet lacks an atmosphere to redistribute heat, a > 400 K surface temperature contrast can maintain an asymmetric degree 1 pattern of mantle convection in which the surface of the planet moves preferentially toward subduction zones on the cold night side. The planetary surface features a hemispheric dichotomy, with plate-like tectonics on the night side and a continuously evolving mobile lid day side with diffuse surface deformation and vigorous volcanism. If volcanic outgassing establishes an atmosphere and redistributes heat, plate tectonics is globally replaced by diffuse surface deformation and volcanism accelerates and becomes distributed more uniformly across the planetary surface.", "keyphrases": ["plate tectonic", "volcanism", "mantle convection"]}
{"id": "1710.02417", "title": "Holographic dark energy: constraints on the interaction from diverse observational data sets", "abstract": "The present work deals with holographic dark energy models with Hubble horizon as the infra-red cut-off. The interaction rate between dark energy and dark matter has been reconstructed with three different choices of the interaction term. It is shown that the coupling parameter of the interaction term should evolve with redshift to allow the successful transition from decelerated to accelerated phase of expansion. Constraints on the model parameters are obtained from Markov Chain Monte Carlo (MCMC) analysis using the supernova distance modulus data and observational measurements of the Hubble parameter. Results show that the model with the coupling parameter increasing with redshift (z) or equivalently decreasing with the evolution, are ruled out. On the other hand, coupling parameters, increasing or slowly varying with the evolution, are consistent with the observed evolution scenario. A Bayesian evidence calculation has been carried out for statistical selection of the reconstructed models. Though the kinematical parameters are well behaved for these models, the physical variables which determine the nature of the components in the matter sector, are not at all realistic. We have concluded that the existence of spatial curvature is essential for this particular type of dark energy models.", "keyphrases": ["dark energy", "holographic dark energy", "cosmology"]}
{"id": "0910.5134", "title": "Stochastic gravitational waves from a new type of modified Chaplygin gas", "abstract": "We propose a new scenario for the early universe where there is a smooth transition between an early de Sitter-like phase and a radiation dominated era. In this model, the matter content is modelled by a new type of generalised Chaplygin gas for the early universe, with an underlying scalar field description. We study the gravitational waves generated by the quantum fluctuations. In particular, we calculate the gravitational wave power spectrum, as it would be measured today, following the method of the Bogoliubov coefficients. We show that the high frequencies region of the spectrum depends strongly on one of the parameters of the model. On the other hand, we use the number of e-folds, along with the power spectra and spectral index of the scalar perturbations, to constrain the model observationally.", "keyphrases": ["gravitational wave", "chaplygin gas", "early universe", "scalar field description"]}
{"id": "1303.3028", "title": "Stellar Multiplicity", "abstract": "Stellar multiplicity is an ubiquitous outcome of the star formation process. Characterizing the frequency and main characteristics of multiple systems and their dependencies on primary mass and environment is therefore a powerful tool to probe this process. While early attempts were fraught with selection biases and limited completeness, instrumentation breakthroughs in the last two decades now enable robust analyses. In this review, we summarize our current empirical knowledge of stellar multiplicity for Main Sequence stars and brown dwarfs, as well as among populations of Pre-Main Sequence stars and embedded protostars. Clear trends as a function of both primary mass and stellar evolutionary stage are identified that will serve as a comparison basis for numerical and analytical models of star formation.", "keyphrases": ["characteristic", "stellar multiplicity", "multiple star system"]}
{"id": "1705.08797", "title": "Conjoined constraints on modified gravity from the expansion history and cosmic growth", "abstract": "In this paper we present conjoined constraints on several cosmological models from the expansion history H(z) and cosmic growth f\u03c3_8(z). The models we study include the CPL w_0w_a parametrization, the Holographic Dark Energy (HDE) model, the Time varying vacuum (\u039b_tCDM) model, the Dvali, Gabadadze and Porrati (DGP) and Finsler-Randers (FRDE) models, a power law f(T) model and finally the Hu-Sawicki f(R) model. In all cases we perform a simultaneous fit to the SnIa, CMB, BAO, H(z) and growth data, while also following the conjoined visualization of H(z) and f\u03c3_8(z) as in Linder (2017). Furthermore, we introduce the Figure of Merit (FoM) in the H(z)-f\u03c3_8(z) parameter space as a way to constrain models that jointly fit both probes well. We use both the latest H(z) and f\u03c3_8(z) data, but also LSST-like mocks with 1% measurements and we find that the conjoined method of constraining the expansion history and cosmic growth simultaneously is able not only to place stringent constraints on these parameters but also to provide an easy visual way to discriminate cosmological models. Finally, we confirm the existence of a tension between the growth rate and Planck CMB data and we find that the FoM in the conjoined parameter space of H(z)-f\u03c3_8(z) can be used to discriminate between the \u039bCDM model and certain classes of modified gravity models, namely the DGP and f(T).", "keyphrases": ["gravity", "expansion history", "cosmological model", "growth rate"]}
{"id": "1705.01881", "title": "Hearing the birth of the lightest intermediate mass black holes with the second generation gravitational wave detectors", "abstract": "Intermediate mass black holes (IMBHs) with a mass between 10^2 and 10^5 times that of the sun, which bridges the mass gap between the stellar-mass black holes and the supermassive black holes, are crucial in understanding the evolution of the black holes. Although they are widely believed to exist, decisive evidence has long been absent. Motivated by the successful detection of massive stellar-mass black holes by advanced LIGO, through the gravitational wave radiation during the binary merger, in this work we investigate the prospect of detecting/identifying the lightest IMBHs (LIMBHs; the black holes \u2273 100M_\u2299) with the second generation gravitational wave detectors. In general, the chance of hearing the birth of the LIMBHs is significantly higher than that to identify pre-merger IMBHs. The other formation channel of LIMBHs, where stars with huge mass/low-metallicity directly collapse, is likely \"silent\", so the merger-driven birth of the LIMBHs may be the only \"observable\" scenario in the near future. Moreover, the prospect of establishing the presence of (lightest) intermediate mass black holes in the O3 run and beyond of advanced LIGO is found quite promising, implying that such an instrument could make another breakthrough on astronomy in the near future. The joining of other detectors like advanced Virgo would only increase the detection rate.", "keyphrases": ["black hole", "gravitational wave detector", "final mass"]}
{"id": "2002.12539", "title": "Spectropolarimetric analysis of FRB 181112 at microsecond resolution: Implications for Fast Radio Burst emission mechanism", "abstract": "We have developed a new coherent dedispersion mode to study the emission of Fast Radio Bursts that trigger the voltage capture capability of the Australian SKA Pathfinder (ASKAP) interferometer. In principle the mode can probe emission timescales down to 3 ns with full polarimetric information preserved. Enabled by the new capability, here we present a spectropolarimetric analysis of FRB 181112 detected by ASKAP, localized to a galaxy at redshift 0.47. At microsecond time resolution the burst is resolved into four narrow pulses with a rise time of just 15 \u03bcs for the brightest. The pulses have a diversity of morphology, but do not show evidence for temporal broadening by turbulent plasma along the line of sight, nor is there any evidence for periodicity in their arrival times. The pulses are highly polarized (up to 95 polarization position angle varying both between and within pulses. The pulses have apparent rotation measures that vary by 15\u00b1 2 rad m^-2 and apparent dispersion measures that vary by 0.041\u00b1 0.004 pc cm^-3. Conversion between linear and circular polarization is observed across the brightest pulse. We conclude that the FRB 181112 pulses are most consistent with being a direct manifestation of the emission process or the result of propagation through a relativistic plasma close to the source. This demonstrates that our method, which facilitates high-time-resolution polarimetric observations of FRBs, can be used to study not only burst emission processes, but also a diversity of propagation effects present on the gigaparsec paths they traverse.", "keyphrases": ["frb", "burst", "time resolution", "spectropolarimetric analysis"]}
{"id": "2103.07139", "title": "Multiple measurements of quasars acting as standard probes: model independent calibration and exploring the Dark Energy Equation of States", "abstract": "Recently, two classes of quasar samples were identified, which are promising as new cosmological probes extending to higher redshifts. The first sample uses the nonlinear relation between the ultraviolet and X-ray luminosities of quasars to derive luminosity distances, whereas the linear sizes of compact radio quasars in the second sample can serve as standardized rulers, providing angular-diameter distances. In this study, under the assumption of a flat universe, we refreshed the calibration of multiple measurements of high-redshift quasars (in the framework of a cosmological-model-independent method with the newest Hubble parameters data). Furthermore, we placed constraints on four models that characterize the cosmic equation of state (w). The obtained results show that: 1) the two quasar samples could provide promising complementary probes at much higher redshifts, whereas compact radio quasars perform better than ultraviolet and X-ray quasars at the current observational level; 2) strong degeneracy between the cosmic equation of state (w) and Hubble constant (H_0) is revealed, which highlights the importance of independent determination of H_0 from time-delay measurements of strongly lensed Quasars; 3)together with other standard ruler probes, such as baryon acoustic oscillation distance measurements, the combined QSO+BAO measurements are consistent with the standard \u039bCDM model at a constant equation of state w=-1; 4) ranking the cosmological models, the polynomial parametrization gives a rather good fit among the four cosmic-equation-of-state models, whereas the Jassal-Bagla-Padmanabhan (JBP) parametrization is substantially penalized by the Akaike Information Criterion and Bayesian Information Criterion criterion.", "keyphrases": ["quasar", "x-ray luminosity", "multiple measurement"]}
{"id": "2102.06523", "title": "A survey of exoplanet phase curves with Ariel", "abstract": "The ESA-Ariel mission will include a tier dedicated to exoplanet phase curves corresponding to 10 observing strategy for studying exoplanet phase curves with Ariel. We define science questions, requirements and a list of potential targets. We also estimate the precision of phase curve reconstruction and atmospheric retrieval using simulated phase curves. Based on this work, we found that full-orbit phase variations for 35-40 exoplanets could be observed during the 3.5-yr mission. This statistical sample would provide key constraints on atmospheric dynamics, composition, thermal structure and clouds of warm exoplanets, complementary to the scientific yield from spectroscopic transits/eclipses measurements.", "keyphrases": ["exoplanet phase curve", "ariel", "mission"]}
{"id": "1604.03487", "title": "Gravity at the horizon: on relativistic effects, CMB-LSS correlations and ultra-large scales in Horndeski's theory", "abstract": "We address the impact of consistent modifications of gravity on the largest observable scales, focusing on relativistic effects in galaxy number counts and the cross-correlation between the matter large scale structure (LSS) distribution and the cosmic microwave background (CMB). Our analysis applies to a very broad class of general scalar-tensor theories encoded in the Horndeski Lagrangian and is fully consistent on linear scales, retaining the full dynamics of the scalar field and not assuming quasi-static evolution. As particular examples we consider self-accelerating Covariant Galileons, Brans-Dicke theory and parameterizations based on the effective field theory of dark energy, using the code to address the impact of these models on relativistic corrections to LSS observables. We find that especially effects which involve integrals along the line of sight (lensing convergence, time delay and the integrated Sachs-Wolfe effect \u2013 ISW) can be considerably modified, and even lead to \ud835\udcaa(1000%) deviations from General Relativity in the case of the ISW effect for Galileon models, for which standard probes such as the growth function only vary by \ud835\udcaa(10%). These effects become dominant when correlating galaxy number counts at different redshifts and can lead to \u223c 50% deviations in the total signal that might be observable by future LSS surveys. Because of their integrated nature, these deep-redshift cross-correlations are sensitive to modifications of gravity even when probing eras much before dark energy domination. We further isolate the ISW effect using the cross-correlation between LSS and CMB temperature anisotropies and use current data to further constrain Horndeski models (abridged).", "keyphrases": ["ultra-large scale", "scalar-tensor theory", "gravity"]}
{"id": "0912.1856", "title": "Cold Quark Matter", "abstract": "We perform an O(alpha_s^2) perturbative calculation of the equation of state of cold but dense QCD matter with two massless and one massive quark flavor, finding that perturbation theory converges reasonably well for quark chemical potentials above 1 GeV. Using a running coupling constant and strange quark mass, and allowing for further non-perturbative effects, our results point to a narrow range where absolutely stable strange quark matter may exist. Absent stable strange quark matter, our findings suggest that quark matter in compact star cores becomes confined to hadrons only slightly above the density of atomic nuclei. Finally, we show that equations of state including quark matter lead to hybrid star masses up to M 2M_solar, in agreement with current observations. For strange stars, we find maximal masses of M 2.75M_solar and conclude that confirmed observations of compact stars with M>2M_solar would strongly favor the existence of stable strange quark matter.", "keyphrases": ["quark matter", "star", "perturbative qcd", "color-superconductivity"]}
{"id": "1002.2280", "title": "Fermi Large Area Telescope First Source Catalog", "abstract": "We present a catalog of high-energy gamma-ray sources detected by the Large Area Telescope (LAT), the primary science instrument on the Fermi Gamma-ray Space Telescope (Fermi), during the first 11 months of the science phase of the mission, which began on 2008 August 4. The First Fermi-LAT catalog (1FGL) contains 1451 sources detected and characterized in the 100 MeV to 100 GeV range. Source detection was based on the average flux over the 11-month period, and the threshold likelihood Test Statistic is 25, corresponding to a significance of just over 4 sigma. The 1FGL catalog includes source location regions, defined in terms of elliptical fits to the 95 power-law spectral fits as well as flux measurements in 5 energy bands for each source. In addition, monthly light curves are provided. Using a protocol defined before launch we have tested for several populations of gamma-ray sources among the sources in the catalog. For individual LAT-detected sources we provide firm identifications or plausible associations with sources in other astronomical catalogs. Identifications are based on correlated variability with counterparts at other wavelengths, or on spin or orbital periodicity. For the catalogs and association criteria that we have selected, 630 of the sources are unassociated. Care was taken to characterize the sensitivity of the results to the model of interstellar diffuse gamma-ray emission used to model the bright foreground, with the result that 161 sources at low Galactic latitudes and toward bright local interstellar clouds are flagged as having properties that are strongly dependent on the model or as potentially being due to incorrectly modeled structure in the Galactic diffuse emission.", "keyphrases": ["large area telescope", "month", "1fgl", "galactic latitude", "fermi"]}
{"id": "1101.4936", "title": "Asymmetric Dark Matter from Leptogenesis", "abstract": "We present a new realization of asymmetric dark matter in which the dark matter and lepton asymmetries are generated simultaneously through two-sector leptogenesis. The right-handed neutrinos couple both to the Standard Model and to a hidden sector where the dark matter resides. This framework explains the lepton asymmetry, dark matter abundance and neutrino masses all at once. In contrast to previous realizations of asymmetric dark matter, the model allows for a wide range of dark matter masses, from keV to 10 TeV. In particular, very light dark matter can be accommodated without violating experimental constraints. We discuss several variants of our model that highlight interesting phenomenological possibilities. In one, late decays repopulate the symmetric dark matter component, providing a new mechanism for generating a large annihilation rate at the present epoch and allowing for mixed warm/cold dark matter. In a second scenario, dark matter mixes with the active neutrinos, thus presenting a distinct method to populate sterile neutrino dark matter through leptogenesis. At late times, oscillations and dark matter decays lead to interesting indirect detection signals.", "keyphrases": ["two-sector leptogenesis", "asymmetric dark matter", "baryon"]}
{"id": "1502.02091", "title": "Searching for Dark Matter Annihilation to Monoenergetic Neutrinos with Liquid Scintillation Detectors", "abstract": "We consider searches for dark matter annihilation to monoenergetic neutrinos in the core of the Sun. We find that liquid scintillation neutrino detectors have enhanced sensitivity to this class of dark matter models, due to the energy and angular resolution possible for electron neutrinos and antineutrinos that scatter via charged-current interactions. In particular we find that KamLAND, utilizing existing data, could provide better sensitivity to such models than any current direct detection experiment for m_X \u2272 15 GeV. KamLAND's sensitivity is signal-limited, and future liquid scintillation or liquid argon detectors with similar energy and angular resolution, but with larger exposure, will provide significantly better sensitivity. These detectors may be particularly powerful probes of dark matter with mass \ud835\udcaa(10) GeV.", "keyphrases": ["dark matter annihilation", "monoenergetic neutrino", "liquid scintillation"]}
{"id": "1409.5736", "title": "Antimatter and antistars in the universe and in the Galaxy", "abstract": "We consider consequences of hypothetical existence of baryo-dense stars created in the very early universe within an extension of Affleck-Dine scenario of baryogenesis. New constraints on the possible number of compact antimatter objects are derived. The contemporary observational data do not exclude significant amount of antimatter in the Galaxy (and in other galaxies) in the form of the baryo-dense low-massive stars.", "keyphrases": ["galaxy", "early universe", "antimatter"]}
{"id": "1605.02106", "title": "Primordial features and Planck polarization", "abstract": "With the Planck 2015 Cosmic Microwave Background (CMB) temperature and polarization data, we search for possible features in the primordial power spectrum (PPS). We revisit the Wiggly Whipped Inflation (WWI) framework and demonstrate how generation of some particular primordial features can improve the fit to Planck data. WWI potential allows the scalar field to transit from a steeper potential to a nearly flat potential through a discontinuity either in potential or in its derivatives. WWI offers the inflaton potential parametrizations that generate a wide variety of features in the primordial power spectra incorporating most of the localized and non-local inflationary features that are obtained upon reconstruction from temperature and polarization angular power spectrum. At the same time, in a single framework it allows us to have a background parameter estimation with a nearly free-form primordial spectrum. Using Planck 2015 data, we constrain the primordial features in the context of Wiggly Whipped Inflation and present the features that are supported both by temperature and polarization. WWI model provides more than 13 improvement in \u03c7^2 fit to the data with respect to the best fit power law model considering combined temperature and polarization data from Planck and B-mode polarization data from BICEP and Planck dust map. We use 2-4 extra parameters in the WWI model compared to the featureless strict slow roll inflaton potential. We find that the differences between the temperature and polarization data in constraining background cosmological parameters such as baryon density, cold dark matter density are reduced to a good extent if we use primordial power spectra from WWI. We also discuss the extent of bispectra obtained from the best potentials in arbitrary triangular configurations using the BI-spectra and Non-Gaussianity Operator (BINGO).", "keyphrases": ["polarization", "fit", "primordial feature"]}
{"id": "1801.10548", "title": "Can the cosmological dark sector be modeled by a single scalar field?", "abstract": "In a previous paper it was shown that a minimally coupled scalar field of mass M \u223c H_0 can describe both components of the dark sector in a unified way. In the solution found, the dark energy component decays linearly with the Hubble parameter, with a homogeneous creation of dark matter. In the present note we show that a \u039bCDM dark sector can also be modeled by such a single field. More generally, we show that the system of Klein-Gordon and Einstein equations admits a uniparametric family of solutions that is equivalent to a non-adiabatic (with zero sound speed) generalised Chaplygin gas.", "keyphrases": ["dark sector", "scalar field", "dark matter"]}
{"id": "1702.08449", "title": "First Data Release of the Hyper Suprime-Cam Subaru Strategic Program", "abstract": "The Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) is a three-layered imaging survey aimed at addressing some of the most outstanding questions in astronomy today, including the nature of dark matter and dark energy. The survey has been awarded 300 nights of observing time at the Subaru Telescope and it started in March 2014. This paper presents the first public data release of HSC-SSP. This release includes data taken in the first 1.7 years of observations (61.5 nights) and each of the Wide, Deep, and UltraDeep layers covers about 108, 26, and 4 square degrees down to depths of i 26.4, 26.5, and 27.0 mag, respectively (5sigma for point sources). All the layers are observed in five broad bands (grizy), and the Deep and UltraDeep layers are observed in narrow bands as well. We achieve an impressive image quality of 0.6 arcsec in the i-band in the Wide layer. We show that we achieve 1-2 per cent PSF photometry (rms) both internally and externally (against Pan-STARRS1), and 10 mas and 40 mas internal and external astrometric accuracy, respectively. Both the calibrated images and catalogs are made available to the community through dedicated user interfaces and database servers. In addition to the pipeline products, we also provide value-added products such as photometric redshifts and a collection of public spectroscopic redshifts. Detailed descriptions of all the data can be found online. The data release website is https://hsc-release.mtk.nao.ac.jp/.", "keyphrases": ["hyper suprime-cam", "subaru strategic program", "first data release", "ssp"]}
{"id": "1801.00748", "title": "Habitability of Exoplanet Waterworlds", "abstract": "Many habitable zone exoplanets are expected to form with water mass fractions higher than that of the Earth. For rocky exoplanets with 10-1000x Earth's H2O but without H2, we model the multi-Gyr evolution of ocean temperature and chemistry, taking into account C partitioning, high-pressure ice phases, and atmosphere-lithosphere exchange. Within our model, for Sun-like stars, we find that: (1) the duration of habitable surface water is strongly affected by ocean chemistry; (2) possible ocean pH spans a wide range; (3) surprisingly, many waterworlds retain habitable surface water for >1 Gyr, and (contrary to previous claims) this longevity does not necessarily involve geochemical cycling. The key to this cycle-independent planetary habitability is that C exchange between the convecting mantle and the water ocean is curtailed by seafloor pressure on waterworlds, so the planet is stuck with the ocean mass and ocean cations that it acquires during the first 1 model, the sum of positive charges leached from the planetary crust by early water-rock interactions is - coincidentally - often within an order of magnitude of the early-acquired atmosphere+ocean inorganic C inventory overlaps. As a result, pCO2 is frequently in the \"sweet spot\" (0.2-20 bar) for which the range of semimajor axis that permits surface liquid water is about as wide as it can be. Because the width of the HZ in semimajor axis defines (for Sun-like stars) the maximum possible time span of surface habitability, this effect allows for Gyr of habitability as the star brightens. We illustrate our findings by using the output of an ensemble of N-body simulations as input to our waterworld evolution code. Thus (for the first time in an end-to-end calculation) we show that chance variation of initial conditions, with no need for geochemical cycling, can yield multi-Gyr surface habitability on waterworlds.", "keyphrases": ["waterworld", "ocean chemistry", "habitability"]}
{"id": "1904.11917", "title": "Scalar correlation functions in de Sitter space from the stochastic spectral expansion", "abstract": "We consider light scalar fields during inflation and show how the stochastic spectral expansion method can be used to calculate two-point correlation functions of an arbitrary local function of the field in de Sitter space. In particular, we use this approach for a massive scalar field with quartic self-interactions to calculate the fluctuation spectrum of the density contrast and compare it to other approximations. We find that neither Gaussian nor linear approximations accurately reproduce the power spectrum, and in fact always overestimate it. For example, for a scalar field with only a quartic term in the potential, V=\u03bb\u03d5^4/4, we find a blue spectrum with spectral index n-1=0.579\u221a(\u03bb).", "keyphrases": ["correlation function", "sitter space", "quartic term", "spectator scalar"]}
{"id": "1808.02497", "title": "Millisecond pulsars and the gamma-ray excess in Andromeda", "abstract": "The Fermi Gamma-Ray Space Telescope has provided evidence for diffuse gamma-ray emission in the central parts of the Milky Way and the Andromeda galaxy. This excess has been interpreted either as dark matter annihilation emission or as emission from thousands of millisecond pulsars (MSPs). We have recently shown that old massive globular clusters may move towards the center of the Galaxy by dynamical friction and carry within them enough MSPs to account for the observed gamma-ray excess. In this paper we revisit the MSP scenario for the Andromeda galaxy, by modeling the formation and disruption of its globular cluster system. We find that our model predicts gamma-ray emission \u223c 2-3 times larger than for the Milky Way, but still nearly an order of magnitude smaller than the observed Fermi excess in the Andromeda. Our MSP model can reproduce the observed excess only by assuming \u223c 8 times larger number of old clusters than inferred from galaxy scaling relations. To explain the observations we require either that Andromeda deviates significantly from the scaling relations, or that a large part of its high-energy emission comes from additional sources.", "keyphrases": ["gamma-ray excess", "andromeda galaxy", "millisecond pulsar"]}
{"id": "1205.6085", "title": "Searching for Standard Clocks in the Primordial Universe", "abstract": "Classically oscillating massive fields can be used as \"standard clocks\" in the primordial universe. They generate features in primordial density perturbations that directly record the scale factor evolution a(t). Detecting and measuring these \"fingerprint\" signals is challenging but would provide a direct evidence for a specific primordial universe paradigm. In this paper, such a search is performed for the power spectrum of the Cosmic Microwave Background (CMB) anisotropies using the WMAP7 data. Although a good fit to the data privileges a scale around k=0.01 Mpc^(-1), we do not find statistical significance for, neither against, the presence of any feature. We then forecast the expected constraints a Planck-like CMB experiment can impose on the fingerprint parameters by using Markov-Chain-Monte-Carlo (MCMC) methods on mock data. We exhibit a high sensitivity zone for wavenumbers ranging from 0.01 Mpc^(-1) to 0.1 Mpc^(-1) in which fingerprints show up first on the posterior probability distribution of the wavenumber at which they occur, and then on the modulation frequency. Within the sensitivity zone, we show that the inflationary paradigm can be inferred from a single feature generating at least a 20 sensitively depends on the modulation frequency.", "keyphrases": ["standard clock", "universe", "oscillation"]}
{"id": "1510.07240", "title": "Constraints on a possible variation of the fine structure constant from galaxy cluster data", "abstract": "We propose a new method to probe a possible time evolution of the fine structure constant \u03b1 from X-ray and Sunyaev-Zeldovich measurements of the gas mass fraction (f_gas) in galaxy clusters. Taking into account a direct relation between variations of \u03b1 and violations of the distance-duality relation, we discuss constraints on \u03b1 for a class of dilaton runaway models. Although not yet competitive with bounds from high-z quasar absorption systems, our constraints, considering a sample of 29 measurements of f_gas, in the redshift interval 0.14 < z < 0.89, provide an independent estimate of \u03b1 variation at low and intermediate redshifts. Furthermore, current and planned surveys will provide a larger amount of data and thus allow to improve the limits on \u03b1 variation obtained in the present analysis.", "keyphrases": ["fine structure", "galaxy cluster data", "sunyaev-zeldovich measurement"]}
{"id": "1801.00672", "title": "Primordial Black Holes as Generators of Cosmic Structures", "abstract": "Primordial black holes (PBHs) could provide the dark matter in various mass windows below 10^2 M_\u2299 and those of 30 M_\u2299 might explain the LIGO events. PBHs much larger than this might have important consequences even if they provide only a small fraction of the dark matter. In particular, they could generate cosmological structure either individually through through the `seed' effect or collectively through the `Poisson' effect, thereby alleviating some problems associated with the standard CDM scenario. If the PBHs all have a similar mass and make a small contribution to the dark matter, then the seed effect dominates on small scales, in which case PBHs could seed the supermassive black holes in galactic nuclei or even galaxies themselves. If they have a similar mass and provide the dark matter, the Poisson effect dominates on all scales and the first bound clouds would form earlier than in the usual scenario, with interesting observational consequences. If the PBHs have an extended mass spectrum, which is more likely, they could fulfill all three roles - providing the dark matter, binding the first bound clouds and generating galaxies. In this case, the galactic mass function naturally has the observed form, with the galaxy mass being simply related to the black hole mass. The stochastic gravitational wave background from the PBHs in this scenario would extend continuously from the LIGO frequency to the LISA frequency, offering a potential goal for future surveys.", "keyphrases": ["black hole", "dark matter", "early universe"]}
{"id": "1010.2284", "title": "Collinear solution to the general relativistic three-body problem", "abstract": "The three-body problem is reexamined in the framework of general relativity. The Newtonian three-body problem admits Euler's collinear solution, where three bodies move around the common center of mass with the same orbital period and always line up. The solution is unstable. Hence it is unlikely that such a simple configuration would exist owing to general relativistic forces dependent not only on the masses but also on the velocity of each body. However, we show that the collinear solution remains true with a correction to the spatial separation between masses. Relativistic corrections to the Sun-Jupiter Lagrange points L1, L2 and L3 are also evaluated.", "keyphrases": ["three-body problem", "collinear solution", "post-newtonian collinear configuration"]}
{"id": "1003.5567", "title": "Strong Lensing by Galaxies", "abstract": "Strong lensing is a powerful tool to address three major astrophysical issues: understanding the spatial distribution of mass at kpc and sub-kpc scale, where baryons and dark matter interact to shape galaxies as we see them; determining the overall geometry, content, and kinematics of the universe; studying distant galaxies, black holes, and active nuclei that are too small or too faint to be resolved or detected with current instrumentation. After summarizing strong gravitational lensing fundamentals, I present a selection of recent important results. I conclude by discussing the exciting prospects of strong gravitational lensing in the next decade.", "keyphrases": ["galaxy", "major astrophysical issue", "geometry", "strong gravitational lensing", "mass distribution"]}
{"id": "1904.06759", "title": "Relativistic Shapiro delay measurements of an extremely massive millisecond pulsar", "abstract": "Despite its importance to our understanding of physics at supranuclear densities, the equation of state (EoS) of matter deep within neutron stars remains poorly understood. Millisecond pulsars (MSPs) are among the most useful astrophysical objects in the Universe for testing fundamental physics, and place some of the most stringent constraints on this high-density EoS. Pulsar timing - the process of accounting for every rotation of a pulsar over long time periods - can precisely measure a wide variety of physical phenomena, including those that allow the measurement of the masses of the components of a pulsar binary system (Lorimer Kramer 2005). One of these, called relativistic Shapiro delay (Shapiro 1964), can yield precise masses for both an MSP and its companion; however, it is only easily observed in a small subset of high-precision, highly inclined (nearly edge-on) binary pulsar systems. By combining data from the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) 12.5-year data set with recent orbital-phase-specific observations using the Green Bank Telescope, we have measured the mass of the MSP J0740+6620 to be 2.14^+0.10_-0.09 solar masses (68.3 credibility interval; 95.4 2.14^+0.20_-0.18 solar masses). It is highly likely to be the most massive neutron star yet observed, and serves as a strong constraint on the neutron star interior EoS.", "keyphrases": ["millisecond pulsar", "neutron star", "american nanohertz observatory", "gravitational waves", "orbital-phase-specific observation"]}
{"id": "1402.6823", "title": "Gravitational lensing in Tangherlini spacetime in the weak gravitational field and the strong gravitational field", "abstract": "The gravitational lensing effects in the weak gravitational field by exotic lenses have been investigated intensively to find nonluminous exotic objects. Gravitational lensing based on 1/r^n fall-off metric, as a one-parameter model that can treat by hand both the Schwarzschild lens (n=1) and the Ellis wormhole (n=2) in the weak field, has been recently studied. Only for n=1 case, however, it has been explicitly shown that effects of relativistic lens images by the strong field on the light curve can be neglected. We discuss whether relativistic images by the strong field can be neglected for n>1 in the Tangherlini spacetime which is one of the simplest models for our purpose. We calculate the divergent part of the deflection angle for arbitrary n and the regular part for n=1, 2 and 4 in the strong field limit, the deflection angle for arbitrary n under the weak gravitational approximation. We also compare the radius of the Einstein ring with the radii of the relativistic Einstein rings for arbitrary n. We conclude that the images in the strong gravitational field have little effect on the total light curve and that the time-symmetric demagnification parts in the light curve will appear even after taking account of the images in the strong gravitational field for n>1.", "keyphrases": ["tangherlini spacetime", "weak gravitational field", "higher-dimensional einstein equation"]}
{"id": "1409.6568", "title": "Generalised tensor fluctuations and inflation", "abstract": "Using an effective field theory approach to inflation, we examine novel properties of the spectrum of inflationary tensor fluctuations, that arise when breaking some of the symmetries or requirements usually imposed on the dynamics of perturbations. During single-clock inflation, time-reparameterization invariance is broken by a time-dependent cosmological background. In order to explore more general scenarios, we consider the possibility that spatial diffeomorphism invariance is also broken by effective mass terms or by derivative operators for the metric fluctuations in the Lagrangian. We investigate the cosmological consequences of the breaking of spatial diffeomorphisms, focussing on operators that affect the power spectrum of fluctuations. We identify the operators for tensor fluctuations that can provide a blue spectrum without violating the null energy condition, and operators for scalar fluctuations that lead to non-conservation of the comoving curvature perturbation on superhorizon scales even in single-clock inflation. In the last part of our work, we also examine the consequences of operators containing more than two spatial derivatives, discussing how they affect the sound speed of tensor fluctuations, and showing that they can mimic some of the interesting effects of symmetry breaking operators, even in scenarios that preserve spatial diffeomorphism invariance.", "keyphrases": ["tensor fluctuation", "effective field theory", "solid inflation"]}
{"id": "1412.6099", "title": "Distinguishing Dark Matter from Unresolved Point Sources in the Inner Galaxy with Photon Statistics", "abstract": "Data from the Fermi Large Area Telescope suggests that there is an extended excess of GeV gamma-ray photons in the Inner Galaxy. Identifying potential astrophysical sources that contribute to this excess is an important step in verifying whether the signal originates from annihilating dark matter. In this paper, we focus on the potential contribution of unresolved point sources, such as millisecond pulsars (MSPs). We propose that the statistics of the photons\u2014in particular, the flux probability density function (PDF) of the photon counts below the point-source detection threshold\u2014can potentially distinguish between the dark-matter and point-source interpretations. We calculate the flux PDF via the method of generating functions for these two models of the excess. Working in the framework of Bayesian model comparison, we then demonstrate that the flux PDF can potentially provide evidence for an unresolved MSP-like point-source population.", "keyphrases": ["dark matter", "inner galaxy", "photon"]}
{"id": "1103.2302", "title": "The Cauchy problem for f(R)-gravity: an overview", "abstract": "We review the Cauchy problem for f(R) theories of gravity, in metric and metric-affine for- mulations, pointing out analogies and differences with respect to General Relativity. The role of conformal transformations, effective scalar fields and sources in the field equations is discussed in view of the well-posedness of the problem. Finally, criteria of viability of the f(R)-models are considered according to the various matter fields acting as sources.", "keyphrases": ["cauchy problem", "overview", "gravity"]}
{"id": "2010.12432", "title": "Combined magnetic and gravity measurements probe the deep zonal flows of the gas giants", "abstract": "During the past few years, both the Cassini mission at Saturn and the Juno mission at Jupiter, provided measurements with unprecedented accuracy of the gravity and magnetic fields of the two gas giants. Using the gravity measurements, it was found that the strong zonal flows observed at the cloud-level of the gas giants are likely to extend thousands of kilometers deep into the planetary interior. However, the gravity measurements alone, which are by definition an integrative measure of mass, cannot constrain with high certainty the exact vertical structure of the flow. Taking into account the recent Cassini magnetic field measurements of Saturn, and past secular variations of Jupiter's magnetic field, we obtain an additional physical constraint on the vertical decay profile of the observed zonal flows on these planets. Our combined gravity-magnetic analysis reveals that the cloud-level winds on Saturn (Jupiter) extend with very little decay, i.e., barotropically, down to a depth of around 7,000 km (2,000 km) and then decay rapidly in the semiconducting region, so that within the next 1,000 km (600 km) their value reduces to about 1% of that at the cloud-level. These results indicate that there is no significant mechanism acting to decay the flow in the outer neutral region, and that the interaction with the magnetic field in the semiconducting region might play a central role in the decay of the flows.", "keyphrases": ["gravity measurement", "zonal flow", "gas giant"]}
{"id": "1003.5917", "title": "DBI and the Galileon reunited", "abstract": "We derive the relativistic generalization of the Galileon, by studying the brane position modulus of a relativistic probe brane embedded in a five- dimensional bulk. In the appropriate Galilean contraction limit, we recover the complete Galileon generalization of the DGP decoupling theory and its conformal extension. All higher order interactions for the Galileon and its relativistic generalization naturally follow from the brane tension, induced curvature, and the Gibbons-Hawking-York boundary terms associated with all bulk Lovelock invariants. Our approach makes the coupling to gravity straightforward, in particular allowing a simple rederivation of the nonmini- mal couplings required by the Covariant Galileon. The connection with the Lovelock invariants makes the well-defined Cauchy problem manifest, and gives a natural unification of four dimensional effective field theories of the DBI type and the Galileon type.", "keyphrases": ["galileon", "field theory", "galilean symmetry", "minkowski bulk", "high dimensional setup"]}
{"id": "1602.06854", "title": "Computer-generated visual morphology catalog of 3,000,000 SDSS galaxies", "abstract": "We applied computer analysis to classify the broad morphological type of 3,000,000 SDSS galaxies. The catalog provides for each galaxy the DR8 object ID, right ascension, declination, and the certainty of the automatic classification to spiral or elliptical. The certainty of the classification allows controlling the accuracy of a subset of galaxies by sacrificing some of the least certain classifications. The accuracy of the catalog was tested using galaxies that were classified by the manually annotated Galaxy Zoo catalog. The results show that the catalog contains 900,000 spiral galaxies and 600,000 elliptical galaxies with classification certainty that has a statistical agreement rate of 98 demonstrates the ability of computers to turn large datasets of galaxy images into structured catalogs of galaxy morphology. The catalog can be downloaded at http://vfacstaff.ltu.edu/lshamir/data/morph_catalog , and can be accessed through public tables on CAS: public.broadMorph.LargeGM, public.broadMorph.LargeWnnGM, and public.broadMorph.SpectraGM. The image analysis software that was used to create the catalog is also publicly available.", "keyphrases": ["galaxy", "large dataset", "photometric difference", "clockwise"]}
{"id": "1004.3007", "title": "Principles of Einstein-Finsler Gravity and Perspectives in Modern Cosmology", "abstract": "We study the geometric and physical foundations of Finsler gravity theories with metric compatible connections defined on tangent bundles, or (pseudo) Riemannian manifolds). There are analyzed alternatives to Einstein gravity (including theories with broken local Lorentz invariance) and shown how general relativity and modifications can be equivalently re-formulated in Finsler like variables. We focus on prospects in modern cosmology and Finsler acceleration of Universe. All known formalisms are outlined - anholonomic frames with associated nonlinear connection structure, the geometry of the Levi-Civita and Finsler type connections, all defined by the same metric structure, Einstein equations in standard form and/or with nonholonomic/ Finsler variables - and the following topics are discussed: motivation for Finsler gravity; generalized principles of equivalence and covariance; fundamental geometric/ physical structures; field equations and nonholonomic constraints; equivalence with other models of gravity and viability criteria. Einstein-Finsler gravity theories are elaborated following almost the same principles as in the general relativity theory but extended to Finsler metrics and connections. Gravity models with anisotropy can be defined on (co) tangent bundles or on nonholonomic pseudo-Riemannian manifolds. In the second case, Finsler geometries can be modelled as exact solutions in Einstein gravity. Finally, some examples of generic off-diagonal metrics and generalized connections, defining anisotropic cosmological Einstein-Finsler spaces are analyzed; certain criteria for Finsler accelerating evolution are analyzed.", "keyphrases": ["gravity", "modern cosmology", "finsler geometry"]}
{"id": "1711.09915", "title": "Primordial black holes from fifth forces", "abstract": "Primordial black holes can be produced by a long range attractive fifth force stronger than gravity, mediated by a light scalar field interacting with nonrelativistic \"heavy\" particles. As soon as the energy fraction of heavy particles reaches a threshold, the fluctuations rapidly become nonlinear. The overdensities collapse into black holes or similar screened objects, without the need for any particular feature in the spectrum of primordial density fluctuations generated during inflation. We discuss whether such primordial black holes can constitute the total dark matter component in the Universe.", "keyphrases": ["fifth force", "universe", "primordial black hole"]}
{"id": "1810.09200", "title": "Astrophysical Signatures of Black holes in Generalized Proca Theories", "abstract": "Explaining the late time acceleration is one of the most challenging tasks for theoretical physicists today. Infra-red modification of Einstein's general theory of relativity (GR) is a possible route to model late time acceleration. In this regard, vector-tensor theory as a part of gravitational interactions on large cosmological scales, has been proposed recently. This involves generalization of massive Proca lagrangian in curved space time. Black hole solutions in such theories have also been constructed. In this paper, we study different astrophysical signatures of such black holes. We first study the strong lensing and time delay effect of such static spherically symmetric black hole solutions, in particular for the case of gravitational lensing of the star S2 by Sagittarius A* at the centre of Milky Way. We also construct the rotating black hole solution from this static spherically symmetric solution in Proca theories using the Newman-Janis algorithm and subsequently study lensing, time delay and black hole shadow effect in this rotating black hole space time. We discuss the possibility of detecting Proca hair in future observations.", "keyphrases": ["black hole", "relativity", "astrophysical signature"]}
{"id": "1209.0457", "title": "Accelerated expansion from ghost-free bigravity: a statistical analysis with improved generality", "abstract": "We study the background cosmology of the ghost-free, bimetric theory of gravity. We perform an extensive statistical analysis of the model using both frequentist and Bayesian frameworks and employ the constraints on the expansion history of the Universe from the observations of supernovae, the cosmic microwave background and the large scale structure to estimate the model's parameters and test the goodness of the fits. We explore the parameter space of the model with nested sampling to find the best-fit chi-square, obtain the Bayesian evidence, and compute the marginalized posteriors and mean likelihoods. We mainly focus on a class of sub-models with no explicit cosmological constant (or vacuum energy) term to assess the ability of the theory to dynamically cause a late-time accelerated expansion. The model behaves as standard gravity without a cosmological constant at early times, with an emergent extra contribution to the energy density that converges to a cosmological constant in the far future. The model can in most cases yield very good fits and is in perfect agreement with the data. This is because many points in the parameter space of the model exist that give rise to time-evolution equations that are effectively very similar to those of the \u039bCDM. This similarity makes the model compatible with observations as in the \u039bCDM case, at least at the background level. Even though our results indicate a slightly better fit for the \u039bCDM concordance model in terms of the p-value and evidence, none of the models is statistically preferred to the other. However, the parameters of the bigravity model are in general degenerate. A similar but perturbative analysis of the model as well as more data will be required to break the degeneracies and constrain the parameters, in case the model will still be viable compared to the \u039bCDM.", "keyphrases": ["bigravity", "gravity", "cosmological solution"]}
{"id": "1710.05860", "title": "Multimessenger tests of the weak equivalence principle from GW170817 and its electromagnetic counterparts", "abstract": "The coincident detection of a gravitational-wave (GW) event GW170817 with electromagnetic (EM) signals (e.g., a short gamma-ray burst SGRB 170817A or a macronova) from a binary neutron star merger within the nearby galaxy NGC 4933 provides a new, multimessenger test of the weak equivalence principle (WEP), extending the WEP test with GWs and photons. Assuming that the arrival time delay between the GW signals from GW170817 and the photons from SGRB 170817A or the macronova is mainly attributed to the gravitational potential of the Milky Way, we demonstrate that the strict upper limits on the deviation from the WEP are \u0394\u03b3<1.4\u00d710^-3 for GW170817/macronova and \u0394\u03b3 <5.9\u00d710^-8 for GW170817/SGRB 170817A. A much more severe constraint on the WEP accuracy can be achieved (\u223c0.9\u00d710^-10) for GW170817/SGRB 170817A when we consider the gravitational potential of the Virgo Cluster, rather than the Milky Way's gravity. This provides the tightest limit to date on the WEP through the relative differential variations of the \u03b3 parameter for two different species of particles. Compared with other multimessenger (photons and neutrinos) results, our limit is 7 orders of magnitude tighter than that placed by the neutrinos and photons from supernova 1987A, and is almost as good as or is an improvement of 6 orders of magnitude over the limits obtained by the low-significance neutrinos correlated with GRBs and a blazar flare.", "keyphrases": ["weak equivalence principle", "gravity", "multimessenger test"]}
{"id": "1011.3079", "title": "Nonparametric Dark Energy Reconstruction from Supernova Data", "abstract": "Understanding the origin of the accelerated expansion of the Universe poses one of the greatest challenges in physics today. Lacking a compelling fundamental theory to test, observational efforts are targeted at a better characterization of the underlying cause. If a new form of mass-energy, dark energy, is driving the acceleration, the redshift evolution of the equation of state parameter w(z) will hold essential clues as to its origin. To best exploit data from observations it is necessary to develop a robust and accurate reconstruction approach, with controlled errors, for w(z). We introduce a new, nonparametric method for solving the associated statistical inverse problem based on Gaussian Process modeling and Markov chain Monte Carlo sampling. Applying this method to recent supernova measurements, we reconstruct the continuous history of w out to redshift z=1.5.", "keyphrases": ["dark energy", "reconstruction", "gaussian processes", "cosmology"]}
{"id": "1911.05791", "title": "The Assembly of the First Massive Black Holes", "abstract": "The existence of \u224810^9 Msun supermassive black holes (SMBHs) within the first billion year of the universe has stimulated numerous ideas for the prompt formation and rapid growth of BHs in the early universe. Here we review ways in which the seeds of massive BHs may have first assembled, how they may have subsequently grown as massive as \u224810^9 Msun, and how multi-messenger observations could distinguish between different SMBH assembly scenarios. We conclude the following: (1) The ultra-rare \u224810^9 Msun SMBHs represent only the tip of the iceberg. Early BHs likely fill a continuum from stellar-mass (approx. 10 Msun) to the super-massive (\u224810^9 Msun) regime, reflecting a range of initial masses and growth histories. (2) Stellar-mass BHs were likely left behind by the first generation of stars at redshifts as high as z=30, but their initial growth was typically stunted due to the shallow potential wells of their host galaxies. (3) Conditions in some larger, metal-poor galaxies soon became conducive to the rapid formation and growth of massive `seed' holes, via gas accretion and by mergers in dense stellar clusters. (4) BH masses depend on the environment (such as the number and properties of nearby radiation sources and the local baryonic streaming velocity), and on the metal enrichment and assembly history of the host galaxy. (5) Distinguishing between assembly mechanisms will be difficult, but a combination of observations by LISA (probing massive BH growth via mergers) and by deep multi-wavelength electromagnetic observations (probing growth via gas accretion) is particularly promising.", "keyphrases": ["black hole", "universe", "eddington-limited accretion"]}
{"id": "0810.4919", "title": "On the radiative efficiencies, Eddington ratios, and duty cycles of luminous high-redshift quasars", "abstract": "We investigate the characteristic radiative efficiency \u03f5, Eddington ratio \u03bb, and duty cycle P_0 of high-redshift active galactic nuclei (AGN), drawing on measurements of the AGN luminosity function at z=3-6 and, especially, on recent measurements of quasar clustering at z=3-4.5 from the Sloan Digital Sky Survey. The free parameters of our models are \u03f5, \u03bb, and the normalization, scatter, and redshift evolution of the relation between black hole mass and halo virial velocity V_vir. We compute the luminosity function from the implied growth of the black hole mass function and the quasar correlation length from the bias of the host halos. We test our adopted formulae for the halo mass function and halo bias against measurements from the large N-body simulation developed by the MICE collaboration. The strong clustering of AGNs observed at z=3 and, especially, at z=4 implies that massive black holes reside in rare, massive dark matter halos. Reproducing the observed luminosity function then requires high efficiency \u03f5and/or low Eddington ratio \u03bb, with a lower limit (based on 2\u03c3agreement with the measured z=4 correlation length) \u03f5> 0.7\u03bb/(1+0.7\u03bb), implying \u03f5> 0.17 for \u03bb> 0.25. Successful models predict high duty cycles, P_0 0.2, 0.5, and 0.9 at z=3.1, 4.5 and 6, respectively, and they require that the fraction of halo baryons locked in the central black hole is much larger than the locally observed value. The rapid drop in the abundance of the massive and rare host halos at z>7 implies a proportionally rapid decline in the number density of luminous quasars, much stronger than simple extrapolations of the z=3-6 luminosity function would predict. (abridged)", "keyphrases": ["radiative efficiency", "quasar", "agn luminosity function"]}
{"id": "1910.05610", "title": "An Introduction to Particle Dark Matter", "abstract": "We review the features of Dark Matter as a particle, presenting some old and new instructive models, and looking for their physical implications in the early universe and in the process of structure formation. We also present a schematic of Dark Matter searches and introduce the most promising candidates to the role of Dark Matter particle.", "keyphrases": ["particle", "dark matter", "cosmology"]}
{"id": "1112.5335", "title": "Backreaction in late-time cosmology", "abstract": "We review the effect of the formation of nonlinear structures on the expansion rate, spatial curvature and light propagation in the universe, focusing on the possibility that it could explain cosmological observations without the introduction of dark energy or modified gravity. We concentrate on explaining the relevant physics and highlighting open questions.", "keyphrases": ["cosmology", "cosmic backreaction", "spacetime"]}
{"id": "0903.1636", "title": "Minor mergers and the size evolution of elliptical galaxies", "abstract": "Using a high resolution hydrodynamical cosmological simulation of the formation of a massive spheroidal galaxy we show that elliptical galaxies can be very compact and massive at high redshift in agreement with recent observations. Accretion of stripped in-falling stellar material increases the size of the system with time and the central concentration is reduced by dynamical friction of the surviving stellar cores. In a specific case of a spheroidal galaxy with a final stellar mass of 1.5 \u00d7 10^11 M_\u2299 we find that the effective radius r_e increases from 0.7 \u00b1 0.2 kpc at z = 3 to r_e = 2.4 \u00b1 0.4 kpc at z = 0 with a concomitant decrease in the effective density of an order of magnitude and a decrease of the central velocity dispersion by approximately 20 argument based on the virial theorem shows that during the accretion of weakly bound material (minor mergers) the radius can increase as the square of the mass in contrast to the usual linear rate of increase for major mergers. By undergoing minor mergers compact high redshift spheroids can evolve into present-day systems with sizes and concentrations similar to observed local ellipticals. This indicates that minor mergers may be the main driver for the late evolution of sizes and densities of early-type galaxies.", "keyphrases": ["galaxy", "stellar mass", "minor merger"]}
{"id": "2005.00391", "title": "Gravitational production of nearly thermal fermionic Dark Matter", "abstract": "We consider the cosmological production of fermionic dark matter during inflation and a post-inflationary radiation dominated era. This fermion only interacts gravitationally, has a mass m much smaller than the Hubble scale during inflation (but is otherwise arbitrary) and is in its Bunch-Davies vacuum state during inflation. We focus on superhorizon modes at the end of inflation, and assume instantaneous reheating. We obtain the full energy momentum tensor discussing its renormalization, and show that the contribution from particle production is of the kinetic-fluid form near matter-radiation equality. We find exactly the distribution function of produced particles |B(k)|^2=1/2[1-(1-e^-k^2/2mT_H)^1/2] which exhibits an \" emergent temperature\" T_H=H_0\u221a(\u03a9_R)\u2243 10^-36(eV). The abundance of the produced particles \u03a9_pp is very similar to that of a non-relativistic degree of freedom thermalized at temperature T_H, \u03a9_pp\u221d m (m T_H)^3/2\u2243(m/10^8GeV))^5/2 and \"cold\" equation of state w(a) \u2243 (T_H/m a^2), both dominated by superhorizon modes at the end of inflation. We discuss subtle aspects of isocurvature perturbations.", "keyphrases": ["fermion", "dark matter", "bunch-davie vacuum state", "gravitational production", "scalar field"]}
{"id": "1506.03047", "title": "Phenomenology of dark energy: general features of large-scale perturbations", "abstract": "We present a systematic exploration of dark energy and modified gravity models containing a single scalar field non-minimally coupled to the metric. Even though the parameter space is large, by exploiting an effective field theory (EFT) formulation and by imposing simple physical constraints such as stability conditions and (sub-)luminal propagation of perturbations, we arrive at a number of generic predictions. (1) The linear growth rate of matter density fluctuations is generally suppressed compared to \u039bCDM at intermediate redshifts (0.5 \u2272 z \u2272 1), despite the introduction of an attractive long-range scalar force. This is due to the fact that, in self-accelerating models, the background gravitational coupling weakens at intermediate redshifts, over-compensating the effect of the attractive scalar force. (2) At higher redshifts, the opposite happens; we identify a period of super-growth when the linear growth rate is larger than that predicted by \u039bCDM. (3) The gravitational slip parameter \u03b7 - the ratio of the space part of the metric perturbation to the time part - is bounded from above. For Brans-Dicke-type theories \u03b7 is at most unity. For more general theories, \u03b7 can exceed unity at intermediate redshifts, but not more than about 1.5 if, at the same time, the linear growth rate is to be compatible with current observational constraints. We caution against phenomenological parametrization of data that do not correspond to predictions from viable physical theories. We advocate the EFT approach as a way to constrain new physics from future large-scale-structure data.", "keyphrases": ["dark energy", "gravitational coupling", "high redshift"]}
{"id": "1206.5755", "title": "Orbits, masses, and evolution of main belt triple (87) Sylvia", "abstract": "Sylvia is a triple asteroid system located in the main belt. We report new adaptive optics observations of this system that extend the baseline of existing astrometric observations to a decade. We present the first fully dynamical 3-body model for this system by fitting to all available astrometric measurements. This model simultaneously fits for individual masses, orbits, and primary oblateness. We find that Sylvia is composed of a dominant central mass surrounded by two satellites orbiting at 706.5 +/- 2.5 km and 1357 +/- 4.0 km, i.e., about 5 and nearly 10 primary radii. We derive individual masses of 1.484 -0.014/+0.016 x 10^19 kg for the primary (corresponding to a density of 1.29 +/- 0.39 g cm^-3), 7.33 -2.3/+4.7 x 10^14 kg for the inner satellite, and 9.32 -8.3/+20.7 x 10^14 kg for the outer satellite. The oblateness of the primary induces substantial precession and the J_2 value can be constrained to the range of 0.0985-0.1. The orbits of the satellites are relatively circular with eccentricities less than 0.04. The spin axis of the primary body and the orbital poles of both satellites are all aligned within about two degrees of each other, indicating a nearly coplanar configuration and suggestive of satellite formation in or near the equatorial plane of the primary. We also investigate the past orbital evolution of the system by simulating the effects of a recent passage through 3:1 mean-motion eccentricity-type resonances. In some scenarios this allow us to place constraints on interior structure and past eccentricities.", "keyphrases": ["main belt", "sylvia", "orbit"]}
{"id": "1106.5658", "title": "Probing the dynamics of dark energy with divergence-free parametrizations: A global fit study", "abstract": "The CPL parametrization is very important for investigating the property of dark energy with observational data. However, the CPL parametrization only respects the past evolution of dark energy but does not care about the future evolution of dark energy, since w(z) diverges in the distant future. In a recent paper [J.Z. Ma and X. Zhang, Phys. Lett. B 699, 233 (2011)], a robust, novel parametrization for dark energy, w(z)=w_0+w_1(ln (2+z) 1+z-ln2), has been proposed, successfully avoiding the future divergence problem in the CPL parametrization. On the other hand, an oscillating parametrization (motivated by an oscillating quintom model) can also avoid the future divergence problem. In this Letter, we use the two divergence-free parametrizations to probe the dynamics of dark energy in the whole evolutionary history. In light of the data from 7-year WMAP temperature and polarization power spectra, matter power spectrum of SDSS DR7, and SN Ia Union2 sample, we perform a full Markov Chain Monte Carlo exploration for the two dynamical dark energy models. We find that the best-fit dark energy model is a quintom model with the EOS across -1 during the evolution. However, though the quintom model is more favored, we find that the cosmological constant still cannot be excluded.", "keyphrases": ["dark energy", "divergence-free parametrization", "cosmological constant"]}
{"id": "1401.6562", "title": "Planck stars", "abstract": "A star that collapses gravitationally can reach a further stage of its life, where quantum-gravitational pressure counteracts weight. The duration of this stage is very short in the star proper time, yielding a bounce, but extremely long seen from the outside, because of the huge gravitational time dilation. Since the onset of quantum-gravitational effects is governed by energy density \u2014not by size\u2014 the star can be much larger than planckian in this phase. The object emerging at the end of the Hawking evaporation of a black hole can then be larger than planckian by a factor (m/m_ P)^n, where m is the mass fallen into the hole, m_ P is the Planck mass, and n is positive. We consider arguments for n=1/3 and for n=1. There is no causality violation or faster-than-light propagation. The existence of these objects alleviates the black-hole information paradox. More interestingly, these objects could have astrophysical and cosmological interest: they produce a detectable signal, of quantum gravitational origin, around the 10^-14 cm wavelength.", "keyphrases": ["star", "hawking evaporation", "black hole", "rovelli"]}
{"id": "2005.01401", "title": "The Sun is less active than other solar-like stars", "abstract": "Magnetic activity of the Sun and other stars causes their brightness to vary. We investigate how typical the Sun's variability is compared to other solar-like stars, i.e. those with near-solar effective temperatures and rotation periods. By combining four years of photometric observations from the Kepler space telescope with astrometric data from the Gaia spacecraft, we measure photometric variabilities of 369 solar-like stars. Most of the solar-like stars with well-determined rotation periods show higher variability than the Sun and are therefore considerably more active. These stars appear nearly identical to the Sun, except for their higher variability. Their existence raises the question of whether the Sun can also experience epochs of such high variability.", "keyphrases": ["sun", "solar-like star", "rotation period"]}
{"id": "2210.04680", "title": "A luminous fast radio burst that probes the Universe at redshift 1", "abstract": "Fast radio bursts (FRBs) are millisecond-duration pulses of radio emission originating from extragalactic distances. Radio dispersion on each burst is imparted by intervening plasma mostly located in the intergalactic medium. We observe a burst, FRB 20220610A, in a morphologically complex host galaxy system at redshift z=1.016 \u00b1 0.002. The burst redshift and dispersion are consistent with passage through a substantial column of material from the intergalactic medium. The burst shows evidence for passage through additional turbulent magnetized plasma, potentially associated with the host galaxy. We use the burst energy of 2 \u00d7 10^42 erg, to revise the maximum energy of an FRB.", "keyphrases": ["fast radio burst", "redshift", "host galaxy"]}
{"id": "1110.5328", "title": "New limits on Early Dark Energy from the South Pole Telescope", "abstract": "We present new limits on early dark energy (EDE) from the cosmic microwave background (CMB) using data from the WMAP satellite on large angular scales and South Pole Telescope (SPT) on small angular scales. We find a strong upper limit on the EDE density of Omega_e < 0.018 at 95 three improvement over WMAP data alone. We show that adding lower-redshift probes of the expansion rate to the CMB data improves constraints on the dark energy equation of state, but not the EDE density. We also explain how the small-scale CMB temperature anisotropy constrains EDE.", "keyphrases": ["early dark energy", "south pole telescope", "cosmic microwave background", "large angular scale", "new limit"]}
{"id": "1806.09625", "title": "Constraining the Expansion History and Early Dark Energy with Line Intensity Mapping", "abstract": "We consider the potential for line intensity mapping (IM) experiments to measure the baryon acoustic oscillations (BAO) from 3 < z < 6. This would constrain the expansion history in a redshift range that is currently unexplored. We calculate the map depths that future IM experiments targeting the CO(1-0) rotational transition line and [CII] ionized carbon fine-structure line would need to achieve in order to measure the BAO. We find that near-future IM experiments could constrain the BAO scale to 5 depending on CO/[CII] model amplitude. This measurement is at a precision that could make competitive constraints on models of early dark energy.", "keyphrases": ["expansion history", "early dark energy", "line intensity mapping", "galaxy survey"]}
{"id": "1607.02212", "title": "A Global Model For Circumgalactic and Cluster-Core Precipitation", "abstract": "We provide an analytic framework for interpreting observations of multiphase circumgalactic gas that is heavily informed by recent numerical simulations of thermal instability and precipitation in cool-core galaxy clusters. We start by considering the local conditions required for the formation of multiphase gas via two different modes: (1) uplift of ambient gas by galactic outflows, and (2) condensation in a stratified stationary medium in which thermal balance is explicitly maintained. Analytic exploration of these two modes provides insights into the relationships between the local ratio of the cooling and freefall time scales (i.e., t_cool / t_ff), the large-scale gradient of specific entropy, and development of precipitation and multiphase media in circumgalactic gas. We then use these analytic findings to interpret recent simulations of circumgalactic gas in which global thermal balance is maintained. We show that long-lasting configurations of gas with 5 < t_cool / t_ff < 20 and radial entropy profiles similar to observations of local cool-core galaxy cluster cores are a natural outcome of precipitation-regulated feedback. We conclude with some observational predictions that follow from these models. This work focuses primarily on precipitation and AGN feedback in galaxy cluster cores, because that is where the observations of multiphase gas around galaxies are most complete. However, many of the physical principles that govern condensation in those environments apply to circumgalactic gas around galaxies of all masses.", "keyphrases": ["precipitation", "galaxy cluster", "condensation"]}
{"id": "1306.5680", "title": "Oscillatory features in the curvature power spectrum after a sudden turn of the inflationary trajectory", "abstract": "In the context of two-field inflation characterized by a light direction and a heavy direction, we revisit the question of the impact of the massive modes on the power spectrum produced after a turn in the inflationary trajectory. We consider in particular the resonant effect due to the background oscillations following a sharp turn. Working in the mass basis, i.e. in the basis spanned by the eigenvectors of the effective mass matrix for the perturbations, we provide an analytical estimate of the resonant effect, using the in-in formalism. In comparison with earlier estimates, we find the same the spectral dependence but a smaller amplitude. We also compute, again via the in-in formalism, the effect of the direct coupling between the light and heavy modes at the instant of the turn and confirm our previous results obtained via a different method.", "keyphrases": ["power spectrum", "inflationary trajectory", "curvature perturbation"]}
{"id": "1506.01712", "title": "Approximately A Thousand Ultra Diffuse Galaxies in the Coma cluster", "abstract": "We report the discovery of 854 ultra diffuse galaxies (UDGs) in the Coma cluster using deep R band images, with partial B, i, and Halpha band coverage, obtained with the Subaru telescope. Many of them (332) are Milky Way-sized with very large effective radii of r_e>1.5kpc. This study was motivated by the recent discovery of 47 UDGs by van-Dokkum et al. (2015); our discovery suggests >1,000 UDGs after accounting for the smaller Subaru field. The new UDGs show a distribution concentrated around the cluster center, strongly suggesting that the great majority are (likely longtime) cluster members. They are a passively evolving population, lying along the red sequence in the CM diagram with no Halpha signature. Star formation was, therefore, quenched in the past. They have exponential light profiles, effective radii re 800 pc- 5 kpc, effective surface brightnesses mu_e(R)=25-28 mag arcsec-2, and stellar masses 1x10^7 - 5x10^8Msun. There is also a population of nucleated UDGs. Some MW-sized UDGs appear closer to the cluster center than previously reported; their survival in the strong tidal field, despite their large sizes, possibly indicates a large dark matter fraction protecting the diffuse stellar component. The indicated baryon fraction <1 have been removed from the possibly massive dark halo. The UDG population appears to be elevated in the Coma cluster compared to the field, indicating that the gas removal mechanism is related primarily to the cluster environment.", "keyphrases": ["ultra diffuse galaxy", "coma cluster", "subaru telescope"]}
{"id": "1411.4875", "title": "Many-body forces in the equation of state of hyperonic matter", "abstract": "In this work we introduce an extended version of the formalism proposed originally by Taurines et al. that considers the effects of many-body forces simulated by non-linear self-couplings and meson-meson interaction contributions. In this extended version of the model, we assume that matter is at zero temperature, charge neutral and in beta-equilibrium, considering that the baryon octet interacts by the exchange of scalar-isoscalar (\u03c3,\u03c3^*), vector-isoscalar (\u03c9,\u03d5), vector-isovector (\u03f1) and scalar-isovector (\u03b4) meson fields. Using nuclear matter properties, we constrain the parameters of the model that describe the intensity of the indirectly density dependent baryon-meson couplings to a small range of possible values. We then investigate asymmetric hyperonic matter properties. We report that the formalism developed in this work is in agreement with experimental data and also allows for the existence of massive hyperon stars (with more than 2M_\u2299) with small radii, compatible with astrophysical observations.", "keyphrases": ["many-body force", "hyperon puzzle", "gravitational wave physics"]}
{"id": "1107.1286", "title": "A Model of Habitability Within the Milky Way Galaxy", "abstract": "We present a model of the Galactic Habitable Zone (GHZ), described in terms of the spatial and temporal dimensions of the Galaxy that may favour the development of complex life. The Milky Way galaxy is modelled using a computational approach by populating stars and their planetary systems on an individual basis using Monte-Carlo methods. We begin with well-established properties of the disk of the Milky Way, such as the stellar number density distribution, the initial mass function, the star formation history, and the metallicity gradient as a function of radial position and time. We vary some of these properties, creating four models to test the sensitivity of our assumptions. To assess habitability on the Galactic scale, we model supernova rates, planet formation, and the time required for complex life to evolve. Our study improves on other literature on the GHZ by populating stars on an individual basis and by modelling SNII and SNIa sterilizations by selecting their progenitors from within this preexisting stellar population. Furthermore, we consider habitability on tidally locked and non-tidally locked planets separately, and study habitability as a function of height above and below the Galactic midplane. In the model that most accurately reproduces the properties of the Galaxy, the results indicate that an individual SNIa is 5.6 \u00d7more lethal than an individual SNII on average. In addition, we predict that 1.2 of all stars host a planet that may have been capable of supporting complex life at some point in the history of the Galaxy. Of those stars with a habitable planet, 75 configuration with their host star. The majority of these planets that may support complex life are found towards the inner Galaxy, distributed within, and significantly above and below, the Galactic midplane.", "keyphrases": ["habitability", "milky way galaxy", "galactic habitable zone"]}
{"id": "2105.01096", "title": "The consistency of chemical clocks among coeval stars", "abstract": "The abundance ratios of some chemical species have been found to correlate with stellar age, leading to the possibility of using stellar atmospheric abundances as stellar age indicators. These chemical clocks have been calibrated with solar-twins, open clusters and red giants, but it remains to be seen whether they can be effective at identifying coeval stars in a field population that spans a broad parameter space (i.e., the promise of chemical tagging). Since the components of wide binaries are known to be stars of common origins, they constitute ideal laboratories for testing the usefulness of chemical clocks for the age dating of field stars. We determined the abundances of a new sample of 5 binaries and collected data for other 31 systems from the literature in order to test the applicability of chemical clocks. We recover the well known result that the components of wide binaries have more consistent chemistry than that of random pairs. However, we also show for the first time that abundance ratios designed as chemical clocks are even more consistent among the components of wide binaries than their [X/Fe] ratios. Not only that, but the special case of the pair HIP 34426/HIP 34407 may indicate that chemical clocks are consistent for coeval stars even when the individual abundances are not. If the assumption that chemical clocks are reliable age indicators is correct, this would constitute first quantitative, statistically significant evidence that the components of wide binaries in the Galactic field are indeed coeval, validating a large body of published work that relies on that to be the case. Moreover, our results provide strong evidence that chemical clocks indeed carry important information about stellar birthplaces and chemical evolution, and thus we propose that including them in chemical tagging efforts may facilitate the identification of nowadays dissolved stellar groups.", "keyphrases": ["chemical clock", "coeval star", "abundance"]}
{"id": "1208.5975", "title": "Gravitational wave signal from massive gravity", "abstract": "We discuss the detectability of gravitational waves with a time dependent mass contribution, by means of the stochastic gravitational wave observations. Such a mass term typically arises in the cosmological solutions of massive gravity theories. We conduct the analysis based on a general quadratic action, and thus the results apply universally to any massive gravity theories in which modification of general relativity appears primarily in the tensor modes. The primary manifestation of the modification in the gravitational wave spectrum is a sharp peak. The position and height of the peak carry information on the present value of the mass term, as well as the duration of the inflationary stage. We also discuss the detectability of such a gravitational wave signal using the future-planned gravitational wave observatories.", "keyphrases": ["wave signal", "gravity", "cosmological solution"]}
{"id": "1111.4275", "title": "Reconstructing f(R,T) gravity from holographic dark energy", "abstract": "We consider cosmological scenarios based on f(R,T) theories of gravity (R is the Ricci scalar and T is the trace of the energy-momentum tensor) and numerically reconstruct the function f(R,T) which is able to reproduce the same expansion history generated, in the standard General Relativity theory, by dark matter and holographic dark energy. We consider two special f(R,T) models: in the first instance, we investigate the modification R + 2f(T), i.e. the usual Einstein-Hilbert term plus a f(T) correction. In the second instance, we consider a f(R)+\u03bb T theory, i.e. a T correction to the renown f(R) theory of gravity.", "keyphrases": ["gravity", "holographic dark energy", "cosmological scenario"]}
{"id": "1702.03221", "title": "Relativistic initial conditions for N-body simulations", "abstract": "Initial conditions for (Newtonian) cosmological N-body simulations are usually set by re-scaling the present-day power spectrum obtained from linear (relativistic) Boltzmann codes to the desired initial redshift of the simulation. This back-scaling method can account for the effect of inhomogeneous residual thermal radiation at early times, which is absent in the Newtonian simulations. We analyse this procedure from a fully relativistic perspective, employing the recently-proposed Newtonian motion gauge framework. We find that N-body simulations for LambdaCDM cosmology starting from back-scaled initial conditions can be self-consistently embedded in a relativistic space-time with first-order metric potentials calculated using a linear Boltzmann code. This space-time coincides with a simple \"N-body gauge\" for z<50 for all observable modes. Care must be taken, however, when simulating non-standard cosmologies. As an example, we analyse the back-scaling method in a cosmology with decaying dark matter, and show that metric perturbations become large at early times in the back-scaling approach, indicating a breakdown of the perturbative description. We suggest a suitable \"forwards approach\" for such cases.", "keyphrases": ["initial condition", "n-body simulation", "newtonian simulation", "relativistic space-time"]}
{"id": "1812.07310", "title": "Topology and Geometry of Gaussian random fields I: on Betti Numbers, Euler characteristic and Minkowski functionals", "abstract": "This study presents a numerical analysis of the topology of a set of cosmologically interesting three-dimensional Gaussian random fields in terms of their Betti numbers \u03b2_0, \u03b2_1 and \u03b2_2. We show that Betti numbers entail a considerably richer characterization of the topology of the primordial density field. Of particular interest is that Betti numbers specify which topological features - islands, cavities or tunnels - define its spatial structure. A principal characteristic of Gaussian fields is that the three Betti numbers dominate the topology at different density ranges. At extreme density levels, the topology is dominated by a single class of features. At low levels this is a Swiss-cheeselike topology, dominated by isolated cavities, at high levels a predominantly Meatball-like topology of isolated objects. At moderate density levels, two Betti number define a more Sponge-like topology. At mean density, the topology even needs three Betti numbers, quantifying a field consisting of several disconnected complexes, not of one connected and percolating overdensity. A second important aspect of Betti number statistics is that they are sensitive to the power spectrum. It reveals a monotonic trend in which at a moderate density range a lower spectral index corresponds to a considerably higher (relative) population of cavities and islands. We also assess the level of complementary information that Betti numbers represent, in addition to conventional measures such as Minkowski functionals. To this end, we include an extensive description of the Gaussian Kinematic Formula (GKF), which represents a major theoretical underpinning for this discussion.", "keyphrases": ["random field", "betti number", "minkowski functional"]}
{"id": "0905.1115", "title": "Modeling the Extragalactic Background Light from Stars and Dust", "abstract": "The extragalactic background light (EBL) from the far infrared through the visible and extending into the ultraviolet is thought to be dominated by starlight, either through direct emission or through absorption and reradiation by dust. This is the most important energy range for absorbing -rays from distant sources such as blazars and gamma-ray bursts and producing electron positron pairs. In previous work we presented EBL models in the optical through ultraviolet by consistently taking into account the star formation rate (SFR), initial mass function (IMF) and dust extinction, and treating stars on the main sequence as blackbodies. This technique is extended to include post-main sequence stars and reprocessing of starlight by dust. In our simple model, the total energy absorbed by dust is assumed to be re-emitted as three blackbodies in the infrared, one at 40 K representing warm, large dust grains, one at 70 K representing hot, small dust grains, and one at 450 K representing polycyclic aromatic hydrocarbons. We find our best fit model combining the Hopkins and Beacom SFR using the Cole et al. parameterization with the Baldry and Glazebrook IMF agrees with available luminosity density data at a variety of redshifts. Our resulting EBL energy density is quite close to the lower limits from galaxy counts and in some cases below the lower limits, and agrees fairly well with other recent EBL models shortward of about 5 \u03bcm. Deabsorbing TeV -ray spectra of various blazars with our EBL model gives results consistent with simple shock acceleration theory. We also find that the universe should be optically thin to -rays with energies less than 20 GeV.", "keyphrases": ["extragalactic background light", "dust", "starlight"]}
{"id": "1504.06472", "title": "Signatures of a two million year old supernova in the spectra of cosmic ray protons, antiprotons and positrons", "abstract": "The locally observed cosmic ray spectrum has several puzzling features, such as the excess of positrons and antiprotons above \u223c 20 GeV and the discrepancy in the slopes of the spectra of cosmic ray protons and heavier nuclei in the TeV-PeV energy range. We show that these features are consistently explained by a nearby source which was active \u223c 2 Myr ago and has injected (1-2)\u00d7 10^50 erg in cosmic rays. The transient nature of the source and its overall energy budget point to the supernova origin of this local cosmic ray source. The age of the supernova suggests that the local cosmic ray injection was produced by the same supernova that has deposited ^60Fe isotopes in the deep ocean crust.", "keyphrases": ["supernova", "antiproton", "cosmic ray spectrum"]}
{"id": "1111.6049", "title": "Hyperons and massive neutron stars: the role of hyperon potentials", "abstract": "The constituents of cold dense matter are still far from being understood. However, neutron star observations such as the recently observed pulsar PSR J1614-2230 with a mass of 1.97+/-0.04 M_solar help to considerably constrain the hadronic equation of state (EoS). We systematically investigate the influence of the hyperon potentials on the stiffness of the EoS. We find that they have but little influence on the maximum mass compared to the inclusion of an additional vector meson mediating repulsive interaction amongst hyperons. The new mass limit can only be reached with this additional meson regardless of the hyperon potentials. Further, we investigate the impact of the nuclear compression modulus and the effective mass of the nucleon at saturation density on the high density regime of the EoS. We show that the maximum mass of purely nucleonic stars is very sensitive to the effective nucleon mass but only very little to the compression modulus.", "keyphrases": ["neutron star", "hyperon potential", "gravitational wave physics"]}
{"id": "1104.1300", "title": "Is the Universe homogeneous?", "abstract": "The standard model of cosmology is based on the existence of homogeneous surfaces as the background arena for structure formation. Homogeneity underpins both general relativistic and modified gravity models and is central to the way in which we interpret observations of the CMB and the galaxy distribution. However, homogeneity cannot be directly observed in the galaxy distribution or CMB, even with perfect observations, since we observe on the past lightcone and not on spatial surfaces. We can directly observe and test for isotropy, but to link this to homogeneity, we need to assume the Copernican Principle. First, we discuss the link between isotropic observations on the past lightcone and isotropic spacetime geometry: what observations do we need to be isotropic in order to deduce spacetime isotropy? Second, we discuss what we can say with the Copernican assumption. The most powerful result is based on the CMB: the vanishing of the dipole, quadrupole and octupole of the CMB is sufficient to impose homogeneity. Real observations lead to near-isotropy on large scales - does this lead to near-homogeneity? There are important partial results, and we discuss why this remains a difficult open question. Thus we are currently unable to prove homogeneity of the Universe on large-scales, even with the Copernican Principle. However we can use observations of the CMB, galaxies and clusters to test homogeneity itself.", "keyphrases": ["universe", "galaxy distribution", "past lightcone", "copernican principle", "hypersurface"]}
{"id": "1201.0926", "title": "BINGO: A code for the efficient computation of the scalar bi-spectrum", "abstract": "We present a new and accurate Fortran code, the BI-spectra and Non-Gaussianity Operator (BINGO), for the efficient numerical computation of the scalar bi-spectrum and the non-Gaussianity parameter f_NL in single field inflationary models involving the canonical scalar field. The code can calculate all the different contributions to the bi-spectrum and the parameter f_NL for an arbitrary triangular configuration of the wavevectors. Focusing firstly on the equilateral limit, we illustrate the accuracy of BINGO by comparing the results from the code with the spectral dependence of the bi-spectrum expected in power law inflation. Then, considering an arbitrary triangular configuration, we contrast the numerical results with the analytical expression available in the slow roll limit, for, say, the case of the conventional quadratic potential. Considering a non-trivial scenario involving deviations from slow roll, we compare the results from the code with the analytical results that have recently been obtained in the case of the Starobinsky model in the equilateral limit. As an immediate application, we utilize BINGO to examine of the power of the non-Gaussianity parameter f_NL to discriminate between various inflationary models that admit departures from slow roll and lead to similar features in the scalar power spectrum. We close with a summary and discussion on the implications of the results we obtain.", "keyphrases": ["computation", "scalar bi-spectrum", "triangular configuration", "bingo"]}
{"id": "1212.1463", "title": "Cosmological Evolution of Galaxies", "abstract": "I review the subject of the cosmological evolution of galaxies, including different aspects of growth in disk galaxies, by focussing on the angular momentum problem, mergers, and their by-products. I discuss the alternative to merger-driven growth \u2013 cold accretion and related issues. In the follow-up, I review possible feedback mechanisms and their role in galaxy evolution. Special attention is paid to high-redshift galaxies and their properties. In the next step, I discuss a number of processes, gas- and stellar-dynamical, within the central kiloparsec of disk galaxies, and their effect on the larger spatial scales, as well as on the formation and fuelling of the seed black holes in galactic centres at high redshifts.", "keyphrases": ["galaxy", "alternative", "black hole", "cosmological evolution"]}
{"id": "1010.5740", "title": "Kaluza-Klein models: can we construct a viable example?", "abstract": "In Kaluza-Klein models, we investigate soliton solutions of Einstein equation. We obtain the formulas for perihelion shift, deflection of light, time delay of radar echoes and PPN parameters. We find that the solitonic parameter k should be very big: |k|\u22652.3\u00d710^4. We define a soliton solution which corresponds to a point-like mass source. In this case the soliton parameter k=2, which is clearly contrary to this restriction. Similar problem with the observations takes place for static spherically symmetric perfect fluid with the dust-like equation of state in all dimensions. The common for both of these models is the same equations of state in our three dimensions and in the extra dimensions. All dimensions are treated at equal footing. To be in agreement with observations, it is necessary to break the symmetry between the external/our and internal spaces. It takes place for black strings which are particular examples of solitons with k\u2192\u221e. For such k, black strings are in concordance with the observations. Moreover, we show that they are the only solitons which are at the same level of agreement with the observations as in general relativity. Black strings can be treated as perfect fluid with dust-like equation of state p_0=0 in the external/our space and very specific equation of state p_1=-(1/2)\u03f5in the internal space. The latter equation is due to negative tension in the extra dimension. We also demonstrate that dimension 3 for the external space is a special one. Only in this case we get the latter equation of state. We show that the black string equations of state satisfy the necessary condition of the internal space stabilization. Therefore, black strings are good candidates for a viable model of astrophysical objects (e.g., Sun) if we can provide a satisfactory explanation of negative tension for particles constituting these objects.", "keyphrases": ["extra dimension", "kaluza-klein model", "previous paper", "post-newtonian parameter", "experimental restriction"]}
{"id": "1812.10606", "title": "Melanopogenesis: Dark Matter of (almost) any Mass and Baryonic Matter from the Evaporation of Primordial Black Holes weighing a Ton (or less)", "abstract": "The evaporation of primordial black holes with a mass in the 1 gram\u2272 M_ PBH\u22721000 kg range can lead to the production of dark matter particles of almost any mass in the range 0.1 MeV\u2272 m_ DM\u2272 10^18 GeV with the right relic density at very early times, \u03c4\u2272 10^-10 s. We calculate, as a function of the primordial black holes mass and initial abundance, the combination of dark matter particle masses and number of effective dark degrees of freedom leading to the right abundance of dark matter today, whether or not evaporation stops around the Planck scale. In addition, since black hole evaporation can also lead to the production of a baryon asymmetry, we calculate where dark matter production and baryogenesis can concurrently happen, under a variety of assumptions: baryogenesis via grand unification boson decay, via leptogenesis, or via asymmetric co-genesis of dark matter and ordinary matter. Finally, we comment on possible ways to test this scenario.", "keyphrases": ["dark matter", "black hole", "leptogenesis", "pbh evaporation"]}
{"id": "1604.08676", "title": "SGR-like behaviour of the repeating FRB 121102", "abstract": "Fast radio bursts (FRBs) are millisecond-duration radio signals occurring at cosmological distances. However the physical model of FRBs is mystery, many models have been proposed. Here we study the frequency distributions of peak flux, fluence, duration and waiting time for the repeating FRB 121102. The cumulative distributions of peak flux, fluence and duration show power-law forms. The waiting time distribution also shows power-law distribution, and is consistent with a non-stationary Poisson process. These distributions are similar as those of soft gamma repeaters (SGRs). We also use the statistical results to test the proposed models for FRBs. These distributions are consistent with the predictions from avalanche models of slowly driven nonlinear dissipative systems.", "keyphrases": ["frb", "radio burst", "power-law distribution"]}
{"id": "0911.5644", "title": "Constraints on Cosmological Models and Reconstructing the Acceleration History of the Universe with Gamma-Ray Burst Distance Indicators", "abstract": "Gamma-ray bursts (GRBs) have been regarded as standard candles at very high redshift for cosmology research. We have proposed a new method to calibrate GRB distance indicators with Type Ia supernova (SNe Ia) data in a completely cosmology-independent way to avoid the circularity problem that had limited the direct use of GRBs to probe cosmology [N. Liang, W. K. Xiao, Y. Liu, and S. N. Zhang, Astrophys. J. 685, 354 (2008).]. In this paper, a simple method is provided to combine GRB data into the joint observational data analysis to constrain cosmological models; in this method those SNe Ia data points used for calibrating the GRB data are not used to avoid any correlation between them. We find that the \u039bCDM model is consistent with the joint data in the 1-\u03c3 confidence region, using the GRB data at high redshift calibrated with the interpolating method, the Constitution set of SNe Ia, the cosmic microwave background radiation from Wilkinson Microwave Anisotropy Probe five year observation, the baryonic acoustic oscillation from the spectroscopic Sloan Digital Sky Survey Data Release 7 galaxy sample, the x-ray baryon mass fraction in clusters of galaxies, and the observational Hubble parameter versus redshift data. Comparing to the joint constraints with GRBs and without GRBs, we find that the contribution of GRBs to the joint cosmological constraints is a slight shift in the confidence regions of cosmological parameters to better enclose the \u039bCDM model. Finally, we reconstruct the acceleration history of the Universe up to z>6 with the distance moduli of SNe Ia and GRBs and find some features that deviate from the \u039bCDM model and seem to favor oscillatory cosmology models; however further investigations are needed to better understand the situation.", "keyphrases": ["universe", "high redshift", "cosmological constraint"]}
{"id": "1112.0417", "title": "Layzer-Irvine equation: new perspectives and the role of interacting dark energy", "abstract": "We derive the Layzer-Irvine equation in the presence of a homogeneous (or quasi-homogeneous) dark energy component with an arbitrary equation of state. We extend the Layzer-Irvine equation to homogeneous and isotropic universes with an arbitrary number of dimensions and obtain the corresponding virial relation for sufficiently relaxed objects. We find analogous equations describing the dynamics of cosmic string loops and other p-branes of arbitrary dimensionality, discussing the corresponding relativistic and non-relativistic limits. Finally, we generalize the Layzer-Irvine equation to account for a non-minimal interaction between dark matter and dark energy, discussing its practical use as a signature of such an interaction.", "keyphrases": ["dark energy", "dark matter", "layzer-irvine equation"]}
{"id": "2012.02786", "title": "Two populations of LIGO-Virgo black holes", "abstract": "We analyse the LIGO-Virgo data, including the recently released GWTC-2 dataset, to test a hypothesis that the data contains more than one population of black holes. We perform a maximum likelihood analysis including a population of astrophysical black holes with a truncated power-law mass function whose merger rate follows from star formation rate, and a population of primordial black holes for which we consider log-normal and critical collapse mass functions. We find that primordial black holes alone are strongly disfavoured by the data, while the best fit is obtained for the template combining astrophysical and primordial merger rates. Alternatively, the data may hint towards two different astrophysical black hole populations. We also update the constraints on primordial black hole abundance from LIGO-Virgo observations finding that in the 2-400M_\u2299 mass range they must comprise less than 0.2 of dark matter.", "keyphrases": ["black hole", "ligo-virgo observation", "dark matter", "primordial origin"]}
{"id": "0912.0817", "title": "Stochastic excitation of acoustic modes in stars", "abstract": "For more than ten years, solar-like oscillations have been detected and frequencies measured for a growing number of stars with various characteristics (e.g. different evolutionary stages, effective temperatures, gravities, metal abundances ...). Excitation of such oscillations is attributed to turbulent convection and takes place in the uppermost part of the convective envelope. Since the pioneering work of Goldreich Keely (1977), more sophisticated theoretical models of stochastic excitation were developed, which differ from each other both by the way turbulent convection is modeled and by the assumed sources of excitation. We review here these different models and their underlying approximations and assumptions. We emphasize how the computed mode excitation rates crucially depend on the way turbulent convection is described but also on the stratification and the metal abundance of the upper layers of the star. In turn we will show how the seismic measurements collected so far allow us to infer properties of turbulent convection in stars.", "keyphrases": ["excitation", "star", "solar-like oscillation"]}
{"id": "1407.6349", "title": "Atmospheric dynamics of terrestrial exoplanets over a wide range of orbital and atmospheric parameters", "abstract": "The recent discoveries of terrestrial exoplanets and super-Earths extending over a broad range of orbital and physical parameters suggest that these planets will span a wide range of climatic regimes. Characterization of the atmospheres of warm super-Earths has already begun and will be extended to smaller and more distant planets over the coming decade. The habitability of these worlds may be strongly affected by their three-dimensional atmospheric circulation regimes, since the global climate feedbacks that control the inner and outer edges of the habitable zone including transitions to Snowball-like states and runaway-greenhouse feedbacks depend on the equator-to-pole temperature differences, patterns of relative humidity, and other aspects of the dynamics. Here, using an idealized moist atmospheric general circulation model including a hydrological cycle, we study the dynamical principles governing the atmospheric dynamics on such planets. We show how the planetary rotation rate, stellar flux, atmospheric mass, surface gravity, optical thickness, and planetary radius affect the atmospheric circulation and temperature distribution on such planets. Our simulations demonstrate that equator-to-pole temperature differences, meridional heat transport rates, structure and strength of the winds, and the hydrological cycle vary strongly with these parameters, implying that the sensitivity of the planet to global climate feedbacks will depend significantly on the atmospheric circulation. We elucidate the possible climatic regimes and diagnose the mechanisms controlling the formation of atmospheric jet streams, Hadley and Ferrel cells, and latitudinal temperature differences. Finally, we discuss the implications for understanding how the atmospheric circulation influences the global climate.", "keyphrases": ["terrestrial exoplanet", "planetary rotation rate", "atmospheric dynamic"]}
{"id": "1203.2601", "title": "Creation of the CMB spectrum: precise analytic solutions for the blackbody photosphere", "abstract": "The blackbody spectrum of CMB was created in the blackbody photosphere at redshifts z>2x10^6. At these early times, the Universe was dense and hot enough that complete thermal equilibrium between baryonic matter (electrons and ions) and photons could be established. Any perturbation away from the blackbody spectrum was suppressed exponentially. New physics, for example annihilation and decay of dark matter, can add energy and photons to CMB at redshifts z>10^5 and result in a Bose-Einstein spectrum with a non-zero chemical potential (\u03bc). Precise evolution of the CMB spectrum around the critical redshift of z 2x10^6 is required in order to calculate the \u03bc-type spectral distortion and constrain the underlying new physics. Although numerical calculation of important processes involved (double Compton process, comptonization and bremsstrahlung) is not difficult, analytic solutions are much faster and easier to calculate and provide valuable physical insights. We provide precise (better than 1 epoch, including all three processes, double Compton, Compton scattering on thermal electrons and bremsstrahlung in the limit of small distortions. This is a significant improvement over the existing solutions with accuracy 10 worse. We also give a census of important sources of energy injection into CMB in standard cosmology. In particular, calculations of distortions from electron-positron annihilation and primordial nucleosynthesis illustrate in a dramatic way the strength of the equilibrium restoring processes in the early Universe. Finally, we point out the triple degeneracy in standard cosmology, i.e., the \u03bc and y distortions from adiabatic cooling of baryons and electrons, Silk damping and annihilation of thermally produced WIMP dark matter are of similar order of magnitude ( 10^-8-10^-10).", "keyphrases": ["cmb spectrum", "analytic solution", "blackbody", "redshift", "photon"]}
{"id": "1508.01082", "title": "A model with cosmological Bell inequalities", "abstract": "We discuss the possibility of devising cosmological observables which violate Bell's inequalities. Such observables could be used to argue that cosmic scale features were produced by quantum mechanical effects in the very early universe. As a proof of principle, we propose a somewhat elaborate inflationary model where a Bell inequality violating observable can be constructed.", "keyphrases": ["bell inequality", "universe", "massive field"]}
{"id": "1105.6127", "title": "Big bounce from spin and torsion", "abstract": "The Einstein-Cartan-Sciama-Kibble theory of gravity naturally extends general relativity to account for the intrinsic spin of matter. Spacetime torsion, generated by spin of Dirac fields, induces gravitational repulsion in fermionic matter at extremely high densities and prevents the formation of singularities. Accordingly, the big bang is replaced by a bounce that occurred when the energy density \u03f5\u221d gT^4 was on the order of n^2/m_Pl^2 (in natural units), where n\u221d gT^3 is the fermion number density and g is the number of thermal degrees of freedom. If the early Universe contained only the known standard-model particles (g\u2248 100), then the energy density at the big bounce was about 15 times larger than the Planck energy. The minimum scale factor of the Universe (at the bounce) was about 10^32 times smaller than its present value, giving \u2248 50. If more fermions existed in the early Universe, then the spin-torsion coupling causes a bounce at a lower energy and larger scale factor. Recent observations of high-energy photons from gamma-ray bursts indicate that spacetime may behave classically even at scales below the Planck length, supporting the classical spin-torsion mechanism of the big bounce. Such a classical bounce prevents the matter in the contracting Universe from reaching the conditions at which a quantum bounce could possibly occur.", "keyphrases": ["spin", "torsion", "big bounce", "astrophysic"]}
{"id": "1206.6165", "title": "Constraining Scale-Dependent Non-Gaussianity with Future Large-Scale Structure and the CMB", "abstract": "We forecast combined future constraints from the cosmic microwave background and large-scale structure on the models of primordial non-Gaussianity. We study the generalized local model of non-Gaussianity, where the parameter f_NL is promoted to a function of scale, and present the principal component analysis applicable to an arbitrary form of f_NL(k). We emphasize the complementarity between the CMB and LSS by using Planck, DES and BigBOSS surveys as examples, forecast constraints on the power-law f_NL(k) model, and introduce the figure of merit for measurements of scale-dependent non-Gaussianity.", "keyphrases": ["non-gaussianity", "large-scale structure", "cosmic microwave background"]}
{"id": "1306.6586", "title": "The impact of the phase-space density on the indirect detection of dark matter", "abstract": "We study the indirect detection of dark matter when the local dark matter velocity distribution depends upon position, as expected for the Milky Way and its dwarf spheroidal satellites, and the annihilation cross-section is not purely s-wave. Using a phase-space distribution consistent with the dark matter density profile, we present estimates of cosmic and gamma-ray fluxes from dark matter annihilations. The expectations for the indirect detection of dark matter can differ significantly from the usual calculation that assumes that the velocity of the dark matter particles follows a Maxwell-Boltzmann distribution.", "keyphrases": ["dark matter", "matter velocity distribution", "annihilation cross section"]}
{"id": "1405.1508", "title": "Constraints on the spacetime geometry around 10 stellar-mass black hole candidates from the disk's thermal spectrum", "abstract": "In a previous paper, one of us has described a code to compute the thermal spectrum of geometrically thin and optically thick accretion disks around generic stationary and axisymmetric black holes, which are not necessarily of the Kerr type. As the structure of the accretion disk and the propagation of electromagnetic radiation from the disk to the distant observer depend on the background metric, the analysis of the thermal spectrum of thin disks can be used to test the actual nature of black hole candidates. In this paper, we consider the 10 stellar-mass black hole candidates for which the spin parameter has been already estimated from the analysis of the disk's thermal spectrum and under the assumption of the Kerr background, and we translate the measurements reported in the literature into constraints on the spin parameter\u2013deformation parameter plane. The analysis of the disk's thermal spectrum can be used to estimate only one parameter of the geometry close to the compact object, and therefore it is not possible to get independent measurements of both the spin and the deformation parameters. The constraints obtained here will be used in combination with other measurements in future work, with the final goal to break the degeneracy between the spin and possible deviations from the Kerr solution and thus test the Kerr black hole hypothesis.", "keyphrases": ["spacetime geometry", "black hole candidate", "accretion disk"]}
{"id": "1208.0635", "title": "Shadows of Multi-Black Holes: Analytic Exploration", "abstract": "Shadows of multi-black holes have structures distinct from the mere superposition of the shadow of a single black hole: the eyebrow-like structures outside the main shadows and the deformation of the shadows. We present analytic estimates of these structures using the static multi-black hole solution (Majumdar-Papapetrou solution). We show that the width of the eyebrow is related with the distance between the black holes and that the shadows are deformed into ellipses due to the presence of the second black holes. These results are helpful to understand qualitatively the features of the shadows of colliding black holes. We also present the shadows of colliding/coalescing black holes in the Kastor-Traschen solution.", "keyphrases": ["multi-black hole", "shadow", "spacetime"]}
{"id": "1308.0535", "title": "Bimodal Distribution of Magnetic Fields and Areas of Sunspots", "abstract": "We applied automatic identification of sunspot umbrae and penumbrae to daily observations from the Helioseismic Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO) to study their magnetic flux (B) and area (A). The results confirm a previously known logarithmic relationship between the area of sunspots and their maximum flux density. In addition, we find that the relation between average magnetic flux (Bavg) and sunspot area shows a bimodal distribution: for small sunspots and pores (A < 20 millionth of solar hemisphere, MSH), Bavg = 800 G (gauss), and for large sunspots (A > 100 MSH), Bavg is about 600 G. For intermediate sunspots, average flux density linearly decreases from about 800 G to 600 G. A similar bimodal distribution was found in several other integral parameters of sunspots. We show that this bimodality can be related to different stages of sunspot penumbra formation and can be explained by the difference in average inclination of magnetic fields at the periphery of small and large sunspots.", "keyphrases": ["area", "sunspot", "bimodal distribution"]}
{"id": "0911.4463", "title": "Leptogenesis as a Common Origin for Matter and Dark Matter", "abstract": "We propose a model of asymmetric dark matter (DM) where the dark sector is an identical copy of both forces and matter of the standard model (SM) as in the mirror universe models discussed in literature. In addition to being connected by gravity, the SM and DM sectors are also connected at high temperature by a common set of heavy right-handed Majorana neutrinos via their Yukawa couplings to leptons and Higgs bosons. The lightest nucleon in the dark (mirror) sector is a candidate for dark matter. The out of equilibrium decay of right-handed neutrino produces equal lepton asymmetry in both sectors via resonant leptogenesis which then get converted to baryonic and dark baryonic matter. The dark baryon asymmetry due to higher dark nucleon masses leads to higher dark matter density compared to the familiar baryon density that is observed. The standard model neutrinos in this case acquire masses from the inverse seesaw mechanism. A kinetic mixing between the U(1) gauge fields of the two sectors is introduced to guarantee the success of Big-Bang Nucleosynthesis.", "keyphrases": ["dark matter", "lepton", "higgs boson", "right-handed neutrino", "leptogenesis"]}
{"id": "1001.5444", "title": "The Birth Environment of the Solar System", "abstract": "This paper reviews our current understanding of the possible birth environments of our Solar System. Since most stars form within groups and clusters, the question becomes one of determining the nature of the birth aggregate of the Sun. This discussion starts by reviewing Solar System properties that provide constraints on our environmental history. We then outline the range of star-forming environments that are available in the Galaxy, and discuss how they affect star and planet formation. The nature of the solar birth cluster is constrained by many physical considerations, including radiation fields provided by the background environment, dynamical scattering interactions, and by the necessity of producing the short-lived radioactive nuclear species inferred from meteoritic measurements. Working scenarios for the solar birth aggregate can be constructed, as discussed herein, although significant uncertainties remain.", "keyphrases": ["birth environment", "solar system", "star-forming environment"]}
{"id": "1207.2086", "title": "Cosmological Inflation and the Quantum Measurement Problem", "abstract": "According to cosmological inflation, the inhomogeneities in our universe are of quantum mechanical origin. This scenario is phenomenologically very appealing as it solves the puzzles of the standard hot big bang model and naturally explains why the spectrum of cosmological perturbations is almost scale invariant. It is also an ideal playground to discuss deep questions among which is the quantum measurement problem in a cosmological context. Although the large squeezing of the quantum state of the perturbations and the phenomenon of decoherence explain many aspects of the quantum to classical transition, it remains to understand how a specific outcome can be produced in the early universe, in the absence of any observer. The Continuous Spontaneous Localization (CSL) approach to quantum mechanics attempts to solve the quantum measurement question in a general context. In this framework, the wavefunction collapse is caused by adding new non linear and stochastic terms to the Schroedinger equation. In this paper, we apply this theory to inflation, which amounts to solving the CSL parametric oscillator case. We choose the wavefunction collapse to occur on an eigenstate of the Mukhanov-Sasaki variable and discuss the corresponding modified Schroedinger equation. Then, we compute the power spectrum of the perturbations and show that it acquires a universal shape with two branches, one which remains scale invariant and one with nS=4, a spectral index in obvious contradiction with the Cosmic Microwave Background (CMB) anisotropy observations. The requirement that the non-scale invariant part be outside the observational window puts stringent constraints on the parameter controlling the deviations from ordinary quantum mechanics... (Abridged).", "keyphrases": ["quantum measurement problem", "universe", "cosmological inflation"]}
{"id": "1301.5721", "title": "Shapes of primordial non-Gaussianities in the Horndeski's most general scalar-tensor theories", "abstract": "In the Horndeski's most general scalar-tensor theories, we derive the three-point correlation function of scalar non-Gaussianities generated during single-field inflation in the presence of slow-variation corrections to the leading-order term. Unlike previous works, the resulting bispectrum is valid for any shape of non-Gaussianities. In the squeezed limit, for example, this gives rise to the same consistency relation as that derived by Maldacena in standard single-field slow-roll inflation. We estimate the shape close to the squeezed one at which the effect of the term inversely proportional to the scalar propagation speed squared begins to contribute to the bispectrum. We also show that the leading-order bispectrum can be expressed by the linear combination of two convenient bases whose shapes are highly correlated with equilateral and orthogonal types respectively. We present concrete models in which the orthogonal and enfolded shapes can dominate over the equilateral one.", "keyphrases": ["scalar-tensor theory", "scalar propagation speed", "non-gaussianitie"]}
{"id": "1104.3579", "title": "Technically natural dark energy from Lorentz breaking", "abstract": "We construct a model of dark energy with a technically natural small contribution to cosmic acceleration, i.e. this contribution does not receive corrections from other scales in the theory. The proposed acceleration mechanism appears generically in the low-energy limit of gravity theories with violation of Lorentz invariance that contain a derivatively coupled scalar field Theta. The latter may be the Goldstone field of a broken global symmetry. The model, that we call Theta-CDM, is a valid effective field theory up to a high cutoff just a few orders of magnitude below the Planck scale. Furthermore, it can be ultraviolet-completed in the context of Horava gravity. We discuss the observational predictions of the model. Even in the absence of a cosmological constant term, the expansion history of the Universe is essentially indistinguishable from that of Lambda-CDM. The difference between the two theories appears at the level of cosmological perturbations. We find that in Theta-CDM the matter power spectrum is enhanced at subhorizon scales compared to Lambda-CDM. This property can be used to discriminate the model from Lambda-CDM with current cosmological data.", "keyphrases": ["dark energy", "cosmic acceleration", "low-energy limit", "violation", "lorentz invariance"]}
{"id": "1303.3307", "title": "Cosmography with the Sunyaev-Zeldovich effect and X-ray data", "abstract": "Cosmography provides a direct method to map the expansion history of the Universe in a model-independent way. Recently, different kinds of observations have been used in cosmographic analyses, such as SNe Ia and gamma ray bursts measurements, weak and strong lensing, cosmic microwave background anisotropies, etc. In this work we examine the prospects for constraining cosmographic parameters from current and future measurements of galaxy clusters distances based on their Sunyaev-Zeldovich effect (SZE) and X-ray observations. By assuming the current observational error distribution, we perform Monte Carlo simulations based on a well-behaved parameterization for the deceleration parameter to generate samples with different characteristics and study the improvement on the determination of the cosmographic parameters from upcoming data. The influence of galaxy clusters (GC) morphologies on the H_0- q_0 plane is also investigated.", "keyphrases": ["sunyaev-zeldovich effect", "x-ray observation", "cosmography"]}
{"id": "1009.4620", "title": "The 511 keV emission from positron annihilation in the Galaxy", "abstract": "The first gamma-ray line originating from outside the solar system that was ever detected is the 511 keV emission from positron annihilation in the Galaxy. Despite 30 years of intense theoretical and observational investigation, the main sources of positrons have not been identified up to now. Observations in the 1990's with OSSE/CGRO showed that the emission is strongly concentrated towards the Galactic bulge. In the 2000's, the SPI instrument aboard ESA's INTEGRAL gamma-ray observatory allowed scientists to measure that emission across the entire Galaxy, revealing that the bulge/disk luminosity ratio is larger than observed in any other wavelength. This mapping prompted a number of novel explanations, including rather \"exotic ones (e.g. dark matter annihilation). However, conventional astrophysical sources, like type Ia supernovae, microquasars or X-ray binaries, are still plausible candidates for a large fraction of the observed total 511 keV emission of the bulge. A closer study of the subject reveals new layers of complexity, since positrons may propagate far away from their production sites, making it difficult to infer the underlying source distribution from the observed map of 511 keV emission. However, contrary to the rather well understood propagation of high energy (>GeV) particles of Galactic cosmic rays, understanding the propagation of low energy ( MeV) positrons in the turbulent, magnetized interstellar medium, still remains a formidable challenge. We review the spectral and imaging properties of the observed 511 keV emission and we critically discuss candidate positron sources and models of positron propagation in the Galaxy.", "keyphrases": ["positron annihilation", "galaxy", "x-ray binary"]}
{"id": "1409.5533", "title": "Coupled dark energy with perturbed Hubble expansion rate", "abstract": "The coupling between dark sectors provides a possible approach to mitigate the coincidence problem of cosmological standard model. In this paper, dark energy is treated as a fluid with a constant equation of state, whose coupling with dark matter is proportional the Hubble parameter and energy density of dark energy, that is, Q\u0305=3\u03be_xH\u0305\u03c1\u0305_x. Particularly, we consider the Hubble expansion rate to be perturbed in the perturbation evolutions of dark sectors. Using jointing data sets which include cosmic microwave background radiation, baryon acoustic oscillation, type Ia supernovae, and redshift-space distortions, we perform a full Monte Carlo Markov Chain likelihood analysis for the coupled model. The results show that the mean value with errors of interaction rate is: \u03be_x=0.00305_-0.00305-0.00305-0.00305^+0.000645+0.00511+0.00854 for Q^\u03bc_A\u2225 u^\u03bc_c; \u03be_x=0.00317_-0.00317-0.00317-0.00317^+0.000628+0.00547+0.00929 for Q^\u03bc_A\u2225 u^\u03bc_x, which means that the recently cosmic observations favored small interaction rate which is up to the order of 10^-3. Moreover, in contrast to the coupled model with unperturbed expansion rate, we find perturbed Hubble expansion rate could bring about negligible impact on the model parameter space.", "keyphrases": ["dark energy", "hubble expansion rate", "cosmology", "dark matter"]}
{"id": "1911.03964", "title": "Forecasts on Primordial non-Gaussianity from 21 cm Intensity Mapping experiments", "abstract": "We forecast ability of dedicated 21 cm intensity mapping experiments to constraint primordial non-Gaussianity using power spectrum and bispectrum. We model the signal including the non-linear biasing expansion using a generalized halo model approach. We consider the importance of foreground filtering scale and of the foreground wedge. We find that the current generation intensity mapping experiments like CHIME do not posses sufficient sensitivity to be competitive with the existing limits. On the other hand, upcoming experiments like HIRAX can improve the current constraints and the proposed PUMA experiment can substantially improve them, reaching sensitivities below \u03c3 (f_ NL)<5 for equilateral and orthogonal configurations and \u03c3( f_ NL) < 1 for the local shape if good foreground control is achieved.", "keyphrases": ["primordial non-gaussianity", "power spectrum", "forecast"]}
{"id": "1111.5360", "title": "Emergent Universe by Tunneling", "abstract": "In this work we propose an alternative scheme for an Emergent Universe scenario where the universe is initially in a static state supported by a scalar field located in a false vacuum. The universe begins to evolve when, by quantum tunneling, the scalar field decays into a state of true vacuum. The Emergent Universe models are interesting since they provide specific examples of nonsingular inflationary universes.", "keyphrases": ["universe", "alternative scheme", "static state", "scalar field", "vacuum"]}
{"id": "1807.04390", "title": "The string swampland constraints require multi-field inflation", "abstract": "An important unsolved problem that affects practically all attempts to connect string theory to cosmology and phenomenology is how to distinguish effective field theories belonging to the string landscape from those that are not consistent with a quantum theory of gravity at high energies (the \"string swampland\"). It was recently proposed that potentials of the string landscape must satisfy at least two conditions, the \"swampland criteria\", that severely restrict the types of cosmological dynamics they can sustain. The first criterion states that the (multi-field) effective field theory description is only valid over a field displacement \u0394\u03d5\u2264\u0394\u223c\ud835\udcaa(1) (in units where the Planck mass is 1), measured as a distance in the target space geometry. A second, more recent, criterion asserts that, whenever the potential V is positive, its slope must be bounded from below, and suggests |\u2207 V| / V \u2265 c \u223c\ud835\udcaa(1). A recent analysis concluded that these two conditions taken together practically rule out slow-roll models of inflation. In this note we show that the two conditions rule out inflationary backgrounds that follow geodesic trajectories in field space, but not those following curved, non-geodesic, trajectories (which are parametrized by a non-vanishing bending rate \u03a9 of the multi-field trajectory). We derive a universal lower bound on \u03a9 (relative to the Hubble parameter H) as a function of \u0394, c and the number of efolds N_e, assumed to be at least of order 60. If later studies confirm c and \u0394 to be strictly \ud835\udcaa(1), the bound implies strong turns with \u03a9 / H \u2265 3 N_e \u223c 180. Slow-roll inflation in the landscape is not ruled out, but it is strongly multi-field.", "keyphrases": ["multi-field inflation", "field space", "swampland conjecture"]}
{"id": "1906.05726", "title": "Robust model comparison tests of DAMA/LIBRA annual modulation", "abstract": "We evaluate the statistical significance of the DAMA/LIBRA claims for annual modulation using three independent model comparison techniques, viz frequentist, information theory, and Bayesian analysis. We fit the data from the DAMA/LIBRA experiment to both cosine and a constant model, and carry out model comparison by choosing the constant model as the null hypothesis. For the frequentist test, we invoke Wilk's theorem and calculate the significance using \u0394\u03c7^2 between the two models. For information theoretical tests, we calculate the difference in Akaike Information Criterion (AIC) and Bayesian Information criterion (BIC) between the two models. We also compare the two models in a Bayesian context by calculating the Bayes factor. We also search for higher harmonics in the DAMA/LIBRA data using generalized Lomb-Scargle periodogram. We finally test the sensitivity of these model comparison techniques in discriminating between pure noise and a cosine signal using synthetic data. This is the first proof of principles application of AIC, BIC as well as Bayes factor to the DAMA data. All our analysis codes along with the data used in this work have been made publicly available.", "keyphrases": ["dama", "annual modulation", "null hypothesis"]}
{"id": "1307.3898", "title": "Phantom dark energy from non-local infrared modifications of General Relativity", "abstract": "We discuss the cosmological consequences of a model based on a non-local infrared modification of Einstein equations. We find that the model generates a dynamical dark energy that can account for the presently observed value of \u03a9_ DE, without introducing a cosmological constant. Tuning a free mass parameter m to a value m\u2243 0.67 H_0 we reproduce the observed value \u03a9_ DE\u2243 0.68. This leaves us with no free parameter and we then get a pure prediction for the EOS parameter of dark energy. Writing w_ DE(a)=w_0+(1-a) w_a, we find w_0\u2243-1.04 and w_a\u2243 -0.02, consistent with the Planck data, and on the phantom side. We also argue that non-local equations of the type that we propose must be understood as purely classical effective equations, such as those derived in semiclassical gravity for the in-in matrix elements of the metric. As such, any apparent ghost instability in such equations only affects the classical dynamics, but there is no propagating degree of freedom associated to the ghost, and no issue of ghost-induced quantum vacuum decay.", "keyphrases": ["dark energy", "non-local infrared modification", "gravity"]}
{"id": "1204.5505", "title": "Establishing homogeneity of the universe in the shadow of dark energy", "abstract": "Assuming the universe is spatially homogeneous on the largest scales lays the foundation for almost all cosmology. This idea is based on the Copernican principle, that we are not at a particularly special place in the universe. Surprisingly, this philosophical assumption has yet to be rigorously demonstrated independently of the standard paradigm. This issue has been brought to light by cosmological models which can potentially explain apparent acceleration by spatial inhomogeneity rather than dark energy. These models replace the temporal fine tuning associated with Lambda with a spatial fine tuning, and so violate the Copernican assumption. While is seems unlikely that such models can really give a realistic solution to the dark energy problem, they do reveal how poorly constrained radial inhomogeneity actually is. So the bigger issue remains: How do we robustly test the Copernican principle independently of dark energy or theory of gravity?", "keyphrases": ["universe", "cosmological model", "time-constant hypersurface", "new physics"]}
{"id": "1311.6374", "title": "Fluctuations in strongly coupled cosmologies", "abstract": "In the early Universe, a dual component made of coupled CDM and a scalar field \u03a6, if their coupling \u03b2 > \u221a(3)/2, owns an attractor solution, making them a stationary fraction of cosmic energy during the radiation dominated era. Along the attractor, both such components expand \u221d a^-4 and have early density parameters \u03a9_d = 1/ (4\u03b2^2) and \u03a9_c= 2, \u03a9_d (field and CDM, respectively). In a previous paper it was shown that, if a further component, expanding \u221d a^-3, breaks such stationary expansion at z \u223c 3\u20135 \u00d7 10^3, cosmic components gradually acquire densities consistent with observations. This paper, first of all, considers the case that this component is warm. However, its main topic is the analysis of fluctuation evolution: out of horizon modes are then determined; their entry into horizon is numerically evaluated as well as the dependence of Meszaros effect on the coupling \u03b2; finally, we compute: (i) transfer function and linear spectral function; (ii) CMB C_l spectra. Both are close to standard \u039bCDM models; in particular, the former one can be so down to a scale smaller than Milky Way, in spite of its main DM component being made of particles of mass <1 keV. The previously coupled CDM component, whose present density parameter is O(10^-3), exhibits wider fluctuations \u03b4\u03c1/\u03c1, but approximately \u03b2-independent \u03b4\u03c1 values. We discuss how lower scale features of these cosmologies might ease quite a few problems that \u039bCDM does not easily solve.", "keyphrases": ["cosmology", "radiation", "fluctuation"]}
{"id": "1411.0267", "title": "Unbounded energies of debris from head-on particle collisions near black holes", "abstract": "If two particles move toward a black hole and collide near the horizon, the energy E_c.m. in the centre of mass can grow unbounded. This is a so-called Ba\u00f1ados-Silk-West (BSW) effect. One of problems creating obstacles to the possibility of its observation consists in that individual energy E of a fragment at infinity remains finite because of redshift. We show that in the case of head-on collision, debris may have unbounded energy E. An essential ingredient of this scenario is a particle moving away from a black hole in the near-horizon region. It can appear due to precedent collision that implies multiple scattering.", "keyphrases": ["debris", "black hole", "head-on collision"]}
{"id": "1609.02279", "title": "CERES: A Set of Automated Routines for Echelle Spectra", "abstract": "We present the Collection of Elemental Routines for Echelle Spectra (CERES). These routines were developed for the construction of automated pipelines for the reduction, extraction and analysis of spectra acquired with different instruments, allowing the obtention of homogeneous and standardised results. This modular code includes tools for handling the different steps of the processing: CCD image reductions, identification and tracing of the echelle orders, optimal and rectangular extraction, computation of the wavelength solution, estimation of radial velocities, and rough and fast estimation of the atmospheric parameters. Currently, CERES has been used to develop automated pipelines for thirteen different spectrographs, namely CORALIE, FEROS, HARPS, ESPaDOnS, FIES, PUCHEROS, FIDEOS, CAFE, DuPont/Echelle, Magellan/Mike, Keck/HIRES, Magellan/PFS and APO/ARCES, but the routines can be easily used in order to deal with data coming from other spectrographs. We show the high precision in radial velocity that CERES achieves for some of these instruments and we briefly summarize some results that have already been obtained using the CERES pipelines.", "keyphrases": ["echelle spectra", "reduction", "ceres"]}
{"id": "1503.07442", "title": "Vector interaction enhanced bag model for astrophysical applications", "abstract": "For quark matter studies in astrophysics the thermodynamic bag model (tdBAG) has been widely used. Despite its success it fails to account for various phenomena expected from Quantum-Chromo-Dynamics (QCD). We suggest a straightforward extension of tdBAG in order to take the dynamical breaking of chiral symmetry and the influence of vector interactions explicitly into account. As for tdBAG the model mimics confinement in a phenomenological approach. It is based on an analysis of the Nambu\u2013Jona-Lasinio (NJL) model at finite density. Furthermore, we demonstrate how NJL and bag models in this regime follow from the more general and QCD based framework of Dyson-Schwinger (DS) equations in medium by assuming a simple gluon contact interaction. Based on our simple and novel model, we construct quark hadron hybrid equations of state (EoS) and study systematically chiral and deconfinement phase transitions, the appearance of s-quarks and the role of vector interaction. We further study these aspects for matter in beta-equilibrium at zero temperature, with particular focus on the current 2 solar masses maximum mass constraint for neutron stars. Our approach indicates that the currently only theoretical evidence for the hypothesis of stable strange matter is an artifact of tdBAG and results from neglecting the dynamical breaking of chiral symmetry.", "keyphrases": ["bag model", "vector interaction", "astrophysical study"]}
{"id": "1701.03418", "title": "Direct Probe of Dark Energy through Gravitational Lensing Effect", "abstract": "We show that gravitational lensing can provide a direct method to probe the nature of dark energy at astrophysical scales. For lensing system as an isolated astrophysical object, we derive the dark energy contribution to gravitational potential as a repulsive power-law term, containing a generic equation of state parameter w. We find that it generates w-dependent and position-dependent modification to the conventional light orbital equation of w=-1. With post-Newtonian approximation, we compute its direct effect for an isolated lensing system at astrophysical scales and find that the dark energy force can deflect the path of incident light rays. We demonstrate that the dark-energy-induced deflection angle \u0394\u03b1_DE^\u221d M^(1+1/3w) (with 1+1/3w>0), which increases with the lensing mass M and consistently approaches zero in the limit M \u2192 0. This effect is distinctive because dark energy tends to diffuse the rays and generates concave lensing effect. This is in contrast to the conventional convex lensing effect caused by both visible and dark matter. Measuring such concave lensing effect can directly probe the existence and nature of dark energy. We estimate this effect and show that the current gravitational lensing experiments are sensitive to the direct probe of dark energy at astrophysical scales. For the special case w=-1, our independent study favors the previous works that the cosmological constant can affect light bending, although our prediction qualitatively and quantitatively differ from the literature, including our consistent realization of \u0394\u03b1_DE\u2192 0 (under M \u2192 0) at the leading order.", "keyphrases": ["dark energy", "astrophysical scale", "dark matter", "spacetime"]}
{"id": "1311.7346", "title": "The Origin of Galactic Cosmic Rays", "abstract": "One century ago Viktor Hess carried out several balloon flights that led him to conclude that the penetrating radiation responsible for the discharge of electroscopes was of extraterrestrial origin. One century from the discovery of this phenomenon seems to be a good time to stop and think about what we have understood about Cosmic Rays. The aim of this review is to illustrate the ideas that have been and are being explored in order to account for the observable quantities related to cosmic rays and to summarize the numerous new pieces of observation that are becoming available. In fact, despite the possible impression that development in this field is somewhat slow, the rate of new discoveries in the last decade or so has been impressive, and mainly driven by beautiful pieces of observation. At the same time scientists in this field have been able to propose new, fascinating ways to investigate particle acceleration inside the sources, making use of multifrequency observations that range from the radio, to the optical, to X-rays and gamma rays. These ideas can now be confronted with data. I will mostly focus on supernova remnants as the most plausible sources of Galactic cosmic rays, and I will review the main aspects of the modern theory of diffusive particle acceleration at supernova remnant shocks, with special attention for the dynamical reaction of accelerated particles on the shock and the phenomenon of magnetic field amplification at the shock. Cosmic ray escape from the sources is discussed as a necessary step to determine the spectrum of cosmic rays at the Earth. In the end of this review I will also discuss the phenomenon of cosmic ray acceleration at shocks propagating in partially ionized media and the implications of this phenomenon in terms of width of the Balmer line emission.", "keyphrases": ["cosmic ray", "century", "supernova remnant", "likely source"]}
{"id": "1608.03707", "title": "ABS: an Analytical method of Blind Separation of CMB from foregrounds", "abstract": "Extracting CMB B-mode polarization from complicated foregrounds is a challenging task in searching for inflationary gravitational waves. We propose the ABS method as a blind and analytical solution to this problem. It applies to the measured cross bandpower between different frequency bands and obtains the CMB B-mode bandpower analytically. It does not rely on assumptions of foregrounds and does not require multiple parameter fitting. Testing against a variety of foregrounds, survey frequency configurations and instrument noise, we verify its applicability and numerical stability. The ABS method also applies to CMB temperature, E-mode polarization, the thermal Sunyaev Zel'dovich effect, spectral distortion, and even significantly different problems such as cosmic magnification.", "keyphrases": ["blind separation", "foreground", "instrument noise", "abs"]}
{"id": "2106.08362", "title": "Diffusion of cosmic rays in MHD turbulence with magnetic mirrors", "abstract": "As the fundamental physical process with many astrophysical implications, the diffusion of cosmic rays (CRs) is determined by their interaction with magnetohydrodynamic (MHD) turbulence. We consider the magnetic mirroring effect arising from MHD turbulence on the diffusion of CRs. Due to the intrinsic superdiffusion of turbulent magnetic fields, CRs with large pitch angles that undergo mirror reflection, i.e., bouncing CRs, are not trapped between magnetic mirrors, but move diffusively along the turbulent magnetic field, leading to a new type of parallel diffusion, i.e., mirror diffusion. This mirror diffusion is in general slower than the diffusion of non-bouncing CRs with small pitch angles that undergo gyroresonant scattering. The critical pitch angle at the balance between magnetic mirroring and pitch-angle scattering is important for determining the diffusion coefficients of both bouncing and non-bouncing CRs and their scalings with the CR energy. We find non-universal energy scalings of diffusion coefficients, depending on the properties of MHD turbulence.", "keyphrases": ["cosmic ray", "mhd turbulence", "magnetic field"]}
{"id": "1412.7136", "title": "Imperfect Dark Matter", "abstract": "We consider cosmology of the recently introduced mimetic matter with higher derivatives (HD). Without HD this system describes irrotational dust - Dark Matter (DM) as we see it on cosmologically large scales. DM particles correspond to the shift-charges - Noether charges of the shifts in the field space. Higher derivative corrections usually describe a deviation from the thermodynamical equilibrium in the relativistic hydrodynamics. Thus we show that mimetic matter with HD corresponds to an imperfect DM which: i) renormalises the Newton's constant in the Friedmann equations, ii) has zero pressure when there is no extra matter in the universe, iii) survives the inflationary expansion which puts the system on a dynamical attractor with a vanishing shift-charge, iv) perfectly tracks any external matter on this attractor, v) can become the main (and possibly the only) source of DM, provided the shift-symmetry in the HD terms is broken during some small time interval in the radiation domination era. In the second part of the paper we present a hydrodynamical description of general anisotropic and inhomogeneous configurations of the system. This imperfect mimetic fluid has an energy flow in the field's rest frame. We find that in the Eckart and in the Landau-Lifshitz frames the mimetic fluid possesses nonvanishing vorticity appearing already at the first order in the HD. Thus, the structure formation and gravitational collapse should proceed in a rather different fashion from the simple irrotational DM models.", "keyphrases": ["dark matter", "dust", "fluid", "high derivative term", "gravity"]}
{"id": "1011.3212", "title": "Notes on Ghost Dark Energy", "abstract": "We study a phenomenological dark energy model which is rooted in the Veneziano ghost of QCD. In this dark energy model, the energy density of dark energy is proportional to Hubble parameter and the proportional coefficient is of the order \u039b^3_QCD, where \u039b_QCD is the mass scale of QCD. The universe has a de Sitter phase at late time and begins to accelerate at redshift around z_acc\u223c0.6. We also fit this model and give the constraints on model parameters, with current observational data including SnIa, BAO, CMB, BBN and Hubble parameter data. We find that the squared sound speed of the dark energy is negative, which may cause an instability. We also study the cosmological evolution of the dark energy with interaction with cold dark matter.", "keyphrases": ["dark energy", "bao", "dark matter", "gde model"]}
{"id": "1601.04725", "title": "The impact of baryons on the direct detection of dark matter", "abstract": "The spatial and velocity distributions of dark matter particles in the Milky Way Halo affect the signals expected to be observed in searches for dark matter. Results from direct detection experiments are often analyzed assuming a simple isothermal distribution of dark matter, the Standard Halo Model (SHM). Yet there has been skepticism regarding the validity of this simple model due to the complicated gravitational collapse and merger history of actual galaxies. In this paper we compare the SHM to the results of cosmological hydrodynamical simulations of galaxy formation to investigate whether or not the SHM is a good representation of the true WIMP distribution in the analysis of direct detection data. We examine two Milky Way-like galaxies from the MaGICC cosmological simulations (a) with dark matter only and (b) with baryonic physics included. The inclusion of baryons drives the shape of the DM halo to become more spherical and makes the velocity distribution of dark matter particles less anisotropic especially at large heliocentric velocities, thereby making the SHM a better fit. We also note that we do not find a significant disk-like rotating dark matter component in either of the two galaxy halos with baryons that we examine, suggesting that dark disks are not a generic prediction of cosmological hydrodynamical simulations. We conclude that in the Solar neighborhood, the SHM is in fact a good approximation to the true dark matter distribution in these cosmological simulations (with baryons) which are reasonable representations of the Milky Way, and hence can also be used for the purpose of dark matter direct detection calculations.", "keyphrases": ["baryon", "way-like galaxy", "cosmological simulation"]}
{"id": "1002.4740", "title": "Measuring Unified Dark Matter with 3D Cosmic Shear", "abstract": "We present parameter estimation forecasts for future 3D cosmic shear surveys for a class of Unified Dark Matter (UDM) models, where a single scalar field mimics both Dark Matter (DM) and Dark Energy (DE). These models have the advantage that they can describe the dynamics of the Universe with a single matter component providing an explanation for structure formation and cosmic acceleration. A crucial feature of the class of UDM models we use in this work is characterised by a parameter, c_inf (in units of the speed of light c=1), that is the value of the sound speed at late times, and on which structure formation depends. We demonstrate that the properties of the DM-like behaviour of the scalar field can be estimated with very high precision with large-scale, fully 3D weak lensing surveys. We found that 3D weak lensing significantly constrains c_inf, and we find minimal errors 0.00003, for the fiducial value c_inf=0.001, and 0.000026, for c_inf=0.012. Moreover, we compute the Bayesian evidence for UDM models over the LCDM model as a function of c_inf. For this purpose, we can consider the LCDM model as a UDM model with c_inf=0. We find that the expected evidence clearly shows that the survey data would unquestionably favour UDM models over the LCDM model, for the values c_inf>0.001.", "keyphrases": ["unified dark matter", "scalar field", "dark energy"]}
{"id": "1801.07721", "title": "On the diversity and statistical properties of protostellar discs", "abstract": "We present results from the first population synthesis study of protostellar discs. We analyse the evolution and properties of a large sample of protostellar discs formed in a radiation hydrodynamical simulation of star cluster formation. Due to the chaotic nature of the star formation process, we find an enormous diversity of young protostellar discs, including misaligned discs, and discs whose orientations vary with time. Star-disc interactions truncate discs and produce multiple systems. Discs may be destroyed in dynamical encounters and/or through ram-pressure stripping, but reform by later gas accretion. We quantify the distributions of disc mass and radii for protostellar ages up to \u2248 10^5 yrs. For low-mass protostars, disc masses tend to increase with both age and protostellar mass. Disc radii range from of order ten to a few hundred au, grow in size on timescales \u2264 10^4 yr, and are smaller around lower-mass protostars. The radial surface density profiles of isolated protostellar discs are flatter than the minimum mass solar nebula model, typically scaling as \u03a3\u221d r^-1. Disc to protostar mass ratios rarely exceed two, with a typical range of M_ d/M_* = 0.1-1 to ages \u2264 10^4 yrs and decreasing thereafter. We quantify the relative orientation angles of circumstellar discs and the orbit of bound pairs of protostars, finding a preference for alignment that strengths with decreasing separation. We also investigate how the orientations of the outer parts of discs differ from the protostellar and inner disc spins for isolated protostars and pairs.", "keyphrases": ["protostellar disc", "disc", "gas accretion"]}
{"id": "1006.5210", "title": "Teraelectronvolt Astronomy", "abstract": "Ground-based gamma-ray astronomy, which provides access to the TeV energy range, is a young and rapidly developing discipline. Recent discoveries in this waveband have important consequences for a wide range of topics in astrophysics and astroparticle physics. This article is an attempt to review the experimental status of this field and to provide the basic formulae and concepts required to begin the interpretation of TeV observations.", "keyphrases": ["astronomy", "atmospheric cherenkov telescope", "iacts", "gamma-ray source"]}
{"id": "0911.3805", "title": "Simple Types of Anisotropic Inflation", "abstract": "We display some simple cosmological solutions of gravity theories with quadratic Ricci curvature terms added to the Einstein-Hilbert lagrangian which exhibit anisotropic inflation. The Hubble expansion rates are constant and unequal in three orthogonal directions. We describe the evolution of the simplest of these homogeneous and anisotropic cosmological models from its natural initial state and evaluate the deviations they will create from statistical isotropy in the fluctuations produced during a period of anisotropic inflation. The anisotropic inflation is not a late-time attractor in these models but the rate of approach to a final isotropic de Sitter state is slow and is conducive to the creation of observable anisotropic statistical effects in the microwave background. The statistical anisotropy would not be scale invariant and the level of statistical anisotropy will grow with scale.", "keyphrases": ["anisotropic inflation", "anisotropy", "cosmic no-hair conjecture", "challenge", "theoretical possibility"]}
{"id": "1406.7714", "title": "The origin of galactic cosmic rays", "abstract": "Initial discovery of CRs dates back to a century ago (1912). Their identification as particles rather than radiation dates to about 20 years later and in 20 more years also the first suggestion that they were associated with SNRs was in place. The basic mechanism behind their acceleration was suggested almost 40 years ago. Much work has been done since then to the aim of proving that both the acceleration mechanism and site are well understood, but no definite proof has been obtained: in spite of impressive progress of both theory and observations, the evidence in support of the commonly accepted interpretation is only circumstantial. In the following I will try to make the point on where we stand in terms of how our theories confront with data: I will review recent progress on the subject and try to point to avenues to pursue in order to gather new proofs, if not smoking gun evidence of the origin of Galactic Cosmic Rays.", "keyphrases": ["galactic cosmic ray", "century", "supernova remnant"]}
{"id": "1309.1579", "title": "Bispectrum from open inflation", "abstract": "We calculate the bispectrum of primordial curvature perturbations, \u03b6, generated during \"open inflation.\" Inflation occurs inside a bubble nucleated via quantum tunneling from the background false vacuum state. Our universe lives inside the bubble, which can be described as a Friedman-Lema\u00eetre-Robertson-Walker (FLRW) universe with negative spatial curvature, undergoing slow-roll inflation. We pay special attention to the issue of an initial state for quantum fluctuations. A \"vacuum state\" defined by a positive-frequency mode in de Sitter space charted by open coordinates is different from the Euclidean vacuum (which is equivalent to the so-called \"Bunch-Davies vacuum\"). Quantum tunneling then modifies the initial state away from the original Euclidean vacuum. While most of the previous study on modifications of the initial quantum state introduces, by hand, an initial time at which the quantum state is modified as well as the form of the modification, an effective initial time naturally emerges and the form is fixed by quantum tunneling in open inflation models. Therefore, open inflation enables a self-consistent computation of the effect of a modified initial state on the bispectrum. We find a term which goes as <\u03b6_k_1 \u03b6_k_2 \u03b6_k_3> \u221d1/k_1^2k_3^4 in the so-called squeezed configurations, k_3\u226ak_1\u2248k_2, in agreement with the previous study. The bispectrum in the exact folded limit, e.g., k_1=k_2+k_3, is also enhanced and remains finite. However, these terms are exponentially suppressed when the wavelength of \u03b6is smaller than the curvature radius of the universe. The leading-order bispectrum is equal to the usual one from single-field slow-roll inflation; the terms specific for open inflation arise only in the sub-leading order when the wavelength of \u03b6is smaller than the curvature radius.", "keyphrases": ["open inflation", "vacuum", "universe"]}
{"id": "1908.04854", "title": "Tomographic analyses of the CMB lensing and galaxy clustering to probe the linear structure growth", "abstract": "In a tomographic approach, we measure the cross-correlation between the CMB lensing reconstructed from the Planck satellite and the galaxies of the photometric redshift catalogue based on the combination of the South Galactic Cap u-band Sky Survey (SCUSS), Sloan Digital Sky Survey (SDSS), and Wide-field Infrared Survey Explorer (WISE) data. We perform the analyses considering six redshift bins spanning the range of 0.1 <z<0.7. From the estimates of the galaxy-galaxy and galaxy-CMB lensing power spectrum, we derive the galaxy bias and the amplitude of the cross-correlation for each redshift bin. We have finally applied these tomographic measurements to estimate the linear structure growth using the bias-independent D\u0302_G estimator introduced by Giannantonio et al. 2016. We find that the amplitude of the structure growth with respect to the fiducial cosmology is A_D=1.16\u00b1 0.13, closely consistent with the predictions of the \u039bCDM model (A_D^\u039b CDM=1). We perform several tests for consistency of our results, finding no significant evidence for systematic effects.", "keyphrases": ["galaxy", "structure growth", "cross-correlation"]}
{"id": "1504.01763", "title": "Electromagnetically-Induced Frame-Dragging around Astrophysical Objects", "abstract": "Frame dragging (Lense-Thirring effect) is generally associated with rotating astrophysical objects. However, it can also be generated by electromagnetic fields if electric and magnetic fields are simultaneously present. In most models of astrophysical objects, macroscopic charge neutrality is assumed and the entire electromagnetic field is characterized in terms of a magnetic dipole component. Hence, the purely electromagnetic contribution to the frame dragging vanishes. However, strange stars may posses independent electric dipole and neutron stars independent electric quadrupole moments that may lead to the presence of purely electromagnetic contributions to the frame dragging. Moreover, recent observations have shown that in stars with strong electromagnetic fields, the magnetic quadrupole may have a significant contribution to the dynamics of stellar processes. As an attempt to characterized and quantify the effect of electromagnetic frame-dragging in this kind of astrophysical objects, an analytic solution to the Einstein-Maxwell equations is constructed here on the basis that the electromagnetic field is generated by the combination of arbitrary magnetic and electric dipoles plus arbitrary magnetic and electric quadrupole moments. The effect of each multipole contribution on the vorticity scalar and the Poynting vector is described in detail. Corrections on important quantities such the innermost stable circular orbit (ISCO) and the epyciclic frequencies are also considered.", "keyphrases": ["frame-dragging", "astrophysical object", "electromagnetic field"]}
{"id": "1510.08205", "title": "Infinite efficiency of collisional Penrose process: Can over-spinning Kerr geometry be the source of ultra-high-energy cosmic rays and neutrinos ?", "abstract": "The origin of the ultra-high-energy particles we receive on the Earth from the outer space such as EeV cosmic rays and PeV neutrinos remains an enigma. All mechanisms known to us currently make use of electromagnetic interaction to accelerate charged particles. In this paper we propose a mechanism exclusively based on gravity rather than electromagnetic interaction. We show that it is possible to generate ultra-high-energy particles starting from particles with moderate energies using the collisional Penrose process in an overspinning Kerr spacetime transcending the Kerr bound only by an infinitesimal amount, i.e., with the Kerr parameter a=M(1+\u03f5), where we take the limit \u03f5\u2192 0^+. We consider two massive particles starting from rest at infinity that collide at r=M with divergent center-of-mass energy and produce two massless particles. We show that massless particles produced in the collision can escape to infinity with the ultra-high energies exploiting the collisional Penrose process with the divergent efficiency \u03b7\u223c1/\u221a(\u03f5)\u2192\u221e. Assuming the isotropic emission of massless particles in the center-of-mass frame of the colliding particles, we show that half of the particles created in the collisions escape to infinity with the divergent energies. To a distant observer, ultra-high-energy particles appear to originate from a bright spot which is at the angular location \u03be\u223c2M/r_obs with respect to the singularity on the side which is rotating towards the observer. We show that the anisotropy in emission in the center-of-mass frame, which is dictated by the differential cross-section of underlying particle physics process, leaves a district signature on the spectrum of ultra-high-energy massless particles. Thus, it provides a unique probe into fundamental particle physics.", "keyphrases": ["collisional penrose process", "cosmic ray", "kerr spacetime"]}
{"id": "1003.3178", "title": "Embedding realistic surveys in simulations through volume remapping", "abstract": "Connecting cosmological simulations to real-world observational programs is often complicated by a mismatch in geometry: while surveys often cover highly irregular cosmological volumes, simulations are customarily performed in a periodic cube. We describe a technique to remap this cube into elongated box-like shapes that are more useful for many applications. The remappings are one-to-one, volume-preserving, keep local structures intact, and involve minimal computational overhead.", "keyphrases": ["simulation", "volume", "periodic cube"]}
{"id": "1912.13173", "title": "Measurements of the low energy neutron and gamma ray accompaniment of extensive air showers in the knee region of primary cosmic ray spectrum", "abstract": "Purposeful investigation of radiation fluxes strongly delayed in relation to the main particles front of extensive air shower (EAS) was undertaken at the Tien Shan Mountain Cosmic Ray Station. It was found that the passage of the EAS can be accompanied by the delayed thermal neutrons and by the soft (30-50) keV gamma rays, mostly concentrated within a region of about (5-10) m around shower axis, where the integral radiation fluence can vary in the limits of (10^-4-1) cm^-2 for neutrons, and of (0.1-1000) cm^-2 for gamma rays. The dependence of signal multiplicity on the shower size N_e has a power shape both for the neutron and gamma ray components, with a sharp increase of its power index around the value of N_e\u2248 10^6, which corresponds to the position of the 3\u00b710^15 eV knee in the primary cosmic ray spectrum. Total duration of detectable radiation signal after the EAS passage can be of some tens of milliseconds in the case of neutron component, and up to a few whole seconds for gamma rays. The delayed accompaniment of low-energy radiation particles can be an effective probe to study the interaction of the hadronic component of EAS.", "keyphrases": ["extensive air shower", "cosmic ray spectrum", "neutron component"]}
{"id": "1003.5753", "title": "Energy cross-calibration from the first CREAM flight: transition radiation detector versus calorimeter", "abstract": "The Cosmic Ray Energetics And Mass (CREAM) balloon experiment had two successful flights in 2004/05 and 2005/06. It was designed to perform energy measurements from a few GeV up to 1000 TeV, taking advantage of different detection techniques. The first instrument, CREAM-1, combined a transition radiation detector with a calorimeter to provide independent energy measurements of cosmicraynuclei. Each detector was calibrated with particle beams in a limited range of energies. In order to assess the absolute energy scale of the instrument and to investigate the systematic effects of each technique, a cross-calibration was performed by comparing the two independent energy estimates on selected samples of oxygen and carbon nuclei.", "keyphrases": ["cross-calibration", "transition radiation detector", "calorimeter"]}
{"id": "1501.03163", "title": "Galaxy bias and gauges at second order in General Relativity", "abstract": "We discuss the question of gauge choice when analysing relativistic density perturbations at second order. We compare Newtonian and General Relativistic approaches. Some misconceptions in the recent literature are addressed. We show that the comoving-synchronous gauge is the unique gauge in General Relativity that corresponds to the Lagrangian frame and is entirely appropriate to describe the matter overdensity at second order. The comoving-synchronous gauge is the simplest gauge in which to describe Lagrangian bias at second order.", "keyphrases": ["gauge", "general relativity", "comoving-synchronous gauge", "galaxy bias"]}
{"id": "0909.3524", "title": "Ghost instabilities of cosmological models with vector fields nonminimally coupled to the curvature", "abstract": "We prove that many cosmological models characterized by vectors nonminimally coupled to the curvature (such as the Turner-Widrow mechanism for the production of magnetic fields during inflation, and models of vector inflation or vector curvaton) contain ghosts. The ghosts are associated with the longitudinal vector polarization present in these models, and are found from studying the sign of the eigenvalues of the kinetic matrix for the physical perturbations. Ghosts introduce two main problems: (1) they make the theories ill-defined at the quantum level in the high energy/sub horizon regime (and create serious problems for finding a well behaved UV completion); (2) they create an instability already at the linearized level. This happens because the eigenvalue corresponding to the ghost crosses zero during the cosmological evolution. At this point the linearized equations for the perturbations become singular (we show that this happens for all the models mentioned above). We explicitly solve the equations in the simplest cases of a vector without vev in a FRW geometry, and of a vector with vev plus a cosmological constant, and we show that indeed the solutions of the linearized equations diverge when these equations become singular.", "keyphrases": ["cosmological model", "ghost instability", "tachyonic"]}
{"id": "1706.06645", "title": "Towards optimal extraction of cosmological information from nonlinear data", "abstract": "One of the main unsolved problems of cosmology is how to maximize the extraction of information from nonlinear data. If the data are nonlinear the usual approach is to employ a sequence of statistics (N-point statistics, counting statistics of clusters, density peaks or voids etc.), along with the corresponding covariance matrices. However, this approach is computationally prohibitive and has not been shown to be exhaustive in terms of information content. Here we instead develop a Bayesian approach, expanding the likelihood around the maximum posterior of linear modes, which we solve for using optimization methods. By integrating out the modes using perturbative expansion of the likelihood we construct an initial power spectrum estimator, which for a fixed forward model contains all the cosmological information if the initial modes are gaussian distributed. We develop a method to construct the window and covariance matrix such that the estimator is explicitly unbiased and nearly optimal. We then generalize the method to include the forward model parameters, including cosmological and nuisance parameters, and primordial non-gaussianity. We apply the method in the simplified context of nonlinear structure formation, using either simplified 2-LPT dynamics or N-body simulations as the nonlinear mapping between linear and nonlinear density, and 2-LPT dynamics in the optimization steps used to reconstruct the initial density modes. We demonstrate that the method gives an unbiased estimator of the initial power spectrum, providing among other a near optimal reconstruction of linear baryonic acoustic oscillations.", "keyphrases": ["extraction", "cosmological information", "nonlinear data", "bayesian approach"]}
{"id": "1104.1167", "title": "Light-cone averaging in cosmology: formalism and applications", "abstract": "We present a general gauge invariant formalism for defining cosmological averages that are relevant for observations based on light-like signals. Such averages involve either null hypersurfaces corresponding to a family of past light-cones or compact surfaces given by their intersection with timelike hypersurfaces. Generalized Buchert-Ehlers commutation rules for derivatives of these light-cone averages are given. After introducing some adapted \"geodesic light-cone\" coordinates, we give explicit expressions for averaging the redshift to luminosity-distance relation and the so-called \"redshift drift\" in a generic inhomogeneous Universe.", "keyphrases": ["formalism", "redshift drift", "light-cone"]}
{"id": "1307.5949", "title": "Entropic cosmology for a generalized black-hole entropy", "abstract": "An entropic-force scenario, i.e., entropic cosmology, assumes that the horizon of the universe has an entropy and a temperature. In the present study, in order to examine entropic cosmology, we derive entropic-force terms not only from the Bekenstein entropy but also from a generalized black-hole entropy proposed by C. Tsallis and L.J.L. Cirto [Eur. Phys. J. C 73, 2487 (2013)]. Unlike the Bekenstein entropy, which is proportional to area, the generalized entropy is proportional to volume because of appropriate nonadditive generalizations. The entropic-force term derived from the generalized entropy is found to behave as if it were an extra driving term for bulk viscous cosmology, in which a bulk viscosity of cosmological fluids is assumed. Using an effective description similar to bulk viscous cosmology, we formulate the modified Friedmann, acceleration, and continuity equations for entropic cosmology. Based on this formulation, we propose two entropic-force models derived from the Bekenstein and generalized entropies. In order to examine the properties of the two models, we consider a homogeneous, isotropic, and spatially flat universe, focusing on a single-fluid-dominated universe. The two entropic-force models agree well with the observed supernova data. Interestingly, the entropic-force model derived from the generalized entropy predicts a decelerating and accelerating universe, as for a fine-tuned standard \u039bCDM (lambda cold dark matter) model, whereas the entropic-force model derived from the Bekenstein entropy predicts a uniformly accelerating universe.", "keyphrases": ["black-hole entropy", "universe", "entropic-force model", "entropic cosmology", "bulk viscous model"]}
{"id": "1802.09177", "title": "The multidimensional dependence of halo bias in the eye of a machine: a tale of halo structure, assembly and environment", "abstract": "We develop a novel approach in exploring the joint dependence of halo bias on multiple halo properties using Gaussian process regression. Using a \u039bCDM N-body simulation, we carry out a comprehensive study of the joint bias dependence on halo structure, formation history and environment. We show that the bias is a multivariate function of halo properties that falls into three regimes. For massive haloes, halo mass explains the majority of bias variation. For early-forming haloes, bias depends sensitively on the recent mass accretion history. For low-mass and late-forming haloes, bias depends more on the structure of a halo such as its shape and spin. Our framework enables us to convincingly prove that V_max/V_vir is a lossy proxy of formation time for bias modelling, whereas the mass, spin, shape and formation time variables are non-redundant with respect to each other. Combining mass and formation time largely accounts for the mass accretion history dependence of bias. Combining all the internal halo properties fully accounts for the density profile dependence inside haloes, and predicts the clustering variation of individual haloes to a 20% level at \u223c 10Mpch^-1. When an environmental density is measured outside 1Mpch^-1 from the halo centre, it outperforms and largely accounts for the bias dependence on the internal halo structure, explaining the bias variation above a level of 30%.", "keyphrases": ["halo bias", "environment", "formation time"]}
{"id": "1602.04735", "title": "Electromagnetic Counterparts to Black Hole Mergers Detected by LIGO", "abstract": "Mergers of stellar-mass black holes (BHs), such as GW150914 observed by LIGO, are not expected to have electromagnetic counterparts. However, the Fermi GBM detector identified of a gamma-ray transient 0.4 s after the gravitational wave (GW) signal GW150914 with consistent sky localization. I show that the two signals might be related if the BH binary detected by LIGO originated from two clumps in a dumbbell configuration that formed when the core of a rapidly rotating massive star collapsed. In that case, the BH binary merger was followed by a gamma-ray burst (GRB) from a jet that originated in the accretion flow around the remnant BH. A future detection of a GRB afterglow could be used to determine the redshift and precise localization of the source. A population of standard GW sirens with GRB redshifts would provide a new approach for precise measurements of cosmological distances as a function of redshift.", "keyphrases": ["black hole merger", "gamma-ray burst", "electromagnetic counterpart"]}
{"id": "2007.13399", "title": "Speed of sound constraints from tidal deformability of neutron stars", "abstract": "The upper bound of the speed of sound in dense nuclear matter is one of the most interesting but still unsolved problems in Nuclear Physics. Theoretical studies in connection with recent observational data of isolated neutron stars as well as binary neutron stars systems offer an excellent opportunity to shed light on this problem. In the present work, we suggest a method to directly relate the measured tidal deformability (polarizability) of binary neutron stars system (before merger) to the maximum neutron star mass scenario and possible upper bound on the speed of sound. This method is based on the simple but efficient idea that while the upper limit of the effective tidal deformability favors soft equations of state, the recent high measured values of neutron star mass favor stiff ones. In the present work, firstly, using a simple well established model we parametrize the stiffness of the equation of state with the help of the speed of sound. Secondly, in comparison with the recent observations by LIGO/VIRGO collaboration of two events, GW170817 and GW190425, we suggest possible robust constraints. Moreover, we evaluate and postulate, in the framework of the present method, what kind of future measurements could help us to improve the stringent of the constraints on the neutron star equation of state.", "keyphrases": ["tidal deformability", "neutron star", "nuclear matter"]}
{"id": "1308.4488", "title": "Observational signatures of anisotropic inflationary models", "abstract": "We study observational signatures of two classes of anisotropic inflationary models in which an inflaton field couples to (i) a vector kinetic term F_mu nuF^mu nu and (ii) a two-form kinetic term H_mu nu lambdaH^mu nu lambda. We compute the corrections from the anisotropic sources to the power spectrum of gravitational waves as well as the two-point cross correlation between scalar and tensor perturbations. The signs of the anisotropic parameter g_* are different depending on the vector and the two-form models, but the statistical anisotropies generally lead to a suppressed tensor-to-scalar ratio r and a smaller scalar spectral index n_s in both models. In the light of the recent Planck bounds of n_s and r, we place observational constraints on several different inflaton potentials such as those in chaotic and natural inflation in the presence of anisotropic interactions. In the two-form model we also find that there is no cross correlation between scalar and tensor perturbations, while in the vector model the cross correlation does not vanish. The non-linear estimator f_NL of scalar non-Gaussianities in the two-form model is generally smaller than that in the vector model for the same orders of |g_*|, so that the former is easier to be compatible with observational bounds of non-Gaussianities than the latter.", "keyphrases": ["inflationary model", "tensor perturbation", "observational signature"]}
{"id": "2110.13919", "title": "The Impact of the First Galaxies on Cosmic Dawn and Reionization", "abstract": "The formation of the first galaxies during cosmic dawn and reionization (at redshifts z=5-30), triggered the last major phase transition of our universe, as hydrogen evolved from cold and neutral to hot and ionized. The 21-cm line of neutral hydrogen will soon allow us to map these cosmic milestones and study the galaxies that drove them. To aid in interpreting these observations, we upgrade the publicly available code 21cmFAST. We introduce a new, flexible parametrization of the additive feedback from: an inhomogeneous, H_2-dissociating (Lyman-Werner; LW) background; and dark matter \u2013 baryon relative velocities; which recovers results from recent, small-scale hydrodynamical simulations with both effects. We perform a large, \"best-guess\" simulation as the 2021 installment of the Evolution of 21-cm Structure (EOS) project. This improves the previous release with a galaxy model that reproduces the observed UV luminosity functions (UVLFs), and by including a population of molecular-cooling galaxies. The resulting 21-cm global signal and power spectrum are significantly weaker, primarily due to a more rapid evolution of the star-formation rate density required to match the UVLFs. Nevertheless, we forecast high signal-to-noise detections for both HERA and the SKA. We demonstrate how the stellar-to-halo mass relation of the unseen, first galaxies can be inferred from the 21-cm evolution. Finally, we show that the spatial modulation of X-ray heating due to relative velocities provides a unique acoustic signature that is detectable at z \u2248 10-15 in our fiducial model. Ours are the first public simulations with joint inhomogeneous LW and relative-velocity feedback across the entire cosmic dawn and reionization.", "keyphrases": ["galaxy", "cosmic dawn", "reionization"]}
{"id": "1808.00377", "title": "Non-parametric Reconstruction of Growth Index via Gaussian Processes", "abstract": "The accelerated cosmic expansion could be due to dark energy within general relativity (GR), or modified gravity. It is of interest to differentiate between them, by using both the expansion history and the growth history. In the literature, it was proposed that the growth index \u03b3 is useful to distinguish these two scenarios. In this work, we consider the non-parametric reconstruction of the growth index \u03b3 as a function of redshift z from the latest observational data as of July 2018 via Gaussian Processes. We find that f(R) theories and dark energy models within GR (especially \u039bCDM) are inconsistent with the results in the moderate redshift range far beyond 3\u03c3 confidence level. A modified gravity scenario different from f(R) theories is favored. However, these results can also be due to other non-trivial possibilities, in which dark energy models within GR (especially \u039bCDM) and f(R) theories might still survive. In all cases, our results suggest that new physics is required.", "keyphrases": ["growth index", "gaussian processes", "non-parametric reconstruction", "late observational data"]}
{"id": "1405.1418", "title": "Properties of galaxies reproduced by a hydrodynamic simulation", "abstract": "Previous simulations of the growth of cosmic structures have broadly reproduced the 'cosmic web' of galaxies that we see in the Universe, but failed to create a mixed population of elliptical and spiral galaxies due to numerical inaccuracies and incomplete physical models. Moreover, because of computational constraints, they were unable to track the small scale evolution of gas and stars to the present epoch within a representative portion of the Universe. Here we report a simulation that starts 12 million years after the Big Bang, and traces 13 billion years of cosmic evolution with 12 billion resolution elements in a volume of (106.5 Mpc)^3. It yields a reasonable population of ellipticals and spirals, reproduces the distribution of galaxies in clusters and statistics of hydrogen on large scales, and at the same time the metal and hydrogen content of galaxies on small scales.", "keyphrases": ["galaxy", "hydrodynamic simulation", "dark matter", "scale structure"]}
{"id": "1706.08539", "title": "The Galaxy in circular polarization: all-sky radio prediction, detection strategy, and the charge of the leptonic cosmic rays", "abstract": "The diffuse Galactic synchrotron emission should exhibit a low level of diffuse circular polarization (CP) due to the circular motions of the emitting relativistic electrons. This probes the Galactic magnetic field in a similar way as the product of total Galactic synchrotron intensity times Faraday depth. We use this to construct an all sky prediction of the so far unexplored Galactic CP from existing measurements. This map can be used to search for this CP signal in low frequency radio data even prior to imaging. If detected as predicted, it would confirm the expectation that relativistic electrons, and not positrons, are responsible for the Galactic radio emission. Furthermore, the strength of real to predicted circular polarization would provide statistical information on magnetic structures along the line-of-sights.", "keyphrases": ["galaxy", "circular polarization", "galactic magnetic field"]}
{"id": "0912.0533", "title": "The Interior Structure, Composition, and Evolution of Giant Planets", "abstract": "We discuss our current understanding of the interior structure and thermal evolution of giant planets. This includes the gas giants, such as Jupiter and Saturn, that are primarily composed of hydrogen and helium, as well as the \"ice giants,\" such as Uranus and Neptune, which are primarily composed of elements heavier than H/He. The effect of different hydrogen equations of state (including new first-principles computations) on Jupiter's core mass and heavy element distribution is detailed. This variety of the hydrogen equations of state translate into an uncertainty in Jupiter's core mass of 18 M_Earth. For Uranus and Neptune we find deep envelope metallicities up to 0.95, perhaps indicating the existence of an eroded core, as also supported by their low luminosity. We discuss the results of simple cooling models of our solar system's planets, and show that more complex thermal evolution models may be necessary to understand their cooling history. We review how measurements of the masses and radii of the 50 transiting extrasolar giant planets are changing our understanding of giant planets. In particular a fraction of these planets appear to be larger than can be accommodated by standard models of planetary contraction. We review the proposed explanations for the radii of these planets. We also discuss very young giant planets, which are being directly imaged with ground- and space-based telescopes.", "keyphrases": ["interior structure", "giant planet", "core mass"]}
{"id": "1307.1947", "title": "Dipole anisotropy in sky brightness and source count distribution in radio NVSS data", "abstract": "We study the dipole anisotropy in number counts and flux density weighted number counts or sky brightness in the NRAO VLA Sky Survey (NVSS) data. The dipole anisotropy is expected due to our local motion with respect to the CMBR rest frame. We analyse data with an improved fit to the number density, n(S), as a function of the flux density S, which allows deviation from a pure power law behaviour. We also impose more stringent cuts to remove the contribution due to clustering dipole. In agreement with earlier results, we find that the amplitude of anisotropy is significantly larger in comparison to the prediction based on CMBR measurements. The extracted speed is found to be roughly 3 times the speed corresponding to CMBR. The significance of deviation is smaller, roughly 2 sigma, in comparison to earlier estimates. For the cut, S>30 mJy, the speed is found to be 1110\u00b1370 Km/s using the source count analysis. The direction of the dipole anisotropy is found to be approximately in agreement with CMBR. We find that the results are relatively insensitive to the lower as well as upper limit imposed on the flux density. Our results suggest that the Universe is intrinsically anisotropic with the axis of anisotropy axis pointing roughly towards the CMBR dipole direction. Finally we present a method which may allow an independent extraction of the local speed and an intrinsic dipole anisotropy, provided a larger data set becomes available in future.", "keyphrases": ["sky brightness", "flux density", "dipole anisotropy"]}
{"id": "1808.07673", "title": "Non-linear wavefront reconstruction methods for pyramid sensors using Landweber and Landweber-Kaczmarz iteration", "abstract": "Accurate and robust wavefront reconstruction methods for pyramid wavefront sensors are in high demand as these sensors are planned to be part of many instruments currently under development for ground based telescopes. The pyramid sensor relates the incoming wavefront and its measurements in a non-linear way. Nevertheless, almost all existing reconstruction algorithms are based on a linearization of the model. The assumption of a linear pyramid sensor response is justifiable in closed loop AO when the measured phase information is small but may not be reasonable in reality due to unpreventable errors depending on the system such as non common path aberrations. In order to solve the non-linear inverse problem of wavefront reconstruction from pyramid sensor data we introduce two new methods based on the non-linear Landweber and Landweber-Kaczmarz iteration. Using these algorithms we experience high-quality wavefront estimation especially for the non-modulated sensor by still keeping the numerical effort feasible for large-scale AO systems.", "keyphrases": ["reconstruction method", "pyramid sensor", "wavefront sensor"]}
{"id": "0912.3248", "title": "Large-Scale Magnetic Fields, Dark Energy and QCD", "abstract": "Cosmological magnetic fields are being observed with ever increasing correlation lengths, possibly reaching the size of superclusters, therefore disfavouring the conventional picture of generation through primordial seeds later amplified by galaxy-bound dynamo mechanisms. In this paper we put forward a fundamentally different approach that links such large-scale magnetic fields to the cosmological vacuum energy. In our scenario the dark energy is due to the Veneziano ghost (which solves the U(1)_A problem in QCD). The Veneziano ghost couples through the triangle anomaly to the electromagnetic field with a constant which is unambiguously fixed in the standard model. While this interaction does not produce any physical effects in Minkowski space, it triggers the generation of a magnetic field in an expanding universe at every epoch. The induced energy of the magnetic field is thus proportional to cosmological vacuum energy: \u03c1_EM\u2243 B^2 \u2243 (\u03b1/4\u03c0)^2 \u03c1_DE, \u03c1_DE hence acting as a source for the magnetic energy \u03c1_EM. The corresponding numerical estimate leads to a magnitude in the nG range. There are two unique and distinctive predictions of our proposal: an uninterrupted active generation of Hubble size correlated magnetic fields throughout the evolution of the universe; the presence of parity violation on the enormous scales 1/H, which apparently has been already observed in CMB. These predictions are entirely rooted into the standard model of particle physics.", "keyphrases": ["magnetic field", "dark energy", "qcd"]}
{"id": "1509.03978", "title": "Dust processing in elliptical galaxies", "abstract": "We reconsider the origin and processing of dust in elliptical galaxies. We theoretically formulate the evolution of grain size distribution, taking into account dust supply from asymptotic giant branch (AGB) stars and dust destruction by sputtering in the hot interstellar medium (ISM), whose temperature evolution is treated by including two cooling paths: gas emission and dust emission (i.e. gas cooling and dust cooling). With our new full treatment of grain size distribution, we confirm that dust destruction by sputtering is too efficient to explain the observed dust abundance even if AGB stars continue to supply dust grains, and that, except for the case where the initial dust-to-gas ratio in the hot gas is as high as \u223c 0.01, dust cooling is negligible compared with gas cooling. However, we show that, contrary to previous expectations, cooling does not help to protect the dust; rather, the sputtering efficiency is raised by the gas compression as a result of cooling. We additionally consider grain growth after the gas cools down. Dust growth by the accretion of gas-phase metals in the cold medium increase the dust-to-gas ratio up to \u223c 10^-3 if this process lasts >10/(n_H/10^3 cm^-3) Myr, where n_H is the number density of hydrogen nuclei. We show that the accretion of gas-phase metals is a viable mechanism of increasing the dust abundance in elliptical galaxies to a level consistent with observations, and that the steepness of observed extinction curves is better explained with grain growth by accretion.", "keyphrases": ["elliptical galaxy", "interstellar medium", "dust growth"]}
{"id": "2105.08659", "title": "Bumblebee field as a source of cosmological anisotropies", "abstract": "In this work, a bumblebee field is adopted in order to generate cosmological anisotropies. For that purpose, we assume a Bianchi I cosmology, as the background geometry, and a bumblebee field coupled to it. Bumblebee models are examples of a mechanism for the Lorentz symmetry violation by assuming a nonzero vacuum expectation value for the bumblebee field. When coupled to the Bianchi I geometry, which is not in agreement with a cosmological principle, the bumblebee field plays the role of a source of anisotropies and produces a preferred axis. Thus, a fraction of the cosmic anisotropies would come from the Lorentz symmetry violation. In the last part of the article, we try to assume an upper bound on the bumblebee field using the quadrupole and octopole moments of the cosmic microwave background radiation.", "keyphrases": ["cosmological anisotropy", "bianchi", "bumblebee field"]}
{"id": "1305.3575", "title": "Halo-independent methods for inelastic dark matter scattering", "abstract": "We present halo-independent methods to analyze the results of dark matter direct detection experiments assuming inelastic scattering. We focus on the annual modulation signal reported by DAMA/LIBRA and present three different halo-independent tests. First, we compare it to the upper limit on the unmodulated rate from XENON100 using (a) the trivial requirement that the amplitude of the annual modulation has to be smaller than the bound on the unmodulated rate, and (b) a bound on the annual modulation amplitude based on an expansion in the Earth's velocity. The third test uses the special predictions of the signal shape for inelastic scattering and allows for an internal consistency check of the data without referring to any astrophysics. We conclude that a strong conflict between DAMA/LIBRA and XENON100 in the framework of spin-independent inelastic scattering can be established independently of the local properties of the dark matter halo.", "keyphrases": ["dark matter", "halo-independent method", "astrophysical uncertainty"]}
{"id": "1907.11594", "title": "The BAO+BBN take on the Hubble tension", "abstract": "Many attempts to solve the Hubble tension with extended cosmological models combine an enhanced relic radiation density, acting at the level of background cosmology, with new physical ingredients affecting the evolution of cosmological perturbations. Several authors have pointed out the ability of combined Baryon Acoustic Oscillation (BAO) and Big Bang Nucleosynthesis (BBN) data to probe the background cosmological history independently of both CMB maps and supernovae data. Using state-of-the-art assumptions on BBN, we confirm that combined BAO, deuterium, and helium data are in tension with the SH0ES measurements under the \u039bCDM assumption at the 3.2\u03c3 level, while being in close agreement with the CMB value. We subsequently show that floating the radiation density parameter N_eff only reduces the tension down to the 2.6\u03c3 level. This conclusion, totally independent of any CMB data, shows that a high N_eff accounting for extra relics (either free-streaming or self-interacting) does not provide an obvious solution to the crisis, not even at the level of background cosmology. To circumvent this strong bound, (i) the extra radiation has to be generated after BBN to avoid helium bounds, and (ii) additional ingredients have to be invoked at the level of perturbations to reconcile this extra radiation with CMB and LSS data.", "keyphrases": ["hubble tension", "bao", "big bang nucleosynthesis", "bbn"]}
{"id": "2011.12504", "title": "One line to run them all: SuperEasy massive neutrino linear response in N-body simulations", "abstract": "We present in this work a novel and yet extremely simple method for incorporating the effects of massive neutrinos in cosmological N-body simulations. This so-called \"SuperEasy linear response\" approach is based upon analytical solutions to the collisionless Boltzmann equation in the clustering and free-streaming limits, which are then connected by a rational function interpolation function with cosmology-dependent coefficients given by simple algebraic expressions of the cosmological model parameters. The outcome is a one-line modification to the gravitational potential that requires only the cold matter density contrast as a real-time input, and that can be incorporated into any N-body code with a Particle\u2013Mesh component with no additional implementation cost. To demonstrate its power, we implement the SuperEasy method in the publicly available code, and show that for neutrino mass sums not exceeding \u2211 m_\u03bd\u2243 1 eV, the total matter and cold matter power spectra are in sub-1% and sub-0.1% agreement with those from state-of-the-art linear response simulations in literature. Aside from its minimal implementation cost, compared with existing massive neutrino simulation methods, the SuperEasy approach has better memory efficiency, incurs no runtime overhead relative to a standard \u039bCDM simulation, and requires no post-processing. The minimal nature of the method allows limited computational resources to be diverted to modelling other physical effects of interest, e.g., baryonic physics via hydrodynamics.", "keyphrases": ["neutrino", "n-body simulation", "gravitational potential"]}
{"id": "1209.5393", "title": "Major Galaxy Mergers Only Trigger the Most Luminous AGN", "abstract": "Using multiwavelength surveys of active galactic nuclei across a wide range of bolometric luminosities (10^43<L_bol(erg/s<5x10^46) and redshifts (0<z<3), we find a strong, redshift-independent correlation between the AGN luminosity and the fraction of host galaxies undergoing a major merger. That is, only the most luminous AGN phases are connected to major mergers, while less luminous AGN appear to be driven by secular processes. Combining this trend with AGN luminosity functions to assess the overall cosmic growth of black holes, we find that 50 only 10 events. Our results suggest that to reach the highest AGN luminosities -where the most massive black holes accreted the bulk of their mass - a major merger appears to be required. The luminosity dependence of the fraction of AGN triggered by major mergers can successfully explain why the observed scatter in the M-\u03c3relation for elliptical galaxies is significantly lower than in spirals. The lack of a significant redshift dependence of the L_bol-f_merger relation suggests that downsizing, i.e., the general decline in AGN and star formation activity with decreasing redshift, is driven by a decline in the frequency of major mergers combined with a decrease in the availability of gas at lower redshifts.", "keyphrases": ["galaxy", "luminous agn", "major merger"]}
{"id": "1503.06578", "title": "Bouncing alternatives to inflation", "abstract": "Although the inflationary paradigm is the most widely accepted explanation for the current cosmological observations, it does not necessarily correspond to what actually happened in the early stages of our Universe. To decide on this issue, two paths can be followed: first, all the possible predictions it makes must be derived thoroughly and compared with available data, and second, all imaginable alternatives must be ruled out. Leaving the first task to all other contributors of this volume, we concentrate here on the second option, focusing on the bouncing alternatives and their consequences.", "keyphrases": ["alternative", "inflationary paradigm", "bounce", "primordial perturbation"]}
{"id": "0911.2655", "title": "Cosmic Rays from Cosmic Strings with Condensates", "abstract": "We re-visit the production of cosmic rays by cusps on cosmic strings. If a scalar field (\u201cHiggs\u201d) has a linear interaction with the string world-sheet, such as would occur if there is a bosonic condensate on the string, cusps on string loops emit narrow beams of very high energy Higgses which then decay to give a flux of ultra high energy cosmic rays. The ultra-high energy flux and the gamma to proton ratio agree with observations if the string scale is \u223c 10^13 GeV. The diffuse gamma ray and proton fluxes are well below current bounds. Strings that are lighter and have linear interactions with scalars produce an excess of direct and diffuse cosmic rays and are ruled out by observations, while heavier strings (\u223c 10^15 GeV) are constrained by their gravitational signatures. This leaves a narrow window of parameter space for the existence of cosmic strings with bosonic condensates.", "keyphrases": ["string", "condensate", "cosmic ray"]}
{"id": "1004.4692", "title": "Vortices in Bose-Einstein Condensate Dark Matter", "abstract": "If dark matter in the galactic halo is composed of bosons that form a Bose-Einstein condensate then it is likely that the rotation of the halo will lead to the nucleation of vortices. After a review of the Gross-Pitaevskii equation, the Thomas-Fermi approximation and vortices in general, we consider vortices in detail. We find strong bounds for the boson mass, interaction strength, the shape and quantity of vortices in the halo, the critical rotational velocity for the nucleation of vortices and, in the Thomas-Fermi regime, an exact solution for the mass density of a single, axisymmetric vortex.", "keyphrases": ["dark matter", "boson mass", "einstein condensate"]}
{"id": "1404.3956", "title": "Large-Scale Structure Formation: from the first non-linear objects to massive galaxy clusters", "abstract": "The large-scale structure of the Universe formed from initially small perturbations in the cosmic density field, leading to galaxy clusters with up to 10^15 Msun at the present day. Here, we review the formation of structures in the Universe, considering the first primordial galaxies and the most massive galaxy clusters as extreme cases of structure formation where fundamental processes such as gravity, turbulence, cooling and feedback are particularly relevant. The first non-linear objects in the Universe formed in dark matter halos with 10^5-10^8 Msun at redshifts 10-30, leading to the first stars and massive black holes. At later stages, larger scales became non-linear, leading to the formation of galaxy clusters, the most massive objects in the Universe. We describe here their formation via gravitational processes, including the self-similar scaling relations, as well as the observed deviations from such self-similarity and the related non-gravitational physics (cooling, stellar feedback, AGN). While on intermediate cluster scales the self-similar model is in good agreement with the observations, deviations from such self-similarity are apparent in the core regions, where numerical simulations do not reproduce the current observational results. The latter indicates that the interaction of different feedback processes may not be correctly accounted for in current simulations. Both in the most massive clusters of galaxies as well as during the formation of the first objects in the Universe, turbulent structures and shock waves appear to be common, suggesting them to be ubiquitous in the non-linear regime.", "keyphrases": ["structure formation", "first non-linear object", "galaxy cluster", "star"]}
{"id": "0903.0631", "title": "Non-Gaussianity in a Matter Bounce", "abstract": "A nonsingular bouncing cosmology in which the scales of interest today exit the Hubble radius in a matter-dominated contracting phase yields an alternative to inflation for producing a scale-invariant spectrum of adiabatic cosmological fluctuations. In this paper we identify signatures in the non-Gaussianities of the fluctuations which are specific to this scenario and allow it to be distinguished from the results of inflationary models.", "keyphrases": ["matter bounce", "matter-dominated contracting phase", "non-gaussianity"]}
{"id": "1712.03240", "title": "GW170817 Most Likely Made a Black Hole", "abstract": "There are two outstanding issues regarding the neutron-star merger event GW170817: the nature of the compact remnant and the interstellar shock. The mass of the remnant of GW170817, \u223c2.7 M_\u2299, implies the remnant could be either a massive, rotating, neutron star, or a black hole. We report Chandra Director's Discretionary Time observations made in 2017 December and 2018 January, and we reanalyze earlier observations from 2017 August and 2017 September, in order to address these unresolved issues. We estimate the X-ray flux from a neutron star remnant and compare that to the measured X-ray flux. If we assume that the spin-down luminosity of any putative neutron star is converted to pulsar wind nebula X-ray emission in the 0.5-8 keV band with an efficiency of 10^-3, for a dipole magnetic field with 3 \u00d7 10^11 G < B < 10^14 G, a rising X-ray signal would result and would be brighter than that observed by day 107, we therefore conclude that the remnant of GW170817 is most likely a black hole. Independent of any assumptions of X-ray efficiency, however, if the remnant is a rapidly-rotating, magnetized, neutron star, the total energy in the external shock should rise by a factor \u223c10^2 (to \u223c10^52 erg) after a few years, therefore, Chandra observations over the next year or two that do not show substantial brightening will rule out such a remnant. The same observations can distinguish between two different models for the relativistic outflow, either an angular or radially varying structure.", "keyphrases": ["black hole", "remnant", "x-ray flux"]}
{"id": "0902.1340", "title": "Fermi Large Area Telescope Bright Gamma-ray Source List", "abstract": "Following its launch in June 2008, the Fermi Gamma-ray Space Telescope (Fermi) began a sky survey in August. The Large Area Telescope (LAT) on Fermi in 3 months produced a deeper and better-resolved map of the gamma-ray sky than any previous space mission. We present here initial results for energies above 100 MeV for the 205 most significant (statistical significance greater than 10-sigma) gamma-ray sources in these data. These are the best-characterized and best-localized point-like (i.e., spatially unresolved) gamma-ray sources in the early-mission data.", "keyphrases": ["gamma-ray source", "source list", "space telescope", "fermi", "star-burst galaxy"]}
{"id": "1404.7031", "title": "Nucleon effective masses within the Brueckner-Hartree-Fock theory: Impact on stellar neutrino emission", "abstract": "We calculate the effective masses of neutrons and protons in dense nuclear matter within the microscopic Brueckner-Hartree-Fock many-body theory and study the impact on the neutrino emissivity processes of neutron stars. We compare results based on different nucleon-nucleon potentials and nuclear three-body forces. Useful parametrizations of the numerical results are given. We find substantial in-medium suppression of the emissivities, strongly dependent on the interactions.", "keyphrases": ["effective masse", "neutron star", "nucleon"]}
{"id": "1606.04246", "title": "Astrophysical imaging of Kerr black holes with scalar hair", "abstract": "We address the astrophysical imaging of a family of deformed Kerr black holes (BHs). These are stationary, asymptotically flat black hole (BH) spacetimes, that are solutions of General Relativity minimally coupled to a massive, complex scalar field: Kerr BHs with scalar hair (KBHsSH). Such BHs bifurcate from the vacuum Kerr solution and can be regarded as a horizon within a rotating boson star. In a recent letter, it was shown that KBHsSH can exhibit very distinct shadows from the ones of their vacuum counterparts. The setup therein, however, considered the light source to be a celestial sphere sufficiently far away from the BH. Here, we analyse KBHsSH surrounded by an emitting torus of matter, simulating a more realistic astrophysical environment, and study the corresponding lensing of light as seen by a very far away observer, to appropriately model ground-based observations of Sgr A*. We find that the differences in imaging between KBHsSH and comparable vacuum Kerr BHs remain, albeit less dramatic than those observed for the corresponding shadows in the previous setup. In particular, we highlight two observables that might allow differentiating KBHsSH and Kerr BHs. The first is the angular size of the photon ring (in a Kerr spacetime) or lensing ring (in a KBHSH spacetime), the latter being significantly smaller for sufficiently non-Kerr-like spacetimes. The second is the existence of an edge in the intensity distribution (the photon ring in Kerr spacetime). This edge can disappear for very non-Kerr-like KBHsSH. It is plausible, therefore, that sufficiently precise Very Long Baseline Interferometric observations of BH candidates can constrain this model.", "keyphrases": ["black hole", "boson star", "astrophysical imaging"]}
{"id": "1102.4454", "title": "A Star Harbouring a Wormhole at its Core", "abstract": "We consider a configuration consisting of a wormhole filled by a perfect fluid. Such a model can be applied to describe stars as well as neutron stars with a nontrivial topology. The presence of a tunnel allows for motion of the fluid, including oscillations near the core of the system. Choosing the polytropic equation of state for the perfect fluid, we obtain static regular solutions. Based on these solutions, we consider small radial oscillations of the configuration and show that the solutions are stable with respect to linear perturbations in the external region.", "keyphrases": ["star", "wormhole", "massless ghost", "polytropic fluid"]}
{"id": "1307.3330", "title": "Review of axino dark matter", "abstract": "We review the status of axino dark matter. Two hierarchy problems, the strong CP problem and the gauge hierarchy problem, have led to introducing into particle physics a spontaneously broken global Peccei-Quinn symmetry and a softly broken supersymmetry, respectively. Combining them implies the presence of not only an axion, but also of its scalar component, saxion, and their fermionic partner, axino. Among these, the axion and the axino are attractive dark matter candidates. Various possibilities for the axino as dark matter are discussed.", "keyphrases": ["dark matter", "axion", "fermionic partner"]}
{"id": "1703.03407", "title": "LIGER: mock relativistic light-cones from Newtonian simulations", "abstract": "We introduce a method to create mock galaxy catalogues in redshift space including general relativistic effects to linear order in the cosmological perturbations. We dub our method LIGER, short for `light cones with general relativity'. LIGER takes a (N-body or hydrodynamic) Newtonian simulation as an input and outputs the distribution of galaxies in comoving redshift space. This result is achieved making use of a coordinate transformation and simultaneously accounting for lensing magnification. The calculation includes both local corrections and terms that have been integrated along the line of sight. Our fast implementation allows the production of many realizations that can be used to forecast the performance of forthcoming wide-angle surveys and to estimate the covariance matrix of the observables. To facilitate this use, we also present a variant of LIGER designed for large-volume simulations with low mass resolution. In this case, the galaxy distribution on large scales is obtained by biasing the matter-density field. Finally, we present two sample applications of LIGER. First, we discuss the impact of weak gravitational lensing onto the angular clustering of galaxies in a Euclid-like survey. In agreement with previous analytical studies, we find that magnification bias can be measured with high confidence. Second, we focus on two generally neglected Doppler-induced effects: magnification and the change of number counts with redshift. We show that the corresponding redshift-space distortions can be detected at 5.5\u03c3 significance with the completed Square Kilometre Array.", "keyphrases": ["newtonian simulation", "galaxy", "general relativity", "first-order statistic"]}
{"id": "2006.00526", "title": "Numerical determination of the cutoff frequency in solar models", "abstract": "In stratified atmospheres, acoustic waves can only propagate if their frequency is above the cutoff value. Different theories provide different cutoff values. We developed an alternative method to derive the cutoff frequency in several standard solar models, including various quiet-Sun and umbral atmospheres. We performed numerical simulations of wave propagation in the solar atmosphere. The cutoff frequency is determined from the inspection of phase difference spectra computed between the velocity signal at two atmospheric heights. The process is performed by choosing pairs of heights across all the layers between the photosphere and the chromosphere, to derive the vertical stratification of the cutoff in the solar models. The cutoff frequency predicted by the theoretical calculations departs significantly from our measurements. In quiet-Sun atmospheres, the cutoff shows a strong dependence on the magnetic field for adiabatic wave propagation. When radiative losses are taken into account, the cutoff frequency is greatly reduced and the variation of the cutoff with the strength of the magnetic field is lower. The effect of the radiative losses in the cutoff is necessary to understand recent quiet-Sun and sunspot observations. In the presence of inclined magnetic fields, our numerical calculations confirm the reduction of the cutoff frequency due to the reduced gravity experienced by waves propagating along field lines. An additional reduction is also found in regions with significant changes in the temperature, due to the lower temperature gradient along the path of field-guided waves. Our results show that the cutoff values are not correctly captured by theoretical estimates. In addition, most of the widely-used analytical cutoff formulae neglect the impact of magnetic fields and radiative losses, whose role is critical to determine the evanescent or propagating nature of the waves.", "keyphrases": ["cutoff frequency", "solar model", "radiative loss"]}
{"id": "1306.2683", "title": "Growth Index after the Planck Results", "abstract": "The growth index \u03b3_L was proposed to investigate the possible deviation from the standard \u039bCDM model and Einstein's gravity theory in a dynamical perspective. Recently, thanks to the measurement of the cosmic growth rate via the redshift-space distortion, one can understand the evolution of density contrast through f\u03c3_8(z), where f(z)=dln\u03b4/d ln a is the growth rate of matter and \u03c3_8(z) is the rms amplitude of the density contrast \u03b4 at the comoving 8h^-1 Mpc scale. In this paper, we use the redshift space distortion data points to study the growth index on the bases of Einstein's gravity theory and a modified gravity theory under the assumption of f=\u03a9_m(a)^\u03b3_L. The cosmic background evolution is fixed by the cosmic observations from the type Ia supernovae SNLS3, cosmic microwave background radiation data from Planck and baryon acoustic oscillations. Via the Markov Chain Monte Carlo method, we found the \u03b3_L values for Einstein's gravity with a cosmological constant, w=constant dark energy and a modified gravity theory in the 1,2,3\u03c3 regions respectively: 0.675_-0.0662-0.120-0.155^+0.0611+0.129+0.178, 0.745_-0.0819-0.146-0.190^+0.0755+0.157+0.205 and 0.555_-0.0167-0.0373-0.0516^+0.0193+0.0335+0.0436. In the Einstein's gravity theory, the values of growth index \u03b3_L show almost 2\u03c3 deviation from the theoretical prediction 6/11 for the \u039bCDM model. However in the modified gravity framework, a deviation from the Einstein's relativity is not detected in 1\u03c3 region. That implies that the currently available cosmic observations don't expect an alternative modified gravity theory beyond the \u039bCDM model under Einstein's gravity, but that the simple assumption of f=\u03a9_m^\u03b3_L should be improved.", "keyphrases": ["redshift-space distortion", "growth index", "model parameter space"]}
{"id": "2105.13197", "title": "Sensitivity of third-generation interferometers to extra polarizations in the Stochastic Gravitational Wave Background", "abstract": "When modified theories of gravity are considered, at most six gravitational wave polarization modes are allowed and classified in tensor modes, the only ones predicted by General Relativity (GR), along with additional vector and scalar modes. Therefore, gravitational waves represent a powerful tool to test alternative theories of gravitation. In this paper, we forecast the sensitivity of third-generation ground-based interferometers, Einstein Telescope and Cosmic Explorer, to non-GR polarization modes focusing on the stochastic gravitational wave background. We consider the latest technical specifications of the two independent detectors and the full network in order to estimate both the optimal signal-to-noise ratio and the detectable energy density limits relative to all polarization modes in the stochastic background for several locations on Earth and orientations of the two observatories. By considering optimal detector configurations, we find that in 5 years of observation the detection limit for tensor and extra polarization modes could reach h_0^2\u03a9^T,V,S_GW\u2248 10^-12-10^-11, depending on the network configuration and the stochastic background (i.e., if only one among vector and scalar modes exists or both are present). This means that the network sensitivity to different polarization modes can be approximately improved by a factor 10^3 with respect to second-generation interferometers. We finally discuss the possibility of breaking the scalar modes degeneracy by considering both detectors angular responses to sufficiently high gravitational wave frequencies.", "keyphrases": ["interferometer", "extra polarization", "gravitational wave background"]}
{"id": "1003.3999", "title": "Cosmological parameters from large scale structure - geometric versus shape information", "abstract": "The matter power spectrum as derived from large scale structure (LSS) surveys contains two important and distinct pieces of information: an overall smooth shape and the imprint of baryon acoustic oscillations (BAO). We investigate the separate impact of these two types of information on cosmological parameter estimation, and show that for the simplest cosmological models, the broad-band shape information currently contained in the SDSS DR7 halo power spectrum (HPS) is by far superseded by geometric information derived from the baryonic features. An immediate corollary is that contrary to popular beliefs, the upper limit on the neutrino mass m_\u03bdpresently derived from LSS combined with cosmic microwave background (CMB) data does not in fact arise from the possible small-scale power suppression due to neutrino free-streaming, if we limit the model framework to minimal LambdaCDM+m_\u03bd. However, in more complicated models, such as those extended with extra light degrees of freedom and a dark energy equation of state parameter w differing from -1, shape information becomes crucial for the resolution of parameter degeneracies. This conclusion will remain true even when data from the Planck surveyor become available. In the course of our analysis, we introduce a new dewiggling procedure that allows us to extend consistently the use of the SDSS HPS to models with an arbitrary sound horizon at decoupling. All the cases considered here are compatible with the conservative 95", "keyphrases": ["large scale structure", "neutrino mass", "cosmic microwave background", "cosmological scenario"]}
{"id": "0910.0974", "title": "Electron-positron pairs in physics and astrophysics: from heavy nuclei to black holes", "abstract": "From the interaction of physics and astrophysics we are witnessing in these years a splendid synthesis of theoretical, experimental and observational results originating from three fundametal physical processes. They were originally proposed by Dirac, by Breit and Wheeler and by Sauter, Heisenberg, Euler and Schwinger. The vacuum polarization process in strong electromagnetic field, pioneered by Sauter, Heisenberg, Euler and Schwinger, introduced the concept of critical electric field. It has been searched without success for more than forty years by heavy-ion collisions in many of the leading particle accelerators worldwide. The novel situation today is that these same processes can be studied on a much more grandiose scale during the gravitational collapse leading to the formation of a black hole being observed in Gamma Ray Bursts. This report is dedicated to the scientific race in act. The theoretical and experimental work developed in Earth-based laboratories is confronted with the theoretical interpretation of space-based observations of phenomena originating on cosmological scales. What has become clear in the last ten years is that all the three above mentioned processes, duly extended in the general relativistic framework, are necessary for the understanding of the physics of the gravitational collapse to a black hole. Vice versa, the natural arena where these processes can be observed in mutual interaction and on an unprecedented scale, is indeed the realm of relativistic astrophysics.", "keyphrases": ["astrophysic", "black hole", "vacuum polarization process"]}
{"id": "2012.02761", "title": "Oscillations in the stochastic gravitational wave background from sharp features and particle production during inflation", "abstract": "We identify a characteristic pattern in the scalar-induced stochastic gravitational wave background from particle production during inflation. If particle production is sufficiently efficient, the scalar power spectrum exhibits \ud835\udcaa(1) oscillations periodic in k, characteristic of a sharp feature, with an exponentially enhanced envelope. We systematically study the properties of the induced spectrum of gravitational waves sourced after inflation and find that this inherits the periodic structure in k, resulting in a peak in the gravitational wave energy density spectrum with \ud835\udcaa(10 %) modulations. The frequency of the oscillation in the scalar power spectrum is determined by the scale of the feature during inflation and in turn sets the frequency of modulations in the gravitational wave signal. We present an explicit realisation of this phenomenon in the framework of multifield inflation, in the form of a strong sharp turn in the inflationary trajectory. The resulting stochastic background is potentially detectable in future gravitational wave observatories, and considerations of backreaction and perturbativity can be used to constrain the parameter space from the theoretical side. Our work motivates more extensive research linking primordial features to observable properties of the stochastic background of gravitational waves, and dedicated development in data analysis for their detection.", "keyphrases": ["gravitational wave background", "particle production", "power spectrum", "perturbativity", "oscillation"]}
{"id": "1503.03240", "title": "No-hair theorem for Black Holes in Astrophysical Environments", "abstract": "According to the no-hair theorem, static black holes are described by a Schwarzschild spacetime provided there are no other sources of the gravitational field. This requirement, however, is in astrophysical realistic scenarios often violated, e.g., if the black hole is part of a binary system or if it is surrounded by an accretion disk. In these cases, the black hole is distorted due to tidal forces. Nonetheless, the subsequent formulation of the no-hair theorem holds: The contribution of the distorted black hole to the multipole moments that describe the gravitational field close to infinity and, thus, all sources is that of a Schwarzschild black hole. It still has no hair. This implies that there is no multipole moment induced in the black hole and that its second Love numbers, which measure some aspects of the distortion, vanish as was already shown in approximations to general relativity. But here we prove this property for astrophysical relevant black holes in full general relativity.", "keyphrases": ["black hole", "general relativity", "no-hair theorem"]}
{"id": "1305.1247", "title": "No-Scale Supergravity Realization of the Starobinsky Model of Inflation", "abstract": "We present a model for cosmological inflation based on a no-scale supergravity sector with an SU(2,1)/U(1) Kahler potential, a single modulus T and an inflaton superfield Phi described by a Wess-Zumino model with superpotential parameters (mu, lambda). This model yields a scalar spectral index n_s and a tensor-to-scalar ratio r that are compatible with the Planck measurements for values of lambda simeq mu/3M_P. For the specific choice lambda = mu/3M_P, the model is a no-scale supergravity realization of the R+R^2 Starobinsky model.", "keyphrases": ["no-scale supergravity realization", "inflaton field", "starobinsky-like inflation"]}
{"id": "1303.4143", "title": "Primordial power spectrum: a complete analysis with the WMAP nine-year data", "abstract": "We have improved further the error sensitive Richardson-Lucy deconvolution algorithm making it applicable directly on the un-binned measured angular power spectrum of Cosmic Microwave Background observations to reconstruct the form of the primordial power spectrum. This improvement makes the application of the method significantly more straight forward by removing some intermediate stages of analysis allowing a reconstruction of the primordial spectrum with higher efficiency and precision and with lower computational expenses. Applying the modified algorithm we fit the WMAP 9 year data using the optimized reconstructed form of the primordial spectrum with more than 300 improvement in \u03c7^2 with respect to the best fit power-law. This is clearly beyond the reach of other alternative approaches and reflects the efficiency of the proposed method in the reconstruction process and allow us to look for any possible feature in the primordial spectrum projected in the CMB data. Though the proposed method allow us to look at various possibilities for the form of the primordial spectrum, all having good fit to the data, proper error-analysis is needed to test for consistency of theoretical models since, along with possible physical artefacts, most of the features in the reconstructed spectrum might be arising from fitting noises in the CMB data. Reconstructed error-band for the form of the primordial spectrum using many realizations of the data, all bootstrapped and based on WMAP 9 year data, shows proper consistency of power-law form of the primordial spectrum with the WMAP 9 data at all wave numbers. Including WMAP polarization data in to the analysis have not improved much our results due to its low quality but we expect Planck data will allow us to make a full analysis on CMB observations on both temperature and polarization separately and in combination.", "keyphrases": ["possible feature", "cmb data", "primordial power spectrum"]}
{"id": "0901.0549", "title": "The Effective Theory of Inflation in the Standard Model of the Universe and the CMB+LSS data analysis", "abstract": "Inflation is part of the Standard Model of the Universe supported by CMB and large scale structure LSS datasets. This review presents new developments of inflation in three main chapters. (I): The effective theory of inflation a la Ginsburg-Landau (GL): the inflaton potential is a polynomial with universal form making explicit the inflation energy scale M, the Planck mass and the inflation e-folds number N 60. The slow-roll expansion becomes a systematic 1/N expansion and the inflaton couplings are naturally small as powers of (M/M_Pl)^2. The spectral index (n_s - 1) and the ratio of tensor/scalar fluctuations r are O(1/N), the running index is O(1/N^2). M 0.7 10^16 GeV is completely determined by the scalar adiabatic fluctuations amplitude. (II): A Monte Carlo Markov Chains (MCMC) analysis of the CMB+LSS data (including WMAP5) with our analytic theoretical results yields: a lower bound for r (new inflation): r > 0.023 (95 potential is a double well, even function of the field yielding as most probable values n_s 0.964, r 0.051. This value for r is within reach of forthcoming CMB observations. Slow-roll inflation is generically preceded by a short fast-roll stage which leads to a suppression of the CMB quadrupoles. MCMC analysis of the WMAP+SDSS data shows that fast-roll fits the TT, TE and EE modes well reproducing the quadrupole suppression and fixes the total number of efolds of inflation to be N_total 64. (III) Quantum loop corrections are very small and controlled by powers of (H /M_Pl)^2 10^-9 which validates the effective theory of inflation. We show how powerful is the GL theory of inflation in predicting observables.", "keyphrases": ["effective theory", "universe", "new inflation"]}
{"id": "0902.1313", "title": "What the small angle CMB really tells us about the curvature of the Universe", "abstract": "It is well known that observations of the cosmic microwave background (CMB) are highly sensitive to the spatial curvature of the Universe, k. Here we find that what is in fact being tightly constrained by small angle fluctuations is spatial curvature near the surface of last scattering, and that if we allow k to be a function of position, rather than taking a constant value everywhere, then considerable spatial curvature is permissible within our own locale. This result is of interest for the giant void models that attempt to explain the supernovae observations without Dark Energy. We find voids models with a homogeneous big bang can be compatible with the observed small angle CMB, but only if they exist in a positively curved universe. To be compatible with local measurements of H_0, however, we find that a radially varying bang time is required.", "keyphrases": ["small angle cmb", "curvature", "cosmological model"]}
{"id": "1610.06585", "title": "Assessment of the Information Content of the Power Spectrum and Bispectrum", "abstract": "The covariance matrix of the matter and halo power spectrum and bispectrum are studied. Using a large suite of simulations, we find that the non-Gaussianity in the covariance is significant already at mildly nonlinear scales. We compute the leading disconnected non-Gaussian correction to the matter bispectrum covariance using perturbation theory, and find that the corrections result in good agreement in the mildly nonlinear regime. The shot noise contribution to the halo power spectrum and bispectrum covariance is computed using the Poisson model, and the model yields decent agreement with simulation results. However, when the shot noise is estimated from the individual realization, which is usually done in reality, we find that the halo covariance is substantially reduced and gets close to the Gaussian covariance. This is because most of the non-Gaussianity in the covariance arises from the fluctuations in the Poisson shot noise. We use the measured non-Gaussian covariance to access the information content of the power spectrum and bispectrum. The signal-to-noise ratio, S/N, of the matter and halo power spectrum levels off in the mildly nonlinear regime, k \u223c 0.1 - 0.2 Mpc h^-1. In the nonlinear regime the S/N of the matter and halo bispectrum increases but much slower than the Gaussian results suggest. We find that both the S/N for power spectrum and bispectrum are overestimated by the Gaussian covariances, but the problem being much more serious for the bispectrum. Because the bispectrum is affected strongly by nonlinearity and shot noise, inclusion of the bispectrum only adds modest amount of S/N compared to that of the power spectrum.", "keyphrases": ["information content", "power spectrum", "non-gaussianity", "assessment"]}
{"id": "1407.4682", "title": "Fluctuations of differential number counts of radio continuum sources", "abstract": "We investigate the differential number counts of sources in radio continuum surveys, including all terms at linear order in cosmological perturbations. Our framework does not assume a specific gauge condition. This general approach allows us to recover gauge invariance explicitly. With the complete derivations of the covariant volume integral on the past light cone, we have identified several contributions in the number counts. To clarify their underlying physics, we present each contributions in terms of scalar, vector and tensor modes. This theoretical framework promises to be widely applicable to continuum radio galaxy surveys to model the expected angular power spectrum and two-point correlation.", "keyphrases": ["differential number count", "fluctuation", "radio source"]}
{"id": "1003.0925", "title": "Orbital migration of low-mass planets in evolutionary radiative models: Avoiding catastrophic infall", "abstract": "Outward migration of low-mass planets has recently been shown to be a possibility in non-barotropic disks. We examine the consequences of this result in evolutionary models of protoplanetary disks. Planet migration occurs towards equilibrium radii with zero torque. These radii themselves migrate inwards because of viscous accretion and photoevaporation. We show that as the surface density and temperature fall, the planet orbital migration and disk depletion timescales eventually become comparable, with the precise timing depending on the mass of the planet. When this occurs, the planet decouples from the equilibrium radius. At this time, however, the gas surface density is already too low to drive substantial further migration. A higher mass planet, of 10 Earth masses, can open a gap during the late evolution of the disk, and stops migrating. Low mass planets, with 1 or 0.1 Earth masses, released beyond 1 AU in our models, avoid migrating into the star. Our results provide support for the reduced migration rates adopted in recent planet population synthesis models.", "keyphrases": ["planet", "protoplanetary disk", "orbital migration"]}
{"id": "1410.1537", "title": "Momentum Injection by Supernovae in the Interstellar Medium", "abstract": "Supernova (SN) explosions deposit prodigious energy and momentum in their environments, with the former regulating multiphase thermal structure and the latter regulating turbulence and star formation rates in the interstellar medium (ISM). However, systematic studies quantifying the impact of SNe in realistic inhomogeneous ISM conditions have been lacking. Using three-dimensional hydrodynamic simulations, we investigate the dependence of radial momentum injection on both physical conditions (considering a range of mean density n=0.1-100) and numerical parameters. Our inhomogeneous simulations adopt two-phase background states that result from thermal instability in atomic gas. Although the SNR morphology becomes highly complex for inhomogeneous backgrounds, the radial momentum injection is remarkably insensitive to environmental details. For our two-phase simulations, the final momentum produced by a single SN is given by 2.8*10^5 M_sun*km/s n^-0.17. This is only 5 with the same mean density, and only 30 of shell formation. The maximum mass in hot gas is quite insensitive to environmental inhomogeneity. Strong magnetic fields alter the hot gas mass at very late times, but the momentum injection remains the same. Initial experiments with multiple spatially-correlated SNe show a momentum per event nearly as large as single-SN cases. We also present a full numerical parameter study to assess convergence requirements. For convergence in the momentum and other quantities, we find that the numerical resolution dx and the initial size of the SNR r_init must satisfy dx, r_init<r_sf/3, where the shell formation radius is given by r_sf = 30 pc n^-0.46 for two-phase models (or 30 for a homogeneous medium).", "keyphrases": ["supernova", "interstellar medium", "momentum injection"]}
{"id": "1109.4052", "title": "The First Magnetic Fields", "abstract": "We review current ideas on the origin of galactic and extragalactic magnetic fields. We begin by summarizing observations of magnetic fields at cosmological redshifts and on cosmological scales. These observations translate into constraints on the strength and scale magnetic fields must have during the early stages of galaxy formation in order to seed the galactic dynamo. We examine mechanisms for the generation of magnetic fields that operate prior during inflation and during subsequent phase transitions such as electroweak symmetry breaking and the quark-hadron phase transition. The implications of strong primordial magnetic fields for the reionization epoch as well as the first generation of stars is discussed in detail. The exotic, early-Universe mechanisms are contrasted with astrophysical processes that generate fields after recombination. For example, a Biermann-type battery can operate in a proto-galaxy during the early stages of structure formation. Moreover, magnetic fields in either an early generation of stars or active galactic nuclei can be dispersed into the intergalactic medium.", "keyphrases": ["magnetic field", "phase transition", "primordial magnetic field", "star", "early-universe mechanism"]}
{"id": "1710.07005", "title": "A First Transients Survey with JWST: the FLARE project", "abstract": "JWST was conceived and built to answer one of the most fundamental questions that humans can address empirically: \"How did the Universe make its first stars?\". Our First Lights At REionization (FLARE) project transforms the quest for the epoch of reionization from the static to the time domain. It targets the complementary question: \"What happened to those first stars?\". It will be answered by observations of the most luminous events: supernovae and accretion on to black holes formed by direct collapse from the primordial gas clouds. These transients provide direct constraints on star-formation rates (SFRs) and the truly initial Initial Mass Function (IMF), and they may identify possible stellar seeds of supermassive black holes (SMBHs). Furthermore, our knowledge of the physics of these events at ultra-low metallicity will be much expanded. JWST's unique capabilities will detect these most luminous and earliest cosmic messengers easily in fairly shallow observations. However, these events are very rare at the dawn of cosmic structure formation and so require large area coverage. Time domain astronomy can be advanced to an unprecedented depth by means of a shallow field of JWST reaching 27 mag AB in 2 and 4.4 microns over a field as large as 0.1 square degree visited multiple times each year. Such a survey may set strong constraints or detect massive Pop III SNe at redshifts beyond 10, pinpointing the redshift of the first stars, or at least their death. Based on our current knowledge of superluminous supernovae (SLSNe), such a survey will find one or more SLSNe at redshifts above 6 in five years and possibly several direct collapse black holes. Although JWST is not designed as a wide field survey telescope, we show that such a wide field survey is possible with JWST and is critical in addressing several of its key scientific goals.", "keyphrases": ["jwst", "flare project", "first lights", "supernovae", "redshift"]}
{"id": "1608.01422", "title": "Turning Around along the Cosmic Web", "abstract": "A bound-violation designates a case that the turn-around radius of a bound object exceeds the upper limit put by the spherical collapse model based on the standard \u039bCDM paradigm. Given that the turn-around radius of a bound object is a stochastic quantity and that the spherical model overly simplifies the true gravitational collapse which actually proceeds anisotropically along the cosmic web, the rarity of the occurrence of a bound violation may depend on the web environment. Assuming a Planck cosmology, we numerically construct the bound-zone peculiar velocity profiles along the cosmic web (filaments and sheets) around the isolated groups with virial mass M_ v\u2265 3\u00d7 10^13 h^-1M_\u2299 identified in the Small MultiDark Planck simulations and determine the radial distances at which their peculiar velocities equal the Hubble expansion speed as the turn-around radii of the groups. It is found that although the average turn-around radii of the isolated groups are well below the spherical bound-limit on all mass scales, the bound violations are not forbidden for individual groups and that the cosmic web has an effect of reducing the rarity of the occurrence of a bound violation. Explaining that the spherical bound limit on the turn-around radius in fact represents the threshold distance up to which the intervention of the external gravitational field in the bound-zone peculiar velocity profiles around the non-isolated groups stays negligible, we discuss the possibility of using the threshold distance scale to constrain locally the equation of state of dark energy .", "keyphrases": ["cosmic web", "turn-around radius", "peculiar velocity profile"]}
{"id": "0912.2734", "title": "On Loops in Inflation", "abstract": "We study loop corrections to correlation functions of inflationary perturbations. Previous calculations have found that the two-point function can have a logarithmic running of the form log(k/mu), where k is the wavenumber of the perturbation, and mu is the renormalization scale. We highlight that this result would have profound consequences for both eternal inflation and the predictivity of standard inflation. We find a different result. We consider two sets of theories: one where the inflaton has a large cubic self-interaction and one where the inflaton interacts gravitationally with N massless spectator scalar fields. We find that there is a logarithmic running but of the form log(H/mu), where H is the Hubble constant during inflation. We find this result in three independent ways: by performing the calculation with a sharp cutoff in frequency-momentum space, in dimensional regularization and by the simple procedure of making the loop integral dimensionless. For the simplest of our theories we explicitly renormalize the correlation function proving that the divergencies can be reabsorbed and that the correlation function for super-horizon modes does not depend on time (once the tadpole terms have been properly taken into account). We prove the time-independence of the super-horizon correlation function in several additional ways: by doing the calculation of the correlation function at finite time using both the regularizations and by developing a formalism which expresses loop corrections directly in terms of renormalized quantities at each time. We find this last formalism particularly helpful to develop intuition which we then use to generalize our results to higher loops and different interactions.", "keyphrases": ["loop correction", "logarithmic running", "perturbation theory"]}
{"id": "1504.04402", "title": "Ensemble modeling of CMEs using the WSA-ENLIL+Cone model", "abstract": "Ensemble modeling of CMEs provides a probabilistic forecast of CME arrival time which includes an estimation of arrival time uncertainty from the spread and distribution of predictions and forecast confidence in the likelihood of CME arrival. The real-time ensemble modeling of CME propagation uses the WSA-ENLIL+Cone model installed at the CCMC and executed in real-time. The current implementation evaluates the sensitivity of WSA-ENLIL+Cone model simulations of CME propagation to initial CME parameters. We discuss the results of real-time ensemble simulations for a total of 35 CME events between January 2013 - July 2014. For the 17 events where the CME was predicted to arrive at Earth, the mean absolute arrival time prediction error was 12.3 hours, which is comparable to the errors reported in other studies. For predictions of CME arrival at Earth the correct rejection rate is 62 false-alarm rate is 38 arrival predictions for 8 out of 17 events. The Brier Score for CME arrival predictions is 0.15 (where 1 is a perfect forecast), indicating that on average, the predicted likelihood of CME arrival is fairly accurate. The reliability of ensemble CME arrival predictions is heavily dependent on the initial distribution of CME input parameters, particularly the median and spread. Preliminary analysis of the probabilistic forecasts suggests undervariability, indicating that these ensembles do not sample a wide enough spread in CME input parameters. Prediction errors can also arise from ambient model parameters, the accuracy of the solar wind background derived from coronal maps, or other model limitations. Finally, predictions of the Kp geomagnetic index differ from observed values by less than one for 11 out of 17 of the ensembles and Kp prediction errors computed from the mean predicted Kp show a mean absolute error of 1.3.", "keyphrases": ["wsa-enlil+cone model", "cme input parameter", "ensemble modeling"]}
{"id": "1708.08121", "title": "Earth as a Hybrid Planet - The Anthropocene in an Evolutionary Astrobiological Context", "abstract": "We develop a classification scheme for the evolutionary state of planets based on the non-equilibrium thermodynamics of their coupled systems, including the presence of a biosphere and the possibility of what we call an agency-dominated biosphere (i.e. an energy-intensive technological species). The premise is that Earths entry into the Anthropocene represents what might be from an astrobiological perspective a predictable planetary transition. We explore this problem from the perspective of the solar system and exoplanet studies. Our classification discriminates planets by the forms of free energy generation driven from stellar forcing. We then explore how timescales for global evolutionary processes on Earth might be synchronized with ecological transformations driven by increases in energy harvesting and its consequences (which might have reached a turning point with global urbanization). Finally, we describe quantitatively the classification scheme based on the maintenance of chemical disequilibrium in the past and current Earth systems and on other worlds in the solar system. In this perspective, the beginning of the Anthropocene can be seen as the onset of the hybridization of the planet - a transitional stage from one class of planetary systems interaction to another. For Earth, this stage occurs as the effects of human civilization yield not just new evolutionary pressures, but new selected directions for novel planetary ecosystem functions and their capacity to generate disequilibrium and enhance planetary dissipation.", "keyphrases": ["anthropocene", "planetary transition", "earth"]}
{"id": "1005.4053", "title": "Large-scale Perturbations from the Waterfall Field in Hybrid Inflation", "abstract": "We estimate large-scale curvature perturbations from isocurvature fluctuations in the waterfall field during hybrid inflation, in addition to the usual inflaton field perturbations. The tachyonic instability at the end of inflation leads to an explosive growth of super-Hubble scale perturbations, but they retain the steep blue spectrum characteristic of vacuum fluctuations in a massive field during inflation. The power spectrum thus peaks around the Hubble-horizon scale at the end of inflation. We extend the usual delta-N formalism to include the essential role of these small fluctuations when estimating the large-scale curvature perturbation. The resulting curvature perturbation due to fluctuations in the waterfall field is second-order and the spectrum is expected to be of order 10^-54 on cosmological scales.", "keyphrases": ["hybrid inflation", "curvature perturbation", "tachyonic instability", "cosmological scale"]}
{"id": "1112.5565", "title": "Kinetic Equations for Baryogenesis via Sterile Neutrino Oscillation", "abstract": "We investigate baryogenesis in the \u03bdMSM (neutrino Minimal Standard Model), which is the MSM extended by three right-handed neutrinos with masses below the electroweak scale. The baryon asymmetry of the universe can be generated by the mechanism via flavor oscillation of right-handed (sterile) neutrinos which are responsible to masses of active neutrinos confirmed by various experiments. We present the kinetic equations for the matrix of densities of leptons which describe the generation of asymmetries. Especially, the momentum dependence of the matrix of densities is taken into account. By solving these equations numerically, it is found that the momentum distribution is significantly distorted from the equilibrium one, since the production for the modes with lower momenta k \u226a T (T is the temperature of the universe) is enhanced, while suppressed for higher modes. As a result, the most important mode for the yields of sterile neutrinos as well as the baryon asymmetry is k \u2243 2 T, which is smaller than < k > inferred from the thermal average. The comparison with the previous works is also discussed.", "keyphrases": ["baryogenesis", "sterile neutrino", "electroweak scale"]}
{"id": "1605.00646", "title": "Mass Transport and Turbulence in Gravitationally Unstable Disk Galaxies II: The Effects of Star Formation Feedback", "abstract": "Self-gravity and stellar feedback are capable of driving turbulence and transporting mass and angular momentum in disk galaxies, but the balance between them is not well understood. In the previous paper in this series, we showed that gravity alone can drive turbulence in galactic disks, regulate their Toomre Q parameters to \u223c 1, and transport mass inwards at a rate sufficient to fuel star formation in the centers of present-day galaxies. In this paper we extend our models to include the effects of star formation feedback. We show that feedback suppresses galaxies' star formation rates by a factor of \u223c 5 and leads to the formation of a multi-phase atomic and molecular ISM. Both the star formation rate and the phase balance produced in our simulations agree well with observations of nearby spirals. After our galaxies reach steady state, we find that the inclusion of feedback actually lowers the gas velocity dispersion slightly compared to the case of pure self-gravity, and also slightly reduces the rate of inward mass transport. Nevertheless, we find that, even with feedback included, our galactic disks self-regulate to Q \u223c 1, and transport mass inwards at a rate sufficient to supply a substantial fraction of the inner disk star formation. We argue that gravitational instability is therefore likely to be the dominant source of turbulence and transport in galactic disks, and that it is responsible for fueling star formation in the inner parts of galactic disks over cosmological times.", "keyphrases": ["turbulence", "star formation feedback", "gravitational instability"]}
{"id": "1601.00557", "title": "On the number density of \"direct collapse\" black hole seeds", "abstract": "Supermassive black holes (BHs) of millions solar masses and above reside in the center of most local galaxies, but they also power active galactic nuclei and quasars, detected up to z=7. This observational evidence puts strong constraints on the BH growth and the mass of the first BH seeds. The scenario of \"direct collapse\" is very appealing as it leads to the formation of large mass BH seeds in the range 10^4-10^6 Msun, which eases explaining how quasars at z=6-7 are powered by BHs with masses >10^9 Msun. Direct collapse, however, appears to be rare, as the conditions required by the scenario are that gas is metal-free, the presence of a strong photo-dissociating Lyman-Werner flux, and large inflows of gas at the center of the halo, sustained for 10-100 Myr. We performed several cosmological hydrodynamical simulations that cover a large range of box sizes and resolutions, thus allowing us to understand the impact of several physical processes on the distribution of direct collapse BHs. We identify halos where direct collapse can happen, and derive the number density of BHs. We also investigate the discrepancies between hydrodynamical simulations, direct or post-processed, and semi-analytical studies. We find that for direct collapse to account for BHs in normal galaxies, the critical Lyman-Werner flux required for direct collapse must be much less than predicted by 3D simulations that include detailed chemical models. However, when supernova feedback is relatively weak, enough direct collapse BHs to explain z=6-7 quasars can be obtained for more realistic values of the critical Lyman Werner flux.", "keyphrases": ["number density", "direct collapse", "black hole"]}
{"id": "1701.07029", "title": "Are pulsars spun up or down by SASI spiral modes?", "abstract": "Pulsars may either be spun up or down by hydrodynamic instabilities during the supernova explosion of massive stars. Besides rapidly-rotating cases related to bipolar explosions, stellar rotation may affect the explosion of massive stars in the more common situations where the centrifugal force is minor. Using 2D simulations of a simplified setup in cylindrical geometry, we examine the impact of rotation on the Standing Accretion Shock Instability (SASI) and the corotation instability, also known as low-T/|W|. The influence of rotation on the saturation amplitude of these instabilities depends on the specific angular momentum in the accretion flow and the ratio of the shock to the neutron star radii. The spiral mode of SASI becomes more vigorous with faster rotation only if this ratio is large enough. A corotation instability develops at large rotation rates and impacts the dynamics more dramatically, leading to a strong one-armed spiral wave. Non-axisymmetric instabilities are able to redistribute angular momentum radially and affect the pulsar spin at birth. A systematic study of the relationship between the core rotation period of the progenitor and the initial pulsar spin is performed. Stellar rotation rates for which pulsars are spun up or down by SASI are estimated. Rapidly spinning progenitors are modestly spun down by spiral modes, less than \u223c 30%, when a corotation instability develops. Given the observational constraints on pulsar spin periods at birth, this suggests that rapid rotation might not play a significant hydrodynamic role in most core-collapse supernovae.", "keyphrases": ["pulsar", "spiral mode", "accretion shock instability"]}
{"id": "0901.3258", "title": "Measuring the neutron star equation of state with gravitational wave observations", "abstract": "We report the results of a first study that uses numerical simulations to estimate the accuracy with which one can use gravitational wave observations of double neutron star inspiral to measure parameters of the neutron-star equation of state. The simulations use the evolution and initial-data codes of Shibata and Uryu to compute the last several orbits and the merger of neutron stars, with matter described by a parametrized equation of state. Previous work suggested the use of an effective cutoff frequency to place constraints on the equation of state. We find, however, that greater accuracy is obtained by measuring departures from the point-particle limit of the gravitational waveform produced during the late inspiral. As the stars approach their final plunge and merger, the gravitational wave phase accumulates more rapidly for smaller values of the neutron star compactness (the ratio of the mass of the neutron star to its radius). We estimate that realistic equations of state will lead to gravitational waveforms that are distinguishable from point particle inspirals at an effective distance (the distance to an optimally oriented and located system that would produce an equivalent waveform amplitude) of 100 Mpc or less. As Lattimer and Prakash observed, neutron-star radius is closely tied to the pressure at density not far above nuclear. Our results suggest that broadband gravitational wave observations at frequencies between 500 and 1000 Hz will constrain this pressure, and we estimate the accuracy with which it can be measured. Related first estimates of radius measurability show that the radius can be determined to an accuracy of 1 km at 100 Mpc.", "keyphrases": ["neutron star", "gravitational wave observation", "point-particle limit"]}
{"id": "1501.00963", "title": "The Eleventh and Twelfth Data Releases of the Sloan Digital Sky Survey: Final Data from SDSS-III", "abstract": "The third generation of the Sloan Digital Sky Survey (SDSS-III) took data from 2008 to 2014 using the original SDSS wide-field imager, the original and an upgraded multi-object fiber-fed optical spectrograph, a new near-infrared high-resolution spectrograph, and a novel optical interferometer. All the data from SDSS-III are now made public. In particular, this paper describes Data Release 11 (DR11) including all data acquired through 2013 July, and Data Release 12 (DR12) adding data acquired through 2014 July (including all data included in previous data releases), marking the end of SDSS-III observing. Relative to our previous public release (DR10), DR12 adds one million new spectra of galaxies and quasars from the Baryon Oscillation Spectroscopic Survey (BOSS) over an additional 3000 sq. deg of sky, more than triples the number of H-band spectra of stars as part of the Apache Point Observatory (APO) Galactic Evolution Experiment (APOGEE), and includes repeated accurate radial velocity measurements of 5500 stars from the Multi-Object APO Radial Velocity Exoplanet Large-area Survey (MARVELS). The APOGEE outputs now include measured abundances of 15 different elements for each star. In total, SDSS-III added 2350 sq. deg of ugriz imaging; 155,520 spectra of 138,099 stars as part of the Sloan Exploration of Galactic Understanding and Evolution 2 (SEGUE-2) survey; 2,497,484 BOSS spectra of 1,372,737 galaxies, 294,512 quasars, and 247,216 stars over 9376 sq. deg; 618,080 APOGEE spectra of 156,593 stars; and 197,040 MARVELS spectra of 5,513 stars. Since its first light in 1998, SDSS has imaged over 1/3 of the Celestial sphere in five bands and obtained over five million astronomical spectra.", "keyphrases": ["data release", "sdss-iii", "star", "photometric data"]}
{"id": "1103.3835", "title": "Lower Bounds on Intergalactic Magnetic Fields from Simultaneously Observed GeV-TeV Light Curves of the Blazar Mrk 501", "abstract": "We derive lower bounds on intergalactic magnetic fields (IGMFs) from upper limits on the pair echo emission from the blazar Mrk 501, that is, delayed GeV emission from secondary e^-e^+ pairs produced via interactions of primary TeV gamma rays with the cosmic infrared background. Utilizing only simultaneous GeV-TeV light curves observed by VERITAS, MAGIC and Fermi-LAT during a multiwavelength campaign in 2009 that included a TeV flare, bounds are deduced on the IGMF strength of B \u2273 10^-20 G at 90 for a field coherence length of 1 kpc. Since our analysis is based firmly on the observational data alone and nearly free of assumptions concerning the primary TeV flux in unobserved periods or spectral bands, our evaluation of the pair echo flux is conservative and the evidence for a non-zero IGMF is more robust compared to previous studies.", "keyphrases": ["magnetic field", "intergalactic medium", "extragalactic magnetic field"]}
{"id": "0911.3346", "title": "Further explorations of Skyrme-Hartree-Fock-Bogoliubov mass formulas. XI: Stabilizing neutron stars against a ferromagnetic collapse", "abstract": "We construct a new Hartree-Fock-Bogoliubov (HFB) mass model, labeled HFB-18, with a generalized Skyrme force. The additional terms that we have introduced into the force are density-dependent generalizations of the usual t_1 and t_2 terms, and are chosen in such a way as to avoid the high-density ferromagnetic instability of neutron stars that is a general feature of conventional Skyrme forces, and in particular of the Skyrme forces underlying all the HFB mass models that we have developed in the past. The remaining parameters of the model are then fitted to essentially all the available mass data, an rms deviation \u03c3 of 0.585 MeV being obtained. The new model thus gives almost as good a mass fit as our best-fit model HFB-17 (\u03c3 = 0.581 MeV), and has the advantage of avoiding the ferromagnetic collapse of neutron stars.", "keyphrases": ["neutron star", "ferromagnetic collapse", "mass model"]}
{"id": "1809.03598", "title": "Measuring the Hubble constant and spatial curvature from supernova apparent magnitude, baryon acoustic oscillation, and Hubble parameter data", "abstract": "Cosmic microwave background (CMB) anisotropy (spatial inhomogeneity) data provide the tightest constraints on the Hubble constant, matter density, spatial curvature, and dark energy dynamics. Other data, sensitive to the evolution of only the spatially homogeneous part of the cosmological model, such as Type Ia supernova apparent magnitude, baryon acoustic oscillation distance, and Hubble parameter measurements, can be used in conjunction with the CMB data to more tightly constrain parameters. Recent joint analyses of CMB and such non-CMB data indicate that slightly closed spatial hypersurfaces are favored in nonflat untilted inflation models and that dark energy dynamics cannot be ruled out, and favor a smaller Hubble constant. We show that the constraints that follow from these non-CMB data alone are consistent with those that follow from the CMB data alone and so also consistent with, but weaker than, those that follow from the joint analyses of the CMB and non-CMB data.", "keyphrases": ["hubble", "spatial curvature", "apparent magnitude"]}
{"id": "1202.1346", "title": "Early structure formation from cosmic string loops", "abstract": "We examine the effects of cosmic strings on structure formation and on the ionization history of the universe. While Gaussian perturbations from inflation are known to provide the dominant contribution to the large scale structure of the universe, density perturbations due to strings are highly non-Gaussian and can produce nonlinear structures at very early times. This could lead to early star formation and reionization of the universe. We improve on earlier studies of these effects by accounting for high loop velocities and for the filamentary shape of the resulting halos. We find that for string energy scales G\u03bc> 10^-7 the effect of strings on the CMB temperature and polarization power spectra can be significant and is likely to be detectable by the Planck satellite. We mention shortcomings of the standard cosmological model of galaxy formation which may be remedied with the addition of cosmic strings, and comment on other possible observational implications of early structure formation by strings.", "keyphrases": ["cosmic string", "reionization", "early structure formation"]}
{"id": "1405.1369", "title": "Exploring Bouncing Cosmologies with Cosmological Surveys", "abstract": "In light of the recent observational data coming from the sky we have two significant directions in the field of theoretical cosmology recently. First, we are now able to make use of present observations, such as the Planck and BICEP2 data, to examine theoretical predictions from the standard inflationary \u039bCDM which were made decades of years ago. Second, we can search for new cosmological signatures as a way to explore physics beyond the standard cosmic paradigm. In particular, a subset of early universe models admit a nonsingular bouncing solution that attempts to address the issue of the big bang singularity. These models have achieved a series of considerable developments in recent years, in particular in their perturbative frameworks, which made brand-new predictions of cosmological signatures that could be visible in current and forthcoming observations. In this article we present two representative paradigms of very early universe physics. The first is the so-called new matter (or matter-ekpyrotic) bounce scenario in which the universe starts with a matter-dominated contraction phase and transitions into an ekpyrotic phase. In the setting of this paradigm, we propose some possible mechanisms of generating a red tilt for primordial curvature perturbations and confront its general predictions with recent cosmological observations. The second is the matter-bounce inflation scenario which can be viewed as an extension of inflationary cosmology with a matter contraction before inflation. We present a class of possible model constructions and review its implications on the current CMB experiments. Last, we review the significant achievements of these paradigms beyond the inflationary \u039bCDM model, which we expect to shed new light on the direction of observational cosmology in the next decade years.", "keyphrases": ["cosmology", "curvature perturbation", "cosmological observation", "matter bounce scenario"]}
{"id": "1001.4525", "title": "Symmetron Fields: Screening Long-Range Forces Through Local Symmetry Restoration", "abstract": "We present a screening mechanism that allows a scalar field to mediate a long range ( Mpc) force of gravitational strength in the cosmos while satisfying local tests of gravity. The mechanism hinges on local symmetry restoration in the presence of matter. In regions of sufficiently high matter density, the field is drawn towards \u03d5= 0 where its coupling to matter vanishes and the \u03d5-> -\u03d5symmetry is restored. In regions of low density, however, the symmetry is spontaneously broken, and the field couples to matter with gravitational strength. We predict deviations from general relativity in the solar system that are within reach of next-generation experiments, as well as astrophysically observable violations of the equivalence principle. The model can be distinguished experimentally from Brans-Dicke gravity, chameleon theories and brane-world modifications of gravity.", "keyphrases": ["force", "local symmetry restoration", "screening mechanism", "scalar field", "symmetron mechanism"]}
{"id": "1003.0674", "title": "Aharonov-Bohm Radiation of Fermions", "abstract": "We analyze Aharonov-Bohm radiation of charged fermions from oscillating solenoids and cosmic strings. We find that the angular pattern of the radiation has features that differ significantly from that for bosons. For example, fermionic radiation in the lowest harmonic is approximately isotropically distributed around an oscillating solenoid, whereas for bosons the radiation is dipolar. We also investigate the spin polarization of the emitted fermion-antifermion pair. Fermionic radiation from kinks and cusps on cosmic strings is shown to depend linearly on the ultraviolet cut-off, suggesting strong emission at an energy scale comparable to the string energy scale.", "keyphrases": ["fermion", "cosmic string", "aharonov-bohm radiation"]}
{"id": "2002.11355", "title": "Multi-messenger constraints on the neutron-star equation of state and the Hubble constant", "abstract": "Observations of neutron-star mergers based on distinct messengers, including gravitational waves and electromagnetic signals, can be used to study the behavior of matter denser than an atomic nucleus, and to measure the expansion rate of the Universe described by the Hubble constant. We perform a joint analysis of the gravitational-wave signal GW170817 with its electromagnetic counterparts AT2017gfo and GRB170817A, and the gravitational-wave signal GW190425, both originating from neutron-star mergers. We combine these with previous measurements of pulsars using X-ray and radio observations, and nuclear-theory computations using chiral effective field theory to constrain the neutron-star equation of state. We find that the radius of a 1.4 solar mass neutron star is 11.75^+0.86_-0.81 km at 90% confidence and the Hubble constant is 66.2^+4.4_-4.2 km Mpc^-1 s^-1 at 1\u03c3 uncertainty.", "keyphrases": ["neutron-star equation", "hubble constant", "atomic nucleus"]}
{"id": "1810.03195", "title": "The spectral shapes of the fluxes of electrons and positrons and the average residence time of cosmic rays in the Galaxy", "abstract": "The cosmic ray energy spectra encode very important information about the mechanisms that generate relativistic particles in the Milky Way, and about the properties of the Galaxy that control their propagation. Relativistic electrons and positrons traveling in interstellar space lose energy much more rapidly than more massive particles such as protons and nuclei, with a rate that grows quadratically with the particle energy E. One therefore expects that the effects of energy loss should leave observable signatures in the e^\u2213 spectra, in the form of softenings centered at the critical energy E^*. This quantity is determined by the condition that the total energy loss suffered by particles during their residence time in the Galaxy is of the same order of the initial energy. If the electrons and positrons are accelerated in discrete (quasi) point\u2013like astrophysical objects, such as Supernova explosions or Pulsars, the stochastic nature of the sources should also leave observable signatures in the e^\u2213 energy spectra and angular distributions above a second (higher) critical energy E^\u2020, determined by the condition that particles with E \u2273 E^\u2020 can propagate only for a maximum distance shorter than the average separation between sources. In this work we discuss the theoretically expectations for the signatures of the energy loss effects on the electron and positron spectra, and compare these predictions with the existing observations. Recent measurements of the (e^- + e^+) flux have discovered the existence of a prominent spectral break at E \u2243 1 TeV. This spectral feature can perhaps be identified with the critical energy E^*. An alternative hypothesis is to assmume that E^* has a much lower value of order few GeV. Resolving this ambiguity is of great importance for our understanding of Galactic cosmic rays.", "keyphrases": ["flux", "galaxy", "spectral feature"]}
{"id": "1207.0633", "title": "Pulsar glitches: The crust is not enough", "abstract": "Pulsar glitches are traditionally viewed as a manifestation of vortex dynamics associated with a neutron superfluid reservoir confined to the inner crust of the star. In this Letter we show that the non-dissipative entrainment coupling between the neutron superfluid and the nuclear lattice leads to a less mobile crust superfluid, effectively reducing the moment of inertia associated with the angular momentum reservoir. Combining the latest observational data for prolific glitching pulsars with theoretical results for the crust entrainment we find that the required superfluid reservoir exceeds that available in the crust. This challenges our understanding of the glitch phenomenon, and we discuss possible resolutions to the problem.", "keyphrases": ["glitch", "inner crust", "pulsar", "neutron star"]}
{"id": "1009.4157", "title": "Hunting Down the Best Model of Inflation with Bayesian Evidence", "abstract": "We present the first calculation of the Bayesian evidence for different prototypical single field inflationary scenarios, including representative classes of small field and large field models. This approach allows us to compare inflationary models in a well-defined statistical way and to determine the current \"best model of inflation\". The calculation is performed numerically by interfacing the inflationary code FieldInf with MultiNest. We find that small field models are currently preferred, while large field models having a self-interacting potential of power p>4 are strongly disfavoured. The class of small field models as a whole has posterior odds of approximately 3:1 when compared with the large field class. The methodology and results presented in this article are an additional step toward the construction of a full numerical pipeline to constrain the physics of the early Universe with astrophysical observations. More accurate data (such as the Planck data) and the techniques introduced here should allow us to identify conclusively the best inflationary model.", "keyphrases": ["bayesian evidence", "inflationary model", "cosmic microwave background", "scalar power spectrum"]}
{"id": "1004.1154", "title": "Electron Acceleration by Multi-Island Coalescence", "abstract": "Energetic electrons of up to tens of MeV are created during explosive phenomena in the solar corona. While many theoretical models consider magnetic reconnection as a possible way of generating energetic electrons, the precise roles of magnetic reconnection during acceleration and heating of electrons still remain unclear. Here we show from 2D particle-in-cell simulations that coalescence of magnetic islands that naturally form as a consequence of tearing mode instability and associated magnetic reconnection leads to efficient energization of electrons. The key process is the secondary magnetic reconnection at the merging points, or the `anti-reconnection', which is, in a sense, driven by the converging outflows from the initial magnetic reconnection regions. By following the trajectories of the most energetic electrons, we found a variety of different acceleration mechanisms but the energization at the anti-reconnection is found to be the most important process. We discuss possible applications to the energetic electrons observed in the solar flares. We anticipate our results to be a starting point for more sophisticated models of particle acceleration during the explosive energy release phenomena.", "keyphrases": ["coalescence", "reconnection", "magnetic island", "particle acceleration"]}
{"id": "1503.07060", "title": "Innermost stable circular orbits of spinning test particles in Schwarzschild and Kerr space-times", "abstract": "We consider the motion of classical spinning test particles in Schwarzschild and Kerr metrics and investigate innermost stable circular orbits (ISCO). The main goal of this work is to find analytically the small-spin corrections for the parameters of ISCO (radius, total angular momentum, energy, orbital angular frequency) of spinning test particles in the case of vectors of black hole spin, particle spin and orbital angular momentum being collinear to each other. We analytically derive the small-spin linear corrections for arbitrary Kerr parameter a. The cases of Schwarzschild, slowly rotating and extreme Kerr black hole are considered in details. For a slowly rotating black hole the ISCO parameters are obtained up to quadratic in a and particle's spin s terms. From the formulae obtained it is seen that the spin-orbital coupling has attractive character when spin and angular momentum are parallel and repulsive when they are antiparallel. For the case of the extreme Kerr black hole with co-rotating particle we succeed to find the exact analytical solution for the limiting ISCO parameters for arbitrary spin. It has been shown that the limiting values of ISCO radius and frequency do not depend on the particle's spin while values of energy and total angular momentum depend on it. We have also considered circular orbits of arbitrary radius and have found small-spin linear corrections for the total angular momentum and energy at given radius. System of equations for numerical calculation of ISCO parameters for arbitrary a and s is also explicitly written.", "keyphrases": ["orbit", "test particle", "black hole"]}
{"id": "1510.06228", "title": "Relaxation of the chiral imbalance and the generation of magnetic fields in magnetars", "abstract": "The model for the generation of magnetic fields in a neutron star, based on the magnetic field instability caused by the electroweak interaction between electrons and nucleons, is developed. Using the methods of the quantum field theory, the helicity flip rate of electrons in their scattering off protons in dense matter of a neutron star is calculated. The influence of the electroweak interaction between electrons and background nucleons on the process of the helicity flip is studied. The kinetic equation for the evolution of the chital imbalance is derived. The obtained results are applied for the description of the magnetic fields evolution in magnetars.", "keyphrases": ["chiral imbalance", "magnetic field", "field instability", "spin-flip"]}
{"id": "1306.5220", "title": "Universality Class in Conformal Inflation", "abstract": "We develop a new class of chaotic inflation models with spontaneously broken conformal invariance. Observational consequences of a broad class of such models are stable with respect to strong deformations of the scalar potential. This universality is a critical phenomenon near the point of enhanced symmetry, SO(1,1), in case of conformal inflation. It appears because of the exponential stretching of the moduli space and the resulting exponential flattening of scalar potentials upon switching from the Jordan frame to the Einstein frame in this class of models. This result resembles stretching and flattening of inhomogeneities during inflationary expansion. It has a simple interpretation in terms of velocity versus rapidity near the Kahler cone in the moduli space, similar to the light cone of special theory of relativity. This effect makes inflation possible even in the models with very steep potentials. We describe conformal and superconformal versions of this cosmological attractor mechanism.", "keyphrases": ["conformal inflation", "scalar potential", "supergravity", "conformal attractor"]}
{"id": "1101.5205", "title": "Introduction to dark matter experiments", "abstract": "This is a set of four lectures presented at the Theoretical Advanced Study Institute (TASI-09) in June 2009. I provide an introduction to experiments designed to detect WIMP dark matter directly, focusing on building intuitive understanding of the characteristics of potential WIMP signals and the experimental techniques. After deriving the characteristics of potential signals in direct-detection experiments for standard WIMP models, I summarize the general experimental methods shared by most direct-detection experiments and review the advantages, challenges, and status of such searches (as of late 2009). Experiments are already probing SUSY models, with best limits on the spin-independent coupling below 10^-7 pb.", "keyphrases": ["gravitational lensing", "astrophysical evidence", "universe"]}
{"id": "1703.03696", "title": "Exotic Compact Objects and How to Quench their Ergoregion Instability", "abstract": "Gravitational-wave astronomy can give us access to the structure of black holes, potentially probing microscopic or even Planckian corrections at the horizon scale, as those predicted by some quantum-gravity models of exotic compact objects. A generic feature of these models is the replacement of the horizon by a reflective surface. Objects with these properties are prone to the so-called ergoregion instability when they spin sufficiently fast. We investigate in detail a simple model consisting of scalar perturbations of a Kerr geometry with a reflective surface near the horizon. The instability depends on the spin, on the compactness, and on the reflectivity at the surface. The instability time scale increases only logarithmically in the black-hole limit and, for a perfectly reflecting object, this is not enough to prevent the instability from occurring on dynamical time scales. However, we find that an absorption rate at the surface as small as 0.4 coefficient as large as | R|^2=0.996) is sufficient to quench the instability completely. Our results suggest that exotic compact objects are not necessarily ruled out by the ergoregion instability.", "keyphrases": ["exotic compact object", "black-hole spacetime", "matter configuration", "quantum theory"]}
{"id": "1901.08260", "title": "Gravitational waves from very massive stars collapsing to a black hole", "abstract": "We compute gravitational waves emitted by the collapse of a rotating very massive star (VMS) core leading directly to a black hole in axisymmetric numerical-relativity simulations. The evolved rotating VMS is derived by a stellar evolution calculation and its initial mass and the final carbon-oxygen core mass are 320M_\u2299 and \u2248 150M_\u2299, respectively. We find that for the moderately rapidly rotating cases, the peak strain amplitude and the corresponding frequency of gravitational waves are \u223c 10^-22 and f \u2248 300\u2013600 Hz for an event at the distance of D=50 Mpc. Such gravitational waves will be detectable only for D \u2272 10 Mpc by second generation detectors, advanced LIGO, advanced VIRGO, and KAGRA, even if the designed sensitivity for these detectors is achieved. However, third-generation detectors will be able to detect such gravitational waves for an event up to D \u223c 100 Mpc. The detection of the gravitational-wave signal will provide a potential opportunity for verifying the presence of VMSs with mass \u2273 300M_\u2299 and their pair-unstable collapse in the universe.", "keyphrases": ["massive star", "black hole", "initial mass", "gravitational wave"]}
{"id": "1004.5580", "title": "Extra polarization states of cosmological gravitational waves in alternative theories of gravity", "abstract": "Cosmological Gravitational Waves (GWs) are usually associated with the transverse-traceless part of the metric perturbations in the context of the theory of cosmological perturbations. These modes are just the usual polarizations `+' and `x' which appear in the general relativity theory. However, in the majority of the alternative theories of gravity, GWs can present more than these two polarization states. In this context, the Newman-Penrose formalism is particularly suitable for evaluating the number of non-null GW modes. In the present work we intend to take into account these extra polarization states for cosmological GWs in alternative theories of gravity. As an application, we derive the dynamical equations for cosmological GWs for two specific theories, namely, a general scalar-tensor theory which presents four polarization states and a massive bimetric theory which is in the most general case with six polarization states for GWs. The mathematical tool presented here is quite general, so it can be used to study cosmological perturbations in all metric theories of gravity.", "keyphrases": ["gravity", "scalar-tensor theory", "extra polarization state"]}
{"id": "0901.4786", "title": "Buoyancy Instabilities in Galaxy Clusters: Convection Due to Adiabatic Cosmic Rays and Anisotropic Thermal Conduction", "abstract": "Using a linear stability analysis and two and three-dimensional nonlinear simulations, we study the physics of buoyancy instabilities in a combined thermal and relativistic (cosmic ray) plasma, motivated by the application to clusters of galaxies. We argue that cosmic ray diffusion is likely to be slow compared to the buoyancy time on large length scales, so that cosmic rays are effectively adiabatic. If the cosmic ray pressure p_cr is \u2273 25 the thermal pressure, and the cosmic ray entropy (p_cr/\u03c1^4/3;\u03c1is the thermal plasma density) decreases outwards, cosmic rays drive an adiabatic convective instability analogous to Schwarzschild convection in stars. Global simulations of galaxy cluster cores show that this instability saturates by reducing the cosmic ray entropy gradient and driving efficient convection and turbulent mixing. At larger radii in cluster cores, the thermal plasma is unstable to the heat flux-driven buoyancy instability (HBI), a convective instability generated by anisotropic thermal conduction and a background conductive heat flux. Cosmic-ray driven convection and the HBI may contribute to redistributing metals produced by Type 1a supernovae in clusters. Our calculations demonstrate that adiabatic simulations of galaxy clusters can artificially suppress the mixing of thermal and relativistic plasma; anisotropic thermal conduction allows more efficient mixing, which may contribute to cosmic rays being distributed throughout the cluster volume.", "keyphrases": ["convection", "anisotropic thermal conduction", "cosmic-ray"]}
{"id": "1112.1400", "title": "Measuring our Peculiar Velocity by \"Pre-deboosting\" the CMB", "abstract": "It was recently shown that our peculiar velocity \u03b2with respect to the CMB induces mixing among multipoles and off-diagonal correlations at all scales which can be used as a measurement of \u03b2, which is independent of the standard measurement using the CMB temperature dipole. The proposed techniques rely however on a perturbative expansion which breaks down for \u2113\u22731/(\u03b2) \u2248800. Here we propose a technique which consists of deboosting the CMB temperature in the time-ordered data and show that it extends the validity of the perturbation analysis multipoles up to \u2113\u223c10000. We also obtain accurate fitting functions for the mixing between multipoles valid in a full non-linear treatment. Finally we forecast the achievable precision with which these correlations can be measured in a number of current and future CMB missions. We show that Planck could measure the velocity with a precision of around 60 km/s, ACTPol in 4 years around 40 km/s, while proposed future experiments could further shrink this error bar by over a factor of around 2.", "keyphrases": ["peculiar velocity", "cmb temperature", "fitting function"]}
{"id": "2105.11662", "title": "The Hipparcos-Gaia Catalog of Accelerations: Gaia EDR3 Edition", "abstract": "We present a cross-calibration of Hipparcos and Gaia EDR3 intended to identify astrometrically accelerating stars and to fit orbits to stars with faint, massive companions. The resulting catalog, the EDR3 edition of the Hipparcos-Gaia Catalog of Accelerations (HGCA), provides three proper motions with calibrated uncertainties on the EDR3 reference frame: the Hipparcos proper motion, the Gaia EDR3 proper motion, and the long-term proper motion given by the difference in position between Hipparcos and Gaia EDR3. Our approach is similar to that for the Gaia DR2 edition of the HGCA, but offers a factor of 3 improvement in precision thanks to the longer time baseline and improved data processing of Gaia EDR3. We again find that a 60/40 mixture of the two Hipparcos reductions outperforms either reduction individually, and we find strong evidence for locally variable frame rotations between all pairs of proper motion measurements. The substantial global frame rotation seen in DR2 proper motions has been removed in EDR3. We also correct for color- and magnitude-dependent frame rotations at a level of up to 50 \u03bcas/yr in Gaia EDR3. We calibrate the Gaia EDR3 uncertainties using a sample of radial velocity standard stars without binary companions; we find an error inflation factor (a ratio of total to formal uncertainty) of 1.37. This is substantially lower than the position dependent factor of 1.7 found for Gaia DR2 and reflects the improved data processing in EDR3. While the catalog should be used with caution, its proper motion residuals provide a powerful tool to measure the masses and orbits of faint, massive companions to nearby stars.", "keyphrases": ["hipparcos-gaia catalog", "accelerations", "companion"]}
{"id": "1505.02772", "title": "Directional detection of dark matter in universal bound states", "abstract": "It has been suggested that several small-scale structure anomalies in \u039bCDM cosmology can be solved by strong self-interaction between dark matter particles. It was shown by Braaten and Hammer that the presence of a near threshold S-wave resonance can make the scattering cross section at nonrelativistic speeds come close to saturating the unitarity bound. This can result in the formation of a stable bound state of two asymmetric dark matter particles (we call the bound state as darkonium). Laha and Braaten studied the nuclear recoil energy spectrum in dark matter direct detection experiments due to this incident bound state. Here we study the angular recoil spectrum, and show that it is uniquely determined up to normalization by the S-wave scattering length. Observing this angular recoil spectrum in a dark matter directional detection experiment will uniquely determine many of the low-energy properties of dark matter independent of the underlying dark matter microphysics.", "keyphrases": ["dark matter", "matter particle", "darkonium", "recoil energy spectrum", "directional detection"]}
{"id": "1203.1312", "title": "Fermi LAT Search for Internal Bremsstrahlung Signatures from Dark Matter Annihilation", "abstract": "A commonly encountered obstacle in indirect searches for galactic dark matter is how to disentangle possible signals from astrophysical backgrounds. Given that such signals are most likely subdominant, the search for pronounced spectral features plays a key role for indirect detection experiments; monochromatic gamma-ray lines or similar features related to internal bremsstrahlung, in particular, provide smoking gun signatures. We perform a dedicated search for the latter in the data taken by the Fermi gamma-ray space telescope during its first 43 months. To this end, we use a new adaptive procedure to select optimal target regions that takes into account both standard and contracted dark matter profiles. The behaviour of our statistical method is tested by a subsampling analysis of the full sky data and found to reproduce the theoretical expectations very well. The limits on the dark matter annihilation cross-section that we derive are stronger than what can be obtained from the observation of dwarf galaxies and, at least for the model considered here, collider searches. While these limits are still not quite strong enough to probe annihilation rates expected for thermally produced dark matter, future prospects to do so are very good. In fact, we already find a weak indication, with a significance of 3.1\u03c3(4.3\u03c3) when (not) taking into account the look-elsewhere effect, for an internal bremsstrahlung-like signal that would correspond to a dark matter mass of \u223c150 GeV; the same signal is also well fitted by a gamma-ray line at around 130 GeV. Although this would be a fascinating possibility, we caution that a much more dedicated analysis and additional data will be necessary to rule out or confirm this option.", "keyphrases": ["internal bremsstrahlung", "dark matter annihilation", "fermi data", "lepton"]}
{"id": "1312.5725", "title": "BBN And The CMB Constrain Light, Electromagnetically Coupled WIMPs", "abstract": "(Abridged) In the presence of a light WIMP (< 30 MeV), there are degeneracies among the nature of the WIMP, its couplings to standard model particles, its mass m_chi, and the number of equivalent neutrinos beyond the standard model, Delta N_nu. These degeneracies cannot be broken by the CMB constraint on the effective number of neutrinos, N_eff. However, big bang nucleosynthesis (BBN) is affected by a light WIMP and equivalent neutrinos, so the combination of BBN and CMB can break some of the degeneracies. Here, BBN predictions for abundances in the presence of a light WIMP and equivalent neutrinos are explored, and estimates of their observationally determined relic abundances are used to limit m_chi, Delta N_nu, and the present Universe baryon density (Omega_B h^2). These constraints are explored for Majorana and Dirac fermion WIMPs, as well as for real and complex scalar WIMPs that couple to electrons, positrons, and photons. In a separate paper this analysis is repeated for WIMPs that couple only to the standard model neutrinos, and constraints for the two cases are contrasted. Without a light WIMP but allowing for equivalent neutrinos, the combined BBN and CMB constraints favor N_eff = 3.46 +/- 0.17, Omega_B h^2 = 0.0224 +/- 0.0003, and Delta N_nu = 0.40 +/- 0.17. In this case, standard BBN (Delta N_nu = 0) is disfavored at 98 presence of one sterile neutrino (Delta N_nu = 1) is disfavored at > 99 confidence. Allowing a light WIMP and Delta N_nu equivalent neutrinos together, the combined BBN and CMB data provide lower limits to the WIMP masses (> 0.5 - 5 MeV) that depend on the nature of the WIMP, favor m_chi 8 MeV slightly over no WIMP, and loosen constraints on equivalent neutrinos, Delta N_nu = 0.65+0.46-0.35. While Delta N_nu = 0 is still disfavored at 95 with a light WIMP, Delta N_nu = 1 is now allowed.", "keyphrases": ["light wimp", "standard model", "neutrino", "photon", "bbn"]}
{"id": "1307.4166", "title": "Quark-Meson Coupling Model, Nuclear Matter Constraints and Neutron Star Properties", "abstract": "We explore the equation of state for nuclear matter in the quark-meson coupling model, including full Fock terms. The comparison with phenomenological constraints can be used to restrict the few additional parameters appearing in the Fock terms which are not present at Hartree level. Because the model is based upon the in-medium modification of the quark structure of the bound hadrons, it can be applied without additional parameters to include hyperons and to calculate the equation of state of dense matter in beta-equilibrium. This leads naturally to a study of the properties of neutron stars, including their maximum mass, their radii and density profiles.", "keyphrases": ["nuclear matter", "neutron star", "quark-meson coupling model"]}
{"id": "1206.1616", "title": "Strong Evidence for Gamma-ray Line Emission from the Inner Galaxy", "abstract": "Using 3.7 years of -LAT data, we examine the diffuse 80-200 GeV emission in the inner Galaxy and find a resolved gamma-ray feature at \u223c 110-140 GeV. We model the spatial distribution of this emission with a \u223c3 FWHM Gaussian, finding a best fit position 1.5 West of the Galactic Center. Even better fits are obtained for off-center Einasto and power-law profiles, which are preferred over the null (no line) hypothesis by 6.5\u03c3 (5.0\u03c3/5.4\u03c3 after trials factor correction for one/two line case) assuming an NFW density profile centered at (\u2113, b)=(-1.5,0) with a power index \u03b1=1.2 . The energy spectrum of this structure is consistent with a single spectral line (at energy 127.0\u00b1 2.0 GeV with \u03c7^2=4.48 for 4 d.o.f.). A pair of lines at 110.8\u00b1 4.4 GeV and 128.8\u00b1 2.7 GeV provides a marginally better fit (with \u03c7^2=1.25 for 2 d.o.f.). The total luminosity of the structure is (3.2\u00b10.6)\u00d7 10^35 erg/s, or (1.7\u00b10.4)\u00d7 10^36 photons/sec. The energies in the two-line case are compatible with a 127.3 \u00b1 2.7 GeV WIMP annihilating through \u03b3\u03b3 and \u03b3 Z (with \u03c7^2=1.67 for 3 d.o.f.). We describe a possible change to the scan strategy that would accumulate S/N on spectral lines in the Galactic center 4 times as fast as the current survey strategy.", "keyphrases": ["gamma-ray line", "line emission", "inner galaxy"]}
{"id": "1106.5795", "title": "Gravitational wave background from binary systems", "abstract": "Basic aspects of the background of gravitational waves and its mathematical characterization are reviewed. The spectral energy density parameter \u03a9(f), commonly used as a quantifier of the background, is derived for an ensemble of many identical sources emitting at different times and locations. For such an ensemble, \u03a9(f) is generalized to account for the duration of the signals and of the observation, so that one can distinguish the resolvable and unresolvable parts of the background. The unresolvable part, often called confusion noise or stochastic background, is made by signals that cannot be either individually identified or subtracted out of the data. To account for the resolvability of the background, the overlap function is introduced. This function is a generalization of the duty cycle, which has been commonly used in the literature, in some cases leading to incorrect results. The spectra produced by binary systems (stellar binaries and massive black hole binaries) are presented over the frequencies of all existing and planned detectors. A semi-analytical formula for \u03a9(f) is derived in the case of stellar binaries (containing white dwarfs, neutron stars or stellar-mass black holes). Besides a realistic expectation of the level of background, upper and lower limits are given, to account for the uncertainties in some astrophysical parameters such as binary coalescence rates. One interesting result concerns all current and planned ground-based detectors (including the Einstein Telescope). In their frequency range, the background of binaries is resolvable and only sporadically present. In other words, there is no stochastic background of binaries for ground-based detectors.", "keyphrases": ["binary system", "black hole", "white dwarf", "gravitational wave background"]}
{"id": "1307.6069", "title": "The small scale power asymmetry in the cosmic microwave background", "abstract": "We investigate the hemispherical power asymmetry in the cosmic microwave background on small angular scales. We find an anomalously high asymmetry in the multipole range l=601-2048, with a naive statistical significance of 6.5 sigma. However, we show that this extreme anomaly is simply a coincidence of three other effects, relativistic power modulation, edge effects from the mask applied, and inter-scale correlations. After correcting for all of these effects, the significance level drops to 1 sigma, i.e., there is no anomalous intrinsic asymmetry in the small angular scales. Using this null result, we derive a constraint on a potential dipolar modulation amplitude, A(k)<0.0045 on the 10 Mpc-scale, at 95 theoretical model attempting to explain the hemispherical asymmetry at large angular scales.", "keyphrases": ["power asymmetry", "cosmic microwave background", "angular scale"]}
{"id": "2006.03608", "title": "Constraints on Primordial Black Holes From Big Bang Nucleosynthesis Revisited", "abstract": "As space expands, the energy density in black holes increases relative to that of radiation, providing us with motivation to consider scenarios in which the early universe contained a significant abundance of such objects. In this study, we revisit the constraints on primordial black holes derived from measurements of the light element abundances. Black holes and their Hawking evaporation products can impact the era of Big Bang Nucleosynthesis (BBN) by altering the rate of expansion at the time of neutron-proton freeze-out, as well as by radiating mesons which can convert protons into neutrons and vice versa. Such black holes can thus enhance the primordial neutron-to-proton ratio, and increase the amount of helium that is ultimately produced. Additionally, the products of Hawking evaporation can break up helium nuclei, which both reduces the helium abundance and increases the abundance of primordial deuterium. Building upon previous work, we make use of modern deuterium and helium measurements to derive stringent constraints on black holes which evaporate in t_ evap\u223c 10^-1 s to \u223c 10^13 s (corresponding to M \u223c 6\u00d7 10^8 g to \u223c 2 \u00d7 10^13 g, assuming Standard Model particle content). We also consider how physics beyond the Standard Model could impact these constraints. Due to the gravitational nature of Hawking evaporation, the rate at which a black hole evaporates, and the types of particles that are produced through this process, depend on the complete particle spectrum. Within this context, we discuss scenarios which feature a large number of decoupled degrees-of-freedom ( large hidden sectors), as well as models of TeV-scale supersymmetry.", "keyphrases": ["black hole", "big bang nucleosynthesis", "early universe"]}
{"id": "1010.5495", "title": "Anisotropic Inflation from Charged Scalar Fields", "abstract": "We consider models of inflation with U(1) gauge fields and charged scalar fields including symmetry breaking potential, chaotic inflation and hybrid inflation. We show that there exist attractor solutions where the anisotropies produced during inflation becomes comparable to the slow-roll parameters. In the models where the inflaton field is a charged scalar field the gauge field becomes highly oscillatory at the end of inflation ending inflation quickly. Furthermore, in charged hybrid inflation the onset of waterfall phase transition at the end of inflation is affected significantly by the evolution of the background gauge field. Rapid oscillations of the gauge field and its coupling to inflaton can have interesting effects on preheating and non-Gaussianities.", "keyphrases": ["gauge field", "inflaton field", "anisotropic inflation"]}
{"id": "1101.6046", "title": "Inflection point inflation: WMAP constraints and a solution to the fine-tuning problem", "abstract": "We consider observational constraints and fine-tuning issues in a renormalizable model of inflection point inflation, with two independent parameters. We derive constraints on the parameter space of this model arising from the WMAP 7-year power spectrum. It has previously been shown that it is possible to successfully embed this potential in the MSSM. Unfortunately, to do this requires severe fine-tuning. We address this issue by introducing a hybrid field to dynamically uplift the potential with a subsequent smooth phase transition to end inflation at the necessary point. Large parameter regions exist where this drastically reduces the fine-tuning required without ruining the viability of the model. A side effect of this mechanism is that it increases the width of the slow-roll region of the potential, thus also alleviating the problem of the fine-tuning of initial conditions. The MSSM embedding we study has been previously shown to be able to explain the smallness of the neutrino masses. The hybrid transition does not spoil this feature as there exist parameter regions where the fine-tuning parameter is as large as 10^-1 and the neutrino masses remain small.", "keyphrases": ["mssm", "smallness", "inflection point inflation"]}
{"id": "1309.2954", "title": "Characterizing unknown systematics in large scale structure surveys", "abstract": "Photometric large scale structure (LSS) surveys probe the largest volumes in the Universe, but are inevitably limited by systematic uncertainties. Imperfect photometric calibration leads to biases in our measurements of the density fields of LSS tracers such as galaxies and quasars, and as a result in cosmological parameter estimation. Earlier studies have proposed using cross-correlations between different redshift slices or cross-correlations between different surveys to reduce the effects of such systematics. In this paper we develop a method to characterize unknown systematics. We demonstrate that while we do not have sufficient information to correct for unknown systematics in the data, we can obtain an estimate of their magnitude. We define a parameter to estimate contamination from unknown systematics using cross-correlations between different redshift slices and propose discarding bins in the angular power spectrum that lie outside a certain contamination tolerance level. We show that this method improves estimates of the bias using simulated data and further apply it to photometric luminous red galaxies in the Sloan Digital Sky Survey as a case study.", "keyphrases": ["unknown systematic", "cross-correlation", "angular power spectrum"]}
{"id": "1305.4509", "title": "Clustering of quintessence on horizon scales and its imprint on HI intensity mapping", "abstract": "Quintessence can cluster only on horizon scales. What is the effect on the observed matter distribution? To answer this, we need a relativistic approach that goes beyond the standard Newtonian calculation and deals properly with large scales. Such an approach has recently been developed for the case when dark energy is vacuum energy, which does not cluster at all. We extend this relativistic analysis to deal with dynamical dark energy. Using three quintessence potentials as examples, we compute the angular power spectrum for the case of an HI intensity map survey. Compared to the concordance model with the same small-scale power at z=0, quintessence boosts the angular power by up to 15 redshifts. The difference is mainly due to the background evolution, driven mostly by the normalization of the power spectrum today. The dark energy perturbations make only a small contribution on the largest scales, and a negligible contribution on smaller scales. Ironically, the dark energy perturbations remove the false boost of large-scale power that arises if we impose the (unphysical) assumption that the dark energy is smooth.", "keyphrases": ["quintessence", "horizon scale", "large scale", "dark energy", "gravity"]}
{"id": "0902.1084", "title": "Scale-dependent bias from primordial non-Gaussianity in general relativity", "abstract": "In this note we examine the derivation of scale-dependent bias due to primordial non-Gaussianity of the local type in the context of general relativity. We justify the use of the Poisson equation in general relativistic perturbation theory and thus the derivation of scale-dependent bias as a test of primordial non-Gaussianity, using the spherical collapse model. The corollary is that the form of scale-dependent bias does not receive general relativistic corrections on scales larger than the Hubble radius. This leads to a formally divergent correlation function for biased tracers of the mass distribution which we discuss.", "keyphrases": ["bias", "primordial non-gaussianity", "general relativity", "spherical collapse model"]}
{"id": "0811.4406", "title": "Electrodynamics at non-zero temperature, chemical potential, and Bose condensate", "abstract": "Electrodynamics of charged scalar bosons and spin 1/2 fermions is studied at non-zero temperature, chemical potentials, and possible Bose condensate of the charged scalars. Debye screening length, plasma frequency, and the photon dispersion relation are calculated. It is found that in presence of the condensate the time-time component of the photon polarization operator in the first order in electric charge squared acquires infrared singular parts proportional to inverse powers of the spatial photon momentum k.", "keyphrases": ["non-zero temperature", "bose condensate", "fermion", "electrodynamic"]}
{"id": "0808.0186", "title": "Circumstantial evidence for a soft nuclear symmetry energy at supra-saturation densities", "abstract": "Within an isospin- and momentum-dependent hadronic transport model it is shown that the recent FOPI data on the \u03c0^-/\u03c0^+ ratio in central heavy-ion collisions at SIS/GSI energies (Willy Reisdorf et al., NPA 781, 459 (2007)) provide circumstantial evidence suggesting a rather soft nuclear symmetry energy at \u03c1\u2265 2\u03c1_0 compared to the Akmal-Pandharipande-Ravenhall prediction. Some astrophysical implications and the need for further experimental confirmations are discussed.", "keyphrases": ["nuclear symmetry energy", "supra-saturation density", "neutron-rich nucleonic matter"]}
{"id": "1906.05748", "title": "Atmospheric Dynamics on Terrestrial Planets: The Seasonal Response to changes in Orbital, Rotational and Radiative Timescales", "abstract": "Thousands of exoplanets have been detected to date, and with future planned missions this tally will increase. Understanding the climate dependence on the planetary parameters is vital for the study of terrestrial exoplanet habitability. Using an idealized general circulation model with a seasonal cycle, we study the seasonal response of the surface temperature and Hadley circulation to changes in the orbital, rotational and radiative timescales. Analyzing the climate's seasonal response to variations in these timescales, we find a regime transition between planets controlled by the annual mean insolation to planets controlled by the seasonal variability depending on the relation between the length of the orbital period, obliquity and radiative timescale. Consequently, planets with obliquity greater than 54^\u2218 and short orbital period will have a minimum surface temperature at the equator. We also show that in specific configurations, mainly high atmospheric mass and short orbital periods, high obliquity planets can still have an equable climate. Based on the model results, we suggest an empirical power law for the ascending and descending branches of the Hadley circulation and its strength. These power laws show that the Hadley circulation becomes wider and stronger by increasing the obliquity and orbital period or by decreasing the atmospheric mass and rotation rate. Consistent with previous studies, we show that the rotation rate plays an essential role in dictating the width of the Hadley circulation.", "keyphrases": ["planet", "seasonal response", "general circulation model"]}
{"id": "1211.5619", "title": "Correlating features in the primordial spectra", "abstract": "Heavy fields coupled to the inflaton reduce the speed of sound in the effective theory of the adiabatic mode each time the background inflationary trajectory deviates from a geodesic. This can result in features in the primordial spectra. We compute the corresponding bispectrum and show that if a varying speed of sound induces features in the power spectrum, the change in the bispectrum is given by a simple formula involving the change in the power spectrum and its derivatives. In this manner, we provide a uniquely discriminable signature of a varying sound speed for the adiabatic mode during inflation that indicates the influence of heavy fields. We find that features in the bispectrum peak in the equilateral limit and, in particular, in the squeezed limit we find considerable enhancement entirely consistent with the single field consistency relation. From the perspective of the underlying effective theory, our results generalize to a wide variety of inflationary models where features are sourced by the time variation of background quantities. A positive detection of such correlated features would be unambiguous proof of the inflaton's nature as a single light scalar degree of freedom embedded in a theory that is UV completable.", "keyphrases": ["primordial spectra", "heavy field", "adiabatic mode", "power spectrum", "curvature perturbation"]}
{"id": "1512.05807", "title": "Time-Sliced Perturbation Theory for Large Scale Structure I: General Formalism", "abstract": "We present a new analytic approach to describe large scale structure formation in the mildly non-linear regime. The central object of the method is the time-dependent probability distribution function generating correlators of the cosmological observables at a given moment of time. Expanding the distribution function around the Gaussian weight we formulate a perturbative technique to calculate non-linear corrections to cosmological correlators, similar to the diagrammatic expansion in a three-dimensional Euclidean quantum field theory, with time playing the role of an external parameter. For the physically relevant case of cold dark matter in an Einstein\u2013de Sitter universe, the time evolution of the distribution function can be found exactly and is encapsulated by a time-dependent coupling constant controlling the perturbative expansion. We show that all building blocks of the expansion are free from spurious infrared enhanced contributions that plague the standard cosmological perturbation theory. This paves the way towards the systematic resummation of infrared effects in large scale structure formation. We also argue that the approach proposed here provides a natural framework to account for the influence of short-scale dynamics on larger scales along the lines of effective field theory.", "keyphrases": ["field theory", "resummation", "time-sliced perturbation theory", "non-linear evolution"]}
{"id": "1301.5699", "title": "A Single Field Inflation Model with Large Local Non-Gaussianity", "abstract": "A detection of large local form non-Gaussianity is considered to be able to rule out all single field inflation models. This statement is based on a single field consistency condition. Despite the awareness of some implicit assumptions in the derivation of this condition and the demonstration of corresponding examples that illustrate these caveats, to date there is still no explicit and self-consistent model which can serve as a counterexample to this statement. We present such a model in this Letter.", "keyphrases": ["local non-gaussianity", "non-attractor inflation", "non-canonical kinetic term"]}
{"id": "1804.11279", "title": "Primordial fluctuations and non-Gaussianities in sidetracked inflation", "abstract": "Heavy scalar fields can undergo an instability during inflation as a result of their kinetic couplings with the inflaton. This is known as the geometrical destabilization of inflation, as it relies on the effect of the negative curvature of the field-space manifold overcoming the stabilizing force of the potential. This instability can drive the system away from its original path in field space into a new inflationary attractor, a scenario that we dub sidetracked inflation. We study this second phase and its observable consequences in several classes of two-field models. We show that cosmological fluctuations exhibit varied behaviours depending on the potential and the field space geometry, and that they can be captured by single-field effective theories with either a modified dispersion relation, a reduced speed of sound, or an imaginary one \u2014 the latter case describing a transient tachyonic growth of the fluctuations. We also numerically calculate the bispectrum with the transport approach, finding large non-Gaussianities of equilateral and orthogonal shapes. In the hyperbolic geometry the potentials of our models present a pole at the boundary of the Poincar\u00e9 disk and we discuss their relationships with \u03b1-attractors.", "keyphrases": ["fluctuation", "non-gaussianitie", "inflation model"]}
{"id": "1507.03875", "title": "The anamorphic universe", "abstract": "We introduce \"anamorphic\" cosmology, an approach for explaining the smoothness and flatness of the universe on large scales and the generation of a nearly scale-invariant spectrum of adiabatic density perturbations. The defining feature is a smoothing phase that acts like a contracting universe based on some Weyl frame-invariant criteria and an expanding universe based on other frame-invariant criteria. An advantage of the contracting aspects is that it is possible to avoid the multiverse and measure problems that arise in inflationary models. Unlike ekpyrotic models, anamorphic models can be constructed using only a single field and can generate a nearly scale-invariant spectrum of tensor perturbations. Anamorphic models also differ from pre-big bang and matter bounce models that do not explain the smoothness. We present some examples of cosmological models that incorporate an anamorphic smoothing phase.", "keyphrases": ["universe", "advantage", "ijjas", "early universe cosmology"]}
{"id": "1804.09140", "title": "Structure formation beyond shell-crossing: nonperturbative expansions and late-time attractors", "abstract": "Structure formation in 1+1 dimensions is considered, with emphasis on the effects of shell-crossing. The breakdown of the perturbative expansion beyond shell-crossing is discussed, and it is shown, in a simple example, that the perturbative series can be extended to a transseries including nonperturbative terms. The latter converges to the exact result well beyond the range of validity of perturbation theory. The crucial role of the divergences induced by shell-crossing is discussed. They provide constraints on the structure of the transseries and act as a bridge between the perturbative and the nonperturbative sectors. Then, we show that the dynamics in the deep multistreaming regime is governed by attractors. In the case of simple initial conditions, these attractors coincide with the asymptotic configurations of the adhesion model, but in general they may differ. These results are applied to a cosmological setting, and an algorithm to build the attractor solution starting from the Zel'dovich approximation is developed. Finally, this algorithm is applied to the search of `haloes' and the results are compared with those obtained from the exact dynamical equations.", "keyphrases": ["shell-crossing", "attractor", "nonperturbative term", "structure formation"]}
{"id": "1706.01835", "title": "Geometrical destabilization, premature end of inflation and Bayesian model selection", "abstract": "By means of Bayesian techniques, we study how a premature ending of inflation, motivated by geometrical destabilization, affects the observational evidences of typical inflationary models. Large field models are worsened, and inflection point potentials are drastically improved for a specific range of the field-space curvature characterizing the geometrical destabilization. For other models we observe shifts in the preferred values of the model parameters. For quartic hilltop models for instance, contrary to the standard case, we find preference for theoretically natural sub-Planckian hill widths. Eventually, the Bayesian ranking of models becomes substantially reordered with a premature end of inflation. Such a phenomenon also modifies the constraints on the reheating expansion history, which has to be properly accounted for since it determines the position of the observational window with respect to the end of inflation. Our results demonstrate how the interpretation of cosmological data in terms of fundamental physics is considerably modified in the presence of premature end of inflation mechanisms.", "keyphrases": ["destabilization", "premature end", "bayesian technique", "inflationary model", "field space"]}
{"id": "1312.2434", "title": "The relativistic Feynman-Metropolis-Teller treatment at finite temperatures", "abstract": "The Feynman-Metropolis-Teller treatment of compressed atoms has been recently generalized to relativistic regimes and applied to the description of static and rotating white dwarfs in general relativity. We present here the extension of this treatment to the case of finite temperatures and construct the corresponding equation of state (EOS) of the system; applicable in a wide regime of densities that includes both white dwarfs and neutron star outer crusts. We construct the mass-radius relation of white dwarfs at finite temperatures obeying this new EOS and apply it to the analysis of ultra low-mass white dwarfs with M\u2272 0.2 M_\u2299. In particular, we analyze the case of the white dwarf companion of PSR J1738+0333. The formulation is then extrapolated to compressed nuclear matter cores of stellar dimensions, systems with mass numbers A\u2248 (m_ Planck/m_n)^3 or mass M_ core\u2248 M_\u2299, where m_ Planck and m_n are the Planck and the nucleon mass. For T \u226a m_e c^2/k_B \u2248 5.9\u00d7 10^9 K, a family of equilibrium configurations can be obtained with analytic solutions of the ultra-relativistic Thomas-Fermi equation at finite temperatures. Such configurations fulfill global but not local charge neutrality and have strong electric fields on the core surface. We find that the maximum electric field at the core surface is enhanced at finite temperatures with respect to the degenerate case.", "keyphrases": ["finite temperature", "white dwarf", "mass-radius relation"]}
{"id": "1104.3894", "title": "Cosmological 3-point correlators from holography", "abstract": "We investigate the non-Gaussianity of primordial cosmological perturbations using holographic methods. In particular, we derive holographic formulae that relate all cosmological 3-point correlation functions, including both scalar and tensor perturbations, to stress-energy correlation functions of a holographically dual three-dimensional quantum field theory. These results apply to general single scalar inflationary universes that at late times approach either de Sitter spacetime or accelerating power-law cosmologies. We further show that in Einstein gravity all 3-point functions involving tensors can be obtained from correlators containing only positive helicity gravitons, with the ratios of these to the correlators involving one negative helicity graviton being given by universal functions of momenta, irrespectively of the potential of the scalar field. As a by-product of this investigation, we obtain holographic formulae for the full 3-point function of the stress-energy tensor along general holographic RG flows. These results should have applications in a wider holographic context.", "keyphrases": ["correlator", "holographic formulae", "inflationary universe", "universe", "dual qft"]}
{"id": "1306.4511", "title": "Generation of the Higgs Condensate and Its Decay after Inflation", "abstract": "We investigate the dynamics of the Standard Model higgs with a minimal coupling to gravity during and after inflation. In the regime where the Standard Model vacuum is stable, we find that the higgs becomes a light spectator field after about 30 efolds of inflation, irrespectively of its initial value. Once the higgs has become light, its root-mean-square value h_* relaxes to equilibrium in about 85 efolds for the inflationary scale of H_*=10^4 GeV and in 20 efolds for H_*=10^10 GeV. The equilibrium value is given by h_* 0.36 lambda^-1/4H_*, where lambda=0.09 ... 0.0005 is the higgs self coupling at the scales H_*=10^4 ... 10^10 GeV. We show that the main decay channel of the higgs condensate after inflation is the resonant production of Standard Model gauge bosons. For a set of parameters we find that a significant part of the condensate has decayed in between 340 and 630 Hubble times after the onset of higgs oscillations, depending on H_* in a non-trivial way. The higgs perturbations correspond to isocurvature modes during inflation but they could generate significant adiabatic perturbations at a later stage for example through a modulation of the reheating stage. However, this requires that the inflaton(s) decay no later than a few hundred Hubble times after the onset of higgs oscillations.", "keyphrases": ["higgs condensate", "gauge boson", "non-perturbative production", "new physics"]}
{"id": "2009.08970", "title": "CARPool: fast, accurate computation of large-scale structure statistics by pairing costly and cheap cosmological simulations", "abstract": "To exploit the power of next-generation large-scale structure surveys, ensembles of numerical simulations are necessary to give accurate theoretical predictions of the statistics of observables. High-fidelity simulations come at a towering computational cost. Therefore, approximate but fast simulations, surrogates, are widely used to gain speed at the price of introducing model error. We propose a general method that exploits the correlation between simulations and surrogates to compute fast, reduced-variance statistics of large-scale structure observables without model error at the cost of only a few simulations. We call this approach Convergence Acceleration by Regression and Pooling (CARPool). In numerical experiments with intentionally minimal tuning, we apply CARPool to a handful of GADGET-III N-body simulations paired with surrogates computed using COmoving Lagrangian Acceleration (COLA). We find \u223c 100-fold variance reduction even in the non-linear regime, up to k_max\u2248 1.2 h Mpc^-1 for the matter power spectrum. CARPool realises similar improvements for the matter bispectrum. In the nearly linear regime CARPool attains far larger sample variance reductions. By comparing to the 15,000 simulations from the Quijote suite, we verify that the CARPool estimates are unbiased, as guaranteed by construction, even though the surrogate misses the simulation truth by up to 60% at high k. Furthermore, even with a fully configuration-space statistic like the non-linear matter density probability density function, CARPool achieves unbiased variance reduction factors of up to \u223c 10, without any further tuning. Conversely, CARPool can be used to remove model error from ensembles of fast surrogates by combining them with a few high-accuracy simulations.", "keyphrases": ["simulation", "theoretical prediction", "carpool"]}
{"id": "1907.10625", "title": "Tensions between the Early and the Late Universe", "abstract": "The standard cosmological model successfully describes many observations from widely different epochs of the Universe, from primordial nucleosynthesis to the accelerating expansion of the present day. However, as the basic cosmological parameters of the model are being determined with increasing and unprecedented precision, it is not guaranteed that the same model will fit more precise observations from widely different cosmic epochs. Discrepancies developing between observations at early and late cosmological time may require an expansion of the standard model, and may lead to the discovery of new physics. The workshop \"Tensions between the Early and the Late Universe\" was held at the Kavli Institute for Theoretical Physics on July 15-17 2019 (More details of the workshop (including on-line presentations) are given at the website: https://www.kitp.ucsb.edu/activities/enervac-c19) to evaluate increasing evidence for these discrepancies, primarily in the value of the Hubble constant as well as ideas recently proposed to explain this tension. Multiple new observational results for the Hubble constant were presented in the time frame of the workshop using different probes: Cepheids, strong lensing time delays, tip of the red giant branch (TRGB), megamasers, Oxygen-rich Miras and surface brightness fluctuations (SBF) resulting in a set of six new ones in the last several months. Here we present the summary plot of the meeting that shows combining any three independent approaches to measure H_0 in the late universe yields tension with the early Universe values between 4.0\u03c3 and 5.8\u03c3. This shows that the discrepancy does not appear to be dependent on the use of any one method, team, or source. Theoretical ideas to explain the discrepancy focused on new physics in the decade of expansion preceding recombination as the most plausible. This is a brief summary of the workshop.", "keyphrases": ["late universe", "hubble constant", "crisis", "corresponding difference"]}
{"id": "1606.08879", "title": "BlackHoleCam: fundamental physics of the Galactic center", "abstract": "Einstein's General Theory of Relativity (GR) successfully describes gravity. The most fundamental predictions of GR are black holes (BHs), but in spite of many convincing BH candidates in the Universe, there is no conclusive experimental proof of their existence using astronomical observations in the electromagnetic spectrum. Are BHs real astrophysical objects? Does GR hold in its most extreme limit or are alternatives needed? The prime target to address these fundamental questions is in the center of our own Galaxy, which hosts the closest and best-constrained supermassive BH candidate in the Universe, Sagittarius A* (Sgr A*). Three different types of experiments hold the promise to test GR in a strong-field regime using observations of Sgr A* with new-generation instruments. The first experiment aims to image the relativistic plasma emission which surrounds the event horizon and forms a \"shadow\" cast against the background, whose predicted size ( 50 microarcseconds) can now be resolved by upcoming VLBI experiments at mm-waves such as the Event Horizon Telescope (EHT). The second experiment aims to monitor stars orbiting Sgr A* with the upcoming near-infrared interferometer GRAVITY at the Very Large Telescope (VLT). The third experiment aims to time a radio pulsar in tight orbit about Sgr A* using radio telescopes (including the Atacama Large Millimeter Array or ALMA). The BlackHoleCam project exploits the synergy between these three different techniques and aims to measure the main BH parameters with sufficient precision to provide fundamental tests of GR and probe the spacetime around a BH in any metric theory of gravity. Here, we review our current knowledge of the physical properties of Sgr A* as well as the current status of such experimental efforts towards imaging the event horizon, measuring stellar orbits, and timing pulsars around Sgr A*.", "keyphrases": ["gravity", "black hole", "event horizon telescope"]}
{"id": "1206.3496", "title": "Growth Histories in Bimetric Massive Gravity", "abstract": "We perform cosmological perturbation theory in Hassan-Rosen bimetric gravity for general homogeneous and isotropic backgrounds. In the de Sitter approximation, we obtain decoupled sets of massless and massive scalar gravitational fluctuations. Matter perturbations then evolve like in Einstein gravity. We perturb the future de Sitter regime by the ratio of matter to dark energy, producing quasi-de Sitter space. In this more general setting the massive and massless fluctuations mix. We argue that in the quasi-de Sitter regime, the growth of structure in bimetric gravity differs from that of Einstein gravity.", "keyphrases": ["gravity", "perturbation theory", "cosmological solution", "phenomenological advantage"]}
{"id": "1009.4505", "title": "Notes on the Missing Satellites Problem", "abstract": "The Missing Satellites Problem (MSP) broadly refers to the overabundance of predicted Cold Dark Matter (CDM) subhalos compared to satellite galaxies known to exist in the Local Group. The most popular interpretation of the MSP is that the smallest dark matter halos in the universe are extremely inefficient at forming stars. The question from that standpoint is to identify the feedback source that makes small halos dark and to identify any obvious mass scale where the truncation in the efficiency of galaxy formation occurs. Among the most exciting developments in near-field cosmology in recent years is the discovery of a new population satellite galaxies orbiting the Milky Way and M31. Wide field, resolved star surveys have more than doubled the dwarf satellite count in less than a decade, revealing a population of ultrafaint galaxies that are less luminous that some star clusters. For the first time, there are empirical reasons to believe that there really are missing satellite galaxies in the Local Group, lurking just beyond our ability to detect them, or simply inhabiting a region of the sky that has yet to have been surveyed. Both kinematic studies and completeness-correction studies seem to point to a characteristic potential well depth for satellite subhalos that is quite close to the mass scale where photoionization and atomic cooling should limit galaxy formation. Among the more pressing problems associated with this interpretation is to understand the selection biases that limit our ability to detect the lowest mass galaxies. The least massive satellite halos are likely to host stealth galaxies with very-low surface brightness and this may be an important limitation in the hunt for low-mass fossils from the epoch of reionization.", "keyphrases": ["missing satellites problem", "satellite galaxy", "milky way"]}
{"id": "2009.05517", "title": "Galaxy imaging surveys as spin-sensitive detector for cosmological colliders", "abstract": "Galaxy imaging surveys provide us with information on both the galaxy distribution and their shapes. In this paper, we systematically investigate the sensitivity of galaxy shapes to new physics in the initial conditions. For this purpose, we decompose the galaxy shape function into spin components, and compute the contributions to each spin component from both intrinsic alignment and weak lensing. We then consider the angular-dependent primordial non-Gaussianity, which is generated by a non-zero integer spin particle when active during inflation, and show that a galaxy imaging survey essentially functions as a spin-sensitive detector of such particles in the early universe. We also perform a forecast of the PNG generated from a higher spin particle, considering a Rubin Observatory LSST-like galaxy survey.", "keyphrases": ["spin-sensitive detector", "collider", "galaxy imaging survey"]}
{"id": "1912.05659", "title": "The electromagnetic counterparts of compact binary mergers", "abstract": "Mergers of binaries consisting of two neutron stars, or a black hole and a neutron star, offer a unique opportunity to study a range of physical and astrophysical processes using two different and almost orthogonal probes - gravitational waves (GW) and electromagnetic (EM) emission. The GW signal probes the binary and the physical processes that take place during the last stages of the merger, while the EM emission provides clues to the material that is thrown out following the merger. The accurate localization, which only the EM emission can provide, also indicates the astrophysical setting in which the merger took place. In addition, the combination of the two signals provides constraints on the nature of gravity and on the expansion rate of the Universe. The first detection of a binary neutron star merger by the LIGO-Virgo collaboration, GW170817, initiated the era of multi-messenger GW-EM astrophysics and demonstrated the great promise it holds. The event produced an unprecedented data set, and although it was only a single event, it provided remarkable results that revolutionized our knowledge of neutron star mergers. GW170817 is especially exciting since we know that it is not one of a kind and that many more events will be detected during the next decade. In this review, I summarize, first, the theory of EM emission from compact binary mergers, highlighting the unique information that the combined GW-EM detection provides. I then describe the entire set of GW and EM observations of GW170817, and summarize the range of insights that it offers. This includes clues about the role that similar events play in the r-process elements budget of the Universe, the neutron star equation of state, the properties of the relativistic outflow that followed the merger, and the connection between neutron star binary mergers and short gamma-ray bursts.", "keyphrases": ["compact binary merger", "neutron star", "gravitational wave"]}
{"id": "1012.3208", "title": "What a Two Solar Mass Neutron Star Really Means", "abstract": "The determination of neutron star masses is reviewed in light of a new measurement of 1.97 M_\u2299 for PSR J1614-2230 and an estimate of 2.4 M_\u2299 for the black widow pulsar. Using a simple analytic model related to the so-called maximally compact equation of state, model-independent upper limits to thermodynamic properties in neutron stars, such as energy density, pressure, baryon number density and chemical potential, are established which depend upon the neutron star maximum mass. Using the largest well-measured neutron star mass, 1.97 M_\u2299, it is possible to show that the energy density can never exceed about 2 GeV, the pressure about 1.3 GeV, and the baryon chemical potential about 2.1 GeV. Further, if quark matter comprises a significant component of neutron star cores, these limits are reduced to 1.3 GeV, 0.9 GeV, and 1.5 GeV, respectively. We also find that the maximum binding energy of any neutron star is about 25 properties and astrophysical constraints additionally imply an upper limit to the neutron star maximum mass of about 2.4 M_\u2299. A measured mass of 2.4 M\u2299 would be incompatible with hybrid star models containing significant proportions of exotica in the form of hyperons, Bose condensates or quark matter.", "keyphrases": ["neutron star", "quark matter", "mass limit"]}
{"id": "1103.6135", "title": "Pearson's random walk in the space of the CMB phases: evidence for parity asymmetry", "abstract": "The temperature fluctuations of the Cosmic Microwave Background (CMB) are supposed to be distributed randomly in both magnitude and phase, following to the simplest model of inflation. In this paper, we look at the odd and even multipoles of the spherical harmonic decomposition of the CMB, and the different characteristics of these, giving rise to a parity asymmetry. We compare the even and odd multipoles in the CMB power spectrum, and also the even and odd mean angles. We find for the multipoles of the power spectrum, that there is power excess in odd multipoles, compared to even ones, meaning that we have a parity asymmetry. Further, for the phases, we present a random walk for the mean angles, and find a significant separation for even/odd mean angles, especially so for galactic coordinates. This is further tested and confirmed with a directional parity test, comparing the parity asymmetry in galactic and ecliptic coordinates.", "keyphrases": ["random walk", "parity asymmetry", "odd multipole", "cmb power spectrum"]}
{"id": "1707.03021", "title": "The observational evidence for horizons: from echoes to precision gravitational-wave physics", "abstract": "The existence of black holes and of spacetime singularities is a fundamental issue in science. Despite this, observations supporting their existence are scarce, and their interpretation unclear. We overview how strong a case for black holes has been made in the last few decades, and how well observations adjust to this paradigm. Unsurprisingly, we conclude that observational evidence for black holes is impossible to come by. However, just like Popper's black swan, alternatives can be ruled out or confirmed to exist with a single observation. These observations are within reach. In the next few years and decades, we will enter the era of precision gravitational-wave physics with more sensitive detectors. Just as accelerators require larger and larger energies to probe smaller and smaller scales, more sensitive gravitational-wave detectors will be probing regions closer and closer to the horizon, potentially reaching Planck scales and beyond. What may be there, lurking?", "keyphrases": ["horizon", "echo", "black hole", "compact horizonless object"]}
{"id": "1812.01531", "title": "Two-integral distribution functions in axisymmetric galaxies: implications for dark matter searches", "abstract": "We address the problem of reconstructing the phase-space distribution function for an extended collisionless system, with known density profile and in equilibrium within an axisymmetric gravitational potential. Assuming that it depends on only two integrals of motion, namely the energy and the component of the angular momentum along the axis of symmetry L_z, there is a one-to-one correspondence between the density profile and the component of the distribution function that is even in L_z, as well as between the weighted azimuthal velocity profile and the odd component. This inversion procedure was originally proposed by Lynden-Bell and later refined in its numerical implementation by Hunter Qian; after overcoming a technical difficulty, we apply it here for the first time in presence of a strongly flattened component, as a novel approach of extracting the phase-space distribution function for dark matter particles in the halo of spiral galaxies. We compare results obtained for realistic axisymmetric models to those in the spherical symmetric limit as assumed in previous analyses, showing the rather severe shortcomings in the latter. We then apply the scheme to the Milky Way and discuss the implications for the direct dark matter searches. In particular, we reinterpret the null results of the Xenon1T experiment for spin-(in)dependent interactions and make predictions for the annual modulation of the signal for a set of axisymmetric models, including a self-consistently defined co-rotating halo.", "keyphrases": ["distribution function", "galaxy", "dark matter search", "phase-space distribution function"]}
{"id": "1909.10887", "title": "Waveform of gravitational waves in the general parity-violating gravities", "abstract": "As an extension of our previous work [J.Qiao, T.Zhu, W.Zhao A.Wang, arXiv:1909.03815], in this article, we calculate the effects of parity violation on gravitational-wave (GW) waveforms during their propagation in the most general parity-violating gravities, including Chern-Simons modified gravity, ghost-free scalar-tensor gravity, symmetric teleparallel equivalence of GR theory, Ho\u0159ava-Lifshitz gravity and so on. For this purpose, we consider the GWs generated by the coalescence of compact binaries and concentrate on the imprints of the parity violation in the propagation of GWs. With a unified description of GW in the theories of parity-violating gravity, we study the effects of velocity and amplitude birefringence on the GW waveforms. Decomposing the GWs into the circular polarization modes, the two birefringence effects exactly correspond to the modifications in phase and amplitude of GW waveforms respectively. We find that, for each circular polarization mode, the amplitude, phase and velocity of GW can be modified by both the parity-violating terms and parity-conserving terms in gravity. Therefore, in order to test the parity symmetry in gravity, we should compare the difference between two circular polarization modes, rather than measuring an individual mode. Combining two circular modes, we obtain the GW waveforms in the Fourier domain, and obtain the deviations from those in General Relativity. The GW waveforms derived in this paper are also applicable to the theories of parity-conserving gravity, which have the modified dispersion relations (e.g. massive gravity, double special relativity theory, extra-dimensional theories, etc), or/and have the modified friction terms (e.g. nonlocal gravity, gravitational theory with time-dependent Planck mass, etc).", "keyphrases": ["gravity", "parity violation", "ghost mode"]}
{"id": "1306.2314", "title": "Warm Dark Matter as a solution to the small scale crisis: new constraints from high redshift Lyman-alpha forest data", "abstract": "We present updated constraints on the free-streaming of warm dark matter (WDM) particles derived from an analysis of the Lya flux power spectrum measured from high-resolution spectra of 25 z > 4 quasars obtained with the Keck High Resolution Echelle Spectrometer (HIRES) and the Magellan Inamori Kyocera Echelle (MIKE) spectrograph. We utilize a new suite of high-resolution hydrodynamical simulations that explore WDM masses of 1, 2 and 4 keV (assuming the WDM consists of thermal relics), along with different physically motivated thermal histories. We carefully address different sources of systematic error that may affect our final results and perform an analysis of the Lya flux power with conservative error estimates. By using a method that samples the multi-dimensional astrophysical and cosmological parameter space, we obtain a lower limit mwdm > 3.3 keV (2sigma) for warm dark matter particles in the form of early decoupled thermal relics. Adding the Sloan Digital Sky Survey (SDSS) Lya flux power spectrum does not improve this limit. Thermal relics of masses 1 keV, 2 keV and 2.5 keV are disfavoured by the data at about the 9sigma, 4sigma and 3sigma C.L., respectively. Our analysis disfavours WDM models where there is a suppression in the linear matter power spectrum at (non-linear) scales corresponding to k=10h/Mpc which deviates more than 10 Given this limit, the corresponding \"free-streaming mass\" below which the mass function may be suppressed is 2x10^8 Msun/h. There is thus very little room for a contribution of the free-streaming of WDM to the solution of what has been termed the small scale crisis of cold dark matter.", "keyphrases": ["thermal relic", "warm dark matter", "sterile neutrino"]}
{"id": "1710.03116", "title": "Coincident General Relativity", "abstract": "The metric-affine variational principle is applied to generate teleparallel and symmetric teleparallel theories of gravity. From the latter is discovered an exceptional class which is consistent with a vanishing affine connection. Based on this remarkable property, this work proposes a simpler geometrical formulation of General Relativity that is oblivious to the affine spacetime structure, thus fundamentally depriving gravity of any inertial character. The resulting theory is described by the Hilbert action purged from the boundary term and is more robustly underpinned by the spin-2 field theory, where an extra symmetry is now manifest, possibly related to the double copy structure of the gravity amplitudes. This construction also provides a novel starting point for modified gravity theories, and the paper presents new and simple generalisations where analytical self-accelerating cosmological solutions arise naturally in the early and late time universe.", "keyphrases": ["exceptional class", "coincident general relativity", "non-metricity", "curvature", "stegr"]}
{"id": "1611.05055", "title": "The maximum sizes of large scale structures in alternative theories of gravity", "abstract": "The maximum size of a cosmic structure is given by the maximum turnaround radius \u2013 the scale where the attraction due to its mass is balanced by the repulsion due to dark energy. We derive generic formulae for the estimation of the maximum turnaround radius in any theory of gravity obeying the Einstein equivalence principle, in two situations: on a spherically symmetric spacetime and on a perturbed Friedman-Robertson-Walker spacetime. We show that the two formulae agree. As an application of our formula, we calculate the maximum turnaround radius in the case of the Brans-Dicke theory of gravity. We find that for this theory, such maximum sizes always lie above the value, by a factor 1 + 1/3\u03c9, where \u03c9\u226b 1 is the Brans-Dicke parameter, implying consistency of the theory with current data.", "keyphrases": ["maximum size", "alternative theory", "gravity", "einstein equivalence principle"]}
{"id": "1509.03930", "title": "Quantum Primordial Standard Clocks", "abstract": "In this paper, we point out and study a generic type of signals existing in the primordial universe models, which can be used to model-independently distinguish the inflation scenario from alternatives. These signals are generated by massive fields that function as standard clocks. The role of massive fields as standard clocks has been realized in previous works. Although the existence of such massive fields is generic, the previous realizations require sharp features to classically excite the oscillations of the massive clock fields. Here, we point out that the quantum fluctuations of massive fields can actually serve the same purpose as the standard clocks. We show that they are also able to directly record the defining property of the scenario type, namely, the scale factor of the primordial universe as a function of time a(t), but through shape-dependent oscillatory features in non-Gaussianities. Since quantum fluctuating massive fields exist in any realistic primordial universe models, these quantum primordial standard clock signals are present in any inflation models, and should exist quite generally in alternative-to-inflation scenarios as well. However, the amplitude of such signals is very model-dependent.", "keyphrases": ["standard clock", "universe", "massive field", "particle physics", "field inflation"]}
{"id": "1901.07120", "title": "Constraints on Earth-mass primordial black holes from OGLE 5-year microlensing events", "abstract": "We constrain the abundance of primordial black holes (PBH) using 2622 microlensing events obtained from 5-years observations of stars in the Galactic bulge by the Optical Gravitational Lensing Experiment (OGLE). The majority of microlensing events display a single or at least continuous population that has a peak around the light curve timescale t_ E\u2243 20 days and a wide distribution over the range t_ E\u2243 [1, 300] days, while the data also indicates a second population of 6 ultrashort-timescale events in t_ E\u2243 [0.1,0.3] days, which are advocated to be due to free-floating planets. We confirm that the main population of OGLE events can be well modeled by microlensing due to brown dwarfs, main sequence stars and stellar remnants (white dwarfs and neutron stars) in the standard Galactic bulge and disk models for their spatial and velocity distributions. Using the dark matter (DM) model for the Milky Way (MW) halo relative to the Galactic bulge/disk models, we obtain the tightest upper bound on the PBH abundance in the mass range M_ PBH\u2243[10^-6,10^-3]M_\u2299 (Earth-Jupiter mass range), if we employ null hypothesis that the OGLE data does not contain any PBH microlensing event. More interestingly, we also show that Earth-mass PBHs can well reproduce the 6 ultrashort-timescale events, without the need of free-floating planets, if the mass fraction of PBH to DM is at a per cent level, which is consistent with other constraints such as the microlensing search for Andromeda galaxy (M31) and the longer timescale OGLE events. Our result gives a hint of PBH existence, and can be confirmed or falsified by microlensing search for stars in M31, because M31 is towards the MW halo direction and should therefore contain a much less number of free-floating planets, even if exist, than the direction to the MW center.", "keyphrases": ["primordial black hole", "microlensing event", "mass scale"]}
{"id": "2208.05738", "title": "Implicit large eddy simulations of global solar convection: effects of numerical resolution in non-rotating and rotating cases", "abstract": "Simulating deep solar convection and its coupled mean-field motions is a formidable challenge where few observational results constrain models that suffer from the non-physical influence of the grid resolution. We present hydrodynamic global Implicit Large-Eddy simulations (ILES) of deep solar convection performed with the EULAG-MHD code, and explore the effects of grid resolution on the properties of rotating and non-rotating convection. The results, based on low-order moments and turbulent spectra reveal that convergence could be achieved in non-rotating simulations provided sufficient resolution in the radial direction. The flow is highly anisotropic, with the energy contained in horizontal divergent motions exceeding by more than three orders of magnitude their radial counterpart. By contrast, in rotating simulations the largest energy is in the toroidal part of the horizontal motions. As the grid resolution increases, the turbulent correlations change in such a way that a solar-like differential rotation, obtained in the simulation with the coarser grid, transitions to the anti-solar differential rotation. The reason for this change is the contribution of the effective viscosity to the balance of the forces driving large-scale flows. As the effective viscosity decreases, the angular momentum balance improves, yet the force balance in the meridional direction lessens, favoring a strong meridional flow that advects angular momentum towards the poles. The results suggest that obtaining the correct distribution of angular momentum may not be a mere issue of numerical resolution. Accounting for additional physics, such as magnetism or the near-surface shear layer, may be necessary in simulating the solar interior.", "keyphrases": ["solar convection", "numerical resolution", "near-surface shear layer"]}
{"id": "1008.4236", "title": "Generalized Galileon cosmology", "abstract": "We study the cosmology of a generalized Galileon field \u03d5 with five covariant Lagrangians in which \u03d5 is replaced by general scalar functions f_i(\u03d5) (i=1,...,5). For these theories, the equations of motion remain at second-order in time derivatives. We restrict the functional forms of f_i(\u03d5) from the demand to obtain de Sitter solutions responsible for dark energy. There are two possible choices for power-law functions f_i(\u03d5), depending on whether the coupling F(\u03d5) with the Ricci scalar R is independent of \u03d5 or depends on \u03d5. The former corresponds to the covariant Galileon theory that respects the Galilean symmetry in the Minkowski space-time. For generalized Galileon theories we derive the conditions for the avoidance of ghosts and Laplacian instabilities associated with scalar and tensor perturbations as well as the condition for the stability of de Sitter solutions. We also carry out detailed analytic and numerical study for the cosmological dynamics in those theories.", "keyphrases": ["cosmology", "covariant galileon theory", "tensor perturbation"]}
{"id": "1207.6105", "title": "The Average Star Formation Histories of Galaxies in Dark Matter Halos from z=0-8", "abstract": "We present a robust method to constrain average galaxy star formation rates, star formation histories, and the intracluster light as a function of halo mass. Our results are consistent with observed galaxy stellar mass functions, specific star formation rates, and cosmic star formation rates from z=0 to z=8. We consider the effects of a wide range of uncertainties on our results, including those affecting stellar masses, star formation rates, and the halo mass function at the heart of our analysis. As they are relevant to our method, we also present new calibrations of the dark matter halo mass function, halo mass accretion histories, and halo-subhalo merger rates out to z=8. We also provide new compilations of cosmic and specific star formation rates; more recent measurements are now consistent with the buildup of the cosmic stellar mass density at all redshifts. Implications of our work include: halos near 10^12 Msun are the most efficient at forming stars at all redshifts, the baryon conversion efficiency of massive halos drops markedly after z 2.5 (consistent with theories of cold-mode accretion), the ICL for massive galaxies is expected to be significant out to at least z 1-1.5, and dwarf galaxies at low redshifts have higher stellar mass to halo mass ratios than previous expectations and form later than in most theoretical models. Finally, we provide new fitting formulae for star formation histories that are more accurate than the standard declining tau model. Our approach places a wide variety of observations relating to the star formation history of galaxies into a self-consistent framework based on the modern understanding of structure formation in LCDM. Constraints on the stellar mass-halo mass relationship and star formation rates are available for download at http://www.peterbehroozi.com/data.html .", "keyphrases": ["galaxy", "star formation rate", "halo mass"]}
{"id": "1606.09286", "title": "Axionic extension of the Einstein-aether theory", "abstract": "We extend the Einstein-aether theory to take into account the interaction between a pseudoscalar field, which describes the axionic dark matter, and a time-like dynamic unit vector field, which characterizes the velocity of the aether motion. The Lagrangian of the Einstein-aether-axion theory includes cross-terms based on the axion field and its gradient four-vector, on the covariant derivative of the aether velocity four-vector, and on the Riemann tensor and its convolutions. We follow the principles of the Effective Field theory, and include into the Lagrangian of interactions all possible terms up to the second order in the covariant derivative. Interpretation of new couplings is given in terms of irreducible parts of the covariant derivative of the aether velocity, namely, the acceleration four-vector, the shear and vorticity tensors, and the expansion scalar. A spatially isotropic and homogeneous cosmological model with dynamic unit vector field and axionic dark matter is considered as an application of the established theory; new exact solutions are discussed, which describe models with a Big Rip, Pseudo Rip and de Sitter-type asymptotic behavior.", "keyphrases": ["einstein-aether theory", "pseudoscalar field", "expansion scalar"]}
{"id": "1006.0034", "title": "Spectrum of Galactic Cosmic Rays Accelerated in Supernova Remnants", "abstract": "The spectra of high-energy protons and nuclei accelerated by supernova remnant shocks are calculated taking into account magnetic field amplification and Alfvenic drift both upstream and downstream of the shock for different types of supernova remnants during their evolution. The maximum energy of accelerated particles may reach 5\u00b710^18 eV for Fe ions in Type IIb SNRs. The calculated energy spectrum of cosmic rays after propagation through the Galaxy is in good agreement with the spectrum measured at the Earth.", "keyphrases": ["cosmic ray", "supernova remnant", "diffusive shock acceleration"]}
{"id": "2005.11178", "title": "A peculiar hard X-ray counterpart of a Galactic fast radio burst", "abstract": "Fast radio bursts are bright, millisecond-scale radio flashes of yet unknown physical origin. Recently, their extragalactic nature has been demonstrated and an increasing number of the sources have been found to repeat. Young, highly magnetized, isolated neutron stars - magnetars - have been suggested as the most promising candidates for fast radio burst progenitors owing to their energetics and high X-ray flaring activity. Here we report the detection with the Konus-Wind of a hard X-ray event of April 28, 2020, temporarily coincident with a bright, two-peak radio burst from the Galactic magnetar SGR 1935+2154 with properties remarkably similar to those of fast radio bursts. We show that two peaks of the double-peaked X-ray burst coincide in time with the radio peaks, confirming that the X-ray and radio emission most likely have a common origin. Thus, this is the first simultaneous detection of a fast radio burst from a Galactic magnetar and its high-energy counterpart. The total energy emitted in X-rays in this burst is typical of bright short magnetar bursts, but an unusual hardness of its energy spectrum strongly distinguish the April 28 event among multiple \"ordinary\" flares detected from SGR 1935+2154 previously. This, and a recent non-detection of radio emission from about one hundred typical soft bursts from SGR 1935+2154 favors the idea that bright, FRB-like magnetar signals are associated with rare, hard-spectrum X-ray bursts, which implied rate (\u223c 0.04 yr^-1 magnetar^-1) appears consistent with the rate estimate of SGR 1935+2154-like radio bursts (0.007 - 0.04 yr^-1 magnetar^-1).", "keyphrases": ["hard x-ray counterpart", "radio burst", "galactic magnetar"]}
{"id": "1106.0172", "title": "Cosmic Bounces and Cyclic Universes", "abstract": "Cosmological models involving a bounce from a contracting to an expanding universe can address the standard cosmological puzzles and generate \"primordial\" density perturbations without the need for inflation. Some such models, in particular the ekpyrotic and cyclic models that we focus on, fit rather naturally into string theory. We discuss a number of topics related to these models: the reasoning that leads to the ekpyrotic phase, the predictions for upcoming observations, the differences between singular and non-singular models of the bounce as well as the predictive and explanatory power offered by these models.", "keyphrases": ["bounce", "cosmology", "string theory"]}
{"id": "1107.4045", "title": "Peculiar motions, accelerated expansion and the cosmological axis", "abstract": "Peculiar velocities change the expansion rate of any observer moving relative to the smooth Hubble flow. As a result, observers in a galaxy like our Milky Way can experience accelerated expansion within a globally decelerating universe, even when the drift velocities are small. The effect is local, but the affected scales can be large enough to give the false impression that the whole cosmos has recently entered an accelerating phase. Generally, peculiar velocities are also associated with dipole-like anisotropies, triggered by the fact that they introduce a preferred spatial direction. This implies that observers experiencing locally accelerated expansion, as a result of their own drift motion, may also find that the acceleration is maximised in one direction and minimised in the opposite. We argue that, typically, such a dipole anisotropy should be relatively small and the axis should probably lie fairly close to the one seen in the spectrum of the Cosmic Microwave Background.", "keyphrases": ["peculiar velocity", "anisotropy", "drift motion"]}
{"id": "0902.4669", "title": "Dynamical Chern-Simons Modified Gravity I: Spinning Black Holes in the Slow-Rotation Approximation", "abstract": "The low-energy limit of string theory contains an anomaly-canceling correction to the Einstein-Hilbert action, which defines an effective theory: Chern-Simons (CS) modified gravity. The CS correction consists of the product of a scalar field with the Pontryagin density, where the former can be treated as a background field (non-dynamical formulation) or as an evolving field (dynamical formulation). Many solutions of general relativity persist in the modified theory; a notable exception is the Kerr metric, which has sparked a search for rotating black hole solutions. Here, for the first time, we find a solution describing a rotating black hole within the dynamical framework, and in the small-coupling/slow-rotation limit. The solution is axisymmetric and stationary, constituting a deformation of the Kerr metric with dipole scalar \"hair,\" whose effect on geodesic motion is to weaken the frame-dragging effect and shift the location of the inner-most stable circular orbit outwards (inwards) relative to Kerr for co-rotating (counter-rotating) geodesics. We further show that the correction to the metric scales inversely with the fourth power of the radial distance to the black hole, suggesting it will escape any meaningful bounds from weak-field experiments. For example, using binary pulsar data we can only place an initial bound on the magnitude of the dynamical coupling constant of \u03be^1/4\u2272 10^4km. More stringent bounds will require observations of inherently strong-field phenomena.", "keyphrases": ["gravity", "slow-rotation approximation", "black hole solution"]}
{"id": "1412.3342", "title": "Measuring the bulk Lorentz factors of gamma-ray bursts with Fermi", "abstract": "Gamma-ray bursts (GRBs) are powered by ultra-relativistic jets. Usually a minimum value of the Lorentz factor of the relativistic bulk motion is obtained based on the argument that the observed high energy photons (\u226b MeV) can escape without suffering from absorption due to pair production. The exact value, rather than a lower limit, of the Lorentz factor can be obtained if the spectral cutoff due to such absorption is detected. With the good spectral coverage of the Large Area Telescope (LAT) on Fermi, measurements of such cutoff become possible, and two cases (GRB 090926A and GRB 100724B) have been reported to have high-energy cutoffs or breaks. We systematically search for such high energy spectral cutoffs/breaks from the LAT and the Gamma-ray burst monitor (GBM) observations of the prompt emission of GRBs detected since August 2011. Six more GRBs are found to have cutoff-like spectral feature at energies of \u223c10-500 MeV. Assuming that these cutoffs are caused by pair-production absorption within the source, the bulk Lorentz factors of these GRBs are obtained. We further find that the Lorentz factors are correlated with the isotropic gamma-ray luminosity of the bursts, indicating that more powerful GRB jets move faster.", "keyphrases": ["bulk lorentz factor", "gamma-ray burst", "fermi", "high energy"]}
{"id": "1407.2274", "title": "Supersonic Relative Velocity between Dark Matter and Baryons: A Review", "abstract": "In this review we summarize the effect of relative supersonic velocities between gas and dark matter created right after recombination on astrophysics and cosmology. The relative velocities formally introduce a second order effect on the standard results and thus have been neglected in the framework of linear theory. However, when properly considered, the velocities yield a non-perturbative contribution to the growth of structures which is then inherited by the majority of cosmic signals coming from redshifts above z 10, and in certain cases may even propagate to various low-redshift observables such as the Baryon Acoustic Oscillations measured from the distribution of galaxies. At higher redshifts, the supersonic velocities have thus strong impact affecting the abundance of first star forming halos in an inhomogeneous way, hindering creation of the first stars, leaving traces in the redshifted 21-cm signal of neutral hydrogen, as well as having other important contributions at high redshifts all of which we review in this manuscript.", "keyphrases": ["dark matter", "astrophysic", "cosmology"]}
{"id": "1401.0254", "title": "Nonlocal Models of Cosmic Acceleration", "abstract": "I review a class of nonlocally modified gravity models which were proposed to explain the current phase of cosmic acceleration without dark energy. Among the topics considered are deriving causal and conserved field equations, adjusting the model to make it support a given expansion history, why these models do not require an elaborate screening mechanism to evade solar system tests, degrees of freedom and kinetic stability, and the negative verdict of structure formation. Although these simple models are not consistent with data on the growth of cosmic structures many of their features are likely to carry over to more complicated models which are in better agreement with the data.", "keyphrases": ["cosmic acceleration", "field equation", "infrared graviton", "cosmology"]}
{"id": "1303.1523", "title": "Inflation, Cosmic Perturbations and Non-Gaussianities", "abstract": "We review the theory of inflationary perturbations. Perturbations at both linear and nonlinear orders are reviewed. We also review a variety of inflation models, emphasizing their signatures on cosmic perturbations.", "keyphrases": ["inflation model", "non-gaussianitie", "bispectrum", "early universe", "observational constraint"]}
{"id": "0911.0505", "title": "Scientific Data Mining in Astronomy", "abstract": "We describe the application of data mining algorithms to research problems in astronomy. We posit that data mining has always been fundamental to astronomical research, since data mining is the basis of evidence-based discovery, including classification, clustering, and novelty discovery. These algorithms represent a major set of computational tools for discovery in large databases, which will be increasingly essential in the era of data-intensive astronomy. Historical examples of data mining in astronomy are reviewed, followed by a discussion of one of the largest data-producing projects anticipated for the coming decade: the Large Synoptic Survey Telescope (LSST). To facilitate data-driven discoveries in astronomy, we envision a new data-oriented research paradigm for astronomy and astrophysics \u2013 astroinformatics. Astroinformatics is described as both a research approach and an educational imperative for modern data-intensive astronomy. An important application area for large time-domain sky surveys (such as LSST) is the rapid identification, characterization, and classification of real-time sky events (including moving objects, photometrically variable objects, and the appearance of transients). We describe one possible implementation of a classification broker for such events, which incorporates several astroinformatics techniques: user annotation, semantic tagging, metadata markup, heterogeneous data integration, and distributed data mining. Examples of these types of collaborative classification and discovery approaches within other science disciplines are presented.", "keyphrases": ["astronomy", "classification", "data-intensive astronomy"]}
{"id": "1211.3246", "title": "Zonal flow regimes in rotating anelastic spherical shells: an application to giant planets", "abstract": "The surface zonal winds observed in the giant planets form a complex jet pattern with alternating prograde and retrograde direction. While the main equatorial band is prograde on the gas giants, both ice giants have a pronounced retrograde equatorial jet. We use three-dimensional numerical models of compressible convection in rotating spherical shells to explore the properties of zonal flows in different regimes where either rotation or buoyancy dominates the force balance. We conduct a systematic parameter study to quantify the dependence of zonal flows on the background density stratification and the driving of convection. We find that the direction of the equatorial zonal wind is controlled by the ratio of buoyancy and Coriolis force. The prograde equatorial band maintained by Reynolds stresses is found in the rotation-dominated regime. In cases where buoyancy dominates Coriolis force, the angular momentum per unit mass is homogenised and the equatorial band is retrograde, reminiscent to those observed in the ice giants. In this regime, the amplitude of the zonal jets depends on the background density contrast with strongly stratified models producing stronger jets than comparable weakly stratified cases. Furthermore, our results can help to explain the transition between solar-like and \"anti-solar\" differential rotations found in anelastic models of stellar convection zones. In the strongly stratified cases, we find that the leading order force balance can significantly vary with depth (rotation-dominated inside and buoyancy-dominated in a thin surface layer). This so-called \"transitional regime\" has a visible signature in the main equatorial jet which shows a pronounced dimple where flow amplitudes notably decay towards the equator. A similar dimple is observed on Jupiter, which suggests that convection in the planet interior could possibly operate in this regime.", "keyphrases": ["spherical shell", "giant planet", "zonal flow"]}
{"id": "1803.03272", "title": "What does the first highly-redshifted 21-cm detection tell us about early galaxies?", "abstract": "The Experiment to Detect the Global Epoch of Reionization Signature (EDGES) recently reported a strong 21-cm absorption signal relative to the cosmic microwave background at z \u223c 18. While its anomalous amplitude may indicate new physics, in this work we focus on the timing of the signal, as it alone provides an important constraint on galaxy formation models. Whereas rest-frame ultraviolet luminosity functions (UVLFs) over a broad range of redshifts are well fit by simple models in which galaxy star formation histories track the assembly of dark matter halos, we find that these same models, with reasonable assumptions about X-ray production in star-forming galaxies, cannot generate a narrow absorption trough at z \u223c 18. If verified, the EDGES signal therefore requires the fundamental inputs of galaxy formation models to evolve rapidly at z \u2273 10. Unless extremely faint sources residing in halos below the atomic cooling threshold are responsible for the EDGES signal, star formation in \u223c 10^8-10^10 M_\u2299 halos must be more efficient than expected, implying that the faint-end of the UVLF at M_UV\u2272 -12 must steepen at the highest redshifts. This steepening provides a concrete test for future galaxy surveys with the James Webb Space Telescope and ongoing efforts in lensed fields, and is required regardless of whether the amplitude of the EDGES signal is due to new cooling channels or a strong radio background in the early Universe. However, the radio background solution requires that galaxies at z > 15 emit 1-2 GHz photons with an efficiency \u223c 10^3 times greater than local star-forming galaxies, posing a challenge for models of low-frequency photon production in the early Universe.", "keyphrases": ["galaxy", "radio background", "early universe"]}
{"id": "1904.03430", "title": "Baryon acoustic oscillations from the cross-correlation of Ly\u03b1 absorption and quasars in eBOSS DR14", "abstract": "We present a measurement of the baryon acoustic oscillation (BAO) scale at redshift z=2.35 from the three-dimensional correlation of Lyman-\u03b1 (Ly\u03b1) forest absorption and quasars. The study uses 266,590 quasars in the redshift range 1.77<z<3.5 from the Sloan Digital Sky Survey (SDSS) Data Release 14 (DR14). The sample includes the first two years of observations by the SDSS-IV extended Baryon Oscillation Spectroscopic Survey (eBOSS), providing new quasars and re-observations of BOSS quasars for improved statistical precision. Statistics are further improved by including Ly\u03b1 absorption occurring in the Ly\u03b2 wavelength band of the spectra. From the measured BAO peak position along and across the line of sight, we determined the Hubble distance D_H and the comoving angular diameter distance D_M relative to the sound horizon at the drag epoch r_d: D_H(z=2.35)/r_d=9.20\u00b1 0.36 and D_M(z=2.35)/r_d=36.3\u00b1 1.8. These results are consistent at 1.5\u03c3 with the prediction of the best-fit spatially-flat cosmological model with the cosmological constant reported for the Planck (2016) analysis of cosmic microwave background anisotropies. Combined with the Ly\u03b1 auto-correlation measurement presented in a companion paper, the BAO measurements at z=2.34 are within 1.7\u03c3 of the predictions of this model.", "keyphrases": ["ly\u03b1 absorption", "quasar", "cosmological model", "baryon acoustic oscillation"]}
{"id": "1501.03155", "title": "Gusty, gaseous flows of FIRE: galactic winds in cosmological simulations with explicit stellar feedback", "abstract": "We present an analysis of the galaxy-scale gaseous outflows from the FIRE (Feedback in Realistic Environments) simulations. This suite of hydrodynamic cosmological zoom simulations resolves formation of star-forming giant molecular clouds to z=0, and features an explicit stellar feedback model on small scales. Our simulations reveal that high redshift galaxies undergo bursts of star formation followed by powerful gusts of galactic outflows that eject much of the ISM and temporarily suppress star formation. At low redshift, however, sufficiently massive galaxies corresponding to L*-progenitors develop stable disks and switch into a continuous and quiescent mode of star formation that does not drive outflows far into the halo. Mass-loading factors for winds in L*-progenitors are \u03b7\u2248 10 at high redshift, but decrease to \u03b7\u226a 1 at low redshift. Although lower values of \u03b7 are expected as halos grow in mass over time, we show that the strong suppression of outflows with decreasing redshift cannot be explained by mass evolution alone. Circumgalactic outflow velocities are variable and broadly distributed, but typically range between one and three times the circular velocity of the halo. Much of the ejected material builds a reservoir of enriched gas within the circumgalactic medium, some of which could be later recycled to fuel further star formation. However, a fraction of the gas that leaves the virial radius through galactic winds is never regained, causing most halos with mass M_h \u2264 10^12 M_\u2299 to be deficient in baryons compared to the cosmic mean by z=0.", "keyphrases": ["galactic wind", "cosmological simulation", "stellar feedback"]}
{"id": "1205.0786", "title": "Refining inflation using non-canonical scalars", "abstract": "This paper revisits the Inflationary scenario within the framework of scalar field models possessing a non-canonical kinetic term. We obtain closed form solutions for all essential quantities associated with chaotic inflation including slow roll parameters, scalar and tensor power spectra, spectral indices, the tensor-to-scalar ratio, etc. We also examine the Hamilton-Jacobi equation and demonstrate the existence of an inflationary attractor. Our results highlight the fact that non-canonical scalars can significantly improve the viability of inflationary models. They accomplish this by decreasing the tensor-to-scalar ratio while simultaneously increasing the value of the scalar spectral index, thereby redeeming models which are incompatible with the cosmic microwave background (CMB) in their canonical version. For instance, the non-canonical version of the chaotic inflationary potential, V(\u03d5) \u223c\u03bb\u03d5^4, is found to agree with observations for values of \u03bb as large as unity ! The exponential potential can also provide a reasonable fit to CMB observations. A central result of this paper is that steep potentials (such as V \u221d\u03d5^-n) usually associated with dark energy, can drive inflation in the non-canonical setting. Interestingly, non-canonical scalars violate the consistency relation r = -8n_T, which emerges as a smoking gun test for this class of models.", "keyphrases": ["non-canonical scalar", "inflationary scenario", "chaotic inflation"]}
{"id": "1004.0926", "title": "Electronic screening and damping in magnetars", "abstract": "We calculate the screening of the ion-ion potential due to electrons in the presence of a large background magnetic field, at densities of relevance to neutron star crusts. Using the standard approach to incorporate electron screening through the one-loop polarization function, we show that the magnetic field produces important corrections both at short and long distances. In extreme fields, realized in highly magnetized neutron stars called magnetars, electrons occupy only the lowest Landau levels in the relatively low density region of the crust. Here our results show that the screening length for Coulomb interactions between ions can be smaller than the inter-ion spacing. More interestingly, we find that the screening is anisotropic and the screened potential between two static charges exhibits long range Friedel oscillations parallel to the magnetic field. This long-range oscillatory behavior is likely to affect the lattice structure of ions, and can possibly create rod-like structures in the magnetar crusts. We also calculate the imaginary part of the electron polarization function which determines the spectrum of electron-hole excitations and plays a role in damping lattice phonon excitations. We demonstrate that even for modest magnetic fields this damping is highly anisotropic and will likely lead to anisotropic phonon heat transport in the outer neutron star crust.", "keyphrases": ["screening", "magnetar", "ion-ion potential"]}
{"id": "1804.08030", "title": "Event horizon image within black hole shadow", "abstract": "We argue that a genuine image of the black hole viewed by a distant observer is not its shadow, but a more compact event horizon image probed by the luminous matter plunging into black hole. The external border of the black hole shadow is washed out by radiation from matter plunging into black hole and approaching the event horizon. This effect will crucially influence the results of future observations by the Event Horizon Telescope. We show that gravitational lensing of the luminous matter plunging into black hole provides the possibility for visualization of the event horizon. The lensed image of the event horizon is formed by the highly red-shifted photons emitted by the plunging matter very near the black hole event horizon and detected by a distant observer. The resulting event horizon image is a gravitationally lensed projection on the celestial sphere of the whole black hole event horizon sphere. Seemingly, black holes are the unique objects in the Universe which may be viewed by distant observers at once from both the front and back sides.", "keyphrases": ["black hole shadow", "distant observer", "photon", "event horizon image"]}
{"id": "1711.10989", "title": "Interpretations of the DAMPE electron data", "abstract": "The DArk Matter Particle Explorer (DAMPE), a high energy cosmic ray and \u03b3-ray detector in space, has recently reported the new measurement of the total electron plus positron flux between 25 GeV and 4.6 TeV. A spectral softening at \u223c0.9 TeV and a tentative peak at \u223c1.4 TeV have been reported. We study the physical implications of the DAMPE data in this work. The presence of the spectral break significantly tightens the constraints on the model parameters to explain the electron/positron excesses. The spectral softening can either be explained by the maximum acceleration limits of electrons by astrophysical sources, or a breakdown of the common assumption of continuous distribution of electron sources at TeV energies in space and time. The tentive peak at \u223c1.4 TeV implies local sources of electrons/positrons with quasi-monochromatic injection spectrum. We find that the cold, ultra-relativistic e^+e^- winds from pulsars may give rise to such a structure. The pulsar is requird to be middle-aged, relatively slowly-rotated, mildly magnetized, and isolated in a density cavity. The annihilation of DM particles (m_\u03c7\u223c1.5 TeV) into e^+e^- pairs in a nearby clump or an over-density region may also explain the data. In the DM scenario, the inferred clump mass (or density enhancement) is about 10^7-10^8 M_\u2299 (or 17-35 times of the canonical local density) assuming a thermal production cross section, which is relatively extreme compared with the expectation from numerical simulations. A moderate enhancement of the annihilation cross section via, e.g., the Sommerfeld mechanism or non-thermal production, is thus needed.", "keyphrases": ["spectral softening", "electron source", "annihilation", "interpretation", "kpc"]}
{"id": "1010.1000", "title": "Testing the No-Hair Theorem with Observations in the Electromagnetic Spectrum. III. Quasi-Periodic Variability", "abstract": "According to the no-hair theorem, astrophysical black holes are uniquely described by their masses and spins. An observational test of the no-hair theorem can be performed by measuring at least three different multipole moments of the spacetime of a black hole and verifying whether their values are consistent with the unique combinations of the Kerr solution. In this paper, we study quasi-periodic variability observed in the emission from black holes across the electromagnetic spectrum as a test of the no-hair theorem. We derive expressions for the Keplerian and epicyclic frequencies in a quasi-Kerr spacetime, in which the quadrupole moment is a free parameter in addition to mass and spin. We show that, for moderate spins, the Keplerian frequency is practically independent of small deviations of the quadrupole moment from the Kerr value, while the epicyclic frequencies exhibit significant variations. We apply this framework to quasi-periodic oscillations in black-hole X-ray binaries in two different scenarios. In the case that a pair of quasi-periodic oscillations can be identified as the fundamental g- and c-modes in the accretion disk, we show that the no-hair theorem can be tested in conjunction with an independent mass measurement. If, on the other hand, the pairs of oscillations are identified with non-parametric resonance of dynamical frequencies in the accretion disk, then testing the no-hair theorem also requires an independent measurement of the black-hole spin. In addition, we argue that VLBI observations of Sgr A* may test the no-hair theorem through a combination of imaging observations and the detection of quasi-periodic variability.", "keyphrases": ["electromagnetic spectrum", "quasi-periodic variability", "small deviation", "accretion"]}
{"id": "1705.08198", "title": "Origin and Structures of Solar Eruptions I: Magnetic Flux Rope (Invited Review)", "abstract": "Coronal mass ejections (CMEs) and solar flares are the large-scale and most energetic eruptive phenomena in our solar system and able to release a large quantity of plasma and magnetic flux from the solar atmosphere into the solar wind. When these high-speed magnetized plasmas along with the energetic particles arrive at the Earth, they may interact with the magnetosphere and ionosphere, and seriously affect the safety of human high-tech activities in outer space. The travel time of a CME to 1 AU is about 1-3 days, while energetic particles from the eruptions arrive even earlier. An efficient forecast of these phenomena therefore requires a clear detection of CMEs/flares at the stage as early as possible. To estimate the possibility of an eruption leading to a CME/flare, we need to elucidate some fundamental but elusive processes including in particular the origin and structures of CMEs/flares. Understanding these processes can not only improve the prediction of the occurrence of CMEs/flares and their effects on geospace and the heliosphere but also help understand the mass ejections and flares on other solar-type stars. The main purpose of this review is to address the origin and early structures of CMEs/flares, from multi-wavelength observational perspective. First of all, we start with the ongoing debate of whether the pre-eruptive configuration, i.e., a helical magnetic flux rope (MFR), of CMEs/flares exists before the eruption and then emphatically introduce observational manifestations of the MFR. Secondly, we elaborate on the possible formation mechanisms of the MFR through distinct ways. Thirdly, we discuss the initiation of the MFR and associated dynamics during its evolution toward the CME/flare. Finally, we come to some conclusions and put forward some prospects in the future.", "keyphrases": ["eruption", "magnetic flux rope", "coronal mass ejection", "solar atmosphere"]}
{"id": "1510.07316", "title": "Nonlocal Newtonian Cosmology", "abstract": "We explore some of the cosmological implications of the recent classical nonlocal generalization of Einstein's theory of gravitation in which nonlocality is due to the gravitational memory of past events. In the Newtonian regime of this theory, the nonlocal character of gravity simulates dark matter in spiral galaxies and clusters of galaxies. However, dark matter is considered indispensable as well for structure formation in standard models of cosmology. Can nonlocal gravity solve the problem of structure formation without recourse to dark matter? Here we make a beginning in this direction by extending nonlocal gravity in the Newtonian regime to the cosmological domain. The nonlocal analog of the Zel'dovich solution is formulated and the consequences of the resulting nonlocal Zel'dovich model are investigated in detail.", "keyphrases": ["cosmological implication", "newtonian regime", "gravity", "nonlocal newtonian cosmology"]}
{"id": "1110.5107", "title": "Multiple physical elements to determine the gravitational-wave signatures of core-collapse supernovae", "abstract": "We review recent progress in the theoretical predictions of gravitational waves (GWs) of core-collapse supernovae. Following a brief summary of the methods in the numerical modeling, we summarize multiple physical elements that determine the GW signatures which have been considered to be important in extracting the information of the long-veiled explosion mechanism from the observation of the GWs. We conclude with a summary of the most urgent tasks to make the dream come true.", "keyphrases": ["core-collapse supernovae", "gravitational wave", "neutrino-driven explosion", "explosion energy"]}
{"id": "1404.1207", "title": "Spontaneous creation of the universe from nothing", "abstract": "An interesting idea is that the universe could be spontaneously created from nothing, but no rigorous proof has been given. In this paper, we present such a proof based on the analytic solutions of the Wheeler-DeWitt equation (WDWE). Explicit solutions of the WDWE for the special operator ordering factor p=-2 (or 4) show that, once a small true vacuum bubble is created by quantum fluctuations of the metastable false vacuum, it can expand exponentially no matter whether the bubble is closed, flat or open. The exponential expansion will end when the bubble becomes large and thus the early universe appears. With the de Broglie-Bohm quantum trajectory theory, we show explicitly that it is the quantum potential that plays the role of the cosmological constant and provides the power for the exponential expansion of the true vacuum bubble. So it is clear that the birth of the early universe completely depends on the quantum nature of the theory.", "keyphrases": ["universe", "operator", "vacuum bubble", "spontaneous creation"]}
{"id": "1104.2846", "title": "On graviton non-Gaussianities during inflation", "abstract": "We consider the most general three point function for gravitational waves produced during a period of exactly de Sitter expansion. The de Sitter isometries constrain the possible shapes to only three: two preserving parity and one violating parity. These isometries imply that these correlation functions should be conformal invariant. One of the shapes is produced by the ordinary gravity action. The other shape is produced by a higher derivative correction and could be as large as the gravity contribution. The parity violating shape does not contribute to the bispectrum [1106.3228, 1108.0175], even though it is present in the wavefunction. We also introduce a spinor helicity formalism to describe de Sitter gravitational waves with circular polarization. These results also apply to correlation functions in Anti-de Sitter space. They also describe the general form of stress tensor correlation functions, in momentum space, in a three dimensional conformal field theory. Here all three shapes can arise, including the parity violating one.", "keyphrases": ["gravitational wave", "conformal invariance", "non-gaussianitie", "cosmological bootstrap", "slow-roll inflation"]}
{"id": "1912.03986", "title": "Updated fundamental constant constraints from Planck 2018 data and possible relations to the Hubble tension", "abstract": "We present updated constraints on the variation of the fine structure constant, \u03b1_ EM, and effective electron rest mass, m_ e, during the cosmological recombination era. These two fundamental constants directly affect the ionization history at redshift z\u2243 1100 and thus modify the temperature and polarisation anisotropies of the cosmic microwave background (CMB) measured precisely with Planck . The constraints on \u03b1_ EM tighten slightly due to improved Planck 2018 polarisation data but otherwise remain similar to previous CMB analysis. However, a comparison with the 2015 constraints reveals a mildly discordant behaviour for m_ e, which from CMB data alone is found below its local value. Adding baryon acoustic oscillation data brings m_ e back to the fiducial value, m_ e=(1.0078\u00b10.0067) m_ e,0, and also drives the Hubble parameter to H_0=69.1\u00b1 1.2 [in units of km s^-1 Mpc^-1]. Further adding supernova data yields m_ e=(1.0190\u00b10.0055) m_ e,0 with H_0=71.24\u00b10.96. We perform several comparative analyses using the latest cosmological recombination calculations to further understand the various effects. Our results indicate that a single-parameter extension allowing for a slightly increased value of m_ e (\u2243 3.5\u03c3 above m_ e,0) could play a role in the Hubble tension.", "keyphrases": ["hubble tension", "recombination era", "ionization history"]}
{"id": "1504.05461", "title": "Asteroid family ages", "abstract": "A new family classification, based on a catalog of proper elements with \u223c 384,000 numbered asteroids and on new methods is available. For the 45 dynamical families with >250 members identified in this classification, we present an attempt to obtain statistically significant ages: we succeeded in computing ages for 37 collisional families. We used a rigorous method, including a least squares fit of the two sides of a V-shape plot in the proper semimajor axis, inverse diameter plane to determine the corresponding slopes, an advanced error model for the uncertainties of asteroid diameters, an iterative outlier rejection scheme and quality control. The best available Yarkovsky measurement was used to estimate a calibration of the Yarkovsky effect for each family. The results are presented separately for the families originated in fragmentation or cratering events, for the young, compact families and for the truncated, one-sided families. For all the computed ages the corresponding uncertainties are provided. We found 2 cases where two separate dynamical families form together a single V-shape with compatible slopes, thus indicating a single collisional event. We have also found 3 examples of dynamical families containing multiple collisional families, plus a dubious case. We have found 2 cases of families containing a conspicuous subfamily, such that it is possible to measure the slope of a distinct V-shape, thus the age of the secondary collision. We also provide data on the central gaps appearing in some families. The ages computed in this paper are obtained with a single and uniform methodology, thus the ages of different families can be compared, providing a first example of collisional chronology of the asteroid main belt.", "keyphrases": ["age", "v-shape", "main belt", "asteroid"]}
{"id": "1403.1605", "title": "Probing small-scale cosmological fluctuations with the 21 cm forest: effects of neutrino mass, running spectral index and warm dark matter", "abstract": "Although the cosmological paradigm based on cold dark matter and adiabatic, nearly scale-invariant primordial fluctuations is consistent with a wide variety of existing observations, it has yet to be sufficiently tested on scales smaller than those of massive galaxies, and various alternatives have been proposed that differ significantly in the consequent small-scale power spectrum (SSPS) of large-scale structure. Here we show that a powerful probe of the SSPS at k\u2273 10 Mpc^-1 can be provided by the 21 cm forest, that is, systems of narrow absorption lines due to intervening, cold neutral hydrogen in the spectra of high-redshift background radio sources in the cosmic reionization epoch. Such features are expected to be caused predominantly by collapsed gas in starless minihalos, whose mass function can be very sensitive to the SSPS. As specific examples, we consider the effects of neutrino mass, running spectral index (RSI) and warm dark matter (WDM) on the SSPS, and evaluate the expected distribution in optical depth of 21 cm absorbers out to different redshifts. Within the current constraints on quantities such as the sum of neutrino masses \u2211 m_\u03bd, running of the primordial spectral index d n_s/d ln k and WDM particle mass m_ WDM, the statistics of the 21 cm forest manifest observationally significant differences that become larger at higher redshifts. In particular, it may be possible to probe the range of m_ WDM\u2273 10 keV that may otherwise be inaccessible. Future observations of the 21 cm forest by the Square Kilometer Array may offer a unique and valuable probe of the SSPS, as long as radio sources such as quasars or Population III gamma-ray bursts with sufficient brightness and number exist at redshifts of z \u2273 10 - 20, and the astrophysical effects of reionization and heating can be discriminated.", "keyphrases": ["fluctuation", "neutrino mass", "warm dark matter", "high redshift"]}
{"id": "2101.11026", "title": "The Highest Energy HAWC Sources are Likely Leptonic and Powered by Pulsars", "abstract": "The HAWC Collaboration has observed gamma rays at energies above 56 TeV from a collection of nine sources. It has been suggested that this emission could be hadronic in nature, requiring that these systems accelerate cosmic-ray protons or nuclei up to PeV-scale energies. In this paper, we instead show that the spectra of these objects favor a leptonic (inverse Compton) origin for their emission. More specifically, the gamma-ray emission from these objects can be straightforwardly accommodated within a model in which \u223c\ud835\udcaa(10%) of the host pulsar's spindown power is transferred into the acceleration of electrons and positrons with a power-law spectrum that extends to several hundred TeV or higher. The spectral break that is observed among these sources is naturally explained within the context of this simple model, and occurs at the energy where the timescale for energy losses matches the age of the pulsar. In contrast, this spectral feature cannot be straightforwardly accommodated in hadronic scenarios. Furthermore, hadronic models predict that these sources should produce more emission at GeV-scale energies than is observed. In light of these considerations, we conclude that HAWC's highest energy sources should be interpreted as TeV halos or pulsar wind nebulae, which produce their emission through inverse Compton scattering, and are powered by the rotational kinetic energy of their host pulsar.", "keyphrases": ["pulsar", "gamma-ray emission", "rotational kinetic energy"]}
{"id": "2110.10175", "title": "The origins of massive black holes", "abstract": "Massive black holes (MBHs) inhabit galaxy centers, power luminous quasars and Active Galactic Nuclei (AGN) and shape their cosmic environment with the energy they produce. The origins of MBHs remain a mystery and the recent detection by LIGO/Virgo of an almost 150 solar mass black hole has revitalized the question of whether there is a continuum between \"stellar\" and \"massive\" black holes and what the seeds of MBHs are. Seeds could have formed in the first galaxies, or could be also related to the collapse of horizon-sized regions in the early Universe. Understanding the origins of MBHs straddles fundamental physics, cosmology and astrophysics and it bridges the fields of gravitational wave physics and traditional astronomy. With several facilities in the next 10-15 years we foresee the possibility of discovering MBHs' avenues of formation. In this article we link three main topics: the channels of black hole seed formation, the journey from seeds to massive black holes, the diagnostics on the origins of MBHs. We highlight and critically discuss current unsolved problems and touch on recent developments that stirred the community.", "keyphrases": ["black hole", "mystery", "cosmology", "astrophysic"]}
{"id": "2202.00700", "title": "Induced gravitational waves from the cosmic coincidence", "abstract": "The induced gravitational wave (GW) background from enhanced primordial scalar perturbations is one of the most promising observational consequences of primordial black hole (PBH) formation from inflation. We investigate the induced GW spectrum \u03a9_IGW from single-field inflation in the general ultra-slow-roll (USR) framework, restricting the peak frequency band to be inside 10^-3-1 Hz and saturating PBH abundance to comprise all dark matter (DM) in the ultralight asteroid-mass window. By invoking successful baryogenesis driven by USR inflation, we verify the viable parameter space for the specific density ratio between baryons and PBH DM observed today, the so-called \"cosmic coincidence.\" We show that the cosmic coincidence requirement bounds the spectral index n_ UV in the high frequency limit, \u03a9_IGW(f\u226b 1)\u221d f^-2n_ UV, into 0 < n_ UV < 1, which implies that baryogenesis triggered by USR inflation for PBHs in the mass range of 10^-16-10^-12 M_\u2299 can be tested by upcoming Advanced LIGO and Virgo data and next generation experiments such as LISA, Einstein Telescope, TianQin and DECIGO.", "keyphrases": ["gravitational wave", "coincidence", "primordial scalar perturbation", "black hole"]}
{"id": "2107.08205", "title": "A bimodal burst energy distribution of a repeating fast radio burst source", "abstract": "The event rate, energy distribution, and time-domain behaviour of repeating fast radio bursts (FRBs) contains essential information regarding their physical nature and central engine, which are as yet unknown. As the first precisely-localized source, FRB 121102 has been extensively observed and shows non-Poisson clustering of bursts over time and a power-law energy distribution. However, the extent of the energy distribution towards the fainter end was not known. Here we report the detection of 1652 independent bursts with a peak burst rate of 122 hr^-1, in 59.5 hours spanning 47 days. A peak in the isotropic equivalent energy distribution is found to be 4.8 x 10^37 erg at 1.25 GHz, below which the detection of bursts is suppressed. The burst energy distribution is bimodal, and well characterized by a combination of a log-normal function and a generalized Cauchy function. The large number of bursts in hour-long spans allow sensitive periodicity searches between 1 ms and 1000 s. The non-detection of any periodicity or quasi-periodicity poses challenges for models involving a single rotating compact object. The high burst rate also implies that FRBs must be generated with a high radiative efficiency, disfavoring emission mechanisms with large energy requirements or contrived triggering conditions.", "keyphrases": ["bimodal", "energy distribution", "frb", "periodicity"]}
{"id": "1604.04222", "title": "Reconciling CMB and structure growth measurements with dark energy interactions", "abstract": "We study a coupled quintessence model with pure momentum exchange and present the effects of such an interaction on the Cosmic Microwave Background (CMB) and matter power spectrum. For a wide range of negative values of the coupling parameter \u03b2 structure growth is suppressed and the model can reconcile the tension between Cosmic Microwave Background observations and structure growth inferred from cluster counts. We find that this model is as good as \u039bCDM for CMB and baryon acoustic oscillation (BAO) data, while the addition of cluster data makes the model strongly preferred, improving the best-fit \u03c7^2-value by more than 16.", "keyphrases": ["growth", "dark energy", "non-gravitational coupling", "cdm cosmology"]}
{"id": "1306.3471", "title": "The Starobinsky Model from Superconformal D-Term Inflation", "abstract": "We point out that in the large field regime, the recently proposed superconformal D-term inflation model coincides with the Starobinsky model. In this regime, the inflaton field dominates over the Planck mass in the gravitational kinetic term in the Jordan frame. Slow-roll inflation is realized in the large field regime for sufficiently large gauge couplings. The Starobinsky model generally emerges as an effective description of slow-roll inflation if a Jordan frame exists where, for large inflaton field values, the action is scale invariant and the ratio \u03bb\u0302 of the inflaton self-coupling and the nonminimal coupling to gravity is tiny. The interpretation of this effective coupling is different in different models. In superconformal D-term inflation it is determined by the scale of grand unification, \u03bb\u0302 (\u039b_GUT/M_P)^4.", "keyphrases": ["starobinsky model", "superconformal d-term inflation", "gravity", "supergravity model"]}
{"id": "1707.07943", "title": "Baryon Asymmetry and Gravitational Waves from Pseudoscalar Inflation", "abstract": "In models of inflation driven by an axion-like pseudoscalar field, the inflaton, a, may couple to the standard model hypercharge via a Chern-Simons-type interaction, L \u2282 a/(4\u039b) FF\u0303. This coupling results in explosive gauge field production during inflation, especially at its last stage, which has interesting phenomenological consequences: For one thing, the primordial hypermagnetic field is maximally helical. It is thus capable of sourcing the generation of nonzero baryon number, via the standard model chiral anomaly, around the time of electroweak symmetry breaking. For another thing, the gauge field production during inflation feeds back into the primordial tensor power spectrum, leaving an imprint in the stochastic background of gravitational waves (GWs). In this paper, we focus on the correlation between these two phenomena. Working in the approximation of instant reheating, we (1) update the investigation of baryogenesis via hypermagnetic fields from pseudoscalar inflation and (2) examine the corresponding implications for the GW spectrum. We find that successful baryogenesis requires a suppression scale Lambda of around Lambda 3 x 10^17 GeV, which corresponds to a relatively weakly coupled axion. The gauge field production at the end of inflation is then typically accompanied by a peak in the GW spectrum at frequencies in the MHz range or above. The detection of such a peak is out of reach of present-day technology; but in the future, it may serve as a smoking-gun signal for baryogenesis from pseudoscalar inflation. Conversely, models that do yield an observable GW signal suffer from the overproduction of baryon number, unless the reheating temperature is lower than the electroweak scale.", "keyphrases": ["pseudoscalar inflation", "axion", "baryon asymmetry"]}
{"id": "1007.0821", "title": "PAMELA results on the cosmic-ray antiproton flux from 60 MeV to 180 GeV in kinetic energy", "abstract": "The satellite-borne experiment PAMELA has been used to make a new measurement of the cosmic-ray antiproton flux and the antiproton-to-proton flux ratio which extends previously published measurements down to 60 MeV and up to 180 GeV in kinetic energy. During 850 days of data acquisition approximately 1500 antiprotons were observed. The measurements are consistent with purely secondary production of antiprotons in the galaxy. More precise secondary production models are required for a complete interpretation of the results.", "keyphrases": ["antiproton flux", "kinetic energy", "cosmic ray", "hadron", "anti-matter asymmetry"]}
{"id": "1901.04525", "title": "A Second Source of Repeating Fast Radio Bursts", "abstract": "The discovery of a repeating Fast Radio Burst (FRB) source, FRB 121102, eliminated models involving cataclysmic events for this source. No other repeating FRB has yet been detected in spite of many recent FRB discoveries and follow-ups, suggesting repeaters may be rare in the FRB population. Here we report the detection of six repeat bursts from FRB 180814.J0422+73, one of the 13 FRBs detected by the Canadian Hydrogen Intensity Mapping Experiment (CHIME) FRB project during its pre-commissioning phase in July and August 2018. These repeat bursts are consistent with originating from a single position on the sky, with the same dispersion measure (DM), 189 pc cm-3. This DM is approximately twice the expected Milky Way column density, and implies an upper limit on the source redshift of 0.1, at least a factor of 2 closer than FRB 121102. In some of the repeat bursts, we observe sub-pulse frequency structure, drifting, and spectral variation reminiscent of that seen in FRB 121102, suggesting similar emission mechanisms and/or propagation effects. This second repeater, found among the first few CHIME/FRB discoveries, suggests that there exists \u2013 and that CHIME/FRB and other wide-field, sensitive radio telescopes will find \u2013 a substantial population of repeating FRBs.", "keyphrases": ["repeater", "fast radio burst", "discovery", "frb", "pulsar"]}
{"id": "1004.1201", "title": "A Naturally Large Four-Point Function in Single Field Inflation", "abstract": "Non-Gaussianities of the primordial density perturbations have emerged as a very powerful possible signal to test the dynamics that drove the period of inflation. While in general the most sensitive observable is the three-point function in this paper we show that there are technically natural inflationary models where the leading source of non-Gaussianity is the four-point function. Using the recently developed Effective Field Theory of Inflation, we are able to show that it is possible to impose an approximate parity symmetry and an approximate continuos shift symmetry on the inflaton fluctuations that allow, when the dispersion relation is of the form \u03c9\u223c c_s k, for a unique quartic operator, while approximately forbidding all the cubic ones. The resulting shape for the four-point function is unique. In the models where the dispersion relation is of the form \u03c9\u223c k^2/M a similar construction can be carried out and additional shapes are possible.", "keyphrases": ["four-point function", "single field inflation", "effective field theory"]}
{"id": "1003.4285", "title": "Cosmological Perturbations in the New Higgs Inflation", "abstract": "We study the cosmological perturbations created during the New Higgs inflationary phase. In the New Higgs Inflation, the Higgs boson is kinetically coupled to the Einstein tensor and only three perturbative degrees of freedom, a scalar and two tensorial (gravitational waves), propagate during Inflation. Scalar perturbations are found to match the latest WMAP-7yrs data within Standard Model Higgs parameters. Primordial gravitational waves also, although propagating with superluminal speed, are consistent with present data. Finally, we estimate the values of the parameter of the New Higgs Inflation in relation to the Higgs mass, the spectral index and amplitude of the primordial scalar perturbations showing that the unitarity bound of the theory is not violated.", "keyphrases": ["new higgs inflation", "higgs boson", "cosmological perturbation"]}
{"id": "1109.1047", "title": "G-Bounce", "abstract": "We present a wide class of models which realise a bounce in a spatially flat Friedmann universe in standard General Relativity. The key ingredient of the theories we consider is a noncanonical, minimally coupled scalar field belonging to the class of theories with Kinetic Gravity Braiding / Galileon-like self-couplings. In these models, the universe smoothly evolves from contraction to expansion, suffering neither from ghosts nor gradient instabilities around the turning point. The end-point of the evolution can be a standard radiation-domination era or an inflationary phase. We formulate necessary restrictions for Lagrangians needed to obtain a healthy bounce and illustrate our results with phase portraits for simple systems including the recently proposed Galilean Genesis scenario.", "keyphrases": ["bounce", "scalar field", "contraction", "gradient instability", "cosmology"]}
{"id": "1007.2654", "title": "A Matter Bounce By Means of Ghost Condensation", "abstract": "Assuming the existence of a scalar field which undergoes \"ghost condensation\" and which has a suitably chosen potential, it is possible to obtain a non-singular bouncing cosmology in the presence of regular matter and radiation. The potential for the ghost condensate field can be chosen such that the cosmological bounce is stable against the presence of anisotropic stress. Cosmological fluctuations on long wavelengths relevant to current cosmological observations pass through the bounce unaffected by the new physics which yields the bounce. Thus, this model allows for the realization of the \"matter bounce\" scenario, an alternative to inflationary cosmology for the generation of the observed primordial fluctuations in which the inhomogeneities originate as quantum vacuum perturbations which exit the Hubble radius in the matter-dominated phase of contraction.", "keyphrases": ["bounce", "ghost condensation", "scalar field"]}
{"id": "1203.4663", "title": "Observable Spectra of Induced Gravitational Waves from Inflation", "abstract": "Measuring the primordial power spectrum on small scales is a powerful tool in inflation model building, yet constraints from Cosmic Microwave Background measurements alone are insufficient to place bounds stringent enough to be appreciably effective. For the very small scale spectrum, those which subtend angles of less than 0.3 degrees on the sky, an upper bound can be extracted from the astrophysical constraints on the possible production of primordial black holes in the early universe. A recently discovered observational by-product of an enhanced power spectrum on small scales, induced gravitational waves, have been shown to be within the range of proposed space based gravitational wave detectors; such as NASA's LISA and BBO detectors, and the Japanese DECIGO detector. In this paper we explore the impact such a detection would have on models of inflation known to lead to an enhanced power spectrum on small scales, namely the Hilltop-type and running mass models. We find that the Hilltop-type model can produce observable induced gravitational waves within the range of BBO and DECIGO for integral and fractional powers of the potential within a reasonable number of e-folds. We also find that the running mass model can produce a spectrum within the range of these detectors, but require that inflation terminates after an unreasonably small number of e-folds. Finally, we argue that if the thermal history of the Universe were to accomodate such a small number of e-folds the Running Mass Model can produce Primordial Black Holes within a mass range compatible with Dark Matter, i.e. within a mass range 10^20g< M_BH<10^27g.", "keyphrases": ["power spectrum", "primordial black holes", "early universe", "scalar perturbation", "second-order gws"]}
{"id": "1712.01860", "title": "An 800-million-solar-mass black hole in a significantly neutral Universe at redshift 7.5", "abstract": "Quasars are the most luminous non-transient objects known and as a result they enable studies of the Universe at the earliest cosmic epochs. Despite extensive efforts, however, the quasar ULAS J1120+0641 at z=7.09 has remained the only one known at z>7 for more than half a decade. Here we report observations of the quasar ULAS J134208.10+092838.61 (hereafter J1342+0928) at redshift z=7.54. This quasar has a bolometric luminosity of 4e13 times the luminosity of the Sun and a black hole mass of 8e8 solar masses. The existence of this supermassive black hole when the Universe was only 690 million years old\u2014just five percent of its current age\u2014reinforces models of early black-hole growth that allow black holes with initial masses of more than about 1e4 solar masses or episodic hyper-Eddington accretion. We see strong evidence of absorption of the spectrum of the quasar redwards of the Lyman alpha emission line (the Gunn-Peterson damping wing), as would be expected if a significant amount (more than 10 per cent) of the hydrogen in the intergalactic medium surrounding J1342+0928 is neutral. We derive a significant fraction of neutral hydrogen, although the exact fraction depends on the modelling. However, even in our most conservative analysis we find a fraction of more than 0.33 (0.11) at 68 per cent (95 per cent) probability, indicating that we are probing well within the reionization epoch of the Universe.", "keyphrases": ["black hole", "solar masse", "high redshift"]}
{"id": "1311.2603", "title": "Short-Duration Gamma-Ray Bursts", "abstract": "Gamma-ray bursts (GRBs) display a bimodal duration distribution, with a separation between the short- and long-duration bursts at about 2 sec. The progenitors of long GRBs have been identified as massive stars based on their association with Type Ic core-collapse supernovae, their exclusive location in star-forming galaxies, and their strong correlation with bright ultraviolet regions within their host galaxies. Short GRBs have long been suspected on theoretical grounds to arise from compact object binary mergers (NS-NS or NS-BH). The discovery of short GRB afterglows in 2005, provided the first insight into their energy scale and environments, established a cosmological origin, a mix of host galaxy types, and an absence of associated supernovae. In this review I summarize nearly a decade of short GRB afterglow and host galaxy observations, and use this information to shed light on the nature and properties of their progenitors, the energy scale and collimation of the relativistic outflow, and the properties of the circumburst environments. The preponderance of the evidence points to compact object binary progenitors, although some open questions remain. Based on this association, observations of short GRBs and their afterglows can shed light on the on- and off-axis electromagnetic counterparts of gravitational wave sources from the Advanced LIGO/Virgo experiments.", "keyphrases": ["gamma-ray burst", "galaxy", "short grb", "binary merger", "neutron star"]}
{"id": "1407.8053", "title": "The expected anisotropy in solid inflation", "abstract": "Solid inflation is an effective field theory of inflation in which isotropy and homogeneity are accomplished via a specific combination of anisotropic sources (three scalar fields that individually break isotropy). This results in specific observational signatures that are not found in standard models of inflation: a non-trivial angular dependence for the squeezed bispectrum, and a possibly long period of anisotropic inflation (to drive inflation, the \"solid\" must be very insensitive to any deformation, and thus background anisotropies are very slowly erased). In this paper we compute the expected level of statistical anisotropy in the power spectrum of the curvature perturbations of this model. To do so, we account for the classical background values of the three scalar fields that are generated on large (superhorizon) scales during inflation via a random walk sum, as the perturbation modes leave the horizon. Such an anisotropy is unavoidably generated, even starting from perfectly isotropic classical initial conditions. The expected level of anisotropy is related to the duration of inflation and to the amplitude of the squeezed bispectrum. If this amplitude is close to its current observational limit (so that one of the most interesting predictions of the model can be observed in the near future), we find that a level of statistical anisotropy \u2273 3% in the power spectrum is to be expected, if inflation lasted \u2273 20-30 e-folds more than the final 50-60 efolds required to generare the CMB modes. We also comment and point out various similarities between solid inflation and models of inflation where a suitable coupling of the inflaton to a vector kinetic term F^2 gives frozen and scale invariant vector perturbations on superhorizon scales.", "keyphrases": ["solid inflation", "bispectrum", "curvature perturbation"]}
{"id": "1302.6620", "title": "Galaxies in X-ray Groups. III. Satellite Color and Morphology Transformations", "abstract": "While the star formation rates and morphologies of galaxies have long been known to correlate with their local environment, the process by which these correlations are generated is not well understood. Galaxy groups are thought to play an important role in shaping the physical properties of galaxies before entering massive clusters at low redshift, and transformations of satellite galaxies likely dominate the buildup of local environmental correlations. To illuminate the physical processes that shape galaxy evolution in dense environments, we study a sample of 116 X-ray selected galaxy groups at z=0.2-1 with halo masses of 10^13-10^14 M_sun and centroids determined with weak lensing. We analyze morphologies based on HST imaging and colors determined from 31 photometric bands for a stellar mass-limited population of 923 satellite galaxies and a comparison sample of 16644 field galaxies. Controlling for variations in stellar mass across environments, we find significant trends in the colors and morphologies of satellite galaxies with group-centric distance and across cosmic time. Specifically at low stellar mass (log(M_stellar/M_sun) = 9.8-10.3), the fraction of disk-dominated star-forming galaxies declines from >50 the centers of groups. This decline is accompanied by a rise in quenched galaxies with intermediate bulge+disk morphologies, and only a weak increase in red bulge-dominated systems. These results show that both color and morphology are influenced by a galaxy's location within a group halo. We suggest that strangulation and disk fading alone are insufficient to explain the observed morphological dependence on environment, and that galaxy mergers or close tidal encounters must play a role in building up the population of quenched galaxies with bulges seen in dense environments at low redshift.", "keyphrases": ["x-ray", "close tidal encounter", "galaxy"]}
{"id": "1004.0890", "title": "Gravitational-Wave Stochastic Background from Kinks and Cusps on Cosmic Strings", "abstract": "We compute the contribution of kinks on cosmic string loops to stochastic background of gravitational waves (SBGW).We find that kinks contribute at the same order as cusps to the SBGW.We discuss the accessibility of the total background due to kinks as well as cusps to current and planned gravitational wave detectors, as well as to the big bang nucleosynthesis (BBN), the cosmic microwave background (CMB), and pulsar timing constraints. As in the case of cusps, we find that current data from interferometric gravitational wave detectors, such as LIGO, are sensitive to areas of parameter space of cosmic string models complementary to those accessible to pulsar, BBN, and CMB bounds.", "keyphrases": ["stochastic background", "cosmic string", "pulsar", "gravity wave"]}
{"id": "1305.3510", "title": "The Nuclear Equation of State and Neutron Star Masses", "abstract": "Neutron stars are valuable laboratories for the study of dense matter. Recent observations have uncovered both massive and low-mass neutron stars and have also set constraints on neutron star radii. The largest mass measurements are powerfully influencing the high-density equation of state because of the existence of the neutron star maximum mass. The smallest mass measurements, and the distributions of masses, have implications for the progenitors and formation mechanisms of neutron stars. The ensemble of mass and radius observations can realistically restrict the properties of dense matter, and, in particular, the behavior of the nuclear symmetry energy near the nuclear saturation density. Simultaneously, various nuclear experiments are progressively restricting the ranges of parameters describing the symmetry properties of the nuclear equation of state. In addition, new theoretical studies of pure neutron matter are providing insights. These observational, experimental and theoretical constraints of dense matter, when combined, are now revealing a remarkable convergence.", "keyphrases": ["nuclear equation", "neutron star", "small spin", "black hole"]}
{"id": "1010.2724", "title": "Emergent Flux from Particle Collisions Near a Kerr Black Hole", "abstract": "The escape fraction at infinity is evaluated for massless particles produced in collisions of weakly interacting particles accreted into a density spike near the particle horizon of an extremal Kerr black hole, for the case of equatorial orbits. We compare with the Schwarzschild case, and argue that in the case of extremal black holes, redshifted signatures can be produced that could potentially explore the physics of particle collisions at centre of mass energies that extend beyond those of any feasible terrestrial accelerator.", "keyphrases": ["particle collision", "black hole", "escape fraction", "emergent flux", "dark matter particle"]}
{"id": "1412.7536", "title": "A Millisecond Interferometric Search for Fast Radio Bursts with the Very Large Array", "abstract": "We report on the first millisecond timescale radio interferometric search for the new class of transient known as fast radio bursts (FRBs). We used the Very Large Array (VLA) for a 166-hour, millisecond imaging campaign to detect and precisely localize an FRB. We observed at 1.4 GHz and produced visibilities with 5 ms time resolution over 256 MHz of bandwidth. Dedispersed images were searched for transients with dispersion measures from 0 to 3000 pc/cm3. No transients were detected in observations of high Galactic latitude fields taken from September 2013 though October 2014. Observations of a known pulsar show that images typically had a thermal-noise limited sensitivity of 120 mJy/beam (8 sigma; Stokes I) in 5 ms and could detect and localize transients over a wide field of view. Our nondetection limits the FRB rate to less than 7e4/sky/day (95 Euclidean flux distribution, the VLA rate limit is inconsistent with the published rate of Thornton et al. We recalculate previously published rates with a homogeneous consideration of the effects of primary beam attenuation, dispersion, pulse width, and sky brightness. This revises the FRB rate downward and shows that the VLA observations had a roughly 60 typical FRB and that a 95 hours of similar VLA observing. Our survey also limits the repetition rate of an FRB to 2 times less than any known repeating millisecond radio transient.", "keyphrases": ["interferometric search", "large array", "time resolution"]}
{"id": "1509.07521", "title": "Scale-dependent gravitational waves from a rolling axion", "abstract": "We consider a model in which a pseudo-scalar field \u03c3 rolls for some e-folds during inflation, sourcing one helicity of a gauge field. These fields are only gravitationally coupled to the inflaton, and therefore produce scalar and tensor primordial perturbations only through gravitational interactions. These sourced signals are localized on modes that exit the horizon while the roll of \u03c3 is significant. We focus our study on cases in which the model can simultaneously produce (i) a large gravitational wave signal, resulting in observable B-modes of the CMB polarizations, and (ii) sufficiently small scalar perturbations, so to be in agreement with the current limits from temperature anisotropies. Different choice of parameters can instead lead to a localized and visible departure from gaussianity in the scalar sector, either at CMB or LSS scales.", "keyphrases": ["gravitational wave", "axion", "b-modes", "vacuum fluctuation"]}
{"id": "1406.4827", "title": "Primordial power spectrum from Planck", "abstract": "Using modified Richardson-Lucy algorithm we reconstruct the primordial power spectrum (PPS) from Planck Cosmic Microwave Background (CMB) temperature anisotropy data. In our analysis we use different combinations of angular power spectra from Planck to reconstruct the shape of the primordial power spectrum and locate possible features. Performing an extensive error analysis we found the dip near \u2113\u223c750-850 represents the most prominent feature in the data. Feature near \u2113\u223c1800-2000 is detectable with high confidence only in 217 GHz spectrum and is apparently consequence of a small systematic as described in the revised Planck 2013 papers. Fixing the background cosmological parameters and the foreground nuisance parameters to their best fit baseline values, we report that the best fit power law primordial power spectrum is consistent with the reconstructed form of the PPS at 2\u03c3 C.L. of the estimated errors (apart from the local features mentioned above). As a consistency test, we found the reconstructed primordial power spectrum from Planck temperature data can also substantially improve the fit to WMAP-9 angular power spectrum data (with respect to power-law form of the PPS) allowing an overall amplitude shift of \u223c2.5%. In this context low-\u2113 and 100 GHz spectrum from Planck which have proper overlap in the multipole range with WMAP data found to be completely consistent with WMAP-9 (allowing amplitude shift). As another important result of our analysis we do report the evidence of gravitational lensing through the reconstruction analysis. Finally we present two smooth form of the PPS containing only the important features. These smooth forms of PPS can provide significant improvements in fitting the data (with respect to the power law PPS) and can be helpful to give hints for inflationary model building.", "keyphrases": ["planck", "pps", "fit", "primordial power", "wavenumber"]}
{"id": "1509.02171", "title": "Tidal Love numbers of a slowly spinning neutron star", "abstract": "By extending our recent framework to describe the tidal deformations of a spinning compact object, we compute for the first time the tidal Love numbers of a spinning neutron star to linear order in the angular momentum. The spin of the object introduces couplings between electric and magnetic distortions and new classes of spin-induced (\"rotational\") tidal Love numbers emerge. We focus on stationary tidal fields, which induce axisymmetric perturbations. We present the perturbation equations for both electric-led and magnetic-led rotational Love numbers for generic multipoles and explicitly solve them for various tabulated equations of state and for a tidal field with an electric (even parity) and magnetic (odd parity) component with \u2113=2,3,4. For a binary system close to the merger, various components of the tidal field become relevant. In this case we find that an octupolar magnetic tidal field can significantly modify the mass quadrupole moment of a neutron star. Preliminary estimates, assuming a spin parameter \u03c7\u22480.05, show modifications \u227310% relative to the static case, at an orbital distance of five stellar radii. Furthermore, the rotational Love numbers as functions of the moment of inertia are much more sensitive to the equation of state than in the static case, where approximate universal relations at the percent level exist. For a neutron-star binary approaching the merger, we estimate that the approximate universality of the induced mass quadrupole moment deteriorates from 1% in the static case to roughly 6% when \u03c7\u22480.05. Our results suggest that spin-tidal couplings can introduce important corrections to the gravitational waveforms of spinning neutron-star binaries approaching the merger.", "keyphrases": ["neutron star", "angular momentum", "spin-tidal coupling", "tidal love number"]}
{"id": "1112.3286", "title": "Hairy Black Holes and Null Circular Geodesics", "abstract": "Einstein-matter theories in which hairy black-hole configurations have been found are studied. We prove that the nontrivial behavior of the hair must extend beyond the null circular orbit (the photonsphere) of the corresponding spacetime. We further conjecture that the region above the photonsphere contains at least 50 analytical and numerical results.", "keyphrases": ["hairy black-hole configuration", "hair", "spacetime", "conjecture", "effective length"]}
{"id": "1903.11433", "title": "General Cosmography Model with Spatial Curvature", "abstract": "The cosmographic approach is adopted to determine the spatial curvature (i.e., \u03a9_K) combining the latest released cosmic chronometers data (CC), the Pantheon sample of type Ia supernovae observations, and the baryon acoustic oscillation measurements. We use the expanded transverse comoving distance D_M(z) as a basic function for deriving H(z) and the other cosmic distances. In this scenario, \u03a9_K can be constrained only by CC data. To overcome the convergence issues at high-redshift domains, two methods are applied: the Pad\u00e9 approximants and the Taylor series in terms of the new redshift y=z/(1+z). Adopting the Bayesian evidence, we find that there is positive evidence for the Pad\u00e9 approximant up to order (2,2) and weak evidence for the Taylor series up to 3-rd order against \u039bCDM+\u03a9_K model. The constraint results show that a closed universe is preferred by the present observations under all the approximants used in this study. And the tension level of the Hubble constant H_0 is less than 2\u03c3 significance between different approximants and the local distance ladder determination. For each assumed approximant, H_0 is anti-correlated with \u03a9_K and the sound horizon at the end of the radiation drag epoch, which indicates that the H_0 tension problem can be slightly relaxed by introducing \u03a9_K or any new physics which can reduce the sound horizon in the early universe.", "keyphrases": ["spatial curvature", "cosmographic approach", "universe"]}
{"id": "1401.2461", "title": "Antihelium from Dark Matter", "abstract": "Cosmic-ray anti-nuclei provide a promising discovery channel for the indirect detection of particle dark matter. Hadron showers produced by the pair-annihilation or decay of Galactic dark matter generate anti-nucleons which can in turn form light anti-nuclei. Previous studies have only focused on the spectrum and flux of low energy antideuterons which, although very rarely, are occasionally also produced by cosmic-ray spallation. Heavier elements (A\u22653) have instead entirely negligible astrophysical background and a primary yield from dark matter which could be detectable by future experiments. Using a Monte Carlo event generator and an event-by-event phase space analysis, we compute, for the first time, the production spectrum of and for dark matter annihilating or decaying to bb\u0305 and W^+W^- final states. We then employ a semi-analytic model of interstellar and heliospheric propagation to calculate the flux as well as to provide tools to relate the anti-helium spectrum corresponding to an arbitrary antideuteron spectrum. Finally, we discuss prospects for current and future experiments, including GAPS and AMS-02.", "keyphrases": ["dark matter", "decay", "astrophysical background", "antihelium nucleus"]}
{"id": "1308.2317", "title": "Reconstruction of the primordial power spectrum of curvature perturbations using multiple data sets", "abstract": "Detailed knowledge of the primordial power spectrum of curvature perturbations is essential both in order to elucidate the physical mechanism (`inflation') which generated it, and for estimating the cosmological parameters from observations of the cosmic microwave background and large-scale structure. Hence it ought to be extracted from such data in a model-independent manner, however this is difficult because relevant cosmological observables are given by a convolution of the primordial perturbations with some smoothing kernel which depends on both the assumed world model and the matter content of the universe. Moreover the deconvolution problem is ill-conditioned so a regularisation scheme must be employed to control error propagation. We demonstrate that `Tikhonov regularisation' can robustly reconstruct the primordial spectrum from multiple cosmological data sets, a significant advantage being that both its uncertainty and resolution are then quantified. Using Monte Carlo simulations we investigate several regularisation parameter selection methods and find that generalised cross-validation and Mallow's C_p method give optimal results. We apply our inversion procedure to data from the Wilkinson Microwave Anisotropy Probe, other ground-based small angular scale CMB experiments, and the Sloan Digital Sky Survey. The reconstructed spectrum (assuming the standard \u039bCDM cosmology) is not scale-free but has an infrared cutoff at k \u2272 5 \u00d7 10^-4 Mpc^-1 (due to the anomalously low CMB quadrupole) and several features with \u223c 2 \u03c3 significance at k/Mpc^-1\u223c 0.0013\u20130.0025, 0.0362\u20130.0402 and 0.051\u20130.056, reflecting the `WMAP glitches'. To test whether these are indeed real will require more accurate data, such as from the Planck satellite and new ground-based experiments.", "keyphrases": ["primordial power spectrum", "curvature perturbation", "cosmological data set", "reconstructed spectrum"]}
{"id": "1312.3293", "title": "Searching for primordial non-Gaussianity in Planck CMB maps using a combined estimator", "abstract": "The extensive search for deviations from Gaussianity in cosmic microwave background radiation (CMB) data is very important due to the information about the very early moments of the universe encoded there. Recent analyses from Planck CMB data do not exclude the presence of non-Gaussianity of small amplitude, although they are consistent with the Gaussian hypothesis. The use of different techniques is essential to provide information about types and amplitudes of non-Gaussianities in the CMB data. In particular, we find interesting to construct an estimator based upon the combination of two powerful statistical tools that appears to be sensitive enough to detect tiny deviations from Gaussianity in CMB maps. This estimator combines the Minkowski functionals with a Neural Network, maximizing a tool widely used to study non-Gaussian signals with a reinforcement of another tool designed to identify patterns in a data set. We test our estimator by analyzing simulated CMB maps contaminated with different amounts of local primordial non-Gaussianity quantified by the dimensionless parameter fNL. We apply it to these sets of CMB maps and find \u227398 intensity local non-Gaussianity like fNL = 38 +/- 18, the current limit from Planck data for large angular scales. Additionally, we test the suitability to distinguish between primary and secondary non-Gaussianities and find out that our method successfully classifies 95 analyze the foreground-cleaned Planck maps obtaining constraints for non-Gaussianity at large-angles that are in good agreement with recent constraints. Finally, we also test the robustness of our estimator including cut-sky masks and realistic noise maps measured by Planck, obtaining successful results as well.", "keyphrases": ["primordial non-gaussianity", "cmb map", "estimator", "microwave background radiation"]}
{"id": "1309.3557", "title": "Single-Field Consistency Relations of Large Scale Structure", "abstract": "We derive consistency relations for the late universe (CDM and \u039bCDM): relations between an n-point function of the density contrast \u03b4and an (n+1)-point function in the limit in which one of the (n+1) momenta becomes much smaller than the others. These are based on the observation that a long mode, in single-field models of inflation, reduces to a diffeomorphism since its freezing during inflation all the way until the late universe, even when the long mode is inside the horizon (but out of the sound horizon). These results are derived in Newtonian gauge, at first and second order in the small momentum q of the long mode and they are valid non-perturbatively in the short-scale \u03b4. In the non-relativistic limit our results match with (Kehagias and Riotto '13) and (Peloso and Pietroni '13). These relations are a consequence of diffeomorphism invariance; they are not satisfied in the presence of extra degrees of freedom during inflation or violation of the Equivalence Principle (extra forces) in the late universe.", "keyphrases": ["large scale structure", "long mode", "single-field model", "non-relativistic limit", "diffeomorphism invariance"]}
{"id": "1206.2727", "title": "Accreting Millisecond X-Ray Pulsars", "abstract": "Accreting Millisecond X-Ray Pulsars (AMXPs) are astrophysical laboratories without parallel in the study of extreme physics. In this chapter we review the past fifteen years of discoveries in the field. We summarize the observations of the fifteen known AMXPs, with a particular emphasis on the multi-wavelength observations that have been carried out since the discovery of the first AMXP in 1998. We review accretion torque theory, the pulse formation process, and how AMXP observations have changed our view on the interaction of plasma and magnetic fields in strong gravity. We also explain how the AMXPs have deepened our understanding of the thermonuclear burst process, in particular the phenomenon of burst oscillations. We conclude with a discussion of the open problems that remain to be addressed in the future.", "keyphrases": ["millisecond x-ray pulsars", "accretion", "neutron star"]}
{"id": "1210.0872", "title": "Constraints on Dark Matter Annihilation in Clusters of Galaxies from Diffuse Radio Emission", "abstract": "Annihilation of dark matter can result in the production of stable Standard Model particles including electrons and positrons that, in the presence of magnetic fields, lose energy via synchrotron radiation, observable as radio emission. Galaxy clusters are excellent targets to search for or to constrain the rate of dark matter annihilation, as they are both massive and dark matter dominated. In this study, we place limits on dark matter annihilation in a sample of nearby clusters using upper limits on the diffuse radio emission, low levels of observed diffuse emission, or detections of radio mini-haloes. We find that the strongest limits on the annihilation cross section are better than limits derived from the non-detection of clusters in the gamma-ray band by a factor of approximately 3 or more when the same annihilation channel and subtructure model, but different best-case clusters, are compared. The limits on the cross section depend on the assumed amount of substructure, varying by as much as 2 orders of magnitude for increasingly optimistic substructure models as compared to a smooth NFW profile. In our most optimistic case, using the results of the Phoenix Project (Gao et al. 2012b) we find that the derived limits reach below the thermal relic cross section of 3x10^-26 cm^3 s^-1 for dark matter masses as large as 400 GeV, for the bbar annihilation channel. We discuss uncertainties due to the limited available data on the magnetic field structure of individual clusters. We also report the discovery of diffuse radio emission from the central 30-40 kpc regions of the groups M49 and NGC4636.", "keyphrases": ["dark matter annihilation", "diffuse radio emission", "galaxy cluster"]}
{"id": "1608.06530", "title": "X-ray Pulsars", "abstract": "X-ray pulsars shine thanks to the conversion of the gravitational energy of accreted material to X-ray radiation. The accretion rate is modulated by geometrical and hydrodynamical effects in the stellar wind of the pulsar companions and/or by instabilities in accretion discs. Wind driven flows are highly unstable close to neutron stars and responsible for X-ray variability by factors 10^3 on time scale of hours. Disk driven flows feature slower state transitions and quasi periodic oscillations related to orbital motion and precession or resonance. On shorter time scales, and closer to the surface of the neutron star, X-ray variability is dominated by the interactions of the accreting flow with the spinning magnetosphere. When the pulsar magnetic field is large, the flow is confined in a relatively narrow accretion column, whose geometrical properties drive the observed X-ray emission. In low magnetized systems, an increasing accretion rate allows the ignition of powerful explosive thermonuclear burning at the neutron star surface. Transitions from rotation- to accretion-powered activity has been observed in rare cases and proved the link between these classes of pulsars.", "keyphrases": ["neutron star", "x-ray pulsar", "low-mass white dwarf", "companion star"]}
{"id": "1903.05924", "title": "Prospective constraints on the primordial black hole abundance from the stochastic gravitational-wave backgrounds produced by coalescing events and curvature perturbations", "abstract": "For a variety of on-going and planned gravitational-wave (GW) experiments, we study expected constraints on the fraction (f_ PBH) of primordial black holes (PBHs) in dark matter by evaluating the energy-density spectra of two kinds of stochastic GW backgrounds. The first one is produced from an incoherent superposition of GWs emitted from coalescences of all the binary PBHs. The second one is induced through non-linear mode couplings of large primordial curvature perturbations inevitably associated with the generation of PBHs in the early Universe. In this paper, we focus on the PBHs with their masses of 10^-8M_\u2299\u2264 M_PBH < 1M_\u2299, since they are not expected to be of a stellar origin. In almost all ranges of the masses, we show that the experiments are sensitive to constrain the fraction for 10^-5\u2272 f_ PBH\u2272 1 by considering the GWs from coalescing events and 10^-13\u2272 f_ PBH\u2272 1 by considering the GWs from curvature perturbations. Exceptionally, only in a narrow range of masses for M_PBH\u2243 10^-7 M_\u2299, the fraction cannot be constrained for f_ PBH\u2272 10^-13 by those two GW backgrounds.", "keyphrases": ["primordial black hole", "early universe", "gravitational wave", "pbh mass function"]}
{"id": "1502.04028", "title": "Neutrinos in the holographic dark energy model: constraints from latest measurements of expansion history and growth of structure", "abstract": "The model of holographic dark energy (HDE) with massive neutrinos and/or dark radiation is investigated in detail. The background and perturbation evolutions in the HDE model are calculated. We employ the PPF approach to overcome the gravity instability difficulty (perturbation divergence of dark energy) led by the equation-of-state parameter w evolving across the phantom divide w=-1 in the HDE model with c<1. We thus derive the evolutions of density perturbations of various components and metric fluctuations in the HDE model. The impacts of massive neutrino and dark radiation on the CMB anisotropy power spectrum and the matter power spectrum in the HDE scenario are discussed. Furthermore, we constrain the models of HDE with massive neutrinos and/or dark radiation by using the latest measurements of expansion history and growth of structure, including the Planck CMB temperature data, the baryon acoustic oscillation data, the JLA supernova data, the Hubble constant direct measurement, the cosmic shear data of weak lensing, the Planck CMB lensing data, and the redshift space distortions data. We find that \u2211 m_\u03bd<0.186 eV (95% CL) and N_ eff=3.75^+0.28_-0.32 in the HDE model from the constraints of these data.", "keyphrases": ["holographic dark energy", "dark energy model", "neutrino mass", "cosmology"]}
{"id": "1510.05223", "title": "The IceCube Neutrino Observatory - Contributions to ICRC 2015 Part II: Atmospheric and Astrophysical Diffuse Neutrino Searches of All Flavors", "abstract": "Papers on atmospheric and astrophysical diffuse neutrino searches of all flavors submitted to the 34th International Cosmic Ray Conference (ICRC 2015, The Hague) by the IceCube Collaboration.", "keyphrases": ["icecube neutrino observatory", "atmospheric background", "ultra-high energy"]}
{"id": "1006.3944", "title": "Dynamically avoiding fine-tuning the cosmological constant: the \"Relaxed Universe\"", "abstract": "We demonstrate that there exists a large class of action functionals of the scalar curvature and of the Gauss-Bonnet invariant which are able to relax dynamically a large cosmological constant (CC), whatever it be its starting value in the early universe. Hence, it is possible to understand, without fine-tuning, the very small current value of the CC as compared to its theoretically expected large value in quantum field theory and string theory. In our framework, this relaxation appears as a pure gravitational effect, where no ad hoc scalar fields are needed. The action involves a positive power of a characteristic mass parameter, M, whose value can be, interestingly enough, of the order of a typical particle physics mass of the Standard Model of the strong and electroweak interactions or extensions thereof, including the neutrino mass. The model universe emerging from this scenario (the \"Relaxed Universe\") falls within the class of the so-called LXCDM models of the cosmic evolution. Therefore, there is a \"cosmon\" entity X (represented by an effective object, not a field), which in this case is generated by the effective functional and is responsible for the dynamical adjustment of the cosmological constant. This model universe successfully mimics the essential past epochs of the standard (or \"concordance\") cosmological model (LCDM). Furthermore, it provides interesting clues to the coincidence problem and it may even connect naturally with primordial inflation.", "keyphrases": ["universe", "dynamical adjustment", "relaxation mechanism"]}
{"id": "1401.5473", "title": "Ultra Low Surface Brightness Imaging with the Dragonfly Telephoto Array", "abstract": "We describe the Dragonfly Telephoto Array, a robotic imaging system optimized for the detection of extended ultra low surface brightness structures. The array consists of eight Canon 400mm f/2.8 telephoto lenses coupled to eight science-grade commercial CCD cameras. The lenses are mounted on a common framework and are co-aligned to image simultaneously the same position on the sky. The system provides an imaging capability equivalent to a 0.4m aperture f/1.0 refractor with a 2.6 deg X 1.9 deg field of view. The system has no obstructions in the light path, optimized baffling, and internal optical surfaces coated with a new generation of anti-reflection coatings based on sub-wavelength nanostructures. As a result, the array's point spread function has a factor of 10 less scattered light at large radii than well-baffled reflecting telescopes. The Dragonfly Telephoto Array is capable of imaging extended structures to surface brightness levels below 30 mag/arcsec^2 in 10h integrations (without binning or foreground star removal). This is considerably deeper than the surface brightness limit of any existing wide-field telescope. At present no systematic errors limiting the usefulness of much longer integration times has been identified. With longer integrations (50-100h), foreground star removal and modest binning the Dragonfly Telephoto Array is capable of probing structures with surface brightnesses below 32 mag/arcsec^2. Detection of structures at these surface brightness levels may hold the key to solving the \"missing substructure\" and \"missing satellite\" problems of conventional hierarchical galaxy formation models. The Dragonfly Telephoto Array is therefore executing a fully-automated multi-year imaging survey of a complete sample of nearby galaxies in order to undertake the first census of ultra-faint substructures in the nearby Universe.", "keyphrases": ["surface brightness", "dragonfly telephoto array", "imaging system", "telescope"]}
{"id": "1107.5617", "title": "Primordial Non-Gaussianity and Extreme-Value Statistics of Galaxy Clusters", "abstract": "What is the size of the most massive object one expects to find in a survey of a given volume? In this paper, we present a solution to this problem using Extreme-Value Statistics, taking into account primordial non-Gaussianity and its effects on the abundance and the clustering of rare objects. We calculate the probability density function (pdf) of extreme-mass clusters in a survey volume, and show how primordial non-Gaussianity shifts the peak of this pdf. We also study the sensitivity of the extreme-value pdfs to changes in the mass functions, survey volume, redshift coverage and the normalization of the matter power spectrum, \u03c3_8. For 'local' non-Gaussianity parametrized by f_NL, our correction for the extreme-value pdf due to the bias is important when f_NL > O(100), and becomes more significant for wider and deeper surveys. Applying our formalism to the massive high-redshift cluster XMMUJ0044.0-2-33, we find that its existence is consistent with f_NL = 0, although the conclusion is sensitive to the assumed values of the survey area and \u03c3_8. We also discuss the convergence of the extreme-value distribution to one of the three possible asymptotic forms, and argue that the convergence is insensitive to the presence of non-Gaussianity.", "keyphrases": ["extreme-value statistics", "cluster", "primordial non-gaussianity"]}
{"id": "1008.0395", "title": "Fitting the integrated Spectral Energy Distributions of Galaxies", "abstract": "Fitting the spectral energy distributions (SEDs) of galaxies is an almost universally used technique that has matured significantly in the last decade. Model predictions and fitting procedures have improved significantly over this time, attempting to keep up with the vastly increased volume and quality of available data. We review here the field of SED fitting, describing the modelling of ultraviolet to infrared galaxy SEDs, the creation of multiwavelength data sets, and the methods used to fit model SEDs to observed galaxy data sets. We touch upon the achievements and challenges in the major ingredients of SED fitting, with a special emphasis on describing the interplay between the quality of the available data, the quality of the available models, and the best fitting technique to use in order to obtain a realistic measurement as well as realistic uncertainties. We conclude that SED fitting can be used effectively to derive a range of physical properties of galaxies, such as redshift, stellar masses, star formation rates, dust masses, and metallicities, with care taken not to over-interpret the available data. Yet there still exist many issues such as estimating the age of the oldest stars in a galaxy, finer details ofdust properties and dust-star geometry, and the influences of poorly understood, luminous stellar types and phases. The challenge for the coming years will be to improve both the models and the observational data sets to resolve these uncertainties. The present review will be made available on an interactive, moderated web page (sedfitting.org), where the community can access and change the text. The intention is to expand the text and keep it up to date over the coming years.", "keyphrases": ["spectral energy distribution", "galaxy", "sed", "challenge"]}
{"id": "1110.3099", "title": "Primordial Fluctuations within Teleparallelism", "abstract": "We study the cosmological perturbations for the possible inflation scenario in the teleparallel equivalence of general relativity specified with parallelizable topological conditions. By acquiring the identical physical observables to general relativity under the teleparallel formalism, we perform a 3+1 decomposition of the vierbein field, which can be interpreted as the time gauge fixing between coordinate and tangent frames. We also extend our discussion to the higher-order action, f(T) gravity.", "keyphrases": ["gravity", "cosmological implication", "tegr"]}
{"id": "1802.03709", "title": "Considerations for a Multi-beam Multi-purpose Survey with FAST", "abstract": "Having achieved 'first-light' right before the opening ceremony on September 25, 2016, the Five-hundred-meter Aperture Spherical radio Telescope (FAST) is being busily commissioned. Its innovative design requires 1000 points to be measured and driven instead of just the two axes of motion, e.g. Azimuth and Elevation for most of the conventional antennae, to realize pointing and tracking. We have devised a survey plan to utilized the full sensitivity of FAST, while minimizing the complexities in operation the system. The 19-beam L band focal plan array will be rotated to specific angles and taking continuous data streams while the surface shape and the focal cabin stay fixed. Such a survey will cover the northern sky in about 220 full days. Our aim is to obtain data for pulsar search, HI (neutral hydrogen) galaxies, HI imaging, and radio transients, simultaneously, through multiple backends. These data sets could be a significant contribution to all related fields in radio astronomy and remain relevant for decades.", "keyphrases": ["fast", "pulsar search", "radio astronomy"]}
{"id": "1805.12563", "title": "Flattened non-Gaussianities from the effective field theory of inflation with imaginary speed of sound", "abstract": "Inflationary perturbations in multi-field theories can exhibit a transient tachyonic instability as a consequence of their non-trivial motion in the internal field space. When an effective single-field description is applicable, the resulting theory is characterized by fluctuations that propagate with an imaginary speed of sound. We use the effective field theory of fluctuations to study such a set-up in a model-independent manner, highlighting the peculiarities and subtleties that make it different from the standard case. In particular, perturbations feature exponentially growing and decaying modes whose relative amplitude is undetermined within the effective field theory. Nevertheless, we prove that in an interesting limit the dimensionless bispectrum is in fact universal, depending only on the speed of sound and on the cutoff scale that limits the validity of the effective theory. Contrary to the power spectrum, we find that the bispectrum does not display an exponential enhancement. The amplitude of non-Gaussianities in the equilateral configuration is similar to the one of conventional models, but it is enhanced in flattened configurations in a way that is ultraviolet sensitive.", "keyphrases": ["effective field theory", "imaginary speed", "bispectrum", "non-gaussianitie"]}
{"id": "0912.4641", "title": "Evolution of linear cosmological perturbations and its observational implications in Galileon-type modified gravity", "abstract": "A scalar-tensor theory of gravity can be made not only to account for the current cosmic acceleration, but also to satisfy solar-system and laboratory constraints, by introducing a non-linear derivative interaction for the scalar field. Such an additional scalar degree of freedom is called \"Galileon\". The basic idea is inspired by the DGP braneworld, but one can construct a ghost-free model that admits a self-accelerating solution. We perform a fully relativistic analysis of linear perturbations in Galileon cosmology. Although the Galileon model can mimic the background evolution of standard \u039bCDM cosmology, the behavior of perturbation is quite different. It is shown that there exists a super-horizon growing mode in the metric and Galileon perturbations at early times, suggesting that the background is unstable. A fine-tuning of the initial condition for the Galileon fluctuation is thus required in order to promote a desirable evolution of perturbations at early times. Assuming the safe initial condition, we then compute the late-time evolution of perturbations and discuss observational implications in Galileon cosmology. In particular, we find anticorrelations in the cross-correlation of the integrated Sachs-Wolfe effect and large scale structure, similar to the normal branch of the DGP model.", "keyphrases": ["cosmology", "gravity", "matter density perturbation"]}
{"id": "1604.08308", "title": "Gravitational bending angle of light for finite distance and the Gauss-Bonnet theorem", "abstract": "We discuss a possible extension of calculations of the bending angle of light in a static, spherically symmetric and asymptotically flat spacetime to a non-asymptotically flat case. We examine a relation between the bending angle of light and the Gauss-Bonnet theorem by using the optical metric. A correspondence between the deflection angle of light and the surface integral of the Gaussian curvature may allow us to take account of the finite distance from a lens object to a light source and a receiver. Using this relation, we propose a method for calculating the bending angle of light for such cases. Finally, this method is applied to two examples of the non-asymptotically flat spacetimes to suggest finite-distance corrections: Kottler (Schwarzschild-de Sitter) solution to the Einstein equation and an exact solution in Weyl conformal gravity.", "keyphrases": ["theorem", "spacetime", "optical metric", "deflection angle", "spherical symmetry"]}
{"id": "1107.2308", "title": "Linearized flavor-stability analysis of dense neutrino streams", "abstract": "Neutrino-neutrino interactions in dense neutrino streams, like those emitted by a core-collapse supernova, can lead to self-induced neutrino flavor conversions. While this is a nonlinear phenomenon, the onset of these conversions can be examined through a standard stability analysis of the linearized equations of motion. The problem is reduced to a linear eigenvalue equation that involves the neutrino density, energy spectrum, angular distribution, and matter density. In the single-angle case, we reproduce previous results and use them to identify two generic instabilities: The system is stable above a cutoff density (\"cutoff mode\"), or can approach an asymptotic instability for increasing density (\"saturation mode\"). We analyze multi-angle effects on these generic types of instabilities and find that even the saturation mode is suppressed at large densities. For both types of modes, a given multi-angle spectrum typically is unstable when the neutrino and electron densities are comparable, but stable when the neutrino density is much smaller or much larger than the electron density. The role of an instability in the SN context depends on the available growth time and on the range of affected modes. At large matter density, most modes are off-resonance even when the system is unstable.", "keyphrases": ["dense neutrino stream", "neutrino-neutrino interaction", "flavor conversion"]}
{"id": "1004.4016", "title": "On Dark Matter, Spiral Galaxies, and the Axioms of General Relativity", "abstract": "Beginning with a geometric motivation for dark matter going back to the axioms of general relativity, we show how scalar field dark matter, which naturally forms dark matter density waves due to its wave nature, may cause the observed barred spiral pattern density waves in many disk galaxies and triaxial shapes with plausible brightness profiles in many elliptical galaxies. If correct, this would provide a unified explanation for spirals and bars in spiral galaxies and for the brightness profiles of elliptical galaxies. We compare the results of preliminary computer simulations with photos of actual galaxies.", "keyphrases": ["dark matter", "general relativity", "disk galaxy", "actual galaxy"]}
{"id": "1301.2424", "title": "Axially symmetric static sources: A general framework and some analytical solutions", "abstract": "We provide all basic equations and concepts required to carry out a general study on axially symmetric static sources. The Einstein equations and the conservation equations are written down for a general anisotropic static fluid endowed with axial symmetry. The structure scalars are calculated and the inhomogeneity factors are identified. Finally some exact analytical solutions were found. One of these solutions describes an incompressible spheroid with isotropic pressure and becomes the well known interior Schwarzschild solution in the spherically symmetric limit, however it cannot be matched smoothly to any Weyl exterior metric. Another family of solutions was found that corresponds to an anisotropic fluid distribution and can in principle be matched to a Weyl exterior.", "keyphrases": ["symmetric static source", "hydrostatic equilibrium equation", "symmetric spacetime"]}
{"id": "2002.00095", "title": "Variation of fundamental constants and white dwarfs", "abstract": "Theories that attempt to unify the four fundamental interactions and alternative theories of gravity predict time and/or spatial variation of the fundamental constants of nature. Different versions of these theories predict different behaviours for these variations. In consequence, experimental and observational bounds are an important tool to check the validity of such proposals. In this paper, we review constraints on the possible variation of the fundamental constants from astronomical observations and geophysical experiments designed to test the constancy of the fundamental constants of nature over different timescales. We also focus on the limits that can be obtained from white dwarfs, which can constrain the variation of the constants with the gravitational potential.", "keyphrases": ["fundamental constant", "white dwarf", "astronomical observation", "gravitational potential"]}
{"id": "1607.00027", "title": "Open clusters and associations in the Gaia era", "abstract": "Open clusters and associations are groups of young stars, respectively bound and unbound, that share the same origin and disperse over time into the galactic field. As such, their formation and evolution are the key to understand the origin and properties of galactic stellar populations. Moreover, since their members have about the same age, they are ideal laboratories to study the properties of young stars and constrain stellar evolution theories. In this contribution, I present our current knowledge on open clusters and associations. I focus on the methods used to derive the statistical properties (IMF, spatial distribution, IMF) of young stars and briefly discuss how they depend on the environment. I then describe how open clusters can be used as probes to investigate the structure, dynamics and chemical composition of the Milky Way. I conclude by presenting the Gaia mission and discuss how it will revolutionize this field of research.", "keyphrases": ["cluster", "star", "research"]}
{"id": "1712.05897", "title": "Recent searches for continuous gravitational waves", "abstract": "Gravitational wave astronomy opened dramatically in September 2015 with the LIGO discovery of a distant and massive binary black hole coalescence. The more recent discovery of a binary neutron star merger, followed by a gamma ray burst and a kilonova, reinforces the excitement of this new era, in which we may soon see other sources of gravitational waves, including continuous, nearly monochromatic signals. Potential continuous wave (CW) sources include rapidly spinning galactic neutron stars and more exotic possibilities, such as emission from axion Bose Einstein \"clouds\" surrounding black holes. Recent searches in Advanced LIGO data are presented, and prospects for more sensitive future searches discussed.", "keyphrases": ["gravitational wave", "neutron star", "recent search"]}
{"id": "1109.5932", "title": "An Observational Overview of Solar Flares", "abstract": "We present an overview of solar flares and associated phenomena, drawing upon a wide range of observational data primarily from the RHESSI era. Following an introductory discussion and overview of the status of observational capabilities, the article is split into topical sections which deal with different areas of flare phenomena (footpoints and ribbons, coronal sources, relationship to coronal mass ejections) and their interconnections. We also discuss flare soft X-ray spectroscopy and the energetics of the process. The emphasis is to describe the observations from multiple points of view, while bearing in mind the models that link them to each other and to theory. The present theoretical and observational understanding of solar flares is far from complete, so we conclude with a brief discussion of models, and a list of missing but important observations.", "keyphrases": ["solar flare", "coronal mass ejection", "atmosphere", "electromagnetic spectrum"]}
{"id": "1005.3493", "title": "How to Run Through Walls: Dynamics of Bubble and Soliton Collisions", "abstract": "It has recently been shown in high resolution numerical simulations that relativistic collisions of bubbles in the context of a multi-vacua potential may lead to the creation of bubbles in a new vacuum. In this paper, we show that scalar fields with only potential interactions behave like free fields during high-speed collisions; the kick received by them in a collision can be deduced simply by a linear superposition of the bubble wall profiles. This process is equivalent to the scattering of solitons in 1+1 dimensions. We deduce an expression for the field excursion (shortly after a collision), which is related simply to the field difference between the parent and bubble vacua, i.e. contrary to expectations, the excursion cannot be made arbitrarily large by raising the collision energy. There is however a minimum energy threshold for this excursion to be realized. We verify these predictions using a number of 3+1 and 1+1 numerical simulations. A rich phenomenology follows from these collision induced excursions - they provide a new mechanism for scanning the landscape, they might end/begin inflation, and they might constitute our very own big bang, leaving behind a potentially observable anisotropy.", "keyphrases": ["bubble", "numerical simulation", "classical transition"]}
{"id": "1705.07816", "title": "The Drake Equation as a Function of Spectral Type and Time", "abstract": "This chapter draws upon astronomical observations and modeling to constrain the prevalence of communicative civilizations in the galaxy. We discuss the dependence of the Drake equation parameters on the spectral type of the host star and the time since the galaxy formed, which allow us to examine trajectories for the emergence of communicative civilizations over the history of the galaxy. We suggest that the maximum lifetime of communicative civilizations depends on the spectral type of the host star, which implies that F- and G-dwarf stars are the best places to search for signs of technological intelligence today.", "keyphrases": ["spectral type", "drake equation parameter", "trajectory"]}
{"id": "1706.04191", "title": "On the time lags of the LIGO signals", "abstract": "To date, the LIGO collaboration has detected three gravitational wave (GW) events appearing in both its Hanford and Livingston detectors. In this article we reexamine the LIGO data with regard to correlations between the two detectors. With special focus on GW150914, we report correlations in the detector noise which, at the time of the event, happen to be maximized for the same time lag as that found for the event itself. Specifically, we analyze correlations in the calibration lines in the vicinity of 35 Hz as well as the residual noise in the data after subtraction of the best-fit theoretical templates. The residual noise for the other two events, GW151226 and GW170104, exhibits similar behavior. A clear distinction between signal and noise therefore remains to be established in order to determine the contribution of gravitational waves to the detected signals.", "keyphrases": ["time lag", "ligo data", "residual noise", "gw150914 signal"]}
{"id": "1306.1536", "title": "Limits on Neutrino-Neutrino Scattering in the Early Universe", "abstract": "In the standard model neutrinos are assumed to have streamed across the Universe since they last scattered at the weak decoupling epoch when the temperature of the standard-model plasma was MeV. The shear stress of free-streaming neutrinos imprints itself gravitationally on the Cosmic Microwave Background (CMB) and makes the CMB a sensitive probe of neutrino scattering. Yet, the presence of nonstandard physics in the neutrino sector may alter this standard chronology and delay neutrino free-streaming until a much later epoch. We use observations of the CMB to constrain the strength of neutrino self-interactions G_eff and put limits on new physics in the neutrino sector from the early Universe. Recent measurements of the CMB at large multipoles made by the Planck satellite and high-l experiments are critical for probing this physics. Within the context of conventional LambdaCDM parameters cosmological data are compatible with G_eff < 1/(56 MeV)^2 and neutrino free-streaming might be delayed until their temperature has cooled to as low as 25 eV. Intriguingly, we also find an alternative cosmology compatible with cosmological data in which neutrinos scatter off each other until z 10^4 with a preferred interaction strength in a narrow region around G_ eff\u2243 1/( 10 MeV)^2\u2243 8.6\u00d710^8 G_ F, where G_ F is the Fermi constant. This distinct self-interacting neutrino cosmology is characterized by somewhat lower values of both the scalar spectral index and the amplitude of primordial fluctuations. While we phrase our discussion here in terms of a specific scenario in which a late onset of neutrino free-streaming could occur, our constraints on the neutrino visibility function are very general.", "keyphrases": ["early universe", "self-interacting neutrino", "heavy scalar", "hidden dark sector"]}
{"id": "1805.00023", "title": "Planet Populations as a Function of Stellar Properties", "abstract": "Exoplanets around different types of stars provide a window into the diverse environments in which planets form. This chapter describes the observed relations between exoplanet populations and stellar properties and how they connect to planet formation in protoplanetary disks. Giant planets occur more frequently around more metal-rich and more massive stars. These findings support the core accretion theory of planet formation, in which the cores of giant planets form more rapidly in more metal-rich and more massive protoplanetary disks. Smaller planets, those with sizes roughly between Earth and Neptune, exhibit different scaling relations with stellar properties. These planets are found around stars with a wide range of metallicities and occur more frequently around lower mass stars. This indicates that planet formation takes place in a wide range of environments, yet it is not clear why planets form more efficiently around low mass stars. Going forward, exoplanet surveys targeting M dwarfs will characterize the exoplanet population around the lowest mass stars. In combination with ongoing stellar characterization, this will help us understand the formation of planets in a large range of environments.", "keyphrases": ["stellar property", "planet", "low-mass star"]}
{"id": "1101.1520", "title": "Testing standard perturbation theory and the Eulerian local biasing scheme against N-body simulations", "abstract": "We test third-order standard perturbation theory (SPT) as an approximation to non-linear cosmological structure formation. A novel approach is used to numerically calculate the three-dimensional dark matter density field using SPT from the initial conditions of two high-resolution cosmological simulations. The calculated density field is compared to the non-linear dark matter field of the simulations both point-by-point and statistically. For smoothing scales above 8 Mpc/h it shows a good agreement up to redshift 0. We present a simple fitting formula to relate the linear and non-linear density contrast that accurately recovers the non-linear time evolution for 0 <= z <= 10 at the per cent level. To address the problem of biasing between the matter field and the haloes identified in the simulation, we employ the Eulerian local bias model (ELB), including non-linear bias up to the third order. The bias parameters are obtained by fitting a scatter plot of halo and matter density (both from the simulation and from SPT). Using these bias parameters, we can reconstruct the halo density field. We find that this reconstruction is not able to capture all the details of the halo distribution. We investigate how well the large scale bias can be described by a constant and if it corresponds to the linear bias parameter b_1 of the local bias model. We also discuss how well the halo-halo power spectrum and the halo-mass cross spectrum from the reconstructed halo density field agree with the corresponding statistics from the simulation. The results show that while SPT is an excellent approximation for the matter field for suitably large smoothing scales even at redshift 0, the ELB model can only account for some of the properties of the halo density field.", "keyphrases": ["standard perturbation theory", "simulation", "density field"]}
{"id": "1009.2684", "title": "Astrophysical Fluid Dynamics via Direct Statistical Simulation", "abstract": "In this paper we introduce the concept of Direct Statistical Simulation (DSS) for astrophysical flows. This technique may be appropriate for problems in astrophysical fluids where the instantaneous dynamics of the flows are of secondary importance to their statistical properties. We give examples of such problems including mixing and transport in planets, stars and disks. The method is described for a general set of evolution equations, before we consider the specific case of a spectral method optimised for problems on a spherical surface. The method is illustrated for the simplest non-trivial example of hydrodynamics and MHD on a rotating spherical surface. We then discuss possible extensions of the method both in terms of computational methods and the range of astrophysical problems that are of interest.", "keyphrases": ["direct statistical simulation", "astrophysical flow", "spherical surface"]}
{"id": "1210.3860", "title": "Linearized Gravitational Waves in Nonlocal General Relativity", "abstract": "We investigate gravitational radiation in the linear approximation within the framework of the recent nonlocal generalization of Einstein's theory of gravitation. In this theory, nonlocality can simulate dark matter; in fact, in the Newtonian regime, we recover the phenomenological Tohline-Kuhn approach to modified gravity. To account for the observational data regarding the rotation curves of spiral galaxies, nonlocality is associated with a characteristic length scale of order \u03bb_0 = 10 kpc. It follows that in nonlocal gravity, the treatment of extremely low-frequency ( 10^-12 Hz) gravitational waves with wavelengths of order \u03bb_0 would be quite different than in general relativity. However, for radiation of frequency > 10^-8 Hz, which is the frequency range that is the focus of current observational searches, the corresponding wavelengths are very small compared to \u03bb_0. We find that in this frequency regime the nonlocal deviations from general relativity essentially average out and can be safely neglected in practice.", "keyphrases": ["gravitational wave", "nonlocal general relativity", "radiation", "dark matter"]}
{"id": "0910.1041", "title": "Higgs boson, renormalization group, and naturalness in cosmology", "abstract": "We consider the renormalization group improvement in the theory of the Standard Model (SM) Higgs boson playing the role of an inflaton with a strong non-minimal coupling to gravity. At the one-loop level with the running of constants taken into account, it leads to a range of the Higgs mass that is entirely determined by the lower WMAP bound on the cosmic microwave background (CMB) spectral index. We find that the SM phenomenology is sensitive to current cosmological data, which suggests to perform more precise CMB measurements as a SM test complementary to the LHC program. By using the concept of a field-dependent cutoff, we show the naturalness of the gradient and curvature expansion in this model within the conventional perturbation theory range of the SM. We also discuss the relation of these results to two-loop calculations and the limitations of the latter caused by parametrization and gauge dependence problems.", "keyphrases": ["cosmology", "renormalization group improvement", "non-minimal coupling", "higgs boson", "higgs field"]}
{"id": "1510.05675", "title": "Atmospheric Cherenkov Gamma-ray Telescopes", "abstract": "The stereoscopic imaging atmospheric Cherenkov technique, developed in the 1980s and 1990s, is now used by a number of existing and planned gamma-ray observatories around the world. It provides the most sensitive view of the very high energy gamma-ray sky (above 30 GeV), coupled with relatively good angular and spectral resolution over a wide field-of-view. This Chapter summarizes the details of the technique, including descriptions of the telescope optical systems and cameras, as well as the most common approaches to data analysis and gamma-ray reconstruction.", "keyphrases": ["telescope", "atmospheric cherenkov technique", "astronomy", "energy range"]}
{"id": "2104.02623", "title": "Simple-graduated dark energy and spatial curvature", "abstract": "In this work, we first discuss the possibility that dark energy models with negative energy density values in the past can alleviate the H_0 tension, as well as the discrepancy with the baryon acoustic oscillation (BAO) Lyman-\u03b1 data, both which prevail within the \u039bCDM model. We then investigate whether two minimal extensions of the \u039bCDM model, together or separately, can successfully realize such a scenario: (i) the spatial curvature, which, in the case of spatially closed universe, mimics a negative density source and (ii) simple-graduated dark energy (gDE), which promotes the null inertial mass density of the usual vacuum energy to an arbitrary constant\u2013if negative, the corresponding energy density decreases with redshift similar to the phantom models, but unlike them crosses below zero at a certain redshift. We find that, when the Planck data are not included in the observational analysis, the models with simple-gDE predict interesting and some significant deviations from the \u039bCDM model. In particular, a spatially closed universe along with a simple-gDE of positive inertial mass density, which work in contrast to each other, results in minor improvement to the H_0 tension. The joint dataset, including the Planck data, presents no evidence for a deviation from spatial flatness but almost the same evidence for a cosmological constant and the simple-gDE with an inertial mass density of order \ud835\udcaa(10^-12) eV^4. The latter case predicts almost no deviation from the \u039bCDM model up until today\u2013so that it results in no improvement regarding the BAO Ly-\u03b1 data\u2013except that it slightly aggravates the H_0 tension. We also study via dynamical analysis the history of the Universe in the models, as the simple-gDE results in futures different than the de Sitter future of the \u039bCDM model.", "keyphrases": ["dark energy", "spatial curvature", "discrepancy", "bao", "usual vacuum energy"]}
{"id": "1007.0970", "title": "Impact of a global quadratic potential on galactic rotation curves", "abstract": "We have made a conformal gravity fit to an available sample of 110 spiral galaxies, and report here on the 20 of those galaxies whose rotation curve data points extend the furthest from galactic centers. We identify the impact on the 20 galaxy data set of a universal de Sitter-like potential term V(r)=-\u03ba c^2r^2/2 that is induced by inhomogeneities in the cosmic background. This quadratic term accompanies a universal linear potential term V(r)=\u03b3_0c^2r/2 that is associated with the cosmic background itself. We find that when these two potential terms are taken in conjunction with the contribution generated by the local luminous matter within the galaxies, the conformal theory is able to account for the rotation curve systematics that is observed in the entire 110 galaxy sample, without the need for any dark matter whatsoever. With the two universal coefficients being found to be of global magnitude, viz. \u03ba =9.54\u00d7 10^-54 cm^-2 and \u03b3_0=3.06\u00d7 10^-30 cm^-1, our study suggests that invoking the presence of dark matter may be nothing more than an attempt to describe global effects in purely local galactic terms. With the quadratic potential term having negative sign, galaxies are only able to support bound orbits up to distances of order \u03b3_0/\u03ba = 3.21\u00d7 10^23 cm, with global physics thus imposing a natural limit on the size of galaxies.", "keyphrases": ["rotation curve", "conformal gravity", "galaxy", "dark matter", "optical disk"]}
{"id": "1002.1311", "title": "Measuring the Speed of Dark: Detecting Dark Energy Perturbations", "abstract": "The nature of dark energy can be probed not only through its equation of state, but also through its microphysics, characterized by the sound speed of perturbations to the dark energy density and pressure. As the sound speed drops below the speed of light, dark energy inhomogeneities increase, affecting both CMB and matter power spectra. We show that current data can put no significant constraints on the value of the sound speed when dark energy is purely a recent phenomenon, but can begin to show more interesting results for early dark energy models. For example, the best fit model for current data has a slight preference for dynamics (w(a)-1), degrees of freedom distinct from quintessence (c_s1), and early presence of dark energy (Omega_ de(a<<1)0). Future data may open a new window on dark energy by measuring its spatial as well as time variation.", "keyphrases": ["dark energy perturbation", "sound speed", "pressure", "energy model", "cosmic microwave background"]}
{"id": "1006.5178", "title": "A Catalog of Quasar Properties from SDSS DR7", "abstract": "We present a compilation of properties of the 105,783 quasars in the SDSS Data Release 7 (DR7) quasar catalog. In this value-added product, we compile continuum and emission line measurements around the Halpha, Hbeta, MgII and CIV regions, as well as other quantities such as radio properties, broad absorption line quasar (BALQSO) flags, and disk emitters. We also compile virial black hole mass estimates based on various calibrations. For the fiducial virial mass estimates we use the Vestergaard Peterson (VP06) calibrations for Hbeta and CIV, and our own calibration for MgII which matches the VP06 Hbeta masses on average. We describe the construction of this catalog, and discuss its limitations. The catalog and its future updates will be made publicly available online.", "keyphrases": ["catalog", "quasar", "sdss data release"]}
{"id": "1404.5220", "title": "Parametrized Post-Friedmann Framework for Interacting Dark Energy", "abstract": "Dark energy might directly interact with cold dark matter. However, in such a scenario, an early-time large-scale instability occurs occasionally, which may be due to the incorrect treatment for the pressure perturbation of dark energy as a nonadiabatic fluid. To avoid this nonphysical instability, we establish a new framework to correctly calculate the cosmological perturbations in the interacting dark energy models. Inspired by the well-known parametrized post-Friedmann approach, the condition of the dark energy pressure perturbation is replaced with the relationship between the momentum density of dark energy and that of other components on large scales. By reconciling the perturbation evolutions on the large and small scales, one can complete the perturbation equations system. The large-scale instability can be successfully avoided and the well-behaved density and metric perturbations are obtained within this framework. Our test results show that this new framework works very well and is applicable to all the interacting dark energy models.", "keyphrases": ["dark energy", "dark matter", "large-scale instability", "parameterized post-friedmann"]}
{"id": "1306.5021", "title": "Pinning down the cosmic ray source mechanism with new IceCube data", "abstract": "Very recently the IceCube Collaboration has reported an observation of 28 neutrino candidates with energies between 50 TeV and 2 PeV, constituting a 4.1\u03c3 excess compared to the atmospheric background. In this article we investigate the compatibility between the data and a hypothesized unbroken power-law neutrino spectrum for various values of spectral index \u0393>= 2. We show that \u0393 2.3 is consistent at the 1.5\u03c3 level with the observed events up to 2 PeV and to the null observation of events at higher energies. We then assume that the sources of this unbroken spectrum are Galactic, and deduce (i) an energy-transfer fraction from parent protons to pions, and (ii) a way of discriminating among models which have been put forth to explain the \"knee\" and \"ankle\" features of the cosmic ray spectrum. Future IceCube data will test the unbroken power law hypothesis and provide a multi-messenger approach to explaining features of the cosmic ray spectrum, including the transition from Galactic to extragalactic dominance.", "keyphrases": ["icecube data", "unbroken power-law spectrum", "neutrino flux"]}
{"id": "1312.1320", "title": "The Cauchy problem in hybrid metric-Palatini f(X)-gravity", "abstract": "The well-formulation and the well-posedness of the Cauchy problem is discussed for hybrid metric-Palatini gravity, a recently proposed modified gravitational theory consisting of adding to the Einstein-Hilbert Lagrangian an f(R) term constructed \u00e0 la Palatini. The theory can be recast as a scalar-tensor one predicting the existence of a light long-range scalar field that evades the local Solar System tests and is able to modify galactic and cosmological dynamics, leading to the late-time cosmic acceleration. In this work, adopting generalized harmonic coordinates, we show that the initial value problem can always be well-formulated and, furthermore, can be well-posed depending on the adopted matter sources.", "keyphrases": ["cauchy problem", "lagrangian", "matter source"]}
{"id": "1207.3873", "title": "Celestial Ephemerides in an Expanding Universe", "abstract": "Post-Newtonian theory was instrumental in conducting the critical experimental tests of general relativity and in building the astronomical ephemerides of celestial bodies in the solar system with an unparalleled precision. The cornerstone of the theory is the postulate that the solar system is gravitationally isolated from the rest of the universe and the background spacetime is asymptotically flat. The present article extends this theoretical concept and formulates the principles of celestial dynamics of particles and light moving in gravitational field of a localized astronomical system embedded to the expanding Friedmann-Lemaitre-Robertson-Walker (FLRW) universe. We formulate the precise mathematical concept of the Newtonian limit of Einstein's field equations in the conformally-flat FLRW spacetime and analyze the geodesic motion of massive particles and light in this limit. We prove that by doing conformal spacetime transformations, one can reduce the equations of motion of particles and light to the classical form of the Newtonian theory. However, the time arguments in the equations of motion of particles and light differ from each other in terms being proportional to the Hubble constant, H. This leads to the important conclusion that the equations of light propagation used currently by Space Navigation Centers for fitting range and Doppler-tracking observations of celestial bodies are missing some terms of the cosmological origin that are proportional to the Hubble constant, H. We also prove that the Hubble expansion does not affect the atomic time scale used in creation of astronomical ephemerides. We derive the cosmological correction to the light travel time equation and argue that their measurement opens an exciting opportunity to determine the local value of the Hubble constant, H, in the solar system independently of cosmological observations.", "keyphrases": ["universe", "celestial dynamic", "local physics"]}
{"id": "1110.4706", "title": "A simplified view of blazars: clearing the fog around long-standing selection effects", "abstract": "We propose a scenario where blazars are classified as flat-spectrum radio quasars (FSRQs), BL Lacs, low synchrotron, or high synchrotron peaked objects according to a varying mix of the Doppler boosted radiation from the jet, the emission from the accretion disk, the broad line region, and the light from the host galaxy. In this framework the peak energy of the synchrotron power (nu_peak) in blazars is independent of source type and of radio luminosity. We test this new approach, which builds upon unified schemes, using extensive Monte Carlo simulations and show that it can provide simple answers to a number of long-standing issues including, amongst others, the different cosmological evolution of BL Lacs selected in the radio and X-ray bands, the larger nu_peak values observed in BL Lacs, the fact that high synchrotron peaked blazars are always of the BL Lac type, and the existence of FSRQ/BL Lac transition objects. Objects so far classified as BL Lacs on the basis of their observed weak, or undetectable, emission lines are of two physically different classes: intrinsically weak lined objects, more common in X-ray selected samples, and heavily diluted broad lined sources, more frequent in radio selected samples, which explains some of the confusion in the literature. We also show that strong selection effects are the main cause of the diversity observed in radio and X-ray samples, and that the correlation between luminosity and nu_peak, that led to the proposal of the \"blazar sequence\", is also a selection effect arising from the comparison of shallow radio and X-ray surveys, and to the fact that high nu_peak-high radio power objects have never been considered because their redshift is not measurable.", "keyphrases": ["blazar", "selection effect", "jet", "broad line region"]}
{"id": "1705.03373", "title": "Small-scale filament eruptions as the driver of solar coronal hole X-ray jets", "abstract": "Solar X-ray jets are evidently made by a burst of reconnection of closed magnetic field in a jet's base with ambient \"open\" field (1,2). In the widely-accepted version of the \"emerging-flux\" model, that reconnection occurs at a current sheet between the open field and emerging closed field and also makes a compact hot brightening that is usually observed at the edge of the jet's base (1,3). Here we report on high-resolution X-ray and EUV observations of 20 randomly-selected X-ray jets in polar coronal holes. In each jet, contrary to the emerging-flux model, a miniature version of the filament eruptions that initiate coronal mass ejections (CMEs) (4-7) drives the jet-producing reconnection, and the compact hot brightening is made by internal reconnection of the legs of the minifilament-carrying erupting closed field, analogous to solar flares of larger-scale eruptions. Previous observations have found that some jets are driven by base-field eruptions (8-10,12), but only one such study, of only one jet, provisionally questioned the emerging-flux model (13). Our observations support the view that solar filament eruptions are made by a fundamental explosive magnetic process that occurs on a vast range of scales, from the biggest CME/flare eruptions down to X-ray jets, and perhaps down to even smaller jets that are candidates for powering coronal heating (10,14,15). A picture similar to that suggested by our observations was drawn before, inferred from different observations and based on a different origin of the erupting minifilament flux rope (11) (see Methods).", "keyphrases": ["filament eruption", "x-ray jet", "coronal mass ejection"]}
{"id": "1105.1130", "title": "Analysis of matter suppression in collective neutrino oscillations during the supernova accretion phase", "abstract": "The usual description of self-induced neutrino flavor conversions in core collapse supernovae (SNe) is based on the dominance of the neutrino density n_nu over the net electron density n_e. However, this condition is not met during the post-bounce accretion phase, when the dense matter in a SN is piled up above the neutrinosphere. As recently pointed-out, a dominant matter term in the anisotropic SN environment would dephase the flavor evolution for neutrinos traveling on different trajectories, challenging the occurrence of the collective behavior in the dense neutrino gas. Using the results from recent long term simulations of core-collapse SN explosions, based on three flavor Boltzmann neutrino transport in spherical symmetry, we find that both the situations of complete matter suppression (when n_e >> n_nu) and matter-induced decoherence (when n_e \u2273n_nu) of flavor conversions are realized during the accretion phase. The matter suppression at high densities prevents any possible impact of the neutrino oscillations on the neutrino heating and hence on the dynamics of the explosion. Furthermore, it changes the interpretation of the Earth matter effect on the SN neutrino signal during the accretion phase, allowing the possibility of the neutrino mass hierarchy discrimination at not too small values of the leptonic mixing angle \u03b8_13 (i.e. sin^2\u03b8_13 \u227310^-3).", "keyphrases": ["neutrino oscillation", "complete matter suppression", "matter density"]}
{"id": "1102.4333", "title": "Phenomenology of a Pseudo-Scalar Inflaton: Naturally Large Nongaussianity", "abstract": "Many controlled realizations of chaotic inflation employ pseudo-scalar axions. Pseudo-scalars \u03d5are naturally coupled to gauge fields through c \u03d5F F\u0303. In the presence of this coupling, gauge field quanta are copiously produced by the rolling inflaton. The produced gauge quanta, in turn, source inflaton fluctuations via inverse decay. These new cosmological perturbations add incoherently with the \"vacuum\" perturbations, and are highly nongaussian. This provides a natural mechanism to generate large nongaussianity in single or multi field slow-roll inflation. The resulting phenomenological signatures are highly distinctive: large nongaussianity of (nearly) equilateral shape, in addition to detectably large values of both the scalar spectral tilt and tensor-to-scalar ratio (both being typical of large field inflation). The WMAP bound on nongaussianity implies that the coupling, c, of the pseudo-scalar inflaton to any gauge field must be smaller than about 10^2 M_p^-1.", "keyphrases": ["pseudo-scalar inflaton", "chaotic inflation", "gauge field", "chiral gravitational wave"]}
{"id": "1710.04853", "title": "Coleman-Weinberg linear inflation: metric vs. Palatini formulation", "abstract": "It has been previously shown that the linear inflation appears naturally as a solution of Coleman-Weinberg inflation, provided that the inflaton has a non-minimal coupling to gravity and the Planck scale is dynamically generated. We revisit the previous study by improving the discussion of reheating and by comparing the results of the metric and the Palatini formulations of non-minimal gravity. We find that both formulations predict linear inflation but a different number of e-folds. If the non-minimal coupling is larger than one, future experimental sensitivity can discriminate between the two realizations.", "keyphrases": ["linear inflation", "palatini formulation", "non-minimal coupling", "gravity", "metric formulation"]}
{"id": "1804.01092", "title": "21-cm Fluctuations from Charged Dark Matter", "abstract": "The epoch of the formation of the first stars, known as the cosmic dawn, has emerged as a new arena in the search for dark matter. In particular, the first claimed 21-cm detection exhibits a deeper global absorption feature than expected, which could be caused by a low baryonic temperature, and has been interpreted as a sign for electromagnetic interactions between baryons and dark matter. This hypothesis has a striking prediction: large temperature anisotropies sourced by the velocity-dependent cooling of the baryons. However, in order to remain consistent with the rest of cosmological observations, only part of the dark matter is allowed to be charged, and thus interactive. Here we compute, for the first time, the 21-cm fluctuations caused by a charged subcomponent of the dark matter, including both the pre- and post-recombination evolution of all fluids. We find that, for the same parameters that can explain the anomalous 21-cm absorption signal, any percent-level fraction of charged dark matter would source novel 21-cm fluctuations with a unique acoustic spectrum, and with an amplitude above any other known effects. These fluctuations are uncorrelated with the usual adiabatic anisotropies, and would be observable at high significance with interferometers such as LOFAR and HERA, thus providing a novel probe of dark matter at cosmic dawn.", "keyphrases": ["dark matter", "cosmic dawn", "21-cm fluctuation", "small fraction", "anomaly"]}
{"id": "1804.08379", "title": "Improving cosmological parameter estimation with the future gravitational-wave standard siren observation from the Einstein Telescope", "abstract": "Detection of gravitational waves produced by merger of binary compact objects could provide an independent way for measuring the luminosity distance to the gravitational-wave burst source, indicating that gravitational-wave observation, combined with observation of electromagnetic counterparts, can provide \"standard sirens\" for investigating the expansion history of the universe in cosmology. In this work, we wish to investigate how the future gravitational-wave standard siren observations would break the parameter degeneracies existing in the conventional optical observations and how they help improve the parameter estimation in cosmology. We take the third-generation ground-based gravitational-wave detector, the Einstein Telescope, as an example to make an analysis. By simulating 1000 events data in the redshift range between 0 and 5 based on the ten-year observation of the Einstein Telescope, we find that the gravitational-wave data could largely break the degeneracy between the matter density and the Hubble constant, thus significantly improving the cosmological constraints. We further show that the constraint on the equation-of-state parameter of dark energy could also be significantly improved by including the gravitational-wave data in the cosmological fit.", "keyphrases": ["cosmological parameter estimation", "cosmology", "dark energy model"]}
{"id": "1003.4777", "title": "McVittie's Legacy: Black Holes in an Expanding Universe", "abstract": "We prove that a class of solutions to Einstein's equations\u2014originally discovered by G. C. McVittie in 1933\u2014includes regular black holes embedded in Friedman-Robertson-Walker cosmologies. If the cosmology is dominated at late times by a positive cosmological constant, the metric is regular everywhere on and outside the black hole horizon and away from the big bang singularity, and the solutions asymptote in the future and near the horizon to the Schwarzschild-de Sitter geometry. For solutions without a positive cosmological constant the would-be horizon is a weak null singularity.", "keyphrases": ["black hole", "cosmology", "mcvittie spacetime"]}
{"id": "2107.14057", "title": "Multi-wavelength spectroscopic probes: prospects for primordial non-Gaussianity and relativistic effects", "abstract": "Next-generation cosmological surveys will observe larger cosmic volumes than ever before, enabling us to access information on the primordial Universe, as well as on relativistic effects. We consider forthcoming 21cm intensity mapping surveys (SKAO) and optical galaxy surveys (DESI and Euclid), combining the information via multi-tracer cross-correlations that suppress cosmic variance on ultra-large scales. In order to fully incorporate wide-angle effects and redshift-bin cross-correlations, together with lensing magnification and other relativistic effects, we use the angular power spectra, C_\u2113(z_i,z_j). Applying a Fisher analysis, we forecast the expected precision on f_ NL and the detectability of lensing and other relativistic effects. We find that the full combination of two pairs of 21cm and galaxy surveys, one pair at low redshift and one at high redshift, could deliver \u03c3(f_ NL)\u223c 1.5, detect the Doppler effect with a signal-to-noise ratio \u223c8 and measure the lensing convergence contribution at \u223c2% precision. In a companion paper, we show that the best-fit values of f_ NL and of standard cosmological parameters are significantly biased if the lensing contribution neglected.", "keyphrases": ["relativistic effect", "doppler effect", "signal-to-noise ratio"]}
{"id": "1306.6401", "title": "Screening the fifth force in the Horndeski's most general scalar-tensor theories", "abstract": "We study how the Vainshtein mechanism operates in the most general scalar-tensor theories with second-order equations of motion. The field equations of motion, which can be also applicable to most of other screening scenarios proposed in literature, are generally derived in a spherically symmetric space-time with a matter source. In the presence of a field coupling to the Ricci scalar, we clarify conditions under which the Vainshtein mechanism is at work in a weak gravitational background. We also obtain the solutions of the field equation inside a spherically symmetric body and show how they can be connected to exterior solutions that accommodate the Vainshtein mechanism. We apply our general results to a number of concrete models such as the covariant/extended Galileons and the DBI Galileons with Gauss-Bonnet and other terms. In these models the fifth force can be suppressed to be compatible with solar-system constraints, provided that non-linear field kinetic terms coupled to the Einstein tensor do not dominate over other non-linear field self-interactions.", "keyphrases": ["fifth force", "scalar-tensor theory", "symmetric background", "horndeski theory"]}
{"id": "1112.3305", "title": "Planetary Rings", "abstract": "Planetary rings are the only nearby astrophysical disks, and the only disks that have been investigated by spacecraft. Although there are significant differences between rings and other disks, chiefly the large planet/ring mass ratio that greatly enhances the flatness of rings (aspect ratios as small as 1e-7), understanding of disks in general can be enhanced by understanding the dynamical processes observed at close-range and in real-time in planetary rings. We review the known ring systems of the four giant planets, as well as the prospects for ring systems yet to be discovered. We then review planetary rings by type. The main rings of Saturn comprise our system's only dense broad disk and host many phenomena of general application to disks including spiral waves, gap formation, self-gravity wakes, viscous overstability and normal modes, impact clouds, and orbital evolution of embedded moons. Dense narrow rings are the primary natural laboratory for understanding shepherding and self-stability. Narrow dusty rings, likely generated by embedded source bodies, are surprisingly found to sport azimuthally-confined arcs. Finally, every known ring system includes a substantial component of diffuse dusty rings. Planetary rings have shown themselves to be useful as detectors of planetary processes around them, including the planetary magnetic field and interplanetary impactors as well as the gravity of nearby perturbing moons. Experimental rings science has made great progress in recent decades, especially numerical simulations of self-gravity wakes and other processes but also laboratory investigations of coefficient of restitution and spectroscopic ground truth. The age of self-sustained ring systems is a matter of debate; formation scenarios are most plausible in the context of the early solar system, while signs of youthfulness indicate at least that rings have never been static phenomena.", "keyphrases": ["ring", "planet", "saturn", "moon", "solar system"]}
{"id": "1603.05184", "title": "Redshift-space distortions around voids", "abstract": "We have derived estimators for the linear growth rate of density fluctuations using the cross-correlation function of voids and haloes in redshift space, both directly and in Fourier form. In linear theory, this cross-correlation contains only monopole and quadrupole terms. At scales greater than the void radius, linear theory is a good match to voids traced out by haloes in N-body simulations; small-scale random velocities are unimportant at these radii, only tending to cause small and often negligible elongation of the redshift-space cross-correlation function near its origin. By extracting the monopole and quadrupole from the cross-correlation function, we measure the linear growth rate without prior knowledge of the void profile or velocity dispersion. We recover the linear growth parameter \u03b2 to 9 volume of 3(Gpc/h)^3 using voids with radius greater than 25Mpc/h. Smaller voids are predominantly sub-voids, which may be more sensitive to the random velocity dispersion; they introduce noise and do not help to improve the measurement. Adding velocity dispersion as a free parameter allows us to use information at radii as small as half of the void radius. The precision on \u03b2 is reduced to approximately 5 distortion pattern in overdensities, voids show diverse shapes in redshift space, and can appear either elongated or flattened along the line of sight. This can be explained by the competing amplitudes of the local density contrast, plus the radial velocity profile and its gradient, with the latter two factors being determined by the cumulative density profile of voids. The distortion pattern is therefore determined solely by the void profile and is different for void-in-cloud and void-in-void. This diversity of redshift-space void morphology complicates measurements of the Alcock-Paczynski effect using voids.", "keyphrases": ["void", "cross-correlation function", "redshift space"]}
{"id": "1512.06968", "title": "From Planetesimals to Planets in Turbulent Protoplanetary Disks I. Onset of Runaway Growth", "abstract": "When planetesimals grow via collisions in a turbulent disk, stirring through density fluctuation caused by turbulence effectively increases the relative velocities between planetesimals, which suppresses the onset of runaway growth. We investigate the onset of runaway growth in a turbulent disk through simulations that calculate the mass and velocity evolution of planetesimals. When planetesimals are small, the average relative velocity between planetesimals, v_ r, is much greater than their surface escape velocity, v_ esc, so that runaway growth does not occur. As planetesimals become large via collisional growth, v_ r approaches v_ esc. When v_ r\u2248 1.5 v_ esc, runaway growth of the planetesimals occurs. During the oligarchic growth subsequent to runaway growth, a small number of planetary embryos produced via runaway growth become massive through collisions with planetesimals with radii of that at the onset of runaway growth, r_ p,run. We analytically derive r_ p,run as a function of the turbulent strength. Growing \u223c 10 M_\u2295 embryos that are suitable to become the cores of Jupiter and Saturn requires r_ p,run\u223c 100 km, which is similar to the proposed fossil feature in the size distribution of main belt asteroids. In contrast, the formation of Mars as quickly as suggested from Hf-W isotope studies requires small planetesimals at the onset of runaway growth. Thus, the conditions required to form Mars, Jupiter, and Saturn and the size distribution of the main-belt asteroids indicate that the turbulence increased in amplitude relative to the sound speed with increasing distance from the young Sun.", "keyphrases": ["planetesimal", "collisional growth", "main-belt asteroid"]}
{"id": "1005.2536", "title": "Planetary Growth with Collisional Fragmentation and Gas Drag", "abstract": "As planetary embryos grow, gravitational stirring of planetesimals by embryos strongly enhances random velocities of planetesimals and makes collisions between planetesimals destructive. The resulting fragments are ground down by successive collisions. Eventually the smallest fragments are removed by the inward drift due to gas drag. Therefore, the collisional disruption depletes the planetesimal disk and inhibits embryo growth. We provide analytical formulae for the final masses of planetary embryos, taking into account planetesimal depletion due to collisional disruption. Furthermore, we perform the statistical simulations for embryo growth (which excellently reproduce results of direct N-body simulations if disruption is neglected). These analytical formulae are consistent with the outcome of our statistical simulations. Our results indicate that the final embryo mass at several AU in the minimum-mass solar nebula can reach about \u223c 0.1 Earth mass within 10^7 years. This brings another difficulty in formation of gas giant planets, which requires cores with \u223c 10 Earth masses for gas accretion. However, if the nebular disk is 10 times more massive than the minimum-mass solar nebula and the initial planetesimal size is larger than 100 km, as suggested by some models of planetesimal formation, the final embryo mass reaches about 10 Earth masses at 3-4 AU. The enhancement of embryos' collisional cross sections by their atmosphere could further increase their final mass to form gas giant planets at 5-10 AU in the solar system.", "keyphrases": ["gas drag", "planetesimal", "accretion"]}
{"id": "1304.7785", "title": "Symmetries of Vector Perturbations during the de Sitter Epoch", "abstract": "We analyze the class of models where a suitable coupling between the inflaton field and the vector field gives rise to scale-invariant vector perturbations. We exploit the fact that the de Sitter isometry group acts as conformal group on the three-dimensional Euclidean space for the super-Hubble fluctuations in order to characterize the correlators involving the inflaton and the vector fields.", "keyphrases": ["vector field", "conformal group", "three-dimensional euclidean space"]}
{"id": "1106.3087", "title": "SPIDER: Probing the Early Universe with a Suborbital Polarimeter", "abstract": "We evaluate the ability of SPIDER, a balloon-borne polarimeter, to detect a divergence-free polarization pattern (\"B-modes\") in the Cosmic Microwave Background (CMB). In the inflationary scenario, the amplitude of this signal is proportional to that of the primordial scalar perturbations through the tensor-to-scalar ratio r. We show that the expected level of systematic error in the SPIDER instrument is significantly below the amplitude of an interesting cosmological signal with r=0.03. We present a scanning strategy that enables us to minimize uncertainty in the reconstruction of the Stokes parameters used to characterize the CMB, while accessing a relatively wide range of angular scales. Evaluating the amplitude of the polarized Galactic emission in the SPIDER field, we conclude that the polarized emission from interstellar dust is as bright or brighter than the cosmological signal at all SPIDER frequencies (90 GHz, 150 GHz, and 280 GHz), a situation similar to that found in the \"Southern Hole.\" We show that two 20-day flights of the SPIDER instrument can constrain the amplitude of the B-mode signal to r<0.03 (99 foreground contamination is taken into account. In the absence of foregrounds, the same limit can be reached after one 20-day flight.", "keyphrases": ["polarimeter", "cosmic microwave background", "angular scale", "spider"]}
{"id": "1506.04065", "title": "Spacetime curvature and Higgs stability after inflation", "abstract": "We investigate the dynamics of the Higgs field at the end of inflation in the minimal scenario consisting of an inflaton field coupled to the Standard Model only through the non-minimal gravitational coupling \u03be of the Higgs field. Such a coupling is required by renormalisation of the Standard Model in curved space, and in the current scenario also by vacuum stability during high-scale inflation. We find that for \u03be\u2273 1, rapidly changing spacetime curvature at the end of inflation leads to significant production of Higgs particles, potentially triggering a transition to a negative-energy Planck scale vacuum state and causing an immediate collapse of the Universe.", "keyphrases": ["curvature", "vacuum stability", "conformal coupling"]}
{"id": "1612.02036", "title": "Matter bounce cosmology with a generalized single field: non-Gaussianity and an extended no-go theorem", "abstract": "We extend the matter bounce scenario to a more general theory in which the background dynamics and cosmological perturbations are generated by a k-essence scalar field with an arbitrary sound speed. When the sound speed is small, the curvature perturbation is enhanced, and the tensor-to-scalar ratio, which is excessively large in the original model, can be sufficiently suppressed to be consistent with observational bounds. Then, we study the primordial three-point correlation function generated during the matter-dominated contraction stage and find that it only depends on the sound speed parameter. Similar to the canonical case, the shape of the bispectrum is mainly dominated by a local form, though for some specific sound speed values a new shape emerges and the scaling behaviour changes. Meanwhile, a small sound speed also results in a large amplitude of non-Gaussianities, which is disfavored by current observations. As a result, it does not seem possible to suppress the tensor-to-scalar ratio without amplifying the production of non-Gaussianities beyond current observational constraints (and vice versa). This suggests an extension of the previously conjectured no-go theorem in single field nonsingular matter bounce cosmologies, which rules out a large class of models. However, the non-Gaussianity results remain as a distinguishable signature of matter bounce cosmology and have the potential to be detected by observations in the near future.", "keyphrases": ["single field", "non-gaussianity", "no-go theorem", "tensor-to-scalar ratio", "matter bounce cosmology"]}
{"id": "0905.2962", "title": "Exponential Gravity", "abstract": "We investigate a f(R) modification of gravity that is exponential in the Ricci scalar R to explain cosmic acceleration. The steepness of this dependence provides extra freedom to satisfy solar system and other curvature regime constraints. With a parameter to alleviate the usual fine tuning of having the modification strengthen near the present, the total number of parameters is only one more than LCDM. The resulting class of solutions asymptotes to w=-1 but has no cosmological constant. We calculate the dynamics in detail, examine the effect on the matter power spectrum, and provide a simple fitting form relating the two.", "keyphrases": ["exponential gravity", "viable model", "linder", "researcher", "crossing"]}
{"id": "1809.09148", "title": "Cosmology from cosmic shear power spectra with Subaru Hyper Suprime-Cam first-year data", "abstract": "We measure cosmic weak lensing shear power spectra with the Subaru Hyper Suprime-Cam (HSC) survey first-year shear catalog covering 137deg^2 of the sky. Thanks to the high effective galaxy number density of \u223c17 arcmin^-2 even after conservative cuts such as magnitude cut of i<24.5 and photometric redshift cut of 0.3\u2264 z \u2264 1.5, we obtain a high significance measurement of the cosmic shear power spectra in 4 tomographic redshift bins, achieving a total signal-to-noise ratio of 16 in the multipole range 300 \u2264\u2113\u2264 1900. We carefully account for various uncertainties in our analysis including the intrinsic alignment of galaxies, scatters and biases in photometric redshifts, residual uncertainties in the shear measurement, and modeling of the matter power spectrum. The accuracy of our power spectrum measurement method as well as our analytic model of the covariance matrix are tested against realistic mock shear catalogs. For a flat \u039b cold dark matter (\u039bCDM) model, we find S_8\u2261\u03c3_8(\u03a9_ m/0.3)^\u03b1=0.800^+0.029_-0.028 for \u03b1=0.45 (S_8=0.780^+0.030_-0.033 for \u03b1=0.5) from our HSC tomographic cosmic shear analysis alone. In comparison with Planck cosmic microwave background constraints, our results prefer slightly lower values of S_8, although metrics such as the Bayesian evidence ratio test do not show significant evidence for discordance between these results. We study the effect of possible additional systematic errors that are unaccounted in our fiducial cosmic shear analysis, and find that they can shift the best-fit values of S_8 by up to \u223c 0.6\u03c3 in both directions. The full HSC survey data will contain several times more area, and will lead to significantly improved cosmological constraints.", "keyphrases": ["shear power spectra", "cosmic microwave background", "universe"]}
{"id": "1504.00417", "title": "Clustering of Local Group distances: publication bias or correlated measurements? III. The Small Magellanic Cloud", "abstract": "Aiming at providing a firm mean distance estimate to the Small Magellanic Cloud (SMC), and thus to place it within the internally consistent Local Group distance framework we recently established, we compiled the current-largest database of published distance estimates to the galaxy. Based on careful statistical analysis, we derive mean distance estimates to the SMC using eclipsing binary systems, variable stars, stellar population tracers, and star cluster properties. Their weighted mean leads to a final recommendation for the mean SMC distance of (m-M)_0^ SMC = 18.96 \u00b1 0.02 mag, where the uncertainty represents the formal error. Systematic effects related to lingering uncertainties in extinction corrections, our physical understanding of the stellar tracers used, and the SMC's complex geometry\u2014including its significant line-of-sight depth, its irregular appearance which renders definition of the galaxy's center uncertain, as well as its high inclination and possibly warped disk\u2014may contribute additional uncertainties possibly exceeding 0.15\u20130.20 mag.", "keyphrases": ["cloud", "mean distance estimate", "database"]}
{"id": "1201.2544", "title": "Eddington-inspired Born-Infeld gravity: astrophysical and cosmological constraints", "abstract": "In this letter we compute stringent astrophysical and cosmological constraints on a recently proposed Eddington-inspired Born-Infeld theory of gravity. We find, using a generalized version of the Zel'dovich approximation, that in this theory a pressureless cold dark matter fluid has a non-zero effective sound speed. We compute the corresponding effective Jeans length and show that it is approximately equal to the fundamental length of the theory R_*=\u03ba^1/2 G^-1/2, where \u03ba is the only additional parameter of theory with respect to general relativity and G is the gravitational constant. This scale determines the minimum size of compact objects which are held together by gravity. We also estimate the critical mass above which pressureless compact objects are unstable to colapse into a black hole, showing that it is approximately equal to the fundamental mass M_* = \u03ba^1/2 c^2 G^-3/2, and we show that the maximum density attainable inside stable compact stars is roughly equal to the fundamental density \u03c1_*=\u03ba^-1 c^2, where c is the speed of light in vacuum. We find that the mere existence of astrophysical objects of size R which are held together by their own gravity leads to the constraint \u03ba < G R^2. In the case of neutron stars this implies that \u03ba < 10^-2 m^5 kg^-1 s^-2, a limit which is stronger by about 10 orders of magnitude than big bang nucleosynthesis constraints and by more than 7 orders of magnitude than solar constraints.", "keyphrases": ["cosmological constraint", "critical mass", "star", "eibi theory"]}
{"id": "1802.04271", "title": "Machine learning cosmological structure formation", "abstract": "We train a machine learning algorithm to learn cosmological structure formation from N-body simulations. The algorithm infers the relationship between the initial conditions and the final dark matter haloes, without the need to introduce approximate halo collapse models. We gain insights into the physics driving halo formation by evaluating the predictive performance of the algorithm when provided with different types of information about the local environment around dark matter particles. The algorithm learns to predict whether or not dark matter particles will end up in haloes of a given mass range, based on spherical overdensities. We show that the resulting predictions match those of spherical collapse approximations such as extended Press-Schechter theory. Additional information on the shape of the local gravitational potential is not able to improve halo collapse predictions; the linear density field contains sufficient information for the algorithm to also reproduce ellipsoidal collapse predictions based on the Sheth-Tormen model. We investigate the algorithm's performance in terms of halo mass and radial position and perform blind analyses on independent initial conditions realisations to demonstrate the generality of our results.", "keyphrases": ["cosmological structure formation", "halo collapse model", "insight", "machine"]}
{"id": "1007.0871", "title": "Discrete dark matter", "abstract": "We propose a new motivation for the stability of dark matter (DM). We suggest that the same non-abelian discrete flavor symmetry which accounts for the observed pattern of neutrino oscillations, spontaneously breaks to a Z2 subgroup which renders DM stable. The simplest scheme leads to a scalar doublet DM potentially detectable in nuclear recoil experiments, inverse neutrino mass hierarchy, hence a neutrinoless double beta decay rate accessible to upcoming searches, while reactor angle equal to zero gives no CP violation in neutrino oscillations.", "keyphrases": ["dark matter", "flavor symmetry", "neutrino"]}
{"id": "1202.2309", "title": "Constraints on the Hubble Parameter from galaxy clusters and the Validity of the Cosmic Distance Duality Relation", "abstract": "Constraints on the Hubble parameter, H_0, via X-ray surface brightness and Sunyaev-Zel'dovich effect (SZE) observations of the galaxy clusters depend on the validity of the cosmic distance duality relation (DD relation), \u03b7= D_L(z)(1+z)^-2/D_A(z) = 1, where D_L and D_A are the luminosity distance and angular diameter distance (ADD), respectively. In this work, we argue that if the DD relation does not hold the X-ray plus SZE technique furnishes a H^*_0=H_0/\u03b7^2. We use 25 ADD of galaxy clusters to obtain simultaneous constraints on H_0 and possible violation of the DD relation in a flat \u039bCDM model. Such a violation is parametrized by two functions: \u03b7(z) = 1 + \u03b7_0z and \u03b7(z) = 1 + \u03b7_0z/(1+z), where \u03b7_0 is a constant parameter quantifying possible departures from the strict validity. Finally, by marginalizing on the \u03b7_0 in both parameterizations, we obtain constraints on H_0 regardless of the validity of the DD relation. For the linear and non linear \u03b7(z) functions, we obtain H_0= 75^+ 7_-7 km/s/Mpc and H_0= 75^+ 10_-7 km/s/Mpc, respectively (without systematic erros). Our results support recent H_0 measurements by using X-ray and SZE observations of galaxy clusters which have taken the distance duality as valid.", "keyphrases": ["hubble parameter", "galaxy cluster", "distance duality relation", "x-ray surface brightness"]}
{"id": "1304.6712", "title": "A Simplified Approach to General Scalar-Tensor Theories", "abstract": "The most general covariant action describing gravity coupled to a scalar field with only second order equations of motion, Horndeski's theory (also known as \"Generalized Galileons\"), provides an all-encompassing model in which single scalar dark energy models may be constrained. However, the generality of the model makes it cumbersome to manipulate. In this paper, we demonstrate that when considering linear perturbations about a Friedmann-Robertson-Walker background, the theory is completely specified by only six functions of time, two of which are constrained by the background evolution. We utilise the ideas of the Effective Field Theory of Inflation/Dark Energy to explicitly construct these six functions of time in terms of the free functions appearing in Horndeski's theory. These results are used to investigate the behavior of the theory in the quasistatic approximation. We find that only four functions of time are required to completely specify the linear behavior of the theory in this limit, which can further be reduced if the background evolution is fixed. This presents a significantly reduced parameter space from the original presentation of Horndeski's theory, giving hope to the possibility of constraining the parameter space. This work provides a cross-check for previous work on linear perturbations in this theory, and also generalizes it to include spatial curvature.", "keyphrases": ["scalar field", "second order", "dark energy", "construction", "eft language"]}
{"id": "1011.2233", "title": "Quark core impact on hybrid star cooling", "abstract": "In this paper we investigate the thermal evolution of hybrid stars, objects composed of a quark matter core, enveloped by ordinary hadronic matter. Our purpose is to investigate how important are the microscopic properties of the quark core to the thermal evolution of the star. In order to do that we use a simple MIT bag model for the quark core, and a relativistic mean field model for the hadronic envelope. By choosing different values for the microscopic parameters (bag constant, strange quark mass, strong coupling constant) we obtain hybrid stars with different quark core properties. We also consider the possibility of color superconductivity in the quark core. With this simple approach, we have found a set of microscopic parameters that lead to a good agreement with observed cooling neutron stars. Our results can be used to obtain clues regarding the properties of the quark core in hybrid stars, and can be used to refine more sophisticated models for the equation of state of quark matter.", "keyphrases": ["hybrid star", "neutron star", "quark core"]}
{"id": "1911.10849", "title": "Low-density in-medium effects on light clusters from heavy-ion data", "abstract": "The modification of the ground state properties of light atomic nuclei in the nuclear and stellar medium is addressed, using chemical equilibrium constants evaluated from a new analysis of the intermediate energy heavy-ion (Xe+Sn) collision data measured by the INDRA collaboration. Three different reactions are considered, mainly differing by the isotopic content of the emission source. The thermodynamic conditions of the data samples are extracted from the measured multiplicities allowing for a parametrization of the in-medium modification, determined with the single hypothesis that the different nuclear species in a given sample correspond to a unique common value for the density of the expanding source. We show that this correction, which was not considered in previous analyses of chemical constants from heavy ion collisions, is necessary, since the observables of the analyzed systems show strong deviations from the expected results for an ideal gas of free clusters. This data set is further compared to a relativistic mean-field model, and seen to be reasonably compatible with a universal correction of the attractive \u03c3-meson coupling.", "keyphrases": ["cluster", "new analysis", "heavy ion collision"]}
{"id": "1005.1931", "title": "Testing the No-Hair Theorem with Observations in the Electromagnetic Spectrum: II. Black-Hole Images", "abstract": "According to the no-hair theorem, all astrophysical black holes are fully described by their masses and spins. This theorem can be tested observationally by measuring (at least) three different multipole moments of the spacetimes of black holes. In this paper, we analyze images of black holes within a framework that allows us to calculate observables in the electromagnetic spectrum as a function of the mass, spin, and, independently, the quadrupole moment of a black hole. We show that a deviation of the quadrupole moment from the expected Kerr value leads to images of black holes that are either prolate or oblate depending on the sign and magnitude of the deviation. In addition, there is a ring-like structure around the black-hole shadow with a diameter of about 10 black-hole masses that is substantially brighter than the image of the underlying accretion flow and that is independent of the astrophysical details of accretion flow models. We show that the shape of this ring depends directly on the mass, spin, and quadrupole moment of the black hole and can be used for an independent measurement of all three parameters. In particular, we demonstrate that this ring is highly circular for a Kerr black hole with a spin a<0.9M, independent of the observer's inclination, but becomes elliptical and asymmetric if the no-hair theorem is violated. Near-future very-long baseline interferometric observations of Sgr A* will image this ring and may allow for an observational test of the no-hair theorem.", "keyphrases": ["no-hair theorem", "electromagnetic spectrum", "black hole"]}
{"id": "1902.08772", "title": "Formation of planetary systems by pebble accretion and migration: Hot super-Earth systems from breaking compact resonant chains", "abstract": "At least 30% of main sequence stars host planets with sizes of between 1 and 4 Earth radii and orbital periods of less than 100 days. We use N-body simulations including a model for gas-assisted pebble accretion and disk\u2013planet tidal interaction to study the formation of super-Earth systems. We show that the integrated pebble mass reservoir creates a bifurcation between hot super-Earths or hot-Neptunes (\u227215M_\u2295) and super-massive planetary cores potentially able to become gas giant planets (\u227315M_\u2295). Simulations with moderate pebble fluxes grow multiple super-Earth-mass planets that migrate inwards and pile up at the inner edge of the disk forming long resonant chains. We follow the long-term dynamical evolution of these systems and use the period ratio distribution of observed planet-pairs to constrain our model. Up to \u223c95% of resonant chains become dynamically unstable after the gas disk dispersal, leading to a phase of late collisions that breaks the original resonant configurations. Our simulations naturally match observations when they produce a dominant fraction (\u227395%) of unstable systems with a sprinkling (\u22725%) of stable resonant chains (the Trappist-1 system represents one such example). Our results demonstrate that super-Earth systems are inherently multiple (N\u22652) and that the observed excess of single-planet transits is a consequence of the mutual inclinations excited by the planet\u2013planet instability. In simulations in which planetary seeds are initially distributed in the inner and outer disk, close-in super-Earths (abridged).", "keyphrases": ["pebble accretion", "super-earth system", "planet"]}
{"id": "2107.02350", "title": "A New Catalog of Asymptotic Giant Branch Stars in Our Galaxy", "abstract": "We present a new catalog of 11,209 O-rich AGB stars and 7172 C-rich AGB stars in our Galaxy identifying more AGB stars in the bulge component and considering more visual carbon stars. For each object, we cross-identify the IRAS, AKARI, MSX, WISE, 2MASS, and AAVSO counterparts. We present the new catalog in two parts: one is based on the IRAS PSC for brighter or more isolated objects; the other one is based on the ALLWISE source catalog for less bright objects or objects in crowded regions. We present various infrared two-color diagrams (2CDs) for the sample stars. We find that the theoretical dust shell models can roughly explain the observations of AGB stars on the various IR 2CDs. We investigate IR properties of SiO and OH maser emission sources in the catalog. For Mira variables in the sample stars, we find that the IR colors get redder for longer pulsation periods. We also study infrared variability of the sample stars using the WISE photometric data in the last 12 yr: the ALLWISE multiepoch data and the Near-Earth Object WISE Reactivation (NEOWISE-R) 2021 data release. We generate light curves using the WISE data at W1 and W2 bands and compute the Lomb-Scargle periodograms for all of the sample stars. From the WISE light curves, we have found useful variation parameters for 3710 objects in the catalog, for which periods were either known or unknown in previous works.", "keyphrases": ["new catalog", "galaxy", "agb star", "two-color diagram"]}
{"id": "1909.07992", "title": "Ultraviolet Freeze-in and Non-Standard Cosmologies", "abstract": "A notable feature of UV freeze-in is that the relic density is strongly dependent on the highest temperatures of the thermal bath, and a common assumption is that the relevant 'highest temperature' should be the reheating temperature after inflation T_RH. However, the temperature of the thermal bath can be significantly higher in certain scenarios, reaching a value denoted T max , a fact which is only apparent away from the instantaneous decay approximation. Interestingly, it has been shown that if the operators are of sufficiently high mass dimension then the dark matter abundance can be enhanced by a 'boost factor' depending on (T_max/T_RH) relative to naive estimates assuming instantaneous reheating. We highlight here that in non-standard cosmological histories the critical mass dimension of the operator above at which the instantaneous decay approximation breaks down, and the exponent of the boost factor, depend on the equation of state \u03c9 prior to reheating. We highlight four examples in which the dark matter abundance receives a significant enhancement in the context of gravitino dark matter, the moduli portal, the Higgs portal, and the spin-2 portal (as might arise in bimetric gravity models). We comment on the transition from kination domination to radiation domination as a motivated example of non-standard cosmologies.", "keyphrases": ["non-standard cosmology", "dark matter", "massive particle"]}
{"id": "0902.2006", "title": "Consistency among distance measurements: transparency, BAO scale and accelerated expansion", "abstract": "We explore consistency among different distance measures, including Supernovae Type Ia data, measurements of the Hubble parameter, and determination of the Baryon acoustic oscillation scale. We present new constraints on the cosmic transparency combining H(z) data together with the latest Supernova Type Ia data compilation. This combination, in the context of a flat \u039bCDM model, improves current constraints by nearly an order of magnitude. We re-examine the recently reported tension between the Baryon acoustic oscillation scale and Supernovae data in light of possible deviations from transparency, concluding that the source of the discrepancy may most likely be found among systematic effects of the modelling of the low redshift data or a simple \u223c 2-\u03c3 statistical fluke, rather than in exotic physics. Finally, we attempt to draw model-independent conclusions about the recent accelerated expansion, determining the acceleration redshift to be z_acc=0.35^+0.20_-0.13 (1-\u03c3).", "keyphrases": ["transparency", "accelerated expansion", "acoustic oscillation scale", "redshift", "consistency"]}
{"id": "1901.01410", "title": "Origin of the Heaviest Elements: the Rapid Neutron-Capture Process", "abstract": "The production of about half of the heavy elements found in nature is assigned to a specific astrophysical nucleosynthesis process: the rapid neutron capture process (r-process). Although this idea has been postulated more than six decades ago, the full understanding faces two types of uncertainties/open questions: (a) The nucleosynthesis path in the nuclear chart runs close to the neutron-drip line, where presently only limited experimental information is available, and one has to rely strongly on theoretical predictions for nuclear properties. (b) While for many years the occurrence of the r-process has been associated with supernovae, more recent studies have cast substantial doubts on this environment. Alternative scenarios include the mergers of neutron stars, neutron-star black hole mergers, but possibly also rare classes of supernovae as well as hypernovae/collapsars with polar jet ejecta and also accretion disk outflows related to the collapse of fast rotating massive stars with high magnetic fields. Stellar r-process abundance observations, have provided insights into, and constraints on the frequency of and conditions in the responsible stellar production sites. One of them, neutron star mergers, was just identified and related to the Gravitational Wave event GW170817. High resolution observations, increasingly more precise due to improved experimental atomic data, have been particularly important in defining the heavy element abundance patterns of the old halo stars, and thus determining the extent, and nature, of the earliest nucleosynthesis in our Galaxy. Combining new results and important breakthroughs in the related nuclear, atomic and astronomical fields of science, this review attempts to provide an answer to the question \"How Were the Elements from Iron to Uranium Made?\" (Abridged)", "keyphrases": ["element", "neutron-capture process", "nucleosynthesis", "r-process"]}
{"id": "1002.2639", "title": "Initial Conditions for Non-Canonical Inflation", "abstract": "We investigate the dynamics of homogeneous phase space for single-field models of inflation. Inflationary trajectories are formally attractors in phase space, but since in practice not all initial conditions lead to them, some degree of fine tuning is required for successful inflation. We explore how the dynamics of non-canonical inflation, which has additional kinetic terms that are powers of the kinetic energy, can play a role in ameliorating the initial conditions fine tuning problem. We present a qualitative analysis of inflationary phase space based on the dynamical behavior of the scalar field. This allows us to construct the flow of trajectories, finding that trajectories generically decay towards the inflationary solution at a steeper angle for non-canonical kinetic terms, in comparison to canonical kinetic terms, so that a larger fraction of the initial-conditions space leads to inflation. Thus, non-canonical kinetic terms can be important for removing the initial conditions fine-tuning problem of some small-field inflation models.", "keyphrases": ["non-canonical inflation", "phase space", "non-canonical kinetic term", "initial condition"]}
{"id": "1307.0752", "title": "Galactic rotation curves in hybrid metric-Palatini gravity", "abstract": "Generally, the dynamics of test particles around galaxies, as well as the corresponding mass deficit, is explained by postulating the existence of a hypothetical dark matter. In fact, the behavior of the rotation curves shows the existence of a constant velocity region, near the baryonic matter distribution, followed by a quick decay at large distances. In this work, we consider the possibility that the behavior of the rotational velocities of test particles gravitating around galaxies can be explained within the framework of the recently proposed hybrid metric-Palatini gravitational theory. The latter is constructed by modifying the metric Einstein-Hilbert action with an f(R) term in the Palatini formalism. It was shown that the theory unifies local constraints and the late-time cosmic acceleration, even if the scalar field is very light. In the intermediate galactic scale, we show explicitly that in the hybrid metric-Palatini model the tangential velocity can be explicitly obtained as a function of the scalar field of the equivalent scalar-tensor description. The possibility of constraining the form of the scalar field and the parameters of the model by using the stellar velocity dispersions is also analyzed. Furthermore, the Doppler velocity shifts are also obtained in terms of the scalar field. All the physical and geometrical quantities and the numerical parameters in the hybrid metric-Palatini model can be expressed in terms of observable/measurable parameters, such as the tangential velocity, the baryonic mass of the galaxy, the Doppler frequency shifts, and the stellar dispersion velocity, respectively. Therefore, the obtained results open the possibility of testing the hybrid metric-Palatini gravitational models at the galactic or extra-galactic scale by using direct astronomical and astrophysical observations.", "keyphrases": ["gravity", "dark matter", "galactic rotation curve"]}
{"id": "1303.3549", "title": "Non-Gaussian Mode Coupling and the Statistical Cosmological Principle", "abstract": "Local-type primordial non-Gaussianity couples statistics of the curvature perturbation \u03b6on vastly different physical scales. Because of this coupling, statistics (i.e. the polyspectra) of \u03b6in our Hubble volume may not be representative of those in the larger universe \u2013 that is, they may be biased. The bias depends on the local background value of \u03b6, which includes contributions from all modes with wavelength k < H_0 and is therefore enhanced if the entire post-inflationary patch is large compared with our Hubble volume. We study the bias to locally-measured statistics for general local-type non-Gaussianity. We consider three examples in detail: (i) the usual fNL, gNL model, (ii) a strongly non-Gaussian model with \u03b6 \u03b6_G^p, and (iii) two-field non-Gaussian initial conditions. In each scenario one may generate statistics in a Hubble-size patch that are weakly Gaussian and consistent with observations despite the fact that the statistics in the larger, post-inflationary patch look very different.", "keyphrases": ["mode coupling", "fluctuation", "non-gaussianity"]}
{"id": "1702.06160", "title": "Mass Transfer and Disc Formation in AGB Binary Systems", "abstract": "We investigate mass transfer and the formation of disc in binary systems using a combination of numerical simulations and theory. We consider six models distinguished by binary separation, secondary mass and outflow mechanisms. Each system consists of an asymptotic-giant-branch (AGB) star and an accreting secondary. The AGB star loses its mass via a wind. In one of our six models, the AGB star incurs a short period of outburst. In all cases, the secondary accretes part of the ejected mass and also influences the mass-loss rate of the AGB star. The ejected mass may remain gravitationally bound to the binary system and form a circumbinary disk, or contribute to an accretion disk around the secondary. In other cases, the ejecta will escape the binary system. The accretion rate on to the secondary changes non-linearly with binary separation. In our closest binary simulations, our models exemplify the wind Roche lobe overflow while in our wide binary cases, the mass transfer exhibits Bondi-Hoyle accretion. The morphologies of the outflows in the binary systems are varied. The variety may provide clues to how the late AGB phase influences planetary nebulae shaping. We employ the adaptive-mesh-refinement code ASTROBEAR for our simulations and include ray-tracing, radiation transfer, cooling and dust formation. To attain the highest computational efficiency and the most stable results, all simulations are run in the corotating frame.", "keyphrases": ["agb star", "accretion disk", "mass transfer"]}
{"id": "1205.1805", "title": "Mass Measurements of Black Holes in X-Ray Transients: Is There a Mass Gap?", "abstract": "We explore possible systematic errors in the mass measurements of stellar mass black holes. We find that significant errors can arise from the assumption of zero or constant emission from the accretion flow, which is commonly used when determining orbital inclination by modelling ellipsoidal variations. For A0620-00, the system with the best available data, we show that typical data sets and analysis procedures can lead to systematic underestimates of the inclination by ten degrees or more. A careful examination of the available data for the 15 other X-ray transients with low-mass donors suggests that this effect may significantly reduce the black hole mass estimates in several other cases, most notably that of GRO J0422+32. With these revisions, our analysis of the black hole mass distribution in soft X-ray transients does not suggest any \"mass gap\" between the low end of the distribution and the maximum theoretical neutron star mass, as has been identified in previous studies. Nevertheless, we find that the mass distribution retains other previously identified characteristics, namely a peak around 8M\u2299, a paucity of sources with masses below 5M\u2299, and a sharp drop-off above 10M\u2299.", "keyphrases": ["black hole", "x-ray transient", "mass gap", "accretion flow"]}
{"id": "1907.04317", "title": "Baryon-CDM isocurvature galaxy bias with IllustrisTNG", "abstract": "We study the impact that baryon-CDM relative density perturbations \u03b4_bc have on galaxy formation using cosmological simulations with the IllustrisTNG model. These isocurvature (non-adiabatic) perturbations can be induced primordially, if multiple fields are present during inflation, and are generated before baryon-photon decoupling when baryons did not comove with CDM. The presence of long-wavelength \u03b4_bc perturbations in our simulations is mimicked by modifying the ratios of the cosmic densities of baryons \u03a9_b and CDM \u03a9_c, at fixed total matter density \u03a9_m. We measure the corresponding galaxy bias parameter b_\u03b4^bc as the response of galaxy abundances to \u03b4_bc. When selecting by total host halo mass, b_\u03b4^bc is negative and it decreases with mass and redshift. Stellar-mass selected simulated galaxies show a weaker or even the opposite trend because of the competing effects of \u03b4_bc on the halo mass function and stellar-to-halo-mass relations. We show that simple modeling of the latter two effects describes b_\u03b4^bc for stellar-mass-selected objects well. We find b_\u03b4^bc =0.6 for M_* = 10^11 M_\u2299/h and z=0.5, which is representative of BOSS DR12 galaxies. For \u03b4_bc modes generated by baryon-photon interactions, we estimate the impact on the DR12 power spectrum to be below 1%, and shifts on inferred distance and growth rate parameters should not exceed 0.1%.", "keyphrases": ["galaxy", "cosmological simulation", "baryon"]}
{"id": "1412.5169", "title": "Biased Tracers and Time Evolution", "abstract": "We study the effect of time evolution on galaxy bias. We argue that at any order in perturbations, the galaxy density contrast can be expressed in terms of a finite set of locally measurable operators made of spatial and temporal derivatives of the Newtonian potential. This is checked in an explicit third order calculation. There is a systematic way to derive a basis for these operators. This basis spans a larger space than the expansion in gravitational and velocity potentials usually employed, although new operators only appear at fourth order. The basis is argued to be closed under renormalization. Most of the arguments also apply to the structure of the counter-terms in the effective theory of large-scale structure.", "keyphrases": ["time evolution", "eftoflss", "biased tracer", "perturbative expansion", "non-linear regime"]}
{"id": "0907.0018", "title": "A novel determination of the local dark matter density", "abstract": "We present a novel study on the problem of constructing mass models for the Milky Way, concentrating on features regarding the dark matter halo component. We have considered a variegated sample of dynamical observables for the Galaxy, including several results which have appeared recently, and studied a 7- or 8-dimensional parameter space - defining the Galaxy model - by implementing a Bayesian approach to the parameter estimation based on a Markov Chain Monte Carlo method. The main result of this analysis is a novel determination of the local dark matter halo density which, assuming spherical symmetry and either an Einasto or an NFW density profile is found to be around 0.39 GeV cm^-3 with a 1-\u03c3 error bar of about 7 0.385 \u00b10.027 GeV cm^-3for the Einasto profile and\u03c1_DM(R_0) = 0.389 \u00b10.025 GeV cm^-3for the NFW. This is in contrast to the standard assumption that\u03c1_DM(R_0)is about 0.3 GeV cm^-3with an uncertainty of a factor of 2 to 3. A very precise determination of the local halo density is very important for interpreting direct dark matter detection experiments. Indeed the results we produced, together with the recent accurate determination of the local circular velocity, should be very useful to considerably narrow astrophysical uncertainties on direct dark matter detection.", "keyphrases": ["dark matter density", "mass model", "galaxy", "surface density"]}
{"id": "1205.0868", "title": "New Cosmic Accelerating Scenario without Dark Energy", "abstract": "We propose an alternative, nonsingular, cosmic scenario based on gravitationally induced particle production. The model is an attempt to evade the coincidence and cosmological constant problems of the standard model (\u039bCDM) and also to connect the early and late time accelerating stages of the Universe. Our space-time emerges from a pure initial de Sitter stage thereby providing a natural solution to the horizon problem. Subsequently, due to an instability provoked by the production of massless particles, the Universe evolves smoothly to the standard radiation dominated era thereby ending the production of radiation as required by the conformal invariance. Next, the radiation becomes sub-dominant with the Universe entering in the cold dark matter dominated era. Finally, the negative pressure associated with the creation of cold dark matter (CCDM model) particles accelerates the expansion and drives the Universe to a final de Sitter stage. The late time cosmic expansion history of the CCDM model is exactly like in the standard \u039bCDM model, however, there is no dark energy. This complete scenario is fully determined by two extreme energy densities, or equivalently, the associated de Sitter Hubble scales connected by \u03c1_I/\u03c1_f=(H_I/H_f)^2\u223c 10^122, a result that has no correlation with the cosmological constant problem. We also study the linear growth of matter perturbations at the final accelerating stage. It is found that the CCDM growth index can be written as a function of the \u039b growth index, \u03b3_\u039b\u2243 6/11. In this framework, we also compare the observed growth rate of clustering with that predicted by the current CCDM model. Performing a \u03c7^2 statistical test we show that the CCDM model provides growth rates that match sufficiently well with the observed growth rate of structure.", "keyphrases": ["dark energy", "massless particle", "cold dark matter", "general relativity"]}
{"id": "0909.4538", "title": "Self-Accelerating Universe in Galileon Cosmology", "abstract": "We present a cosmological model with a solution that self-accelerates at late-times without signs of ghost instabilities on small scales. The model is a natural extension of the Brans-Dicke (BD) theory including a non-linear derivative interaction, which appears in a theory with the Galilean shift symmetry. The existence of the self-accelerating universe requires a negative BD parameter but, thanks to the non-linear term, small fluctuations around the solution are stable on small scales. General relativity is recovered at early times and on small scales by this non-linear interaction via the Vainshtein mechanism. At late time, gravity is strongly modified and the background cosmology shows a phantom-like behaviour and the growth rate of structure formation is enhanced. Thus this model leaves distinct signatures in cosmological observations and it can be distinguished from standard \u039bCDM cosmology.", "keyphrases": ["universe", "galileon cosmology", "matter density perturbation", "galileon gravity"]}
{"id": "1512.09010", "title": "Implications of Planck2015 for inflationary, ekpyrotic and anamorphic bouncing cosmologies", "abstract": "The results from Planck2015, when combined with earlier observations from WMAP, ACT, SPT and other experiments, were the first observations to disfavor the \"classic\" inflationary paradigm. To satisfy the observational constraints, inflationary theorists have been forced to consider plateau-like inflaton potentials that introduce more parameters and more fine-tuning, problematic initial conditions, multiverse-unpredictability issues, and a new 'unlikeliness problem.' Some propose turning instead to a \"postmodern\" inflationary paradigm in which the cosmological properties in our observable universe are only locally valid and set randomly, with completely different properties (and perhaps even different physical laws) existing in most regions outside our horizon. By contrast, the new results are consistent with the simplest versions of ekpyrotic cyclic models in which the universe is smoothed and flattened during a period of slow contraction followed by a bounce, and another promising bouncing theory, anamorphic cosmology, has been proposed that can produce distinctive predictions.", "keyphrases": ["cosmology", "inflationary paradigm", "primordial perturbation"]}
{"id": "1112.2522", "title": "Circular geodesics and accretion disks in Janis-Newman-Winicour and Gamma metric", "abstract": "We study here circular timelike geodesics in the Janis-Newman-Winicour and Gamma metric spacetimes which contain a strong curvature naked singularity and reduce to the Schwarzschild metric for a specific value of one of the parameters. We show that for both the metrics the range of allowed parameters can be divided into three regimes where structure of the circular geodesics is qualitatively different. It follows that the properties of the accretion disks around such naked singularities can be significantly different from those of disks around black holes. This adds to previous studies showing that if naked singularities exist in nature, their observational signature would be significantly different from that of the black hole.", "keyphrases": ["accretion disk", "spacetime", "black hole", "circular geodesic"]}
{"id": "1611.05077", "title": "Evolving black holes from conformal transformations of static solutions", "abstract": "A class of nonstationary spacetimes is obtained by means of a conformal transformation of the Schwarzschild metric, where the conformal factor a(t) is an arbitrary function of the time coordinate only. We investigate several situations including some where the final state is a central object with constant mass. The metric is such that there is an initial big-bang type singularity and the final state depends on the chosen conformal factor. The Misner-Sharp mass is computed and a localized central object may be identified. The trapping horizons, geodesic and causal structure of the resulting spacetimes are investigated in detail. When a(t) asymptotes to a constant in a short enough time scale, the spacetime presents an event horizon and its analytical extension reveals black-hole or white-hole regions. On the other hand, when a(t) is unbounded from above as in cosmological models, the spacetime presents no event horizons and may present null singularities in the future. The energy-momentum content and other properties of the respective spacetimes are also investigated.", "keyphrases": ["black hole", "conformal transformation", "thakurta spacetime"]}
{"id": "2012.07554", "title": "Limits on Clustering and Smooth Quintessence from the EFTofLSS", "abstract": "We apply the Effective Field Theory of Large-Scale Structure (EFTofLSS) to analyze cosmological models with clustering quintessence, which allows us to consistently describe the parameter region in which the quintessence equation of state w < - 1. First, we extend the description of biased tracers in redshift space to the presence of clustering quintessence, and compute the one-loop power spectrum. We solve the EFTofLSS equations using the exact time dependence, which is relevant to obtain unbiased constraints. Then, fitting the full shape of BOSS pre-reconstructed power spectrum measurements, the BOSS post-reconstruction BAO measurements, BAO measurements from 6DF/MGS and eBOSS, the Supernovae from Pantheon, and a prior from BBN, we bound the clustering quintessence equation of state parameter w=-1.011_-0.048^+0.053 at 68% C.L.. Further combining with Planck, we obtain w=-1.028_-0.030^+0.037 at 68% C.L.. We also obtain constraints on smooth quintessence, in the physical regime w \u2265 -1: combining all datasets, we get -1\u2264 w < - 0.979 at 68% C.L.. These results strongly support a cosmological constant.", "keyphrases": ["clustering", "smooth quintessence", "eftoflss", "eboss", "cosmological constant"]}
{"id": "1106.5777", "title": "Nonlinear small-scale dynamos at low magnetic Prandtl numbers", "abstract": "Saturated small-scale dynamo solutions driven by isotropic non-helical turbulence are presented at low magnetic Prandtl numbers Pm down to 0.01. For Pm < 0.1, most of the energy is dissipated via Joule heat and, in agreement with earlier results for helical large-scale dynamos, kinetic energy dissipation is shown to diminish proportional to Pm^1/2 down to values of 0.1. In agreement with earlier work, there is, in addition to a short Golitsyn k^-11/3 spectrum near the resistive scale also some evidence for a short k^-1 spectrum on larger scales. The rms magnetic field strength of the small-scale dynamo is found to depend only weakly on the value of Pm and decreases by about a factor of 2 as Pm is decreased from 1 to 0.01. The possibility of dynamo action at Pm=0.1 in the nonlinear regime is argued to be a consequence of a suppression of the bottleneck seen in the kinetic energy spectrum in the absence of a dynamo and, more generally, a suppression of kinetic energy near the dissipation wavenumber.", "keyphrases": ["prandtl number", "turbulence", "dynamo action"]}
{"id": "1904.07133", "title": "Asymptotic safety casts its shadow", "abstract": "We set out to bridge the gap between regular black-hole spacetimes and observations of a black-hole shadow by the Event Horizon Telescope. We explore modifications of spinning and non-spinning black-hole spacetimes inspired by asymptotically safe quantum gravity which features a scale dependence of the Newton coupling. As a consequence, the predictions of our model, such as the shadow shape and size, depend on one free parameter determining the curvature scale at which deviations from General Relativity set in. In more general new-physics settings, it can also depart substantially from the Planck scale. In this case, the free parameter is constrained by observations, since the corresponding curvature scale is significantly below the Planck-scale. The leading new-physics effect can be recast as a scale-dependent black-hole mass, resulting in distinct observational signatures of our model. As a concrete example, we show that two mass-measurements, extracted from the size of the shadow and from Keplerian orbital motion of stars, allow to distinguish the classical from the modified, regular black-hole spacetime, yielding a bound on the free parameter. For spinning black holes, we further find that the singularity-resolving new physics puts a characteristic dent in the shadow. Finally, we argue, based on the underlying physical mechanism, that the effects we derive could be generic consequences of a large class of quantum-gravity theories.", "keyphrases": ["shadow", "general relativity", "hole solution"]}
{"id": "1512.08979", "title": "Searching for a matter bounce cosmology with low redshift observations", "abstract": "The matter bounce scenario allows for a sizable parameter space where cosmological fluctuations originally exited the Hubble radius when the background energy density was small. In this scenario and its extended versions, the low energy degrees of freedom are likely responsible for the statistical properties of the cosmic microwave background power spectrum at large length scales. An interesting consequence is that these modes might be observable only at relatively late times. Therefore low redshift observations could provide evidence for, or even falsify, various bouncing models. We provide an example where a recently hinted potential deviation from \u039b-cold-dark-matter cosmology results from a dark matter and dark energy interaction. The same interaction allows matter bounce models to generate a red tilt for the primordial curvature perturbations in corroboration with cosmic microwave background experiments.", "keyphrases": ["low redshift observation", "matter bounce scenario", "dark matter"]}
{"id": "1409.6840", "title": "Helical cosmological magnetic fields from extra-dimensions", "abstract": "We study the inflationary generation of helical cosmological magnetic fields in a higher-dimensional generalization of the electromagnetic theory. For this purpose, we also include a parity breaking piece to the electromagnetic action. The evolution of extra-dimensional scale factor allows the breaking of conformal invariance of the effective electromagnetic action in 1+3 dimensions required for such generation. Analytical solutions for the vector potential can be obtained in terms of Coulomb wave-functions for some special cases. We also present numerical solutions for the vector potential evolution in more general cases. In the presence of a higher-dimensional cosmological constant there exist solutions for the scale factors in which both normal and extra dimensional space either inflate or deflate simultaneously with the same rate. In such a scenario, with the number of extra dimensions D=4, a scale invariant spectrum of helical magnetic field is obtained. The net helicity arises, as one helical mode comes to dominate over the other at the superhorizon scales. A magnetic field strength of the order of 10^-9 G can be obtained for the inflationary scale H\u2243 10^-3 M_pl. Weaker fields will be generated for lower scales of inflation. Magnetic fields generated in this model respects the bounds on magnetic fields by Planck and \u03b3-ray observations (i.e. 10^-16 G < B_obs<3.4\u00d7 10^-9 G).", "keyphrases": ["cosmological magnetic field", "magnetic field", "conformal invariance", "helicity"]}
{"id": "1910.08085", "title": "An EFT description of galaxy intrinsic alignments", "abstract": "We present a general perturbative effective field theory (EFT) description of galaxy shape correlations, which are commonly known as intrinsic alignments. This rigorous approach extends current analytical modelling strategies in that it only relies on the equivalence principle. We present our results in terms of three-dimensional statistics for two- and three-point functions of both galaxy shapes and number counts. In case of the two-point function, we recover the well-known linear alignment result at leading order, but also present the full next-to-leading order expressions. In case of the three-point function we present leading order results for all the auto- and cross-correlations of galaxy shapes and densities. We use a spherical tensor basis to decompose the tensor perturbations in different helicity modes, which allows us to make use of isotropy and parity properties in the correlators. Combined with the results on projection presented in a forthcoming companion paper, our framework is directly applicable to accounting for intrinsic alignment contamination in weak lensing surveys, and to extracting cosmological information from intrinsic alignments.", "keyphrases": ["eft", "alignment", "effective field theory"]}
{"id": "1212.4176", "title": "Empty Black Holes, Firewalls, and the Origin of Bekenstein-Hawking Entropy", "abstract": "We propose a novel solution for the endpoint of gravitational collapse, in which spacetime ends (and is orbifolded) at a microscopic distance from black hole event horizons. This model is motivated by the emergence of singular event horizons in the gravitational aether theory, a semi-classical solution to the cosmological constant problem(s), and thus suggests a catastrophic breakdown of general relativity close to black hole event horizons. A similar picture emerges in fuzzball models of black holes in string theory, as well as the recent firewall proposal to resolve the information paradox. We then demonstrate that positing a surface fluid in thermal equilibrium with Hawking radiation, with vanishing energy density (but non-vanishing pressure) at the new boundary of spacetime, which is required by Israel junction conditions, yields a thermodynamic entropy that is identical to the Bekenstein-Hawking area law, S_BH, for charged rotating black holes. To our knowledge, this is the first derivation of black hole entropy which only employs local thermodynamics. Furthermore, a model for the microscopic degrees of freedom of the surface fluid (which constitute the micro-states of the black hole) is suggested, which has a finite, but Lorentz-violating, quantum field theory. Finally, we comment on the effects of physical boundary on Hawking radiation, and show that relaxing the assumption of equilibrium with Hawking radiation sets S_BH as an upper limit for Black Hole entropy.", "keyphrases": ["entropy", "hole event horizon", "bekenstein-hawking area law"]}
{"id": "1002.4948", "title": "Magnetic Fields of Black Holes and the Variability Plane", "abstract": "We estimated the magnetic field strength at the horizon radius of black holes, that is derived by the magnetic coupling process and depended on the black hole mass M_BH and the accretion rate \u1e40. Our estimation is based on the use of the fundamental variability plane for stellar mass black holes, AGNs and QSOs. The typical values of magnetic field strength on the black hole horizon are appeared at the level of B_BH\u223c 10^8G for stellar mass black holes and B_BH\u223c 10^4G for the supermassive black holes. We have obtained the relation p_l\u223c\u03bd^-1/2_b between the intrinsic polarization of the accretion disk radiation and the characteristic frequency of the black hole X-ray variability.", "keyphrases": ["black hole", "horizon radius", "magnetic field"]}
{"id": "1811.00899", "title": "The Future of Fast Radio Burst Science", "abstract": "The field of Fast Radio Burst (FRB) science is currently thriving and growing rapidly. The lines of active investigation include theoretical and observational aspects of these enigmatic millisecond radio signals. These pursuits are for the most part intertwined so that each keeps the other in check, characteristic of the healthy state of the field. The immediate future for FRB science is full of promise \u2014 we will in the next few years see two orders of magnitude more FRBs discovered by the now diverse group of instruments spread across the globe involved in these efforts. This increased crop, and the increased information obtained per event, will allow a number of fundamental questions to be answered, and FRBs' potential as astrophysical and cosmological tools to be exploited. Questions as to the exact detailed nature of FRB progenitors and whether or not there are one or more types of progenitor will be answered. Questions as to source counts, the luminosity distribution and cosmological density of FRBs will also be addressed. Looking further ahead, applications involving FRBs at the highest redshifts look set to be a major focus of the field. The potential exists to evolve to a point where statistically robust cosmological tests, orthogonal to those already undertaken in other ways, will be achieved. Related work into FRB foregrounds, as well as how to identify new events in ever more challenging radio-frequency interference environments, also appear likely avenues for extensive investigations in the coming years.", "keyphrases": ["fast radio burst", "frbs", "astronomy", "millisecond duration"]}
{"id": "1204.0514", "title": "Multiple Dark Matter as a self-regulating mechanism for dark sector interactions", "abstract": "(Abridged) Present cosmological constraints and the absence of a direct detection and identification of any dark matter particle candidate leave room to the possibility that the dark sector of the Universe be actually more complex than it is normally assumed. In particular, more than one new fundamental particle could be responsible for the observed dark matter density in the Universe, and possible new interactions between dark energy and dark matter might characterize the dark sector. In the present work, we investigate the possibility that two dark matter particles exist in nature, with identical physical properties except for the sign of their coupling constant to dark energy. Extending previous works on similar scenarios, we study the evolution of the background cosmology as well as the growth of linear density perturbations for a wide range of parameters of such model. Interestingly, our results show how the simple assumption that dark matter particles carry a \"charge\" with respect to their interaction with the dark energy field allows for new long-range scalar forces of gravitational strength in the dark sector without conflicting with present observations both at the background and linear levels. Our scenario does not introduce new parameters with respect to the case of a single dark matter species for which such strong dark interactions have been already ruled out.", "keyphrases": ["dark matter", "dark energy", "scalar field"]}
{"id": "1803.04294", "title": "Imprints of relativistic effects on the asymmetry of the halo cross-correlation function: from linear to non-linear scales", "abstract": "The apparent distribution of large-scale structures in the universe is sensitive to the velocity/potential of the sources as well as the potential along the line-of-sight through the mapping from real space to redshift space (redshift-space distortions, RSD). Since odd multipoles of the halo cross-correlation function vanish when considering standard Doppler RSD, the dipole is a sensitive probe of relativistic and wide-angle effects. We build a catalogue of ten million haloes (Milky-Way size to galaxy-cluster size) from the full-sky light-cone of a new \"RayGalGroupSims\" N-body simulation which covers a volume of (2.625 h^-1Gpc)^3 with 4096^3 particles. Using ray-tracing techniques, we find the null geodesics connecting all the sources to the observer. We then self-consistently derive all the relativistic contributions (in the weak-field approximation) to RSD: Doppler, transverse Doppler, gravitational, lensing and integrated Sachs-Wolfe. It allows us, for the first time, to disentangle all contributions to the dipole from linear to non-linear scales. At large scale, we recover the linear predictions dominated by a contribution from the divergence of neighbouring line-of-sights. While the linear theory remains a reasonable approximation of the velocity contribution to the dipole at non-linear scales it fails to reproduce the potential contribution below 30-60 h^-1Mpc (depending on the halo mass). At scales smaller than \u223c 10 h^-1Mpc, the dipole is dominated by the asymmetry caused by the gravitational redshift. The transition between the two regimes is mass dependent as well. We also identify a new non-trivial contribution from the non-linear coupling between potential and velocity terms.", "keyphrases": ["relativistic effect", "asymmetry", "halo cross-correlation function", "galaxy"]}
{"id": "1310.5350", "title": "Time Delay between Relativistic Images as a probe of Cosmic Censorship", "abstract": "We study the time delay between successive relativistic images in gravitational lensing as a possible discriminator between various collapse end states and hence as a probe of cosmic censorship. Specifically we consider both black hole and naked singularity spacetimes admitting photon spheres where an infinite number of relativistic Einstein Rings can be formed at almost the same radius and naked singularity spacetimes without a photon sphere where multiple relativistic Einstein Rings can form almost up to the center of the lens. The metrics we have considered to sample these scenarios are the Schwarzschild black hole, Janis-Newman-Winicour (naked singularity with photon sphere), Joshi-Malafarina-Narayan, and Tolman-VI (naked singularities without photon sphere) which are a fair sample of the theoretical possibilities. We show that the differential time delay between the relativistic images for naked singularities without a photon sphere progressively decreases for the models we study as opposed to that for black holes and naked singularities with a photon sphere, where it is known to be roughly constant. This characteristic difference in the time delay between successive images for these two cases can be potentially exploited for a source with known intrinsic variability to discriminate between these scenarios even when the images are not spatially resolved.", "keyphrases": ["cosmic censorship", "singularity", "photon sphere", "time delay"]}
{"id": "1305.0474", "title": "Scaling attractors in interacting teleparallel dark energy", "abstract": "It has been proposed recently the existence of a non-minimal coupling between a canonical scalar field (quintessence) and gravity in the framework of teleparallel gravity, motivated by similar constructions in the context of General Relativity. The dynamics of the model, known as teleparallel dark energy, has been further developed, but no scaling attractor has been found. Here we consider a model in which the non-minimal coupling is ruled by a dynamically changing coefficient \u03b1\u2261 f_,\u03d5/\u221a(f), with f(\u03d5) an arbitrary function of the scalar field \u03d5. It is shown that in this case the existence of scaling attractors is possible, which means that the universe will eventually enter these scaling attractors, regardless of the initial conditions. As a consequence, the cosmological coincidence problem could be alleviated without fine-tunings.", "keyphrases": ["attractor", "teleparallel dark energy", "gravity"]}
{"id": "1401.2997", "title": "The clustering of baryonic matter. I: a halo-model approach", "abstract": "In this paper I generalize the halo model for the clustering of dark matter in order to produce the power spectra of the two main baryonic matter components in the Universe: stars and hot gas. As a natural extension, this can be also used to describe the clustering of all mass. According to the design of the halo model, the large-scale power spectra of the various matter components are physically connected with the distribution of each component within bound structures and thus, ultimately, with the complete set of physical processes that drive the formation of galaxies and galaxy clusters. Besides being practical for cosmological and parametric studies, the semi-analytic model presented here has also other advantages. Most importantly, it allows one to understand on physical ground what is the relative contribution of each matter component to the total clustering of mass as a function of scale, and thus it opens an interesting new window to infer the distribution of baryons through high precision cosmic shear measurements. This is particularly relevant for future wide-field photometric surveys such as Euclid. In this work the concept of the model and its uncertainties are illustrated in detail, while in a companion paper we use a set of numerical hydrodynamic simulations to show a practical application and to investigate where the model itself needs to be improved.", "keyphrases": ["clustering", "halo model", "dark matter", "star", "hot gas"]}
{"id": "1207.2109", "title": "Nonlinear relativistic corrections to cosmological distances, redshift and gravitational lensing magnification. I - Key results", "abstract": "The next generation of telescopes will usher in an era of precision cosmology, capable of determining the cosmological model to beyond the percent level. For this to be effective, the theoretical model must be understood to at least the same level of precision. A range of subtle relativistic effects remain to be explored theoretically, and offer the potential for probing general relativity in this new regime. We present the distance-redshift relation to second order in cosmological perturbation theory for a general dark energy model. This relation determines the magnification of sources at high precision, as well as redshift space distortions in the mildly non-linear regime. We identify a range of new lensing effects, including: double-integrated and nonlinear integrated Sach-Wolfe contributions, transverse Doppler effects, lensing from the induced vector mode and gravitational wave backgrounds, in addition to lensing from the second-order potential. Modifications to Doppler lensing from redshift-space distortions are identified. Finally, we find a new double-coupling between the density fluctuations integrated along the line of sight, and gradients in the density fluctuations coupled to transverse velocities along the line of sight. These can be large and thus offer important new probes of gravitational lensing and general relativity. This paper accompanies arXiv:1402.1933, where a comprehensive derivation is given.", "keyphrases": ["redshift", "magnification", "perturbation theory"]}
{"id": "1402.7088", "title": "Linking the spin evolution of massive black holes to galaxy kinematics", "abstract": "We present the results of a semianalytical model that evolves the masses and spins of massive black holes together with the properties of their host galaxies along the cosmic history. As a consistency check, our model broadly reproduces a number of observations, e.g. the cosmic star formation history, the black hole mass and luminosity function and the galaxy mass function at low redshift, the black hole to bulge mass relation, and the morphological distribution at low redshift. For the first time in a semianalytical investigation, we relax the simplifying assumptions of perfect coherency or perfect isotropy of the gas fueling the black holes. The dynamics of gas is instead linked to the morphological properties of the host galaxies, resulting in different spin distributions for black holes hosted in different galaxy types. We compare our results with the observed sample of spin measurements obtained through broad K\u03b1 iron line fitting. The observational data disfavor both accretion along a fixed direction and isotropic fueling. Conversely, when the properties of the accretion flow are anchored to the kinematics of the host galaxy, we obtain a good match between theoretical expectations and observations. A mixture of coherent accretion and phases of activity in which the gas dynamics is similar to that of the stars in bulges (i.e., with a significant velocity dispersion superimposed to a net rotation) best describes the data, adding further evidence in support to the coevolution of massive black holes and their hosts.", "keyphrases": ["spin evolution", "black hole", "star", "redshift"]}
{"id": "0903.4895", "title": "Residual Gas Motions in the Intracluster Medium and Bias in Hydrostatic Measurements of Mass Profiles of Clusters", "abstract": "We present analysis of bulk and random gas motions in the intracluster medium using high-resolution Eulerian cosmological simulations of sixteen simulated clusters, including both very relaxed and unrelaxed systems and spanning a virial mass range of 5*10^13 - 2*10^15 Msun/h. We investigate effects of the residual subsonic gas motions on the hydrostatic estimates of mass profiles and concentrations of galaxy clusters. In agreement with previous studies we find that the gas motions contribute up to 5 relaxed clusters with contribution increasing with cluster-centric radius. The fractional pressure support is higher in unrelaxed systems. This contribution would not be accounted for in hydrostatic estimates of the total mass profile and would lead to systematic underestimate of mass. We demonstrate that total mass can be recovered accurately if pressure due to gas motions measured in simulations is explicitly taken into account in the equation of hydrostatic equilibrium. Given that the underestimate of mass is increasing at larger radii, where gas is less relaxed and contribution of gas motions to pressure is larger, the total density profile derived from hydrostatic analysis is more concentrated than the true profile. This may at least partially explain some high values of concentrations of clusters estimated from hydrostatic analysis of X-ray data.", "keyphrases": ["cluster", "cosmological simulation", "galaxy cluster", "hydrostatic equilibrium"]}
{"id": "1004.2915", "title": "General CMB and Primordial Trispectrum Estimation", "abstract": "We present trispectrum estimation methods which can be applied to general non-separable primordial and CMB trispectra. We present a general optimal estimator for the connected part of the trispectrum, for which we derive a quadratic term to incorporate the effects of inhomogeneous noise and masking. We describe a general algorithm for creating simulated maps with given arbitrary (and independent) power spectra, bispectra and trispectra. We propose a universal definition of the trispectrum parameter T_NL, so that the integrated bispectrum on the observational domain can be consistently compared between theoretical models. We define a shape function for the primordial trispectrum, together with a shape correlator and a useful parametrisation for visualizing the trispectrum. We derive separable analytic CMB solutions in the large-angle limit for constant and local models. We present separable mode decompositions which can be used to describe any primordial or CMB bispectra on their respective wavenumber or multipole domains. By extracting coefficients of these separable basis functions from an observational map, we are able to present an efficient estimator for any given theoretical model with a nonseparable trispectrum. The estimator has two manifestations, comparing the theoretical and observed coefficients at either primordial or late times. These mode decomposition methods are numerically tractable with order l^5 operations for the CMB estimator and approximately order l^6 for the general primordial estimator (reducing to order l^3 in both cases for a special class of models). We also demonstrate how the trispectrum can be reconstructed from observational maps using these methods.", "keyphrases": ["trispectrum", "estimator", "shape correlator", "regan et.al"]}
{"id": "1812.02654", "title": "CMB statistical isotropy confirmation at all scales using multipole vectors", "abstract": "We present an efficient numerical code and conduct, for the first time, a null and model-independent CMB test of statistical isotropy using Multipole Vectors (MVs) at all scales. Because MVs are insensitive to the angular power spectrum C_\u2113, our results are independent from the assumed cosmological model. We avoid a posteriori choices and use pre-defined ranges of scales \u2113\u2208[2,30], \u2113\u2208[2,600] and \u2113\u2208[2,1500] in our analyses. We find that all four masked Planck maps, from both 2015 and 2018 releases, are in agreement with statistical isotropy for \u2113\u2208[2,30], \u2113\u2208[2,600]. For \u2113\u2208[2,1500] we detect anisotropies but this is indicative of simply the anisotropy in the noise: there is no anisotropy for \u2113 < 1300 and an increasing level of anisotropy at higher multipoles. Our findings of no large-scale anisotropies seem to be a consequence of avoiding a posteriori statistics. We also find that the degree of anisotropy in the full sky (i.e. unmasked) maps vary enormously (between less than 5 and over 1000 standard deviations) among the different mapmaking procedures and data releases.", "keyphrases": ["multipole vector", "good agreement", "temperature data"]}
{"id": "1209.3142", "title": "Anti-lensing: the bright side of voids", "abstract": "More than half of the volume of our Universe is occupied by cosmic voids. The lensing magnification effect from those under-dense regions is generally thought to give a small dimming contribution: objects on the far side of a void are supposed to be observed as slightly smaller than if the void were not there, which together with conservation of surface brightness implies net reduction in photons received. This is predicted by the usual weak lensing integral of the density contrast along the line of sight. We show that this standard effect is swamped at low redshifts by a relativistic Doppler term that is typically neglected. Contrary to the usual expectation, objects on the far side of a void are brighter than they would be otherwise. Thus the local dynamics of matter in and near the void is crucial and is only captured by the full relativistic lensing convergence. There are also significant nonlinear corrections to the relativistic linear theory, which we show actually under-predicts the effect. We use exact solutions to estimate that these can be more than 20 errors for weak lensing density reconstruction in galaxy surveys and for supernovae observations, and may be the cause of the reported extra scatter of field supernovae located on the edge of voids compared to those in clusters.", "keyphrases": ["void", "photon", "low redshift"]}
{"id": "1908.03216", "title": "Evidences of low-diffusion bubbles around Galactic pulsars", "abstract": "Recently, a few-degrees extended \u03b3-ray halo in the direction of Geminga pulsar has been detected by HAWC, Milagro and Fermi-LAT. These observations can be interpreted with positrons (e^+) and electrons (e^-) accelerated by Geminga pulsar wind nebula (PWN), released in a Galactic environment with a low diffusion coefficient (D_0), and inverse Compton scattering (ICS) with the interstellar radiation fields. We inspect here how the morphology of the ICS \u03b3-ray flux depends on the energy, the pulsar age and distance, and the strength and extension of the low-diffusion bubble. In particular we show that \u03b3-ray experiments with a peak of sensitivity at TeV energies are the most promising ones to detect ICS halos. We perform a study of the sensitivity of HAWC, HESS and the future CTA experiment finding that, with efficiencies of the order of a few should have already detected a few tens of ICS halos while the latter will increase the number of detections by a factor of 4. We then consider a sample of sources associated to PWNe and detected in the HESS Galactic plane survey and in the second HAWC catalog. We use the information available in these catalogs for the \u03b3-ray spatial morphology and flux of these sources to inspect the value of D_0 around them and the e^\u00b1 injection spectrum. All sources are detected as extended with a \u03b3-ray emission extended about 15-80 pc. Assuming that most of the e^\u00b1 accelerated by these sources have been released in the interstellar medium, the diffusion coefficient is 2-30 \u00b7 10^26 cm^2/s at 1 TeV, i.e. two orders of magnitude smaller than the value considered to be the average in the Galaxy. These observations imply that Galactic PWNe have low-diffusion bubbles with a size of at least 80 pc.", "keyphrases": ["low-diffusion bubble", "pulsar", "interstellar medium"]}
{"id": "1612.03903", "title": "Spreading out and staying sharp - Creating diverse rotation curves via baryonic and self-interaction effects", "abstract": "Galactic rotation curves are a fundamental constraint for any cosmological model. We use controlled N-body simulations of galaxies to study the gravitational effect of baryons in a scenario with collisionless cold dark matter (CDM) versus one with a self-interacting dark matter (SIDM) component. In particular, we examine the inner profiles of the rotation curves in the velocity range Vmax = 30-250 km/s, whose diversity has been found to be greater than predicted by the Lambda-CDM scenario. We find that the scatter in the observed rotation curves exceeds that predicted by dark matter only mass-concentration relations in either the CDM nor SIDM models. Allowing for realistic baryonic content and spatial distributions, however, helps create a large variety of rotation curve shapes; which is in better agreement with observations in the case of self-interactions due to the characteristic cored profiles being more accommodating to the slowly rising rotation curves than CDM. We find individual fits to model two of the most remarkable outliers of similar Vmax, UGC 5721 and IC 2574, the former a cusp-like rotation curve and the latter a seemingly 8 kpc cored profile. This diversity in SIDM arises as permutations of overly concentrated halos with compact baryonic distributions versus underdense halos with extended baryonic disks. The SIDM solution is promising and its feasibility ultimately depends on the sampling of the halo mass-concentration relation and its interplay with the baryonic profiles, emphasising the need for a better understanding of the frequency of extreme outliers present in current observational samples.", "keyphrases": ["rotation curve", "self-interaction", "self-interacting dark matter", "underdense halo", "extended baryonic disk"]}
{"id": "1902.10093", "title": "Open problems on classical de Sitter solutions", "abstract": "Classical 10d string backgrounds with a 4d de Sitter space-time, D-brane and orientifold sources, are commonly believed to satisfy the following: 1. There is no classical de Sitter solution with parallel sources. 2. Classical de Sitter solutions with intersecting sources are unstable. 3. Classical de Sitter solutions cannot have at the same time a large internal volume, a small string coupling, a bounded number of orientifolds and quantized fluxes. These three conjectures are of particular relevance to the swampland program, and if true, they challenge the connection of string theory to cosmology. We restrict here to a standard solution ansatz for which the problem is well-defined, and we still fail to prove analytically any of these conjectures. While developing new tools and obtaining new constraints, we identify remaining corners of parameter space where counter-examples to these conjectures could be found.", "keyphrases": ["sitter solution", "volume", "conjecture", "string theory"]}
{"id": "1311.6813", "title": "Lensing and time-delay contributions to galaxy correlations", "abstract": "Galaxy clustering on very large scales can be probed via the 2-point correlation function in the general case of wide and deep separations, including all the lightcone and relativistic effects. Using our recently developed formalism, we analyze the behavior of the local and integrated contributions and how these depend on redshift range, linear and angular separations and luminosity function. Relativistic corrections to the local part of the correlation can be non-negligible but they remain generally sub-dominant. On the other hand, the additional correlations arising from lensing convergence and time-delay effects can become very important and even dominate the observed total correlation function. We investigate different configurations formed by the observer and the pair of galaxies, and we find that the case of near-radial large-scale separations is where these effects will be the most important.", "keyphrases": ["galaxy", "correlation function", "time-delay effect"]}
{"id": "1201.4312", "title": "The hybrid inflation waterfall and the primordial curvature perturbation", "abstract": "Without demanding a specific form for the inflaton potential, we obtain an estimate of the contribution to the curvature perturbation generated during the linear era of the hybrid inflation waterfall. The spectrum of this contribution peaks at some wavenumber k=k_*, and goes like k^3 for k\u226a k_*, making it typically negligible on cosmological scales. The scale k_* can be outside the horizon at the end of inflation, in which case \u03b6=- (g^2 - g^2) with g gaussian. Taking this into account, the cosmological bound on the abundance of black holes is likely to be satisfied if the curvaton mass m much bigger than the Hubble parameter H, but is likely to be violated if m H. Coming to the contribution to \u03b6 from the rest of the waterfall, we are led to consider the use of the `end-of-inflation' formula, giving the contribution to \u03b6 generated during a sufficiently sharp transition from nearly-exponential inflation to non-inflation, and we state for the first time the criterion for the transition to be sufficiently sharp. Our formulas are applied to supersymmetric GUT inflation and to supernatural/running-mass inflation", "keyphrases": ["hybrid inflation waterfall", "curvature perturbation", "cosmological scale", "black hole"]}
{"id": "2006.03371", "title": "Nested sampling cross-checks using order statistics", "abstract": "Nested sampling (NS) is an invaluable tool in data analysis in modern astrophysics, cosmology, gravitational wave astronomy and particle physics. We identify a previously unused property of NS related to order statistics: the insertion indexes of new live points into the existing live points should be uniformly distributed. This observation enabled us to create a novel cross-check of single NS runs. The tests can detect when an NS run failed to sample new live points from the constrained prior and plateaus in the likelihood function, which break an assumption of NS and thus leads to unreliable results. We applied our cross-check to NS runs on toy functions with known analytic results in 2 - 50 dimensions, showing that our approach can detect problematic runs on a variety of likelihoods, settings and dimensions. As an example of a realistic application, we cross-checked NS runs performed in the context of cosmological model selection. Since the cross-check is simple, we recommend that it become a mandatory test for every applicable NS run.", "keyphrases": ["sampling", "cross-check", "order statistic", "mcmc"]}
{"id": "1109.4256", "title": "Testing the Kerr black hole hypothesis", "abstract": "It is thought that the final product of the gravitational collapse is a Kerr black hole and astronomers have discovered several good astrophysical candidates. While there is some indirect evidence suggesting that the latter have an event horizon, and therefore that they are black holes, a proof that the space-time around these objects is described by the Kerr geometry is still lacking. Recently, there has been an increasing interest in the possibility of testing the Kerr black hole hypothesis with present and future experiments. In this paper, I briefly review the state of the art of the field, focussing on some recent results and work in progress.", "keyphrases": ["black hole hypothesis", "space-time", "general relativity", "accretion disk"]}
{"id": "1001.0993", "title": "Particle physics models of inflation and curvaton scenarios", "abstract": "We review the particle theory origin of inflation and curvaton mechanisms for generating large scale structures and the observed temperature anisotropy in the cosmic microwave background (CMB) radiation. Since inflaton or curvaton energy density creates all matter, it is important to understand the process of reheating and preheating into the relevant degrees of freedom required for the success of Big Bang Nucleosynthesis. We discuss two distinct classes of models, one where inflaton and curvaton belong to the hidden sector, which are coupled to the Standard Model gauge sector very weakly. There is another class of models of inflaton and curvaton, which are embedded within Minimal Supersymmetric Standard Model (MSSM) gauge group and beyond, and whose origins lie within gauge invariant combinations of supersymmetric quarks and leptons. Their masses and couplings are all well motivated from low energy physics, therefore such models provide us with a unique opportunity that they can be verified/falsified by the CMB data and also by the future collider and non-collider based experiments. We then briefly discuss stringy origin of inflation, alternative cosmological scenarios, and bouncing universes.", "keyphrases": ["particle physics model", "string theory", "primordial inflation", "higgs boson"]}
{"id": "1811.00194", "title": "Multiple messengers of fast radio bursts", "abstract": "We review the potential information that can be gleaned from multi-wavelength and multi-messenger detections of Fast Radio Bursts (FRBs). The primary function of such detections, following FRB localization, will be to reveal the progenitors of FRB events. However, these observations serve a more basic function in host galaxy identification, subsequent redshift measurement, and in disentangling the contributions of various line-of-sight contributions to properties of FRBs measured at radio wavelengths.", "keyphrases": ["fast radio burst", "frbs", "astronomy", "cosmology"]}
{"id": "1511.08212", "title": "The Lifecycle of Clusters in Galaxies", "abstract": "We review many of the basic properties of star cluster systems, and focus in particular on how they relate to their host galaxy properties and ambient environment. The cluster mass and luminosity functions are well approximated by power-laws of the form Ndm \u221d M^\u03b1dm, with \u03b1\u223c-2 over most of the observable range. However, there is now clear evidence that both become steeper at high masses/luminosities, with the value of the downward turn dependent on environment. The host galaxy properties also appear to affect the cluster formation efficiency (\u0393 - i.e., the fraction of stars that form in bound clusters), with higher star-formation rate density galaxies having higher \u0393 values. Within individual galaxies, there is evidence for \u0393 to vary by a factor of 3-4, likely following the molecular gas surface density, in agreement with recent predictions. Finally, we discuss cluster disruption and its effect on the observed properties of a population, focussing on the age distribution of clusters. We briefly discuss the expectations of theoretical and numerical studies, and also the observed distributions in a number of galaxies. Most observational studies now find agreement with theoretical expectations, namely nearly a constant cluster age distribution for ages up to 100 Myr (i.e. little disruption), and a drastic steepening above this value caused by a combination of cluster disruption and incompleteness. Rapid cluster disruption for clusters with ages < 100 Myr is ruled out for most galaxies.", "keyphrases": ["galaxy", "cluster formation efficiency", "gas surface density", "age", "star formation rate"]}
{"id": "1505.01445", "title": "Volume Weighting the Measure of the Universe from Classical Slow-Roll Expansion", "abstract": "One of the most frustrating issues in early universe cosmology centers on how to reconcile the vast choice of universes in string theory and in its most plausible high energy sibling, eternal inflation, that jointly generate the string landscape with the fine-tuned and hence relatively small number of universes that have undergone a large expansion and can accommodate observers and, in particular, galaxies. We show that such observations are highly favored for any system whereby physical parameters are distributed at a high energy scale, due to the conservation of the Liouville measure and the gauge nature of volume, asymptotically approaching a period of large isotropic expansion characterised by w=-1. Our interpretation predicts that all observational probes for deviations from w=-1 in the foreseeable future are doomed to failure. The purpose of this paper is not to introduce a new measure for the multiverse, but rather to show how what is perhaps the most natural and well known measure, volume weighting, arises as a consequence of the conservation of the Liouville measure on phase space during the classical slow-roll expansion.", "keyphrases": ["universe", "slow-roll expansion", "volume weighting"]}
{"id": "1105.5189", "title": "Cosmological dynamics of dark matter Bose-Einstein Condensation", "abstract": "Once the critical temperature of a cosmological boson gas is less than the critical temperature, a Bose-Einstein Condensation process can always take place during the cosmic history of the universe. In the Bose-Einstein Condensation model, dark matter can be described as a non-relativistic, Newtonian gravitational condensate, whose density and pressure are related by a barotropic equation of state, with barotropic index equal to one. In the present work, we study the Bose-Einstein Condensation process in a cosmological context, by assuming that this process can be described (at least approximately) as a first order phase transition. We analyze the evolution of the physical quantities relevant for the physical description of the early universe, namely, the energy density, temperature and scale factor, before, during and after the Bose-Einstein Condensation (phase transition). We also consider in detail the epoch when the universe evolved through a mixed condensate - normal dark matter phase, with a monotonically growing Bose-Einstein dark matter component. An important parameter characterizing the Bose-Einstein Condensation is the condensate dark matter fraction, whose time evolution describes the time dynamics of the conversion process. The behavior of this parameter during the cosmological condensation process is also analyzed in detail. To study the cosmological dynamics and evolution we use both analytical and numerical methods. The presence of the condensate dark matter and of the Bose-Einstein phase transition could have modified drastically the cosmological evolution of the early universe, as well as the large scale structure formation process.", "keyphrases": ["dark matter", "matter bose-einstein condensation", "cosmological dynamic", "condensate state physic"]}
{"id": "1003.1255", "title": "Small magnetic loops connecting the quiet surface and the hot outer atmosphere of the Sun", "abstract": "Sunspots are the most spectacular manifestation of solar magnetism, yet, 99 of the solar surface remains 'quiet' at any time of the solar cycle. The quiet sun is not void of magnetic fields, though; they are organized at smaller spatial scales and evolve relatively fast, which makes them difficult to detect. Thus, although extensive quiet Sun magnetism would be a natural driver to a uniform, steady heating of the outer solar atmosphere, it is not clear what the physical processes involved would be due to lack of observational evidence. We report the topology and dynamics of the magnetic field in very quiet regions of the Sun from spectropolarimetric observations of the Hinode satellite, showing a continuous injection of magnetic flux with a well organized topology of Omega-loop from below the solar surface into the upper layers. At first stages, when the loop travels across the photosphere, it has a flattened (staple-like) geometry and a mean velocity ascent of \u223c3 km/s. When the loop crosses the minimum temperature region, the magnetic fields at the footpoints become almost vertical and the loop topology ressembles a potential field. The mean ascent velocity at chromospheric height is \u223c12 km/s. The energy input rate of these small-scale loops in the lower boundary of the chromosphere is (at least) of 1.4x10^6-2.2x10^7 erg cm-2 s-1. Our findings provide empirical evidence for solar magnetism as a multi-scale system, in which small-scale low-flux magnetism plays a crucial role, at least as important as active regions, coupling different layers of the solar atmosphere and being an important ingredient for chromospheric and coronal heating models.", "keyphrases": ["sun", "magnetic field", "chromosphere"]}
{"id": "1701.02726", "title": "Low Mass X-Ray Binaries in the Inner Galaxy: Implications for Millisecond Pulsars and the GeV Excess", "abstract": "If millisecond pulsars (MSPs) are responsible for the excess gamma-ray emission observed from the region surrounding the Galactic Center, the same region should also contain a large population of low-mass X-ray binaries (LMXBs). In this study, we compile and utilize a sizable catalog of LMXBs observed in the the Milky Way's globular cluster system and in the Inner Galaxy, as well as the gamma-ray emission observed from globular clusters, to estimate the flux of gamma rays predicted from MSPs in the Inner Galaxy. From this comparison, we conclude that only up to \u223c4-23 gamma-ray excess is likely to originate from MSPs. This result is consistent with, and more robust than, previous estimates which utilized smaller samples of both globular clusters and LMXBs. If MSPs had been responsible for the entirety of the observed excess, INTEGRAL should have detected \u223c10^3 LMXBs from within a 10^\u2218 radius around the Galactic Center, whereas only 42 LMXBs (and 46 additional LMXB candidates) have been observed.", "keyphrases": ["inner galaxy", "millisecond pulsar", "low-mass x-ray binary"]}
{"id": "1512.03818", "title": "Sgr A* and General Relativity", "abstract": "General relativity has been widely tested in weak gravitational fields but still stands largely untested in the strong-field regime. According to the no-hair theorem, black holes in general relativity depend only on their masses and spins and are described by the Kerr metric. Mass and spin are the first two multipole moments of the Kerr spacetime and completely determine all higher-order moments. The no-hair theorem and, hence, general relativity can be tested by measuring potential deviations from the Kerr metric affecting such higher-order moments. Sagittarius A* (Sgr A*) is a prime target for precision tests of general relativity with several experiments across the electromagnetic spectrum. First, near-infrared (NIR) monitoring of stars orbiting around Sgr A* with current and new instruments is expected to resolve their orbital precessions. Second, timing observations of radio pulsars near the Galactic center may detect characteristic residuals induced by the spin and quadrupole moment of Sgr A*. Third, the Event Horizon Telescope, a global network of mm and sub-mm telescopes, aims to study Sgr A* on horizon scales and to image its shadow cast against the surrounding accretion flow using very-long baseline interferometric (VLBI) techniques. Both NIR and VLBI observations may also detect quasiperiodic variability of the emission from the accretion flow of Sgr A*. In this review, I discuss our current understanding of the spacetime of Sgr A* and the prospects of NIR, timing, and VLBI observations to test its Kerr nature in the near future. [abridged]", "keyphrases": ["general relativity", "black hole", "event horizon telescope", "kerr nature", "radiation"]}
{"id": "0910.0008", "title": "Robust Neutrino Constraints by Combining Low Redshift Observations with the CMB", "abstract": "We illustrate how recently improved low-redshift cosmological measurements can tighten constraints on neutrino properties. In particular we examine the impact of the assumed cosmological model on the constraints. We first consider the new HST H0 = 74.2 +/- 3.6 measurement by Riess et al. (2009) and the sigma8*(Omegam/0.25)^0.41 = 0.832 +/- 0.033 constraint from Rozo et al. (2009) derived from the SDSS maxBCG Cluster Catalog. In a Lambda CDM model and when combined with WMAP5 constraints, these low-redshift measurements constrain sum mnu<0.4 eV at the 95 for the running of the spectral index or for primordial tensor perturbations. When adding also Supernovae and BAO constraints, we obtain a 95 sum mnu<0.3 eV. We test the sensitivity of the neutrino mass constraint to the assumed expansion history by both allowing a dark energy equation of state parameter w to vary, and by studying a model with coupling between dark energy and dark matter, which allows for variation in w, Omegak, and dark coupling strength xi. When combining CMB, H0, and the SDSS LRG halo power spectrum from Reid et al. 2009, we find that in this very general model, sum mnu < 0.51 eV with 95 vary in a Lambda CDM model with sum mnu = 0, we find Nrel = 3.76^+0.63_-0.68 (^+1.38_-1.21) for the 68 intervals. We also report prior-independent constraints, which are in excellent agreement with the Bayesian constraints.", "keyphrases": ["cosmology", "neutrino mass", "galaxy", "upper limit", "cosmic microwave background"]}
{"id": "1609.02312", "title": "Charting the Parameter Space of the Global 21-cm Signal", "abstract": "The early star-forming Universe is still poorly constrained, with the properties of high-redshift stars, the first heating sources, and reionization highly uncertain. This leaves observers planning 21-cm experiments with little theoretical guidance. In this work we explore the possible range of high-redshift parameters including the star formation efficiency and the minimal mass of star-forming halos; the efficiency, spectral energy distribution, and redshift evolution of the first X-ray sources; and the history of reionization. These parameters are only weakly constrained by available observations, mainly the optical depth to the cosmic microwave background. We use realistic semi-numerical simulations to produce the global 21-cm signal over the redshift range z = 6-40 for each of 193 different combinations of the astrophysical parameters spanning the allowed range. We show that the expected signal fills a large parameter space, but with a fixed general shape for the global 21-cm curve. Even with our wide selection of models we still find clear correlations between the key features of the global 21-cm signal and underlying astrophysical properties of the high redshift Universe, namely the Ly\u03b1 intensity, the X-ray heating rate, and the production rate of ionizing photons. These correlations can be used to directly link future measurements of the global 21-cm signal to astrophysical quantities in a mostly model-independent way. We identify additional correlations that can be used as consistency checks.", "keyphrases": ["global 21-cm signal", "minimal mass", "depth", "astrophysical parameter", "mhz"]}
{"id": "1309.4173", "title": "Hypernuclear matter in a complete SU(3) symmetry group", "abstract": "Using the well known quantum hadrodynamics (QHD), we study the effects of meson-hyperon coupling constants on the onset of hyperons in dense nuclear matter. We use the SU(3) symmetry group to fix all these coupling constants, constrained to experimental nuclear matter results and astrophysical observations. While the discovery of massive pulsars PSR J1614-2230 and PSR J0348+0432 points towards a very stiff equation of state at very large densities, results from heavy ion collisions point in opposite direction for densities below five times the nuclear saturation density. We study some well known parametrizations and see that most of them cannot satisfy both types of constraints. Indeed, although in our model we can simulate a 2.25 M_\u2299 hyperonic neutron star, the heavy ion collision constraints limits the maximum mass around 2.06 M_\u2299.", "keyphrases": ["symmetry group", "hyperon puzzle", "gravitational wave physics"]}
{"id": "0911.3165", "title": "Asymptotically Safe Inflation", "abstract": "Inflation is studied in the context of asymptotically safe theories of gravitation. Conditions are explored under which it is possible to have a long period of nearly exponential expansion that eventually comes to an end.", "keyphrases": ["gravity", "critical surface", "short distance scale", "ultraviolet"]}
{"id": "1002.4197", "title": "Current constraints on the cosmic growth history", "abstract": "We present constraints on the cosmic growth history with recent cosmological data, allowing for deviations from Lambda CDM as might arise if cosmic acceleration is due to modifications to GR or inhomogeneous dark energy. We combine measures of the cosmic expansion history, from Type 1a supernovae, baryon acoustic oscillations and the CMB, with constraints on the growth of structure from recent galaxy, CMB and weak lensing surveys along with ISW-galaxy cross-correlations. Deviations from Lambda CDM are parameterized by phenomenological modifications to the Poisson equation and the relationship between the two Newtonian potentials. We find modifications that are present at the time the CMB is formed are tightly constrained through their impact on the well-measured CMB acoustic peaks. By contrast, constraints on late-time modifications to the growth history, as might arise if modifications are related to the onset of cosmic acceleration, are far weaker, but remain consistent with Lambda CDM at the 95 modifications we find that differences in the evolution on large and small scales could provide an interesting signature by which to search for modified growth histories with future wide angular coverage, large scale structure surveys.", "keyphrases": ["cosmic growth history", "newtonian potential", "gravity", "matter density contrast"]}
{"id": "1609.00528", "title": "Fast neutrino flavor conversions near the supernova core with realistic flavor-dependent angular distributions", "abstract": "It has been recently pointed out that neutrino fluxes from a supernova can show substantial flavor conversions almost immediately above the core. Using linear stability analyses and numerical solutions of the fully nonlinear equations of motion, we perform a detailed study of these fast conversions, focussing on the region just above the supernova core. We carefully specify the instabilities for evolution in space or time, andfind that neutrinos travelling towards the core make fast conversions more generic, i.e., possible for a wider range of flux ratios and angular asymmetries that produce a crossing between the zenith-angle spectra of \u03bd_e and \u03bd\u0305_e. Using fluxes and angular distributions predicted by supernova simulations, we find that fast conversions can occur within tens of nanoseconds, only a few meters away from the putative neutrinospheres. If these fast flavor conversions indeed take place, they would have important implications for the supernova explosion mechanism and nucleosynthesis.", "keyphrases": ["neutrino", "supernova core", "fast flavor conversion"]}
{"id": "1707.01480", "title": "Gravitational Waves from Primordial Black Hole Mergers", "abstract": "We study the production of primordial black hole (PBH) binaries and the resulting merger rate, accounting for an extended PBH mass function and the possibility of a clustered spatial distribution. Under the hypothesis that the gravitational wave events observed by LIGO were caused by PBH mergers, we show that it is possible to satisfy all present constraints on the PBH abundance, and find the viable parameter range for the lognormal PBH mass function. The non-observation of gravitational wave background allows us to derive constraints on the fraction of dark matter in PBHs, which are stronger than any other current constraint in the PBH mass range 0.5-30M_\u2299. We show that the predicted gravitational wave background can be observed by the coming runs of LIGO, and non-observation would indicate that the observed events are not of primordial origin. As the PBH mergers convert matter into radiation, they may have interesting cosmological implications, for example, in the context of relieving the tension between the high and low redshift measurements of the Hubble constant. However, we find that these effects are negligible as, after recombination, no more that 1% of DM can be converted into gravitational waves.", "keyphrases": ["primordial black hole", "pbh mass function", "primordial origin", "gravitational wave"]}
{"id": "0907.1445", "title": "Spin-down of neutron stars by neutrino emission", "abstract": "We study the spin-down of a neutron star during its early stages due to the neutrino emission. The mechanism we consider is the subsequent collisions of the produced neutrinos with the outer shells of the star. We find that this mechanism can indeed slow down the star rotation but only in the first tens of seconds of the core formation, which is when the appropriate conditions of flux and collision rate are met. We find that this mechanism can extract less than 1 estimated by other authors.", "keyphrases": ["neutron star", "neutrino emission", "spin-down"]}
{"id": "1606.07817", "title": "Constraints on Assembly Bias from Galaxy Clustering", "abstract": "We constrain the newly-introduced decorated Halo Occupation Distribution (HOD) model using SDSS DR7 measurements of projected galaxy clustering or r-band luminosity threshold samples. The decorated HOD is a model for the galaxy-halo connection that augments the HOD by allowing for the possibility of galaxy assembly bias: galaxy luminosity may be correlated with dark matter halo properties besides mass, Mvir. We demonstrate that it is not possible to rule out galaxy assembly bias using DR7 measurements of galaxy clustering alone. Moreover, galaxy samples with Mr < -20 and Mr < -20.5 favor strong central galaxy assembly bias. These samples prefer scenarios in which high-concentration are more likely to host a central galaxy relative to low-concentration halos of the same mass. We exclude zero assembly bias with high significance for these samples. Satellite galaxy assembly bias is significant for the faintest sample, Mr < -19. We find no evidence for assembly bias in the Mr < -21 sample. Assembly bias should be accounted for in galaxy clustering analyses or attempts to exploit galaxy clustering to constrain cosmology. In addition to presenting the first constraints on HOD models that accommodate assembly bias, our analysis includes several improvements over previous analyses of these data. Therefore, our inferences supersede previously-published results even in the case of a standard HOD analysis.", "keyphrases": ["assembly bias", "galaxy", "hod", "connection"]}
{"id": "1305.6928", "title": "Cosmology on Ultralarge Scales with Intensity Mapping of the Neutral Hydrogen 21 cm Emission: Limits on Primordial Non-Gaussianity", "abstract": "The large-scale structure of the Universe supplies crucial information about the physical processes at play at early times. Unresolved maps of the intensity of 21 cm emission from neutral hydrogen HI at redshifts z 1-5 are the best hope of accessing the ultralarge-scale information, directly related to the early Universe. A purpose-built HI intensity experiment may be used to detect the large scale effects of primordial non-Gaussianity, placing stringent bounds on different models of inflation. We argue that it may be possible to place tight constraints on the non-Gaussianity parameter f_NL, with an error close to 1.", "keyphrases": ["primordial non-gaussianity", "cosmology", "ultra-large scale", "relativistic effect"]}
{"id": "1310.1899", "title": "Long-time relaxation in pilot-wave theory", "abstract": "We initiate the study of relaxation to quantum equilibrium over long timescales in pilot-wave theory. We simulate the time evolution of the coarse-grained H-function Hbar(t) for a two-dimensional harmonic oscillator. For a (periodic) wave function that is a superposition of the first 25 energy states we confirm an approximately exponential decay of Hbar over five periods. For a superposition of only the first four energy states we are able to calculate Hbar(t) over 50 periods. We find that, depending on the set of phases in the initial wave function, Hbar can decay to a large nonequilibrium residue exceeding 10 (the equilibrium value). We show that a large residue in Hbar is caused by a tendency for the trajectories to be confined to sub-regions of configuration space for some wave functions, and that this is less likely to occur for larger numbers of energy states (if the initial phases are chosen randomly). Possible cosmological implications are briefly discussed.", "keyphrases": ["relaxation", "pilot-wave theory", "quantum equilibrium", "long timescale"]}
{"id": "0903.3619", "title": "The Evershed Flow and the Brightness of the Penumbra", "abstract": "The Evershed flow is a systematic motion of gas that occurs in the penumbra of all sunspots. Discovered in 1909, it still lacks a satisfactory explanation. We know that the flow is magnetized, often supersonic, and that it shows conspicuous fine structure on spatial scales of 0.2\"-0.3\", but its origin remains unclear. The hope is that a good observational understanding of the relation between the flow and the penumbral magnetic field will help us determine its nature. Here I review advances in the characterization of the Evershed flow and sunspot magnetic fields from high-resolution spectroscopic and spectropolarimetric measurements. Using this information as input for 2D heat transfer simulations, it has been demonstrated that hot Evershed upflows along nearly horizontal field lines are capable of explaining one of the most intriguing aspects of sunspots: the surplus brightness of the penumbra relative to the umbra. They also explain the existence of penumbral filaments with dark cores. These results support the idea that the Evershed flow is largely responsible for the transport of energy in the penumbra.", "keyphrases": ["evershed flow", "brightness", "penumbra", "fine structure", "magnetic field"]}
{"id": "0906.3126", "title": "The Subdominant Curvaton", "abstract": "We present a systematic study of the amplitude of the primordial perturbation in curvaton models with self-interactions, treating both renormalizable and non-renormalizable interactions. In particular, we consider the possibility that the curvaton energy density is subdominant at the time of the curvaton decay. We find that large regions in the parameter space give rise to the observed amplitude of primordial perturbation even for non-renormalizable curvaton potentials, for which the curvaton energy density dilutes fast. At the time of its decay, the curvaton energy density may typically be subdominant by a relative factor of 10^-3 and still produce the observed perturbation. Field dynamics turns out to be highly non-trivial, and for non-renormalizable potentials and certain regions of the parameter space we observe a non-monotonous relation between the final curvature perturbation and the initial curvaton value. In those cases, the time evolution of the primordial perturbation also displays an oscillatory behaviour before the curvaton decay.", "keyphrases": ["primordial perturbation", "curvaton model", "non-quadratic part"]}
{"id": "1007.4925", "title": "Topological Constraints on Magnetic Relaxation", "abstract": "The final state of turbulent magnetic relaxation in a reversed field pinch is well explained by Taylor's hypothesis. However, recent resistive-magnetohydrodynamic simulations of the relaxation of braided solar coronal loops have led to relaxed fields far from the Taylor state, despite the conservation of helicity. We point out the existence of an additional topological invariant in any flux tube with non-zero field: the topological degree of the field line mapping. We conjecture that this constrains the relaxation, explaining why only one of three example simulations reaches the Taylor state.", "keyphrases": ["magnetic relaxation", "helicity", "topological invariant"]}
{"id": "1103.4967", "title": "Quantum Gravitational Contributions to the CMB Anisotropy Spectrum", "abstract": "We derive the primordial power spectrum of density fluctuations in the framework of quantum cosmology. For this purpose we perform a Born-Oppenheimer approximation to the Wheeler-DeWitt equation for an inflationary universe with a scalar field. In this way we first recover the scale-invariant power spectrum that is found as an approximation in the simplest inflationary models. We then obtain quantum gravitational corrections to this spectrum and discuss whether they lead to measurable signatures in the CMB anisotropy spectrum. The non-observation so far of such corrections translates into an upper bound on the energy scale of inflation.", "keyphrases": ["cmb anisotropy spectrum", "quantum gravity", "cosmic microwave background", "high energy"]}
{"id": "0905.3532", "title": "Horava-Lifshitz Dark Energy", "abstract": "We formulate Horava-Lifshitz cosmology with an additional scalar field that leads to an effective dark energy sector. We find that, due to the inherited features from the gravitational background, Horava-Lifshitz dark energy naturally presents very interesting behaviors, possessing a varying equation-of-state parameter, exhibiting phantom behavior and allowing for a realization of the phantom divide crossing. In addition, Horava-Lifshitz dark energy guarantees for a bounce at small scale factors and it may trigger the turnaround at large scale factors, leading naturally to cyclic cosmology.", "keyphrases": ["dark energy", "cosmology", "gravity", "many author"]}
{"id": "1006.4321", "title": "Nuclear symmetry energy and its density slope at normal density extracted from global nucleon optical potentials", "abstract": "Based on the Hugenholtz-Van Hove theorem, it is shown that both the symmetry energy E_sym(\u03c1) and its density slope L(\u03c1) at normal density \u03c1_0 are completely determined by the global nucleon optical potentials that can be extracted directly from nucleon-nucleus scatterings, (p,n) charge exchange reactions and single-particle energy levels of bound states. Adopting a value of m^*/m=0.7 for the nucleon effective k-mass in symmetric nuclear matter at \u03c1_0 and averaging all phenomenological isovector nucleon potentials constrained by world data available in the literature since 1969, the best estimates of E_sym(\u03c1_0)=31.3 MeV and L(\u03c1_0)=52.7 MeV are simultaneously obtained. Uncertainties involved in the estimates are discussed.", "keyphrases": ["nuclear matter", "nuclear symmetry energy", "astrophysic"]}
{"id": "2006.09368", "title": "Galaxy bias and primordial non-Gaussianity: insights from galaxy formation simulations with IllustrisTNG", "abstract": "We study the impact that large-scale perturbations of (i) the matter density and (ii) the primordial gravitational potential with local primordial non-Gaussianity (PNG) have on galaxy formation using the IllustrisTNG model. We focus on the linear galaxy bias b_1 and the coefficient b_\u03d5 of the scale-dependent bias induced by PNG, which describe the response of galaxy number counts to these two types of perturbations, respectively. We perform our study using separate universe simulations, in which the effect of the perturbations is mimicked by changes to the cosmological parameters: modified cosmic matter density for b_1 and modified amplitude \ud835\udc9c_s of the primordial scalar power spectrum for b_\u03d5. We find that the widely used universality relation b_\u03d5 = 2\u03b4_c(b_1 - 1) is a poor description of the bias of haloes and galaxies selected by stellar mass M_*, which is instead described better by b_\u03d5(M_*) = 2\u03b4_c(b_1(M_*) - p) with p \u2208 [0.4, 0.7]. This is explained by the different impact that matter overdensities and local PNG have on the median stellar-to-halo-mass relation. A simple model of this impact allows us to describe the stellar mass dependence of b_1 and b_\u03d5 fairly well. Our results also show a nontrivial relation between b_1 and b_\u03d5 for galaxies selected by color and black hole mass accretion rate. Our results provide refined priors on b_\u03d5 for local PNG constraints and forecasts using galaxy clustering. Given that the widely used universality relation underpredicts b_\u03d5(M_*), existing analyses may underestimate the true constraining power on local PNG.", "keyphrases": ["bias", "primordial non-gaussianity", "galaxy formation simulation", "illustristng model", "universality relation"]}
{"id": "1210.3852", "title": "Unidentified sources in the Fermi-LAT second source catalog: the case for DM subhalos", "abstract": "The Large Area Telescope (LAT) aboard the Fermi satellite allows us to study the high-energy gamma-ray sky with unprecedented sensitivity. However, the origin of 31 population of unassociated gamma-ray sources may contain new object classes, among them sources of photons from self-annihilating or decaying non-baryonic dark matter. Fermi-LAT might be capable to detect up to a few of these dark matter subhalos as faint and moderately extended gamma-ray sources with a temporally steady high-energy emission. After applying corresponding selection cuts to the second year Fermi catalog 2FGL, we investigate 13 candidate objects in more detail including their multi-wavelength properties in the radio, infrared, optical, UV, and X-ray bands. For the gamma-ray band, we analyze both the 24-month and 42-month Fermi-LAT data sets. We probe the gamma-ray spectra for indications of a spectral cutoff, which singles out four sources of particular interest. We find all sources to be compatible with a point-source scenario. Multi-wavelength associations and, in particular, their infrared color-color data indicate no source to be compatible with a dark matter origin, and we find the majority of the candidates to probably originate from faint, high-frequency peaked BL Lac type objects. We discuss possibilities to further investigate source candidates and future prospects to search for dark matter subhalos.", "keyphrases": ["fermi-lat", "large area telescope", "gamma-ray source", "unidentified source"]}
{"id": "1506.06019", "title": "Jumping Neptune Can Explain the Kuiper Belt Kernel", "abstract": "The Kuiper belt is a population of icy bodies beyond the orbit of Neptune. A particularly puzzling and up-to-now unexplained feature of the Kuiper belt is the so-called `kernel', a concentration of orbits with semimajor axes a 44 AU, eccentricities e 0.05, and inclinations i<5 deg. Here we show that the Kuiper belt kernel can be explained if Neptune's otherwise smooth migration was interrupted by a discontinuous change of Neptune's semimajor axis when Neptune reached 28 AU. Before the discontinuity happened, planetesimals located at 40 AU were swept into Neptune's 2:1 resonance, and were carried with the migrating resonance outwards. The 2:1 resonance was at 44 AU when Neptune reached 28 AU. If Neptune's semimajor axis changed by fraction of AU at this point, perhaps because Neptune was scattered off of another planet, the 2:1 population would have been released at 44 AU, and would remain there to this day. We show that the orbital distribution of bodies produced in this model provides a good match to the orbital properties of the kernel. If Neptune migration was conveniently slow after the jump, the sweeping 2:1 resonance would deplete the population of bodies at 45-47 AU, thus contributing to the paucity of the low-inclination orbits in this region. Special provisions, probably related to inefficiencies in the accretional growth of sizable objects, are still needed to explain why only a few low-inclination bodies have been so far detected beyond 47 AU.", "keyphrases": ["neptune", "kuiper belt kernel", "migration", "discontinuous change"]}
{"id": "1608.00672", "title": "Impacts of dark energy on weighing neutrinos: mass hierarchies considered", "abstract": "Taking into account the mass splittings between three active neutrinos, we investigate impacts of dark energy on constraining the total neutrino mass \u2211 m_\u03bd by using recent cosmological observations. We consider two typical dark energy models, namely, the wCDM model and the holographic dark energy (HDE) model, which both have an additional free parameter compared with the \u039bCDM model. We employ the Planck 2015 data of CMB temperature and polarization anisotropies, combined with low-redshift measurements on BAO distance scales, type Ia supernovae, Hubble constant, and Planck lensing. Compared to the \u039bCDM model, our study shows that the upper limit on \u2211 m_\u03bd becomes much looser in the wCDM model while much tighter in the HDE model. In the HDE model, we obtain the 95% CL upper limit \u2211 m_\u03bd<0.105 eV for three degenerate neutrinos. This might be the most stringent constraint on \u2211 m_\u03bd by far and is almost on the verge of diagnosing the neutrino mass hierachies in the HDE model. However, the difference of \u03c7^2 is still not significant enough to distinguish the neutrino mass hierarchies, even though the minimal \u03c7^2 of the normal hierarchy is slightly smaller than that of the inverted hierarchy.", "keyphrases": ["neutrino", "dark energy model", "holographic dark energy", "cosmological scenario"]}
{"id": "0910.3855", "title": "Probing interaction and spatial curvature in the holographic dark energy model", "abstract": "In this paper we place observational constraints on the interaction and spatial curvature in the holographic dark energy model. We consider three kinds of phenomenological interactions between holographic dark energy and matter, i.e., the interaction term Q is proportional to the energy densities of dark energy (\u03c1_\u039b), matter (\u03c1_m), and matter plus dark energy (\u03c1_m+\u03c1_\u039b). For probing the interaction and spatial curvature in the holographic dark energy model, we use the latest observational data including the type Ia supernovae (SNIa) Constitution data, the shift parameter of the cosmic microwave background (CMB) given by the five-year Wilkinson Microwave Anisotropy Probe (WMAP5) observations, and the baryon acoustic oscillation (BAO) measurement from the Sloan Digital Sky Survey (SDSS). Our results show that the interaction and spatial curvature in the holographic dark energy model are both rather small. Besides, it is interesting to find that there exists significant degeneracy between the phenomenological interaction and the spatial curvature in the holographic dark energy model.", "keyphrases": ["holographic dark energy", "dark energy model", "non-gravitational coupling"]}
{"id": "1609.02557", "title": "Staying away from the bar: the local dynamical signature of slow and fast bars in the Milky Way", "abstract": "Both the three-dimensional density of red clump giants and the gas kinematics in the inner Galaxy indicate that the pattern speed of the Galactic bar could be much lower than previously estimated. Here, we show that such slow bar models are unable to reproduce the bimodality observed in local stellar velocity space. We do so by computing the response of stars in the Solar neighbourhood to the gravitational potential of slow and fast bars, in terms of their perturbed distribution function in action-angle space up to second order, as well as by identifying resonantly trapped orbits. We also check that the bimodality is unlikely to be produced through perturbations from spiral arms, and conclude that, contrary to gas kinematics, local stellar kinematics still favour a fast bar in the Milky Way, with a pattern speed of the order of almost twice (and no less than 1.8 times) the circular frequency at the Sun's position. This leaves open the question of the nature of the long flat extension of the bar in the Milky Way.", "keyphrases": ["bar", "milky way", "pattern speed", "velocity space"]}
{"id": "1306.1455", "title": "Alfven Wave Collisions, The Fundamental Building Block of Plasma Turbulence I: Asymptotic Solution", "abstract": "The nonlinear interaction between counterpropagating Alfven waves is the physical mechanism underlying the cascade of energy to small scales in astrophysical plasma turbulence. Beginning with the equations for incompressible MHD, an asymptotic analytical solution for the nonlinear evolution of these Alfven wave collisions is derived in the weakly nonlinear limit. The resulting qualitative picture of nonlinear energy transfer due to this mechanism involves two steps: first, the primary counterpropagating Alfven waves interact to generate an inherently nonlinear, purely magnetic secondary fluctuation with no parallel variation; second, the two primary waves each interact with this secondary fluctuation to transfer energy secularly to two tertiary Alfven waves. These tertiary modes are linear Alfven waves with the same parallel wavenumber as the primary waves, indicating the lack of a parallel cascade. The amplitude of these tertiary modes increases linearly with time due to the coherent nature of the resonant four-wave interaction responsible for the nonlinear energy transfer. The implications of this analytical solution for turbulence in astrophysical plasmas is discussed. The solution presented here provides valuable intuition about the nonlinear interactions underlying magnetized plasma turbulence, in support of an experimental program to verify in the laboratory the nature of this fundamental building block of astrophysical plasma turbulence.", "keyphrases": ["plasma turbulence", "weakly nonlinear limit", "alfv\u00e9n wave"]}
{"id": "1109.6012", "title": "21-cm cosmology", "abstract": "Imaging the Universe during the first hundreds of millions of years remains one of the exciting challenges facing modern cosmology. Observations of the redshifted 21 cm line of atomic hydrogen offer the potential of opening a new window into this epoch. This would transform our understanding of the formation of the first stars and galaxies and of the thermal history of the Universe. A new generation of radio telescopes is being constructed for this purpose with the first results starting to trickle in. In this review, we detail the physics that governs the 21 cm signal and describe what might be learnt from upcoming observations. We also generalize our discussion to intensity mapping of other atomic and molecular lines.", "keyphrases": ["cosmology", "hydrogen", "new generation", "dark matter", "hyperfine splitting"]}
{"id": "1311.1514", "title": "Cosmology with massive neutrinos III: the halo mass function and an application to galaxy clusters", "abstract": "We use a suite of N-body simulations that incorporate massive neutrinos as an extra-set of particles to investigate their effect on the halo mass function. We show that for cosmologies with massive neutrinos the mass function of dark matter haloes selected using the spherical overdensity (SO) criterion is well reproduced by the fitting formula of Tinker et al. (2008) once the cold dark matter power spectrum is considered instead of the total matter power, as it is usually done. The differences between the two implementations, i.e. using P_ cdm(k) instead of P_ m(k), are more pronounced for large values of the neutrino masses and in the high end of the halo mass function: in particular, the number of massive haloes is higher when P_ cdm(k) is considered rather than P_ m(k). As a quantitative application of our findings we consider a Planck-like SZ-clusters survey and show that the differences in predicted number counts can be as large as 30% for \u2211 m_\u03bd = 0.4 eV. Finally, we use the Planck-SZ clusters sample, with an approximate likelihood calculation, to derive Planck-like constraints on cosmological parameters. We find that, in a massive neutrino cosmology, our correction to the halo mass function produces a shift in the \u03c3_8(\u03a9_ m/0.27)^\u03b3 relation which can be quantified as \u0394\u03b3\u223c 0.05 and \u0394\u03b3\u223c 0.14 assuming one (N_\u03bd=1) or three (N_\u03bd=3) degenerate massive neutrino, respectively. The shift results in a lower mean value of \u03c3_8 with \u0394\u03c3_8 = 0.01 for N_\u03bd=1 and \u0394\u03c3_8 = 0.02 for N_\u03bd=3, respectively. Such difference, in a cosmology with massive neutrinos, would increase the tension between cluster abundance and Planck CMB measurements.", "keyphrases": ["massive neutrino", "halo mass function", "cosmology"]}
{"id": "2110.13160", "title": "Galaxy Formation and Reionization: Key Unknowns and Expected Breakthroughs by the James Webb Space Telescope", "abstract": "The scheduled launch of James Webb Space Telescope (JWST) in late 2021 marks a new start for studies of galaxy formation at high redshift z> 6 during the era of Cosmic Reionization. JWST can capture sensitive, high-resolution images and multi-object spectroscopy in the infrared that will transform our view of galaxy formation during the first billion years of cosmic history. This review summarizes our current knowledge of the role of galaxies in reionizing intergalactic hydrogen ahead of JWST, achieved through observations with Hubble Space Telescope and ground-based facilities including Keck, the Very Large Telescope, Subaru, and the Atacama Large Millimeter/Submillimeter Array. We identify outstanding questions in the field that JWST can address during its mission lifetime, including with the planned JWST Cycle 1 programs. (Abridged)", "keyphrases": ["hubble space telescope", "galaxy formation", "intergalactic medium", "star"]}
{"id": "1803.05508", "title": "Dark matter constraints from dwarf galaxies: a data-driven analysis", "abstract": "Dwarf galaxies represent a powerful probe of annihilating dark matter particle models, with gamma-ray data setting some of the best bounds available. A major issue in improving over existing constraints consists in the limited knowledge of the astrophysical background (mostly diffuse photons, but also unresolved sources). Perhaps more worrisome, several approaches in the literature suffer of the difficulty of assessing the systematic error due to background mis-modelling. Here we propose a data-driven method to estimate the background at the dwarf position and its uncertainty, relying on an appropriate use of the whole-sky data, via an optimisation procedure of the interpolation weights. While this article is mostly methodologically oriented, we also report the bounds based on latest Fermi-LAT data and updated information for J-factors for both isolated and stacked dwarfs. Our results are very competitive with the Fermi-LAT ones, while being derived with a more general and flexible method. We discuss the impact of profiling over the J-factor as well as over the background probability distribution function, with the latter resulting for instance crucial in drawing conclusions of compatibility with DM interpretations of the so-called Galactic Centre Excess.", "keyphrases": ["dwarf galaxy", "astrophysical background", "data-driven method"]}
{"id": "1701.06087", "title": "Ho\u0159ava Gravity at a Lifshitz Point: A Progress Report", "abstract": "Ho\u0159ava gravity at a Lifshitz point is a theory intended to quantize gravity by using techniques of traditional quantum field theories. To avoid Ostrogradsky's ghosts, a problem that has been plaguing quantization of general relativity since the middle of 1970's, Ho\u0159ava chose to break the Lorentz invariance by a Lifshitz-type of anisotropic scaling between space and time at the ultra-high energy, while recovering (approximately) the invariance at low energies. With the stringent observational constraints and self-consistency, it turns out that this is not an easy task, and various modifications have been proposed, since the first incarnation of the theory in 2009. In this review, we shall provide a progress report on the recent developments of Ho\u0159ava gravity. In particular, we first present four most-studied versions of Ho\u0159ava gravity, by focusing first on their self-consistency and then their consistency with experiments, including the solar system tests and cosmological observations. Then, we provide a general review on the recent developments of the theory in three different but also related areas: (i) universal horizons, black holes and their thermodynamics; (ii) non-relativistic gauge/gravity duality; and (iii) quantization of the theory. The studies in these areas can be generalized to other gravitational theories with broken Lorentz invariance.", "keyphrases": ["lifshitz point", "progress report", "ho\u0159ava gravity"]}
{"id": "1210.7166", "title": "Probing dark energy with redshift-drift", "abstract": "Future redshift-drift measurements (also known as Sandage-Loeb signal) will be crucial to probe the so called \"redshift desert\", thus providing a new tool for cosmological studies. In this paper we quantify the ability of a future measurement of the Sandage-Loeb signal by a CODEX-like spectrograph to constrain a phenomenological parametrization of dynamical dark energy, specifically by obtaining constraints on w_0 and w_a. We also demonstrate that if used alongside CMB data, the Sandage-Loeb measurements will be able to break degeneracies between expansion parameters, thus greatly improving cosmological constraints.", "keyphrases": ["dark energy", "redshift desert", "cosmological parameter estimation", "quasar"]}
{"id": "1607.06049", "title": "Energy-Momentum Squared Gravity", "abstract": "A new covariant generalization of Einstein's general relativity is developed which allows the existence of a term proportional to T_\u03b1\u03b2T^\u03b1\u03b2 in the action functional of the theory (T_\u03b1\u03b2 is the energy-momentum tensor). Consequently the relevant field equations are different from general relativity only in the presence of matter sources. In the case of a charged black hole, we find exact solutions for the field equations. Applying this theory to a homogeneous and isotropic space-time, we find that there is a maximum energy density \u03c1_max, and correspondingly a minimum length a_min, at early universe. This means that there is a bounce at early times and this theory avoids the existence of an early time singularity. Moreover we show that this theory possesses a true sequence of cosmological eras. Also, we argue that although in the context of the standard cosmological model the cosmological constant \u039b does not play any important role in the early times and becomes important only after the matter dominated era, in this theory the \"repulsive\" nature of the cosmological constant plays a crucial role at early times for resolving the singularity.", "keyphrases": ["tensor", "bounce", "energy-momentum squared gravity", "matter part"]}
{"id": "1403.1004", "title": "Recursive structure in the definitions of gauge-invariant variables for any order perturbations", "abstract": "The construction of gauge-invariant variables for any order perturbations is discussed. Explicit constructions of the gauge-invariant variables for perturbations to 4th order are shown. From these explicit construction, the recursive structure in the definitions of gauge-invariant variables for any order perturbations is found. Through this recursive structure, the correspondence with the fully non-linear exact perturbations is briefly discussed.", "keyphrases": ["definition", "gauge-invariant variable", "order perturbation"]}
{"id": "1111.4595", "title": "Nonsingular, big-bounce cosmology from spinor-torsion coupling", "abstract": "The Einstein-Cartan-Sciama-Kibble theory of gravity removes the constraint of general relativity that the affine connection be symmetric by regarding its antisymmetric part, the torsion tensor, as a dynamical variable. The minimal coupling between the torsion tensor and Dirac spinors generates a spin-spin interaction which is significant in fermionic matter at extremely high densities. We show that such an interaction averts the unphysical big-bang singularity, replacing it with a cusp-like bounce at a finite minimum scale factor, before which the Universe was contracting. This scenario also explains why the present Universe at largest scales appears spatially flat, homogeneous and isotropic.", "keyphrases": ["cosmology", "spinor-torsion coupling", "fermionic matter", "black hole"]}
{"id": "1403.2967", "title": "Origin of very high and ultra high energy cosmic rays", "abstract": "While there is some level of consensus on a Galactic origin of cosmic rays up to the knee (E_k\u223c 3\u00d7 10^15 eV) and on an extragalactic origin of cosmic rays with energy above \u223c 10^19 eV, the debate on the genesis of cosmic rays in the intermediate energy region has received much less attention, mainly because of the ambiguity intrinsic in defining such a region. The energy range between 10^17 eV and \u223c 10^19 eV is likely to be the place where the transition from Galactic to extragalactic cosmic rays takes place. Hence the origin of these particles, though being of the highest importance from the physics point of view, it is also one of the most difficult aspects to investigate. Here I will illustrate some ideas concerning the sites of acceleration of these particles and the questions that their investigation may help answer, including the origin of ultra high energy cosmic rays.", "keyphrases": ["ultra high energy", "cosmic ray", "structure formation shock", "pulsar", "galactic nucleus"]}
{"id": "1103.5134", "title": "A Gravitational Mechanism for Cosmological Screening", "abstract": "Infrared gravitons are continually produced during inflation. Like all particles, their contribution to the vacuum energy comes not only from their bare kinetic energy but also from the interactions they have with other gravitons. These interactions can be substantial \u2013 despite the particles being highly infrared \u2013 because they occur over the enormous spatial volume of the universe. Furthermore, the interactions grow with time evolution because more and more such gravitons come into causal contact with one another. Since gravity is universally attractive, these interactions can act to slow and eventually stop accelerated expansion.", "keyphrases": ["graviton", "universe", "primordial inflation"]}
{"id": "1805.12265", "title": "Cosmology with Gravitational Wave/Fast Radio Burst Associations", "abstract": "Recently, some theoretical models predicted that a small fraction of fast radio bursts (FRBs) could be associated with gravitational waves (GWs). In this work, we discuss the possibility of using GW/FRB association systems, if commonly detected in the future, as a complementary cosmic probe. We propose that upgraded standard sirens can be constructed from the joint measurements of luminosity distances D_L derived from GWs and dispersion measures DM_IGM derived from FRBs (i.e., the combination D_L\u00b7 DM_IGM). Moreover, unlike the traditional standard-siren approach (i.e., the D_L method) and the DM_IGM method that rely on the optimization of the Hubble constant H_0, this D_L\u00b7 DM_IGM method has the advantage of being independent of H_0. Through Monte Carlo simulations, we prove that the D_L\u00b7 DM_IGM method is more effective to constrain cosmological parameters than D_L or DM_IGM separately, and enables us to achieve accurate multimessenger cosmology from around 100 GW/FRB systems. Additionally, even if GW/FRB associations are not exist, the methodology developed here can still be applied to those GWs and FRBs that occur at the same redshifts.", "keyphrases": ["gravitational wave", "luminosity distance", "cosmology"]}
{"id": "1204.5176", "title": "The VPOS: a vast polar structure of satellite galaxies, globular clusters and streams around the Milky Way", "abstract": "It has been known for a long time that the satellite galaxies of the Milky Way (MW) show a significant amount of phase-space correlation, they are distributed in a highly inclined Disc of Satellites (DoS). We have extended the previous studies on the DoS by analysing for the first time the orientations of streams of stars and gas, and the distributions of globular clusters within the halo of the MW. It is shown that the spatial distribution of MW globular clusters classified as young halo clusters (YH GC) is very similar to the DoS, while 7 of the 14 analysed streams align with the DoS. The probability to find the observed clustering of streams is only 0.3 per cent when assuming isotropy. The MW thus is surrounded by a vast polar structure (VPOS) of subsystems (satellite galaxies, globular clusters and streams), spreading from Galactocentric distances as small as 10 kpc out to 250 kpc. These findings demonstrate that a near-isotropic infall of cosmological sub-structure components onto the MW is essentially ruled out because a large number of infalling objects would have had to be highly correlated, to a degree not natural for dark matter sub-structures. The majority of satellites, streams and YH GCs had to be formed as a correlated population. This is possible in tidal tails consisting of material expelled from interacting galaxies. We discuss the tidal scenario for the formation of the VPOS, including successes and possible challenges. The potential consequences of the MW satellites being tidal dwarf galaxies are severe. If all the satellite galaxies and YH GCs have been formed in an encounter between the young MW and another gas-rich galaxy about 10-11 Gyr ago, then the MW does not have any luminous dark-matter substructures and the missing satellites problem becomes a catastrophic failure of the standard cosmological model.", "keyphrases": ["vast polar structure", "satellite galaxy", "globular cluster"]}
{"id": "0907.2126", "title": "Velocities as a probe of dark sector interactions", "abstract": "Dark energy in General Relativity is typically non-interacting with other matter. However, it is possible that the dark energy interacts with the dark matter, and in this case, the dark matter can violate the universality of free fall (the weak equivalence principle). We show that some forms of the dark sector interaction do not violate weak equivalence. For those interactions that do violate weak equivalence, there are no available laboratory experiments to probe this violation for dark matter. But cosmology provides a test for violations of the equivalence principle between dark matter and baryons \u2013 via a test for consistency of the observed galaxy velocities with the Euler equation.", "keyphrases": ["dark sector interaction", "dark energy", "cosmology", "galaxy velocity", "non-gravitational coupling"]}
{"id": "1805.02496", "title": "IMAGINE: A comprehensive view of the interstellar medium, Galactic magnetic fields and cosmic rays", "abstract": "In this white paper we introduce the IMAGINE Consortium and its scientific background, goals and structure. Our purpose is to coordinate and facilitate the efforts of a diverse group of researchers in the broad areas of the interstellar medium, Galactic magnetic fields and cosmic rays, and our goal is to develop more comprehensive insights into the structures and roles of interstellar magnetic fields and their interactions with cosmic rays. To achieve a higher level of self-consistency, depth and rigour can only be achieved by the coordinated efforts of experts in diverse areas of astrophysics involved in observational, theoretical and numerical work. We present our view of the present status of this topic, identify its key unsolved problems and suggest a strategy that will underpin our work. The backbone of the consortium is the Interstellar MAGnetic field INference Engine, a publicly available Bayesian platform that employs robust statistical methods to explore the multi-dimensional likelihood space using any number of modular inputs. It provides an interpretation and modelling framework that has the power and flexibility to include a variety of observational, theoretical and numerical lines of evidence into a self-consistent and comprehensive picture of the thermal and non-thermal interstellar media. An important innovation is that a consistent understanding of the phenomena that are directly or indirectly influenced by the Galactic magnetic field, such as the deflection of ultra-high energy cosmic rays or extragalactic backgrounds, is made an integral part of the modelling. The IMAGINE Consortium, which is informal by nature and open to new participants, hereby presents a methodological framework for the modelling and understanding of Galactic magnetic fields that is available to all communities whose research relies on a state-of-the-art solution to this problem. (Abridged.)", "keyphrases": ["interstellar medium", "galactic magnetic field", "cosmic ray"]}
{"id": "0911.4967", "title": "Galaxy rotation curves from General Relativity with Renormalization Group corrections", "abstract": "We consider the application of quantum corrections computed using renormalization group arguments in the astrophysical domain and show that, for the most natural interpretation of the renormalization group scale parameter, a gravitational coupling parameter G varying 10^-7 of its value across a galaxy (which is roughly a variation of 10^-12 per light-year) is sufficient to generate galaxy rotation curves in agreement with the observations. The quality of the resulting fit is similar to the Isothermal profile quality once both the shape of the rotation curve and the mass-to-light ratios are considered for evaluation. In order to perform the analysis, we use recent high quality data from nine regular disk galaxies. For the sake of comparison, the same set of data is modeled also for the Modified Newtonian Dynamics (MOND) and for the recently proposed Scalar Tensor Vector Gravity (STVG). At face value, the model based on quantum corrections clearly leads to better fits than these two alternative theories.", "keyphrases": ["general relativity", "renormalization group correction", "galaxy rotation curve"]}
{"id": "1906.01657", "title": "BlueMUSE: Project Overview and Science Cases", "abstract": "We present the concept of BlueMUSE, a blue-optimised, medium spectral resolution, panoramic integral field spectrograph based on the MUSE concept and proposed for the Very Large Telescope. With an optimised transmission down to 350 nm, a larger FoV (1.4 x 1.4 arcmin^2) and a higher spectral resolution compared to MUSE, BlueMUSE will open up a new range of galactic and extragalactic science cases allowed by its specific capabilities, beyond those possible with MUSE. For example a survey of massive stars in our galaxy and the Local Group will increase the known population of massive stars by a factor >100, to answer key questions about their evolution. Deep field observations with BlueMUSE will also significantly increase samples of Lyman-alpha emitters, spanning the era of Cosmic Noon. This will revolutionise the study of the distant Universe: allowing the intergalactic medium to be detected unambiguously in emission, enabling the study of the exchange of baryons between galaxies and their surroundings. By 2030, at a time when the focus of most of the new large facilities (ELT, JWST) will be on the infra-red, BlueMUSE will be a unique facility, outperforming any ELT instrument in the Blue/UV. It will have a strong synergy with ELT, JWST as well as ALMA, SKA, Euclid and Athena.", "keyphrases": ["science case", "fov", "capability", "bluemuse"]}
{"id": "1207.6784", "title": "Photoionization, fluorescence, and inner-shell processes", "abstract": "Major advances in state-of-the-art theoretical methods coupled with advances in computational architectures have opened the doorway to large-scale computations on elements across the periodic table, allowing the inclusion of fully relativistic effects. Whenever possible results have been benchmarked against high resolution measurements obtained from either synchrotron radiation facilities or satellite observations. Various stages of ionization, necessary for the many applications in astrophysics, can be studied in the absence of experimental values to obtain the necessary data. A simple review is presented of photoionization, fluorescence and inner-shell processes recently investigated.", "keyphrases": ["fluorescence", "inner-shell process", "photoionization"]}
{"id": "2210.12070", "title": "The DAMIC-M Experiment: Status and First Results", "abstract": "The DAMIC-M (DArk Matter In CCDs at Modane) experiment employs thick, fully depleted silicon charged-coupled devices (CCDs) to search for dark matter particles with a target exposure of 1 kg-year. A novel skipper readout implemented in the CCDs provides single electron resolution through multiple non-destructive measurements of the individual pixel charge, pushing the detection threshold to the eV-scale. DAMIC-M will advance by several orders of magnitude the exploration of the dark matter particle hypothesis, in particular of candidates pertaining to the so-called \"hidden sector.\" A prototype, the Low Background Chamber (LBC), with 20g of low background Skipper CCDs, has been recently installed at Laboratoire Souterrain de Modane and is currently taking data. We will report the status of the DAMIC-M experiment and first results obtained with LBC commissioning data.", "keyphrases": ["damic-m experiment", "status", "first result"]}
{"id": "1009.1250", "title": "Spherical Boson Stars as Black Hole mimickers", "abstract": "We present spherically symmetric boson stars as black hole mimickers based on the power spectrum of a simple accretion disk model. The free parameters of the boson star are the mass of the boson and the fourth order self-interaction coefficient in the scalar field potential. We show that even if the mass of the boson is the only free parameter it is possible to find a configuration that mimics the power spectrum of the disk due to a black hole of the same mass. We also show that for each value of the self-interaction a single boson star configuration can mimic a black hole at very different astrophysical scales in terms of the mass of the object and the accretion rate. In order to show that it is possible to distinguish one of our mimickers from a black hole we also study the deflection of light.", "keyphrases": ["boson star", "black hole mimicker", "accretion disk"]}
{"id": "1403.5407", "title": "Reheating the Universe Once More: The Dissipation of Acoustic Waves as a Novel Probe of Primordial Inhomogeneities on Even Smaller Scales", "abstract": "We provide a simple but robust bound on the primordial curvature perturbation in the range 10^4 Mpc^-1 < k < 10^5 Mpc^-1, which has not been constrained so far unlike low wavenumber modes. Perturbations on these scales dissipate the energy of their acoustic oscillations by the Silk damping after primordial nucleosynthesis but before the redshift z \u223c 2 \u00d7 10^6 and reheat the photon bath without invoking CMB distortions. This acoustic reheating results in the decrease of the baryon-photon ratio. By combining independent measurements probing the nucleosynthesis era and around the recombination epoch, we find an upper bound on the amplitude of the curvature perturbation over the above wavenumber range as P_\u03b6 < 0.06. Implications for super massive black holes are also discussed.", "keyphrases": ["curvature perturbation", "small scale", "reheating"]}
{"id": "1904.04261", "title": "The E-MOSAICS project: tracing galaxy formation and assembly with the age-metallicity distribution of globular clusters", "abstract": "We present 25 cosmological zoom-in simulations of Milky Way-mass galaxies in the `MOdelling Star cluster population Assembly In Cosmological Simulations within EAGLE' (E-MOSAICS) project. E-MOSAICS couples a detailed physical model for the formation, evolution, and disruption of star clusters to the EAGLE galaxy formation simulations. This enables following the co-formation and co-evolution of galaxies and their star cluster populations, thus realising the long-standing promise of using globular clusters (GCs) as tracers of galaxy formation and assembly. The simulations show that the age-metallicity distributions of GC populations exhibit strong galaxy-to-galaxy variations, resulting from differences in their evolutionary histories. We develop a formalism for systematically constraining the assembly histories of galaxies using GC age-metallicity distributions. These distributions are characterised through 13 metrics that we correlate with 30 quantities describing galaxy formation and assembly (e.g. halo properties, formation/assembly redshifts, stellar mass assembly time-scales, galaxy merger statistics), resulting in 20 statistically (highly) significant correlations. The GC age-metallicity distribution is a sensitive probe of the mass growth, metal enrichment, and minor merger history of the host galaxy. No such relation is found between GCs and major mergers, which play a sub-dominant role in GC formation for Milky Way-mass galaxies. Finally, we show how the GC age-metallicity distribution enables the reconstruction of the host galaxy's merger tree, allowing us to identify all progenitors with masses M_*\u227310^8 M_\u2299 for redshifts 1\u2264 z\u22642.5. These results demonstrate that cosmological simulations of the co-formation and co-evolution of GCs and their host galaxies successfully unlock the potential of GCs as quantitative tracers of galaxy formation and assembly.", "keyphrases": ["galaxy formation", "age-metallicity distribution", "globular cluster"]}
{"id": "1306.4686", "title": "Cosmological Constraints from Galaxy Clustering and the Mass-to-Number Ratio of Galaxy Clusters: Marginalizing over the Physics of Galaxy Formation", "abstract": "Many approaches to obtaining cosmological constraints rely on the connection between galaxies and dark matter. However, the distribution of galaxies is dependent on their formation and evolution as well as the cosmological model, and galaxy formation is still not a well-constrained process. Thus, methods that probe cosmology using galaxies as a tracer for dark matter must be able to accurately estimate the cosmological parameters without knowing the details of galaxy formation a priori. We apply this reasoning to the method of obtaining \u03a9_m and \u03c3_8 from galaxy clustering combined with the mass-to-number ratio of galaxy clusters. To test the sensitivity of this method to variations due to galaxy formation, we consider several different models applied to the same cosmological dark matter simulation. The cosmological parameters are then estimated using the observables in each model, marginalizing over the parameters of the Halo Occupation Distribution (HOD). We find that for models where the galaxies can be well represented by a parameterized HOD, this method can successfully extract the desired cosmological parameters for a wide range of galaxy formation prescriptions.", "keyphrases": ["mass-to-number ratio", "galaxy formation", "cosmological constraint"]}
{"id": "1610.05192", "title": "Metastable Dark Energy with Radioactive-like Decay", "abstract": "We propose a new class of metastable dark energy (DE) phenomenological models in which the DE decay rate does not depend on external parameters such as the scale factor or the curvature of the Universe. Instead, the DE decay rate is assumed to be a constant depending only on intrinsic properties of DE and the type of a decay channel, similar to case of the radioactive decay of unstable particles and nuclei. As a consequence, the DE energy density becomes a function of the proper time elapsed since its formation, presumably in the very early Universe. Such a natural type of DE decay can profoundly affect the expansion history of the Universe and its age. Metastable DE can decay in three distinct ways: (i) exponentially, (ii) into dark matter, (iii) into dark radiation. Testing metastable DE models with observational data we find that the decay half-life must be many times larger than the age of the Universe. Models in which dark energy decays into dark matter lead to lower values of the Hubble parameter at large redshifts relative to \u039bCDM. Consequently these models provide a better fit to cosmological BAO data (especially data from from high redshift quasars) than concordance (\u039bCDM) cosmology.", "keyphrases": ["decay", "dark matter", "metastable dark energy", "gravitational theory", "universe content"]}
{"id": "1811.07541", "title": "Constraints on massive vector dark energy models from integrated Sachs-Wolfe-galaxy cross-correlations", "abstract": "The gravitational-wave event GW170817, together with the electromagnetic counterpart, shows that the speed of tensor perturbations c_T on the cosmological background is very close to that of light c for the redshift z<0.009. In generalized Proca theories, the Lagrangians compatible with the condition c_T=c are constrained to be derivative interactions up to cubic order, besides those corresponding to intrinsic vector modes. We place observational constraints on a dark energy model in cubic-order generalized Proca theories with intrinsic vector modes by running the Markov chain Monte Carlo (MCMC) code. We use the cross-correlation data of the integrated Sachs-Wolfe (ISW) signal and galaxy distributions in addition to the data sets of cosmic microwave background, baryon acoustic oscillations, type Ia supernovae, local measurements of the Hubble expansion rate, and redshift-space distortions. We show that, unlike cubic-order scalar-tensor theories, the existence of intrinsic vector modes allows the possibility for evading the ISW-galaxy anticorrelation incompatible with the current observational data. As a result, we find that the dark energy model in cubic-order generalized Proca theories exhibits a better fit to the data than the cosmological constant, even by including the ISW-galaxy correlation data in the MCMC analysis.", "keyphrases": ["dark energy model", "cross-correlation", "effective gravitational coupling"]}
{"id": "1312.2913", "title": "Gamma-ray Pulsar Revolution", "abstract": "Isolated Neutron Stars (INSs) were the first sources identified in the field of high-energy gamma-ray astronomy. At first, in the 70s, there were only two identified sources, the Crab and Vela pulsars. However, although few in number, these objects were crucial in establishing the very concept of a gamma-ray source. Moreover, they opened up significant discovery space both in the theoretical and phenomenological fronts. The need to explain the copious gamma-ray emission of these pulsars led to breakthrough developments in understanding the structure and physics of neutron star magnetospheres. In parallel, the 20-year-long chase to understand the nature of Geminga unveiled the existence of a radio-quiet, gamma-ray-emitting, INS, adding a new dimension to the INS family. Today we are living through an extraordinary time of discovery. The current generation of gamma-ray detectors has vastly increased the population of known of gamma-ray-emitting neutron stars. The 100 mark was crossed in 2011 and we are now approaching 150. The gamma-ray-emitting neutron star population exhibits roughly equal numbers of radio-loud and radio-quiet young INSs, plus an astonishing, and unexpected, group of isolated and binary millisecond pulsars (MSPs). The number of MSPs is growing so rapidly that they are on their way to becoming the most numerous members of the family of gamma-ray-emitting Neutron Stars (NSs) . Even as these findings have set the stage for a revolution in our understanding of gamma-ray-emitting neutron stars, long term monitoring of the gamma-ray sky has revealed evidence of flux variability in the Crab Nebula as well as in the pulsed emission from PSR J2021+4026, challenging a four-decade-old, constant-emission paradigm. Now we know that both pulsars and their nebulae can, indeed, display variable emission.", "keyphrases": ["pulsar", "neutron star", "gamma-ray sky", "lat", "large area telescope"]}
{"id": "1404.0022", "title": "Simplified Dark Matter Models for the Galactic Center Gamma-Ray Excess", "abstract": "Motivated by the gamma-ray excess observed from the region surrounding the Galactic Center, we explore particle dark matter models that could potentially account for the spectrum and normalization of this signal. Taking a model-independent approach, we consider an exhaustive list of tree-level diagrams for dark matter annihilation, and determine which could account for the observed gamma-ray emission while simultaneously predicting a thermal relic abundance equal to the measured cosmological dark matter density. We identify a wide variety of models that can meet these criteria without conflicting with existing constraints from direct detection experiments or the Large Hadron Collider (LHC). The prospects for detection in near future dark matter experiments and/or the upcoming 14 TeV LHC appear quite promising.", "keyphrases": ["dark matter model", "gamma-ray excess", "astrophysical origin"]}
{"id": "2005.11208", "title": "Fermi Large Area Telescope Fourth Source Catalog Data Release 2", "abstract": "We present an incremental version (4FGL-DR2, for Data Release 2) of the fourth Fermi-LAT catalog of gamma-ray sources. Based on the first ten years of science data in the energy range from 50 MeV to 1 TeV, it uses the same analysis methods as the 4FGL catalog did for eight years of data. The spectral parameters, spectral energy distributions and associations are updated for all sources. Light curves are rebuilt for all sources with 1-year intervals (not 2-month intervals). Among the 5064 4FGL sources, 120 are formally below the detection threshold over 10 years (but are kept in the list), while 53 are newly associated and four associations were withdrawn. We report 723 new sources, mostly just above the detection threshold, among which two are considered identified and 341 have a plausible counterpart at other wavelengths.", "keyphrases": ["large area telescope", "data release", "4fgl-dr2", "fermi-lat catalog"]}
{"id": "1011.1499", "title": "Particle Physics Implications for CoGeNT, DAMA, and Fermi", "abstract": "Recent results from the CoGeNT collaboration (as well as the annual modulation reported by DAMA/LIBRA) point toward dark matter with a light (5-10 GeV) mass and a relatively large elastic scattering cross section with nucleons (\u03c3 10^-40 cm^2). In order to possess this cross section, the dark matter must communicate with the Standard Model through mediating particles with small masses and/or large couplings. In this Letter, we explore with a model independent approach the particle physics scenarios that could potentially accommodate these signals. We also discuss how such models could produce the gamma rays from the Galactic Center observed in the data of the Fermi Gamma Ray Space Telescope. We find multiple particle physics scenarios in which each of these signals can be accounted for, and in which the dark matter can be produced thermally in the early Universe with an abundance equal to the measured cosmological density.", "keyphrases": ["cogent", "dama", "dark matter", "cross section", "nucleon"]}
{"id": "1603.01269", "title": "Towards the most general scalar-tensor theories of gravity: a unified approach in the language of differential forms", "abstract": "We use a description based on differential forms to systematically explore the space of scalar-tensor theories of gravity. Within this formalism, we propose a basis for the scalar sector at the lowest order in derivatives of the field and in any number of dimensions. This minimal basis is used to construct a finite and closed set of Lagrangians describing general scalar-tensor theories invariant under Local Lorentz Transformations in a pseudo-Riemannian manifold, which contains ten physically distinct elements in four spacetime dimensions. Subsequently, we compute their corresponding equations of motion and find which combinations are at most second order in derivatives in four as well as arbitrary number of dimensions. By studying the possible exact forms (total derivatives) and algebraic relations between the basis components, we discover that there are only four Lagrangian combinations producing second order equations, which can be associated with Horndeski's theory. In this process, we identify a new second order Lagrangian, named kinetic Gauss-Bonnet, that was not previously considered in the literature. However, we show that its dynamics is already contained in Horndeski's theory. Finally, we provide a full classification of the relations between different second order theories. This allows us to clarify, for instance, the connection between different covariantizations of Galileons theory. In conclusion, our formulation affords great computational simplicity with a systematic structure. As a first step we focus on theories with second order equations of motion. However, this new formalism aims to facilitate advances towards unveiling the most general scalar-tensor theories.", "keyphrases": ["scalar-tensor theory", "gravity", "differential form"]}
{"id": "2104.08475", "title": "Analytic solutions of the nonlinear radiation diffusion equation with an instantaneous point source in non-homogeneous media", "abstract": "Analytic solutions to the nonlinear radiation diffusion equation with an instantaneous point source for a non-homogeneous medium with a power law spatial density profile, are presented. The solutions are a generalization of the well known solutions for a homogeneous medium. It is shown that the solutions take various qualitatively different forms according to the value of the spatial exponent. These different forms are studied in detail for linear and non linear heat conduction. In addition, by inspecting the generalized solutions, we show that there exist values of the spatial exponent such the conduction front has constant speed or even accelerates. Finally, the various solution forms are compared in detail to numerical simulations, and a good agreement is achieved.", "keyphrases": ["radiation diffusion equation", "non-homogeneous medium", "analytic solution"]}
{"id": "2105.07694", "title": "Primordial black holes and secondary gravitational waves from string inspired general no-scale supergravity", "abstract": "The formation of primordial black hole (PBH) dark matter and the generation of scalar induced secondary gravitational waves (SIGWs) have been studied in the generic no-scale supergravity inflationary models. By adding an exponential term to the K\u00e4hler potential, the inflaton experiences a period of ultraslow-roll and the amplitude of primordial power spectrum at small scales is enhanced to \ud835\udcaa(10^-2). The enhanced power spectra of primordial curvature perturbations can have both sharp and broad peaks. A wide mass range of PBHs can be produced in our model, and the frequencies of the accompanied SIGWs are ranged form nanohertz to kilohertz. We show four benchmark points where the generated PBH masses are around \ud835\udcaa(10^-16M_\u2299), \ud835\udcaa(10^-12M_\u2299), \ud835\udcaa(10^-2M_\u2299) and \ud835\udcaa(10^2M_\u2299). The PBHs with masses around \ud835\udcaa(10^-16M_\u2299) and \ud835\udcaa(10^-12M_\u2299) can make up almost all the dark matter, and the accompanied SIGWs can be probed by the upcoming space-based gravitational wave observatory. Also, the SIGWs accompanied with the formation of stellar mass PBHs can be used to interpret the stochastic GW background in the nanohertz band, detected by the North American Nanohertz Observatory for gravitational waves, and can be tested by future interferometric gravitational wave observatory.", "keyphrases": ["secondary gravitational wave", "no-scale supergravity", "primordial black hole"]}
{"id": "2003.06245", "title": "The Evolution of the Star-forming Interstellar Medium across Cosmic Time", "abstract": "Over the past decade increasingly robust estimates of the dense molecular gas content in galaxy populations between redshift 0 and the peak of cosmic galaxy/star formation from redshift 1-3 have become available. This rapid progress has been possible due to the advent of powerful ground-based, and space telescopes for combined study of several millimeter to far-IR, line or continuum tracers of the molecular gas and dust components. The main conclusions of this review are: 1. Star forming galaxies contained much more molecular gas at earlier cosmic epochs than at the present time. 2. The galaxy integrated depletion time scale for converting the gas into stars depends primarily on z or Hubble time, and at a given z, on the vertical location of a galaxy along the star-formation rate versus stellar mass \"main-sequence\" (MS) correlation. 3. Global rates of galaxy gas accretion primarily control the evolution of the cold molecular gas content and star formation rates of the dominant MS galaxy population, which in turn vary with the cosmological expansion. A second key driver may be global disk fragmentation in high-z, gas rich galaxies, which ties local free-fall time scales to galactic orbital times, and leads to rapid radial matter transport and bulge growth. Third, the low star formation efficiency inside molecular clouds is plausibly set by super-sonic streaming motions, and internal turbulence, which in turn may be driven by conversion of gravitational energy at high-z, and/or by local feedback from massive stars at low-z. 4. A simple 'gas regulator' model is remarkably successful in predicting the combined evolution of molecular gas fractions, star formation rates, galactic winds, and gas phase metallicities.", "keyphrases": ["cosmic time", "molecular gas", "star formation"]}
{"id": "2006.13621", "title": "Electroweak baryogenesis by primordial black holes in Brans-Dicke modified gravity", "abstract": "A successful baryogenesis mechanism is proposed in the cosmological framework of Brans-Dicke modified gravity. Primordial black holes with small mass are produced at the end of the Brans-Dicke field domination era. The Hawking radiation reheats a spherical region around every black hole to a high temperature and the electroweak symmetry is restored there. A domain wall is formed separating the region with the symmetric vacuum from the asymmetric region where electroweak baryogenesis takes place. First order phase transition is not needed. In Brans-Dicke cosmologies black hole accretion can be strong enough to lead to black holes domination which extends the lifetime of black holes and therefore baryogenesis. The analysis of the whole scenario, finally, results in the observed baryon number which can be achieved for a CP-violation angle that is predicted by observationally accepted Two-Higgs Doublet Models. The advantage of our proposed scenario is that naturally provides both black hole domination and more efficient baryogenesis for smaller CP violating angles compared to the same mechanism applied in a FRW cosmological background.", "keyphrases": ["baryogenesis", "primordial black hole", "brans-dicke modified gravity"]}
{"id": "0905.4001", "title": "Preferred frame parameters in the tensor-vector-scalar theory of gravity and its generalization", "abstract": "The Tensor-Vector-Scalar theory of gravity, which was designed as a relativistic implementation to the modified dynamics paradigm, has fared quite well as an alternative to dark matter, on both galactic and cosmological scales. However, its performance in the solar system, as embodied in the post-Newtonian formalism, has not yet been fully investigated. Tamaki has recently attempted to calculate the preferred frame parameters for TeVeS, but ignored the cosmological value of the scalar field, thus concluding that the Newtonian potential must be static in order to be consistent with the vector equation. We show that when the cosmological value of the scalar field is taken into account, there is no constraint on the Newtonian potential; however, the cosmological value of the scalar field is tightly linked to the vector field coupling constant K, preventing the former from evolving as predicted by its equation of motion. We then proceed to investigate the post-Newtonian limit of a generalized version of TeVeS, with \u00c6ther type vector action, and show that its \u03b2,\u03b3and \u03beparameters are as in GR, while solar system constraints on the preferred frame parameters \u03b1_1 and \u03b1_2 can be satisfied within a modest range of small values of the scalar and vector fields coupling parameters, and for values of the cosmological scalar field consistent with evolution within the framework of existing models.", "keyphrases": ["tensor-vector-scalar theory", "gravity", "preferred frame parameter"]}
{"id": "1210.3692", "title": "Violation of non-Gaussianity consistency relation in a single field inflationary model", "abstract": "In this paper we present a simple, toy model of single field inflation in which the standard non-Gaussianity consistency condition is violated. In this model the curvature perturbations on super-horizon scales are not conserved and the decaying modes of perturbations are not negligible in the non-atractor phase. As a result a large local non-Gaussianity can be obtained in the squeezed limit which violates the standard non-Gaussianity consistency condition for the single field models.", "keyphrases": ["non-gaussianity consistency relation", "inflationary model", "single field inflation"]}
{"id": "0910.1066", "title": "Axion Cosmology Revisited", "abstract": "The misalignment mechanism for axion production depends on the temperature-dependent axion mass. The latter has recently been determined within the interacting instanton liquid model (IILM), and provides for the first time a well-motivated axion mass for all temperatures. We reexamine the constraints placed on the axion parameter space in the light of this new mass function. We find an accurate and updated constraint f_a \u2264 2.8(\u00b12)\u00d7 10^11GeV or m_a \u2265 21(\u00b12) \u03bc eV from the misalignment mechanism in the classic axion window (thermal scenario). However, this is superseded by axion string radiation which leads to f_a \u2272 3.2^+4_-2\u00d7 10^10GeV or m_a \u2273 0.20 ^+0.2_-0.1meV. In this analysis, we take care to precisely compute the effective degrees of freedom and, to fill a gap in the literature, we present accurate fitting formulas. We solve the evolution equations exactly, and find that analytic results used to date generally underestimate the full numerical solution by a factor 2-3. In the inflationary scenario, axions induce isocurvature fluctuations and constrain the allowed inflationary scale H_I. Taking anharmonic effects into account, we show that these bounds are actually weaker than previously computed. Considering the fine-tuning issue of the misalignment angle in the whole of the anthropic window, we derive new bounds which open up the inflationary window near \u03b8_a \u2192\u03c0. In particular, we find that inflationary dark matter axions can have masses as high as 0.01\u20131meV, covering the whole thermal axion range, with values of H_I up to 10^9GeV. Quantum fluctuations during inflation exclude dominant dark matter axions with masses above m_a\u2272 1meV.", "keyphrases": ["dark matter", "axion", "early universe"]}
{"id": "1206.0562", "title": "Deriving an Accurate Formula of Scale-dependent Bias with Primordial Non-Gaussianity: An Application of the Integrated Perturbation Theory", "abstract": "We apply the integrated perturbation theory (Matsubara 2011, PRD 83, 083518) to evaluate the scale-dependent bias in the presence of primordial non-Gaussianity. The integrated perturbation theory is a general framework of nonlinear perturbation theory, in which a broad class of bias models can be incorporated into perturbative evaluations of biased power spectrum and higher-order polyspectra. Approximations such as the high-peak limit or the peak-background split are not necessary to derive the scale-dependent bias in this framework. Applying the halo approach, previously known formulas are re-derived as limiting cases of a general formula in this work, and it is implied that modifications should be made in general situations. Effects of redshift-space distortions are straightforwardly incorporated. It is found that the slope of the scale-dependent bias on large scales is determined only by the behavior of primordial bispectrum in the squeezed limit, and is not sensitive to bias models in general. It is the amplitude of scale-dependent bias that is sensitive to the bias models. The effects of redshift-space distortions turn out to be quite small for the monopole component of the power spectrum, while the quadrupole component is proportional to the monopole component on large scales, and thus also sensitive to the primordial non-Gaussianity.", "keyphrases": ["scale-dependent bias", "non-gaussianity", "integrated perturbation theory"]}
{"id": "1906.04354", "title": "Dependence of outer boundary condition on protoneutron star asteroseismology with gravitational-wave signatures", "abstract": "To obtain the eigenfrequencies of a protoneutron star (PNS) in the postbounce phase of core-collapse supernovae (CCSNe), we perform a linear perturbation analysis of the angle-averaged PNS profiles using results from a general relativistic CCSN simulation of a 15 M_\u2299 star. In this work, we investigate how the choice of the outer boundary condition could affect the PNS oscillation modes in the linear analysis. By changing the density at the outer boundary of the PNS surface in a parametric manner, we show that the eigenfrequencies strongly depend on the surface density. By comparing with the gravitational wave (GW) signatures obtained in the hydrodynamics simulation, the so-called surface g-mode of the PNS can be well ascribed to the fundamental oscillations of the PNS. The frequency of the fundamental oscillations can be fitted by a function of the mass and radius of the PNS similar to the case of cold neutron stars. In the case that the position of the outer boundary is chosen to cover not only the PNS but also the surrounding postshock region, we obtain the eigenfrequencies close to the modulation frequencies of the standing accretion-shock instability (SASI). However, we point out that these oscillation modes are unlikely to have the same physical origin of the SASI modes seen in the hydrodynamics simulation. We discuss possible limitations of applying the angle-averaged, linear perturbation analysis to extract the full ingredients of the CCSN GW signatures.", "keyphrases": ["asteroseismology", "core-collapse supernovae", "neutron star"]}
{"id": "1505.02196", "title": "Fine-structure constant constraints on dark energy", "abstract": "We use astrophysical and atomic clock tests of the stability of the fine-structure constant \u03b1, together with Type Ia supernova and Hubble parameter data, to constrain the simplest class of dynamical dark energy models where the same degree of freedom is assumed to provide both the dark energy and (through a dimensionless coupling, \u03b6, to the electromagnetic sector) the \u03b1 variation. We show how current data tightly constrains a combination of \u03b6 and the dark energy equation of state w_0. At the 95% confidence level and marginalizing over w_0 we find |\u03b6|<5\u00d710^-6, with the atomic clock tests dominating the constraints. The forthcoming generation of high-resolution ultra-stable spectrographs will enable significantly tighter constraints.", "keyphrases": ["dark energy", "dimensionless coupling", "electromagnetic sector", "confidence level"]}
{"id": "1009.3319", "title": "Electron Injection by Whistler Waves in Non-relativistic Shocks", "abstract": "Electron acceleration to non-thermal, ultra-relativistic energies ( 10-100 TeV) is revealed by radio and X-ray observations of shocks in young supernova remnants (SNRs). The diffusive shock acceleration (DSA) mechanism is usually invoked to explain this acceleration, but the way in which electrons are initially energized or 'injected' into this acceleration process starting from thermal energies is an unresolved problem. In this paper we study the initial acceleration of electrons in non-relativistic shocks from first principles, using two- and three-dimensional particle-in-cell (PIC) plasma simulations. We systematically explore the space of shock parameters (the Alfv\u00e9nic Mach number, M_A, the shock velocity, v_sh, the angle between the upstream magnetic field and the shock normal, theta_Bn, and the ion to electron mass ratio, m_i/m_e). We find that significant non-thermal acceleration occurs due to the growth of oblique whistler waves in the foot of quasi-perpendicular shocks. The obtained electron energy distributions show power law tails with spectral indices up to alpha 3-4. The maximum energies of the accelerated particles are consistent with the electron Larmor radii being comparable to that of the ions, indicating potential injection into the subsequent DSA process. This injection mechanism, however, requires the shock waves to have fairly low Alf\u00e9nic Mach numbers, M_A < 20, which is consistent with the theoretical conditions for the growth of whistler waves in the shock foot (M_A < (m_i/m_e)^1/2). Thus, if the whistler mechanism is the only robust electron injection process at work in SNR shocks, then SNRs that display non-thermal emission must have significantly amplified upstream magnetic fields. Such field amplification is likely achieved by the escaping cosmic rays, so electron and proton acceleration in SNR shocks must be interconnected.", "keyphrases": ["whistler wave", "non-relativistic shock", "plasma simulation", "electron injection process"]}
{"id": "1611.09638", "title": "Nonlinear reconstruction", "abstract": "We present a direct approach to nonparametrically reconstruct the linear density field from an observed nonlinear map. We solve for the unique displacement potential consistent with the nonlinear density and positive definite coordinate transformation using a multigrid algorithm. We show that we recover the linear initial conditions up to the nonlinear scale (r_\u03b4_r\u03b4_L>0.5 for k\u22721 h/Mpc) with minimal computational cost. This reconstruction approach generalizes the linear displacement theory to fully nonlinear fields, potentially substantially expanding the baryon acoustic oscillations and redshift space distortions information content of dense large scale structure surveys, including for example SDSS main sample and 21cm intensity mapping initiatives.", "keyphrases": ["reconstruction", "density field", "displacement potential", "definite coordinate transformation", "initial condition"]}
{"id": "1808.01386", "title": "MOND as the weak field limit of an extended metric theory of gravity with a matter-curvature coupling", "abstract": "In this article we construct an extended relativistic f(R) theory of gravity with matter-curvature couplings F(R,L_matt) for which its weak field limit of approximation recovers the simplest version of MOND. We do this by (a) performing an order of magnitude approach and (b) by perturbing the resulting field equations of the theory to the weakest field limit of approximation. We also compute the geodesic equation of the resulting theory and show that it has an extra force, a fact that commonly appears in general matter-curvature couplings. This arxiv version includes a section at the end with an Erratum.", "keyphrases": ["field limit", "gravity", "matter-curvature coupling"]}
{"id": "1103.3927", "title": "Constraint on the early Universe by relic gravitational waves: From pulsar timing observations", "abstract": "Recent pulsar timing observations by the Parkers Pulsar Timing Array and European Pulsar Timing Array teams obtained the constraint on the relic gravitational waves at the frequency f_*=1/ yr, which provides the opportunity to constrain H_*, the Hubble parameter when these waves crossed the horizon during inflation. In this paper, we investigate this constraint by considering the general scenario for the early Universe: we assume that the effective (average) equation-of-state w before the big bang nucleosynthesis stage is a free parameter. In the standard hot big-bang scenario with w=1/3, we find that the current PPTA result follows a bound H_*\u2264 1.15\u00d710^-1, and the EPTA result follows H_*\u2264 6.92\u00d710^-2. We also find that these bounds become much tighter in the nonstandard scenarios with w>1/3. When w=1, the bounds become H_*\u22645.89\u00d710^-3 for the current PPTA and H_*\u22643.39\u00d710^-3 for the current EPTA. In contrast, in the nonstandard scenario with w=0, the bound becomes H_*\u22647.76 for the current PPTA.", "keyphrases": ["early universe", "relic gravitational wave", "pulsar timing observation"]}
{"id": "2009.03286", "title": "CosmoBit: A GAMBIT module for computing cosmological observables and likelihoods", "abstract": "We introduce CosmoBit, a module within the open-source GAMBIT software framework for exploring connections between cosmology and particle physics with joint global fits. CosmoBit provides a flexible framework for studying various scenarios beyond \u039bCDM, such as models of inflation, modifications of the effective number of relativistic degrees of freedom, exotic energy injection from annihilating or decaying dark matter, and variations of the properties of elementary particles such as neutrino masses and the lifetime of the neutron. Many observables and likelihoods in CosmoBit are computed via interfaces to AlterBBN, CLASS, DarkAges, MontePython, MultiModeCode, and plc. This makes it possible to apply a wide range of constraints from large-scale structure, Type Ia supernovae, Big Bang Nucleosynthesis and the cosmic microwave background. Parameter scans can be performed using the many different statistical sampling algorithms available within the GAMBIT framework, and results can be combined with calculations from other GAMBIT modules focused on particle physics and dark matter. We include extensive validation plots and a first application to scenarios with non-standard relativistic degrees of freedom and neutrino temperature, showing that the corresponding constraint on the sum of neutrino masses is much weaker than in the standard scenario.", "keyphrases": ["gambit module", "likelihood", "relativistic degree", "big bang nucleosynthesis", "cosmobit"]}
{"id": "1410.6899", "title": "Bose-Einstein condensate strings", "abstract": "We consider the possible existence of gravitationally bound general relativistic strings consisting of Bose-Einstein condensate (BEC) matter which is described, in the Newtonian limit, by the zero temperature time-dependent nonlinear Schr\u00f6dinger equation (the Gross-Pitaevskii equation), with repulsive interparticle interactions. In the Madelung representation of the wave function, the quantum dynamics of the condensate can be formulated in terms of the classical continuity equation and the hydrodynamic Euler equations. In the case of a condensate with quartic nonlinearity, the condensates can be described as a gas with two pressure terms, the interaction pressure, which is proportional to the square of the matter density, and the quantum pressure, which is without any classical analogue though, when the number of particles in the system is high enough, the latter may be neglected. Assuming cylindrical symmetry, we analyze the physical properties of the BEC strings in both the interaction pressure and quantum pressure dominated limits, by numerically integrating the gravitational field equations. In this way we obtain a large class of stable stringlike astrophysical objects, whose basic parameters (mass density and radius) depend sensitively on the mass and scattering length of the condensate particle, as well as on the quantum pressure of the Bose-Einstein gas.", "keyphrases": ["relativistic string", "einstein condensate", "bose", "dark matter"]}
{"id": "1309.0519", "title": "Mainly axion cold dark matter from natural supersymmetry", "abstract": "By eschewing finetuning from the electroweak and QCD sectors of supersymmetry (natural supersymmetry or SUSY), and by invoking the Kim-Nilles solution to the SUSY mu problem, one is lead to models wherein the dark matter is comprised of a mixture of axions and higgsino-like WIMPs. Over a large range of Peccei-Quinn breaking scale f_a 10^9-10^12 GeV, one then expects about 90-95 matter. In such a scenario, both axion and WIMP direct detection may be expected.", "keyphrases": ["axion", "dark matter", "natural supersymmetry"]}
{"id": "0912.3217", "title": "Bipolar Harmonic encoding of CMB correlation patterns", "abstract": "Deviations from statistical isotropy can be modeled in various ways, for instance, anisotropic cosmological models (Bianchi models), compact topologies and presence of primordial magnetic field. Signature of anisotropy manifests itself in CMB correlation patterns. Here we explore the symmetries of the correlation function and its implications on the observable measures constructed within the Bipolar harmonic formalism for these variety of models. Different quantifiers within the Bipolar harmonic representation are used to distinguish between plausible models of breakdown of statistical isotropy and as a spectroscopic tool for discriminating between distinct cosmic topology.", "keyphrases": ["cmb correlation pattern", "bipolar spherical harmonic", "biposhs"]}
{"id": "1807.11180", "title": "Shark: introducing an open source, free and flexible semi-analytic model of galaxy formation", "abstract": "We present a new, open source, free semi-analytic model (SAM) of galaxy formation, Shark, designed to be highly flexible and modular, allowing easy exploration of different physical processes and ways of modelling them. We introduce the philosophy behind Shark and provide an overview of the physical processes included in the model. Shark is written in C++11 and has been parallelized with OpenMP. In the released version (v1.1), we implement several different models for gas cooling, active galactic nuclei, stellar and photo-ionisation feedback, and star formation (SF). We demonstrate the basic performance of Shark using the Planck15 cosmology SURFS simulations, by comparing against a large set of observations, including: the stellar mass function (SMF) and stellar-halo mass relation at z=0-4; the cosmic evolution of the star formation rate density (SFRD), stellar mass, atomic and molecular hydrogen; local gas scaling relations; and structural galaxy properties, finding excellent agreement. Significant improvements over previous SAMs are seen in the mass-size relation for disks/bulges, the gas-stellar mass and stellar mass-metallicity relations. To illustrate the power of Shark in exploring the systematic effects of the galaxy formation modelling, we quantify how the scatter of the SF main sequence and the gas scaling relations changes with the adopted SF law, and the effect of the starbursts H_2 depletion timescale on the SFRD and \u03a9_ H_2. We compare Shark with other SAMs and the hydrodynamical simulation EAGLE, and find that SAMs have a much higher halo baryon fractions due to large amounts of intra-halo gas, which in the case of EAGLE is in the intergalactic medium.", "keyphrases": ["open source", "semi-analytic model", "galaxy formation"]}
{"id": "1305.5178", "title": "Formation of the First Stars", "abstract": "Understanding the formation of the first stars is one of the frontier topics in modern astrophysics and cosmology. Their emergence signaled the end of the cosmic dark ages, a few hundred million years after the Big Bang, leading to a fundamental transformation of the early Universe through the production of ionizing photons and the initial enrichment with heavy chemical elements. We here review the state of our knowledge, separating the well understood elements of our emerging picture from those where more work is required. Primordial star formation is unique in that its initial conditions can be directly inferred from the Lambda Cold Dark Matter (LCDM) model of cosmological structure formation. Combined with gas cooling that is mediated via molecular hydrogen, one can robustly identify the regions of primordial star formation, the so-called minihalos, having total masses of 10^6 M_sun and collapsing at redshifts z 20-30. Within this framework, a number of studies have defined a preliminary standard model, with the main result that the first stars were predominantly massive. This model has recently been modified to include a ubiquitous mode of fragmentation in the protostellar disks, such that the typical outcome of primordial star formation may be the formation of a binary or small multiple stellar system. We will also discuss extensions to this standard picture due to the presence of dynamically significant magnetic fields, of heating from self-annihalating WIMP dark matter, or cosmic rays. We conclude by discussing possible strategies to empirically test our theoretical models.", "keyphrases": ["star", "primordial star formation", "molecular hydrogen"]}
{"id": "0911.1249", "title": "High-Redshift Cosmography", "abstract": "We constrain the parameters describing the kinematical state of the universe using a cosmographic approach, which is fundamental in that it requires a very minimal set of assumptions (namely to specify a metric) and does not rely on the dynamical equations for gravity. On the data side, we consider the most recent compilations of Supernovae and Gamma Ray Bursts catalogues. This allows to further extend the cosmographic fit up to z = 6.6, i.e. up to redshift for which one could start to resolve the low z degeneracy among competing cosmological models. In order to reliably control the cosmographic approach at high redshifts, we adopt the expansion in the improved parameter y = z/(1+z). This series has the great advantage to hold also for z > 1 and hence it is the appropriate tool for handling data including non-nearby distance indicators. We find that Gamma Ray Bursts, probing higher redshifts than Supernovae, have constraining power and do require (and statistically allow) a cosmographic expansion at higher order than Supernovae alone. Exploiting the set of data from Union and GRBs catalogues, we show (for the first time in a purely cosmographic approach parametrized by deceleration q_0, jerk j_0, snap s_0) a definitively negative deceleration parameter q_0 up to the 3\u03c3 confidence level. We present also forecasts for realistic data sets that are likely to be obtained in the next few years.", "keyphrases": ["cosmography", "redshift", "powerful model-independent approach"]}
{"id": "1209.5539", "title": "Prospects of antideuteron detection from dark matter annihilations or decays at AMS-02 and GAPS", "abstract": "The search for cosmic antideuterons has been proposed as a promising method to indirectly detect dark matter, due to the very small background flux from spallations expected at the energies relevant to experiments. The antideuteron flux from dark matter annihilations or decays is, however, severely constrained by the non-observation of an excess in the antiproton-to-proton fraction measured by PAMELA. In this paper we calculate, for representative dark matter annihilation and decay channels, upper limits on the number of antideuteron events at AMS-02 and GAPS from requiring that the associated antiproton flux is in agreement with the PAMELA data. To this end, we first analyze in detail the formation of antideuterons in the coalescence model using an event-by-event Monte Carlo simulation and using data from various high energy experiments. We find that the resulting coalescence momentum shows a dependence on the underlying process and on the center of mass energy involved. Then, we calculate, using a diffusion model, the flux of antideuterons at the Earth from dark matter annihilations or decays. Our results indicate that, despite the various sources of uncertainty, the observation of an antideuteron flux at AMS-02 or GAPS from dark matter annihilations or decays will be challenging.", "keyphrases": ["dark matter annihilation", "antideuteron flux", "astrophysical background"]}
{"id": "0912.0725", "title": "Lorentz symmetry violation, dark matter and dark energy", "abstract": "Taking into account the experimental results of the HiRes and AUGER collaborations, the present status of bounds on Lorentz symmetry violation (LSV) patterns is discussed. Although significant constraints will emerge, a wide range of models and values of parameters will still be left open. Cosmological implications of allowed LSV patterns are discussed focusing on the origin of our Universe, the cosmological constant, dark matter and dark energy. Superbradyons (superluminal preons) may be the actual constituents of vacuum and of standard particles, and form equally a cosmological sea leading to new forms of dark matter and dark energy.", "keyphrases": ["dark matter", "dark energy", "lorentz symmetry violation"]}
{"id": "1210.2471", "title": "Exoplanet Detection Methods", "abstract": "This chapter reviews various methods of detecting planetary companions to stars from an observational perspective, focusing on radial velocities, astrometry, direct imaging, transits, and gravitational microlensing. For each method, this chapter first derives or summarizes the basic observable phenomena that are used to infer the ex- istence of planetary companions, as well as the physical properties of the planets and host stars that can be derived from the measurement of these signals. This chapter then outlines the general experimental requirements to robustly detect the signals us- ing each method, by comparing their magnitude to the typical sources of measurement uncertainty. This chapter goes on to compare the various methods to each other by outlining the regions of planet and host star parameter space where each method is most sensitive, stressing the complementarity of the ensemble of the methods at our disposal. Finally, there is a brief review of the history of the young exoplanet field, from the first detections to current state-of-the-art surveys for rocky worlds.", "keyphrases": ["radial velocity", "planet", "exoplanet", "one-parameter degeneracy"]}
{"id": "1003.3401", "title": "New decay modes of gravitino dark matter", "abstract": "We consider the three-body decays of gravitino dark matter in supersymmetric scenarios with bilinear R-parity violation. In particular, gravitino decays into lepton+W^* (lepton ff\u0305') and \u03bd+Z^* (\u03bdff\u0305) are examined for gravitino masses below Mw. After computing the gravitino decay rates into these three-body final states and studying their dependence on supersymmetric parameters, we find that these new decay modes are often more important than the two-body decay, into a photon and a neutrino, considered in previous works. Consequently, the gravitino lifetime and its branching ratios are substantially modified, with important implications for the indirect detection of gravitino dark matter.", "keyphrases": ["gravitino", "dark matter", "new decay mode"]}
{"id": "1806.10437", "title": "Coupling matter in modified Q-gravity", "abstract": "We present a novel theory of gravity by considering an extension of symmetric teleparallel gravity. This is done by introducing, in the framework of the metric-affine formalism, a new class of theories where the nonmetricity Q is nonminimally coupled to the matter Lagrangian. More specifically, we consider a Lagrangian of the form L \u223c f_1(Q) + f_2(Q) L_M, where f_1 and f_2 are generic functions of Q, and L_M is the matter Lagrangian. This nonminimal coupling entails the nonconservation of the energy-momentum tensor, and consequently the appearance of an extra force. The motivation is to verify whether the subtle improvement of the geometrical formulation, when implemented in the matter sector, would allow more universally consistent and viable realisations of the nonminimal curvature-matter coupling theories. Furthermore, we consider several cosmological applications by presenting the evolution equations and imposing specific functional forms of the functions f_1(Q) and f_2(Q), such as power-law and exponential dependencies of the nonminimal couplings. Cosmological solutions are considered in two general classes of models, and found to feature accelerating expansion at late times.", "keyphrases": ["symmetric teleparallel gravity", "metric-affine formalism", "matter lagrangian"]}
{"id": "1906.04748", "title": "Distinguishing cosmologies using the turn-around radius near galaxy clusters", "abstract": "Outside galaxy clusters the competition between the inwards gravitational attraction and the outwards expansion of the Universe leads to a special radius of velocity cancellation, which is called the turn-around radius. Measurements of the turn-around radius hold promises of constraining cosmological parameters, and possibly even properties of gravity. Such a measurement is, however, complicated by the fact that the surroundings of galaxy clusters are not spherical, but instead are a complicated collection of filaments, sheets and voids. In this paper we use the results of numerically simulated universes to quantify realistic error-bars of the measurement of the turn-around radius. We find that for a \u039bCDM cosmology these error-bars are typically of the order of 20%. We numerically simulate three different implementations of dark energy models and of a scalar dark sector interaction to address whether the turn-around radius can be used to constrain non-trivial cosmologies, and we find that only rather extreme models can be distinguished from a \u039bCDM universe due to the large error-bars arising from the non-trivial cluster environments.", "keyphrases": ["cosmology", "turn-around radius", "galaxy cluster"]}
{"id": "1009.5592", "title": "The origin of cosmic rays: Explosions of massive stars with magnetic winds and their supernova mechanism", "abstract": "One prediction of particle acceleration in the supernova remnants in the magnetic wind of exploding Wolf Rayet and Red Super Giant stars is that the final spectrum is a composition of a spectrum E^-7/3 and a polar cap component of E^-2 at the source. This polar cap component contributes to the total energy content with only a few percent, but dominates the spectrum at higher energy. The sum of both components gives spectra which curve upwards. The upturn was predicted to occur always at the same rigidity. An additional component of cosmic rays from acceleration by supernovae exploding into the Inter-Stellar Medium (ISM) adds another component for Hydrogen and for Helium. After transport the predicted spectra J(E) for the wind-SN cosmic rays are E^-8/3 and E^-7/3; the sum leads to an upturn from the steeper spectrum. An upturn has now been seen. Here, we test the observations against the predictions, and show that the observed properties are consistent with the predictions. Hydrogen can be shown to also have a noticeable wind-SN-component. The observation of the upturn in the heavy element spectra being compatible with the same rigidity for all heavy elements supports the magneto-rotational mechanism for these supernovae. This interpretation predicts the observed upturn to continue to curve upwards and approach the E^-7/3 spectrum. If confirmed, this would strengthen the case that supernovae of very massive stars with magnetic winds are important sources of Galactic cosmic rays.", "keyphrases": ["cosmic ray", "massive star", "magnetic wind"]}
{"id": "1303.7340", "title": "Anisotropic Non-Gaussianity from a Two-Form Field", "abstract": "We study an inflationary scenario with a two-form field to which an inflaton couples non-trivially. First, we show that anisotropic inflation can be realized as an attractor solution and that the two-form hair remains during inflation. A statistical anisotropy can be developed because of a cumulative anisotropic interaction induced by the background two-form field. The power spectrum of curvature perturbations has a prolate-type anisotropy, in contrast to the vector models having an oblate-type anisotropy. We also evaluate the bispectrum and trispectrum of curvature perturbations by employing the in-in formalism based on the interacting Hamiltonians. We find that the non-linear estimators f_NL and \u03c4_NL are correlated with the amplitude g_* of the statistical anisotropy in the power spectrum. Unlike the vector models, both f_NL and \u03c4_NL vanish in the squeezed limit. However, the estimator f_NL can reach the order of 10 in the equilateral and enfolded limits. These results are consistent with the latest bounds on f_NL constrained by Planck.", "keyphrases": ["two-form field", "anisotropic inflation", "anisotropy", "bispectrum", "gauge field"]}
{"id": "1803.01157", "title": "Parametrizing theories of gravity on large and small scales in cosmology", "abstract": "We present a link between parametrizations of alternative theories of gravity on large and small scales in cosmology. This relationship is established using theoretical consistency conditions only. We find that in both limits the \"slip\" and \"effective Newton's constant\" can be written in terms of a set of four functions of time, two of which are direct generalizations of the \u03b1 and \u03b3 parameters from post-Newtonian physics. This generalizes previous work that has constructed frameworks for testing gravity on small scales, and is to the best of our knowledge the first time that a link between parametrizations of gravity on such very different scales has been established. We expect our result to facilitate the imposition of observational constraints, by drastically reducing the number of functional degrees of freedom required to consistently test gravity on multiple scales in cosmology.", "keyphrases": ["gravity", "small scale", "cosmology"]}
{"id": "1101.1381", "title": "Interstellar gamma rays and cosmic rays: new insights from Fermi-LAT AND INTEGRAL", "abstract": "In over two years of operation Fermi-LAT has revolutionized our knowledge of the gamma-ray sky. Interstellar gamma rays are part of this new era and allow unprecedented tests for models of cosmic rays in the Galaxy. The extension to lower energies with INTEGRAL/SPI data is also evolving. The global multiwavelength luminosity of the Milky Way has been derived, with implications for the Galactic energy balance and the radio-FIR correlation.", "keyphrases": ["cosmic ray", "fermi-lat", "interstellar gamma ray"]}
{"id": "1109.4939", "title": "The Mildly Non-Linear Regime of Structure Formation", "abstract": "We present a simple physically motivated picture for the mildly non-linear regime of structure formation, which captures the effects of the bulk flows. We apply this picture to develop a method to significantly reduce the sample variance in cosmological N-body simulations at the scales relevant to the Baryon Acoustic Oscillations (BAO). The results presented in this paper will allow for a speed-up of an order of magnitude (or more) in the scanning of the cosmological parameter space using N-body simulations for studies which require a good handle of the mildly non-linear regime, such as those targeting the BAO. Using this physical picture we develop a simple formula, which allows for the rapid calculation of the mildly non-linear matter power spectrum to percent level accuracy, and for robust estimation of the BAO scale.", "keyphrases": ["structure formation", "sample variance", "n-body simulation", "perturbation theory", "lpt"]}
{"id": "1202.6069", "title": "Testing the No-Hair Theorem with Observations in the Electromagnetic Spectrum. IV. Relativistically Broadened Iron Lines", "abstract": "According to the no-hair theorem, astrophysical black holes are fully characterized by their masses and spins and are described by the Kerr metric. This theorem can be tested observationally by measuring (at least) three different multipole moments of the spacetimes of black holes. In this paper, we calculate the profiles of fluorescent iron lines emitted from the accretion flows around black hole candidates within a framework that allows us to perform the calculation as a function of its mass and spin as well as of a free parameter that measures potential deviations from the Kerr metric. We show that such deviations lead to line profiles that are significantly altered and may exhibit a modified flux ratio of the two peaks in their characteristic double-peaked shape. We also show that the disk inclination can be measured independently of the spin and the deviation parameter at low to intermediate inclination angles as in the case of Kerr black holes. We estimate the precision that near-future X-ray missions such as Astro-H and ATHENA+ are required to achieve in order to resolve deviations from the Kerr metric in iron line profiles and show that constraints on such deviations will be strongest for rapidly spinning black holes. More generally, we show that measuring the line profile with a precision of 5 constraints the deviation parameter to order unity for values of the spin a>0.5M.", "keyphrases": ["no-hair theorem", "accretion disk", "astrophysical model", "electromagnetic radiation", "x-ray reflection spectroscopy"]}
{"id": "1109.6086", "title": "Mapping the large-angle deviation from Gaussianity in simulated CMB maps", "abstract": "[Abridged] In recent works we have proposed two new large-angle non-Gaussianity indicators based on skewness and kurtosis of patches of CMB sky-sphere, and used them to find out significant deviation from Gaussianity in frequency bands and foreground-reduced CMB maps. Simulated CMB maps with assigned type and amplitude of primordial non-Gaussianity are important tools to determine the strength, sensitivity and limitations of non-Gaussian estimators. Here we investigate whether and to what extent our non-Gaussian indicators have sensitivity to detect non-Gaussianity of local type, particularly with amplitude within the seven-year WMAP bounds. We make a systematic study by employing our statistical tools to generate maps of skewness and kurtosis from several thousands of simulated maps equipped with non-Gaussianity of local type of various amplitudes. We show that our indicators can be used to detect large-angle local-type non-Gaussianity only for relatively large values of the non-linear parameter f_ NL^ local. Thus, our indicators have not enough sensitivity to detect deviation from Gaussianity with the non-linear parameter within the seven-year WMAP bounds. This result along with the outcomes of frequency bands and foreground-reduced analyses suggest that non-Gaussianity captured in the previous works by our indicators is not of primordial origin, although it might have a primordial component. We have also made a comparative study of non-Gaussianity of simulated maps and of the full-sky WMAP foreground-reduced seven-year ILC-7yr map. An outcome of this analysis is that the level of non-Gaussianity of ILC-7yr map is higher than that of the simulated maps for f_ NL^ local within WMAP bounds. This provides quantitative indications on the suitability of the ILC-7yr map as a Gaussian reconstruction of the full-sky CMB.", "keyphrases": ["gaussianity", "cmb map", "estimator", "simulated map", "spherical cell"]}
{"id": "1509.05038", "title": "TORUS-3DPDR: A self-consistent code treating three-dimensional photoionization and photodissociation regions", "abstract": "The interaction of ionizing and far-ultraviolet radiation with the interstellar medium is of great importance. It results in the formation of regions in which the gas is ionized, beyond which are photodissociation regions (PDRs) in which the gas transitions to its atomic and molecular form. Several numerical codes have been implemented to study these two main phases of the interstellar medium either dynamically or chemically. In this paper we present TORUS-3DPDR, a new self-consistent code for treating the chemistry of three-dimensional photoionization and photodissociation regions. It is an integrated code coupling the two codes TORUS, a hydrodynamics and Monte Carlo radiation transport code, and 3D-PDR, a photodissociation regions code. The new code uses a Monte Carlo radiative transfer scheme to account for the propagation of the ionizing radiation including the diffusive component as well as a ray-tracing scheme based on the HEALPix package in order to account for the escape probability and column density calculations. Here, we present the numerical techniques we followed and we show the capabilities of the new code in modelling three-dimensional objects including single or multiple sources. We discuss the effects introduced by the diffusive component of the UV field in determining the thermal balance of PDRs as well as the effects introduced by a multiple sources treatment of the radiation field. We find that diffuse radiation can positively contribute to the formation of CO. With this new code, three-dimensional synthetic observations for the major cooling lines are possible, for making feasible a detailed comparison between hydrodynamical simulations and observations.", "keyphrases": ["three-dimensional photoionization", "photodissociation region", "torus-3dpdr"]}
{"id": "1806.09781", "title": "Model-independent Curvature Determination from Gravitational-Wave Standard Sirens and Cosmic Chronometers", "abstract": "The detection of gravitational waves (GWs) provides a direct way to measure the luminosity distance, which enables us to probe cosmology. In this paper, we continue to expand the application of GW standard sirens in cosmology, and propose that the spatial curvature can be estimated in a model-independent way by comparing the distances from future GW sources and current cosmic-chronometer observations. We expect an electromagnetic counterpart of the GW event to give the source redshift, and simulate hundreds of GW data from the coalescence of double neutron stars and black hole\u2013neutron star binaries using the Einstein Telescope as reference. Our simulations show that, from 100 simulated GW events and 31 current cosmic-chronometer measurements, the error of the curvature parameter \u03a9_K is expected to be constrained at the level of \u223c0.125. If 1000 GW events are observed, the uncertainty of \u03a9_K would be further reduced to \u223c0.040. We also find that adding 50 mock H(z) data (consisting of 81 cosmic-chronometer data and 1000 simulated GW events) could result in much tighter constraint on the zero cosmic curvature, for which, \u03a9_K=-0.002\u00b10.028. Compared to some actual model-independent curvature tests involving the distances from other cosmic probes, this method with GW data achieves constraints with much higher precision.", "keyphrases": ["gravitational wave", "cosmology", "spatial curvature"]}
{"id": "1309.6334", "title": "Measuring Supermassive Black Hole Spins in Active Galactic Nuclei", "abstract": "Measuring the spins of supermassive black holes (SMBHs) in active galactic nuclei (AGN) can inform us about the relative role of gas accretion vs. mergers in recent epochs of the life of the host galaxy and its AGN. Recent advances in theory and observation have enabled spin measurements for a handful of SMBHs thus far, but this science is still very much in its infancy. Herein, I discuss how and why we seek to measure black hole spin in AGN, using recent results from long X-ray observing campaigns on three radio-quiet AGN (MCG-6-30-15, NGC 3783 and Fairall 9) to illustrate this process and its caveats. I then present our current knowledge of the distribution of SMBH spins in the local universe. I also address prospects for improving the accuracy, precision and quantity of these spin constraints in the next decade and beyond with instruments such as NuSTAR, Astro-H and a future generation large-area X-ray telescope.", "keyphrases": ["black hole", "hole spin", "accretion disk", "active galactic nucleus"]}
{"id": "1810.05836", "title": "A Living Theory Catalogue for Fast Radio Bursts", "abstract": "At present, we have almost as many theories to explain Fast Radio Bursts as we have Fast Radio Bursts observed. This landscape will be changing rapidly with CHIME/FRB, recently commissioned in Canada, and HIRAX, under construction in South Africa. This is an opportune time to review existing theories and their observational consequences, allowing us to efficiently curtail viable astrophysical models as more data becomes available. In this article we provide a currently up to date catalogue of the numerous and varied theories proposed for Fast Radio Bursts so far. We also launch an online evolving repository for the use and benefit of the community to dynamically update our theoretical knowledge and discuss constraints and uses of Fast Radio Bursts.", "keyphrases": ["fast radio bursts", "frb", "date", "compact object"]}
{"id": "1804.06849", "title": "Tree-Level Bispectrum in the Effective Field Theory of Large-Scale Structure extended to Massive Neutrinos", "abstract": "We compute the tree-level bispectrum of dark matter in the presence of massive neutrinos in the mildly non-linear regime in the context of the effective field theory of large-scale structure (EFTofLSS). For neutrinos, whose typical free streaming wavenumber (k_ fs) is longer than the non-linear scale (k_NL), we solve a Boltzmann equation coupled to the effective fluid equation for dark matter. We solve perturbatively the coupled system by expanding in powers of the neutrino density fraction (f_\u03bd) and the ratio of the wavenumber of interest over the non-linear scale (k/k_NL) and add suitable counterterms to remove the dependence from short distance physics. For equilateral configurations, we find that the total-matter tree-level bispectrum is approximately 16f_\u03bd times the dark matter one on short scales (k > k_ fs). The largest contribution stems from the back-reaction of massive neutrinos on the dark matter growth factor. On large scales (k < k_ fs) the contribution of neutrinos to the bispectrum is smaller by up to two orders of magnitude.", "keyphrases": ["effective field theory", "neutrino", "tree-level bispectrum"]}
{"id": "1708.08458", "title": "Quantifying the non-Gaussianity in the EoR 21-cm signal through bispectrum", "abstract": "The epoch of reionization (EoR) 21-cm signal is expected to be highly non-Gaussian in nature and this non-Gaussianity is also expected to evolve with the progressing state of reionization. Therefore the signal will be correlated between different Fourier modes (k). The power spectrum will not be able capture this correlation in the signal. We use a higher-order estimator \u2013 the bispectrum \u2013 to quantify this evolving non-Gaussianity. We study the bispectrum using an ensemble of simulated 21-cm signal and with a large variety of k triangles. We observe two competing sources driving the non-Gaussianity in the signal: fluctuations in the neutral fraction (x_ HI) field and fluctuations in the matter density field. We find that the non-Gaussian contribution from these two sources vary, depending on the stage of reionization and on which k modes are being studied. We show that the sign of the bispectrum works as a unique marker to identify which among these two components is driving the non-Gaussianity. We propose that the sign change in the bispectrum, when plotted as a function of triangle configuration cos\u03b8 and at a certain stage of the EoR can be used as a confirmative test for the detection of the 21-cm signal. We also propose a new consolidated way to visualize the signal evolution (with evolving x_ HI or redshift), through the trajectories of the signal in a power spectrum and equilateral bispectrum i.e. P(k)-B(k, k, k) space.", "keyphrases": ["non-gaussianity", "eor 21-cm signal", "bispectrum"]}
{"id": "1004.3311", "title": "The Diffuse Supernova Neutrino Background", "abstract": "The Diffuse Supernova Neutrino Background (DSNB) is the weak glow of MeV neutrinos and antineutrinos from distant core-collapse supernovae. The DSNB has not been detected yet, but the Super-Kamiokande (SK) 2003 upper limit on the electron antineutrino flux is close to predictions, now quite precise, based on astrophysical data. If SK is modified with dissolved gadolinium to reduce detector backgrounds and increase the energy range for analysis, then it should detect the DSNB at a rate of a few events per year, providing a new probe of supernova neutrino emission and the cosmic core-collapse rate. If the DSNB is not detected, then new physics will be required. Neutrino astronomy, while uniquely powerful, has proven extremely difficult \u2013 only the Sun and the nearby Supernova 1987A have been detected to date \u2013 so the promise of detecting new sources soon is exciting indeed.", "keyphrases": ["neutrino", "distant core-collapse supernovae", "star-formation rate"]}
{"id": "2010.03225", "title": "Large anisotropies of the stochastic gravitational wave background from cosmic domain walls", "abstract": "We investigate the stochastic gravitational wave background (SGWB) from cosmic domain walls (DWs) caused by quantum fluctuations of a light scalar field \u03d5 during inflation. Perturbations of \u03d5 remain almost constant after leaving the Hubble horizon. The probabilities of the two domains depend on the averaged value of \u03d5 at each large scale region, leading to large scale perturbations of DW energy density and large anisotropies in the SGWB. We find that the angular power spectrum is scale-invariant and at least of the order of 10^-2, which is expected to be detected by future gravitational-wave (GW) detectors. Since we have not detected primordial GWs yet, anisotropies of the SGWB could help us to verify the rationality of inflation and determine the energy scale of inflation.", "keyphrases": ["gravitational wave background", "cosmic domain wall", "large anisotropy"]}
{"id": "1509.05374", "title": "Kinematic dipole detection with galaxy surveys: forecasts and requirements", "abstract": "Upcoming or future deep galaxy samples with wide sky coverage can provide independent measurement of the kinematic dipole - our motion relative to the rest frame defined by the large-scale structure. Such a measurement would present an important test of the standard cosmological model, as the standard model predicts the galaxy measurement should precisely agree with the existing precise measurements made using the CMB. However, the required statistical precision to measure the kinematic dipole typically makes the measurement susceptible to bias from the presence of the local-structure-induced dipole contamination. In order to minimize the latter, a sufficiently deep survey is required. We forecast both the statistical error and the systematic bias in the kinematic dipole measurements. We find that a survey covering \u223c 75% of the sky in both hemispheres and having \u223c 30 million galaxies can detect the kinematic dipole at 5\u03c3, while its median redshift should be at least z_med\u223c 0.75 for negligible bias from the local structure.", "keyphrases": ["galaxy survey", "sky", "kinematic dipole"]}
{"id": "1701.01555", "title": "The second flight of the SUNRISE balloon-borne solar observatory: overview of instrument updates, the flight, the data and first results", "abstract": "The SUNRISE balloon-borne solar observatory, consisting of a 1 m aperture telescope that provided a stabilized image to a UV filter imager and an imaging vector polarimeter, carried out its second science flight in June 2013. It provided observations of parts of active regions at high spatial resolution, including the first high-resolution images in the Mg ii k line. The obtained data are of very high quality, with the best UV images reaching the diffraction limit of the telescope at 3000 \u00c5 after Multi-Frame Blind Deconvolution reconstruction accounting for phase-diversity information. Here a brief update is given of the instruments and the data reduction techniques, which includes an inversion of the polarimetric data. Mainly those aspects that evolved compared with the first flight are described. A tabular overview of the observations is given. In addition, an example time series of a part of the emerging active region NOAA AR 11768 observed relatively close to disk centre is described and discussed in some detail. The observations cover the pores in the trailing polarity of the active region, as well as the polarity inversion line where flux emergence was ongoing and a small flare-like brightening occurred in the course of the time series. The pores are found to contain magnetic field strengths ranging up to 2500 G and, while large pores are clearly darker and cooler than the quiet Sun in all layers of the photosphere, the temperature and brightness of small pores approach or even exceed those of the quiet Sun in the upper photosphere.", "keyphrases": ["second flight", "sunrise", "balloon-borne solar observatory"]}
{"id": "1312.1614", "title": "Velocity filtration and temperature inversion in a system with long-range interactions", "abstract": "Temperature inversion due to velocity filtration, a mechanism originally proposed to explain the heating of the solar corona, is demonstrated to occur also in a simple paradigmatic model with long-range interactions, the Hamiltonian mean-field model. Using molecular dynamics simulations, we show that when the system settles into an inhomogeneous quasi-stationary state in which the velocity distribution has suprathermal tails, the temperature and density profiles are anticorrelated: denser parts of the system are colder than dilute ones. We argue that this may be a generic property of long-range interacting systems.", "keyphrases": ["temperature inversion", "long-range interaction", "velocity filtration"]}
{"id": "1407.6431", "title": "Jeans analysis in modified gravity", "abstract": "MOdified Gravity (MOG) is a covariant modification of Einstein's general relativity. This theory is one of the current alternatives to dark matter models. We describe dynamics of collisionless self-gravitating systems in the context of MOG. By studying the weak field approximation of this theory, we derive the equations governing the dynamics of the self-gravitating systems. More specifically, we consider the Jeans instability for self-gravitating fluid and stellar systems, and derive new Jeans mass limit M\u0303_J and wave-number k\u0303_J. Furthermore, considering the gravitational instability in star forming regions, we show that MOG has not a significant difference with general relativity on this astrophysical scale. However, at larger scales such as intergalactic space MOG may lead to different galaxy and structure formation processes.", "keyphrases": ["mog", "galaxy", "rotation curve", "scalar-tensor-vector-gravity"]}
{"id": "1606.06751", "title": "Is there evidence for anomalous dipole anisotropy in the large-scale structure?", "abstract": "We probe the anisotropy of the large-scale structure (LSS) with the WISE-2MASS catalogue. This analysis is performed by a directional comparison of the galaxy number counts through the entire celestial sphere once systematic effects, such as star-galaxy separation and foregrounds contamination, are properly taken into account. We find a maximal hemispherical asymmetry whose dipolar component is A = 0.0507 \u00b1 0.0014 toward the (l,b) = (323^\u2218,-5^\u2218) direction, whose result is consistent with previous estimations of our proper motion in low and intermediate redshifts, as those carried out with Type Ia Supernovae and similar LSS catalogues. Furthermore, this dipole amplitude is statistically consistent (p-value = 0.061) with mock catalogues simulated according to the expected \u039bCDM matter density fluctuations, in addition to observational biases such as the incomplete celestial coverage and anisotropic sky exposure. Our results suggest, therefore, that there is no strong evidence for anomalous anisotropy in the LSS, given the limitations and systematics of current data, in the concordance model scenario.", "keyphrases": ["dipole anisotropy", "large-scale structure", "redshift"]}
{"id": "1706.02464", "title": "CMB-S4 Technology Book, First Edition", "abstract": "CMB-S4 is a proposed experiment to map the polarization of the Cosmic Microwave Background (CMB) to nearly the cosmic variance limit for angular scales that are accessible from the ground. The science goals and capabilities of CMB-S4 in illuminating cosmic inflation, measuring the sum of neutrino masses, searching for relativistic relics in the early universe, characterizing dark energy and dark matter, and mapping the matter distribution in the universe have been described in the CMB-S4 Science Book. This Technology Book is a companion volume to the Science Book. The ambitious science goals of CMB-S4, a \"Stage-4\" experiment, require a step forward in experimental capability from the current Stage=II experiments. To guide this process, we summarize the current state of CMB instrumentation technology, and identify R D efforts necessary to advance it for use in CMB-S4. The book focuses on technical challenges in four broad areas: Telescope Design; Receiver Optics; Focal-Plane Optical Coupling; and Focal-Plane Sensor and Readout.", "keyphrases": ["challenge", "sensor", "cmb-s4"]}
{"id": "1108.5203", "title": "Coarse-Grained Cosmological Perturbation Theory", "abstract": "Semi-analytical methods, based on Eulerian perturbation theory, are a promising tool to follow the time evolution of cosmological perturbations at small redshifts and at mildly nonlinear scales. All these schemes are based on two approximations: the existence of a smoothing scale and the single-stream approximation, where velocity dispersion of the dark matter fluid, as well as higher moments of the particle distributions, are neglected. Despite being widely recognized, these two assumptions are, in principle, incompatible, since any finite smoothing scale gives rise to velocity dispersion and higher moments at larger scales. We describe a new approach to perturbation theory, where the Vlasov and fluid equations are derived in presence of a finite coarse-graining scale: this allows a clear separation between long and short distance modes and leads to a hybrid approach where the former are treated perturbatively and the effect of the latter is encoded in external source terms for velocity, velocity dispersion, and all the higher order moments, which can be computed from N-body simulations. We apply the coarse-grained perturbation theory to the computation of the power spectrum and the cross-spectrum between density and velocity dispersion, and compare the results with N-body simulations, finding good agreement.", "keyphrases": ["cosmological perturbation theory", "scheme", "single-stream approximation", "length scale"]}
{"id": "1307.2453", "title": "Supersymmetry, Nonthermal Dark Matter and Precision Cosmology", "abstract": "Within the Minimal Supersymmetric Standard Model (MSSM), LHC bounds suggest that scalar superpartner masses are far above the electroweak scale. Given a high superpartner mass, nonthermal dark matter is a viable alternative to WIMP dark matter generated via freezeout. In the presence of moduli fields nonthermal dark matter production is associated with a long matter dominated phase, modifying the spectral index and primordial tensor amplitude relative to those in a thermalized primordial universe. Nonthermal dark matter can have a higher self-interaction cross-section than its thermal counterpart, enhancing astrophysical bounds on its annihilation signals. We constrain the contributions to the neutralino mass from the bino, wino and higgsino using existing astrophysical bounds and direct detection experiments for models with nonthermal neutralino dark matter. Using these constraints we quantify the expected change to inflationary observables resulting from the nonthermal phase.", "keyphrases": ["nonthermal dark matter", "precision cosmology", "supersymmetry"]}
{"id": "1608.01982", "title": "Speed of Gravitational Waves and the Fate of Scalar-Tensor Gravity", "abstract": "The direct detection of gravitational waves (GWs) is an invaluable new tool to probe gravity and the nature of cosmic acceleration. A large class of scalar-tensor theories predict that GWs propagate with velocity different than the speed of light, a difference that can be \ud835\udcaa(1) for many models of dark energy. We determine the conditions behind the anomalous GW speed, namely that the scalar field spontaneously breaks Lorentz invariance and couples to the metric perturbations via the Weyl tensor. If these conditions are realized in nature, the delay between GW and electromagnetic (EM) signals from distant events will run beyond human timescales, making it impossible to measure the speed of GWs using neutron star mergers or other violent events. We present a robust strategy to exclude or confirm an anomalous speed of GWs using eclipsing binary systems, whose EM phase can be exquisitely determined. he white dwarf binary J0651+2844 is a known example of such system that can be used to probe deviations in the GW speed as small as c_g/c-1\u2273 2\u00b7 10^-12 when LISA comes online. This test will either eliminate many contender models for cosmic acceleration or wreck a fundamental pillar of general relativity.", "keyphrases": ["gravity", "scalar-tensor theory", "propagation", "dark energy"]}
{"id": "1505.03523", "title": "ALMA Census of Faint 1.2 mm Sources Down to 0.02 mJy: Extragalactic Background Light and Dust-Poor High-z Galaxies", "abstract": "We present statistics of 133 faint 1.2-mm continuum sources detected in about 120 deep ALMA pointing data that include all the archival deep data available by 2015 June. We derive number counts of 1.2 mm continuum sources down to 0.02 mJy partly with the assistance of gravitational lensing, and find that the total integrated 1.2 mm flux of the securely identified sources is 22.9^(+6.7)_(-5.6) Jy deg^(-2) that corresponds to 104^(+31)_(-25) extragalactic background light (EBL) measured by COBE observations. These results suggest that the major 1.2 mm EBL contributors are sources with 0.02 mJy, and that very faint 1.2 mm sources with < 0.02 mJy contribute negligibly to the EBL with the possible flattening and/or truncation of number counts in this very faint flux regime. To understand the physical origin of our faint ALMA sources, we measure the galaxy bias bg by the counts-in-cells technique, and place a stringent upper limit of bg < 3.5 that is not similar to bg values of massive DRGs and SMGs but comparable to those of UV-bright sBzKs and LBGs. Moreover, in optical and near-infrared (NIR) deep fields, we identify optical-NIR counterparts for 59 have luminosities, colors, and the IRX-beta relation same as sBzKs and LBGs. We thus conclude that about a half of our faint ALMA sources are dust-poor high-z galaxies as known as sBzKs and LBGs in optical studies, and that these faint ALMA sources are not miniature (U)LIRGs simply scaled down with the infrared brightness.", "keyphrases": ["faint", "extragalactic background light", "dust-poor high-z galaxy"]}
{"id": "1709.05695", "title": "Detecting higher spin fields through statistical anisotropy in the CMB and galaxy power spectra", "abstract": "Primordial inflation may represent the most powerful collider to test high-energy physics models. In this paper we study the impact on the inflationary power spectrum of the comoving curvature perturbation in the specific model where massive higher spin fields are rendered effectively massless during a de Sitter epoch through suitable couplings to the inflaton field. In particular, we show that such fields with spin s induce a distinctive statistical anisotropic signal on the power spectrum, in such a way that not only the usual g_2M-statistical anisotropy coefficients, but also higher-order ones (i.e., g_4M, g_6M, \u22ef, g_(2s-2)M and g_(2s) M) are nonvanishing. We examine their imprints in the cosmic microwave background and galaxy power spectra. Our Fisher matrix forecasts indicate that the detectability of g_LM depends very weakly on L: all coefficients could be detected in near future if their magnitudes are bigger than about 10^-3.", "keyphrases": ["galaxy power spectra", "curvature perturbation", "high spin field"]}
{"id": "1004.0697", "title": "CoGeNT Interpretations", "abstract": "Recently, the CoGeNT experiment has reported events in excess of expected background. We analyze dark matter scenarios which can potentially explain this signal. Under the standard case of spin independent scattering with equal couplings to protons and neutrons, we find significant tensions with existing constraints. Consistency with these limits is possible if a large fraction of the putative signal events is coming from an additional source of experimental background. In this case, dark matter recoils cannot be said to explain the excess, but are consistent with it. We also investigate modifications to dark matter scattering that can evade the null experiments. In particular, we explore generalized spin independent couplings to protons and neutrons, spin dependent couplings, momentum dependent scattering, and inelastic interactions. We find that some of these generalizations can explain most of the CoGeNT events without violation of other constraints. Generalized couplings with some momentum dependence, allows further consistency with the DAMA modulation signal, realizing a scenario where both CoGeNT and DAMA signals are coming from dark matter. A model with dark matter interacting and annihilating into a new light boson can realize most of the scenarios considered.", "keyphrases": ["proton", "matter interaction", "cogent", "cross section", "gev"]}
{"id": "1709.02923", "title": "The status of varying constants: a review of the physics, searches and implications", "abstract": "The observational evidence for the recent acceleration of the universe demonstrates that canonical theories of cosmology and particle physics are incomplete\u2014if not incorrect\u2014and that new physics is out there, waiting to be discovered. A key task for the next generation of laboratory and astrophysical facilities is to search for, identify and ultimately characterize this new physics. Here we highlight recent developments in tests of the stability of nature's fundamental couplings, which provide a direct handle on new physics: a detection of variations will be revolutionary, but even improved null results provide competitive constraints on a range of cosmological and particle physics paradigms. A joint analysis of all currently available data shows a preference for variations of \u03b1 and \u03bc at about the two-sigma level, but inconsistencies between different sub-sets (likely due to hidden systematics) suggest that these statistical preferences need to be taken with caution. On the other hand, these measurements strongly constrain Weak Equivalence Principle violations. Plans and forecasts for forthcoming studies with facilities such as ALMA, ESPRESSO and the ELT, which should clarify these issues, are also discussed, and synergies with other probes are briefly highlighted. The goal is to show how a new generation of precision consistency tests of the standard paradigm will soon become possible.", "keyphrases": ["status", "universe", "stability", "fundamental coupling", "fine-structure constant"]}
{"id": "1503.03934", "title": "Cosmological long-wavelength solutions and primordial black hole formation", "abstract": "We construct cosmological long-wavelength solutions without symmetry in general gauge conditions compatible with the long-wavelength scheme. We then specify the relationship among the solutions in different time slicings. Applying this general framework to spherical symmetry, we derive the correspondence relation between long-wavelength solutions in the constant mean curvature slicing with conformally flat spatial coordinates and asymptotic quasihomogeneous solutions in the comoving gauge and compare the numerical results of PBH formation in these two different approaches. To discuss the PBH formation, it is convenient and conventional to use \u03b4\u0303_c, the value which the averaged density perturbation at threshold in the comoving slicing would take at horizon entry in the lowest-order long-wavelength expansion. We numerically find that within compensated models, the sharper the transition from the overdense region to the FRW universe is, the larger the \u03b4\u0303_c becomes. We suggest that, for the equation of state p=(\u0393-1)\u03c1, we can apply the analytic formulas for the minimum \u03b4\u0303_c, min\u2243 [3\u0393/(3\u0393+2)]sin^2[\u03c0\u221a(\u0393-1)/(3\u0393-2)] and the maximum \u03b4\u0303_c, max\u2243 3\u0393/(3\u0393+2). As for the threshold peak value of the curvature variable \u03c8_0,c, we find that the sharper the transition is, the smaller the \u03c8_0,c becomes. We analytically explain this feature. Using simplified models, we also analytically deduce an environmental effect that \u03c8_0,c can be significantly larger (smaller) if the underlying density perturbation of much longer wavelength is positive (negative).", "keyphrases": ["gauge condition", "density perturbation", "comoving slicing", "universe", "cosmological long-wavelength solution"]}
{"id": "1811.07741", "title": "Resummed Kinetic Field Theory: Using Mesoscopic Particle Hydrodynamics to Describe Baryonic Matter in a Cosmological Framework", "abstract": "Recently, Bartelmann et al. presented a 'Kinetic Field Theory' (KFT) formalism to tackle the difficulties of large scale structure formation. In this approach, the dynamics of a non-equilibrium ensemble of classical particles are examined based on methods of statistical field theory. So far, only contributions coming from dark matter were considered, which is assumed to pose an accurate description of our universe on very large scales. Nevertheless, going to smaller scales, also baryonic contributions have to be taken into account. Building on the ideas of Viermann et al. we present an effective particle model of hydrodynamics to describe baryonic matter in a cosmological framework. Using this model, the baryonic density contrast power spectrum is computed to lowest perturbative order within the resummed KFT framework of Lilow et al. We discuss the qualitative differences to the dark matter case and perform a quantitative comparison to the baryonic spectrum obtained from Eulerian perturbation theory. A subsequent paper will resolve the problem of coupling both theories describing dark and baryonic matter, respectively, to gain a full model of cosmic matter. Even though our focus is on cosmological systems only, we want to emphasize that all methods presented here are of a quite general fashion, making it applicable also to other fields.", "keyphrases": ["mesoscopic particle hydrodynamics", "baryonic matter", "cosmological framework"]}
{"id": "1508.03409", "title": "Can thermal inflation be consistent with baryogenesis in gauge-mediated SUSY breaking models?", "abstract": "Thermal inflation is an attractive idea to dilute cosmic density of unwanted particles such as moduli fields which cause cosmological difficulties. However, it also dilutes preexisting baryon asymmetry and some viable baryogenesis is necessary for a cosmologically consistent scenario. We investigate whether the Affleck-Dine mechanism can produce baryon asymmetry enough to survive after the dilution in gauge-mediated SUSY breaking models. Flat directions except for LH_u flat direction cannot provide such huge baryon number because of Q-ball formation. We show that although the LH_u flat direction is special in terms of having \u03bc-term which prevents Q-ball formation, it cannot explain the observed baryon asymmetry either.", "keyphrases": ["thermal inflation", "baryogenesis", "susy breaking model"]}
{"id": "1006.2879", "title": "Examining subgrid models of supermassive black holes in cosmological simulation", "abstract": "While supermassive black holes (SMBHs) play an important role in galaxy and cluster evolution, at present they can only be included in large-scale cosmological simulation via subgrid techniques. However, these subgrid models have not been studied in a systematic fashion. Using a newly-developed fast, parallel spherical overdensity halo finder built into the simulation code FLASH, we perform a suite of dark matter-only cosmological simulations to study the effects of subgrid model choice on relations between SMBH mass and dark matter halo mass and velocity dispersion. We examine three aspects of SMBH subgrid models: the choice of initial black hole seed mass, the test for merging two black holes, and the frequency of applying the subgrid model. We also examine the role that merging can play in determining the relations, ignoring the complicating effects of SMBH-driven accretion and feedback. We find that the choice of subgrid model can dramatically affect the black hole merger rate, the cosmic SMBH mass density, and the low-redshift relations to halo properties. We also find that it is possible to reproduce observations of the low-redshift relations without accretion and feedback, depending on the choice of subgrid model.", "keyphrases": ["subgrid model", "supermassive black hole", "cosmological simulation"]}
{"id": "1408.6205", "title": "Geodesic completeness and homogeneity condition for cosmic inflation", "abstract": "There are two disjointed problems in cosmology within General Relativity (GR), which can be addressed simultaneously by studying the nature of geodesics around t\u2192 0, where t is the physical time. One is related to the past geodesic completeness of the inflationary trajectory due to the presence of a cosmological singularity, and the other one is related to the homogeneity condition required to inflate a local space-time patch of the universe. We will show that both the problems have a common origin, arising from how the causal structure of null and timelike geodesics are structured within GR. In particular, we will show how a non-local extension of GR can address both problems, while satisfying the null energy condition for the matter sources.", "keyphrases": ["homogeneity condition", "cosmological singularity", "geodesic completeness"]}
{"id": "1507.08481", "title": "Consistency relations for sharp features in the primordial spectra", "abstract": "We study the generation of sharp features in the primordial spectra within the framework of effective field theory of inflation, wherein curvature perturbations are the consequence of the dynamics of a single scalar degree of freedom. We identify two sources in the generation of features: rapid variations of the sound speed c_s (at which curvature fluctuations propagate) and rapid variations of the expansion rate H during inflation. With this in mind, we propose a non-trivial relation linking these two quantities that allows us to study the generation of sharp features in realistic scenarios where features are the result of the simultaneous occurrence of these two sources. This relation depends on a single parameter with a value determined by the particular model (and its numerical input) responsible for the rapidly varying background. As a consequence, we find a one-parameter consistency relation between the shape and size of features in the bispectrum and features in the power spectrum. To substantiate this result, we discuss several examples of models for which this one-parameter relation (between c_s and H) holds, including models in which features in the spectra are both sudden and resonant.", "keyphrases": ["sharp feature", "primordial spectra", "consistency relation"]}
{"id": "1311.1575", "title": "Non-Gaussianity Consistency Relations, Initial States and Back-reaction", "abstract": "We explore the consistency relations for the three-point functions, in the squeezed limit, of scalar and tensor perturbations in single-field inflation with general initial conditions for the perturbations. For slow-roll inflation, we find that all the three-point functions of scalar and tensor perturbations with a coherent state as the initial state are identical to the three-point functions with the Bunch-Davies initial state. On the other hand, there is an apparent violation of some of the consistency relations for initial states that are related to the Bunch-Davies state by Bogoliubov transformations and we identify the reason for this violation. The back-reaction calculations indicate that the three-point functions for these states can be large enough to violate the consistency relations, however, they are too small to be observed in the near future.", "keyphrases": ["consistency relation", "initial state", "three-point function", "tensor perturbation"]}
{"id": "1802.09530", "title": "The frequency of very young galaxies in the local Universe: I. A test for galaxy formation and cosmological models", "abstract": "In the local Universe, the existence of very young galaxies (VYGs), having formed at least half their stellar mass in the last 1 Gyr, is debated. We predict the present-day fraction of VYGs among central galaxies as a function of galaxy stellar mass. For this, we apply to high mass resolution Monte-Carlo halo merger trees (MCHMTs) three (one) analytical models of galaxy formation, where the ratio of stellar to halo mass (mass growth rate) is a function of halo mass and redshift. Galaxy merging is delayed until orbital decay by dynamical friction. With starbursts associated with halo mergers, our models predict typically one percent of VYGs up to galaxy masses of 10^10 M_\u2299, falling rapidly at higher masses, and VYGs are usually associated with recent major mergers of their haloes. Without these starbursts, two of the models have VYG fractions reduced by 1 or 2 dex at low or intermediate stellar masses, and VYGs are rarely associated with major halo mergers. In comparison, the state-of-the-art semi-analytical model (SAM) of Henriques et al. produces only 0.01 MCMHTs with Warm Dark Matter cosmology generates 10 times more VYGs at masses below 10^8 M_\u2299 than when run with Cold Dark Matter. The wide range in these VYG fractions illustrates the usefulness of VYGs to constrain both galaxy formation and cosmological models.", "keyphrases": ["local universe", "galaxy formation", "cosmological model"]}
{"id": "0903.5296", "title": "New Parametrization for the Scale Dependent Growth Function in General Relativity", "abstract": "We demonstrate the scale dependence of the growth function of cosmological perturbations in dark energy models based on General Relativity. This scale dependence is more prominent on cosmological scales of 100h^-1Mpc or larger. We derive a new scale dependent parametrization which generalizes the well known Newtonian approximation result f_0(a)\u2261dln\u03b4_0/dln a=(a)^\u03b3 (\u03b3 =6/11 for ) which is a good approximation on scales less than 50h^-1Mpc. Our generalized parametrization is of the form f(a)=f_0(a)/1+\u03be(a,k) where \u03be(a,k)=3 H_0^2/a k^2. We demonstrate that this parametrization fits the exact result of a full general relativistic evaluation of the growth function up to horizon scales for both and dynamical dark energy. In contrast, the scale independent parametrization does not provide a good fit on scales beyond 5", "keyphrases": ["parametrization", "growth function", "general relativity"]}
{"id": "1610.00115", "title": "Power-law modulation of the scalar power spectrum from a heavy field with a monomial potential", "abstract": "The effects of heavy fields modulate the scalar power spectrum during inflation. We analytically calculate the modulations of the scalar power spectrum from a heavy field with a separable monomial potential, i.e. V(\u03d5) \u03d5^n. In general the modulation is characterized by a power-law oscillation which is reduced to the logarithmic oscillation in the case of n=2.", "keyphrases": ["scalar power", "heavy field", "monomial potential"]}
{"id": "0903.4450", "title": "Topological Currents in Neutron Stars: Kicks, Precession, Toroidal Fields, and Magnetic Helicity", "abstract": "The effects of anomalies in high density QCD are striking. We consider a direct application of one of these effects, namely topological currents, on the physics of neutron stars. All the elements required for topological currents are present in neutron stars: degenerate matter, large magnetic fields, and P-parity violating processes. These conditions lead to the creation of vector currents capable of carrying momentum and inducing magnetic fields. We estimate the size of these currents for many representative states of dense matter in the neutron star and argue that they could be responsible for the large proper motion of neutron stars (kicks), the toroidal magnetic field and finite magnetic helicity needed for stability of the poloidal field, and the resolution of the conflict between type-II superconductivity and precession. Though these observational effects appear unrelated, they likely originate from the same physics \u2013 they are all P-odd phenomena that stem from a topological current generated by parity violation.", "keyphrases": ["neutron star", "magnetic helicity", "toroidal magnetic field"]}
{"id": "1801.06578", "title": "Fast radio bursts' recipes for the distributions of dispersion measures, flux densities, and fluences", "abstract": "We investigate how the statistical properties of dispersion measure (DM) and apparent flux density/fluence of (non-repeating) fast radio bursts (FRBs) are determined by unknown cosmic rate density history [(z)] and luminosity function (LF) of the transient events. We predict the distributions of DMs, flux densities, and fluences of FRBs taking account of the variation of the receiver efficiency within its beam, using analytical models of (z) and LF. Comparing the predictions with the observations, we show that the cumulative distribution of apparent fluences suggests that FRBs originate at cosmological distances and increases with redshift resembling cosmic star formation history (CSFH). We also show that a LF model with a bright-end cutoff at log_10L_\u03bd [erg s^-1Hz^-1] \u223c 34 are favored to reproduce the observed DM distribution if (z)\u221d CSFH, although the statistical significance of the constraints obtained with the current size of the observed sample is not high. Finally, we find that the correlation between DM and flux density of FRBs is potentially a powerful tool to distinguish whether FRBs are at cosmological distances or in the local universe more robustly with future observations.", "keyphrases": ["dispersion measure", "flux density", "fast radio burst"]}
{"id": "1103.2426", "title": "Discontinuous Galerkin methods for general-relativistic hydrodynamics: formulation and application to spherically symmetric spacetimes", "abstract": "We have developed the formalism necessary to employ the discontinuous-Galerkin approach in general-relativistic hydrodynamics. The formalism is firstly presented in a general 4-dimensional setting and then specialized to the case of spherical symmetry within a 3+1 splitting of spacetime. As a direct application, we have constructed a one-dimensional code, EDGES, which has been used to asses the viability of these methods via a series of tests involving highly relativistic flows in strong gravity. Our results show that discontinuous Galerkin methods are able not only to handle strong relativistic shock waves but, at the same time, to attain very high orders of accuracy and exponential convergence rates in smooth regions of the flow. Given these promising prospects and their affinity with a pseudospectral solution of the Einstein equations, discontinuous Galerkin methods could represent a new paradigm for the accurate numerical modelling in relativistic astrophysics.", "keyphrases": ["general-relativistic hydrodynamic", "spacetime", "discontinuous galerkin method"]}
{"id": "1507.03948", "title": "Energy source for the magnetic field growth in magnetars driven by the electron-nucleon interaction", "abstract": "We study the magnetic field generation in a neutron star within the model based on the magnetic field instability in the nuclear matter owing to the electron-nucleon parity violating interaction. We suggest that the growing magnetic field takes the energy from thermal background fermions in the neutron star matter. The system of kinetic equations for the spectra of the magnetic helicity density and magnetic energy density as well as the chiral imbalance are solved numerically accounting for this energy source. We obtain that, for the initial conditions corresponding to a typical neutron star, the large scale magnetic field \u223c 10^15G is generated during (10^4-10^5)yr. We suggest that the proposed model describes strong magnetic fields observed in magnetars.", "keyphrases": ["magnetic field", "electron-nucleon interaction", "field instability"]}
{"id": "1106.5402", "title": "Finite escape fraction for ultrahigh energy collisions around Kerr naked singularity", "abstract": "We investigate here the issue of observability of high energy collisions around Kerr naked singu- larity and show that the results are in contrast with the Kerr black hole case. We had shown earlier that it would be possible to have ultrahigh energy collisions between the particles close to the loca- tion r = M around the Kerr naked singularity if the Kerr spin parameter transcends the unity by an infinitesimally small amount a \u2192 1^+. The collision is between initially ingoing particle that turns back as an outgoing particle due to angular momentum barrier, with another ingoing particle. We assume that two massless particles are produced in such a collision and their angular distribution is isotropic in the center of mass frame. We calculate the escape fraction for the massless particles to reach infinity. We show that escape fraction is finite and approximately equal to half for ultrahigh energy collisions. Therefore the particles produced in high energy collisions would escape to infinity providing signature of the nature of basic interactions at those energies. This result is in contract with the extremal Kerr black hole case where almost all particles produced in high energy collisions are absorbed by the black hole, thus rendering the collisions unobservable.", "keyphrases": ["escape fraction", "ultrahigh energy collision", "singularity"]}
{"id": "0911.0017", "title": "Structure formation from non-Gaussian initial conditions: multivariate biasing, statistics, and comparison with N-body simulations", "abstract": "We study structure formation in the presence of primordial non-Gaussianity of the local type with parameters f_NL and g_NL. We show that the distribution of dark-matter halos is naturally described by a multivariate bias scheme where the halo overdensity depends not only on the underlying matter density fluctuation delta, but also on the Gaussian part of the primordial gravitational potential phi. This corresponds to a non-local bias scheme in terms of delta only. We derive the coefficients of the bias expansion as a function of the halo mass by applying the peak-background split to common parametrizations for the halo mass function in the non-Gaussian scenario. We then compute the halo power spectrum and halo-matter cross spectrum in the framework of Eulerian perturbation theory up to third order. Comparing our results against N-body simulations, we find that our model accurately describes the numerical data for wavenumbers k < 0.1-0.3 h/Mpc depending on redshift and halo mass. In our multivariate approach, perturbations in the halo counts trace phi on large scales and this explains why the halo and matter power spectra show different asymptotic trends for k -> 0. This strongly scale-dependent bias originates from terms at leading order in our expansion. This is different from what happens using the standard univariate local bias where the scale-dependent terms come from badly behaved higher-order corrections. On the other hand, our biasing scheme reduces to the usual local bias on smaller scales where |phi| is typically much smaller than the density perturbations. We finally discuss the halo bispectrum in the context of multivariate biasing and show that, due to its strong scale and shape dependence, it is a powerful tool for the detection of primordial non-Gaussianity from future galaxy surveys.", "keyphrases": ["multivariate biasing", "n-body simulation", "structure formation"]}
{"id": "0912.3428", "title": "D-Foam Phenomenology: Dark Energy, the Velocity of Light and a Possible D-Void", "abstract": "In a D-brane model of space-time foam, there are contributions to the dark energy that depend on the D-brane velocities and on the density of D-particle defects. The latter may also reduce the speeds of photons linearly with their energies, establishing a phenomenological connection with astrophysical probes of the universality of the velocity of light. Specifically, the cosmological dark energy density measured at the present epoch may be linked to the apparent retardation of energetic photons propagating from nearby AGNs. However, this nascent field of `D-foam phenomenology' may be complicated by a dependence of the D-particle density on the cosmological epoch. A reduced density of D-particles at redshifts z 1 - a `D-void' - would increase the dark energy while suppressing the vacuum refractive index, and thereby might reconcile the AGN measurements with the relatively small retardation seen for the energetic photons propagating from GRB 090510, as measured by the Fermi satellite.", "keyphrases": ["dark energy", "d-void", "d-foam phenomenology"]}
{"id": "1507.00912", "title": "On stars, galaxies and black holes in massive bigravity", "abstract": "In this paper we study the phenomenology of stars and galaxies in massive bigravity. We give parameter conditions for the existence of viable star solutions when the radius of the star is much smaller than the Compton wavelength of the graviton. If these parameter conditions are not met, we constrain the ratio between the coupling constants of the two metrics, in order to give viable conditions for e.g. neutron stars. For galaxies, we put constraints on both the Compton wavelength of the graviton and the conformal factor and coupling constants of the two metrics. The relationship between black holes and stars, and whether the former can be formed from the latter, is discussed. We argue that the different asymptotic structure of stars and black holes makes it unlikely that black holes form from the gravitational collapse of stars in massive bigravity.", "keyphrases": ["galaxy", "black hole", "massive bigravity"]}
{"id": "1611.00359", "title": "Model-independent estimations for the curvature from standard candles and clocks", "abstract": "Model-independent estimations for the spatial curvature not only provide a test for the fundamental Copernican principle assumption, but also can effectively break the degeneracy between curvature and dark energy properties. In this paper, we propose to achieve model-independent constraints on the spatial curvature from observations of standard candles and standard clocks, without assuming any fiducial cosmology and other priors. We find that, for the popular Union2.1 type Ia supernovae (SNe Ia ) observations, the spatial curvature is constrained to be \u03a9_K=-0.045_-0.172^+0.176. For the latest joint light-curve analysis (JLA) of SNe Ia observations, we obtain \u03a9_K=-0.140_-0.158^+0.161. It is suggested that these results are in excellent agreement with the spatially flat Universe. Moreover, compared to other approaches aiming for model-independent estimations of spatial curvature, this method also achieves constraints with competitive precision.", "keyphrases": ["curvature", "clock", "model-independent estimation"]}
{"id": "1709.09695", "title": "Higher-derivative operators and effective field theory for general scalar-tensor theories", "abstract": "We discuss the extent to which it is necessary to include higher-derivative operators in the effective field theory of general scalar-tensor theories. We explore the circumstances under which it is correct to restrict to second-order operators only, and demonstrate this using several different techniques, such as reduction of order and explicit field redefinitions. These methods are applied, in particular, to the much-studied Horndeski theories. The goal is to clarify the application of effective field theory techniques in the context of popular cosmological models, and to explicitly demonstrate how and when higher-derivative operators can be cast into lower-derivative forms suitable for numerical solution techniques.", "keyphrases": ["operator", "field theory", "general scalar-tensor theory"]}
{"id": "1104.3337", "title": "Angular 21 cm Power Spectrum of a Scaling Distribution of Cosmic String Wakes", "abstract": "Cosmic string wakes lead to a large signal in 21 cm redshift maps at redshifts larger than that corresponding to reionization. Here, we compute the angular power spectrum of 21 cm radiation as predicted by a scaling distribution of cosmic strings whose wakes have undergone shock heating.", "keyphrases": ["cosmic string", "string wake", "angular power spectrum", "shock heating"]}
{"id": "0911.0422", "title": "Halo Shape and Relic Density Exclusions of Sommerfeld-Enhanced Dark Matter Explanations of Cosmic Ray Excesses", "abstract": "Dark matter with Sommerfeld-enhanced annihilation has been proposed to explain observed cosmic ray positron excesses in the 10 GeV to TeV energy range. We show that the required enhancement implies thermal relic densities that are too small to be all of dark matter. We also show that the dark matter is sufficiently self-interacting that observations of elliptical galactic dark matter halos exclude large Sommerfeld enhancement for light force carriers. Resonant Sommerfeld enhancement does not modify these conclusions, and the astrophysical boosts required to resolve these discrepancies are disfavored, especially when significant self-interactions suppress halo substructure.", "keyphrases": ["dark matter", "thermal relic density", "dwarf galaxy"]}
{"id": "1606.09250", "title": "The Gamma-Ray Pulsar Population of Globular Clusters: Implications for the GeV Excess", "abstract": "It has been suggested that the GeV excess, observed from the region surrounding the Galactic Center, might originate from a population of millisecond pulsars that formed in globular clusters. With this in mind, we employ the publicly available Fermi data to study the gamma-ray emission from 157 globular clusters, identifying a statistically significant signal from 25 of these sources (ten of which are not found in existing gamma-ray catalogs). We combine these observations with the predicted pulsar formation rate based on the stellar encounter rate of each globular cluster to constrain the gamma-ray luminosity function of millisecond pulsars in the Milky Way's globular cluster system. We find that this pulsar population exhibits a luminosity function that is quite similar to those millisecond pulsars observed in the field of the Milky Way (i.e. the thick disk). After pulsars are expelled from a globular cluster, however, they continue to lose rotational kinetic energy and become less luminous, causing their luminosity function to depart from the steady-state distribution. Using this luminosity function and a model for the globular cluster disruption rate, we show that millisecond pulsars born in globular clusters can account for only a few percent or less of the observed GeV excess. Among other challenges, scenarios in which the entire GeV excess is generated from such pulsars are in conflict with the observed mass of the Milky Way's Central Stellar Cluster.", "keyphrases": ["pulsar", "globular cluster", "luminosity function", "central stellar cluster"]}
{"id": "2003.06586", "title": "Hunting for the host galaxy groups of binary black holes and the application in constraining Hubble constant", "abstract": "The discovery of gravitational-wave (GW) signals, produced by the coalescence of stellar-mass binary black holes (SBBHs), opens a new window to study the astrophysical origins and dynamical evolutions of compact binaries. In addition, these GW events can be treated as the standard sirens to constrain various cosmological parameters. Both issues require the host identification for these GW events, with help of the spatial resolution of GW detector networks. In this paper, we investigate the capabilities of various detector networks for identifying the SBBHs' host galaxy groups, rather than their host galaxies, which can overcome the influence of galaxies' proper motions in dark matter halos for measuring the cosmological parameters. In our analysis, the group catalog of SDSS DR7 with redshift z\u2208(0.01,0.1) is considered as an example of the application. We find that for the second-generation (2G) detector network, the host galaxy groups of around (0.7-6.9) SBBHs can be identified per year assuming all sources are 30-30 M_\u2299 binaries, and that all five detectors in the network are in lock 100% of the time. For the 3G detector network, this number becomes (3.9-40.0) yr^-1. We also investigate the potential constraint on the Hubble constant H_0 by these GW events, if their redshift information is extracted from the candidates of host galaxy groups. We find that, by five-year's full time observations, 2G detector network is expected to give a constraint of \u0394 H_0/H_0\u223c (1%,4%), which can be more than two order smaller if considering the 3G detector network.", "keyphrases": ["host galaxy group", "binary black hole", "hubble constant", "cosmological parameter"]}
{"id": "1510.01566", "title": "Lensing signals from Spin-2 perturbations", "abstract": "We compute the angular power spectra of the E-type and B-type lensing potentials for gravitational waves from inflation and for tensor perturbations induced by scalar perturbations. We derive the tensor-lensed CMB power spectra for both cases. We also apply our formalism to determine the linear lensing potential for a Bianchi I spacetime with small anisotropy.", "keyphrases": ["gravitational wave", "tensor perturbation", "possible contribution"]}
{"id": "1903.01129", "title": "Constraints on ultra-low-frequency gravitational waves with statistics of pulsar spin-down rates", "abstract": "We probe ultra-low-frequency gravitational waves (GWs) with statistics of spin-down rates of milli-second pulsars (MSPs) by a method proposed in our prevous work (Yonemaru et al. 2016). The considered frequency range is 10^-12 Hz\u2272 f_ GW\u2272 10^-10Hz, which cannot be accessed by the conventional pulsar timing array. The effect of such low-frequency GWs appears as a bias to spin-down rates which has a quadrupole pattern in the sky. We use the skewness of the spin-down rate distribution and the number of MSPs with negative spin-down rates to search for the bias induced by GWs. Applying this method to 149 MSPs selected from the ATNF pulsar catalog, we derive upper bounds on the time derivative of the GW amplitudes of \u1e23 < 6.2 \u00d7 10^-18 sec^-1 and \u1e23 < 8.1 \u00d7 10^-18 sec^-1 in the directions of the Galactic Center and M87, respectively. Approximating the GW amplitude as \u1e23\u223c 2 \u03c0 f_ GW h, the bounds translate into h < 3 \u00d7 10^-9 and h < 4 \u00d7 10^-9, respectively, for f_ GW = 1/(100 yr). Finally, we give the implications to possible super-massive black hole binaries at these sites.", "keyphrases": ["ultra-low-frequency gravitational wave", "pulsar", "spin-down rate"]}
{"id": "1002.0849", "title": "Vector field models of modified gravity and the dark sector", "abstract": "We present a comprehensive investigation of cosmological constraints on the class of vector field formulations of modified gravity called Generalized Einstein-Aether models. Using linear perturbation theory we generate cosmic microwave background and large-scale structure spectra for general parameters of the theory, and then constrain them in various ways. We investigate two parameter regimes: a dark-matter candidate where the vector field sources structure formation, and a dark-energy candidate where it causes late-time acceleration. We find that the dark matter candidate does not fit the data, and identify five physical problems that can restrict this and other theories of dark matter. The dark energy candidate does fit the data, and we constrain its fundamental parameters; most notably we find that the theory's kinetic index parameter n_ae can differ significantly from its \u039bCDM value.", "keyphrases": ["gravity", "cosmology", "dark matter", "einstein-\u00e6ther theory"]}
{"id": "1503.07437", "title": "Hydrodynamic representation of the Klein-Gordon-Einstein equations in the weak field limit: I. General formalism and perturbations analysis", "abstract": "Using a generalization of the Madelung transformation, we derive the hydrodynamic representation of the Klein-Gordon-Einstein equations in the weak field limit. We consider a complex self-interacting scalar field with a \u03bb|\u03c6|^4 potential. We study the evolution of the homogeneous background in the fluid representation and derive the linearized equations describing the evolution of small perturbations in a static and in an expanding universe. We compare the results with simplified models in which the gravitational potential is introduced by hand in the Klein-Gordon equation, and assumed to satisfy a (generalized) Poisson equation. We study the evolution of the perturbations in the matter era using the nonrelativistic limit of our formalism. Perturbations whose wavelength is below the Jeans length oscillate in time while pertubations whose wavelength is above the Jeans length grow linearly with the scale factor as in the cold dark matter model. The growth of perturbations in the scalar field model is substantially faster than in the cold dark matter model. When the wavelength of the pertubations approaches the cosmological horizon (Hubble length), a relativistic treatment is mandatory. In that case, we find that relativistic effects attenuate or even prevent the growth of pertubations. This paper exposes the general formalism and provides illustrations in simple cases. Other applications of our formalism will be considered in companion papers.", "keyphrases": ["klein-gordon-einstein equation", "weak field limit", "hydrodynamic representation"]}
{"id": "1006.1642", "title": "The CMB Bispectrum", "abstract": "We use a separable mode expansion estimator with WMAP data to estimate the bispectrum for all the primary families of non-Gaussian models. We review the late-time mode expansion estimator methodology which can be applied to any non-separable primordial and CMB bispectrum model, and we demonstrate how the method can be used to reconstruct the CMB bispectrum from an observational map. We extend the previous validation of the general estimator using local map simulations. We apply the estimator to the coadded WMAP 5-year data, reconstructing the WMAP bispectrum using l<500 multipoles and n=31 orthonormal 3D eigenmodes. We constrain all popular nearly scale-invariant models, ensuring that the theoretical bispectrum is well-described by a convergent mode expansion. Constraints from the local model =54.4\u00b1 29.4 and the equilateral model =143.5\u00b1 151.2 (= 25.1\u00b1 26.4) are consistent with previously published results. (Here, we use a nonlinearity parameter normalised to the local case, to allow more direct comparison between different models.) Notable new constraints from our method include those for the constant model = 35.1 \u00b1 27.4, the flattened model = 35.4\u00b1 29.2, and warm inflation = 10.3\u00b1 27.2. We investigate feature models surveying a wide parameter range in both the scale and phase, and we find no significant evidence of non-Gaussianity in the models surveyed. We propose a measure for the total integrated bispectrum and find that the measured value is consistent with the null hypothesis that CMB anisotropies obey Gaussian statistics. We argue that this general bispectrum survey with the WMAP data represents the best evidence for Gaussianity to date and we discuss future prospects, notably from the Planck satellite.", "keyphrases": ["cmb bispectrum", "estimator", "non-gaussianity", "wmap bispectrum"]}
{"id": "1605.03212", "title": "K-essence model from the mechanical approach point of view: coupled scalar field and the late cosmic acceleration", "abstract": "In this paper, we consider the Universe at the late stage of its evolution and deep inside the cell of uniformity. At these scales, we can consider the Universe to be filled with dust-like matter in the form of discretely distributed galaxies, a K-essence scalar field, playing the role of dark energy, and radiation as matter sources. We investigate such a Universe in the mechanical approach. This means that the peculiar velocities of the inhomogeneities (in the form of galaxies) as well as the fluctuations of the other perfect fluids are non-relativistic. Such fluids are designated as coupled because they are concentrated around the inhomogeneities. In the present paper, we investigate the conditions under which the K-essence scalar field with the most general form for its action can become coupled. We investigate at the background level three particular examples of the K-essence models: (i) the pure kinetic K-essence field, (ii) a K-essence with a constant speed of sound and (iii) the K-essence model with the Lagrangian bX+cX^2-V(\u03d5). We demonstrate that if the K-essence is coupled, all these K-essence models take the form of multicomponent perfect fluids where one of the component is the cosmological constant. Therefore, they can provide the late-time cosmic acceleration and be simultaneously compatible with the mechanical approach.", "keyphrases": ["scalar field", "cosmic acceleration", "k-essence model"]}
{"id": "2009.14325", "title": "Probing dark photons in the early universe with big bang nucleosynthesis", "abstract": "We perform calculations of dark photon production and decay in the early universe for ranges of dark photon masses and vacuum coupling with standard model photons. Simultaneously and self-consistently with dark photon production and decay, our calculations include a complete treatment of weak decoupling and big bang nucleosynthesis (BBN) physics. These calculations incorporate all relevant weak, electromagnetic, and strong nuclear reactions, including charge-changing (isospin-changing) lepton capture and decay processes. They reveal a rich interplay of dark photon production, decay, and associated out-of-equilibrium transport of entropy into the decoupling neutrino seas. Most importantly, the self-consistent nature of our simulations allows us to capture the magnitude and phasing of entropy injection and dilution. Entropy injection-induced alteration of the time-temperature-scale factor relation during weak decoupling and BBN leads to changes in the light element abundance yields and the total radiation content (as parametrized by N_ eff). These changes suggest ways to extend previous dark photon BBN constraints. However, our calculations also identify ranges of dark photon mass and couplings not yet constrained, but perhaps accessible and probable, in future Stage-4 cosmic microwave background experiments and future high precision primordial deuterium abundance measurements.", "keyphrases": ["dark photon", "early universe", "big bang nucleosynthesis"]}
{"id": "1605.07311", "title": "Quantum-to-classical transition and imprints of continuous spontaneous localization in classical bouncing universes", "abstract": "The perturbations in the early universe are generated as a result of the interplay between quantum field theory and gravitation. Since these primordial perturbations lead to the anisotropies in the cosmic microwave background and eventually to the inhomogeneities in the Large Scale Structure (LSS), they provide a unique opportunity to probe issues which are fundamental to our understanding of quantum physics and gravitation. One such fundamental issue that remains to be satisfactorily addressed is the transition of the primordial perturbations from their quantum origins to the LSS which can be characterized completely in terms of classical quantities. Classical bouncing universes provide an alternative to the more conventional inflationary paradigm as they can help overcome the horizon problem in a fashion very similar to inflation. While the problem of the quantum-to-classical transition of the primordial perturbations has been investigated extensively in the context of inflation, we find that there has been a rather limited effort towards studying the issue in classical bouncing universes. In this work, we analyze certain aspects of this problem with the example of tensor perturbations produced in classical matter and near-matter bouncing universes. We investigate the issue mainly from two perspectives. Firstly, we approach the problem by examining the extent of squeezing of a quantum state associated with the tensor perturbations with the help of the Wigner function. Secondly, we analyze the issue from the perspective of the quantum measurement problem. In particular, we study the effects of wave function collapse, using a phenomenological model known as continuous spontaneous localization, on the tensor power spectra. We conclude with a discussion of results.", "keyphrases": ["spontaneous localization", "universe", "quantum-to-classical transition"]}
{"id": "1404.2660", "title": "Pulsar Glitches: The Crust may be Enough", "abstract": "Pulsar glitches-the sudden spin-up in the rotational frequency of a neutron star-suggest the existence of an angular-momentum reservoir confined to the inner crust of the neutron star. Large and regular glitches observed in the Vela pulsar have originally constrained the fraction of the stellar moment of inertia that must reside in the solid crust to about 1.4 entrainment-which until very recently has been ignored-suggests that in order to account for the Vela glitches, the fraction of the moment of inertia residing in the crust must increase to about 7 required angular momentum reservoir may exceed that which is available in the crust. We explore the possibility that uncertainties in the equation of state provide enough flexibility for the construction of models that predict a large crustal thickness and consequently a large crustal moment of inertia. Given that analytic results suggest that the crustal moment of inertia is sensitive to the transition pressure at the crust-core interface, we tune the parameters of the model to maximize the transition pressure, while still providing an excellent description of nuclear observables. In this manner we are able to obtain fractional moments of inertia as large as 7 masses below 1.6 solar masses. In particular, we find that if the neutron-skin thickness of 208Pb falls within the (0.20-0.26) fm range, large enough transition pressures can be generated to explain the large Vela glitches without invoking an additional angular-momentum reservoir beyond that confined to the solid crust. Our results suggest that the crust may be enough.", "keyphrases": ["neutron star", "pulsar glitches", "relativistic mean-field model"]}
{"id": "1103.2335", "title": "Inhomogeneity effects in Cosmology", "abstract": "This article looks at how inhomogeneous spacetime models may be significant for cosmology. First it looks at how the averaging process may affect large scale dynamics, with backreaction effects leading to effective contributions to the averaged energy-momentum tensor. Secondly it considers how local inhomogeneities may affect cosmological observations in cosmology, possibly significantly affecting the concordance model parameters. Thirdly it presents the possibility that the universe is spatially inhomogeneous on Hubble scales, with a violation of the Copernican principle leading to an apparent acceleration of the universe. This could perhaps even remove the need for the postulate of dark energy.", "keyphrases": ["cosmology", "cosmological observation", "inhomogeneity"]}
{"id": "1709.07479", "title": "Primordial non-Gaussianity and power asymmetry with quantum gravitational effects in loop quantum cosmology", "abstract": "Loop quantum cosmology (LQC) provides a resolution of the classical big bang singularity in the deep Planck era. The evolution, prior to the usual slow-roll inflation, naturally generates excited states at the onset of the slow-roll inflation. It is expected that these quantum gravitational effects could leave its fingerprints on the primordial perturbation spectrum and non-Gaussianity, and lead to some observational evidences in the cosmic microwave background (CMB). While the impact of the quantum effects on the primordial perturbation spectrum has been already studied and constrained by current data, in this paper we continue studying such effects on the non-Gaussianity of the primordial curvature perturbations. In this paper, we present detailed and analytical calculations of the non-Gaussianity and show explicitly that the corrections due to quantum effects are in the same magnitude of the slow-roll parameters in the observable scales and thus are well within current observational constraints. Despite this, we show that the non-Gaussianity in the squeezed limit can be enhanced at superhorizon scales and further, these effects may yield a large statistical anisotropy on the power spectrum through the Erickcek-Kamionkowski-Carroll mechanism.", "keyphrases": ["non-gaussianity", "gravitational effect", "loop quantum cosmology"]}
{"id": "1102.2833", "title": "Non-gaussianity in the strong regime of warm inflation", "abstract": "The bispectrum of scalar mode density perturbations is analysed for the strong regime of warm inflationary models. This analysis generalises previous results by allowing damping terms in the inflaton equation of motion that are dependent on temperature. A significant amount of non-gaussianity emerges with constant (or local) non-linearity parameter f_NL\u223c 20, in addition to the terms with non-constant f_NL which are characteristic of warm inflation.", "keyphrases": ["strong regime", "warm inflation", "non-gaussianity"]}
{"id": "1508.06157", "title": "Dark energy and Equivalence Principle constraints from astrophysical tests of the stability of the fine-structure constant", "abstract": "Astrophysical tests of the stability of fundamental couplings, such as the fine-structure constant \u03b1, are becoming an increasingly powerful probe of new physics. Here we discuss how these measurements, combined with local atomic clock tests and Type Ia supernova and Hubble parameter data, constrain the simplest class of dynamical dark energy models where the same degree of freedom is assumed to provide both the dark energy and (through a dimensionless coupling, \u03b6, to the electromagnetic sector) the \u03b1 variation. Specifically, current data tightly constrains a combination of \u03b6 and the present dark energy equation of state w_0. Moreover, in these models the new degree of freedom inevitably couples to nucleons (through the \u03b1 dependence of their masses) and leads to violations of the Weak Equivalence Principle. We obtain indirect bounds on the E\u00f6tv\u00f6s parameter \u03b7 that are typically stronger than the current direct ones. We discuss the model-dependence of our results and briefly comment on how the forthcoming generation of high-resolution ultra-stable spectrographs will enable significantly tighter constraints.", "keyphrases": ["astrophysical test", "fundamental coupling", "dark energy"]}
{"id": "1211.5403", "title": "Cosmologies in Horndeski's second-order vector-tensor theory", "abstract": "Horndeski derived a most general vector-tensor theory in which the vector field respects the gauge symmetry and the resulting dynamical equations are of second order. The action contains only one free parameter, \u03bb, that determines the strength of the non-minimal coupling between the gauge field and gravity. We investigate the cosmological consequences of this action and discuss observational constraints. For \u03bb<0 we identify singularities where the deceleration parameter diverges within a finite proper time. This effectively rules out any sensible cosmological application of the theory for a negative non-minimal coupling. We also find a range of parameter that gives a viable cosmology and study the phenomenology for this case. Observational constraints on the value of the coupling are rather weak since the interaction is higher-order in space-time curvature.", "keyphrases": ["horndeski", "vector-tensor theory", "cosmology"]}
{"id": "2008.01715", "title": "Tensor non-Gaussianity in chiral scalar-tensor theories of gravity", "abstract": "Violation of parity symmetry in the gravitational sector, which manifests into unequal left and right circular polarization states of primordial gravitational waves, represents a way to test high-energy modifications to general relativity. In this paper we study inflation within recently proposed chiral scalar-tensor theories of gravity, that extend Chern-Simons gravity by including parity-violating operators containing first and second derivatives of the non-minimally coupled scalar (inflaton) field. Given the degeneracy between different parity-violating theories at the level of the power spectrum statistics, we make a detailed analysis of the parity violation on primordial tensor non-Gaussianity. We show, with an explicit computation, that no new contributions arise in the graviton bispectra if the couplings in the new operators are constant in a pure de Sitter phase. On the other hand, if the coupling functions are time-dependent during inflation, the tensor bispectra acquire non-vanishing contributions from the parity-breaking operators even in the exact de Sitter limit, with maximal signal in the squeezed and equilateral configurations. We also comment on the consistency relation of the three-point function of tensor modes in this class of models and discuss prospects of detecting parity-breaking signatures through Cosmic Microwave Background B-mode bispectra.", "keyphrases": ["chiral scalar-tensor theory", "gravity", "tensor non-gaussianity"]}
{"id": "2006.00682", "title": "Gravitational lens without asymptotic flatness: Its application to the Weyl gravity", "abstract": "We discuss, without assuming asymptotic flatness, a gravitational lens for an observer and source that are within a finite distance from a lens object. The proposed lens equation is consistent with the deflection angle of light that is defined for nonasymptotic observer and source by Takizawa et al. [Phys. Rev. D 101, 104032 (2020)] based on the Gauss-Bonnet theorem with using the optical metric. This lens equation, though it is shown to be equivalent to the Bozza lens equation[Phys. Rev. D 78, 103005 (2008)], is linear in the deflection angle. Therefore, the proposed equation is more convenient for the purpose of doing an iterative analysis. As an explicit example of an asymptotically nonflat spacetime, we consider a static and spherically symmetric solution in Weyl conformal gravity, especially a case that \u03b3 parameter in the Weyl gravity model is of the order of the inverse of the present Hubble radius. For this case, we examine iterative solutions for the finite-distance lens equation up to the third order. The effect of the Weyl gravity on the lensed image position begins at the third order and it is linear in the impact parameter of light. The deviation of the lensed image position from the general relativistic one is \u223c 10^-2 microarcsecond for the lens and source with a separation angle of \u223c 1 arcminute, where we consider a cluster of galaxies with 10^14 M_\u2299 at \u223c 1 Gpc for instance. The deviation becomes \u223c 10^-1 microarcseconds, even if the separation angle is \u223c 10 arcminutes. Therefore, effects of the Weyl gravity model are negligible in current and near-future observations of gravitational lensing. On the other hand, the general relativistic corrections at the third order \u223c 0.1 milliarcseconds can be relevant with VLBI observations.", "keyphrases": ["flatness", "weyl gravity", "gravitational lens"]}
{"id": "1712.01715", "title": "Moment of inertia, quadrupole moment, Love number of neutron star and their relations with strange matter equations of state", "abstract": "We investigate the impact of strange matter equations of state involving \u039b hyperons, Bose-Einstein condensate of K^- mesons and first order hadron-quark phase transition on moment of inertia, quadrupole moment and tidal deformability parameter of slowly rotating neutron stars. All these equations of state are compatible with the 2 M_solar constraint. The main findings of this investigation are the universality of the I-Q and I-Love number relations, which are preserved by the EoSs including \u039b hyperons and antikaon condensates, but broken in presence of a first order hadron-quark phase transition. Furthermore, it is also noted that the quadrupole moment approaches the Kerr value of a black hole for maximum mass neutron stars.", "keyphrases": ["inertia", "quadrupole moment", "neutron star"]}
{"id": "1401.2219", "title": "The Earliest Stages of Star and Planet Formation: Core Collapse, and the Formation of Disks and Outflows", "abstract": "(Abridged) In this review we focus on the observations and theory of the formation of early disks and outflows, and their connections with the first phases of planet formation. Large rotationally supported circumstellar disks, although common around more evolved young stellar objects, are rarely detected during the earliest, \"Class 0\" phase; however, a few excellent candidates have been discovered recently around both low and high mass protostars. In this early phase, prominent outflows are ubiquitously observed; they are expected to be associated with at least small magnetized disks. Disk formation - once thought to be a simple consequence of the conservation of angular momentum during hydrodynamic core collapse - is far more subtle in magnetized gas. In this case, the rotation can be strongly magnetically braked. Indeed, both analytic arguments and numerical simulations have shown that disk formation is suppressed in the strict ideal magnetohydrodynamic (MHD) limit for the observed level of core magnetization. We review what is known about this \"magnetic braking catastrophe\", possible ways to resolve it, and the current status of early disk observations. Outflows are also intimately linked to disk formation; they are a natural product of magnetic fields and rotation and are important signposts of star formation. We review new developments on early outflow generation since PPV. The properties of early disks and outflows are a key component of planet formation in its early stages and we review these major connections.", "keyphrases": ["star", "planet formation", "core collapse"]}
{"id": "1604.02179", "title": "Limits of the circles-in-the-sky searches in the determination of cosmic topology of nearly flat universes", "abstract": "[Abridged] An observable signature of a detectable nontrivial spatial topology of the Universe is the circles-in-the-sky in the CMB sky. In the most general search, pairs of circles with deviation from antipodality 0^\u2218\u2264\u03b8\u2264 169^\u2218 and radii 10^\u2218\u2264\u03bb\u2264 90^\u2218 were investigated, but no matching circles were found. Assuming this negative result, we examine the question as to whether there are nearly flat universes with compact topology that would give rise to circles whose observable parameters \u03bb and \u03b8 fall o outside the ranges covered by this search. We derive the expressions for the deviation from antipodality and for the radius of the circles associated to a pair elements (\u03b3,\u03b3^-1) of the holonomy group \u0393 which define the spatial section of any positively curved universe with a nontrivial topology. We show that there is a critical position that maximizes the deviation from antipodality, and prove that no matter how nearly flat the Universe is, it can always have a nontrivial spatial topology that gives rise to circles whose deviation from antipodality \u03b8 is larger than 169^\u2218, and whose radii of the circles \u03bb are smaller than 10^\u2218 for some observers. This makes apparent that slightly positively curved universes with cosmological parameters within Planck bounds can be endowed with a nontrivial spatial topology with values of the parameters \u03bb and \u03b8 outside the ranges covered by the searches for circles carried out so far. Thus, these circles searches so far undertaken are not sufficient to exclude the possibility of a universe with a detectable nontrivial cosmic topology. We present concrete examples of such nearly flat universes, and discuss the implications of our results in view of unavoidable practical limits of the circles-in-the-sky method.", "keyphrases": ["circles-in-the-sky search", "cosmic topology", "flat universe"]}
{"id": "1610.08725", "title": "Constraints on the Primordial Black Hole Abundance from the First Advanced LIGO Observation Run Using the Stochastic Gravitational-Wave Background", "abstract": "Advanced LIGO's discovery of gravitational-wave events is stimulating extensive studies on the origin of binary black holes. Assuming that the gravitational-wave events can be explained by binary primordial black hole mergers, we utilize the upper limits on the stochastic gravitational-wave background given by Advanced LIGO as a new observational window to independently constrain the abundance of primordial black holes in dark matter. We show that Advanced LIGO's first observation run gives the best constraint on the primordial black hole abundance in the mass range 1 M_\u2299\u2272 M_PBH\u2272 100 M_\u2299, pushing the previous microlensing and dwarf galaxy dynamics constraints tighter by 1 order of magnitude. Moreover, we discuss the possibility to detect the stochastic gravitational-wave background from primordial black holes, in particular from subsolar mass primordial black holes, by Advanced LIGO in the near future.", "keyphrases": ["primordial black hole", "stochastic gravitational-wave background", "early universe"]}
{"id": "1909.09385", "title": "Silhouette of M87*: A new window to peek into the world of hidden dimensions", "abstract": "The recent observation of the shadow of the supermassive black hole M87*, located at the centre of the M87 galaxy, by the Event Horizon Telescope collaboration has opened up a new window to probe the strong gravity regime. In this letter, we explicitly demonstrate the consequences of this observation on brane world black holes, characterized by existence of a negative tidal charge. Our results based on three observables associated with the shadow, namely, angular diameter, deviation from circularity and axis ratio reveal that the existence of a negative tidal charge is more favoured, possibly marking a deviation from general relativity.", "keyphrases": ["new window", "dimension", "relativity"]}
{"id": "1702.02571", "title": "The Fermi blazar sequence", "abstract": "We revisit the blazar sequence exploiting the complete, flux limited sample of blazars with known redshift detected by the Fermi satellite after 4 years of operations (the 3LAC sample). We divide the sources into gamma-ray luminosity bins, collect all the archival data for all blazars, and construct their spectral energy distribution (SED). We describe the average SED of blazars in the same luminosity bin through a very simple, completely phenomenological function consisting of two broken power laws connecting with a power law of fixed slope describing the radio emission. We do that separately for BL Lacs and for flat spectrum radio quasars (FSRQs) and also for all blazars together. The main results are: i) FSRQs display approximately the same SED as the luminosity increases, except for the fact that the relative importance of the high energy peak increases; ii) as a consequence, X-ray spectra of FSRQs become harder for larger luminosities; iii) BL Lacs form indeed a sequence: they become redder (i.e. the peak frequencies becomes smaller) for increasing luminosities, with a steeper gamma-ray slope and a larger dominance of the high energy peak; iv) for all blazars (BL Lacs+FSRQs) these properties becomes more prominent, as the highest luminosity bin is populated mostly by FSRQs and the lowest luminosity bin mostly by BL Lacs. This agrees with the original blazar sequence, although BL Lacs never have an average gamma-ray slope as hard as found in the original sequence. v) At high luminosities, a large fraction of FSRQs shows signs of thermal emission from the accretion disc, contributing in the optical-UV.", "keyphrases": ["blazar sequence", "sequence", "sed", "fsrqs", "average bll"]}
{"id": "1511.01003", "title": "Luminosity of ultrahigh energy cosmic rays and bounds on magnetic luminosity of radio-loud active galactic nuclei", "abstract": "We investigate the production of magnetic flux from rotating black holes in active galactic nuclei (AGNs) and compare it with the upper limit of ultrahigh energy cosmic ray (UHECR) luminosities, calculated from observed integral flux of GeV-TeV gamma rays for nine UHECR AGN sources. We find that, for the expected range of black hole rotations (0.44<a<0.80), the corresponding bounds of theoretical magnetic luminosities from AGNs coincides with the calculated UHECR luminosity. We argue that such result possibly can contribute to constrain AGN magnetic and dynamic properties as phenomenological tools to explain the requisite conditions to proper accelerate the highest energy cosmic rays.", "keyphrases": ["cosmic ray", "magnetic luminosity", "active galactic nucleus"]}
{"id": "1204.6044", "title": "Astrophysical Tests of Modified Gravity: Constraints from Distance Indicators in the Nearby Universe", "abstract": "We use distance measurements in the nearby universe to carry out new tests of gravity, surpassing other astrophysical tests by over two orders of magnitude for chameleon theories. The three nearby distance indicators \u2013 cepheids, tip of the red giant branch (TRGB) stars, and water masers \u2013 operate in gravitational fields of widely different strengths. This enables tests of scalar-tensor gravity theories because they are screened from enhanced forces to different extents. Inferred distances from cepheids and TRGB stars are altered (in opposite directions) over a range of chameleon gravity theory parameters well below the sensitivity of cosmological probes. Using published data we have compared cepheid and TRGB distances in a sample of unscreened dwarf galaxies within 10 Mpc. As a control sample we use a comparable set of screened galaxies. We find no evidence for the order unity force enhancements expected in these theories. Using a two-parameter description of the models (the coupling strength and background field value) we obtain constraints on chameleon and symmetron screening scenarios. In particular we show that f(R) models with background field values fR0 above 5e-7 are ruled out at the 95 confidence level. We also compare TRGB and maser distances to the galaxy NGC 4258 as a second test for larger field values. While there are several approximations and caveats in our study, our analysis demonstrates the power of gravity tests in the local universe. We discuss the prospects for additional, improved tests with future observations.", "keyphrases": ["gravity", "distance indicator", "nearby universe", "dwarf galaxy"]}
{"id": "1304.4832", "title": "Fluid phonons, protoinflationary dynamics and large-scale gravitational fluctuations", "abstract": "We explore what can be said on the effective temperature and sound speed of a statistical ensemble of fluid phonons present at the onset of a conventional inflationary phase. The phonons are the actual normal modes of the gravitating and irrotational fluid that dominates the protoinflationary dynamics. The bounds on the tensor to scalar ratio result in a class of novel constraints involving the slow roll parameter, the sound speed of the phonons and the temperature of the plasma prior to the onset of inflation. If the current size of the Hubble radius coincides with the inflationary event horizon redshifted down to the present epoch, the sound speed of the phonons can be assessed from independent measurements of the tensor to scalar ratio and of the tensor spectral index.", "keyphrases": ["protoinflationary dynamic", "epoch", "fluid phonon"]}
{"id": "2111.11526", "title": "Velocity reconstruction with the cosmic microwave background and galaxy surveys", "abstract": "The kinetic Sunyaev Zel'dovich (kSZ) and moving lens effects, secondary contributions to the cosmic microwave background (CMB), carry significant cosmological information due to their dependence on the large-scale peculiar velocity field. Previous work identified a promising means of extracting this cosmological information using a set of quadratic estimators for the radial and transverse components of the velocity field. These estimators are based on the statistically anisotropic components of the cross-correlation between the CMB and a tracer of large scale structure, such as a galaxy redshift survey. In this work, we assess the challenges to the program of velocity reconstruction posed by various foregrounds and systematics in the CMB and galaxy surveys, as well as biases in the quadratic estimators. To do so, we further develop the quadratic estimator formalism and implement a numerical code for computing properly correlated spectra for all the components of the CMB (primary/secondary blackbody components and foregrounds) and a photometric redshift survey, with associated redshift errors, to allow for accurate forecasting. We create a simulation framework for generating realizations of properly correlated CMB maps and redshift binned galaxy number counts, assuming the underlying fields are Gaussian, and use this to validate a velocity reconstruction pipeline and assess map-based systematics such as masking. We highlight the most significant challenges for velocity reconstruction, which include biases associated with: modelling errors, characterization of redshift errors, and coarse graining of cosmological fields on our past light cone. Despite these challenges, the outlook for velocity reconstruction is quite optimistic, and we use our reconstruction pipeline to confirm that these techniques will be feasible with near-term CMB experiments and photometric galaxy redshift surveys.", "keyphrases": ["cosmic microwave background", "galaxy survey", "velocity reconstruction"]}
{"id": "2202.08778", "title": "VETTAM: A scheme for radiation hydrodynamics with adaptive mesh refinement using the variable Eddington tensor method", "abstract": "We present Variable Eddington Tensor-closed Transport on Adaptive Meshes (), a new algorithm to solve the equations of radiation hydrodynamics (RHD) with support for adaptive mesh refinement (AMR) in a frequency-integrated, two-moment formulation. The method is based on a non-local Variable Eddington Tensor (VET) closure computed with a hybrid characteristics scheme for ray tracing. We use a Godunov method for the hyperbolic transport of radiation with an implicit backwards-Euler temporal update to avoid the explicit timestep constraint imposed by the light-crossing time, and a fixed-point Picard iteration scheme to handle the nonlinear gas-radiation exchange term, with the two implicit update stages jointly iterated to convergence. We also develop a modified wave-speed correction method for AMR, which we find to be crucial for obtaining accurate results in the diffusion regime. We demonstrate the robustness of our scheme with a suite of pure radiation and RHD tests, and show that it successfully captures the streaming, static diffusion, and dynamic diffusion regimes and the spatial transitions between them, casts sharp shadows, and yields accurate results for rates of momentum and energy exchange between radiation and gas. A comparison between different closures for the radiation moment equations, with the Eddington approximation (0th-moment closure) and the M_1 approximation (1st-moment closure), demonstrates the advantages of the VET method (2nd-moment closure) over the simpler closure schemes. has been coupled to the AMR (magneto-)hydrodynamics code and we summarize by reporting performance features and bottlenecks of our implementation.", "keyphrases": ["scheme", "radiation hydrodynamic", "adaptive mesh refinement"]}
{"id": "2107.07979", "title": "On the moment of inertia of PSR J0737-3039 A from LIGO/Virgo and NICER", "abstract": "We perform a Bayesian analysis of neutrons star moment of inertia by utilizing the available gravitational-wave data from LIGO/Virgo (GW170817 and GW190425) and mass-radius measurements from the Neutron Star Interior Composition Explorer (PSR J0030+0415 and PSR J0740+6620), incorporating the possible phase transition in the pulsar inner core. We find that the moment of inertia of pulsar A in the double pulsar binary J0737-3039 is \u223c1.30\u00d710^45 g cm^2, which only slightly depends on the employed hadronic equation of states. We also demonstrate how a moment of inertia measurement would improve our knowledge of the equation of state and the mass-radius relation for neutron stars and discuss whether a quark deconfinement phase transition is supported by the available data and forthcoming data that could be consistent with this hypothesis. We find that if pulsar A is a quark star, that its moment of inertia is a large value of \u223c1.55\u00d710^45 g cm^2 suggesting the possibility of distinguishing it from (hybrid-)neutron stars with measurements of PSR J0737-3039A moment of inertia. We finally demonstrate the moment-of-inertia-compactness universal relations and provide analytical fits for both (hybrid-)neutron star and quark star results based on our analysis.", "keyphrases": ["inertia", "psr j0737", "virgo"]}
{"id": "1206.2164", "title": "Resonant Signatures of Heavy Scalar Fields in the Cosmic Microwave Background", "abstract": "We investigate the possibility that a heavy scalar field, whose mass exceeds the Hubble scale during inflation, could leave non-negligible signatures in the Cosmic Microwave Background (CMB) temperature anisotropy power spectrum through the parametric resonance between its background oscillations and the inflaton fluctuations. By assuming the heavy scalar field couples with the inflaton derivatively, we show that the resonance can be efficient without spoiling the slow-roll inflation. The primordial power spectrum modulated by the resonance has a sharp peak at a specific scale and could be an origin of the anomalies observed in the angular power spectrum of the CMB. In some values of parameters, the modulated spectrum can fit the observed data better than the simple power-law power spectrum, though the resultant improvement of the fit is not large enough and hence other observations such as non-Gaussianity are necessary to confirm that the CMB anomalies are originated from the resonant effect of the heavy scalar field. The resonant signatures can provide an opportunity to observe heavy degrees of freedom during inflation and improve our understanding of physics behind inflation.", "keyphrases": ["cosmic microwave background", "inflaton fluctuation", "heavy field"]}
{"id": "1803.03798", "title": "Vacuum birefringence and the X-ray polarization from black-hole accretion disks", "abstract": "In the next decade, x-ray polarimetry will open a new window on the high-energy Universe, as several missions that include an x-ray polarimeter are currently under development. Observations of the polarization of x-rays coming from the accretion disks of stellar-mass and supermassive black holes are among the new polarimeters' major objectives. In this paper, we show that these observations can be affected by the quantum electrodynamic (QED) effect of vacuum birefringence: after an x-ray photon is emitted from the accretion disk, its polarization changes as the photon travels through the accretion disk's magnetosphere, as a result of the vacuum becoming birefringent in presence of a magnetic field. We show that this effect can be important for black holes in the energy band of the upcoming polarimeters, and has to be taken into account in a complete model of the x-ray polarization that we expect to detect from black-hole accretion disks, both for stellar mass and for supermassive black holes. We find that, for a chaotic magnetic field in the disk, QED can significantly decrease the linear polarization fraction of edge-on photons, depending on the spin of the hole and on the strength of the magnetic field. This effect can provide, for the first time, a direct way to probe the magnetic field strength close to the innermost stable orbit of black-hole accretion disks and to study the role of magnetic fields in astrophysical accretion in general.", "keyphrases": ["x-ray polarization", "black-hole accretion disk", "vacuum birefringence"]}
{"id": "1304.5599", "title": "Comptonization efficiencies of the variability classes of GRS 1915+105", "abstract": "The Galactic microquasar GRS 1915+105 exhibits at least seventeen types of variability classes. Intra and inter class transitions are reported to be observed within seconds to hours. Since the observation was not continuous, these classes appeared to be exhibited in a random order. Our goal is to predict a sequence of these classes. In this paper, we compute the ratio of the photon counts obtained from the power-law component and the blackbody component of each class and call this ratio as the `Comptonizing efficiency' (CE) of that class. We sequence the classes in the ascending order of CE and find that this sequence matches with a few class transitions observed by RXTE satellite and IXAE instruments on board IRS-P3. A change in CE corresponds to a change in the optical depth of the Compton cloud. Our result implies that the optical depth of the Compton cloud gradually rises as the variability class becomes harder.", "keyphrases": ["variability class", "grs", "sequence", "compton cloud", "comptonizing efficiency"]}
{"id": "1007.3563", "title": "Conformal equivalence in classical gravity: the example of \"veiled\" General Relativity", "abstract": "In the theory of General Relativity, gravity is described by a metric which couples minimally to the fields representing matter. We consider here its \"veiled\" versions where the metric is conformally related to the original one and hence is no longer minimally coupled to the matter variables. We show on simple examples that observational predictions are nonetheless exactly the same as in General Relativity, with the interpretation of this \"Weyl\" rescaling \"\u00e0 la Dicke\", that is, as a spacetime dependence of the inertial mass of the matter constituents.", "keyphrases": ["gravity", "scalar-tensor theory", "non-minimal coupling", "classical level"]}
{"id": "1702.02992", "title": "The 2HWC HAWC Observatory Gamma Ray Catalog", "abstract": "We present the first catalog of TeV gamma-ray sources realized with the recently completed High Altitude Water Cherenkov Observatory (HAWC). It is the most sensitive wide field-of-view TeV telescope currently in operation, with a 1-year survey sensitivity of 5-10 instantaneous field of view >1.5 sr and >90 surveys and monitors the sky for gamma ray energies between hundreds GeV and tens of TeV. HAWC is located in Mexico at a latitude of 19 degree North and was completed in March 2015. Here, we present the 2HWC catalog, which is the result of the first source search realized with the complete HAWC detector. Realized with 507 days of data and represents the most sensitive TeV survey to date for such a large fraction of the sky. A total of 39 sources were detected, with an expected contamination of 0.5 due to background fluctuation. Out of these sources, 16 are more than one degree away from any previously reported TeV source. The source list, including the position measurement, spectrum measurement, and uncertainties, is reported. Seven of the detected sources may be associated with pulsar wind nebulae, two with supernova remnants, two with blazars, and the remaining 23 have no firm identification yet.", "keyphrases": ["observatory", "gamma-ray source", "pulsar", "hawc catalog", "galactic source"]}
{"id": "2202.09378", "title": "The Very Knotty Lenser: exploring the role of regularization in source and potential reconstructions using Gaussian Process Regression", "abstract": "Reconstructing lens potentials and lensed sources can easily become an underconstrained problem, even when the degrees of freedom are low, due to degeneracies, particularly when potential perturbations superimposed on a smooth lens are included. Regularization has traditionally been used to constrain the solutions where the data failed to do so, e.g. in unlensed parts of the source. In this exploratory work, we go beyond the usual choices of regularization and adopt observationally motivated priors for the source brightness. We also perform a similar comparison when reconstructing lens potential perturbations, which are assumed to be stationary, i.e. permeate the entire field of view. We find that physically motivated priors lead to lower residuals, avoid overfitting, and are decisively preferred within a Bayesian quantitative framework in all the examples considered. For the perturbations, choosing the wrong regularization can have a detrimental effect that even high-quality data cannot correct for, while using a purely smooth lens model can absorb them to a very high degree and lead to biased solutions. Finally, our new implementation of the semi-linear inversion technique provides the first quantitative framework for measuring degeneracies between the source and the potential perturbations.", "keyphrases": ["regularization", "lens", "degeneracy", "potential perturbation", "choice"]}
{"id": "1307.7625", "title": "Neutrino flavor pendulum in both mass hierarchies", "abstract": "We construct a simple example for self-induced flavor conversion in dense neutrino gases showing new solutions that violate the symmetries of initial conditions. Our system consists of two opposite momentum modes 1 and 2, each initially occupied with equal densities of nu_e and anti-nu_e. Restricting solutions to symmetry under 1 <-> 2 allows for the usual bimodal instability (\"flavor pendulum\") in the inverted neutrino mass hierarchy (IH) and stability (no self-induced flavor conversion) in the normal hierarchy (NH). Lifting this symmetry restriction allows for a second pendulum-like solution that occurs in NH where the modes 1 and 2 swing in opposite directions in flavor space. Any small deviation from 1-2 symmetry in the initial condition triggers the new instability in NH. This effect corresponds to the recently identified multi-azimuth angle (MAA) instability of supernova neutrino fluxes. Both cases show explicitly that solutions of the equations of collective flavor oscillations need not inherit the symmetries of initial conditions, although this has been universally assumed.", "keyphrases": ["flavor conversion", "neutrino", "axial symmetry"]}
{"id": "1411.4335", "title": "Generation of large-scale magnetic fields, non-Gaussianity, and primordial gravitational waves in inflationary cosmology", "abstract": "The generation of large-scale magnetic fields in inflationary cosmology is explored, in particular, in a kind of moduli inflation motivated by racetrack inflation in the context of the Type IIB string theory. In this model, the conformal invariance of the hypercharge electromagnetic fields is broken thanks to the coupling of both the scalar and pseudoscalar fields to the hypercharge electromagnetic fields. The following three cosmological observable quantities are first evaluated: The current magnetic field strength on the Hubble horizon scale, which is much smaller than the upper limit from the back reaction problem, local non-Gaussianity of the curvature perturbations due to the existence of the massive gauge fields, and the tensor-to-scalar ratio. It is explicitly demonstrated that the resultant values of local non-Gaussianity and the tensor-to-scalar ratio are consistent with the Planck data.", "keyphrases": ["large-scale magnetic field", "inflationary cosmology", "conformal invariance"]}
{"id": "1901.07047", "title": "Machine and Deep Learning Applied to Galaxy Morphology \u2013 A Comparative Study", "abstract": "Morphological classification is a key piece of information to define samples of galaxies aiming to study the large-scale structure of the universe. In essence, the challenge is to build up a robust methodology to perform a reliable morphological estimate from galaxy images. Here, we investigate how to substantially improve the galaxy classification within large datasets by mimicking human classification. We combine accurate visual classifications from the Galaxy Zoo project with machine and deep learning methodologies. We propose two distinct approaches for galaxy morphology: one based on non-parametric morphology and traditional machine learning algorithms; and another based on Deep Learning. To measure the input features for the traditional machine learning methodology, we have developed a system called CyMorph, with a novel non-parametric approach to study galaxy morphology. The main datasets employed comes from the Sloan Digital Sky Survey Data Release 7 (SDSS-DR7). We also discuss the class imbalance problem considering three classes. Performance of each model is mainly measured by Overall Accuracy (OA). A spectroscopic validation with astrophysical parameters is also provided for Decision Tree models to assess the quality of our morphological classification. In all of our samples, both Deep and Traditional Machine Learning approaches have over 94.5 OA to classify galaxies in two classes (elliptical and spiral). We compare our classification with state-of-the-art morphological classification from literature. Considering only two classes separation, we achieve 99 accuracy in average when using our deep learning models, and 82 three classes. We provide a catalog with 670,560 galaxies containing our best results, including morphological metrics and classification.", "keyphrases": ["deep learning", "galaxy morphology", "machine"]}
{"id": "2112.11159", "title": "Equation of state and neutrino transfer in supernovae and neutron stars", "abstract": "We overview the progress of the tables of the equation of state for astrophysical simulations and the numerical methods of neutrino transfer. Hot and dense matter play essential roles in core-collapse supernovae and neutron stars. Equation of state determines the structure of compact objects and their dynamics through its behavior of thermodynamic quantities. In addition, neutrinos are trapped in supernova cores and neutron star mergers and frequently interact with matter to crucially affect dynamics in determining the explosion mechanism and the final form of compact objects. Therefore, it is essential to implement detailed processes of nuclear and neutrino physics in numerical simulations by having reliable data set of the equation of state and reaction rates. We show examples of developments of the equation of state and the neutrino transfer and discuss research directions toward understanding the explosive phenomena by the first principle calculation.", "keyphrases": ["neutrino transfer", "supernovae", "neutron star"]}
{"id": "0902.0493", "title": "Science with a lunar low-frequency array: from the dark ages of the Universe to nearby exoplanets", "abstract": "Low-frequency radio astronomy is limited by severe ionospheric distortions below 50 MHz and complete reflection of radio waves below 10-30 MHz. Shielding of man-made interference from long-range radio broadcasts, strong natural radio emission from the Earth's aurora, and the need for setting up a large distributed antenna array make the lunar far side a supreme location for a low-frequency radio array. A number of new scientific drivers for such an array, such as the study of the dark ages and epoch of reionization, exoplanets, and ultra-high energy cosmic rays, have emerged and need to be studied in greater detail. Here we review the scientific potential and requirements of these and other new scientific drivers and discuss the constraints for various lunar surface arrays. In particular we describe observability constraints imposed by the interstellar and interplanetary medium, calculate the achievable resolution, sensitivity, and confusion limit of a dipole array using general scaling laws, and apply them to various scientific questions. Whichever science is deemed most important, pathfinder arrays are needed to test the feasibility of these experiments in the not too distant future. Lunar low-frequency arrays are thus a timely option to consider, offering the potential for significant new insights into a wide range of today's crucial scientific topics. This would open up one of the last unexplored frequency domains in the electromagnetic spectrum.", "keyphrases": ["lunar low-frequency array", "dark age", "science"]}
{"id": "2110.11249", "title": "Relativistic second-order initial conditions for simulations of large-scale structure", "abstract": "Relativistic corrections to the evolution of structure can be used to test general relativity on cosmological scales. They are also a well-known systematic contamination in the search for a primordial non-Gaussian signal. We present a numerical framework to generate RELativistic second-order Initial Conditions () based on a generic (not necessarily separable) second-order kernel for the density perturbations. In order to keep the time complexity manageable we introduce a scale cut that separates long and short scales, and neglect the \"short-short\" coupling that will eventually be swamped by uncontrollable higher-order effects. To test our approach, we use the second-order Einstein-Boltzmann code to provide the numerical second-order kernel in a \u039bCDM model, and we demonstrate that the realisations generated by reproduce the bispectra well whenever at least one of the scales is a \"long\" mode. We then present a generic algorithm that takes a perturbed density field as an inputand provides particle initial data that matches this input to arbitrary order in perturbations for a given particle-mesh scheme. We implement this algorithm in the relativistic N-body code to demonstrate how our framework can be used to set precise initial conditions for cosmological simulations of large-scale structure.", "keyphrases": ["initial condition", "simulation", "large-scale structure"]}
{"id": "1307.7753", "title": "Empirical evidences for a planetary modulation of total solar irradiance and the TSI signature of the 1.09-year Earth-Jupiter conjunction cycle", "abstract": "The time series of total solar irradiance (TSI) satellite observations since 1978 provided by ACRIM and PMOD TSI composites are studied. We find empirical evidence for planetary-induced forcing and modulation of solar activity. Power spectra and direct data pattern analysis reveal a clear signature of the 1.09-year Earth-Jupiter conjunction cycle, in particular during solar cycle 23 maximum. This appears to suggest that the Jupiter side of the Sun is slightly brighter during solar maxima. The effect is observed when the Earth crosses the Sun-Jupiter conjunction line every 1.09 years. Multiple spectral peaks are observed in the TSI records that are coherent with known planetary harmonics such as the spring, orbital and synodic periods among Mercury, Venus, Earth and Jupiter: the Mercury-Venus spring-tidal cycle (0.20 year); the Mercury orbital cycle (0.24 year); the Venus-Jupiter spring-tidal cycle (0.32 year); the Venus-Mercury synodic cycle (0.40 year); the Venus-Jupiter synodic cycle (0.65 year); and the Venus-Earth spring tidal cycle (0.80 year). Strong evidence is also found for a 0.5-year TSI cycle that could be driven by the Earth's crossing the solar equatorial plane twice a year and may indicate a latitudinal solar-luminosity asymmetry. Because both spring and synodic planetary cycles appear to be present and the amplitudes of their TSI signatures appear enhanced during sunspot cycle maxima, we conjecture that on annual and sub-annual scales both gravitational and electro-magnetic planet-sun interactions and internal non-linear feedbacks may be modulating solar activity. Gravitational tidal forces should mostly stress spring cycles while electro-magnetic forces could be linked to the solar wobbling dynamics, and would mostly stress the synodic cycles.", "keyphrases": ["planetary modulation", "total solar irradiance", "earth-jupiter conjunction cycle"]}
{"id": "1101.0219", "title": "Hydrostatic equilibrium and stellar structure in f(R)-gravity", "abstract": "We investigate the hydrostatic equilibrium of stellar structure by taking into account the modi- fied La\u00e9-Emden equation coming out from f(R)-gravity. Such an equation is obtained in metric approach by considering the Newtonian limit of f(R)-gravity, which gives rise to a modified Poisson equation, and then introducing a relation between pressure and density with polytropic index n. The modified equation results an integro-differential equation, which, in the limit f(R) \u2192R, becomes the standard La\u00e9-Emden equation. We find the radial profiles of gravitational potential by solving for some values of n. The comparison of solutions with those coming from General Relativity shows that they are compatible and physically relevant.", "keyphrases": ["stellar structure", "f(r)-gravity", "hydrostatic equilibrium"]}
{"id": "1309.2146", "title": "Boulware-Deser ghost in extended quasidilaton massive gravity", "abstract": "In the extended quasidilaton massive gravity we perform a nonlinear transformation of the shift vector and then calculate the second derivatives of the Hamiltonian density with respect to the lapse function and the (nonlinearly transformed) shift vector. It is then shown that the 4\u00d7 4 Hessian matrix is invertible, meaning that the equations of motion for the lapse function and the shift vector simply determine themselves. Therefore, there is no primary constraint that removes the Boulware-Deser ghost.", "keyphrases": ["ghost", "extended quasidilaton", "massive gravity"]}
{"id": "1209.3384", "title": "CMB power spectra induced by primordial cross-bispectra between metric perturbations and vector fields", "abstract": "We study temperature and polarization anisotropies of the cosmic microwave background (CMB) radiation sourced from primordial cross-bispectra between metric perturbations and vector fields, which are generated from the inflation model where an inflaton and a vector field are coupled. In case the vector field survives after the reheating, both the primordial scalar and tensor fluctuations can be enhanced by the anisotropic stress composed of the vector fields during radiation dominated era. We show that through this enhancement the primordial cross-bispectra generate not only CMB bispectra but also CMB power spectra. In general, we can expect such cross-bispectra produce the non-trivial mode-coupling signals between the scalar and tensor fluctuations. However, we explicitly show that such mode-coupling signals do not appear in CMB power spectra. Through the numerical analysis of the CMB scalar-mode power spectra, we find that although signals from these cross-bispectra are smaller than primary non-electromagnetic ones, these have some characteristic features such as negative auto-correlations of the temperature and polarization modes, respectively. On the other hand, signals from tensor modes are almost comparable to primary non-electromagnetic ones and hence the shape of observed B-mode spectrum may deviate from the prediction in the non-electromagnetic case. The above imprints may help us to judge the existence of the coupling between the scalar and vector fields in the early Universe.", "keyphrases": ["primordial cross-bispectra", "metric perturbation", "cmb power spectra"]}
{"id": "1902.03300", "title": "The mass distribution of Galactic double neutron stars", "abstract": "The conventional wisdom, dating back to 2012, is that the mass distribution of Galactic double neutron stars is well-fit by a Gaussian distribution with a mean of 1.33 M_\u2299 and a width of 0.09 M_\u2299. With the recent discovery of new Galactic double neutron stars and GW170817, the first neutron star merger event to be observed with gravitational waves, it is timely to revisit this model. In order to constrain the mass distribution of double neutron stars, we perform Bayesian inference using a sample of 17 Galactic double neutron stars effectively doubling the sample used in previous studies. We expand the space of models so that the recycled neutron star need not be drawn from the same distribution as the non-recycled companion. Moreover, we consider different functional forms including uniform, single-Gaussian, and two-Gaussian distributions. While there is insufficient data to draw firm conclusions, we find positive support (a Bayes factor of 9) for the hypothesis that recycled and non-recycled neutron stars have distinct mass distributions. The most probable model\u2014preferred with a Bayes factor of 29 over the conventional model\u2014is one in which the recycled neutron star mass is distributed according to a two-Gaussian distribution and the non-recycled neutron star mass is distributed uniformly. We show that precise component mass measurements of \u2248 20 double neutron stars are required in order to determine with high confidence (a Bayes factor of 150) if recycled and non-recycled neutron stars come from a common distribution. Approximately 60 are needed in order to establish the detailed shape of the distributions.", "keyphrases": ["mass distribution", "galactic", "double neutron star"]}
{"id": "1610.07015", "title": "On the IceCube spectral anomaly", "abstract": "Recently it was noted that different IceCube datasets are not consistent with the same power law spectrum of the cosmic neutrinos: this is the IceCube spectral anomaly, that suggests that they observe a multicomponent spectrum. In this work, the main possibilities to enhance the description in terms of a single extragalactic neutrino component are examined. The hypothesis of a sizable contribution of Galactic high-energy neutrino events distributed as E^-2.7 [ApJ 826, 185 (2016)] is critically analyzed and its natural generalization is considered. The stability of the expectations is studied by introducing free parameters, motivated by theoretical considerations and observational facts. The upgraded model here examined has 1) a Galactic component with different normalization and shape E^- 2.4; 2) an extragalactic neutrino spectrum based on new data; 3) a non-zero prompt component of atmospheric neutrinos. The two key predictions of the model concern the `high-energy starting events' collected from the Southern sky. The Galactic component produces a softer spectrum and a testable angular anisotropy. A second, radically different class of models, where the second component is instead isotropic, plausibly extragalactic and with a relatively soft spectrum, is disfavored instead by existing observations of muon neutrinos from the Northern sky and below few 100 TeV.", "keyphrases": ["icecube", "spectral anomaly", "tev."]}
{"id": "1211.5482", "title": "CMB from CFT", "abstract": "During inflation, spacetime is approximately described by de Sitter space which is conformally invariant with the symmetry group SO(1,4). This symmetry can significantly constrain the quantum perturbations which arise in the inflationary epoch. We consider a general situation of single field inflation and show that the three point function involving two scalar modes and one tensor mode is uniquely determined, up to small corrections, by the conformal symmetries. Special conformal transformations play an important role in our analysis. Our result applies only to models where the inflaton sector also approximately preserves the full conformal group and shows that this three point function is a good way to test if special conformal invariance was preserved during inflation.", "keyphrases": ["sitter space", "correlator", "consistency relation", "conformal consistency relation", "single-field model"]}
{"id": "1712.00002", "title": "A Precision Search for WIMPs with Charged Cosmic Rays", "abstract": "AMS-02 has reached the sensitivity to probe canonical thermal WIMPs by their annihilation into antiprotons. Due to the high precision of the data, uncertainties in the astrophysical background have become the most limiting factor for indirect dark matter detection. In this work we systematically quantify and \u2013 where possible \u2013 reduce uncertainties in the antiproton background. We constrain the propagation of charged cosmic rays through the combination of antiproton, B/C and positron data. Cross section uncertainties are determined from a wide collection of accelerator data and are \u2013 for the first time ever \u2013 fully taken into account. This allows us to robustly constrain even subdominant dark matter signals through their spectral properties. For a standard NFW dark matter profile we are able to exclude thermal WIMPs with masses up to 570 GeV which annihilate into bottom quarks. While we confirm a reported excess compatible with dark matter of mass around 80 GeV, its local (global) significance only reaches 2.2 sigma (1.1 sigma) in our analysis.", "keyphrases": ["wimp", "antiproton", "dark matter", "possible excess"]}
{"id": "1106.2556", "title": "Relativistic shock breakouts - a variety of gamma-ray flares: from low luminosity gamma-ray bursts to type Ia supernovae", "abstract": "A large variety of explosions result in mildly or ultra relativistic shock breakouts. Here we calculate the luminosity and spectrum that these breakouts produce. In order to do so we improve an analytic description of relativistic radiation mediated shocks and follow the system from the breakout itself, through the planar phase and into the spherical phase. We limit our calculation to cases where the post breakout acceleration of the gas ends during the planar phase. (i.e., the final gas Lorentz factor < 30). We find that spherical relativistic breakouts produce a flash of gamma-rays with energy, temperature, and duration that always satisfy a specific relation between them as well as providing the breakout radius and Lorentz factor. The breakout flare is typically followed, on longer time scales, by X-rays that carry a comparable energy. We apply our model to a variety of explosions, including Ia and .Ia supernovae (SNe), AIC, energetic SNe and gamma-ray bursts (GRBs). We find that all these events produce detectable gamma-ray signals, some of which may have already been seen. Some particular examples are: (i) Relativistic shock breakouts provide a natural explanation to the energy, temperature and time scales, as well as many other observed features, of all low luminosity GRBs. (ii) Nearby broad-line Ib/c (like SN 2002ap) may produce a detectable gamma-ray signal. (iii) Galactic Ia SNe produce detectable gamma-ray flares, if their progenitors are single degenerate. We conclude that relativistic shock breakout is a generic process for the production of gamma-ray flares, which opens a new window for the study and detection of a variety of stellar explosions.", "keyphrases": ["shock breakout", "flare", "gamma-ray burst"]}
{"id": "1207.1721", "title": "First measurement of the bulk flow of nearby galaxies using the cosmic microwave background", "abstract": "Peculiar velocities in the nearby Universe can be measured via the kinetic Sunyaev-Zel'dovich (kSZ) effect. Using a statistical method based on an optimised cross-correlation with nearby galaxies, we extract the kSZ signal generated by plasma halo of galaxies from the Cosmic Microwave Background (CMB) temperature anisotropies observed by the Wilkinson Microwave Anisotropy Probe (WMAP). Marginalising over the thermal Sunyaev-Zel'dovich contribution from clusters of galaxies, possible unresolved point source contamination, and Galactic foregrounds (dust, synchrotron and free-free emission), we report a kSZ bulk flow signal present at the 90 data. When only galaxies within 50 Mpc/h are included in the kSZ template we find a bulk flow in the CMB frame of |V|=533 +/- 263 km/s, in the direction l=324 +/- 27, b=-7 +/- 17, consistent with bulk flow measurements on a similar scale using classical distance indicators. We show how this comparison constrains the (ionised) baryonic budget in the local universe. On very large ( 500 Mpc/h) scales, we find a 95 some analyses of bulk flow of clusters from the kSZ. We estimate that the significance of the bulk flow signal may increase to 3-5 sigma using data from the PLANCK probe.", "keyphrases": ["bulk flow", "nearby galaxy", "cosmic microwave background"]}
{"id": "1002.2928", "title": "Reconstruction of signals with unknown spectra in information field theory with parameter uncertainty", "abstract": "The optimal reconstruction of cosmic metric perturbations and other signals requires knowledge of their power spectra and other parameters. If these are not known a priori, they have to be measured simultaneously from the same data used for the signal reconstruction. We formulate the general problem of signal inference in the presence of unknown parameters within the framework of information field theory. We develop a generic parameter uncertainty renormalized estimation (PURE) technique and address the problem of reconstructing Gaussian signals with unknown power-spectrum with five different approaches: (i) separate maximum-a-posteriori power spectrum measurement and subsequent reconstruction, (ii) maximum-a-posteriori power reconstruction with marginalized power-spectrum, (iii) maximizing the joint posterior of signal and spectrum, (iv) guessing the spectrum from the variance in the Wiener filter map, and (v) renormalization flow analysis of the field theoretical problem providing the PURE filter. In all cases, the reconstruction can be described or approximated as Wiener filter operations with assumed signal spectra derived from the data according to the same recipe, but with differing coefficients. All of these filters, except the renormalized one, exhibit a perception threshold in case of a Jeffreys prior for the unknown spectrum. Data modes, with variance below this threshold do not affect the signal reconstruction at all. Filter (iv) seems to be similar to the so called Karhune-Loeve and Feldman-Kaiser-Peacock estimators for galaxy power spectra used in cosmology, which therefore should also exhibit a marginal perception threshold if correctly implemented. We present statistical performance tests and show that the PURE filter is superior to the others.", "keyphrases": ["information field theory", "parameter uncertainty", "reconstruction"]}
{"id": "1712.07425", "title": "Probing primordial features with next-generation photometric and radio surveys", "abstract": "We investigate the possibility of using future photometric and radio surveys to constrain the power spectrum of primordial fluctuations that is predicted by inflationary models with a violation of the slow-roll phase. We forecast constraints with a Fisher analysis on the amplitude of the parametrized features on ultra-large scales, in order to assess whether these could be distinguishable over the cosmic variance. We find that the next generation of photometric and radio surveys has the potential to test these models at a sensitivity better than current CMB experiments and that the synergy between galaxy and CMB observations is able to constrain models with many extra parameters. In particular, an SKA continuum survey with a huge sky coverage and a flux threshold of a few \u03bcJy could confirm the presence of a new phase in the early Universe at more than 3\u03c3.", "keyphrases": ["primordial feature", "photometric", "radio survey"]}
{"id": "1711.07696", "title": "Exoplanet phase curves: observations and theory", "abstract": "Phase curves are the best technique to probe the three dimensional structure of exoplanets' atmospheres. In this chapter we first review current exoplanets phase curve observations and the particular challenges they face. We then describe the different physical mechanisms shaping the atmospheric phase curves of highly irradiated tidally locked exoplanets. Finally, we discuss the potential for future missions to further advance our understanding of these new worlds.", "keyphrases": ["phase curve", "atmosphere", "exoplanet", "orbit"]}
{"id": "1809.03496", "title": "Gravity in mimetic scalar-tensor theories after GW170817", "abstract": "We derive the most general mimetic scalar-tensor theory assuming a healthy \"seed\" action and accounting for the constraints on the speed of gravitational-wave propagation arising from the GW170817 event. By analysing linear perturbations around a flat FLRW background in this model, we obtain a suitable form of the Poisson equation, which allows us to calculate the effective gravitational constant felt by \"ordinary\" matter. By restricting to a minimally coupled model, such an effective gravitational constant is equivalent to that obtained within General Relativity, with cold dark matter plus a perfect fluid dark energy component, with vanishing sound speed. Assuming, further, a \u039bCDM background, the effective gravitational constant cannot be distinguished from that of the standard \u039bCDM model, at linear order. For the full non-minimally coupled mimetic gravity model we obtain a non-vanishing gravitational slip and an effective gravitational constant which always differs from that of standard \u039bCDM.", "keyphrases": ["mimetic scalar-tensor theory", "dark matter", "mimetic gravity", "gravity"]}
{"id": "1612.06420", "title": "The special growth history of central galaxies in groups and clusters", "abstract": "Central galaxies (CGs) in galaxy groups and clusters are believed to form and assemble a good portion of their stellar mass at early times, but they also accrete significant mass at late times via galactic cannibalism, that is merging with companion group or cluster galaxies that experience dynamical friction against the common host dark-matter halo. The effect of these mergers on the structure and kinematics of the CG depends not only on the properties of the accreted satellites, but also on the orbital parameters of the encounters. Here we present the results of numerical simulations aimed at estimating the distribution of merging orbital parameters of satellites cannibalized by the CGs in groups and clusters. As a consequence of dynamical friction, the satellites' orbits evolve losing energy and angular momentum, with no clear trend towards orbit circularization. The distributions of the orbital parameters of the central-satellite encounters are markedly different from the distributions found for halo-halo mergers in cosmological simulations. The orbits of satellites accreted by the CGs are on average less bound and less eccentric than those of cosmological halo-halo encounters. We provide fits to the distributions of the central-satellite merging orbital parameters that can be used to study the merger-driven evolution of the scaling relations of CGs.", "keyphrases": ["growth history", "central galaxy", "group"]}
{"id": "1402.2336", "title": "Higher moments of primordial non-Gaussianity and N-body simulations", "abstract": "We perform cosmological N-body simulations with non-Gaussian initial conditions generated from two independent fields. The dominant contribution to the perturbations comes from a purely Gaussian field, but we allow the second field to have local non-Gaussianity that need not be weak. This scenario allows us to adjust the relative importance of non-Gaussian contributions beyond the skewness, producing a scaling of the higher moments different from (and stronger than) the scaling in the usual single field local ansatz. We compare semi-analytic prescriptions for the non-Gaussian mass function, large scale halo bias, and stochastic bias against the simulation results. We discuss applications of this work to large scale structure measurements that can test a wider range of models for the primordial fluctuations than is usually explored.", "keyphrases": ["moment", "non-gaussianity", "n-body simulation"]}
{"id": "1006.0687", "title": "Analytical model for CMB temperature angular power spectrum from cosmic (super-)strings", "abstract": "We present a new analytical method to calculate the small angle CMB temperature angular power spectrum due to cosmic (super-)string segments. In particular, using our method, we clarify the dependence on the intercommuting probability P. We find that the power spectrum is dominated by Poisson-distributed string segments. The power spectrum for a general value of P has a plateau on large angular scales and shows a power-law decrease on small angular scales. The resulting spectrum in the case of conventional cosmic strings is in very good agreement with the numerical result obtained by Fraisse et al.. Then we estimate the upper bound on the dimensionless tension of the string for various values of P by assuming that the fraction of the CMB power spectrum due to cosmic (super-)strings is less than ten percents at various angular scales up to \u2113=2000. We find that the amplitude of the spectrum increases as the intercommuting probability. As a consequence, strings with smaller intercommuting probabilities are found to be more tightly constrained.", "keyphrases": ["angular power spectrum", "super-)string", "cosmic string"]}
{"id": "2008.11688", "title": "Cosmology with Rayleigh Scattering of the Cosmic Microwave Background", "abstract": "The cosmic microwave background (CMB) has been a treasure trove for cosmology. Over the next decade, current and planned CMB experiments are expected to exhaust nearly all primary CMB information. To further constrain cosmological models, there is a great benefit to measuring signals beyond the primary modes. Rayleigh scattering of the CMB is one source of additional cosmological information. It is caused by the additional scattering of CMB photons by neutral species formed during recombination and exhibits a strong and unique frequency scaling (\u221d\u03bd^4). We will show that with sufficient sensitivity across frequency channels, the Rayleigh scattering signal should not only be detectable but can significantly improve constraining power for cosmological parameters, with limited or no additional modifications to planned experiments. We will provide heuristic explanations for why certain cosmological parameters benefit from measurement of the Rayleigh scattering signal, and confirm these intuitions using the Fisher formalism. In particular, observation of Rayleigh scattering allows significant improvements on measurements of N_ eff and \u2211 m_\u03bd.", "keyphrases": ["rayleigh scattering", "cosmic microwave background", "cosmology"]}
{"id": "1902.01419", "title": "The properties of merging black holes and neutron stars across cosmic time", "abstract": "The next generation ground-based gravitational wave interferometers will possibly observe mergers of binary black holes (BBHs) and binary neutron stars (BNSs) to redshift z\u227310 and z\u22732, respectively. Here, we characterize the properties of merging BBHs, BNSs and neutron star-black hole binaries across cosmic time, by means of population-synthesis simulations combined with the Illustris cosmological simulation. We find that the mass of merging compact objects does not depend (or depends very mildly) on the merger redshift. Even the mass distribution of black holes depends only mildly on redshift, because BBHs originating from metal-poor progenitors (Z\u22644\u00d710^-3) dominate the entire population of merging BBHs across cosmic time. For a common-envelope efficiency \u03b1\u22653, the main difference between the mass distribution of BBHs merging in the last Gyr and that of BBHs merging more than 11 Gyr ago is that there is an excess of heavy merging black holes (20-35 M_\u2299) in the last Gyr. This excess is explained by the longer delay time of massive BBHs.", "keyphrases": ["black hole", "neutron star", "cosmic time"]}
{"id": "0903.1119", "title": "Extreme Sensitivity of the YORP Effect to Small-Scale Topography", "abstract": "Radiation recoil (YORP) torques are shown to be extremely sensitive to small-scale surface topography. Starting from simulated objects representative of the near-Earth object population, random realizations of three types of small-scale topography are added: Gaussian surface fluctuations, craters, and boulders. For each, the resulting expected relative errors in the spin and obliquity components of the YORP torque are computed. Gaussian power produces errors of order 100 harmonic order l < 10. A single crater with diameter roughly half the object's mean radius, placed at random locations, results in errors of several tens of percent. Boulders create torque errors roughly 3 times larger than do craters of the same diameter. A single boulder comparable to Yoshinodai on 25143 Itokawa, moved by as little as twice its own diameter, can alter the magnitude of the torque by factors of several, and change the sign of its spin component at all obliquities. A YORP torque prediction derived from groundbased data can be expected to be in error by of order 100 surface changes caused by slow spin-up or spin-down may have significant stochastic effects on the spin evolution of small bodies. For rotation periods between roughly 2 and 10 hours, these unpredictable changes may reverse the sign of the YORP torque. Objects in this spin regime may random-walk up and down in spin rate before the rubble-pile limit is exceeded and fissioning or loss of surface objects occurs. Similar behavior may be expected at rotation rates approaching the limiting values for tensile-strength dominated objects.", "keyphrases": ["yorp effect", "small-scale topography", "single crater", "location"]}
{"id": "1712.10148", "title": "Magnetic field buoyancy in accretion disks of young stars", "abstract": "Buoyancy of the fossil magnetic field in the accretion disks of young stars is investigated. It is assumed that the Parker instability leads to the formation of slender flux tubes of toroidal magnetic field in the regions of effective magnetic field generation. Stationary solution of the induction equation is written in the form in which buoyancy is treated as the additional mechanism of the magnetic flux escape. We calculate the fossil magnetic field intensity in the accretion disks of young T Tauri stars for the cases when radius of the magnetic flux tubes a_mft = 0.1H, 0.5 H or 1H, where H is the accretion disk height scale. Calculations show that the buoyancy limits toroidal magnetic field growth, so that its strength is comparable with the vertical magnetic field strength for the case a_mft=0.1H.", "keyphrases": ["accretion disk", "young star", "magnetic field buoyancy"]}
{"id": "0902.0697", "title": "Big Bounce and inhomogeneities", "abstract": "The dynamics of an inhomogeneous universe is studied with the methods of Loop Quantum Cosmology as an example of the quantization of vacuum cosmological spacetimes containing gravitational waves (Gowdy spacetimes). The analysis performed at the effective level shows that: (i) The initial Big Bang singularity is replaced (as in the case of homogeneous cosmological models) by a Big Bounce, joining deterministically two large universes, (ii) the universe size at the bounce is at least of the same order of magnitude as that of the background homogeneous universe, (iii) for each gravitational wave mode, the difference in amplitude at very early and very late times has a vanishing statistical average when the bounce dynamics is strongly dominated by the inhomogeneities, whereas this average is positive when the dynamics is in a near-vacuum regime, so that statistically the inhomogeneities are amplified.", "keyphrases": ["inhomogeneity", "cosmology", "alternative"]}
{"id": "1710.00827", "title": "Neutrino transport in black hole-neutron star binaries: neutrino emission and dynamical mass ejection", "abstract": "We study the merger of black hole-neutron star binaries by fully general-relativistic neutrino-radiation-hydrodynamics simulations throughout the coalescence, particularly focusing on the role of neutrino irradiation in dynamical mass ejection. Neutrino transport is incorporated by an approximate transfer scheme based on the truncated moment formalism. While we fix the mass ratio of the black hole to the neutron star to be 4 and the dimensionless spin parameter of the black hole to be 0.75, the equations of state for finite-temperature neutron-star matter are varied. The hot accretion disk formed after tidal disruption of the neutron star emits a copious amount of neutrinos with the peak total luminosity 1\u20133x10^53 erg s^(-1) via thermal pair production and subsequent electron/positron captures on free nucleons. Nevertheless, the neutrino irradiation does not modify significantly the electron fraction of the dynamical ejecta from the neutrinoless beta-equilibrium value at zero temperature of initial neutron stars. The mass of the wind component driven by neutrinos from the remnant disk is negligible compared to the very neutron-rich dynamical component, throughout our simulations performed until a few tens milliseconds after the onset of merger, for the models considered in this study. These facts suggest that the ejecta from black hole-neutron star binaries are very neutron rich and are expected to accommodate strong r-process nucleosynthesis, unless magnetic or viscous processes contribute substantially to the mass ejection from the disk. We also find that the peak neutrino luminosity does not necessarily increase as the disk mass increases, because tidal disruption of a compact neutron star can result in a remnant disk with a small mass but high temperature.", "keyphrases": ["hole-neutron star binary", "dynamical mass ejection", "neutrino transport"]}
{"id": "2010.12722", "title": "A set of orbital elements to fully represent the zonal harmonics around an oblate celestial body", "abstract": "This work introduces a new set of orbital elements to fully represent the zonal harmonics problem around an oblate celestial body. This new set of orbital elements allows to obtain a complete linear system for the unperturbed problem and, in addition, a complete polynomial system when considering the perturbation produced by the zonal harmonics from the gravitational force of an oblate celestial body. These orbital elements present no singularities and are able to represent any kind of orbit, including elliptic, parabolic and hyperbolic orbits. In addition, an application to this formulation of the Poincar\u00e9-Lindstedt perturbation method is included to obtain an approximate first order solution of the problem for the case of the J2 perturbation.", "keyphrases": ["orbital element", "zonal harmonic", "celestial body"]}
{"id": "1608.00291", "title": "The SAMI Galaxy Survey: the link between angular momentum and optical morphology", "abstract": "We investigate the relationship between stellar and gas specific angular momentum j, stellar mass M_* and optical morphology for a sample of 488 galaxies extracted from the SAMI Galaxy Survey. We find that j, measured within one effective radius, monotonically increases with M_* and that, for M_*>10^9.5 M_\u2299, the scatter in this relation strongly correlates with optical morphology (i.e., visual classification and S\u00e9rsic index). These findings confirm that massive galaxies of all types lie on a plane relating mass, angular momentum and stellar light distribution, and suggest that the large-scale morphology of a galaxy is regulated by its mass and dynamical state. We show that the significant scatter in the M_*-j relation is accounted for by the fact that, at fixed stellar mass, the contribution of ordered motions to the dynamical support of galaxies varies by at least a factor of three. Indeed, the stellar spin parameter (quantified via \u03bb_R) correlates strongly with S\u00e9rsic and concentration indices. This correlation is particularly strong once slow-rotators are removed from the sample, showing that late-type galaxies and early-type fast rotators form a continuous class of objects in terms of their kinematic properties.", "keyphrases": ["sami galaxy survey", "angular momentum", "optical morphology"]}
{"id": "2001.02986", "title": "Concerns regarding the use of black hole shadows as standard rulers", "abstract": "Recently, Tsupko et al. have put forward the very interesting proposal to use the shadows of high-redshift supermassive black holes (SMBHs) as standard rulers. This would in principle allow us to probe the expansion history within a redshift range which would otherwise be challenging to access. In this note, we critically examine this proposal, and identify a number of important issues which had been previously overlooked. These include difficulties in obtaining reliable SMBH mass estimates and reaching the required angular resolution, and an insufficient knowledge of the accretion dynamics of high-redshift SMBHs. While these issues currently appear to prevent high-redshift SMBH shadows from being used as robust standard rulers, we hope that our flagging them early will help in making this probe theoretically mature by the time it will be experimentally feasible.", "keyphrases": ["black hole", "shadow", "standard ruler"]}
{"id": "1505.05756", "title": "Angular momentum fluctuations in the convective helium shell of massive stars", "abstract": "We find significant fluctuations of angular momentum within the convective helium shell of a pre-collapse massive star - a core-collapse supernova progenitor - which may facilitate the formation of accretion disks and jets that can explode the star. The convective flow in our model of an evolved M_ZAMS=15Msun star, computed with the sub-sonic hydrodynamic solver MAESTRO, contains entire shells with net angular momentum in different directions. This phenomenon may have important implications for the late evolutionary stages of massive stars, and for the dynamics of core-collapse.", "keyphrases": ["convective helium shell", "massive star", "angular momentum"]}
{"id": "2003.06411", "title": "The Halo Void (Dust) Model of Large Scale Structure", "abstract": "Within the Halo Model of large scale structure, all matter is contained in dark matter halos. This simple yet powerful framework has been broadly applied to multiple data sets and enriched our comprehension of how matter is distributed in the Universe. In this work we extend this assumption by allowing for matter to rest not only inside halos but also within cosmic voids and in between halos and voids (which we call 'dust'). This assumption leads to additional contributions (1Void, 2Void, Halo-Void, etc.) to the predictions of correlation functions, spectra and profiles for both halos and voids. Whereas the Halo Model can only make predictions for halo quantities, the Halo Void Model extends those for void statistics and halo-void cross-correlations. We provide recipes for all new ingredients of the Halo Void (Dust) Model, such as the void abundance, linear bias and density profile and test their validity in a N-body simulation. Including voids and dust into the calculations improves the transition between the 1Halo and the 2Halo terms by up to \u223c 6%. It also eliminates the need to include low-mass structures on the normalization of large-scale terms, suggesting that halos and voids are complementary cosmic structures to effectively describe matter distribution on large scales of the Universe.", "keyphrases": ["halo void", "dust", "large scale structure"]}
{"id": "1212.0754", "title": "Triangular solution to general relativistic three-body problem for general masses", "abstract": "Continuing work initiated in an earlier publication [Ichita, Yamada and Asada, Phys. Rev. D 83, 084026 (2011)], we reexamine the post-Newtonian effects on Lagrange's equilateral triangular solution for the three-body problem. For three finite masses, it is found that a triangular configuration satisfies the post-Newtonian equation of motion in general relativity, if and only if it has the relativistic corrections to each side length. This post-Newtonian configuration for three finite masses is not always equilateral and it recovers previous results for the restricted three-body problem when one mass goes to zero. For the same masses and angular velocity, the post-Newtonian triangular configuration is always smaller than the Newtonian one.", "keyphrases": ["three-body problem", "general masse", "triangular solution"]}
{"id": "1201.2814", "title": "Eddington-inspired Born-Infeld gravity. Phenomenology of non-linear gravity-matter coupling", "abstract": "Viable corrections to the matter sector of Poisson's equation may result in qualitatively different astrophysical phenomenology, for example the gravitational collapse and the properties of compact objects can change drastically. We discuss a class of modified non-relativistic theories and focus on a relativistic completion, Eddington-inspired Born-Infeld gravity. This recently proposed theory is equivalent to General Relativity in vacuum, but its non-trivial coupling to matter prevents singularities in early cosmology and in the non-relativistic collapse of non-interacting particles. We extend our previous analysis, discussing further developments. We present a full numerical study of spherically symmetric non-relativistic gravitational collapse of dust. For any positive coupling, the final state of the collapse is a regular pressureless star rather than a singularity. We also argue that there is no Chandrasekhar limit for the mass of non-relativistic white dwarf in this theory. Finally, we extend our previous results in the fully relativistic theory by constructing static and slowly rotating compact stars governed by nuclear-physics inspired equations of state. In the relativistic theory, there exists an upper bound on the mass of compact objects, suggesting that black holes can still be formed in the relativistic collapse.", "keyphrases": ["born-infeld gravity", "gravitational collapse", "general relativity", "cosmology"]}
{"id": "1309.2315", "title": "Leptogenesis and Primordial Magnetic Fields", "abstract": "The anomalous conversion of leptons into baryons during leptogenesis is shown to produce a right-handed helical magnetic field; in contrast, the magnetic field produced during electroweak baryogenesis is known to be left-handed. If the cosmological medium is turbulent, the magnetic field evolves to have a present day coherence scale and field strength that are of astrophysical interest. Observations of the amplitude, coherence scale, and helicity of the intergalactic magnetic field promise to provide a powerful probe of physics beyond the Standard Model and the very early universe.", "keyphrases": ["magnetic field", "early universe", "leptogenesis"]}
{"id": "1705.04065", "title": "SkyFACT: High-dimensional modeling of gamma-ray emission with adaptive templates and penalized likelihoods", "abstract": "We present SkyFACT (Sky Factorization with Adaptive Constrained Templates), a new approach for studying, modeling and decomposing diffuse gamma-ray emission. Like most previous analyses, the approach relies on predictions from cosmic-ray propagation codes like GALPROP and DRAGON. However, in contrast to previous approaches, we account for the fact that models are not perfect and allow for a very large number (\u227310^5) of nuisance parameters to parameterize these imperfections. We combine methods of image reconstruction and adaptive spatio-spectral template regression in one coherent hybrid approach. To this end, we use penalized Poisson likelihood regression, with regularization functions that are motivated by the maximum entropy method. We introduce methods to efficiently handle the high dimensionality of the convex optimization problem as well as the associated semi-sparse covariance matrix, using the L-BFGS-B algorithm and Cholesky factorization. We test the method both on synthetic data as well as on gamma-ray emission from the inner Galaxy, |\u2113|<90^\u2218 and |b|<20^\u2218, as observed by the Fermi Large Area Telescope. We finally define a simple reference model that removes most of the residual emission from the inner Galaxy, based on conventional diffuse emission components as well as components for the Fermi bubbles, the Fermi Galactic center excess, and extended sources along the Galactic disk. Variants of this reference model can serve as basis for future studies of diffuse emission in and outside the Galactic disk.", "keyphrases": ["gamma-ray emission", "template", "skyfact"]}
{"id": "1804.10489", "title": "Attractor Behaviour in Multifield Inflation", "abstract": "We study multifield inflation in scenarios where the fields are coupled non-minimally to gravity via \u03be_I(\u03d5^I)^n g^\u03bc\u03bdR_\u03bc\u03bd, where \u03be_I are coupling constants, \u03d5^I the fields driving inflation, g_\u03bc\u03bd the space-time metric, R_\u03bc\u03bd the Ricci tensor, and n>0. We consider the so-called \u03b1-attractor models in two formulations of gravity: in the usual metric case where R_\u03bc\u03bd=R_\u03bc\u03bd(g_\u03bc\u03bd), and in the Palatini formulation where R_\u03bc\u03bd is an independent variable. As the main result, we show that, regardless of the underlying theory of gravity, the field-space curvature in the Einstein frame has no influence on the inflationary dynamics at the limit of large \u03be_I, and one effectively retains the single-field case. However, the gravity formulation does play an important role: in the metric case the result means that multifield models approach the single-field \u03b1-attractor limit, whereas in the Palatini case the attractor behaviour is lost also in the case of multifield inflation. We discuss what this means for distinguishing between different models of inflation.", "keyphrases": ["multifield inflation", "gravity", "attractor behaviour"]}
{"id": "1109.3187", "title": "Warm dark matter in the galaxies:theoretical and observational progresses. Highlights and conclusions of the chalonge meudon workshop 2011", "abstract": "Warm Dark Matter (WDM) research is progressing fast, the subject is new and WDM essentially works, naturally reproducing the astronomical observations over all scales: small (galactic) and large (cosmological) scales (LambdaWDM). Evidence that Cold Dark Matter (LambdaCDM) and its proposed tailored cures do not work at small scales is staggering. Fedor Bezrukov, Pier-Stefano Corasaniti, Hector J. de Vega, Stefano Ettori, Frederic Hessmann, Ayuki Kamada, Marco Lombardi, Alexander Merle, Christian Moni Bidin, Angelo Nucciotti on behalf of the MARE collaboration, Sinziana Paduroiu, Henri Plana, Norma Sanchez, Patrick Valageas, Shun Zhou present here their highlights of the Workshop. LambdaWDM simulations with keV particles remarkably reproduce the observations, small and large structures and velocity functions. Cored DM halos and WDM are clearly determined from theory and astronomical observations, they naturally produce the observed structures at all scales. keV sterile neutrinos are the leading candidates, they naturally appear extensions of the standard model of particle physics. Astrophysical constraints including Lyman alpha bounds put its mass in the range 1< m <13 keV. Predictions for EUCLID and PLANCK have been presented. MARE and an adapted KATRIN experiment could detect a keV sterile neutrino. It will be a fantastic discovery to detect dark matter in a beta decay. A formidable WDM work to perform is ahead of us, these highlights point out some relevant research directions to put the effort. Photos of the Workshop are included (Abridged).", "keyphrases": ["astronomical observation", "warm dark matter", "galactic scale"]}
{"id": "1801.09630", "title": "Gauge invariant variables for cosmological perturbation theory using geometrical clocks", "abstract": "Using the extended ADM-phase space formulation in the canonical framework we analyze the relationship between various gauge choices made in cosmological perturbation theory and the choice of geometrical clocks in the relational formalism. We show that various gauge invariant variables obtained in the conventional analysis of cosmological perturbation theory correspond to Dirac observables tied to a specific choice of geometrical clocks. As examples, we show that the Bardeen potentials and the Mukhanov-Sasaki variable emerge naturally in our analysis as observables when gauge fixing conditions are determined via clocks in the Hamiltonian framework. Similarly other gauge invariant variables for various gauges can be systematically obtained. We demonstrate this by analyzing five common gauge choices: longitudinal, spatially flat, uniform field, synchronous and comoving gauge. For all these, we apply the observable map in the context of the relational formalism and obtain the corresponding Dirac observables associated with these choices of clocks. At the linear order, our analysis generalizes the existing results in canonical cosmological perturbation theory twofold. On the one hand we can include also gauges that can only be analyzed in the context of the extended ADM-phase space and furthermore, we obtain a set of natural gauge invariant variables, namely the Dirac observables, for each considered choice of gauge conditions. Our analysis provides insights on which clocks should be used to extract the relevant natural physical observables both at the classical and quantum level. We also discuss how to generalize our analysis in a straightforward way to higher orders in the perturbation theory to understand gauge conditions and the construction of gauge invariant quantities beyond linear order.", "keyphrases": ["cosmological perturbation theory", "geometrical clock", "gauge"]}
{"id": "2012.05220", "title": "Estimating distances from parallaxes. V: Geometric and photogeometric distances to 1.47 billion stars in Gaia Early Data Release 3", "abstract": "Stellar distances constitute a foundational pillar of astrophysics. The publication of 1.47 billion stellar parallaxes from Gaia is a major contribution to this. Yet despite Gaia's precision, the majority of these stars are so distant or faint that their fractional parallax uncertainties are large, thereby precluding a simple inversion of parallax to provide a distance. Here we take a probabilistic approach to estimating stellar distances that uses a prior constructed from a three-dimensional model of our Galaxy. This model includes interstellar extinction and Gaia's variable magnitude limit. We infer two types of distance. The first, geometric, uses the parallax together with a direction-dependent prior on distance. The second, photogeometric, additionally uses the colour and apparent magnitude of a star, by exploiting the fact that stars of a given colour have a restricted range of probable absolute magnitudes (plus extinction). Tests on simulated data and external validations show that the photogeometric estimates generally have higher accuracy and precision for stars with poor parallaxes. We provide a catalogue of 1.47 billion geometric and 1.35 billion photogeometric distances together with asymmetric uncertainty measures. Our estimates are quantiles of a posterior probability distribution, so they transform invariably and can therefore also be used directly in the distance modulus (5log10(r)-5). The catalogue may be downloaded or queried using ADQL at various sites (see http://www.mpia.de/homes/calj/gedr3_distances.html) where it can also be cross-matched with the Gaia catalogue.", "keyphrases": ["parallax", "photogeometric distance", "star"]}
{"id": "2210.13413", "title": "Razor-thin dust layers in protoplanetary disks: Limits on the vertical shear instability", "abstract": "Context: Recent observations with the Atacama Large Millimeter Array (ALMA) have shown that the large dust aggregates observed at millimeter wavelengths settle to the midplane into a remarkably thin layer. Aims: We intend to find out if the geometric thinness of these layers is evidence against the vertical shear instability (VSI) operating in these disks. Methods: We performed hydrodynamic simulations of a protoplanetary disk with a locally isothermal equation of state, and let the VSI fully develop. We sprinkled dust particles and followed their motion as they got stirred up by the VSI. We determined for which grain size the layer becomes geometrically thin enough to be consistent with ALMA observations. We then verified if, with these grain sizes, it is still possible to generate a moderately optically thick layer at millimeter wavelengths, as observations appear to indicate. Results: We found that even very large dust aggregates with Stokes numbers close to unity get stirred up to relatively large heights above the midplane by the VSI, which is in conflict with the observed geometric thinness. For grains so large that the Stokes number exceeds unity, the layer can be made to remain thin, but we show that it is hard to make dust layers optically thick at ALMA wavelengths (e.g., tau(1.3mm)>=1) with such large dust aggregates. Conclusions: We conclude that protoplanetary disks with geometrically thin midplane dust layers cannot be VSI unstable, at least not down to the disk midplane. Explanations for the inhibition of the VSI include a reduced dust-to-gas ratio of the small dust grains that are responsible for the radiative cooling of the disk. A reduction of small grains by a factor of between 10 and 100 is sufficient to quench the VSI. Such a reduction is plausible in dust growth models, and still consistent with observations at optical and infrared wavelengths.", "keyphrases": ["dust layer", "protoplanetary disk", "vertical shear instability"]}
{"id": "1101.1619", "title": "Exploring a string-like landscape", "abstract": "We explore inflationary trajectories within randomly-generated two-dimensional potentials, considered as a toy model of the string landscape. Both the background and perturbation equations are solved numerically, the latter using the two-field formalism of Peterson and Tegmark which fully incorporates the effect of isocurvature perturbations. Sufficient inflation is a rare event, occurring for only roughly one in 10^5 potentials. For models generating sufficient inflation, we find that the majority of runs satisfy current constraints from WMAP. The scalar spectral index is less than 1 in all runs. The tensor-to-scalar ratio is below the current limit, while typically large enough to be detected by next-generation CMB experiments and perhaps also by Planck. In many cases the inflationary consistency equation is broken by the effect of isocurvature modes.", "keyphrases": ["landscape", "toy model", "current constraint", "random potential"]}
{"id": "1909.07366", "title": "Consistency relations for large-scale structure in modified gravity and the matter bispectrum", "abstract": "We study perturbation theory for large-scale structure in the most general scalar-tensor theories propagating a single scalar degree of freedom, which include Horndeski theories and beyond. We model the parameter space using the effective field theory of dark energy. For Horndeski theories, the gravitational field and fluid equations are invariant under a combination of time-dependent transformations of the coordinates and fields. This symmetry allows one to construct a physical adiabatic mode which fixes the perturbation-theory kernels in the squeezed limit and ensures that the well-known consistency relations for large-scale structure, originally derived in general relativity, hold in modified gravity as well. For theories beyond Horndeski, instead, one generally cannot construct such an adiabatic mode. Because of this, the perturbation-theory kernels are modified in the squeezed limit and the consistency relations for large-scale structure do not hold. We show, however, that the modification of the squeezed limit depends only on the linear theory. We investigate the observational consequences of this violation by computing the matter bispectrum. In the squeezed limit, the largest effect is expected when considering the cross-correlation between different tracers. Moreover, the individual contributions to the 1-loop matter power spectrum do not cancel in the infrared limit of the momentum integral, modifying the power spectrum on non-linear scales.", "keyphrases": ["large-scale structure", "gravity", "consistency relation"]}
{"id": "2201.02635", "title": "The Automated Photometry Of Transients (AutoPhOT) pipeline", "abstract": "We present the Automated Photometry Of Transients (AutoPhOT) package, a novel automated pipeline that is designed for rapid, publication-quality photometry of astronomical transients. AutoPhOT is built from the ground up using Python 3 - with no dependencies on legacy software. Capabilities of AutoPhOT include aperture and point-spread-function photometry, template subtraction, and calculation of limiting magnitudes through artificial source injection. AutoPhOT is also capable of calibrating photometry against either survey catalogues, or using a custom set of local photometric standards, and is designed primarily for ground-based optical and infrared images. We show that both aperture and point-spread-function photometry from AutoPhOT is consistent with commonly used software, for example DAOPHOT, and also demonstrate that AutoPhOT can reproduce published light curves for a selection of transients with minimal human intervention.", "keyphrases": ["transients", "autophot", "pipeline"]}
{"id": "1303.7080", "title": "LOPES 3D - vectorial measurements of radio emission from cosmic ray induced air showers", "abstract": "LOPES 3D is able to measure all three components of the electric field vector of the radio emission from air showers. This allows a better comparison with emission models. The measurement of the vertical component increases the sensitivity to inclined showers. By measuring all three components of the electric field vector LOPES 3D demonstrates by how much the reconstruction accuracy of primary cosmic ray parameters increases. Thus LOPES 3D evaluates the usefulness of vectorial measurements for large scale applications.", "keyphrases": ["vectorial measurement", "radio emission", "air shower"]}
{"id": "1711.03776", "title": "Generalized framework for testing gravity with gravitational-wave propagation. II. Constraints on Horndeski theory", "abstract": "Gravitational waves (GW) are generally affected by modification of a gravity theory during propagation in cosmological distance. We numerically perform a quantitative analysis on Horndeski theory at cosmological scale to constrain the Horndeski theory by GW observations in model-independent way. We formulate a parameterization for a numerical simulation based on the Monte Carlo method and obtain the classification of the models that agrees with cosmic accelerating expansion within observational errors of the Hubble parameter. As a result, we find that a large group of the models in the Horndeski theory that mimic cosmic expansion of \u039bCDM model can be excluded from the simultaneous detection of a GW and its electromagnetic transient counterpart. Based on our result and the latest detection of GW170817 and GRB170817A, we conclude that the subclass of Horndeski theory including arbitrary functions G_4 and G_5 can hardly explain cosmic accelerating expansion without fine-tuning.", "keyphrases": ["horndeski theory", "gravitational wave", "tensor mode"]}
{"id": "1711.06997", "title": "Generation of circular polarization in CMB radiation via nonlinear photon-photon interaction", "abstract": "Standard cosmological models do predict a measurable amount of anisotropies in the intensity and linear polarization of the Cosmic Microwave Background radiation (CMB) via Thomson scattering, even though these theoretical models do not predict circular polarization for CMB radiation. In other hand, the circular polarization of CMB has not been excluded in observational evidences. Here we estimate the circular polarization power spectrum C_l^V(S) in CMB radiation due to Compton scattering and non-linear photon-photon forward scattering via Euler-Heisenberg Effective Lagrangian. We have estimated the average value of circular power spectrum is 1(l+1) C_l^V(S)/(2\u03c0)\u223c 10^-4\u03bc K^2 for l\u223c300 at present time which is smaller than recently reported data (SPIDER collaboration) but in the range of the future achievable experimental data. We also show that the generation of B-mode polarization for CMB photons in the presence of the primordial scalar perturbation via Euler-Heisenberg interaction is possible however this contribution for B-mode polarization is not remarkable.", "keyphrases": ["circular polarization", "cmb radiation", "photon-photon interaction"]}
{"id": "1410.7379", "title": "Towards Understanding Stellar Radial Velocity Jitter as a Function of Wavelength: The Sun as a Proxy", "abstract": "Using solar spectral irradiance measurements from the SORCE spacecraft and the F/F' technique, we have estimated the radial velocity (RV) scatter induced on the Sun by stellar activity as a function of wavelength. Our goal was to evaluate the potential advantages of using new near-infrared (NIR) spectrographs to search for low-mass planets around bright F, G, and K stars by beating down activity effects. Unlike M dwarfs, which have higher fluxes and therefore greater RV information content in the NIR, solar-type stars are brightest at visible wavelengths, and, based solely on information content, are better suited to traditional optical RV surveys. However, we find that the F/F' estimated RV noise induced by stellar activity is diminished by up to a factor of 4 in the NIR versus the visible. Observations with the upcoming future generation of NIR instruments can be a valuable addition to the search for low-mass planets around bright FGK stars in reducing the amount of stellar noise affecting RV measurements.", "keyphrases": ["radial velocity", "wavelength", "star"]}
{"id": "2001.06926", "title": "Supernova Magnitude Evolution and PAge Approximation", "abstract": "The evidence of environmental dependence of Type Ia supernova luminosity has inspired recent discussion about whether the late-universe cosmic acceleration is still supported by supernova data. We adopt the \u0394HR/\u0394age parameter, which describes the dependence of supernova absolute magnitude on the age of supernova progenitor, as an additional nuisance parameter. Using the Pantheon supernova data, a lower bound \u2265 12 Gyr on the cosmic age, and a Gaussian prior H_0 = 70\u00b1 2 km s^-1Mpc^-1 on the Hubble constant, we reconstruct the cosmic expansion history. Within the flat \u039b cold dark matter (\u039bCDM) framework, we still find a 5.6\u03c3 detection of cosmic acceleration. This is because a matter dominated decelerating universe would be too young to accommodate observed old stars with age \u2273 12 Gyr. A decelerating but non-flat universe is marginally consistent with the data, however, only in the presence of a negative spatial curvature \u223c two orders of magnitude beyond the current constraint from cosmic microwave background data. Finally, we propose a more general Parameterization based on the cosmic Age (PAge), which is not directly tied to the dark energy concept and hence is ideal for a null test of the cosmic acceleration. We find that, for a magnitude evolution rate \u0394HR/\u0394age\u2272 0.3 mag/5.3 Gyr (Kang et al. 2020), a spatially flat and decelerating PAge universe is fully consistent with the supernova data and the cosmic age bound, and has no tension with the geometric constraint from the observed CMB acoustic angular scales.", "keyphrases": ["page", "cosmic age", "late-time model", "wide redshift range"]}
{"id": "1807.03779", "title": "A Lonely Giant: The Sparse Satellite Population of M94 Challenges Galaxy Formation", "abstract": "The dwarf satellites of `giant' Milky Way (MW)-mass galaxies are our primary probes of low-mass dark matter halos. The number and velocities of the satellite galaxies of the MW and M31 initially puzzled galaxy formation theorists, but are now reproduced well by many models. Yet, are the MW's and M31's satellites representative? Were galaxy formation models `overfit'? These questions motivate deep searches for satellite galaxies outside the Local Group. We present a deep survey of the `classical' satellites (M_\u22c6\u2a7e4\u00d710^5 M_\u2299) of the MW-mass galaxy M94 out to 150 kpc projected distance. We find only two satellites, each with M_\u22c6\u223c10^6 M_\u2299, compared with 6-12 such satellites in the four other MW-mass systems with comparable data (MW, M31, M81, M101). Using a `standard' prescription for occupying dark matter halos (taken from the fully hydrodynamical EAGLE simulation) with galaxies, we find that such a sparse satellite population occurs in <0.2 probability among a sample of five (known systems + M94). In order to produce an M94-like system more frequently we make satellite galaxy formation much more stochastic than is currently predicted by dramatically increasing the slope and scatter of the stellar mass-halo mass (SMHM) relation. Surprisingly, the SMHM relation must be altered even for halos masses up to 10^11M_\u2299 - significantly above the mass scales predicted to have increased scatter from current hydrodynamical models. The sparse satellite population of this `lonely giant' thus advocates for an important modification to ideas of how the satellites around MW-mass galaxies form.", "keyphrases": ["lonely giant", "giant", "sparse satellite population"]}
{"id": "1911.10609", "title": "Tension of the E_G statistic and RSD data with Planck/\u039bCDM and implications for weakening gravity", "abstract": "The E_G statistic is a powerful probe for detecting deviations from GR by combining weak lensing (WL), real-space clustering and redshift space distortion (RSD) measurements thus probing both the lensing and the growth effective Newton constants (G_L and G_eff). We construct an up to date compilation of E_G statistic data including both redshift and scale dependence (E_G(R,z)). We combine this E_G data compilation with an up to date compilation of f\u03c3_8 data from RSD observations to identify the current level of tension between the Planck/\u039bCDM standard model based on general relativity and a general model independent redshift evolution parametrization of G_L and G_eff. Each f\u03c3_8 datapoint considered has been published separately in the context of independent analyses of distinct galaxy samples. However, there are correlations among the datapoints considered due to overlap of the analyzed galaxy samples. Due to these correlations the derived levels of tension of the best fit parameters with Planck/\u039bCDM are somewhat overestimated but this is the price to pay for maximizing the information encoded in the compilation considered. We find that the level of tension increases from about 3.5\u03c3 for the f\u03c3_8 data compilation alone to about 6\u03c3 when the E_G data are also included in the analysis. The direction of the tension is the same as implied by the f\u03c3_8 RSD growth data alone (lower \u03a9_m and/or weaker effective Newton constant at low redshifts for both the lensing and the growth effective Newton constants (G_L and G_eff)). These results further amplify the hints for weakening modified gravity discussed in other recent analyses.", "keyphrases": ["e_g statistic", "rsd data", "gravity"]}
{"id": "1007.5199", "title": "Horava-Lifshitz Cosmology: A Review", "abstract": "This article reviews basic construction and cosmological implications of a power-counting renormalizable theory of gravitation recently proposed by Horava. We explain that (i) at low energy this theory does not exactly recover general relativity but instead mimic general relativity plus dark matter; that (ii) higher spatial curvature terms allow bouncing and cyclic universes as regular solutions; and that (iii) the anisotropic scaling with the dynamical critical exponent z=3 solves the horizon problem and leads to scale-invariant cosmological perturbations even without inflation. We also comment on issues related to an extra scalar degree of freedom called scalar graviton. In particular, for spherically-symmetric, static, vacuum configurations we prove non-perturbative continuity of the lambda->1+0 limit, where lambda is a parameter in the kinetic action and general relativity has the value lambda=1. We also derive the condition under which linear instability of the scalar graviton does not show up.", "keyphrases": ["cosmology", "general relativity", "dark matter", "vacuum configuration", "spin-0 graviton decouple"]}
{"id": "1711.09226", "title": "Inferring the population properties of binary neutron stars with gravitational-wave measurements of spin", "abstract": "The recent LIGO-Virgo detection of gravitational waves from a binary neutron star inspiral event GW170817 and the discovery of its accompanying electromagnetic signals mark a new era for multimessenger astronomy. In the coming years, advanced gravitational-wave detectors are likely to detect tens to hundreds of similar events. Neutron stars in binaries can possess significant spin, which is imprinted on the gravitational waveform via the effective spin parameter \u03c7_eff. We explore the astrophysical inferences made possible by gravitational-wave measurements of \u03c7_eff. First, using a fiducial model informed by radio observations, we estimate that \u224815-30% of binary neutron stars should have spins measurable at \u2273 90% confidence level by advanced detectors assuming the spin axis of the recycled neutron star aligns with the total orbital angular momentum of the binary. Second, using Bayesian inference, we show that it is possible to tell whether or not the spin axis of the recycled neutron star tends to be aligned with the binary orbit using \u2273 30 detections. Finally, interesting constraints can be placed on neutron star magnetic field decay after \u2273 300 detections, if the spin periods and magnetic field strengths of Galactic binary neutron stars are representative of the merging population.", "keyphrases": ["binary neutron star", "gravitational-wave measurement", "spin"]}
{"id": "1912.06621", "title": "Primordial non-Gaussianity without tails \u2013 how to measure fNL with the bulk of the density PDF", "abstract": "We investigate the possibility to detect primordial non-Gaussianity by analysing the bulk of the probability distribution function (PDF) of late-time cosmic density fluctuations. For this purpose we devise a new method to predict the impact of general non-Gaussian initial conditions on the late-time density PDF. At redshift z=1 and for a smoothing scale of 30Mpc/h our predictions agree with the high-resolution Quijote N-body simulations to \u223c 0.2% precision. This is within cosmic variance of a \u223c 100(Gpc/h)^3 survey volume. When restricting to this 30Mpc/h smoothing scale and to mildly non-linear densities (\u03b4[30Mpc/h] \u2208 [-0.3, 0.4]) and also marginalizing over potential ignorance of the amplitude of the non-linear power spectrum an analysis of the PDF for such a survey volume can still measure the amplitude of different primordial bispectrum shapes to an accuracy of \u0394 f_NL^loc=\u00b1 7.4 , \u0394 f_NL^equi=\u00b1 22.0 , \u0394 f_NL^ortho=\u00b1 46.0 . When pushing to smaller scales and assuming a joint analysis of the PDF with smoothing radii of 30Mpc/h and 15Mpc/h (\u03b4[15Mpc/h] \u2208 [-0.4, 0.5]) this improves to \u0394 f_NL^loc=\u00b1 3.3 , \u0394 f_NL^equi=\u00b1 11.0 , \u0394 f_NL^ortho=\u00b1 17.0 - even when marginalizing over the non-linear variances at both scales as two free parameters. Especially, such an analysis could simultaneously measure f_NL and the amplitude and slope of the non-linear power spectrum. However, at 15Mpc/h our predictions are only accurate to \u2272 0.8% for the considered density range. We discuss how this has to be improved in order to push to these small scales and make full use of upcoming surveys with a PDF-based analysis.", "keyphrases": ["bulk", "density pdf", "primordial non-gaussianity"]}
{"id": "1005.2687", "title": "Constrained Local UniversE Simulations (CLUES)", "abstract": "The local universe is the best known part of our universe. Within the CLUES project (http://clues-project.org - Constrained Local UniversE Simulations) we perform numerical simulations of the evolution of the local universe. For these simulations we construct initial conditions based on observational data of the galaxy distribution in the local universe. Here we review the technique of these constrained simulations. In the second part we summarize our predictions of a possible Warm Dark Matter cosmology for the observed local distribution of galaxies and the local spectrum of mini-voids as well as a study of the satellite dynamics in a simulated Local Group.", "keyphrases": ["local universe", "simulations", "galaxy", "density field"]}
{"id": "1706.00010", "title": "Synthetic nebular emission from massive galaxies I: origin of the cosmic evolution of optical emission-line ratios", "abstract": "Galaxies occupy different regions of the [OIII]\u03bb5007/H\u03b2-versus-[NII]\u03bb6584/H\u03b1 emission-line ratio diagram in the distant and local Universe. We investigate the origin of this intriguing result by modelling self-consistently, for the first time, nebular emission from young stars, accreting black holes (BHs) and older, post-asymptotic-giant-branch (post-AGB) stellar populations in galaxy formation simulations in a full cosmological context. In post-processing, we couple new-generation nebular-emission models with high-resolution, cosmological zoom-in simulations of massive galaxies to explore which galaxy physical properties drive the cosmic evolution of the optical-line ratios [OIII]\u03bb5007/H\u03b2, [NII]\u03bb6584/H\u03b1, [SII]\u03bb\u03bb6717,6731/H\u03b1 and [OI]\u03bb6300/H\u03b1. The line ratios of simulated galaxies agree well with observations of both star-forming and active local SDSS galaxies. Towards higher redshifts, at fixed galaxy stellar mass, the average [OIII]/H\u03b2 increases and [NII]/H\u03b1, [SII]/H\u03b1 and [OI]/H\u03b1 decrease \u2013 widely consistent with observations. At fixed stellar mass, we identify star formation history, which controls nebular emission from young stars via the ionization parameter, as the primary driver of the cosmic evolution of [OIII]/H\u03b2 and [NII]/H\u03b1. For [SII]/H\u03b1 and [OI]/H\u03b1, this applies only to redshifts above z=1.5, the evolution at lower redshift being driven in roughly equal parts by nebular emission from AGN and post-AGB stars. Instead, changes in the hardness of ionizing radiation, ionized-gas density, the prevalence of BH accretion relative to star formation and the dust-to-metal mass ratio (whose impact on the gas-phase N/O ratio we model at fixed O/H) play at most a minor role in the cosmic evolution of simulated galaxy line ratios.", "keyphrases": ["nebular emission", "galaxy", "cosmic evolution"]}
{"id": "1906.07422", "title": "Probing the origin of ultra-high-energy cosmic rays with neutrinos in the EeV energy range using the Pierre Auger Observatory", "abstract": "Neutrinos with energies above 10^17 eV are detectable with the Surface Detector Array of the Pierre Auger Observatory. The identification is efficiently performed for neutrinos of all flavors interacting in the atmosphere at large zenith angles, as well as for Earth-skimming \u03c4 neutrinos with nearly tangential trajectories relative to the earth. No neutrino candidates were found in \u223c 14.7 years of data taken up to 31 August 2018. This leads to restrictive upper bounds on their flux. The 90% C.L. single-flavor limit to the diffuse flux of ultra-high-energy neutrinos with an E_\u03bd^-2 spectrum in the energy range 1.0 \u00d7 10^17 eV - 2.5 \u00d7 10^19 eV is E^2 dN_\u03bd/ dE_\u03bd < 4.4 \u00d7 10^-9 GeV cm^-2 s^-1 sr^-1, placing strong constraints on several models of neutrino production at EeV energies and on the properties of the sources of ultra-high-energy cosmic rays.", "keyphrases": ["ultra-high-energy cosmic ray", "neutrino", "eev energy range"]}
{"id": "1109.0249", "title": "Testing alternative theories of gravity using the Sun", "abstract": "We propose a new approach to test possible corrections to Newtonian gravity using solar physics. The high accuracy of current solar models and new precise observations allow one to constrain corrections to standard gravity at unprecedented levels. Our case study is Eddington-inspired gravity, an attractive modified theory of gravity which results in non-singular cosmology and collapse. The theory is equivalent to standard gravity in vacuum, but it sensibly differs from it within matter, for instance it affects the evolution and the equilibrium structure of the Sun, giving different core temperature profiles, deviations in the observed acoustic modes and in solar neutrino fluxes. Comparing the predictions from a modified solar model with observations, we constrain the coupling parameter of the theory, |kappa_g| < 3x10^5 m^5 s^2 / kg. Our results show that the Sun can be used to efficiently constraint alternative theories of gravity.", "keyphrases": ["alternative theory", "gravity", "sun"]}
{"id": "2101.04907", "title": "The Physics of Fast Radio Bursts", "abstract": "In 2007, a very bright radio pulse was identified in the archival data of the Parkes Telescope in Australia, marking the beginning of a new research branch in astrophysics. In 2013, this kind of millisecond bursts with extremely high brightness temperature takes a unified name, fast radio burst (FRB). Over the first few years, FRBs seemed very mysterious because the sample of known events was limited. With the improvement of instruments over the last five years, hundreds of new FRBs have been discovered. The field is now undergoing a revolution and understanding of FRB has rapidly increased as new observational data increasingly accumulates. In this review, we will summarize the basic physics of FRBs and discuss the current research progress in this area. We have tried to cover a wide range of FRB topics, including the observational property, propagation effect, population study, radiation mechanism, source model, and application in cosmology. A framework based on the latest observational facts is now under construction. In the near future, this exciting field is expected to make significant breakthroughs.", "keyphrases": ["fast radio burst", "frbs", "propagation effect", "radiation mechanism", "millisecond duration"]}
{"id": "1912.04509", "title": "Formation rate of LB-1-like systems through dynamical interactions", "abstract": "We estimate formation rates of LB-1-like systems through dynamical interactions in the framework of the theory of stellar evolution before the discovery of the LB-1 system. The LB-1 system contains \u223c 70M_\u2299 black hole (BH), so-called pair instability (PI)-gap BH, and B-type star with solar metallicity, and has nearly zero eccentricity. The most efficient formation mechanism is as follows. In an open cluster, a naked helium (He) star (with \u223c 20M_\u2299) collides with a heavy main-sequence (MS) star (with \u223c 50M_\u2299) which has a B-type companion. The collision results in a binary consisting of the collision product and B-type star with a high eccentricity. The binary can be circularized through the dynamical tide with radiative damping of the collision-product envelope. Finally, the collision product collapses to a PI-gap BH, avoiding pulsational pair instability and pair instability supernovae because its He core is as massive as the pre-colliding naked He star. We find that the number of LB-1-like systems in the Milky Way galaxy is \u223c 0.01 (\u03c1_ oc / 10^4 M_\u2299^-3), where \u03c1_ oc is the initial mass densities of open clusters. If we take into account LB-1-like systems with O-type companion stars, the number increases to \u223c 0.03 (\u03c1_ oc / 10^4 M_\u2299^-3). This mechanism can form LB-1-like systems at least 10 times more efficiently than the other mechanisms: captures of B-type stars by PI-gap BHs, stellar collisions between other type stars, and stellar mergers in hierarchical triple systems. We conclude that no dynamical mechanism can explain the presence of the LB-1 system.", "keyphrases": ["lb-1-like system", "dynamical interaction", "formation rate"]}
{"id": "1712.04229", "title": "Observational Constraint on Spherical Inhomogeneity with CMB and Local Hubble Parameter", "abstract": "We derive an observational constraint on a spherical inhomogeneity of the void centered at our position from the angular power spectrum of the cosmic microwave background(CMB) and local measurements of the Hubble parameter. The late time behaviour of the void is assumed to be well described by the so-called \u039b-Lema\u00eetre-Tolman-Bondi (\u039bLTB) solution. Then, we restrict the models to the asymptotically homogeneous models each of which is approximated by a flat Friedmann-Lema\u00eetre-Robertson-Walker model. The late time \u039bLTB models are parametrized by four parameters including the value of the cosmological constant and the local Hubble parameter. The other two parameters are used to parametrize the observed distance-redshift relation. Then, the \u039bLTB models are constructed so that they are compatible with the given distance-redshift relation. Including conventional parameters for the CMB analysis, we characterize our models by seven parameters in total. The local Hubble measurements are reflected in the prior distribution of the local Hubble parameter. As a result of a Markov-Chains-Monte-Carlo analysis for the CMB temperature and polarization anisotropies, we found that the inhomogeneous universe models with vanishing cosmological constant are ruled out as is expected. However, a significant under-density around us is still compatible with the angular power spectrum of CMB and the local Hubble parameter.", "keyphrases": ["spherical inhomogeneity", "local hubble parameter", "observational constraint"]}
{"id": "1608.07961", "title": "Constraints on shear and rotation with massive galaxy clusters", "abstract": "A precise determination of the mass function is an important tool to verify cosmological predictions of the \u039bCDM model and to infer more precisely the better model describing the evolution of the Universe. Galaxy clusters have been currently used to infer cosmological parameters, in particular the matter density parameter \u03a9_ m, the matter power spectrum normalization \u03c3_8 and the equation of state parameter w_ de of the dark energy fluid. In this work, using data on massive galaxy clusters (M>8\u00d7 10^14 h^-1 M_\u2299) in the redshift range 0.05\u2272 z\u2272 0.83 we put constraints on the parameter \u03b1 introduced within the formalism of the extended spherical collapse model to quantify deviations from sphericity due to shear and rotation. Since at the moment there is no physical model describing its functional shape, we assume it to be a logarithmic function of the cluster mass. By holding \u03c3_8 fixed and restricting our analysis to a \u039bCDM model, we find, at 1-\u03c3 confidence level, \u03a9_ m=0.284\u00b10.0064, h=0.678\u00b10.017 and \u03b2=0.0019^+0.0008_-0.0015, where \u03b2 represents the slope of the parameter \u03b1. This results translates into a 9% decrement of the number of massive clusters with respect to a standard \u039bCDM mass function, but better data are required to better constrain this quantity, since at the 2-\u03c3 and 3-\u03c3 confidence level we are only able to infer upper limits.", "keyphrases": ["shear", "rotation", "massive galaxy cluster"]}
{"id": "1403.3141", "title": "Clustering of Local Group distances: publication bias or correlated measurements? I. The Large Magellanic Cloud", "abstract": "The distance to the Large Magellanic Cloud (LMC) represents a key local rung of the extragalactic distance ladder. Yet, the galaxy's distance modulus has long been an issue of contention, in particular in view of claims that most newly determined distance moduli cluster tightly - and with a small spread - around the \"canonical\" distance modulus, (m-M)_0 = 18.50 mag. We compiled 233 separate LMC distance determinations published between 1990 and 2013. Our analysis of the individual distance moduli, as well as of their two-year means and standard deviations resulting from this largest data set of LMC distance moduli available to date, focuses specifically on Cepheid and RR Lyrae variable-star tracer populations, as well as on distance estimates based on features in the observational Hertzsprung-Russell diagram. We conclude that strong publication bias is unlikely to have been the main driver of the majority of published LMC distance moduli. However, for a given distance tracer, the body of publications leading to the tightly clustered distances is based on highly non-independent tracer samples and analysis methods, hence leading to significant correlations among the LMC distances reported in subsequent articles. Based on a careful, weighted combination, in a statistical sense, of the main stellar population tracers, we recommend that a slightly adjusted canonical distance modulus of (m-M)_0 = 18.49 +- 0.09 mag be used for all practical purposes that require a general distance scale without the need for accuracies of better than a few percent.", "keyphrases": ["publication bias", "cloud", "lmc distance", "date", "body"]}
{"id": "1209.0013", "title": "From dust to planetesimals: an improved model for collisional growth in protoplanetary disks", "abstract": "Planet formation occurs within the gas and dust rich environments of protoplanetary disks. Observations of these objects show that the growth of primordial sub micron sized particles into larger aggregates occurs at the earliest stages of the disks. However, theoretical models of particle growth that use the Smoluchowski equation to describe collisional coagulation and fragmentation have so far failed to produce large particles while maintaining a significant populations of small grains. This has been generally attributed to the existence of two barriers impeding growth due to bouncing and fragmentation of colliding particles. In this paper, we demonstrate that the importance of these barriers has been artificially inflated through the use of simplified models that do not take into account the stochastic nature of the particle motions within the gas disk. We present a new approach in which the relative velocities between two particles is described by a probability distribution function that models both deterministic motion and stochastic motion. Taking both into account can give quite different results to what has been considered recently in other studies. We demonstrate the vital effect of two \"ingredients\" for particle growth: the proper implementation of a velocity distribution function that overcomes the bouncing barrier and, in combination with mass transfer in high-mass-ratio collisions, boosts the growth of larger particles beyond the fragmentation barrier. A robust result of our simulations is the emergence of two particle populations (small and large), potentially explaining simultaneously a number of long-standing problems in protoplanetary disks, including planetesimal formation close to the central star, the presence of mm to cm size particles far out in the disk, and the persistence of micron-size grains for millions of years.", "keyphrases": ["planetesimal", "collisional growth", "protoplanetary disk"]}
{"id": "1510.00358", "title": "Observation of the new emission line at 3.5 keV in X-ray spectra of galaxies and galaxy clusters", "abstract": "The detection of an unidentified emission line in X-ray spectra of cosmic objects would be a 'smoking gun' signature for particle physics beyond the Standard Model. More than a decade of its extensive searches results in several narrow faint emission lines reported at 3.5, 8.7, 9.4 and 10.1 keV. The most promising of them is the emission line at 3.5 keV reported in spectra of several nearby galaxies and galaxy clusters. Here I summarize its up-to-date status, overview its possible interpretations, including an intriguing connection with radiatively decaying dark matter, and outline future directions for its studies.", "keyphrases": ["emission line", "x-ray spectra", "galaxy cluster"]}
{"id": "1305.0824", "title": "The Observed Squeezed Limit of Cosmological Three-Point Functions", "abstract": "The squeezed limit of the three-point function of cosmological perturbations is a powerful discriminant of different models of the early Universe. We present a conceptually simple and complete framework to relate any primordial bispectrum in this limit to late time observables, such as the CMB temperature bispectrum and the scale-dependent halo bias. We employ a series of convenient coordinate transformations to capture the leading non-linear effects of cosmological perturbation theory on these observables. This makes crucial use of Fermi Normal Coordinates and their conformal generalization, which we introduce here and discuss in detail. As an example, we apply our formalism to standard slow-roll single-field inflation. We show explicitly that Maldacena's results for the squeezed limits of the scalar bispectrum [proportional to (ns-1) in comoving gauge] and the tensor-scalar-scalar bispectrum lead to no deviations from a Gaussian universe, except for projection effects. In particular, the primordial contributions to the squeezed CMB bispectrum and scale dependent halo bias vanish, and there are no primordial \"fossil\" correlations between long-wavelength tensor perturbations and small-scale perturbations. The contributions to observed correlations are then only due to projection effects such as gravitational lensing and redshift perturbations.", "keyphrases": ["universe", "perturbation theory", "single-field inflation", "single-field model", "conformal fermi coordinates"]}
{"id": "2005.05278", "title": "Detecting circular polarisation in the stochastic gravitational-wave background from a first-order cosmological phase transition", "abstract": "We discuss the observability of circular polarisation of the stochastic gravitational-wave background (SGWB) generated by helical turbulence following a first-order cosmological phase transition, using a model that incorporates the effects of both direct and inverse energy cascades. We explore the strength of the gravitational-wave signal and the dependence of its polarisation on the helicity fraction, \u03b6_*, the strength of the transition, \u03b1, the bubble size, R_*, and the temperature, T_*, at which the transition finishes. We calculate the prospective signal-to-noise ratios of the SGWB strength and polarisation signals in the LISA experiment, exploring the parameter space in a way that is minimally sensitive to the underlying particle physics model. We find that discovery of SGWB polarisation is generally more challenging than measuring the total SGWB signal, but would be possible for appropriately strong transitions with large bubble sizes and a substantial polarisation fraction.", "keyphrases": ["circular polarisation", "gravitational-wave background", "cosmological phase transition"]}
{"id": "1609.07155", "title": "Late time cooling of neutron star transients and the physics of the inner crust", "abstract": "An accretion outburst onto a neutron star transient heats the neutron star's crust out of thermal equilibrium with the core. After the outburst the crust thermally relaxes toward equilibrium with the neutron star core and the surface thermal emission powers the quiescent X-ray light curve. Crust cooling models predict that thermal equilibrium of the crust will be established \u2248 1000 d into quiescence. Recent observations of the cooling neutron star transient MXB 1659-29, however, suggest that the crust did not reach thermal equilibrium with the core on the predicted timescale and continued to cool after \u2248 2500 d into quiescence. Because the quiescent light curve reveals successively deeper layers of the crust, the observed late time cooling of MXB 1659-29 depends on the thermal transport in the inner crust. In particular, the observed late time cooling is consistent with a low thermal conductivity layer near the depth predicted for nuclear pasta that maintains a temperature gradient between the neutron star's inner crust and core for thousands of days into quiescence. As a result, the temperature near the crust-core boundary remains above the critical temperature for neutron superfluidity and a layer of normal neutrons forms in the inner crust. We find that the late time cooling of MXB 1659-29 is consistent with heat release from a normal neutron layer near the crust-core boundary with a long thermal time.", "keyphrases": ["neutron star transient", "inner crust", "late time cooling"]}
{"id": "1806.03628", "title": "Fast Radio Bursts", "abstract": "The phenomenon of fast radio bursts (FRBs) was discovered in 2007. These are powerful (0.1-100 Jy) single radio pulses with durations of several milliseconds, large dispersion measures, and record high brightness temperatures suggesting coherent emission mechanism. As of time of writing, 32 FRBs were recorded. There is also one repeating source from which already hundreds of bursts have been detected. The FRB rate is estimated to amount up to several thousand per day over the sky, and their isotropic sky distribution likely suggests a cosmological origin. Since the discovery, different hypotheses on the possible FRB nature have been proposed, however up to now the origin of these transient events remains obscure. The most prospective models treat them as being related to a bursting emission from magnetars \u2013 neutron stars whose activity is due to their magnetic field dissipation, \u2013 or as being analogs of giant pulses observed from several radio pulsars . Future increase in the statistics of the observed FRBs and an improvement upon the FRB population characteristics will make possible to use them as a new tool to probe the intergalactic medium and to test fundamental physical theories.", "keyphrases": ["frbs", "magnetar", "fast radio bursts"]}
{"id": "1501.00142", "title": "Constraints on primordial magnetic fields from the optical depth of the cosmic microwave background", "abstract": "Damping of magnetic fields via ambipolar diffusion and decay of magnetohydrodynamical (MHD) turbulence in the post decoupling era heats the intergalactic medium (IGM). Delayed recombination of hydrogen atoms in the IGM yields an optical depth to scattering of the cosmic microwave background (CMB). The optical depth generated at z\u226b 10 does not affect the \"reionization bump\" of the CMB polarization power spectrum at low multipoles, but affects the temperature and polarization power spectra at high multipoles. Writing the present-day energy density of fields smoothed over the damping scale at the decoupling epoch as \u03c1_B,0=B_0^2/2, we constrain B_0 as a function of the spectral index, n_B. Using the Planck 2013 likelihood code that uses the Planck temperature and lensing data together with the WMAP 9-year polarization data, we find the 95 n_B=-2.9, -2.5, and -1.5, respectively. For these spectral indices, the optical depth is dominated by dissipation of the decaying MHD turbulence that occurs shortly after the decoupling epoch. Our limits are stronger than the previous limits ignoring the effects of the fields on ionization history. Inverse Compton scattering of CMB photons off electrons in the heated IGM distorts the thermal spectrum of CMB. Our limits on B_0 imply that the y-type distortion from dissipation of fields in the post decoupling era should be smaller than 10^-9, 4\u00d710^-9, and 10^-9, respectively.", "keyphrases": ["magnetic field", "cosmic microwave background", "ionization history"]}
{"id": "1112.5220", "title": "The Active Asteroids", "abstract": "Some asteroids eject dust, unexpectedly producing transient, comet-like comae and tails. First ascribed to the sublimation of near-surface water ice, mass losing asteroids (also called \"main-belt comets\") can in fact be driven by a surprising diversity of mechanisms. In this paper, we consider eleven dynamical asteroids losing mass, in nine of which the ejected material is spatially resolved. We address mechanisms for producing mass loss including rotational instability, impact ejection, electrostatic repulsion, radiation pressure sweeping, dehydration stresses and thermal fracture, in addition to the sublimation of ice. In two objects (133P and 238P) the repetitive nature of the observed activity leaves ice sublimation as the only reasonable explanation while, in a third ((596) Scheila), a recent impact is the cause. Another impact may account for activity in P/2010 A2 but this tiny object can also be explained as having shed mass after reaching rotational instability. Mass loss from (3200) Phaethon is probably due to cracking or dehydration at extreme ( 1000 K) perihelion temperatures, perhaps aided by radiation pressure sweeping. For the other bodies, the mass loss mechanisms remain unidentified, pending the acquisition of more and better data. While the active asteroid sample size remains small, the evidence for an astonishing diversity of mass loss processes in these bodies is clear.", "keyphrases": ["asteroid", "main-belt comet", "rotational instability"]}
{"id": "1702.01712", "title": "Testing lowered isothermal models with direct N-body simulations of globular clusters - II: Multimass models", "abstract": "Lowered isothermal models, such as the multimass Michie-King models, have been successful in describing observational data of globular clusters. In this study we assess whether such models are able to describe the phase space properties of evolutionary N-body models. We compare the multimass models as implemented in (Gieles & Zocchi) to N-body models of star clusters with different retention fractions for the black holes and neutron stars evolving in a tidal field. We find that multimass models successfully reproduce the density and velocity dispersion profiles of the different mass components in all evolutionary phases and for different remnants retention. We further use these results to study the evolution of global model parameters. We find that over the lifetime of clusters, radial anisotropy gradually evolves from the low-mass to the high-mass components and we identify features in the properties of observable stars that are indicative of the presence of stellar-mass black holes. We find that the model velocity scale depends on mass as m^-\u03b4, with \u03b4\u22430.5 for almost all models, but the dependence of central velocity dispersion on m can be shallower, depending on the dark remnant content, and agrees well with that of the N-body models. The reported model parameters, and correlations amongst them, can be used as theoretical priors when fitting these types of mass models to observational data.", "keyphrases": ["isothermal model", "globular cluster", "multimass model"]}
{"id": "1606.03633", "title": "Efficient exploration of cosmology dependence in the EFT of LSS", "abstract": "The most effective use of data from current and upcoming large scale structure (LSS) and CMB observations requires the ability to predict the clustering of LSS with very high precision. The Effective Field Theory of Large Scale Structure (EFTofLSS) provides an instrument for performing analytical computations of LSS observables with the required precision in the mildly nonlinear regime. In this paper, we develop efficient implementations of these computations that allow for an exploration of their dependence on cosmological parameters. They are based on two ideas. First, once an observable has been computed with high precision for a reference cosmology, for a new cosmology the same can be easily obtained with comparable precision just by adding the difference in that observable, evaluated with much less precision. Second, most cosmologies of interest are sufficiently close to the Planck best-fit cosmology that observables can be obtained from a Taylor expansion around the reference cosmology. These ideas are implemented for the matter power spectrum at two loops and are released as public codes. When applied to cosmologies that are within 3\u03c3 of the Planck best-fit model, the first method evaluates the power spectrum in a few minutes on a laptop, with results that have 1% or better precision, while with the Taylor expansion the same quantity is instantly generated with similar precision. The ideas and codes we present may easily be extended for other applications or higher-precision results.", "keyphrases": ["lss", "effective field theory", "matter power spectrum"]}
{"id": "1905.05654", "title": "Swampland conjecture in f(R) gravity by the Noether Symmetry Approach", "abstract": "Swampland conjecture has been recently proposed to connect early time cosmological models with the string landscape, and then to understand if related scalar fields and potentials can come from some fundamental theory in the high energy regime. In this paper, we discuss swampland criteria for f(R) gravity considering models where duality symmetry is present. In this perspective, specific f(R) models can naturally belong to the string landscape. In particular, it is possible to show that duality is a Noether symmetry emerging from dynamics. The selected f(R) models, satisfying the swampland conjecture, are consistent, in principle, with both early and late-time cosmological behaviors.", "keyphrases": ["gravity", "noether symmetry approach", "swampland conjecture"]}
{"id": "2002.01079", "title": "Full analytical approximation to the stochastic gravitational wave background generated by cosmic string networks", "abstract": "We derive a full analytical approximation to the stochastic gravitational wave background generated by the loops that are produced throughout the cosmological evolution of cosmic string networks. We show that this approximation not only predicts the amplitude of the radiation-era plateau exactly, but also provides a good fit to the high-frequency cut-off and to the low-frequency peak generated by the loops that decay during the matter era, irrespective of cosmic string tension and of the length of loops created. We then find that it provides a good quantitative description of the full stochastic gravitational wave background across the relevant frequency range.", "keyphrases": ["gravitational wave background", "string network", "full analytical approximation"]}
{"id": "1812.11936", "title": "Fast Radio Bursts and cosmological tests", "abstract": "We consider future cosmological tests based on observations of Fast Radio Bursts (FRBs). We use Illustris Simulation to realistically estimate the scatter in the dispersion measure (DM) of FRBs caused by the inhomogeneous distribution of ionized gas in the Intergalactic Medium (IGM). We find 13 scatter in DM to a source at z=1 and 7 of DM is close to Gaussian. We simulate samples of FRBs and examine their applicability to simple cosmological tests. Our calculations show that using a sample of 100 FRBs and fixing cosmological model one can find the redshift and sample averaged fraction of ionized gas with 1 ionized fraction with 1 000 FRBs with known redshifts. Because DM is proportional to the product of ionized fraction, baryon density and the Hubble constant it is impossible to constrain these parameters separately with FRBs. Constraints on cosmological densities are possible in a flat LCDM model but give uninterestingly low accuracy. Using FRBs with other type of data improves the constraints, but the role of FRBs is not crucial. Thus constraints on the distribution of ionized gas are probably the most promising application of FRBs which allow for \"tomography\" if sources redshifts are known, as opposed to measuring electron scattering optical depth or S-Z y parameters with CMB observations.", "keyphrases": ["cosmological test", "intergalactic medium", "redshift", "fast radio bursts"]}
{"id": "1702.02768", "title": "Dark matter in the Sun: scattering off electrons vs nucleons", "abstract": "The annihilation of dark matter (DM) particles accumulated in the Sun could produce a flux of neutrinos, which is potentially detectable with neutrino detectors/telescopes and the DM elastic scattering cross section can be constrained. Although the process of DM capture in astrophysical objects like the Sun is commonly assumed to be due to interactions only with nucleons, there are scenarios in which tree-level DM couplings to quarks are absent, and even if loop-induced interactions with nucleons are allowed, scatterings off electrons could be the dominant capture mechanism. We consider this possibility and study in detail all the ingredients necessary to compute the neutrino production rates from DM annihilations in the Sun (capture, annihilation and evaporation rates) for velocity-independent and isotropic, velocity-dependent and isotropic and momentum-dependent scattering cross sections for DM interactions with electrons and compare them with the results obtained for the case of interactions with nucleons. Moreover, we improve the usual calculations in a number of ways and provide analytical expressions in three appendices. Interestingly, we find that the evaporation mass in the case of interactions with electrons could be below the GeV range, depending on the high-velocity tail of the DM distribution in the Sun, which would open a new mass window for searching for this type of scenarios.", "keyphrases": ["sun", "nucleon", "dark matter"]}
{"id": "1102.0537", "title": "Supermassive black holes, pseudobulges, and the narrow-line Seyfert 1 galaxies", "abstract": "We present HST/ACS observations of ten galaxies that host narrow-line Seyfert 1 (NLS1) nuclei, believed to contain relatively smaller mass black holes accreting at high Eddington ratios. We deconvolve each ACS image into a nuclear point source (AGN), a bulge, and a disk, and fitted the bulge with a Sersic profile and the disk with an exponential profile. We find that at least five galaxies can be classified as having pseudobulges. All ten galaxies lie below the \u2013L_bulge relation, confirming earlier results. Their locus is similar to that occupied by pseudobulges. This leads us to conclude that the growth of BHs in NLS1s is governed by secular processes rather than merger-driven. Active galaxies in pseudobulges point to an alternative track of black hole\u2013galaxy co-evolution. Because of the intrinsic scatter in black hole mass\u2013bulge properties scaling relations caused by a combination of factors such as the galaxy morphology, orientation, and redshift evolution, application of scaling relations to determine BH masses may not be as straightforward as has been hoped.", "keyphrases": ["black hole", "narrow-line seyfert", "galaxy"]}
{"id": "1707.04266", "title": "Dielectric haloscopes: sensitivity to the axion dark matter velocity", "abstract": "We study the effect of the axion dark matter velocity in the recently proposed dielectric haloscopes, a promising avenue to search for well-motivated high mass (40-400 \u03bceV) axions. We describe non-zero velocity effects for axion-photon mixing in a magnetic field and for the phenomenon of photon emission from interfaces between different dielectric media. As velocity effects are only important when the haloscope is larger than about 20 axion de Broglie wavelength, for the planned MADMAX experiment with 80 dielectric disks the velocity dependence can safely be neglected. However, an augmented MADMAX or a second generation experiment would be directionally sensitive to the axion velocity, and thus a sensitive measure of axion astrophysics.", "keyphrases": ["haloscope", "axion", "dark matter velocity"]}
{"id": "1212.5167", "title": "Testing modified gravity at large distances with the HI Nearby Galaxy Survey's rotation curves", "abstract": "Recently a new -quantum motivated- theory of gravity has been proposed that modifies the standard Newtonian potential at large distances when spherical symmetry is considered. Accordingly, Newtonian gravity is altered by adding an extra Rindler acceleration term that has to be phenomenologically determined. Here we consider a standard and a power-law generalization of the Rindler modified Newtonian potential. The new terms in the gravitational potential are hypothesized to play the role of dark matter in galaxies. Our galactic model includes the mass of the integrated gas, and stars for which we consider three stellar mass functions (Kroupa, diet-Salpeter, and free mass model). We test this idea by fitting rotation curves of seventeen low surface brightness galaxies from The HI Nearby Galaxy Survey (THINGS). We find that the Rindler parameters do not perform a suitable fit to the rotation curves in comparison to standard dark matter profiles (Navarro-Frenk-White and Burkert) and, in addition, the computed parameters of the Rindler gravity show a high spread, posing the model as a nonacceptable alternative to dark matter.", "keyphrases": ["gravity", "large distance", "rotation curve"]}
{"id": "1111.1985", "title": "The fragmentation of protostellar discs: the Hill criterion for spiral arms", "abstract": "We present a new framework to explain the link between cooling and fragmentation in gravitationally unstable protostellar discs. This framework consists of a simple model for the formation of spiral arms, as well as a criterion, based on the Hill radius, to determine if a spiral arm will fragment. This detailed model of fragmentation is based on the results of numerical simulations of marginally stable protostellar discs, including those found in the literature, as well as our new suite of 3-D radiation hydrodynamics simulations of an irradiated, optically-thick protostellar disc surrounding an A star. Our set of simulations probes the transition to fragmentation through a scaling of the physical opacity. This model allows us to directly calculate the critical cooling time of Gammie (2001), with results that are consistent with those found from numerical experiment. We demonstrate how this model can be used to predict fragmentation in irradiated protostellar discs. These numerical simulations, as well as the model that they motivate, provide strong support for the hypothesis that gravitational instability is responsible for creating systems with giant planets on wide orbits.", "keyphrases": ["fragmentation", "protostellar disc", "spiral arm"]}
{"id": "1107.4209", "title": "Collective excitations in the neutron star inner crust", "abstract": "We study the spectrum of collective excitations in the inhomogeneous phases in the neutron star inner crust within a superfluid hydrodynamics approach. Our aim is to describe the whole range of wavelengths, from the long-wavelength limit which can be described by macroscopic approaches and which is crucial for the low-energy part of the spectrum, to wavelengths of the order of the dimensions of the Wigner-Seitz cells, corresponding to the modes usually described in microscopic calculations. As an application, we will discuss the contribution of these collective modes to the specific heat of the \"lasagna\" phase in comparison with other known contributions.", "keyphrases": ["neutron star", "inner crust", "collective excitation"]}
{"id": "1711.07436", "title": "Vortices and the saturation of the vertical shear instability in protoplanetary disks", "abstract": "If sufficiently irradiated by its central star, a protoplanetary disks falls into an equilibrium state exhibiting vertical shear. This state may be subject to a hydrodynamical instability, the `vertical shear instability' (VSI), whose breakdown into turbulence transports a moderate amount of angular momentum while also facilitating planet formation, possibly via the production of small-scale vortices. In this paper, we show that VSI modes (a) exhibit arbitrary spatial profiles and (b) remain nonlinear solutions to the incompressible local equations, no matter their amplitude. The modes are themselves subject to parasitic Kelvin-Helmholtz instability, though the disk rotation significantly impedes the parasites and permits the VSI to attain large amplitudes (fluid velocities < 10 saturation probably explains the prominence of the VSI linear modes in global simulations. More generally, the parasites may set the amplitude of VSI turbulence in strongly irradiated disks. They are also important in breaking the axisymmetry of the flow, via the unavoidable formation of vortices. The vortices, however, are not aligned with the orbital plane and thus express a pronounced z-dependence. We also briefly demonstrate that the vertical shear has little effect on the magnetorotational instability, whereas magnetic fields easily quench the VSI, a potential issue in the ionised surface regions of the disk and also at larger radii.", "keyphrases": ["vertical shear instability", "protoplanetary disk", "vortex"]}
{"id": "1704.08606", "title": "Recurrence network measures for hypothesis testing using surrogate data: application to black hole light curves", "abstract": "Recurrence networks and the associated statistical measures have become important tools in the analysis of time series data. In this work, we test how effective the recurrence network measures are in analyzing real world data involving two main types of noise, white noise and colored noise. We use two prominent network measures as discriminating statistic for hypothesis testing using surrogate data for a specific null hypothesis that the data is derived from a linear stochastic process. We show that the characteristic path length is especially efficient as a discriminating measure with the conclusions reasonably accurate even with limited number of data points in the time series. We also highlight an additional advantage of the network approach in identifying the dimensionality of the system underlying the time series through a convergence measure derived from the probability distribution of the local clustering coefficients. As examples of real world data, we use the light curves from a prominent black hole system and show that a combined analysis using three primary network measures can provide vital information regarding the nature of temporal variability of light curves from different spectroscopic classes.", "keyphrases": ["hypothesis testing", "surrogate data", "recurrence network measure"]}
{"id": "1904.00673", "title": "Fisher matrix for multiple tracers: model independent constraints on the redshift distortion parameter", "abstract": "We show how to obtain constraints on \u03b2=f/b, the ratio of the matter growth rate and the bias that quantifies the linear redshift-space distortions, that are independent of the cosmological model, using multiple tracers of large-scale structure. For a single tracer the uncertainties on \u03b2 are constrained by the uncertainties in the amplitude and shape of the power spectrum, which is limited by cosmic variance. However, for two or more tracers this limit does not apply, since taking the ratio of power spectra cosmic variance cancels out, and in the linear (Kaiser) approximation one measures directly the quantity (1+ \u03b2_1 \u03bc^2)^2/(1+ \u03b2_2 \u03bc^2)^2, where \u03bc is the angle of a given mode with the line of sight. We provide analytic formulae for the Fisher matrix for one and two tracers, and quantify the signal-to-noise ratio needed to make effective use of the multiple-tracer technique. We also forecast the errors on \u03b2 for a survey like Euclid.", "keyphrases": ["multiple tracer", "redshift distortion parameter", "fisher matrix"]}
{"id": "1408.2337", "title": "Supermassive black holes with high accretion rates in active galactic nuclei: II. the most luminous standard candles in the Universe", "abstract": "This is the second in a series of papers reporting on a large reverberation mapping (RM) campaign to measure black hole (BH) mass in high accretion rate active galactic nuclei (AGNs). The goal is to identify super-Eddington accreting massive black holes (SEAMBHs) and to use their unique properties to construct a new method for measuring cosmological distances. Based on theoretical models, the saturated bolometric luminosity of such sources is proportional to the BH mass which can be used to obtain their distance. Here we report on five new RM measurements and show that in four of the cases we can measure the BH mass and three of these sources are SEAMBHs. Together with the three sources from our earlier work, we now have six new sources of this type. We use a novel method based on a minimal radiation efficiency to identify nine additional SEAMBHs from earlier RM-based mass measurements. We use a Bayesian analysis to determine the parameters of the new distance expression, and the method uncertainties, from the observed properties of the objects in the sample. The ratio of the newly measured distances to the standard cosmological ones has a mean scatter of 0.14 dex, indicating that SEAMBHs can be use as cosmological distance probes. With their high luminosity, long period of activity and large numbers at high redshifts, SEAMBHs have a potential to extend the cosmic distance ladder beyond the range now explored by type Ia supernovae.", "keyphrases": ["black hole", "high accretion rate", "active galactic nucleus"]}
{"id": "2003.05544", "title": "Factorization of Antenna Efficiency of Aperture-type antenna: Beam Coupling and Two Spillovers", "abstract": "Antenna efficiency is one of the most important figures-of-merit of a radio telescope for observations especially at millimeter wavelengths or shorter wavelengths, even for a multibeam radio telescope. To analyze a system with a beam waveguide, a lossless antenna consisting of two apertures in series is considered in the frame of the scalar wave approximation. We found that the antenna efficiency can be evaluated with the field distribution over the second aperture, and that the antenna efficiency is factorized into three factors: efficiencies of beam coupling, transmission spillover, and reception spillover. The factorization is applicable to general aperture-type antennas with beam waveguides, and can relate the aperture efficiency to the pupil function. We numerically confirmed our factorization with an optical simulation. This evaluation enables us to manage the aberrations and is useful in design of multibeam radio telescopes.", "keyphrases": ["antenna efficiency", "aperture-type antenna", "beam coupling"]}
{"id": "2205.16002", "title": "Towards a data-driven model of the sky from low Earth orbit as observed by the Hubble Space Telescope", "abstract": "The sky observed by space telescopes in Low Earth Orbit (LEO) can be dominated by stray light from multiple sources including the Earth, Sun and Moon. This stray light presents a significant challenge to missions that aim to make a secure measurement of the Extragalactic Background Light (EBL). In this work we quantify the impact of stray light on sky observations made by the Hubble Space Telescope (HST) Advanced Camera for Surveys. By selecting on orbital parameters we successfully isolate images with sky that contain minimal and high levels of Earthshine. In addition, we find weather observations from CERES satellites correlates with the observed HST sky surface brightness indicating the value of incorporating such data to characterise the sky. Finally we present a machine learning model of the sky trained on the data used in this work to predict the total observed sky surface brightness. We demonstrate that our initial model is able to predict the total sky brightness under a range of conditions to within 3.9 we find that the model matches the stray light-free observations better than current physical Zodiacal light models.", "keyphrases": ["sky", "low earth orbit", "hubble space telescope"]}
{"id": "1510.06459", "title": "Extended Skyrme interactions for nuclear matter, finite nuclei and neutron stars", "abstract": "Recent progress in theory, experiment and observation challenges the mean field models using the conventional Skyrme interaction, suggesting that the extension of the conventional Skyrme interaction is necessary. In this work, by fitting the experimental data of a number of finite nuclei together with a few additional constraints on nuclear matter using the simulated annealing method, we construct three Skyrme interaction parameter sets, namely, eMSL07, eMSL08 and eMSL09, based on an extended Skyrme interaction which includes additional momentum and density dependent two-body forces to effectively simulate the momentum dependence of the three-body force. The three new interactions can reasonably describe the ground-state properties and the isoscalar giant monopole resonance energies of various spherical nuclei used in the fit as well as the ground-state properties of many other spherical nuclei, nicely conform to the current knowledge on the equation of state of asymmetric nuclear matter, eliminate the notorious unphysical instabilities of symmetric nuclear matter and pure neutron matter up to a very high density of 1.2 fm^-3, and simultaneously support heavier neutron stars with mass larger than two times solar mass. One important difference of the three new interactions is about the prediction of the symmetry energy at supra-saturation densities, and these new interactions are thus potentially useful for the determination of the largely uncertain high-density symmetry energy in future. In addition, a comparison is made for the predictions of nuclear matter, finite nuclei and neutron stars with the three new interactions versus those with three typical interactions BSk22, BSk24 and BSk26 from Brussels group.", "keyphrases": ["skyrme interaction", "nuclear matter", "neutron star"]}
{"id": "1204.5492", "title": "Galileons in the Sky", "abstract": "We review the different frameworks in which Galileon scalar fields have been seen to emerge such an in DGP, New Massive Gravity and Ghost-free massive Gravity and emphasize their relation with the Lovelock invariant in braneworld models. The existence of a non-renormalization theorem for Galileon scalar fields makes them especially attractive candidates for inflation as well as for late-time acceleration. In particular we review the self-accelerating and degravitating branches of solutions present in Galileon models when arising from Massive Gravity and discuss their phenomenology.", "keyphrases": ["gravity", "galileon", "dark energy", "progress"]}
{"id": "1007.4146", "title": "General description of electromagnetic radiation processes based on instantaneous charge acceleration in `endpoints'", "abstract": "We present a new methodology for calculating the electromagnetic radiation from accelerated charged particles. Our formulation \u2014 the `endpoint formulation' \u2014 combines numerous results developed in the literature in relation to radiation arising from particle acceleration using a complete, and completely general, treatment. We do this by describing particle motion via a series of discrete, instantaneous acceleration events, or `endpoints', with each such event being treated as a source of emission. This method implicitly allows for particle creation/destruction, and is suited to direct numerical implementation in either the time- or frequency-domains. In this paper, we demonstrate the complete generality of our method for calculating the radiated field from charged particle acceleration, and show how it reduces to the classical named radiation processes such as synchrotron, Tamm's description of Vavilov-Cherenkov, and transition radiation under appropriate limits. Using this formulation, we are immediately able to answer outstanding questions regarding the phenomenology of radio emission from ultra-high-energy particle interactions in both the Earth's atmosphere and the Moon. In particular, our formulation makes it apparent that the dominant emission component of the Askaryan Effect (coherent radio-wave radiation from high-energy particle cascades in dense media) comes from coherent `bremsstrahlung' from particle acceleration, rather than coherent Vavilov-Cherenkov radiation.", "keyphrases": ["radiation process", "particle acceleration", "radio emission"]}
{"id": "1605.00213", "title": "Distinguish three time-dependent dark energy models using statefinder pairs with error bars and Bayesian evidence", "abstract": "In this work, two completely different approaches, statefinder with error bars and Bayesian evidence, are used to distinguish and judge three time-dependent dark energy models. The parameters constrain for the three dark energy models are given using the current cosmic observational data sets : Planck 2015, SNIa, BAO and OHD. Using the statefinder pairs with error bars, we find that the error region of the dark energy model, whose equation of state parameter is given by w(a) = w_0+w_31-a/a^2+(1-a)^2, is relativity compact than the other two models during the all the evolving history. Meanwhile, the Bayesian evidence also provide that this model is significantly better than the other two models and the other two models are inconclusive. Then, there are reasons for believing that this model is a preferential candidate in dark energy investigation rather than the other two.", "keyphrases": ["dark energy model", "statefinder pair", "bayesian evidence"]}
{"id": "0905.1959", "title": "Reconstructing the Neutron-Star Equation of State from Astrophysical Measurements", "abstract": "The properties of matter at ultra-high densities, low temperatures, and with a significant asymmetry between protons and neutrons can be studied exclusively through astrophysical observations of neutron stars. We show that measurements of the masses and radii of neutron stars can lead to tight constraints on the pressure of matter at three fiducial densities, from 1.85 to 7.4 times the density of nuclear saturation, in a manner that is largely model-independent and that captures the key characteristics of the equation of state. We demonstrate that observations with 10 stars can lead to measurements of the pressure at these fiducial densities with an accuracy of 0.11 dex or 30 uncertainties are sufficient to distinguish at a better than 3-sigma confidence level between currently proposed equations of state. In the electromagnetic spectrum, such accurate measurements will become possible for weakly-magnetic neutron stars during thermonuclear flashes and in quiescence with future missions such as the International X-ray Observatory (IXO).", "keyphrases": ["ultra-high density", "neutron star", "mass-radius relation"]}
{"id": "1204.4048", "title": "Teleparallel Dark Energy with Purely Non-minimal Coupling to Gravity", "abstract": "We propose the simplest model of teleparallel dark energy with purely a non-minimal coupling to gravity but no self-potential, a single model possessing various interesting features: simplicity, self-potential-free, the guaranteed late-time cosmic acceleration driven by the non-minimal coupling to gravity, tracker behavior of the dark energy equation of state at earlier times, a crossing of the phantom divide at a late time, and the existence of a finite-time future singularity. We find the analytic solutions of the dark-energy scalar field respectively in the radiation, matter, and dark energy dominated eras, thereby revealing the above features. We further illustrate possible cosmic evolution patterns and present the observational constraint of this model obtained by numerical analysis and data fitting.", "keyphrases": ["non-minimal coupling", "gravity", "teleparallel dark energy"]}
{"id": "1705.01544", "title": "Superradiant instability of massive vector fields around spinning black holes in the relativistic regime", "abstract": "We study the superradiant instability of massive vector fields, i.e. Proca fields, around spinning black holes in the test field limit. This is motivated by the possibility that observations of astrophysical black holes can probe the existence of ultralight bosons subject to this mechanism. By making use of time-domain simulations, we characterize the growth rate, frequency, spatial distribution, and other properties of the unstable modes, including in the regime where the black hole is rapidly spinning and the Compton wavelength of the Proca field is comparable to the black hole radius. We find that relativistic effects in this regime increase the range of Proca masses that are unstable, as well as the maximum instability rate. We also study the gravitational waves that can be sourced by such an instability, finding that they can be significantly stronger than in the massive scalar field case.", "keyphrases": ["massive vector field", "black hole", "superradiant instability"]}
{"id": "1908.11794", "title": "Testing the Schwarzschild metric in a strong field region with the Event Horizon Telescope", "abstract": "Testing gravity theory in the strong field region becomes a reality due to the observations of gravitational waves and black hole shadows. In this paper, we discuss how to constrain the possible deviations of the classical general relativity with the image of M87* observed by the Event Horizon Telescope. More precisely, we want to know where is the event horizon for a non-rotating black hole. General relativity predicts the horizon is located at the Schwarzschild radius r_s, while other gravity theories may give different predictions. We propose a parameterized Schwarzschild metric (PSM) in which the horizon is located at r=nr_s, where n is a real free parameter, and prove general relativity with nonlinear electrodynamics allows n\u22601. In the weak field region, the PSM is equivalent to the Schwarzschild metric regardless of the value of n. In the strong field region, the difference between the PSM and Schwarzschild metric would leave an imprint on the shadow image. We present detailed calculations and discussions on the black hole shadows with large background light source and accretion disk in the PSM framework. More importantly, we point out that n\u22482 can be used to explain why the black hole mass measured by the shadow is a factor of about two larger than the previous gas dynamics measurements. If this explanation is confirmed to be right, then this phenomenon, together with the late-time cosmological acceleration, will be very important to test gravity theories.", "keyphrases": ["event horizon telescope", "gravity theory", "black hole"]}
{"id": "1102.2750", "title": "The distance duality relation and the temperature profile of Galaxy Clusters", "abstract": "The validity of distance duality relation, \u03b7=D_L(z)(1+z)^-2/D_A(z)=1, an exact result required by the Etherington reciprocity theorem, where D_A(z) and D_L(z) are the angular and luminosity distances, plays an essential part in cosmological observations and model constraints. In this paper, we investigate some consequences of such a relation by assuming \u03b7 a constant or a function of the redshift. In order to constrain the parameters concerning \u03b7, we consider two groups of cluster gas mass fraction data including 52 X-ray luminous galaxy clusters observed by Chandra in the redshift range 0.3\u223c 1.273 and temperature range T_ gas> 4 keV, under the assumptions of two different temperature profiles [1]. We find that the constant temperature profile is in relatively good agreement with no violation of the distance duality relation for both parameterizations of \u03b7, while the one with temperature gradient (the Vikhlinin et al. temperature profile) seems to be incompatible even at 99", "keyphrases": ["distance duality relation", "temperature profile", "galaxy cluster"]}
{"id": "1007.3746", "title": "Towards an improved understanding of the relative scintillation efficiency of nuclear recoils in liquid xenon", "abstract": "Liquid xenon (LXe) particle detectors are a powerful technology in the field of dark matter direct detection, having shown impressive results in recent years and holding strong possibility for leading the field in sensitivity to galactic weakly interacting massive particles (WIMPs) in the future. The search for WIMPs requires the capability to detect the recoiling nuclei that result when these particles interact with normal matter. In order to make meaningful statements about an observed signal, or lack thereof, the energy scale of recoiling nuclei in LXe must be known. Our understanding of this energy scale is contained in a quantity called the relative scintillation efficiency of nuclear recoils, or L_eff, and has been studied extensively in the literature, producing seemingly contradictory results. I examine all the measurements of L_eff that exist, both direct and indirect, and extract the energy dependent behavior that is statistically consistent globally with all values. Additionally, I examine the measurements covering low energies (> 10 keV, where the largest disagreements exist) and attempt to diagnose the systematic effects that have led to the observed inconsistencies. I show that virtually all major disparity arises due to efficiency roll-off of the detectors at the low energies, and, when taking this into account, find that the observed behavior of L_eff supports a slowly and smoothly decreasing value with decreasing energy. Finally, I discuss the prospects for future measurements, and derive a practical limit to what can be achieved.", "keyphrases": ["relative scintillation efficiency", "nuclear recoil", "xenon"]}
{"id": "1310.2943", "title": "Simulations of Ion Acceleration at Non-relativistic Shocks. I. Acceleration Efficiency", "abstract": "We use 2D and 3D hybrid (kinetic ions - fluid electrons) simulations to investigate particle acceleration and magnetic field amplification at non-relativistic astrophysical shocks. We show that diffusive shock acceleration operates for quasi-parallel configurations (i.e., when the background magnetic field is almost aligned with the shock normal) and, for large sonic and Alfv\u00e9nic Mach numbers, produces universal power-law spectra proportional to p^(-4), where p is the particle momentum. The maximum energy of accelerated ions increases with time, and it is only limited by finite box size and run time. Acceleration is mainly efficient for parallel and quasi-parallel strong shocks, where 10-20 energetic particles, and becomes ineffective for quasi-perpendicular shocks. Also, the generation of magnetic turbulence correlates with efficient ion acceleration, and vanishes for quasi-perpendicular configurations. At very oblique shocks, ions can be accelerated via shock drift acceleration, but they only gain a factor of a few in momentum, and their maximum energy does not increase with time. These findings are consistent with the degree of polarization and the morphology of the radio and X-ray synchrotron emission observed, for instance, in the remnant of SN 1006. We also discuss the transition from thermal to non-thermal particles in the ion spectrum (supra-thermal region), and we identify two dynamical signatures peculiar of efficient particle acceleration, namely the formation of an upstream precursor and the alteration of standard shock jump conditions.", "keyphrases": ["ion acceleration", "plasma simulation", "shock kinetic energy"]}
{"id": "0907.0427", "title": "Power spectra from an inflaton coupled to the Gauss-Bonnet term", "abstract": "We consider power-law inflation with a Gauss-Bonnet correction inspired by string theory. We analyze the stability of cosmological perturbations and obtain the allowed parameter space. We find that for GB-dominated inflation ultra-violet instabilities of either scalar or tensor perturbations show up on small scales. The Gauss-Bonnet correction with a positive (or negative) coupling may lead to a reduction (or enhancement) of the tensor-to-scalar ratio in the potential-dominated case. We place tight constraints on the model parameters by making use of the WMAP 5-year data.", "keyphrases": ["power-law inflation", "string theory", "einstein-gauss-bonnet theory", "gravity"]}
{"id": "1207.3993", "title": "Global modelling of the early Martian climate under a denser CO2 atmosphere: Water cycle and ice evolution", "abstract": "We discuss 3D global simulations of the early Martian climate that we have performed assuming a faint young Sun and denser CO2 atmosphere. We include a self-consistent representation of the water cycle, with atmosphere-surface interactions, atmospheric transport, and the radiative effects of CO2 and H2O gas and clouds taken into account. We find that for atmospheric pressures greater than a fraction of a bar, the adiabatic cooling effect causes temperatures in the southern highland valley network regions to fall significantly below the global average. Long-term climate evolution simulations indicate that in these circumstances, water ice is transported to the highlands from low-lying regions for a wide range of orbital obliquities, regardless of the extent of the Tharsis bulge. In addition, an extended water ice cap forms on the southern pole, approximately corresponding to the location of the Noachian/Hesperian era Dorsa Argentea Formation. Even for a multiple-bar CO2 atmosphere, conditions are too cold to allow long-term surface liquid water. Limited melting occurs on warm summer days in some locations, but only for surface albedo and thermal inertia conditions that may be unrealistic for water ice. Nonetheless, meteorite impacts and volcanism could potentially cause intense episodic melting under such conditions. Because ice migration to higher altitudes is a robust mechanism for recharging highland water sources after such events, we suggest that this globally sub-zero, `icy highlands' scenario for the late Noachian climate may be sufficient to explain most of the fluvial geology without the need to invoke additional long-term warming mechanisms or an early warm, wet Mars.", "keyphrases": ["early martian climate", "denser co2 atmosphere", "water cycle"]}
{"id": "2003.06255", "title": "How galaxies populate haloes in very low-density environments? An analysis of the Halo Occupation Distribution in cosmic voids", "abstract": "Evidence shows properties of dark matter haloes may vary with large-scale environment. By studying the halo occupation distribution in cosmic voids it is possible to obtain useful information that can shed light on the subject. The history of the formation of the haloes and galaxies residing in these regions is likely to differ from the global behaviour given their extreme environment. We use two public access simulated galaxy catalogues constructed with different methods: a semi-analytical model and a hydrodynamic simulation. In both, we identify cosmic voids and we measure the halo occupation distribution inside these regions for different absolute magnitude thresholds. We compare these determinations with the overall results and we study the dependence of different characteristics of the voids. Also, we analyze the stellar content and the formation time of the haloes inside voids and confront the general halo population results. Inside the voids, we find a significantly different halo occupation distribution with respect to the general results. This is present in all absolute magnitude ranges explored. We obtain no signs of variation related to void characteristics indicating that the effects depend only on the density of the large-scale environment. Additionally, we find that the stellar mass content also differs within voids, which host haloes with less massive central galaxies (10 content (30 of the haloes which are younger in voids than the average population. These characteristics indicate that haloes populating voids have had a different formation history, inducing significant changes on the halo occupation distribution.", "keyphrases": ["galaxy", "halo occupation distribution", "cosmic void"]}
{"id": "0907.4445", "title": "The 10 Meter South Pole Telescope", "abstract": "The South Pole Telescope (SPT) is a 10 m diameter, wide-field, offset Gregorian telescope with a 966-pixel, multi-color, millimeter-wave, bolometer camera. It is located at the Amundsen-Scott South Pole station in Antarctica. The design of the SPT emphasizes careful control of spillover and scattering, to minimize noise and false signals due to ground pickup. The key initial project is a large-area survey at wavelengths of 3, 2 and 1.3 mm, to detect clusters of galaxies via the Sunyaev-Zeldovich effect and to measure the small-scale angular power spectrum of the cosmic microwave background (CMB). The data will be used to characterize the primordial matter power spectrum and to place constraints on the equation of state of dark energy. A second-generation camera will measure the polarization of the CMB, potentially leading to constraints on the neutrino mass and the energy scale of inflation.", "keyphrases": ["south pole telescope", "cosmic microwave background", "sky", "geographic south pole"]}
{"id": "1411.0805", "title": "Trajectories of point particles in cosmology and the Zel'dovich approximation", "abstract": "Using a Green's function approach, we compare the trajectories of classical Hamiltonian point particles in an expanding space-time to the effectively inertial trajectories in the Zel'dovich approximation. It is shown that the effective gravitational potential accelerating the particles relative to the Zel'dovich trajectories vanishes exactly initially as a consequence of the continuity equation, and acts only during a short, early period. The Green's function approach suggests an iterative scheme for improving the Zel'dovich trajectories, which can be analytically solved. We construct these trajectories explicitly and show how they interpolate between the Zel'dovich and the exact trajectories. The effective gravitational potential acting on the improved trajectories is substantially smaller at late times than the potential acting on the exact trajectories. The results may be useful for Lagrangian perturbation theory and for numerical simulations.", "keyphrases": ["point particle", "cosmology", "zel'dovich approximation"]}
{"id": "2105.07083", "title": "Assessing the detectability of the secondary spin in extreme mass-ratio inspirals with fully-relativistic numerical waveforms", "abstract": "Extreme mass-ratio inspirals (EMRIs) detectable by the Laser Inteferometric Space Antenna (LISA) are unique probes of astrophysics and fundamental physics. Parameter estimation for these sources is challenging, especially because the waveforms are long, complicated, known only numerically, and slow to compute in the most relevant regime, where the dynamics is relativistic. We perform a time-consuming Fisher-matrix error analysis of the EMRI parameters using fully-relativistic numerical waveforms to leading order in an adiabatic expansion on a Kerr background, taking into account the motion of the LISA constellation, higher harmonics, and also including the leading correction from the spin of the secondary in the post-adiabatic approximation. We pay particular attention to the convergence of the numerical derivatives in the Fisher matrix and to the numerical stability of the covariance matrix, which for some systems requires computing the numerical waveforms with approximately 90-digit precision. Our analysis confirms previous results (obtained with approximated but much more computationally efficient waveforms) for the measurement errors on the binary's parameters. We also show that the inclusion of higher harmonics improves the errors on the luminosity distance and on the orbital angular momentum angles by one order and two orders of magnitude, respectively, which might be useful to identify the environments where EMRIs live. We particularly focus on the measurability of the spin of the secondary, confirming that it cannot be measured with sufficient accuracy. However, due to correlations, its inclusion in the waveform model can deteriorate the accuracy on the measurements of other parameters by orders of magnitude, unless a physically-motivated prior on the secondary spin is imposed.", "keyphrases": ["secondary spin", "mass-ratio inspiral", "fully-relativistic numerical waveform"]}
{"id": "1310.7031", "title": "What Next-Generation 21 cm Power Spectrum Measurements Can Teach Us About the Epoch of Reionization", "abstract": "A number of experiments are currently working towards a measurement of the 21 cm signal from the Epoch of Reionization. Whether or not these experiments deliver a detection of cosmological emission, their limited sensitivity will prevent them from providing detailed information about the astrophysics of reionization. In this work, we consider what types of measurements will be enabled by a next-generation of larger 21 cm EoR telescopes. To calculate the type of constraints that will be possible with such arrays, we use simple models for the instrument, foreground emission, and the reionization history. We focus primarily on an instrument modeled after the \u223c 0.1 km^2 collecting area Hydrogen Epoch of Reionization Array (HERA) concept design, and parameterize the uncertainties with regard to foreground emission by considering different limits to the recently described \"wedge\" footprint in k-space. Uncertainties in the reionization history are accounted for using a series of simulations which vary the ionizing efficiency and minimum virial temperature of the galaxies responsible for reionization, as well as the mean free path of ionizing photons through the IGM. Given various combinations of models, we consider the significance of the possible power spectrum detections, the ability to trace the power spectrum evolution versus redshift, the detectability of salient power spectrum features, and the achievable level of quantitative constraints on astrophysical parameters. Ultimately, we find that 0.1 km^2 of collecting area is enough to ensure a very high significance (\u227330\u03c3) detection of the reionization power spectrum in even the most pessimistic scenarios. This sensitivity should allow for meaningful constraints on the reionization history and astrophysical parameters, especially if foreground subtraction techniques can be improved and successfully implemented.", "keyphrases": ["next-generation", "epoch", "reionization"]}
{"id": "1101.1026", "title": "Cosmological structure formation with clustering quintessence", "abstract": "We study large-scale structure formation in the presence of a quintessence component with zero speed of sound in the framework of Eulerian Perturbation Theory. Due to the absence of pressure gradients, quintessence and dark matter are comoving and can be studied as a unique fluid in terms of the total energy density contrast and the common velocity. In this description the clustering of quintessence enhances the linear term proportional to the velocity divergence in the continuity equation by a factor (1+w) Omega_Q / Omega_m. This is responsible for a rapid evolution of the growth rate at low redshifts, and modifies the standard relation between the velocity divergence and the growth factor. For the total fluid, the solutions for the linear growth function and growth rate can be written in integral forms and admit simple fitting formulae, as in the LambdaCDM case. At second order in perturbation theory, we derive an explicit expression for the kernels F_2 and G_2. They receive modifications of the order of the ratio between quintessence and total energy density perturbations, which affect the corresponding tree-level bispectra. We finally compute the cumulative signal-to-noise in the power spectrum, bispectrum and reduced bispectrum, expected for departures from a LambdaCDM cosmology both in the clustering and smooth quintessence scenarios. The reduced bispectrum, in particular, receives sensible modifications only in the clustering case and can potentially be used to detect or rule out the model.", "keyphrases": ["structure formation", "dark matter", "cosmology"]}
{"id": "1610.05305", "title": "Testing cosmic-ray acceleration with radio relics: a high-resolution study using MHD and tracers", "abstract": "Weak shocks in the intracluster medium may accelerate cosmic-ray protons and cosmic-ray electrons differently depending on the angle between the upstream magnetic field and the shock normal. In this work, we investigate how shock obliquity affects the production of cosmic rays in high-resolution simulations of galaxy clusters. For this purpose, we performed a magneto-hydrodynamical simulation of a galaxy cluster using the mesh refinement code . We use Lagrangian tracers to follow the properties of the thermal gas, the cosmic rays and the magnetic fields over time. We tested a number of different acceleration scenarios by varying the obliquity-dependent acceleration efficiencies of protons and electrons, and by examining the resulting hadronic \u03b3-ray and radio emission. We find that the radio emission does not change significantly if only quasi-perpendicular shocks are able to accelerate cosmic-ray electrons. Our analysis suggests that radio emitting electrons found in relics have been typically shocked many times before z=0. On the other hand, the hadronic \u03b3-ray emission from clusters is found to decrease significantly if only quasi-parallel shocks are allowed to accelerate cosmic-ray protons. This might reduce the tension with the low upper limits on \u03b3-ray emission from clusters set by the Fermi-satellite.", "keyphrases": ["radio relic", "cosmic-ray electron", "galaxy cluster"]}
{"id": "1004.2288", "title": "Mechanism of spontaneous formation of stable magnetic structures on the Sun", "abstract": "One of the puzzling features of solar magnetism is formation of long-living compact magnetic structures; such as sunspots and pores, in the highly turbulent upper layer of the solar convective zone. We use realistic radiative 3D MHD simulations to investigate the interaction between magnetic field and turbulent convection. In the simulations, a weak vertical uniform magnetic field is imposed in a region of fully developed granular convection; and the total magnetic flux through the top and bottom boundaries is kept constant. The simulation results reveal a process of spontaneous formation of stable magnetic structures, which may be a key to understanding of the magnetic self-organization on the Sun and formation of pores and sunspots. This process consists of two basic steps: 1) formation of small-scale filamentary magnetic structures associated with concentrations of vorticity and whirlpool-type motions, and 2) merging of these structures due to the vortex attraction, caused by converging downdrafts around magnetic concentration below the surface. In the resulting large-scale structure maintained by the converging plasma motions, the magnetic field strength reaches 1.5 kG at the surface and 6 kG in the interior; and the surface structure resembles solar pores. The magnetic structure remains stable for the whole simulation run of several hours with no sign of decay.", "keyphrases": ["spontaneous formation", "stable magnetic structure", "sun"]}
{"id": "1405.7351", "title": "Toward an Understanding of Foreground Emission in the BICEP2 Region", "abstract": "BICEP2 has reported the detection of a degree-scale B-mode polarization pattern in the Cosmic Microwave Background (CMB) and has interpreted the measurement as evidence for primordial gravitational waves. Motivated by the profound importance of the discovery of gravitational waves from the early Universe, we examine to what extent a combination of Galactic foregrounds and lensed E-modes could be responsible for the signal. We reanalyze the BICEP2 results and show that the 100x150 GHz and 150x150 GHz data are consistent with a cosmology with r=0.2 and negligible foregrounds, but also with a cosmology with r=0 and a significant dust polarization signal. We give independent estimates of the dust polarization signal in the BICEP2 region using four different approaches. While these approaches are consistent with each other, the expected amplitude of the dust polarization power spectrum remains uncertain by about a factor of three. The lower end of the prediction leaves room for a primordial contribution, but at the higher end the dust in combination with the standard CMB lensing signal could account for the BICEP2 observations, without requiring the existence of primordial gravitational waves. By measuring the cross-correlations between the pre-Planck templates used in the BICEP2 analysis and between different versions of a data-based template, we emphasize that cross-correlations between models are very sensitive to noise in the polarization angles and that measured cross-correlations are likely underestimates of the contribution of foregrounds to the map. These results suggest that BICEP1 and BICEP2 data alone cannot distinguish between foregrounds and a primordial gravitational wave signal, and that future Keck Array observations at 100 GHz and Planck observations at higher frequencies will be crucial to determine whether the signal is of primordial origin. (abridged)", "keyphrases": ["foreground emission", "foreground contamination", "poorly-understood interstellar dust"]}
{"id": "0903.3412", "title": "Dark energy from a quintessence (phantom) field rolling near potential minimum (maximum)", "abstract": "We examine dark energy models in which a quintessence or a phantom field, \u03d5, rolls near the vicinity of a local minimum or maximum, respectively, of its potential V(\u03d5). Under the approximation that (1/V)(dV/d\u03d5) \u226a 1, [although (1/V)(d^2 V/d\u03d5^2) can be large], we derive a general expression for the equation of state parameter w as a function of the scale factor for these models. The dynamics of the field depends on the value of (1/V)(d^2 V/d\u03d5^2) near the extremum, which describes the potential curvature. For quintessence models, when (1/V)(d^2 V/d\u03d5^2)<3/4 at the potential minimum, the equation of state parameter w(a) evolves monotonically, while for (1/V)(d^2 V/d\u03d5^2)>3/4, w(a) has oscillatory behavior. For phantom fields, the dividing line between these two types of behavior is at (1/V)(d^2 V/d\u03d5^2) = -3/4. Our analytical expressions agree within 1 (numerically-derived) behavior, for all of the particular cases examined, for both quintessence and phantom fields. We present observational constraints on these models.", "keyphrases": ["quintessence", "potential minimum", "dark energy"]}
{"id": "1108.0593", "title": "Bouncing Galileon Cosmologies", "abstract": "We present nonsingular, homogeneous and isotropic bouncing solutions of the conformal Galileon model. We show that such solutions necessarily begin with a radiation-dominated contracting phase. This is followed by a quintom scenario in which the background equation of state crosses the cosmological constant boundary allowing for a nonsingular bounce which in turn is followed by Galilean Genesis. We analyze the spectrum of cosmological perturbations in this background. Our results show that the fluctuations evolve smoothly and without any pathology, but the adiabatic modes form a blue tilted spectrum. In order to achieve a scale-invariant primordial power spectrum as required by current observations, we introduce a light scalar field coupling to the Galileon kinetically. We find two couplings which yield a scale-invariant spectrum, one of which requires a fine tuning of the initial conditions. This model also predicts a blue tilted spectrum of gravitational waves stemming from quantum vacuum fluctuations in the contracting phase.", "keyphrases": ["galileon", "cosmology", "scalar field"]}
{"id": "1001.3237", "title": "Equipartition of energy and the first law of thermodynamics at the apparent horizon", "abstract": "We apply the holographic principle and the equipartition law of energy to the apparent horizon of a Friedmann-Robertson-Walker universe and derive the Friedmann equation describing the dynamics of the universe. We also show that the equipartition law of energy can be interpreted as the first law of thermodynamics at the apparent horizon.", "keyphrases": ["first law", "apparent horizon", "friedmann equation", "cosmology"]}
{"id": "1106.2798", "title": "Oscillations in the inflaton potential: Complete numerical treatment and comparison with the recent and forthcoming CMB datasets", "abstract": "Amongst the multitude of inflationary models currently available, models that lead to features in the primordial scalar spectrum are drawing increasing attention, since certain features have been found to provide a better fit to the CMB data than the conventional, nearly scale invariant, primordial spectrum. In this work, we carry out a complete numerical analysis of two models that lead to oscillations over all scales in the scalar power spectrum. We consider the model described by a quadratic potential which is superposed by a sinusoidal modulation and the recently popular axion monodromy model. Since the oscillations continue even on to arc minute scales, in addition to the WMAP data, we also compare the models with the small scale data from ACT. Though, both the models, broadly, result in oscillations in the spectrum, interestingly, we find that, while the monodromy model leads to a considerably better fit to the data in comparison to the standard power law spectrum, the quadratic potential superposed with a sinusoidal modulation does not improve the fit to a similar extent. We also carry out forecasting of the parameters using simulated Planck data for both the models. We show that the Planck mock data performs better in constraining the model parameters as compared to the presently available CMB datasets.", "keyphrases": ["inflaton potential", "primordial spectrum", "axion monodromy model"]}
{"id": "1509.05334", "title": "Stars, Gas, and Dark Matter in the Solar Neighborhood", "abstract": "The surface density and vertical distribution of stars, stellar remnants, and gas in the solar vicinity form important ingredients for understanding the star formation history of the Galaxy as well as for inferring the local density of dark matter by using stellar kinematics to probe the gravitational potential. In this paper we review the literature for these baryonic components, reanalyze data, and provide tables of the surface densities and exponential scale heights of main sequence stars, giants, brown dwarfs, and stellar remnants. We also review three components of gas (H2, HI, and HII), give their surface densities at the solar circle, and discuss their vertical distribution. We find a local total surface density of M dwarfs of 17.3 pm 2.3 Mo/pc^2. Our result for the total local surface density of visible stars, 27.0 pm 2.7 Mo/pc^2, is close to previous estimates due to a cancellation of opposing effects: more mass in M dwarfs, less mass in the others. The total local surface density in white dwarfs is 4.9 pm 0.6 Mo/pc^2; in brown dwarfs, it is 1.2 Mo/pc^2. We find that the total local surface density of stars and stellar remnants is 33.4 pm 3 Mo/pc^2, somewhat less than previous estimates. We analyze data on 21 cm emission and absorption and obtain good agreement with recent results on the local amount of neutral atomic hydrogen obtained with the Planck satellite. The local surface density of gas is 13.7 pm 1.6 Mo/pc^2. The total baryonic mass surface density that we derive for the solar neighborhood is 47.1 pm 3.4 Mo/pc^2. Combining these results with others' measurements of the total surface density of matter within 1-1.1 kpc of the plane, we find that the local density of dark matter is 0.013 pm 0.003Mo/pc^3.The local density of all matter is 0.097 pm 0.013 Mo/pc^3. We discuss limitations on the properties of a possible thin disk of dark matter.", "keyphrases": ["dark matter", "solar neighborhood", "star"]}
{"id": "0912.4421", "title": "Thermal Relics in Modified Cosmologies: Bounds on Evolution Histories of the Early Universe and Cosmological Boosts for PAMELA", "abstract": "Alternative cosmologies, based on extensions of General Relativity, predict modified thermal histories in the Early Universe during the pre Big Bang Nucleosynthesis (BBN) era, epoch which is not directly constrained by cosmological observations. When the expansion rate is enhanced with respect to the standard case, thermal relics typically decouple with larger relic abundances. The correct value of the relic abundance is therefore obtained for larger annihilation cross\u2013sections, as compared to standard cosmology. A direct consequence is that indirect detection rates are enhanced. Extending previous analyses of ours, we derive updated astrophysical bounds on the dark matter annihilation cross sections and use them to constrain alternative cosmologies in the pre\u2013BBN era. We also determine the characteristics of these alternative cosmologies in order to provide the correct value of relic abundance for a thermal relic for the (large) annihilation cross\u2013section required to explain the PAMELA results on the positron fraction, therefore providing a \"cosmological boost\" solution to the dark matter interpretation of the PAMELA data.", "keyphrases": ["early universe", "alternative cosmology", "relic abundance"]}
{"id": "1609.05908", "title": "The effects of supernovae on the dynamical evolution of binary stars and star clusters", "abstract": "In this chapter I review the effects of supernovae explosions on the dynamical evolution of (1) binary stars and (2) star clusters. (1) Supernovae in binaries can drastically alter the orbit of the system, sometimes disrupting it entirely, and are thought to be partially responsible for `runaway' massive stars - stars in the Galaxy with large peculiar velocities. The ejection of the lower-mass secondary component of a binary occurs often in the event of the more massive primary star exploding as a supernova. The orbital properties of binaries that contain massive stars mean that the observed velocities of runaway stars (10s - 100s km s^-1) are consistent with this scenario. (2) Star formation is an inherently inefficient process, and much of the potential in young star clusters remains in the form of gas. Supernovae can in principle expel this gas, which would drastically alter the dynamics of the cluster by unbinding the stars from the potential. However, recent numerical simulations, and observational evidence that gas-free clusters are observed to be bound, suggest that the effects of supernova explosions on the dynamics of star clusters are likely to be minimal.", "keyphrases": ["supernovae", "dynamical evolution", "star"]}
{"id": "1807.08732", "title": "Cosmological constraints from noisy convergence maps through deep learning", "abstract": "Deep learning is a powerful analysis technique that has recently been proposed as a method to constrain cosmological parameters from weak lensing mass maps. Due to its ability to learn relevant features from the data, it is able to extract more information from the mass maps than the commonly used power spectrum, and thus achieve better precision for cosmological parameter measurement. We explore the advantage of Convolutional Neural Networks (CNN) over the power spectrum for varying levels of shape noise and different smoothing scales applied to the maps. We compare the cosmological constraints from the two methods in the \u03a9_M-\u03c3_8 plane for sets of 400 deg^2 convergence maps. We find that, for a shape noise level corresponding to 8.53 galaxies/arcmin^2 and the smoothing scale of \u03c3_s = 2.34 arcmin, the network is able to generate 45 scale of \u03c3_s = 1.17 the improvement can reach \u223c 50 %, while for larger smoothing scale of \u03c3_s = 5.85, the improvement decreases to 19 The advantage generally decreases when the noise level and smoothing scales increase. We present a new training strategy to train the neural network with noisy data, as well as considerations for practical applications of the deep learning approach.", "keyphrases": ["convergence map", "deep learning", "cosmological constraint"]}
{"id": "0905.4117", "title": "Thermodynamics and classification of cosmological models in the Horava-Lifshitz theory of gravity", "abstract": "We study thermodynamics of cosmological models in the Horava-Lifshitz theory of gravity, and systematically investigate the evolution of the universe filled with a perfect fluid that has the equation of state p=w\u03c1, where p and \u03c1 denote, respectively, the pressure and energy density of the fluid, and w is an arbitrary real constant. Depending on specific values of the free parameters involved in the models, we classify all of them into various cases. In each case the main properties of the evolution are studied in detail, including the periods of deceleration and/or acceleration, and the existence of big bang, big crunch, and big rip singularities. We pay particular attention on models that may give rise to a bouncing universe.", "keyphrases": ["cosmological model", "horava-lifshitz theory", "gravity"]}
{"id": "1104.0663", "title": "Connection between the Accretion Disk and Jet in the Radio Galaxy 3C 111", "abstract": "We present the results of extensive multi-frequency monitoring of the radio galaxy 3C 111 between 2004 and 2010 at X-ray (2.4\u201310 keV), optical (R band), and radio (14.5, 37, and 230 GHz) wave bands, as well as multi-epoch imaging with the Very Long Baseline Array (VLBA) at 43 GHz. Over the six years of observation, significant dips in the X-ray light curve are followed by ejections of bright superluminal knots in the VLBA images. This shows a clear connection between the radiative state near the black hole, where the X-rays are produced, and events in the jet. The X-ray continuum flux and Fe line intensity are strongly correlated, with a time lag shorter than 90 days and consistent with zero. This implies that the Fe line is generated within 90 light-days of the source of the X-ray continuum. The power spectral density function of X-ray variations contains a break, with steeper slope at shorter timescales. The break timescale of 13 (+12,-6) days is commensurate with scaling according to the mass of the central black hole based on observations of Seyfert galaxies and black hole X-ray binaries (BHXRBs). The data are consistent with the standard paradigm, in which the X-rays are predominantly produced by inverse Compton scattering of thermal optical/UV seed photons from the accretion disk by a distribution of hot electrons \u2014 the corona \u2014 situated near the disk. Most of the optical emission is generated in the accretion disk due to reprocessing of the X-ray emission. The relationships that we have uncovered between the accretion disk and the jet in 3C 111, as well as in the FR I radio galaxy 3C 120 in a previous paper, support the paradigm that active galactic nuclei and Galactic BHXRBs are fundamentally similar, with characteristic time and size scales proportional to the mass of the central black hole", "keyphrases": ["accretion disk", "jet", "radio galaxy"]}
{"id": "1307.4000", "title": "Filtergraph: An Interactive Web Application for Visualization of Astronomy Datasets", "abstract": "Filtergraph is a web application being developed and maintained by the Vanderbilt Initiative in Data-intensive Astrophysics (VIDA) to flexibly and rapidly visualize a large variety of astronomy datasets of various formats and sizes. The user loads a flat-file dataset into Filtergraph which automatically generates an interactive data portal that can be easily shared with others. From this portal, the user can immediately generate scatter plots of up to 5 dimensions as well as histograms and tables based on the dataset. Key features of the portal include intuitive controls with auto-completed variable names, the ability to filter the data in real time through user-specified criteria, the ability to select data by dragging on the screen, and the ability to perform arithmetic operations on the data in real time. To enable seamless data visualization and exploration, changes are quickly rendered on screen and visualizations can be exported as high quality graphics files. The application is optimized for speed in the context of large datasets: for instance, a plot generated from a stellar database of 3.1 million entries renders in less than 2 seconds on a standard web server platform. This web application has been created using the Web2py web framework based on the Python programming language. Filtergraph is free to use at http://filtergraph.vanderbilt.edu/.", "keyphrases": ["visualization", "astronomy dataset", "filtergraph"]}
{"id": "1611.10074", "title": "Universality for quintessence", "abstract": "Several recent works suggested the possibility of describing inflation by means of a renormalization group equation. In this paper we discuss the application of these methods to models of quintessence. In this framework a period of exponential expansion corresponds to the slow evolution of the scalar field in the neighborhood of a fixed point. A minimal set of universality classes for models of quintessence is defined and the transition from a matter dominated to quintessence dominated universe is studied. Models in which quintessence is non-minimally coupled with gravity are also discussed. We show that the formalism proves to be extremely convenient to describe quintessence and moreover we find that in most of the models discussed in this work quintessence naturally takes over ordinary matter.", "keyphrases": ["quintessence", "formalism", "universality"]}
{"id": "1110.1635", "title": "Missing Black Holes Unveil The Supernova Explosion Mechanism", "abstract": "It is firmly established that the stellar mass distribution is smooth, covering the range 0.1-100 Msun. It is to be expected that the masses of the ensuing compact remnants correlate with the masses of their progenitor stars, and thus it is generally thought that the remnant masses should be smoothly distributed from the lightest white dwarfs to the heaviest black holes. However, this intuitive prediction is not borne out by observed data. In the rapidly growing population of remnants with observationally determined masses, a striking mass gap has emerged at the boundary between neutron stars and black holes. The heaviest neutron stars reach a maximum of two solar masses, while the lightest black holes are at least five solar masses. Over a decade after the discovery, the gap has become a significant challenge to our understanding of compact object formation. We offer new insights into the physical processes that bifurcate the formation of remnants into lower mass neutron stars and heavier black holes. Combining the results of stellar modeling with hydrodynamic simulations of supernovae, we both explain the existence of the gap, and also put stringent constraints on the inner workings of the supernova explosion mechanism. In particular, we show that core-collapse supernovae are launched within 100-200 milliseconds of the initial stellar collapse, implying that the explosions are driven by instabilities with a rapid (10-20 ms) growth time. Alternatively, if future observations fill in the gap, this will be an indication that these instabilities develop over a longer (>200 milliseconds) timescale.", "keyphrases": ["black hole", "supernova explosion mechanism", "mass gap", "compact object formation"]}
{"id": "1912.12499", "title": "Non-linear damping of superimposed primordial oscillations on the matter power spectrum in galaxy surveys", "abstract": "Galaxy surveys are an important probe for superimposed oscillations on the primordial power spectrum of curvature perturbations, which are predicted in several theoretical models of inflation and its alternatives. In order to exploit the full cosmological information in galaxy surveys it is necessary to study the matter power spectrum to fully non-linear scales. We therefore study the non-linear clustering in models with superimposed linear and logarithmic oscillations to the primordial power spectrum by running high-resolution dark-matter-only N-body simulations. We fit a Gaussian envelope for the non-linear damping of superimposed oscillations in the matter power spectrum to the results of the N-body simulations for k \u2272 0.6 h/Mpc at 0 \u2264 z \u2264 5 with an accuracy below the percent. We finally use this fitting formula to forecast the capabilities of future galaxy surveys, such as Euclid and Subaru, to probe primordial oscillation down to non-linear scales alone and in combination with the information contained in CMB anisotropies.", "keyphrases": ["primordial oscillation", "galaxy survey", "non-linear damping"]}
{"id": "1010.3021", "title": "Strongly Coupled Perturbations in Two-Field Inflationary Models", "abstract": "We study models of inflation with two scalar fields and non-canonical kinetic terms, focusing on the case in which the curvature and isocurvature perturbations are strongly coupled to each other. In the regime where a heavy mode can be identified and integrated out, we clarify the passage from the full two-field model to an effectively single-field description. However, the strong coupling sets a new scale in the system, and affects the evolution of the perturbations as well as the beginning of the regime of validity of the effective field theory. In particular, the predictions of the model are sensitive to the relative hierarchy between the coupling and the mass of the heavy mode. As a result, observables are not given unambiguously in terms of the parameters of an effectively single field model with non-trivial sound speed. Finally, the requirement that the sound horizon crossing occurs within the regime of validity of the effective theory leads to a lower bound on the sound speed. Our analysis is done in an extremely simple toy model of slow-roll inflation, which is chosen for its tractability, but is non-trivial enough to illustrate the richness of the dynamics in non-canonical multi-field models.", "keyphrases": ["two-field model", "heavy field", "curvature perturbation"]}
{"id": "1402.2498", "title": "Fast Radio Burst/Gamma-Ray Burst Cosmography", "abstract": "Recently, both theoretical arguments and observational evidence suggested that a small fraction of fast radio bursts (FRBs) could be associated with gamma-ray bursts (GRBs). If such FRB/GRB association systems are commonly detected in the future, the combination of dispersion measure (DM) derived from FRBs and redshifts derived from GRBs makes these systems a plausible tool to conduct cosmography. We quantify uncertainties in deriving the redshift-dependent DM_IGM as a function of z, and test how well dark energy models can be constrained with Monte Carlo simulations. We show that with potentially several 10s of FRB/GRB systems detected in a decade or so, one may reach reasonable constraints on wCDM models. When combined with SN Ia data, unprecedented constraints on dark energy equation of state may be achieved, thanks to the prospects of detecting FRB/GRB systems at relatively high redshifts. The ratio between the mean value < DM_IGM (z)> and luminosity distance (D_L (z)) is insensitive to dark energy models. This gives the prospects of applying SN Ia data to calibrate < DM_IGM (z)> using a relatively small sample of FRB/GRB systems, allowing a reliable constraint on the baryon inhomogeneity distribution as a function of redshift. The methodology developed in this paper can also be applied, if the FRB redshifts can be measured by other means. Some caveats of putting this method into practice are also discussed.", "keyphrases": ["redshift", "fast radio burst", "cosmology"]}
{"id": "1106.5438", "title": "Equilibrium configurations from gravitational collapse", "abstract": "We develop here a new procedure within Einstein's theory of gravity to generate equilibrium configurations that result as the final state of gravitational collapse from regular initial conditions. As a simplification, we assume that the collapsing fluid is supported only by tangential pressure. We show that the equilibrium geometries generated by this method form a subset of static solutions to the Einstein equations, and that they can either be regular or develop a naked singularity at the center. When a singularity is present, there are key differences in the properties of stable circular orbits relative to those around a Schwarzschild black hole with the same mass. Therefore, if an accretion disk is present around such a naked singularity it could be observationally distinguished from a disk around a black hole.", "keyphrases": ["gravitational collapse", "singularity", "equilibrium configuration"]}
{"id": "1811.01959", "title": "F-theory and Dark Energy", "abstract": "Motivated by its potential use as a starting point for solving various cosmological constant problems, we study F-theory compactified on the warped product \u211d_time\u00d7 S^3 \u00d7 Y_8 where Y_8 is a Spin(7) manifold, and the S^3 factor is the target space of an SU(2) Wess\u2013Zumino\u2013Witten (WZW) model at level N. Reduction to M-theory exploits the abelian duality of this WZW model to an S^3 / \u2124_N orbifold. In the large N limit, the untwisted sector is captured by 11D supergravity. The local dynamics of intersecting 7-branes in the Spin(7) geometry is controlled by a Donaldson\u2013Witten twisted gauge theory coupled to defects. At late times, the system is governed by a 1D quantum mechanics system with a ground state annihilated by two real supercharges, which in four dimensions would appear as \"\ud835\udca9 = 1/2 supersymmetry\" on a curved background. This leads to a cancellation of zero point energies in the 4D field theory but a split mass spectrum for superpartners of order \u0394 m_4D\u223c\u221a(M_IR M_UV) specified by the IR and UV cutoffs of the model. This is suggestively close to the TeV scale in some scenarios. The classical 4D geometry has an intrinsic instability which can produce either a collapsing or expanding Universe, the latter providing a promising starting point for a number of cosmological scenarios. The resulting 1D quantum mechanics in the time direction also provides an appealing starting point for a more detailed study of quantum cosmology.", "keyphrases": ["dark energy", "f-theory", "string theory", "cosmological implication"]}
{"id": "2011.03500", "title": "The Physical Mechanisms of Fast Radio Bursts", "abstract": "Fast radio bursts are mysterious millisecond-duration transients prevalent in the radio sky. Rapid accumulation of data in recent years has facilitated an understanding of the underlying physical mechanisms of these events. Knowledge gained from the neighboring fields of gamma-ray bursts and radio pulsars also offered insight. Here I review developments in this fast-moving field.Two generic categories of radiation model invoking either magnetospheres of compact objects (neutron stars or black holes) or relativistic shocks launched from such objects have been much debated. The recent detection of a Galactic fast radio burst in association with a soft gamma-ray repeater suggests that magnetar engines can produce at least some, and probably all, fast radio bursts. Other engines that could produce fast radio bursts are not required, but are also not impossible.", "keyphrases": ["fast radio burst", "gamma-ray repeater", "frbs", "millisecond duration", "radiation mechanism"]}
{"id": "1503.08539", "title": "Solar Dynamics, Rotation, Convection and Overshoot", "abstract": "We discuss recent observational, theoretical and modeling progress made in understanding the Sun's internal dynamics, including its rotation, meridional flow, convection and overshoot. Over the past few decades, substantial theoretical and observational effort has gone into appreciating these aspects of solar dynamics. A review of these observations, related helioseismic methodology and inference and computational results in relation to these problems is undertaken here.", "keyphrases": ["rotation", "convection", "overshoot"]}
{"id": "1607.01363", "title": "Angular dependence of primordial trispectra and CMB spectral distortions", "abstract": "Under the presence of anisotropic sources in the inflationary era, the trispectrum of the primordial curvature perturbation has a very specific angular dependence between each wavevector that is distinguishable from the one encountered when only scalar fields are present, characterized by an angular dependence described by Legendre polynomials. We examine the imprints left by curvature trispectra on the TT\u03bc bispectrum, generated by the correlation between temperature anisotropies (T) and chemical potential spectral distortions (\u03bc) of the Cosmic Microwave Background (CMB). Due to the angular dependence of the primordial signal, the corresponding TT\u03bc bispectrum strongly differs in shape from TT\u03bc sourced by the usual g_ NL or \u03c4_ NL local trispectra, enabling us to obtain an unbiased estimation. From a Fisher matrix analysis, we find that, in a cosmic-variance-limited (CVL) survey of TT\u03bc, a minimum detectable value of the quadrupolar Legendre coefficient is d_2 \u223c 0.01, which is 4 orders of magnitude better than the best value attainable from the TTTT CMB trispectrum. In the case of an anisotropic inflationary model with a f(\u03d5)F^2 interaction (coupling the inflaton field \u03d5 with a vector kinetic term F^2), the size of the curvature trispectrum is related to that of quadrupolar power spectrum asymmetry, g_*. In this case, a CVL measurement of TT\u03bc makes it possible to measure g_* down to 10^-3.", "keyphrases": ["trispectra", "spectral distortion", "angular dependence"]}
{"id": "0906.3046", "title": "On the Extra Mode and Inconsistency of Horava Gravity", "abstract": "We address the consistency of Horava's proposal for a theory of quantum gravity from the low-energy perspective. We uncover the additional scalar degree of freedom arising from the explicit breaking of the general covariance and study its properties. The analysis is performed both in the original formulation of the theory and in the Stueckelberg picture. A peculiarity of the new mode is that it satisfies an equation of motion that is of first order in time derivatives. At linear level the mode is manifest only around spatially inhomogeneous and time-dependent backgrounds. We find two serious problems associated with this mode. First, the mode develops very fast exponential instabilities at short distances. Second, it becomes strongly coupled at an extremely low cutoff scale. We also discuss the \"projectable\" version of Horava's proposal and argue that this version can be understood as a certain limit of the ghost condensate model. The theory is still problematic since the additional field generically forms caustics and, again, has a very low strong coupling scale. We clarify some subtleties that arise in the application of the Stueckelberg formalism to Horava's model due to its non-relativistic nature.", "keyphrases": ["gravity", "explicit breaking", "extra graviton mode"]}
{"id": "0909.1507", "title": "Galaxy distribution and extreme value statistics", "abstract": "We consider the conditional galaxy density around each galaxy, and study its fluctuations in the newest samples of the Sloan Digital Sky Survey Data Release 7. Over a large range of scales, both the average conditional density and its variance show a nontrivial scaling behavior, which resembles to criticality. The density depends, for 10 < r < 80 Mpc/h, only weakly (logarithmically) on the system size. Correspondingly, we find that the density fluctuations follow the Gumbel distribution of extreme value statistics. This distribution is clearly distinguishable from a Gaussian distribution, which would arise for a homogeneous spatial galaxy configuration. We also point out similarities between the galaxy distribution and critical systems of statistical physics.", "keyphrases": ["extreme value statistic", "mpc", "galaxy distribution"]}
{"id": "1111.6876", "title": "Leptogenesis via hypermagnetic fields and baryon asymmetry", "abstract": "We study baryon asymmetry generation originated from the leptogenesis in the presence of hypermagnetic fields in the early Universe plasma before the electroweak phase transition (EWPT). For the simplest Chern-Simons (CS) wave configuration of hypermagnetic field we find the baryon asymmetry growth when the hypermagnetic field value changes due to alpha^2-dynamo and the lepton asymmetry rises due to the Abelian anomaly. We solve the corresponding integro-differential equations for the lepton asymmetries describing such self-consistent dynamics for lepto- and baryogenesis in the two scenarios : (i) when a primordial lepton asymmetry sits in right electrons e_R; and (ii) when, in addition to e_R, a left lepton asymmetry for e_L and nu_eL arises due to chirality flip reactions provided by inverse Higgs decays at the temperatures, T<T_RL 10 TeV. We find that the baryon asymmetry of the Universe (BAU) rises very fast through such leptogenesis, especially, in strong hypermagnetic fields. Varying (decreasing) the CS wave number parameter k_0 < 10^-7 T_EW one can recover the observable value of BAU, eta_B 10^-9, where k_0 = 10^-7 T_EW corresponds to the maximum value for CS wave number surviving ohmic dissipation of hypermagnetic field. In the scenario (ii) one predicts the essential difference of the lepton numbers of right - and left electrons at EWPT time, L_eR - L_eL (mu_eR - mu_eL) / T_EW = Delta mu / T_EW 10^-5 that can be used as an initial condition for chiral asymmetry after EWPT.", "keyphrases": ["baryon asymmetry", "electroweak phase transition", "abelian anomaly", "lepto-", "chiral asymmetry"]}
{"id": "2012.04959", "title": "MICADO PSF-Reconstruction work package description", "abstract": "The point spread function reconstruction (PSF-R) capability is a deliverable of the MICADO@ESO-ELT project. The PSF-R team works on the implementation of the instrument software devoted to reconstruct the point spread function (PSF), independently of the science data, using adaptive optics (AO) telemetry data, both for Single Conjugate (SCAO) and Multi-Conjugate Adaptive Optics (MCAO) mode of the MICADO camera and spectrograph. The PSF-R application will provide reconstructed PSFs through an archive querying system to restore the telemetry data synchronous to each science frame that MICADO will generate. Eventually, the PSF-R software will produce the output according to user specifications. The PSF-R service will support the state-of-the-art scientific analysis of the MICADO imaging and spectroscopic data.", "keyphrases": ["function reconstruction", "psf-r", "micado"]}
{"id": "1507.06170", "title": "The dynamical structure of the MEO region: long-term stability, chaos, and transport", "abstract": "It has long been suspected that the Global Navigation Satellite Systems exist in a background of complex resonances and chaotic motion; yet, the precise dynamical character of these phenomena remains elusive. Recent studies have shown that the occurrence and nature of the resonances driving these dynamics depend chiefly on the frequencies of nodal and apsidal precession and the rate of regression of the Moon's nodes. Woven throughout the inclination and eccentricity phase space is an exceedingly complicated web-like structure of lunisolar secular resonances, which become particularly dense near the inclinations of the navigation satellite orbits. A clear picture of the physical significance of these resonances is of considerable practical interest for the design of disposal strategies for the four constellations. Here we present analytical and semi-analytical models that accurately reflect the true nature of the resonant interactions, and trace the topological organization of the manifolds on which the chaotic motions take place. We present an atlas of FLI stability maps, showing the extent of the chaotic regions of the phase space, computed through a hierarchy of more realistic, and more complicated, models, and compare the chaotic zones in these charts with the analytical estimation of the width of the chaotic layers from the heuristic Chirikov resonance-overlap criterion. As the semi-major axis of the satellite is receding, we observe a transition from stable Nekhoroshev-like structures at three Earth radii, where regular orbits dominate, to a Chirikov regime where resonances overlap at five Earth radii. From a numerical estimation of the Lyapunov times, we find that many of the inclined, nearly circular orbits of the navigation satellites are strongly chaotic and that their dynamics are unpredictable on decadal timescales.", "keyphrases": ["meo region", "chaos", "moon", "circular orbit", "important effect"]}
{"id": "2107.12465", "title": "Varying fundamental constants principal component analysis: additional hints about the Hubble tension", "abstract": "Varying fundamental constants (VFC) [e.g., the fine-structure constant, \u03b1_ EM] can arise in numerous extended cosmologies. Through their effect on the decoupling of baryons and photons during last scattering and reionisation, these models can be directly constrained using measurements of the cosmic microwave background (CMB) temperature and polarization anisotropies. Previous investigations focused mainly on time-independent changes to the values of fundamental constants. Here we generalize to time-dependent variations. Instead of directly studying various VFC parameterizations, we perform a model-independent principal component analysis (PCA), directly using an eigenmode decomposition of the varying constant during recombination. After developing the formalism, we use Planck 2018 data to obtain new VFC limits, showing that three independent VFC modes can be constrained at present. No indications for significant departures from the standard model are found with Planck data. Cosmic variance limited modes are also compared and simple forecasts for The Simons Observatory are carried out, showing that in the future improvements of the current constraints by a factor of \u2243 3 can be anticipated. Our modes focus solely on VFC at redshifts z\u2265 300. This implies that they do not capture some of the degrees of freedom relating to the reionisation era. This aspect provides important new insights into the possible origin of the Hubble tension, hinting that indeed a combined modification of recombination and reionisation physics could be at work. An extended PCA, covering both recombination and reionisation simultaneously, could shed more light on this question, as we emphasize here.", "keyphrases": ["principal component analysis", "hubble tension", "fine-structure constant"]}
{"id": "1003.2096", "title": "Analytic formulae of the CMB bispectra generated from non-Gaussianity in the tensor and vector perturbations", "abstract": "We present a complete set of formulae for calculating the bispectra of CMB temperature and polarization anisotropies generated from non-Gaussianity in the vector and tensor mode perturbations. In the all-sky analysis it is found that the bispectrum formulae for the tensor and vector-mode non-Gaussianity formally take complicated forms compared to the scalar mode one because the photon transfer functions in the tensor and vector modes depend on the azimuthal angle between the direction of the wave number vector of the photon's perturbation and that of the line of sight. We demonstrate that flat-sky approximations remove this difficulty because this kind of azimuthal angle dependence apparently vanishes in the flat-sky limit. Through the flat-sky analysis, we also find that the vector or tensor bispectrum of B-mode polarization vanishes in the squeezed limit, unless the cosmological parity is violated at the nonlinear level.", "keyphrases": ["cmb bispectra", "non-gaussianity", "tensor"]}
{"id": "1101.0822", "title": "The Matter Bounce Curvaton Scenario", "abstract": "Massless scalar fields originating in a quantum vacuum state acquire a scale-invariant spectrum of fluctuations in a matter-dominated contracting universe. We show that these isocurvature fluctuations transfer to a scale-invariant spectrum of curvature fluctuations during a non-singular bounce phase. This provides a mechanism for enhancing the primordial adiabatic fluctuations and suppressing the ratio of tensor to scalar perturbations. Moreover, this mechanism leads to new sources of non-Gaussianity of curvature perturbations.", "keyphrases": ["scalar field", "matter bounce scenario", "loop quantum cosmology", "holonomy"]}
{"id": "1107.1840", "title": "Conformal invariance of curvature perturbation", "abstract": "We show that in the single component situation all perturbation variables in the comoving gauge are conformally invariant to all perturbation orders. Generally we identify a special time slicing, the uniform-conformal transformation slicing, where all perturbations are again conformally invariant to all perturbation orders. We apply this result to the delta N formalism, and show its conformal invariance.", "keyphrases": ["curvature perturbation", "frame", "non-linear order", "equivalence", "coordinate approach"]}
{"id": "1802.10132", "title": "Occurrence Rates from Direct Imaging Surveys", "abstract": "The occurrence rate of young giant planets from direct imaging surveys is a fundamental tracer of the efficiency with which planets form and migrate at wide orbital distances. These measurements have progressively converged to a value of about 1 averaged over all stellar masses at separations spanning a few tens to a few hundreds of AU. The subtler statistical properties of this population are beginning to emerge with ever-increasing sample sizes: there is tentative evidence that planets on wide orbits are more frequent around stars that possess debris disks; brown dwarf companions exist at comparable (or perhaps slightly higher) rates as their counterparts in the planetary-mass regime; and the substellar companion mass function appears to be smooth and may extend down to the opacity limit for fragmentation. Within a few years, the conclusion of second-generation direct imaging surveys will enable more definitive interpretations with the ultimate goal of identifying the dominant origin of this population and uncovering its relationship to planets at smaller separations.", "keyphrases": ["direct imaging survey", "wide orbit", "separation", "star", "occurrence rate"]}
{"id": "1012.1885", "title": "Smoothed Particle Hydrodynamics and Magnetohydrodynamics", "abstract": "This paper presents an overview and introduction to Smoothed Particle Hydrodynamics and Magnetohydrodynamics in theory and in practice. Firstly, we give a basic grounding in the fundamentals of SPH, showing how the equations of motion and energy can be self-consistently derived from the density estimate. We then show how to interpret these equations using the basic SPH interpolation formulae and highlight the subtle difference in approach between SPH and other particle methods. In doing so, we also critique several `urban myths' regarding SPH, in particular the idea that one can simply increase the `neighbour number' more slowly than the total number of particles in order to obtain convergence. We also discuss the origin of numerical instabilities such as the pairing and tensile instabilities. Finally, we give practical advice on how to resolve three of the main issues with SPMHD: removing the tensile instability, formulating dissipative terms for MHD shocks and enforcing the divergence constraint on the particles, and we give the current status of developments in this area. Accompanying the paper is the first public release of the NDSPMHD SPH code, a 1, 2 and 3 dimensional code designed as a testbed for SPH/SPMHD algorithms that can be used to test many of the ideas and used to run all of the numerical examples contained in the paper.", "keyphrases": ["magnetohydrodynamics", "spmhd", "smoothed particle hydrodynamics"]}
{"id": "1207.2153", "title": "Schwarzschild black holes can wear scalar wigs", "abstract": "We study the evolution of a massive scalar field surrounding a Schwarzschild black hole and find configurations that can survive for arbitrarily long times, provided the black hole or the scalar field mass is small enough. In particular, both ultra-light scalar field dark matter around supermassive black holes and axion-like scalar fields around primordial black holes can survive for cosmological times. Moreover, these results are quite generic, in the sense that fairly arbitrary initial data evolves, at late times, as a combination of those long-lived configurations.", "keyphrases": ["black hole", "scalar field", "long time", "schwarzschild"]}
{"id": "1207.4791", "title": "Galaxy Pairs in the Sloan Digital Sky Survey - V. Tracing changes in star formation rate and metallicity out to separations of 80 kpc", "abstract": "We present a sample of 1899 galaxies with a close companion taken from the SDSS DR7. The galaxy pairs are selected to have velocity differences < 300 km/s, projected separations (rp) < 80 kpc/h, mass ratios between 0.1 and 10, and robust measurements of star formation rates and gas-phase metallicities. We match the galaxies in total stellar mass, redshift, and local density to a set of 10 control galaxies per pair galaxy. For each pair galaxy we can therefore calculate the statistical change in star formation rate (SFR) and metallicity associated with the interaction process. Relative to the control sample, we find that galaxies in pairs show typical SFR enhancements that are, on average, 60 demonstrate more modest SFR enhancements of 30 widest separations in our sample). Galaxies in both major and minor mergers show significant SFR enhancements at all rp, although the strongest starbursts (with SFR enhancements of a factor of 10) appear to be found only in the major mergers. For the first time, we are also able to trace the metallicity changes in galaxy pairs as a function of projected separation. The metallicity is generally diluted in galaxy pairs by 0.02 dex, with an average metallicity decrement of -0.03 dex at the smallest separations. The SFR and metallicity trends with projected separation are interpreted through a comparison with theoretical models. These simulations indicate that the peak in SFR enhancements at small separations is due to systems near the end of the merger process. The extended plateau in SFR enhancements out to at least 80 kpc/h is dominated by galaxies that have made a pericentric passage and are now experiencing triggered star formation on their trajectory towards apogalacticon, or on a subsequent close approach. (Abridged)", "keyphrases": ["star formation rate", "metallicity", "kpc"]}
{"id": "2010.15986", "title": "Data Compression and Covariance Matrix Inspection: Cosmic Shear", "abstract": "Covariance matrices are among the most difficult pieces of end-to-end cosmological analyses. In principle, for two-point functions, each component involves a four-point function, and the resulting covariance often has hundreds of thousands of elements. We investigate various compression mechanisms capable of vastly reducing the size of the covariance matrix in the context of cosmic shear statistics. This helps identify which of its parts are most crucial to parameter estimation. We start with simple compression methods, by isolating and \"removing\" 200 modes associated with the lowest eigenvalues, then those with the lowest signal-to-noise ratio, before moving on to more sophisticated schemes like compression at the tomographic level and, finally, with the Massively Optimized Parameter Estimation and Data compression (MOPED). We find that, while most of these approaches prove useful for a few parameters of interest, like \u03a9_m, the simplest yield a loss of constraining power on the intrinsic alignment (IA) parameters as well as S_8. For the case considered \u2013 cosmic shear from the first year of data from the Dark Energy Survey \u2013 only MOPED was able to replicate the original constraints in the 16-parameter space. Finally, we apply a tolerance test to the elements of the compressed covariance matrix obtained with MOPED and confirm that the IA parameter A_IA is the most susceptible to inaccuracies in the covariance matrix.", "keyphrases": ["covariance matrix", "cosmic shear", "data compression"]}
{"id": "1307.5854", "title": "The environment of bright QSOs at z 6: Star forming galaxies and X-ray emission", "abstract": "We employ cosmological hydrodynamical simulations to investigate models in which the supermassive black holes (BHs) powering luminous z 6 QSOs grow from massive seeds. We simulate at high resolution 18 fields sampling regions with densities ranging from the mean cosmic density all the way to the highest sigma peaks in the Millennium simulation volume. Only in the most massive halos, BHs can grow to masses up to 10^9 Msun by z 6 without invoking super-Eddington accretion. Accretion onto the most massive BHs becomes limited by thermal AGN feedback by z 9-8 with further BH growth proceeding in short Eddington limited bursts. Our modelling suggests that current flux-limited surveys of QSOs at high redshift preferentially detect objects at their peak luminosity and therefore miss a substantial population of QSOs powered by similarly massive BHs but with low accretion rates. To test whether the required host halo masses are consistent with the observed galaxy environment of z 6 QSOs, we produce realistic rest-frame UV images of our simulated galaxies. Without strong stellar feedback, our simulations predict numbers of bright galaxies larger than observed by a factor ten or more. Supernova-driven galactic winds reduce the predicted numbers to a level consistent with observations indicating that stellar feedback was already very efficient at high redshifts. We have further investigated the effect of thermal AGN feedback on the surrounding gas. Our adopted AGN feedback prescription drives mostly energy-driven highly anisotropic outflows with gas speeds of >= 1000 km/s to distances of >= 10 kpc consistent with observations. The spatially extended thermal X-ray emission around bright QSOs powered by these outflows can exceed by large factors the emission expected without AGN feedback and is an important diagnostic of the mechanism whereby AGN feedback energy couples to surrounding gas.", "keyphrases": ["bright qso", "galaxy", "x-ray emission"]}
{"id": "1509.04499", "title": "KWISP: an ultra-sensitive force sensor for the Dark Energy sector", "abstract": "An ultra-sensitive opto-mechanical force sensor has been built and tested in the optics laboratory at INFN Trieste. Its application to experiments in the Dark Energy sector, such as those for Chameleon-type WISPs, is particularly attractive, as it enables a search for their direct coupling to matter. We present here the main characteristics and the absolute force calibration of the KWISP (Kinetic WISP detection) sensor. It is based on a thin Si3N4 micro-membrane placed inside a Fabry-Perot optical cavity. By monitoring the cavity characteristic frequencies it is possible to detect the tiny membrane displacements caused by an applied force. Far from the mechanical resonant frequency of the membrane, the measured force sensitivity is 5.0e-14 N/sqrt(Hz), corresponding to a displacement sensitivity of 2.5e-15 m/sqrt(Hz), while near resonance the sensitivity is 1.5e-14 N/sqrt(Hz), reaching the estimated thermal limit, or, in terms of displacement, 7.5e-16 N/sqrt(Hz). These displacement sensitivities are comparable to those that can be achieved by large interferometric gravitational wave detectors.", "keyphrases": ["force sensor", "dark energy sector", "kwisp"]}
{"id": "1409.3223", "title": "Relativistic Effect in Galaxy Clustering", "abstract": "The general relativistic description of galaxy clustering provides a complete and unified treatment of all the effects in galaxy clustering such as the redshift-space distortion, gravitational lensing, Sachs-Wolfe effects, and their relativistic effects. In particular, the relativistic description resolves the gauge issues in the standard Newtonian description of galaxy clustering by providing the gauge-invariant expression for the observed galaxy number density. The relativistic effect in galaxy clustering is significant on large scales, in which dark energy models or alternative theories of modified gravity deviate from general relativity. In this paper, we review the relativistic effect in galaxy clustering by providing a pedagogical derivation of the relativistic formula and by computing the observed galaxy two-point statistics. The relativistic description of galaxy clustering is an essential tool for testing general relativity and probing the early Universe on large scales in the era of precision cosmology.", "keyphrases": ["galaxy clustering", "universe", "relativistic effect"]}
{"id": "0901.4044", "title": "Signatures of Initial State Modifications on Bispectrum Statistics", "abstract": "Modifications of the initial-state of the inflaton field can induce a departure from Gaussianity and leave a testable imprint on the higher order correlations of the CMB and large scale structures in the Universe. We focus on the bispectrum statistics of the primordial curvature perturbation and its projection on the CMB. For a canonical single-field action the three-point correlator enhancement is localized, maximizing in the collinear limit, corresponding to enfolded or squashed triangles in comoving momentum space. We show that the available local and equilateral template are very insensitive to this localized enhancement and do not generate noteworthy constraints on initial-state modifications. On the other hand, when considering the addition of a dimension 8 higher order derivative term, we find a dominant rapidly oscillating contribution, which had previously been overlooked and whose significantly enhanced amplitude is independent of the triangle under consideration. Nevertheless, the oscillatory nature of (the sign of) the correlation function implies the signal is nearly orthogonal to currently available observational templates, strongly reducing the sensitivity to the enhancement. Constraints on departures from the standard Bunch-Davies vacuum state can be derived, but also depend on the next-to-leading terms. We emphasize that the construction and application of especially adapted templates could lead to CMB bispectrum constraints on modified initial states already competing with those derived from the power spectrum.", "keyphrases": ["initial state", "bispectrum", "curvature perturbation", "non-gaussianity", "bunch-davies state"]}
{"id": "1106.1297", "title": "Imaging the Epoch of Reionization: limitations from foreground confusion and imaging algorithms", "abstract": "Tomography of redshifted 21 cm transition from neutral Hydrogen using Fourier synthesis telescopes is a promising tool to study the Epoch of Reionization (EoR). Limiting the confusion from Galactic and Extragalactic foregrounds is critical to the success of these telescopes. Instrumental response or the Point Spread Function (PSF) of such telescopes is inherently 3 dimensional with frequency mapping to the Line of Sight (LOS) distance. EoR signals will necessarily have to be detected in data where continuum confusion persists; therefore, it is important that the PSF has acceptable frequency structure so that the residual foreground does not confuse the EoR signature. This paper aims to understand the 3 dimensional PSF and foreground contamination in the same framework. We develop a formalism to estimate the foreground contamination along frequency, or equivalently LOS dimension, and establish a relationship between foreground contamination in the image plane and visibility weights on the Fourier plane. We identify two dominant sources of LOS foreground contamination-'PSF contamination' and 'gridding contamination'. We show that 'PSF contamination' is localized in LOS wavenumber space, beyond which there potentially exists an 'EoR window' with negligible foreground contamination where we may focus our efforts to detect EoR. 'PSF contamination' in this window may be substantially reduced by judicious choice of a frequency window function. Gridding and imaging algorithms create additional 'gridding contamination' and we propose a new imaging algorithm using the Chirp Z Transform (CZT) that significantly reduces this contamination. Finally, we demonstrate the analytical relationships and the merit of the new imaging algorithm for the case of imaging with the Murchison Widefield Array (MWA).", "keyphrases": ["epoch", "reionization", "imaging algorithm", "foreground contamination"]}
{"id": "1401.2927", "title": "Fast radio bursts as a cosmic probe?", "abstract": "We discuss the possibility of using fast radio bursts (FRBs), if cosmological, as a viable cosmic probe. We find out that the contribution of the host galaxies to the detected dispersion measures can be inapparent for the FRBs not from galaxy centers or star forming regions. The inhomogeneity of the intergalactic medium (IGM), however, causes significant deviation of the dispersion measure from that predicted in the simplified homogeneous IGM model for individual event. Fortunately, with sufficient FRBs along different sightlines but within a very narrow redshift interval (e.g., \u0394 z \u223c 0.05 or \u0394 z \u223c 0.05(1+z)), the mean from averaging observed dispersion measures does not suffer such a problem and hence may be used as a cosmic probe. We show that in the optimistic case (e.g., tens FRBs in each \u0394 z have been measured; the most distant FRBs were at redshift \u2265 3; the host galaxies and the FRB sources contribute little to the detected dispersion measures) and with all the uncertainties (i.e. the inhomogeneity of the IGM, the contribution and uncertainty of host galaxies as well as the evolution and error of f_ IGM) considered, FRBs could help constrain the equation of state of dark energy.", "keyphrases": ["cosmic probe", "cosmology", "host galaxy", "redshift", "fast radio burst"]}
{"id": "1001.2321", "title": "Analytic Minkowski Functionals of the Cosmic Microwave Background: Second-order Non-Gaussianity with Bispectrum and Trispectrum", "abstract": "Analytic formulas of Minkowski functionals in two-dimensional random fields are derived, including effects of second-order non-Gaussianity in the presence of both the bispectrum and trispectrum. The set of formulas provides a promising method to constrain the primordial non-Gaussianity of the universe by temperature fluctuations in the cosmic microwave background radiation. In a case of local-type non-Gaussianity, the Minkowski functionals are analytically given by powers of quadratic and cubic parameters, f_ NL and g_ NL. Our formulas are not restricted to this particular model, and applicable to a wide class of non-Gaussian models. The analytic formulas are compared to numerical evaluations from non-Gaussian realizations of temperature maps, showing very good agreements.", "keyphrases": ["minkowski functionals", "second-order non-gaussianity", "bispectrum"]}
{"id": "1203.6195", "title": "Current status of turbulent dynamo theory: From large-scale to small-scale dynamos", "abstract": "Several recent advances in turbulent dynamo theory are reviewed. High resolution simulations of small-scale and large-scale dynamo action in periodic domains are compared with each other and contrasted with similar results at low magnetic Prandtl numbers. It is argued that all the different cases show similarities at intermediate length scales. On the other hand, in the presence of helicity of the turbulence, power develops on large scales, which is not present in non-helical small-scale turbulent dynamos. At small length scales, differences occur in connection with the dissipation cutoff scales associated with the respective value of the magnetic Prandtl number. These differences are found to be independent of whether or not there is large-scale dynamo action. However, large-scale dynamos in homogeneous systems are shown to suffer from resistive slow-down even at intermediate length scales. The results from simulations are connected to mean field theory and its applications. Recent work on helicity fluxes to alleviate large-scale dynamo quenching, shear dynamos, nonlocal effects and magnetic structures from strong density stratification are highlighted. Several insights which arise from analytic considerations of small-scale dynamos are discussed.", "keyphrases": ["turbulent dynamo theory", "small-scale dynamos", "astrophysic"]}
{"id": "1605.03204", "title": "Georgia Tech Catalog of Gravitational Waveforms", "abstract": "This paper introduces a catalog of gravitational waveforms from the bank of simulations by the numerical relativity effort at Georgia Tech. Currently, the catalog consists of 452 distinct waveforms from more than 600 binary black hole simulations: 128 of the waveforms are from binaries with black hole spins aligned with the orbital angular momentum, and 324 are from precessing binary black hole systems. The waveforms from binaries with non-spinning black holes have mass-ratios q = m_1/m_2 \u2264 15, and those with precessing, spinning black holes have q \u2264 8. The waveforms expand a moderate number of orbits in the late inspiral, the burst during coalescence, and the ring-down of the final black hole. Examples of waveforms in the catalog matched against the widely used approximate models are presented. In addition, predictions of the mass and spin of the final black hole by phenomenological fits are tested against the results from the simulation bank. The role of the catalog in interpreting the GW150914 event and future massive binary black-hole search in LIGO is discussed. The Georgia Tech catalog is publicly available at einstein.gatech.edu/catalog.", "keyphrases": ["binary", "black hole", "georgia tech catalog", "mass ratio", "relativity code"]}
{"id": "1108.1856", "title": "Testing Unimodular Gravity", "abstract": "We consider models of gravitation that are based on unimodular general coordinate transformations (GCT). These transformations include only those which do not change the determinant of the metric. We treat the determinant as a separate field which transforms as a scalar under unimodular GCT. We consider a class of such theories. In general, these theories do not transform covariantly under the full GCT. We characterize the violation of general coordinate invariance by introducing a new parameter. We show that the theory is consistent with observations for a wide range of this parameter. This parameter may serve as a test for possible violations of general coordinate invariance. We also consider the cosmic evolution within the framework of these models. We show that in general we do not obtain consistent cosmological solutions if we assume the standard cosmological constant or the standard form of non-relativistic matter. We propose a suitable generalization which is consistent with cosmology. We fit the resulting model to the high redshift supernova data. We find that we can obtain a good fit to this data even if include only a single component, either cosmological constant or non-relativistic matter.", "keyphrases": ["unimodular gravity", "gct", "cosmological constant"]}
{"id": "1506.02513", "title": "Antideuteron Sensitivity for the GAPS Experiment", "abstract": "The General Antiparticle Spectrometer (GAPS) is a novel approach for indirect dark matter searches that exploits cosmic antiparticles, especially antideuterons. The GAPS antideuteron measurement utilizes distinctive detection methods using atomic X-rays and charged particles from the decay of exotic atoms as well as the timing and stopping range of the incoming particle, which together provide excellent antideuteron identification. Prior to the future balloon experiment, an accelerator test and a prototype flight were successfully conducted in 2005 and 2012 respectively, in order to verify the GAPS detection concept. This paper describes how the sensitivity of GAPS to antideuterons was estimated using a Monte Carlo simulation along with the atomic cascade model and the Intra-Nuclear Cascade model. The sensitivity for the GAPS antideuteron search obtained using this method is 2.0 \u00d7 10^-6 [m^-2s^-1sr^-1(GeV/n)^-1] for the proposed long duration balloon program (LDB, 35 days \u00d7 3 flights), indicating that GAPS has a strong potential to probe a wide variety of dark matter annihilation and decay models through antideuteron measurements. GAPS is proposed to fly from Antarctica in the austral summer of 2019-2020.", "keyphrases": ["gaps", "general antiparticle spectrometer", "ldb", "antarctica", "antideuteron"]}
{"id": "1011.0899", "title": "Dark and luminous matter in THINGS dwarf galaxies", "abstract": "We present mass models for the dark matter component of seven dwarf galaxies taken from \"The HI Nearby Galaxy Survey\" (THINGS) and compare these with those from numerical Lambda Cold Dark Matter (LCDM) simulations. The THINGS high-resolution data significantly reduce observational uncertainties and thus allow us to derive accurate dark matter distributions in these systems. We here use the bulk velocity fields when deriving the rotation curves of the galaxies. Compared to other types of velocity fields, the bulk velocity field minimizes the effect of small-scale random motions more effectively and traces the underlying kinematics of a galaxy more properly. The \"Spitzer Infrared Nearby Galaxies Survey\" (SINGS) 3.6 micron and ancillary optical data are used for separating the baryons from their total matter content in the galaxies. The sample dwarf galaxies are found to be dark matter dominated over most radii. We find discrepancies between the derived dark matter distributions of the galaxies and those of LCDM simulations, even after corrections for non-circular motions have been applied. The observed solid body-like rotation curves of the galaxies rise too slowly to reflect the cusp-like dark matter distribution in CDM halos. Instead, they are better described by core-like models such as pseudo-isothermal halo models dominated by a central constant-density core. The mean value of the logarithmic inner slopes of the mass density profiles is alpha = -0.29 +- 0.07. They are significantly different from the steep slope of -1.0 inferred from previous dark-matter-only simulations, and are more consistent with shallower slopes found in recent LCDM simulations of dwarf galaxies in which the effects of baryonic feedback processes are included.", "keyphrases": ["thing dwarf galaxy", "dark matter", "central constant-density core"]}
{"id": "1105.1873", "title": "Wide binaries as a critical test of Classical Gravity", "abstract": "Modified gravity scenarios where a change of regime appears at acceleration scales a<a_0 have been proposed. Since for 1 M_\u2299 systems the acceleration drops below a_0 at scales of around 7000 AU, a statistical survey of wide binaries with relative velocities and separations reaching 10^4 AU and beyond should prove useful to the above debate. We apply the proposed test to the best currently available data. Results show a constant upper limit to the relative velocities in wide binaries which is independent of separation for over three orders of magnitude, in analogy with galactic flat rotation curves in the same a<a_0 acceleration regime. Our results are suggestive of a breakdown of Kepler's third law beyond a \u2248 a_0 scales, in accordance with generic predictions of modified gravity theories designed not to require any dark matter at galactic scales and beyond.", "keyphrases": ["law", "dark matter", "galactic scale", "wide binary", "mond-like gravity"]}
{"id": "1801.03587", "title": "Extreme Gravity Tests with Gravitational Waves from Compact Binary Coalescences: (II) Ringdown", "abstract": "The LIGO/Virgo detections of binary black hole mergers marked a watershed moment in astronomy, ushering in the era of precision tests of Kerr dynamics. We review theoretical and experimental challenges that must be overcome to carry out black hole spectroscopy with present and future gravitational wave detectors. Among other topics, we discuss quasinormal mode excitation in binary mergers, astrophysical event rates, tests of black hole dynamics in modified theories of gravity, parameterized \"post-Kerr\" ringdown tests, exotic compact objects, and proposed data analysis methods to improve spectroscopic tests of Kerr dynamics by stacking multiple events.", "keyphrases": ["gravity", "black hole", "astronomy", "late-merger"]}
{"id": "1705.05857", "title": "LensExtractor: A Convolutional Neural Network in Search of Strong Gravitational Lenses", "abstract": "In this work, we present our classification algorithm to identify strong gravitational lenses from wide-area surveys using machine learning convolutional neural network; LensExtractor. We train and test the algorithm using a wide variety of strong gravitational lens configurations from simulations of lensing events. Images are processed through multiple convolutional layers which extract feature maps necessary to assign a lens probability to each image. LensExtractor provides a ranking scheme for all sources which could be used to identify potential gravitational lens candidates significantly reducing the number of images that have to be visually inspected. We further apply our algorithm to the HST/ACS i-band observations of the COSMOS field and present our sample of identified lensing candidates. The developed machine learning algorithm is much more computationally efficient than classical lens identification algorithms and is ideal for discovering such events across wide areas from current and future surveys such as LSST and WFIRST.", "keyphrases": ["convolutional neural network", "strong gravitational lense", "lensextractor"]}
{"id": "1606.03057", "title": "Testing for New Physics: Neutrinos and the Primordial Power Spectrum", "abstract": "We test the sensitivity of neutrino parameter constraints from combinations of CMB and LSS data sets to the assumed form of the primordial power spectrum (PPS) using Bayesian model selection. Significantly, none of the tested combinations, including recent high-precision local measurements of H_0 and cluster abundances, indicate a signal for massive neutrinos or extra relativistic degrees of freedom. For PPS models with a large, but fixed number of degrees of freedom, neutrino parameter constraints do not change significantly if the location of any features in the PPS are allowed to vary, although neutrino constraints are more sensitive to PPS features if they are known a priori to exist at fixed intervals in log k. Although there is no support for a non-standard neutrino sector from constraints on both neutrino mass and relativistic energy density, we see surprisingly strong evidence for features in the PPS when it is constrained with data from Planck 2015, SZ cluster counts, and recent high-precision local measurements of H_0. Conversely combining Planck with matter power spectrum and BAO measurements yields a much weaker constraint. Given that this result is sensitive to the choice of data this tension between SZ cluster counts, Planck and H_0 measurements is likely an indication of unmodeled systematic bias that mimics PPS features, rather than new physics in the PPS or neutrino sector.", "keyphrases": ["new physics", "neutrino", "primordial power spectrum", "dark radiation"]}
{"id": "1903.00154", "title": "Clustering and redshift-space distortions in modified gravity models with massive neutrinos", "abstract": "Modified gravity and massive neutrino cosmologies are two of the most interesting scenarios that have been recently explored to account for possible observational deviations from the concordance \u039b-cold dark matter (\u039bCDM) model. In this context, we investigated the large-scale structure of the Universe by exploiting the simulations that implement, simultaneously, the effects of f(R) gravity and massive neutrinos. To study the possibility of breaking the degeneracy between these two effects, we analysed the redshift-space distortions in the clustering of dark matter haloes at different redshifts. Specifically, we focused on the monopole and quadrupole of the two-point correlation function, both in real and redshift space. The deviations with respect to \u039bCDM model have been quantified in terms of the linear growth rate parameter. We found that redshift-space distortions provide a powerful probe to discriminate between \u039bCDM and modified gravity models, especially at high redshifts (z \u2273 1), even in the presence of massive neutrinos.", "keyphrases": ["redshift-space distortion", "gravity model", "massive neutrino"]}
{"id": "1201.4858", "title": "Millicharged Atomic Dark Matter", "abstract": "We present a simplified version of the atomic dark matter scenario, in which charged dark constituents are bound into atoms analogous to hydrogen by a massless hidden sector U(1) gauge interaction. Previous studies have assumed that interactions between the dark sector and the standard model are mediated by a second, massive Z' gauge boson, but here we consider the case where only a massless gamma' kinetically mixes with the standard model hypercharge and thereby mediates direct detection. This is therefore the simplest atomic dark matter model that has direct interactions with the standard model, arising from the small electric charge for the dark constituents induced by the kinetic mixing. We map out the parameter space that is consistent with cosmological constraints and direct searches, assuming that some unspecified mechanism creates the asymmetry that gives the right abundance, since the dark matter cannot be a thermal relic in this scenario. In the special case where the dark \"electron\" and \"proton\" are degenerate in mass, inelastic hyperfine transitions can explain the CoGeNT excess events. In the more general case, elastic transitions dominate, and can be close to current direct detection limits over a wide range of masses.", "keyphrases": ["dark matter", "dark sector", "thermal relic", "photon"]}
{"id": "2005.05326", "title": "Orbital precession in the distant solar system; further constraining the Planet Nine hypothesis with numerical simulations", "abstract": "The longitudes of perihelia and orbital poles of the solar system's dozen or so most remote detected objects are clustered in a manner inconsistent with that of a random sample of uniformly distributed orbits. While small number statistics and observational biases may explain these features, the statistical significance of the clustering has led to the recent development of the \"Planet Nine hypothesis.\" In the proposed scenario, orbits in the distant solar system are shepherded via secular perturbations from an undetected massive planet on an eccentric orbit. However, the precession of perihelia and nodes in the outer Kuiper Belt and inner Oort Cloud are also affected by the the giant planets, passing stars, and the galactic tide. We perform a large suite of numerical simulations designed to study the orbital alignment of Extreme Trans-Neptunian Objects (ETNOs) and Inner Oort Cloud Objects (IOCOs). In our various integrations that include Planet Nine, we consistently find that >60 and IOCOs that are detectable after 4 Gyr are also anti-aligned in perihelia with the distant massive perturber. However, when we randomly select 17 objects from this sample of remaining orbits, there is significant scatter in the degree of longitude of perihelion and orbital pole clustering that might be observed. Furthermore, we argue that, in the absence of Planet Nine, 17 randomly drawn orbits should still exhibit some clustering even if the underlying distribution is uniform. Thus, we find that still more ETNO and IOCO detections are required to confidently infer the presence of Planet Nine.", "keyphrases": ["precession", "distant solar system", "planet"]}
{"id": "1604.00141", "title": "Ultra slow-roll G-inflation", "abstract": "The conventional slow-roll approximation is broken in the so-called \"ultra slow-roll\" models of inflation, for which the inflaton potential is exactly (or extremely) flat. The interesting nature of (canonical) ultra slow-roll inflation is that the curvature perturbation grows on superhorizon scales, but has a scale-invariant power spectrum. We study the ultra slow-roll inflationary dynamics in the presence of non-canonical kinetic terms of the scalar field, namely ultra slow-roll G-inflation. We compute the evolution of the curvature perturbation and show that the primordial power spectrum follows a broken power law with an oscillation feature. It is demonstrated that this could explain the lack of large-scale power in the cosmic microwave background temperature anisotropies. We also point out that the violation of the null energy condition is prohibited in ultra slow-roll G-inflation and hence a blue tensor tilt is impossible as long as inflation is driven by the potential. This statement is, however, not true if the energy density is dominated by the kinetic energy of the scalar field.", "keyphrases": ["scalar field", "ultra slow-roll g-inflation", "era"]}
{"id": "1310.4107", "title": "Supermassive black holes with high accretion rates in active galactic nuclei: I. First results from a new reverberation mapping campaign", "abstract": "We report first results from a large project to measure black hole (BH) mass in high accretion rate active galactic nuclei (AGNs). Such objects may be different from other AGNs in being powered by slim accretion disks and showing saturated accretion luminosities, but both are not yet fully understood. The results are part of a large reverberation mapping (RM) campaign using the 2.4-m Shangri-La telescope at the Yunnan Observatory in China. The goals are to investigate the gas distribution near the BH and the properties of the central accretion disks, to measure BH mass and Eddington ratios, and to test the feasibility of using such objects as a new type of cosmological candles. The paper presents results for three objects, Mrk 335, Mrk 142 and IRAS F12397+3333 with H\u03b2 time lags relative to the 5100\u00c5 continuum of 10.6^+1.7_-2.9, 6.4^+0.8_-2.2 and 11.4^+2.9_-1.9 days, respectively. The corresponding BH masses are (8.3_-3.2^+2.6)\u00d7 10^6M_\u2299, (3.4_-1.2^+0.5)\u00d7 10^6M_\u2299 and (7.5_-4.1^+4.3)\u00d7 10^6M_\u2299, and the lower limits on the Eddington ratios 0.6, 2.3, and 4.6 for the minimal radiative efficiency of 0.038. Mrk 142 and IRAS F12397+333 (extinction corrected) clearly deviate from the currently known relation between H\u03b2 lag and continuum luminosity. The three Eddington ratios are beyond the values expected in thin accretion disks and two of them are the largest measured so far among objects with RM-based BH masses. We briefly discuss implications for slim disks, BH growth and cosmology.", "keyphrases": ["black hole", "high accretion rate", "reverberation mapping campaign"]}
{"id": "1309.1321", "title": "Asymmetric galaxy correlation functions", "abstract": "We study the two-point cross-correlation function between two populations of galaxies: for instance a bright population and a faint population. We show that this cross-correlation is asymmetric under the exchange of the line-of-sight coordinate of the galaxies, i.e. that the correlation is different if the bright galaxy is in front of, or behind, the faint galaxy. We give an intuitive, quasi-Newtonian derivation of all the effects that contribute to such an asymmetry in large-scale structure: gravitational redshift, Doppler shift, lensing, light-cone, evolution and Alcock-Paczynski effects - interestingly, the gravitational redshift term is exactly canceled by some of the others, assuming geodesic motion. Most of these effects are captured by previous calculations of general relativistic corrections to the observed galaxy density fluctuation; the asymmetry arises from terms that are suppressed by the ratio H/k - H is the Hubble constant and k is the wavenumber - which are more readily observable than the terms suppressed by (H/k)^2. Some of the contributions to the asymmetry, however, arise from terms that are generally considered 'Newtonian' - the lensing and evolution - and thus represent a contaminant in the search for general relativistic corrections. We propose methods to disentangle these different contributions. A simple method reduces the contamination to a level of < 10 relation to recent work on measuring gravitational redshifts by stacking clusters.", "keyphrases": ["galaxy", "correlation function", "correction", "relativistic contribution"]}
{"id": "1505.01281", "title": "Hydromagnetics of advective accretion flows around black holes: Removal of angular momentum by large scale magnetic stresses", "abstract": "We show that the removal of angular momentum is possible in the presence of large scale magnetic stresses in geometrically thick, advective, sub-Keplerian accretion flows around black holes in steady-state, in the complete absence of alpha-viscosity. The efficiency of such an angular momentum transfer could be equivalent to that of alpha-viscosity with alpha=0.01-0.08. Nevertheless, required field is well below its equipartition value, leading to a magnetically stable disk flow. This is essentially important in order to describe the hard spectral state of the sources, when the flow is non/sub-Keplerian. We show in our simpler 1.5-dimensional, vertically averaged disk model that larger the vertical-gradient of azimuthal component of magnetic field, stronger the rate of angular momentum transfer is, which in turn may lead to a faster rate of outflowing matter. Finding efficient angular momentum transfer, in black hole disks, via magnetic stresses alone is very interesting, when the generic origin of alpha-viscosity is still being explored.", "keyphrases": ["accretion", "black hole", "magnetic stress"]}
{"id": "1304.4250", "title": "A scaling-relation for disc galaxies: circular-velocity gradient versus central surface brightness", "abstract": "For disc galaxies, a close relation exists between the distribution of light and the shape of the rotation curve. We quantify this relation by measuring the inner circular-velocity gradient d_RV(0) for spiral and irregular galaxies with high-quality rotation curves. We find that d_RV(0) correlates with the central surface brightness mu_0 over more than two orders of magnitude in d_RV(0) and four orders of magnitudes in mu_0. This is a scaling-relation for disc galaxies. It shows that the central stellar density of a galaxy closely relates to the inner shape of the potential well, also for low-luminosity and low-surface-brightness galaxies that are expected to be dominated by dark matter.", "keyphrases": ["disc galaxy", "circular-velocity gradient", "central surface brightness", "dark matter"]}
{"id": "1504.05993", "title": "Imprints of Massive Primordial Fields on Large-Scale Structure", "abstract": "Attention has focussed recently on models of inflation that involve a second or more fields with a mass near the inflationary Hubble parameter H, as may occur in supersymmetric theories if the supersymmetry-breaking scale is not far from H. Quasi-single-field (QsF) inflation is a relatively simple family of phenomenological models that serve as a proxy for theories with additional fields with masses m\u223c H. Since QsF inflation involves fields in addition to the inflaton, the consistency conditions (ccs) between correlations that arise in single-clock inflation are not necessarily satisfied. As a result, correlation functions in the squeezed limit may be larger than in single-field inflation. Scalar non-Gaussianities mediated by the massive isocurvature field in QsF have been shown to be potentially observable. These are especially interesting since they would convey information about the mass of the isocurvature field. Here we consider non-Gaussian correlators involving tensor modes and their observational signatures. A physical correlation between a (long-wavelength) tensor mode and two scalar modes (tss), for instance, may give rise to local departures from statistical isotropy or, in other words, a non-trivial four-point function. The presence of the tensor mode may moreover be inferred geometrically from the shape dependence of the four-point function. We compute tss and stt (one soft curvature mode and two hard tensors) bispectra in QsF inflation, identifying the conditions necessary for these to \"violate\" the ccs. We find that while ccs are violated by stt correlations, they are preserved by the tss in the minimal QsF model. Our study of primordial correlators which include gravitons in seeking imprints of additional fields with masses m\u223c H during inflation can be seen as complementary to the recent \"cosmological collider physics\" proposal.", "keyphrases": ["cosmological collider physics", "quasi-single field inflation", "particle physics"]}
{"id": "1111.3290", "title": "Extragalactic propagation of ultrahigh energy cosmic-rays", "abstract": "In this paper we review the extragalactic propagation of ultrahigh energy cosmic-rays (UHECR). We present the different energy loss processes of protons and nuclei, and their expected influence on energy evolution of the UHECR spectrum and composition. We discuss the possible implications of the recent composition analyses provided by the Pierre Auger Observatory. The influence of extragalactic magnetic fields and possible departures from the rectilinear case are also mentioned as well as the production of secondary cosmogenic neutrinos and photons and the constraints their observation would imply for the UHECRs origin. Finally, we conclude by briefly discussing the relevance of a multi messenger approach for solving the mystery of UHECRs.", "keyphrases": ["ultrahigh energy cosmic-ray", "neutrino", "extragalactic propagation"]}
{"id": "1903.03620", "title": "Dust settling against hydrodynamic turbulence in protoplanetary discs", "abstract": "Enhancing the local dust-to-gas ratio in protoplanetary discs is a necessary first step to planetesimal formation. In laminar discs, dust settling is an efficient mechanism to raise the dust-to-gas ratio at the disc midplane. However, turbulence, if present, can stir and lift dust particles, which ultimately hinders planetesimal formation. In this work, we study dust settling in protoplanetary discs with hydrodynamic turbulence sustained by the vertical shear instability. We perform axisymmetric numerical simulations to investigate the effect of turbulence, particle size, and solid abundance or metallicity on dust settling. We highlight the positive role of drag forces exerted onto the gas by the dust for settling to overcome the vertical shear instability. In typical disc models we find particles with a Stokes number \u223c 10^-3 can sediment to \u2272 10% of the gas scale-height, provided that \u03a3_d/\u03a3_g\u2273 0.02-0.05, where \u03a3_d,g are the surface densities in dust and gas, respectively. This coincides with the metallicity condition for small particles to undergo clumping via the streaming instability. Super-solar metallicities, at least locally, are thus required for a self-consistent picture of planetesimal formation. Our results also imply that dust rings observed in protoplanetary discs should have smaller scale-heights than dust gaps, provided that the metallicity contrast between rings and gaps exceed the corresponding contrast in gas density.", "keyphrases": ["hydrodynamic turbulence", "protoplanetary disc", "dust"]}
{"id": "0906.1197", "title": "CMB Constraints on WIMP Annihilation: Energy Absorption During the Recombination Epoch", "abstract": "We compute in detail the rate at which energy injected by dark matter annihilation heats and ionizes the photon-baryon plasma at z 1000, and provide accurate fitting functions over the relevant redshift range for a broad array of annihilation channels and DM masses. The resulting perturbations to the ionization history can be constrained by measurements of the CMB temperature and polarization angular power spectra. We show that models which fit recently measured excesses in 10-1000 GeV electron and positron cosmic rays are already close to the 95 Planck satellite will be capable of ruling out a wide range of DM explanations for these excesses. In models of dark matter with Sommerfeld-enhanced annihilation, where sigma v rises with decreasing WIMP velocity until some saturation point, the WMAP5 constraints imply that the enhancement must be close to saturation in the neighborhood of the Earth.", "keyphrases": ["recombination epoch", "dark matter", "photon-baryon plasma", "annihilation cross section"]}
{"id": "1406.3697", "title": "On the realizability of relativistic acoustic geometry under a generalized perturbation scheme for axisymmetric matter flow onto black holes", "abstract": "We propose a novel linear perturbation scheme to study the stability properties of the stationary transonic integral solutions for axisymmetric matter flow around astrophysical black holes for the Schwarzschild as well as for rotating Rindler space time. We discuss the emergence of the relativistic acoustic geometry as a consequence of such stability analysis. Our work thus makes a crucial connection between two apparently non-overlapping fields of research - the accretion astrophysics and the analogue gravity phenomena.", "keyphrases": ["relativistic acoustic geometry", "axisymmetric matter", "black hole"]}
{"id": "1311.5524", "title": "Equal-time Consistency Relations in the Large-Scale Structure of the Universe", "abstract": "We discuss the consistency relations involving the soft limit of the (n + 1)-correlator functions of dark matter at equal times and their consequences for the halo model.", "keyphrases": ["consistency relation", "large-scale structure", "equal time", "standard perturbation theory"]}
{"id": "1007.1034", "title": "Scattering of Dark Matter and Dark Energy", "abstract": "We demonstrate how the two dominant constituents of the Universe, dark energy and dark matter, could possess a large scattering cross-section without considerably impacting observations. Unlike models involving energy exchange between the two fluids, the background cosmology remains unaltered, leaving fewer observational signatures. Following a brief review of the scattering cross-sections between cosmologically significant particles, we explore the implications of an elastic interaction between dark matter and dark energy. The growth of large scale structure is suppressed, yet this effect is found to be weak due to the persistently low dark energy density. Thus we conclude that the dark matter-dark energy cross section may exceed the Thomson cross-section by several orders of magnitude.", "keyphrases": ["dark matter", "dark energy", "thomson cross-section"]}
{"id": "1807.05530", "title": "Cross-correlations between scalar perturbations and magnetic fields in bouncing universes", "abstract": "Bouncing scenarios offer an alternative to the inflationary paradigm for the generation of perturbations in the early universe. Recently, there has been a surge in interest in examining the issue of primordial magnetogenesis in the context of bouncing universes. As in the case of inflation, the conformal invariance of the electromagnetic action needs to be broken in bouncing scenarios in order to generate primordial magnetic fields which correspond to observed strengths today. The non-minimal coupling, which typically depends on a scalar field that possibly drives the homogeneous background, leads to a cross-correlation at the level of the three-point function between the perturbation in the scalar field and the magnetic fields. This has been studied in some detail in the context of inflation and, specifically, it has been established that the three-point function satisfies the so-called consistency relation in the squeezed limit. In this work, we study the cross-correlation between the magnetic fields and the perturbation in an auxiliary scalar field in a certain class of bouncing scenarios. We consider couplings that lead to scale invariant spectra of the magnetic field and evaluate the corresponding cross-correlation between the magnetic field and the perturbation in the scalar field. We find that, when compared to de Sitter inflation, the dimensionless non-Gaussianity parameter that characterizes the amplitude of the cross-correlations proves to be considerably larger in bouncing scenarios. We also show that the aforementioned consistency condition governing the cross-correlation is violated in the bouncing models. We discuss the implications of our results.", "keyphrases": ["magnetic field", "universe", "cross-correlation"]}
{"id": "1703.05815", "title": "Assessing the Habitability of the TRAPPIST-1 System Using a 3D Climate Model", "abstract": "The TRAPPIST-1 system provides an extraordinary opportunity to study multiple terrestrial extrasolar planets and their atmospheres. Here we use the National Center for Atmospheric Research Community Atmosphere Model version 4 to study the possible climate and habitability of the planets in the TRAPPIST-1 system. We assume ocean-covered worlds, with atmospheres comprised of N2, CO2, and H2O, and with orbital and geophysical properties defined from observation. Model results indicate that the inner three planets (b, c, and d) presently reside interior to the inner edge of the traditional liquid water habitable zone. Thus if water ever existed on the inner planets, they would have undergone a runaway greenhouse and lost their water to space, leaving them dry today. Conversely the outer 3 planets (f, g, and h) fall beyond the maximum CO2 greenhouse outer edge of the habitable zone. Model results indicate that the outer planets cannot be warmed despite as much as 30 bar CO2 atmospheres, instead entering a snowball state. The middle planet (e) represents the best chance for a presently habitable ocean-covered world in the TRAPPIST-1 system. Planet e can maintain at least some habitable surface area with 0 - 2 bar CO2, depending on the background N2 content. Near present day Earth surface temperatures can be maintained for an ocean-covered planet e with either 1 bar N2 and 0.4 bar CO2, or a 1.3 bar pure CO2 atmosphere.", "keyphrases": ["habitability", "trappist-1 system", "climate model"]}
{"id": "1610.00713", "title": "The candidate cluster and protocluster catalog (CCPC) II: Spectroscopically identified structures spanning 2 < z < 6.6", "abstract": "The Candidate Cluster and Protocluster Catalog (CCPC) is a list of objects at redshifts z > 2 composed of galaxies with spectroscopically confirmed redshifts that are coincident on the sky and in redshift. These protoclusters are identified by searching for groups in volumes corresponding to the expected size of the most massive protoclusters at these redshifts. In CCPC1 we identified 43 candidate protoclusters among 14,000 galaxies between 2.74 < z < 3.71. Here we expand our search to more than 40,000 galaxies with spectroscopic redshifts z > 2.00, resulting in an additional 173 candidate structures. The most significant of these are 36 protoclusters with overdensities \u03b4 > 7. We also identify three large proto-supercluster candidates containing multiple protoclusters at z = 2.3, 3.5 and z = 6.56. Eight candidates with N > 10 or more galaxies are found at redshifts z > 4.0. The last system in the catalog is the most distant spectroscopic protocluster candidate known to date at z = 6.56.", "keyphrases": ["candidate cluster", "protocluster catalog", "ccpc"]}
{"id": "0904.1741", "title": "Entropy of quasiblack holes", "abstract": "We trace the origin of the black hole entropy S replacing a black hole by a quasiblack hole. Let the boundary of a static body approach its own gravitational radius, in such a way that a quasihorizon forms. We show that if the body is thermal with the temperature taking the Hawking value at the quasihorizon limit, it follows, in the nonextremal case, from the first law of thermodynamics that the entropy approaches the Bekenstein-Hawking value S=A/4. In this setup, the key role is played by the surface stresses on the quasihorizon and one finds that the entropy comes from the quasihorizon surface. Any distribution of matter inside the surface leads to the same universal value for the entropy in the quasihorizon limit. This can be of some help in the understanding of black hole entropy. Other similarities between black holes and quasiblack holes, such as the mass formulas for both objects had been found previously. We also discuss the entropy for extremal quasiblack holes, a more subtle issue.", "keyphrases": ["quasiblack hole", "black hole", "entropy"]}
{"id": "0905.1073", "title": "The Cold Spot as a Large Void: Lensing Effect on CMB Two and Three Point Correlation Functions", "abstract": "The \"Cold Spot\" in the CMB sky could be due to the presence of an anomalous huge spherical underdense region - a \"Void\" - of a few hundreds Mpc/h radius. Such a structure would have an impact on the CMB two-point (power spectrum) and three-point (bispectrum) correlation functions not only at low-l, but also at high-l through Lensing, which is a unique signature of a Void. Modeling such an underdensity with an LTB metric, we show that for the power spectrum the effect should be visible already in the WMAP data only if the Void radius is at least L \u22731 Gpc/h, while it will be visible by the Planck satellite if L \u2273500 Mpc/h. We also speculate that this could be linked to the high-l detection of an hemispherical power asymmetry in the sky. Moreover, there should be non-zero correlations in the non-diagonal two-point function. For the bispectrum, the effect becomes important for squeezed triangles with two very high l's: this signal can be detected by Planck if the Void radius is at least L \u2273300 Mpc/h, while higher resolution experiments should be able to probe the entire parameter space. We have also estimated the contamination of the primordial non-Gaussianity f_NL due to this signal, which turns out to be negligible.", "keyphrases": ["cold spot", "lensing", "underdensity", "non-diagonal two-point function", "cmb power spectrum"]}
{"id": "1409.0310", "title": "Constraining the Cardoso-Pani-Rico metric with future observations of SgrA^*", "abstract": "SgrA^*, the supermassive black hole candidate at the center of our Galaxy, seems to be one of the most promising object to test the Kerr black hole hypothesis with near future observations. In a few years, it will hopefully be possible to measure a number of relativistic effects around this body, and the combination of different observations can be used to constrain possible deviations from the Kerr solution. In this paper, I discuss the combination of three promising techniques in the framework of the Cardoso-Pani-Rico parametrization: the observation of blobs of plasma orbiting near the innermost stable circular orbit, the detection of the black hole shadow, and timing observations of a radio pulsar in a compact orbit. The observations of blobs of plasma and of the shadow can probe the strong gravitational field around SgrA^*, while the radio pulsar would be sensitive to the weak field region at larger radii. In the case of a fast-rotating object, the combination of the three measurements could provide strong constraints on the actual nature of SgrA^*. For a non-rotating or slow-rotating object, the bounds would be weak.", "keyphrases": ["future observation", "degeneracy", "different measurement"]}
{"id": "1301.2856", "title": "Searching for Cosmic Strings in New Observational Windows", "abstract": "Cosmic strings are predicted in many models beyond the Standard Model of particle physics. In models which admit strings, a network of strings will inevitably be formed in a phase transition in the early universe and will persist to the present time. Strings leave behind distinctive features in cosmology. Searching for these signatures in new observational windows provides a way to constrain particle physics at the high energy scale and is thus complementary to searches for new physics at the low energy end, for example at the LHC. Specifically, I will discuss signatures of cosmic strings in cosmic microwave background polarization maps and in 21cm redshift surveys.", "keyphrases": ["cosmic string", "string", "observational window", "particle physics"]}
{"id": "2102.04596", "title": "Directional recoil detection", "abstract": "Searches for dark matter-induced recoils have made impressive advances in the last few years. Yet the field is confronted by several outstanding problems. First, the inevitable background of solar neutrinos will soon inhibit the conclusive identification of many dark matter models. Second, and more fundamentally, current experiments have no practical way of confirming a detected signal's galactic origin. The concept of directional detection addresses both of these issues while offering opportunities to study novel dark matter and neutrino-related physics. The concept remains experimentally challenging, but gas time projection chambers are an increasingly attractive option, and when properly configured, would allow directional measurements of both nuclear and electron recoils. In this review, we reassess the required detector performance and survey relevant technologies. Fortuitously, the highly-segmented detectors required to achieve good directionality also enable several fundamental and applied physics measurements. We comment on near-term challenges and how the field could be advanced.", "keyphrases": ["recoil energy", "detection experiment", "underground detector", "isotropic background", "experimental strategy"]}
{"id": "1610.02369", "title": "Vertical stability of circular orbits in relativistic razor-thin disks", "abstract": "During the last few decades, there has been a growing interest in exact solutions of Einstein equations describing razor-thin disks. Despite the progress in the area, the analytical study of geodesic motion crossing the disk plane in these systems is not yet so developed. In the present work, we propose a definite vertical stability criterion for circular equatorial timelike geodesics in static, axially symmetric thin disks, possibly surrounded by other structures preserving axial symmetry. It turns out that the strong energy condition for the disk stress-energy content is sufficient for vertical stability of these orbits. Moreover, adiabatic invariance of the vertical action variable gives us an approximate third integral of motion for oblique orbits which deviate slightly from the equatorial plane. Such new approximate third integral certainly points to a better understanding of the analytical properties of these orbits. The results presented here, derived for static spacetimes, may be a starting point to study the motion around rotating, stationary razor-thin disks. Our results also allow us to conjecture that the strong energy condition should be sufficient to assure transversal stability of periodic orbits for any singular timelike hypersurface, provided it is invariant under the geodesic flow.", "keyphrases": ["orbit", "razor-thin disk", "vertical stability"]}
{"id": "1001.1897", "title": "Slow-roll inflation with a Gauss-Bonnet correction", "abstract": "We consider slow-roll inflation for a single scalar field with an arbitrary potential and an arbitrary nonminimal coupling to the Gauss-Bonnet term. By introducing a combined hierarchy of Hubble and Gauss-Bonnet flow functions, we analytically derive the power spectra of scalar and tensor perturbations. The standard consistency relation between the tensor-to-scalar ratio and the spectral index of tensor perturbations is broken. We apply this formalism to a specific model with a monomial potential and an inverse monomial Gauss-Bonnet coupling and constrain it by the 7-year Wilkinson Microwave Anisotropy Probe data. The Gauss-Bonnet term with a positive (or negative) coupling may lead to a reduction (or enhancement) of the tensor-to-scalar ratio and hence may revive the quartic potential ruled out by recent cosmological data.", "keyphrases": ["tensor-to-scalar ratio", "einstein-gauss-bonnet theory", "slow-roll inflation", "universe"]}
{"id": "1904.00343", "title": "Bow shocks, bow waves, and dust waves. III. Diagnostics", "abstract": "Stellar bow shocks, bow waves, and dust waves all result from the action of a star's wind and radiation pressure on a stream of dusty plasma that flows past it. The dust in these bows emits prominently at mid-infrared wavelengths in the range 8 to 60 micron. We propose a novel diagnostic method, the tau-eta diagram, for analyzing these bows, which is based on comparing the fractions of stellar radiative energy and stellar radiative momentum that is trapped by the bow shell. This diagram allows the discrimination of wind-supported bow shocks, radiation-supported bow waves, and dust waves in which grains decouple from the gas. For the wind-supported bow shocks, it allows the stellar wind mass-loss rate to be determined. We critically compare our method with a previous method that has been proposed for determining wind mass-loss rates from bow shock observations. This comparison points to ways in which both methods can be improved and suggests a downward revision by a factor of two with respect to previously reported mass-loss rates. From a sample of 23 mid-infrared bow-shaped sources, we identify at least 4 strong candidates for radiation-supported bow waves, which need to be confirmed by more detailed studies, but no strong candidates for dust waves.", "keyphrases": ["dust wave", "star", "mass-loss rate", "bow shock"]}
{"id": "1609.04372", "title": "QUBIC Technical Design Report", "abstract": "QUBIC is an instrument aiming at measuring the B mode polarisation anisotropies at medium scales angular scales (30-200 multipoles). The search for the primordial CMB B-mode polarization signal is challenging, because of many difficulties: smallness of the expected signal, instrumental systematics that could possibly induce polarization leakage from the large E signal into B, brighter than anticipated polarized foregrounds (dust) reducing to zero the initial hope of finding sky regions clean enough to have a direct primordial B-modes observation. The QUBIC instrument is designed to address all aspects of this challenge with a novel kind of instrument, a Bolometric Interferometer, combining the background-limited sensitivity of Transition-Edge-Sensors and the control of systematics allowed by the observation of interference fringe patterns, while operating at two frequencies to disentangle polarized foregrounds from primordial B mode polarization. Its characteristics are described in details in this Technological Design Report.", "keyphrases": ["instrument", "control", "qubic"]}
{"id": "1210.0553", "title": "Baryogenesis from Mixing of Lepton Doublets", "abstract": "It is shown that the mixing of lepton doublets of the Standard Model can yield sizeable contributions to the lepton asymmetry, that is generated through the decays of right-handed neutrinos at finite temperature in the early Universe. When calculating the flavour-mixing correlations, we account for the effects of Yukawa as well as of gauge interactions. We compare the freeze-out asymmetry from lepton-doublet mixing to the standard contributions from the mixing and direct decays of right-handed neutrinos. The asymmetry from lepton mixing is considerably large when the mass ratio between the right-handed neutrinos is of order of a few, while it becomes Maxwell-suppressed for larger hierarchies. For an intermediate range between the case of degenerate right-handed neutrinos (resonant Leptogenesis) and the hierarchical case, lepton mixing can yield the main contribution to the lepton asymmetry.", "keyphrases": ["lepton doublet", "right-handed neutrino", "leptogenesis", "baryogenesis"]}
{"id": "1812.04023", "title": "Observatory science with eXTP", "abstract": "In this White Paper we present the potential of the enhanced X-ray Timing and Polarimetry (eXTP) mission for studies related to Observatory Science targets. These include flaring stars, supernova remnants, accreting white dwarfs, low and high mass X-ray binaries, radio quiet and radio loud active galactic nuclei, tidal disruption events, and gamma-ray bursts. eXTP will be excellently suited to study one common aspect of these objects: their often transient nature. Developed by an international Consortium led by the Institute of High Energy Physics of the Chinese Academy of Science, the eXTP mission is expected to be launched in the mid 2020s.", "keyphrases": ["extp", "mission", "observatory science"]}
{"id": "1112.0303", "title": "A Class of Effective Field Theory Models of Cosmic Acceleration", "abstract": "We explore a class of effective field theory models of cosmic acceleration involving a metric and a single scalar field. These models can be obtained by starting with a set of ultralight pseudo-Nambu-Goldstone bosons whose couplings to matter satisfy the weak equivalence principle, assuming that one boson is lighter than all the others, and integrating out the heavier fields. The result is a quintessence model with matter coupling, together with a series of correction terms in the action in a covariant derivative expansion, with specific scalings for the coefficients. After eliminating higher derivative terms and exploiting the field redefinition freedom, we show that the resulting theory contains nine independent free functions of the scalar field when truncated at four derivatives. This is in contrast to the four free functions found in similar theories of single-field inflation, where matter is not present. We discuss several different representations of the theory that can be obtained using the field redefinition freedom. For perturbations to the quintessence field today on subhorizon lengthscales larger than the Compton wavelength of the heavy fields, the theory is weakly coupled and natural in the sense of t'Hooft. The theory admits a regime where the perturbations become modestly nonlinear, but very strong nonlinearities lie outside its domain of validity.", "keyphrases": ["effective field theory", "cosmic acceleration", "glpv theory"]}
{"id": "1204.1271", "title": "Filamentary Diffusion of Cosmic Rays on Small Scales", "abstract": "We investigate the diffusion of cosmic rays (CR) close to their sources. Propagating individual CRs in purely isotropic turbulent magnetic fields with maximal scale of spatial variations Lmax, we find that CRs diffuse anisotropically at distances r < Lmax from their sources. As a result, the CR densities around the sources are strongly irregular and show filamentary structures. We determine the transition time t* to standard diffusion as t* 10^4 yr (Lmax/150 pc)^b (E/PeV)^(-g) (Brms/4 muG)^g, with b 2 and g = 0.25-0.5 for a turbulent field with Kolmogorov power spectrum. We calculate the photon emission due to CR interactions with gas and the resulting irregular source images.", "keyphrases": ["diffusion", "cosmic ray", "turbulent magnetic field", "filamentary structure", "random field"]}
{"id": "2102.10100", "title": "Hubble tension vs two flows", "abstract": "The Hubble tension is shown to be solvable, without any free parameter, conceptually and quantitatively, within the approach of modified weak-field General Relativity involving the cosmological constant \u039b. That approach enables one to describe in a unified picture both the dynamics of dark matter containing galaxies and the accelerated expansion of the Universe, thus defining a local Hubble constant of a local flow and the global one. The data on the dark matter content of peculiar galaxy samples are shown to be compatible to that unified picture. Future more refined surveys of galaxy distribution, hierarchical dynamics and flows within the vicinity of the Local group and the Virgo supercluster can be decisive in revealing the possible common nature of the dark sector.", "keyphrases": ["flow", "universe", "hubble tension"]}
{"id": "2008.10825", "title": "Helical magnetic fields from Riemann coupling", "abstract": "We study the inflationary generation of helical magnetic fields from the Riemann coupling with the electromagnetic field. Most models in the literature introduce non-minimal coupling to the electromagnetic fields with a scalar field, hence, breaking the conformal invariance. In this work, we show that non-minimal coupling to the Riemann tensor generates sufficient primordial helical magnetic fields at all observable scales. We explicitly show that one of the helical states decay while the other helical mode increases, leading to a net non-zero helicity. Our model has three key features: (i) the helical power-spectrum has a slight red-tilt for slow-roll inflation consistent with bounds from observations and free from backreaction problem, (ii) the energy density of the helical fields generated is at least one order of magnitude larger than the scalar-field coupled models, and (iii) unlike the scalar field coupled models, the generated helical fields are insensitive to the reheating dynamics. We show that our model generates the magnetic field of strength 0.01 PicoGauss over Mpc scale.", "keyphrases": ["non-minimal coupling", "conformal invariance", "helical magnetic field"]}
{"id": "2012.09620", "title": "Approximate Analytical Solution to the Zonal Harmonics Problem Using Koopman Operator Theory", "abstract": "This work introduces the use of the Koopman operator theory to generate approximate analytical solutions for the zonal harmonics problem of a satellite orbiting a non-spherical celestial body. Particularly, the solution proposed directly provides the osculating evolution of the system under the effects of any order of the zonal harmonics, and can be automated to obtain any level of accuracy in the approximated solution. Moreover, this paper defines a modified set of orbital elements that can be applied to any kind of orbit and that allows the Koopman operator to have a fast convergence. In that regard, several examples of application are included, showing that the proposed methodology can be used in any kind of orbit, including circular, elliptic, parabolic and hyperbolic orbits.", "keyphrases": ["zonal harmonics problem", "koopman operator theory", "approximate analytical solution", "other perturbation method"]}
{"id": "1502.07361", "title": "WS1: one more new Galactic bona fide luminous blue variable", "abstract": "In this Letter, we report the results of spectroscopic and photometric monitoring of the candidate luminous blue variable (LBV) WS1, which was discovered in 2011 through the detection of a mid-infrared circular shell and follow-up optical spectroscopy of its central star. Our monitoring showed that WS1 brightened in the B, V and I bands by more than 1 mag during the last three years, while its spectrum revealed dramatic changes during the same time period, indicating that the star became much cooler. The light curve of WS1 demonstrates that the brightness of this star has reached maximum in 2013 December and then starts to decline. These findings unambiguously proved the LBV nature of WS1 and added one more member to the class of Galactic bona fide LBVs, bringing their number to sixteen (an updated census of these objects is provided).", "keyphrases": ["galactic bona", "luminous blue variable", "central star"]}
{"id": "1107.2155", "title": "The XENON100 Dark Matter Experiment", "abstract": "The XENON100 dark matter experiment uses liquid xenon (LXe) in a time projection chamber (TPC) to search for Xe nuclear recoils resulting from the scattering of dark matter Weakly Interacting Massive Particles (WIMPs). In this paper we present a detailed description of the detector design and present performance results, as established during the commissioning phase and during the first science runs. The active target of XENON100 contains 62 kg of LXe, surrounded by an LXe veto of 99 kg, both instrumented with photomultiplier tubes (PMTs) operating inside the liquid or in Xe gas. The LXe target and veto are contained in a low-radioactivity stainless steel vessel, embedded in a passive radiation shield. The experiment is installed underground at the Laboratori Nazionali del Gran Sasso (LNGS), Italy and has recently published results from a 100 live-days dark matter search. The ultimate design goal of XENON100 is to achieve a spin-independent WIMP-nucleon scattering cross section sensitivity of \u03c3= 2x10^-45 cm^2 for a 100 GeV/c^2 WIMP.", "keyphrases": ["xenon100", "recoil", "dark matter search"]}
{"id": "1410.0252", "title": "On the scalar consistency relation away from slow roll", "abstract": "As is well known, the non-Gaussianity parameter f__ NL, which is often used to characterize the amplitude of the scalar bi-spectrum, can be expressed completely in terms of the scalar spectral index n_ s in the squeezed limit, a relation that is referred to as the consistency condition. This relation, while it is largely discussed in the context of slow roll inflation, is actually expected to hold in any single field model of inflation, irrespective of the dynamics of the underlying model, provided inflation occurs on the attractor at late times. In this work, we explicitly examine the validity of the consistency relation, analytically as well as numerically, away from slow roll. Analytically, we first arrive at the relation in the simple case of power law inflation. We also consider the non-trivial example of the Starobinsky model involving a linear potential with a sudden change in its slope (which leads to a brief period of fast roll), and establish the condition completely analytically. We then numerically examine the validity of the consistency relation in three inflationary models that lead to the following features in the scalar power spectrum due to departures from slow roll: (i) a sharp cut off at large scales, (ii) a burst of oscillations over an intermediate range of scales, and (iii) small, but repeated, modulations extending over a wide range of scales. It is important to note that it is exactly such spectra that have been found to lead to an improved fit to the CMB data, when compared to the more standard power law primordial spectra, by the Planck team. We evaluate the scalar bi-spectrum for an arbitrary triangular configuration of the wavenumbers in these inflationary models and explicitly illustrate that, in the squeezed limit, the consistency condition is indeed satisfied even in situations consisting of strong deviations from slow roll.", "keyphrases": ["consistency relation", "slow roll", "single field model", "conformal symmetry", "three-point function"]}
{"id": "1312.5815", "title": "Cosmological Magnetogenesis From Extra-dimensional Gauss Bonnet Gravity", "abstract": "Generation of primordial magnetic fields during inflation typically requires the breaking of conformal invariance of the Electromagnetic action. In this paper this has been achieved naturally in a higher dimensional cosmological model with a Gauss-Bonnet term in the action. The evolution of the scale factor of the extra dimension (whose dynamics is influenced by the Gauss-Bonnet term) acts as the cause for the breaking of conformal invariance. Different cases have been investigated, each of which is characterized by the number of higher dimensions, the value of the Gauss-Bonnet parameter, and the cosmological constant. Many of the scenarios considered are highly constrained by the requirements that the cosmic evolution is stable, that the normal dimensions expand and that there is no back reaction due to growing electric fields. However there do exist scenarios which satisfy the above requirements and are well suited for magnetogenesis. In particular, a scenario where the number of extra dimensions D=4 and the cosmological constant is non-zero, turns out to be best suited for generating primordial magnetic fields. It is shown that for these values of parameters, a scale invariant magnetic field of the order of 10^-10-10^-9 G can be produced. Even in these most favorable scenarios, the higher dimensional space expands during inflation at the same rate as the normal dimension. Hence if a mechanism could freeze the evolution of the higher dimension, this seems to be a viable mechanism to produce acceptable primordial magnetic fields.", "keyphrases": ["magnetogenesis", "primordial magnetic field", "conformal invariance", "inflationary magnetogenesis"]}
{"id": "1706.04226", "title": "On primordial black holes from an inflection point", "abstract": "Recently, it has been claimed that inflationary models with an inflection point in the scalar potential can produce a large resonance in the power spectrum of curvature perturbation. In this paper however we show that the previous analyses are incorrect. The reason is twofold: firstly, the inflaton is over-shot from a stage of standard inflation and so deviates from the slow-roll attractor before reaching the inflection. Secondly, on the (or close to) the inflection point, the ultra-slow-roll trajectory supersede the slow-roll one and thus, the slow-roll approximations used in the literature cannot be used. We then reconsider the model and provide a recipe for how to produce nevertheless a large peak in the matter power spectrum via fine-tuning of parameters.", "keyphrases": ["primordial black hole", "single field inflation", "quasi-inflection point"]}
{"id": "1905.08825", "title": "Extragalactic Background Light: Inventory of light throughout the cosmic history", "abstract": "The Extragalactic Background Light (EBL) stands for the mean surface brightness of the sky as we would see it from a representative vantage point in the intergalactic space outside of our Milky Way Galaxy. Averaged over the whole 4 pi solid angle it represents the collective light from all luminous matter radiated throughout the cosmic history. Part of the EBL is resolved into galaxies that, with the increasing detecting power of giant telescopes and sensitive detectors, are seen to deeper and deeper limiting magnitudes. This resolved part is now known to contribute a substantial or even the major part of the EBL. There still remains, however, the challenge of finding out to what extent galaxies too faint or too diffuse to be discerned individually, individual stars or emission by gas outside the galaxies, or more speculatively, some hitherto unknown light sources such as decaying elementary particles are accounting for the remaining EBL. We review the recent progress that has been made in the measurement of EBL. The current photometric results suggest that there is, beyond the resolved galaxies, an EBL component that cannot be explained by diffuse galaxy halos or intergalactic stars.", "keyphrases": ["cosmic history", "galaxy", "extragalactic background light"]}
{"id": "1203.2065", "title": "Thermonuclear burst oscillations", "abstract": "Burst oscillations, a phenomenon observed in a significant fraction of Type I (thermonuclear) X-ray bursts, involve the development of highly asymmetric brightness patches in the burning surface layers of accreting neutron stars. Intrinsically interesting as nuclear phenomena, they are also important as probes of dense matter physics and the strong gravity, high magnetic field environment of the neutron star surface. Burst oscillation frequency is also used to measure stellar spin, and doubles the sample of rapidly rotating (above 10 Hz) accreting neutron stars with known spins. Although the mechanism remains mysterious, burst oscillation models must take into account thermonuclear flame spread, nuclear processes, rapid rotation, and the dynamical role of the magnetic field. This review provides a comprehensive summary of the observational properties of burst oscillations, an assessment of the status of the theoretical models that are being developed to explain them, and an overview of how they can be used to constrain neutron star properties such as spin, mass and radius.", "keyphrases": ["oscillation", "neutron star", "thermonuclear"]}
{"id": "2008.03879", "title": "The Shape of the Black Hole Photon Ring: A Precise Test of Strong-Field General Relativity", "abstract": "We propose a new test of strong-field general relativity (GR) based on the universal interferometric signature of the black hole photon ring. The photon ring is a narrow ring-shaped feature, predicted by GR but not yet observed, that appears on images of sources near a black hole. It is caused by extreme bending of light within a few Schwarzschild radii of the event horizon and provides a direct probe of the unstable bound photon orbits of the Kerr geometry. We show that the precise shape of the observable photon ring is remarkably insensitive to the astronomical source profile and can therefore be used as a stringent test of GR. We forecast that a tailored space-based interferometry experiment targeting M87* could test the Kerr nature of the source to the sub-sub-percent level.", "keyphrases": ["black hole", "hole photon ring", "strong-field general relativity"]}
{"id": "1407.6014", "title": "Einstein-aether theory with a Maxwell field: General formalism", "abstract": "We extend the Einstein-aether theory to include the Maxwell field in a nontrivial manner by taking into account its interaction with the time-like unit vector field characterizing the aether. We also include a generic matter term. We present a model with a Lagrangian that includes cross-terms linear and quadratic in the Maxwell tensor, linear and quadratic in the covariant derivative of the aether velocity four-vector, linear in its second covariant derivative and in the Riemann tensor. We decompose these terms with respect to the irreducible parts of the covariant derivative of the aether velocity, namely, the acceleration four-vector, the shear and vorticity tensors, and the expansion scalar. Furthermore, we discuss the influence of an aether non-uniform motion on the polarization and magnetization of the matter in such an aether environment, as well as on its dielectric and magnetic properties. The total self-consistent system of equations for the electromagnetic and the gravitational fields, and the dynamic equations for the unit vector aether field are obtained. Possible applications of this system are discussed. Based on the principles of effective field theories, we display in an appendix all the terms up to fourth order in derivative operators that can be considered in a Lagrangian that includes the metric, the electromagnetic and the aether fields.", "keyphrases": ["maxwell tensor", "einstein-aether theory", "-gauge invariance"]}
{"id": "1502.04166", "title": "The extragalactic background light, the Hubble constant, and anomalies: conclusions from 20 years of TeV gamma-ray observations", "abstract": "Ground-based observatories have been collecting 0.2 - 20 TeV gamma rays from blazars for about twenty years. These gamma rays can experience absorption along the line of sight due to interactions with the extragalactic background light (EBL). In this paper, we show that the gamma-ray optical depth can be reduced to the convolution product of an EBL kernel with the EBL intensity, assuming a particular form for the EBL evolution. We extract the absorption signal from the most extensive set of TeV spectra from blazars collected so far and unveil a broad-band EBL spectrum from mid-ultraviolet to far infrared. This spectrum is in good agreement with the accumulated emission of galaxies, constraining unresolved populations of sources. We propose a data-driven estimate of the Hubble constant based on the comparison of local and gamma-ray measurements of the EBL. After setting stringent upper-limits on the redshift of four TeV blazars, we investigate the 106 gamma-ray spectra in our sample and find no significant evidence for anomalies. The intrinsic TeV spectra are not harder than their GeV counterpart, and no spectral upturn is visible at the highest optical depths. Finally, we investigate a modification of the pair-creation threshold due to Lorentz invariance violation. A mild excess prevents us from ruling out an effect at the Planck energy, and we constrain for the first time the energy scale of the modification to values larger than sixty percent of the Planck energy.", "keyphrases": ["extragalactic background light", "anomaly", "gamma-ray observation", "galaxy"]}
{"id": "1906.11823", "title": "Anisotropic halo assembly bias and redshift-space distortions", "abstract": "We study the effect of large-scale tidal fields on internal halo properties using a set of N-body simulations. We measure significant cross-correlations between large-scale tidal fields and several non-scalar halo properties: shapes, velocity dispersion, and angular momentum. Selection effects that couple to these non-scalar halo properties can produce anisotropic clustering even in real-space. We investigate the size of this effect and show that it can produce a non-zero quadrupole similar in size to the one generated by linear redshift-space distortions (RSD). Finally, we investigate the clustering properties of halos identified in redshift-space and find enormous deviations from the standard linear RSD model, again caused by anisotropic assembly bias. These effects could contaminate the values of cosmological parameters inferred from the observed redshift-space clustering of galaxies, groups, or 21cm emission from atomic hydrogen, if their selection depends on properties affected by halo assembly bias. We briefly discuss ways in which this effect can be measured in existing and future large-scale structure surveys.", "keyphrases": ["halo assembly bias", "redshift-space distortion", "tidal field"]}
{"id": "1308.1397", "title": "Inadequacies of the Fisher Information Matrix in gravitational-wave parameter estimation", "abstract": "The Fisher Information Matrix (FIM) has been the standard approximation to the accuracy of parameter estimation on gravitational-wave signals from merging compact binaries due to its ease-of-use and rapid computation time. While the theoretical failings of this method, such as the signal-to-noise ratio (SNR) limit on the validity of the lowest-order expansion and the difficulty of using non-Gaussian priors, are well understood, the practical effectiveness compared to a real parameter estimation technique (e.g. Markov-chain Monte Carlo) remains an open question. We present a direct comparison between the FIM error estimates and the Bayesian probability density functions produced by the parameter estimation code lalinference_mcmc. In addition to the low-SNR issues usually considered, we find that the FIM can greatly overestimate the uncertainty in parameter estimation achievable by the MCMC. This was found to be a systematic effect for systems composed of binary black holes, with the disagreement increasing with total mass. In some cases, the MCMC search returned standard deviations on the marginalized posteriors that were smaller by several orders of magnitude than the FIM estimates. We conclude that the predictions of the FIM do not represent the capabilities of real gravitational-wave parameter estimation.", "keyphrases": ["fisher information matrix", "gravitational-wave parameter estimation", "fim"]}
{"id": "1311.3422", "title": "Measurement of Neutrino Masses from Relative Velocities", "abstract": "We present a new technique to measure neutrino masses using their flow field relative to dark matter. Present day streaming motions of neutrinos relative to dark matter and baryons are several hundred km/s, comparable with their thermal velocity dispersion. This results in a unique dipole anisotropic distortion of the matter-neutrino cross power spectrum, which is observable through the dipole distortion in the cross correlation of different galaxy populations. Such a dipole vanishes if not for this relative velocity and so it is a clean signature for neutrino mass. We estimate the size of this effect and find that current and future galaxy surveys may be sensitive to these signature distortions.", "keyphrases": ["neutrino", "relative velocity", "baryon"]}
{"id": "2110.07539", "title": "BOSS Correlation Function Analysis from the Effective Field Theory of Large-Scale Structure", "abstract": "After calibrating the predictions of the Effective Field Theory of Large-Scale Structure against several sets of simulations, as well as implementing a new method to assert the scale cut of the theory without the use of any simulation, we analyze the Full Shape of the BOSS Correlation Function. Imposing a prior from Big Bang Nucleosynthesis on the baryon density, we are able to measure all the parameters in \u039bCDM + massive neutrinos in normal hierarchy, except for the total neutrino mass, which is just bounded. When combining the BOSS Full Shape with the Baryon Acoustic Oscillation measurements from BOSS, 6DF/MGS and eBOSS, we determine the present day Hubble constant, H_0, the present matter fraction, \u03a9_m, the amplitude of the primordial power spectrum, A_s, and the tilt of the primordial power spectrum, n_s, to 1.4 %, 4.5 %, 23.5% and 7.6% precision, respectively, at 68 %-confidence level, finding H_0=68.19 \u00b1 0.99 (km/s)/Mpc, \u03a9_m=0.309\u00b1 0.014, ln (10^10A_s )=3.12^+0.21_-0.26 and n_s=0.963^+0.062_-0.085, and we bound the total neutrino mass to 0.87 eV at 95 %-confidence level. These constraints are fully consistent with Planck results and the ones obtained from BOSS power spectrum analysis. In particular, we find no tension in H_0 or \u03c3_8 with Planck measurements, finding consistency at 1.2\u03c3 and 0.6\u03c3, respectively.", "keyphrases": ["effective field theory", "large-scale structure", "boss"]}
{"id": "1704.07065", "title": "Wormhole Shadows", "abstract": "We propose a new method of detecting Ellis wormholes by use of the images of wormholes surrounded by optically thin dust. First, we derive steady solutions of dust and more general medium surrounding the wormhole by solving relativistic Euler equations. We find two types of dust solutions: one is a static solution with arbitrary density profile, and the other is a solution of dust which passes into the wormhole and escapes into the other side with constant velocity. Next, solving null geodesic equations and radiation transfer equations, we investigate the images of the wormhole surrounded by dust for the above steady solutions. Because the wormhole spacetime possesses unstable circular orbits of photons, a bright ring appears in the image, just as in Schwarzschild spacetime. This indicates that the appearance of a bright ring solely confirms neither a black hole nor a wormhole. However, we find that the intensity contrast between the inside and the outside of the ring are quite different. Therefore, we could tell the difference between an Ellis wormhole and a black hole with high-resolution very-long-baseline-interferometry observations in the near future.", "keyphrases": ["shadow", "thin dust", "wormhole"]}
{"id": "1307.6382", "title": "Multi-scale gravity and cosmology", "abstract": "The gravitational dynamics and cosmological implications of three classes of recently introduced multi-scale spacetimes (with, respectively, ordinary, weighted and q-derivatives) are discussed. These spacetimes are non-Riemannian: the metric structure is accompanied by an independent measure-differential structure with the characteristics of a multi-fractal, namely, different dimensionality at different scales and, at ultra-short distances, a discrete symmetry known as discrete scale invariance. Under this minimal paradigm, five general features arise: (a) the big-bang singularity can be replaced by a finite bounce, (b) the cosmological constant problem is reinterpreted, since accelerating phases can be mimicked by the change of geometry with the time scale, without invoking a slowly rolling scalar field, (c) the discreteness of geometry at Planckian scales can leave an observable imprint of logarithmic oscillations in cosmological spectra and (d) give rise to an alternative mechanism to inflation or (e) to a fully analytic model of cyclic mild inflation, where near scale invariance of the perturbation spectrum can be produced without strong acceleration. Various properties of the models and exact dynamical solutions are discussed. In particular, the multi-scale geometry with weighted derivatives is shown to be a Weyl integrable spacetime.", "keyphrases": ["cosmology", "multi-scale spacetime", "derivative"]}
{"id": "1412.5722", "title": "Hyperon Puzzle of Neutron Stars with Skyrme Force Models", "abstract": "We consider the so called hyperon puzzle of neutron star (NS). We employ Skyrme force models for the description of in-medium nucleon-nucleon, nucleon-Lambda hyperon (N\u039b), and Lambda-Lambda (\u039b\u039b) interactions. A phenomenological finite-range force for the \u039b\u039b interaction is considered as well. Equation of state (EoS) of NS matter is obtained in the framework of density functional theory, and Tolman-Oppenheimer-Volkoff equations are solved to obtain the mass-radius relations of NSs. It has been generally known that the existence of hyperons in the NS matter is not well supported by the recent discovery of large-mass NSs (M \u2243 2 M_\u2299) since hyperons make the EoS softer than the one without them. For the selected interaction models, N\u039b interactions reduce the maximum mass of NS by about 30 %, while \u039b\u039b interactions can give about 10 % enhancement. Consequently, we find that some Skyrme force models predict the maximum mass of NS consistent with the observation of 2 M_\u2299 NSs, and at the same time satisfy observationally constrained mass-radius relations.", "keyphrases": ["neutron star", "skyrme force model", "hyperon puzzle"]}
{"id": "2002.06656", "title": "Enhanced spectrum of primordial perturbations, galaxy formation and small scale structure", "abstract": "The standard structure formation scenario is successful on linear scales. Several apparent problems affect it however at galactic scales, such as the small scale problems at low redshift and more recent issues involving early massive galaxy and black hole formation. As these problems arise where complex baryonic physics becomes important, the associated unknowns are often assumed to be behind the problems. But the same scales are also those where the primordial spectrum is relatively unconstrained, and there are several ways in which it can be modified. We focus on that arising from effects possibly associated with the crossing of high energy cutoff scale by fluctuation modes during inflation. Elementary arguments show that adiabatic evolution cannot modify the near scale invariance, we thus discuss a simple model for the contrary extreme of sudden transition. Numerical calculations and simple arguments suggest that its predictions, for parameters considered here, are more generic than may be expected, with significant modifications requiring a rapid transition. We examine the implications of such a scenario, in this simplest form of sudden jump, on the matter power spectrum and halo mass function in light of the limitations imposed by particle production. We show that enhancement and oscillation in the power spectrum on currently nonlinear scales can potentially simultaneously alleviate both the apparent problem of early structure formation and, somewhat counterintuitively, problems at low redshift such as the apparent dearth of dwarf galaxies. We discuss consequences that can observationally constrain the scenario and its parameters, including an inflationary Hubble scale \u2272 10^-8 M_ Pl, while touching on the possibility of simultaneous modification of power on the largest scales.", "keyphrases": ["primordial perturbation", "galaxy formation", "baryonic physics"]}
{"id": "1907.06243", "title": "Vector Coherent Oscillation Dark Matter", "abstract": "We construct a model of hidden massive vector boson dark matter as a homogeneous coherent oscillation in the entire universe without any dangerous instability. We make use of a particular form of the vector boson coupling to a scalar field through the gauge kinetic function. This scenario may be distinguished from other dark matter models through the observation of statistical anisotropy in the dark matter isocurvature perturbation.", "keyphrases": ["dark matter", "vector boson", "dark photon"]}
{"id": "1704.04501", "title": "Exploring Cosmic Origins with CORE: B-mode Component Separation", "abstract": "We demonstrate that, for the baseline design of the CORE satellite mission, the polarized foregrounds can be controlled at the level required to allow the detection of the primordial cosmic microwave background (CMB) B-mode polarization with the desired accuracy at both reionization and recombination scales, for tensor-to-scalar ratio values of r\u2273 5\u00d7 10^-3. We consider detailed sky simulations based on state-of-the-art CMB observations that consist of CMB polarization with \u03c4=0.055 and tensor-to-scalar values ranging from r=10^-2 to 10^-3, Galactic synchrotron, and thermal dust polarization with variable spectral indices over the sky, polarized anomalous microwave emission, polarized infrared and radio sources, and gravitational lensing effects. Using both parametric and blind approaches, we perform full component separation and likelihood analysis of the simulations, allowing us to quantify both uncertainties and biases on the reconstructed primordial B-modes. Under the assumption of perfect control of lensing effects, CORE would measure an unbiased estimate of r=(5 \u00b1 0.4)\u00d7 10^-3 after foreground cleaning. In the presence of both gravitational lensing effects and astrophysical foregrounds, the significance of the detection is lowered, with CORE achieving a 4\u03c3-measurement of r=5\u00d7 10^-3 after foreground cleaning and 60 ratios (r=10^-3) the overall uncertainty on r is dominated by foreground residuals, not by the 40 residual contribution of unprocessed polarized point-sources can be the dominant foreground contamination to primordial B-modes at this r level, even on relatively large angular scales, \u2113\u223c 50. Finally, we report two sources of potential bias for the detection of the primordial B-modes.[abridged]", "keyphrases": ["b-modes", "component separation", "angular scale"]}
{"id": "1609.05197", "title": "Parametric Resonance in the Early Universe - A Fitting Analysis", "abstract": "Particle production via parametric resonance in the early Universe, is a nonperturbative, non-linear and out-of-equilibrium phenomenon. Although it is a well studied topic, whenever a new scenario exhibits parametric resonance, a full re-analysis is normally required. To avoid this tedious task, many works present often only a simplified linear treatment of the problem. In order to surpass this circumstance in the future, we provide a fitting analysis of parametric resonance through all its relevant stages: initial linear growth, non-linear evolution, and relaxation towards equilibrium. Using lattice simulations in an expanding grid in 3 + 1 dimensions, we parametrize the dynamics outcome scanning over the relevant ingredients: role of the oscillatory field, particle coupling strength, initial conditions, and background expansion rate. We emphasize the inaccuracy of the linear calculation of the decay time of the oscillatory field, and propose a more appropriate definition of this scale based on the subsequent non-linear dynamics. We provide simple fits to the relevant time scales and particle energy fractions at each stage. Our fits can be applied to post-inflationary preheating scenarios, where the oscillatory field is the inflaton, or to spectator-field scenarios, where the oscillatory field can be e.g. a curvaton, or the Standard Model Higgs.", "keyphrases": ["early universe", "fitting analysis", "parametric resonance", "scalar field"]}
{"id": "2107.00467", "title": "Small scale effects in the observable power spectrum at large angular scales", "abstract": "In this paper we show how effects from small scales can enter the angular-redshift power spectrum C_\u2113(z,z'). In particular, we show that spectroscopic surveys with high redshift resolution are already affected on large angular scales, i.e. at low multipoles, by features from small scales. When considering the angular power spectrum with spectroscopic redshift resolution, it is therefore important to account for non-linearities relevant on small scales, even at low multipoles. This may also motivate the use of the correlation function in relatively wide redshift bins, which is not affected by non-linearities on large scales, instead of the angular power spectrum. The extent to which small-scale effects become visible on large scales, which is more relevant for bin auto-correlations than for cross-correlations, is quantified in detail.", "keyphrases": ["power spectrum", "large angular scale", "spectroscopic survey"]}
{"id": "1705.05526", "title": "Tidal Disruption of a White Dwarf by a Black Hole: The Diversity of Nucleosynthesis, Explosion Energy, and the Fate of Debris Streams", "abstract": "We run a suite of hydrodynamics simulations of tidal disruption events (TDEs) of a white dwarf (WD) by a black hole (BH) with a wide range of WD/BH masses and orbital parameters. We implement nuclear reactions to study nucleosynthesis and its dynamical effect through release of nuclear energy. The released nuclear energy effectively increases the fraction of unbound ejecta. This effect is weaker for a heavy WD with 1.2 M_\u2299, because the specific orbital energy distribution of the debris is predominantly determined by the tidal force, rather than by the explosive reactions. The elemental yield of a TDE depends critically on the initial composition of a WD, while the BH mass and the orbital parameters also affect the total amount of synthesized elements. Tanikawa et al. (2017) find that simulations of WD-BH TDEs with low resolution suffer from spurious heating and inaccurate nuclear reaction results. In order to examine the validity of our calculations, we compare the amounts of the synthesized elements with the upper limits of them derived in a way where we can avoid uncertainties due to low resolution. The results are largely consistent, and thus support our findings. We find particular TDEs where early self-intersection of a WD occurs during the first pericentre passage, promoting formation of an accretion disc. We expect that relativistic jets and/or winds would form in these cases because accretion rates would be super-Eddington. The WD-BH TDEs result in a variety of events depending on the WD/BH mass and pericentre radius of the orbit.", "keyphrases": ["white dwarf", "black hole", "nucleosynthesis"]}
{"id": "1808.02002", "title": "A rigorous EFT-based forward model for large-scale structure", "abstract": "Conventional approaches to cosmology inference from galaxy redshift surveys are based on n-point functions, which are under rigorous perturbative control on sufficiently large scales. Here, we present an alternative approach, which employs a likelihood at the level of the galaxy density field. By integrating out small-scale modes based on effective-field theory arguments, we prove that this likelihood is under perturbative control if certain specific conditions are met. We further show that the information captured by this likelihood is equivalent to the combination of the next-to-leading order galaxy power spectrum, leading-order bispectrum, and BAO reconstruction. Combined with MCMC sampling and MAP optimization techniques, our results allow for fully Bayesian cosmology inference from large-scale structure that is under perturbative control. We illustrate this via a first demonstration of unbiased cosmology inference from nonlinear large-scale structure using this likelihood. In particular, we show unbiased estimates of the power spectrum normalization \u03c3_8 from a catalog of simulated dark matter halos, where nonlinear information is crucial in breaking the b_1 - \u03c3_8 degeneracy.", "keyphrases": ["forward model", "large-scale structure", "likelihood", "eft", "progress"]}
{"id": "1305.2701", "title": "Anisotropy of Cosmic Acceleration", "abstract": "In this paper, we study the anisotropy of cosmic acceleration by dividing the Union2 Type Ia supernova dataset into 12 subsets according to their positions in Galactic coordinate system. In each region, we derive the deceleration parameter q_0 as the diagnostic to quantify the anisotropy level in the corresponding direction, and construct q_0 anisotropic maps by combining these q_0 values. In addition to the monopole component, we find the significant dipole effect in the q_0-maps with the amplitude A_1=0.466^+0.255_-0.205, which deviates from zero at more than 2-\u03c3 level. The direction of the best-fit dipole is (\u03b8=108.8^\u2218, \u03d5=187.0^\u2218) in Galactic system. Interesting enough, we find the direction of this dipole is nearly perpendicular to the CMB kinematic dipole, and the angle between them is 95.7^\u2218. The perpendicular relation is anomalous at the 1-in-10 level.", "keyphrases": ["cosmic acceleration", "anisotropy", "snia"]}
{"id": "1003.3281", "title": "Cosmic expansion and growth histories in Galileon scalar-tensor models of dark energy", "abstract": "We study models of late-time cosmic acceleration in terms of scalar-tensor theories generalized to include a certain class of non-linear derivative interaction of the scalar field. The non-linear effect suppress the scalar-mediated force at short distances to pass solar-system tests of gravity. It is found that the expansion history until today is almost indistinguishable from that of the \u039bCDM model or some (phantom) dark energy models, but the fate of the universe depends clearly on the model parameter. The growth index of matter density perturbations is computed to show that its past asymptotic value is given by 9/16, while the value today is as small as 0.4.", "keyphrases": ["matter density perturbation", "galileon gravity model", "general relativity", "cosmology"]}
{"id": "1509.03835", "title": "First-order Cosmological Perturbations Engendered by Point-like Masses", "abstract": "In the framework of the concordance cosmological model the first-order scalar and vector perturbations of the homogeneous background are derived in the weak gravitational field limit without any supplementary approximations. The sources of these perturbations (inhomogeneities) are presented in the discrete form of a system of separate point-like gravitating masses. The found expressions for the metric corrections are valid at all (sub-horizon and super-horizon) scales and converge at all points except at locations of the sources. The average values of these metric corrections are zero (thus, first-order backreaction effects are absent). Both the Minkowski background limit and the Newtonian cosmological approximation are reached under certain well-defined conditions. An important feature of the velocity-independent part of the scalar perturbation is revealed: up to an additive constant this part represents a sum of Yukawa potentials produced by inhomogeneities with the same finite time-dependent Yukawa interaction range. The suggested connection between this range and the homogeneity scale is briefly discussed along with other possible physical implications.", "keyphrases": ["point-like masse", "gravitational field limit", "universe"]}
{"id": "1105.1194", "title": "Mapping Growth and Gravity with Robust Redshift Space Distortions", "abstract": "Redshift space distortions caused by galaxy peculiar velocities provide a window onto the growth rate of large scale structure and a method for testing general relativity. We investigate through a comparison of N-body simulations to various extensions of perturbation theory beyond the linear regime, the robustness of cosmological parameter extraction, including the gravitational growth index, \u03b3. We find that the Kaiser formula and some perturbation theory approaches bias the growth rate by 1-sigma or more relative to the fiducial at scales as large as k > 0.07 h/Mpc. This bias propagates to estimates of the gravitational growth index as well as \u03a9_m and the equation of state parameter and presents a significant challenge to modelling redshift space distortions. We also determine an accurate fitting function for a combination of line of sight damping and higher order angular dependence that allows robust modelling of the redshift space power spectrum to substantially higher k.", "keyphrases": ["redshift space distortion", "galaxy", "growth rate"]}
{"id": "1102.1977", "title": "The Cosmic Core-collapse Supernova Rate does not match the Massive-Star Formation Rate", "abstract": "We identify a \"supernova rate problem\": the measured cosmic core-collapse supernova rate is a factor of 2 smaller (with significance 2 sigma) than that predicted from the measured cosmic massive-star formation rate. The comparison is critical for topics from galaxy evolution and enrichment to the abundance of neutron stars and black holes. We systematically explore possible resolutions. The accuracy and precision of the star formation rate data and conversion to the supernova rate are well supported, and proposed changes would have far-reaching consequences. The dominant effect is likely that many supernovae are missed because they are either optically dim (low-luminosity) or dark, whether intrinsically or due to obscuration. We investigate supernovae too dim to have been discovered in cosmic surveys by a detailed study of all supernova discoveries in the local volume. If possible supernova impostors are included, then dim supernovae are common enough by fraction to solve the supernova rate problem. If they are not included, then the rate of dark core collapses is likely substantial. Other alternatives are that there are surprising changes in our understanding of star formation or supernova rates, including that supernovae form differently in small galaxies than in normal galaxies. These possibilities can be distinguished by upcoming supernova surveys, star formation measurements, searches for disappearing massive stars, and measurements of supernova neutrinos.", "keyphrases": ["supernovae", "massive-star formation rate", "galaxy"]}
{"id": "1211.1005", "title": "Superdense galaxies and the mass-size relation at low redshift", "abstract": "We search for massive and compact galaxies (superdense galaxies, hereafter SDGs) at z=0.03-0.11 in the Padova-Millennium Galaxy and Group Catalogue, a spectroscopically complete sample representative of the local Universe general field population. We find that compact galaxies with radii and mass densities comparable to high-z massive and passive galaxies represent 4.4 galaxies with stellar masses above 3 X 10^10 M_sun, yielding a number density of 4.3 X 10^-4 h^3 Mpc^-3. Most of them are S0s (70 red and have intermediate-to-old stellar populations, with a median luminosity-weighted age of 5.4 Gyr and a median mass-weighted age of 9.2 Gyr. Their velocity dispersions and dynamical masses are consistent with the small radii and high stellar mass estimates. Comparing with the WINGS sample of cluster galaxies at similar redshifts, the fraction of superdense galaxies is three times smaller in the field than in clusters, and cluster SDGs are on average 4 Gyr older than field SDGs. We confirm the existence of a universal trend of smaller radii for older luminosity-weighted ages at fixed galaxy mass. On top of the well known dependence of stellar age on galaxy mass, the luminosity-weighted age of galaxies depends on galaxy compactness at fixed mass, and, for a fixed mass and radius, on environment. This effect needs to be taken into account in order not to overestimate the evolution of galaxy sizes from high- to low-z. Our results and hierarchical simulations suggest that a significant fraction of the massive compact galaxies at high-z have evolved into compact galaxies in galaxy clusters today. When stellar age and environmental effects are taken into account, the average amount of size evolution of individual galaxies between high- and low-z is mild, a factor 1.6. (abridged)", "keyphrases": ["redshift", "local universe", "superdense galaxy"]}
{"id": "1303.5597", "title": "The initial mass function modeled by a left truncated beta distribution", "abstract": "The initial mass function (IMF) for the stars is usually fitted by three straight lines, which means seven parameters. The presence of brown dwarfs (BD) increases to four the straight lines and to nine the parameters. Another common fitting function is the lognormal distribution, which is characterized by two parameters. This paper is devoted to demonstrating the advantage of introducing a left truncated beta probability density function, which is characterized by four parameters. The constant of normalization, the mean, the mode and the distribution function are calculated for the left truncated beta distribution. The normal-beta (NB) distribution which results from convolving independent normally distributed and beta distributed components is also derived. The chi-square test and the K-S test are performed on a first sample of stars and BDs which belongs to the massive young cluster NGC 6611 and on a second sample which represents the star's masses of the cluster NGC 2362.", "keyphrases": ["initial mass function", "beta distribution", "dwarf"]}
{"id": "2003.08416", "title": "Chiral Symmetry and the Cosmological Constant", "abstract": "In this work we provide a link between a nearly vanishing cosmological constant and chiral symmetry. This is accomplished with a modification of General Relativity coupled to a topological field theory, namely BF theory by introducing fermions charged under the BF theory gauge group. We find that the cosmological constant sources a chiral anomaly for the fermions, providing a `technical naturalness' explanation for the smallness of the observed cosmological constant. Applied to the early universe, we show that production of fermions during inflation can provide all the dark matter in the universe today, in the form of superheavy dark baryons.", "keyphrases": ["cosmological constant", "topological field theory", "chiral symmetry"]}
{"id": "1512.03566", "title": "Optimising the measurement of relativistic distortions in large-scale structure", "abstract": "It has been shown recently that relativistic distortions generate a dipolar modulation in the two-point correlation function of galaxies. To measure this relativistic dipole it is necessary to cross-correlate different populations of galaxies with for example different luminosities or colours. In this paper, we construct an optimal estimator to measure the dipole with multiple populations. We show that this estimator increases the signal-to-noise of the dipole by up to 35 percent. Using 6 populations of galaxies, in a survey with halos and number densities similar to those of the millennium simulation, we forecast a cumulative signal-to-noise of 4.4. For the main galaxy sample of SDSS at low redshift z<0.2 our optimal estimator predicts a cumulative signal-to-noise of 2.4. Finally we forecast a cumulative signal-to-noise of 7.4 in the upcoming DESI survey. These forecasts indicate that with the appropriate choice of estimator the relativistic dipole should be detectable in current and future surveys.", "keyphrases": ["relativistic distortion", "two-point correlation function", "galaxy"]}
{"id": "1307.4082", "title": "Wino Dark Matter Under Siege", "abstract": "A fermion triplet of SU(2)_L - a wino - is a well-motivated dark matter candidate. This work shows that present-day wino annihilations are constrained by indirect detection experiments, with the strongest limits coming from H.E.S.S. and Fermi. The bounds on wino dark matter are presented as a function of mass for two scenarios: thermal (winos constitute a subdominant component of the dark matter for masses less than 3.1 TeV) and non-thermal (winos comprise all the dark matter). Assuming the NFW halo model, the H.E.S.S. search for gamma-ray lines excludes the 3.1 TeV thermal wino; the combined H.E.S.S. and Fermi results completely exclude the non-thermal scenario. Uncertainties in the exclusions are explored. Indirect detection may provide the only probe for models of anomaly plus gravity mediation where the wino is the lightest superpartner and scalars reside at the 100 TeV scale.", "keyphrases": ["dark matter profile", "wino", "sommerfeld enhancement"]}
{"id": "1907.05042", "title": "Primordial Black Holes from Inflation with Nonminimal Derivative Coupling", "abstract": "We propose a novel enhancement mechanism of the curvature perturbations in the nonminimal derivative coupling inflation model with a coupling parameter related to the inflaton field. By considering a special form of the coupling parameter as a function of the inflaton, a period of ultra-slow-roll inflation can be realized due to the gravitationally enhanced friction, and the resulting power spectrum of the curvature perturbations has a sharp peak, which is large enough to produce the primordial black holes. Under this mechanism, we can easily obtain a sharp mass spectrum of primordial black holes around specific masses such as \ud835\udcaa(10)M_\u2299, \ud835\udcaa(10^-5)M_\u2299, and \ud835\udcaa(10^-12)M_\u2299, which can explain the LIGO events, the ultrashort-timescale microlensing events in OGLE data, and the most of dark matter, respectively.", "keyphrases": ["curvature perturbation", "inflaton field", "primordial black hole"]}
{"id": "1205.6676", "title": "Bouncing Eddington-inspired Born-Infeld cosmologies: an alternative to Inflation ?", "abstract": "We study the dynamics of a homogeneous and isotropic Friedmann-Robertson-Walker universe in the context of the Eddington-inspired Born-Infeld theory of gravity. We generalize earlier results, obtained in the context of a radiation dominated universe, to account for the evolution of a universe permeated by a perfect fluid with an arbitrary equation of state parameter w. We show that a bounce may occur for \u03ba >0, if w is time-dependent, and we demonstrate that it is free from tensor singularities. We argue that Eddington-inspired Born-Infeld cosmologies may be a viable alternative to the inflationary paradigm as a solution to fundamental problems of the standard cosmological model.", "keyphrases": ["eddington-inspired born-infeld cosmology", "universe", "inflationary paradigm", "standard cosmological model", "born-infeld gravity"]}
{"id": "1712.07453", "title": "Dark Matter Freeze-in Production in Fast-Expanding Universes", "abstract": "If the dark matter is produced in the early universe prior to Big Bang nucleosynthesis, a modified cosmological history can drastically affect the abundance of relic dark matter particles. Here, we assume that an additional species to radiation dominates at early times, causing the expansion rate at a given temperature to be larger than in the standard radiation-dominated case. We demonstrate that, if this is the case, dark matter production via freeze-in (a scenario when dark matter interacts very weakly, and is dumped in the early universe out of equilibrium by decay or scattering processes involving particles in the thermal bath) is dramatically suppressed. We illustrate and quantitatively and analytically study this phenomenon for three different paradigmatic classes of freeze-in scenarios. For the frozen-in dark matter abundance to be as large as observations, couplings between the dark matter and visible-sector particles must be enhanced by several orders of magnitude. This sheds some optimistic prospects for the otherwise dire experimental and observational outlook of detecting dark matter produced by freeze-in.", "keyphrases": ["early universe", "dark matter", "non-standard cosmology"]}
{"id": "2112.03863", "title": "The Pantheon+ Analysis: The Full Dataset and Light-Curve Release", "abstract": "Here we present 1701 light curves of 1550 spectroscopically confirmed Type Ia supernovae (SNe Ia) that will be used to infer cosmological parameters as part of the Pantheon+ SN analysis and the SH0ES (Supernovae and H0 for the Equation of State of dark energy) distance-ladder analysis. This effort is one part of a series of works that perform an extensive review of redshifts, peculiar velocities, photometric calibration, and intrinsic-scatter models of SNe Ia. The total number of light curves, which are compiled across 18 different surveys, is a significant increase from the first Pantheon analysis (1048 SNe), particularly at low redshift (z). Furthermore, unlike in the Pantheon analysis, we include light curves for SNe with z<0.01 such that SN systematic covariance can be included in a joint measurement of the Hubble constant (H_0) and the dark energy equation-of-state parameter (w). We use the large sample to compare properties of 151 SNe Ia observed by multiple surveys and 12 pairs/triplets of \"SN siblings\" - SNe found in the same host galaxy. Distance measurements, application of bias corrections, and inference of cosmological parameters are discussed in the companion paper by Brout et al. (2022b), and the determination of H_0 is discussed by Riess et al. (2022). These analyses will measure w with \u223c3% precision and H_0 with 1 km/s/Mpc precision.", "keyphrases": ["pantheon+", "light curve", "different survey"]}
{"id": "1511.01434", "title": "Efficient Production of High-energy Nonthermal Particles during Magnetic Reconnection in a Magnetically-dominated Ion-Electron Plasma", "abstract": "Magnetic reconnection is a leading mechanism for dissipating magnetic energy and accelerating nonthermal particles in Poynting-flux dominated flows. In this letter, we investigate nonthermal particle acceleration during magnetic reconnection in a magnetically-dominated ion-electron plasma using fully kinetic simulations. For an ion-electron plasma with the total magnetization \u03c3_0=B^2/(4\u03c0 n(m_i+m_e)c^2), the magnetization for each species is \u03c3_i \u223c\u03c3_0 and \u03c3_e \u223c (m_i/m_e) \u03c3_0, respectively. We have studied the magnetically dominated regime by varying \u03c3_e = 10^3 - 10^5 with initial ion and electron temperatures T_i = T_e = 5 - 20 m_ec^2 and mass ratio m_i/m_e = 1 - 1836. The results demonstrate that reconnection quickly establishes power-law energy distributions for both electrons and ions within several (2-3) light-crossing times. For the cases with periodic boundary conditions, the power-law index is 1<s<2 for both electrons and ions. The hard spectra limit the power-law energies for electrons and ions to be \u03b3_be\u223c\u03c3_e and \u03b3_bi\u223c\u03c3_i, respectively. The main acceleration mechanism is a Fermi-like acceleration through the drift motions of charged particles. When comparing the spectra for electrons and ions in momentum space, the spectral indices s_p are identical as predicted in Fermi acceleration. We also find that the bulk flow can carry a significant amount of energy during the simulations. We discuss the implication of this study in the context of Poynting-flux dominated jets and pulsar winds especially the applications for explaining the nonthermal high-energy emissions.", "keyphrases": ["magnetic reconnection", "magnetically-dominated ion-electron plasma", "high-energy emission"]}
{"id": "1203.2635", "title": "Inflationary perturbation theory is geometrical optics in phase space", "abstract": "A pressing problem in comparing inflationary models with observation is the accurate calculation of correlation functions. One approach is to evolve them using ordinary differential equations (\"transport equations\"), analogous to the Schwinger-Dyson hierarchy of in-out quantum field theory. We extend this approach to the complete set of momentum space correlation functions. A formal solution can be obtained using raytracing techniques adapted from geometrical optics. We reformulate inflationary perturbation theory in this language, and show that raytracing reproduces the familiar \"delta N\" Taylor expansion. Our method produces ordinary differential equations which allow the Taylor coefficients to be computed efficiently. We use raytracing methods to express the gauge transformation between field fluctuations and the curvature perturbation, zeta, in geometrical terms. Using these results we give a compact expression for the nonlinear gauge-transform part of fNL in terms of the principal curvatures of uniform energy-density hypersurfaces in field space.", "keyphrases": ["taylor expansion", "field space", "inflationary perturbation theory"]}
{"id": "2101.10081", "title": "Pulsar Timing Array Experiments", "abstract": "Pulsar timing is a technique that uses the highly stable spin periods of neutron stars to investigate a wide range of topics in physics and astrophysics. Pulsar timing arrays (PTAs) use sets of extremely well-timed pulsars as a Galaxy-scale detector with arms extending between Earth and each pulsar in the array. These challenging experiments look for correlated deviations in the pulsars' timing that are caused by low-frequency gravitational waves (GWs) traversing our Galaxy. PTAs are particularly sensitive to GWs at nanohertz frequencies, which makes them complementary to other space- and ground-based detectors. In this chapter, we will describe the methodology behind pulsar timing; provide an overview of the potential uses of PTAs; and summarise where current PTA-based detection efforts stand. Most predictions expect PTAs to successfully detect a cosmological background of GWs emitted by supermassive black-hole binaries and also potentially detect continuous-wave emission from binary supermassive black holes, within the next several years.", "keyphrases": ["array", "nanohertz frequency", "pulsar"]}
{"id": "1012.5821", "title": "Quantum Leptogenesis I", "abstract": "Thermal leptogenesis explains the observed matter-antimatter asymmetry of the universe in terms of neutrino masses, consistent with neutrino oscillation experiments. We present a full quantum mechanical calculation of the generated lepton asymmetry based on Kadanoff-Baym equations. Origin of the asymmetry is the departure from equilibrium of the statistical propagator of the heavy Majorana neutrino, together with CP violating couplings. The lepton asymmetry is calculated directly in terms of Green's functions without referring to \"number densities\". Compared to Boltzmann and quantum Boltzmann equations, the crucial difference are memory effects, rapid oscillations much faster than the heavy neutrino equilibration time. These oscillations strongly suppress the generated lepton asymmetry, unless the standard model gauge interactions, which cause thermal damping, are properly taken into account. We find that these damping effects essentially compensate the enhancement due to quantum statistical factors, so that finally the conventional Boltzmann equations again provide rather accurate predictions for the lepton asymmetry.", "keyphrases": ["leptogenesis", "lepton asymmetry", "propagator"]}
{"id": "2004.07239", "title": "Pebble-driven Planet Formation around Very Low-mass Stars and Brown Dwarfs", "abstract": "We conduct a pebble-driven planet population synthesis study to investigate the formation of planets around very low-mass stars and brown dwarfs, in the (sub)stellar mass range between 0.01 M_\u2299 and 0.1 M_\u2299. Based on the extrapolation of numerical simulations of planetesimal formation by the streaming instability, we obtain the characteristic mass of the planetesimals and the initial masses of the protoplanets (largest bodies from the planetesimal size distributions), in either the early self-gravitating phase or the later non-self-gravitating phase of the protoplanetary disk evolution. We find that the initial protoplanets form with masses that increase with host mass, orbital distance and decrease with disk age. Around late M-dwarfs of 0.1 M_\u2299, these protoplanets can grow up to Earth-mass planets by pebble accretion. However, around brown dwarfs of 0.01 M_\u2299, planets do not grow larger than Mars mass when the initial protoplanets are born early in self-gravitating disks, and their growth stalls at around 0.01 Earth-mass when they are born late in non-self-gravitating disks. Around these low mass stars and brown dwarfs, we find no channel for gas giant planet formation because the solid cores remain too small. When the initial protoplanets form only at the water-ice line, the final planets typically have \u2273 15% water mass fraction. Alternatively, when the initial protoplanets form log-uniformly distributed over the entire protoplanetary disk, the final planets are either very water-rich (water mass fraction \u227315%) or entirely rocky (water mass fraction \u22725%).", "keyphrases": ["planet formation", "brown dwarfs", "pebble accretion"]}
{"id": "0901.4806", "title": "Complementarity in the Multiverse", "abstract": "In the multiverse, as in AdS, light-cones relate bulk points to boundary scales. This holographic UV-IR connection defines a preferred global time cut-off that regulates the divergences of eternal inflation. An entirely different cut-off, the causal patch, arises in the holographic description of black holes. Remarkably, I find evidence that these two regulators define the same probability measure in the multiverse. Initial conditions for the causal patch are controlled by the late-time attractor regime of the global description.", "keyphrases": ["multiverse", "light-cone", "causal patch", "measure"]}
{"id": "1612.00266", "title": "Echoes from the Abyss: Tentative evidence for Planck-scale structure at black hole horizons", "abstract": "In classical General Relativity (GR), an observer falling into an astrophysical black hole is not expected to experience anything dramatic as she crosses the event horizon. However, tentative resolutions to problems in quantum gravity, such as the cosmological constant problem, or the black hole information paradox, invoke significant departures from classicality in the vicinity of the horizon. It was recently pointed out that such near-horizon structures can lead to late-time echoes in the black hole merger gravitational wave signals that are otherwise indistinguishable from GR. We search for observational signatures of these echoes in the gravitational wave data released by advanced Laser Interferometer Gravitational-Wave Observatory (LIGO), following the three black hole merger events GW150914, GW151226, and LVT151012. In particular, we look for repeating damped echoes with time-delays of 8 M log M (+spin corrections, in Planck units), corresponding to Planck-scale departures from GR near their respective horizons. Accounting for the \"look elsewhere\" effect due to uncertainty in the echo template, we find tentative evidence for Planck-scale structure near black hole horizons at false detection probability of 1% (corresponding to 2.5\u03c3 significance level). Future observations from interferometric detectors at higher sensitivity, along with more physical echo templates, will be able to confirm (or rule out) this finding, providing possible empirical evidence for alternatives to classical black holes, such as in firewall or fuzzball paradigms.", "keyphrases": ["black hole horizon", "hole merger", "spacetime"]}
{"id": "1801.04946", "title": "Neutrino masses and their ordering: Global Data, Priors and Models", "abstract": "We present a Bayesian analysis of the combination of current neutrino oscillation, neutrinoless double beta decay and CMB observations. Our major goal is to carefully investigate the possibility to single out one neutrino mass ordering, Normal Ordering or Inverted Ordering, with current data. Two possible parametrizations (three neutrino masses versus the lightest neutrino mass plus the two oscillation mass splittings) and priors (linear versus logarithmic) are examined. We find that the preference for NO is only driven by neutrino oscillation data. Moreover, the values of the Bayes factor indicate that the evidence for NO is strong only when the scan is performed over the three neutrino masses with logarithmic priors; for every other combination of parameterization and prior, the preference for NO is only weak. As a by-product of our Bayesian analyses, we are able to a) compare the Bayesian bounds on the neutrino mixing parameters to those obtained by means of frequentist approaches, finding a very good agreement; b) determine that the lightest neutrino mass plus the two mass splittings parametrization, motivated by the physical observables, is strongly preferred over the three neutrino mass eigenstates scan and c) find that there is a weak-to-moderate preference for logarithmic priors. These results establish the optimal strategy to successfully explore the neutrino parameter space, based on the use of the oscillation mass splittings and a logarithmic prior on the lightest neutrino mass. We also show that the limits on the total neutrino mass \u2211 m_\u03bd can change dramatically when moving from one prior to the other. These results have profound implications for future studies on the neutrino mass ordering, as they crucially state the need for self-consistent analyses which explore the best parametrization and priors, without combining results that involve different assumptions.", "keyphrases": ["mass ordering", "neutrino masse", "cosmology"]}
{"id": "2005.12906", "title": "SIRIUS project. I. Star formation models for star-by-star simulations of star clusters and galaxy formation", "abstract": "Most stars are formed as star clusters in galaxies, which then disperse into galactic disks. Upcoming exascale supercomputational facilities will enable performing simulations of galaxies and their formation by resolving individual stars (star-by-star simulations). This will substantially advance our understanding of star formation in galaxies, star cluster formation, and assembly histories of galaxies. In previous galaxy simulations, a simple stellar population approximation was used. It is, however, difficult to improve the mass resolution with this approximation. Therefore, a model for forming individual stars that can be used in simulations of galaxies must be established. In this first paper of a series of the SIRIUS (SImulations Resolving IndividUal Stars) project, we demonstrate a stochastic star formation model for star-by-star simulations. An assumed stellar initial mass function (IMF) is randomly assigned to newly formed stars. We introduce a maximum search radius to assemble the mass from surrounding gas particles to form star particles. In this study, we perform a series of N-body/smoothed particle hydrodynamics simulations of star cluster formations from turbulent molecular clouds and ultra-faint dwarf galaxies as test cases. The IMF can be correctly sampled if a maximum search radius that is larger than the value estimated from the threshold density for star formation is adopted. In small clouds, the formation of massive stars is highly stochastic because of the small number of stars. We confirm that the star formation efficiency and threshold density do not strongly affect the results. We find that our model can naturally reproduce the relationship between the most massive stars and the total stellar mass of star clusters. Herein, we demonstrate that our models can be applied to simulations varying from star clusters to galaxies for a wide range of resolutions.", "keyphrases": ["star-by-star simulation", "star cluster", "mass function"]}
{"id": "1402.3468", "title": "Collective electronic pulsation around giant nuclei in the Thomas-Fermi model", "abstract": "Based on the Thomas-Fermi solution for compressed electron gas around a giant nucleus, Z\u2248 10^6, we study electric pulsations of electron number-density, pressure and electric fields, which could be caused by an external perturbations acting on the nucleus or the electrons themselves. We numerically obtain the eigen-frequencies and eigen-functions for stationary pulsation modes that fulfill the boundary-value problem established by electron-number and energy-momentum conservation, equation of state, laws of thermodynamics, and Maxwell's equations, as well as physical boundary conditions. We choose a proton number of Z=10^6 and assume the nucleons in \u03b2-equilibrium at nuclear density. Similar systems with non-spherical geometry are hypothesized to exist in the lower crust of neutron stars, commonly referred to as pasta equation of state. The lowest modes turn out to be heavily influenced by the relativistic plasma frequency induced by the positive charge background in the nucleus. We discuss the possibility to apply our results to dynamic nuclei using the spectral method and mention mechanisms that could stimulate such dynamics in the astrophysical context.", "keyphrases": ["pulsation", "thomas-fermi model", "giant nucleus"]}
{"id": "1901.07460", "title": "General relativistic effects in the galaxy bias at second order", "abstract": "The local galaxy bias formalism relies on the energy constraint equation at the formation time to relate the metric perturbation to the matter density contrast. In the Newtonian approximation, this relationship is linear, which allows us to specify the initial galaxy density as a function of local physical operators. In general relativity however, the relationship is intrinsically nonlinear and a modulation of the short-wavelength mode by the long-wavelength mode might be expected. We describe in detail how to obtain local coordinates where the coupling of the long- to the short-wavelength modes is removed through a change of coordinates (in the absence of the primordial non-Gaussianity). We derive the general-relativistic correction to the galaxy bias expansion at second order. The correction does not come from the modulation of small-scale clustering by the long-wavelength mode; instead, it arises from distortions of the volume element by the long-wavelength mode and it does not lead to new bias parameters.", "keyphrases": ["galaxy bias", "primordial non-gaussianity", "general relativistic effect"]}
{"id": "2010.10525", "title": "Progress on Cosmological Magnetic Fields", "abstract": "A variety of observations impose upper limits at the nano Gauss level on magnetic fields that are coherent on inter-galactic scales while blazar observations indicate a lower bound \u223c 10^-16 Gauss. Such magnetic fields can play an important astrophysical role, for example at cosmic recombination and during structure formation, and also provide crucial information for particle physics in the early universe. Magnetic fields with significant energy density could have been produced at the electroweak phase transition. The evolution and survival of magnetic fields produced on sub-horizon scales in the early universe, however, depends on the magnetic helicity which is related to violation of symmetries in fundamental particle interactions. The generation of magnetic helicity requires new CP violating interactions that can be tested by accelerator experiments via decay channels of the Higgs particle.", "keyphrases": ["cosmology", "magnetic field", "astrophysic"]}
{"id": "1509.07137", "title": "Bayesian inference on the sphere beyond statistical isotropy", "abstract": "We present a general method for Bayesian inference of the underlying covariance structure of random fields on a sphere. We employ the Bipolar Spherical Harmonic (BipoSH) representation of general covariance structure on the sphere. We illustrate the efficacy of the method as a principled approach to assess violation of statistical isotropy (SI) in the sky maps of Cosmic Microwave Background (CMB) fluctuations. SI violation in observed CMB maps arise due to known physical effects such as Doppler boost and weak lensing; yet unknown theoretical possibilities like cosmic topology and subtle violations of the cosmological principle, as well as, expected observational artefacts of scanning the sky with a non-circular beam, masking, foreground residuals, anisotropic noise, etc. We explicitly demonstrate the recovery of the input SI violation signals with their full statistics in simulated CMB maps. Our formalism easily adapts to exploring parametric physical models with non-SI covariance, as we illustrate for the inference of the parameters of a Doppler boosted sky map. Our approach promises to provide a robust quantitative evaluation of the evidence for SI violation related anomalies in the CMB sky by estimating the BipoSH spectra along with their complete posterior.", "keyphrases": ["isotropy", "biposh", "bayesian inference"]}
{"id": "2204.06304", "title": "Primordial Gravitational Waves Predictions for GW170817-compatible Einstein-Gauss-Bonnet Theory", "abstract": "In this work we shall calculate in detail the effect of an GW170817-compatible Einstein-Gauss-Bonnet theory on the energy spectrum of the primordial gravitational waves. The spectrum is affected by two characteristics, the overall amplification/damping factor caused by the GW170817-compatible Einstein-Gauss-Bonnet theory and by the tensor spectral index and the tensor-to-scalar ratio. We shall present the formalism for studying the inflationary dynamics and post-inflationary dynamics of GW170817-compatible Einstein-Gauss-Bonnet theories for all redshifts starting from the radiation era up to the dark energy era. We exemplify our formalism by using two characteristic models, which produce viable inflationary and dark energy eras. As we demonstrate, remarkably the overall damping/amplification factor is of the order of unity, thus the GW170817-compatible Einstein-Gauss-Bonnet models affect the primordial gravitational waves energy spectrum only via their tensor spectral index and the tensor-to-scalar ratio. Both models have a blue tilted tensor spectrum, and therefore the predicted energy spectrum of the primordial gravity waves can be detectable by most of the future gravitational waves experiments, for various reheating temperatures.", "keyphrases": ["einstein-gauss-bonnet theory", "wave energy spectrum", "primordial gravitational wave"]}
{"id": "1007.3748", "title": "Inflation and the Scale Dependent Spectral Index: Prospects and Strategies", "abstract": "We consider the running of the spectral index as a probe of both inflation itself, and of the overall evolution of the very early universe. Surveying a collection of simple single field inflationary models, we confirm that the magnitude of the running is relatively consistent, unlike the tensor amplitude, which varies by orders of magnitude. Given this target, we confirm that the running is potentially detectable by future large scale structure or 21 cm observations, but that only the most futuristic measurements can distinguish between these models on the basis of their running. For any specified inflationary scenario, the combination of the running index and unknown post-inflationary expansion history induces a theoretical uncertainty in the predicted value of the spectral index. This effect can easily dominate the statistical uncertainty with which Planck and its successors are expected to measure the spectral index. More positively, upcoming cosmological experiments thus provide an intriguing probe of physics between TeV and GUT scales by constraining the reheating history associated with any specified inflationary model, opening a window into the \"primordial dark age\" that follows the end of inflation.", "keyphrases": ["spectral index", "inflationary model", "primordial fluctuation"]}
{"id": "1011.4307", "title": "The PRIsm MUlti-Object Survey (PRIMUS) I: Survey Overview and Characteristics", "abstract": "We present the PRIsm MUlti-object Survey (PRIMUS), a spectroscopic faint galaxy redshift survey to z 1. PRIMUS uses a low-dispersion prism and slitmasks to observe 2,500 objects at once in a 0.18 deg^2 field of view, using the IMACS camera on the Magellan I Baade 6.5m telescope at Las Campanas Observatory. PRIMUS covers a total of 9.1 deg^2 of sky to a depth of i_AB 23.5 in seven different deep, multi-wavelength fields that have coverage from GALEX, Spitzer and either XMM or Chandra, as well as multiple-band optical and near-IR coverage. PRIMUS includes 130,000 robust redshifts of unique objects with a redshift precision of dz/(1+z) 0.005. The redshift distribution peaks at z=0.6 and extends to z=1.2 for galaxies and z=5 for broad-line AGN. The motivation, observational techniques, fields, target selection, slitmask design, and observations are presented here, with a brief summary of the redshift precision; a companion paper presents the data reduction, redshift fitting, redshift confidence, and survey completeness. PRIMUS is the largest faint galaxy survey undertaken to date. The high targeting fraction ( 80 survey size will allow for precise measures of galaxy properties and large-scale structure to z 1.", "keyphrases": ["prism multi-object survey", "primus", "low-dispersion prism"]}
{"id": "1907.05213", "title": "Low-frequency Gravitational Waves from Double-inflection-point Inflation", "abstract": "We study the production of gravitational waves from primordial scalar perturbations in double-inflection-point inflation, in which one of the inflection points predicts the power spectra consistent with CMB observations at large scales and the other generates a large peak in the power spectrum of scalar perturbations at small scales. We find that the reduced gravitational waves at low frequencies can be detected by future space-based laser interferometers.", "keyphrases": ["gravitational wave", "double-inflection-point inflation", "primordial scalar perturbation"]}
{"id": "0911.4798", "title": "Enrichment by supernovae in globular clusters with multiple populations", "abstract": "The most massive globular cluster in the Milky Way, omega Centauri, is thought to be the remaining core of a disrupted dwarf galaxy, as expected within the model of hierarchical merging. It contains several stellar populations having different heavy elemental abundances supplied by supernovae \u2013 a process known as metal enrichment. Although M22 appears to be similar to omega Cen, other peculiar globular clusters do not. Therefore omega Cen and M22 are viewed as exceptional, and the presence of chemical inhomogeneities in other clusters is seen as `pollution' from the intermediate-mass asymptotic-giant-branch stars expected in normal globular clusters. Here we report Ca abundances for seven globular clusters and compare them to omega Cen. Calcium and other heavy elements can only be supplied through numerous supernovae explosions of massive stars in these stellar systems, but the gravitational potentials of the present-day clusters cannot preserve most of the ejecta from such explosions. We conclude that these globular clusters, like omega Cen, are most probably the relics of more massive primeval dwarf galaxies that merged and disrupted to form the proto-Galaxy.", "keyphrases": ["supernovae", "globular cluster", "dwarf galaxy"]}
{"id": "1705.03413", "title": "Classifying Radio Galaxies with Convolutional Neural Network", "abstract": "We present the application of deep machine learning technique to classify radio images of extended sources on a morphological basis using convolutional neural networks. In this study, we have taken the case of Fanaroff-Riley (FR) class of radio galaxies as well as radio galaxies with bent-tailed morphology. We have used archival data from the Very Large Array (VLA) - Faint Images of the Radio Sky at Twenty Centimeters (FIRST) survey and existing visually classified samples available in literature to train a neural network for morphological classification of these categories of radio sources. Our training sample size for each of these categories is approximately 200 sources, which has been augmented by rotated versions of the same. Our study shows that convolutional neural networks can classify images of the FRI and FRII and bent-tailed radio galaxies with high accuracy (maximum precision at 95 well-defined samples and fusion classifier, which combines the results of binary classifications, while allowing for a mechanism to find sources with unusual morphologies. The individual precision is highest for bent-tailed radio galaxies at 95 whereas the recall is highest for FRI and FRIIs at 91 class has a recall of 79 to that of manual classification while being much faster. Finally, we discuss the computational and data-related challenges associated with morphological classification of radio galaxies with convolutional neural networks.", "keyphrases": ["radio galaxy", "convolutional neural network", "classification"]}
{"id": "1709.05128", "title": "Dark matter scenarios with multiple spin-2 fields", "abstract": "We study ghost-free multimetric theories for (N+1) tensor fields with a coupling to matter and maximal global symmetry group S_N\u00d7(Z_2)^N. Their mass spectra contain a massless mode, the graviton, and N massive spin-2 modes. One of the massive modes is distinct by being the heaviest, the remaining (N-1) massive modes are simply identical copies of each other. All relevant physics can therefore be understood from the case N=2. Focussing on this case, we compute the full perturbative action up to cubic order and derive several features that hold to all orders in perturbation theory. The lighter massive mode does not couple to matter and neither of the massive modes decay into massless gravitons. We propose the lighter massive particle as a candidate for dark matter and investigate its phenomenology in the parameter region where the matter coupling is dominated by the massless graviton. The relic density of massive spin-2 can originate from a freeze-in mechanism or from gravitational particle production, giving rise to two different dark matter scenarios. The allowed parameter regions are very different from those in scenarios with only one massive spin-2 field and more accessible to experiments.", "keyphrases": ["spin-2 field", "graviton", "dark matter scenario"]}
{"id": "2012.12678", "title": "The SOXS Data-Reduction Pipeline", "abstract": "The SOXS is a dual-arm spectrograph (UV-VIS NIR) and AC due to mounted on the ESO 3.6m NTT in La Silla. Designed to simultaneously cover the optical and NIR wavelength range from 350-2050 nm, the instrument will be dedicated to the study of transient and variable events with many Target of Opportunity requests expected. The goal of the SOXS Data Reduction pipeline is to use calibration data to remove all instrument signatures from the SOXS scientific data frames for each of the supported instrument modes, convert this data into physical units and deliver them with their associated error bars to the ESO SAF as Phase 3 compliant science data products, all within 30 minutes. The primary reduced product will be a detrended, wavelength and flux calibrated, telluric corrected 1D spectrum with UV-VIS + NIR arms stitched together. The pipeline will also generate QC metrics to monitor telescope, instrument and detector health. The pipeline is written in Python 3 and has been built with an agile development philosophy that includes adaptive planning and evolutionary development. The pipeline is to be used by the SOXS consortium and the general user community that may want to perform tailored processing of SOXS data. Test driven development has been used throughout the build using `extreme' mock data. We aim for the pipeline to be easy to install and extensively and clearly documented.", "keyphrases": ["soxs data-reduction pipeline", "soxs subsystem", "series", "development status"]}
{"id": "1803.02845", "title": "Black Hole Echology: The Observer's Manual", "abstract": "While recent detections of gravitational waves from the mergers of binary black holes match well with the predictions of General Relativity (GR), they cannot directly confirm the existence of event horizons. Exotic compact objects (ECOs) are motivated by quantum models of black holes, and can have exotic structure (or a \"wall\") just outside the (would-be) horizon. ECOs produce similar ringdown waveforms to the GR black holes, but they are followed by delayed \"echoes\". By solving linearized Einstein equations we can model these echoes and provide analytic templates that can be used to compare to observations. For concreteness, we consider GW150914 event, detected by the LIGO/Virgo collaboration, and study the model dependence of its echo properties. We find that echoes are reasonably approximated by complex gaussians, with amplitudes that decay as a power law in time, while their width in time (frequency) grows (shrinks) over subsequent echoes. We also show that trapped modes between a perfectly reflecting wall and angular momentum barrier in Kerr metric can exhibit superradiant instability over long times, as expected.", "keyphrases": ["gravitational wave", "echo", "remnant"]}
{"id": "1309.2015", "title": "Multi-field Conformal Cosmological Attractors", "abstract": "We describe a broad class of multi-field inflationary models with spontaneously broken conformal invariance. It generalizes the recently discovered class of cosmological attractors with a single inflaton field. In the new multi-field theories, just as in the previously studied single-field models, the moduli space has a boundary (Kahler cone) in terms of the original homogeneous conformal variables. Upon spontaneous breaking of the conformal invariance and switching to the Einstein frame, this boundary moves to infinity in terms of the canonically normalized inflaton field. This results in the exponential stretching and flattening of scalar potentials in the vicinity of the boundary of the moduli space, which makes even very steep potentials perfectly suitable for the slow-roll inflation. These theories, just like their single-field versions, typically lead to inflationary perturbations with n_s =1-2/N and r = 12/N^2, where N is the number of e-foldings.", "keyphrases": ["attractor", "inflaton field", "slow-roll inflation", "multi-field conformal attractor"]}
{"id": "1711.10981", "title": "Direct detection of a break in the teraelectronvolt cosmic-ray spectrum of electrons and positrons", "abstract": "High energy cosmic ray electrons plus positrons (CREs), which lose energy quickly during their propagation, provide an ideal probe of Galactic high-energy processes and may enable the observation of phenomena such as dark-matter particle annihilation or decay. The CRE spectrum has been directly measured up to \u223c 2 TeV in previous balloon- or space-borne experiments, and indirectly up to \u223c 5 TeV by ground-based Cherenkov \u03b3-ray telescope arrays. Evidence for a spectral break in the TeV energy range has been provided by indirect measurements of H.E.S.S., although the results were qualified by sizeable systematic uncertainties. Here we report a direct measurement of CREs in the energy range 25 GeV-4.6 TeV by the DArk Matter Particle Explorer (DAMPE) with unprecedentedly high energy resolution and low background. The majority of the spectrum can be properly fitted by a smoothly broken power-law model rather than a single power-law model. The direct detection of a spectral break at E \u223c0.9 TeV confirms the evidence found by H.E.S.S., clarifies the behavior of the CRE spectrum at energies above 1 TeV and sheds light on the physical origin of the sub-TeV CREs.", "keyphrases": ["cosmic ray electron", "energy resolution", "power-law model"]}
{"id": "1812.04021", "title": "Dense matter with eXTP", "abstract": "In this White Paper we present the potential of the Enhanced X-ray Timing and Polarimetry (eXTP) mission for determining the nature of dense matter; neutron star cores host an extreme density regime which cannot be replicated in a terrestrial laboratory. The tightest statistical constraints on the dense matter equation of state will come from pulse profile modelling of accretion-powered pulsars, burst oscillation sources, and rotation-powered pulsars. Additional constraints will derive from spin measurements, burst spectra, and properties of the accretion flows in the vicinity of the neutron star. Under development by an international Consortium led by the Institute of High Energy Physics of the Chinese Academy of Science, the eXTP mission is expected to be launched in the mid 2020s.", "keyphrases": ["extp", "mission", "dense matter"]}
{"id": "1103.2475", "title": "Probability of Inflation in Loop Quantum Cosmology", "abstract": "Inflationary models of the early universe provide a natural mechanism for the formation of large scale structure. This success brings to forefront the question of naturalness: Does a sufficiently long slow roll inflation occur generically or does it require a careful fine tuning of initial parameters? In recent years there has been considerable controversy on this issue. In particular, for a quadratic potential, Kofman, Linde and Mukhanov have argued that the probability of inflation with at least 65 e-foldings is close to one, while Gibbons and Turok have argued that this probability is suppressed by a factor of 0^-85. We first clarify that such dramatically different predictions can arise because the required measure on the space of solutions is intrinsically ambiguous in general relativity. We then show that this ambiguity can be naturally resolved in loop quantum cosmology (LQC) because the big bang is replaced by a big bounce and the bounce surface can be used to introduce the structure necessary to specify a satisfactory measure. The second goal of the paper is to present a detailed analysis of the inflationary dynamics of LQC using analytical and numerical methods. By combining this information with the measure on the space of solutions, we address a sharper question than those investigated in the literature: What is the probability of a sufficiently long slow roll inflation WHICH IS COMPATIBLE WITH THE SEVEN YEAR WMAP DATA? We show that the probability is very close to 1. The material is so organized that cosmologists who may be more interested in the inflationary dynamics in LQC than in the subtleties associated with measures can skip that material without loss of continuity.", "keyphrases": ["loop quantum cosmology", "universe", "inflationary phase"]}
{"id": "1802.10157", "title": "SCARLET: Source separation in multi-band images by Constrained Matrix Factorization", "abstract": "We present the source separation framework SCARLET for multi-band images, which is based on a generalization of the Non-negative Matrix Factorization to alternative and several simultaneous constraints. Our approach describes the observed scene as a mixture of components with compact spatial support and uniform spectra over their support. We present the algorithm to perform the matrix factorization and introduce constraints that are useful for optical images of stars and distinct stellar populations in galaxies, in particular symmetry and monotonicity with respect to the source peak position. We also derive the treatment of correlated noise and convolutions with band-dependent point spread functions, rendering our approach applicable to coadded images observed under variable seeing conditions. SCARLET thus yields a PSF-matched photometry measurement with an optimally chosen weight function given by the mean morphology in all available bands. We demonstrate the performance of SCARLET for deblending crowded extragalactic scenes and on an AGN jet \u2013 host galaxy separation problem in deep 5-band imaging from the Hyper Suprime-Cam Stategic Survey Program. Using simulations with prominent crowding we show that SCARLET yields superior results to the HSC-SDSS deblender for the recovery of total fluxes, colors, and morphologies. Due to its non-parametric nature, a conceptual limitation of SCARLET is its sensitivity to undetected sources or multiple stellar population within detected sources, but an iterative strategy that adds components at the location of significant residuals appears promising. The code is implemented in Python with C++ extensions and is available at https://github.com/fred3m/scarlet", "keyphrases": ["multi-band image", "noise", "scarlet"]}
{"id": "1304.4717", "title": "Galactic structure explained with dissipative mirror dark matter", "abstract": "Dissipative dark matter, such as mirror dark matter and related hidden sector dark matter candidates, requires an energy source to stabilize dark matter halos in spiral galaxies. It has been proposed previously that supernovae could be the source of this energy. Recently, it has been argued that this mechanism might explain two galactic scaling relations inferred from observations of spiral galaxies. One of which is that \u03c1_0 r_0 is roughly constant, and another relates the galactic luminosity to r_0. [\u03c1_0 is the dark matter central density and r_0 is the core radius.] Here we derive equations for the heating of the halo via supernova energy, and the cooling of the halo via thermal bremsstrahlung. These equations are numerically solved to obtain constraints on the \u03c1_0, r_0 parameters appropriate for spiral galaxies. These constraints are in remarkable agreement with the aforementioned scaling relations.", "keyphrases": ["dark matter", "galaxy", "supernovae"]}
{"id": "1002.4779", "title": "Applicability of the linearly perturbed FRW metric and Newtonian cosmology", "abstract": "It has been argued that the effect of cosmological structure formation on the average expansion rate is negligible, because the linear approximation to the metric remains applicable in the regime of non-linear density perturbations. We discuss why the arguments based on the linear theory are not valid. We emphasise the difference between Newtonian gravity and the weak field, small velocity limit of general relativity in the cosmological setting.", "keyphrases": ["cosmology", "newtonian gravity", "perturbative expansion"]}
{"id": "1202.2590", "title": "Holographic Dark Energy Model Characterized by the Conformal-age-like Length", "abstract": "A holographic dark energy model characterized by the conformal-age-like length scale L= 1/a^4(t)\u222b_0^tdt' a^3(t') is motivated from the four dimensional spacetime volume at cosmic time t in the flat Friedmann-Robertson-Walker universe. It is shown that when the background constituent with constant equation of state w_m dominates the universe in the early time, the fractional energy density of the dark energy scales as \u03a9_de\u22439/4(3+w_m)^2d^2a^2 with the equation of state given by w_de\u2243-2/3 +w_m. The value of w_m is taken to be w_m\u2243-1 during inflation, w_m=1/3 in radiation-dominated epoch and w_m=0 in matter-dominated epoch respectively. When the model parameter d takes the normal value at order one, the fractional density of dark energy is naturally negligible in the early universe, \u03a9_de\u226a 1 at a \u226a 1. With such an analytic feature, the model can be regarded as a single-parameter model like the \u039bCDM model, so that the present fractional energy density \u03a9_de(a=1) can solely be determined by solving the differential equation of \u03a9_de once d is given. We further extend the model to the general case in which both matter and radiation are present. The scenario involving possible interaction between the dark energy and the background constituent is also discussed.", "keyphrases": ["dark energy model", "conformal-age-like length", "spacetime volume"]}
{"id": "1403.6243", "title": "Effective No-Hair Relations for Neutron Stars and Quark Stars: Relativistic Results", "abstract": "Astrophysical charge-free black holes are known to satisfy no-hair relations through which all multipole moments can be specified in terms of just their mass and spin angular momentum. We here investigate the possible existence of no-hair-like relations among multipole moments for neutron stars and quark stars that are independent of their equation of state. We calculate the multipole moments of these stars up to hexadecapole order by constructing uniformly-rotating and unmagnetized stellar solutions to the Einstein equations. For slowly-rotating stars, we construct stellar solutions to quartic order in spin in a slow-rotation expansion, while for rapidly-rotating stars, we solve the Einstein equations numerically with the LORENE and RNS codes. We find that the multipole moments extracted from these numerical solutions are consistent with each other. We confirm that the current-dipole is related to the mass-quadrupole in an approximately equation of state independent fashion, which does not break for rapidly rotating neutron stars or quark stars. We further find that the current-octupole and the mass-hexadecapole moments are related to the mass-quadrupole in an approximately equation of state independent way to \u223c 10 findings are in good agreement with previous work that considered stellar solutions to leading-order in a weak-field expansion. The quartic in spin, slowly-rotating solutions found here allow us to estimate the systematic errors in the measurement of the neutron star's mass and radius with future X-ray observations, such as NICER and LOFT. We find that the effect of these quartic-in-spin terms on the quadrupole and hexadecapole moments and stellar eccentricity may dominate the error budget for very rapidly-rotating neutron stars. The new universal relations found here should help to reduce such systematic errors.", "keyphrases": ["neutron star", "quark star", "angular momentum"]}
{"id": "1712.06771", "title": "Solar Radius at Subterahertz Frequencies and its Relation to Solar Activity", "abstract": "The Sun emits radiation at several wavelengths of the electromagnetic spectrum. In the optical band, the solar radius is 695,700 km and this is what defines the photosphere, the visible surface of the Sun. However, as the altitude increases, the electromagnetic radiation is produced at other frequencies, causing the solar radius to change as function of wavelength. These measurements enable a better understanding of the solar atmosphere and the radius dependence on the solar cycle is a good indicator of the changes that occur in the atmospheric structure. We measure the solar radius at the subterahertz frequencies of 0.212 and 0.405 THz \u2013 i.e., the altitude where these emissions are primarily generated \u2013 and also analyse the radius variation over the 11-year solar activity cycle. For this, we used radio maps of the solar disk for the period between 1999 and 2017, reconstructed from daily scans made by the Solar Submillimeter-wave Telescope (SST), installed at El Leoncito Astronomical Complex (CASLEO) in the Argentinean Andes. Our measurements yield radii of 966.5\" \u00b1 2.8\" for 0.2 THz and 966.5\" \u00b1 2.7\" for 0.4 THz. This implies a height of (5.0 \u00b1 2.0 \u00d7 10^6) m above the photosphere. Furthermore, we also observed strong anti-correlation between the radius variation and the solar activity at both frequencies.", "keyphrases": ["solar activity", "wavelength", "solar radius"]}
{"id": "1208.1094", "title": "Spin-dependent WIMP scattering off nuclei", "abstract": "Chiral effective field theory (EFT) provides a systematic expansion for the coupling of WIMPs to nucleons at the momentum transfers relevant to direct cold dark matter detection. We derive the currents for spin-dependent WIMP scattering off nuclei at the one-body level and include the leading long-range two-body currents, which are predicted in chiral EFT. As an application, we calculate the structure factor for spin-dependent WIMP scattering off 129,131Xe nuclei, using nuclear interactions that have been developed to study nuclear structure and double-beta decays in this region. We provide theoretical error bands due to the nuclear uncertainties of WIMP currents in nuclei.", "keyphrases": ["effective field theory", "two-body current", "chiral eft", "spin-dependent wimp"]}
{"id": "1011.0452", "title": "Holographic Non-Gaussianity", "abstract": "We investigate the non-Gaussianity of primordial cosmological perturbations within our recently proposed holographic description of inflationary universes. We derive a holographic formula that determines the bispectrum of cosmological curvature perturbations in terms of correlation functions of a holographically dual three-dimensional non-gravitational quantum field theory (QFT). This allows us to compute the primordial bispectrum for a universe which started in a non-geometric holographic phase, using perturbative QFT calculations. Strikingly, for a class of models specified by a three-dimensional super-renormalisable QFT, the primordial bispectrum is of exactly the factorisable equilateral form with f_nl^eq=5/36, irrespective of the details of the dual QFT. A by-product of this investigation is a holographic formula for the three-point function of the trace of the stress-energy tensor along general holographic RG flows, which should have applications outside the remit of this work.", "keyphrases": ["non-gaussianity", "universe", "quantum field theory", "holographic framework", "non-geometric phase"]}
{"id": "1611.02986", "title": "Gamma-Rays from Non-Blazar AGN", "abstract": "Non-blazar Active Galactic Nuclei (AGN) have emerged as a new gamma-ray emitting source class on the extragalactic sky and started to deepen our understanding of the physical processes and the nature of AGN in general. The detection of Narrow Line Seyfert 1 galaxies in the Fermi-LAT energy regime, for example, offers important information for our understanding of jet formation and radio-loudness. Radio galaxies, on the other hand, have become particularly interesting at high (HE) and very high (VHE) gamma-ray energies. With their jets not directly pointing towards us (i.e. misaligned), they offer a unique tool to probe into the nature of the fundamental (and often hidden) physical processes in AGN. This review highlights and discusses some of the observational and theoretical progress achieved in the gamma-ray regime during recent years, including the evidence for unexpected spectral hardening in Centaurus A and extreme short-term variability as seen in IC 310 and M87.", "keyphrases": ["non-blazar agn", "radio galaxy", "gamma-ray"]}
{"id": "1403.2783", "title": "The Evolution of Galaxy Structure over Cosmic Time", "abstract": "I present a comprehensive review of the evolution of galaxy structure in the universe from the first galaxies we can currently observe at z 6 down to galaxies we see in the local universe. I further address how these changes reveal galaxy formation processes that galaxy structural analyses can provide. This review is pedagogical and begins with a detailed discussion of the major methods in which galaxies are studied morphologically and structurally. This includes the well-established visual method; Sersic fitting to measure galaxy sizes and surface brightness profile shapes; non-parametric structural methods including the concentration (C), asymmetry (A), clumpiness (S) (CAS) method, as well as newer structural indices. Included is a discussion of how these structural indices measure fundamental properties of galaxies such as their scale, star formation rate, and ongoing merger activity. Extensive observational results are shown demonstrating how broad galaxy morphologies and structures change with time up to z 3, from small, compact and peculiar systems in the distant universe to the formation of the Hubble sequence we find today. This review further addresses how structural methods measure accurately the merger history out to z 3. The properties and evolution of bulges, disks, bars, and at z>1 large star forming clumps are also described, along with how morphological galaxy quenching occurs. Furthermore, the role of environment in producing structure in galaxies over cosmic time is treated. Alongside the evolution of general structure, I also delineate how galaxy sizes change with time, with measured sizes up to a factor of 2-5 smaller at high redshift at a given stellar mass. This review concludes with a discussion of how galaxy structure reveals the formation mechanisms behind galaxies, providing a new and unique way to test theories of galaxy formation.", "keyphrases": ["galaxy structure", "cosmic time", "clump"]}
{"id": "1407.8262", "title": "Primordial quantum nonequilibrium and large-scale cosmic anomalies", "abstract": "We study incomplete relaxation to quantum equilibrium at long wavelengths, during a pre-inflationary phase, as a possible explanation for the reported large-scale anomalies in the cosmic microwave background (CMB). Our scenario makes use of the de Broglie-Bohm pilot-wave formulation of quantum theory, in which the Born probability rule has a dynamical origin. The large-scale power deficit could arise from incomplete relaxation for the amplitudes of the primordial perturbations. We show, by numerical simulations for a spectator scalar field, that if the pre-inflationary era is radiation dominated then the deficit in the emerging power spectrum will have a characteristic shape (an inverse-tangent dependence on wavenumber k, with oscillations). It is found that our scenario is able to produce a power deficit in the observed region and of the observed (approximate) magnitude for an appropriate choice of cosmological parameters. We also discuss the large-scale anisotropy, which might arise from incomplete relaxation for the phases of the primordial perturbations. We present numerical simulations for phase relaxation, and we show how to define characteristic scales for amplitude and phase nonequilibrium. The extent to which the data might support our scenario is left as a question for future work. Our results suggest that we have a potentially viable model that might explain two apparently independent cosmic anomalies by means of a single mechanism.", "keyphrases": ["quantum nonequilibrium", "cosmic anomaly", "large-scale power deficit"]}
{"id": "1308.5972", "title": "Cosmological Information in the Intrinsic Alignments of Luminous Red Galaxies", "abstract": "The intrinsic alignments of galaxies are usually regarded as a contaminant to weak gravitational lensing observables. The alignment of Luminous Red Galaxies, detected unambiguously in observations from the Sloan Digital Sky Survey, can be reproduced by the linear tidal alignment model of Catelan, Kamionkowski Blandford (2001) on large scales. In this work, we explore the cosmological information encoded in the intrinsic alignments of red galaxies. We make forecasts for the ability of current and future spectroscopic surveys to constrain local primordial non-Gaussianity and Baryon Acoustic Oscillations (BAO) in the cross-correlation function of intrinsic alignments and the galaxy density field. For the Baryon Oscillation Spectroscopic Survey, we find that the BAO signal in the intrinsic alignments is marginally significant with a signal-to-noise ratio of 1.8 and 2.2 with the current LOWZ and CMASS samples of galaxies, respectively, and increasing to 2.3 and 2.7 once the survey is completed. For the Dark Energy Spectroscopic Instrument and for a spectroscopic survey following the EUCLID redshift selection function, we find signal-to-noise ratios of 12 and 15, respectively. Local type primordial non-Gaussianity, parametrized by fNL = 10, is only marginally significant in the intrinsic alignments signal with signal-to-noise ratios < 2 for the three surveys considered.", "keyphrases": ["intrinsic alignment", "red galaxy", "cosmological information"]}
{"id": "1908.02921", "title": "Causal concept for black hole shadows", "abstract": "Causal concept for the general black hole shadow is investigated, instead of the photon sphere. We define several `wandering null geodesics' as complete null geodesics accompanied by repetitive conjugate points, which would correspond to null geodesics on the photon sphere in Schwarzschild spacetime. We also define a `wandering set', that is, a set of totally wandering null geodesics as a counterpart of the photon sphere, and moreover, a truncated wandering null geodesic to symbolically discuss its formation. Then we examine the existence of a wandering null geodesic in general black hole spacetimes mainly in terms of Weyl focusing. We will see the essence of the black hole shadow is not the stationary cycling of the photon orbits which is the concept only available in a stationary spacetime, but their accumulation. A wandering null geodesic implies that this accumulation will be occur somewhere in an asymptotically flat spacetime.", "keyphrases": ["black hole shadow", "spacetime", "causal concept"]}
{"id": "1010.4306", "title": "Particle Acceleration on Megaparsec Scales in a Merging Galaxy Cluster", "abstract": "Galaxy clusters form through a sequence of mergers of smaller galaxy clusters and groups. Models of diffusive shock acceleration (DSA) suggest that in shocks that occur during cluster mergers, particles are accelerated to relativistic energies, similar to supernova remnants. Together with magnetic fields these particles emit synchrotron radiation and may form so-called radio relics. Here we report the detection of a radio relic for which we find highly aligned magnetic fields, a strong spectral index gradient, and a narrow relic width, giving a measure of the magnetic field in an unexplored site of the universe. Our observations prove that DSA also operates on scales much larger than in supernova remnants and that shocks in galaxy clusters are capable of producing extremely energetic cosmic rays.", "keyphrases": ["galaxy cluster", "diffusive shock acceleration", "relativistic electron", "turbulent magnetic field", "merger-driven shock"]}
{"id": "1909.03736", "title": "Measurement of Void Bias Using Separate Universe Simulations", "abstract": "Cosmic voids are biased tracers of the large-scale structure of the universe. Separate universe simulations (SUS) enable accurate measurements of this biasing relation by implementing the peak-background split (PBS). In this work, we apply the SUS technique to measure the void bias parameters. We confirm that the PBS argument works well for underdense tracers. The response of the void size distribution depends on the void radius. For voids larger (smaller) than the size at the peak of the distribution, the void abundance responds negatively (positively) to a long wavelength mode. The linear bias from the SUS is in good agreement with the cross power spectrum measurement on large scales. Using the SUS, we have detected the quadratic void bias for the first time in simulations. We find that b_2 is negative when the magnitude of b_1 is small, and that it becomes positive and increases rapidly when |b_1| increases. We compare the results from voids identified in the halo density field with those from the dark matter distribution, and find that the results are qualitatively similar, but the biases generally shift to the larger voids sizes.", "keyphrases": ["void bias", "separate universe simulation", "bias parameter"]}
{"id": "1309.4302", "title": "Hypermagnetic helicity evolution in early universe: leptogenesis and hypermagnetic diffusion", "abstract": "We study hypermagnetic helicity and lepton asymmetry evolution in plasma of the early Universe before the electroweak phase transition (EWPT) accounting for chirality flip processes via inverse Higgs decays and sphaleron transitions which violate the left lepton number and wash out the baryon asymmetry of the Universe (BAU). In the scenario where the right electron asymmetry supports the BAU alone through the conservation law B/3 - L_eR=const at temperatures T>T_RL\u2243 10 TeV the following universe cooling leads to the production of a non-zero left lepton (electrons and neutrinos) asymmetry. This is due to the Higgs decays becoming more faster when entering the equilibrium at T=T_RL with the universe expansion, \u0393_RL\u223c T> H\u223c T^2, resulting in the parallel evolution of both the right and the left electron asymmetries at T<T_RL through the corresponding Abelian anomalies in SM in the presence of a seed hypermagnetic field. The hypermagnetic helicity evolution proceeds in a self-consistent way with the lepton asymmetry growth. The role of sphaleron transitions decreasing the left lepton number turns out to be negligible in given scenario. The hypermagnetic helicity can be a supply for the magnetic one in Higgs phase assuming a strong seed hypermagnetic field in symmetric phase.", "keyphrases": ["early universe", "abelian anomaly", "hypermagnetic helicity evolution", "left lepton doublet"]}
{"id": "1301.0371", "title": "Cool Gas in High Redshift Galaxies", "abstract": "Over the last decade, observations of the cool interstellar medium in distant galaxies via molecular and atomic fine structure line emission has gone from a curious look into a few extreme, rare objects, to a mainstream tool to study galaxy formation, out to the highest redshifts. Molecular gas has now been observed in close to 200 galaxies at z>1, including numerous AGN host-galaxies out to z 7, highly starforming sub-millimeter galaxies (median redshift z 2.5), and increasing samples of 'main-sequence' star forming galaxies at z 1.5-2.5. Studies have moved well beyond simple detections, to dynamical imaging at kpc-scale resolution, and multi-line, multi-species studies that determine the physical conditions in the interstellar medium. Observations of the cool gas are the required complement to studies of the stellar density and star formation history of the Universe, as they reveal the phase of the interstellar medium that immediately precedes star formation. Current observations suggest that the order of magnitude increase in the cosmic star formation rate density from z 0 to 2 is commensurate with a similar increase in the gas to stellar mass ratio in star forming disk galaxies. Progress has been made on determining the CO luminosity to H_2 mass conversion factor at high-z, and the dichotomy between high versus low depletion time values for main sequence versus starburst galaxies, respectively, with a likely dependence on metallicity and other local physical conditions. Studies of atomic fine structure line emission are rapidly progressing, with some tens of galaxies detected in the exceptionally bright [CII] 158 micron line to date. This line is proving to be a unique tracer of galaxy dynamics in the early Universe and has the potential to be the most direct means of obtaining spectroscopic redshifts for the first galaxies during cosmic reionization.", "keyphrases": ["high redshift galaxy", "star formation rate", "cool gas"]}
{"id": "1301.0455", "title": "Bayesian inference on EMRI signals using low frequency approximations", "abstract": "Extreme mass ratio inspirals (EMRIs) are thought to be one of the most exciting gravitational wave sources to be detected with LISA. Due to their complicated nature and weak amplitudes the detection and parameter estimation of such sources is a challenging task. In this paper we present a statistical methodology based on Bayesian inference in which the estimation of parameters is carried out by advanced Markov chain Monte Carlo (MCMC) algorithms such as parallel tempering MCMC. We analysed high and medium mass EMRI systems that fall well inside the low frequency range of LISA. In the context of the Mock LISA Data Challenges, our investigation and results are also the first instance in which a fully Markovian algorithm is applied for EMRI searches. Results show that our algorithm worked well in recovering EMRI signals from different (simulated) LISA data sets having single and multiple EMRI sources and holds great promise for posterior computation under more realistic conditions. The search and estimation methods presented in this paper are general in their nature, and can be applied in any other scenario such as AdLIGO, AdVIRGO and Einstein Telescope with their respective response functions.", "keyphrases": ["emri signal", "mcmc", "bayesian inference"]}
{"id": "1804.06298", "title": "Photon-graviton scattering: A new way to detect anisotropic gravitational waves?", "abstract": "Gravitons are the quantum counterparts of gravitational waves in low-energy theories of gravity. Using Feynman rules one can compute scattering amplitudes describing the interaction between gravitons and other fields. Here, we consider the interaction between gravitons and photons. Using the quantum Boltzmann equation formalism, we derive fully general equations describing the radiation transfer of photon polarization, due to the forward scattering with gravitons. We show that the Q and U photon linear polarization modes couple with the V photon circular polarization mode, if gravitons have anisotropies in their power-spectrum statistics. As an example, we apply our results to the case of primordial gravitons, considering models of inflation where an anisotropic primordial graviton distribution is produced. Finally, we evaluate the effect on cosmic microwave background (CMB) polarization, showing that in general the expected effects on the observable CMB frequencies are very small. However, our result is promising, since it could provide a novel tool for detecting anisotropic backgrounds of gravitational waves, as well as for getting further insight on the physics of gravitational waves.", "keyphrases": ["gravitational wave", "photon", "photon-graviton scattering"]}
{"id": "1205.4679", "title": "A combined measurement of cosmic growth and expansion from clusters of galaxies, the CMB and galaxy clustering", "abstract": "Combining galaxy cluster data from the ROSAT All-Sky Survey and the Chandra X-ray Observatory, cosmic microwave background data from the Wilkinson Microwave Anisotropy Probe, and galaxy clustering data from the WiggleZ Dark Energy Survey, the 6-degree Field Galaxy Survey and the Sloan Digital Sky Survey III, we test for consistency the cosmic growth of structure predicted by General Relativity (GR) and the cosmic expansion history predicted by the cosmological constant plus cold dark matter paradigm (LCDM). The combination of these three independent, well studied measurements of the evolution of the mean energy density and its fluctuations is able to break strong degeneracies between model parameters. We model the key properties of cosmic growth with the normalization of the matter power spectrum, sigma_8, and the cosmic growth index, gamma, and those of cosmic expansion with the mean matter density, Omega_m, the Hubble constant, H_0, and a kinematical parameter equivalent to that for the dark energy equation of state, w. For a spatially flat geometry, w=-1, and allowing for systematic uncertainties, we obtain sigma_8=0.785+-0.019 and gamma=0.570+0.064-0.063 (at the 68.3 per cent confidence level). Allowing both w and gamma to vary we find w=-0.950+0.069-0.070 and gamma=0.533+-0.080. To further tighten the constraints on the expansion parameters, we also include supernova, Cepheid variable and baryon acoustic oscillation data. For w=-1, we have gamma=0.616+-0.061. For our most general model with a free w, we measure Omega_m=0.278+0.012-0.011, H_0=70.0+-1.3 km s^-1 Mpc^-1 and w=-0.987+0.054-0.053 for the expansion parameters, and sigma_8=0.789+-0.019 and gamma=0.604+-0.078 for the growth parameters. These results are in excellent agreement with GR+LCDM (gamma 0.55; w=-1) and represent the tightest and most robust simultaneous constraint on cosmic growth and expansion to date.", "keyphrases": ["cosmic growth", "galaxy", "general relativity"]}
{"id": "1501.03515", "title": "High Energy Physics Signatures from Inflation and Conformal Symmetry of de Sitter", "abstract": "During inflation, the geometry of spacetime is described by a (quasi-)de Sitter phase. Inflationary observables are determined by the underlying (softly broken) de Sitter isometry group SO(1, 4) which acts like a conformal group on R^3: when the fluctuations are on super-Hubble scales, the correlators of the scalar fields are constrained by conformal invariance. Heavy fields with mass m larger than the Hubble rate H correspond to operators with imaginary dimensions in the dual Euclidean three-dimensional conformal field theory. By making use of the dS/CFT correspondence we show that, besides the Boltzmann suppression expected from the thermal properties of de Sitter space, the generic effect of heavy fields in the inflationary correlators of the light fields is to introduce power-law suppressed corrections of the form O(H^2/m^2). This can be seen, for instance, at the level of the four-point correlator for which we provide the correction due to a massive scalar field exchange.", "keyphrases": ["conformal symmetry", "cosmological collider physics", "quasi-single field inflation"]}
{"id": "1803.02008", "title": "Planetary Spectrum Generator: an accurate online radiative transfer suite for atmospheres, comets, small bodies and exoplanets", "abstract": "We have developed an online radiative-transfer suite (https://psg.gsfc.nasa.gov) applicable to a broad range of planetary objects (e.g., planets, moons, comets, asteroids, TNOs, KBOs, exoplanets). The Planetary Spectrum Generator (PSG) can synthesize planetary spectra (atmospheres and surfaces) for a broad range of wavelengths (UV/Vis/near-IR/IR/far-IR/THz/sub-mm/Radio) from any observatory (e.g., JWST, ALMA, Keck, SOFIA), any orbiter (e.g., ExoMars, Juno), or any lander (e.g., MSL). This is achieved by combining several state-of-the-art radiative transfer models, spectroscopic databases and planetary databases (i.e., climatological and orbital). PSG has a 3D (three-dimensional) orbital calculator for most bodies in the solar system, and all confirmed exoplanets, while the radiative-transfer models can ingest billions of spectral signatures for hundreds of species from several spectroscopic repositories. It integrates the latest radiative-transfer and scattering methods in order to compute high resolution spectra via line-by-line calculations, and utilizes the efficient correlated-k method at moderate resolutions, while for computing cometary spectra, PSG handles non-LTE and LTE excitation processes. PSG includes a realistic noise calculator that integrates several telescope / instrument configurations (e.g., interferometry, coronagraphs) and detector technologies (e.g., CCD, heterodyne detectors, bolometers). Such an integration of advanced spectroscopic methods into an online tool can greatly serve the planetary community, ultimately enabling the retrieval of planetary parameters from remote sensing data, efficient mission planning strategies, interpretation of current and future planetary data, calibration of spectroscopic data, and development of new instrument/spacecraft concepts.", "keyphrases": ["atmosphere", "exoplanet", "psg", "planetary spectrum generator"]}
{"id": "1608.01299", "title": "A Direct Probe of the Evolutionary History of the Primordial Universe", "abstract": "Since Hubble and Lamaitre's discovery of the expanding universe using galaxies till the recent discovery of the accelerating universe using standard candles, direct measurements of the evolution of the scale factor of the universe a(t) have played central roles in establishing the standard model of cosmology. In this letter, we show that such a measurement may be extended to the primordial universe using massive fields as standard clocks, providing a direct evidence for the scenario responsible for the Big Bang. This is a short and non-technical introduction to the idea of classical and quantum primordial standard clocks.", "keyphrases": ["primordial universe", "massive field", "field inflation"]}
{"id": "0912.4319", "title": "Empirical analysis of the solar contribution to global mean air surface temperature change", "abstract": "The solar contribution to global mean air surface temperature change is analyzed by using an empirical bi-scale climate model characterized by both fast and slow characteristic time responses to solar forcing: \u03c4_1 =0.4 \u00b1 0.1 yr, and \u03c4_2= 8 \u00b1 2 yr or \u03c4_2=12 \u00b1 3 yr. Since 1980 the solar contribution to climate change is uncertain because of the severe uncertainty of the total solar irradiance satellite composites. The sun may have caused from a slight cooling, if PMOD TSI composite is used, to a significant warming (up to 65 used. The model is calibrated only on the empirical 11-year solar cycle signature on the instrumental global surface temperature since 1980. The model reconstructs the major temperature patterns covering 400 years of solar induced temperature changes, as shown in recent paleoclimate global temperature records.", "keyphrases": ["solar contribution", "climate change", "irradiance", "cooling"]}
{"id": "1905.03601", "title": "Einstein-Gauss-Bonnet gravity in 4-dimensional space-time", "abstract": "In this Letter we present a general covariant modified theory of gravity in D=4 space-time dimensions which propagates only the massless graviton and bypasses the Lovelock's theorem. The theory we present is formulated in D>4 dimensions and its action consists of the Einstein-Hilbert term with a cosmological constant, and the Gauss-Bonnet term multiplied by a factor 1/(D-4). The four-dimensional theory is defined as the limit D\u21924. In this singular limit the Gauss-Bonnet invariant gives rise to non-trivial contributions to gravitational dynamics, while preserving the number of graviton degrees of freedom and being free from Ostrogradsky instability. We report several appealing new predictions of this theory, including the corrections to the dispersion relation of cosmological tensor and scalar modes, singularity resolution for spherically symmetric solutions, and others.", "keyphrases": ["gravity", "non-trivial contribution", "black hole", "dimensional einstein-gauss-bonnet"]}
{"id": "1103.0005", "title": "The overdensity and masses of the friends-of-friends halos and universality of the halo mass function", "abstract": "The friends-of-friends algorithm (hereafter, FOF) is a percolation algorithm which is routinely used to identify dark matter halos from N-body simulations. We use results from percolation theory to show that the boundary of FOF halos does not correspond to a single density threshold but to a range of densities close to a critical value that depends upon the linking length parameter, b. We show that for the commonly used choice of b = 0.2, this critical density is equal to 81.62 times the mean matter density. Consequently, halos identified by the FOF algorithm enclose an average overdensity which depends on their density profile (concentration) and therefore changes with halo mass contrary to the popular belief that the average overdensity is 180. We derive an analytical expression for the overdensity as a function of the linking length parameter b and the concentration of the halo. Results of tests carried out using simulated and actual FOF halos identified in cosmological simulations show excellent agreement with our analytical prediction. We also find that the mass of the halo that the FOF algorithm selects crucially depends upon mass resolution. We find a percolation theory motivated formula that is able to accurately correct for the dependence on number of particles for the mock realizations of spherical and triaxial Navarro-Frenk-White halos. However, we show that this correction breaks down when applied to the real cosmological FOF halos due to presence of substructures. Given that abundance of substructure depends on redshift and cosmology, we expect that the resolution effects due to substructure on the FOF mass and halo mass function will also depend on redshift and cosmology and will be difficult to correct for in general. Finally, we discuss the implications of our results for the universality of the mass function.", "keyphrases": ["overdensity", "universality", "halo mass function", "friends-of-friend algorithm"]}
{"id": "2011.13423", "title": "Starlight coupling through atmospheric turbulence into few-mode fibers and photonic lanterns in the presence of partial adaptive optics correction", "abstract": "Starlight corrupted by atmospheric turbulence cannot couple efficiently into astronomical instruments based on integrated optics as they require light of high spatial coherence to couple into their single-mode waveguides. Low-order adaptive optics in combination with photonic lanterns offer a practical approach to achieve efficient coupling into multiplexed astrophotonic devices. We investigate, aided by simulations and an experimental testbed, the trade-off between the degrees of freedom of the adaptive optics system and those of the input waveguide of an integrated optic component leading to a cost-effective hybrid system that achieves a signal-to-noise ratio higher than a standalone device fed by a single-mode fiber.", "keyphrases": ["atmospheric turbulence", "fiber", "photonic lantern"]}
{"id": "1503.05802", "title": "Consistent generation of magnetic fields in axion inflation models", "abstract": "There has been a growing evidence for the existence of magnetic fields in the extra-galactic regions, while the attempt to associate their origin with the inflationary epoch alone has been found extremely challenging. We therefore take into account the consistent post-inflationary evolution of the magnetic fields that are originated from vacuum fluctuations during inflation. In the model of our interest, the electromagnetic (EM) field is coupled to a pseudo-scalar inflaton \u03d5 through the characteristic term \u03d5 FF\u0303, breaking the conformal invariance. This interaction dynamically breaks the parity and enables a continuous production of only one of the polarization states of the EM field through tachyonic instability. The produced magnetic fields are thus helical. We find that the dominant contribution to the observed magnetic fields in this model comes from the modes that leave the horizon near the end of inflation, further enhanced by the tachyonic instability right after the end of inflation. The EM field is subsequently amplified by parametric resonance during the period of inflaton oscillation. Once the thermal plasma is formed (reheating), the produced helical magnetic fields undergo a turbulent process called inverse cascade, which shifts their peak correlation scales from smaller to larger scales. We consistently take all these effects into account within the regime where the perturbation of \u03d5 is negligible and obtain B_ eff\u223c 10^-19G, indicating the necessity of additional mechanisms to accommodate the observations.", "keyphrases": ["tachyonic instability", "magnetogenesis", "inflationary magnetogenesis"]}
{"id": "1804.05520", "title": "Bulk flow in the combined 2MTF and 6dFGSv surveys", "abstract": "We create a combined sample of 10,904 late and early-type galaxies from the 2MTF and 6dFGSv surveys in order to accurately measure bulk flow in the local Universe. Galaxies and groups of galaxies common between the two surveys are used to verify that the difference in zero-points is <0.02 dex. We introduce a maximum likelihood estimator (\u03b7MLE) for bulk flow measurements which allows for more accurate measurement in the presence non-Gaussian measurement errors. To calibrate out residual biases due to the subtle interaction of selection effects, Malmquist bias and anisotropic sky distribution, the estimator is tested on mock catalogues generated from 16 independent large-scale GiggleZ and SURFS simulations. The bulk flow of the local Universe using the combined data set, corresponding to a scale size of 40 h^-1 Mpc, is 288\u00b124 km s^-1 in the direction (l,b)=(296\u00b16^\u2218, 21\u00b15^\u2218). This is the most accurate bulk flow measurement to date, and the amplitude of the flow is consistent with the \u039bCDM expectation for similar size scales.", "keyphrases": ["2mtf", "group", "bulk flow"]}
{"id": "1305.3044", "title": "Planck constraints on single-field inflation", "abstract": "We place observational constraints on slow-variation single-field inflationary models by carrying out the cosmological Monte Carlo simulation with the recent data of Planck combined with the WMAP large-angle polarization, baryon acoustic oscillations, and ACT/SPT temperature data. Our analysis covers a wide variety of models with second-order equations of motion\u2013 including potential-driven slow-roll inflation, non-minimally coupled models, running kinetic couplings, Brans-Dicke theories, potential-driven Galileon inflation, field-derivative couplings to the Einstein tensor, and k-inflation. In the presence of running kinetic exponential couplings, covariant Galileon terms, and field-derivative couplings, the tensor-to-scalar ratio of the self-coupling potential gets smaller relative to that in standard slow-roll inflation, but the models lie outside the 68 k-inflation models can be tightly constrained by adding the bounds from the scalar non-Gaussianities. The small-field inflationary models with asymptotic flat Einstein-frame potentials in the regime phi >> M_pl generally fit the data very well. These include the models such as Kahler-moduli inflation, non-minimally coupled Higgs inflation, and inflation in Brans-Dicke theories in the presence of the potential V(phi)=3M^2 (phi-M_pl)^2/4 with the Brans-Dicke parameter omega_BD<O(1) (which covers the Starobinsky's model f(R)=R+R^2/(6M^2) as a special case).", "keyphrases": ["inflationary model", "k-inflation", "tensor-to-scalar ratio", "gravity", "string theory"]}
{"id": "1511.09223", "title": "Revisiting the distance duality relation using a non-parametric regression method", "abstract": "The interdependence of luminosity distance, D_L and angular diameter distance, D_A given by the distance duality relation (DDR) is very significant in observational cosmology. It is very closely tied with the temperature- redshift relation of Cosmic Microwave Background (CMB) radiation. Any deviation from \u03b7(z)\u2261D_L/D_A (1+z)^2 =1 indicates a possible emergence of new physics. Our aim in this work is to check the consistency of these relations using a non-parametric regression method namely, LOESS with SIMEX. This technique avoids dependency on the cosmological model and works with a minimal set of assumptions. Further, to analyze the efficiency of the methodology, we simulate a dataset of 200 points of \u03b7 (z) data based on a phenomenological model \u03b7(z)= (1+z)^\u03f5. The error on the simulated data points is obtained by using the temperature of CMB radiation at various redshifts. For testing the distance duality relation, we use the JLA SNe Ia data for luminosity distances, while the angular diameter distances are obtained from radio galaxies datasets. Since the DDR is linked with CMB temperature - redshift relation, therefore we also use the CMB temperature data to reconstruct \u03b7 (z). It is important to note that with CMB data, we are able to study the evolution of DDR up to a very high redshift z = 2.418. In this analysis, we find no evidence of deviation from \u03b7=1 within a 1\u03c3 region in the entire redshift range used in this analysis (0 < z \u2264 2.418).", "keyphrases": ["distance duality relation", "non-parametric regression method", "simex"]}
{"id": "1805.11415", "title": "Abundance gradients along the Galactic disc from chemical evolution models", "abstract": "In this paper, we study the formation and chemical evolution of the Milky Way disc with particular focus on the abundance patterns ([\u03b1/Fe] vs. [Fe/H]) at different Galactocentric distances, the present-time abundance gradients along the disc and the time evolution of abundance gradients. We consider the chemical evolution models for the Galactic disc developed by Grisoni et al. (2017) for the solar neighborhood, both the two-infall and the one-infall ones, and we extend our analysis to the other Galactocentric distances. In particular, we examine the processes which mainly influence the formation of the abundance gradients: the inside-out scenario, a variable star formation efficiency, and radial gas flows. We compare our model results with recent abundance patterns obtained along the Galactic disc from the APOGEE survey and with abundance gradients observed from Cepheids, open clusters, HII regions and PNe. We conclude that the inside-out scenario is a key ingredient, but cannot be the only one to explain abundance patterns at different Galactocentric distances and abundance gradients. Further ingredients, such as radial gas flows and variable star formation efficiency, are needed to reproduce the observed features in the thin disc. The evolution of abundance gradients with time is also shown, although firm conclusions cannot still be drawn.", "keyphrases": ["galactic disc", "chemical evolution model", "star formation efficiency", "abundance gradient"]}
{"id": "1009.2461", "title": "Neutrino lumps and the Cosmic Microwave Background", "abstract": "The interaction between the cosmon and neutrinos may solve the \"why now problem\" for dark energy cosmologies. Within growing neutrino quintessence it leads to the formation of nonlinear neutrino lumps. For a test of such models by the integrated Sachs-Wolfe effect for the cosmic microwave background (CMB) we estimate the size and time evolution of the gravitational potential induced by these lumps. A population of lumps with size of 100 Mpc or more could lead to observable effects on the CMB anisotropies for low angular momenta. The linear approximation is found to be invalid for the relevant length scales. Quantitative estimates depend strongly on the details of the transition between the linear and nonlinear regimes. In particular, important backreaction effects arise from the nonlinearities of the cosmon interactions. At the present stage the uncertainties of the estimate make it difficult to constrain the parameter space of growing neutrino models. We explicitly discuss scenarios and models that are compatible with the CMB observations.", "keyphrases": ["cosmic microwave background", "gravitational potential", "neutrino"]}
{"id": "1301.1778", "title": "Early Universe Tomography with CMB and Gravitational Waves", "abstract": "We discuss how one can reconstruct the thermal history of the Universe by combining cosmic microwave background (CMB) measurements and gravitational wave (GW) direct detection experiments. Assuming various expansion eras to take place after the inflationary reheating and before Big-Bang Nucleosynthesis (BBN), we show how measurements of the GW spectrum can be used to break the degeneracies associated with CMB data, the latter being sensitive to the total amount of cosmic expansion only. In this context, we argue that the expected constraints from future CMB and GW experiments can probe a scenario in which there exists late-time entropy production in addition to the standard reheating. We show that, for some cases, combining data from future CMB and GW direct detection experiments allows the determination of the reheating temperature, the amount of entropy produced and the temperature at which the standard radiation era started.", "keyphrases": ["universe", "thermal history", "reheating"]}
{"id": "1907.12216", "title": "Coupled vector dark energy", "abstract": "We provide a general framework for studying the evolution of background and cosmological perturbations in the presence of a vector field A_\u03bc coupled to cold dark matter (CDM). We consider an interacting Lagrangian of the form Q f(X) T_c, where Q is a coupling constant, f is an arbitrary function of X=-A_\u03bcA^\u03bc/2, and T_c is a trace of the CDM energy-momentum tensor. The matter coupling affects the no-ghost condition and sound speed of linear scalar perturbations deep inside the sound horizon, while those of tensor and vector perturbations are not subject to modifications. The existence of interactions also modifies the no-ghost condition of CDM density perturbations. We propose a concrete model of coupled vector dark energy with the tensor propagation speed equivalent to that of light. In comparison to the Q=0 case, we show that the decay of CDM to the vector field leads to the phantom dark energy equation of state w_ DE closer to -1. This alleviates the problem of observational incompatibility of uncoupled models in which w_ DE significantly deviates from -1. The maximum values of w_ DE reached during the matter era are bounded from the CDM no-ghost condition of future de Sitter solutions.", "keyphrases": ["vector", "dark energy", "lagrangian"]}
{"id": "1503.03876", "title": "Planet formation around binary stars: Tatooine made easy", "abstract": "We examine characteristics of circumbinary orbits in the context of current planet formation scenarios. Analytical perturbation theory predicts the existence of nested circumbinary orbits that are generalizations of circular paths around a single star. These orbits have forced eccentric motion aligned with the binary as well as higher frequency oscillations, yet they do not cross, even in the presence of massive disks and perturbations from large planets. For this reason, dissipative gas and planetesimals can settle onto these \"most circular\" orbits, facilitating the growth of protoplanets. Outside a region close to the binary where orbits are generally unstable, circumbinary planets form in much the same way as their cousins around a single star. Here, we review the theory and confirm its predictions with a suite of representative simulations. We then consider the circumbinary planets discovered with NASA's Kepler satellite. These Neptune- and Jupiter-size planets, or their planetesimal precursors, may have migrated inward to reach their observed orbits, since their current positions are outside of unstable zones caused by overlapping resonances. In situ formation without migration seems less likely, only because the surface density of the protoplanetary disks must be implausibly high. Otherwise, the circumbinary environment is friendly to planet formation, and we expect that many Earth-like \"Tatooines\" will join the growing census of circumbinary planets.", "keyphrases": ["star", "protoplanetary disk", "planet formation"]}
{"id": "1102.5421", "title": "Networks of gravitational wave detectors and three figures of merit", "abstract": "This paper develops a general framework for studying the effectiveness of networks of interferometric gravitational wave detectors and then uses it to show that enlarging the existing LIGO-VIRGO network with one or more planned or proposed detectors in Japan (LCGT), Australia, and India brings major benefits, including much larger detection rate increases than previously thought... I show that there is a universal probability distribution function (pdf) for detected SNR values, which implies that the most likely SNR value of the first detected event will be 1.26 times the search threshold. For binary systems, I also derive the universal pdf for detected values of the orbital inclination, taking into account the Malmquist bias; this implies that the number of gamma-ray bursts associated with detected binary coalescences should be 3.4 times larger than expected from just the beaming fraction of the gamma burst. Using network antenna patterns, I propose three figures of merit that characterize the relative performance of different networks... Adding any new site to the planned LIGO-VIRGO network can dramatically increase, by factors of 2 to 4, the detected event rate by allowing coherent data analysis to reduce the spurious instrumental coincident background. Moving one of the LIGO detectors to Australia additionally improves direction-finding by a factor of 4 or more. Adding LCGT to the original LIGO-VIRGO network not only improves direction-finding but will further increase the detection rate over the extra-site gain by factors of almost 2, partly by improving the network duty cycle... Enlarged advanced networks could look forward to detecting three to four hundred neutron star binary coalescences per year.", "keyphrases": ["gravitational wave detector", "merit", "site", "network"]}
{"id": "2104.00880", "title": "Refined Mass and Geometric Measurements of the High-Mass PSR J0740+6620", "abstract": "We report results from continued timing observations of PSR J0740+6620, a high-mass, 2.8-ms radio pulsar in orbit with a likely ultra-cool white dwarf companion. Our data set consists of combined pulse arrival-time measurements made with the 100-m Green Bank Telescope and the Canadian Hydrogen Intensity Mapping Experiment telescope. We explore the significance of timing-based phenomena arising from general-relativistic dynamics and variations in pulse dispersion. When using various statistical methods, we find that combining \u223c 1.5 years of additional, high-cadence timing data with previous measurements confirms and improves upon previous estimates of relativistic effects within the PSR J0740+6620 system, with the pulsar mass m_ p = 2.08^+0.07_-0.07 M_\u2299 (68.3% credibility) determined by the relativistic Shapiro time delay. For the first time, we measure secular variation in the orbital period and argue that this effect arises from apparent acceleration due to significant transverse motion. After incorporating contributions from Galactic differential rotation and off-plane acceleration in the Galactic potential, we obtain a model-dependent distance of d = 1.14^+0.17_-0.15 kpc (68.3% credibility). This improved distance confirms the ultra-cool nature of the white dwarf companion determined from recent optical observations. We discuss the prospects for future observations with next-generation facilities, which will likely improve the precision on m_ p for J0740+6620 by an order of magnitude within the next few years.", "keyphrases": ["psr j0740", "pulsar", "kpc", "neutron star"]}
{"id": "1004.0575", "title": "Modifications to Lorentz invariant dispersion in relatively boosted frames", "abstract": "We investigate the implications of energy-dependence of the speed of photons, one of the candidate effects of quantum-gravity theories that has been most studied recently, from the perspective of observations in different reference frames. We examine how a simultaneous burst of photons would be measured by two observers with a relative velocity, establishing some associated conditions for the consistency of theories. For scenarios where the Lorentz transformations remain valid these consistency conditions allow us to characterize the violations of Lorentz symmetry through an explicit description of the modification of the quantum-gravity scale in boosted frames with respect to its definition in a preferred frame. When applied to relativistic scenarios with a deformation of Lorentz invariance that preserves the equivalence of inertial observers, we find an insightful characterization of the necessity to adopt in such frameworks non-classical features of spacetime geometry, e.g. events that are at the same spacetime point for one observer cannot be considered at the same spacetime point for other observers. Our findings also suggest that, at least in principle (and perhaps one day even in practice), measurements of the dispersion of photons in relatively boosted frames can be particularly valuable for the purpose of testing these scenarios.", "keyphrases": ["lorentz invariance", "dispersion", "frame"]}
{"id": "1809.06381", "title": "The Carnegie Supernova Project: Absolute Calibration and the Hubble Constant", "abstract": "We present an analysis of the final data release of the Carnegie Supernova Project I, focusing on the absolute calibration of the luminosity-decline-rate relation for Type Ia supernovae (SNeIa) using new intrinsic color relations with respect to the color-stretch parameter, s_BV, enabling improved dust extinction corrections. We investigate to what degree the so-called fast-declining SNeIa can be used to determine accurate extragalactic distances. We estimate the intrinsic scatter in the luminosity-decline-rate relation, and find it ranges from \u00b1 0.13 mag to \u00b1 0.18 mag with no obvious dependence on wavelength. Using the Cepheid variable star data from the SH0ES project (Riess et al., 2016), the SNIa distance scale is calibrated and the Hubble constant is estimated using our optical and near-infrared sample, and these results are compared to those determined exclusively from a near-infrared sub-sample. The systematic effect of the supernova's host galaxy mass is investigated as a function of wavelength and is found to decrease toward redder wavelengths, suggesting this effect may be due to dust properties of the host. Using estimates of the dust extinction derived from optical and NIR wavelengths, and applying these to H band, we derive a Hubble constant H_0 = 73.2 \u00b1 2.3 km/s/Mpc, whereas using a simple B-V color-correction applied to B band yields H_0 = 72.7 \u00b1 2.1 km/s/Mpc. Photometry of two calibrating SNeIa from the CSP-II sample, SN2012ht and SN2015F, is presented and used to improve the calibration of the SNIa distance ladder.", "keyphrases": ["carnegie supernova project", "absolute calibration", "hubble constant", "dust extinction correction"]}
{"id": "1106.1635", "title": "Fingerprints of Primordial Universe Paradigms as Features in Density Perturbations", "abstract": "Experimentally distinguishing different primordial universe paradigms that lead to the Big Bang model is an outstanding challenge in modern cosmology and astrophysics. We show that a generic type of signals that exist in primordial universe models can be used for such purpose. These signals are induced by tiny oscillations of massive fields and manifest as features in primordial density perturbations. They are capable of recording the time-dependence of the scale factor of the primordial universe, and therefore provide direct evidence for specific paradigm.", "keyphrases": ["primordial universe", "density perturbation", "massive field"]}
{"id": "2001.11564", "title": "The Milky Way's stellar streams and globular clusters do not align in a Vast Polar Structure", "abstract": "There is increasing evidence that a substantial fraction of Milky Way satellite galaxies align in a rotationally-supported plane of satellites, a rare configuration in cosmological simulations of galaxy formation. It has been suggested that other Milky Way substructures (namely young halo globular clusters and stellar/gaseous streams) similarly tend to align with this plane, accordingly dubbed the Vast Polar Structure (VPOS). Using systemic proper motions inferred from Gaia data, we find that globular cluster orbital poles are not clustered in the VPOS direction, though the population with the highest VPOS membership fraction is the young halo clusters ( 30 provide a current census of stellar streams, including new streams discovered using the Dark Energy Survey and Gaia datasets, and find that stellar stream normals are also not clustered in the direction of the VPOS normal. We also find that, based on orbit modeling, there is a likely association between NGC 3201 and the Gj\u00f6ll stellar stream and that, based on its orbital pole, NGC 4147 is likely not a Sagittarius globular cluster. That the Milky Way's accreted globular clusters and streams do not align in the same planar configuration as its satellites suggests that the plane of satellites is either a particularly stable orbital configuration or a population of recently accreted satellites. Neither of these explanations is particularly likely in light of other recent studies, leaving the plane of satellites problem as one of the more consequential open problems in galaxy formation and cosmology.", "keyphrases": ["stellar stream", "globular cluster", "vast polar structure", "cosmology"]}
{"id": "1503.00342", "title": "Beyond Mixing-length Theory: a step toward 321D", "abstract": "We examine the physical basis for algorithms to replace mixing-length theory (MLT) in stellar evolutionary computations. Our 321D procedure is based on numerical solutions of the Navier-Stokes equations. These implicit large eddy simulations (ILES) are three-dimensional (3D), time-dependent, and turbulent, including the Kolmogorov cascade. We use the Reynolds-averaged Navier-Stokes (RANS) formulation to make concise the 3D simulation data, and use the 3D simulations to give closure for the RANS equations. We further analyze this data set with a simple analytical model, which is non-local and time-dependent, and which contains both MLT and the Lorenz convective roll as particular subsets of solutions. A characteristic length (the damping length) again emerges in the simulations; it is determined by an observed balance between (1) the large-scale driving, and (2) small-scale damping. The nature of mixing and convective boundaries is analyzed, including dynamic, thermal and compositional effects, and compared to a simple model. We find that (1) braking regions (boundary layers in which mixing occurs) automatically appear beyond the edges of convection as defined by the Schwarzschild criterion, (2) dynamic (non-local) terms imply a non-zero turbulent kinetic energy flux (unlike MLT), (3) the effects of composition gradients on flow can be comparable to thermal effects, and (4) convective boundaries in neutrino-cooled stages differ in nature from those in photon-cooled stages (different P\u00e9clet numbers). The algorithms are based upon ILES solutions to the Navier-Stokes equations, so that, unlike MLT, they do not require any calibration to astronomical systems in order to predict stellar properties. Implications for solar abundances, helioseismology, asteroseismology, nucleosynthesis yields, supernova progenitors and core collapse are indicated.", "keyphrases": ["mixing-length theory", "simulation", "formulation", "lorenz", "convection"]}
{"id": "1811.03702", "title": "Systematical study of pulsar light curves with special relativistic effects", "abstract": "We systematically study pulsar light curves, taking into account the special relativistic effect, i.e., the Doppler factor due to the fast spin of the neutron stars, together with the time delay, which comes from the difference of the travel times depending on the position of the spots. For this purpose, first we derive the basic equations with the general expression of the metric for the static, spherically symmetric spacetime, where for simplicity we adopt the pointlike spot approximation for the antipodal spots associated with the magnetic polar cap model. Then, we calculate the light curves from the neutron star models in general relativity, with various angle between rotational and magnetic axes and the inclination angle. As the results, unlike the case for a slowly rotating stellar model, we find that the light curve from a fast rotating stellar model depends not only the stellar compactness but also the stellar radius. We also find that the amplitude of the light curve becomes larger as the stellar radius increases and as the stellar compactness decreases. Thus, via careful observations of the light curves from the rotating neutron star, one would determine the stellar compactness together with the stellar radius, if it rotates fast enough.", "keyphrases": ["pulsar light curve", "special relativistic effect", "neutron star"]}
{"id": "1205.4033", "title": "On the local dark matter density", "abstract": "An analysis of the kinematics of 412 stars at 1-4 kpc from the Galactic mid-plane by Moni Bidin et al. (2012) has claimed to derive a local density of dark matter that is an order of magnitude below standard expectations. We show that this result is incorrect and that it arises from the assumption that the mean azimuthal velocity of the stellar tracers is independent of Galactocentric radius at all heights. We substitute the assumption, supported by data, that the circular speed is independent of radius in the mid-plane. We demonstrate that the assumption of constant mean azimuthal velocity is implausible by showing that it requires the circular velocity to drop more steeply than allowed by any plausible mass model, with or without dark matter, at large heights above the mid-plane. Using the approximation that the circular velocity curve is flat in the mid-plane, we find that the data imply a local dark-matter density of 0.008 +/- 0.003 Msun/pc^3 = 0.3 +/- 0.1 GeV/cm3, fully consistent with standard estimates of this quantity. This is the most robust direct measurement of the local dark-matter density to date.", "keyphrases": ["dark matter", "galactocentric radius", "plausible mass model"]}
{"id": "2005.13161", "title": "A census of baryons in the Universe from localized fast radio bursts", "abstract": "More than three quarters of the baryonic content of the Universe resides in a highly diffuse state that is difficult to observe, with only a small fraction directly observed in galaxies and galaxy clusters. Censuses of the nearby Universe have used absorption line spectroscopy to observe these invisible baryons, but these measurements rely on large and uncertain corrections and are insensitive to the majority of the volume, and likely mass. Specifically, quasar spectroscopy is sensitive either to only the very trace amounts of Hydrogen that exists in the atomic state, or highly ionized and enriched gas in denser regions near galaxies. Sunyaev-Zel'dovich analyses provide evidence of some of the gas in filamentary structures and studies of X-ray emission are most sensitive to gas near galaxy clusters. Here we report the direct measurement of the baryon content of the Universe using the dispersion of a sample of localized fast radio bursts (FRBs), thus utilizing an effect that measures the electron column density along each sight line and accounts for every ionised baryon. We augment the sample of published arcsecond-localized FRBs with a further four new localizations to host galaxies which have measured redshifts of 0.291, 0.118, 0.378 and 0.522, completing a sample sufficiently large to account for dispersion variations along the line of sight and in the host galaxy environment to derive a cosmic baryon density of \u03a9_b = 0.051_-0.025^+0.021 h_70^-1 (95 measurement is consistent with Cosmic Microwave Background and Big Bang Nucleosynthesis values.", "keyphrases": ["baryon", "universe", "fast radio burst", "host galaxy", "redshift"]}
{"id": "1005.1878", "title": "Chameleon Cosmology Model Describing the Phantom Divide Line Crossing", "abstract": "An exact solution describing the evolution of the type Bang-to-Rip with the phantom divide line crossing is constructed in the Chameleon cosmology model, based on two independent functions of the scalar field.", "keyphrases": ["scalar field", "chameleon cosmology model", "cosmological evolution"]}
{"id": "1906.05772", "title": "A Tip for Landscape Riders: Multi-Field Inflation Can Fulfill the Swampland Distance Conjecture", "abstract": "We study how both the swampland distance conjecture and the Lyth bound affect the parameter space of multi-field models of inflation. A generic feature of multi-field inflation is that the geodesic distance [\u0394\u03d5]_G separating any two points laying along the inflationary trajectory differs from the non-geodesic distance [\u0394\u03d5]_NG traversed by the inflaton between those points. These distances must respect a relation of the form [\u0394\u03d5]_G = f([\u0394\u03d5]_NG) \u2264[\u0394\u03d5]_NG, where f is a function determined by the specific multi-field model under scrutiny. We show that this relation leads to important constraints on the parameter space characterizing the multi-field dynamics. Indeed, the swampland distance conjecture implies an upper bound on [\u0394\u03d5]_G set by the details of the ultraviolet completion of inflation, whereas the Lyth bound implies a lower bound on [\u0394\u03d5]_NG determined by the value of the tensor-to-scalar ratio. If future observations confirm the existence of primordial tensor perturbations, these two bounds combined lead to tight constraints on the possible values of the entropy mass of the isocurvature fields orthogonal to the inflationary trajectory and the rate of turn of the inflationary trajectory in multi-field space. We analyze the emerging constraints in detail for the particular case of two-field inflation in hyperbolic field spaces.", "keyphrases": ["multi-field inflation", "swampland distance conjecture", "field space"]}
{"id": "2006.03060", "title": "Optimal filters for the moving lens effect", "abstract": "We assess the prospects for detecting the moving lens effect using cosmological surveys. The bulk motion of cosmological structure induces a small-scale dipolar temperature anisotropy of the cosmic microwave radiation (CMB), centered around halos and oriented along the transverse velocity field. We introduce a set of optimal filters for this signal, and forecast that a high significance detection can be made with upcoming experiments. We discuss the prospects for reconstructing the bulk transverse velocity field on large scales using matched filters, finding good agreement with previous work using quadratic estimators.", "keyphrases": ["lens effect", "upcoming experiment", "optimal filter"]}
{"id": "1208.6563", "title": "Euclidean quantum gravity and stochastic inflation", "abstract": "In this paper, we compare dispersions of a scalar field in Euclidean quantum gravity with stochastic inflation. We use Einstein gravity and a minimally coupled scalar field with a quadratic potential. We restrict our attention to small mass and small field cases. In the Euclidean approach, we introduce the ground state wave function which is approximated by instantons. We used a numerical technique to find instantons that satisfy classicality. In the stochastic approach, we introduce the probability distribution of Hubble patches that can be approximated by locally homogeneous universes down to a smoothing scale. We assume that the ground state wave function should correspond to the stationary state of the probability distribution of the stochastic universe. By comparing the dispersion of both approaches, we conclude three main results. (1) For a statistical distribution with a certain value, we can find a corresponding instanton in the Euclidean side, and it should be a complex-valued instanton. (2) The size of the universe of the Euclidean approach corresponds to the smoothing scale of the stochastic side; the universe is homogeneous up to the Euclidean instanton. (3) In addition, as the mass increases up to a critical value, both approaches break at the same time. Hence, generation of classical inhomogeneity in the stochastic approach and the instability of classicality in the Euclidean approach are related.", "keyphrases": ["stochastic inflation", "universe", "euclidean quantum gravity"]}
{"id": "1511.03218", "title": "Primordial Statistical Anisotropies: The Effective Field Theory Approach", "abstract": "In this work we present the effective field theory of primordial statistical anisotropies generated during anisotropic inflation involving a background U(1) gauge field. Besides the usual Goldstone boson associated with the breaking of time diffeomorphism we have two additional Goldstone bosons associated with the breaking of spatial diffeomorphisms. We further identify these two new Goldstone bosons with the expected two transverse degrees of the U(1) gauge field fluctuations. Upon defining the appropriate unitary gauge, we present the most general quadratic action which respects the remnant symmetry in the unitary gauge. The interactions between various Goldstone bosons leads to statistical anisotropy in curvature perturbation power spectrum. Calculating the general results for power spectrum anisotropy, we recover the previously known results in specific models of anisotropic inflation. In addition, we present novel results for statistical anisotropy in models with non-trivial sound speed for inflaton fluctuations. Also we identify the interaction which leads to birefringence-like effects in anisotropic power spectrum in which the speed of gauge field fluctuations depends on the direction of the mode propagation and the two polarization of gauge field fluctuations contribute differently in statistical anisotropy. As another interesting application, our EFT approach naturally captures interactions generating parity violating statistical anisotropies.", "keyphrases": ["field theory", "anisotropic inflation", "gauge field"]}
{"id": "1503.01579", "title": "Gauss-Bonnet Inflation", "abstract": "We consider an Einstein-Scalar-Gauss-Bonnet gravitational theory, and argue that at early times the Ricci scalar can be safely ignored. We then demonstrate that the pure scalar-Gauss-Bonnet theory, with a quadratic coupling function, naturally supports inflationary \u2013 de Sitter \u2013 solutions. During inflation, the scalar field decays exponentially and its effective potential remains always bounded. The theory contains also solutions where these de Sitter phases possess a natural exit mechanism and are replaced by linearly expanding \u2013 Milne \u2013 phases.", "keyphrases": ["natural exit mechanism", "einstein-gauss-bonnet theory", "gravity", "era"]}
{"id": "1009.1874", "title": "The propeller and the frog", "abstract": "\"Propellers\" in planetary rings are disturbances in ring material excited by moonlets that open only partial gaps. We describe a new type of co-orbital resonance that can explain the observed non-Keplerian motions of propellers. The resonance is between the moonlet underlying the propeller, and co-orbiting ring particles downstream of the moonlet where the gap closes. The moonlet librates within the gap about an equilibrium point established by co-orbiting material and stabilized by the Coriolis force. In the limit of small libration amplitude, the libration period scales linearly with the gap azimuthal width and inversely as the square root of the co-orbital mass. The new resonance recalls but is distinct from conventional horseshoe and tadpole orbits; we call it the \"frog\" resonance, after the relevant term in equine hoof anatomy. For a ring surface density and gap geometry appropriate for the propeller Bl\u00e9riot in Saturn's A ring, our theory predicts a libration period of 4 years, similar to the 3.7 year period over which Bl\u00e9riot's orbital longitude is observed to vary. These librations should be subtracted from the longitude data before any inferences about moonlet migration are made.", "keyphrases": ["propeller", "frog", "migration"]}
{"id": "1506.01369", "title": "Measuring the lensing potential with tomographic galaxy number counts", "abstract": "We investigate how the lensing potential can be measured tomographically with future galaxy surveys using their number counts. Such a measurement is an independent test of the standard \u039bCDM framework and can be used to discern modified theories of gravity. We perform a Fisher matrix forecast based on galaxy angular-redshift power spectra, assuming specifications consistent with future photometric Euclid-like surveys and spectroscopic SKA-like surveys. For the Euclid-like survey we derive a fitting formula for the magnification bias. Our analysis suggests that the cross correlation between different redshift bins is very sensitive to the lensing potential such that the survey can measure the amplitude of the lensing potential at the same level of precision as other standard \u039bCDM cosmological parameters.", "keyphrases": ["galaxy survey", "magnification", "cosmological parameter", "correlation function"]}
{"id": "1007.0675", "title": "Viscous dark fluid universe", "abstract": "We investigate the cosmological perturbation dynamics for a universe consisting of pressureless baryonic matter and a viscous fluid, the latter representing a unified model of the dark sector. In the homogeneous and isotropic background the total energy density of this mixture behaves as a generalized Chaplygin gas. The perturbations of this energy density are intrinsically non-adiabatic and source relative entropy perturbations. The resulting baryonic matter power spectrum is shown to be compatible with the 2dFGRS and SDSS (DR7) data. A joint statistical analysis, using also Hubble-function and supernovae Ia data, shows that, different from other studies, there exists a maximum in the probability distribution for a negative present value q_0 \u2248 - 0.53 of the deceleration parameter. Moreover, while previous descriptions on the basis of generalized Chaplygin gas models were incompatible with the matter power spectrum data since they required a much too large amount of pressureless matter, the unified model presented here favors a matter content that is of the order of the baryonic matter abundance suggested by big-bang nucleosynthesis.", "keyphrases": ["baryon", "viscous fluid", "dark sector"]}
{"id": "1908.10352", "title": "Stringent constraints on neutron-star radii from multimessenger observations and nuclear theory", "abstract": "The properties of neutron stars are determined by the nature of the matter that they contain. These properties can be constrained by measurements of the star's size. We obtain stringent constraints on neutron-star radii by combining multimessenger observations of the binary neutron-star merger GW170817 with nuclear theory that best accounts for density-dependent uncertainties in the equation of state. We construct equations of state constrained by chiral effective field theory and marginalize over these using the gravitational-wave observations. Combining this with the electromagnetic observations of the merger remnant that imply the presence of a short-lived hyper-massive neutron star, we find that the radius of a 1.4 M_\u2299 neutron star is R_1.4 M_\u2299 = 11.0^+0.9_-0.6 km (90 interval). Using this constraint, we show that neutron stars are unlikely to be disrupted in neutron-star black-hole mergers; subsequently, such events will not produce observable electromagnetic emission.", "keyphrases": ["nuclear theory", "neutron-star radius", "gravitational wave"]}
{"id": "0710.4881", "title": "Inclusive charged-current neutrino-nucleus reactions calculated with the relativistic quasiparticle random phase approximation", "abstract": "Inclusive neutrino-nucleus cross sections are calculated using a consistent relativistic mean-field theoretical framework. The weak lepton-hadron interaction is expressed in the standard current-current form, the nuclear ground state is described with the relativistic Hartree-Bogoliubov model, and the relevant transitions to excited nuclear states are calculated in the relativistic quasiparticle random phase approximation. Illustrative test calculations are performed for charged-current neutrino reactions on ^12C, ^16O, ^56Fe, and ^208Pb, and results compared with previous studies and available data. Using the experimental neutrino fluxes, the averaged cross sections are evaluated for nuclei of interest for neutrino detectors. We analyze the total neutrino-nucleus cross sections, and the evolution of the contribution of the different multipole excitations as a function of neutrino energy. The cross sections for reactions of supernova neutrinos on ^16O and ^208Pb target nuclei are analyzed as functions of the temperature and chemical potential.", "keyphrases": ["charged-current neutrino-nucleus reaction", "relativistic quasiparticle", "proton-neutron qrpa"]}
{"id": "1403.7098", "title": "Adiabatic contraction revisited: implications for primordial black holes", "abstract": "We simulate the adiabatic contraction of a dark matter (DM) distribution during the process of the star formation, paying particular attention to the phase space distribution of the DM particles after the contraction. Assuming the initial uniform density and Maxwellian distribution of DM velocities, we find that the number n(r) of DM particles within the radius r scales like n(r) \u221d r^1.5, leading to the DM density profile \u03c1\u221d r^-1.5, in agreement with the Liouville theorem and previous numerical studies. At the same time, the number of DM particles \u03bd(r) with periastra smaller than r is parametrically larger, \u03bd(r) \u221d r, implying that many particles contributing at any given moment into the density \u03c1(r) at small r have very elongated orbits and spend most of their time at distances larger than r. This has implications for the capture of DM by stars in the process of their formation. As a concrete example we consider the case of primordial black holes (PBH). We show that accounting for very eccentric orbits boosts the amount of captured PBH by a factor of up to 2\u00d7 10^3 depending on the PBH mass, improving correspondingly the previously derived constraints on the PBH abundance.", "keyphrases": ["primordial black hole", "star formation", "adiabatic contraction"]}
{"id": "1207.6003", "title": "Very-high energy gamma-ray astronomy: A 23-year success story in high-energy astroparticle physics", "abstract": "Very-high energy (VHE) gamma quanta contribute only a minuscule fraction - below one per million - to the flux of cosmic rays. Nevertheless, being neutral particles they are currently the best \"messengers\" of processes from the relativistic/ultra-relativistic Universe because they can be extrapolated back to their origin. The window of VHE gamma rays was opened only in 1989 by the Whipple collaboration, reporting the observation of TeV gamma rays from the Crab nebula. After a slow start, this new field of research is now rapidly expanding with the discovery of more than 150 VHE gamma-ray emitting sources. Progress is intimately related with the steady improvement of detectors and rapidly increasing computing power. We give an overview of the early attempts before and around 1989 and the progress after the pioneering work of the Whipple collaboration. The main focus of this article is on the development of experimental techniques for Earth-bound gamma-ray detectors; consequently, more emphasis is given to those experiments that made an initial breakthrough rather than to the successors which often had and have a similar (sometimes even higher) scientific output as the pioneering experiments. The considered energy threshold is about 30 GeV. At lower energies, observations can presently only be performed with balloon or satellite-borne detectors. Irrespective of the stormy experimental progress, the success story could not have been called a success story without a broad scientific output. Therefore we conclude this article with a summary of the scientific rationales and main results achieved over the last two decades.", "keyphrases": ["astronomy", "gamma ray", "very-high energy"]}
{"id": "1503.05206", "title": "Powerful Outflows and Feedback from Active Galactic Nuclei", "abstract": "Active Galactic Nuclei (AGN) represent the growth phases of the supermassive black holes in the center of almost every galaxy. Powerful, highly ionized winds, with velocities \u223c 0.1- 0.2c are a common feature in X\u2013ray spectra of luminous AGN, offering a plausible physical origin for the well known connections between the hole and properties of its host. Observability constraints suggest that the winds must be episodic, and detectable only for a few percent of their lifetimes. The most powerful wind feedback, establishing the M -\u03c3 relation, is probably not directly observable at all. The M - \u03c3 relation signals a global change in the nature of AGN feedback. At black hole masses below M-\u03c3 feedback is confined to the immediate vicinity of the hole. At the M-\u03c3 mass it becomes much more energetic and widespread, and can drive away much of the bulge gas as a fast molecular outflow.", "keyphrases": ["outflow", "active galactic nuclei", "galaxy"]}
{"id": "1205.2695", "title": "WIMP-nucleus scattering in chiral effective theory", "abstract": "We discuss long-distance QCD corrections to the WIMP-nucleon(s) interactions in the framework of chiral effective theory. For scalar-mediated WIMP-quark interactions, we calculate all the next-to-leading-order corrections to the WIMP-nucleus elastic cross-section, including two-nucleon amplitudes and recoil-energy dependent shifts to the single-nucleon scalar form factors. As a consequence, the scalar-mediated WIMP-nucleus cross-section cannot be parameterized in terms of just two quantities, namely the neutron and proton scalar form factors at zero momentum transfer, but additional parameters appear, depending on the short-distance WIMP-quark interaction. Moreover, multiplicative factorization of the cross-section into particle, nuclear and astro-particle parts is violated. In practice, while the new effects are of the natural size expected by chiral power counting, they become very important in those regions of parameter space where the leading order WIMP-nucleus amplitude is suppressed, including the so-called \"isospin-violating dark matter\" regime. In these regions of parameter space we find order-of-magnitude corrections to the total scattering rates and qualitative changes to the shape of recoil spectra.", "keyphrases": ["chiral effective theory", "two-nucleon amplitude", "dark matter"]}
{"id": "1305.7225", "title": "CMB Faraday rotation as seen through the Milky Way", "abstract": "Faraday Rotation (FR) of CMB polarization, as measured through mode-coupling correlations of E and B modes, can be a promising probe of a stochastic primordial magnetic field (PMF). While the existence of a PMF is still hypothetical, there will certainly be a contribution to CMB FR from the magnetic field of the Milky Way. We use existing estimates of the Milky Way rotation measure (RM) to forecast its detectability with upcoming and future CMB experiments. We find that the galactic RM will not be seen in polarization measurements by Planck, but that it will need to be accounted for by CMB experiments capable of detecting the weak lensing contribution to the B-mode. We then discuss prospects for constraining the PMF in the presence of FR due to the galaxy under various assumptions that include partial de-lensing and partial subtraction of the galactic FR. We find that a realistic future sub-orbital experiment, covering a patch of the sky near the galactic poles, can detect a scale-invariant PMF of 0.1 nano-Gauss at better than 95 confidence level, while a dedicated space-based experiment can detect even smaller fields.", "keyphrases": ["faraday rotation", "milky way", "magnetic field"]}
{"id": "1303.4395", "title": "Light inflaton after LHC8 and WMAP9 results", "abstract": "We update the allowed parameter space of the simple chaotic inflationary model with quartic potential and light inflaton [Bezrukov,Gorbunov'2009] taking into account recent results from cosmology (CMB observations from SPT, ACT and WMAP) and from particle physics (LHC hints of the SM Higgs boson). The non-minimal (yet small) coupling to gravity of the inflaton becomes essential to fit the observational data. The inflaton has mass above 300 MeV and can be searched for at B-factories in B-meson two-body decays to kaon and inflaton. The inflaton lifetime depends on the model parameters, resulting in various inflaton signatures: either a missing energy, or a displaced vertex from the B-meson decay position, or a resonance in the Dalitz plot of a three particle decay. We also discuss the implementation of the inflaton model to the nuMSM, where the inflaton can be responsible for production of the dark matter sterile neutrino in the early Universe.", "keyphrases": ["sterile neutrino", "light inflaton", "tiny non-minimal coupling"]}
{"id": "1411.2608", "title": "Hierarchical probabilistic inference of cosmic shear", "abstract": "Point estimators for the shearing of galaxy images induced by gravitational lensing involve a complex inverse problem in the presence of noise, pixelization, and model uncertainties. We present a probabilistic forward modeling approach to gravitational lensing inference that has the potential to mitigate the biased inferences in most common point estimators and is practical for upcoming lensing surveys. The first part of our statistical framework requires specification of a likelihood function for the pixel data in an imaging survey given parameterized models for the galaxies in the images. We derive the lensing shear posterior by marginalizing over all intrinsic galaxy properties that contribute to the pixel data (i.e., not limited to galaxy ellipticities) and learn the distributions for the intrinsic galaxy properties via hierarchical inference with a suitably flexible conditional probabilitiy distribution specification. We use importance sampling to separate the modeling of small imaging areas from the global shear inference, thereby rendering our algorithm computationally tractable for large surveys. With simple numerical examples we demonstrate the improvements in accuracy from our importance sampling approach, as well as the significance of the conditional distribution specification for the intrinsic galaxy properties when the data are generated from an unknown number of distinct galaxy populations with different morphological characteristics.", "keyphrases": ["inference", "shear", "galaxy"]}
{"id": "0911.1811", "title": "Matter instabilities in general Gauss-Bonnet gravity", "abstract": "We study the evolution of cosmological perturbations in f(G) gravity, where the Lagrangian is the sum of a Ricci scalar R and an arbitrary function f in terms of a Gauss-Bonnet term G. We derive the equations for perturbations assuming matter to be described by a perfect fluid with a constant equation of state w. We show that density perturbations in perfect fluids exhibit negative instabilities during both the radiation and the matter domination, irrespective of the form of f(G). This growth of perturbations gets stronger on smaller scales, which is difficult to be compatible with the observed galaxy spectrum unless the deviation from General Relativity is very small. Thus f(G) cosmological models are effectively ruled out from this Ultra-Violet instability, even though they can be compatible with the late-time cosmic acceleration and local gravity constraints.", "keyphrases": ["gravity", "perfect fluid", "negative instability", "ultra-violet instability"]}
{"id": "1411.0753", "title": "Dark matter and dark energy from Bose-Einstein condensate", "abstract": "We show that Dark Matter consisting of bosons of mass of about 1eV or less has critical temperature exceeding the temperature of the universe at all times, and hence would have formed a Bose-Einstein condensate at very early epochs. We also show that the wavefunction of this condensate, via the quantum potential it produces, gives rise to a cosmological constant which may account for the correct dark energy content of our universe. We argue that massive gravitons or axions are viable candidates for these constituents. In the far future this condensate is all that remains of our universe.", "keyphrases": ["bose-einstein condensate", "graviton", "dark matter"]}
{"id": "1008.1097", "title": "The Evolution of PSR J0737-3039B and a Model for Relativistic Spin Precession", "abstract": "We present the evolution of the radio emission from the 2.8-s pulsar of the double pulsar system PSR J0737-3039A/B. We provide an update on the Burgay et al. (2005) analysis by describing the changes in the pulse profile and flux density over five years of observations, culminating in the B pulsar's radio disappearance in 2008 March. Over this time, the flux density decreases by 0.177 mJy/yr at the brightest orbital phases and the pulse profile evolves from a single to a double peak, with a separation rate of 2.6 deg/yr. The pulse profile changes are most likely caused by relativistic spin precession, but can not be easily explained with a circular hollow-cone beam as in the model of Clifton Weisberg (2008). Relativistic spin precession, coupled with an elliptical beam, can model the pulse profile evolution well. This particular beam shape predicts geometrical parameters for the two bright orbital phases which are consistent and similar to those derived by Breton et al. (2008). However, the observed decrease in flux over time and B's eventual disappearance cannot be easily explained by the model and may be due to the changing influence of A on B.", "keyphrases": ["psr j0737", "relativistic spin precession", "pulsar"]}
{"id": "2003.00286", "title": "Probing Einstein-dilaton Gauss-Bonnet Gravity with the inspiral and ringdown of gravitational waves", "abstract": "Gravitational waves from extreme gravity events such as the coalescence of two black holes in a binary system fill our observable universe, bearing with them the underlying theory of gravity driving their process. One compelling alternative theory of gravity \u2013 known as Einstein-dilaton Gauss-Bonnet gravity motivated by string theory \u2013 describes the presence of an additional dilaton scalar field coupled directly to higher orders of the curvature, effectively describing a \"fifth force\" interaction and the emission of scalar dipole radiation between two scalarized black holes. Most previous studies focused on considering only the leading correction to the inspiral portion of the binary black hole waveforms. In our recent paper, we carried out inspiral-merger-ringdown consistency tests in this string-inspired gravity by including corrections to both the inspiral and ringdown portions, as well as those to the mass and spin of remnant black holes, valid to quadratic order in spin. We here extend the analysis by directly computing bounds on the theoretical coupling constant using the full inspiral-merger-ringdown waveform rather than treating the inspiral and merger-ringdown portions separately. We also consider the corrections valid to quartic order in spin to justify the validity of black hole's slow-rotation approximation. We find the quasinormal mode corrections to the waveform to be particularly important for high-mass events such as GW170729, in which the dilaton fields' small-coupling approximation fails without such effects included. We also show that future space-based and multiband gravitational-wave observations have the potential to go beyond existing bounds on the theory. The bounds presented here are comparable to those found in via the inspiral-merger-ringdown consistency tests.", "keyphrases": ["einstein-dilaton gauss-bonnet gravity", "gravitational wave", "scalar field"]}
{"id": "1505.05863", "title": "The cosmological constant and entropy problems: mysteries of the present with profound roots in the past", "abstract": "An accelerated universe should naturally have a vacuum energy density determined by its dynamical curvature. The cosmological constant is most likely a temporary description of a dynamical variable that has been drastically evolving from the early inflationary era to the present. In this Essay we propose a unified picture of the cosmic history implementing such an idea, in which the cosmological constant problem is fixed at early times. All the main stages, from inflation and its (\"graceful\") exit into a standard radiation regime, as well as the matter and dark energy epochs, are accounted for. Finally, we show that for a generic Grand Unified Theory associated to the inflationary phase, the amount of entropy generated from primeval vacuum decay can explain the huge measured value today.", "keyphrases": ["cosmological constant", "vacuum energy density", "history"]}
{"id": "1006.0196", "title": "One-loop corrections to the power spectrum in general single-field inflation", "abstract": "We perform a thorough computation of the one-loop corrections from both scalar and tensor degrees of freedom to the power spectrum of curvature fluctuations for non-canonical Lagrangians in single-field inflation. We consider models characterized by a small sound speed c_s, which produce large non-Gaussianities. As expected, the corrections turn out to be inversely proportional to powers of c_s; evaluating their amplitudes it is then possible to derive some theoretical bounds on the sound speed by requesting the conditions necessary for perturbation theory to hold.", "keyphrases": ["single-field inflation", "perturbation theory", "one-loop correction"]}
{"id": "1609.08580", "title": "Gravitational focusing of Imperfect Dark Matter", "abstract": "Motivated by the projectable Horava\u2013Lifshitz model/mimetic matter scenario, we consider a particular modification of standard gravity, which manifests as an imperfect low pressure fluid. While practically indistinguishable from a collection of non-relativistic weakly interacting particles on cosmological scales, it leaves drastically different signatures in the Solar system. The main effect stems from gravitational focusing of the flow of Imperfect Dark Matter passing near the Sun. This entails strong amplification of Imperfect Dark Matter energy density compared to its average value in the surrounding halo. The enhancement is many orders of magnitude larger than in the case of Cold Dark Matter, provoking deviations of the metric in the second order in the Newtonian potential. Effects of gravitational focusing are prominent enough to substantially affect the planetary dynamics. Using the existing bound on the PPN parameter \u03b2_PPN, we deduce a stringent constraint on the unique constant of the model.", "keyphrases": ["imperfect dark matter", "gravity", "cold dark matter"]}
{"id": "1802.01580", "title": "The Effective Theory of Shift-Symmetric Cosmologies", "abstract": "A shift symmetry is a ubiquitous ingredient in inflationary models, both in effective constructions and in UV-finite embeddings such as string theory. It has also been proposed to play a key role in certain Dark Energy and Dark Matter models. Despite the crucial role it plays in cosmology, the observable, model independent consequences of a shift symmetry are yet unknown. Here, assuming an exact shift symmetry, we derive these consequences for single-clock cosmologies within the framework of the Effective Field Theory of Inflation. We find an infinite set of relations among the otherwise arbitrary effective coefficients, which relate non-Gaussianity to their time dependence. For example, to leading order in derivatives, these relations reduce the infinitely many free functions in the theory to just a single one. Our Effective Theory of shift-symmetric cosmologies describes, among other systems, perfect and imperfect superfluids coupled to gravity and driven superfluids in the decoupling limit. Our results are the first step to determine observationally whether a shift symmetry is at play in the laws of nature and whether it is broken by quantum gravity effects.", "keyphrases": ["effective theory", "shift-symmetric cosmology", "shift symmetry"]}
{"id": "1707.06627", "title": "KiDS-450 + 2dFLenS: Cosmological parameter constraints from weak gravitational lensing tomography and overlapping redshift-space galaxy clustering", "abstract": "We perform a combined analysis of cosmic shear tomography, galaxy-galaxy lensing tomography, and redshift-space multipole power spectra (monopole and quadrupole) using 450 deg^2 of imaging data by the Kilo Degree Survey (KiDS) overlapping with two spectroscopic surveys: the 2-degree Field Lensing Survey (2dFLenS) and the Baryon Oscillation Spectroscopic Survey (BOSS). We restrict the galaxy-galaxy lensing and multipole power spectrum measurements to the overlapping regions with KiDS, and self-consistently compute the full covariance between the different observables using a large suite of N-body simulations. We methodically analyze different combinations of the observables, finding that galaxy-galaxy lensing measurements are particularly useful in improving the constraint on the intrinsic alignment amplitude (by 30 at 3.5\u03c3 in the fiducial data analysis), while the multipole power spectra are useful in tightening the constraints along the lensing degeneracy direction (e.g. factor of two stronger matter density constraint in the fiducial analysis). The fully combined constraint on S_8 \u2261\u03c3_8 \u221a(\u03a9_ m/0.3) = 0.742 \u00b1 0.035, which is an improvement by 20 compared to KiDS alone, corresponds to a 2.6\u03c3 discordance with Planck, and is not significantly affected by fitting to a more conservative set of scales. Given the tightening of the parameter space, we are unable to resolve the discordance with an extended cosmology that is simultaneously favored in a model selection sense, including the sum of neutrino masses, curvature, evolving dark energy, and modified gravity. The complementarity of our observables allows for constraints on modified gravity degrees of freedom that are not simultaneously bounded with either probe alone, and up to a factor of three improvement in the S_8 constraint in the extended cosmology compared to KiDS alone.", "keyphrases": ["galaxy", "matter density", "cosmic microwave background"]}
{"id": "1112.3701", "title": "Unified Dark Fluid with Constant Adiabatic Sound Speed and Cosmic Constraints", "abstract": "As is known above 90 dark component. Usually this dark fluid is separated into two parts: dark matter and dark energy. However, it may be a mixture of these two energy components, or just one exotic unknown fluid. This property is dubbed as dark degeneracy. With this motivation, in this paper, a unified dark fluid having constant adiabatic sound speed c_s^2=\u03b1, which is in the range [0,1], is studied. At first, via the energy conservation equation, its energy density, \u03c1_d/\u03c1_d0=(1-B_s)+B_s a^-3(1+\u03b1) where B_s is related to integration constant from energy conservation equation as another model parameter, is presented. Then by using Markov Chain Monte Carlo method with currently available cosmic observational data sets which include type Ia supernova Union 2, baryon acoustic oscillation and WMAP 7-year data of cosmic background radiation, we show that small values of \u03b1 are favored in this unified dark fluid model. Furthermore, we show that smaller values of \u03b1<10^-5 are required to match matter (baryon) power spectrum from SDSS DR7.", "keyphrases": ["adiabatic sound speed", "baryon", "cosmic background radiation", "unified dark fluid"]}
{"id": "1610.03336", "title": "Recovering the fundamental plane of galaxies by f(R) gravity", "abstract": "The fundamental plane (FP) of galaxies can be recovered in the framework of f(R) gravity avoiding the issues related to dark matter to fit the observations. In particular, the power-law version f(R)\u221d R^n, resulting from the existence of Noether symmetries for f(R), is sufficient to implement the approach. In fact, relations between the FP parameters and the corrected Newtonian potential, coming from R^n, can be found and justified from a physical point of view. Specifically, we analyze the velocity distribution of elliptical galaxies and obtain that r_c, the scale-length depending on the gravitational system properties, is proportional to r_e, the galaxy effective radius. This fact points out that the gravitational corrections induced by f(R) can lead photometry and dynamics of the system. Furthermore, the main byproduct of such an approach is that gravity could work in different ways depending on the scales of self-gravitating systems.", "keyphrases": ["fundamental plane", "galaxy", "effective radius"]}
{"id": "1706.08656", "title": "Formation of Massive, Dense Cores by Cloud-Cloud Collisions", "abstract": "We performed sub-parsec (\u223c 0.014 pc) scale simulations of cloud-cloud collisions of two idealized turbulent molecular clouds (MCs) with different masses in the range of 0.76 - 2.67 \u00d7 10^4M_\u2299 and with collision speeds of 5 - 30 km/s. Those parameters are larger than Takahira, Tasker and Habe (2014) (paper I) in which the colliding system showed a partial gaseous arc morphology that supports the NANTEN observations of objects indicated to be colliding MCs by numerical simulations. Gas clumps with density greater than 10^-20 g cm^-3 were identified as pre-stellar cores and tracked through the simulation to investigate the effect of mass of colliding clouds and collision speeds on the resulting core population. Our results demonstrate that smaller cloud property is more important for results of cloud cloud collisions. The mass function of formed cores can be approximated by a power law relation with index \u03b3 = -1.6 in slower cloud cloud collisions (v \u223c 5 km/s), in good agreement with observation of MCs. A faster relative velocity increases the number of cores formed in the early stage of collisions and shortens gas accretion phase of cores in the shocked region, leading to suppression of core growth. The bending point appears in the high mass part of the core mass function and the bending point mass decreases with increasing of the collision velocity for the same combination of colliding clouds. The high mass part of the core mass function than the bending point mass can be approximated by a power law with \u03b3 = -2.3 that is very similar to the power index of the massive part of the observed initial stellar mass function. We discuss implication of our results for the massive star formation in our Galaxy.", "keyphrases": ["cloud-cloud collision", "core growth", "massive star formation"]}
{"id": "2007.08582", "title": "3HWC: The Third HAWC Catalog of Very-High-Energy Gamma-ray Sources", "abstract": "We present a new catalog of TeV gamma-ray sources using 1523 days of data from the High Altitude Water Cherenkov (HAWC) observatory. The catalog represents the most sensitive survey of the Northern gamma-ray sky at energies above several TeV, with three times the exposure compared to the previous HAWC catalog, 2HWC. We report 65 sources detected at \u2265 5 sigma significance, along with the positions and spectral fits for each source. The catalog contains eight sources that have no counterpart in the 2HWC catalog, but are within 1^\u2218 of previously detected TeV emitters, and twenty sources that are more than 1^\u2218 away from any previously detected TeV source. Of these twenty new sources, fourteen have a potential counterpart in the fourth Fermi Large Area Telescope catalog of gamma-ray sources. We also explore potential associations of 3HWC sources with pulsars in the ATNF pulsar catalog and supernova remnants in the Galactic supernova remnant catalog.", "keyphrases": ["hawc", "catalog", "observatory", "pulsar"]}
{"id": "1509.05772", "title": "Giant Impact: An Efficient Mechanism for the Devolatilization of Super-Earths", "abstract": "Mini-Neptunes and volatile-poor super-Earths coexist on adjacent orbits in proximity to host stars such as Kepler-36 and Kepler-11. Several post-formation processes have been proposed for explaining the origin of the compositional diversity: the mass loss via stellar XUV irradiation, degassing of accreted material, and in-situ accumulation of the disk gas. Close-in planets are also likely to experience giant impacts during the advanced stage of planet formation. This study examines the possibility of transforming volatile-rich super-Earths / mini-Neptunes into volatile-depleted super-Earths through giant impacts. We present the results of three-dimensional giant impact simulations in the accretionary and disruptive regimes. Target planets are modeled with a three-layered structure composed of an iron core, silicate mantle and hydrogen/helium envelope. In the disruptive case, the giant impact can remove most of the H/He atmosphere immediately and homogenize the refractory material in the planetary interior. In the accretionary case, the planet can retain more than half of the gaseous envelope, while a compositional gradient suppresses efficient heat transfer as its interior undergoes double-diffusive convection. After the giant impact, a hot and inflated planet cools and contracts slowly. The extended atmosphere enhances the mass loss via both a Parker wind induced by thermal pressure and hydrodynamic escape driven by the stellar XUV irradiation. As a result, the entire gaseous envelope is expected to be lost due to the combination of those processes in both cases. We propose that Kepler-36b may have been significantly devolatilized by giant impacts, while a substantial fraction of Kepler-36c's atmosphere may remain intact. Furthermore, the stochastic nature of giant impacts may account for the large dispersion in the mass\u2013radius relationship of close-in super-Earths and mini-Neptunes.", "keyphrases": ["super-earth", "mass loss", "giant impact"]}
{"id": "1711.11539", "title": "Does Anisotropic \"Inflation\" Produce a Small Statistical Anisotropy?", "abstract": "Anisotropic inflation is an interesting model with an U(1) gauge field and it predicts the statistical anisotropy of the curvature perturbation characterized by a parameter g_*. However, we find that the background gauge field does not follow the classical attractor solution due to the stochastic effect. We develop the stochastic formalism of a vector field and solve Langevin and Fokker-Planck equations. It is shown that this model is excluded by the CMB constraint g_*\u2264 10^-2 with a high probability about 99.999%.", "keyphrases": ["anisotropic inflation", "gauge field", "curvature perturbation"]}
{"id": "1301.2470", "title": "Exact Relation with Two-point Correlation Functions and Phenomenological Approach for Compressible Magnetohydrodynamic Turbulence", "abstract": "Compressible isothermal magnetohydrodynamic turbulence is analyzed under the assumption of statistical homogeneity and in the asymptotic limit of large kinetic and magnetic Reynolds numbers. Following Kolmogorov we derive an exact relation for some two-point correlation functions which generalizes the expression recently found for hydrodynamics. We show that the magnetic field brings new source and flux terms into the dynamics which may act on the inertial range similarly as a source or a sink for the mean energy transfer rate. The introduction of a uniform magnetic field simplifies significantly the exact relation for which a simple phenomenology may be given. A prediction for axisymmetric energy spectra is eventually proposed.", "keyphrases": ["two-point correlation function", "turbulence", "exact relation"]}
{"id": "1105.3420", "title": "Strongly Coupled Chameleons and the Neutronic Quantum Bouncer", "abstract": "We consider the potential detection of chameleons using bouncing ultracold neutrons. We show that the presence of a chameleon field over a planar plate would alter the energy levels of ultra cold neutrons in the terrestrial gravitational field. When chameleons are strongly coupled to nuclear matter, \u03b2\u2273 10^8, we find that the shift in energy levels would be detectable with the forthcoming GRANIT experiment, where a sensitivity of order one percent of a peV is expected. We also find that an extremely large coupling \u03b2\u2273 10^11 would lead to new bound states at a distance of order 2 microns, which is already ruled out by previous Grenoble experiments. The resulting bound, \u03b2\u2272 10^11, is already three orders of magnitude better than the upper bound, \u03b2\u2272 10^14, from precision tests of atomic spectra.", "keyphrases": ["neutron", "chameleon field", "energy level", "gravitational field"]}
{"id": "2203.09930", "title": "Demographics of young stars and their protoplanetary disks: lessons learned on disk evolution and its connection to planet formation", "abstract": "Since Protostars and Planets VI (PPVI), our knowledge of the global properties of protoplanetary and debris disks, as well as of young stars, has dramatically improved. At the time of PPVI, mm-observations and optical to near-infrared spectroscopic surveys were largely limited to the Taurus star-forming region, especially of its most massive disk and stellar population. Now, near-complete surveys of multiple star-forming regions cover both spectroscopy of young stars and mm interferometry of their protoplanetary disks. This provides an unprecedented statistical sample of stellar masses and mass accretion rates, as well as disk masses and radii, for almost 1000 young stellar objects within 300 pc from us, while also sampling different evolutionary stages, ages, and environments. At the same time, surveys of debris disks are revealing the bulk properties of this class of more evolved objects. This chapter reviews the statistics of these measured global star and disk properties and discusses their constraints on theoretical models describing global disk evolution. Our comparisons of observations to theoretical model predictions extends beyond the traditional viscous evolution framework to include analytical descriptions of magnetic wind effects. Finally, we discuss how recent observational results can provide a framework for models of planet population synthesis and planet formation.", "keyphrases": ["disk evolution", "planet formation", "star-forming region"]}
{"id": "1709.06376", "title": "The Rossiter-McLaughlin effect in Exoplanet Research", "abstract": "The Rossiter-McLaughlin effect occurs during a planet's transit. It provides the main means of measuring the sky-projected spin-orbit angle between a planet's orbital plane, and its host star's equatorial plane. Observing the Rossiter-McLaughlin effect is now a near routine procedure. It is an important element in the orbital characterisation of transiting exoplanets. Measurements of the spin-orbit angle have revealed a surprising diversity, far from the placid, Kantian and Laplacian ideals, whereby planets form, and remain, on orbital planes coincident with their star's equator. This chapter will review a short history of the Rossiter-McLaughlin effect, how it is modelled, and will summarise the current state of the field before describing other uses for a spectroscopic transit, and alternative methods of measuring the spin-orbit angle.", "keyphrases": ["rossiter-mclaughlin effect", "exoplanet", "orbital plane", "obliquity"]}
{"id": "1406.2384", "title": "X-ray states of redback millisecond pulsars", "abstract": "Compact binary millisecond pulsars with main-sequence donors, often referred to as \"redbacks\", constitute the long-sought link between low-mass X-ray binaries and millisecond radio pulsars, and offer a unique probe of the interaction between pulsar winds and accretion flows. We present a systematic study of eight nearby redbacks, using more than 100 observations obtained with Swift's X-ray Telescope. We distinguish between three main states: pulsar, disk and outburst states. We find X-ray mode switching in the disk state of PSR J1023+0038 and XSS J12270-4859, similar to what was found in the other redback which showed evidence for accretion: rapid, recurrent changes in X-ray luminosity (0.5-10 keV, L_X), between [6-9]\u00d710^32 erg s^-1 (disk-passive state) and [3-5]\u00d710^33 erg s^-1 (disk-active state). This strongly suggests that mode switching -which has not been observed in quiescent low-mass X-ray binaries- is universal among redback millisecond pulsars in the disk state. We briefly explore the implications for accretion disk truncation, and find that the inferred magnetospheric radius in the disk state of PSR J1023+0038 and XSS J12270-4859 lies outside the light cylinder. Finally, we note that all three redbacks which have developed accretion disks have relatively high L_X in the pulsar state (>10^32 erg s^-1).", "keyphrases": ["millisecond pulsar", "x-ray luminosity", "accretion disk"]}
{"id": "2111.12576", "title": "Is \"Dark Energy\" a Quantum Vacuum Energy?", "abstract": "We review the origins, motivations, and implications for cosmology and black holes, of our proposal that \"dark energy\" is not a quantum vacuum energy, but rather arises from a Weyl scaling invariant nonderivative component of the gravitational action.", "keyphrases": ["dark energy", "quantum vacuum energy", "cosmology"]}
{"id": "1304.2593", "title": "The Effect of Covariance Estimator Error on Cosmological Parameter Constraints", "abstract": "Extracting parameter constraints from cosmological observations requires accurate determination of the covariance matrix for use in the likelihood function. We show here that uncertainties in the elements of the covariance matrix propagate directly to increased uncertainties in cosmological parameters. When the covariance matrix is determined by simulations, the resulting variance of the each parameter increases by a factor of order 1+N_b/N_s where N_b is the number of bands in the measurement and N_s is the number of simulations.", "keyphrases": ["error", "cosmological parameter", "parameter constraint"]}
{"id": "1604.00318", "title": "The microphysics of collisionless shock waves", "abstract": "Collisionless shocks, that is shocks mediated by electromagnetic processes, are customary in space physics and in astrophysics. They are to be found in a great variety of objects and environments: magnetospheric and heliospheric shocks, supernova remnants, pulsar winds and their nebul\u00e6, active galactic nuclei, gamma-ray bursts and clusters of galaxies shock waves. Collisionless shock microphysics enters at different stages of shock formation, shock dynamics and particle energization and/or acceleration. It turns out that the shock phenomenon is a multi-scale non-linear problem in time and space. It is complexified by the impact due to high-energy cosmic rays in astrophysical environments. This review adresses the physics of shock formation, shock dynamics and particle acceleration based on a close examination of available multi-wavelength or in-situ observations, analytical and numerical developments. A particular emphasize is made on the different instabilities triggered during the shock formation and in association with particle acceleration processes with regards to the properties of the background upstream medium. It appears that among the most important parameters the background magnetic field through the magnetization and its obliquity is the dominant one. The shock velocity that can reach relativistic speeds has also a strong impact over the development of the micro-instabilities and the fate of particle acceleration. Recent developments of laboratory shock experiments has started to bring some new insights in the physics of space plasma and astrophysical shock waves. A special section is dedicated to new laser plasma experiments probing shock physics", "keyphrases": ["collisionless shock", "high-energy cosmic ray", "relativistic speed"]}
{"id": "1612.04044", "title": "Finite-distance corrections to the gravitational bending angle of light in the strong deflection limit", "abstract": "Continuing work initiated in an earlier publication [Ishihara, Suzuki, Ono, Kitamura, Asada, Phys. Rev. D 94, 084015 (2016) ], we discuss a method of calculating the bending angle of light in a static, spherically symmetric and asymptotically flat spacetime, especially by taking account of the finite distance from a lens object to a light source and a receiver. For this purpose, we use the Gauss-Bonnet theorem to define the bending angle of light, such that the definition can be valid also in the strong deflection limit. Finally, this method is applied to Schwarzschild spacetime in order to discuss also possible observational implications. The proposed corrections for Sgr A^\u2217 for instance are able to amount to \u223c 10^-5 arcseconds for some parameter range, which may be within the capability of near-future astronomy, while also the correction for the Sun in the weak field limit is \u223c 10^-5 arcseconds.", "keyphrases": ["angle", "strong deflection limit", "spacetime", "spherical symmetry"]}
{"id": "1902.08963", "title": "Perturbative Resonance in WIMP paradigm and its Cosmological Implications on Cosmic Reheating and Primordial Gravitational Wave Detection", "abstract": "We investigate the co-evolution of dark matter (DM) density perturbation and metric perturbation in the WIMP paradigm. Instead of adopting the conventional assumption that DM starts out in thermal equilibrium, we propose a simple phase of DM production for the WIMP paradigm and extend our analysis to this phase. Being free from the envelop of thermal equilibrium, an amplified perturbative resonance between DM density perturbation and scalar modes of metric perturbation takes place during the DM production phase, and consequently results in a suppression of the tensor-to-scalar ratio of metric perturbation. By specifying the cosmic background with a typical realization of cosmic reheating, we establish a relation between DM particle mass m_\u03c7 and the tensor-to-scalar ratio r in the WIMP paradigm, which also contains two reheating parameters, the reheating temperature T_R_f and the dissipative constant \u0393_0. Notably, for a sizeable parameter region of WIMP candidate and cosmic reheating, this relation predicts a smaller value of r in comparing with the conventional expectation obtained by assuming DM starts out in thermal equilibrium. Once the suppression of r is measured in future observations of primordial gravitational wave in CMB, this relation can be used to constrain m_\u03c7, T_R_f and \u0393_0 in principle.", "keyphrases": ["cosmic reheating", "scalar mode", "perturbative resonance"]}
{"id": "1409.7205", "title": "Exploring the full parameter space for an interacting dark energy model with recent observations including redshift-space distortions: Application of the parametrized post-Friedmann approach", "abstract": "Dark energy can modify the dynamics of dark matter if there exists a direct interaction between them. Thus a measurement of the structure growth, e.g., redshift-space distortions (RSD), can provide a powerful tool to constrain the interacting dark energy (IDE) models. For the widely studied Q=3\u03b2 H\u03c1_de model, previous works showed that only a very small coupling (\u03b2\u223c\ud835\udcaa(10^-3)) can survive in current RSD data. However, all these analyses had to assume w>-1 and \u03b2>0 due to the existence of the large-scale instability in the IDE scenario. In our recent work [Phys. Rev. D 90, 063005 (2014)], we successfully solved this large-scale instability problem by establishing a parametrized post-Friedmann (PPF) framework for the IDE scenario. So we, for the first time, have the ability to explore the full parameter space of the IDE models. In this work, we reexamine the observational constraints on the Q=3\u03b2 H\u03c1_de model within the PPF framework. By using the Planck data, the baryon acoustic oscillation data, the JLA sample of supernovae, and the Hubble constant measurement, we get \u03b2=-0.010^+0.037_-0.033 (1\u03c3). The fit result becomes \u03b2=-0.0148^+0.0100_-0.0089 (1\u03c3) once we further incorporate the RSD data in the analysis. The error of \u03b2 is substantially reduced with the help of the RSD data. Compared with the previous results, our results show that a negative \u03b2 is favored by current observations, and a relatively larger interaction rate is permitted by current RSD data.", "keyphrases": ["full parameter space", "dark energy model", "redshift-space distortion", "large-scale instability problem"]}
{"id": "1608.07452", "title": "Tensor Minkowski Functionals: first application to the CMB", "abstract": "Tensor Minkowski Functionals (TMFs) are tensorial generalizations of the usual Minkowski Functionals which are scalar quantities. We introduce them here for use in cosmological analysis, in particular to analyze CMB maps. They encapsulate information about the shapes and the orientation of structures. We focus on one of the TMFs, namely W_2^1,1, which is the generalization of the genus. The ratio of the eigenvalues of the average of W_2^1,1 over all structures, \u03b1, encodes the net orientation; and the average of the ratios of the eigenvalues of W_2^1,1 for each structure, \u03b2, encodes the net anisotropy. We have developed a code that computes W_2^1,1, and from it \u03b1 and \u03b2, for a set of structures on the plane. We compute \u03b1 and \u03b2 as functions of threshold levels for simulated Gaussian and isotropic CMB fields. We obtain \u03b1 to be one for both temperature and E mode, which means that we recover the input statistical isotropy of density fluctuations in the simulations. The level of net anisotropy of hotspots and coldspots in the CMB fields is quantified by \u03b2\u223c 0.62. Then we compute \u03b1 and \u03b2 for data from PLANCK. We find that the temperature field agrees with the standard LCDM prediction of no net orientation within 3-\u03c3. However, we find that E mode data shows a net orientation that deviates from the theoretical expectation at 14-\u03c3. The possible origin of this deviation may be instrumental effects or other sources and needs to be investigated further. For the net anisotropy we obtain values of \u03b2 for both temperature and E mode that are consistent with the expectations from the standard LCDM simulations. Accurate measurements of \u03b1 and \u03b2 can be used to test the standard model of cosmology and to search for deviations from it.", "keyphrases": ["plane", "random field", "cmt"]}
{"id": "1610.08287", "title": "Hierarchical fringe tracker to co-phase and coherence very large optical interferometers", "abstract": "The full scientific potential of the VLTI with its second generation instruments MATISSE and GRAVITY require fringe tracking up to magnitudes K>14 with the UTs and K>10 with the ATs. The GRAVITY fringe tracker (FT) will be limited to K 10.5 with UTs and K 7.5 with ATs, for fundamental conceptual reasons: the flux of each telescope is distributed among 3 cophasing pairs and then among 5 spectral channels for coherencing. To overcome this limit we propose a new FT concept, called Hierarchical Fringe Tracker (HFT) that cophase pairs of apertures with all the flux from two apertures and only one spectral channel. When the pair is cophased, most of the flux is transmitted as if it was produced by an unique single mode beam and then used to cophase pairs of pairs and then pairs of groups. At the deeper level, the flux is used in an optimized dispersed fringe device for coherencing. On the VLTI such a system allows a gain of about 3 magnitudes over the GRAVITY FT. On interferometers with more apertures such as CHARA (6 telescopes) or a future Planet Formation Imager (12 to 20 telescopes), the HFT would be even more decisive, as its performance does not decrease with the number of apertures. It would allow building a PFI reaching a coherent magnitude H 10 with 16 apertures with diameters smaller than 2 m. We present the HFT concept, the first steps of its feasibility demonstration from computer simulations and the optical design of a 4 telescopes HFT prototype.", "keyphrases": ["interferometer", "aperture", "hierarchical fringe tracker"]}
{"id": "2207.13459", "title": "Early results from GLASS-JWST. VI: Extreme rest-optical equivalent widths detected in NIRISS Wide Field Slitless Spectroscopy", "abstract": "Wide Field Slitless Spectroscopy (WFSS) provides a powerful tool for detecting strong line emission in star forming galaxies (SFGs) without the need for target pre-selection. As part of the GLASS-JWST-ERS program, we leverage the near-infrared wavelength capabilities of NIRISS (1-2.2\u03bcm) to observe rest-optical emission lines out to z\u223c 3.4, to a depth and with a spatial resolution higher than ever before (H\u03b1 to z<2.4; [OIII]+H\u03b2 to z<3.4). In this letter we constrain the rest-frame [OIII]\u03bb5007 equivalent width (EW) distribution for a sample of 76 1<z<3.4 SFGs in the Abell 2744 Hubble Frontier Field and determine an abundance fraction of extreme emission line galaxies with EW>750A in our sample to be 12%. We determine a strong correlation between the measured H\u03b2 and [OIII]\u03bb5007 EWs, supporting that the high [OIII]\u03bb5007 EW objects require massive stars in young stellar populations to generate the high energy photons needed to doubly ionise oxygen. We extracted spectra for objects up to 2 mag fainter in the near-infrared than previous WFSS studies with the Hubble Space Telescope. Thus, this work clearly highlights the potential of JWST/NIRISS to provide high quality WFSS datasets in crowded cluster environments.", "keyphrases": ["equivalent width", "field slitless spectroscopy", "galaxy"]}
{"id": "1102.2181", "title": "COrE (Cosmic Origins Explorer) A White Paper", "abstract": "COrE (Cosmic Origins Explorer) is a fourth-generation full-sky, microwave-band satellite recently proposed to ESA within Cosmic Vision 2015-2025. COrE will provide maps of the microwave sky in polarization and temperature in 15 frequency bands, ranging from 45 GHz to 795 GHz, with an angular resolution ranging from 23 arcmin (45 GHz) and 1.3 arcmin (795 GHz) and sensitivities roughly 10 to 30 times better than PLANCK (depending on the frequency channel). The COrE mission will lead to breakthrough science in a wide range of areas, ranging from primordial cosmology to galactic and extragalactic science. COrE is designed to detect the primordial gravitational waves generated during the epoch of cosmic inflation at more than 3\u03c3 for r=(T/S)>=10^-3. It will also measure the CMB gravitational lensing deflection power spectrum to the cosmic variance limit on all linear scales, allowing us to probe absolute neutrino masses better than laboratory experiments and down to plausible values suggested by the neutrino oscillation data. COrE will also search for primordial non-Gaussianity with significant improvements over Planck in its ability to constrain the shape (and amplitude) of non-Gaussianity. In the areas of galactic and extragalactic science, in its highest frequency channels COrE will provide maps of the galactic polarized dust emission allowing us to map the galactic magnetic field in areas of diffuse emission not otherwise accessible to probe the initial conditions for star formation. COrE will also map the galactic synchrotron emission thirty times better than PLANCK. This White Paper reviews the COrE science program, our simulations on foreground subtraction, and the proposed instrumental configuration.", "keyphrases": ["cosmic origins explorer", "white paper", "gravitational wave"]}
{"id": "1110.6260", "title": "Large peculiar motion of the solar system from the dipole anisotropy in sky brightness due to distant radio sources", "abstract": "According to the cosmological principle, the Universe should appear isotropic, without any preferred directions, to an observer whom we may consider to be fixed in the co-moving co-ordinate system of the expanding Universe. Such an observer is stationary with respect to the average distribution of the matter in the Universe and the sky brightness at any frequency should appear uniform in all directions to such an observer. However a peculiar motion of such an observer, due to a combined effect of Doppler boosting and aberration, will introduce a dipole anisotropy in the observed sky brightness; in reverse an observed dipole anisotropy in the sky brightness could be used to infer the peculiar velocity of the observer with respect to the average Universe. We determine the peculiar velocity of the solar system relative to the frame of distant radio sources, by studying the anisotropy in the sky brightness from discrete radio sources, i.e., an integrated emission from discrete sources per unit solid angle. Our results give a direction of the velocity vector in agreement with the Cosmic Microwave Background Radiation (CMBR) value, but the magnitude (\u223c 1600\u00b1 400 km/s) is \u223c 4 times the CMBR value (369\u00b1 1 km/s) at a statistically significant (\u223c 3\u03c3) level. A genuine difference between the two dipoles would imply anisotropic Universe, with the anisotropy changing with the epoch. This would violate the cosmological principle where the isotropy of the Universe is assumed for all epochs, and on which the whole modern cosmology is based upon.", "keyphrases": ["peculiar motion", "solar system", "sky brightness", "dipole amplitude"]}
{"id": "1905.11516", "title": "Anomaly Detection in the Open Supernova Catalog", "abstract": "In the upcoming decade large astronomical surveys will discover millions of transients raising unprecedented data challenges in the process. Only the use of the machine learning algorithms can process such large data volumes. Most of the discovered transients will belong to the known classes of astronomical objects. However, it is expected that some transients will be rare or completely new events of unknown physical nature. The task of finding them can be framed as an anomaly detection problem. In this work, we perform for the first time an automated anomaly detection analysis in the photometric data of the Open Supernova Catalog (OSC), which serves as a proof of concept for the applicability of these methods to future large scale surveys. The analysis consists of the following steps: 1) data selection from the OSC and approximation of the pre-processed data with Gaussian processes, 2) dimensionality reduction, 3) searching for outliers with the use of the isolation forest algorithm, 4) expert analysis of the identified outliers. The pipeline returned 81 candidate anomalies, 27 (33 be from astrophysically peculiar objects. Found anomalies correspond to a selected sample of 1.4 2000 objects. Among the identified outliers we recognised superluminous supernovae, non-classical Type Ia supernovae, unusual Type II supernovae, one active galactic nucleus and one binary microlensing event. We also found that 16 anomalies classified as supernovae in the literature are likely to be quasars or stars. Our proposed pipeline represents an effective strategy to guarantee we shall not overlook exciting new science hidden in the data we fought so hard to acquire. All code and products of this investigation are made publicly available.", "keyphrases": ["open supernova catalog", "osc", "anomaly detection"]}
{"id": "2106.05284", "title": "A new way to test the Cosmological Principle: measuring our peculiar velocity and the large scale anisotropy independently", "abstract": "We present a novel approach to disentangle two key contributions to the largest-scale anisotropy of the galaxy distribution: (i) the intrinsic dipole due to clustering and anisotropic geometry, and (ii) the kinematic dipole due to our peculiar velocity. Including the redshift and angular size of galaxies, in addition to their fluxes and positions allows us to measure both the direction and amplitude of our velocity independently of the intrinsic dipole of the source distribution. We find that this new approach applied to future galaxy surveys (LSST and Euclid) and a SKA radio continuum survey will allow to measure our velocity (\u03b2 = v/c) with a relative error in the amplitude \u03c3(\u03b2)/\u03b2\u223c (1.3 - 4.5)% and in direction, \u03b8_\u03b2\u223c 0.9^\u2218 - 3.9^\u2218, well beyond what can be achieved when analysing only the number count dipole. We also find that galaxy surveys are able to measure the intrinsic large-scale anisotropy with a relative uncertainty of \u2272 5% (measurement error, not including cosmic variance). Our method enables two simultaneous tests of the Cosmological Principle: comparing the observations of our peculiar velocity with the CMB dipole, and testing for a significant intrinsic anisotropy on large scales which would indicate effects beyond the standard cosmological model.", "keyphrases": ["cosmological principle", "velocity", "large scale", "galaxy survey"]}
{"id": "1211.0379", "title": "Demagnifying gravitational lenses toward hunting a clue of exotic matter and energy", "abstract": "We examine a gravitational lens model inspired by modified gravity theories and exotic matter and energy. We study an asymptotically flat, static, and spherically symmetric spacetime that is modified in such a way that the spacetime metric depends on the inverse distance to the power of positive n in the weak-field approximation. It is shown analytically and numerically that there is a lower limit on the source angular displacement from the lens object to get demagnification. Demagnifying gravitational lenses could appear, provided the source position \u03b2 and the power n satisfy \u03b2 > 2/(n+1) in the units of the Einstein ring radius under a large-n approximation. Unusually, the total amplification of the lensed images, though they are caused by the gravitational pull, could be less than unity. Therefore, time-symmetric demagnification parts in numerical light curves by gravitational microlensing (F.Abe, Astrophys. J. 725, 787, 2010) may be evidence of an Ellis wormhole (being an example of traversable wormholes), but they do not always prove it. Such a gravitational demagnification of the light might be used for hunting a clue of exotic matter and energy that are described by an equation of state more general than the Ellis wormhole case. Numerical calculations for the n=3 and 10 cases show maximally \u223c 10 and \u223c 60 percent depletion of the light, when the source position is \u03b2\u223c 1.1 and \u03b2\u223c 0.7, respectively.", "keyphrases": ["gravitational lense", "clue", "exotic matter", "lens model"]}
{"id": "1801.02518", "title": "General Relativistic corrections in density-shear correlations", "abstract": "We investigate the corrections which relativistic light-cone computations induce on the correlation of the tangential shear with galaxy number counts, also known as galaxy-galaxy lensing. The standard-approach to galaxy-galaxy lensing treats the number density of sources in a foreground bin as observable, whereas it is in reality unobservable due to the presence of relativistic corrections. We find that already in the redshift range covered by the DES first year data, these currently neglected relativistic terms lead to a systematic correction of up to 50 for the highest redshift bins. This correction is dominated by the the fact that a redshift bin of number counts does not only lens sources in a background bin, but is itself again lensed by all masses between the observer and the counted source population. Relativistic corrections are currently ignored in the standard galaxy-galaxy analyses, and the additional lensing of a counted source populations is only included in the error budget (via the covariance matrix). At increasingly higher redshifts and larger scales, these relativistic and lensing corrections become however increasingly more important, and we here argue that it is then more efficient, and also cleaner, to account for these corrections in the density-shear correlations.", "keyphrases": ["relativistic correction", "density-shear correlation", "galaxy-galaxy"]}
{"id": "1005.4147", "title": "The Early Solar System - Chapter 6", "abstract": "This chapter presents a (partial) review of the information we can derive on the early history of the Solar System from radioactive nuclei of very different half-life, which were recognized to have been present alive in pristine solids. In fact, radioactivities open for us a unique window on the evolution of the solar nebula and provide tools for understanding the crucial events that determined and accompanied the formation of the Sun. Discussing these topics will require consideration of (at least) the following issues. i) The determination of an age for solar system bodies, as it emerged especially from the application of radioactive dating. ii) A synthetic account of the measurements that proved the presence of radioactive nuclei (especially those of half-life lower than about 100 Myr) in the Early Solar System (hereafter ESS). iii) An explanation of their existence in terms of galactic nucleosynthesis, and/or of local processes (either exotic or in-situ) preceding and accompanying the formation of the Sun. This will also need some reference to the present scenarios for star formation, as applied to the ESS.", "keyphrases": ["early solar system", "chapter", "radioactivity"]}
{"id": "1009.3933", "title": "Kernel-Phase in Fizeau Inteferometry", "abstract": "The detection of high contrast companions at small angular separation appears feasible in conventional direct images using the self-calibration properties of interferometric observable quantities. The friendly notion of closure-phase, which is key to the recent observational successes of non-redundant aperture masking interferometry used with Adaptive Optics, appears to be one example of a wide family of observable quantities that are not contaminated by phase-noise. In the high-Strehl regime, soon to be available thanks to the coming generation of extreme Adaptive Optics systems on ground based telescopes, and already available from space, closure-phase like information can be extracted from any direct image, even taken with a redundant aperture. These new phase-noise immune observable quantities, called kernel-phases, are determined a-priori from the knowledge of the geometry of the pupil only. Re-analysis of archive data acquired with the Hubble Space Telescope NICMOS instrument, using this new kernel-phase algorithm demonstrates the power of the method as it clearly detects and locates with milli-arcsecond precision a known companion to a star at angular separation less than the diffraction limit.", "keyphrases": ["notion", "aperture", "kernel phase"]}
{"id": "1609.04576", "title": "Anomalous spectral lines and relic quantum nonequilibrium", "abstract": "We describe features that could be observed in the line spectra of relic cosmological particles should quantum nonequilibrium be preserved in their statistics. According to our arguments, these features would represent a significant departure from those of a conventional origin. Among other features, we find a possible spectral broadening that is proportional to the energy resolution of the recording telescope (and so could be much larger than any conventional broadening). Notably, for a range of possible initial conditions we find the possibility of spectral line \"narrowing\", whereby a telescope could observe a line that is narrower than it is conventionally able to resolve. We discuss implications for the indirect search for dark matter, with particular reference to some recent controversial spectral lines.", "keyphrases": ["spectral line", "cosmological particle", "cosmic microwave background"]}
{"id": "1206.6564", "title": "Using Synthetic Spacecraft Data to Interpret Compressible Fluctuations in Solar Wind Turbulence", "abstract": "Kinetic plasma theory is used to generate synthetic spacecraft data to analyze and interpret the compressible fluctuations in the inertial range of solar wind turbulence. The kinetic counterparts of the three familiar linear MHD wave modes\u2014the fast, Alfven, and slow waves\u2014are identified and the properties of the density-parallel magnetic field correlation for these kinetic wave modes is presented. The construction of synthetic spacecraft data, based on the quasi-linear premise\u2014that some characteristics of magnetized plasma turbulence can be usefully modeled as a collection of randomly phased, linear wave modes\u2014is described in detail. Theoretical predictions of the density-parallel magnetic field correlation based on MHD and Vlasov-Maxwell linear eigenfunctions are presented and compared to the observational determination of this correlation based on 10 years of Wind spacecraft data. It is demonstrated that MHD theory is inadequate to describe the compressible turbulent fluctuations and that the observed density-parallel magnetic field correlation is consistent with a statistically negligible kinetic fast wave energy contribution for the large sample used in this study. A model of the solar wind inertial range fluctuations is proposed comprised of a mixture of a critically balanced distribution of incompressible Alfvenic fluctuations and a critically balanced or more anisotropic than critical balance distribution of compressible slow wave fluctuations. These results imply that there is little or no transfer of large scale turbulent energy through the inertial range down to whistler waves at small scales.", "keyphrases": ["synthetic spacecraft data", "compressible fluctuation", "solar wind turbulence"]}
{"id": "1003.2787", "title": "Transport coefficients for the shear dynamo problem at small Reynolds numbers", "abstract": "We build on the formulation developed in Sridhar Singh (JFM, 664, 265, 2010), and present a theory of the shear dynamo problem for small magnetic and fluid Reynolds numbers, but for arbitrary values of the shear parameter. Specializing to the case of a mean magnetic field that is slowly varying in time, explicit expressions for the transport coefficients, \u03b1_il and \u03b7_iml, are derived. We prove that, when the velocity field is non helical, the transport coefficient \u03b1_il vanishes. We then consider forced, stochastic dynamics for the incompressible velocity field at low Reynolds number. An exact, explicit solution for the velocity field is derived, and the velocity spectrum tensor is calculated in terms of the Galilean\u2013invariant forcing statistics. We consider forcing statistics that is non helical, isotropic and delta-correlated-in-time, and specialize to the case when the mean-field is a function only of the spatial coordinate X_3 and time \u03c4; this reduction is necessary for comparison with the numerical experiments of Brandenburg, R\u00e4dler, Rheinhardt K\u00e4pyl\u00e4 (ApJ, 676, 740, 2008). Explicit expressions are derived for all four components of the magnetic diffusivity tensor, \u03b7_ij(\u03c4). These are used to prove that the shear-current effect cannot be responsible for dynamo action at small and , but for all values of the shear parameter.", "keyphrases": ["shear dynamo problem", "mean magnetic field", "transport coefficient"]}
{"id": "1610.01016", "title": "Modified Gravity Explains Dark Matter?", "abstract": "We explore a new horizon of modified gravity from the viewpoint of the particle physics. As a concrete example, we take the F(R) gravity to raise a question: can a scalar particle (\"scalaron\") derived from the F(R) gravity be a dark matter candidate? We place the limit on the parameter in a class of F(R) gravity model from the constraint on the scalaron as a dark matter. The role of the screening mechanism and compatibility with the dark energy problem are addressed.", "keyphrases": ["dark matter", "scalaron", "modified gravity"]}
{"id": "2012.10345", "title": "The Simons Observatory: Overview of data acquisition, control, monitoring, and computer infrastructure", "abstract": "The Simons Observatory (SO) is an upcoming polarized cosmic microwave background (CMB) survey experiment with three small-aperture telescopes and one large-aperture telescope that will observe from the Atacama Desert in Chile. In total, SO will field over 60,000 transition-edge sensor (TES) bolometers in six spectral bands centered between 27 and 280 GHz to achieve the sensitivity necessary to measure or constrain numerous cosmological parameters, including the tensor-to-scalar ratio, effective number of relativistic species, and sum of the neutrino masses. The SO scientific goals require coordination and control of the hardware distributed among the four telescopes on site. To meet this need, we have designed and built an open-sourced platform for distributed system management, called the Observatory Control System (ocs). This control system interfaces with all subsystems including the telescope control units, the microwave multiplexing readout electronics, and the cryogenic thermometry. We have also developed a system for live monitoring of housekeeping data and alerting, both of which are critical for remote observation. We take advantage of existing open source projects, such as crossbar for RPC and PubSub, twisted for asynchronous events, grafana for online remote monitoring, and docker for containerization. We provide an overview of the SO software and computer infrastructure, including the integration of SO-developed code with open source resources and lessons learned while testing at SO labs developing hardware systems as we prepare for deployment.", "keyphrases": ["simons observatory", "monitoring", "computer infrastructure", "observatory control system"]}
{"id": "1810.09466", "title": "The Circular Velocity Curve of the Milky Way from 5 to 25 kpc", "abstract": "We measure the circular velocity curve v_ c(R) of the Milky Way with the highest precision to date across Galactocentric distances of 5\u2264 R \u2264 25 kpc. Our analysis draws on the 6-dimensional phase-space coordinates of \u2273 23,000 luminous red-giant stars, for which we previously determined precise parallaxes using a data-driven model that combines spectral data from APOGEE with photometric information from WISE, 2MASS, and Gaia. We derive the circular velocity curve with the Jeans equation assuming an axisymmetric gravitational potential. At the location of the Sun we determine the circular velocity with its formal uncertainty to be v_ c(R_\u2299) = (229.0\u00b10.2) km s^-1 with systematic uncertainties at the \u223c 2-5% level. We find that the velocity curve is gently but significantly declining at (-1.7\u00b10.1) km s^-1 kpc^-1, with a systematic uncertainty of 0.46 km s^-1 kpc^-1, beyond the inner 5 kpc. We exclude the inner 5 kpc from our analysis due to the presence of the Galactic bar, which strongly influences the kinematic structure and requires modeling in a non-axisymmetric potential. Combining our results with external measurements of the mass distribution for the baryonic components of the Milky Way from other studies, we estimate the Galaxy's dark halo mass within the virial radius to be M_ vir = (7.25\u00b10.26)\u00b7 10^11M_\u2299 and a local dark matter density of \u03c1_ dm(R_\u2299) = 0.30\u00b10.03 GeV cm^-3.", "keyphrases": ["circular velocity curve", "kpc", "baryonic component"]}
{"id": "1302.3544", "title": "Power spectrum for inflation models with quantum and thermal noises", "abstract": "We determine the power spectrum for inflation models covering all regimes from cold (isentropic) to warm (nonisentropic) inflation. We work in the context of the stochastic inflation approach, which can nicely describe both types of inflationary regimes concomitantly. A throughout analysis is carried out to determine the allowed parameter space for simple single field polynomial chaotic inflation models that is consistent with the most recent cosmological data from the nine-year Wilkinson Microwave Anisotropy Probe (WMAP) and in conjunction with other observational cosmological sources. We present the results for both the amplitude of the power spectrum, the spectral index and for the tensor to scalar curvature perturbation amplitude ratio. We briefly discuss cases when running is present. Despite single field polynomial-type inflaton potential models be strongly disfavored, or even be already ruled out in their simplest versions in the case of cold inflation, this is not the case for nonisentropic inflation models in general (warm inflation in particular), though higher order polynomial potentials (higher than quartic order) tend to become less favorable also in this case, presenting a much smaller region of parameter space compatible with the recent observational cosmological data. Our findings also remain valid in face of the recently released Planck results.", "keyphrases": ["inflation model", "curvature perturbation", "primordial spectrum", "inflaton field"]}
{"id": "1805.11112", "title": "Opening a New Window onto the Universe with IceCube", "abstract": "Weakly interacting neutrinos are ideal astronomical messengers because they travel through space without deflection by magnetic fields and, essentially, without absorption. Their weak interaction also makes them notoriously difficult to detect, with observation of high-energy neutrinos from distant sources requiring kilometer-scale detectors. The IceCube project transformed a cubic kilometer of natural Antarctic ice at the geographic South Pole into a Cherenkov detector. It discovered a flux of cosmic neutrinos in the energy range from 10 TeV to 10 PeV, predominantly extragalactic in origin. Their corresponding energy density is close to that of high-energy photons detected by gamma-ray satellites and ultra-high-energy cosmic rays observed with large surface detectors. Neutrinos are therefore ubiquitous in the nonthermal universe, suggesting a more significant role of protons (nuclei) relative to electrons than previously anticipated. Thus, anticipating an essential role for multimessenger astronomy, IceCube is planning significant upgrades of the present instrument as well as a next-generation detector. Similar detectors are under construction in the Mediterranean Sea and Lake Baikal.", "keyphrases": ["universe", "icecube", "high-energy neutrino"]}
{"id": "1205.1045", "title": "Fermi 130 GeV gamma-ray excess and dark matter annihilation in sub-haloes and in the Galactic centre", "abstract": "We analyze publicly available Fermi-LAT high-energy gamma-ray data and confirm the existence of clear spectral feature peaked at E=130GeV. Scanning over the Galaxy we identify several disconnected regions where the observed excess originates from. Our best optimized fit is obtained for the central region of Galaxy with a clear peak at 130GeV with local statistical significance 4.5 sigma. The observed excess is not correlated with Fermi bubbles. We compute the photon spectra induced by dark matter annihilations into two and four standard model particles, the latter via two light intermediate states, and fit the spectra with data. Since our fits indicate sharper and higher signal peak than in the previous works, data favors dark matter direct two-body annihilation channels into photons or other channels giving only line-like spectra. If Einasto halo profile correctly predicts the central cusp of Galaxy, dark matter annihilation cross-section to two photons is of order ten percent of the standard thermal freeze-out cross-section. The large dark matter two-body annihilation cross-section to photons may signal a new resonance that should be searched for at the CERN LHC experiments.", "keyphrases": ["dark matter annihilation", "galactic centre", "gamma-ray line", "four-year fermi data"]}
{"id": "2011.04673", "title": "Deep Potential: Recovering the gravitational potential from a snapshot of phase space", "abstract": "One of the major goals of the field of Milky Way dynamics is to recover the gravitational potential field. Mapping the potential would allow us to determine the spatial distribution of matter - both baryonic and dark - throughout the Galaxy. We present a novel method for determining the gravitational field from a snapshot of the phase-space positions of stars, based only on minimal physical assumptions. We first train a normalizing flow on a sample of observed phase-space positions, obtaining a smooth, differentiable approximation of the phase-space distribution function. Using the collisionless Boltzmann equation, we then find the gravitational potential - represented by a feed-forward neural network - that renders this distribution function stationary. This method is far more flexible than previous parametric methods, which fit narrow classes of analytic models to the data. This is a promising approach to uncovering the density structure of the Milky Way, using rich datasets of stellar kinematics that will soon become available.", "keyphrases": ["gravitational potential", "snapshot", "collisionless boltzmann equation"]}
{"id": "1906.04204", "title": "Dark matter capture in celestial objects: Improved treatment of multiple scattering and updated constraints from white dwarfs", "abstract": "We revisit dark matter (DM) capture in celestial objects, including the impact of multiple scattering, and obtain updated constraints on the DM-proton cross section using observations of white dwarfs. Considering a general form for the energy loss distribution in each scattering, we derive an exact formula for the capture probability through multiple scatterings. We estimate the maximum number of scatterings that can take place, in contrast to the number required to bring a dark matter particle to rest. We employ these results to compute a \"dark\" luminosity L_ DM, arising solely from the thermalized annihilation products of the captured dark matter. Demanding that L_ DM not exceed the luminosity of the white dwarfs in the M4 globular cluster, we set a bound on the DM-proton cross section: \u03c3_p\u2272 10^-44 cm^2, almost independent of the dark matter mass between 100 GeV and 1 PeV and mildly weakening beyond. This is a stronger constraint than those obtained by direct detection experiments in both large mass (M \u2273 5 TeV) and small mass (M \u2272 10 GeV) regimes. For dark matter lighter than 350 MeV, which is beyond the sensitivity of present direct detection experiments, this is the strongest available constraint.", "keyphrases": ["celestial object", "white dwarf", "dark matter"]}
{"id": "1801.01218", "title": "Results from the Atacama B-mode Search (ABS) Experiment", "abstract": "The Atacama B-mode Search (ABS) is an experiment designed to measure cosmic microwave background (CMB) polarization at large angular scales (\u2113>40). It operated from the ACT site at 5190 m elevation in northern Chile at 145 GHz with a net sensitivity (NEQ) of 41 \u03bcK\u221a( s). It employed an ambient-temperature sapphire half-wave plate rotating at 2.55 Hz to modulate the incident polarization signal and reduce systematic effects. We report here on the analysis of data from a 2400 deg^2 patch of sky centered at declination -42^\u2218 and right ascension 25^\u2218. We perform a blind analysis. After unblinding, we find agreement with the Planck TE and EE measurements on the same region of sky. We marginally detect polarized dust emission and give an upper limit on the tensor-to-scalar ratio of r<2.3 (95 cl) with the equivalent of 100 on-sky days of observation. We also present a new measurement of the polarization of Tau A and introduce new methods associated with HWP-based observations.", "keyphrases": ["atacama b-mode search", "abs", "large angular scale"]}
{"id": "1807.00043", "title": "Massive Boson Superradiant Instability of Black Holes: Nonlinear Growth, Saturation, and Gravitational Radiation", "abstract": "We study the superradiant instability of a massive boson around a spinning black hole in full general relativity without assuming spatial symmetries. We focus on the case of a rapidly spinning black hole in the presence of a vector boson with a Compton wavelength comparable to the black hole radius, which is the regime where relativistic effects are maximized. We follow the growth of the boson cloud through superradiance into the nonlinear regime as it spins down the black hole, reaches a maximum energy, and begins to dissipate through the emission of gravitational waves. We find that the superradiant instability can efficiently convert a significant fraction of a black hole's rotational energy into gravitational radiation.", "keyphrases": ["superradiant instability", "black hole", "gravitational radiation"]}
{"id": "1203.6351", "title": "Conformal Symmetries of Adiabatic Modes in Cosmology", "abstract": "We remark on the existence of non-linearly realized conformal symmetries for scalar adiabatic perturbations in cosmology. These conformal symmetries are present for any cosmological background, beyond any slow-roll or quasi-de Sitter approximation. The dilatation transformation shifts the curvature perturbation by a constant, and corresponds to the well-known symmetry under spatial rescaling. We argue that the scalar sector is also invariant under special conformal transformations, which shift the curvature perturbation by a term linear in the spatial coordinates. We discuss whether these conformal symmetries can be extended to include tensor perturbations. Tensor modes introduce their own set of non-linearly realized symmetries. We identify an infinite set of large gauge transformations which maintain the transverse, traceless gauge condition, while shifting the tensor mode non-trivially.", "keyphrases": ["scalar sector", "conformal consistency relation", "goldstone boson", "single-field inflation"]}
{"id": "1603.06733", "title": "Galactic and extragalactic contributions to the astrophysical muon neutrino signal", "abstract": "Spectral and anisotropy properties of IceCube astrophysical neutrino signal reveal an evidence for a significant Galactic contribution to the neutrino flux in Southern hemisphere. We check if the Galactic contribution is detectable in the astrophysical muon neutrino flux observed from a low positive declinations region of the Northern sky. Estimating the Galactic neutrino flux in this part of the sky from gamma-ray and Southern sky neutrino data, we find that the Northern sky astrophysical muon neutrino signal shows an excess over the Galactic flux. This points to the presence of an additional hard spectrum (extragalactic or large scale Galactic halo) component of astrophysical neutrino flux. We show that the Galactic flux component should still be detectable in the muon neutrino data in a decade long IceCube exposure.", "keyphrases": ["extragalactic contribution", "muon", "neutrino flux"]}
{"id": "1703.00879", "title": "COLA with scale-dependent growth: applications to screened modified gravity models", "abstract": "We present a general parallelized and easy-to-use code to perform numerical simulations of structure formation using the COLA (COmoving Lagrangian Acceleration) method for cosmological models that exhibit scale-dependent growth at the level of first and second order Lagrangian perturbation theory. For modified gravity theories we also include screening using a fast approximate method that covers all the main examples of screening mechanisms in the literature. We test the code by comparing it to full simulations of two popular modified gravity models, namely f(R) gravity and nDGP, and find good agreement in the modified gravity boost-factors relative to \u039bCDM even when using a fairly small number of COLA time steps.", "keyphrases": ["scale-dependent growth", "gravity model", "lagrangian acceleration", "cosmological model", "cola"]}
{"id": "1403.4852", "title": "Relic Neutrinos, thermal axions and cosmology in early 2014", "abstract": "We present up to date cosmological bounds on the sum of active neutrino masses as well as on extended cosmological scenarios with additional thermal relics, as thermal axions or sterile neutrino species. Our analyses consider all the current available cosmological data in the beginning of year 2014, including the very recent and most precise Baryon Acoustic Oscillation (BAO) measurements from the Baryon Oscillation Spectroscopic Survey. In the minimal three active neutrino scenario, we find Sum m_nu < 0.22 eV at 95 combination of CMB, BAO and Hubble Space Telescope measurements of the Hubble constant. A non zero value for the sum of the three active neutrino masses of about 0.3 eV is significantly favoured at more than 3 standard deviations when adding the constraints on sigma_8 and Omega_m from the Planck Cluster catalog on galaxy number counts. This preference for non zero thermal relic masses disappears almost completely in both the thermal axion and massive sterile neutrino schemes. Extra light species contribute to the effective number of relativistic degrees of freedom, parameterised via Neff. We found that when the recent detection of B mode polarization from the BICEP2 experiment is considered, an analysis of the combined CMB data in the framework of LCDM+r models gives Neff=4.00pm0.41, suggesting the presence of an extra relativistic relic at more than 95", "keyphrases": ["thermal axion", "sterile neutrino specie", "cosmological data"]}
{"id": "1105.0159", "title": "Galactic rotation curves in brane world models", "abstract": "In the braneworld scenario the four dimensional effective Einstein equation has extra source terms, which arise from the embedding of the 3-brane in the bulk. These non-local effects, generated by the free gravitational field of the bulk, may provide an explanation for the dynamics of the neutral hydrogen clouds at large distances from the galactic center, which is usually explained by postulating the existence of the dark matter. In the present paper we consider the asymptotic behavior of the galactic rotation curves in the brane world models, and we compare the theoretical results with observations of both High Surface Brightness and Low Surface Brightness galaxies. For the chosen sample of galaxies we determine first the baryonic parameters by fitting the photometric data to the adopted galaxy model; then we test the hypothesis of the Weyl fluid acting as dark matter on the chosen sample of spiral galaxies by fitting the tangential velocity equation of the combined baryonic-Weyl model to the rotation curves. We give an analytical expression for the rotational velocity of a test particle on a stable circular orbit in the exterior region to a galaxy, with Weyl fluid contributions included. The model parameter ranges for which the \u03c7^2 test provides agreement (within 1\u03c3 confidence level) with observations on the velocity fields of the chosen galaxy sample are then determined. There is a good agreement between the theoretical predictions and observations, showing that extra-dimensional models can be effectively used as a viable alternative to the standard dark matter paradigm.", "keyphrases": ["brane world model", "dark matter", "galactic rotation curve"]}
{"id": "0911.4482", "title": "Molecular Clouds as a Probe of Cosmic-Ray Acceleration in a Supernova Remnant", "abstract": "We study cosmic-ray acceleration in a supernova remnant (SNR) and the escape from it. We model nonthermal particle and photon spectra for the hidden SNR in the open cluster Westerlund 2, and the old-age mixed-morphology SNR W 28. We assume that the SNR shock propagates in a low-density cavity, which is created and heated through the activities of the progenitor stars and/or previous supernova explosions. We indicate that the diffusion coefficient for cosmic-rays around the SNRs is less than 1 our predictions with the gamma-ray spectra of molecular clouds illuminated by the cosmic-rays (Fermi and H.E.S.S.). We found that the spectral indices of the particles are 2.3. This may be because the particles were accelerated at the end of the Sedov phase, and because energy dependent escape and propagation of particles did not much affect the spectrum.", "keyphrases": ["cosmic-ray acceleration", "supernova remnant", "molecular cloud"]}
{"id": "2104.06577", "title": "A Dark Energy model from Generalized Proca Theory", "abstract": "We consider a specific dark energy model, which only includes the Lagrangian up to the cubic order in terms of the vector field self-interactions in the generalized Proca theory. We examine the cosmological parameters in the model by using the data sets of CMB and CMB+HST, respectively. In particular, the Hubble constant is found to be H_0=71.80^+1.07_-0.72 (72.48^+0.72_-0.60) kms^-1Mpc^-1 at 68% C.L. with CMB (CMB+HST), which would alleviate the Hubble constant tension. We also obtain that the reduced \u03c7^2 values in our model are close to unity when fitting with CMB and CMB+HST, illustrating that our model is a good candidate to describe the cosmological evolutions of the universe.", "keyphrases": ["dark energy model", "generalized proca theory", "universe"]}
{"id": "1807.01482", "title": "Fifth force constraints from the separation of galaxy mass components", "abstract": "One of the most common consequences of extensions to the standard models of particle physics or cosmology is the emergence of a fifth force. While generic fifth forces are tightly constrained at Solar System scales and below, they may escape detection by means of a screening mechanism which effectively removes them in dense environments. We constrain the strength \u0394 G/G_N and range \u03bb_C of a chameleon- or symmetron-screened fifth force with Yukawa coupling \u2013 as well as an unscreened fifth force with differential coupling to galactic mass components \u2013 by searching for the displacement it predicts between galaxies' stellar and gas mass centroids. Taking data from the Alfalfa HI survey, identifying galaxies' gravitational environments with the maps of Desmond et al. (2018a) and forward-modelling with a Bayesian likelihood framework, we find 6.6\u03c3 evidence for \u0394 G>0 at \u03bb_C \u2243 2 Mpc, with \u0394 G/G_N = 0.025 at maximum-likelihood. A similar fifth-force model without screening gives no increase in likelihood over the case \u0394 G = 0 for any \u03bb_C. Although we validate these results by several methods, we do not claim screened modified gravity to provide the only possible explanation for the signal: this would require knowing that \"galaxy formation\" physics could not be responsible. We show also the results of a more conservative \u2013 though less well motivated \u2013 noise model which yields only upper limits on \u0394 G/G_N, ranging from \u223c10^-1 for \u03bb_C \u2243 0.5 Mpc to \u223c few\u00d7 10^-4 at \u03bb_C \u2243 50 Mpc. We show how these constraints may be improved by future galaxy surveys and identify the key features of an observational programme for directly constraining fifth forces on galactic scales. This paper provides a complete description of the analysis summarised in Desmond et al. (2018b).", "keyphrases": ["separation", "galaxy", "fifth force"]}
{"id": "1501.02589", "title": "The Millisecond Magnetar Central Engine in short GRBs", "abstract": "One favored progenitor model for short duration gamma-ray bursts (SGRBs) is the coalescence of two neutron stars (NS-NS). One possible outcome of such a merger would be a rapidly spinning, strongly magnetized neutron star (known as a millisecond magnetar). These magnetars may be \"supra-massive\", implying they would collapse to black holes after losing centrifugal support due to magnetic dipole spindown. By systematically analyzing the BAT-XRT light curves of all short GRBs detected by swift, we test how well the data are consistent with this central engine model of short GRBs. We find that the so-called \"extended emission\" observed with BAT in some short GRBs are fundamentally the same component as the \"internal X-ray plateau\" as observed in many short GRBs, which is defined as a plateau in the lightcurve followed by a very rapid drop. Based on how likely a short GRB hosts a magnetar, we characterize the entire Swift short GRB sample into three categories: the \"internal plateau\" sample, the \"external plateau\" sample, and the \"no plateau\" sample. The derived magnetar surface magnetic field B_ p and the initial spin period P_0 fall into the reasonable range. No GRBs in the internal plateau sample have the total energy exceeding the maximum energy budget of a millisecond magnetar. Assuming that the rapid fall time at the end of the internal plateau is the collapse time of a supra-massive magnetar to a black hole, and applying the measured mass distribution of NS-NS systems in our Galaxy, we constrain the neutron star equation of state (EOS). The data suggest that the NS equation of state is close to the GM1 model, which has a maximum non-rotating NS mass M_ TOV\u223c 2.37 M_\u2299.", "keyphrases": ["millisecond magnetar", "short grb", "neutron star"]}
{"id": "1709.09730", "title": "Beyond the plane-parallel approximation for redshift surveys", "abstract": "Redshift space distortions privilege the location of the observer in cosmological redshift surveys, breaking the translational symmetry of the underlying theory. This violation of statistical homogeneity has consequences for the modeling of clustering observables, leading to what are frequently called `wide angle effects'. We study these effects analytically, computing their signature in the clustering of the multipoles in configuration and Fourier space. We take into account both physical wide angle contributions as well as the terms generated by the galaxy selection function. Similar considerations also affect the way power spectrum estimators are constructed. We quantify, in an analytical way the biases which enter and clarify the relation between what we measure and the underlying theoretical modeling. The presence of an angular window function is also discussed. Motivated by this analysis we present new estimators for the three dimensional Cartesian power spectrum and bispectrum multipoles written in terms of spherical Fourier-Bessel coefficients. We show how the latter have several interesting properties, allowing in particular a clear separation between angular and radial modes.", "keyphrases": ["redshift survey", "multipole", "estimator"]}
{"id": "1712.04317", "title": "Cosmic acceleration from a single fluid description", "abstract": "We here propose a new class of barotropic factor for matter, motivated by properties of isotropic deformations of crystalline solids. Our approach is dubbed Anton-Schmidt's equation of state and provides a non-vanishing, albeit small, pressure term for matter. The corresponding pressure is thus proportional to the logarithm of universe's volume, i.e. to the density itself since V\u221d\u03c1^-1. In the context of solid state physics, we demonstrate that by only invoking standard matter with such a property, we are able to frame the universe speed up in a suitable way, without invoking a dark energy term by hand. Our model extends a recent class of dark energy paradigms named logotropic dark fluids and depends upon two free parameters, namely n and B. Within the Debye approximation, we find that n and B are related to the Gr\u00fcneisen parameter and the bulk modulus of crystals. We thus show the main differences between our model and the logotropic scenario, and we highlight the most relevant properties of our new equation of state on the background cosmology. Discussions on both kinematics and dynamics of our new model have been presented. We demonstrate that the \u039bCDM model is inside our approach, as limiting case. Comparisons with CPL parametrization have been also reported in the text. Finally, a Monte Carlo analysis on the most recent low-redshift cosmological data allowed us to place constraints on n and B. In particular, we found n=-0.147^+0.113_-0.107 and B=3.54 \u00d7 10^-3.", "keyphrases": ["fluid", "cosmology", "cosmic acceleration"]}
{"id": "1905.01448", "title": "Self-similar solutions for finite size advection-dominated accretion flows", "abstract": "We investigated effects on flow variables of transonic advection-dominated accretion flows (ADAFs) for different outer boundary locations (BLs) with a changing energy constant (E) of the flow. We used the ADAF solutions and investigated a general power index rule of a radial bulk velocity (\u221d r^-p) with different BLs, but the power index with radius for a rotation velocity and sound speed is unchanged. Here, p\u22650.5 is a power index. This power rule gives two types of self-similar solutions; first, when p=0.5 gives a self-similar solution of a first kind and exists for infinite length, which has already been discovered for the ADAFs by Narayan & Yi, and second, when p>0.5 gives a self-similar solution of a second kind and exists for finite length, which corresponds to our new solutions for the ADAFs. By using this index rule in fluid equations, we found that the Mach number (M) and advection factor () vary with the radius when p>0.5. The local energies of the ADAFs and the Keplerian disk are matched very well at the BLs. So, this theoretical study is supporting a two-zone configuration theory of the accretion disk, and we also discussed other possible hybrid disk geometries. The present study can have two main implications with a variation of the p; first, one that can help with the understanding of outflows and non-thermal spectrum variations in black hole candidates, and second, one that can help with solving partial differential equations for any sized advective disk.", "keyphrases": ["advection-dominated accretion", "flow", "self-similar solution"]}
{"id": "1010.4776", "title": "Unifying Einstein and Palatini gravities", "abstract": "We consider a novel class of f() gravity theories where the connection is related to the conformally scaled metric \u011d_\u03bc\u03bd=C()g_\u03bc\u03bd with a scaling that depends on the scalar curvature only. We call them C-theories and show that the Einstein and Palatini gravities can be obtained as special limits. In addition, C-theories include completely new physically distinct gravity theories even when f()=. With nonlinear f(), C-theories interpolate and extrapolate the Einstein and Palatini cases and may avoid some of their conceptual and observational problems. We further show that C-theories have a scalar-tensor formulation, which in some special cases reduces to simple Brans-Dicke-type gravity. If matter fields couple to the connection, the conservation laws in C-theories are modified. The stability of perturbations about flat space is determined by a simple condition on the lagrangian.", "keyphrases": ["palatini gravity", "connection", "c-theories"]}
{"id": "0910.1589", "title": "How many universes are in the multiverse?", "abstract": "We argue that the total number of distinguishable locally Friedmann universes generated by eternal inflation is proportional to the exponent of the entropy of inflationary perturbations and is limited by e^e^3 N, where N is the number of e-folds of slow-roll post-eternal inflation. For simplest models of chaotic inflation, N is approximately equal to de Sitter entropy at the end of eternal inflation; it can be exponentially large. However, not all of these universes can be observed by a local observer. In the presence of a cosmological constant \u039bthe number of distinguishable universes is bounded by e^|\u039b|^-3/4. In the context of the string theory landscape, the overall number of different universes is expected to be exponentially greater than the total number of vacua in the landscape. We discuss the possibility that the strongest constraint on the number of distinguishable universes may be related not to the properties of the multiverse but to the properties of observers.", "keyphrases": ["universe", "multiverse", "string theory landscape"]}
{"id": "1010.3658", "title": "Compressed sensing for wide-field radio interferometric imaging", "abstract": "For the next generation of radio interferometric telescopes it is of paramount importance to incorporate wide field-of-view (WFOV) considerations in interferometric imaging, otherwise the fidelity of reconstructed images will suffer greatly. We extend compressed sensing techniques for interferometric imaging to a WFOV and recover images in the spherical coordinate space in which they naturally live, eliminating any distorting projection. The effectiveness of the spread spectrum phenomenon, highlighted recently by one of the authors, is enhanced when going to a WFOV, while sparsity is promoted by recovering images directly on the sphere. Both of these properties act to improve the quality of reconstructed interferometric images. We quantify the performance of compressed sensing reconstruction techniques through simulations, highlighting the superior reconstruction quality achieved by recovering interferometric images directly on the sphere rather than the plane.", "keyphrases": ["radio", "interferometric imaging", "wide field-of-view"]}
{"id": "1407.8338", "title": "Neutrino constraints: what large-scale structure and CMB data are telling us?", "abstract": "(Abridged) We discuss the reliability of neutrino mass constraints, either active or sterile, from the combination of WMAP 9-year or Planck CMB data with BAO measurements from BOSS DR11, galaxy shear measurements from CFHTLenS, SDSS Ly-\u03b1 forest constraints and galaxy cluster mass function from Chandra observations. To avoid model dependence of the constraints we perform a full likelihood analysis for all the datasets employed. As for the cluster data analysis we rely on to the most recent calibration of massive neutrino effects in the halo mass function and we explore the impact of the uncertainty in the mass bias and re-calibration of the halo mass function due to baryonic feedback processes on cosmological parameters. We find that none of the low redshift probes alone provide evidence for massive neutrinos in combination with CMB measurements, while a larger than 2\u03c3 detection of non zero neutrino mass, either active or sterile, is achieved combining cluster or shear data with CMB and BAO measurements. The preference for massive neutrino is larger in the sterile neutrino scenario, and for the combination of Planck, BAO, shear and cluster datasets we find that the vanilla \u039bCDM model is rejected at more than 3\u03c3 and a sterile neutrino mass as motivated by accelerator anomaly is within the 2\u03c3 errors. Finally, results from the full data combination reflect the tension between the \u03c3_8 constraints obtained from cluster and shear data and that inferred from Ly-\u03b1 forest measurements; in the active neutrino scenario for both CMB datasets employed, the full data combination yields only an upper limits on \u2211 m_\u03bd, while assuming an extra sterile neutrino we still get preference for non-vanishing mass, m_s^ eff=0.26^+0.22_-0.24 eV, and dark contribution to the radiation content, \u0394 N_ eff=0.82\u00b10.55.", "keyphrases": ["cmb data", "upper limit", "neutrino"]}
{"id": "1512.05368", "title": "Observationally constraining gravitational wave emission from short gamma-ray burst remnants", "abstract": "Observations of short gamma-ray bursts indicate ongoing energy injection following the prompt emission, with the most likely candidate being the birth of a rapidly rotating, highly magnetised neutron star. We utilise X-ray observations of the burst remnant to constrain properties of the nascent neutron star, including its magnetic field-induced ellipticity and the saturation amplitude of various oscillation modes. Moreover, we derive strict upper limits on the gravitational wave emission from these objects by looking only at the X-ray light curve, showing the burst remnants are unlikely to be detected in the near future using ground-based gravitational wave interferometers such as Advanced LIGO.", "keyphrases": ["gravitational wave emission", "burst remnant", "neutron star"]}
{"id": "1807.07477", "title": "Enhancing the cross-correlations between magnetic fields and scalar perturbations through parity violation", "abstract": "One often resorts to a non-minimal coupling of the electromagnetic field in order to generate magnetic fields during inflation. The coupling is expected to depend on a scalar field, possibly the same as the one driving inflation. At the level of three-point functions, such a coupling leads to a non-trivial cross-correlation between the perturbation in the scalar field and the magnetic field. This cross-correlation has been evaluated analytically earlier for the case of non-helical electromagnetic fields. In this work, we numerically compute the cross-correlation for helical magnetic fields. Non-Gaussianities are often generated as modes leave the Hubble radius. The helical electromagnetic modes evolve strongly (when compared to the non-helical case) around Hubble exit and one type of polarization is strongly amplified immediately after Hubble exit. We find that helicity considerably boosts the amplitude of the dimensionless non-Gaussianity parameter that characterizes the amplitude and shape of the cross-correlation between the perturbations in the scalar field and the magnetic field. We discuss the implications of the enhancement in the non-Gaussianity parameter due to parity violation.", "keyphrases": ["cross-correlation", "magnetic field", "parity violation", "non-minimal coupling"]}
{"id": "1405.0222", "title": "Lens models and magnification maps of the six Hubble Frontier Fields clusters", "abstract": "We present strong-lensing models, as well as mass and magnification maps, for the cores of the six HST Frontier Fields galaxy clusters. Our parametric lens models are constrained by the locations and redshifts of multiple image systems of lensed background galaxies. We use a combination of photometric redshifts and spectroscopic redshifts of the lensed background sources obtained by us (for Abell 2744 and Abell S1063), collected from the literature, or kindly provided by the lensing community. Using our results, we (1) compare the derived mass distribution of each cluster to its light distribution, (2) quantify the cumulative magnification power of the HFF clusters, (3) describe how our models can be used to estimate the magnification and image multiplicity of lensed background sources at all redshifts and at any position within the cluster cores, and (4) discuss systematic effects and caveats resulting from our modeling methods. We specifically investigate the effect of the use of spectroscopic and photometric redshift constraints on the uncertainties of the resulting models. We find that the photometric redshift estimates of lensed galaxies are generally in excellent agreement with spectroscopic redshifts, where available. However, the flexibility associated with relaxed redshift priors may cause the complexity of large-scale structure that is needed to account for the lensing signal to be underestimated. Our findings thus underline the importance of spectroscopic arc redshifts, or tight photometric redshift constraints, for high precision lens models. All products from our best-fit lens models (magnification, convergence, shear, deflection field) and model simulations for estimating errors are made available via the Mikulski Archive for Space Telescopes.", "keyphrases": ["magnification map", "cluster core", "lens model"]}
{"id": "1408.3352", "title": "N-body methods for relativistic cosmology", "abstract": "We present a framework for general relativistic N-body simulations in the regime of weak gravitational fields. In this approach, Einstein's equations are expanded in terms of metric perturbations about a Friedmann-Lema\u00eetre background, which are assumed to remain small. The metric perturbations themselves are only kept to linear order, but we keep their first spatial derivatives to second order and treat their second spatial derivatives as well as sources of stress-energy fully non-perturbatively. The evolution of matter is modelled by an N-body ensemble which can consist of free-streaming nonrelativistic (e.g. cold dark matter) or relativistic particle species (e.g. cosmic neutrinos), but the framework is fully general and also allows for other sources of stress-energy, in particular additional relativistic sources like modified-gravity models or topological defects. We compare our method with the traditional Newtonian approach and argue that relativistic methods are conceptually more robust and flexible, at the cost of a moderate increase of numerical difficulty. However, for a LambdaCDM cosmology, where nonrelativistic matter is the only source of perturbations, the relativistic corrections are expected to be small. We quantify this statement by extracting post-Newtonian estimates from Newtonian N-body simulations.", "keyphrases": ["cosmology", "n-body simulation", "relativistic effect", "post-newtonian correction", "mean evolution"]}
{"id": "0907.0719", "title": "Constraints on Dark Matter annihilations from reionization and heating of the intergalactic gas", "abstract": "Dark Matter annihilations after recombination and during the epoch of structure formation deposit energy in the primordial intergalactic medium, producing reionization and heating. We investigate the constraints that are imposed by the observed optical depth of the Universe and the measured temperature of the intergalactic gas. We find that the bounds are significant, and have the power to rule out large portions of the `DM mass/cross section' parameter space. The optical depth bound is generally stronger and does not depend significantly on the history of structure formation. The temperature bound can be competitive in some cases for small masses or the hadronic annihilation channels (and is affected somewhat by the details of structure formation). We find in particular that DM particles with a large annihilation cross section into leptons and a few TeV mass, such as those needed to explain the PAMELA and FERMI+HESS cosmic ray excesses in terms of Dark Matter, are ruled out as they produce too many free electrons. We also find that low mass particles (< 10 GeV) tend to heat too much the gas and are therefore disfavored.", "keyphrases": ["dark matter annihilation", "intergalactic gas", "baryon"]}
{"id": "1906.11728", "title": "The rings of Neptune", "abstract": "In 1984, three telescopes in South America recorded an occultation of a star near Neptune. It was attributed to the existence of a partial ring or ring arc. The existence of ring arcs around Neptune was confirmed during subsequent years via other occultation experiments and by the Voyager 2 spacecraft. The Voyager observations established that the Neptunian arcs are concentrations of particles embedded within Neptune's narrow Adams ring, the outermost of six tenuous rings discovered by Voyager and discussed here. Four ring arcs were identified: the trailing arc Fraternit\u00e9, a double-component arc Egalit\u00e9, dubbed Egalit\u00e9 1 and 2, Libert\u00e9, and the leading arc Courage. The arcs varied in extent from \u223c 1^\u2218 to \u223c 10^\u2218, and together were confined to a longitude range of 40^\u2218, with typical radial widths of \u223c 15 km and optical depth of order 0.1. The properties of the dusty component of Neptune's rings are also discussed in this chapter. Although the arcs should have been destroyed in a few months time through differential Keplerian motion, they appeared to persist at least throughout the Voyager era, and well beyond. However, observations from Earth (both with the Hubble Space Telescope and ground-based adaptive optics) show an evolution in the last three decades, with the disappearance of both Courage and Libert\u00e9 by 2009. This chapter reviews the constraints provided on the mean motion of the arcs and Galatea, the satellite possibly responsible for the arc confinement. This in turn constrains the various models that have been proposed to explain the arc longevity.", "keyphrases": ["ring", "neptune", "voyager"]}
{"id": "2001.10690", "title": "Merger rate density of binary black holes formed in open clusters", "abstract": "Several binary black holes (BBHs) have been observed using gravitational wave detectors. For the formation mechanism of BBHs, two main mechanisms, isolated binary evolution and dynamical formation in dense star clusters, have been suggested. Future observations are expected to provide more information about BBH distributions, and it will help us to distinguish the two formation mechanisms. For the star cluster channel, globular clusters have mainly been investigated. However, recent simulations have suggested that BBH formation in open clusters is not negligible. We estimate a local merger rate density of BBHs originated from open clusters using the results of our N-body simulations of open clusters with four different metallicities. We find that the merger rate per cluster is the highest for our 0.1 solar metallicity model. Assuming a cosmic star formation history and a metallicity evolution with dispersion, we estimate the local merger rate density of BBHs originated from open clusters to be \u223c 70 yr^-1 Gpc^-3. This value is comparable to the merger rate density expected from the first and second observation runs of LIGO and Virgo. In addition, we find that BBH mergers obtained from our simulations can reproduce the distribution of primary mass and mass ratio of merging BBHs estimated from the LIGO and Virgo observations.", "keyphrases": ["binary black hole", "globular cluster", "merger rate density"]}
{"id": "1008.1460", "title": "Gravitational waves from nonspinning black hole-neutron star binaries: dependence on equations of state", "abstract": "We report results of a numerical-relativity simulation for the merger of a black hole-neutron star binary with a variety of equations of state (EOSs) modeled by piecewise polytropes. We focus in particular on the dependence of the gravitational waveform at the merger stage on the EOSs. The initial conditions are computed in the moving-puncture framework, assuming that the black hole is nonspinning and the neutron star has an irrotational velocity field. For a small mass ratio of the binaries (e.g., MBH/MNS = 2 where MBH and MNS are the masses of the black hole and neutron star, respectively), the neutron star is tidally disrupted before it is swallowed by the black hole irrespective of the EOS. Especially for less-compact neutron stars, the tidal disruption occurs at a more distant orbit. The tidal disruption is reflected in a cutoff frequency of the gravitational-wave spectrum, above which the spectrum amplitude exponentially decreases. A clear relation is found between the cutoff frequency of the gravitational-wave spectrum and the compactness of the neutron star. This relation also depends weakly on the stiffness of the EOS in the core region of the neutron star, suggesting that not only the compactness but also the EOS at high density is reflected in gravitational waveforms. The mass of the disk formed after the merger shows a similar correlation with the EOS, whereas the spin of the remnant black hole depends primarily on the mass ratio of the binary, and only weakly on the EOS. Properties of the remnant disks are also analyzed.", "keyphrases": ["hole-neutron star binary", "numerical-relativity simulation", "gravitational-wave spectrum"]}
{"id": "1307.5191", "title": "Prompt merger collapse and the maximum mass of neutron stars", "abstract": "We perform hydrodynamical simulations of neutron-star mergers for a large sample of temperature-dependent, nuclear equations of state, and determine the threshold mass above which the merger remnant promptly collapses to form a black hole. We find that, depending on the equation of state, the threshold mass is larger than the maximum mass of a non-rotating star in isolation by between 30 and 70 per cent. Our simulations also show that the ratio between the threshold mass and maximum mass is tightly correlated with the compactness of the non-rotating maximum-mass configuration. We speculate on how this relation can be used to derive constraints on neutron-star properties from future observations.", "keyphrases": ["collapse", "neutron star", "merger remnant"]}
{"id": "1104.1183", "title": "Gravitational waves from extreme mass-ratio inspirals in Dynamical Chern-Simons gravity", "abstract": "Dynamical Chern-Simons gravity is an interesting extension of General Relativity, which finds its way in many different contexts, including string theory, cosmological settings and loop quantum gravity. In this theory, the gravitational field is coupled to a scalar field by a parity-violating term, which gives rise to characteristic signatures. Here we investigate how Chern-Simons gravity would affect the quasi-circular inspiralling of a small, stellar-mass object into a large non-rotating supermassive black hole, and the accompanying emission of gravitational and scalar waves. We find the relevant equations describing the perturbation induced by the small object, and we solve them through the use of Green's function techniques. Our results show that for a wide range of coupling parameters, the Chern-Simons coupling gives rise to an increase in total energy flux, which translates into a fewer number of gravitational-wave cycles over a certain bandwidth. For space-based gravitational-wave detectors such as LISA, this effect can be used to constrain the coupling parameter effectively.", "keyphrases": ["dynamical chern-simon gravity", "black hole", "many study"]}
{"id": "1506.05488", "title": "Small-Scale Anisotropies of Cosmic Rays from Relative Diffusion", "abstract": "The arrival directions of multi-TeV cosmic rays show significant anisotropies at small angular scales. It has been argued that this small-scale structure can naturally arise from cosmic ray scattering in local turbulent magnetic fields that distort a global dipole anisotropy set by diffusion. We study this effect in terms of the power spectrum of cosmic ray arrival directions and show that the strength of small-scale anisotropies is related to properties of relative diffusion. We provide a formalism for how these power spectra can be inferred from simulations and motivate a simple analytic extension of the ensemble-averaged diffusion equation that can account for the effect.", "keyphrases": ["magnetic field", "power spectrum", "small-scale anisotropy"]}
{"id": "1902.10687", "title": "The phenomenology of beyond Horndeski gravity", "abstract": "We study the phenomenology of the beyond Horndeski class of scalar-tensor theories of gravity, which on cosmological scales can be characterised in terms of one extra function of time, \u03b1_ H, as well as the usual four Horndeski set of free functions. We show that \u03b1_ H can be directly related to the the damping of the matter power spectrum on both large and small scales. We also find that the temperature power spectrum of the cosmic microwave background (CMB) is enhanced at low multipoles and the lensing potential is decreased, as a function of \u03b1_ H. We find constraints on \u03b1_ H of order O(1) using measurements of the temperature and polarisation of the CMB, as well as the lensing potential derived from it, combined with large scale structure data. We find that redshift space distortion measurements can play a significant role in constraining these theories. Finally, we comment on the recent constraints from the observation of an electromagnetic counterpart to a gravitational wave signal; we find that these constraints reduce the number of free parameters of the model but do not significantly change the constraints on the remaining parameters.", "keyphrases": ["phenomenology", "gravity", "scale structure data"]}
{"id": "2104.12757", "title": "Evaporation of dark matter from celestial bodies", "abstract": "Scatterings of galactic dark matter (DM) particles with the constituents of celestial bodies could result in their accumulation within these objects. Nevertheless, the finite temperature of the medium sets a minimum mass, the evaporation mass, that DM particles must have in order to remain trapped. DM particles below this mass are very likely to scatter to speeds higher than the escape velocity, so they would be kicked out of the capturing object and escape. Here, we compute the DM evaporation mass for all spherical celestial bodies in hydrostatic equilibrium, spanning the mass range [10^-10 - 10^2] M_\u2299, for constant scattering cross sections and s-wave annihilations. We illustrate the critical importance of the exponential tail of the evaporation rate, which has not always been appreciated in recent literature, and obtain a robust result: for the geometric value of the scattering cross section and for interactions with nucleons, at the local galactic position, the DM evaporation mass for all spherical celestial bodies in hydrostatic equilibrium is approximately given by E_c/T_\u03c7\u223c 30, where E_c is the escape energy of DM particles at the core of the object and T_\u03c7 is their temperature. In that case, the minimum value of the DM evaporation mass is obtained for super-Jupiters and brown dwarfs, m_ evap\u2243 0.7 GeV. For other values of the scattering cross section, the DM evaporation mass only varies by a factor smaller than three within the range 10^-41 cm^2 \u2264\u03c3_p \u2264 10^-31 cm^2, where \u03c3_p is the spin-independent DM-nucleon scattering cross section. Its dependence on parameters such as the galactic DM density and velocity, or the scattering and annihilation cross sections is only logarithmic, and details on the density and temperature profiles of celestial bodies have also a small impact.", "keyphrases": ["dark matter", "celestial body", "evaporation mass"]}
{"id": "1407.4114", "title": "Fermi Bubbles and Bubble-like emission from the Galactic Plane", "abstract": "The diffuse gamma-ray sky revealed 'Bubbles' of emission above and below the Galactic Plane symmetric around the centre of the Milky Way with a height of 10 kpc in both directions. At present there is no convincing explanation for the origin. To understand the role of the Galactic Centre (GC) one has to study the Bubble spectrum inside the disc, a region which has been excluded from previous analysis because of the large foreground. From a novel template fit, which allows a simultaneous determination of the signal and foreground in any direction, we find that bubble-like emission is not only found in the halo, but in the Galactic Plane as well with a width in latitude coinciding with the molecular clouds. The longitude distribution has a width corresponding to the Galactic Bar with an additional contribution from the Scutum-Centaurus arm. The energy spectrum of the Bubbles coincides with the predicted contribution from CRs trapped in sources (SCRs). Also the energetics fits well. Hence, we conclude that the bubble-like emission has a hadronic origin, which arises from SCRs and the Bubbles in the halo arise from hadronic interactions in advected gas. Evidence for advection is provided by the ROSAT X-rays from hot gas in the Bubble region.", "keyphrases": ["bubble-like emission", "galactic bar", "fermi bubbles"]}
{"id": "2207.13020", "title": "Finding Peas in the Early Universe with JWST", "abstract": "The Early Release Observations (EROs) of JWST beautifully demonstrate the promise of JWST in characterizing the universe at cosmic dawn. We analyze the ERO spectra of three z \u223c 8 galaxies to determine their metallicities, gas temperatures and ionization. These galaxies offer the first opportunity to understand the physical properties of epoch-of-reionization galaxies through detailed rest-optical emission line spectroscopy. We show that these objects have metal abundances 12+log[O/H] \u2248 6.9 - 8.2, based on both the T_e method and on a recent calibration of the R_23 metallicity indicator. Since the spectra are some of the earliest science data from JWST, we compare several line ratios with values expected from robust physics, to validate our measurement procedures. We compare the abundances and emission line ratios to a nearby sample of Green Pea galaxies \u2013 a population of nearby emission line galaxies whose UV properties resemble epoch-of-reionization galaxies, and which often have large Lyman continuum escape fractions. The JWST data show striking further similarities between these high redshift galaxies and nearby Green Peas. The z\u223c 8 galaxies span the metallicity range covered by Green Peas. They also show the compact morphology that is typical of emission line dominated galaxies at all redshifts. Based on these similarities with Green Peas, it is likely that these are the first rest-optical spectra of galaxies that are actively driving cosmological reionization", "keyphrases": ["universe", "jwst", "metallicitie"]}
{"id": "1910.01649", "title": "Refined Bounds on MeV-scale Thermal Dark Sectors from BBN and the CMB", "abstract": "New light states thermally coupled to the Standard Model plasma alter the expansion history of the Universe and impact the synthesis of the primordial light elements. In this work, we carry out an exhaustive and precise analysis of the implications of MeV-scale BSM particles in Big Bang Nucleosynthesis (BBN) and for Cosmic Microwave Background (CMB) observations. We find that, BBN observations set a lower bound on the thermal dark matter mass of m_\u03c7 > 0.4 MeV at 2\u03c3. This bound is independent of the spin and number of internal degrees of freedom of the particle, of the annihilation being s-wave or p-wave, and of the annihilation final state. Furthermore, we show that current BBN plus CMB observations constrain purely electrophilic and neutrinophilic BSM species to have a mass, m_\u03c7 > 3.7 MeV at 2\u03c3. We explore the reach of future BBN measurements and show that upcoming CMB missions should improve the bounds on light BSM thermal states to m_\u03c7 > (10-15) MeV. Finally, we demonstrate that very light BSM species thermally coupled to the SM plasma are highly disfavoured by current cosmological observations.", "keyphrases": ["universe", "big bang nucleosynthesis", "cosmic microwave background"]}
{"id": "1907.02638", "title": "A revised catalogue of 294 Galactic supernova remnants", "abstract": "A revised catalogue of Galactic supernova remnants (SNRs) is presented, along with some simple statistics of their properties. Six new SNRs have been added to the catalogue since the previous published version from 2014, and six entries have been removed, as they have been identified as HII regions, leaving the number of entries in the catalogue at 294. Some simple statistics of the remnants in the catalogue, and the selection effects that apply, are discussed, along with some recently proposed Galactic SNR candidates.", "keyphrases": ["catalogue", "galactic supernova remnant", "galactic snr"]}
{"id": "1907.08094", "title": "The galaxy bias at second order in general relativity with Non-Gaussian initial conditions", "abstract": "We present a systematic study of galaxy bias in the presence of primordial non-Gaussianity in General Relativity (GR) at second order in perturbation theory. The non-linearity of the Poisson equation in GR and primordial non-Gaussianity are consistently included. We show that the inclusion of non-local primordial non-Gaussianity in addition to local non-Gaussianity is important to show the absence of the modulation of small scale clustering by the long-wavelength mode in the single field slow-roll inflation. We study the bispectrum of the relativistic galaxy density in several gauges and identify the effect of primordial non-Gaussianity and GR corrections.", "keyphrases": ["galaxy bias", "general relativity", "primordial non-gaussianity"]}
{"id": "1104.2048", "title": "ORIGIN: Metal Creation and Evolution from the Cosmic Dawn", "abstract": "ORIGIN is a proposal for the M3 mission call of ESA aimed at the study of metal creation from the epoch of cosmic dawn. Using high-spectral resolution in the soft X-ray band, ORIGIN will be able to identify the physical conditions of all abundant elements between C and Ni to red-shifts of z=10, and beyond. The mission will answer questions such as: When were the first metals created? How does the cosmic metal content evolve? Where do most of the metals reside in the Universe? What is the role of metals in structure formation and evolution? To reach out to the early Universe ORIGIN will use Gamma-Ray Bursts (GRBs) to study their local environments in their host galaxies. This requires the capability to slew the satellite in less than a minute to the GRB location. By studying the chemical composition and properties of clusters of galaxies we can extend the range of exploration to lower redshifts (z 0.2). For this task we need a high-resolution spectral imaging instrument with a large field of view. Using the same instrument, we can also study the so far only partially detected baryons in the Warm-Hot Intergalactic Medium (WHIM). The less dense part of the WHIM will be studied using absorption lines at low redshift in the spectra for GRBs.", "keyphrases": ["metal creation", "cosmic dawn", "esa"]}
{"id": "0909.5636", "title": "Turbulence, Complexity, and Solar Flares", "abstract": "The issue of predicting solar flares is one of the most fundamental in physics, addressing issues of plasma physics, high-energy physics, and modelling of complex systems. It also poses societal consequences, with our ever-increasing need for accurate space weather forecasts. Solar flares arise naturally as a competition between an input (flux emergence and rearrangement) in the photosphere and an output (electrical current build up and resistive dissipation) in the corona. Although initially localised, this redistribution affects neighbouring regions and an avalanche occurs resulting in large scale eruptions of plasma, particles, and magnetic field. As flares are powered from the stressed field rooted in the photosphere, a study of the photospheric magnetic complexity can be used to both predict activity and understand the physics of the magnetic field. The magnetic energy spectrum and multifractal spectrum are highlighted as two possible approaches to this.", "keyphrases": ["complexity", "plasma", "turbulence"]}
{"id": "2009.07832", "title": "Did NANOGrav see a signal from primordial black hole formation?", "abstract": "We show that the recent NANOGrav result can be interpreted as a stochastic gravitational wave signal associated to formation of primordial black holes from high-amplitude curvature perturbations. The indicated amplitude and power of the gravitational wave spectrum agrees well with formation of primordial seeds for supermassive black holes.", "keyphrases": ["black hole", "nanograv result", "american nanohertz observatory"]}
{"id": "1111.5819", "title": "Bayesian model selection for testing the no-hair theorem with black hole ringdowns", "abstract": "General relativity predicts that a black hole that results from the merger of two compact stars (either black holes or neutron stars) is initially highly deformed but soon settles down to a quiescent state by emitting a superposition of quasi-normal modes (QNMs). The QNMs are damped sinusoids with characteristic frequencies and decay times that depend only on the mass and spin of the black hole and no other parameter - a statement of the no-hair theorem. In this paper we have examined the extent to which QNMs could be used to test the no-hair theorem with future ground- and space-based gravitational-wave detectors. We model departures from general relativity (GR) by introducing extra parameters which change the mode frequencies or decay times from their general relativistic values. With the aid of numerical simulations and Bayesian model selection, we assess the extent to which the presence of such a parameter could be inferred, and its value estimated. We find that it is harder to decipher the departure of decay times from their GR value than it is with the mode frequencies. Einstein Telescope (ET, a third generation ground-based detector) could detect departures of <1 500 Msun black hole, out to a maximum range of 4 Gpc. In contrast, the New Gravitational Observatory (NGO, an ESA space mission to detect gravitational waves) can detect departures of 0.1 luminosity distance of 30 Gpc (z = 3.5).", "keyphrases": ["no-hair theorem", "black hole", "bayesian model selection"]}
{"id": "1401.5876", "title": "Tidal evolution of the spin-orbit angle in exoplanetary systems", "abstract": "The angle between the stellar spin and the planetary orbit axes (spin-orbit angle) is supposed to carry valuable information on the initial condition of the planet formation and the subsequent migration history. Indeed current observations of the Rossiter- McLaughlin effect have revealed a wide range of spin-orbit misalignments for transiting exoplanets. We examine in detail the tidal evolution of a simple system comprising a Sun-like star and a hot Jupiter adopting the equilibrium tide and the inertial wave dissipation effects simultaneously. We find that the combined tidal model works as a very efficient realignment mechanism; it predicts three distinct states of the spin-orbit angle (i.e., parallel, polar, and anti-parallel orbits) for a while, but the latter two states eventually approach the parallel spin-orbit configuration. The intermediate spin-orbit angles as measured in recent observations are difficult to be achieved. Therefore the current model cannot reproduce the observed broad distribution of the spin-orbit angles, at least in its simple form. This indicates that the observed diversity of the spin-orbit angles may emerge from more complicated interactions with outer planets and/or may be the consequence of the primordial misalignment between the proto-planetary disk and the stellar spin, which requires future detailed studies.", "keyphrases": ["spin-orbit angle", "stellar spin", "tidal evolution"]}
{"id": "1410.6567", "title": "Cosmic equation of state from combined angular diameter distances: Does the tension with luminosity distances exist?", "abstract": "Using a relatively complete observational data concerning four angular diameter distance (ADD) measurements and observations representing current luminosity distance (LD) data, this paper investigates the distances considering three classes of dark energy equation of state (EoS) reconstruction. In particular, we use strongly gravitationally lensed systems from various large systematic gravitational lens surveys and galaxy clusters, which yield the Hubble constant independent ratio between two angular diameter distances D_ls/D_s data. Our results demonstrate that, with more general categories of standard ruler data, ADD and LD data are compatible at 1\u03c3 level. Secondly, we note that consistency between ADD and LD data maintained irrespective of the EoS parameterizations: there is a good match between the universally explored CPL model and other formulations of cosmic equation of state. Especially for the truncated GEoS model with \u03b2=-2, the conclusions obtained with ADD and LD are almost the same. Finally, statistical analysis of generalized dark energy equation of state performed on four classes of ADD data provides stringent constraints on the EoS parameters w_0, w_\u03b2 and \u03b2, which suggest that dark energy was a subdominant component at early times. Moreover, the GEoS parametrization with \u03b2\u2243 1 seems to be a more favorable two-parameter model to characterize the cosmic equation of state, because the combined angular diameter distance data (SGL+CBF+BAO+WMAP9) provide the best-fit value \u03b2=0.751^+0.465_-0.480.", "keyphrases": ["luminosity distance", "dark energy", "cosmic equation"]}
{"id": "1807.01729", "title": "On the effect of high order empirical parameters on the nuclear equation of state", "abstract": "A quantitative knowledge of the nuclear Equation of State (EoS) requires an accurate estimation of the uncertainties on the EoS parameters and their mutual correlations. Such correlations are empirically observed in a large set of EoS models by different authors, but they are not always fully understood. We show that some of these correlations can be interpreted from basic physical constraints imposed on a simple Taylor expansion of the binding energy around saturation density. In particular, we investigate the correlations among the following empirical parameters: the symmetry energy E_sym, the slope and curvature of the symmetry energy L_sym and K_sym, and the curvature and skewness of the binding energy in symmetric matter K_sat and Q_sat. The uncertainties on these correlations is estimated through analytical modelling as well as a meta-modelling analysis of the EoS subject to physical constraints. We show that a huge dispersion of the correlations among low order empirical parameters is induced by the unknown higher order empirical parameters, such as K_sym (second order) and Q_sat and Q_sym (third order). We also propose an explanation of the reason why Q_sat is weakly constrained by present experimental data. We conclude that selective observables on high order parameters, such as K_sym and Q_sat, should be better determined before the present uncertainties on the EoS can be further reduced.", "keyphrases": ["high order", "empirical parameter", "nuclear equation", "taylor expansion"]}
{"id": "1401.2656", "title": "Linear Perturbation constraints on Multi-coupled Dark Energy", "abstract": "The Multi-coupled Dark Energy (McDE) scenario has been recently proposed as a specific example of a cosmological model characterized by a non-standard physics of the dark sector of the universe that nevertheless gives an expansion history which does not significantly differ from the one of the standard \u039bCDM model. In this work, we present the first constraints on the McDE scenario obtained by comparing the predicted evolution of linear density perturbations with a large compilation of recent data sets for the growth rate f\u03c3_8, including 6dFGS, LRG, BOSS, WiggleZ and VIPERS. Confirming qualitative expectations, growth rate data provide much tighter bounds on the model parameters as compared to the extremely loose bounds that can be obtained when only the background expansion history is considered. In particular, the 95% confidence level on the coupling strength |\u03b2 | is reduced from |\u03b2 |\u2264 83 (background constraints only) to |\u03b2 |\u2264 0.88 (background and linear perturbation constraints). We also investigate how these constraints further improve when using data from future wide-field surveys such as supernova data from LSST and growth rate data from Euclid-type missions. In this case the 95% confidence level on the coupling further reduce to |\u03b2 |\u2264 0.85. Such constraints are in any case still consistent with a scalar fifth-force of gravitational strength, and we foresee that tighter bounds might be possibly obtained from the investigation of nonlinear structure formation in McDE cosmologies.[Abridged]", "keyphrases": ["multi-coupled dark energy", "universe", "linear perturbation constraint", "single scalar field", "dark matter component"]}
{"id": "1905.03431", "title": "Angular distribution of gamma-ray emission from velocity-dependent dark matter annihilation in subhalos", "abstract": "We consider the effect of velocity-dependent dark matter annihilation on the angular distribution of gamma rays produced in dark matter subhalos. We assume that the dark matter potential is spherically symmetric, characterized by a scale radius and scale density, and the velocity distribution is isotropic. We find that the effect of velocity-dependent dark matter annihilation is largely determined by dimensional analysis; the angular size of gamma-ray emission from an individual subhalo is rescaled by a factor which depends on the form of the dark matter distribution, but not on the halo parameters, while the relative normalization of the gamma-ray flux from different mass subhalos is rescaled by a factor which depends on the halo parameters, but not on the form of the dark matter distribution. We apply our results to a Navarro-Frenk-White profile for the case of an individual subhalo and comment on the application of these results to a distribution of subhalos.", "keyphrases": ["gamma-ray emission", "dark matter annihilation", "matter velocity distribution"]}
{"id": "1705.05328", "title": "Multipole analysis of redshift-space distortions around cosmic voids", "abstract": "We perform a comprehensive redshift-space distortion analysis based on cosmic voids in the large-scale distribution of galaxies observed with the Sloan Digital Sky Survey. To this end, we measure multipoles of the void-galaxy cross-correlation function and compare them with standard model predictions in cosmology. Merely considering linear-order theory allows us to accurately describe the data on the entire available range of scales and to probe void-centric distances down to about 2h^-1 Mpc. Common systematics, such as the Fingers-of-God effect, scale-dependent galaxy bias, and nonlinear clustering do not seem to play a significant role in our analysis. We constrain the growth rate of structure via the redshift-space distortion parameter \u03b2 at two median redshifts, \u03b2(z\u0305=0.32)=0.599^+0.134_-0.124 and \u03b2(z\u0305=0.54)=0.457^+0.056_-0.054, with a precision that is competitive with state-of-the-art galaxy-clustering results. While the high-redshift constraint perfectly agrees with model expectations, we observe a mild 2\u03c3 deviation at z\u0305=0.32, which increases to 3\u03c3 when the data is restricted to the lowest available redshift range of 0.15<z<0.33.", "keyphrases": ["cosmic void", "redshift", "multipole analysis"]}
{"id": "0907.3436", "title": "Turning Big Bang into Big Bounce: I. Classical Dynamics", "abstract": "The big bounce (BB) transition within a flat Friedmann-Robertson-Walker model is analyzed in the setting of loop geometry underlying the loop cosmology. We solve the constraint of the theory at the classical level to identify physical phase space and find the Lie algebra of the Dirac observables. We express energy density of matter and geometrical functions in terms of the observables. It is the modification of classical theory by the loop geometry that is responsible for BB. The classical energy scale specific to BB depends on a parameter that should be fixed either by cosmological data or determined theoretically at quantum level, otherwise the energy scale stays unknown.", "keyphrases": ["big bounce", "phase space", "formalism"]}
{"id": "2011.00283", "title": "Interacting Dark Energy in a closed universe", "abstract": "Recent measurements of the Cosmic Microwave Anisotropies power spectra measured by the Planck satellite show a preference for a closed universe at more than 99 % Confidence Level. Such a scenario is however in disagreement with several low redshift observables, including luminosity distances of Type Ia Supernovae. Here we show that Interacting Dark Energy (IDE) models can ease the discrepancies between Planck and Supernovae Ia data in a closed Universe. Therefore IDE cosmologies remain as very appealing scenarios, as they can provide the solution to a number of observational tensions in different fiducial cosmologies. The results presented here strongly favour broader analyses of cosmological data, and suggest that relaxing the usual flatness and vacuum energy assumptions can lead to a much better agreement among theory and observations.", "keyphrases": ["closed universe", "cosmology", "interacting dark energy"]}
{"id": "1302.5702", "title": "Astrophysical black holes as natural laboratories for fundamental physics and strong-field gravity", "abstract": "Astrophysical tests of general relativity belong to two categories: 1) \"internal\", i.e. consistency tests within the theory (for example, tests that astrophysical black holes are indeed described by the Kerr solution and its perturbations), or 2) \"external\", i.e. tests of the many proposed extensions of the theory. I review some ways in which astrophysical black holes can be used as natural laboratories for both \"internal\" and \"external\" tests of general relativity. The examples provided here (ringdown tests of the black hole \"no-hair\" theorem, bosonic superradiant instabilities in rotating black holes and gravitational-wave tests of massive scalar-tensor theories) are shamelessly biased towards recent research by myself and my collaborators. Hopefully this colloquial introduction aimed mainly at astrophysicists will convince skeptics (if there are any) that space-based detectors will be crucial to study fundamental physics through gravitational-wave observations.", "keyphrases": ["fundamental physics", "general relativity", "astrophysical black hole"]}
{"id": "1004.5098", "title": "Tidal Love Numbers of Neutron and Self-Bound Quark Stars", "abstract": "Gravitational waves from the final stages of inspiralling binary neutron stars are expected to be one of the most important sources for ground-based gravitational wave detectors. The masses of the components are determinable from the orbital and chirp frequencies during the early part of the evolution during which tidal effects provide small correction; however, during this phase the signal is relatively clean. The accumulated phase shift due to tidal corrections is characterized by a single quantity, the Love number, which is sensitive to the compactness parameter M/R and the star's internal structure, and its determination could constrain the star's radius. We show that the Love number of normal neutron stars are much different from those of self-bound strange quark matter stars and could therefore provide an important way to distinguish between these two classes of stars.", "keyphrases": ["love number", "star", "normal neutron star", "quark matter star"]}
{"id": "1609.00391", "title": "The MASSIVE Survey - V. Spatially-Resolved Stellar Angular Momentum, Velocity Dispersion, and Higher Moments of the 41 Most Massive Local Early-Type Galaxies", "abstract": "We present spatially-resolved two-dimensional stellar kinematics for the 41 most massive early-type galaxies (MK < -25.7 mag, stellar mass M* > 10^11.8 Msun) of the volume-limited (D < 108 Mpc) MASSIVE survey. For each galaxy, we obtain high-quality spectra in the wavelength range of 3650 to 5850 A from the 246-fiber Mitchell integral-field spectrograph (IFS) at McDonald Observatory, covering a 107\" x 107\" field of view (often reaching 2 to 3 effective radii). We measure the 2-D spatial distribution of each galaxy's angular momentum (lambda and fast or slow rotator status), velocity dispersion (sigma), and higher-order non-Gaussian velocity features (Gauss-Hermite moments h3 to h6). Our sample contains a high fraction ( 80 lambda < 0.2. When combined with the lower-mass ETGs in the ATLAS3D survey, we find the fraction of slow-rotators to increase dramatically with galaxy mass, reaching 50 rotators show a clear anti-correlation between h3 and V/sigma, and the slope of the anti-correlation is steeper in more round galaxies. The radial profiles of sigma show a clear luminosity and environmental dependence: the 12 most luminous galaxies in our sample (MK < -26 mag) are all brightest cluster/group galaxies (except NGC 4874) and all have rising or nearly flat sigma profiles, whereas five of the seven \"isolated\" galaxies are all fainter than MK = -25.8 mag and have falling sigma. All of our galaxies have positive average h4; the most luminous galaxies have average h4 0.05 while less luminous galaxies have a range of values between 0 and 0.05. Most of our galaxies show positive radial gradients in h4, and those galaxies also tend to have rising sigma profiles. We discuss the implications for the relationship among dynamical mass, sigma, h4, and velocity anisotropy for these massive galaxies.", "keyphrases": ["massive survey", "velocity dispersion", "galaxy mass"]}
{"id": "1604.05349", "title": "Constraints on primordial black holes from Galactic gamma-ray background", "abstract": "The fraction of the Universe going into primordial black holes (PBHs) with initial mass M_* \u22485 \u00d710^14 g, such that they are evaporating at the present epoch, is strongly constrained by observations of both the extragalactic and Galactic gamma-ray backgrounds. However, while the dominant contribution to the extragalactic background comes from the time-integrated emission of PBHs with initial mass M_*, the Galactic background is dominated by the instantaneous emission of those with initial mass slightly larger than M_* and current mass below M_*. Also, the instantaneous emission of PBHs smaller than 0.4 M_* mostly comprises secondary particles produced by the decay of directly emitted quark and gluon jets. These points were missed in the earlier analysis by Lehoucq et al. using EGRET data. For a monochromatic PBH mass function, with initial mass (1+\u03bc) M_* and \u03bc<< 1, the current mass is (3\u03bc)^1/3 M_* and the Galactic background constrains the fraction of the Universe going into PBHs as a function of \u03bc. However, the initial mass function cannot be precisely monochromatic and even a tiny spread of mass around M_* would generate a current low-mass tail of PBHs below M_*. This tail would be the main contributor to the Galactic background, so we consider its form and the associated constraints for a variety of scenarios with both extended and nearly-monochromatic initial mass functions. In particular, we consider a scenario in which the PBHs form from critical collapse and have a mass function which peaks well above M_*. In this case, the largest PBHs could provide the dark matter without the M_* ones exceeding the gamma-ray background limits.", "keyphrases": ["primordial black hole", "gamma-ray background", "pbh mass function"]}
{"id": "1403.7786", "title": "Ruling out the power-law form of the scalar primordial spectrum", "abstract": "Combining Planck CMB temperature [1] and BICEP2 B-mode polarization data [2,3] we show qualitatively that, assuming inflationary consistency relation, the power-law form of the scalar primordial spectrum is ruled out at more than 3\u03c3 CL. This is an important finding, since the power-law form of the scalar primordial spectrum is one of the main assumptions of concordance model of cosmology and also a direct prediction of many inflationary scenarios. We show that a break or step in the form of the primordial scalar perturbation spectrum, similar to what we studied recently analyzing Planck data [4] can address both Planck and BICEP2 results simultaneously. Our findings also indicate that the data may require more flexibilities than what running of scalar spectral index can provide. Finally we show that an inflaton potential, originally appeared in [5] can generate both the step and the break model of scalar primordial spectrum in two different limits. The discussed potential is found to be favored by Planck data but marginally disfavored by BICEP2 results as it produces slightly lower amplitude of tensor primordial spectrum. Hence, if the tensor-to-scalar ratio (r) quoted by BICEP2 persists, it is of importance that we generate inflationary models with large r and at the same time provide suppression in scalar primordial spectrum at large scales.", "keyphrases": ["power-law form", "scalar primordial spectrum", "inflaton potential"]}
{"id": "1408.5097", "title": "Point and Interval Estimation on the Degree and the Angle of Polarization. A Bayesian approach", "abstract": "Linear polarization measurements provide access to two quantities, the degree (DOP) and the angle of polarization (AOP). The aim of this work is to give a complete and concise overview of how to analyze polarimetric measurements. We review interval estimations for the DOP with a frequentist and a Bayesian approach. Point estimations for the DOP and interval estimations for the AOP are further investigated with a Bayesian approach to match observational needs. Point and interval estimations are calculated numerically for frequentist and Bayesian statistics. Monte Carlo simulations are performed to clarify the meaning of the calculations. Under observational conditions, the true DOP and AOP are unknown, so that classical statistical considerations - based on true values - are not directly usable. In contrast, Bayesian statistics handles unknown true values very well and produces point and interval estimations for DOP and AOP, directly. Using a Bayesian approach, we show how to choose DOP point estimations based on the measured signal-to-noise ratio. Interval estimations for the DOP show great differences in the limit of low signal-to-noise ratios between the classical and Bayesian approach. AOP interval estimations that are based on observational data are presented for the first time. All results are directly usable via plots and parametric fits.", "keyphrases": ["angle", "polarization", "bayesian approach", "signal-to-noise ratio"]}
{"id": "1005.2165", "title": "Inhomogeneity and the foundations of concordance cosmology", "abstract": "The apparent accelerating expansion of the Universe is forcing us to examine the foundational aspects of the standard model of cosmology \u2013 in particular, the fact that dark energy is a direct consequence of the homogeneity assumption. We discuss the foundations of the assumption of spatial homogeneity, in the case when the Copernican Principle is adopted. We present results that show how (almost-) homogeneity follows from (almost-) isotropy of various observables. The analysis requires the fully nonlinear field equations \u2013 i.e., it is not possible to use second- or higher-order perturbation theory, since one cannot assume a homogeneous and isotropic background. Then we consider what happens if the Copernican Principle is abandoned in our Hubble volume. The simplest models are inhomogeneous but spherically symmetric universes which do not require dark energy to fit the distance modulus. Key problems in these models are to compute the CMB anisotropies and the features of large-scale structure. We review how to construct perturbation theory on a non-homogeneous cosmological background, and discuss the complexities that arise in using this to determine the growth of large-scale structure.", "keyphrases": ["foundational aspect", "inhomogeneity", "past lightcone", "time-constant hypersurface", "cosmological constant"]}
{"id": "1410.3835", "title": "BayesWave: Bayesian Inference for Gravitational Wave Bursts and Instrument Glitches", "abstract": "A central challenge in Gravitational Wave Astronomy is identifying weak signals in the presence of non-stationary and non-Gaussian noise. The separation of gravitational wave signals from noise requires good models for both. When accurate signal models are available, such as for binary Neutron star systems, it is possible to make robust detection statements even when the noise is poorly understood. In contrast, searches for \"un-modeled\" transient signals are strongly impacted by the methods used to characterize the noise. Here we take a Bayesian approach and introduce a multi-component, variable dimension, parameterized noise model that explicitly accounts for non-stationarity and non-Gaussianity in data from interferometric gravitational wave detectors. Instrumental transients (glitches) and burst sources of gravitational waves are modeled using a Morlet-Gabor continuous wavelet frame. The number and placement of the wavelets is determined by a trans-dimensional Reversible Jump Markov Chain Monte Carlo algorithm. The Gaussian component of the noise and sharp line features in the noise spectrum are modeled using the BayesLine algorithm, which operates in concert with the wavelet model.", "keyphrases": ["bayesian inference", "glitch", "gravitational wave signal"]}
{"id": "1302.2374", "title": "Extended evolution equations for neutrino propagation in astrophysical and cosmological environments", "abstract": "We derive the evolution equations for a system of neutrinos interacting among themselves and with a matter background, based upon the Bogoliubov-Born-Green-Kirkwood-Yvon (BBGKY) hierarchy. This theoretical framework gives an (unclosed) set of first-order coupled integro-differential equations governing the evolution of the reduced density matrices. By employing the hierarchy, we first rederive the mean-field evolution equations for the neutrino one-body density matrix associated with a system of neutrinos and antineutrinos interacting with matter and with an anisotropic neutrino background. Then, we derive extended evolution equations to determine neutrino flavor conversion beyond the commonly used mean-field approximation. To this aim we include neutrino-antineutrino pairing correlations to the two-body density matrix. The inclusion of these new contributions leads to an extended evolution equation for the normal neutrino density and to an equation for the abnormal one involving the pairing mean-field. We discuss the possible impact of neutrino-antineutrino correlations on neutrino flavor conversion in the astrophysical and cosmological environments, and possibly upon the supernova dynamics. Our results can be easily generalized to an arbitrary number of neutrino families.", "keyphrases": ["evolution equation", "neutrino propagation", "cosmological environment", "neutrino-antineutrino correlation"]}
{"id": "1406.3020", "title": "Exoplanet population inference and the abundance of Earth analogs from noisy, incomplete catalogs", "abstract": "No true extrasolar Earth analog is known. Hundreds of planets have been found around Sun-like stars that are either Earth-sized but on shorter periods, or else on year-long orbits but somewhat larger. Under strong assumptions, exoplanet catalogs have been used to make an extrapolated estimate of the rate at which Sun-like stars host Earth analogs. These studies are complicated by the fact that every catalog is censored by non-trivial selection effects and detection efficiencies, and every property (period, radius, etc.) is measured noisily. Here we present a general hierarchical probabilistic framework for making justified inferences about the population of exoplanets, taking into account survey completeness and, for the first time, observational uncertainties. We are able to make fewer assumptions about the distribution than previous studies; we only require that the occurrence rate density be a smooth function of period and radius (employing a Gaussian process). By applying our method to synthetic catalogs, we demonstrate that it produces more accurate estimates of the whole population than standard procedures based on weighting by inverse detection efficiency. We apply the method to an existing catalog of small planet candidates around G dwarf stars (Petigura et al. 2013). We confirm a previous result that the radius distribution changes slope near Earth's radius. We find that the rate density of Earth analogs is about 0.02 (per star per natural logarithmic bin in period and radius) with large uncertainty. This number is much smaller than previous estimates made with the same data but stronger assumptions.", "keyphrases": ["population inference", "catalog", "planet"]}
{"id": "1706.00730", "title": "Distinguishing between Neutrinos and time-varying Dark Energy through Cosmic Time", "abstract": "We study the correlations between parameters characterizing neutrino physics and the evolution of dark energy. Using a fluid approach, we show that time-varying dark energy models exhibit degeneracies with the cosmic neutrino background over extended periods of the cosmic history, leading to a degraded estimation of the total mass and number of species of neutrinos. We investigate how to break degeneracies and combine multiple probes across cosmic time to anchor the behaviour of the two components. We use Planck CMB data and BAO measurements from the BOSS, SDSS and 6dF surveys to present current limits on the model parameters, and then forecast the future reach from the CMB Stage-4 and DESI experiments. We show that a multi-probe analysis of current data provides only marginal improvement on the determination of the individual parameters and no reduction of the correlations. Future observations will better distinguish the neutrino mass and preserve the current sensitivity to the number of species even in case of a time-varying dark energy component.", "keyphrases": ["neutrino", "dark energy", "cosmic time"]}
{"id": "1004.1424", "title": "A CoGeNT confirmation of the DAMA signal", "abstract": "The CoGeNT collaboration has recently reported a rising low energy spectrum in their ultra low noise germanium detector. This is particularly interesting as the energy range probed by CoGeNT overlaps with the energy region in which DAMA has observed their annual modulation signal. We show that the mirror dark matter candidate can simultaneously explain both the DAMA annual modulation signal and the rising low energy spectrum observed by CoGeNT. This constitutes a model dependent confirmation of the DAMA signal and adds weight to the mirror dark matter paradigm.", "keyphrases": ["cogent", "confirmation", "dama signal"]}
{"id": "2106.13290", "title": "Chameleon Early Dark Energy and the Hubble Tension", "abstract": "Early dark energy (EDE) offers a particularly interesting theoretical approach to the Hubble tension, albeit one that introduces its own set of challenges, including a new `why then' problem related to the EDE injection time at matter-radiation equality, and a mild worsening of the large-scale structure (LSS) tension. Both these challenges center on the properties of dark matter, which becomes the dominant component of the Universe at EDE injection and is also responsible for seeding LSS. Motivated by this, we present the potential of couplings between EDE and dark matter to address these challenges, focusing on a mechanism similar to chameleon dark energy theories, deeming this chameleon early dark energy (CEDE). We present relevant background and perturbation equations and study the dynamics of the case of a quartic scalar potential and an exponential coupling.", "keyphrases": ["early dark energy", "hubble tension", "ede"]}
{"id": "2004.04166", "title": "A new approach to modelling gamma-ray burst afterglows: Using Gaussian processes to account for the systematics", "abstract": "The afterglow emission from gamma-ray bursts (GRBs) is a valuable source of information to understand the physics of these energetic explosions. The blast wave model has become the standard to describe the evolution of the afterglow emission over time and frequency. Thanks to recent developments in the theory of afterglows and numerical simulations of relativistic outflows, we are able to model the afterglow emission with realistic dynamics and radiative processes. Although the models agree with observations remarkably well, the afterglow emission still contains additional physics, instrumental systematics, and propagation effects which make the modelling of these events challenging. In this work, we present a new approach to modelling GRB afterglows, using Gaussian processes (GPs) to take into account systematics in the afterglow data. We show that, using this new approach, it is possible to obtain more reliable estimates of the explosion and microphysical parameters of GRBs. We present fit results for 5 long GRBs and find a preliminary correlation between the isotropic energetics and opening angles of GRBs, which confirms the idea of a common energy reservoir for the kinetic energy of long GRBs.", "keyphrases": ["gamma-ray burst", "gaussian process", "grb afterglow"]}
{"id": "1910.02979", "title": "Universal Upper Bound on the Inflationary Energy Scale from the Trans-Planckian Censorship Conjecture", "abstract": "We study the constraint on the inflationary energy scale from the recently proposed Trans-Planckian Censorship Conjecture (TCC). We find a universal upper bound on the inflationary Hubble expansion rate H_inf which is solely determined by the reheating temperature T_rh: H_inf/M_Pl\u2272 T_0/T_rh, where T_0 is the photon temperature today. The upper limit can be saturated by a post-inflationary oscillatory stage with the critical equation-of-state parameter w\u2248-1/3, or by an inflation model with multiple stages. In the lowest reheating temperature required for big bang nucleosynthesis, the upper bound on the tensor-to-scalar ratio r at the CMB scales is r\u227210^-8, which can be realized in many string-inspired inflation models.", "keyphrases": ["inflationary energy scale", "trans-planckian censorship conjecture", "big bang nucleosynthesis"]}
{"id": "1712.07466", "title": "Minkowski Tensors in Two Dimensions - Probing the Morphology and Isotropy of the Matter and Galaxy Density Fields", "abstract": "We apply the Minkowski Tensor statistics to two dimensional slices of the three dimensional density field. The Minkowski Tensors are a set of functions that are sensitive to directionally dependent signals in the data, and furthermore can be used to quantify the mean shape of density peaks. We begin by introducing our algorithm for constructing bounding perimeters around subsets of a two dimensional field, and reviewing the definition of Minkowski Tensors. Focusing on the translational invariant statistic W^1,1_2 - a 2 \u00d7 2 matrix - we calculate its eigenvalues for both the entire excursion set (\u039b_1,\u039b_2) and for individual connected regions and holes within the set (\u03bb_1,\u03bb_2). The ratio of eigenvalues \u039b_2/\u039b_1 informs us of the presence of global anisotropies in the data, and \u27e8\u03bb_2/\u03bb_1\u27e9 is a measure of the mean shape of peaks and troughs in the density field. We study these quantities for a Gaussian field, then consider how they are modified by the effect of gravitational collapse using the latest Horizon Run 4 cosmological simulation. We find \u039b_1,2 are essentially independent of gravitational collapse, as the process maintains statistical isotropy. However, the mean shape of peaks is modified significantly - overdensities become relatively more circular compared to underdensities of the same area. When applying the statistic to a redshift space distorted density field, we find a significant signal in the eigenvalues \u039b_1,2, suggesting that they can be used to probe the large-scale velocity field.", "keyphrases": ["isotropy", "density field", "minkowski tensors"]}
{"id": "1906.08794", "title": "Fast Neutrino Flavor Conversion: Collective Motion vs. Decoherence", "abstract": "In an interacting neutrino gas, flavor coherence becomes dynamical and can propagate as a collective mode. In particular, tachyonic instabilities can appear, leading to \"fast flavor conversion\" that is independent of neutrino masses and mixing angles. On the other hand, without neutrino-neutrino interaction, a prepared wave packet of flavor coherence simply dissipates by kinematical decoherence of infinitely many non-collective modes. We reexamine the dispersion relation for fast flavor modes and show that for any wavenumber,there exists a continuum of non-collective modes besides a few discrete collective ones. So for any initial wave packet, both decoherence and collective motion occurs, although the latter typically dominates for a sufficiently dense gas. We derive explicit eigenfunctions for both collective and non-collective modes. If the angular mode distribution of electron-lepton number crosses between positive and negative values, two non-collective modes can merge to become a tachyonic collective mode. We explicitly calculate the interaction strength for this critical point. As a corollary we find that a single crossing always leads to a tachyonic instability. For an even number of crossings, no instability needs to occur.", "keyphrases": ["collective motion", "neutrino gas", "fast flavor conversion"]}
{"id": "0907.5423", "title": "Galactic masers and the Milky Way circular velocity", "abstract": "Masers found in massive star-forming regions can be located precisely in six-dimensional phase space and therefore serve as a tool for studying Milky Way dynamics. The non-random orbital phases at which the masers are found and the sparseness of current samples require modeling. Here we model the phase-space distribution function of 18 precisely measured Galactic masers, permitting a mean velocity offset and a general velocity dispersion tensor relative to their local standards of rest, and accounting for different pieces of prior information. With priors only on the Sun's distance from the Galactic Center and on its motion with respect to the local standard of rest, the maser data provide a weak constraint on the circular velocity at the Sun of V_c = 246 +/- 30 km/s. Including prior information on the proper motion of Sgr A* leads to V_c = 244 +/- 13 km/s. We do not confirm the value of V_c \u2248254 km/s found in more restrictive models. This analysis shows that there is no conflict between recent determinations of V_c from Galactic Center analyses, orbital fitting of the GD-1 stellar stream, and the kinematics of Galactic masers; a combined estimate is V_c = 236 +/- 11 km/s. Apart from the dynamical parameters, we find that masers tend to occur at post-apocenter, circular-velocity-lagging phases of their orbits.", "keyphrases": ["circular velocity", "sun", "galactic maser"]}
{"id": "1406.4568", "title": "Lorentz violation from gamma-ray bursts", "abstract": "The constancy of light speed is a basic assumption in Einstein's special relativity, and consequently the Lorentz invariance is a fundamental symmetry of space-time in modern physics. However, it is speculated that the speed of light becomes energy-dependent due to the Lorentz invariance violation (LV) in various new physics theories. We analyse the data of the energetic photons from the gamma-ray bursts (GRBs) by the Fermi Gamma-Ray Space Telescope, and find more events to support the energy dependence in the light speed with both linear and quadratic form corrections. We provide two scenarios to understand all the new-released Pass 8 data of bright GRBs by the Fermi-LAT Collaboration, with predictions from such scenarios being testable by future detected GRBs.", "keyphrases": ["gamma-ray burst", "lorentz violation", "energy photon"]}
{"id": "1802.06518", "title": "Frequency-domain gravitational waveform models for inspiraling binary neutron stars", "abstract": "We develop a model for frequency-domain gravitational waveforms from inspiraling binary neutron stars. Our waveform model is calibrated by comparison with hybrid waveforms constructed from our latest high-precision numerical-relativity waveforms and the SEOBNRv2T waveforms in the frequency range of 10\u20131000 Hz. We show that the phase difference between our waveform model and the hybrid waveforms is always smaller than 0.1 rad for the binary tidal deformability, \u039b\u0303, in the range 300\u2272\u039b\u0303\u22721900 and for the mass ratio between 0.73 and 1. We show that, for 10\u20131000 Hz, the distinguishability for the signal-to-noise ratio \u227250 and the mismatch between our waveform model and the hybrid waveforms are always smaller than 0.25 and 1.1\u00d710^-5, respectively. The systematic error of our waveform model in the measurement of \u039b\u0303 is always smaller than 20 with respect to the hybrid waveforms for 300\u2272\u039b\u0303\u22721900. The statistical error in the measurement of binary parameters is computed employing our waveform model, and we obtain results consistent with the previous studies. We show that the systematic error of our waveform model is always smaller than 20% (typically smaller than 10%) of the statistical error for events with the signal-to-noise ratio of 50.", "keyphrases": ["waveform model", "binary neutron star", "frequency-domain gravitational waveform"]}
{"id": "1207.2039", "title": "Improved determination of the WIMP mass from direct detection data", "abstract": "Direct detection experiments searching for weakly interacting massive particle (WIMP) dark matter typically use a simplified model of the Galactic halo to derive parameter constraints. However, there is strong evidence that this Standard Halo Model is not a good approximation to our Galaxy. We discuss previous attempts to extract the WIMP mass, cross-section and speed distribution from direct detection data and show that these lead to significant biases in the reconstructed parameter values. We develop and test an alternative model-independent method based on parametrising the momentum distribution of the WIMPs. This allows us to limit the analysis only to those regions of momentum space to which the experiments are sensitive. The method can be applied to a single experiment to extract information about the distribution function, as well as information on the degenerate WIMP mass and interaction cross-section combined in a single parameter. This degeneracy can be broken by including data from additional experiments, meaning that the WIMP mass and speed distribution can be recovered. We test the momentum parametrisation method using mock datasets from proposed ton-scale direct detection experiments, showing that it exhibits improved coverage properties over previous methods, as well as significantly reduced bias. We are also able to accurately reconstruct the shape of the WIMP speed distribution but distinguishing between different underlying distributions remains difficult.", "keyphrases": ["wimp mass", "direct detection data", "particle physics parameter"]}
{"id": "2208.10479", "title": "Extreme Value Statistics of the Halo and Stellar Mass Distributions at High Redshift: are JWST Results in Tension with \u039bCDM?", "abstract": "The distribution of dark matter halo masses can be accurately predicted in the \u039bCDM cosmology. The presence of a single massive halo or galaxy at a particular redshift, assuming some baryon and stellar fraction for the latter, can therefore be used to test the underlying cosmological model. A number of recent measurements of very large galaxy stellar masses at high redshift (z > 8) motivate an investigation into whether any of these objects are in tension with \u039bCDM. We use extreme value statistics to generate confidence regions in the mass-redshift plane for the most extreme mass haloes and galaxies. Tests against numerical models show no tension, neither in their dark matter halo masses nor their galaxy stellar masses. However, we find tentative > 3\u03c3 tension with recent observational determinations of galaxy masses at high redshift from both HST JWST, despite using conservative estimates for the stellar fraction (f_\u22c6\u223c 1). Either these galaxies are in tension with \u039bCDM, or there are unaccounted for uncertainties in their stellar mass or redshift estimates.", "keyphrases": ["halo", "high redshift", "extreme value statistic"]}
{"id": "2011.13660", "title": "Local primordial non-Gaussianity in the relativistic galaxy bispectrum", "abstract": "Next-generation galaxy and 21cm intensity mapping surveys will rely on a combination of the power spectrum and bispectrum for high-precision measurements of primordial non-Gaussianity. In turn, these measurements will allow us to distinguish between various models of inflation. However, precision observations require theoretical precision at least at the same level. We extend the theoretical understanding of the galaxy bispectrum by incorporating a consistent general relativistic model of galaxy bias at second order, in the presence of local primordial non-Gaussianity. The influence of primordial non-Gaussianity on the bispectrum extends beyond the galaxy bias and the dark matter density, due to redshift-space effects. The standard redshift-space distortions at first and second order produce a well-known primordial non-Gaussian imprint on the bispectrum. Relativistic corrections to redshift-space distortions generate new contributions to this primordial non-Gaussian signal, arising from: (1) a coupling of first-order scale-dependent bias with first-order relativistic observational effects, and (2) linearly evolved non-Gaussianity in the second-order velocity and metric potentials which appear in relativistic observational effects. Our analysis allows for a consistent separation of the relativistic `contamination' from the primordial signal, in order to avoid biasing the measurements by using an incorrect theoretical model. We show that the bias from using a Newtonian analysis of the squeezed bispectrum could be \u0394\u223c 5 for a Stage IV H\u03b1 survey.", "keyphrases": ["galaxy", "bispectrum", "local primordial non-gaussianity"]}
{"id": "1111.6835", "title": "Application of cross correlations between CMB and large scale structure to constraints on the primordial non-Gaussianity", "abstract": "The primordial non-Gaussianity of local type affects the clustering of dark matter halos, and the planned deep and wide photometric surveys are suitable for examining this class of non-Gaussianity. In our previous paper, we investigated the constraint from the cross correlation between CMB lensing potential and galaxy angular distribution on the primordial non-Gaussianity, without taking into account redshift slicing. To improve our previous analysis, in this paper, we add the galaxy lensing shear into our analysis and take into account redshift slicing to follow the redshift evolution of the clustering. By calculating 81 power spectra and using the Fisher matrix method, we find that the constraint on the primordial non-Gaussianity can be improved from \u0394fNL \u223c5.4 to 5.1 by including the galaxy-galaxy lensing shear cross correlations expected from the Hyper Suprime-Cam survey (HSC), in comparison with the constraint without any cross correlations. Moreover, the constraint can go down to \u0394fNL \u223c4.8 by including the galaxy-CMB lensing cross correlations from the ACTPol and Planck experiments.", "keyphrases": ["cross correlation", "primordial non-gaussianity", "galaxy"]}
{"id": "1605.03665", "title": "Constraints on MACHO Dark Matter from Compact Stellar Systems in Ultra-Faint Dwarf Galaxies", "abstract": "I show that a recently discovered star cluster near the center of the ultra-faint dwarf galaxy Eridanus II provides strong constraints on massive compact halo objects (MACHOs) of > 5 M_sun as the main component of dark matter. MACHO dark matter will dynamically heat the cluster, driving it to larger sizes and higher velocity dispersions until it dissolves into its host galaxy. The stars in compact ultra-faint dwarf galaxies themselves will be subject to the same dynamical heating; the survival of at least ten such galaxies places independent limits on MACHO dark matter of masses > 10 M_sun. Both Eri II's cluster and the compact ultra-faint dwarfs are characterized by stellar masses of just a few thousand M_sun and half-light radii of 13 pc (for the cluster) and 30 pc (for the ultra-faint dwarfs). These systems close the 20\u2013100 M_sun window of allowed MACHO dark matter and combine with existing constraints from microlensing, wide binaries, and disk kinematics to rule out dark matter composed entirely of MACHOs from 10^-7 M_sun up to arbitrarily high masses.", "keyphrases": ["macho dark matter", "ultra-faint dwarf galaxy", "star cluster"]}
{"id": "2206.11486", "title": "Systematically smaller single-epoch quasar black hole masses using a radius-luminosity relationship corrected for spectral bias", "abstract": "Determining black hole masses and accretion rates with better accuracy and precision is crucial for understanding quasars as a population. These are fundamental physical properties that underpin models of active galactic nuclei. A primary technique to measure the black hole mass employs the reverberation mapping of low-redshift quasars, which is then extended via the radius-luminosity relationship for the broad-line region to estimate masses based on single-epoch spectra. An updated radius-luminosity relationship incorporates the flux ratio of optical Fe ii to H\u03b2 (\u2261\u211b_ Fe) to correct for a bias in which more highly accreting systems have smaller line-emitting regions than previously realized. In this current work, we demonstrate and quantify the effect of using this Fe-corrected radius-luminosity relationship on mass estimation by employing archival data sets possessing rest-frame optical spectra over a wide range of redshifts. We find that failure to use a Fe-corrected radius predictor results in overestimated single-epoch black hole masses for the most highly accreting quasars. Their accretion rate measures (L_ Bol/ L_ Edd and \u2133\u0307), are similarly underestimated. The strongest Fe-emitting quasars belong to two classes: high-z quasars with rest-frame optical spectra, which given their extremely high luminosities, require high accretion rates, and their low-z analogs, which given their low black holes masses, must have high accretion rates to meet survey flux limits. These classes have mass corrections downward of about a factor of two, on average. These results strengthen the association of the dominant Eigenvector 1 parameter \u211b_ Fe with the accretion process.", "keyphrases": ["black hole masse", "radius-luminosity relationship", "accretion rate"]}
{"id": "1403.0898", "title": "Probing non-standard gravity with the growth index: a background independent analysis", "abstract": "Measurements of the growth index \u03b3(z) provide a clue as to whether Einstein's field equations encompass gravity also on large cosmic scales, those where the expansion of the universe accelerates. We show that the information encoded in this function can be satisfactorily parameterized using a small set of coefficients \u03b3_i in such a way that the true scaling of the growth index is recovered to better than 1% in most dark energy and dark gravity models. We find that the likelihood of current data is maximal for \u03b3_0=0.74\u00b1 0.44 and \u03b3_1=0.01\u00b10.46, a measurement compatible with the \u039bCDM predictions. Moreover data favor models predicting slightly less growth of structures than the Planck LambdaCDM scenario. The main aim of the paper is to provide a prescription for routinely calculating, in an analytic way, the amplitude of the growth indices \u03b3_i in relevant cosmological scenarios, and to show that these parameters naturally define a space where predictions of alternative theories of gravity can be compared against growth data in a manner which is independent from the expansion history of the cosmological background. As the standard \u03a9-plane provides a tool to identify different expansion histories H(t) and their relation to various cosmological models, the \u03b3-plane can thus be used to locate different growth rate histories f(t) and their relation to alternatives model of gravity. As a result, we find that the Dvali-Gabadadze-Porrati gravity model is rejected with a 95% confidence level. By simulating future data sets, such as those that a Euclid-like mission will provide, we also show how to tell apart LambdaCDM predictions from those of more extreme possibilities, such as smooth dark energy models, clustering quintessence or parameterized post-Friedmann cosmological models.", "keyphrases": ["gravity", "growth index", "dark energy"]}
{"id": "1208.2997", "title": "Star Formation Rate Indicators", "abstract": "What else can be said about star formation rate indicators that has not been said already many times over? The `coming of age' of large ground-based surveys and the unprecedented sensitivity, angular resolution and/or field-of-view of infrared and ultraviolet space missions have provided extensive, homogeneous data on both nearby and distant galaxies, which have been used to further our understanding of the strengths and pitfalls of many common star formation rate indicators. The synergy between these surveys has also enabled the calibration of indicators for use on scales that are comparable to those of star-forming regions, thus much smaller than an entire galaxy. These are being used to investigate star formation processes at the sub-galactic scale. I review progress in the field over the past decade or so.", "keyphrases": ["galaxy", "star formation history", "dust extinction"]}
{"id": "1306.1364", "title": "Indistinguishability of Warm Dark Matter, Modified Gravity, and Coupled Cold Dark Matter", "abstract": "The current accelerated expansion of our universe could be due to an unknown energy component with negative pressure (dark energy) or a modification to general relativity (modified gravity). On the other hand, recently warm dark matter (WDM) remarkably rose as an alternative of cold dark matter (CDM). Obviously, it is of interest to distinguish these different types of models. In fact, many attempts have been made in the literature. However, in the present work, we show that WDM, modified gravity and coupled CDM form a trinity, namely, they are indistinguishable by using the cosmological observations of both cosmic expansion history and growth history. Therefore, to break this degeneracy, the other complementary probes beyond the ones of cosmic expansion history and growth history are required.", "keyphrases": ["warm dark matter", "modified gravity", "dark energy"]}
{"id": "1002.4035", "title": "When scalar field is kinetically coupled to the Einstein tensor", "abstract": "We explore the cosmic evolution of a scalar field with the kinetic term coupled to the Einstein tensor. We find that, in the absence of other matter sources or in the presence of only pressureless matter, the scalar behaves as pressureless matter and the sound speed of the scalar is vanishing. These properties enable the scalar field to be a candidate of cold dark matter. By also considering the scalar potential, we find the scalar field may play the role of both dark matter and dark energy. In this case, the equation of state of the scalar can cross the phantom divide, but this can lead to the sound speed becoming superluminal as it crosses the divide, and so is physically forbidden. Finally, if the kinetic term is coupled to more than one Einstein tensor, we find the equation of state is always approximately equal to -1 whether the potential is flat or not, and so the scalar may also be a candidate for the inflaton.", "keyphrases": ["scalar field", "einstein tensor", "kinetic term"]}
{"id": "1006.5394", "title": "Galaxy Formation Theory", "abstract": "We review the current theory of how galaxies form within the cosmological framework provided by the cold dark matter paradigm for structure formation. Beginning with the pre-galactic evolution of baryonic material we describe the analytical and numerical understanding of how baryons condense into galaxies, what determines the structure of those galaxies and how internal and external processes (including star formation, merging, active galactic nuclei etc.) determine their gross properties and evolution. Throughout, we highlight successes and failings of current galaxy formation theory. We include a review of computational implementations of galaxy formation theory and assess their ability to provide reliable modelling of this complex phenomenon. We finish with a discussion of several \"hot topics\" in contemporary galaxy formation theory and assess future directions for this field.", "keyphrases": ["success", "galaxy formation theory", "halo", "galactic nucleus"]}
{"id": "1002.1306", "title": "Dark Matter Decaying into a Fermi Sea of Neutrinos", "abstract": "We study the possible decay of a coherently oscillating scalar field, interpreted as dark matter, into light fermions. Specifically, we consider a scalar field with sub-eV mass decaying into a Fermi sea of neutrinos. We recognize the similarity between our scenario and inflationary preheating where a coherently oscillating scalar field decays into standard model particles. Like the case of fermionic preheating, we find that Pauli blocking controls the dark matter decay into the neutrino sea. The radius of the Fermi sphere depends on the expansion of the universe leading to a time varying equation of state of dark matter. This makes the scenario very rich and we show that the decay rate might be different at different cosmological epochs. We categorize this in two interesting regimes and then study the cosmological perturbations to find the impact on structure formation. We find that the decay may help alleviating some of the standard problems related to cold dark matter.", "keyphrases": ["fermi sea", "neutrino", "dark matter"]}
{"id": "1706.04240", "title": "The Time-Domain Spectroscopic Survey: Target Selection for Repeat Spectroscopy", "abstract": "As astronomers increasingly exploit the information available in the time domain, spectroscopic variability in particular opens broad new channels of investigation. Here we describe the selection algorithms for all targets intended for repeat spectroscopy in the Time Domain Spectroscopic Survey (TDSS), part of the extended Baryon Oscillation Spectroscopic Survey within the Sloan Digital Sky Survey-IV. Also discussed are the scientific rationale and technical constraints leading to these target selections. The TDSS includes a large \"Repeat Quasar Spectroscopy\" (RQS) program delivering 13,000 repeat spectra of confirmed SDSS quasars, and several smaller \"Few-Epoch Spectroscopy\" (FES) programs targeting specific classes of quasars as well as stars. The RQS program aims to provide a large and diverse quasar data set for studying variations in quasar spectra on timescales of years, a comparison sample for the FES quasar programs, and opportunity for discovering rare, serendipitous events. The FES programs cover a wide variety of phenomena in both quasars and stars. Quasar FES programs target broad absorption line quasars, high signal-to-noise ratio normal broad line quasars, quasars with double-peaked or very asymmetric broad emission line profiles, binary supermassive black hole candidates, and the most photometrically variable quasars. Strongly variable stars are also targeted for repeat spectroscopy, encompassing many types of eclipsing binary systems, and classical pulsators like RR Lyrae. Other stellar FES programs allow spectroscopic variability studies of active ultracool dwarf stars, dwarf carbon stars, and white dwarf/M dwarf spectroscopic binaries. We present example TDSS spectra and describe anticipated sample sizes and results.", "keyphrases": ["target selection", "repeat spectroscopy", "tdss"]}
{"id": "1303.4703", "title": "Cosmic inflation in a landscape of heavy-fields", "abstract": "Heavy isocurvature fields may have a strong influence on the low energy dynamics of curvature perturbations during inflation, as long as the inflationary trajectory becomes non-geodesic in the multi-field target space (the landscape). If fields orthogonal to the inflationary trajectory are sufficiently heavy, one expects a reliable effective field theory describing the low energy dynamics of curvature perturbations, with self-interactions determined by the shape of the inflationary trajectory. Previous work analyzing the role of heavy-fields during inflation have mostly focused in the effects on curvature perturbations due to a single heavy-field. In this article we extend the results of these works by studying models of inflation in which curvature perturbations interact with two heavy-fields. We show that the second heavy-field (orthogonal to both tangent and normal directions of the inflationary trajectory) may significantly affect the evolution of curvature modes. We compute the effective field theory for the low energy curvature perturbations obtained by integrating out the two heavy-fields and show that the presence of the second heavy-field implies the existence of additional self-interactions not accounted for in the single heavy-field case. We conclude that future observations will be able to constrain the number of heavy fields interacting with curvature perturbations.", "keyphrases": ["heavy-field", "curvature perturbation", "field theory"]}
{"id": "1609.01282", "title": "A sharper view of Pal 5's tails: Discovery of stream perturbations with a novel non-parametric technique", "abstract": "Only in the Milky Way is it possible to conduct an experiment which uses stellar streams to detect low-mass dark matter subhaloes. In smooth and static host potentials, tidal tails of disrupting satellites appear highly symmetric. However, perturbations from dark subhaloes, as well as from GMCs and the Milky Way bar, can induce density fluctuations that destroy this symmetry. Motivated by the recent release of unprecedentedly deep and wide imaging data around the Pal 5 stellar stream, we develop a new probabilistic, adaptive and non-parametric technique which allows us to bring the cluster's tidal tails into clear focus. Strikingly, we uncover a stream whose density exhibits visible changes on a variety of angular scales. We detect significant bumps and dips, both narrow and broad: two peaks on either side of the progenitor, each only a fraction of a degree across, and two gaps, \u223c2^\u2218 and \u223c9^\u2218 wide, the latter accompanied by a gargantuan lump of debris. This largest density feature results in a pronounced inter-tail asymmetry which cannot be made consistent with an unperturbed stream according to a suite of simulations we have produced. We conjecture that the sharp peaks around Pal 5 are epicyclic overdensities, while the two dips are consistent with impacts by subhaloes. Assuming an age of 3.4 Gyr for Pal 5, these two gaps would correspond to the characteristic size of gaps created by subhaloes in the mass range of 10^6-10^7 M_\u2299 and 10^7-10^8 M_\u2299 respectively. In addition to dark substructure, we find that the bar of the Milky Way can plausibly produce the asymmetric density seen in Pal 5 and that GMCs could cause the smaller gap.", "keyphrases": ["tail", "stream", "non-parametric technique"]}
{"id": "1006.2080", "title": "A Two-Component Power Law Covering Nearly Four Orders of Magnitude in the Power Spectrum of Spitzer Far-Infrared Emission from the Large Magellanic Cloud", "abstract": "Power spectra of Large Magellanic Cloud (LMC) emission at 24, 70 and 160 microns observed with the Spitzer Space Telescope have a two-component power-law structure with a shallow slope of -1.6 at low wavenumber, k, and a steep slope of -2.9 at high k. The break occurs at 1/k 100-200 pc, which is interpreted as the line-of-sight thickness of the LMC disk. The slopes are slightly steeper for longer wavelengths, suggesting the cooler dust emission is smoother than the hot emission. The power spectrum covers 3.5 orders of magnitude and the break in the slope is in the middle of this range on a logarithmic scale. Large-scale driving from galactic and extragalactic processes, including disk self-gravity, spiral waves and bars, presumably cause the low-k structure in what is effectively a two-dimensional geometry. Small-scale driving from stellar processes and shocks cause the high-k structure in a 3D geometry. This transition in dimensionality corresponds to the observed change in power spectrum slope. A companion paper models the observed power-law with a self-gravitating hydrodynamics simulation of a galaxy like the LMC.", "keyphrases": ["power spectrum", "large magellanic cloud", "galaxy"]}
{"id": "2007.04325", "title": "Lower bias, lower noise CMB lensing with foreground-hardened estimators", "abstract": "Extragalactic foregrounds in temperature maps of the Cosmic Microwave Background (CMB) severely limit the ability of standard estimators to reconstruct the weak lensing potential. These foregrounds are not fully removable by multi-frequency cleaning or masking and can lead to large biases if not properly accounted for. For foregrounds made of a number of unclustered point sources, an estimator for the source amplitude can be derived and deprojected, removing any bias to the lensing reconstruction. We show with simulations that all of the extragalactic foregrounds in temperature can be approximated by a collection of sources with identical profiles, and that a simple bias hardening technique is effective at reducing any bias to lensing, at a minimal noise cost. We compare the performance and bias to other methods such as \"shear-only\" reconstruction, and discuss how to jointly deproject any arbitrary number of foregrounds, each with an arbitrary profile. In particular, for a Simons Observatory-like experiment foreground-hardened estimators allow us to extend the maximum multipole used in the reconstruction, increasing the overall statistical power by \u223c 50% over the standard quadratic estimator, both in auto and cross-correlation. We conclude that source hardening outperforms the standard lensing quadratic estimator both in auto and cross-correlation, and in terms of lensing signal-to-noise and foreground bias.", "keyphrases": ["bias", "foreground-hardened estimator", "point source"]}
{"id": "1808.06648", "title": "Simons Observatory large aperture receiver simulation overview", "abstract": "The Simons Observatory (SO) will make precision temperature and polarization measurements of the cosmic microwave background (CMB) using a series of telescopes which will cover angular scales between one arcminute and tens of degrees, contain over 60,000 detectors, and sample frequencies between 27 and 270 GHz. SO will consist of a six-meter-aperture telescope coupled to over 30,000 detectors along with an array of half-meter aperture refractive cameras, which together couple to an additional 30,000+ detectors. SO will measure fundamental cosmological parameters of our universe, find high redshift clusters via the Sunyaev-Zeldovich effect, constrain properties of neutrinos, and seek signatures of dark matter through gravitational lensing. In this paper we will present results of the simulations of the SO large aperture telescope receiver (LATR). We will show details of simulations performed to ensure the structural integrity and thermal performance of our receiver, as well as will present the results of finite element analyses (FEA) of designs for the structural support system. Additionally, a full thermal model for the LATR will be described. The model will be used to ensure we meet our design requirements. Finally, we will present the results of FEA used to identify the primary vibrational modes, and planned methods for suppressing these modes. Design solutions to each of these problems that have been informed by simulation will be presented.", "keyphrases": ["aperture", "telescope", "simons observatory"]}
{"id": "1004.3551", "title": "A Terminal Velocity on the Landscape: Particle Production near Extra Species Loci in Higher Dimensions", "abstract": "We investigate particle production near extra species loci (ESL) in a higher dimensional field space and derive a speed limit in moduli space at weak coupling. This terminal velocity is set by the characteristic ESL-separation and the coupling of the extra degrees of freedom to the moduli, but it is independent of the moduli's potential if the dimensionality of the field space is considerably larger than the dimensionality of the loci, D >> d. Once the terminal velocity is approached, particles are produced at a plethora of nearby ESLs, preventing a further increase in speed via their backreaction. It is possible to drive inflation at the terminal velocity, providing a generalization of trapped inflation with attractive features: we find that more than sixty e-folds of inflation for sub-Planckian excursions in field space are possible if ESLs are ubiquitous, without fine tuning of initial conditions and less tuned potentials. We construct a simple, observationally viable model with a slightly red scalar power-spectrum and suppressed gravitational waves; we comment on the presence of additional observational signatures originating from IR-cascading and individual massive particles. We also show that moduli-trapping at an ESL is suppressed for D >> d, hindering dynamical selection of high-symmetry vacua on the landscape based on this mechanism.", "keyphrases": ["terminal velocity", "landscape", "particle production", "dimensional field space"]}
{"id": "1605.02746", "title": "Gas Loss by Ram Pressure Stripping and Internal Feedback From Low Mass Milky Way Satellites", "abstract": "The evolution of dwarf satellites of the Milky Way is affected by the combination of ram pressure and tidal stripping, and internal feedback from massive stars. We investigate gas loss processes in the smallest satellites of the Milky Way using three-dimensional, high resolution, idealized wind tunnel simulations, accounting for gas loss through both ram pressure stripping and expulsion by supernova feedback. Using initial conditions appropriate for a dwarf galaxy like Leo T, we investigate whether or not environmental gas stripping and internal feedback can quench these low mass galaxies on the expected timescales, shorter than 2 Gyr. We find that supernova feedback contributes negligibly to the stripping rate for these low star formation rate galaxies. However, we also find that ram pressure stripping is less efficient than expected in the stripping scenarios we consider. Our work suggests that, although ram pressure stripping can eventually completely strip these galaxies, other physics is likely at play to reconcile our computed stripping times with the rapid quenching timescales deduced from observations of low mass Milky Way dwarf galaxies. We discuss the roles additional physics may play in this scenario, including host-satellite tidal interactions, cored vs. cuspy dark matter profiles, reionization, and satellite pre-processing. We conclude that a proper accounting of these physics together is necessary to understand the quenching of low mass Milky Way satellites.", "keyphrases": ["ram pressure stripping", "tidal stripping", "gas loss"]}
{"id": "1711.08549", "title": "Non-Gaussianities in a two-field generalization of Natural Inflation", "abstract": "We describe a two-field model that generalizes Natural Inflation, in which the inflaton is the pseudo-Goldstone boson of an approximate symmetry that is spontaneously broken, and the radial mode is dynamical. We analyze how the dynamics fundamentally depends on the mass of the radial mode and calculate/estimate the non-Gaussianities arising from such a scenario.", "keyphrases": ["natural inflation", "non-gaussianitie", "cosmological collider"]}
{"id": "0911.0429", "title": "Alignments in quasar polarizations: pseudoscalar-photon mixing in the presence of correlated magnetic fields", "abstract": "We investigate the effects of pseudoscalar-photon mixing on electromagnetic radiation in the presence of correlated extragalactic magnetic fields. We model the Universe as a collection of magnetic domains and study the propagation of radiation through them. This leads to correlations between Stokes parameters over large scales and consistently explains the observed large-scale alignment of quasar polarizations at different redshifts within the framework of the big bang model.", "keyphrases": ["quasar polarization", "pseudoscalar-photon mixing", "photon"]}
{"id": "1102.3257", "title": "On different types of instabilities in black hole accretion discs. Implications for X-ray binaries and AGN", "abstract": "We discuss two important instability mechanisms that may lead to the limit-cycle oscillations of the luminosity of the accretion disks around compact objects: ionization instability and radiation-pressure instability. Ionization instability is well established as a mechanism of X-ray novae eruptions in black hole binary systems but its applicability to AGN is still problematic. Radiation pressure theory has still very weak observational background in any of these sources. In the present paper we attempt to confront the parameter space of these instabilities with the observational data. At the basis of this simple survey of sources properties we argue that the radiation pressure instability is likely to be present in several Galactic sources with the Eddington ratios above 0.15, and in AGN with the Eddington ratio above 0.025. Our results favor the parameterization of the viscosity through the geometrical mean of the radiation and gas pressure both in Galactic sources and AGN. More examples of the quasi-regular outbursts in the timescales of 100 seconds in Galactic sources, and hundreds of years in AGN are needed to formulate firm conclusions. We also show that the disk sizes in the X-ray novae are consistent with the ionization instability. This instability may also considerably influence the lifetime cycle and overall complexity in the supermassive black hole environment.", "keyphrases": ["black hole", "x-ray binary", "accretion disk"]}
{"id": "1511.01471", "title": "Explaining the most energetic supernovae with an inefficient jet-feedback mechanism", "abstract": "We suggest that the energetic radiation from core-collapse super-energetic supernovae (SESNe) is due to a long lasting accretion process onto the newly born neutron star (NS), resulting from an inefficient operation of the jet-feedback mechanism. The jets that are launched by the accreting NS or black hole (BH) maintain their axis due to a rapidly rotating pre-collapse core, and do not manage to eject core material from near the equatorial plane. The jets are able to eject material from the core along the polar directions, and reduce the gravity near the equatorial plane. The equatorial gas expands, and part of it falls back over a timescale of minutes to days to prolong the jets-launching episode. According to the model for SESNe proposed in the present paper, the principal parameter that distinguishes between the different cases of CCSN explosions, such as between normal CCSNe and SESNe, is the efficiency of the jet-feedback mechanism. This efficiency in turn depends on the pre-collapse core mass, envelope mass, core convection, and most of all on the angular momentum profile in the core. One prediction of the inefficient jet-feedback mechanism for SESNe is the formation of a slow equatorial outflow in the explosion. Typical velocity and mass of this outflow are estimated to be approximately 1000 km/s and greater than about 1 solar mass, respectively, though quantitative values will have to be checked in future hydrodynamic simulations.", "keyphrases": ["supernovae", "jet-feedback mechanism", "neutron star"]}
{"id": "1405.7860", "title": "What is the distance to the CMB?", "abstract": "The success of precision cosmology depends not only on accurate observations, but also on the theoretical model - which must be understood to at least the same level of precision. Subtle relativistic effects can lead to biased measurements if they are neglected. One such effect gives a systematic shift in the distance-redshift relation away from its background value, due to the non- linear relativistic conservation of total photon flux. We also show directly how this shift follows from a fully relativistic analysis of the geodesic deviation equation. We derive the expectation value of the shift using second-order perturbations about a concordance background, and show that the distance to last scattering is increased by 1 shift could lead to a significant bias in the background cosmological parameters, because it alters the meaning of the background model. A naive adjustment of CMB parameter estimation if this shift is really a correction to the background would raise the H0 value inferred from the CMB by 5 potentially removing the tension with local measurements of H0. Other CMB parameters which depend on the distance would also be shifted by 1sigma when combined with local H0 data. While our estimations rely on a simplistic analysis, they nevertheless illustrate that accurately defining the background model in terms of the expectation values of observables is critical when we aim to determine the model parameters at the sub-percent level.", "keyphrases": ["background value", "expectation value", "correction"]}
{"id": "1312.5221", "title": "Signatures of anisotropic sources in the trispectrum of the cosmic microwave background", "abstract": "Soft limits of N-point correlation functions, in which one wavenumber is much smaller than the others, play a special role in constraining the physics of inflation. Anisotropic sources such as a vector field during inflation generate distinct angular dependence in all these correlators. In this paper we focus on the four-point correlator (the trispectrum T). We adopt a parametrization motivated by models in which the inflaton \u03d5 is coupled to a vector field through a I^2 ( \u03d5) F^2 interaction, namely T_\u03b6( k_1, k_2, k_3, k_4) \u2261\u2211_n d_n [ P_n(k\u0302_1 \u00b7k\u0302_3) + P_n(k\u0302_1 \u00b7k\u0302_12) + P_n(k\u0302_3 \u00b7k\u0302_12) ] P_\u03b6(k_1) P_\u03b6(k_3) P_\u03b6(k_12) + (23 perm), where P_n denotes the Legendre polynomials. This shape is enhanced when the wavenumbers of the diagonals of the quadrilateral are much smaller than the sides, k_i. The coefficient of the isotropic part, d_0, is equal to \u03c4_ NL/6 discussed in the literature. A I^2 ( \u03d5) F^2 interaction generates d_2 = 2 d_0 which is, in turn, related to the quadrupole modulation parameter of the power spectrum, g_*, as d_2 \u2248 14 |g_*| N^2 with N \u2248 60. We show that d_0 and d_2 can be equally well-constrained: the expected 68 % CL error bars on these coefficients from a cosmic-variance-limited experiment measuring temperature anisotropy of the cosmic microwave background up to \u2113_ max=2000 are \u03b4 d_2 \u2248 4 \u03b4 d_0 = 105. Therefore, we can reach |g_*|=10^-3 by measuring the angle-dependent trispectrum. The current upper limit on \u03c4_ NL from the Planck temperature maps yields |g_*|<0.02 (95 % CL).", "keyphrases": ["anisotropic source", "cosmic microwave background", "angular dependence"]}
{"id": "1103.1118", "title": "Magnification effect on the detection of primordial non-Gaussianity from photometric surveys", "abstract": "We present forecast results for constraining the primordial non-Gaussianity from photometric surveys through a large-scale enhancement of the galaxy clustering amplitude. In photometric surveys, the distribution of observed galaxies at high redshifts suffers from the gravitational-lensing magnification, which systematically alters the number density for magnitude-limited galaxy samples. We estimate size of the systematic bias in the best-fit cosmological parameters caused by the magnification effect, particularly focusing on the primordial non-Gaussianity. For upcoming deep and/or wide photometric surveys like HSC, DES and LSST, the best-fit value of the non-Gaussian parameter, fNL, obtained from the galaxy count data is highly biased, and the true values of fNL would typically go outside the 3-sigma error of the biased confidence region, if we ignore the magnification effect in the theoretical template of angular power spectrum. The additional information from cosmic shear data helps not only to improve the constraint, but also to reduce the systematic bias. As a result, the size of systematic bias on fNL would become small enough compared to the expected 1-sigma error for HSC and DES, but it would be still serious for deep surveys with z_m > 1.5, like LSST. Tomographic technique improves the constraint on fNL by a factor of 2-3 compared to the one without tomography, but the systematic bias would increase.", "keyphrases": ["primordial non-gaussianity", "photometric survey", "galaxy"]}
{"id": "1412.2745", "title": "Deuterium Enrichment of the Interstellar Medium", "abstract": "Despite low elemental abundance of atomic deuterium in interstellar medium (ISM), observational evidences suggest that several species in gas-phase and in ices could be heavily fractionated. We explore various aspects of deuterium enrichment by constructing a chemical evolution model in gas and grain phases. Depending on various physical parameters, gas and grains are allowed to interact with each other through exchange of their chemical species. It is known that HCO+ and N2H+ are two abundant gas phase ions in ISM and their deuterium fractionation are generally used to predict degree of ionization in various regions of a molecular cloud. To have a more realistic estimation, we consider a density profile of a collapsing cloud. We present radial distributions of important interstellar molecules along with their deuterated isotopomers. We carry out quantum chemical simulation to study effects of isotopic substitution on spectral properties of these important interstellar species. We calculate vibrational (harmonic) frequency of the most important deuterated species (neutral ions). Rotational and distortional constants of these molecules are also computed to predict rotational transitions of these species. We compare vibrational (harmonic) and rotational transitions as computed by us with existing observational, experimental and theoretical results. We hope that our results would assist observers in their quest of several hitherto unobserved deuterated species.", "keyphrases": ["interstellar medium", "molecular cloud", "deuterium enrichment"]}
{"id": "1006.1272", "title": "XMM-Newton observations of unidentified INTEGRAL/IBIS sources", "abstract": "About 30 in that they lack an optical counterpart. To be able to classify them, X-ray observations are of crucial importance as they can place tighter constraints on the high energy error box, which is usually of the order of a few arcminutes, and allow their broad band spectrum to be studied. To this aim we have cross-correlated the list of all unidentified IBIS sources in the fourth catalogue with the archive of all XMM-Newton pointings, finding a set of 6 objects with archival data. For 1 of them, IGR J17331-2406, no X-ray source is detected by XMM inside the IBIS error box, most likely due to the fact that it is a transient object. In the case of IGR J17445-2747 two possible X-ray counterparts are found inside the IBIS error box: one is very weak while the other is bright but only detected once. In each of the remaining 4 cases: IGR J155359-5750, AX J1739.3-2923, AX J1740.2-2903 and IGR J18538-0102, we find instead a convincing association for which we provide an improved X-ray position and information on the optical/infrared counterpart. We also performed a detailed analysis of their XMM-IBIS spectra and on the basis of all information acquired we suggest that IGR J155359-5750 is an AGN of intermediate type, AX J1739.3-2923 and AX J1740.2-2903 are High Mass X-ray Binary systems, IGR J17331-2406 and IGR J17445-2747 are Galactic transient sources and IGR J18538-0102 could be a background AGN.", "keyphrases": ["integral", "ibis source", "x-ray counterpart"]}
{"id": "0912.0004", "title": "Higgs in Space!", "abstract": "We consider the possibility that the Higgs can be produced in dark matter annihilations, appearing as a line in the spectrum of gamma rays at an energy determined by the masses of the WIMP and the Higgs itself. We argue that this phenomenon occurs generally in models in which the the dark sector has large couplings to the most massive states of the SM and provide a simple example inspired by the Randall-Sundrum vision of dark matter, whose 4d dual corresponds to electroweak symmetry-breaking by strong dynamics which respect global symmetries that guarantee a stable WIMP. The dark matter is a Dirac fermion that couples to a Z' acting as a portal to the Standard Model through its strong coupling to top quarks. Annihilation into light standard model degrees of freedom is suppressed and generates a feeble continuum spectrum of gamma rays. Loops of top quarks mediate annihilation into gamma Z, gamma h, and gamma Z', providing a forest of lines in the spectrum. Such models can be probed by the Fermi/GLAST satellite and ground-based Air Cherenkov telescopes.", "keyphrases": ["dark matter", "higgs", "photon"]}
{"id": "1609.07375", "title": "An accreting pulsar with extreme properties drives an ultraluminous x-ray source in NGC 5907", "abstract": "Ultraluminous x-ray sources (ULXs) in nearby galaxies shine brighter than any X-ray source in our Galaxy. ULXs are usually modeled as stellar-mass black holes (BHs) accreting at very high rates or intermediate-mass BHs. We present observations showing that NGC5907 ULX is instead an x-ray accreting neutron star (NS) with a spin period evolving from 1.43 s in 2003 to 1.13 s in 2014. It has an isotropic peak luminosity of about 1000 times the Eddington limit for a NS at 17.1 Mpc. Standard accretion models fail to explain its luminosity, even assuming beamed emission, but a strong multipolar magnetic field can describe its properties. These findings suggest that other extreme ULXs (x-ray luminosity > 10^41 erg/s) might harbor NSs.", "keyphrases": ["pulsar", "neutron star", "high-energy astrophysic"]}
{"id": "1405.4547", "title": "I-Love-Q, Spontaneously: Slowly Rotating Neutron Stars in Scalar-Tensor Theories", "abstract": "We construct models of slowly rotating, perfect-fluid neutron stars by extending the classical Hartle-Thorne formalism to generic scalar-tensor theories of gravity. Working at second order in the dimensionless angular momentum, we compute the mass M, radius R, scalar charge q, moment of inertia I and spin-induced quadrupole moment Q, as well as the tidal and rotational Love numbers. Our formalism applies to generic scalar-tensor theories, but we focus in particular on theories that allow for spontaneous scalarization. It was recently discovered that the moment of inertia, quadrupole moment and Love numbers are connected by approximately universal (i.e., equation-of-state independent) \"I-Love-Q\" relations. We find that similar relations hold also for spontaneously scalarized stars. More interestingly, the I-Love-Q relations in scalar-tensor theories coincide with the general relativistic ones within less than a few percent, even for spontaneously scalarized stars with the largest couplings allowed by current binary-pulsar constraints. This implies that astrophysical measurements of these parameters cannot be used to discriminate between general relativity and scalar-tensor theories, even if spontaneous scalarization occurs in nature. Because of the well known equivalence between f(R) theories and scalar-tensor theories, the theoretical framework developed in this paper can be used to construct rotating compact stellar models in f(R) gravity. Our slow-rotation expansion can also be used as a benchmark for numerical calculations of rapidly spinning neutron stars in generic scalar-tensor theories.", "keyphrases": ["neutron star", "scalar-tensor theory", "i-love-q"]}
{"id": "1601.04064", "title": "An Extended action for the effective field theory of dark energy: a stability analysis and a complete guide to the mapping at the basis of EFTCAMB", "abstract": "We present a generalization of the effective field theory (EFT) formalism for dark energy and modified gravity models to include operators with higher order spatial derivatives. This allows the extension of the EFT framework to a wider class of gravity theories such as Horava gravity. We present the corresponding extended action, both in the EFT and the Arnowitt-Deser-Misner (ADM) formalism, and proceed to work out a convenient mapping between the two, providing a self contained and general procedure to translate a given model of gravity into the EFT language at the basis of the Einstein-Boltzmann solver EFTCAMB. Putting this mapping at work, we illustrate, for several interesting models of dark energy and modified gravity, how to express them in the ADM notation and then map them into the EFT formalism. We also provide for the first time, the full mapping of GLPV models into the EFT framework. We next perform a thorough analysis of the physical stability of the generalized EFT action, in absence of matter components. We work out viability conditions that correspond to the absence of ghosts and modes that propagate with a negative speed of sound in the scalar and tensor sector, as well as the absence of tachyonic modes in the scalar sector. Finally, we extend and generalize the phenomenological basis in terms of \u03b1-functions introduced to parametrize Horndeski models, to cover all theories with higher order spatial derivatives included in our extended action. We elaborate on the impact of the additional functions on physical quantities, such as the kinetic term and the speeds of propagation for scalar and tensor modes.", "keyphrases": ["effective field theory", "dark energy", "gravity"]}
{"id": "1006.0154", "title": "Numerical integration of variational equations", "abstract": "We present and compare different numerical schemes for the integration of the variational equations of autonomous Hamiltonian systems whose kinetic energy is quadratic in the generalized momenta and whose potential is a function of the generalized positions. We apply these techniques to Hamiltonian systems of various degrees of freedom, and investigate their efficiency in accurately reproducing well-known properties of chaos indicators like the Lyapunov Characteristic Exponents (LCEs) and the Generalized Alignment Indices (GALIs). We find that the best numerical performance is exhibited by the `tangent map (TM) method', a scheme based on symplectic integration techniques which proves to be optimal in speed and accuracy. According to this method, a symplectic integrator is used to approximate the solution of the Hamilton's equations of motion by the repeated action of a symplectic map S, while the corresponding tangent map TS, is used for the integration of the variational equations. A simple and systematic technique to construct TS is also presented.", "keyphrases": ["integration", "variational equation", "symplectic integration technique", "date"]}
{"id": "1812.07703", "title": "Characterizing the Gravitational Wave Signal from Core-Collapse Supernovae", "abstract": "We study the gravitational wave signal from eight new 3D core-collapse supernova simulations. We show that the signal is dominated by f- and g-mode oscillations of the protoneutron star and its frequency evolution encodes the contraction rate of the latter, which, in turn, is known to depend on the star's mass, on the equation of state, and on transport properties in warm nuclear matter. A lower-frequency component of the signal, associated with the standing accretion shock instability, is found in only one of our models. Finally, we show that the energy radiated in gravitational waves is proportional to the amount of turbulent energy accreted by the protoneutron star.", "keyphrases": ["gravitational wave signal", "core-collapse supernovae", "protoneutron star"]}
{"id": "1004.4007", "title": "Gravitational signature of Schwarzschild black holes in dynamical Chern-Simons gravity", "abstract": "Dynamical Chern-Simons gravity is an extension of General Relativity in which the gravitational field is coupled to a scalar field through a parity-violating Chern-Simons term. In this framework, we study perturbations of spherically symmetric black hole spacetimes, assuming that the background scalar field vanishes. Our results suggest that these spacetimes are stable, and small perturbations die away as a ringdown. However, in contrast to standard General Relativity, the gravitational waveforms are also driven by the scalar field. Thus, the gravitational oscillation modes of black holes carry imprints of the coupling to the scalar field. This is a smoking gun for Chern-Simons theory and could be tested with gravitational-wave detectors, such as LIGO or LISA. For negative values of the coupling constant, ghosts are known to arise, and we explicitly verify their appearance numerically. Our results are validated using both time evolution and frequency domain methods.", "keyphrases": ["black hole", "dynamical chern-simon gravity", "scalar field"]}
{"id": "1007.2571", "title": "Perturbations in Matter Bounce with Non-minimal Coupling", "abstract": "In this paper, we investigate the perturbations in matter bounce induced from Lee-Wick lagrangian with the involvement of non-minimal coupling to the Einstein Gravity. We find that this extra non-minimal coupling term can cause a red-tilt on the primordial metric perturbation at extremely large scales. It can also lead to large enhancement of reheating of the normal field particles compared to the usual minimal coupling models.", "keyphrases": ["matter bounce", "non-minimal coupling", "primordial power spectrum"]}
{"id": "1710.10264", "title": "Probing the properties of relic neutrinos using the cosmic microwave background, the Hubble Space Telescope and galaxy clusters", "abstract": "We investigate the observational constraints on the cosmic neutrino background (CNB) given by the extended \u039bCDM scenario (\u039bCDM + N_ eff + \u2211 m_\u03bd + c^2_ eff + c^2_ vis + \u03be_\u03bd) using the latest observational data from Planck CMB (temperature power spectrum, low-polarisation and lensing reconstruction), baryon acoustic oscillations (BAOs) , the new recent local value of the Hubble constant from Hubble Space Telescope (HST) and information of the abundance of galaxy clusters (GCs). We study the constraints on the CNB background using CMB + BAO + HST data with and without the GC data. We find \u0394 N_ eff = 0.614 \u00b1 0.26 at 68 per cent confidence level when the GC data are added in the analysis. We do not find significant deviation for sound speed in the CNB rest frame. We also analyze the particular case \u039bCDM + N_ eff + \u2211 m_\u03bd + \u03be_\u03bd with the observational data. Within this scenario, we find \u0394 N_ eff = 0.60 \u00b1 0.28 at 68 per cent confidence level. In both the scenarios, no mean deviations are found for the degeneracy parameter.", "keyphrases": ["cosmic microwave background", "galaxy cluster", "neutrino masse"]}
{"id": "1001.1484", "title": "Clues from nearby galaxies to a better theory of cosmic evolution", "abstract": "The great advances in the network of cosmological tests show that the relativistic Big Bang theory is a good description of our expanding universe. But the properties of nearby galaxies that can be observed in greatest detail suggest a still better theory would more rapidly gather matter into galaxies and groups of galaxies. This happens in theoretical ideas now under discussion.", "keyphrases": ["nearby galaxy", "well theory", "cdm model"]}
{"id": "1209.1616", "title": "No pseudosynchronous rotation for terrestrial planets and moons", "abstract": "We reexamine the popular belief that a telluric planet or satellite on an eccentric orbit can, outside a spin-orbit resonance, be captured in a quasi-static tidal equilibrium called pseudosynchronous rotation. The existence of such configurations was deduced from oversimplified tidal models assuming either a constant tidal torque or a torque linear in the tidal frequency. A more accurate treatment requires that the torque be decomposed into the Darwin-Kaula series over the tidal modes, and that this decomposition be combined with a realistic choice of rheological properties of the mantle. This development demonstrates that there exist no stable equilibrium states for solid planets and moons, other than spin-orbit resonances.", "keyphrases": ["pseudosynchronous rotation", "planet", "moon", "tidal model"]}
{"id": "1209.4236", "title": "Estimation of Radio Interferometer Beam Shapes Using Riemannian Optimization", "abstract": "The knowledge of receiver beam shapes is essential for accurate radio interferometric imaging. Traditionally, this information is obtained by holographic techniques or by numerical simulation. However, such methods are not feasible for an observation with time varying beams, such as the beams produced by a phased array radio interferometer. We propose the use of the observed data itself for the estimation of the beam shapes. We use the directional gains obtained along multiple sources across the sky for the construction of a time varying beam model. The construction of this model is an ill posed non linear optimization problem. Therefore, we propose to use Riemannian optimization, where we consider the constraints imposed as a manifold. We compare the performance of the proposed approach with traditional unconstrained optimization and give results to show the superiority of the proposed approach.", "keyphrases": ["riemannian optimization", "beam model", "estimation"]}
{"id": "0907.1211", "title": "Technical Performance of the MAGIC Telescopes", "abstract": "The MAGIC-I telescope is the largest single-dish Imaging Atmospheric Cherenkov telescope in the world. A second telescope, MAGIC-II, will operate in coincidence with MAGIC-I in stereoscopic mode. MAGIC-II is a clone of MAGIC-I, but with a number of significant improvements, namely a highly pixelized camera with a wider trigger area, improved optical analog signal transmission and a 2-4 GSps fast readout. All the technical elements of MAGIC-II were installed by the end of 2008. The telescope is currently undergoing commissioning and integration with MAGIC-I. An update of the technical performance of MAGIC-I, a description of all the hardware elements of MAGIC-II and first results of the combined technical performance of the two telescopes will be reported.", "keyphrases": ["telescope", "magic-ii", "technical performance"]}
{"id": "1801.00640", "title": "Fast radio bursts: superpulsars, magnetars, or something else?", "abstract": "We briefly review main observational properties of fast radio bursts (FRBs) and discuss two most popular hypothesis for the explanation of these enigmatic intense millisecond radio flashes. FRBs most probably originate on extragalactic distances, and their rate on the sky is about a few thousand per day with fluences above \u223c 1 Jy ms (or with fluxes larger than few tenths of Jy). Two leading scenarios describing these events include strong flares of magnetars and supergiant pulses of young radio pulsars with large rotational energy losses, correspondingly. At the moment, it is impossible to choose between these models. However, new telescopes can help to solve the puzzle of FRBs in near future.", "keyphrases": ["magnetar", "frbs", "fast radio burst"]}
{"id": "1710.02201", "title": "Active correction of aperture discontinuities - optimized stroke minimization II: optimization for future missions", "abstract": "High-contrast imaging and spectroscopy provide unique constraints for exoplanet formation models as well as for planetary atmosphere models. Instrumentation techniques in this field have greatly improved over the last two decades, with the development of stellar coronagraphy, in parallel with specific methods of wavefront sensing and control. Next generation space- and ground-based telescopes will allow the characterization cold solar-system like planets for the first time and maybe even in situ detection of bio-markers. However, the growth of primary mirror diameters, necessary for these detection, comes with an increase of their complexity (segmentation, secondary mirror features). These discontinuities in the aperture can greatly limit the performance of coronagraphic instruments. In this context, we introduced a new technique, Active Correction of Aperture Discontinuities - Optimized Stroke Minimization (ACAD-OSM), to correct for the diffractive effects of aperture discontinuities in the final image plane of a coronagraph, using deformable mirrors. In this paper, we present several tools that can be used to optimize the performance of this technique for its application to future large missions. In particular, we analyze the influence of the deformable setup (size and separating distance) and found that there is an optimal point for this setup, optimizing the performance of the instrument in contrast and throughput while minimizing the strokes applied to the deformable mirrors. These results will help us design future coronagraphic instruments to obtain the best performance.", "keyphrases": ["aperture discontinuities", "final image plane", "deformable mirror", "active correction"]}
{"id": "1712.04956", "title": "Higgs-Dilaton Cosmology: An inflation - dark energy connection and forecasts for future galaxy surveys", "abstract": "The Higgs-Dilaton model is a scale-invariant extension of the Standard Model non-minimally coupled to gravity and containing just one additional degree of freedom on top of the Standard Model particle content. This minimalistic scenario predicts a set of measurable consistency relations between the inflationary observables and the dark-energy equation-of-state parameter. We present an alternative derivation of these consistency relations that highlights the connections and differences with the \u03b1-attractor scenario. We study in how far these constraints allow to distinguish the Higgs-Dilaton model from \u039bCDM and wCDM cosmologies. To this end we first analyze existing data sets using a Markov Chain Monte Carlo approach. Second, we perform forecasts for future galaxy surveys using a Fisher matrix approach, both for galaxy clustering and weak lensing probes. Assuming that the best fit values in the different models remain comparable to the present ones, we show that both Euclid- and SKA2-like missions will be able to discriminate a Higgs-Dilaton cosmology from \u039bCDM and wCDM.", "keyphrases": ["future galaxy survey", "higgs-dilaton cosmology", "scalar field"]}
{"id": "1009.0024", "title": "Particle Acceleration in Relativistic Magnetized Collisionless Electron-Ion Shocks", "abstract": "We investigate shock structure and particle acceleration in relativistic magnetized collisionless electron-ion shocks by means of 2.5D particle-in-cell simulations with ion-to-electron mass ratios (m_i/m_e) ranging from 16 to 1000. We explore a range of inclination angles between the pre-shock magnetic field and the shock normal. In \"subluminal\" shocks, where relativistic particles can escape ahead of the shock along the magnetic field lines, ions are efficiently accelerated via a Fermi-like mechanism. The downstream ion spectrum consists of a relativistic Maxwellian and a high-energy power-law tail, which contains 5 of ions and 30 shock with lower energy than ions, so they are more strongly tied to the field. As a result, only 1 shock before being advected downstream, where they populate a steep power-law tail (with slope -3.5). For \"superluminal\" shocks, where relativistic particles cannot outrun the shock along the field, the self-generated turbulence is not strong enough to permit efficient Fermi acceleration, and the ion and electron downstream spectra are consistent with thermal distributions. The incoming electrons are heated up to equipartition with ions, due to strong electromagnetic waves emitted by the shock into the upstream. Thus, efficient electron heating (>15 relativistic electron-ion shocks, but significant nonthermal acceleration of electrons (>2 to achieve in magnetized flows and requires weakly magnetized shocks (magnetization <1e-3). These findings place important constraints on the models of AGN jets and Gamma Ray Bursts that invoke particle acceleration in relativistic magnetized electron-ion shocks.", "keyphrases": ["relativistic magnetized collisionless", "particle acceleration", "shock acceleration"]}
{"id": "1908.00984", "title": "Formation and evolution of globular clusters in cosmological simulations", "abstract": "In a series of three papers, we introduced a novel cluster formation model that describes the formation, growth, and disruption of star clusters in high-resolution cosmological simulations. We tested this model on a Milky Way-sized galaxy and found that various properties of young massive clusters, such as the mass function and formation efficiency, are consistent with observations in the local universe. Interestingly, most massive clusters \u2013 globular cluster candidates \u2013 are preferentially formed during major merger events. We follow the dynamical evolution of clusters in the galactic tidal field. Due to tidal disruption, the cluster mass function evolves from initial power law to a peaked shape. The surviving clusters at z=0 show a broad range of metallicity [Fe/H] from -3 to -0.5. A robust prediction of the model is the age\u2013metallicity relation, in which metal-rich clusters are systematically younger than metal-poor clusters by up to 3 Gyr.", "keyphrases": ["cluster", "cosmological simulation", "metallicity"]}
{"id": "1210.3903", "title": "Degeneracies in parametrized modified gravity models", "abstract": "We study degeneracies between parameters in some of the widely used parametrized modified gravity models. We investigate how different observables from a future photometric weak lensing survey such as LSST, correlate the effects of these parameters and to what extent the degeneracies are broken. We also study the impact of other degenerate effects, namely massive neutrinos and some of the weak lensing systematics, on the correlations.", "keyphrases": ["gravity model", "degeneracy", "cosmological probe"]}
{"id": "2210.07655", "title": "Robustness of cosmic birefringence measurement against Galactic foreground emission and instrumental systematics", "abstract": "The polarization of the cosmic microwave background (CMB) can be used to search for parity-violating processes like that predicted by a Chern-Simons coupling to a light pseudoscalar field. Such an interaction rotates E modes into B modes in the observed CMB signal by an effect known as cosmic birefringence. Even though isotropic birefringence can be confused with the rotation produced by a miscalibration of the detectors' polarization angles the degeneracy between both effects is broken when Galactic foreground emission is used as a calibrator. In this work, we use realistic simulations of the High-Frequency Instrument of the Planck mission to test the impact that Galactic foreground emission and instrumental systematics have on the recent birefringence measurements obtained through this technique. Our results demonstrate the robustness of the methodology against the miscalibration of polarization angles and other systematic effects, like intensity-to-polarization leakage, beam leakage, or cross-polarization effects. However, our estimator is sensitive to the EB correlation of polarized foreground emission. Here we propose to correct the bias induced by dust EB by modeling the foreground signal with templates produced in Bayesian component-separation analyses that fit parametric models to CMB data. Acknowledging the limitations of currently available dust templates like that of the Commander sky model, high-precision CMB data and a characterization of dust beyond the modified blackbody paradigm are needed to obtain a definitive measurement of cosmic birefringence in the future.", "keyphrases": ["cosmic birefringence", "birefringence measurement", "galactic foreground emission"]}
{"id": "1203.4347", "title": "Inertial waves in a differentially rotating spherical shell", "abstract": "We investigate the properties of small-amplitude inertial waves propagating in a differentially rotating incompressible fluid contained in a spherical shell. For cylindrical and shellular rotation profiles and in the inviscid limit, inertial waves obey a second-order partial differential equation of mixed type. Two kinds of inertial modes therefore exist, depending on whether the hyperbolic domain where characteristics propagate covers the whole shell or not. The occurrence of these two kinds of inertial modes is examined, and we show that the range of frequencies at which inertial waves may propagate is broader than with solid-body rotation. Using high-resolution calculations based on a spectral method, we show that, as with solid-body rotation, singular modes with thin shear layers following short-period attractors still exist with differential rotation. They exist even in the case of a full sphere. In the limit of vanishing viscosities, the width of the shear layers seems to weakly depend on the global background shear, showing a scaling in E^1/3 with the Ekman number E, as in the solid-body rotation case. There also exist modes with thin detached layers of width scaling with E^1/2 as Ekman boundary layers. The behavior of inertial waves with a corotation resonance within the shell is also considered. For cylindrical rotation, waves get dramatically absorbed at corotation. In contrast, for shellular rotation, waves may cross a critical layer without visible absorption, and such modes can be unstable for small enough Ekman numbers.", "keyphrases": ["spherical shell", "shear layer", "inertial wave"]}
{"id": "1010.5790", "title": "The Massive Pulsar PSR J1614-2230: Linking Quantum Chromodynamics, Gamma-ray Bursts, and Gravitational Wave Astronomy", "abstract": "The recent measurement of the Shapiro delay in the radio pulsar PSR J1614-2230 yielded a mass of 1.97 +/- 0.04 M_sun, making it the most massive pulsar known to date. Its mass is high enough that, even without an accompanying measurement of the stellar radius, it has a strong impact on our understanding of nuclear matter, gamma-ray bursts, and the generation of gravitational waves from coalescing neutron stars. This single high mass value indicates that a transition to quark matter in neutron-star cores can occur at densities comparable to the nuclear saturation density only if the quarks are strongly interacting and are color superconducting. We further show that a high maximum neutron-star mass is required if short duration gamma-ray bursts are powered by coalescing neutron stars and, therefore, this mechanism becomes viable in the light of the recent measurement. Finally, we argue that the low-frequency (<= 500 Hz) gravitational waves emitted during the final stages of neutron-star coalescence encode the properties of the equation of state because neutron stars consistent with this measurement cannot be centrally condensed. This will facilitate the measurement of the neutron star equation of state with Advanced LIGO/Virgo.", "keyphrases": ["pulsar", "neutron star", "quark matter"]}
{"id": "1012.4656", "title": "Preheating after Small-Field Inflation", "abstract": "Whereas preheating after chaotic and hybrid inflation models has been abundantly studied in the literature, preheating in small field inflation models, where the curvature of the inflaton potential is negative during inflation, remains less explored. In these models, a tachyonic instability at the end of inflation leads to a succession of exponentially large increases and decreases of the inflaton fluctuations as the inflaton condensate oscillates around the minimum of its potential. The net effect is a competition between low-momentum modes which grow and decrease significantly, and modes with higher momenta which grow less but also decrease less. We develop an analytical description of this process, which is analogous to the quantum mechanical problem of tunneling through a volcano-shaped potential. Depending on the parameters, preheating may be so efficient that it completes in less than one oscillation of the inflaton condensate. Preheating after small field inflation may also be followed by a long matter-dominated stage before the universe thermalizes, depending on the energy scale of inflation and the details of the inflaton interactions. Finally, another feature of these models is that the spectrum of the inflaton fluctuations at the end of preheating may be peaked around the Hubble scale. In fact, because preheating starts when the second slow-roll parameter |\u03b7| becomes of order unity while the first slow-roll parameter \u03f5 is still much smaller than one, the universe is still inflating during preheating and the modes amplified by the initial tachyonic instability leave the Hubble radius. This may lead to an abundant production of primordial black holes and gravitational waves with frequencies today which are naturally small enough to fall into the range accessible by high-sensitivity interferometric experiments.", "keyphrases": ["inflaton fluctuation", "preheating", "hilltop inflation"]}
{"id": "1510.04643", "title": "Core-Collapse Supernovae from 9 to 120 Solar Masses Based on Neutrino-powered Explosions", "abstract": "Nucleosynthesis, light curves, explosion energies, and remnant masses are calculated for a grid of supernovae resulting from massive stars with solar metallicity and masses from 9.0 to 120 solar masses. The full evolution is followed using an adaptive reaction network of up to 2000 nuclei. A novel aspect of the survey is the use of a one-dimensional neutrino transport model for the explosion. This explosion model has been calibrated to give the observed energy for SN 1987A, using several standard progenitors, and for the Crab supernova using a 9.6 solar mass progenitor. As a result of using a calibrated central engine, the final kinetic energy of the supernova is variable and sensitive to the structure of the presupernova star. Many progenitors with extended core structures do not explode, but become black holes, and the masses of exploding stars do not form a simply connected set. The resulting nucleosynthesis agrees reasonably well with the sun provided that a reasonable contribution from Type Ia supernovae is also allowed, but with a deficiency of light s-process isotopes. The resulting neutron star IMF has a mean gravitational mass near 1.4 solar masses. The average black hole mass is about 9 solar masses if only the helium core implodes, and 14 solar masses if the entire presupernova star collapses. Only 10 over 20 solar masses and some of these are Type Ib or Ic. Some useful systematics of Type IIp light curves are explored.", "keyphrases": ["explosion energy", "black hole", "core collapse"]}
{"id": "1704.04243", "title": "Phase-space Analysis in the Group and Cluster environment: Time since Infall and Tidal Mass Loss", "abstract": "Using the latest cosmological hydrodynamic N-body simulations of groups and clusters, we study how location in phase-space coordinates at z=0 can provide information on environmental effects acting in clusters. We confirm the results of previous authors showing that galaxies tend to follow a typical path in phase-space as they settle into the cluster potential. As such, different regions of phase-space can be associated with different times since first infalling into the cluster. However, in addition, we see a clear trend between total mass loss due to cluster tides, and time since infall. Thus we find location in phase-space provides information on both infall time, and tidal mass loss. We find the predictive power of phase-space diagrams remains even when projected quantities are used (i.e. line-of-sight velocities, and projected distances from the cluster). We provide figures that can be directly compared with observed samples of cluster galaxies and we also provide the data used to make them as supplementary data, in order to encourage the use of phase-space diagrams as a tool to understand cluster environmental effects. We find that our results depend very weakly on galaxy mass or host mass, so the predictions in our phase-space diagrams can be applied to groups or clusters alike, or to galaxy populations from dwarfs up to giants.", "keyphrases": ["group", "tidal mass loss", "phase-space diagram"]}
{"id": "1104.2980", "title": "Using the Noether symmetry approach to probe the nature of dark energy", "abstract": "We propose to use a model-independent criterion based on first integrals of motion, due to Noether symmetries of the equations of motion, in order to classify the dark energy models in the context of scalar field (quintessence or phantom) FLRW cosmologies. In general, the Noether symmetries play an important role in physics because they can be used to simplify a given system of differential equations as well as to determine the integrability of the system. The Noether symmetries are computed for nine distinct accelerating cosmological scenarios that contain a homogeneous scalar field associated with different types of potentials. We verify that all the scalar field potentials, presented here, admit the trivial first integral namely energy conservation, as they should. We also find that the exponential potential inspired from scalar field cosmology, as well as some types of hyperbolic potentials, include extra Noether symmetries. This feature suggests that these potentials should be preferred along the hierarchy of scalar field potentials. Finally, using the latter potentials, in the framework of either quintessence or phantom scalar field cosmologies that contain also a non-relativistic matter(dark matter) component, we find that the main cosmological functions, such as the scale factor of the universe, the scalar field, the Hubble expansion rate and the metric of the FRLW space-time, are computed analytically. Interestingly, under specific circumstances the predictions of the exponential and hyperbolic scalar field models are equivalent to those of the \u039bCDM model, as far as the global dynamics and the evolution of the scalar field are concerned. The present analysis suggests that our technique appears to be very competitive to other independent tests used to probe the functional form of a given potential and thus the associated nature of dark energy.", "keyphrases": ["noether symmetry approach", "dark energy", "cosmological scenario"]}
{"id": "2001.08411", "title": "First all-sky search for continuous gravitational-wave signals from unknown neutron stars in binary systems using Advanced LIGO data", "abstract": "Rotating neutron stars can emit continuous gravitational waves, which have not yet been detected. We present a search for continuous gravitational waves from unknown neutron stars in binary systems with orbital period between 15 and 45 days. This is the first time that Advanced LIGO data and the recently developed BinarySkyHough pipeline have been used in a search of this kind. No detections are reported, and upper limits on the gravitational wave amplitude are calculated, which improve the previous results by a factor of 17.", "keyphrases": ["all-sky search", "neutron star", "gravitational wave"]}
{"id": "1205.7063", "title": "Tests of General Relativity in the Strong Gravity Regime Based on X-Ray Spectropolarimetric Observations of Black Holes in X-Ray Binaries", "abstract": "Although General Relativity (GR) has been tested extensively in the weak gravity regime, similar tests in the strong gravity regime are still missing. In this paper we explore the possibility to use X-ray spectropolarimetric observations of black holes in X-ray binaries to distinguish between the Kerr metric and the phenomenological metrics introduced by Johannsen and Psaltis (2011) (which are not vacuum solutions of Einstein's equation) and thus to test the no-hair theorem of GR. To this end, we have developed a numerical code that calculates the radial brightness profiles of accretion disks and parallel transports the wave vector and polarization vector of photons through the Kerr and non-GR spacetimes. We used the code to predict the observational appearance of GR and non-GR accreting black hole systems. We find that the predicted energy spectra and energy dependent polarization degree and polarization direction do depend strongly on the underlying spacetime. However, for large regions of the parameter space, the GR and non-GR metrics lead to very similar observational signatures, making it difficult to observationally distinguish between the two types of models.", "keyphrases": ["general relativity", "black hole", "x-ray binary"]}
{"id": "1210.7319", "title": "Signatures of X-rays in the early Universe", "abstract": "[abridged] With their long mean free paths and efficient heating of the intergalactic medium (IGM), X-rays could have a dramatic impact on the thermal and ionization history of the Universe. We explore this in various signals: (i) Reionization history: including X-rays results in an earlier, more extended reionization. Efficient thermal feedback from X-ray heating could yield an extended, 10 contribution of X-rays to reionization results in a more uniform morphology, though the impact is modest when compared at the same global neutral fraction, xH. However, changes in morphology cannot be countered by increasing the bias of the ionizing sources, making them a robust signature. (iii) The kinetic Sunyaev-Zel'dovich (kSZ) effect: at a fixed reionization history, X-rays decrease the kSZ power at l=3000 by 0.5 microK^2. Our extreme model in which X-rays dominate reionization is the only one that is marginally consistent with upper limits from the South Pole Telescope, assuming no thermal Sunyaev-Zel'dovich (tSZ) - dusty galaxy correlation. Since this extreme model is unlikely, we conclude that there should be a sizable tSZ-dusty galaxy signal. (iv) The cosmic 21cm signal: the impact of X-rays on the 21cm power spectrum during the advanced stages of reionization (xH<0.7) is modest, except in extreme, X-ray dominated models. The largest impact of X-rays is to govern IGM heating. In fact, unless thermal feedback is efficient, the epoch of X-ray heating likely overlaps with the beginning of reionization (xH>0.9). This results in a 21cm power spectrum which is 10-100 times higher than obtained from naive estimates ignoring this overlap. However, if thermal feedback is efficient, the resulting extended epoch between X-ray heating and reionization could provide a clean probe of the matter power spectrum in emission.", "keyphrases": ["x-rays", "universe", "intergalactic medium"]}
{"id": "2002.12700", "title": "Machine Learning meets the redshift evolution of the CMB Temperature", "abstract": "We present a model independent and non-parametric reconstruction with a Machine Learning algorithm of the redshift evolution of the Cosmic Microwave Background (CMB) temperature from a wide redshift range z\u2208[0,3] without assuming any dark energy model, an adiabatic universe or photon number conservation. In particular we use the genetic algorithms which avoid the dependency on an initial prior or a cosmological fiducial model. Through our reconstruction we constrain new physics at late times. We provide novel and updated estimates on the \u03b2 parameter from the parametrisation T(z)=T_0(1+z)^1-\u03b2, the duality relation \u03b7(z) and the cosmic opacity parameter \u03c4(z). Furthermore we place constraints on a temporal varying fine structure constant \u03b1, which would have signatures in a broad spectrum of physical phenomena such as the CMB anisotropies. Overall we find no evidence of deviations within the 1\u03c3 region from the well established \u039bCDM model, thus confirming its predictive potential.", "keyphrases": ["redshift evolution", "new physics", "machine learning"]}
{"id": "1208.4163", "title": "Fab 5: Noncanonical Kinetic Gravity, Self Tuning, and Cosmic Acceleration", "abstract": "We investigate circumstances under which one can generalize Horndeski's most general scalar-tensor theory of gravity. Specifically we demonstrate that a nonlinear combination of purely kinetic gravity terms can give rise to an accelerating universe without the addition of extra propagating degrees of freedom on cosmological backgrounds, and exhibit self tuning to bring a large cosmological constant under control. This nonlinear approach leads to new properties that may be instructive for exploring the behaviors of gravity.", "keyphrases": ["nonlinear combination", "kinetic gravity term", "universe", "fab"]}
{"id": "1812.08518", "title": "Storing magnetic fields in pre-collapse cores of massive stars", "abstract": "We argue that the radiative zone above the iron core in pre-collapse cores of massive stars can store strong magnetic fields. To reach this conclusion we use the stellar evolutionary code MESA to simulate the evolution of two stellar models with initial masses of 15Mo and 25Mo, and reveal the entropy profile above the iron core just before core collapse. Just above the iron core there is a thin zone with convective shells. We assume that a dynamo in these convective shells amplifies magnetic fields and forms magnetic flux loops. By considering the buoyancy of magnetic flux loops we show that the steep entropy rise in the radiative zone above the dynamo can prevent buoyancy of flux loops with magnetic fields below about 10^13G. When this radiative zone collapses on to the newly born neutron star the converging inflow further amplifies the magnetic fields by a factor of about a hundred. After passing through the stalled shock at about a hundred kilometres from the center, these strong magnetic fields together with instabilities can facilitate the launching of jets that explode the star in the frame of the jittering jets explosion mechanism. Our study further supports the claim for the necessity to include magnetic fields in simulating the explosion of CCSNe.", "keyphrases": ["magnetic field", "pre-collapse core", "massive star", "iron core"]}
{"id": "1206.0986", "title": "Dissipation of dark matter", "abstract": "Fluids often display dissipative properties. We explore dissipation in the form of bulk viscosity in the cold dark matter fluid. We constrain this model using current data from supernovae, baryon acoustic oscillations and the cosmic microwave background. Considering the isotropic and homogeneous background only, viscous dark matter is allowed to have a bulk viscosity \u2272 10^7 Pa\u00b7s, also consistent with the expected integrated Sachs-Wolfe effect (which plagues some models with bulk viscosity). We further investigate the small-scale formation of viscous dark matter halos, which turns out to place significantly stronger constraints on the dark matter viscosity. The existence of dwarf galaxies is guaranteed only for much smaller values of the dark matter viscosity, \u2272 10^-3 Pa\u00b7s.", "keyphrases": ["dark matter", "bulk viscosity", "dissipation"]}
{"id": "1910.02892", "title": "Chemical abundances along the 1G sequence of the chromosome maps: The Globular Cluster NGC 3201", "abstract": "The Hubble Space Telescope (HST) UV Legacy Survey of Galactic Globular Clusters (GCs) has investigated multiple stellar populations by means of the \"chromosome map\" (ChM) diagnostic tool that maximises the separation between stars with different chemical composition. One of the most challenging features revealed by ChMs analysis is the apparent inhomogeneity among stars belonging to the first population, a phenomenon largely attributed to He variations. However, this explanation is not supported by the uniformity in p-capture elements of these stars. The HST survey has revealed that the GC NGC 3201 shows an exceptionally wide coverage in the Delta(F275W,F814W) parameter of the ChM. We present a chemical abundance analysis of 24 elements in 18 giants belonging to the first population of this GC, and having a wide range in Delta(F275W,F814W). As far as the p-capture elements are concerned, the chemical abundances are typical of 1G stars, as expected from the location of our targets in the ChM. Based on radial velocities and chemical abundances arguments, we find that the three stars with the lowest Delta(F275W,F814W) values are binary candidates. This suggests that, at least those stars could be explained with binarity. These results are consistent with evidence inferred from multi-band photometry that evolved blue stragglers populate the bluest part of the 1G sequence in the ChM. The remaining 15 spectroscopic targets show a small range in the overall metallicity by 0.10 dex, with stars at higher Delta(F275W,F814W) values having higher absolute abundances. We suggest that a small variation in metals and binarity govern the color spread of the 1G in the ChM, and that evolved blue stragglers contribute to the bluest tail of the 1G sequence.", "keyphrases": ["chromosome map", "metallicity", "chemical abundance"]}
{"id": "1203.0219", "title": "Revisiting Cosmic No-Hair Theorem for Inflationary Settings", "abstract": "In this work we revisit Wald's cosmic no-hair theorem in the context of accelerating Bianchi cosmologies for a generic cosmic fluid with non-vanishing anisotropic stress tensor and when the fluid energy momentum tensor is of the form of a cosmological constant term plus a piece which does not respect strong or dominant energy conditions. Such a fluid is the one appearing in inflationary models. We show that for such a system anisotropy may grow, in contrast to the cosmic no-hair conjecture. In particular, for a generic inflationary model we show that there is an upper bound on the growth of anisotropy. For slow-roll inflationary models our analysis can be refined further and the upper bound is found to be of the order of slow-roll parameters. We examine our general discussions and our extension of Wald's theorem for three classes of slow-roll inflationary models, generic multi-scalar field driven models, anisotropic models involving U(1) gauge fields and the gauge-flation scenario.", "keyphrases": ["cosmic no-hair theorem", "inflationary setting", "gauge field"]}
{"id": "1609.02372", "title": "Scaling regimes in spherical shell rotating convection", "abstract": "Rayleigh-B\u00e9nard convection in rotating spherical shells can be considered as a simplified analogue of many astrophysical and geophysical fluid flows. Here, we use three-dimensional direct numerical simulations to study this physical process. We construct a dataset of more than 200 numerical models that cover a broad parameter range with Ekman numbers spanning 3\u00d7 10^-7\u2264 E \u2264 10^-1, Rayleigh numbers within the range 10^3 < Ra < 2\u00d7 10^10 and a Prandtl number unity. We investigate the scaling behaviours of both local (length scales, boundary layers) and global (Nusselt and Reynolds numbers) properties across various physical regimes from onset of rotating convection to weakly-rotating convection. Close to critical, the convective flow is dominated by a triple force balance between viscosity, Coriolis force and buoyancy. For larger supercriticalities, a subset of our numerical data approaches the asymptotic diffusivity-free scaling of rotating convection Nu\u223c Ra^3/2E^2 in a narrow fraction of the parameter space delimited by 6 Ra_c \u2264 Ra \u2264 0.4 E^-8/5. Using a decomposition of the viscous dissipation rate into bulk and boundary layer contributions, we establish a theoretical scaling of the flow velocity that accurately describes the numerical data. In rapidly-rotating turbulent convection, the fluid bulk is controlled by a triple force balance between Coriolis, inertia and buoyancy, while the remaining fraction of the dissipation can be attributed to the viscous friction in the Ekman layers. Beyond Ra \u2243 E^-8/5, the rotational constraint on the convective flow is gradually lost and the flow properties vary to match the regime changes between rotation-dominated and non-rotating convection. The quantity Ra E^12/7 provides an accurate transition parameter to separate rotating and non-rotating convection.", "keyphrases": ["spherical shell", "convection", "numerical model"]}
{"id": "1411.7953", "title": "A carefully characterised and tracked Trans-Neptunian survey, the size-distribution of the Plutinos and the number of Neptunian Trojans", "abstract": "The Trans-Neptunian Objects (TNOs) may preserve evidence of planet building in their orbital and size-distributions. While all populations show steep size-distributions for large objects, recently relative deficit of Neptunian Trojans and scattering objects with diameters D<100 km were detected. We have investigated this deficit with a 32 square degree survey, detecting 77 TNOs to a limiting r-band magnitude of 24.6. Our Plutinos sample (18 objects in 3:2 mean motion resonance with Neptune) also shows a deficit of D<100 km objects. We reject a single power-law size-distribution and find that the Plutinos favour a divot. The Plutinos are thus added the list of populations with a deficit of D<100 km objects. The fact that three independent samples of three different populations show this trend suggests that it is a real feature, possibly shared by all hot TNO populations as a remnant of \"born big\" planetesimal formation processes. We surmise the existence of 9000\u00b13000 Plutinos with H_r\u22648.66 and 37000^+12000_-10000 Plutinos with H_r\u226410.0. Our survey also discovered one temporary Uranian Trojan, one temporary Neptunian Trojans and one stable Neptunian Trojan, from which we derive populations of 110^+500_-100, 210^+900_-200 and 150^+600_-140 , respectively, with H_r\u226410.0. The Neptunian Trojans are thus less numerous than the main belt asteroids, which has over 700 asteroids with H_r\u226410.0. With such numbers, the temporary Neptunian Trojans cannot be previously stable Trojans that happen to be escaping the resonance now; they must be captured from another reservoir. With three 3:1 and one 4:1 resonators, we add to the growing evidence that the high-order resonances are more populated than expected.", "keyphrases": ["size-distribution", "neptunian trojans", "neptune"]}
{"id": "1412.4777", "title": "Photon-photon dispersion of TeV gamma rays and its role for photon-ALP conversion", "abstract": "The propagation of TeV gamma rays can be strongly modified by B-field induced conversion to axionlike particles (ALPs). We show that, at such high energies, photon dispersion is dominated by background photons - the only example where photon-photon dispersion is of practical relevance. We determine the refractive index for all energies and find that, for fixed energy density, background photons below the pair-production threshold dominate. The cosmic microwave background alone provides an \"effective photon mass\" of (m_gamma)^2 = -(1.01 neV * E/TeV)^2 for E < 1000 TeV. The extragalactic background light is subdominant, but local radiation fields in the galaxy or the source regions provide significant contributions. Photon-photon dispersion is small enough to leave typical scenarios of photon-ALP oscillations unscathed, but big enough to worry about it case by case.", "keyphrases": ["tev gamma ray", "background photon", "photon-photon dispersion"]}
{"id": "1001.0331", "title": "The Kepler Pixel Response Function", "abstract": "Kepler seeks to detect sequences of transits of Earth-size exoplanets orbiting Solar-like stars. Such transit signals are on the order of 100 ppm. The high photometric precision demanded by Kepler requires detailed knowledge of how the Kepler pixels respond to starlight during a nominal observation. This information is provided by the Kepler pixel response function (PRF), defined as the composite of Kepler's optical point spread function, integrated spacecraft pointing jitter during a nominal cadence and other systematic effects. To provide sub-pixel resolution, the PRF is represented as a piecewise-continuous polynomial on a sub-pixel mesh. This continuous representation allows the prediction of a star's flux value on any pixel given the star's pixel position. The advantages and difficulties of this polynomial representation are discussed, including characterization of spatial variation in the PRF and the smoothing of discontinuities between sub-pixel polynomial patches. On-orbit super-resolution measurements of the PRF across the Kepler field of view are described. Two uses of the PRF are presented: the selection of pixels for each star that maximizes the photometric signal to noise ratio for that star, and PRF-fitted centroids which provide robust and accurate stellar positions on the CCD, primarily used for attitude and plate scale tracking. Good knowledge of the PRF has been a critical component for the successful collection of high-precision photometry by Kepler.", "keyphrases": ["response function", "point spread function", "jitter", "kepler photometry", "optical effect"]}
{"id": "0911.0682", "title": "Aharonov-Bohm Radiation", "abstract": "A solenoid oscillating in vacuum will pair produce charged particles due to the Aharonov-Bohm (AB) interaction. We calculate the radiation pattern and power emitted for charged scalar particles. We extend the solenoid analysis to cosmic strings, and find enhanced radiation from cusps and kinks on loops. We argue by analogy with the electromagnetic AB interaction that cosmic strings should emit photons due to the gravitational AB interaction of fields in the conical spacetime of a cosmic string. We calculate the emission from a kink and find that it is of similar order as emission from a cusp, but kinks are vastly more numerous than cusps and may provide a more interesting observational signature.", "keyphrases": ["vacuum", "particle", "cosmic string", "aharonov-bohm radiation"]}
{"id": "1807.00180", "title": "Speeding up the universe using dust with pressure", "abstract": "We revise the cosmological standard model presuming that matter, i.e. baryons and cold dark matter, exhibits a non-vanishing pressure mimicking the cosmological constant effects. In particular, we propose a scalar field Lagrangian \u2112_1 for matter with the introduction of a Lagrange multiplier as constraint. We also add a symmetry breaking effective potential accounting for the classical cosmological constant problem, by adding a second Lagrangian \u2112_2. Investigating the Noether current due to the shift symmetry on the scalar field, \u03c6\u2192\u03c6+c^0, we show that \u2112_1 turns out to be independent from the scalar field \u03c6. Further we find that a positive Helmotz free-energy naturally leads to a negative pressure without introducing by hand any dark energy term. To face out the fine-tuning problem, we investigate two phases: before and after transition due to the symmetry breaking. We propose that during transition dark matter cancels out the quantum field vacuum energy effects. This process leads to a negative and constant pressure whose magnitude is determined by baryons only. The numerical bounds over the pressure and matter densities are in agreement with current observations, alleviating the coincidence problem. Finally assuming a thermal equilibrium between the bath and our effective fluid, we estimate the mass of the dark matter candidate. Our numerical outcomes seem to be compatible with recent predictions on WIMP masses, for fixed spin and temperature. In particular, we predict possible candidates whose masses span in the range 0.5-1.7 TeV.", "keyphrases": ["universe", "dust", "cosmological constant problem"]}
{"id": "1711.11277", "title": "Future Cosmological Constraints from Fast Radio Bursts", "abstract": "We consider the possible observation of Fast Radio Bursts (FRBs) with planned future radio telescopes, and investigate how well the dispersions and redshifts of these signals might constrain cosmological parameters. We construct mock catalogues of FRB dispersion measure (DM) data and employ Markov Chain Monte Carlo (MCMC) analysis, with which we forecast and compare with existing constraints in the flat \u039bCDM model, as well as some popular extensions that include dark energy equation of state and curvature parameters. We find that the scatter in DM observations caused by inhomogeneities in the intergalactic medium (IGM) poses a big challenge to the utility of FRBs as a cosmic probe. Only in the most optimistic case, with a high number of events and low IGM variance, do FRBs aid in improving current constraints. In particular, when FRBs are combined with CMB+BAO+SNe+H_0 data, we find the biggest improvement comes in the \u03a9_bh^2 constraint. Also, we find that the dark energy equation of state is poorly constrained, while the constraint on the curvature parameter \u03a9_k, shows some improvement when combined with current constraints. When FRBs are combined with future BAO data from 21cm Intensity Mapping (IM), we find little improvement over the constraints from BAOs alone. However, the inclusion of FRBs introduces an additional parameter constraint, \u03a9_bh^2, which turns out to be comparable to existing constraints. This suggest that FRBs provide valuable information about the cosmological baryon density in the intermediate redshift Universe, independent of high redshift CMB data.", "keyphrases": ["cosmology", "fast radio bursts", "redshift", "intergalactic medium"]}
{"id": "1311.7246", "title": "Study of the properties of Cosmic rays and solar X-Ray Flares by balloon borne experiments", "abstract": "Indian Centre for Space Physics is engaged in pioneering balloon borne experiments with typical payloads less than 3.5kg. Low cost rubber balloons are used to fly them to a height of about 40km. In a double balloon system, the booster balloon lifts the orbiter balloon to its cruising altitude where data is taken for a longer period of time. In this Paper, we present our first scientific report on the variation of Cosmic Rays and muons with altitude and detection of several solar flares in X-rays between 20keV and 100keV. We found the altitude of the Pfotzer maximum at Tropic of Cancer for cosmic rays and muons and catch several solar flares in hard X-rays. We find that the hard X-ray (> 40keV) sky becomes very transparent above Pfotzer maximum. We find the flare spectrum to have a power-law distribution. From these studies, we infer that valuable scientific research could be carried out in near space using low cost balloon borne experiments. Published in Online version of Indian Journal of Physics.", "keyphrases": ["cosmic ray", "balloon borne experiment", "space physics"]}
{"id": "1803.04356", "title": "SPH simulations of the induced gravitational collapse scenario of long gamma-ray bursts associated with supernovae", "abstract": "We present the first three-dimensional (3D) smoothed-particle-hydrodynamics (SPH) simulations of the induced gravitational collapse (IGC) scenario of long-duration gamma-ray bursts (GRBs) associated with supernovae (SNe). We simulate the SN explosion of a carbon-oxygen core (CO_ core) forming a binary system with a neutron star (NS) companion. We follow the evolution of the SN ejecta, including their morphological structure, subjected to the gravitational field of both the new NS (\u03bdNS) formed at the center of the SN, and the one of the NS companion. We compute the accretion rate of the SN ejecta onto the NS companion as well as onto the \u03bdNS from SN matter fallback. We determine the fate of the binary system for a wide parameter space including different CO_ core and NS companion masses, orbital periods and SN explosion geometry and energies. We identify, for selected NS nuclear equations-of-state, the binary parameters leading the NS companion, by hypercritical accretion, either to the mass-shedding limit, or to the secular axisymmetric instability for gravitational collapse to a black hole (BH), or to a more massive, fast rotating, stable NS. We also assess whether the binary remains or not gravitationally bound after the SN explosion, hence exploring the space of binary and SN explosion parameters leading to \u03bdNS-NS and \u03bdNS-BH binaries. The consequences of our results for the modeling of long GRBs, i.e. X-ray flashes and binary-driven hypernovae, are discussed.", "keyphrases": ["gamma-ray burst", "supernovae", "hypercritical accretion"]}
{"id": "1611.10347", "title": "Wavelet-Bayesian inference of cosmic strings embedded in the cosmic microwave background", "abstract": "Cosmic strings are a well-motivated extension to the standard cosmological model and could induce a subdominant component in the anisotropies of the cosmic microwave background (CMB), in addition to the standard inflationary component. The detection of strings, while observationally challenging, would provide a direct probe of physics at very high energy scales. We develop a new framework for cosmic string inference, constructing a Bayesian analysis in wavelet space where the string-induced CMB component has distinct statistical properties to the standard inflationary component. Our wavelet-Bayesian framework provides a principled approach to compute the posterior distribution of the string tension G\u03bc and the Bayesian evidence ratio comparing the string model to the standard inflationary model. Furthermore, we present a technique to recover an estimate of any string-induced CMB map embedded in observational data. Using Planck-like simulations we demonstrate the application of our framework and evaluate its performance. The method is sensitive to G\u03bc\u223c 5 \u00d7 10^-7 for Nambu-Goto string simulations that include an integrated Sachs-Wolfe (ISW) contribution only and do not include any recombination effects, before any parameters of the analysis are optimised. The sensitivity of the method compares favourably with other techniques applied to the same simulations.", "keyphrases": ["string", "cosmic microwave background", "wavelet transform"]}
{"id": "1001.2384", "title": "Continuum surveys with LOFAR and synergy with future large surveys in the 1-2 GHz band", "abstract": "Radio astronomy is entering the era of large surveys. This paper describes the plans for wide surveys with the LOw Frequency ARray (LOFAR) and their synergy with large surveys at higher frequencies (in particular in the 1-2 GHz band) that will be possible using future facilities like Apertif or ASKAP. The LOFAR Survey Key Science Project aims at conducting large-sky surveys at 15, 30, 60, 120 and 200 MHz taking advantage of the wide instantaneous field of view and of the unprecedented sensitivity of this instrument. Four topics have been identified as drivers for these surveys covering the formation of massive galaxies, clusters and black holes using z>6 radio galaxies as probes, the study of the intercluster magnetic fields using diffuse radio emission and Faraday rotation measures in galaxy clusters as probes and the study of star formation processes in the early Universe using starburst galaxies as probes. The fourth topic is the exploration of new parameter space for serendipitous discovery taking advantage of the new observational spectral window open up by LOFAR. Here, we briefly discuss the requirements of the proposed surveys to address these (and many others!) topics as well as the synergy with other wide area surveys planned at higher frequencies (and in particular in the 1-2 GHz band) with new radio facilities like ASKAP and Apertif. The complementary information provided by these surveys will be crucial for detailed studies of the spectral shape of a variety of radio sources (down to sub-mJy sources) and for studies of the ISM (in particular HI and OH) in nearby galaxies.", "keyphrases": ["large survey", "ghz band", "low frequency array"]}
{"id": "1303.6664", "title": "The spectra of jet bases in FR I radio galaxies: implications for particle acceleration", "abstract": "We present accurate, spatially resolved imaging of radio spectra at the bases of jets in eleven low-luminosity (Fanaroff-Riley I) radio galaxies, derived from Very Large Array (VLA) observations. We pay careful attention to calibration and to the effects of random and systematic errors, and we base the flux-density scale on recent measurements of VLA primary amplitude calibrators by Perley Butler (2013). We show images and profiles of spectral index over the frequency range 1.4 - 8.5 GHz, together with values integrated over fiducial regions defined by our relativistic models of the jets. We find that the spectral index decreases (the spectrum flattens) with distance from the nucleus in all of the jets. The mean spectral indices are 0.66 +/- 0.01 where the jets first brighten abruptly and 0.59 +/- 0.01 after they recollimate. The mean change in spectral index between these locations, which is independent of calibration and flux-density scale errors and is therefore more accurately and robustly measured, is -0.067 +/- 0.006. Our jet models associate the decrease in spectral index with a bulk deceleration of the flow from 0.8c to <0.5c. We suggest that the decrease is the result of a change in the characteristics of ongoing particle acceleration. One possible acceleration mechanism is the first-order Fermi process in mildly relativistic shocks: in the Bohm limit, the index of the electron energy spectrum, p, is slightly larger than 2 and decreases with velocity upstream of the shock. This possibility is consistent with our measurements, but requires shocks throughout the jet volume rather than at a few discrete locations. A second possibility is that two acceleration mechanisms operate in these jets: one (with p = 2.32) dominant close to the galactic nucleus and associated with high flow speeds, another (with p = 2.18) taking over at larger distances and slower flow speeds.", "keyphrases": ["jet", "radio galaxy", "particle acceleration"]}
{"id": "1310.7868", "title": "Automatic Classification of Variable Stars in Catalogs with missing data", "abstract": "We present an automatic classification method for astronomical catalogs with missing data. We use Bayesian networks, a probabilistic graphical model, that allows us to perform inference to pre- dict missing values given observed data and dependency relationships between variables. To learn a Bayesian network from incomplete data, we use an iterative algorithm that utilises sampling methods and expectation maximization to estimate the distributions and probabilistic dependencies of variables from data with missing values. To test our model we use three catalogs with missing data (SAGE, 2MASS and UBVI) and one complete catalog (MACHO). We examine how classification accuracy changes when information from missing data catalogs is included, how our method compares to traditional missing data approaches and at what computational cost. Integrating these catalogs with missing data we find that classification of variable objects improves by few percent and by 15 keeping the computational cost the same.", "keyphrases": ["missing data", "variable object", "automatic classification"]}
{"id": "1309.4787", "title": "ORIGAMI: Delineating Cosmic Structures with Phase-Space Folds", "abstract": "Structures like galaxies and filaments of galaxies in the Universe come about from the origami-like folding of an initially flat three-dimensional manifold in 6D phase space. The ORIGAMI method identifies these structures in a cosmological simulation, delineating the structures according to their outer folds. Structure identification is a crucial step in comparing cosmological simulations to observed maps of the Universe. The ORIGAMI definition is objective, dynamical and geometric: filament, wall and void particles are classified according to the number of orthogonal axes along which dark-matter streams have crossed. Here, we briefly review these ideas, and speculate on how ORIGAMI might be useful to find cosmic voids.", "keyphrases": ["fold", "filament", "origami"]}
{"id": "1307.8150", "title": "Einstein gravity of a diffusing fluid", "abstract": "We discuss Einstein gravity for a fluid consisting of particles interacting with an unidentified environment of some other particles whose dissipative effect is approximated by a diffusion. The environment is described by a time dependent cosmological term which is compensating the lack of the conservation law of the energy momentum of the diffusing fluid. We are interested in a homogeneous flat expanding Universe described by a scale factor a. For a fluid of massless particles at finite temperature we obtain explicit solutions of the diffusion equation which are in the form of a modified Juttner distribution with a time dependent temperature. At later time Universe evolution is described as a diffusion at zero temperature with no equilibration. We find solutions of the diffusion at zero temperature which can be treated as a continuation to a later time of the finite temperature solutions describing an early stage of the Universe. A conservation of the total energy momentum determines the cosmological term up to a constant. The resulting energy momentum inserted into Einstein equations gives a modified Friedmann equation. Solutions of the Friedmann equation depend on the initial value of the cosmological term. The large value of the cosmological constant implies an exponential expansion. If the initial conditions allow a power-like solution for a large time then it must be of the form a\u2243\u03c4 (no deceleration, \u03c4 is the cosmic time). The final stage of the Universe evolution is described by a non-relativistic diffusion of a cold dust.", "keyphrases": ["fluid", "cosmological term", "einstein gravity"]}
{"id": "1808.00908", "title": "FRB event rate counts II \u2014 fluence, redshift and dispersion measure distributions", "abstract": "We examine how the various observable statistical properties of the FRB population relate back to their fundamental physical properties in a model independent manner. We analyse the flux density and fluence distributions of Fast Radio Bursts (FRBs) as a tool to investigate their luminosity distance distribution and the evolution of their prevalence throughout cosmic history. We examine in detail particular scenarios in which the burst population follows some power of the cosmic star formation rate. FRBs present an important additional measurable over source counts of existing cosmological populations, namely the dispersion measure. Based on the known redshift of FRB121102 (the repeater) we expect at least 50 to the inter-galactic medium and hence it can be used as a proxy for distance. We develop the framework to interpret the dispersion measure distribution, and investigate how the effect of Helium reionization in the intergalactic medium is evident in this distribution. Examination of existing data suggests that the FRB luminosity function is flatter than a critical slope, making FRBs easily detectable to large distances; in this regime the reduction in flux density with distance is outweighed by the increase in the number of bright bursts within the search volume.", "keyphrases": ["redshift", "dispersion measure distribution", "burst"]}
{"id": "2006.10752", "title": "Studying galaxy cluster morphological metrics with Mock-X", "abstract": "Dynamically relaxed galaxy clusters have long played a role in galaxy cluster studies because it is thought their properties can be reconstructed more precisely and with less systematics. As relaxed clusters are desirable, there exist a plethora of criteria for classifying a galaxy cluster as relaxed. In this work, we examine 9 commonly used observational and theoretical morphological metrics extracted from 54,000 Mock-X synthetic X-ray images of galaxy clusters taken from the IllustrisTNG, BAHAMAS and MACSIS simulation suites. We find that the simulated criteria distributions are in reasonable agreement with the observed distributions. Many criteria distributions evolve as a function of redshift, cluster mass, numerical resolution and subgrid physics, limiting the effectiveness of a single relaxation threshold value. All criteria are positively correlated with each other, however, the strength of the correlation is sensitive to redshift, mass and numerical choices. Driven by the intrinsic scatter inherent to all morphological metrics and the arbitrary nature of relaxation threshold values, we find the consistency of relaxed subsets defined by the different metrics to be relatively poor. Therefore, the use of relaxed cluster subsets introduces significant selection effects that are non-trivial to resolve.", "keyphrases": ["galaxy cluster", "metric", "selection effect"]}
{"id": "1208.0157", "title": "Flavor stability analysis of dense supernova neutrinos with flavor-dependent angular distributions", "abstract": "Numerical simulations of the supernova (SN) neutrino self-induced flavor conversions, associated with the neutrino-neutrino interactions in the deepest stellar regions, have been typically carried out assuming the \"bulb-model\". In this approximation, neutrinos are taken to be emitted half-isotropically by a common neutrinosphere. In the recent Ref. <cit.> we have removed this assumption by introducing flavor-dependent angular distributions for SN neutrinos, as suggested by core-collapse simulations. We have found that in this case a novel multi-angle instability in the self-induced flavor transitions can arise. In this work we perform an extensive study of this effect, carrying out a linearized flavor stability analysis for different SN neutrino energy fluxes and angular distributions, in both normal and inverted neutrino mass hierarchy. We confirm that spectra of different nu species which cross in angular space (where F_\u03bd_e=F_\u03bd_x and F_\u03bd\u0305_e=F_\u03bd\u0305_x) present a significant enhancement of the flavor instability, and a shift of the onset of the flavor conversions at smaller radii with respect to the case of an isotropic neutrino emission. We also illustrate how a qualitative (and sometimes quantitative) understanding of the dynamics of these systems follows from a stability analysis.", "keyphrases": ["flavor-dependent angular distribution", "neutrinosphere", "flavor stability analysis"]}
{"id": "1808.05045", "title": "Viable Inflation in Scalar-Gauss-Bonnet Gravity and Reconstruction from Observational Indices", "abstract": "In this paper the focus is on inflationary dynamics in the context of Einstein Gauss-Bonnet gravitational theories. We investigate the implications of the slow-roll condition on the slow-roll indices and we investigate how the inflationary dynamical evolution is affected by the presence of the Gauss-Bonnet coupling to the scalar field. For exemplification of our analysis we investigate how the dynamics of inflationary cubic, quartic order and also exponential scalar potentials are affected by the non-trivial Gauss-Bonnet coupling to the scalar field. As we demonstrate it is possible to obtain a viable phenomenology compatible with the observational data, although the canonical scalar field theory with cubic and quartic order potentials does not yield phenomenologically acceptable results. In addition, with regard to the exponential potential example, the Einstein Gauss-Bonnet extension of the single canonical scalar field model has an inherent mechanism that can trigger the graceful exit from inflation. Furthermore we introduce a bottom-up reconstruction technique, in the context of which by fixing the tensor-to-scalar ratio and the Hubble rate as a function of the e-foldings number, one is capable of reproducing the Einstein Gauss-Bonnet theory which generates the aforementioned quantities. We illustrate how the method works by using some relatively simple examples.", "keyphrases": ["scalar field", "einstein-gauss-bonnet gravity", "inflationary scenario"]}
{"id": "1006.3840", "title": "Uranus and Neptune: Shape and Rotation", "abstract": "Both Uranus and Neptune are thought to have strong zonal winds with velocities of several hundred meters per second. These wind velocities, however, assume solid-body rotation periods based on Voyager 2 measurements of periodic variations in the planets' radio signals and of fits to the planets' magnetic fields; 17.24h and 16.11h for Uranus and Neptune, respectively. The realization that the radio period of Saturn does not represent the planet's deep interior rotation and the complexity of the magnetic fields of Uranus and Neptune raise the possibility that the Voyager 2 radio and magnetic periods might not represent the deep interior rotation periods of the ice giants. Moreover, if there is deep differential rotation within Uranus and Neptune no single solid-body rotation period could characterize the bulk rotation of the planets. We use wind and shape data to investigate the rotation of Uranus and Neptune. The shapes (flattening) of the ice giants are not measured, but only inferred from atmospheric wind speeds and radio occultation measurements at a single latitude. The inferred oblateness values of Uranus and Neptune do not correspond to bodies rotating with the Voyager rotation periods. Minimization of wind velocities or dynamic heights of the 1 bar isosurfaces, constrained by the single occultation radii and gravitational coefficients of the planets, leads to solid-body rotation periods of 16.58h for Uranus and 17.46h for Neptune. Uranus might be rotating faster and Neptune slower than Voyager rotation speeds. We derive shapes for the planets based on these rotation rates. Wind velocities with respect to these rotation periods are essentially identical on Uranus and Neptune and wind speeds are slower than previously thought. Alternatively, if we interpret wind measurements in terms of differential rotation on cylinders there are essentially no residual atmospheric winds.", "keyphrases": ["neptune", "rotation", "planet", "uranus", "occultation radius"]}
{"id": "1210.6331", "title": "Redshift drift in a pressure-gradient cosmology", "abstract": "We derive a redshift drift formula for the spherically symmetric inhomogeneous pressure Stephani universes which are complementary to the spherically symmetric inhomogeneous density Lema\u00eetre-Tolman-Bondi models. We show that there is a clear difference between redshift drift predictions for these two models as well as between the Stephani models and the standard \u039bCDM Friedmann models. The Stephani models have positive drift values at small redshift and behave qualitatively (but not quantitatively) as the \u039bCDM models at large redshift, while the drift for LTB models is always negative. This prediction may perhaps be tested in future telescopes such as European Extremely Large Telescope (EELT), Thirty Meter Telescope (TMT), Giant Magellan Telescope (GMT), and especially, in gravitational wave interferometers DECi-Hertz Interferometer Gravitational Wave Observatory and Big Bang Observer (DECIGO/BBO), which aim at low redshift.", "keyphrases": ["drift", "cosmology", "redshift"]}
{"id": "1603.05569", "title": "Key Issues Review: Numerical studies of turbulence in stars", "abstract": "The numerical simulation of turbulence in stars has led to a rich set of possibilities regarding stellar pulsations, asteroseismology, thermonuclear yields, and formation of neutron stars and black holes. The breaking of symmetry by turbulent flow grows in amplitude as collapse is approached, which insures that the conditions at the onset of collapse are not spherical. This lack of spherical symmetry has important implications for the mechanism of explosion and ejected nucleosynthesis products. Numerical resolution of several different types of three\u2013dimensional (3D) stellar simulations are compared; it is suggested that core collapse simulations may be under-resolved. New physical effects which appear in 3D are summarized. Connections between simulations of progenitor explosion and observations of supernova remnants (SNR) are discussed. Present treatment of boundaries, for mixing regions during He\u2013burning, requires revision.", "keyphrases": ["turbulence", "star", "stellar simulation"]}
{"id": "1202.6026", "title": "The electromagnetic model of short GRBs, the nature of prompt tails, supernova-less long GRBs and highly efficient episodic accretion", "abstract": "Many short GRBs show prompt tails lasting up to hundreds of seconds that can be energetically dominant over the initial sub-second spike. In this paper we develop an electromagnetic model of short GRBs that explains the two stages of the energy release, the prompt spike and the prompt tail. The key ingredient of the model is the recent discovery that an isolated black hole can keep its open magnetic flux for times much longer than the collapse time and, thus, can spin-down electromagnetically, driving the relativistic wind. First, the merger is preceded by an electromagnetic precursor wind. If a fraction of the wind power is converted into pulsar-like coherent radio emission, this may produce an observable radio burst of few milliseconds. At the active stage of the merger, two neutron stars produces a black hole surrounded by an accretion torus in which the amplified magnetic field extracts the rotational energy of the black hole and drives an axially-collimated electromagnetic wind. For observers nearly aligned with the orbital normal this is seen as a classical short GRB. After the accretion of the torus, the isolated black hole keeps the open magnetic flux and drives the equatorially (not axially) collimated outflow, which is seen by an observer at intermediate polar angles as a prompt tail. The tail carries more energy than the prompt spike, but its emission is de-boosted for observers along the orbital normal. Observers in the equatorial plane miss the prompt spike and interpret the prompt tail as an energetic supernova-less long GRB. We also demonstrate that episodic accretion onto the BH of magnetized clouds that carry non-zero magnetic flux can be highly efficient in extracting the spin energy of the BH, producing the outflows with the power exceeding the average accretion power.", "keyphrases": ["supernova-less long grb", "episodic accretion", "neutron star"]}
{"id": "1404.0631", "title": "Cosmology in a certain vector-tensor theory of gravitation", "abstract": "We study relevant cosmological topics in the framework of a certain vector-tensor theory of gravitation (hereafter VT). This theory is first compared with the so-called extended electromagnetism (EE). These theories have a notable resemblance and both explain the existence of a cosmological constant. It is shown that, in EE, a positive dark energy density requires a Lagrangian leading to quantum ghosts, whereas VT is free from these ghosts. On account of this fact, the remainder of the paper is devoted to study cosmology in the framework of VT. Initial conditions, at high redshift, are used to solve the evolution equations of all the VT scalar modes. In particular, a certain scalar mode characteristic of VT -which does not appear in general relativity (GR)- is chosen in such a way that it evolves separately. In other words, the scalar modes of the standard model based on GR do not affect the evolution of the VT characteristic mode; however, this scalar mode influences the evolution of the standard GR ones. Some well known suitable codes (CMBFAST and COSMOMC) have been modified to include our VT initial conditions and evolution equations, which are fully general. One of the resulting codes -based on standard statistical methods- has been used to fit VT predictions and observational evidences about both Ia supernovae and cosmic microwave background anisotropy. Seven free parameters are used in this fit. Six of them are often used in GR cosmology and the seventh one is characteristic of VT. From the statistical analysis it follows that VT seems to be advantageous against GR in order to explain cosmological observational evidences.", "keyphrases": ["certain vector-tensor theory", "gravitation", "quantum ghost", "cosmology"]}
{"id": "1612.00697", "title": "The low-mass population in the young cluster Stock 8: Stellar properties and Initial Mass Function", "abstract": "The evolution of HII regions/supershells can trigger a new generation of stars/clusters at their peripheries, with environmental conditions that may affect the initial mass function, disk evolution and star formation efficiency. In this paper we study the stellar content and star formation processes in the young cluster Stock 8, which itself is thought to be formed during the expansion of a supershell. We present deep optical photometry along with JHK and 3.6, 4.5 \u03bcm photometry from UKIDSS and Spitzer-IRAC. We use multi-color criteria to identify the candidate young stellar objects in the region. Using evolutionary models, we obtain a median log(age) of 6.5 ( 3.0 Myr) with an observed age spread of 0.25 dex for the cluster. Monte Carlo simulations of the population of Stock 8, based on estimates for the photometric uncertainty, differential reddening, binarity, and variability, indicate that these uncertainties introduce an age spread of 0.15 dex. The intrinsic age spread in the cluster is 0.2 dex. The fraction of young stellar objects surrounded by disk is 35 the Trapezium cluster. The IMF of Stock 8 has a Salpeter- like slope at >0.5 Msun and the IMF flattens and peaks at 0.4 Msun, below which declines into the substellar regime. Although Stock 8 is surrounded by several massive stars, there seems to be no severe environmental effect in the form of IMF due to the proximity of massive stars around the cluster.", "keyphrases": ["young cluster stock", "initial mass function", "star"]}
{"id": "1911.09270", "title": "An optical test bench for the precision characterization of absolute quantum efficiency for the TESS CCD detectors", "abstract": "The Transiting Exoplanet Survey Satellite (TESS) will search for planets transiting bright stars with Ic<13. TESS has been selected by NASA for launch in 2018 as an Astrophysics Explorer mission, and is expected to discover a thousand or more planets that are smaller in size than Neptune. TESS will employ four wide-field optical charge-coupled device (CCD) cameras with a band-pass of 650 nm-1050 nm to detect temporary drops in brightness of stars due to planetary transits. The 1050 nm limit is set by the quantum efficiency (QE) of the CCDs. The detector assembly consists of four back-illuminated MIT Lincoln Laboratory CCID-80 devices. Each CCID-80 device consists of 2048x2048 imaging array and 2048x2048 frame store regions. Very precise on-ground calibration and characterization of CCD detectors will significantly assist in the analysis of the science data obtained in space. The characterization of the absolute QE of the CCD detectors is a crucial part of the characterization process because QE affects the performance of the CCD significantly over the redder wavelengths at which TESS will be operating. An optical test bench with significantly high photometric stability has been developed to perform precise QE measurements. The design of the test setup along with key hardware, methodology, and results from the test campaign are presented.", "keyphrases": ["optical test bench", "quantum efficiency", "ccd detector"]}
{"id": "2103.02078", "title": "Effects of overlapping sources on cosmic shear estimation: Statistical sensitivity and pixel-noise bias", "abstract": "In Stage-IV imaging surveys, a significant amount of the cosmologically useful information is due to sources whose images overlap with those of other sources on the sky. The cosmic shear signal is primarily encoded in the estimated shapes of observed galaxies and thus directly impacted by overlaps. We introduce a framework based on the Fisher formalism to analyze effects of overlapping sources (blending) on the estimation of cosmic shear. For the Rubin Observatory Legacy Survey of Space and Time (LSST), we present the expected loss in statistical sensitivity for the ten-year survey due to blending. We find that for approximately 62 full-depth LSST images, at least 1 overlapping sources. We also find that the statistical correlations between measures of overlapping galaxies and, to a much lesser extent the higher shot noise level due to their presence, decrease the effective number density of galaxies, N_eff, by \u223c18 39.4 galaxies per arcmin^2 in r band. We study the impact of varying stellar density on N_eff and illustrate the diminishing returns of extending the survey into lower Galactic latitudes. We extend the Fisher formalism to predict the increase in pixel-noise bias due to blending for maximum-likelihood (ML) shape estimators. We find that noise bias is sensitive to the particular shape estimator and measure of ensemble-average shape that is used, and properties of the galaxy that include redshift-dependent quantities such as size and luminosity.", "keyphrases": ["statistical sensitivity", "pixel-noise bias", "galaxy"]}
{"id": "1409.2564", "title": "Parity-violating interactions of cosmic fields with atoms, molecules, and nuclei: Concepts and calculations for laboratory searches and extracting limits", "abstract": "We propose methods and present calculations that can be used to search for evidence of cosmic fields by investigating the parity-violating effects, including parity nonconservation amplitudes and electric dipole moments, that they induce in atoms. The results are used to constrain important fundamental parameters describing the strength of the interaction of various cosmic fields with electrons, protons, and neutrons. Candidates for such fields are dark matter (including axions) and dark energy, as well as several more exotic sources described by standard-model extensions. Existing parity nonconservation experiments in Cs, Dy, Yb, and Tl are combined with our calculations to directly place limits on the interaction strength between the temporal component, b_0, of a static pseudovector cosmic field and the atomic electrons, with the most stringent limit of |b_0^e| < 7*10^(-15) GeV, in the laboratory frame of reference, coming from Dy. From a measurement of the nuclear anapole moment of Cs, and a limit on its value for Tl, we also extract limits on the interaction strength between the temporal component of this cosmic field, as well as a related tensor cosmic-field component d_00, with protons and neutrons. The most stringent limits of |b_0^p| < 4*10^(-8) GeV and |d_00^p| < 5*10^(-8) for protons, and |b_0^n| < 2*10^(-7) GeV and |d_00^n| < 2*10^(-7) for neutrons (in the laboratory frame) come from the results using Cs. Axions may induce oscillating P- and T-violating effects in atoms and molecules through the generation of oscillating nuclear magnetic quadrupole and Schiff moments, which arise from P- and T-odd intranuclear forces and from the electric dipole moments of constituent nucleons. Nuclear-spin-independent parity nonconservation effects may be enhanced in diatomic molecules possessing close pairs of opposite-parity levels in the presence of time-dependent interactions.", "keyphrases": ["cosmic field", "atom", "axion"]}
{"id": "1610.06919", "title": "Analyzing the cosmic variance limit of remote dipole measurements of the cosmic microwave background using the large-scale kinetic Sunyaev Zel'dovich effect", "abstract": "Due to cosmic variance we cannot learn any more about large-scale inhomogeneities from the primary cosmic microwave background (CMB) alone. More information on large scales is essential for resolving large angular scale anomalies in the CMB. Here we consider cross correlating the large-scale kinetic Sunyaev Zel'dovich (kSZ) effect and probes of large-scale structure, a technique known as kSZ tomography. The statistically anisotropic component of the cross correlation encodes the CMB dipole as seen by free electrons throughout the observable Universe, providing information about long wavelength inhomogeneities. We compute the large angular scale power asymmetry, constructing the appropriate transfer functions, and estimate the cosmic variance limited signal to noise for a variety of redshift bin configurations. The signal to noise is significant over a large range of power multipoles and numbers of bins. We present a simple mode counting argument indicating that kSZ tomography can be used to estimate more modes than the primary CMB on comparable scales. A basic forecast indicates that a first detection could be made with next-generation CMB experiments and galaxy surveys. This paper motivates a more systematic investigation of how close to the cosmic variance limit it will be possible to get with future observations.", "keyphrases": ["variance limit", "cosmic microwave background", "dipole field"]}
{"id": "2012.05477", "title": "Image recovery with the solar gravitational lens", "abstract": "We report on the initial results obtained with an image convolution/deconvolution computer code that we developed and used to study the image formation capabilities of the solar gravitational lens (SGL). Although the SGL of a spherical Sun creates a greatly blurred image, knowledge of the SGL's point-spread function (PSF) makes it possible to reconstruct the original image and remove the blur by way of deconvolution. We discuss the deconvolution process, which can be implemented either with direct matrix inversion or with the Fourier quotient method. We observe that the process introduces a \u201cpenalty\u201d in the form of a reduction in the signal-to-noise ratio (SNR) of a recovered image, compared to the SNR at which the blurred image data is collected. We estimate the magnitude of this penalty using an analytical approach and confirm the results with a series of numerical simulations. We find that the penalty is substantially reduced when the spacing between image samples is large compared to the telescope aperture. The penalty can be further reduced with suitable noise filtering, which can yield O(10) or better improvement for low-quality imaging data. Our results confirm that it is possible to use the SGL for imaging purposes. We offer insights on the data collection and image processing strategies that could yield a detailed image of an exoplanet within image data collection times that are consistent with the duration of a realistic space mission.", "keyphrases": ["lens", "telescope", "image"]}
{"id": "1211.2816", "title": "Revisiting the Scaling Relations of Black Hole Masses and Host Galaxy Properties", "abstract": "New kinematic data and modeling efforts in the past few years have substantially expanded and revised dynamical measurements of black hole masses (Mbh) at the centers of nearby galaxies. Here we compile an updated sample of 72 black holes and their host galaxies, and present revised scaling relations between Mbh and stellar velocity dispersion (sigma), V-band luminosity (L), and bulge stellar mass (Mbulge), for different galaxy subsamples. Our best-fitting power law relations for the full galaxy sample are log(Mbh) = 8.32 + 5.64*log(sigma/200 kms), log(Mbh) = 9.23 + 1.11*log(L/10^11 Lsun), and log(Mbh) = 8.46 + 1.05*log(Mbulge/10^11 Msun). A log-quadratic fit to the Mbh-sigma relation with an additional term of beta_2*[log(sigma/200 kms)]^2 gives beta_2 = 1.68 +/- 1.82 and does not decrease the intrinsic scatter in Mbh. When the early- and late-type galaxies are fit separately, we obtain similar slopes of 5.20 and 5.06 for the Mbh-sigma relation but significantly different intercepts \u2013 Mbh in early-type galaxies are about 2 times higher than in late types at a given sigma. Within early-type galaxies, our fits to Mbh(sigma) give Mbh that is about 2 times higher in galaxies with central core profiles than those with central power-law profiles. Our Mbh-L and Mbh-Mbulge relations for early-type galaxies are similar to those from earlier compilations. When the conventional quadrature method is used to determine the intrinsic scatter in Mbh, our dataset shows weak evidence for increased scatter at Mbulge < 10^11 Msun or L_V < 10^10.3 Lsun, while the scatter stays constant for 10^11 < Mbulge < 10^12.3 Msun and 10^10.3 < L_V < 10^11.5 Lsun. A Bayesian analysis indicates a larger sample of Mbh measurements would be needed to detect any statistically significant trend in the scatter with galaxy properties.", "keyphrases": ["black hole", "galaxy", "stellar velocity dispersion"]}
{"id": "0911.4086", "title": "Directional detection as a strategy to discover Galactic Dark Matter", "abstract": "Directional detection of Galactic Dark Matter is a promising search strategy for discriminating genuine WIMP events from background ones. Technical progress on gaseous detectors and read-outs has permitted the design and construction of competitive experiments. However, to take full advantage of this powerful detection method, one need to be able to extract information from an observed recoil map to identify a WIMP signal. We present a comprehensive formalism, using a map-based likelihood method allowing to recover the main incoming direction of the signal and its significance, thus proving its galactic origin. This is a blind analysis intended to be used on any directional data. Constraints are deduced in the (\u03c3_n, m_\u03c7) plane and systematic studies are presented in order to show that, using this analysis tool, unambiguous dark matter detection can be achieved on a large range of exposures and background levels.", "keyphrases": ["galactic dark matter", "galactic origin", "directional detection"]}
{"id": "2103.03251", "title": "Reconstructing the Last Major Merger of the Milky Way with the H3 Survey", "abstract": "Several lines of evidence suggest the Milky Way underwent a major merger at z 2 with a galaxy known as Gaia-Sausage-Enceladus (GSE). Here we use H3 Survey data to argue that GSE entered the Galaxy on a retrograde orbit based on a population of highly retrograde stars with chemistry similar to the largely radial GSE debris. We present the first tailored, high-resolution N-body simulations of the merger. From a grid of 500 simulations we find a GSE with M_*=5\u00d710^8 M_\u2299, M_DM=2\u00d710^11 M_\u2299 (a 2.5:1 total mass merger) best matches the H3 data. This simulation shows the retrograde GSE stars are stripped from its outer disk early in the merger before the orbit loses significant angular momentum. Despite being selected purely on angular momenta and radial distributions, this simulation reproduces and explains the following empirical phenomena: (i) the elongated, triaxial shape of the inner halo (axis ratios 10:7.9:4.5), whose major axis is at 35 to the plane and connects GSE's apocenters, (ii) the Hercules-Aquila Cloud the Virgo Overdensity, which arise due to apocenter pile-up, (iii) the 2 Gyr lag between the quenching of GSE and the truncation of the age distribution of the in-situ halo, which tracks the 2 Gyr gap between the first and final GSE pericenters. We make the following predictions: (i) the inner halo has a \"double-break\" density profile with breaks at both 15-18 kpc and 30 kpc, coincident with the GSE apocenters, (ii) the outer halo has retrograde streams containing 10 retrograde (radial) GSE debris originates from its outer (inner) disk \u2013 exploiting this trend we reconstruct the stellar metallicity gradient of GSE (-0.04\u00b10.01 dex r_50^-1). These simulations imply GSE delivered 20 (ABRIDGED)", "keyphrases": ["major merger", "milky way", "orbit"]}
{"id": "2109.00345", "title": "Unifying an asymmetric bounce to the dark energy in Chern-Simons F(R) gravity", "abstract": "We propose a cosmological scenario in which the universe undergoes through a non-singular bounce, and after the bounce, it decelerates having a matter-like dominated evolution during some regime of the deceleration era, and finally at the present epoch it evolves through an accelerating stage. Our aim is to study such evolution in the context of Chern-Simons corrected F(R) gravity theory and confront the model with various observational data. Using the reconstruction technique, and in addition by employing suitable boundary conditions, we determine the form of F(R) for the entire possible range of the cosmic time. The form of F(R) seems to unify a non-singular bounce with a dark energy epoch, in particular, from a non-singular bounce to a deceleration epoch and from a deceleration epoch to a late time acceleration era. It is important to mention that the bouncing scenario in the present context is an asymmetric bounce, in particular, the Hubble radius monotonically increases and asymptotically diverges at the late contracting era, while it seems to decrease with time at the present epoch. Such evolution of the Hubble radius leads to the primordial perturbation modes generate at the deep contracting era when all the perturbation modes lie within the horizon. We calculate the scalar and tensor power spectra, and as a result, the primordial observables are found to be in agreement with the latest Planck 2018 constraints. In this regard, the Chern-Simons term seems to have considerable effects on the tensor perturbation evolution, however keeping intact the scalar part of the perturbation with that of in the case of a vacuum F(R) model, and as a result, the Chern-Simons term proves to play an important role in making the observable quantities consistent with the Planck results. Furthermore the theoretical expectation of the dark energy observables are confronted with the Planck+SNe+BAO data.", "keyphrases": ["asymmetric bounce", "gravity", "primordial perturbation mode"]}
{"id": "1408.1169", "title": "Constraining Extended Gravity Models by S2 star orbits around the Galactic Centre", "abstract": "We investigate the possibility to explain theoretically the observed deviations of S2 star orbit around the Galactic Centre using gravitational potentials derived from modified gravity models in absence of dark matter. To this aim, an analytic fourth-order theory of gravity, non-minimally coupled with a massive scalar field is considered. Specifically, the interaction term is given by analytic functions f(R) and f(R,\u03d5) where R is the Ricci scalar and \u03d5 is a scalar field whose meaning can be related to further gravitational degrees of freedom. We simulate the orbit of S2 star around the Galactic Centre in f(R) (Yukawa-like) and f(R,\u03d5) (Sanders-like) gravity potentials and compare it with NTT/VLT observations. Our simulations result in strong constraints on the range of gravity interaction. In the case of analytic functions f(R), we are not able to obtain reliable constraints on the derivative constants f_1 and f_2, because the current observations of S2 star indicated that they may be highly mutually correlated. In the case of analytic functions f(R,\u03d5), we are able to obtain reliable constraints on the derivative constants f_0, f_R, f_RR, f_\u03d5, f_\u03d5\u03d5 and f_\u03d5 R. The approach we are proposing seems to be sufficiently reliable to constrain the modified gravity models from stellar orbits around Galactic Centre.", "keyphrases": ["gravity", "galactic centre", "dark matter"]}
{"id": "1608.02640", "title": "Astronomical photonics in the context of infrared interferometry and high-resolution spectroscopy", "abstract": "We review the potential of Astrophotonics, a relatively young field at the interface between photonics and astronomical instrumentation, for spectro-interferometry. We review some fundamental aspects of photonic science that drove the emer- gence of astrophotonics, and highlight the achievements in observational astrophysics. We analyze the prospects for further technological development also considering the potential synergies with other fields of physics (e.g. non-linear optics in condensed matter physics). We also stress the central role of fiber optics in routing and transporting light, delivering complex filters, or interfacing instruments and telescopes, more specifically in the context of a growing usage of adaptive optics.", "keyphrases": ["photonic", "infrared interferometry", "astronomical instrumentation"]}
{"id": "1610.01164", "title": "A Characteristic Scale for Cold Gas", "abstract": "We find that clouds of optically-thin, pressure-confined gas are prone to fragmentation as they cool below \u223c10^6 K. This fragmentation follows the lengthscale \u223cc_s t_cool, ultimately reaching very small scales (\u223c0.1pc/n) as they reach the temperature \u223c10^4 K at which hydrogen recombines. While this lengthscale depends on the ambient pressure confining the clouds, we find that the column density through an individual fragment N_cloudlet\u223c10^17cm^-3 is essentially independent of environment; this column density represents a characteristic scale for atomic gas at 10^4 K. We therefore suggest that \"clouds\" of cold, atomic gas may in fact have the structure of a mist or a fog, composed of tiny fragments dispersed throughout the ambient medium. We show that this scale emerges in hydrodynamic simulations, and that the corresponding increase in the surface area may imply rapid entrainment of cold gas. We also apply it to a number of observational puzzles, including the large covering fraction of diffuse gas in galaxy halos, the broad line widths seen in quasar and AGN spectra, and the entrainment of cold gas in galactic winds. While our simulations make a number of assumptions and thus have associated uncertainties, we show that this characteristic scale is consistent with a number of observations, across a wide range of astrophysical environments. We discuss future steps for testing, improving, and extending our model.", "keyphrases": ["characteristic scale", "cold gas", "cloud", "galactic wind"]}
{"id": "1012.5239", "title": "On light propagation in Swiss-Cheese cosmologies", "abstract": "We study the effect of inhomogeneities on light propagation. The Sachs equations are solved numerically in the Swiss-Cheese models with inhomogeneities modelled by the Lemaitre-Tolman solutions. Our results imply that, within the models we study, inhomogeneities may partially mimic the accelerated expansion of the Universe provided the light propagates through regions with lower than the average density. The effect of inhomogeneities is small and full randomization of the photons' trajectories reduces it to an insignificant level.", "keyphrases": ["light propagation", "cosmology", "swiss-cheese model"]}
{"id": "1310.2637", "title": "Growing dust grains in protoplanetary discs - II. The Radial drift barrier problem", "abstract": "We aim to study the migration of growing dust grains in protoplanetary discs, where growth and migration are tightly coupled. This includes the crucial issue of the radial-drift barrier for growing dust grains. We therefore extend the study performed in Paper I, considering models for grain growth and grain dynamics where both the migration and growth rate depend on the grain size and the location in the disc. The parameter space of disc profiles and growth models is exhaustively explored. In doing so, interpretations for the grain motion found in numerical simulations are also provided. We find that a large number of cases is required to characterise entirely the grains radial motion, providing a large number of possible outcomes. Some of them lead dust particles to be accreted onto the central star and some of them don't. We find then that q<1 is required for discs to retain their growing particles, where q is the exponent of the radial temperature profile T(R) proportional to R^-q. Additionally, the initial dust-to gas ratio has to exceed a critical value for grains to pile up efficiently, thus avoiding being accreted onto the central star. Discs are also found to retain efficiently small dust grains regenerated by fragmentation. We show how those results are sensitive to the turbulent model considered. Even though some physical processes have been neglected, this study allows to sketch a scenario in which grains can survive the radial-drift barrier in protoplanetary discs as they grow.", "keyphrases": ["dust grain", "protoplanetary disc", "radial-drift barrier"]}
{"id": "0909.5203", "title": "Universality of galactic surface densities within one dark halo scale-length", "abstract": "It was recently discovered that the mean dark matter surface density within one dark halo scale length - the radius within which the volume density profile of dark matter remains approximately flat - is constant across a wide range of galaxies. This scaling relation holds for galaxies spanning a luminosity range of 14 magnitudes and the whole Hubble sequence. Here we report that the luminous matter surface density is also constant within one scale length of the dark halo. This means that the gravitational acceleration generated by the luminous component in galaxies is always the same at this radius. Although the total luminous-to-dark matter ratio is not constant, within one halo scale length it is constant. Our finding can be interpreted as a close correlation between the enclosed surface densities of luminous and dark matter in galaxies.", "keyphrases": ["surface density", "galaxy", "baryon"]}
{"id": "1812.09760", "title": "Fuzzy Dark Matter at Cosmic Dawn: New 21-cm Constraints", "abstract": "Potential small-scale discrepancies in the picture of galaxy formation painted by the \u039bCDM paradigm have led to considerations of modified dark matter models. One such dark matter model that has recently attracted much attention is fuzzy dark matter (FDM). In FDM models, the dark matter is envisaged to be an ultra-light scalar field with a particle mass m_ FDM\u223c 10^-22 eV. This yields astronomically large de Broglie wavelengths which can suppress small-scale structure formation and give rise to the observed kpc-sized density cores in dwarf galaxies. We investigate the evolution of the 21-cm signal during Cosmic Dawn and the Epoch of Reionization (EoR) in \u039bFDM cosmologies using analytical models. The delay in source formation and the absence of small halos in \u039bFDM significantly postpone the Ly\u03b1 coupling, heating, as well as the reionization of the neutral hydrogen of the intergalactic medium. As a result, the absorption feature in the evolution of the global 21-cm signal has a significantly smaller full width at half maximum (\u0394 z \u2272 3), than \u039bCDM (\u0394 z \u2243 6). This alone rules out m_ FDM < 6 \u00d7 10^-22 eV as a result of the 2\u03c3 lower limit \u0394 z \u2273 4 from EDGES High-Band. As a result, \u039bFDM is not a viable solution to the potential small-scale problems facing \u039bCDM. Finally, we show that any detection of the 21-cm signal at redshifts z > 14 by interferometers such as the SKA can also exclude \u039bFDM models.", "keyphrases": ["cosmic dawn", "scalar field", "fuzzy dark matter"]}
{"id": "1707.02304", "title": "Gas perturbations in cool cores of galaxy clusters: effective equation of state, velocity power spectra and turbulent heating", "abstract": "We present the statistical analysis of X-ray surface brightness and gas density fluctuations in cool cores of ten, nearby and bright galaxy clusters that have deep Chandra observations and show observational indications of radio-mechanical AGN feedback. Within the central parts of cool cores the total variance of fluctuations is dominated by isobaric and/or isothermal fluctuations on spatial scales 10-60 kpc, which are likely associated with slow gas motions and bubbles of relativistic plasma. Adiabatic fluctuations associated with weak shocks constitute less than 10 per cent of the total variance in all clusters. The typical amplitude of density fluctuations is small, 10 per cent or less on scales of 10-15 kpc. Subdominant contribution of adiabatic fluctuations and small amplitude of density fluctuations support a model of gentle AGN feedback as opposed to periodically explosive scenarios which are implemented in some numerical simulations. Measured one-component velocities of gas motions are typically below 100-150 km/s on scales < 50 kpc, and can be up to 300 km/s on 100 kpc scales. The non-thermal energy is < 12 per cent of the thermal energy. Regardless of the source that drives these motions the dissipation of the energy in such motions provides heat that is sufficient to balance radiative cooling on average, albeit the uncertainties are large. Presented results here support previous conclusions based on the analysis of the Virgo and Perseus Clusters, and agree with the Hitomi measurements. With next generation observatories like Athena and Lynx, these techniques will be yet more powerful.", "keyphrases": ["cool core", "galaxy cluster", "gas motion"]}
{"id": "1104.1639", "title": "Solar models with accretion. I. Application to the solar abundance problem", "abstract": "We generate new standard solar models using newly analyzed nuclear fusion cross sections and present results for helioseismic quantities and solar neutrino fluxes. We discuss the status of the solar abundance problem and investigate whether nonstandard solar models with accretion from the protoplanetary disk might alleviate the problem. We examine a broad range of possibilities, analyzing both metal-enriched and metal-depleted accretion models and exploring three scenarios for the timing of the accretion. Only partial solutions are found: one can bring either the depth of the convective zone or the surface helium abundance into agreement with helioseismic results, but not both simultaneously. In addition, detailed results for solar neutrino fluxes show that neutrinos are a competitive source of information about the solar core and can help constrain possible accretion histories of the Sun. Finally, we briefly discuss how measurements of solar neutrinos from the CN-cycle could shed light on the interaction between the early Sun and its protoplanetary disk.", "keyphrases": ["accretion", "solar abundance problem", "-neutrino flux"]}
{"id": "1711.10492", "title": "SDSS-IV MaNGA: What Shapes The Distribution Of Metals In Galaxies? Exploring The Roles Of The Local Gas Fraction And Escape Velocity", "abstract": "We determine the local metallicity of the ionized gas for more than 9.2\u00d7 10^5 star forming regions (spaxels) located in 1023 nearby galaxies included in the SDSS-IV MaNGA IFU survey. We use the dust extinction derived from the Balmer decrement and stellar template fitting in each spaxel to estimate the local gas and stellar mass densities, respectively. We also use the measured rotation curves to determine the local escape velocity (V_esc). We have then analyze the relationships between the local metallicity and both the local gas fraction (\u03bc) and V_esc. We find that metallicity decreases with both increasing \u03bc and decreasing V_esc. By examining the residuals in these relations we show that the gas fraction plays a more primary role in the local chemical enrichment than V_esc. We show that the gas-regulator model of chemical evolution provides a reasonable explanation of the metallicity on local scales. The best-fit parameters for this model are consistent with metal loss caused by momentum-driven galactic outflows. We also argue that both the gas fraction and local escape velocity are connected to the local stellar surface density, which in turn is a tracer of the epoch at which the dominant local stellar population formed", "keyphrases": ["metallicity", "galaxy", "local gas fraction"]}
{"id": "2001.10792", "title": "Cosmological constraints from line intensity mapping with interlopers", "abstract": "Understanding the formation and evolution of the Universe is crucial for cosmological studies, and the line intensity mapping provides a powerful tool for this kind of study. We propose to make use of multipole moments of redshift-space line intensity power spectrum to constrain the cosmological and astrophysical parameters, such as the equation of state of dark energy, massive neutrinos, primordial non-Gaussianity, and star formation rate density. As an example, we generate mock data of multipole power spectra for H-alpha 6563AA, [OIII] 5007AA and [OII] 3727AA measured by SPHEREx experiment at z=1 considering contaminations from interloper lines, and use Markov Chain Monte Carlo (MCMC) method to constrain the parameters in the model. We find a good fitting result of the parameters compared to their fiducial values, which means that the multipole power spectrum can effectively distinguish signal and interloper lines, and break the degeneracies between parameters, such as line mean intensity and bias. We also explore the cross power spectrum with CSST (Chinese Space Station Telescope) spectroscopic galaxy survey in the constraints. Since more accurate fitting results can be obtained by including measurements of the emission lines at higher redshifts out to z=3 at least and cross-correlations between emission lines can be involved, the line intensity mapping is expected to offer excellent results in future cosmological and astrophysical studies.", "keyphrases": ["line intensity mapping", "interloper", "redshift"]}
{"id": "0908.0540", "title": "Simulations of the Microwave Sky", "abstract": "We create realistic, full-sky, half-arcminute resolution simulations of the microwave sky matched to the most recent astrophysical observations. The primary purpose of these simulations is to test the data reduction pipeline for the Atacama Cosmology Telescope (ACT) experiment; however, we have widened the frequency coverage beyond the ACT bands to make these simulations applicable to other microwave background experiments. Some of the novel features of these simulations are that the radio and infrared galaxy populations are correlated with the galaxy cluster populations, the CMB is lensed by the dark matter structure in the simulation via a ray-tracing code, the contribution to the thermal and kinetic Sunyaev-Zel'dovich (SZ) signals from galaxy clusters, groups, and the IGM has been included, and the gas prescription to model the SZ signals matches the most recent X-ray observations. Regarding the contamination of cluster SZ flux by radio galaxies, we find for 148 GHz (90 GHz) only 3 of halos have their SZ decrements contaminated at a level of 20 find the contamination levels higher for infrared galaxies. However, at 90 GHz, less than 20 their SZ decrements filled in at a level of 20 20 decrements filled in at a level of 50 a population of very high flux infrared galaxies, which are likely lensed sources, contribute most to the SZ contamination of very massive clusters at 90 and 148 GHz. These simulations are publicly available and should serve as a useful tool for microwave surveys to cross-check SZ cluster detection, power spectrum, and cross-correlation analyses.", "keyphrases": ["microwave sky", "radio", "simulation"]}
{"id": "1812.04336", "title": "Bias and scatter in the Hubble diagram from cosmological large-scale structure", "abstract": "An important part of cosmological model fitting relies on correlating distance indicators of objects (for example type Ia supernovae) with their redshift, often illustrated on a Hubble diagram. Comparing the observed correlation with a homogeneous model is one of the key pieces of evidence for dark energy. The presence of cosmic structures introduces a bias and scatter, mainly due to gravitational lensing and peculiar velocities, but also due to smaller non-linear relativistic contributions which are more difficult to account for. For the first time we perform ray tracing onto halos in a relativistic N-body simulation. Our simulation is the largest that takes into account all leading-order corrections from general relativity in the evolution of structure, and we present a novel methodology for working out the non-linear projection of that structure onto the observer's past light cone. We show that the mean of the bias in the Hubble diagram is indeed as small as expected from perturbation theory. However, the distribution of sources is significantly skewed with a very long tail of highly magnified objects and we illustrate that the bias of cosmological parameters strongly depends on the function of distance which we consider.", "keyphrases": ["hubble diagram", "relativistic n-body simulation", "bias"]}
{"id": "1001.5218", "title": "A New Approach to Systematic Uncertainties and Self-Consistency in Helium Abundance Determinations", "abstract": "Tests of big bang nucleosynthesis and early universe cosmology require precision measurements for helium abundance determinations. However, efforts to determine the primordial helium abundance via observations of metal poor H II regions have been limited by significant uncertainties. This work builds upon previous work by providing an updated and extended program in evaluating these uncertainties. Procedural consistency is achieved by integrating the hydrogen based reddening correction with the helium based abundance calculation, i.e., all physical parameters are solved for simultaneously. We include new atomic data for helium recombination and collisional emission based upon recent work by Porter et al. and wavelength dependent corrections to underlying absorption are investigated. The set of physical parameters has been expanded here to include the effects of neutral hydrogen collisional emission. Because of a degeneracy between the solutions for density and temperature, the precision of the helium abundance determinations is limited. Also, at lower temperatures (T \u227213,000 K) the neutral hydrogen fraction is poorly constrained resulting in a larger uncertainty in the helium abundances. Thus the derived errors on the helium abundances for individual objects are larger than those typical of previous studies. The updated emissivities and neutral hydrogen correction generally raise the abundance. From a regression to zero metallicity, we find Y_p as 0.2561 \u00b10.0108, in broad agreement with the WMAP result. Tests with synthetic data show a potential for distinct improvement, via removal of underlying absorption, using higher resolution spectra. A small bias in the abundance determination can be reduced significantly and the calculated helium abundance error can be reduced by \u223c25", "keyphrases": ["helium abundance", "big bang nucleosynthesis", "neutral hydrogen", "broad agreement", "systematic correction"]}
{"id": "1312.4251", "title": "Tensor to scalar ratio and large scale power suppression from pre-slow roll initial conditions", "abstract": "We study corrections to the power spectra of curvature and tensor perturbations and the tensor-to-scalar ratio in single field slow roll inflation due to initial conditions imprinted by a fast-roll stage prior to slow roll. For a wide range of initial inflaton kinetic energy, this stage lasts only a few e-folds and merges smoothly with slow-roll leading to non-Bunch-Davies initial conditions for modes that exit the Hubble radius during slow roll. We describe a program that yields the dynamics in the fast-roll stage while matching to the slow roll stage independent of the inflationary potentials. Corrections to the power spectra are encoded in a transfer function \ud835\udcaf_\u03b1(k). We obtain \ud835\udcaf_\u03b1(k) to leading order in a Born approximation valid for modes of observational relevance today. A fit yields \ud835\udcaf_\u03b1(k) =1+ A_\u03b1k^-pcos[2\u03c0\u03c9 k/H_sr+\u03c6_\u03b1], with 1.5 \u2272 p \u2272 2, \u03c9\u2243 1 and H_sr the Hubble scale during slow roll inflation, where curvature and tensor perturbations feature the same p,\u03c9 for a wide range of initial conditions. These corrections lead to both a suppression of the quadrupole and oscillatory features in both P_R(k) and r(k_0) with a period of the order of the Hubble scale during slow roll inflation. The results are independent of the specific inflationary potentials, depending solely on the ratio of kinetic to potential energy \u03ba and the slow roll parameters to leading order. For a wide range of \u03ba and the values of \u03f5_V;\u03b7_V corresponding to the upper bounds from Planck, we find that the low quadrupole is consistent with the results from Planck, and the oscillations in r(k_0) could be observable if the modes corresponding to the quadrupole and the pivot scale crossed the Hubble radius a few e-folds after the onset of slow roll.", "keyphrases": ["roll", "initial condition", "tensor-to-scalar ratio"]}
{"id": "1305.6686", "title": "High Performance Lyot and PIAA Coronagraphy for Arbitrarily shaped Telescope Apertures", "abstract": "Two high performance coronagraphic approaches compatible with segmented and obstructed telescope pupils are described. Both concepts use entrance pupil amplitude apodization and a combined phase and amplitude focal plane mask to achieve full coronagraphic extinction of an on-axis point source. While the first concept, named Apodized Pupil Complex Mask Lyot Coronagraph (APCMLC), relies on a transmission mask to perform the pupil apodization, the second concept, named Phase-Induced Amplitude Apodization complex mask coronagraph (PIAACMC), uses beam remapping for lossless apodization. Both concepts theoretically offer complete coronagraphic extinction (infinite contrast) of a point source in monochromatic light, with high throughput and sub-lambda/D inner working angle, regardless of aperture shape. The PIAACMC offers nearly 100 imposed by first principles. The steps toward designing the coronagraphs for arbitrary apertures are described for monochromatic light. Designs for the APCMLC and the higher performance PIAACMC are shown for several monolith and segmented apertures, such as the apertures of the Subaru Telescope, Giant Magellan Telescope (GMT), Thirty Meter Telescope (TMT), the European Extremely Large Telescope (E-ELT) and the Large Binocular Telescope (LBT). Performance in broadband light is also quantified, suggesting that the monochromatic designs are suitable for use in up to 20 telescopes.", "keyphrases": ["telescope aperture", "coronagraph", "phase-induced amplitude apodization"]}
{"id": "0910.4803", "title": "Why is the nuclear symmetry energy so uncertain at supra-saturation densities?", "abstract": "Within the interacting Fermi gas model for isospin asymmetric nuclear matter, effects of the in-medium three-body interaction and the two-body short-range tensor force due to the \u03c1 meson exchange as well as the short-range nucleon correlation on the high-density behavior of the nuclear symmetry energy are demonstrated respectively in a transparent way. Possible physics origins of the extremely uncertain nuclear symmetry energy at supra-saturation densities are discussed.", "keyphrases": ["nuclear symmetry energy", "supra-saturation density", "nuclear matter"]}
{"id": "1707.03388", "title": "Is there another coincidence problem at the reionization epoch?", "abstract": "The cosmological coincidences between the matter and radiation energy densities at recombination as well as between the densities of matter and the cosmological constant at present time are well known. We point out that moreover the third intersection between the energy densities of radiation and the cosmological constant coincides with the reionization epoch. To quantify the statistical relevance of this concurrence, we compute the Bayes factor between the concordance cosmology with free Thomson scattering optical depth and a model for which this parameter is inferred from imposing a match between the time of density equality and the epoch of reionization. This is to characterize the potential explanatory gain if one were to find a parameter-free physical connection. We find a very strong preference for such a concurrence on the Jeffreys scale from current cosmological observations. We furthermore discuss the effect of choice of priors, changes in reionization history, and free sum of neutrino masses. We also estimate the impact of adding intermediate polarization data from the Planck High Frequency Instrument and prospects for future 21 cm surveys. In the first case, preference for the correlation remains substantial, whereas future data may give results more decisive in pro or substantial in contra. Finally, we provide a discussion on different interpretations of these findings. In particular, we show how a connection between the star-formation history and the cosmological background dynamics can give rise to this concurrence.", "keyphrases": ["coincidence problem", "reionization epoch", "cosmological constant"]}
{"id": "1001.4585", "title": "Modified Entropic Force", "abstract": "The theory of statistical thermodynamics tells us the equipartition law of energy does not hold in the limit of very low temperatures. It is found the Debye model is very successful in explaining the experimental results for most of the solid objects. Motivated by this fact, we modify the entropic force formula which is proposed very recently. Since the Unruh temperature is proportional to the strength of gravitational field, so the modified entropic force formula is an extension of the Newtonian gravity to weak field. On the contrary, General Relativity extends Newtonian gravity to strong field case. Corresponding to Debye temperature, there exists a Debye acceleration g_D. It is found the Debye acceleration is g_D=10^-15N kg^-1. This acceleration is very much smaller than the gravitational acceleration 10^-4N kg^-1 which is felt by the Neptune and the gravitational acceleration 10^-10N kg^-1 felt by the Sun. Therefore, the modified entropic force can be very well approximated by the Newtonian gravity in the solar system and in the Galaxy. With this Debye acceleration, we find the current cosmic speeding up can be explained without invoking any kind of dark energy.", "keyphrases": ["equipartition law", "experimental result", "gravity", "dark energy", "modified entropic force"]}
{"id": "1707.06192", "title": "Pinning down the mass of Kepler-10c: the importance of sampling and model comparison", "abstract": "Initial RV characterisation of the enigmatic planet Kepler-10c suggested a mass of \u223c17 M_\u2295, which was remarkably high for a planet with radius 2.32 R_\u2295; further observations and subsequent analysis hinted at a (possibly much) lower mass, but masses derived using RVs from two different spectrographs (HARPS-N and HIRES) were incompatible at a 3\u03c3-level. We demonstrate here how such mass discrepancies may readily arise from sub-optimal sampling and/or neglecting to model even a single coherent signal (stellar, planetary, or otherwise) that may be present in RVs. We then present a plausible resolution of the mass discrepancy, and ultimately characterise Kepler-10c as having mass 7.37_-1.19^+1.32 M_\u2295, and mean density 3.14^+0.63_-0.55 g cm^-3.", "keyphrases": ["kepler-10c", "sampling", "planet"]}
{"id": "1803.03781", "title": "The lamppost model: effects of photon trapping, the bottom lamp and disc truncation", "abstract": "We study the lamppost model, in which the primary X-ray sources in accreting black-hole systems are located symmetrically on the rotation axis on both sides of the black hole surrounded by an accretion disc. We show the importance of the emission of the source on the opposite side to the observer. Due to gravitational light bending, its emission can increase the direct (i.e., not re-emitted by the disc) flux by as much as an order of magnitude. This happens for near to face-on observers when the disc is even moderately truncated. For truncated discs, we also consider effects of emission of the top source gravitationally bent around the black hole. We also present results for the attenuation of the observed radiation with respect to that emitted by the lamppost as functions of the lamppost height, black-hole spin and the degree of disc truncation. This attenuation, which is due to the time dilation, gravitational redshift and the loss of photons crossing the black-hole horizon, can be as severe as by several orders of magnitude for low lamppost heights. We also consider the contribution to the observed flux due to re-emission by optically-thick matter within the innermost stable circular orbit.", "keyphrases": ["lamppost model", "disc truncation", "radiation"]}
{"id": "1506.00915", "title": "A relativistic signature in large-scale structure", "abstract": "In General Relativity, the constraint equation relating metric and density perturbations is inherently nonlinear, leading to an effective non-Gaussianity in the dark matter density field on large scales - even if the primordial metric perturbation is Gaussian. Intrinsic non-Gaussianity in the large-scale dark matter overdensity in GR is real and physical. However, the variance smoothed on a local physical scale is not correlated with the large-scale curvature perturbation, so that there is no relativistic signature in the galaxy bias when using the simplest model of bias. It is an open question whether the observable mass proxies such as luminosity or weak lensing correspond directly to the physical mass in the simple halo bias model. If not, there may be observables that encode this relativistic signature.", "keyphrases": ["relativistic signature", "effective non-gaussianity", "matter density field", "galaxy bias"]}
{"id": "1603.05209", "title": "Causality, initial conditions, and inflationary magnetogenesis", "abstract": "The post-inflationary evolution of inflation-produced magnetic fields, conventional or not, can change dramatically when two fundamental issues are accounted for. The first is causality, which demands that local physical processes can never affect superhorizon perturbations. The second is the nature of the transition from inflation to reheating and then to the radiation era, which determine the initial conditions at the start of these epochs. Causality implies that inflationary magnetic fields dot not freeze into the matter until they have re-entered the causal horizon. The nature of the cosmological transitions and the associated initial conditions, on the other hand, determine the large-scale magnetic evolution after inflation. Put together, the two can slow down the adiabatic magnetic decay on superhorizon scales throughout the universe's post-inflationary evolution and thus lead to considerably stronger residual magnetic fields. This is \"good news\" for both the conventional and the non-conventional scenarios of cosmic magnetogenesis. Mechanisms operating outside standard electromagnetism, in particular, do not need to enhance their fields too much during inflation, in order to produce seeds that can feed the galactic dynamo today. In fact, even conventionally produced inflationary magnetic fields might be able to sustain the dynamo.", "keyphrases": ["initial condition", "magnetogenesis", "causality", "conformal invariance"]}
{"id": "1607.03144", "title": "The clustering of galaxies in the completed SDSS-III Baryon Oscillation Spectroscopic Survey: Angular clustering tomography and its cosmological implications", "abstract": "We investigate the cosmological implications of studying galaxy clustering using a tomographic approach applied to the final BOSS DR12 galaxy sample, including both auto- and cross-correlation functions between redshift shells. We model the signal of the full shape of the angular correlation function, \u03c9(\u03b8), in redshift bins using state-of-the-art modelling of non-linearities, bias and redshift-space distortions. We present results on the redshift evolution of the linear bias of BOSS galaxies, which cannot be obtained with traditional methods for galaxy-clustering analysis. We also obtain constraints on cosmological parameters, combining this tomographic analysis with measurements of the cosmic microwave background (CMB) and type Ia supernova (SNIa). We explore a number of cosmological models, including the standard \u039bCDM model and its most interesting extensions, such as deviations from w_DE = -1, non-minimal neutrino masses, spatial curvature and deviations from general relativity using the growth-index \u03b3 parametrisation. These results are, in general, comparable to the most precise present-day constraints on cosmological parameters, and show very good agreement with the standard model. In particular, combining CMB, \u03c9(\u03b8) and SNIa, we find a value of w_DE consistent with -1 to a precision better than 5% when it is assumed to be constant in time, and better than 6% when we also allow for a spatially-curved Universe.", "keyphrases": ["galaxy", "cosmological implication", "redshift shell"]}
{"id": "1303.0345", "title": "Calibrating 100 Years of Polar Faculae Measurements: Implications for the Evolution of the Heliospheric Magnetic Field", "abstract": "Although the Sun's polar magnetic fields are thought to provide important clues for understanding the 11-year sunspot cycle, including the observed variations of its amplitude and period, the current database of high-quality polar-field measurements spans relatively few sunspot cycles. In this paper we address this deficiency by consolidating Mount Wilson Observatory polar faculae data from four data reduction campaigns, validating it through a comparison with facular data counted automatically from MDI intensitygrams, and calibrating it against polar field measurements taken by the Wilcox Solar Observatory and average polar field and total polar flux calculated using MDI line-of-sight magnetograms. Our results show that the consolidated polar facular measurements are in excellent agreement with both polar field and polar flux estimates, making them an ideal proxy to study the evolution of the polar magnetic field. Additionally, we combine this database with sunspot area measurements to study the role of the polar magnetic flux in the evolution of the heliospheric magnetic field (HMF). We find that there is a strong correlation between HMF and polar flux at solar minimum and that, taken together, polar flux and sunspot area are better at explaining the evolution of the HMF during the last century than sunspot area alone.", "keyphrases": ["polar faculae measurement", "heliospheric magnetic field", "polar magnetic field"]}
{"id": "1501.01618", "title": "Fermi/LAT observations of Dwarf Galaxies highly constrain a Dark Matter Interpretation of Excess Positrons seen in AMS-02, HEAT, and PAMELA", "abstract": "It is shown that a Weakly Interacting Massive dark matter Particle (WIMP) interpretation for the positron excess observed in a variety of experiments, HEAT, PAMELA, and AMS-02, is highly constrained by the Fermi/LAT observations of dwarf galaxies. In particular, this paper has focused on the annihilation channels that best fit the current AMS-02 data (Boudaud et al., 2014). The Fermi satellite has surveyed the \u03b3-ray sky, and its observations of dwarf satellites are used to place strong bounds on the annihilation of WIMPs into a variety of channels. For the single channel case, we find that dark matter annihilation into bb\u0305, e^+e^-, \u03bc^+\u03bc^-, \u03c4^+\u03c4^-, 4-e, or 4-\u03c4 is ruled out as an explanation of the AMS positron excess (here b quarks are a proxy for all quarks, gauge and Higgs bosons). In addition, we find that the Fermi/LAT 2\u03c3 upper limits, assuming the best-fit AMS-02 branching ratios, exclude multichannel combinations into bb\u0305 and leptons. The tension between the results might relax if the branching ratios are allowed to deviate from their best-fit values, though a substantial change would be required. Of all the channels we considered, the only viable channel that survives the Fermi/LAT constraint and produces a good fit to the AMS-02 data is annihilation (via a mediator) to 4-\u03bc, or mainly to 4-\u03bc in the case of multichannel combinations.", "keyphrases": ["dark matter annihilation", "fermi", "muon"]}
{"id": "1103.2099", "title": "Resolving Subhaloes' Lives with the Hierarchical Bound-Tracing Algorithm", "abstract": "We develop a new code, the Hierarchical Bound-Tracing (HBT for short) code, to find and trace dark matter subhaloes in simulations based on the merger hierarchy of dark matter haloes. Application of this code to a recent benchmark test of finding subhaloes demonstrates that HBT stands as one of the best codes to trace the evolutionary history of subhaloes. The success of the code lies in its careful treatment of the complex physical processes associated with the evolution of subhaloes and in its robust unbinding algorithm with an adaptive source subhalo management. We keep a full record of the merger hierarchy of haloes and subhaloes, and allow growth of satellite subhaloes through accretion from its \"satellite-of-satellites\", hence allowing mergers among satellites. Local accretion of background mass is omitted, while rebinding of stripped mass is allowed. The justification of these treatments is provided by case studies of the lives of individual subhaloes and by the success in finding the complete subhalo catalogue. We compare our result to other popular subhalo finders and show that HBT is able to well resolve subhaloes in high density environment and keep strict physical track of subhaloes' merger history. This code is fully parallelized and freely available upon request to the authors.", "keyphrases": ["subhaloe", "hierarchical bound-tracing", "life"]}
{"id": "2103.05076", "title": "The impact of baryonic physics on the abundance, clustering, and concentration of halos", "abstract": "We examine the impact of baryonic physics on the halo distribution in hydrodynamic simulations (Illustris, IllustrisTNG, and EAGLE), particularly with regards to how it differs from that in dark matter only (DMO) simulations. We find that, in general, DMO simulations produce halo mass functions (HMF) that are shifted to higher halo masses than their hydrodynamic counterparts, due to the lack of baryonic physics. However, the exact nature of this mass shift is a complex function of mass, halo definition, redshift, and larger-scale environment, and it also depends on the specifics of the baryonic physics implemented in the simulation. We present fitting formulae for the corrections one would need to apply to each DMO halo catalogue in order to reproduce the HMF found in its hydrodynamic counterpart. We provide these formulae for all three simulations, for five different halo definitions at redshifts 0, 1, and 2. Additionally, we explore the dependence on environment of this HMF discrepancy, and find that, in most cases, halos in low density environments are slightly more impacted by baryonic physics than halos in high density environments. We thus also provide environment-dependent mass correction formulae that can reproduce the conditional, as well as global, HMF. We show that our mass corrections also repair the large-scale clustering of halos, though the environment-dependent corrections are required to achieve an accuracy better than 2 the halo mass - concentration relation, and find that its slope in hydrodynamic simulations is consistent with that in DMO simulations. Ultimately, we recommend that any future work relying on DMO halo catalogues incorporate our mass corrections to test the robustness of their results to baryonic effects.", "keyphrases": ["baryonic physics", "halo", "redshift"]}
{"id": "1901.02959", "title": "Disentangling the spatial substructure of Cygnus OB2 from Gaia DR2", "abstract": "For the first time, we have explored the spatial substructure of the Cygnus OB2 association using parallaxes from the recent second Gaia data release. We find significant line-of-sight substructure within the association, which we quantify using a parameterised model that reproduces the observed parallax distribution. This inference approach is necessary due to the non-linearity of the parallax-distance transformation and the asymmetry of the resulting probability distribution. By using a Markov Chain Monte Carlo ensemble sampler and an unbinned maximum likelihood test we identify two different stellar groups superposed on the association. We find the main Cygnus OB2 group at 1760 pc, further away than recent estimates have envisaged, and a foreground group at 1350 pc. We also calculate individual membership probabilities and identify outliers as possible non-members of the association.", "keyphrases": ["spatial substructure", "gaia dr2", "cygnus ob2 group"]}
{"id": "1611.03720", "title": "Non-Gaussianities due to Relativistic Corrections to the Observed Galaxy Bispectrum", "abstract": "High-precision constraints on primordial non-Gaussianity (PNG) will significantly improve our understanding of the physics of the early universe. Among all the subtleties in using large scale structure observables to constrain PNG, accounting for relativistic corrections to the clustering statistics is particularly important for the upcoming galaxy surveys covering progressively larger fraction of the sky. We focus on relativistic projection effects due to the fact that we observe the galaxies through the light that reaches the telescope on perturbed geodesics. These projection effects can give rise to an effective f_ NL that can be misinterpreted as the primordial non-Gaussianity signal and hence is a systematic to be carefully computed and accounted for in modelling of the bispectrum. We develop the technique to properly account for relativistic effects in terms of purely observable quantities, namely angles and redshifts. We give some examples by applying this approach to a subset of the contributions to the tree-level bispectrum of the observed galaxy number counts calculated within perturbation theory and estimate the corresponding non-Gaussianity parameter, f_ NL, for the local, equilateral and orthogonal shapes. For the local shape, we also compute the local non-Gaussianity resulting from terms obtained using the consistency relation for observed number counts. Our goal here is not to give a precise estimate of f_ NL for each shape but rather we aim to provide a scheme to compute the non-Gaussian contamination due to relativistic projection effects. For the terms considered in this work, we obtain contamination of f_ NL^ loc\u223c\ud835\udcaa(1).", "keyphrases": ["relativistic correction", "bispectrum", "primordial non-gaussianity", "ultra-large scale"]}
{"id": "2105.02176", "title": "New general DBI action, its solution to the paradox of the conversion of kinetic and potential energy in equal rights and their true applications to inflationary cosmology", "abstract": "The Dirac-Born-Infeld (DBI) field theory in string theory is important and can provide the field of the universe's inflation. At the same time, it provides a causal mechanism for generating the original density perturbation, thereby providing the necessary density perturbation for existing the dense and sparse matter distributions of the universe. However, there is the paradox of the conversion of potential energy and kinetic energy in equal rights in string theory. Therefore, we give a new general DBI action, which enables the kinetic energy and potential energy in the action to be converted each other in equal rights, i.e., solving the paradox. Therefore, we deduce a new general DBI action, introduce it into inflationary cosmology to calculate various inflation parameters, further calculate the scalar perturbation spectrum and the tensor-scalar ratio, which are compared with Planck + WMAP9 + BAO data, the power spectrum predicted by the new general DBI inflation theory satisfies the CMB Experiment constraints, i.e., is consistent with the current theories and experimental observations. Consequently, the theory of this paper conforms to current experiments and is supplying the current theories, and also a new way of explaining the inflation of the universe.", "keyphrases": ["general dbi action", "inflationary cosmology", "string theory"]}
{"id": "2105.02876", "title": "Galaxy bias from forward models: linear and second-order bias of IllustrisTNG galaxies", "abstract": "We use field-level forward models of galaxy clustering and the EFT likelihood formalism to study, for the first time for self-consistently simulated galaxies, the relations between the linear b_1 and second-order bias parameters b_2 and b_K^2. The forward models utilize all of the information available in the galaxy distribution up to a given order in perturbation theory, which allows us to infer these bias parameters with high signal-to-noise, even from relatively small volumes (L_ box = 205 Mpc/h). We consider galaxies from the IllustrisTNG simulations, and our main result is that the b_2(b_1) and b_K^2(b_1) relations obtained from gravity-only simulations for total mass selected objects are broadly preserved for simulated galaxies selected by stellar mass, star formation rate, color and black hole accretion rate. We also find good agreement between the bias relations of the simulated galaxies and a number of recent estimates for observed galaxy samples. The consistency under different galaxy selection criteria suggests that theoretical priors on these bias relations may be used to improve cosmological constraints based on observed galaxy samples. We do identify some small differences between the bias relations in the hydrodynamical and gravity-only simulations, which we show can be linked to the environmental dependence of the relation between galaxy properties and mass. We also show that the EFT likelihood recovers the value of \u03c3_8 to percent-level from various galaxy samples (including splits by color and star formation rate) and after marginalizing over 8 bias parameters. This demonstration using simulated galaxies adds to previous works based on halos as tracers, and strengthens further the potential of forward models to infer cosmology from galaxy data.", "keyphrases": ["forward model", "bias parameter", "stellar mass", "galaxy"]}
{"id": "2103.15825", "title": "Uncertain Times: The Redshift-Time Relation from Cosmology and Stars", "abstract": "Planck data provide precise constraints on cosmological parameters when assuming the base \u039bCDM model, including a 0.17% measurement of the age of the Universe, t_0=13.797 \u00b1 0.023 Gyr. However, the persistence of the \"Hubble tension\" calls the base \u039bCDM model's completeness into question and has spurred interest in models such as Early Dark Energy (EDE) that modify the assumed expansion history of the Universe. We investigate the effect of EDE on the redshift-time relation z \u2194 t and find that it differs from the base \u039bCDM model by at least \u2248 4% at all t and z. As long as EDE remains observationally viable, any inferred t \u2190 z or z \u2190 t quoted to a higher level of precision do not reflect the current status of our understanding of cosmology. This uncertainty has important astrophysical implications: the reionization epoch - 10>z>6 - corresponds to disjoint lookback time periods in the base \u039bCDM and EDE models, and the EDE value of t_0=13.25 \u00b1 0.17 Gyr is in tension with published ages of some stars, star clusters, and ultra-faint dwarf galaxies. However, most published stellar ages do not include an uncertainty in accuracy (due to, e.g., uncertain distances and stellar physics) that is estimated to be \u223c7-10%, potentially reconciling stellar ages with t_0, EDE. We discuss how the big data era for stars is providing extremely precise ages (<1%) and how improved distances and treatment of stellar physics such as convection could result in ages accurate to 4-5%, comparable to the current accuracy of t \u2194 z. Such precise and accurate stellar ages can provide detailed insight into the high-redshift Universe independent of a cosmological model.", "keyphrases": ["cosmology", "star", "age"]}
{"id": "1106.0701", "title": "Shear viscous effects on the primordial power spectrum from warm inflation", "abstract": "We compute the primordial curvature spectrum generated during warm inflation, including shear viscous effects. The primordial spectrum is dominated by the thermal fluctuations of the radiation bath, sourced by the dissipative term of the inflaton field. The dissipative coefficient \u03a5, computed from first principles in the close-to-equilibrium approximation, depends in general on the temperature T, and this dependence renders the system of the linear fluctuations coupled. Whenever the dissipative coefficient is larger than the Hubble expansion rate H, there is a growing mode in the fluctuations before horizon crossing. However, dissipation intrinsically means departures from equilibrium, and therefore the presence of a shear viscous pressure in the radiation fluid. This in turn acts as an extra friction term for the radiation fluctuations that tends to damp the growth of the perturbations. Independently of the T functional dependence of the dissipation and the shear viscosity, we find that when the shear viscous coefficient \u03b6_s is larger than 3 \u03c1_r/H at horizon crossing, \u03c1_r being the radiation energy density, the shear damping effect wins and there is no growing mode in the spectrum.", "keyphrases": ["warm inflation", "thermal fluctuation", "shear viscous effect"]}
{"id": "1903.06730", "title": "From the microscopic to the macroscopic world: from nucleons to neutron stars", "abstract": "Recent observations of neutron-star properties, in particular the recent detection of gravitational waves emitted from binary neutron stars, GW 170817, open the way to put strong constraints on nuclear interactions. In this paper, we review the state of the art in calculating the equation of state of strongly interacting matter from first principle calculations starting from microscopic interactions among nucleons. We then review selected properties of neutron stars that can be directly compared with present and future observations.", "keyphrases": ["nucleon", "neutron star", "gravitational wave"]}
{"id": "1304.1811", "title": "The Topology and Size of the Universe from CMB Temperature and Polarization Data", "abstract": "We analyze seven year and nine year WMAP temperature maps for signatures of three finite flat topologies M_0=T^3, M_1=T^2 x R^1, and M_2=S^1 x R^2. We use Monte-Carlo simulations with the Feldman-Cousins method to obtain confidence intervals for the size of the topologies considered. We analyze the V, W, and Q frequency bands along with the ILC map and find no significant difference in the results. The 95.5 is 1.5L_0 for M_0, 1.4L_0 for M_1, and 1.1L_0 for M_2, where L_0 is the radius of the last scattering surface. Our results agree very well with the recently released results from the Planck temperature data. We show that the likelihood function is not Gaussian in the size, and therefore simulations are important for obtaining accurate bounds on the size. We then introduce the formalism for including polarization data in the analysis. The improvement that we find from WMAP polarization maps is small because of the high level of instrumental noise, but our forecast for Planck maps shows a much better improvement on the lower bound for L. For the M_0 topology we expect an improvement on the lower bound of L from 1.7L_0 to 1.9L_0 at 95.5 polarization and temperature data is important because it tests the hypothesis that deviations in the TT spectrum at small l originate in the primordial perturbation spectrum.", "keyphrases": ["topology", "universe", "7-year"]}
{"id": "1208.2862", "title": "The G-O Rule and Waldmeier Effect in the Variations of the Numbers of Large and Small Sunspot Groups", "abstract": "We have analysed the combined Greenwich and Solar Optical Observing Network (SOON) sunspot group data during the period of 1874-2011 and determined variations in the annual numbers (counts) of the small, large and big sunspot groups (these classifications are made on the basis of the maximum areas of the sunspot groups). We found that the amplitude of an even-numbered cycle of the number of large groups is smaller than that of its immediately following odd-numbered cycle. This is consistent with the well known Gnevyshev and Ohl rule or G-O rule of solar cycles, generally described by using the Zurich sunspot number (Rz). During cycles 12-21 the G-O rule holds good for the variation in the number of small groups also, but it is violated by cycle pair (22, 23) as in the case of Rz. This behaviour of the variations in the small groups is largely responsible for the anomalous behaviour of Rz in cycle pair (22, 23). It is also found that the amplitude of an odd-numbered cycle of the number of small groups is larger than that of its immediately following even-numbered cycle. This can be called as `reverse G-O rule'. In the case of the number of the big groups, both cycle pairs (12, 13) and (22, 23) violated the G-O rule. In many cycles the positions of the peaks of the small, large, and big groups are different and considerably differ with respect to the corresponding positions of the Rz peaks. In the case of cycle 23, the corresponding cycles of the small and large groups are largely symmetric/less asymmetric (Waldmeier effect is weak/absent) with their maxima taking place two years later than that of Rz. The corresponding cycle of the big groups is more asymmetric (strong Waldmeier effect) with its maximum epoch taking place at the same time as that of Rz.", "keyphrases": ["g-o rule", "waldmeier effect", "sunspot group data"]}
{"id": "1703.10130", "title": "Frequent flaring in the TRAPPIST-1 system - unsuited for life?", "abstract": "We analyze short cadence K2 light curve of the TRAPPIST-1 system. Fourier analysis of the data suggests P_rot=3.295\u00b10.003 days. The light curve shows several flares, of which we analyzed 42 events, these have integrated flare energies of 1.26\u00d710^30-1.24\u00d710^33 ergs. Approximately 12 flaring and the possible rotational modulation shows no obvious correlation. The flaring activity of TRAPPIST-1 probably continuously alters the atmospheres of the orbiting exoplanets, making these less favorable for hosting life.", "keyphrases": ["flare", "trappist-1 system", "life"]}
{"id": "1804.07377", "title": "The Solar Neighborhood XLIV: RECONS Discoveries within 10 Parsecs", "abstract": "We describe the 44 systems discovered to be within 10 parsecs of the Sun by the RECONS team, primarily via the long-term astrometry program at CTIO that began in 1999. The systems \u2014 including 41 with red dwarf primaries, 2 white dwarfs, and 1 brown dwarf \u2014 have been found to have trigonometric parallaxes greater than 100 milliarcseconds (mas), with errors of 0.4\u20132.4 mas in all but one case. We provide updated astrometric, photometric (VRIJHK magnitudes), spectral type, and multiplicity information here. Among these are 14 systems that are new entries to the 10 parsec sample based on parallaxes measured at the CTIO/SMARTS 0.9m telescope. These are the first parallaxes for nine systems, while the remaining five systems had previously measured parallaxes with errors greater than 10 mas or values placing them beyond 10 parsecs. We also present parallaxes from URAT for seven of these systems, providing additional evidence that they are closer than 10 parsecs. In addition, we provide new data for 22 systems that were previously known to lie within 10 parsecs and 9 systems reported to be closer than that horizon but for which new parallaxes place them further away. In total, we provide data for 75 systems, for which 71 have new or updated parallaxes here. The 44 systems added by RECONS comprise one of every seven systems known within 10 parsecs. We illustrate the evolution of the 10 parsec sample from the 191 systems known when the final Yale Parallax Catalog (YPC) was published in 1995 to the 316 systems known today. Even so close to the Sun, additional discoveries of red and brown dwarfs (and perhaps even white dwarfs) are likely, both as primaries and secondaries, although we estimate that at least 90 the stellar systems closer than 10 parsecs have now been identified.", "keyphrases": ["discovery", "parsec", "brown dwarf"]}
{"id": "1905.11339", "title": "Magnetic Fields and Afterglows of BdHNe: Inferences from GRB 130427A, GRB 160509A, GRB 160625B, GRB 180728A and GRB 190114C", "abstract": "GRB 190114C is the first binary-driven hypernova (BdHN) fully observed from the initial supernova appearance to the final emergence of the optical SN signal. It offers an unprecedented testing ground for the BdHN theory and it is here determined and further extended to additional gamma-ray bursts (GRBs). BdHNe comprise two subclasses of long GRBs with progenitors a binary system composed of a carbon-oxygen star (CO_core) and a neutron star (NS) companion. The CO_core explodes as a SN leaving at its center a newborn NS (\u03bdNS). The SN ejecta hypercritically accretes both on the \u03bdNS and the NS companion. BdHNe I are the tightest binaries where the accretion leads the companion NS to gravitational collapse into a black hole (BH). In BdHN II the accretion onto the NS is lower, so there is no BH formation. We observe the same structure of the afterglow for GRB 190114C and other selected examples of BdHNe I (GRB 130427A, GRB 160509A, GRB 160625B) and for BdHN II (GRB 180728A). In all the cases the explanation of the afterglow is reached via the synchrotron emission powered by the \u03bdNS: their magnetic fields structures and their spin are determined. For BdHNe I, we discuss the properties of the magnetic field embedding the newborn BH, inherited from the collapsed NS and amplified during the gravitational collapse process, and surrounded by the SN ejecta.", "keyphrases": ["grb 180728a", "synchrotron emission", "magnetic field", "x-rays"]}
{"id": "1205.0161", "title": "Curvature Perturbation Spectrum in Two-field Inflation with a Turning Trajectory", "abstract": "We revisit a two-component inflaton model with a turning trajectory in the field space, where the field slowly rolls down along the trajectory. We consider the case when the effective mass in the direction perpendicular to the trajectory, namely the isocurvature direction, is either of the same order as or much larger than the Hubble parameter. Assuming that the turning angular velocity is small, we compute analytically the corrections to the power spectrum of curvature perturbation caused by the mediation of the heavy isocurvature perturbation, and compare our analytic results with the numerical ones. Especially, when M_eff^2>>H^2, we find that it is proportional to M_eff^-2. This result is consistent with the one obtained previously by an effective field theory approach.", "keyphrases": ["field space", "cosmological collider physics", "quasi-single field inflation", "curvature perturbation"]}
{"id": "2109.02636", "title": "The matter density PDF for modified gravity and dark energy with Large Deviations Theory", "abstract": "We present an analytical description of the probability distribution function (PDF) of the smoothed three-dimensional matter density field for modified gravity and dark energy. Our approach, based on the principles of Large Deviations Theory, is applicable to general extensions of the standard \u039bCDM cosmology. We show that late-time changes to the law of gravity and background expansion can be included through Einstein-de Sitter spherical collapse dynamics combined with linear theory calculations and a calibration measurement of the non-linear variance of the smoothed density field from a simple numerical simulation. In a comparison to N-body simulations for f(R), DGP and evolving dark energy theories, we find percent level accuracy around the peak of the distribution for predictions in the mildly non-linear regime. A Fisher forecast of an idealised experiment with a Euclid-like survey volume demonstrates the power of combining measurements of the 3D matter PDF with the 3D matter power spectrum. This combination is shown to halve the uncertainty on parameters for an evolving dark energy model, relative to a power spectrum analysis on its own. The PDF is also found to substantially increase the detection significance for small departures from General Relativity, with improvements of up to six times compared to the power spectrum alone. This analysis is therefore very promising for future studies including non-Gaussian statistics, as it has the potential to alleviate the reliance of these analyses on expensive high resolution simulations and emulators.", "keyphrases": ["gravity", "dark energy", "large deviations theory"]}
{"id": "1604.02643", "title": "Quasi-periodic oscillations as a tool for testing the Kerr metric: A comparison with gravitational waves and iron line", "abstract": "QPOs are a common feature in the X-ray power density spectrum of black hole binaries and a potentially powerful tool to probe the spacetime geometry around these objects. Here we discuss their constraining power to test the Kerr black hole hypothesis within the relativistic precession model. We compare our results with the constraints that can be obtained from gravitational waves and iron line. We find that QPOs may provide very precise measurements, but they are strongly affected by parameter degeneracy, and it is difficult to test the Kerr metric with this approach in the absence of independent observations to constrain the mass or the spin.", "keyphrases": ["oscillation", "gravitational wave", "iron line", "precession model", "parameter degeneracy"]}
{"id": "2012.10130", "title": "The Bar and Spiral Arms in the Milky Way: Structure and Kinematics", "abstract": "The Milky Way is a spiral galaxy with the Schechter characteristic luminosity L_*, thus an important anchor point of the Hubble sequence of all spiral galaxies. Yet the true appearance of the Milky Way has remained elusive for centuries. We review the current best understanding of the structure and kinematics of our home galaxy, and present an updated scientifically accurate visualization of the Milky Way structure with almost all components of the spiral arms, along with the COBE image in the solar perspective. The Milky Way contains a strong bar, four major spiral arms, and an additional arm segment (the Local arm) that may be longer than previously thought. The Galactic boxy bulge that we observe is mostly the peanut-shaped central bar viewed nearly end-on with a bar angle of 25-30 degrees from the Sun-Galactic center line. The bar transitions smoothly from a central peanut-shaped structure to an extended thin part that ends around R 5 kpc. The Galactic bulge/bar contains 30-40 of the total stellar mass in the Galaxy. Dynamical modelling of both the stellar and gas kinematics yields a bar pattern rotation speed of 35-40 km/s/kpc, corresponding to a bar rotation period of 160-180 Myr. From a galaxy formation point of view, our Milky Way is probably a pure-disk galaxy with little room for a significant merger-made, \"classical\" spheroidal bulge, and we give a number of reasons why this is the case.", "keyphrases": ["bar", "arm", "milky way"]}
{"id": "1309.2628", "title": "Neutrino Quantum Kinetics", "abstract": "We present a formulation of the quantum kinetic equations (QKEs) which govern the evolution of neutrino flavor at high density and temperature. Here, the QKEs are derived from the ground up, using fundamental neutrino interactions and quantum field theory. We show that the resulting QKEs describe coherent flavor evolution with an effective mass when inelastic scattering is negligible. The QKEs also contain a collision term. This term can reduce to the collision term in the Boltzmann equation when scattering is dominant and the neutrino effective masses and density matrices become diagonal in the interaction basis. We also find that the QKE's include equations of motion for a new dynamical quantity related to neutrino spin. This quantity decouples from the equations of motion for the density matrices at low densities or in isotropic conditions. However, the spin equations of motion allow for the possibility of coherent transformation between neutrinos and antineutrinos at high densities and in the presence of anisotropy. Although the requisite conditions for this exist in the core collapse supernova and compact object merger environments, it is likely that only a self consistent incorporation of the QKEs in a sufficiently realistic model could establish whether or not significant neutrino-antineutrino conversion occurs.", "keyphrases": ["kinetic equation", "qkes", "spin", "neutrino", "flavor conversion"]}
{"id": "1305.3106", "title": "Supernova constraints on Multi-coupled Dark Energy", "abstract": "The persisting consistency of ever more accurate observational data with the predictions of the standard LCDM cosmological model puts severe constraints on possible alternative scenarios, but still does not shed any light on the fundamental nature of the cosmic dark sector.As large deviations from a LCDM cosmology are ruled out by data, the path to detect possible features of alternative models goes necessarily through the definition of cosmological scenarios that leave almost unaffected the background and \u2013 to a lesser extent \u2013 the linear perturbations evolution of the universe. In this context,the Multi-coupled DE (McDE) model was proposed by Baldi 2012 as a particular realization of an interacting Dark Energy field characterized by an effective screening mechanism capable of suppressing the effects of the coupling at the background and linear perturbation level. In the present paper, for the first time, we challenge the McDE scenario through a direct comparison with real data, in particular with the luminosity distance of Type Ia supernovae. By studying the existence and stability conditions of the critical points of the associated background dynamical system, we select only the cosmologically consistent solutions, and confront their background expansion history with data. Confirming previous qualitative results, the McDE scenario appears to be fully consistent with the adopted sample of Type Ia supernovae, even for coupling values corresponding to an associated scalar fifth-force about four orders of magnitude stronger than standard gravity. Our analysis demonstrates the effectiveness of the McDE background screening, and shows some new non-trivial asymptotic solutions for the future evolution of the universe. Our results show how the background expansion history might be highly insensitive to the fundamental nature and to the internal complexity of the dark sector. [Abridged]", "keyphrases": ["dark energy", "scalar field", "dark matter fluid"]}
{"id": "0903.4920", "title": "CMB polarization features from inflation versus reionization", "abstract": "The angular power spectrum of the cosmic microwave background temperature anisotropy observed by WMAP has an anomalous dip at l 20 and bump at l 40. One explanation for this structure is the presence of features in the primordial curvature power spectrum, possibly caused by a step in the inflationary potential. The detection of these features is only marginally significant from temperature data alone. However, the inflationary feature hypothesis predicts a specific shape for the E-mode polarization power spectrum with a structure similar to that observed in temperature at l 20-40. Measurement of the CMB polarization on few-degree scales can therefore be used as a consistency check of the hypothesis. The Planck satellite has the statistical sensitivity to confirm or rule out the model that best fits the temperature features with 3 sigma significance, assuming all other parameters are known. With a cosmic variance limited experiment, this significance improves to 8 sigma. For tests of inflationary models that can explain both the dip and bump in temperature, the primary source of uncertainty is confusion with polarization features created by a complex reionization history, which at most reduces the significance to 2.5 sigma for Planck and 5-6 sigma for an ideal experiment. Smoothing of the polarization spectrum by a large tensor component only slightly reduces the ability of polarization to test for inflationary features, as does requiring that polarization is consistent with the observed temperature spectrum given the expected low level of TE correlation on few-degree scales. A future polarization satellite would enable a decisive test of the feature hypothesis and provide complementary information about the shape of a possible step in the inflationary potential. (Abridged.)", "keyphrases": ["polarization", "inflationary feature", "primordial power spectrum"]}
{"id": "1703.03797", "title": "Effective Description of Higher-Order Scalar-Tensor Theories", "abstract": "Most existing theories of dark energy and/or modified gravity, involving a scalar degree of freedom, can be conveniently described within the framework of the Effective Theory of Dark Energy, based on the unitary gauge where the scalar field is uniform. We extend this effective approach by allowing the Lagrangian in unitary gauge to depend on the time derivative of the lapse function. Although this dependence generically signals the presence of an extra scalar degree of freedom, theories that contain only one propagating scalar degree of freedom, in addition to the usual tensor modes, can be constructed by requiring the initial Lagrangian to be degenerate. Starting from a general quadratic action, we derive the dispersion relations for the linear perturbations around Minkowski and a cosmological background. Our analysis directly applies to the recently introduced Degenerate Higher-Order Scalar-Tensor (DHOST) theories. For these theories, we find that one cannot recover a Poisson-like equation in the static linear regime except for the subclass that includes the Horndeski and so-called \"beyond Horndeski\" theories. We also discuss Lorentz-breaking models inspired by Horava gravity.", "keyphrases": ["higher-order scalar-tensor", "gravity", "effective description", "horndeski theory"]}
{"id": "0908.1664", "title": "Gravitational self force in extreme mass-ratio inspirals", "abstract": "This review is concerned with the gravitational self-force acting on a mass particle in orbit around a large black hole. Renewed interest in this old problem is driven by the prospects of detecting gravitational waves from strongly gravitating binaries with extreme mass ratios. We begin here with a summary of recent advances in the theory of gravitational self-interaction in curved spacetime, and proceed to survey some of the ideas and computational strategies devised for implementing this theory in the case of a particle orbiting a Kerr black hole. We review in detail two of these methods: (i) the standard mode-sum method, in which the metric perturbation is regularized mode-by-mode in a multipole decomposition, and (ii) m-mode regularization, whereby individual azimuthal modes of the metric perturbation are regularized in 2+1 dimensions. We discuss several practical issues that arise, including the choice of gauge, the numerical representation of the particle singularity, and how high-frequency contributions near the particle are dealt with in frequency-domain calculations. As an example of a full end-to-end implementation of the mode-sum method, we discuss the computation of the gravitational self-force for eccentric geodesic orbits in Schwarzschild, using a direct integration of the Lorenz-gauge perturbation equations in the time domain. With the computational framework now in place, researchers have recently turned to explore the physical consequences of the gravitational self force; we will describe some preliminary results in this area. An appendix to this review presents, for the first time, a detailed derivation of the regularization parameters necessary for implementing the mode-sum method in Kerr spacetime.", "keyphrases": ["large black hole", "mass ratio", "kerr spacetime", "gravitational self force", "development"]}
{"id": "1611.01948", "title": "GRB Observational Properties", "abstract": "We summarize basic observational properties of gamma-ray bursts (GRBs), including prompt emission properties, afterglow properties, and classification schemes. We also briefly comment on the current physical understanding of these properties.", "keyphrases": ["gamma-ray burst", "grb", "day", "explosion"]}
{"id": "1006.3272", "title": "Bounds on Scalar Masses in Theories of Moduli Stabilization", "abstract": "In recent years it has been realised that pre-BBN decays of moduli can be a significant source of dark matter production, giving a `non-thermal WIMP miracle' and substantially reduced fine-tuning in cosmological axion physics. We study moduli masses and sharpen the claim that moduli dominated the pre-BBN Universe. We conjecture that in any string theory with stabilized moduli there will be at least one modulus field whose mass is of order (or less than) the gravitino mass. Cosmology then generically requires the gravitino mass not be less than about 30 TeV and the cosmological history of the Universe is non-thermal prior to BBN. Stable LSP's produced in these decays can account for the observed dark matter if they are `wino-like.' We briefly consider implications for the LHC, rare decays, and dark matter direct detection and point out that these results could prove challenging for models attempting to realize gauge mediation in string theory.", "keyphrases": ["universe", "string theory", "modulus"]}
{"id": "1908.10637", "title": "Is the lack of power anomaly in the CMB correlated with the orientation of the Galactic plane?", "abstract": "The lack of power at large angular scales in the CMB temperature anisotropy pattern is a feature known to depend on the size of the Galactic mask. Not only the large scale anisotropy power in the CMB is lower than the best-fit \u039bCDM model predicts, but most of the power seems to be localised close to the Galactic plane, making high-Galactic latitude regions more anomalous. We assess how likely the latter behaviour is in a \u039bCDM model by extracting simulations from the Planck 2018 fiducial model. By comparing the former to Planck data in different Galactic masks, we reproduce the anomaly found in previous works, at a statistical significance of \u223c 3 \u03c3. This result suggests the existence of a bizzarre correlation between the particular orientation of the Galaxy and the lack of power anomaly. To test this hypothesis, we perform random rotations of the Planck 2018 data and compare these to similarly rotated \u039bCDM realisations. We find that, among all possible rotations, the lower-tail probability of the observed high-Galactic latitude data variance is still low at the level of 2.8 \u03c3. Furthermore, the lowering trend of the variance when moving from low- to high-Galactic latitude is anomalous in the data at \u223c 3 \u03c3 when comparing to \u039bCDM rotated realisations. This shows that the lack of power at high Galactic latitude is substantially stable against the \"look elsewhere\" effect induced by random rotations of the Galaxy orientation. Moreover, this analysis turns out to be substantially stable if we employ, in place of generic \u039bCDM simulations, a specific set whose variance is constrained to reproduce the observed data variance.", "keyphrases": ["power anomaly", "galactic plane", "angular scale"]}
{"id": "1012.3960", "title": "Markov Chain Monte Carlo analysis to constrain Dark Matter properties with directional detection", "abstract": "Directional detection is a promising dark matter search strategy. Indeed, weakly interacting massive particle (WIMP)-induced recoils would present a direction dependence toward the Cygnus constellation, while background-induced recoils exhibit an isotropic distribution in the Galactic rest frame. Taking advantage of these characteristic features and even in the presence of a sizeable background, it has recently been shown that data from forthcoming directional detectors could lead either to a competitive exclusion or to a conclusive discovery, depending on the value of the WIMP-nucleon cross section. However, it is possible to further exploit these upcoming data by using the strong dependence of the WIMP signal with : the WIMP mass and the local WIMP velocity distribution. Using a Markov chain Monte Carlo analysis of recoil events, we show for the first time the possibility to constrain the unknown WIMP parameters, both from particle physics (mass and cross section) and Galactic halo (velocity dispersion along the three axis), leading to an identification of non-baryonic dark matter.", "keyphrases": ["dark matter", "cross section", "particle physics", "galactic halo"]}
{"id": "1909.10528", "title": "Higgs field in cosmology", "abstract": "The accelerated expansion of the early universe is an integral part of modern cosmology and dynamically realized by the mechanism of inflation. The simplest theoretical description of the inflationary paradigm is based on the assumption of an additional propagating scalar degree of freedom which drives inflation - the inflaton. In most models of inflation the fundamental nature of the inflaton remains unexplained. In the model of Higgs inflation, the inflaton is identified with the Standard Model Higgs boson and connects cosmology with elementary particle physics. A characteristic feature of this model is a non-minimal coupling of the Higgs boson to gravity. I review and discuss several phenomenological and fundamental aspects of this model, including the impact of quantum corrections and the renormalization group, the derivation of initial conditions for Higgs inflation in a quantum cosmological framework and the classical and quantum equivalence of different field parametrizations.", "keyphrases": ["cosmology", "higgs boson", "higgs field", "scalar field"]}
{"id": "1612.09458", "title": "Triggered O star formation in M20 via cloud-cloud collision: Comparisons between high-resolution CO observations and simulations", "abstract": "High-mass star formation is one of the top-priority issues in astrophysics. Recent observational studies are revealing that cloud-cloud collisions may play a role in high-mass star formation in several places in the Milky Way and the Large Magellanic Cloud. The Trifid Nebula M20 is a well known galactic HII region ionized by a single O7.5 star. In 2011, based on the CO observations with NANTEN2 we reported that the O star was formed by the collision between two molecular clouds 0.3,Myr ago. Those observations identified two molecular clouds towards M20, traveling at a relative velocity of 7.5 km/s. This velocity separation implies that the clouds cannot be gravitationally bound to M20, but since the clouds show signs of heating by the stars there they must be spatially coincident with it. A collision is therefore highly possible. In this paper we present the new CO J=1-0 and J=3-2 observations of the colliding clouds in M20 performed with the Mopra and ASTE telescopes. The high resolution observations revealed the two molecular clouds have peculiar spatial and velocity structures, i.e., the spatially complementary distribution between the two clouds and the bridge feature which connects the two clouds in velocity space. Based on a new comparison with numerical models, we find that this complementary distribution is an expected outcome of cloud-cloud collisions, and that the bridge feature can be interpreted as the turbulent gas excited at the interface of the collision. Our results reinforce the cloud-cloud collision scenario in M20.", "keyphrases": ["star formation", "cloud-cloud collision", "molecular cloud"]}
{"id": "2001.06037", "title": "Electromagnetic precursors to gravitational wave events: Numerical simulations of flaring in pre-merger binary neutron star magnetospheres", "abstract": "The detection of gravitational waves from neutron star merger events has opened up a new field of multi-messenger astronomy linking gravitational waves events to short-gamma ray bursts and kilonova afterglows. A further - yet to be discovered - electromagnetic counterpart is precursor emission produced by the non-trivial interaction of the magnetospheres of the two neutron stars prior to merger. By performing special-relativistic force-free simulations of orbiting neutron stars we discuss the effect of different magnetic field orientations and show how the emission can be significantly enhanced by differential motion present in the binary, either due to stellar spins or misaligned stellar magnetospheres. We find that the built-up of twist in the magnetic flux tube connecting the two stars can lead to the repeated emission of powerful flares for a variety of orbital configurations. We also discuss potential coherent radio emission mechanisms in the flaring process.", "keyphrases": ["gravitational wave event", "neutron star", "magnetosphere"]}
{"id": "1307.7083", "title": "Gamma-ray binaries and related systems", "abstract": "After initial claims and a long hiatus, it is now established that several binary stars emit high (0.1-100 GeV) and very high energy (>100 GeV) gamma rays. A new class has emerged called 'gamma-ray binaries', since most of their radiated power is emitted beyond 1 MeV. Accreting X-ray binaries, novae and a colliding wind binary (eta Car) have also been detected - 'related systems' that confirm the ubiquity of particle acceleration in astrophysical sources. Do these systems have anything in common ? What drives their high-energy emission ? How do the processes involved compare to those in other sources of gamma rays: pulsars, active galactic nuclei, supernova remnants ? I review the wealth of observational and theoretical work that have followed these detections, with an emphasis on gamma-ray binaries. I present the current evidence that gamma-ray binaries are driven by rotation-powered pulsars. Binaries are laboratories giving access to different vantage points or physical conditions on a regular timescale as the components revolve on their orbit. I explain the basic ingredients that models of gamma-ray binaries use, the challenges that they currently face, and how they can bring insights into the physics of pulsars. I discuss how gamma-ray emission from microquasars provides a window into the connection between accretion\u2013ejection and acceleration, while eta Car and novae raise new questions on the physics of these objects - or on the theory of diffusive shock acceleration. Indeed, explaining the gamma-ray emission from binaries strains our theories of high-energy astrophysical processes, by testing them on scales and in environments that were generally not foreseen, and this is how these detections are most valuable.", "keyphrases": ["pulsar", "gamma-ray binary", "neutron star"]}
{"id": "1811.12371", "title": "Mixed Non-Gaussianity from Axion-Gauge Field Dynamics", "abstract": "We study scalar-tensor-tensor cross correlation \u27e8\u03b6 hh \u27e9 generated by the dynamics of interacting axion and SU(2) gauge fields during inflation. We quantize the quadratic action and solve the linear equations by taking into account mixing terms in a non-perturbative manner. Combining that with the in-in formalism, we compute contributions from cubic interactions to the bispectrum B_\u03b6 hh. We find that the bispectrum is peaked at the folded configuration, which is a unique feature encoded by the scalar mixing and localized production of tensor modes. With our parameter choice, the amplitude of the bispectrum is k^6 B_\u03b6 hh\u223c 10^-16. The unique shape dependence, together with the parity-violating nature, is thus a distinguishing feature to search for in the CMB observables.", "keyphrases": ["non-gaussianity", "bispectrum", "gravitational wave"]}
{"id": "1303.5379", "title": "New Light Species and the CMB", "abstract": "We consider the effects of new light species on the Cosmic Microwave Background. In the massless limit, these effects can be parameterized in terms of a single number, the relativistic degrees of freedom. We perform a thorough survey of natural, minimal models containing new light species and numerically calculate the precise contribution of each of these models to this number in the framework of effective field theory. After reviewing the relevant details of early universe thermodynamics, we provide a map between the parameters of any particular theory and the predicted effective number of degrees of freedom. We then use this map to interpret the recent results from the Cosmic Microwave Background survey done by the Planck satellite. Using this data, we present new constraints on the parameter space of several models containing new light species. Future measurements of the Cosmic Microwave Background can be used with this map to further constrain the parameter space of all such models.", "keyphrases": ["radiation", "dark radiation", "recent discussion"]}
{"id": "1106.2832", "title": "Active Learning to Overcome Sample Selection Bias: Application to Photometric Variable Star Classification", "abstract": "Despite the great promise of machine-learning algorithms to classify and predict astrophysical parameters for the vast numbers of astrophysical sources and transients observed in large-scale surveys, the peculiarities of the training data often manifest as strongly biased predictions on the data of interest. Typically, training sets are derived from historical surveys of brighter, more nearby objects than those from more extensive, deeper surveys (testing data). This sample selection bias can cause catastrophic errors in predictions on the testing data because a) standard assumptions for machine-learned model selection procedures break down and b) dense regions of testing space might be completely devoid of training data. We explore possible remedies to sample selection bias, including importance weighting (IW), co-training (CT), and active learning (AL). We argue that AL\u2014where the data whose inclusion in the training set would most improve predictions on the testing set are queried for manual follow-up\u2014is an effective approach and is appropriate for many astronomical applications. For a variable star classification problem on a well-studied set of stars from Hipparcos and OGLE, AL is the optimal method in terms of error rate on the testing data, beating the off-the-shelf classifier by 3.4 3.0 interface which allows for easy light curve visualization and querying of external databases. Finally, we apply active learning to classify variable stars in the ASAS survey, finding dramatic improvement in our agreement with the ACVS catalog, from 65.5 classifier's average confidence for the testing set, from 14.6 a few AL iterations.", "keyphrases": ["sample selection bias", "training data", "active learning"]}
{"id": "1307.3720", "title": "Multiwavelength Observations of an Eruptive Flare: Evidence for Blast Waves and Break-out", "abstract": "Images of an east-limb flare on 3 November 2010 taken in the 131 \u00c5 channel of the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory provide a convincing example of a long current sheet below an erupting plasmoid, as predicted by the standard magnetic reconnection model of eruptive flares. However, the 171 \u00c5 and 193 \u00c5 channel images hint at an alternative scenario. These images reveal that large-scale waves with velocity greater than 1000 km/s propagated alongside and ahead of the erupting plasmoid. Just south of the plasmoid, the waves coincided with type-II radio emission, and to the north, where the waves propagated along plume-like structures, there was increased decimetric emission. Initially the cavity around the hot plasmoid expanded. Later, when the erupting plasmoid reached the height of an overlying arcade system, the plasmoid structure changed, and the lower parts of the cavity collapsed inwards. Hot loops appeared alongside and below the erupting plasmoid. We consider a scenario in which the fast waves and the type-II emission were a consequence of a flare blast wave, and the cavity collapse and the hot loops resulted from the break-out of the flux rope through an overlying coronal arcade.", "keyphrases": ["eruptive flare", "blast wave", "break-out"]}
{"id": "1803.02168", "title": "Central accumulation of magnetic flux in massive Seyfert galaxies as a possible engine to trigger ultrahigh energy cosmic rays", "abstract": "In the present paper we investigate the production of ultrahigh energy cosmic rays (UHECRs) from Seyferts. We discuss the UHECR luminosities obtained by two possible engine trigger models: pure radiative transfer and the energy extraction from poloidal magnetic flux. The first case is modeled by Kerr slim disk or Bondi accretion mechanisms. Since it is assumed that the broadband spectra of Seyferts indicate that at least the outer portions of their accretion disks are cold and geometrically thin, and since our results point that the consequent radiative energy transfer is inefficient, we build the second approach based on massive Seyferts with sufficient central poloidal magnetic field to trigger an outflow of magnetically driven charged particles capable to explain the observed UHECRs and gamma rays in Earth experiments from a given Seyfert source.", "keyphrases": ["magnetic flux", "cosmic ray", "accretion disk"]}
{"id": "2004.08393", "title": "Cosmology-insensitive estimate of IGM baryon mass fraction from five localized fast radio bursts", "abstract": "Five fast radio bursts (FRBs), including three apparently non-repeating ones FRB 180924, FRB 181112, and FRB 190523, and two repeaters, FRB 121102 and FRB 180916.J0158+65, have already been localized so far. We apply a method developed recently by us (Li et al. 2019) to these five localized FRBs to give a cosmology-insensitive estimate of the fraction of baryon mass in the IGM, f_ IGM. Using the measured dispersion measure (DM) and luminosity distance d_ L data (inferred from the FRB redshifts and d_ L of type Ia supernovae at the same redshifts) of the five FRBs, we constrain the local f_ IGM = 0.84^+0.16_-0.22 with no evidence of redshift dependence. This cosmology-insensitive estimate of f_ IGM from FRB observations is in excellent agreement with previous constraints using other probes. Moreover, using the three apparently non-repeating FRBs only we get a little looser but consistent result f_ IGM = 0.74^+0.24_-0.18. In these two cases, reasonable estimations for the host galaxy DM contribution (DM_host) can be achieved by modelling it as a function of star formation rate. The constraints on both f_ IGM and DM_host are expected to be significantly improved with the rapid progress in localizing FRBs.", "keyphrases": ["baryon mass", "fast radio burst", "cosmology-insensitive estimate"]}
{"id": "1404.6707", "title": "Defining the Flora Family: Orbital Properties, Reflectance Properties and Age", "abstract": "The Flora family resides in the densely populated inner main belt, bounded in semimajor axis by the \u03bd_6 secular resonance and the Jupiter 3:1 mean motion resonance. The presence of several large families that overlap dynamically with the Floras (e.g., the Vesta, Baptistina, and Nysa-Polana families), and the removal of a significant fraction of Floras via the nearby \u03bd_6 resonance complicates the Flora family's distinction in both proper orbital elements and reflectance properties. Here we use orbital information from the Asteroids Dynamic Site, color information from the Sloan Digital Sky Survey, and albedo information from the Wide-field Infrared Survey Explorer to obtain the median orbital and reflectance properties of the Floras by sampling the core of the family in multidimensional phase space. We find the median Flora SDSS colors to be a^* = 0.126 \u00b1 0.007 and i-z = -0.037 \u00b1 0.007; the median Flora albedo is p_V = 0.291 \u00b1 0.012. These properties allow us to define ranges for the Flora family in orbital and reflectance properties, as required for a detailed dynamical study. We use the young Karin family, for which we have an age determined via direct backward integration of members' orbits, to calibrate the Yarkovsky drift rates for the Flora family without having to estimate the Floras' material properties. The size-dependent dispersion of the Flora members in semimajor axis (the \"V\" plot) then yields an age for the family of 910^+160_-120 My, with the uncertainty dominated by the uncertainty in the material properties of the family members (e.g., density and surface thermal properties). We discuss the effects on our age estimate of two independent processes that both introduce obliquity variations among the family members on short (My) timescales: 1) the capture of Flora members in spin-orbit resonance, and 2) YORP-driven obliquity variation.", "keyphrases": ["flora family", "reflectance property", "age"]}
{"id": "1002.3153", "title": "Astrophysical Measurement of the Equation of State of Neutron Star Matter", "abstract": "We present the first astrophysical measurement of the pressure of cold matter above nuclear saturation density, based on recently determined masses and radii of three neutron stars. The pressure at higher densities are below the predictions of equations of state that account only for nucleonic degrees of freedom, and thus present a challenge to the microscopic theory of neutron star matter.", "keyphrases": ["neutron star matter", "astrophysical measurement", "low-mass x-ray binary", "stellar radius"]}
{"id": "2009.11025", "title": "Note on gauge invariance of second order cosmological perturbations", "abstract": "We study the gauge invariant cosmological perturbations up to second order. We show that there are infinite families of gauge invariant variables at both of the first and second orders. The conversion formulae among different families are shown to be described by a finite number of bases that are gauge invariant. For the second order cosmological perturbations induced by the first order scalar perturbations, we explicitly represent the equations of motion of them in terms of the gauge invariant Newtonian, synchronous and hybrid variables, respectively.", "keyphrases": ["gauge", "second order", "cosmological perturbation", "gravitational wave"]}
{"id": "1909.05466", "title": "Searching for Eccentricity: Signatures of Dynamical Formation in the First Gravitational-Wave Transient Catalogue of LIGO and Virgo", "abstract": "Binary black holes are thought to form primarily via two channels: isolated evolution and dynamical formation. The component masses, spins, and eccentricity of a binary black hole system provide clues to its formation history. We focus on eccentricity, which can be a signature of dynamical formation. Employing the spin-aligned eccentric waveform model SEOBNRE, we perform Bayesian inference to measure the eccentricity of binary black hole merger events in the first Gravitational-Wave Transient Catalogue of LIGO and Virgo. We find that all of these events are consistent with zero eccentricity. We set upper limits on eccentricity ranging from 0.02 to 0.05 with 90 confidence at a reference frequency of 10 Hz. These upper limits do not significantly constrain the fraction of LIGO-Virgo events formed dynamically in globular clusters, because only 5 eccentricity. However, with the Gravitational-Wave Transient Catalogue set to expand dramatically over the coming months, it may soon be possible to significantly constrain the fraction of mergers taking place in globular clusters using eccentricity measurements.", "keyphrases": ["eccentricity", "dynamical formation", "binary black hole"]}
{"id": "0912.4511", "title": "Effective Dark Matter Model: Relic density, CDMS II, Fermi LAT and LHC", "abstract": "The Cryogenic Dark Matter Search recently announced the observation of two signal events with a 77 it is nevertheless suggestive. In this work we present a model-independent analysis on the implication of a positive signal in dark matter scattering off nuclei. Assuming the interaction between (scalar, fermion or vector) dark matter and the standard model induced by unknown new physics at the scale \u039b, we examine various dimension-6 tree-level induced operators and constrain them using the current experimental data, e.g. the WMAP data of the relic abundance, CDMS II direct detection of the spin-independent scattering, and indirect detection data (Fermi LAT cosmic gamma-ray), etc. Finally, the LHC reach is also explored.", "keyphrases": ["fermi lat", "relic abundance", "dark matter particle", "matter-standard model interaction"]}
{"id": "1204.6206", "title": "Did the ancient egyptians record the period of the eclipsing binary Algol - the Raging one?", "abstract": "The eclipses in binary stars give precise information of orbital period changes. Goodricke discovered the 2.867 days period in the eclipses of Algol in the year 1783. The irregular orbital period changes of this longest known eclipsing binary continue to puzzle astronomers. The mass transfer between the two members of this binary should cause a long-term increase of the orbital period, but observations over two centuries have not confirmed this effect. Here, we present evidence indicating that the period of Algol was 2.850 days three millenia ago. For religious reasons, the ancient Egyptians have recorded this period into the Cairo Calendar, which describes the repetitive changes of the Raging one. Cairo Calendar may be the oldest preserved historical document of the discovery of a variable star.", "keyphrases": ["ancient egyptians", "eclipse", "binary algol"]}
{"id": "0912.1609", "title": "Dark Energy and Dark Matter unification via superfluid Chaplygin gas", "abstract": "A new model describing the dark sector of the universe is established. The model involves Bose-Einstein condensate (BEC) as dark energy (DE) and an excited state above it as dark matter (DM). The condensate is assumed to have a negative pressure and is embodied as an exotic fluid with Chaplygin equation of state. Excitations are described as a quasiparticle gas. It is shown that the model is not in disagreement with the current observations of the cosmic acceleration. The model predicts increase of the effective cosmological constant and a complete disappearance of the matter at the far future.", "keyphrases": ["superfluid chaplygin gas", "bose-einstein condensate", "dark energy"]}
{"id": "1206.1602", "title": "Galaxy correlations and the BAO in a void universe: structure formation as a test of the Copernican Principle", "abstract": "A suggested solution to the dark energy problem is the void model, where accelerated expansion is replaced by Hubble-scale inhomogeneity. In these models, density perturbations grow on a radially inhomogeneous background. This large scale inhomogeneity distorts the spherical Baryon Acoustic Oscillation feature into an ellipsoid which implies that the bump in the galaxy correlation function occurs at different scales in the radial and transverse correlation functions. We compute these for the first time, under the approximation that curvature gradients do not couple the scalar modes to vector and tensor modes. The radial and transverse correlation functions are very different from those of the concordance model, even when the models have the same average BAO scale. This implies that if void models are fine-tuned to satisfy average BAO data, there is enough extra information in the correlation functions to distinguish a void model from the concordance model. We expect these new features to remain when the full perturbation equations are solved, which means that the radial and transverse galaxy correlation functions can be used as a powerful test of the Copernican Principle.", "keyphrases": ["universe", "structure formation", "density perturbation"]}
{"id": "2009.01832", "title": "A geometric origin for quasi-periodic oscillations in black hole X-ray binaries", "abstract": "We expand the relativistic precession model to include nonequatorial and eccentric trajectories and apply it to quasi-periodic oscillations (QPOs) in black hole X-ray binaries (BHXRBs) and associate their frequencies with the fundamental frequencies of the general case of nonequatorial (with Carter's constant, Q\u2260 0) and eccentric (e\u2260 0) particle trajectories, around a Kerr black hole. We study cases with either two or three simultaneous QPOs and extract the parameters {e, r_p, a, Q}, where r_p is the periastron distance of the orbit, and a is the spin of the black hole. We find that the orbits with [Q=0-4] should have e\u2272 0.5 and r_p \u223c 2-20 for the observed range of QPO frequencies, where a \u2208 [0,1], and that the spherical trajectories {e=0, Q \u22600} with Q=2-4 should have r_s \u223c 3-20. We find nonequatorial eccentric solutions for both M82 X-1 and GROJ 1655-40. We see that these trajectories, when taken together, span a torus region and give rise to a strong QPO signal. For two simultaneous QPO cases, we found equatorial eccentric orbit solutions for XTEJ 1550-564, 4U 1630-47, and GRS 1915+105, and spherical orbit solutions for BHXRBs M82 X-1 and XTEJ 1550-564. We also show that the eccentric orbit solution fits the Psaltis-Belloni-Klis correlation observed in BHXRB GROJ 1655-40. Our analysis of the fluid flow in the relativistic disk edge suggests that instabilities cause QPOs to originate in the torus region. We also present some useful formulae for trajectories and frequencies of spherical and equatorial eccentric orbits.", "keyphrases": ["quasi-periodic oscillation", "black hole", "hole x-ray binary"]}
{"id": "1804.09687", "title": "Exploring the posterior surface of the large scale structure reconstruction", "abstract": "The large scale structure (LSS) of the universe is generated by the linear density gaussian modes, which are evolved into the observed nonlinear LSS. The posterior surface of the modes is convex in the linear regime, leading to a unique global maximum (MAP), but this is no longer guaranteed in the nonlinear regime. In this paper we investigate the nature of posterior surface using the recently developed MAP reconstruction method, with a simplified but realistic N-body simulation as the forward model. The reconstruction method uses optimization with analytic gradients from back-propagation through the simulation. For low noise cases we recover the initial conditions well into the nonlinear regime (k\u223c 1 h/Mpc) nearly perfectly. We show that the large scale modes can be recovered more precisely than the linear expectation, which we argue is a consequence of nonlinear mode coupling. For noise levels achievable with current and planned LSS surveys the reconstruction cannot recover very small scales due to noise. We see some evidence of non-convexity, specially for smaller scales where the non-injective nature of the mappings: several very different initial conditions leading to the same near perfect final data reconstruction. We investigate the nature of these phenomena further using a 1-d toy gravity model, where many well separated local maximas are found to have identical data likelihood but differ in the prior. We also show that in 1-d the prior favors some solutions over the true solution, though no clear evidence of these in 3-d. Our main conclusion is that on very small scales and for a very low noise the posterior surface is multi-modal and the global maximum may be unreachable with standard methods, while for realistic noise levels in the context of the current and next generation LSS surveys MAP optimization method is likely to be nearly optimal.", "keyphrases": ["posterior surface", "reconstruction", "initial condition", "mpc"]}
{"id": "1403.4811", "title": "Remarks about the Tensor Mode Detection by the BICEP2 Collaboration and the Super-Planckian Excursions of the Inflaton Field", "abstract": "The recent detection by the BICEP2 collaboration of a high level of tensor modes has relevant implications which we briefly discuss in this short note. In particular, the large angle CMB B- mode polarisation seems to imply problematic super-Planckian excursions of the inflaton field. We provide some comments about this point and in particular we stress a natural resolution to it: given our current (and probably future) observational ignorance about the true source of the scalar perturbations, one should abandon the theoretical prejudice that they are associated to the inflaton fluctuations.", "keyphrases": ["super-planckian excursion", "inflaton field", "scalar perturbation"]}
{"id": "1404.2024", "title": "The Link between Magnetic Fields and Cloud/Star Formation", "abstract": "The question whether magnetic fields play an important role in the processes of molecular cloud and star formation has been debated for decades. Recent observations have revealed a simple picture that may help illuminate these questions: magnetic fields have a tendency to preserve their orientation at all scales that have been probed - from 100-pc scale inter-cloud media down to sub-pc scale cloud cores. This ordered morphology has implications for the way in which self-gravity and turbulence interact with magnetic fields: both gravitational contraction and turbulent velocities should be anisotropic, due to the influence of dynamically important magnetic fields. Such anisotropy is now observed. Here we review these recent observations and discuss how they can improve our understanding of cloud/star formation.", "keyphrases": ["magnetic field", "cloud", "star formation"]}
{"id": "1007.0658", "title": "Neutrino physics from precision cosmology", "abstract": "Cosmology provides an excellent laboratory for testing various aspects of neutrino physics. Here, I review the current status of cosmological searches for neutrino mass, as well as other properties of neutrinos. Future cosmological probes of neutrino properties are also discussed in detail.", "keyphrases": ["cosmology", "neutrino physics", "dark matter"]}
{"id": "2002.06492", "title": "Image formation for extended sources with the solar gravitational lens", "abstract": "We study the image formation process with the solar gravitational lens (SGL) in the case of an extended, resolved source. An imaging telescope, modeled as a convex lens, is positioned within the image cylinder formed by the light received from the source. In the strong interference region of the SGL, this light is greatly amplified, forming the Einstein ring around the Sun, representing a distorted image of the extended source. We study the intensity distribution within the Einstein ring observed in the focal plane of the convex lens. For any particular telescope position in the image plane, we model light received from the resolved source as a combination of two signals: light received from the directly imaged region of the source and light from the rest of the source. We also consider the case when the telescope points away from the extended source or, equivalently, it observes light from sources in sky positions that are some distance away from the extended source, but still in its proximity. At even larger distances from the optical axis, in the weak interference or geometric optics regions, our approach recovers known models related to microlensing, but now obtained via the wave-optical treatment. We then derive the power of the signal and related photon fluxes within the annulus that contains the Einstein ring of the extended source, as seen by the imaging telescope. We discuss the properties of the deconvolution process, especially its effects on noise in the recovered image. We compare anticipated signals from realistic exoplanetary targets against estimates of noise from the solar corona and estimate integration times needed for the recovery of high-quality images of faint sources. The results demonstrate that the SGL offers a unique, realistic capability to obtain resolved images of exoplanets in our galactic neighborhood.", "keyphrases": ["extended source", "galactic neighborhood", "angular resolution"]}
{"id": "1106.1267", "title": "Chameleon stars", "abstract": "We consider a gravitating spherically symmetric configuration consisting of a scalar field non-minimally coupled to ordinary matter in the form of a perfect fluid. For this system we find static, regular, asymptotically flat solutions for both relativistic and non-relativistic cases. It is shown that the presence of the non-minimal interaction leads to substantial changes both in the radial matter distribution of the star and in the star's total mass. A simple stability test indicates that, for the choice of parameters used in the paper, the solutions are unstable.", "keyphrases": ["configuration", "ordinary matter", "fluid", "chameleon star", "influence"]}
{"id": "1203.3213", "title": "From cosmic deceleration to acceleration: new constraints from SN Ia and BAO/CMB", "abstract": "We use type Ia supernovae (SN Ia) data in combination with recent baryonic acoustic oscillations (BAO) and cosmic microwave background (CMB) observations to constrain a kink-like parametrization of the deceleration parameter (q). This q-parametrization can be written in terms of the initial (q_i) and present (q_0) values of the deceleration parameter, the redshift of the cosmic transition from deceleration to acceleration (z_t) and the redshift width of such transition (\u03c4). By assuming a flat space geometry, q_i=1/2 and adopting a likelihood approach to deal with the SN Ia data we obtain, at the 68 \u03c4=0.47^+0.16_-0.20 and q_0=-0.31^+0.11_-0.11 when we combine BAO/CMB observations with SN Ia data processed with the MLCS2k2 light-curve fitter. When in this combination we use the SALT2 fitter we get instead, at the same C.L.: z_t=0.64^+0.13_-0.07, \u03c4=0.36^+0.11_-0.17 and q_0=-0.53^+0.17_-0.13. Our results indicate, with a quite general and model independent approach, that MLCS2k2 favors Dvali-Gabadadze-Porrati-like cosmological models, while SALT2 favors \u039bCDM-like ones. Progress in determining the transition redshift and/or the present value of the deceleration parameter depends crucially on solving the issue of the difference obtained when using these two light-curve fitters.", "keyphrases": ["deceleration", "bao", "redshift"]}
{"id": "2006.07071", "title": "Astrochemistry During the Formation of Stars", "abstract": "Star-forming regions show a rich and varied chemistry, including the presence of complex organic molecules - both in the cold gas distributed on large scales, and in the hot regions close to young stars where protoplanetary disks arise. Recent advances in observational techniques have opened new possibilities for studying this chemistry. In particular, the Atacama Large Millimeter/submillimeter Array (ALMA) has made it possible to study astrochemistry down to Solar System size scales, while also revealing molecules of increasing variety and complexity. In this review, we discuss recent observations of the chemistry of star-forming environments, with a particular focus on complex organic molecules, taking context from the laboratory experiments and chemical models that they have stimulated. The key takeaway points are: The physical evolution of individual sources plays a crucial role in their inferred chemical signatures, and remains an important area for observations and models to elucidate. Comparisons of the abundances measured toward different star-forming environments (high-mass versus low-mass, Galactic center versus Galactic disk) reveal a remarkable similarity, an indication that the underlying chemistry is relatively independent of variations in their physical conditions. Studies of molecular isotopologs in star-forming regions provide a link with measurements in our own Solar System, and thus may shed light on the chemical similarities and differences expected in other planetary systems.", "keyphrases": ["star", "star-forming region", "high-mass", "astrochemistry"]}
{"id": "1309.5695", "title": "Intermediate homogenization of the Universe and the problem of gravitational entropy", "abstract": "This paper studies intermediate homogenization of inhomogeneous cosmological models. It shows that spherically symmetric models, regardless of the equation of state, can undergo intermediate homogenization, i.e. a model can approach a homogeneous and isotropic state (which acts as a saddle point) from a relatively wide range of initial inhomogeneous conditions. The homogenization is not permanent - just temporary. Eventually the model evolves toward a future inhomogeneous state. We also looked at the problem of the gravitational entropy. All definitions of entropy that we checked give decreasing gravitational entropy during the homogenization process. Thus, we should either accept that gravitational entropy can decrease or try to define it in other ways than just via density gradients, as these decrease during homogenization.", "keyphrases": ["gravitational entropy", "inhomogeneous cosmological model", "saddle point", "intermediate homogenization"]}
{"id": "1204.4409", "title": "Large non-Gaussian Halo Bias from Single Field Inflation", "abstract": "We calculate Large Scale Structure observables for non-Gaussianity arising from non-Bunch-Davies initial states in single field inflation. These scenarios can have substantial primordial non-Gaussianity from squeezed (but observable) momentum configurations. They generate a term in the halo bias that may be more strongly scale-dependent than the contribution from the local ansatz. We also discuss theoretical considerations required to generate an observable signature.", "keyphrases": ["non-gaussianity", "halo bias", "single field inflation", "initial state"]}
{"id": "0909.0866", "title": "More about the Tolman-Oppenheimer-Volkoff equations for the generalized Chaplygin gas", "abstract": "We investigate the Tolman-Oppenheimer-Volkoff equations for the generalized Chaplygin gas with the aim of extending the findings of V. Gorini, U. Moschella, A. Y. Kamenshchik, V. Pasquier, and A. A. Starobinsky [Phys. Rev. D 78, 064064 (2008)]. We study both the standard case, where we reproduce some previous results, and the phantom case. In the phantom case we show that even a superluminal group velocity arising for \u03b1 > 1 cannot prevent the divergence of the pressure at a finite radial distance. Finally, we investigate how a modification of the generalized Chaplygin gas equation of state, required by causality arguments at densities very close to \u039b, affects the results found so far.", "keyphrases": ["tolman-oppenheimer-volkoff equation", "generalized chaplygin gas", "energy star", "dark energy"]}
{"id": "1804.09092", "title": "Fast Radio Bursts", "abstract": "More than a decade after their discovery, astronomical Fast Radio Bursts remain enigmatic. They are known to occur at \"cosmological\" distances, implying large energy and radiated power, extraordinarily high brightness and coherent emission. Yet their source objects, the means by which energy is released and their radiation processes remain unknown. This review is organized around these unanswered questions.", "keyphrases": ["fast radio bursts", "frbs", "neutron star"]}
{"id": "1111.2721", "title": "Inhomogeneous non-Gaussianity", "abstract": "We propose a method to probe higher-order correlators of the primordial density field through the inhomogeneity of local non-Gaussian parameters, such as f_NL, measured within smaller patches of the sky. Correlators between n-point functions measured in one patch of the sky and k-point functions measured in another patch depend upon the (n+k)-point functions over the entire sky. The inhomogeneity of non-Gaussian parameters may be a feasible way to detect or constrain higher-order correlators in local models of non-Gaussianity, as well as to distinguish between single and multiple-source scenarios for generating the primordial density perturbation, and more generally to probe the details of inflationary physics.", "keyphrases": ["non-gaussianity", "higher-order correlator", "patch"]}
{"id": "1902.10149", "title": "Primordial power spectrum and cosmology from black-box galaxy surveys", "abstract": "We propose a new, likelihood-free approach to inferring the primordial matter power spectrum and cosmological parameters from arbitrarily complex forward models of galaxy surveys where all relevant statistics can be determined from numerical simulations, i.e. black-boxes. Our approach, which we call simulator expansion for likelihood-free inference (SELFI), builds upon approximate Bayesian computation using a novel effective likelihood, and upon the linearisation of black-box models around an expansion point. Consequently, we obtain simple \"filter equations\" for an effective posterior of the primordial power spectrum, and a straightforward scheme for cosmological parameter inference. We demonstrate that the workload is computationally tractable, fixed a priori, and perfectly parallel. As a proof of concept, we apply our framework to a realistic synthetic galaxy survey, with a data model accounting for physical structure formation and incomplete and noisy galaxy observations. In doing so, we show that the use of non-linear numerical models allows the galaxy power spectrum to be safely fitted up to at least k_max = 0.5 h/Mpc, outperforming state-of-the-art backward-modelling techniques by a factor of \u223c 5 in the number of modes used. The result is an unbiased inference of the primordial matter power spectrum across the entire range of scales considered, including a high-fidelity reconstruction of baryon acoustic oscillations. It translates into an unbiased and robust inference of cosmological parameters. Our results pave the path towards easy applications of likelihood-free simulation-based inference in cosmology. We have made our code pySELFI and our data products publicly available at http://pyselfi.florent-leclercq.eu.", "keyphrases": ["cosmology", "selfi", "expansion point", "primordial power spectrum"]}
{"id": "1405.0272", "title": "Fitting the Galactic Center Gamma-Ray Excess with Cascade Annihilations", "abstract": "The apparent excess of gamma rays in an extended region in the direction of the galactic center has a spatial distribution and amplitude that are suggestive of dark matter annihilations. If this excess is indeed due to dark matter annihilations, it would indicate the presence of both dark matter and an additional particle beyond the Standard Model that mediates the interactions between the dark matter and Standard Model states. We introduce reference models describing dark matter annihilation to pairs of these new mediators, which decouples the SM-mediator coupling from the thermal annihilation cross section and easily explains the lack of direct detection signals. We determine the parameter regions that give good descriptions of the gamma ray excess for several motivated choices of mediator couplings to the SM. We find fermion dark matter with mass 7-26 GeV and a dark vector mediator, or scalar dark matter in the 10-50 GeV range (Higgs portal mediator) or 10-65 GeV range (gluophilic mediator) can provide a comparable or improved fit, compared to the case of direct annihilation. We demonstrate that these models can easily satisfy all constraints from collider experiments, direct detection, and cosmology.", "keyphrases": ["dark matter", "galactic center excess", "astrophysical origin"]}
{"id": "1503.04467", "title": "A Consistency Relation for the Observed Galaxy Bispectrum and the Local non-Gaussianity from Relativistic Corrections", "abstract": "We obtain a consistency relation for the observed three-point correlator of galaxies. It includes relativistic effects and it is valid in the squeezed limit. Furthermore, the consistency relation is non-perturbative and can be used at arbitrarily small scales for the short modes. Our results are also useful to compute the non-linear relativistic corrections which induce a signal in the observations that might be misinterpreted as primordial non-Gaussianity with a local shape. We estimate the effective local non-Gaussianity parameter from the relativistic corrections. The exact value depends on the redshift and the magnification bias. At redshift of z = 1, in the absence of magnification bias, we get f^ GR_ NL\u2243 - 3.7.", "keyphrases": ["observed galaxy bispectrum", "non-gaussianity", "relativistic effect", "universe"]}
{"id": "0911.5108", "title": "Cosmic Discordance: Detection of a modulation in the primordial fluctuation spectrum", "abstract": "As a test of the standard inflationary cosmology, which generically predicts nearly scale-invariant spectrum of primordial curvature fluctuations, we perform Markov-Chain Monte-Carlo analysis to search for possible modulations in the power spectrum and determine its shape together with the cosmological parameters using cosmic microwave background radiation data. By incorporating various three-parameter features on the simple power-law spectrum, we find an oscillatory modulation localized around the comoving wavenumber k\u2243 0.009Mpc^-1 at 99.995 log-likelihood as much as -\u0394 2ln L\u2261\u0394\u03c7^2_ eff=-22. This feature can be detected even if we use only the cross correlation between the temperature and the E-mode polarization anisotropies.", "keyphrases": ["power spectrum", "cosmological parameter", "anomaly"]}
{"id": "1109.1176", "title": "Evolution, nucleosynthesis and yields of low mass AGB stars at different metallicities (II): the FRUITY database", "abstract": "By using updated stellar low mass stars models, we can systematically investigate the nucleosynthesis processes occurring in AGB stars, when these objects experience recurrent thermal pulses and third dredge-up episodes. In this paper we present the database dedicated to the nucleosynthesis of AGB stars: the FRUITY (FRANEC Repository of Updated Isotopic Tables Yields) database. An interactive web-based interface allows users to freely download the full (from H to Bi) isotopic composition, as it changes after each third dredge-up episode and the stellar yields the models produce. A first set of AGB models, having masses in the range 1.5 < M/Msun < 3.0 and metallicities 1e-3 < Z < 2e-2, is discussed here. For each model, a detailed description of the physical and the chemical evolution is provided. In particular, we illustrate the details of the s-process and we evaluate the theoretical uncertainties due to the parametrization adopted to model convection and mass loss. The resulting nucleosynthesis scenario is checked by comparing the theoretical [hs/ls] and [Pb/hs] ratios to those obtained from the available abundance analysis of s-enhanced stars. On the average, the variation with the metallicity of these spectroscopic indexes is well reproduced by theoretical models, although the predicted spread at a given metallicity is substantially smaller than the observed one. Possible explanations for such a difference are briefly discussed. An independent check of the third dredge-up efficiency is provided by the C-stars luminosity function. Consequently, theoretical C-stars luminosity functions for the Galactic disk and the Magellanic Clouds have been derived. We generally find a good agreement with observations.", "keyphrases": ["nucleosynthesis", "agb star", "metallicity"]}
{"id": "1108.2404", "title": "A Method for Measuring (Slopes of) the Mass Profiles of Dwarf Spheroidal Galaxies", "abstract": "We introduce a method for measuring the slopes of mass profiles within dwarf spheroidal (dSph) galaxies directly from stellar spectroscopic data and without adopting a dark matter halo model. Our method combines two recent results: 1) spherically symmetric, equilibrium Jeans models imply that the product of halflight radius and (squared) stellar velocity dispersion provides an estimate of the mass enclosed within the halflight radius of a dSph stellar component, and 2) some dSphs have chemo-dynamically distinct stellar subcomponents that independently trace the same gravitational potential. We devise a statistical method that uses measurements of stellar positions, velocities and spectral indices to distinguish two dSph stellar subcomponents and to estimate their individual halflight radii and velocity dispersions. For a dSph with two detected stellar subcomponents, we obtain estimates of masses enclosed at two discrete points in the same mass profile, immediately defining a slope. Applied to published spectroscopic data, our method distinguishes stellar subcomponents in the Fornax and Sculptor dSphs, for which we measure slopes \u0393\u2261\u0394log M / \u0394log r=2.61_-0.37^+0.43 and \u0393=2.95_-0.39^+0.51, respectively. These values are consistent with 'cores' of constant density within the central few-hundred parsecs of each galaxy and rule out `cuspy' Navarro-Frenk-White (NFW) profiles (dlog M/dlog r \u2264 2 at all radii) with significance 96 method tends systematically to overestimate the mass of the inner stellar subcomponent to a greater degree than that of the outer stellar subcomponent, and therefore to underestimate the slope\u0393(implying that the stated NFW exclusion levels are conservative).", "keyphrases": ["dark matter", "galactic scale", "cusp-core problem"]}
{"id": "1703.09573", "title": "Observational constraints on generalized Proca theories", "abstract": "In a model of the late-time cosmic acceleration within the framework of generalized Proca theories, there exists a de Sitter attractor preceded by the dark energy equation of state w_ DE=-1-s, where s is a positive constant. We run the Markov-Chain-Monte-Carlo code to confront the model with the observational data of Cosmic Microwave Background (CMB), baryon acoustic oscillations, supernovae type Ia, and local measurements of the Hubble expansion rate for the background cosmological solutions and obtain the bound s=0.254^+ 0.118_-0.097 at 95 additional parameter s to those in the \u039b-Cold-Dark-Matter (\u039bCDM) model allows to reduce tensions of the Hubble constant H_0 between the CMB and the low-redshift measurements. Including the cosmic growth data of redshift-space distortions in the galaxy power spectrum and taking into account no-ghost and stability conditions of cosmological perturbations, we find that the bound on s is shifted to s=0.16^+0.08_-0.08 (95 hence the model with s>0 is still favored over the \u039bCDM model. Apart from the quantities s, H_0 and the today's matter density parameter \u03a9_m0, the constraints on other model parameters associated with perturbations are less stringent, reflecting the fact that there are different sets of parameters that give rise to a similar cosmic expansion and growth history.", "keyphrases": ["proca theory", "cosmic expansion", "growth history", "dark energy model", "cdm model"]}
{"id": "1805.11919", "title": "Dark energy in scalar-vector-tensor theories", "abstract": "The scalar-vector-tensor theories with second-order equations of motion can accommodate both Horndeski and generalized Proca theories as specific cases. In the presence of a perfect fluid, we study the cosmology in such a most general scheme of scalar-vector-tensor theories with parity invariance by paying particular attention to the application to dark energy. We obtain a closed-form expression of the background equations of motion by using coefficients appearing in the second-order action of scalar perturbations. We also derive conditions for the absence of ghost and Laplacian instabilities of tensor and vector perturbations and show that the existence of matter does not substantially modify the stabilities of dynamical degrees of freedom in the small-scale limit. On the other hand, the sound speed of scalar perturbations is affected by the presence of matter. Employing the quasi-static approximation for scalar perturbations deep inside the sound horizon, we derive analytic expressions of Newtonian and weak lensing gravitational potentials as well as two scalar perturbations arising from the scalar and vector fields. We apply our general framework to dark energy theories with the tensor propagation speed equivalent to the speed of light and show that the observables associated with the growth of matter perturbations and weak lensing potentials are generally affected by intrinsic vector modes and by interactions between scalar and vector fields.", "keyphrases": ["scalar-vector-tensor theory", "cosmology", "parity invariance", "dark energy"]}
{"id": "2102.02215", "title": "Stationary scalar clouds supported by rapidly-rotating acoustic black holes in a photon-fluid model", "abstract": "It has recently been proved that, in the presence of vortex flows, the fluctuation dynamics of a rotating photon-fluid model is governed by the Klein-Gordon equation of an effective massive scalar field in a (2+1)-dimensional acoustic black-hole spacetime. Interestingly, it has been demonstrated numerically that the rotating acoustic black hole, like the familiar Kerr black-hole spacetime, may support spatially regular stationary density fluctuations (linearized acoustic scalar `clouds') in its exterior regions. In particular, it has been shown that the composed rotating-acoustic-black-hole-stationary-scalar-field configurations of the photon-fluid model exist in the narrow dimensionless regime \u03b1\u2261\u03a9_0/m\u03a9_H\u2208(1,\u03b1_max) with \u03b1_max\u2243 1.08 [here \u03a9_H is the angular velocity of the black-hole horizon and {\u03a9_0,m} are respectively the effective proper mass and the azimuthal harmonic index of the acoustic scalar field]. In the present paper we use analytical techniques in order to explore the physical and mathematical properties of the acoustic scalar clouds of the photon-fluid model in the regime \u03a9_Hr_H\u226b1 of rapidly-spinning central supporting acoustic black holes. In particular, we derive a remarkably compact analytical formula for the discrete resonance spectrum {\u03a9_0(\u03a9_H,m;n)} which characterizes the stationary bound-state acoustic scalar clouds of the photon-fluid model. Interestingly, it is proved that the critical (maximal) mass parameter \u03b1_max, which determines the regime of existence of the composed acoustic-black-hole-stationary-bound-state-massive-scalar-field configurations, is given by the exact dimensionless relation \u03b1_max=\u221a(3227).", "keyphrases": ["acoustic black hole", "photon-fluid model", "black-hole spacetime"]}
{"id": "2111.08750", "title": "Gravitational Wave Gastronomy", "abstract": "The symmetry breaking of grand unified gauge groups in the early Universe often leaves behind relic topological defects such as cosmic strings, domain walls, or monopoles. For some symmetry breaking chains, hybrid defects can form where cosmic strings attach to domain walls or monopoles attach to strings. In general, such hybrid defects are unstable, with one defect \"eating\" the other via the conversion of its rest mass into the other's kinetic energy and subsequently decaying via gravitational waves. In this work, we determine the gravitational wave spectrum from 1) the destruction of a cosmic string network by the nucleation of monopoles which cut up and \"eat\" the strings, 2) the collapse and decay of a monopole-string network by strings that \"eat\" the monopoles, 3) the destruction of a domain wall network by the nucleation of string-bounded holes on the wall that expand and \"eat\" the wall, and 4) the collapse and decay of a string-bounded wall network by walls that \"eat\" the strings. We call the gravitational wave signals produced from the \"eating\" of one topological defect by another gravitational wave gastronomy. We find that the four gravitational wave gastronomy signals considered yield unique spectra that can be used to narrow down the SO(10) symmetry breaking chain to the Standard Model and the scales of symmetry breaking associated with the consumed topological defects. Moreover, the systems we consider are unlikely to have a residual monopole or domain wall problem.", "keyphrases": ["cosmic string", "string", "gravitational wave gastronomy"]}
{"id": "1312.2101", "title": "PkANN - II. A non-linear matter power spectrum interpolator developed using artificial neural networks", "abstract": "In this paper we introduce PkANN, a freely available software package for interpolating the non-linear matter power spectrum, constructed using Artificial Neural Networks (ANNs). Previously, using Halofit to calculate matter power spectrum, we demonstrated that ANNs can make extremely quick and accurate predictions of the power spectrum. Now, using a suite of 6380 N-body simulations spanning 580 cosmologies, we train ANNs to predict the power spectrum over the cosmological parameter space spanning 3\u03c3 confidence level (CL) around the concordance cosmology. When presented with a set of cosmological parameters (\u03a9_ m h^2, \u03a9_ b h^2, n_s, w, \u03c3_8, \u2211 m_\u03bd and redshift z), the trained ANN interpolates the power spectrum for z\u22642 at sub-per cent accuracy for modes up to k\u22640.9 hMpc^-1. PkANN is faster than computationally expensive N-body simulations, yet provides a worst-case error <1 per cent fit to the non-linear matter power spectrum deduced through N-body simulations. The overall precision of PkANN is set by the accuracy of our N-body simulations, at 5 per cent level for cosmological models with \u2211 m_\u03bd<0.5 eV for all redshifts z\u22642. For models with \u2211 m_\u03bd>0.5 eV, predictions are expected to be at 5 (10) per cent level for redshifts z>1 (z\u22641). The PkANN interpolator may be freely downloaded from http://zuserver2.star.ucl.ac.uk/ fba/PkANN", "keyphrases": ["power spectrum", "artificial neural network", "pkann"]}
{"id": "2006.11525", "title": "Mapping the Universe Expansion: Enabling percent-level measurements of the Hubble Constant with a single binary neutron-star merger detection", "abstract": "The joint observation of the gravitational-wave and electromagnetic signal from the binary neutron-star merger GW170817 allowed for a new independent measurement of the Hubble constant H_0, albeit with an uncertainty of about 15% at 1\u03c3. Observations of similar sources with a network of future detectors will allow for more precise measurements of H_0. These, however, are currently largely limited by the intrinsic degeneracy between the luminosity distance and the inclination of the source in the gravitational-wave signal. We show that the higher-order modes in gravitational waves can be used to break this degeneracy in astrophysical parameter estimation in both the inspiral and post-merger phases of a neutron star merger. We show that for systems at distances similar to GW170817, this method enables percent-level measurements of H_0 with a single detection. This would permit the study of time variations and spatial anisotropies of H_0 with unprecedented precision. We investigate how different network configurations affect measurements of H_0, and discuss the implications in terms of science drivers for the proposed 2.5- and third-generation gravitational-wave detectors. Finally, we show that the precision of H_0 measured with these future observatories will be solely limited by redshift measurements of electromagnetic counterparts.", "keyphrases": ["percent-level measurement", "hubble constant", "gravitational wave"]}
{"id": "1209.3662", "title": "Power spectra in the eikonal approximation with adiabatic and non-adiabatic modes", "abstract": "We use the so-called eikonal approximation, recently introduced in the context of cosmological perturbation theory, to compute power spectra for multi-component fluids. We demonstrate that, at any given order in standard perturbation theory, multipoint power spectra do not depend on the large-scale adiabatic modes. Moreover, we employ perturbation theories to decipher how nonadiabatic modes, such as a relative velocity between two different components, damp the small-scale matter power spectrum, a mechanism recently described in the literature. In particular, we do an explicit calculation at 1-loop order of this effect. While the 1-loop result eventually breaks down, we show how the damping effect can be fully captured by the help of the eikonal approximation. A relative velocity not only induces mode damping but also creates large-scale anisotropic modulations of the matter power spectrum amplitude. We illustrate this for the Local Group environment.", "keyphrases": ["eikonal approximation", "fluid", "relative velocity", "power spectra"]}
{"id": "1803.07867", "title": "Transit Photometry as an Exoplanet Discovery Method", "abstract": "Photometry with the transit method has arguably been the most successful exoplanet discovery method to date. A short overview about the rise of that method to its present status is given. The method's strength is the rich set of parameters that can be obtained from transiting planets, in particular in combination with radial velocity observations; the basic principles of these parameters are given. The method has however also drawbacks, which are the low probability that transits appear in randomly oriented planet systems, and the presence of astrophysical phenomena that may mimic transits and give rise to false detection positives. In the second part we outline the main factors that determine the design of transit surveys, such as the size of the survey sample, the temporal coverage, the detection precision, the sample brightness and the methods to extract transit events from observed light curves. Lastly, an overview over past, current and future transit surveys is given. For these surveys we indicate their basic instrument configuration and their planet catch, including the ranges of planet sizes and stellar magnitudes that were encountered. Current and future transit detection experiments concentrate primarily on bright or special targets, and we expect that the transit method remains a principal driver of exoplanet science, through new discoveries to be made and through the development of new generations of instruments.", "keyphrases": ["exoplanet discovery method", "date", "transit event", "transit photometry"]}
{"id": "1611.00368", "title": "Chiral Effective Theory of Dark Matter Direct Detection", "abstract": "We present the effective field theory for dark matter interactions with the visible sector that is valid at scales of O(1 GeV). Starting with an effective theory describing the interactions of fermionic and scalar dark matter with quarks, gluons and photons via higher dimension operators that would arise from dimension-five and dimension-six operators above electroweak scale, we perform a nonperturbative matching onto a heavy baryon chiral perturbation theory that describes dark matter interactions with light mesons and nucleons. This is then used to obtain the coefficients of the nuclear response functions using a chiral effective theory description of nuclear forces. Our results consistently keep the leading contributions in chiral counting for each of the initial Wilson coefficients.", "keyphrases": ["dark matter", "effective field theory", "gluon", "chiral counting"]}
{"id": "1105.2073", "title": "Dark Atoms: Asymmetry and Direct Detection", "abstract": "We present a simple UV completion of Atomic Dark Matter (aDM) in which heavy right-handed neutrinos decay to induce both dark and lepton number densities. This model addresses several outstanding cosmological problems: the matter/anti-matter asymmetry, the dark matter abundance, the number of light degrees of freedom in the early universe, and the smoothing of small-scale structure. Additionally, this realization of aDM may reconcile the CoGeNT excess with recently published null results and predicts a signal in the CRESST Oxygen band. We also find that, due to unscreened long-range interactions, the residual un recombined dark ions settle into a diffuse isothermal halo.", "keyphrases": ["atomic dark matter", "decay", "photon"]}
{"id": "2104.10485", "title": "Jet Properties of XTE J1752-223 During its 2009-2010 Outburst", "abstract": "Galactic short orbital period black hole candidate (BHC) XTE J1752-223 was discovered on 2009 Oct 21 by the Rossi X-ray Timing Explorer (RXTE). We study the spectral properties of this outburst using transonic flow solution based two component advective flow (TCAF) model. TCAF model fitted spectrum gives an estimation of the physical flow parameters, such as the Keplerian disk rate, sub-Keplerian halo rate, properties of the so-called Compton cloud, other than the mass of the source and normalization (N). N is a standardized ratio of emitted to observed photon flux in TCAF which does not include X-ray emission from jets. In the presence of jets, this ratio changes and this deviation is used to obtain the estimation of X-ray contribution from the jets. Nature of the jet is found to be compact during low luminous hard state and discrete or blobby during high luminous intermediate states. We find a correlation between the radio (5.5 GHz) and X-ray (2.5-25 keV) fluxes from different components. The radio (F_R) and jet X-ray (F_ouf) fluxes are found to be correlated within the acceptable range of the standard correlation (0.6 to 0.7). A similar correlation indices were reported by our group for three other short orbital period transient BHCs (Swift J1753.5-0127, MAXI J1836-194 & XTE J1118+480).", "keyphrases": ["xte j1752", "outburst", "jet"]}
{"id": "1009.1352", "title": "Tidal Evolution of Exoplanets", "abstract": "Tidal effects arise from differential and inelastic deformation of a planet by a perturbing body. The continuous action of tides modify the rotation of the planet together with its orbit until an equilibrium situation is reached. It is often believed that synchronous motion is the most probable outcome of the tidal evolution process, since synchronous rotation is observed for the majority of the satellites in the Solar System. However, in the 19th century, Schiaparelli also assumed synchronous motion for the rotations of Mercury and Venus, and was later shown to be wrong. Rather, for planets in eccentric orbits synchronous rotation is very unlikely. The rotation period and axial tilt of exoplanets is still unknown, but a large number of planets have been detected close to the parent star and should have evolved to a final equilibrium situation. Therefore, based on the Solar System well studied cases, we can make some predictions for exoplanets. Here we describe in detail the main tidal effects that modify the secular evolution of the spin and the orbit of a planet. We then apply our knowledge acquired from Solar System situations to exoplanet cases. In particular, we will focus on two classes of planets, \"Hot-Jupiters\" (fluid) and \"Super-Earths\" (rocky with atmosphere).", "keyphrases": ["exoplanet", "planet", "orbital evolution", "equilibrium configuration"]}
{"id": "1805.05609", "title": "Non Gaussianities from Quantum Decoherence during Inflation", "abstract": "Inflationary cosmological perturbations of quantum-mechanical origin generically interact with all degrees of freedom present in the early Universe. Therefore, they must be viewed as an open quantum system in interaction with an environment. This implies that, under some conditions, decoherence can take place. The presence of the environment can also induce modifications in the power spectrum, thus offering an observational probe of cosmic decoherence. Here, we demonstrate that this also leads to non Gaussianities that we calculate using the Lindblad equation formalism. We show that, while the bispectrum remains zero, the four-point correlation functions become non-vanishing. Using the Cosmic Microwave Background measurements of the trispectrum by the Planck satellite, we derive constraints on the strength of the interaction between the perturbations and the environment and show that, in some regimes, they are more stringent than those arising from the power spectrum.", "keyphrases": ["universe", "cosmic decoherence", "non gaussianities"]}
{"id": "1006.0482", "title": "The non-causal origin of the black hole-galaxy scaling relations", "abstract": "We show that the black hole-bulge mass scaling relations observed from the local to the high-z Universe can be largely or even entirely explained by a non-causal origin, i.e. they do not imply the need for any physically coupled growth of black hole and bulge mass, for example through feedback by active galactic nuclei (AGN). Provided some physics for the absolute normalisation, the creation of the scaling relations can be fully explained by the hierarchical assembly of black hole and stellar mass through galaxy merging, from an initially uncorrelated distribution of BH and stellar masses in the early Universe. We show this with a suite of dark matter halo merger trees for which we make assumptions about (uncorrelated) black hole and stellar mass values at early cosmic times. We then follow the halos in the presence of global star formation and black hole accretion recipes that (i) work without any coupling of the two properties per individual galaxy and (ii) correctly reproduce the observed star formation and black hole accretion rate density in the Universe. With disk-to-bulge conversion in mergers included, our simulations even create the observed slope of 1.1 for the M_BH-M_bulge-relations at z=0. This also implies that AGN feedback is not a required (though still a possible) ingredient in galaxy evolution. In light of this, other mechanisms that can be invoked to truncate star formation in massive galaxies are equally justified.", "keyphrases": ["non-causal origin", "scaling relation", "stellar masse"]}
{"id": "1811.02310", "title": "Astrophysics with the Spatially and Spectrally Resolved Sunyaev-Zeldovich Effects: A Millimetre/Submillimetre Probe of the Warm and Hot Universe", "abstract": "In recent years, observations of the Sunyaev-Zeldovich (SZ) effect have had significant cosmological implications and have begun to serve as a powerful and independent probe of the warm and hot gas that pervades the Universe. As a few pioneering studies have already shown, SZ observations both complement X-ray observations \u2013 the traditional tool for studying the intra-cluster medium \u2013 and bring unique capabilities for probing astrophysical processes at high redshifts and out to the low-density regions in the outskirts of galaxy clusters. Advances in SZ observations have largely been driven by developments in centimetre-, millimetre-, and submillimetre-wave instrumentation on ground-based facilities, with notable exceptions including results from the Planck satellite. Here we review the utility of the thermal, kinematic, relativistic, non-thermal, and polarised SZ effects for studies of galaxy clusters and other large scale structures, incorporating the many advances over the past two decades that have impacted SZ theory, simulations, and observations. We also discuss observational results, techniques, and challenges, and aim to give an overview and perspective on emerging opportunities, with the goal of highlighting some of the exciting new directions in this field.", "keyphrases": ["sunyaev-zeldovich effect", "astrophysical process", "low-density region", "galaxy cluster"]}
{"id": "1710.05436", "title": "Illuminating Gravitational Waves: A Concordant Picture of Photons from a Neutron Star Merger", "abstract": "Merging neutron stars offer an exquisite laboratory for simultaneously studying strong-field gravity and matter in extreme environments. We establish the physical association of an electromagnetic counterpart EM170817 to gravitational waves (GW170817) detected from merging neutron stars. By synthesizing a panchromatic dataset, we demonstrate that merging neutron stars are a long-sought production site forging heavy elements by r-process nucleosynthesis. The weak gamma-rays seen in EM170817 are dissimilar to classical short gamma-ray bursts with ultra-relativistic jets. Instead, we suggest that breakout of a wide-angle, mildly-relativistic cocoon engulfing the jet elegantly explains the low-luminosity gamma-rays, the high-luminosity ultraviolet-optical-infrared and the delayed radio/X-ray emission. We posit that all merging neutron stars may lead to a wide-angle cocoon breakout; sometimes accompanied by a successful jet and sometimes a choked jet.", "keyphrases": ["gravitational wave", "neutron star merger", "wide-angle", "infrared transient"]}
{"id": "1309.5872", "title": "Large-Scale Structure Formation with Massive Neutrinos and Dynamical Dark Energy", "abstract": "Over the next decade, cosmological measurements of the large-scale structure of the Universe will be sensitive to the combined effects of dynamical dark energy and massive neutrinos. The matter power spectrum is a key repository of this information. We extend higher-order perturbative methods for computing the power spectrum to investigate these effects over quasi-linear scales. Through comparison with N-body simulations we establish the regime of validity of a Time-Renormalization Group (Time-RG) perturbative treatment that includes dynamical dark energy and massive neutrinos. We also quantify the accuracy of Standard (SPT), Renormalized (RPT) and Lagrangian Resummation (LPT) perturbation theories without massive neutrinos. We find that an approximation that neglects neutrino clustering as a source for nonlinear matter clustering predicts the Baryon Acoustic Oscillation (BAO) peak position to 0.25 for redshifts 1 < z < 3, justifying the use of LPT for BAO reconstruction in upcoming surveys. We release a modified version of the public Copter code which includes the additional physics discussed in the paper.", "keyphrases": ["neutrino", "dynamical dark energy", "perturbation theory", "large-scale structure"]}
{"id": "1705.09290", "title": "Reconstructing Horndeski models from the effective field theory of dark energy", "abstract": "Studying the effects of dark energy and modified gravity on cosmological scales has led to a great number of physical models being developed. The effective field theory (EFT) of cosmic acceleration allows an efficient exploration of this large model space, usually carried out on a phenomenological basis. However, constraints on such parametrized EFT coefficients cannot be trivially connected to fundamental covariant theories. In this paper we reconstruct the class of covariant Horndeski scalar-tensor theories that reproduce the same background dynamics and linear perturbations as a given EFT action. One can use this reconstruction to interpret constraints on parametrized EFT coefficients in terms of viable covariant Horndeski theories. We demonstrate this method with a number of well-known models and discuss a range of future applications.", "keyphrases": ["effective field theory", "dark energy", "cosmic acceleration", "horndeski theory"]}
{"id": "1002.1075", "title": "Cascading Gravity is Ghost Free", "abstract": "We perform a full perturbative stability analysis of the 6D cascading gravity model in the presence of 3-brane tension. We demonstrate that for sufficiently large tension on the (flat) 3-brane, there are no ghosts at the perturbative level, consistent with results that had previously only been obtained in a specific 5D decoupling limit. These results establish the cascading gravity framework as a consistent infrared modification of gravity.", "keyphrases": ["gravity", "ghost", "first order perturbation", "codimension-2 brane"]}
{"id": "1101.2762", "title": "The astrophysical gravitational wave stochastic background", "abstract": "A gravitational wave stochastic background of astrophysical origin may have resulted from the superposition of a large number of unresolved sources since the beginning of stellar activity. Its detection would put very strong constrains on the physical properties of compact objects, the initial mass function or the star formation history. On the other hand, it could be a 'noise' that would mask the stochastic background of cosmological origin. We review the main astrophysical processes able to produce a stochastic background and discuss how it may differ from the primordial contribution by its statistical properties. Current detection methods are also presented.", "keyphrases": ["wave stochastic background", "unresolved source", "universe", "black hole"]}
{"id": "1709.09988", "title": "Higher Derivative Mimetic Gravity", "abstract": "We study cosmological perturbations in mimetic gravity in the presence of classified higher derivative terms which can make the mimetic perturbations stable. We show that the quadratic higher derivative terms which are independent of curvature and the cubic higher derivative terms which come from curvature corrections are sufficient to remove instabilities in mimetic perturbations. The advantage of working with the classified higher derivative terms is that we can control both the background and the perturbation equations allowing us to construct the higher derivative extension of mimetic dark matter and the mimetic nonsingular bouncing scenarios. The latter can be thought as a new higher derivative effective action for the loop quantum cosmology scenario in which the equations of motion coincide with those suggested by loop quantum cosmology. We investigate a possible connection between the mimetic cosmology and the Randall-Sundrum cosmology.", "keyphrases": ["derivative term", "direct coupling", "mimetic field", "spacetime", "difficulty"]}
{"id": "1510.06764", "title": "On the maximal efficiency of the collisional Penrose process", "abstract": "The center of mass (CM) energy in a collisional Penrose process - a collision taking place within the ergosphere of a Kerr black hole - can diverge under suitable extreme conditions (maximal Kerr, near horizon collision and suitable impact parameters). We present an analytic expression for the CM energy, refining expressions given in the literature. Even though the CM energy diverges, we show that the maximal energy attained by a particle that escapes the black hole's gravitational pull and reaches infinity is modest. We obtain an analytic expression for the energy of an escaping particle resulting from a collisional Penrose process, and apply it to derive the maximal energy and the maximal efficiency for several physical scenarios: pair annihilation, Compton scattering, and the elastic scattering of two massive particles. In all physically reasonable cases (in which the incident particles initially fall from infinity towards the black hole) the maximal energy (and the corresponding efficiency) are only one order of magnitude larger than the rest mass energy of the incident particles. The maximal efficiency found is 13.92 and it is obtained for the scattering of an outgoing massless particle by a massive particle.", "keyphrases": ["maximal efficiency", "collisional penrose process", "black hole", "incident particle"]}
{"id": "1207.6679", "title": "Holographic dark energy in a universe with spatial curvature and massive neutrinos: a full Markov Chain Monte Carlo exploration", "abstract": "In this paper, we report the results of constraining the holographic dark energy model with spatial curvature and massive neutrinos, based on a Markov Chain Monte Carlo global fit technique. The cosmic observational data include the full WMAP 7-yr temperature and polarization data, the type Ia supernova data from Union2.1 sample, the baryon acoustic oscillation data from SDSS DR7 and WiggleZ Dark Energy Survey, and the latest measurements of H_0 from HST. To deal with the perturbations of dark energy, we adopt the parameterized post-Friedmann method. We find that, for the simplest holographic dark energy model without spatial curvature and massive neutrinos, the phenomenological parameter c<1 at more than 4\u03c3 confidence level. The inclusion of spatial curvature enlarges the error bars and leads to c<1 only in about 2.5\u03c3 range; in contrast, the inclusion of massive neutrinos does not have significant influence on c. We also find that, for the holographic dark energy model with spatial curvature but without massive neutrinos, the 3\u03c3 error bars of the current fractional curvature density \u03a9_k0 are still in order of 10^-2; for the model with massive neutrinos but without spatial curvature, the 2\u03c3 upper bound of the total mass of neutrinos is \u2211 m_\u03bd < 0.48 eV. Moreover, there exists clear degeneracy between spatial curvature and massive neutrinos in the holographic dark energy model, which enlarges the upper bound of \u2211 m_\u03bd by more than 2 times. In addition, we demonstrate that, making use of the full WMAP data can give better constraints on the holographic dark energy model, compared with the case using the WMAP \u201cdistance priors\u201d.", "keyphrases": ["massive neutrino", "dark energy model", "baryon", "cosmology"]}
{"id": "1002.3966", "title": "Why all these prejudices against a constant?", "abstract": "The expansion of the observed universe appears to be accelerating. A simple explanation of this phenomenon is provided by the non-vanishing of the cosmological constant in the Einstein equations. Arguments are commonly presented to the effect that this simple explanation is not viable or not sufficient, and therefore we are facing the \"great mystery\" of the \"nature of a dark energy\". We argue that these arguments are unconvincing, or ill-founded.", "keyphrases": ["universe", "coincidence problem", "energy density"]}
{"id": "1008.0088", "title": "On mass-constraints implied by the relativistic precession model of twin-peak quasi-periodic oscillations in Circinus X-1", "abstract": "Boutloukos et al. (2006) discovered twin-peak quasi-periodic oscillations (QPOs) in 11 observations of the peculiar Z-source Circinus X-1. Among several other conjunctions the authors briefly discussed the related estimate of the compact object mass following from the geodesic relativistic precession model for kHz QPOs. Neglecting the neutron star rotation they reported the inferred mass M_0 = 2.2 +/- 0.3 M_. We present a more detailed analysis of the estimate which involves the frame-dragging effects associated with rotating spacetimes. For a free mass we find acceptable fits of the model to data for (any) small dimensionless compact object angular momentum j=cJ/GM^2. Moreover, quality of the fit tends to increase very gently with rising j. Good fits are reached when M M_0[1+0.55(j+j^2)]. It is therefore impossible to estimate the mass without the independent knowledge of the angular momentum and vice versa. Considering j up to 0.3 the range of the feasible values of mass extends up to 3M_. We suggest that similar increase of estimated mass due to rotational effects can be relevant for several other sources.", "keyphrases": ["relativistic precession model", "twin-peak quasi-periodic oscillation", "star hartle\u2013thorne model", "near-maximum-mass neutron"]}
{"id": "1207.2160", "title": "The Connection between Galaxies and Dark Matter Structures in the Local Universe", "abstract": "We provide new constraints on the connection between galaxies in the local universe, identified by the Sloan Digital Sky Survey (SDSS), and dark matter halos and their constituent substructures in the \u039bCDM model using WMAP7 cosmological parameters. Predictions for the abundance and clustering properties of dark matter halos, and the relationship between dark matter hosts and substructures, are based on a high-resolution cosmological simulation, the Bolshoi simulation. We associate galaxies with halos and subhalos using subhalo abundance matching, performing a comprehensive analysis which investigates the underlying assumptions of this technique including (a) which halo property is most closely associated with galaxy stellar masses and luminosities, (b) how much scatter is in this relationship, and (c) how much subhalos can be stripped before their galaxies are destroyed. The models are jointly constrained by new measurements of the projected two-point galaxy clustering and the observed conditional stellar mass function of galaxies in groups. The data put tight constraints on the satellite fraction of galaxies as a function of galaxy stellar mass, on the scatter between halo and galaxy properties, and on the underlying conditional stellar mass function. These data rule out several halo properties commonly used in abundance matching, largely because the satellite fractions in the models disagree with those data. We show that an abundance matching model that associates galaxies with the peak circular velocity of their halos is in good agreement with the data, when scatter of 0.20 \u00b1 0.03 dex in stellar mass at a given peak velocity is included. This will yield important constraints for galaxy formation models, and also provides encouraging indications that the galaxy\u2013halo connection can be modeled with sufficient fidelity for future precision studies of the dark Universe.", "keyphrases": ["galaxy", "local universe", "cosmological parameter", "stellar mass"]}
{"id": "1408.2513", "title": "Statistical Analysis of Large-scale EUV Waves Observed by STEREO/EUVI", "abstract": "We present a statistical analysis of 60 strong large-scale EUV wave events that occurred during January 2007 to February 2011 with the STEREO twin spacecraft regarding their kinematical evolution and wave pulse characteristics. For the start velocity, we obtain for the arithmetic mean 312\u00b1115 km s^-1 (within a range of 100-630 km s^-1). For the mean (linear) velocity, the arithmetic mean is 254\u00b176 km s^-1 (within a range of 130-470 km s^-1). 52 deceleration during their propagation (a\u2264-50 m s^-2), the other 48 are consistent with a constant speed within the uncertainties (-50\u2264 a\u226450 m s^-2). The start velocity and the acceleration show a strong anticorrelation with c\u2248-0.8, i.e initially faster events undergo stronger deceleration than slower events. The (smooth) transition between constant propagation for slow events and deceleration in faster events occurs at an EUV wave start velocity of v\u2248230 km s^-1, which corresponds well to the fast-mode speed in the quiet corona. These findings provide strong evidence that the EUV waves under study are indeed large-amplitude fast-mode MHD waves. This interpretation is further supported by the correlations obtained between the peak velocity and the peak amplitude, impulsiveness, and build-up time of the disturbance. We obtained the following association rates of EUV wave events to other solar phenomena: 95 associated with a coronal mass ejection (CME), 74 interplanetary type II bursts, and 22 findings are consistent with the interpretation that the associated CMEs are the EUV waves' driving agent.", "keyphrases": ["euv wave", "stereo", "propagation", "statistical analysis"]}
{"id": "1005.0811", "title": "The Equation of State from Observed Masses and Radii of Neutron Stars", "abstract": "We determine an empirical dense matter equation of state from a heterogeneous dataset of six neutron stars: three type I X-ray bursters with photospheric radius expansion, studied by Ozel et al., and three transient low-mass X-ray binaries. We critically assess the mass and radius determinations from the X-ray burst sources and show explicitly how systematic uncertainties, such as the photospheric radius at touchdown, affect the most probable masses and radii. We introduce a parameterized equation of state and use a Markov Chain Monte Carlo algorithm within a Bayesian framework to determine nuclear parameters such as the incompressibility and the density dependence of the bulk symmetry energy. Using this framework we show, for the first time, that these parameters, predicted solely on the basis of astrophysical observations, all lie in ranges expected from nuclear systematics and laboratory experiments. We find significant constraints on the mass-radius relation for neutron stars, and hence on the pressure-density relation of dense matter. The predicted symmetry energy and the equation of state near the saturation density are soft, resulting in relatively small neutron star radii around 11-12 km for M=1.4 Msun. The predicted equation of state stiffens at higher densities, however, and our preferred model for X-ray bursts suggests that the neutron star maximum mass is relatively large, 1.9-2.2 Msun. Our results imply that several commonly used equations of state are inconsistent with observations.", "keyphrases": ["neutron star", "low-mass x-ray binary", "mass-radius relation"]}
{"id": "2003.10489", "title": "Spitzer's perspective of polycyclic aromatic hydrocarbons in galaxies", "abstract": "Polycyclic aromatic hydrocarbon (PAH) molecules, as revealed by the distinctive set of emission bands at 3.3, 6.2, 7.7, 8.6, 11.3 and 12.7 \u03bcm characteristic of their vibrational modes, are abundant and widespread throughout the Universe. They are ubiquitously seen in a wide variety of astrophysical regions, ranging from planet-forming disks around young stars to the interstellar medium (ISM) of the Milky Way and external galaxies out to high redshifts at z>4. PAHs profoundly influence the thermal budget and chemistry of the ISM by dominating the photoelectric heating of the gas and controlling the ionization balance. Here, we review the current state of knowledge of the astrophysics of PAHs, focusing on their observational characteristics obtained from the Spitzer Space Telescope and their diagnostic power for probing the local physical and chemical conditions and processes. Special attention is paid to the spectral properties of PAHs and their variations revealed by the Infrared Spectrograph (IRS) on board Spitzer across a much broader range of extragalactic environments (e.g., distant galaxies, early-type galaxies, galactic halos, active galactic nuclei, and low-metallicity galaxies) than was previously possible with the Infrared Space Observatory (ISO) or any other telescope facilities. Also highlighted is the relation between the PAH abundance and the galaxy metallicity established for the first time by Spitzer.", "keyphrases": ["aromatic hydrocarbon", "galaxy", "pahs", "emission band"]}
{"id": "2011.00126", "title": "A disk-dominated and clumpy circumgalactic medium of the Milky Way seen in X-ray emission", "abstract": "The Milky Way galaxy is surrounded by a circumgalactic medium (CGM) that may play a key role in galaxy evolution as the source of gas for star formation and a repository of metals and energy produced by star formation and nuclear activity. The CGM may also be a repository for baryons seen in the early universe, but undetected locally. The CGM has an ionized component at temperatures near 2 \u00d7 10^6 K studied primarily in the soft X-ray band. Here we report a survey of the southern Galactic sky with a soft X-ray spectrometer optimized to study diffuse soft X-ray emission. The X-ray emission is best fit with a disc-like model based on the radial profile of the surface density of molecular hydrogen, a tracer of star formation, suggesting that the X-ray emission is predominantly from hot plasma produced via stellar feedback. Strong variations in the X-ray emission on angular scales of \u223c10^\u2218 indicate that the CGM is clumpy. Addition of an extended, and possibly massive, halo component is needed to match the halo density inferred from other observations.", "keyphrases": ["circumgalactic medium", "x-ray emission", "hot plasma"]}
{"id": "0908.2636", "title": "Comparison of Recent SnIa datasets", "abstract": "We rank the six latest Type Ia supernova (SnIa) datasets (Constitution (C), Union (U), ESSENCE (Davis) (E), Gold06 (G), SNLS 1yr (S) and SDSS-II (D)) in the context of the Chevalier-Polarski-Linder (CPL) parametrization w(a)=w_0+w_1 (1-a), according to their Figure of Merit (FoM), their consistency with the cosmological constant (\u039bCDM), their consistency with standard rulers (Cosmic Microwave Background (CMB) and Baryon Acoustic Oscillations (BAO)) and their mutual consistency. We find a significant improvement of the FoM (defined as the inverse area of the 95.4 contour) with the number of SnIa of these datasets ((C) highest FoM, (U), (G), (D), (E), (S) lowest FoM). Standard rulers (CMB+BAO) have a better FoM by about a factor of 3, compared to the highest FoM SnIa dataset (C). We also find that the ranking sequence based on consistency with \u039bCDM is identical with the corresponding ranking based on consistency with standard rulers ((S) most consistent, (D), (C), (E), (U), (G) least consistent). The ranking sequence of the datasets however changes when we consider the consistency with an expansion history corresponding to evolving dark energy (w_0,w_1)=(-1.4,2) crossing the phantom divide line w=-1 (it is practically reversed to (G), (U), (E), (S), (D), (C)). The SALT2 and MLCS2k2 fitters are also compared and some peculiar features of the SDSS-II dataset when standardized with the MLCS2k2 fitter are pointed out. Finally, we construct a statistic to estimate the internal consistency of a collection of SnIa datasets. We find that even though there is good consistency among most samples taken from the above datasets, this consistency decreases significantly when the Gold06 (G) dataset is included in the sample.", "keyphrases": ["snia dataset", "past decade", "likelihood"]}
{"id": "1208.4624", "title": "A Sawtooth-like Timeline for the First Billion Year of Lunar Bombardment", "abstract": "We revisit the early evolution of the Moon's bombardment. Our work combines modeling (based on plausible projectile sources and their dynamical decay rates) with constraints from the lunar crater record, radiometric ages of the youngest lunar basins, and the abundance of highly siderophile elements in the lunar crust and mantle. We deduce that the evolution of the impact flux did not decline exponentially over the first billion years of lunar history, but also there was no prominent and \"narrow\" impact spike some 3.9 Gy ago, unlike that typically envisioned in the lunar cataclysm scenario. Instead, we show the timeline of the lunar bombardment has a sawtooth-like profile, with an uptick in the impact flux near 4.1 Gy ago. The impact flux at the beginning of this weaker cataclysm was 5-10 times higher than the immediately preceding period. The Nectaris basin should have been one of the first basins formed at the sawtooth. We predict the bombardment rate since about 4.1Gy ago declined slowly and adhered relatively close to classic crater chronology models (Neukum and Ivanov (1994)). Overall we expect that the sawtooth event accounted for about 1/4 of the total bombardment suffered by the Moon since its formation. Consequently, considering that about 12-14 basins formed during the sawtooth event, we expect that the net number of basins formed on the Moon was about 45-50. From our expected bombardment timeline, we derived a new and improved lunar chronology suitable for use on Pre-Nectarian surface units. According to this chronology, a significant portion of the oldest lunar cratered terrains has an age of 4.38-4.42 Gyr. Moreover, the largest lunar basin, South Pole Aitken, is older than 4.3Gy, and therefore was not produced during the lunar cataclysm.", "keyphrases": ["timeline", "lunar bombardment", "moon", "lunar basin"]}
{"id": "2204.02930", "title": "Fundamental Physics with ESPRESSO, Constraining a simple parametrisation for varying \u03b1", "abstract": "The spectrograph ESPRESSO recently obtained a limit on the variation of the fine-structure constant, \u03b1, through measurements along the line of sight of a bright quasar with a precision of 1.36 ppm at 1\u03c3 level. This imposes new constraints on cosmological models with a varying \u03b1. We assume such a model where the electromagnetic sector is coupled to a scalar field dark energy responsible for the current acceleration of the Universe. We parametrise the variation of \u03b1 with two extra parameters, one defining the cosmological evolution of the quintessence component and the other fixing the coupling with the electromagnetic field. The objective of this work is to constrain these parameters with both astrophysical and local probes. We also carried out a comparative analysis of how each data probe may constrain our parametrisation. We performed a Bayesian analysis by comparing the predictions of the model with observations. The astrophysical datasets are composed of quasar spectra measurements, including the latest ESPRESSO data point, as well as Planck observations of the cosmic microwave background. We combined these with local results from atomic clocks and the MICROSCOPE experiment. The constraints placed on the quintessence parameter are consistent with a null variation of the field, and are therefore compatible with a \u039bCDM cosmology. The constraints on the coupling to the electromagnetic sector are dominated by the E\u00f6tv\u00f6s parameter local bound. More precise measurements with ESPRESSO will be extremely important to study the cosmological evolution of \u03b1 as it probes an interval of redshift not accessible to other types of observations. However, for this particular model, current available data favour a null variation of \u03b1 resulting mostly from the strong MICROSCOPE limits.", "keyphrases": ["espresso", "parametrisation", "fine-structure constant", "universe"]}
{"id": "1907.13130", "title": "Rapid Reionization by the Oligarchs: The Case for Massive, UV-Bright, Star-Forming Galaxies with High Escape Fractions", "abstract": "The protagonists of cosmic reionization remain elusive. Faint star-forming galaxies are leading candidates because they are numerous and may have significant ionizing photon escape fractions (f_esc). Here we update this picture via an empirical model that successfully predicts latest observations (e.g., the drop in star-formation density at z>8). We generate an ionizing spectrum for each galaxy in our model and constrain f_esc using latest measurements of the reionization timeline (e.g., Ly\u03b1 damping of quasars and galaxies at z>7). Assuming a constant f_esc, we find M_UV<-13.5 galaxies need f_esc=0.21^+0.06_-0.04 to complete reionization. The inferred IGM neutral fraction is [0.9, 0.5, 0.1] at z=[8.2, 6.8, 6.2]\u00b10.2, i.e., the bulk of reionization transpires in 300 Myrs. Inspired by the emergent sample of Lyman Continuum (LyC) leakers that overwhelmingly displays higher-than-average star-formation surface density (\u03a3), we propose a model relating f_esc to \u03a3 and find f_esc\u221d\u03a3^0.4\u00b10.1. Since \u03a3 falls by 2.5 dex between z=8 and z=0, our model explains the humble upper limits on f_esc at lower redshifts and its required evolution to 0.2 at z>6. Within this model, strikingly, <5 >80 relegated to a limited role to ensure high neutral fractions at z=7-8. Shallow faint-end slopes of the UV luminosity function (\u03b1>-2) and/or f_esc distributions skewed toward bright galaxies produce the required late and rapid reionization. We predict LyC leakers like COLA1 (z=6.6, f_esc 30 M_UV=-21.5) become increasingly common towards z 6 and that the drivers of reionization do not lie hidden across the faint-end of the luminosity function, but are already known to us. (abridged)", "keyphrases": ["star-forming galaxy", "photon escape fraction", "rapid reionization", "universe"]}
{"id": "1209.2173", "title": "Stochastic Bias from Non-Gaussian Initial Conditions", "abstract": "In this article, we show that a stochastic form of scale-dependent halo bias arises in multi-source inflationary models, where multiple fields determine the initial curvature perturbation. We derive this effect for general non-Gaussian initial conditions and study various examples, such as curvaton models and quasi-single field inflation. We present a general formula for both the stochastic and the non-stochastic parts of the halo bias, in terms of the N-point cumulants of the curvature perturbation at the end of inflation. At lowest order, the stochasticity arises if the collapsed limit of the four-point function is boosted relative to the square of the three-point function in the squeezed limit. We derive all our results in two ways, using the barrier crossing formalism and the peak-background split method. In a companion paper, we prove that these two approaches are mathematically equivalent.", "keyphrases": ["four-point function", "stochastic bias", "enhancement"]}
{"id": "1203.2695", "title": "Quantum corrections to gravity and their implications for cosmology and astrophysics", "abstract": "The quantum contributions to the gravitational action are relatively easy to calculate in the higher derivative sector of the theory. However, the applications to the post-inflationary cosmology and astrophysics require the corrections to the Einstein-Hilbert action and to the cosmological constant, and those we can not derive yet in a consistent and safe way. At the same time, if we assume that these quantum terms are covariant and that they have relevant magnitude, their functional form can be defined up to a single free parameter, which can be defined on the phenomenological basis. It turns out that the quantum correction may lead, in principle, to surprisingly strong and interesting effects in astrophysics and cosmology.", "keyphrases": ["cosmology", "astrophysic", "quantum correction", "general relativity", "dark matter-like effect"]}
{"id": "1906.08914", "title": "Systematic Opacity Calculations for Kilonovae", "abstract": "Coalescence of neutron stars gives rise to kilonova, thermal emission powered by radioactive decays of freshly synthesized r-process nuclei. Although observational properties are largely affected by bound-bound opacities of r-process elements, available atomic data have been limited. In this paper, we study element-to-element variation of the opacities in the ejecta of neutron star mergers by performing systematic atomic structure calculations of r-process elements for the first time. We show that the distributions of energy levels tend to be higher as electron occupation increases for each electron shell due to the larger energy spacing caused by larger effects of spin-orbit and electron-electron interactions. As a result, elements with a fewer number of electrons in the outermost shells tend to give larger contributions to the bound-bound opacities. This implies that Fe is not representative for the opacities of light r-process elements. The average opacities for the mixture of r-process elements are found to be kappa 20-30 cm^2 g^-1 for the electron fraction of Ye < 0.20, kappa 3-5 cm^2 g^-1 for Ye = 0.25-0.35, and kappa 1 cm^2 g^-1 for Ye = 0.40 at T = 5,000-10,000 K, and they steeply decrease at lower temperature. We show that, even with the same abundance or Ye, the opacity in the ejecta changes with time by one order of magnitude from 1 to 10 days after the merger. Our radiative transfer simulations with the new opacity data confirm that ejecta with a high electron fraction (Ye > 0.25, with no lanthanide) are needed to explain the early, blue emission in GW170817/AT2017gfo while lanthanide-rich ejecta (with a mass fraction of lanthanides 5 x 10^-3) reproduce the long-lasting near-infrared emission.", "keyphrases": ["opacity", "kilonova", "element", "ejecta", "wavelength"]}
{"id": "1302.2291", "title": "Constraints on the Holographic Dark Energy Model from Type Ia Supernovae, WMAP7, Baryon Acoustic Oscillation and Redshift-Space Distortion", "abstract": "In this paper, we use the joint measurement of geometry and growth rate from matter density perturbations to constrain the holographic dark energy model. The geometry measurement includes type Ia supernovae (SN Ia) Union2.1, full information of cosmic microwave background (CMB) from WMAP-7yr and baryon acoustic oscillation (BAO). For the growth rate of matter density perturbations, the results f(z)\u03c3_8(z) measured from the redshift-space distortion (RSD) in the galaxy power spectrum are employed. Via the Markov Chain Monte Carlo method, we try to constrain the model parameters space. The jointed constraint shows that c=0.750_- 0.0999- 0.173- 0.226^+ 0.0976+ 0.215+ 0.319 and \u03c3_8=0.763_- 0.0465- 0.0826- 0.108^+ 0.0477+ 0.0910+ 0.120 with 1,2,3\u03c3 regions. After marginalizing the other irrelevant model parameters, we show the evolution of the equation of state of HDE with respect to the redshift z. Though the current cosmic data points favor a phantom like HDE Universe for the mean values of the model parameters in the future, it can behave like quintessence in 3\u03c3 regions.", "keyphrases": ["dark energy model", "baryon acoustic oscillation", "redshift-space distortion", "cosmological model"]}
{"id": "1008.1730", "title": "Rapid Separable Analysis of Higher Order Correlators in Large Scale Structure", "abstract": "We present an efficient separable approach to the estimation and reconstruction of the bispectrum and the trispectrum from observational (or simulated) large scale structure data. This is developed from general CMB (poly-)spectra methods which exploit the fact that the bispectrum and trispectrum in the literature can be represented by a separable mode expansion which converges rapidly (with n_max=O(30) terms). With an effective grid resolution l_max (number of particles/grid points N=l_max^3), we present a bispectrum estimator which requires only O(n_max\u00d7 l_max^3) operations, along with a corresponding method for direct bispectrum reconstruction. This method is extended to the trispectrum revealing an estimator which requires only O(n_max^4/3\u00d7 l_max^3) operations. The complexity in calculating the trispectrum in this method is now involved in the original decomposition and orthogonalisation process which need only be performed once for each model. However, for non-diagonal trispectra these processes present little extra difficulty and may be performed in O(l_max^4) operations. A discussion of how the methodology may be applied to the quadspectrum is also given. An efficient algorithm for the generation of arbitrary nonGaussian initial conditions for use in N-body codes using this separable approach is described. This prescription allows for the production of nonGaussian initial conditions for arbitrary bispectra and trispectra. A brief outline of the key issues involved in parameter estimation, particularly in the non-linear regime, is also given.", "keyphrases": ["large scale structure", "difficulty", "bispectra"]}
{"id": "1511.01590", "title": "Active Galactic Nuclei as High-Energy Neutrino Sources", "abstract": "Active galactic nuclei (AGN) are believed to be promising candidates of extragalactic cosmic-ray accelerators and sources, and associated high-energy neutrino and hadronic gamma-ray emission has been studied for many years. We review models of high-energy neutrino production in AGN and discuss their implications for the latest IceCube observation of the diffuse neutrino intensity.", "keyphrases": ["neutrino production", "galactic nucleus", "starburst galaxy"]}
{"id": "1304.7684", "title": "Large-scale nuclear structure calculations for spin-dependent WIMP scattering with chiral effective field theory currents", "abstract": "We perform state-of-the-art large-scale shell-model calculations of the structure factors for elastic spin-dependent WIMP scattering off 129,131Xe, 127I, 73Ge, 19F, 23Na, 27Al, and 29Si. This comprehensive survey covers the non-zero-spin nuclei relevant to direct dark matter detection. We include a pedagogical presentation of the formalism necessary to describe elastic and inelastic WIMP-nucleus scattering. The valence spaces and nuclear interactions employed have been previously used in nuclear structure calculations for these mass regions and yield a good spectroscopic description of these isotopes. We use spin-dependent WIMP-nucleus currents based on chiral effective field theory (EFT) at the one-body level and including the leading long-range two-body currents due to pion exchange, which are predicted in chiral EFT. Results for all structure factors are provided with theoretical error bands due to the nuclear uncertainties of WIMP currents in nuclei.", "keyphrases": ["nuclear structure calculation", "spin-dependent wimp", "effective field theory", "chiral symmetry"]}
{"id": "1205.2136", "title": "Stochastic Acceleration by Turbulence", "abstract": "The subject of this paper is stochastic acceleration by plasma turbulence, a process akin to the original model proposed by Fermi. We review the relative merits of different acceleration models, in particular the so called first order Fermi acceleration by shocks and second order Fermi by stochastic processes, and point out that plasma waves or turbulence play an important role in all mechanisms of acceleration. Thus, stochastic acceleration by turbulence is active in most situations. We also show that it is the most efficient mechanism of acceleration of relatively cool non relativistic thermal background plasma particles. In addition, it can preferentially accelerate electrons relative to protons as is needed in many astrophysical radiating sources, where usually there are no indications of presence of shocks. We also point out that a hybrid acceleration mechanism consisting of initial acceleration by turbulence of background particles followed by a second stage acceleration by a shock has many attractive features. It is demonstrated that the above scenarios can account for many signatures of the accelerated electrons, protons and other ions, in particular ^3He and ^4He, seen directly as Solar Energetic Particles and through the radiation they produce in solar flares.", "keyphrases": ["turbulence", "background plasma particle", "electron"]}
{"id": "1402.0933", "title": "Magnetic Helicity and Large Scale Magnetic Fields: A Primer", "abstract": "Magnetic fields of laboratory, planetary, stellar, and galactic plasmas commonly exhibit significant order on large temporal or spatial scales compared to the otherwise random motions within the hosting system. Such ordered fields can be measured in the case of planets, stars, and galaxies, or inferred indirectly by the action of their dynamical influence, such as jets. Whether large scale fields are amplified in situ or a remnant from previous stages of an object's history is often debated for objects without a definitive magnetic activity cycle. Magnetic helicity, a measure of twist and linkage of magnetic field lines, is a unifying tool for understanding large scale field evolution for both mechanisms of origin. Its importance stems from its two basic properties: (1) magnetic helicity is typically better conserved than magnetic energy; and (2) the magnetic energy associated with a fixed amount of magnetic helicity is minimized when the system relaxes this helical structure to the largest scale available. Here I discuss how magnetic helicity has come to help us understand the saturation of and sustenance of large scale dynamos, the need for either local or global helicity fluxes to avoid dynamo quenching, and the associated observational consequences. I also discuss how magnetic helicity acts as a hindrance to turbulent diffusion of large scale fields, and thus a helper for fossil remnant large scale field origin models in some contexts. I briefly discuss the connection between large scale fields and accretion disk theory as well. The goal here is to provide a conceptual primer to help the reader efficiently penetrate the literature.", "keyphrases": ["large scale", "magnetic field", "magnetic helicity"]}
{"id": "2011.12503", "title": "The cosmic neutrino background as a collection of fluids in large-scale structure simulations", "abstract": "A significant challenge for modelling the massive neutrino as a hot dark matter is its large velocity dispersion. In this work, we investigate and implement a multi-fluid perturbation theory that treats the cosmic neutrino population as a collection of fluids with a broad range of bulk velocities. These fluids respond linearly to the clustering of cold matter, which may be linear and described by standard linear perturbation theory, or non-linear, described using either higher-order perturbation theory or N-body simulations. We verify that such an alternative treatment of neutrino perturbations agrees closely with state-of-the-art neutrino linear response calculations in terms of power spectrum and bispectrum predictions. Combining multi-fluid neutrino linear response with a non-linear calculation for the cold matter clustering, we find for a reference nuLambdaCDM cosmology with neutrino mass sum of 0.93 eV an enhancement of the small-scale neutrino power by an order of magnitude relative to a purely linear calculation. The corresponding clustering enhancement in the cold matter, however, is a modest 0.05 multi-fluid approach uniquely enables us to identify that the slowest-moving 25 treatment. Such a precise calculation of neutrino clustering on small scales accompanied by fine-grained velocity information would be invaluable for experiments such as PTOLEMY that probe the local neutrino density and velocity in the solar neighbourhood.", "keyphrases": ["neutrino", "fluid", "dark matter", "cold matter", "gravitational potential"]}
{"id": "1806.04680", "title": "Obscured Active Galactic Nuclei", "abstract": "Active Galactic Nuclei (AGN) are powered by the accretion of material onto a supermassive black hole (SMBH), and are among the most luminous objects in the Universe. However, the huge radiative power of most AGN cannot be seen directly, as the accretion is \"hidden\" behind gas and dust that absorbs many of the characteristic observational signatures. This obscuration presents an important challenge for uncovering the complete AGN population and understanding the cosmic evolution of SMBHs. In this review we describe a broad range of multi-wavelength techniques that are currently employed to identify obscured AGN, and assess the reliability and completeness of each technique. We follow with a discussion of the demographics of obscured AGN activity, explore the nature and physical scales of the obscuring material, and assess the implications of obscured AGN for observational cosmology. We conclude with an outline of the prospects for future progress from both observations and theoretical models, and highlight some of the key outstanding questions.", "keyphrases": ["active galactic nuclei", "supermassive black hole", "dust"]}
{"id": "1707.05125", "title": "Primordial perturbations from inflation with a hyperbolic field-space", "abstract": "We study primordial perturbations from hyperinflation, proposed recently and based on a hyperbolic field-space. In the previous work, it was shown that the field-space angular momentum supported by the negative curvature modifies the background dynamics and enhances fluctuations of the scalar fields qualitatively, assuming that the inflationary background is almost de Sitter. In this work, we confirm and extend the analysis based on the standard approach of cosmological perturbation in multi-field inflation. At the background level, to quantify the deviation from de Sitter, we introduce the slow-varying parameters and show that steep potentials, which usually can not drive inflation, can drive inflation. At the linear perturbation level, we obtain the power spectrum of primordial curvature perturbation and express the spectral tilt and running in terms of the slow-varying parameters. We show that hyperinflation with power-law type potentials has already been excluded by the recent Planck observations, while exponential-type potential with the exponent of order unity can be made consistent with observations as far as the power spectrum is concerned. We also argue that, in the context of a simple D-brane inflation, the hyperinflation requires exponentially large hyperbolic extra dimensions but that masses of Kaluza-Klein gravitons can be kept relatively heavy.", "keyphrases": ["hyperbolic field-space", "scalar field", "multi-field inflation", "primordial perturbation"]}
{"id": "0904.4702", "title": "Size Bias in Galaxy Surveys", "abstract": "Only certain galaxies are included in surveys: those bright and large enough to be detectable as extended sources. Because gravitational lensing can make galaxies appear both brighter and larger, the presence of foreground inhomogeneities can scatter galaxies across not only magnitude cuts but also size cuts, changing the statistical properties of the resulting catalog. Here we explore this size bias, and how it combines with magnification bias to affect galaxy statistics. We demonstrate that photometric galaxy samples from current and upcoming surveys can be even more affected by size bias than by magnification bias.", "keyphrases": ["galaxy", "magnification", "size bias"]}
{"id": "0906.4339", "title": "Massive Binary Black Holes in the Cosmic Landscape", "abstract": "Binary black holes occupy a special place in our quest for understanding the evolution of galaxies along cosmic history. If massive black holes grow at the center of (pre-)galactic structures that experience a sequence of merger episodes, then dual black holes form as inescapable outcome of galaxy assembly. But, if the black holes reach coalescence, then they become the loudest sources of gravitational waves ever in the universe. Nature seems to provide a pathway for the formation of these exotic binaries, and a number of key questions need to be addressed: How do massive black holes pair in a merger? Depending on the properties of the underlying galaxies, do black holes always form a close Keplerian binary? If a binary forms, does hardening proceed down to the domain controlled by gravitational wave back reaction? What is the role played by gas and/or stars in braking the black holes, and on which timescale does coalescence occur? Can the black holes accrete on flight and shine during their pathway to coalescence? N-Body/hydrodynamical codes have proven to be vital tools for studying their evolution, and progress in this field is expected to grow rapidly in the effort to describe, in full realism, the physics of stars and gas around the black holes, starting from the cosmological large scale of a merger. If detected in the new window provided by the upcoming gravitational wave experiments, binary black holes will provide a deep view into the process of hierarchical clustering which is at the heart of the current paradigm of galaxy formation. They will also be exquisite probes for testing General Relativity, as the theory of gravity. The waveforms emitted during the inspiral, coalescence and ring-down phase carry in their shape the sign of a dynamically evolving space-time and the proof of the existence of an horizon.", "keyphrases": ["black hole", "gravitational wave", "galaxy merger"]}
{"id": "1312.5616", "title": "Large-Scale Structure and Gravitational Waves III: Tidal Effects", "abstract": "The leading locally observable effect of a long-wavelength metric perturbation corresponds to a tidal field. We derive the tidal field induced by scalar, vector, and tensor perturbations, and use second order perturbation theory to calculate the effect on the locally measured small-scale density fluctuations. For sub-horizon scalar perturbations, we recover the standard perturbation theory result (F_2 kernel). For tensor modes of wavenumber k_L, we find that effects persist for k_L\u03c4\u226b 1, i.e. even long after the gravitational wave has entered the horizon and redshifted away, i.e. it is a \"fossil\" effect. We then use these results, combined with the \"ruler perturbations\" of arXiv:1204.3625, to predict the observed distortion of the small-scale matter correlation function induced by a long-wavelength tensor mode. We also estimate the observed signal in the B mode of the cosmic shear from a gravitational wave background, including both tidal (intrinsic alignment) and projection (lensing) effects. The non-vanishing tidal effect in the k_L\u03c4\u226b 1 limit significantly increases the intrinsic alignment contribution to shear B modes, especially at low redshifts z \u2272 2.", "keyphrases": ["tidal effect", "tensor mode", "cosmic shear", "large-scale structure", "pgw"]}
{"id": "1302.0943", "title": "The mean-field solar dynamo with double cell meridional circulation pattern", "abstract": "Recent findings of helioseismology as well as advances in direct numerical simulations of global dynamics of the Sun have indicated that in each solar hemisphere the meridional circulation forms the two cells along the in the convection zone. We investigate properties of a mean-field solar dynamo with such double-cell meridional circulation. The dynamo model also includes the realistic profile of solar differential rotation (including the tachocline and subsurface shear layer), and takes into account effects of turbulent pumping, anisotropic turbulent diffusivity, and conservation of magnetic helicity. Contrary to previous flux-transport dynamo models, it is found that the dynamo model can robustly reproduce the basic properties of the solar magnetic cycles for a wide range of model parameters and the circulation speed. The best agreement with observations is achieved when the surface speed of meridional circulation is about 12 m/s. For this circulation speed the simulated sunspot activity shows good synchronization with the polar magnetic fields. Such synchronization was indeed observed during the past sunspot cycles 21 and 22. We compare theoretical and observed phase diagrams of the sunspot number and the polar field strength and discuss the peculiar properties of Cycle 23.", "keyphrases": ["mean-field solar dynamo", "meridional circulation", "dynamo model"]}
{"id": "1010.1025", "title": "The Atacama Cosmology Telescope: Cosmology from Galaxy Clusters Detected via the Sunyaev-Zel'dovich Effect", "abstract": "We present constraints on cosmological parameters based on a sample of Sunyaev-Zel'dovich-selected galaxy clusters detected in a millimeter-wave survey by the Atacama Cosmology Telescope. The cluster sample used in this analysis consists of 9 optically-confirmed high-mass clusters comprising the high-significance end of the total cluster sample identified in 455 square degrees of sky surveyed during 2008 at 148 GHz. We focus on the most massive systems to reduce the degeneracy between unknown cluster astrophysics and cosmology derived from SZ surveys. We describe the scaling relation between cluster mass and SZ signal with a 4-parameter fit. Marginalizing over the values of the parameters in this fit with conservative priors gives sigma_8 = 0.851 +/- 0.115 and w = -1.14 +/- 0.35 for a spatially-flat wCDM cosmological model with WMAP 7-year priors on cosmological parameters. This gives a modest improvement in statistical uncertainty over WMAP 7-year constraints alone. Fixing the scaling relation between cluster mass and SZ signal to a fiducial relation obtained from numerical simulations and calibrated by X-ray observations, we find sigma_8 = 0.821 +/- 0.044 and w = -1.05 +/- 0.20. These results are consistent with constraints from WMAP 7 plus baryon acoustic oscillations plus type Ia supernoava which give sigma_8 = 0.802 +/- 0.038 and w = -0.98 +/- 0.053. A stacking analysis of the clusters in this sample compared to clusters simulated assuming the fiducial model also shows good agreement. These results suggest that, given the sample of clusters used here, both the astrophysics of massive clusters and the cosmological parameters derived from them are broadly consistent with current models.", "keyphrases": ["atacama cosmology telescope", "galaxy cluster", "cosmological parameter"]}
{"id": "1506.02040", "title": "Computing the Three-Point Correlation Function of Galaxies in \ud835\udcaa(N^2) Time", "abstract": "We present an algorithm that computes the multipole coefficients of the galaxy three-point correlation function (3PCF) without explicitly considering triplets of galaxies. Rather, centering on each galaxy in the survey, it expands the radially-binned density field in spherical harmonics and combines these to form the multipoles without ever requiring the relative angle between a pair about the central. This approach scales with number and number density in the same way as the two-point correlation function, allowing runtimes that are comparable, and 500 times faster than a naive triplet count. It is exact in angle and easily handles edge correction. We demonstrate the algorithm on the LasDamas SDSS-DR7 mock catalogs, computing an edge corrected 3PCF out to 90 Mpc/h in under an hour on modest computing resources. We expect this algorithm will render it possible to obtain the large-scale 3PCF for upcoming surveys such as Euclid, LSST, and DESI.", "keyphrases": ["three-point correlation function", "galaxy", "multipole coefficient"]}
{"id": "1312.3253", "title": "General Relativity from a Thermodynamic Perspective", "abstract": "I show that the gravitational dynamics in a bulk region of space can be connected to a thermodynamic description in the boundary of that region, thereby providing clear physical interpretations of several mathematical features of classical general relativity: (1) The Noether charge contained in a bulk region, associated with a specific time evolution vector field, has a direct thermodynamic interpretation as the gravitational heat content of the boundary surface. (2) This result, in turn, shows that all static spacetimes maintain holographic equipartition; in these spacetimes, the number of degrees of freedom in the boundary is equal to the number of degrees of freedom in the bulk. (3) In a general, evolving spacetime, the rate of change of gravitational momentum is related to the difference between the number of bulk and boundary degrees of freedom. It is this departure from the holographic equipartition which drives the time evolution of the spacetime. (4) When the equations of motion hold, the (naturally defined) total energy of the gravity plus matter within a bulk region, will be equal to the boundary heat content. (5) After motivating the need for an alternate description of gravity (if we have to solve the cosmological constant problem), I describe a thermodynamic variational principle based on null surfaces to achieve this goal. The concept of gravitational heat density of the null surfaces arises naturally from the Noether charge associated with the null congruence. The null surface variational principle, in fact, extremises the total heat content of the matter plus gravity system. Several variations on this theme and implications are described. [Abridged]", "keyphrases": ["heat content", "principle", "general relativity"]}
{"id": "2112.09706", "title": "The Return of the Templates: Revisiting the Galactic Center Excess with Multi-Messenger Observations", "abstract": "The Galactic center excess (GCE) remains one of the most intriguing discoveries from the Fermi Large Area Telescope (LAT) observations. We revisit the characteristics of the GCE by first producing a new set of high-resolution galactic diffuse gamma-ray emission templates, which are ultimately due to cosmic-ray interactions with the interstellar medium. Using multi-messenger observations we constrain the properties of the galactic diffuse emission. The broad properties of the GCE that we find in this work are qualitatively unchanged despite the introduction of this new set of templates, though its quantitative features appear mildly different than those obtained in previous analyses. In particular, we find a high-energy tail at higher significance than previously reported. This tail is very prominent in the northern hemisphere, and less so in the southern hemisphere. This strongly affects one prominent interpretation of the excess: known millisecond pulsars are incapable of producing this high-energy emission, even in the relatively softer southern hemisphere, and are therefore disfavored as the sole explanation of the GCE. The annihilation of dark matter particles of mass 40^+10_-7 GeV (95% CL) to b quarks with a cross-section of \u03c3 v = 1.4^+0.6_-0.3\u00d7 10^-26 cm^3s^-1 provides a good fit to the excess especially in the relatively cleaner southern sky. Dark matter of the same mass range annihilating to b quarks or heavier dark matter particles annihilating to heavier Standard Model bosons can combine with millisecond pulsars to provide a good fit to the southern hemisphere emission. As part of this paper, we make publicly available all of our templates and the data covariance matrix we have generated to account for systematic uncertainties.[abridged]", "keyphrases": ["galactic center excess", "multi-messenger observation", "pulsar", "dark matter particle"]}
{"id": "1711.10592", "title": "Intro to Effective Field Theories and Inflation", "abstract": "These notes present an introduction to \u039bCDM cosmology and its possible inflationary precursor, with an emphasis on some of the ways effective field theories are used in its analysis. The intended audience are graduate students in particle physics, such as attended the lectures (prepared for the Les Houches Summer School, Effective Field Theory in Particle Physics and Cosmology, July 2017).", "keyphrases": ["effective field theory", "cosmology", "vacuum energy"]}
{"id": "1205.5616", "title": "Particle creation and particle number in an expanding universe", "abstract": "I describe the logical basis of the method that I developed in 1962 and 1963 to define a quantum operator corresponding to the observable particle number of a quantized free scalar field in a spatially-flat isotropically expanding (and/or contracting) universe. This work also showed for the first time that particles were created from the vacuum by the curved space-time of an expanding spatially-flat FLRW universe. The same process is responsible for creating the nearly scale-invariant spectrum of quantized perturbations of the inflaton scalar field during the inflationary stage of the expansion of the universe. I explain how the method that I used to obtain the observable particle number operator involved adiabatic invariance of the particle number (hence, the name adiabatic regularization) and the quantum theory of measurement of particle number in an expanding universe. I also show how I was led in a surprising way, to the discovery in 1964 that there would be no particle creation by these spatially-flat FLRW universes for free fields of any integer or half-integer spin satisfying field equations that are invariant under conformal transformations of the metric. The methods I used to define adiabatic regularization for particle number, were based on generally-covariant concepts like adiabatic invariance and measurement that were fundamental and determined results that were unique to each given adiabatic order.", "keyphrases": ["universe", "particle creation", "quantum field theory", "momentum conservation", "minkowski space time"]}
{"id": "0910.0252", "title": "The dark side of curvature", "abstract": "Geometrical tests such as the combination of the Hubble parameter H(z) and the angular diameter distance d_A(z) can, in principle, break the degeneracy between the dark energy equation of state parameter w(z), and the spatial curvature Omega_k in a direct, model-independent way. In practice, constraints on these quantities achievable from realistic experiments, such as those to be provided by Baryon Acoustic Oscillation (BAO) galaxy surveys in combination with CMB data, can resolve the cosmic confusion between the dark energy equation of state parameter and curvature only statistically and within a parameterized model for w(z). Combining measurements of both H(z) and d_A(z) up to sufficiently high redshifts around z = 2 and employing a parameterization of the redshift evolution of the dark energy equation of state are the keys to resolve the w(z)-Omega_k degeneracy.", "keyphrases": ["curvature", "degeneracy", "dark energy equation", "bao", "cmb data"]}
{"id": "1902.01251", "title": "Cosmological Shapes of Higher-Spin Gravity", "abstract": "We explore non-Gaussian features of a massless spin-two field in the Vasiliev theory of higher-spin gravity. The theory contains an infinite tower of interacting gauge fields with increasing spin, and admits four-dimensional asymptotically de Sitter configurations. Using a recent proposal for calculating late-time quantum correlations in Vasiliev theory, we provide an exact formula for the tensor non-Gaussianities of the massless spin-two graviton field. By general symmetry considerations, we relate our result to that produced by a tree-level calculation in a gravitational theory containing an Einstein term and a term cubic in the Weyl tensor. The relative coefficient between the two terms is calculated explicitly, exhibiting a significant contribution from the Weyl cubed term. We discuss potential cosmological implications of our results.", "keyphrases": ["higher-spin gravity", "cosmological collider", "energy scale"]}
{"id": "1701.03003", "title": "Globular clusters with Gaia", "abstract": "The treatment of crowded fields in Gaia data will only be a reality in a few years from now. In particular, for globular clusters, only the end-of-mission data (public in 2022-2023) will have the necessary full crowding treatment and will reach sufficient quality for the faintest stars. As a consequence, the work on the deblending and decontamination pipelines is still ongoing. We describe the present status of the pipelines for different Gaia instruments, and we model the end-of-mission crowding errors on the basis of available information. We then apply the nominal post-launch Gaia performances, appropriately worsened by the estimated crowding errors, to a set of 18 simulated globular clusters with different concentration, distance, and field contamination. We conclude that there will be 103-104 stars with astrometric performances virtually untouched by crowding (contaminated by <1 mmag) in the majority of clusters. The most limiting factor will be field crowding, not cluster crowding: the most contaminated clusters will only contain 10-100 clean stars. We also conclude that: (i) the systemic proper motions and parallaxes will be determined to 1 have radial velocities to a few km/s ; (ii) internal kinematics will be of unprecendented quality, cluster masses will be determined to 10 and beyond, and it will be possible to identify differences of a few km/s or less in the kinematics (if any) of cluster sub-populations up to 10 kpc and beyond; (iii) the brightest stars (V<17 mag) will have space-quality, wide-field photometry (mmag errors), and all Gaia photometry will have 1-3 errors on the absolute photometric calibration.", "keyphrases": ["radial velocity", "globular cluster", "bright star"]}
{"id": "1806.11090", "title": "COFFE: a code for the full-sky relativistic galaxy correlation function", "abstract": "We present a public version of the code COFFE (COrrelation Function Full-sky Estimator) available at https://github.com/JCGoran/coffe. The code computes the galaxy two-point correlation function and its multipoles in linear perturbation theory, including all relativistic and wide angle corrections. COFFE also calculates the covariance matrix for two physically relevant estimators of the correlation function multipoles. We illustrate the usefulness of our code by a simple but relevant example: a forecast of the detectability of the lensing signal in the multipoles of the two-point function. In particular, we show that lensing should be detectable in the multipoles of the two-point function, with a signal-to-noise larger than 10, in future surveys like Euclid or the SKA.", "keyphrases": ["galaxy", "two-point correlation function", "relativistic effect"]}
{"id": "1801.07265", "title": "Galaxy Bispectrum from Massive Spinning Particles", "abstract": "Massive spinning particles, if present during inflation, lead to a distinctive bispectrum of primordial perturbations, the shape and amplitude of which depend on the masses and spins of the extra particles. This signal, in turn, leaves an imprint in the statistical distribution of galaxies; in particular, as a non-vanishing galaxy bispectrum, which can be used to probe the masses and spins of these particles. In this paper, we present for the first time a new theoretical template for the bispectrum generated by massive spinning particles, valid for a general triangle configuration. We then proceed to perform a Fisher-matrix forecast to assess the potential of two next-generation spectroscopic galaxy surveys, EUCLID and DESI, to constrain the primordial non-Gaussianity sourced by these extra particles. We model the galaxy bispectrum using tree-level perturbation theory, accounting for redshift-space distortions and the Alcock-Paczynski effect, and forecast constraints on the primordial non-Gaussianity parameters marginalizing over all relevant biases and cosmological parameters. Our results suggest that these surveys would potentially be sensitive to any primordial non-Gaussianity with an amplitude larger than f_ NL\u2248 1, for massive particles with spins 2, 3, and 4. Interestingly, if non-Gaussianities are present at that level, these surveys will be able to infer the masses of these spinning particles to within tens of percent. If detected, this would provide a very clear window into the particle content of our Universe during inflation.", "keyphrases": ["galaxy bispectrum", "cosmological collider physics", "hubble scale"]}
{"id": "1211.4979", "title": "Finding the First Cosmic Explosions I: Pair-Instability Supernovae", "abstract": "The first stars are the key to the formation of primitive galaxies, early cosmological reionization and chemical enrichment, and the origin of supermassive black holes. Unfortunately, in spite of their extreme luminosities, individual Population III stars will likely remain beyond the reach of direct observation for decades to come. However, their properties could be revealed by their supernova explosions, which may soon be detected by a new generation of NIR observatories such as JWST and WFIRST. We present light curves and spectra for Pop III pair-instability supernovae calculated with the Los Alamos radiation hydrodynamics code RAGE. Our numerical simulations account for the interaction of the blast with realistic circumstellar envelopes, the opacity of the envelope, and Lyman absorption by the neutral IGM at high redshift, all of which are crucial to computing the NIR signatures of the first cosmic explosions. We find that JWST will detect pair-instability supernovae out to z > 30, WFIRST will detect them in all-sky surveys out to z 15 - 20 and LSST and Pan-STARRS will find them at z 7 - 8. The discovery of these ancient explosions will probe the first stellar populations and reveal the existence of primitive galaxies that might not otherwise have been detected.", "keyphrases": ["explosion", "pair-instability supernovae", "high redshift"]}
{"id": "1409.7666", "title": "Neutron stars - thermal emitters", "abstract": "Confronting theoretical models with observations of thermal radiation emitted by neutron stars is one of the most important ways to understand the properties of both, superdense matter in the interiors of the neutron stars and dense magnetized plasmas in their outer layers. Here we review the theory of thermal emission from the surface layers of strongly magnetized neutron stars, and the main properties of the observational data. In particular, we focus on the nearby sources for which a clear thermal component has been detected, without being contaminated by other emission processes (magnetosphere, accretion, nebulae). We also discuss the applications of the modern theoretical models of the formation of spectra of strongly magnetized neutron stars to the observed thermally emitting objects.", "keyphrases": ["radiation", "thermal emission", "neutron star"]}
{"id": "1108.2375", "title": "Fourth Order Gravity, Scalar-Tensor-Vector Gravity, and Galaxy Rotation Curves", "abstract": "The Lambda-CDM model is the best fit to cosmological data, and to the observed galactic rotation curves. However, in the absence of a direct detection of dark matter one should explore theories such as MOND, and perhaps also modified gravity theories like fourth order gravity and Scalar-Tensor-Vector Gravity [STVG] as possible explanations for the non-Keplerian behaviour of galaxy rotation curves. STVG has a modified law for gravitational acceleration which attempts to fit data by fixing two free parameters. We show that, remarkably, the biharmonic equation which we get in the weak field limit of the field equations in a fourth order gravity theory implies a modification of Newtonian acceleration which is precisely of the same repulsive Yukawa form as in the STVG theory, and the corrections could in principle be large enough to try and explain the observed rotation curves. We also explain how our model provides a first principles understanding of MOND. We also show that STVG and fourth order gravity predict an acceleration parameter a_0 whose value is of the same order as in MOND.", "keyphrases": ["scalar-tensor-vector gravity", "rotation curve", "dark matter"]}
{"id": "2106.01641", "title": "The Third Order Scalar Induced Gravitational Waves", "abstract": "Since the gravitational waves were detected by LIGO and Virgo, it has been promising that lots of information about the primordial Universe could be learned by further observations on stochastic gravitational waves background. The studies on gravitational waves induced by primordial curvature perturbations are of great interest. The aim of this paper is to investigate the third order induced gravitational waves. Based on the theory of cosmological perturbations, the first order scalar induces the second order scalar, vector and tensor perturbations. At the next iteration, the first order scalar, the second order scalar, vector and tensor perturbations all induce the third order tensor perturbations. We present the energy density spectrum of the third order gravitational waves for a monochromatic primordial power spectrum. The shape of the energy density spectrum of the third order gravitational waves is different from that of the second order scalar induced gravitational waves. And it is found that the third order gravitational waves sourced by the second order scalar perturbations dominate the energy density spectrum.", "keyphrases": ["gravitational wave", "primordial scalar perturbation", "black hole"]}
{"id": "1003.1834", "title": "Boltzmann hierarchy for the cosmic microwave background at second order including photon polarization", "abstract": "Non-gaussianity and B-mode polarization are particularly interesting features of the cosmic microwave background, as \u2013 at least in the standard model of cosmology \u2013 their only sources to first order in cosmological perturbation theory are primordial, possibly generated during inflation. If the primordial sources are small, the question arises how large is the non-gaussianity and B-mode background induced in second-order from the initially gaussian and scalar perturbations. In this paper we derive the Boltzmann hierarchy for the microwave background photon phase-space distributions at second order in cosmological perturbation theory including the complete polarization information, providing the basis for further numerical studies. As an aside we note that the second-order collision term contains new sources of B-mode polarization and that no polarization persists in the tight-coupling limit.", "keyphrases": ["cosmic microwave background", "b-mode polarization", "scalar perturbation", "boltzmann hierarchy"]}
{"id": "1501.06604", "title": "The Structure and Dark Halo Core Properties of Dwarf Spheroidal Galaxies", "abstract": "The structure and dark matter halo core properties of dwarf spheroidal galaxies (dSphs) are investigated. A double-isothermal model of an isothermal stellar system, embedded in an isothermal dark halo core provides an excellent fit to the various observed stellar surface density distributions. The stellar system can be well characterised by King profiles with a broad distribution of concentration parameters c. The core scale length of the stellar system a_* is sensitive to the central dark matter density rho_0. In contrast to single-component systems, the cut-off radius of the stellar system, rs_t, however does not trace the tidal radius but the core radius r_c of its dark matter halo. c is therefore sensitive to the ratio of the stellar to the dark matter velocity dispersion, sigma_*/sigma_0. Simple empirical relationships are derived that allow to calculate the dark halo core parameters rho_0, r_c and sigma_0, given the observable quantities sigma_*, a_* and c. The DIS model is applied to the Milky Way's dSphs. Their halo velocity dispersions lie in a narrow range of 10km/s <= sigma_0 <= 18km/s with halo core radii of 280pc <= r_c <= 1.3kpc and r_c=2a_*. All dSphs follow closely the same universal dark halo core scaling relation rho_0*r_c=75 Msolar/pc^2 that characterises the cores of more massive galaxies over several orders of magnitude in mass. The dark matter core mass is a strong function of core radius. Inside a fixed radius r_u, with r_u the logarithmic mean of the dSph's core radii, the total enclosed mass M_u is however roughly constant, although outliers should exist. For our dSphs we find r_u=400pc and M_u=2.6*10^7 Msolar. The core densities of the Galaxy's dSphs are very high, with rho_0=0.2 Msolar/pc^3. They should therefore be tidally undisturbed. Observational evidence for tidal effects might then provide a serious challenge for the cold dark matter scenario.", "keyphrases": ["dwarf spheroidal galaxy", "dark matter halo", "core radius"]}
{"id": "0906.0926", "title": "Bootstrapping gravity: a consistent approach to energy-momentum self-coupling", "abstract": "It is generally believed that coupling the graviton (a classical Fierz-Pauli massless spin-2 field) to its own energy-momentum tensor successfully recreates the dynamics of the Einstein field equations order by order; however the validity of this idea has recently been brought into doubt [1]. Motivated by this, we present a graviton action for which energy-momentum self-coupling is indeed consistent with the Einstein field equations. The Hilbert energy-momentum tensor for this graviton is calculated explicitly and shown to supply the correct second-order term in the field equations; in contrast, the Fierz-Pauli action fails to supply the correct term. A formalism for perturbative expansions of metric-based gravitational theories is then developed, and these techniques employed to demonstrate that our graviton action is a starting point for a straightforward energy-momentum self-coupling procedure that, order by order, generates the Einstein-Hilbert action (up to a classically irrelevant surface term). The perturbative formalism is extended to include matter and a cosmological constant, and interactions between perturbations of a free matter field and the gravitational field are studied in a vacuum background. Finally, the effect of a non-vacuum background is examined, and the graviton is found to develop a non-vanishing \u201cmass-term\u201d in the action.", "keyphrases": ["energy-momentum self-coupling", "tensor", "gravitational field"]}
{"id": "1503.08491", "title": "Frequency-Dependent Dispersion Measures and Implications for Pulsar Timing", "abstract": "We analyze the frequency dependence of the dispersion measure (DM), the column density of free electrons to a pulsar, caused by multipath scattering from small scale electron-density fluctuations. The DM is slightly different along each propagation path and the transverse spread of paths varies greatly with frequency, yielding time-of-arrival (TOA) perturbations that scale differently than the inverse square of the frequency, the expected dependence for a cold, unmagnetized plasma. We quantify DM and TOA perturbations analytically for thin phase screens and extended media and verify the results with simulations of thin screens. The rms difference between DMs across an octave band near 1.5 GHz \u223c 4\u00d710^-5 pc cm^-3 for pulsars at \u223c 1 kpc distance. TOA errors from chromatic DMs are of order a few to hundreds of nanoseconds for pulsars with DM \u2272 30 pc cm^-3 observed across an octave band but increase rapidly to microseconds or larger for larger DMs and wider frequency ranges. Frequency-dependent DMs introduce correlated noise into timing residuals whose power spectrum is `low pass' in form. The correlation time is of order the geometric mean of the refraction times for the highest and lowest radio frequencies used and thus ranges from days to years, depending on the pulsar. We discuss the implications for methodologies that use large frequency separations or wide bandwidth receivers for timing measurements. Chromatic DMs are partially mitigable by using an additional chromatic term in arrival time models. Without mitigation, our results provide an additional term in the noise model for pulsar timing; they also indicate that in combination with measurement errors from radiometer noise, an arbitrary increase in total frequency range (or bandwidth) will yield diminishing benefits and may be detrimental to overall timing precision.", "keyphrases": ["dispersion measure", "pulsar timing", "timing precision"]}
{"id": "1211.0441", "title": "A longitudinal gauge degree of freedom and the Pais Uhlenbeck field", "abstract": "We show that a longitudinal gauge degree of freedom for a vector field is equivalent to a Pais-Uhlenbeck scalar field. With the help of this equivalence, we can determine natural interactions of this field with scalars and fermions. Since the theory has a global U(1) symmetry, we have the usual conserved current of the charged fields, thanks to which the dynamics of the scalar field is not modified by the interactions. We use this fact to consistently quantize the theory even in the presence of interactions. We argue that such a degree of freedom can only be excited by gravitational effects like the inflationary era of the early universe and may play the role of dark energy in the form of an effective cosmological constant whose value is linked to the inflation scale.", "keyphrases": ["longitudinal gauge degree", "gauge degree", "cosmological constant", "stueckelberg field"]}
{"id": "1304.3253", "title": "Variations on Birkhoff's theorem", "abstract": "The relation between the expanding universe and local vacuum solutions, such as that for the Solar System, is crucially mediated by Birkhoff's theorem. Here we consider how that relation works, and give generalizations of Birkhoff's theorem when there are geometric and matter and perturbations. The issue of to what degree dark matter might influence the solar system emerges as a significant question.", "keyphrases": ["birkhoff", "vacuum solution", "spherical symmetry"]}
{"id": "1312.7702", "title": "Asteroid families classification: exploiting very large data sets", "abstract": "The number of asteroids with accurately determined orbits increases fast. The catalogs of asteroid physical observations have also increased, although the number of objects is still smaller than in the orbital catalogs. We developed a new approach to the asteroid family classification by combining the Hierarchical Clustering Method (HCM) with a method to add new members to existing families. This procedure makes use of the much larger amount of information contained in the proper elements catalogs, with respect to classifications using also physical observations for a smaller number of asteroids. Our work is based on the large catalog of the high accuracy synthetic proper elements (available from AstDyS). We first identify a number of core families; to these we attribute the next layer of smaller objects. Then, we remove all the family members from the catalog, and reapply the HCM to the rest. This gives both halo families which extend the core families and new independent families, consisting mainly of small asteroids. These two cases are discriminated by another step of attribution of new members and by merging intersecting families. By using information from absolute magnitudes, we take advantage of the larger size range in some families to analyze their shape in the proper semimajor axis vs. inverse diameter plane. This leads to a new method to estimate the family age (or ages). The results from the previous steps are then analyzed, using also auxiliary information on physical properties including WISE albedos and SDSS color indexes. This allows to solve some difficult cases of families overlapping in the proper elements space but generated by different collisional events. We analyze some examples of cratering families (Massalia, Vesta, Eunomia) which show internal structures, interpreted as multiple collisions. We also discuss why Ceres has no family.", "keyphrases": ["hierarchical clustering method", "large catalog", "asteroid family classification"]}
{"id": "2004.08369", "title": "Turning in the landscape: a new mechanism for generating Primordial Black Holes", "abstract": "We propose a new model-independent mechanism for producing primordial black holes from a period of multi-field inflation. This requires an enhancement of primordial fluctuations at short scales compared to their value at CMB scales. We show that such an amplification naturally occurs when the inflationary trajectory exhibits a strong turn, that is a limited period during which the trajectory strongly deviates from a geodesic in field space, and is sufficient for subsequently producing primordial black holes with the abundance to be all or a fraction of dark matter. Our mechanism is generic to models of inflation realized in a multi-dimensional field space with an overlying potential and geometry, also referred to as the inflationary landscape, as arises in embeddings of inflation in high-energy theories. We study analytically and numerically how the duration and the strength of the turn impact the primordial fluctuation power spectrum and the abundance of primordial black holes. Our mechanism has the potential of exhibiting unique features accessible to observation through the primordial black hole spectrum and the stochastic background of gravitational waves, offering a precious glimpse at the dynamics of inflation.", "keyphrases": ["black hole", "multi-field inflation", "gravitational wave"]}
{"id": "1504.07632", "title": "On Detecting Halo Assembly Bias with Galaxy Populations", "abstract": "The fact that the clustering of dark matter halos depends not only on their mass, but also the formation epoch, is a prominent, albeit subtle, feature of the cold dark matter structure formation theory, and is known as assembly bias. At low mass scales (\u223c 10^12 h^-1M_\u2299), early-forming halos are predicted to be more strongly clustered than the late-forming ones. In this study we aim to robustly detect the signature of assembly bias observationally, making use of formation time indicators of central galaxies in low mass halos as a proxy for the halo formation history. Weak gravitational lensing is employed to ensure our early- and late-forming halo samples have similar masses, and are free of contamination of satellites from more massive halos. For the two formation time indicators used (resolved star formation history and current specific star formation rate), we do not find convincing evidence of assembly bias. For a pair of early- and late-forming galaxy samples with mean mass M_200c\u2248 9\u00d710^11 h^-1M_\u2299, the relative bias is 1.00\u00b1 0.12. We attribute the lack of detection to the possibilities that either the current measurements of these indicators are too noisy, or they do not correlate well with the halo formation history. Alternative proxies for the halo formation history that should perform better are suggested for future studies.", "keyphrases": ["assembly bias", "star formation rate", "galaxy sample"]}
{"id": "1310.4615", "title": "I-ball formation with logarithmic potential", "abstract": "A coherently oscillating real scalar field with potential shallower than quadratic one fragments into spherical objects called I-balls. We study the I-ball formation for logarithmic potential which appears in many cosmological models. We perform lattice simulations and find that the I-balls are formed when the potential becomes dominated by the quadratic term. Furthermore, we estimate the I-ball profile assuming that the adiabatic invariant is conserved during formation and obtain the result that agrees to the numerical simulations.", "keyphrases": ["logarithmic potential", "spherical object", "quadratic term", "i-ball formation", "oscillon"]}
{"id": "1106.3039", "title": "Warm natural inflation", "abstract": "In warm inflation models there is the requirement of generating large dissipative couplings of the inflaton with radiation, while at the same time, not de-stabilising the flatness of the inflaton potential due to radiative corrections. One way to achieve this without fine tuning unrelated couplings is by supersymmetry. In this paper we show that if the inflaton and other light fields are Pseudo-Nambu-Goldstone Bosons then the radiative corrections to the potential are suppressed and the thermal corrections are small as long as the temperature is below the symmetry breaking scale. In such models it is possible to fulfill the contrary requirements of an inflaton potential which is stable under radiative corrections and the generation of a large dissipative coupling of the inflaton field with other light fields. We construct a warm inflation model which gives the observed CMB-anisotropy amplitude and spectral index where the symmetry breaking is at the GUT scale.", "keyphrases": ["natural inflation", "coefficient", "additional field"]}
{"id": "1104.3096", "title": "Comprehensive cosmographic analysis by Markov Chain Method", "abstract": "We study the possibility to extract model independent information about the dynamics of the universe by using Cosmography. We intend to explore it systematically, to learn about its limitations and its real possibilities. Here we are sticking to the series expansion approach on which Cosmography is based. We apply it to different data sets: Supernovae Type Ia (SNeIa), Hubble parameter extracted from differential galaxy ages, Gamma Ray Bursts (GRBs) and the Baryon Acoustic Oscillations (BAO) data. We go beyond past results in the literature extending the series expansion up to the fourth order in the scale factor, which implies the analysis of the deceleration, q_0, the jerk, j_0 and the snap, s_0. We use the Markov Chain Monte Carlo Method (MCMC) to analyze the data statistically. We also try to relate direct results from Cosmography to dark energy (DE) dynamical models parameterized by the Chevalier-Polarski-Linder (CPL) model, extracting clues about the matter content and the dark energy parameters. The main results are: a) even if relying on a mathematical approximate assumption such as the scale factor series expansion in terms of time, cosmography can be extremely useful in assessing dynamical properties of the Universe; b) the deceleration parameter clearly confirms the present acceleration phase; c) the MCMC method can help giving narrower constraints in parameter estimation, in particular for higher order cosmographic parameters (the jerk and the snap), with respect to the literature; d) both the estimation of the jerk and the DE parameters, reflect the possibility of a deviation from the LCDM cosmological model.", "keyphrases": ["markov chain method", "cosmography", "scale factor"]}
{"id": "1705.01475", "title": "A Robust BAO Extractor", "abstract": "We define a procedure to extract the oscillating part of a given nonlinear Power Spectrum, and derive an equation describing its evolution including the leading effects at all scales. The intermediate scales are taken into account by standard perturbation theory, the long range (IR) displacements are included by using consistency relations, and the effect of small (UV) scales is included via effective coefficients computed in simulations. We show that the UV effects are irrelevant in the evolution of the oscillating part, while they play a crucial role in reproducing the smooth component. Our \"extractor\" operator can be applied to simulations and real data in order to extract the Baryonic Acoustic Oscillations (BAO) without any fitting function and nuisance parameter. We conclude that the nonlinear evolution of BAO can be accurately reproduced at all scales down to z=0 by our fast analytical method, without any need of extra parameters fitted from simulations.", "keyphrases": ["extractor", "procedure", "smooth component"]}
{"id": "1202.5375", "title": "Scalar Domain Wall as the Universe", "abstract": "We develop a formulation where for an arbitrarily given warp factor, we construct a scalar field action which reproduces the warp factor as a solution of the Einstein equation and field equation corresponding to the action. This formulation could be called as the reconstruction. By using the formulation of the reconstruction, we construct models which have an exact solution describing the domain wall. The shape of the domain wall can be flat, de Sitter space-time, or anti-de Sitter space-time. In the constructed domain wall solutions, there often appears ghost with negative kinetic energy. We give, however, an example of the de Sitter domain wall solution without ghost, which could be a toy model of inflation. We also investigate the localization of gravity as in the Randall-Sundrum model. It is demonstrated that the four dimensional Newton law could be reproduced even in the de Sitter space-time domain wall solution. We show that we can construct a space-time, where the domain wall is the general Friedmann-Robertson-Walker (FRW) universe and the warp factor can be arbitrary. For such a construction, we use two scalar fields. It is also illustrated that the scalar field equations are equivalent to the Bianchi identities: \u2207^\u03bc (R_\u03bc\u03bd - 1/2R g_\u03bc\u03bd)=0.", "keyphrases": ["domain wall", "universe", "scalar field", "bianchi identity"]}
{"id": "1001.5396", "title": "Triggering collective oscillations by three-flavor effects", "abstract": "Collective flavor transformations in supernovae, caused by neutrino-neutrino interactions, are essentially a two-flavor phenomenon driven by the atmospheric mass difference and the small mixing angle theta_13. In the two-flavor approximation, the initial evolution depends logarithmically on theta_13 and the system remains trapped in an unstable fixed point for theta_13 = 0. However, any effect breaking exact nu_mu-nu_tau equivalence triggers the conversion. Such three-flavor perturbations include radiative corrections to weak interactions, small differences between the nu_mu and nu_tau fluxes, or non-standard interactions. Therefore, extremely small values of theta_13 are in practice equivalent, the fate of the system depending only on the neutrino spectra and their mass ordering.", "keyphrases": ["neutrino-neutrino interaction", "phenomenon", "collective flavor conversion"]}
{"id": "1709.03845", "title": "Stochastic gravitational waves from cosmic string loops in scaling", "abstract": "If cosmic strings are formed in the early universe, their associated loops emit gravitational waves during the whole cosmic history and contribute to the stochastic gravitational wave background at all frequencies. We provide a new estimate of the stochastic gravitational wave spectrum by considering a realistic cosmological loop distribution, in scaling, as it can be inferred from Nambu-Goto numerical simulations. Our result takes into account various effects neglected so far. We include both gravitational wave emission and backreaction effects on the loop distribution and show that they produce two distinct features in the spectrum. Concerning the string microstructure, in addition to the presence of cusps and kinks, we show that gravitational wave bursts created by the collision of kinks could dominate the signal for wiggly strings, a situation which may be favoured in the light of recent numerical simulations. In view of these new results, we propose four prototypical scenarios, within the margin of the remaining theoretical uncertainties, for which we derive the corresponding signal and estimate the constraints on the string tension put by both the LIGO and European Pulsar Timing Array (EPTA) observations. The less constrained of these scenarios is shown to have a string tension GU < 7.2 x 10^-11, at 95 cusps per oscillation verify the two-sigma bound GU < 1.0 x 10^-11 while the most constrained of all scenarios describes very kinky loops and satisfies GU < 6.7 x 10^-14 at 95", "keyphrases": ["loop distribution", "string tension", "stochastic gravitational wave"]}
{"id": "1503.07579", "title": "Large Scale Power Suppression in a Multifield Landscape", "abstract": "Power suppression of the cosmic microwave background on the largest observable scales could provide valuable clues about the particle physics underlying inflation. Here we consider the prospect of power suppression in the context of the multifield landscape. Based on the assumption that our observable universe emerges from a tunnelling event and that the relevant features originate purely from inflationary dynamics, we find that the power spectrum not only contains information on single-field dynamics, but also places strong con- straints on all scalar fields present in the theory. We find that the simplest single-field models giving rise to power suppression do not generalise to multifield models in a straightforward way, as the resulting superhorizon evolution of the curvature perturbation tends to erase any power suppression present at horizon crossing. On the other hand, multifield effects do present a means of generating power suppression which to our knowledge has so far not been considered. We propose a mechanism to illustrate this, which we dub flume inflation.", "keyphrases": ["multifield landscape", "universe", "power spectrum"]}
{"id": "1808.00357", "title": "Effects of neutrino mass and asymmetry on cosmological structure formation", "abstract": "Light but massive cosmological neutrinos do not cluster significantly on small scales, due to their high thermal velocities. With finite masses, cosmological neutrinos become part of the total matter field and contribute to its smoothing. Structure formation in the presence of massive neutrinos is therefore impeded compared to that in the standard \u039bCDM cosmology with massless neutrinos. Neutrinos' masses also distort the anisotropy power spectrum of cosmic microwave background (CMB). Furthermore, a finite chemical potential \u03bc for cosmological neutrinos, still allowed by current data, would have a non-negligible impact on CMB and structure formation. We consistently evaluate effects of neutrino masses and chemical potentials on the matter power spectrum by use of a neutrino-involved N-body simulation, with cosmological parameters obtained from a Markov-Chian Moonte-Carlo (MCMC) refitting of CMB data. Our results show that while a finite averaged neutrino mass m_\u03bd tends to suppress the matter power spectrum in a range of wave numbers, the neutrino degeneracy parameters \u03be_i \u2261\u03bc_i /T (i=1, 2, 3) enhance the latter, leading to a large parameter degeneracy between m_\u03bd and \u03be_i. We provide an empirical formula for the effects on the matter power spectrum in a selected range of wave numbers induced by m_\u03bd and \u03b7\u2261\u221a(\u2211_i \u03be^2_i). Observing a strong correlation between m_\u03bd and \u03b7, we propose a single redshift-independent parameter m_\u03bd - 4/3\u03b7^2 to characterize the neutrino effects on the matter power spectrum.", "keyphrases": ["neutrino", "matter power spectrum", "parameter degeneracy"]}
{"id": "2010.03976", "title": "NANOGrav Hints on Planet-Mass Primordial Black Holes", "abstract": "Recently, the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) claimed the detection of a stochastic common-spectrum process of the pulsar timing array (PTA) time residuals from their 12.5 year data, which might be the first detection of the stochastic background of gravitational waves (GWs). We show that the amplitude and the power index of such waves imply that they could be the secondary GWs induced by the peaked curvature perturbation with a dust-like post inflationary era with -0.091\u2272 w\u22720.048. Such stochastic background of GWs naturally predicts substantial existence of planet-mass primordial black holes (PBHs), which can be the lensing objects for the ultrashort-timescale microlensing events observed by the Optical Gravitational Lensing Experiment (OGLE).", "keyphrases": ["primordial black hole", "gravitational wave", "nanograv result"]}
{"id": "1805.04520", "title": "Coordinated Assembly of Brightest Cluster Galaxies", "abstract": "Brightest Cluster Galaxies (BCGs) in massive dark matter halos are shaped by complex merging processes. We present a detailed stellar population analysis in the central region of Abell 3827 at z\u223c0.1, including five-nucleus galaxies involved in a BCG assembly. Based on deep spectroscopy from Multi Unit Spectroscopic Explorer (MUSE), we fit the optical spectra of 13 early-type galaxies (ETGs) in the central 70 kpc of the cluster. The stellar populations in the central R=1 kpc of these ETGs are old (6-10 Gyr). Their [Fe/H] increases with \u03c3_\u22c6 and stellar mass. More importantly, [\u03b1/Fe] of galaxies close to the cluster center do not seem to depend on \u03c3_\u22c6 or stellar mass, indicating that the cluster center shapes the [\u03b1/Fe]-\u03c3_\u22c6 and [\u03b1/Fe]-M_\u22c6 relations differently than other environments where [\u03b1/Fe] is observed to increase with increasing \u03c3_\u22c6 or M_\u22c6. Our results reveal the coordinated assembly of BCGs: their building blocks are different from the general low mass populations by their high [\u03b1/Fe]. Massive galaxies thus grow by accreting preferentially high [\u03b1/Fe] systems. The radial profiles also bear the imprint of the coordinated assembly. Their declining [Fe/H] and flat [\u03b1/Fe] radial profiles confirm that the accreted systems have low metallicity and high [\u03b1/Fe] stellar contents.", "keyphrases": ["galaxy", "stellar population", "coordinated assembly"]}
{"id": "1409.3591", "title": "Neutrino-antineutrino correlations in dense anisotropic media", "abstract": "We derive the most general evolution equations describing in-medium (anti)neutrino propagation in the mean-field approximation. In particular, we consider various types of neutrino-antineutrino mixing, for both Dirac and Majorana fields, resulting either from nontrivial pair correlations or from helicity coherence due to the nonvanishing neutrino masses. We show that, unless the medium is spatially homogeneous and isotropic, these correlations are sourced by the usual neutrino and antineutrino densities. This may be of importance in astrophysical environments such as core-collapse supernovae.", "keyphrases": ["neutrino", "astrophysical environment", "neutrino-antineutrino correlation"]}
{"id": "1808.00013", "title": "Gravity's Islands: Parametrizing Horndeski Stability", "abstract": "Cosmic acceleration may be due to modified gravity, with effective field theory or property functions describing the theory. Connection to cosmological observations through practical parametrization of these functions is difficult and also faces the issue that not all assumed time dependence or parts of parameter space give a stable theory. We investigate the relation between parametrization and stability in Horndeski gravity, showing that the results are highly dependent on the function parametrization. This can cause misinterpretations of cosmological observations, hiding and even ruling out key theoretical signatures. We discuss approaches and constraints that can be placed on the property functions and scalar sound speed to preserve some observational properties, but find that parametrizations closest to the observations, e.g. in terms of the gravitational strengths, offer more robust physical interpretations. In addition we present an example of how future observations of the B-mode polarization of the cosmic microwave background from primordial gravitational waves can probe different aspects of gravity.", "keyphrases": ["stability", "gravity", "primordial tensor perturbation", "tensor mode", "late time"]}
{"id": "1702.02483", "title": "The Dipole Repeller", "abstract": "In the standard (LCDM) model of cosmology the universe has emerged out of an early homogeneous and isotropic phase. Structure formation is associated with the growth of density irregularities and peculiar velocities. Our Local Group is moving with respect to the cosmic microwave background (CMB) with a velocity 631+/-20 km s-1 and participates in a bulk flow that extends out to distances of at least 20,000 km s-1. Since the discovery of the CMB dipole, the implicit assumption was that excesses in the abundance of galaxies induce the Local Group motion. Yet, underdense regions push as much as overdensities attract but they are deficient of light and consequently difficult to chart. It was suggested a decade ago that an underdensity in the northern hemisphere roughly 15,000 km s-1 away is a significant actor in the local flow. Here we report on kinematic evidence for such an underdensity. We map the large scale 3D velocity field using a Wiener filter reconstruction from the Cosmicflows-2 dataset of peculiar velocities, and identify the attractors and repellers that dominate the local dynamics. We show here that the local flow is dominated by a single attractor -associated with the Shapley Concentration- and a single previously unidentified repeller. Multipole expansion of the local flow provides further support for the existence and role played by the attractor and repeller. The bulk flow (i.e. dipole moment) is closely (anti)aligned with the repeller at a distance of 16,000+/-4,500 km s-1. The expansion eigenvector of the shear tensor (quadrupole moment) is closely aligned with the Shapley Attractor out to 7,000 km s-1. The close alignment of the local bulk flow with the repeller provides further support for its dominant role in shaping the local flow. This Dipole Repeller is predicted to be associated with a void in the distribution of galaxies.", "keyphrases": ["dipole repeller", "universe", "flow"]}
{"id": "1009.0224", "title": "Weak Corrections are Relevant for Dark Matter Indirect Detection", "abstract": "The computation of the energy spectra of Standard Model particles originated from the annihilation/decay of dark matter particles is of primary importance in indirect searches of dark matter. We compute how the inclusion of electroweak corrections significantly alter such spectra when the mass M of dark matter particles is larger than the electroweak scale: soft electroweak gauge bosons are copiously radiated opening new channels in the final states which otherwise would be forbidden if such corrections are neglected. All stable particles are therefore present in the final spectrum, independently of the primary channel of dark matter annihilation/decay. Such corrections are model independent.", "keyphrases": ["electroweak", "gauge boson", "dark matter annihilation"]}
{"id": "1908.04651", "title": "Progressive steepening of the SNR RX J1713.7-3946 X-ray spectrum from XMM-Newton to INTEGRAL", "abstract": "In this work, we present the first detailed analysis of the supernova remnant RX J1713.7-3946 in the hard X-ray energy range with the IBIS coded-mask telescope on board the INTEGRAL observatory. The shell-type morphology of the entire remnant is mapped in hard X-rays for the first time and significantly detected up to 50 keV. The IBIS sky image of RX J1713.7-3946, accumulated over 14 years of operations, demonstrates two extended hard X-ray sources. These sources are spatially consistent with northwest and southwest rims of RX J1713.7-3946 and are also clearly visible at energies below 10 keV with XMM-Newton. This points to a single emission mechanism operating in soft and hard X-rays. The INTEGRAL 17-120 keV spectrum of RX J1713.7-3946 is characterized by a power-law continuum with the photon index of \u0393\u22483, that is significantly softer than \u0393\u22482 determined by XMM-Newton in the 1-10 keV energy range, suggesting a progressive steepening of the spectrum with the energy.", "keyphrases": ["steepening", "x-ray spectrum", "kev spectrum", "photon index"]}
{"id": "1605.06567", "title": "The Frontier Fields: Survey Design", "abstract": "The Frontier Fields are a director's discretionary time campaign with HST and the Spitzer Space Telescope to see deeper into the universe than ever before. The Frontier Fields combine the power of HST and Spitzer with the natural gravitational telescopes of massive high-magnification clusters of galaxies to produce the deepest observations of clusters and their lensed galaxies ever obtained. Six clusters - Abell 2744, MACSJ0416.1-2403, MACSJ0717.5+3745, MACSJ1149.5+2223, Abell S1063, and Abell 370 - were selected based on their lensing strength, sky darkness, Galactic extinction, parallel field suitability, accessibility to ground-based facilities, HST, Spitzer and JWST observability, and pre-existing ancillary data. These clusters have been targeted by the HST ACS/WFC and WFC3/IR with coordinated parallels of adjacent blank fields for over 840 HST orbits. The Spitzer Space Telescope has dedicated > 1000 hours of director's discretionary time to obtain IRAC 3.6 and 4.5 micron imaging to 26.5, 26.0 ABmag 5-sigma point-source depths in the six cluster and six parallel Frontier Fields. The Frontier Field parallel fields are the second-deepest observations thus far by HST with 29th ABmag 5-sigma point source depths in seven optical - near-infrared bandpasses. Galaxies behind the Frontier Field cluster lenses experience typical magnification factors of a few, with small regions near the critical curves magnified by factors 10-100. Therefore, the Frontier Field cluster HST images achieve intrinsic depths of 30-33 magnitudes over very small volumes. Early studies of the Frontier Fields have probed galaxies fainter than any seen before during the epoch of reionization 6 < z < 10, mapped out the cluster dark matter to unprecedented resolution, and followed lensed transient events.", "keyphrases": ["frontier fields", "target", "wfc3"]}
{"id": "2005.06568", "title": "Tomographic Constraints on Gravity from Angular Redshift Fluctuations in the Late Universe", "abstract": "Fluctuations in sky maps of the galaxy redshifts, dubbed as angular redshift fluctuations (ARF), contain precise information about the growth rate of structures and the nature of gravity in the Universe. Specifically, ARF constrain the combination of cosmological parameters H/H_0 f\u03c3_8(z), while being an intrinsically tomographic probe and largely insensitive to many observational systematic errors, all this without requiring the assumption of any redshift-to-distance relation under a given fiducial cosmology. We present the first cosmological constraints derived from ARF by using BOSS LOWZ+CMASS DR12 galaxy samples, obtaining 7%-accurate constraints on H/H_0 f\u03c3_8(z) at more than 20 redshifts over the range z \u2208 [0.26,0.72]. Our best-fitting value is 10% larger, but compatible at the 1.4\u03c3 level, than the \u039bCDM expectation set by Planck observations of the Cosmic Microwave Background (CMB) radiation. Our tomographic measurements, combined with these CMB data, provides one of the strongest constraints on the gravity index \u03b3, \u03b3=0.44^+0.09_-0.07, which lies within 2\u03c3 from the prediction of General Relativity (\u03b3_ GR\u2243 0.55).", "keyphrases": ["gravity", "redshift", "cosmological constraint"]}
{"id": "2110.05615", "title": "Spirals in galaxies", "abstract": "Spirals in galaxies have long been thought to be caused by gravitational instability in the stellar component of the disk, but discerning the precise mechanism had proved elusive. Tidal interactions, and perhaps bars, may provoke some spiral responses, but spirals in many galaxies must be self-excited. We survey the relevant observational data and aspects of disk dynamical theory. The origin of the recurring spiral patterns in simulations of isolated disk galaxies has recently become clear and it is likely that the mechanism is the same in real galaxies, although evidence to confirm this supposition is hard to obtain. As transient spiral activity increases random motion, the patterns must fade over time unless the disk also contains a dissipative gas component. Continuing spiral activity alters the structure of the disks in other ways: reducing metallicity gradients and flattening rotation curves are two of the most significant. The overwhelming majority of spirals in galaxies have two- or three-fold rotational symmetry, indicating that the cool, thin disk component is massive. Spirals in simulations of halo-dominated disks instead manifest many arms, and consequently do not capture the expected full spiral-driven evolution. We conclude by identifying areas where further work is needed.", "keyphrases": ["galaxy", "spiral pattern", "arm"]}
{"id": "1003.2788", "title": "A New Type of Dark Energy Model", "abstract": "In this paper, we propose a general form of the equation of state (EoS) which is the function of the fractional dark energy density \u03a9_d. At least, five related models, the cosmological constant model, the holographic dark energy model, the agegraphic dark energy model, the modified holographic dark energy model and the Ricci scalar holographic dark energy model are included in this form. Furthermore, if we consider proper interactions, the interactive variants of those models can be included as well. The phase-space analysis shows that the scaling solutions may exist both in the non-interacting and interacting cases. And the stability analysis of the system could give out the attractor solution which could alleviate the coincidence problem.", "keyphrases": ["dark energy model", "phase-space analysis", "coincidence problem"]}
{"id": "1706.02319", "title": "Multifield Stochastic Particle Production: Beyond a Maximum Entropy Ansatz", "abstract": "We explore non-adiabatic particle production for N_ f coupled scalar fields in a time-dependent background with stochastically varying effective masses, cross-couplings and intervals between interactions. Under the assumption of weak scattering per interaction, we provide a framework for calculating the typical particle production rates after a large number of interactions. After setting up the framework, for analytic tractability, we consider interactions (effective masses and cross couplings) characterized by series of Dirac-delta functions in time with amplitudes and locations drawn from different distributions. Without assuming that the fields are statistically equivalent, we present closed form results (up to quadratures) for the asymptotic particle production rates for the N_ f=1 and N_ f=2 cases. We also present results for the general N_ f >2 case, but with more restrictive assumptions. We find agreement between our analytic results and direct numerical calculations of the total occupation number of the produced particles, with departures that can be explained in terms of violation of our assumptions. We elucidate the precise connection between the maximum entropy ansatz (MEA) used in Amin Baumann (2015) and the underlying statistical distribution of the self and cross couplings. We provide and justify a simple to use (MEA-inspired) expression for the particle production rate, which agrees with our more detailed treatment when the parameters characterizing the effective mass and cross-couplings between fields are all comparable to each other. However, deviations are seen when some parameters differ significantly from others. We show that such deviations become negligible for a broad range of parameters when N_ f\u226b 1.", "keyphrases": ["maximum entropy ansatz", "non-adiabatic particle production", "series"]}
{"id": "1801.02699", "title": "Measuring the binary black hole mass spectrum with an astrophysically motivated parameterization", "abstract": "Gravitational-wave detections have revealed a previously unknown population of stellar mass black holes with masses above 20 M_\u2299. These observations provide a new way to test models of stellar evolution for massive stars. By considering the astrophysical processes likely to determine the shape of the binary black hole mass spectrum, we construct a parameterized model to capture key spectral features that relate gravitational-wave data to theoretical stellar astrophysics. In particular, we model the signature of pulsational pair-instability supernovae, which are expected to cause all stars with initial mass 100 M_\u2299\u2272 M \u2272 150 M_\u2299 to form \u223c 40 M_\u2299 black holes. This would cause a cut-off in the black hole mass spectrum along with an excess of black holes near 40 M_\u2299. We carry out a simulated data study to illustrate some of the stellar physics that can be inferred using gravitational-wave measurements of binary black holes and demonstrate several such inferences that might be made in the near future. First, we measure the minimum and maximum stellar black hole mass. Second, we infer the presence of a peak due to pair-instability supernovae. Third, we measure the black hole mass ratio distribution. Finally, we show how inadequate models of the black hole mass spectrum lead to biased estimates of the merger rate and the amplitude of the stochastic gravitational-wave background.", "keyphrases": ["black hole mass", "astrophysic", "pair-instability supernovae"]}
{"id": "0905.3338", "title": "Eta Carinae and the Luminous Blue Variables", "abstract": "We evaluate the place of Eta Carinae amongst the class of luminous blue variables (LBVs) and show that the LBV phenomenon is not restricted to extremely luminous objects like Eta Car, but extends luminosities as low as log(L/Lsun) = 5.4 - corresponding to initial masses 25 Msun, and final masses as low as 10-15 Msun. We present a census of S Doradus variability, and discuss basic LBV properties, their mass-loss behaviour, and whether at maximum light they form pseudo-photospheres. We argue that those objects that exhibit giant Eta Car-type eruptions are most likely related to the more common type of S Doradus variability. Alternative atmospheric models as well as sub-photospheric models for the instability are presented, but the true nature of the LBV phenomenon remains as yet elusive. We end with a discussion on the evolutionary status of LBVs - highlighting recent indications that some LBVs may be in a direct pre-supernova state, in contradiction to the standard paradigm for massive star evolution.", "keyphrases": ["luminous blue variable", "massive star evolution", "eta carinae"]}
{"id": "1809.03229", "title": "Primordial features from ekpyrotic bounces", "abstract": "Certain features in the primordial scalar power spectrum are known to improve the fit to the cosmological data. We examine whether bouncing scenarios can remain viable if future data confirm the presence of such features. In inflation, the fact that the trajectory is an attractor permits the generation of features. However, bouncing scenarios often require fine tuned initial conditions, and it is only the ekpyrotic models that allow attractors. We demonstrate, for the first time, that ekpyrotic scenarios can generate specific features that have been considered in the context of inflation.", "keyphrases": ["bounce", "cosmology", "bkl instability", "alternative", "energy issue"]}
{"id": "0912.0432", "title": "Conformal Invariance in Einstein-Cartan-Weyl space", "abstract": "We consider conformally invariant form of the actions in Einstein, Weyl, Einstein-Cartan and Einstein-Cartan-Weyl space in general dimensions(>2) and investigate the relations among them. In Weyl space, the observational consistency condition for the vector field determining non-metricity of the connection can be obtained from the equation of motion. In Einstein-Cartan space a similar role is played by the vector part of the torsion tensor. We consider the case where the trace part of the torsion is the Kalb-Ramond type of field. In this case, we express conformally invariant action in terms of two scalar fields of conformal weight -1, which can be cast into some interesting form. We discuss some applications of the result.", "keyphrases": ["einstein-cartan-weyl space", "weyl", "scalar field"]}
{"id": "1306.1821", "title": "Methods for Bayesian power spectrum inference with galaxy surveys", "abstract": "We derive and implement a full Bayesian large scale structure inference method aiming at precision recovery of the cosmological power spectrum from galaxy redshift surveys. Our approach improves over previous Bayesian methods by performing a joint inference of the three dimensional density field, the cosmological power spectrum, luminosity dependent galaxy biases and corresponding normalizations. We account for all joint and correlated uncertainties between all inferred quantities. Classes of galaxies with different biases are treated as separate sub samples. The method therefore also allows the combined analysis of more than one galaxy survey. In particular, it solves the problem of inferring the power spectrum from galaxy surveys with non-trivial survey geometries by exploring the joint posterior distribution with efficient implementations of multiple block Markov chain and Hybrid Monte Carlo methods. Our Markov sampler achieves high statistical efficiency in low signal to noise regimes by using a deterministic reversible jump algorithm. We test our method on an artificial mock galaxy survey, emulating characteristic features of the Sloan Digital Sky Survey data release 7, such as its survey geometry and luminosity dependent biases. These tests demonstrate the numerical feasibility of our large scale Bayesian inference frame work when the parameter space has millions of dimensions. The method reveals and correctly treats the anti-correlation between bias amplitudes and power spectrum, which are not taken into account in current approaches to power spectrum estimation, a 20 percent effect across large ranges in k-space. In addition, the method results in constrained realizations of density fields obtained without assuming the power spectrum or bias parameters in advance.", "keyphrases": ["power spectrum", "galaxy survey", "density field"]}
{"id": "1305.5302", "title": "Planck Constraints on Holographic Dark Energy", "abstract": "We perform a detailed investigation on the cosmological constraints on the holographic dark energy (HDE) model by using the Planck data. HDE can provide a good fit to Planck high-l (l>40) temperature power spectrum, while the discrepancy at l=20-40 found in LCDM remains unsolved in HDE. The Planck data alone can lead to strong and reliable constraint on the HDE parameter c. At 68 CL, we get c=0.508+-0.207 with Planck+WP+lensing, favoring the present phantom HDE at > 2sigma CL. Comparably, by using WMAP9 alone we cannot get interesting constraint on c. By combining Planck+WP with the BAO measurements from 6dFGS+SDSS DR7(R)+BOSS DR9, the H0 measurement from HST, the SNLS3 and Union2.1 SNIa data sets, we get 68 0.594+-0.051 and 0.642+-0.066. Constraints can be improved by 2 further add the Planck lensing data. Compared with the WMAP9 results, the Planck results reduce the error by 30 higher CL. We find no evident tension between Planck and BAO/HST. Especially, the strong correlation between Omegam h^3 and dark energy parameters is helpful in relieving the tension between Planck and HST. The residual chi^2_Planck+WP+HST-chi^2_Planck+WP is 7.8 in LCDM, and is reduced to 1.0 or 0.3 if we switch dark energy to the w model or the holographic model. We find SNLS3 is in tension with all other data sets; for Planck+WP, WMAP9 and BAO+HST, the corresponding Delta chi^2 is 6.4, 3.5 and 4.1, respectively. Comparably, Union2.1 is consistent with these data sets, but the combination Union2.1+BAO+HST is in tension with Planck+WP+lensing, corresponding to a Delta chi^2 8.6 (1.4 all-combined (CMB+SNIa+BAO+HST) analysis for HDE when using the Planck data. Our tightest self-consistent constraint is c=0.495+-0.039 obtained from Planck+WP+BAO+HST+lensing.", "keyphrases": ["holographic dark energy", "cosmology", "dark energy model"]}
{"id": "1403.3334", "title": "Far-infrared surveys of galaxy evolution", "abstract": "Roughly half of the radiation from evolving galaxies in the early universe reaches us in the far-infrared and submillimeter wavelength range. Recent major advances in observing capabilities, in particular the launch of the Herschel Space Observatory in 2009, have dramatically enhanced our ability to use this information in the context of multiwavelength studies of galaxy evolution. Near its peak, three quarters of the cosmic infrared background is now resolved into individually detected sources. The use of far-infrared diagnostics of dust-obscured star formation and of interstellar medium conditions has expanded from rare extreme high-redshift galaxies to more typical main sequence galaxies and hosts of active galactic nuclei, out to z> 2. These studies shed light on the evolving role of steady equilibrium processes and of brief starbursts, at and since the peak of cosmic star formation and black hole accretion. This review presents a selection of recent far-infrared studies of galaxy evolution, with an emphasis on Herschel results", "keyphrases": ["galaxy evolution", "universe", "submillimeter wavelength range"]}
{"id": "1407.3905", "title": "Effects of Biases in Domain Wall Network Evolution", "abstract": "We study the evolution of various types of biased domain wall networks in the early universe. We carry out larger numerical simulations than currently available in the literature and provide a more detailed study of the decay of these networks, in particular by explicitly measuring velocities in the simulations. We also use the larger dynamic range of our simulations to test previously suggested decay laws for these networks, including an ad-hoc phenomenological fit to earlier simulations and a decay law obtained by Hindmarsh through analytic arguments. We find the latter to be in good agreement with simulations in the case of a biased potential, but not in the case of biased initial conditions.", "keyphrases": ["domain wall network", "various type", "initial condition"]}
{"id": "1504.05481", "title": "Effective Theory of Interacting Dark Energy", "abstract": "We present a unifying treatment of dark energy and modified gravity that allows distinct conformal-disformal couplings of matter species to the gravitational sector. In this very general approach, we derive the conditions to avoid ghost and gradient instabilities. We compute the equations of motion for background quantities and linear perturbations. We illustrate our formalism with two simple scenarios, where either cold dark matter or a relativistic fluid is nonminimally coupled. This extends previous studies of coupled dark energy to a much broader spectrum of gravitational theories.", "keyphrases": ["dark energy", "gravity", "dark matter"]}
{"id": "1012.1372", "title": "Observable Signatures of Inflaton Decays", "abstract": "We numerically compute features in the power-spectrum that originate from the decay of fields during inflation. Using a simple, phenomenological, multi-field setup, we increase the number of fields from a few to thousands. Whenever a field decays, its associated potential energy is transferred into radiation, causing a jump in the equation of state parameter and mode mixing at the perturbed level. We observe discrete steps in the power-spectrum if the number of fields is low, in agreement with analytic arguments in the literature. These features become increasingly smeared out once many fields decay within a given Hubble time. In this regime we confirm the validity of the analytic approach to staggered inflation, which is based on a coarse-graining procedure. Our numerical approach bridges the aforementioned analytic treatments, and can be used in more complicated scenarios.", "keyphrases": ["power-spectrum", "field annihilation", "high energy physic"]}
{"id": "1211.1015", "title": "Calibration errors unleashed: effects on cosmological parameters and requirements for large-scale structure surveys", "abstract": "Imperfect photometric calibration of galaxy surveys due to either astrophysical or instrumental effects leads to biases in measuring galaxy clustering and in the resulting cosmological parameter measurements. More interestingly (and disturbingly), the spatially varying calibration also generically leads to violations of statistical isotropy of the galaxy clustering signal. Here we develop, for the first time, a formalism to propagate the effects of photometric calibration variations with arbitrary spatial dependence across the sky to the observed power spectra and to the cosmological parameter constraints. We develop an end-to-end pipeline to study the effects of calibration, and illustrate our results using specific examples including Galactic dust extinction and survey-dependent magnitude limits as a function of zenith angle of the telescope. We establish requirements on the control of calibration so that it doesn't significantly bias constraints on dark energy and primordial non-Gaussianity. Two principal findings are: 1) largest-angle photometric calibration variations (dipole, quadrupole and a few more modes, though not the monopole) are the most damaging, and 2) calibration will need to be understood at the 0.1 to accuracy between 0.001 and 0.01 mag), though the precise requirement strongly depends on the faint-end slope of the luminosity function and the redshift distribution of galaxies in the survey.", "keyphrases": ["cosmological parameter", "galaxy survey", "calibration error", "observational systematic", "power spectrum"]}
{"id": "1911.00429", "title": "Quantum-enhanced interferometry for axion searches", "abstract": "We propose an experiment to search for axions and axion-like-particles in the galactic halo using quantum-enhanced interferometry. This proposal is related to the previously reported ideas (Phys. Rev. D 98, 035021, Phys. Rev. Lett. 121, 161301, Phys. Rev. D 100, 023548) but searches for axions in the mass range from 10^-16 eV up to 10^-8 eV using two coupled optical cavities. We also show how to apply squeezed states of light to enhance the sensitivity of the experiment similar to the gravitational-wave detectors. The proposed experiment has a potential to be further scaled up to a multi-km long detector. We show that such an instrument has a potential to set constrains of the axion-photon coupling coefficient of \u223c 10^-18 GeV^-1 for axion masses of 10^-16 eV or detect the signal.", "keyphrases": ["axion", "quantum-enhanced interferometry", "dark matter"]}
{"id": "1203.5777", "title": "What Are Special About Ground-Level Events? Flares, CMEs, Active Regions And Magnetic Field Connection", "abstract": "Ground level events (GLEs) occupy the high-energy end of gradual solar energetic particle (SEP) events. They are associated with coronal mass ejections (CMEs) and solar flares, but we still do not clearly understand the special conditions that produce these rare events. During Solar Cycle 23, a total of 16 GLEs were registered, using ground-based neutron monitor data. We first ask if these GLEs are clearly distinguishable from other SEP events observed from space. Setting aside possible difficulties in identifying all GLEs consistently, we then try to find observables which may unmistakably isolate these GLEs by studying the basic properties of the associated eruptions and the active regions (ARs) that produced them. It is found that neither the magnitudes of the CMEs and flares nor the complexities of the ARs give sufficient conditions for GLEs. It is possible to find CMEs, flares or ARs that are not associated with GLEs but that have more extreme properties than those associated with GLEs. We also try to evaluate the importance of magnetic field connection of the AR with Earth on the detection of GLEs and their onset times. Using the potential field source surface (PFSS) model, a half of the GLEs are found to be well-connected. However, the GLE onset time with respect to the onset of the associated flare and CME does not strongly depend on how well-connected the AR is. The GLE onset behavior may be largely determined by when and where the CME-driven shock develops. We could not relate the shocks responsible for the onsets of past GLEs with features in solar images, but the combined data from the Solar TErrestrial RElations Observatory (STEREO) and the Solar Dynamics Observatory (SDO) have the potential to change this for GLEs that may occur in the rising phase of Solar Cycle 24.", "keyphrases": ["flare", "active region", "magnetic field connection", "sep event"]}
{"id": "1304.1804", "title": "The Cosmophenomenology of Axionic Dark Radiation", "abstract": "Relativistic axions are good candidates for the dark radiation for which there are mounting observational hints. The primordial decays of heavy fields produce axions which are ultra-energetic compared to thermalised matter and inelastic axion-matter scattering can occur with E_CoM\u226b T_\u03b3, thus accessing many interesting processes which are otherwise kinematically forbidden in standard cosmology. Axion-photon scattering into quarks and leptons during BBN affects the light element abundances, and bounds on overproduction of ^4He constrain a combination of the axion decay constant and the reheating temperature. For supersymmetric models, axion scattering into visible sector superpartners can give direct non-thermal production of dark matter at T_\u03b3\u226a T_freezeout. Most axions \u2014 or any other dark radiation candidate from modulus decay \u2014 still linger today as a Cosmic Axion Background with E_axion\u223c\ud835\udcaa(100) eV, and a flux of \u223c 10^6 cm^-2 s^-1.", "keyphrases": ["axionic dark radiation", "extra-radiation", "string theory model"]}
{"id": "0901.3114", "title": "Dipolar Dark Matter and Dark Energy", "abstract": "In previous work [L. Blanchet and A. Le Tiec, Phys. Rev. D 78, 024031 (2008)], a model of dark matter and dark energy based on the concept of gravitational polarization was investigated. This model was shown to recover the concordance cosmological scenario (Lambda-CDM) at cosmological scales, and the phenomenology of the modified Newtonian dynamics (MOND) at galactic scales. In this article we prove that the model can be formulated with a simple and physically meaningful matter action in general relativity. We also provide alternative derivations of the main results of the model, and some details on the variation of the action.", "keyphrases": ["dark matter", "dark energy", "gravitational polarization"]}
{"id": "1108.0588", "title": "First results of the CROME experiment", "abstract": "It is expected that a radio signal in the microwave range is produced in the atmosphere due to molecular bremsstrahlung initiated by extensive air showers. The CROME (Cosmic-Ray Observation via Microwave Emission) experiment was built to search for this microwave signal. Radiation from the atmosphere is monitored in the extended C band (3.4\u20134.2 GHz) in coincidence with showers detected by the KASCADE-Grande experiment. The detector setup consists of several parabolic antennas and fast read-out electronics. The sensitivity of the detector has been measured with different methods. First results after half a year of data taking are presented.", "keyphrases": ["crome", "cosmic-ray observation", "first result"]}
{"id": "1405.4403", "title": "Observed galaxy number counts on the lightcone up to second order: I. Main result", "abstract": "We present the galaxy number overdensity up to second order in redshift space on cosmological scales for a concordance model. The result contains all general relativistic effects up to second order that arise from observing on the past light cone, including all redshift effects, lensing distortions from convergence and shear, and contributions from velocities, Sachs-Wolfe, integrated SW and time-delay terms. This result will be important for accurate calculation of the bias on estimates of non-Gaussianity and on precision parameter estimates, introduced by nonlinear projection effects.", "keyphrases": ["galaxy number count", "cosmological scale", "relativistic effect", "projection effect", "bispectrum"]}
{"id": "1511.06957", "title": "Redshift drift constraints on f(T) gravity", "abstract": "We explore the impact of the Sandage-Loeb (SL) test on the precision of cosmological constraints for f(T) gravity theories. The SL test is an important supplement to current cosmological observations because it measures the redshift drift in the Lyman-\u03b1 forest in the spectra of distant quasars, covering the \"redshift desert\" of 2 \u2272 z \u22725. To avoid data inconsistency, we use the best-fit models based on current combined observational data as fiducial models to simulate 30 mock SL test data. We quantify the impact of these SL test data on parameter estimation for f(T) gravity theories. Two typical f(T) models are considered, the power-law model f(T)_PL and the exponential-form model f(T)_EXP. The results show that the SL test can effectively break the existing strong degeneracy between the present-day matter density \u03a9_m and the Hubble constant H_0 in other cosmological observations. For the considered f(T) models, a 30-year observation of the SL test can improve the constraint precision of \u03a9_m and H_0 enormously but cannot effectively improve the constraint precision of the model parameters.", "keyphrases": ["cosmological constraint", "degeneracy", "redshift drift"]}
{"id": "1907.09866", "title": "Measuring Bias via the Consistency Relations of the Large Scale Structure", "abstract": "Consistency Relations (CR) for the Large Scale Structure are exact equalities between correlation functions of different order. These relations descend from the equivalence principle and hold for primordial perturbations generated by single-field models of inflation. They are not affected by nonlinearities and hold also for biased tracers and in redshift space. We show that Baryonic Acoustic Oscillations (BAO) in the bispectrum (BS) in the squeezed limit are suppressed with respect to those in the power spectrum (PS) by a coefficient that depends on the BS configuration and on the bias parameter (and, in redshift space, also on the growth rate). We test these relations using large volume N-body simulations and show that they provide a novel way to measure large scale halo bias and, potentially, the growth rate. Since bias is obtained by comparing two directly observable quantities, the method is free from theoretical uncertainties both on the computational scheme and on the underlying cosmological model.", "keyphrases": ["consistency relations", "coefficient", "growth rate"]}
{"id": "1306.4673", "title": "Atmospheric Heat Redistribution on Hot Jupiters", "abstract": "Infrared lightcurves of transiting hot Jupiters present a trend in which the atmospheres of the hottest planets are less efficient at redistributing the stellar energy absorbed on their daysides\u2014and thus have a larger day-night temperature contrast\u2014than colder planets. No predictive atmospheric model has been published that identifies which dynamical mechanisms determine the atmospheric heat redistribution efficiency on tidally locked exoplanets. Here we present a two-layer shallow water model of the atmospheric dynamics on synchronously rotating planets that explains the observed trend. Our model shows that planets with weak friction and weak irradiation exhibit a banded zonal flow with minimal day-night temperature differences, while models with strong irradiation and/or strong friction exhibit a day-night flow pattern with order-unity fractional day-night temperature differences. To interpret the model, we develop a scaling theory that shows that the timescale for gravity waves to propagate horizontally over planetary scales, t_wave, plays a dominant role in controlling the transition from small to large temperature contrasts. This implies that heat redistribution is governed by a wave-like process, similar to the one responsible for the weak temperature gradients in the Earth's tropics. When atmospheric drag can be neglected, the transition from small to large day-night temperature contrasts occurs when t_wave sqrt(t_rad/Omega), where t_rad is the radiative relaxation time and Omega is the planetary rotation frequency. Alternatively, this transition criterion can be expressed as t_rad t_vert, where t_vert is the timescale for a fluid parcel to move vertically over the difference in day-night thickness. These results subsume the commonly used timescale comparison for estimating heat redistribution efficiency between t_rad and the global horizontal advection timescale, t_adv.", "keyphrases": ["water model", "atmospheric heat redistribution", "atmosphere"]}
{"id": "1012.3468", "title": "Toward a Universal Formulation of the Halo Mass Function", "abstract": "We compute the dark matter halo mass function using the excursion set formalism for a diffusive barrier with linearly drifting average which captures the main features of the ellipsoidal collapse model. We evaluate the non-Markovian corrections due to the sharp filtering of the linear density field in real space with a path-integral method. We find an unprecedented agreement with N-body simulation data with deviations within 5 range of masses probed by the simulations. This indicates that the Excursion Set in combination with a realistic modelling of the collapse threshold can provide a robust estimation of the halo mass function.", "keyphrases": ["halo mass function", "formalism", "collapse"]}
{"id": "1203.3551", "title": "The Primordial Lithium Problem", "abstract": "Big-bang nucleosynthesis (BBN) theory, together with the precise WMAP cosmic baryon density, makes tight predictions for the abundances of the lightest elements. Deuterium and 4He measurements agree well with expectations, but 7Li observations lie a factor 3-4 below the BBN+WMAP prediction. This 4-5\u03c3mismatch constitutes the cosmic \"lithium problem,\" with disparate solutions possible. (1) Astrophysical systematics in the observations could exist but are increasingly constrained. (2) Nuclear physics experiments provide a wealth of well-measured cross-section data, but 7Be destruction could be enhanced by unknown or poorly-measured resonances, such as 7Be + 3He -> 10C^* -> p + 9B. (3) Physics beyond the Standard Model can alter the 7Li abundance, though D and 4He must remain unperturbed; we discuss such scenarios, highlighting decaying Supersymmetric particles and time-varying fundamental constants. Present and planned experiments could reveal which (if any) of these is the solution to the problem.", "keyphrases": ["lithium problem", "big-bang nucleosynthesis", "abundance"]}
{"id": "2101.03078", "title": "The HERMES-Technologic and Scientific Pathfinder", "abstract": "HERMES-TP/SP (High Energy Rapid Modular Ensemble of Satellites Technologic and Scientific Pathfinder) is a constellation of six 3U nano-satellites hosting simple but innovative X-ray detectors, characterized by a large energy band and excellent temporal resolution, and thus optimized for the monitoring of Cosmic High Energy transients such as Gamma Ray Bursts and the electromagnetic counterparts of Gravitational Wave Events, and for the determination of their positions. The projects are funded by the Italian Ministry of University and Research and by the Italian Space Agency, and by the European Union Horizon 2020 Research and Innovation Program under Grant Agreement No. 821896. HERMES-TP/SP is an in-orbit demonstration, that should be tested starting from 2022. It is intrinsically a modular experiment that can be naturally expanded to provide a global, sensitive all sky monitor for high-energy transients.", "keyphrases": ["scientific pathfinder", "hermes-tp", "project"]}
{"id": "1009.2733", "title": "Current constraints on the epoch of cosmic acceleration", "abstract": "The cosmographic expansion history of the universe is investigated by using the 557 type Ia supernovae from the Union2 Compilation set along with the current estimates involving the product of the CMB acoustic scale \u2113_A and the BAO peak at two different redshifts. Using a well-behaved parameterization for the deceleration parameter, q(z) = q_0 + q_1z/(1 + z), we estimate the accelerating redshift z_acc=-q_0/(q_0 + q_1) (at which the universe switches from deceleration to acceleration) and investigate the influence of a non-vanishing spatial curvature on these estimates. We also use the asymptotic value of q(z) at high-z to place more restrictive bounds on the model parameters q_0 and q_1, which results in a more precise determination of the epoch of cosmic acceleration.", "keyphrases": ["cosmic acceleration", "redshift", "other"]}
{"id": "1009.0916", "title": "Dependence of direct detection signals on the WIMP velocity distribution", "abstract": "The signals expected in WIMP direct detection experiments depend on the ultra-local dark matter distribution. Observations probe the local density, circular speed and escape speed, while simulations find velocity distributions that deviate significantly from the standard Maxwellian distribution. We calculate the energy, time and direction dependence of the event rate for a range of velocity distributions motivated by recent observations and simulations, and also investigate the uncertainty in the determination of WIMP parameters. The dominant uncertainties are the systematic error in the local circular speed and whether or not the MW has a high density dark disc. In both cases there are substantial changes in the mean differential event rate and the annual modulation signal, and hence exclusion limits and determinations of the WIMP mass. The uncertainty in the shape of the halo velocity distribution is less important, however it leads to a 5 detailed direction dependence of the event rate is sensitive to the velocity distribution. However the numbers of events required to detect anisotropy and confirm the median recoil direction do not change substantially.", "keyphrases": ["velocity distribution", "direct detection experiment", "sense"]}
{"id": "1907.06648", "title": "SOFIA/HAWC+ traces the magnetic fields in NGC 1068", "abstract": "We report the first detection of galactic spiral structure by means of thermal emission from magnetically aligned dust grains. Our 89 \u03bcm polarimetric imaging of NGC 1068 with the High-resolution Airborne Wideband Camera/Polarimeter (HAWC+) on NASA's Stratospheric Observatory for Infrared Astronomy (SOFIA) also sheds light on magnetic field structure in the vicinity of the galaxy's inner-bar and active galactic nucleus (AGN). We find correlations between the 89 \u03bcm magnetic field vectors and other tracers of spiral arms, and a symmetric polarization pattern as a function of the azimuthal angle arising from the projection and inclination of the disk field component in the plane of the sky. The observations can be fit with a logarithmic spiral model with pitch angle of 16.9^+2.7_-2.8^\u2218 and a disk inclination of 48\u00b12^\u2218. We infer that the bulk of the interstellar medium from which the polarized dust emission originates is threaded by a magnetic field that closely follows the spiral arms. Inside the central starburst disk (<1.6 kpc), the degree of polarization is found to be lower than for far-infrared sources in the Milky Way, and has minima at the locations of most intense star formation near the outer ends of the inner-bar. Inside the starburst ring, the field direction deviates from the model, becoming more radial along the leading edges of the inner-bar. The polarized flux and dust temperature peak \u223c 3-6\" NE of the AGN at the location of a bow shock between the AGN outflow and the surrounding interstellar medium, but the AGN itself is weakly polarized (< 1", "keyphrases": ["hawc+", "magnetic field", "thermal emission", "polarization", "milky way"]}
{"id": "1410.4323", "title": "Axion Stars and Fast Radio Bursts", "abstract": "We show that fast radio bursts arise from collisions between axion stars and neutron stars. The bursts are emitted in the atmosphere of the neutron stars. The observed frequencies of the bursts are given by the axion mass m_a such as m_a/2\u03c0\u2243 1.4 (m_a/(6\u00d7 10^-6)). From the event rate \u223c 10^-3 per year in a galaxy, we can determine the mass \u223c 10^-11M_\u2299 of the axion stars. Using these values we can explain short durations ( \u223cms ) and amount of radiation energies ( \u223c 10^43GeV ) of the bursts.", "keyphrases": ["fast radio burst", "neutron star", "axion star"]}
{"id": "1503.00562", "title": "Improving the convergence properties of the moving-mesh code AREPO", "abstract": "Accurate numerical solutions of the equations of hydrodynamics play an ever more important role in many fields of astrophysics. In this work, we reinvestigate the accuracy of the moving-mesh code Arepo and show how its convergence order can be improved for general problems. In particular, we clarify that for certain problems Arepo only reaches first-order convergence for its original formulation. This can be rectified by simple modifications we propose to the time integration scheme and the spatial gradient estimates of the code, both improving the accuracy of the code. We demonstrate that the new implementation is indeed second-order accurate under the L^1 norm, and in particular substantially improves conservation of angular momentum. Interestingly, whereas these improvements can significantly change the results of smooth test problems, we also find that cosmological simulations of galaxy formation are unaffected, demonstrating that the numerical errors eliminated by the new formulation do not impact these simulations. In contrast, simulations of binary stars followed over a large number of orbital times are strongly affected, as here it is particularly crucial to avoid a long-term build up of errors in angular momentum conservation.", "keyphrases": ["moving-mesh code arepo", "time integration scheme", "smooth test problem"]}
{"id": "1112.3781", "title": "The population of natural Earth satellites", "abstract": "We have for the first time calculated the population characteristics of the Earth's irregular natural satellites (NES) that are temporarily captured from the near-Earth-object (NEO) population. The steady-state NES size-frequency and residence-time distributions were determined under the dynamical influence of all the massive bodies in the solar system (but mainly the Sun, Earth, and Moon) for NEOs of negligible mass. To this end, we compute the NES capture probability from the NEO population as a function of the latter's heliocentric orbital elements and combine those results with the current best estimates for the NEO size-frequency and orbital distribution. At any given time there should be at least one NES of 1-meter diameter orbiting the Earth. The average temporarily-captured orbiter (TCO; an object that makes at least one revolution around the Earth in a co-rotating coordinate system) completes (2.88\u00b10.82) around the Earth during a capture event that lasts (286\u00b118). We find a small preference for capture events starting in either January or July. Our results are consistent with the single known natural TCO, 2006 RH_120, a few-meter diameter object that was captured for about a year starting in June 2006. We estimate that about 0.1 impacting the Earth were TCOs.", "keyphrases": ["natural earth satellite", "orbiter", "meteor"]}
{"id": "1305.2020", "title": "Precursor of Inflation", "abstract": "We investigate a nonsingular initial state of the Universe which leads to inflation naturally. The model is described by a scalar field with a quadratic potential in Eddington-inspired Born-Infeld gravity. The curvature of this initial state is given by the mass scale of the scalar field which is much smaller than the Planck scale. Therefore, in this model, quantum gravity is not necessary in understanding this pre-inflationary stage, no matter how large the energy density becomes. The initial state in this model evolves eventually to a long inflationary period which is similar to the usual chaotic inflation.", "keyphrases": ["gravity", "inflation model", "eibi theory"]}
{"id": "0902.4463", "title": "SAPPORO: A way to turn your graphics cards into a GRAPE-6", "abstract": "We present Sapporo, a library for performing high-precision gravitational N-body simulations on NVIDIA Graphical Processing Units (GPUs). Our library mimics the GRAPE-6 library, and N-body codes currently running on GRAPE-6 can switch to Sapporo by a simple relinking of the library. The precision of our library is comparable to that of GRAPE-6, even though internally the GPU hardware is limited to single precision arithmetics. This limitation is effectively overcome by emulating double precision for calculating the distance between particles. The performance loss of this operation is small (< 20 compared to the advantage of being able to run at high precision. We tested the library using several GRAPE-6-enabled N-body codes, in particular with Starlab and phiGRAPE. We measured peak performance of 800 Gflop/s for running with 10^6 particles on a PC with four commercial G92 architecture GPUs (two GeForce 9800GX2). As a production test, we simulated a 32k Plummer model with equal mass stars well beyond core collapse. The simulation took 41 days, during which the mean performance was 113 Gflop/s. The GPU did not show any problems from running in a production environment for such an extended period of time.", "keyphrases": ["grape-6", "graphic processing unit", "gpu", "sapporo", "popular way"]}
{"id": "1610.06637", "title": "Decoherence Can Relax Cosmic Acceleration: an Example", "abstract": "We investigate back reaction in de Sitter space in an approach where only states that are observationally accessible are included in the density matrix. Using the Bunch-Davies vacuum as the initial condition we find for a conformal scalar field and a cosmological constant that tracing over the unobservable states beyond the cosmological horizon leads to a thermal spectrum of particles and that such a configuration is unstable under semi-classical back reaction. It is concluded that this prescription results in an instability of de Sitter space with a gradually increasing horizon size.", "keyphrases": ["cosmological horizon", "decoherence", "radiation"]}
{"id": "1511.00014", "title": "Search for Gamma-Ray Lines towards Galaxy Clusters with the Fermi-LAT", "abstract": "We report on a search for monochromatic \u03b3-ray features in the spectra of galaxy clusters observed by the Fermi Large Area Telescope. Galaxy clusters are the largest structures in the Universe that are bound by dark matter (DM), making them an important testing ground for possible self-interactions or decays of the DM particles. Monochromatic \u03b3-ray lines provide a unique signature due to the absence of astrophysical backgrounds and are as such considered a smoking-gun signature for new physics. An unbinned joint likelihood analysis of the sixteen most promising clusters using five years of data at energies between 10 and 400 GeV revealed no significant features. For the case of self-annihilation, we set upper limits on the monochromatic velocity-averaged interaction cross section. These limits are compatible with those obtained from observations of the Galactic Center, albeit weaker due to the larger distance to the studied clusters.", "keyphrases": ["galaxy cluster", "dark matter", "ray line emission"]}
{"id": "1511.01396", "title": "Gamma Ray Bursts as Neutrino Sources", "abstract": "Gamma-ray burst sources appear to fulfill all the conditions for being efficient cosmic ray accelerators, and being extremely compact, are also expected to produce multi-GeV to PeV neutrinos. I review the basic model predictions for the expected neutrino fluxes in classical GRBs as well as in low luminosity and choked bursts, discussing the recent IceCube observational constraints and implications from the observed diffuse neutrino flux.", "keyphrases": ["neutrino", "gamma-ray burst", "astrophysical source", "active galactic nucleus"]}
{"id": "1505.00811", "title": "Revisiting the Unified Model of Active Galactic Nuclei", "abstract": "This review describes recent developments related to the unified model of active galactic nuclei (AGN). It focuses on new ideas about the origin and properties of the central obscurer (torus), and the connection with its surrounding. The review does not address radio unification. AGN tori must be clumpy but the uncertainties about their properties are still large. Todays most promising models involve disk winds of various types and hydrodynamical simulations that link the large scale galactic disk to the inner accretion flow. IR studies greatly improved the understanding of the spectral energy distribution of AGNs but they are hindered by various selection effects. X-ray samples are more complete. A basic relationship which is still unexplained is the dependence of the torus covering factor on luminosity. There is also much confusion regarding \"real type-II AGNs\" that do not fit into a simple unification scheme. The most impressive recent results are due to IR interferometry, which is not in accord with most torus models, and the accurate mapping of central ionization cones. AGN unification may not apply to merging systems and is possibly restricted to secularly evolving galaxies.", "keyphrases": ["galaxy", "active galactic nucleus", "supermassive black hole"]}
{"id": "1908.01774", "title": "Toward a robust inference method for the galaxy bispectrum: likelihood function and model selection", "abstract": "The forthcoming generation of galaxy redshift surveys will sample the large-scale structure of the Universe over unprecedented volumes with high-density tracers. This advancement will make robust measurements of three-point clustering statistics possible. In preparation for this improvement, we investigate how several methodological choices can influence inferences based on the bispectrum about galaxy bias and shot noise. We first measure the real-space bispectrum of dark-matter haloes extracted from 298 N-body simulations covering a volume of approximately 1000 h^-3Gpc^3. We then fit a series of theoretical models based on tree-level perturbation theory to the numerical data. To achieve this, we estimate the covariance matrix of the measurement errors by using 10,000 mock catalogues generated with the Pinocchio code. We study how the model constraints are influenced by the binning strategy for the bispectrum configurations and by the form of the likelihood function. We also use Bayesian model-selection techniques to single out the optimal theoretical description of our data. We find that a three-parameter bias model combined with Poissonian shot noise is necessary to model the halo bispectrum up to scales of k_max\u2272 0.08 h Mpc^-1, although fitting formulae that relate the bias parameters can be helpful to reduce the freedom of the model without compromising accuracy. Our data clearly disfavour local Eulerian and local Lagrangian bias models and do not require corrections to Poissonian shot noise. We anticipate that model-selection diagnostics will be particularly useful to extend the analysis to smaller scales as, in this case, the number of model parameters will grow significantly large.", "keyphrases": ["bispectrum", "likelihood function", "theoretical model", "perturbation theory", "cosmological parameter"]}
{"id": "1901.04524", "title": "Observations of Fast Radio Bursts at Frequencies down to 400 Megahertz", "abstract": "Fast radio bursts (FRBs) are highly dispersed millisecond-duration radio flashes likely arriving from far outside the Milky Way galaxy. This phenomenon was discovered at radio frequencies near 1.4 GHz and to date has been observed in one case at as high as 8 GHz, but not below 700 MHz in spite of significant searches at low frequencies. Here we report detections of FRBs at radio frequencies as low as 400 MHz, on the Canadian Hydrogen Intensity Mapping Experiment (CHIME) using the CHIME/FRB instrument. We present 13 FRBs detected during a telescope pre-commissioning phase, when our sensitivity and field-of-view were not yet at design specifications. Emission in multiple events is seen down to 400 MHz, the lowest radio frequency to which we are sensitive. The FRBs show a variety of temporal scattering behaviours, with the majority significantly scattered, and some apparently unscattered to within measurement uncertainty even at our lowest frequencies. Of the 13 reported here, one event has the lowest dispersion measure yet reported, implying it is among the closest yet known, and another has shown multiple repeat bursts, as described in a companion paper. Our low-scattering events suggest that efforts to detect FRBs at radio frequencies below 400 MHz will eventually be successful. The overall scattering properties of our sample suggest that FRBs as a class are preferentially located in environments that scatter radio waves more strongly than the diffuse interstellar medium (ISM) in the Milky Way.", "keyphrases": ["fast radio burst", "frbs", "telescope"]}
{"id": "2101.07998", "title": "The fast radio burst population evolves, consistent with the star-formation rate", "abstract": "Fast radio bursts (FRBs) are extremely powerful sources of radio waves observed at cosmological distances. We use a sophisticated model of FRB observations \u2013 presented in detail in a companion paper \u2013 to fit FRB population parameters using large samples of FRBs detected by ASKAP and Parkes, including seven sources with confirmed host galaxies. Our fitted parameters demonstrate that the FRB population evolves with redshift in a manner consistent with, or faster than, the star-formation rate (SFR), ruling out a non-evolving population at 99.9% C.L. Our estimated maximum FRB energy is log_10 E_ max [ erg] = 41.84_-0.18^+0.49 (68% C.L.) assuming a 1 GHz emission bandwidth, with slope of the cumulative luminosity distribution \u03b3=-1.16_-0.12^+0.11. We find a log-mean host DM contribution of 145_-60^+64 pc cm^-3 on top of a typical local (ISM and halo) contribution of \u223c80 pc cm^-3, which is higher than most literature values. These results are consistent with the model of FRBs arising as the high-energy limit of magnetar bursts, but allow for FRB progenitors that evolve faster than the SFR.", "keyphrases": ["star-formation rate", "non-evolving population", "frb progenitor"]}
{"id": "1001.5463", "title": "Particle Accelerators inside Spinning Black Holes", "abstract": "On the basis of the Kerr metric as a model for a spinning black hole accreting test particles from rest at infinity, I show that the center-of-mass energy for a pair of colliding particles is generically divergent at the inner horizon. This shows that not only are classical black holes internally unstable, but also that Planck-scale physics is a characteristic feature within black holes at scales much larger that the Planck length. The novel feature of the divergence discussed here is that the phenomenon is present only for black holes with rotation and in this sense it is distinct from the well known Cauchy horizon instability.", "keyphrases": ["black hole", "inner horizon", "particle"]}
{"id": "1602.02771", "title": "A Cosmic Void Catalog of SDSS DR12 BOSS Galaxies", "abstract": "We present a cosmic void catalog using the large-scale structure galaxy catalog from the Baryon Oscillation Spectroscopic Survey (BOSS). This galaxy catalog is part of the Sloan Digital Sky Survey (SDSS) Data Release 12 and is the final catalog of SDSS-III. We take into account the survey boundaries, masks, and angular and radial selection functions, and apply the ZOBOV void finding algorithm to the galaxy catalog. We identify a total of 10,643 voids. After making quality cuts to ensure that the voids represent real underdense regions, we obtain 1,228 voids with effective radii spanning the range 20-100Mpc/h and with central densities that are, on average, 30 sample density. We release versions of the catalogs both with and without quality cuts. We discuss the basic statistics of voids, such as their size and redshift distributions, and measure the radial density profile of the voids via a stacking technique. In addition, we construct mock void catalogs from 1000 mock galaxy catalogs, and find that the properties of BOSS voids are in good agreement with those in the mock catalogs. We compare the stellar mass distribution of galaxies living inside and outside of the voids, and find no significant difference. These BOSS and mock void catalogs are useful for a number of cosmological and galaxy environment studies.", "keyphrases": ["cosmic void catalog", "sdss", "data release"]}
{"id": "2102.05679", "title": "The Kinematics of z 6 Quasar Host Galaxies", "abstract": "We explore the kinematics of 27 z 6 quasar host galaxies observed in [CII]-158 micron ([CII]) emission with the Atacama Large Millimeter/sub-millimeter Array at a resolution of 0.25\u201d. We find that nine of the galaxies show disturbed [CII] emission, either due to a close companion galaxy or recent merger. Ten galaxies have smooth velocity gradients consistent with the emission arising from a gaseous disk. The remaining eight quasar host galaxies show no velocity gradient, suggesting that the gas in these systems is dispersion-dominated. All galaxies show high velocity dispersions with a mean of 129+-10 km/s. To provide an estimate of the dynamical mass within twice the half-light radius of the quasar host galaxy, we model the kinematics of the [CII] emission line using our publicly available kinematic fitting code, qubefit. This results in a mean dynamical mass of 5.0+-0.8(+-3.5) x 10^10 Msun. Comparison between the dynamical mass and the mass of the supermassive black hole reveals that the sample falls above the locally derived bulge mass\u2013black hole mass relation at 2.4sigma significance. This result is robust even if we account for the large systematic uncertainties. Using several different estimators for the molecular mass, we estimate a gas mass fraction of >10 indicating gas makes up a large fraction of the baryonic mass of z 6 quasar host galaxies. Finally, we speculate that the large variety in [CII] kinematics is an indication that gas accretion onto z 6 super massive black holes is not caused by a single precipitating factor.", "keyphrases": ["quasar host galaxy", "dynamical mass", "supermassive black hole"]}
{"id": "0901.2926", "title": "Dark Matter Signals from Cascade Annihilations", "abstract": "A leading interpretation of the electron/positron excesses seen by PAMELA and ATIC is dark matter annihilation in the galactic halo. Depending on the annihilation channel, the electron/positron signal could be accompanied by a galactic gamma ray or neutrino flux, and the non-detection of such fluxes constrains the couplings and halo properties of dark matter. In this paper, we study the interplay of electron data with gamma ray and neutrino constraints in the context of cascade annihilation models, where dark matter annihilates into light degrees of freedom which in turn decay into leptons in one or more steps. Electron and muon cascades give a reasonable fit to the PAMELA and ATIC data. Compared to direct annihilation, cascade annihilations can soften gamma ray constraints from final state radiation by an order of magnitude. However, if dark matter annihilates primarily into muons, the neutrino constraints are robust regardless of the number of cascade decay steps. We also examine the electron data and gamma ray/neutrino constraints on the recently proposed \"axion portal\" scenario.", "keyphrases": ["dark matter annihilation", "muon", "final state radiation", "small coupling"]}
{"id": "1602.03883", "title": "Testing Gravity with Gravitational Wave Source Counts", "abstract": "We show that the gravitational wave source counts distribution can test how gravitational radiation propagates on cosmological scales. This test does not require obtaining redshifts for the sources. If the signal-to-noise ratio (SNR, \u03c1) from a gravitational wave source is proportional to the strain then it falls as R^-1, thus we expect the source counts to follow dN/d\u03c1\u221d\u03c1^-4. However, if gravitational waves decay as they propagate or propagate into other dimensions, then there can be deviations from this generic prediction. We consider the possibility that the strain falls as R^-\u03b3, where \u03b3=1 recovers the expected predictions in a Euclidean uniformly-filled universe, and forecast the sensitivity of future observations to deviations from standard General Relativity. We first consider the case of few objects, 7 sources, with a signal-to-noise from 8 to 24, and impose a lower limit on \u03b3, finding \u03b3>0.33 at 95% confidence level. The distribution of our simulated sample is very consistent with the distribution of the trigger events reported by Advanced LIGO. Future measurements will improve these constraints: with 100 events, we estimate that \u03b3 can be measured with an uncertainty of 15%. We generalize the formalism to account for a range of chirp masses and the possibility that the signal falls as exp(-R/R_0)/R^\u03b3.", "keyphrases": ["gravitational wave source", "redshift", "snr"]}
{"id": "1802.05571", "title": "Planck 2015 constraints on spatially-flat dynamical dark energy models", "abstract": "We determine constraints on spatially-flat tilted dynamical dark energy XCDM and \u03d5CDM inflation models by analyzing Planck 2015 cosmic microwave background (CMB) anisotropy data and baryon acoustic oscillation (BAO) distance measurements. XCDM is a simple and widely used but physically inconsistent parameterization of dynamical dark energy, while the \u03d5CDM model is a physically consistent one in which a scalar field \u03d5 with an inverse power-law potential energy density powers the currently accelerating cosmological expansion. Both these models have one additional parameter compared to standard \u039bCDM and both better fit the TT + lowP + lensing + BAO data than does the standard tilted flat-\u039bCDM model, with \u0394\u03c7^2 = -1.26 (-1.60) for the XCDM (\u03d5CDM) model relative to the \u039bCDM model. While this is a 1.1\u03c3 (1.3\u03c3) improvement over standard \u039bCDM and so not significant, dynamical dark energy models cannot be ruled out. In addition, both dynamical dark energy models reduce the tension between the Planck 2015 CMB anisotropy and the weak lensing \u03c3_8 constraints.", "keyphrases": ["dark energy model", "cosmological constant", "energy inflation model"]}
{"id": "2007.01936", "title": "Probing Dark Low-mass Halos and Primordial Black Holes with Frequency-dependent Gravitational Lensing Dispersions of Gravitational Waves", "abstract": "We explore the possibility of using amplitude and phase fluctuations of gravitational waves due to gravitational lensing as a probe of the small-scale matter power spectrum. The direct measurement of the small-scale matter power spectrum is made possible by making use of the frequency dependence of such gravitational lensing dispersions originating from the wave optics nature of the propagation of gravitational waves. We first study the small-scale behavior of the matter power spectrum in detail taking the so-called halo model approach including effects of baryons and subhalos. We find that the matter power spectrum at the wavenumber k\u223c 10^6h Mpc^-1 is mainly determined by the abundance of dark low-mass halos with mass 1h^-1M_\u2299\u2272 M \u2272 10^4h^-1M_\u2299 and is relatively insensitive to baryonic effects. The matter power spectrum at this wavenumber is probed by gravitational lensing dispersions of gravitational waves at frequencies of f\u223c 0.1-1 Hz with predicted signals of \ud835\udcaa(10^-3). We also find that primordial black holes (PBHs) with M_ PBH\u2273 0.1 M_\u2299 can significantly enhance the matter power spectrum at k \u2273 10^5h Mpc^-1 due to both the enhanced halo formation and the shot noise from PBHs. We find that gravitational lensing dispersions at f\u223c 10-100 Hz are particularly sensitive to PBHs and can be enhanced by more than an order of magnitude depending on the mass and abundance of PBHs.", "keyphrases": ["dark low-mass halo", "primordial black hole", "gravitational wave"]}
{"id": "1102.0487", "title": "Galileons from Lovelock actions", "abstract": "We demonstrate how, for an arbitrary number of dimensions, the Galileon actions and their covariant generalizations can be obtained through a standard Kaluza-Klein compactification of higher-dimensional Lovelock gravity. In this setup, the dilaton takes on the role of the Galileon. In addition, such compactifications uncover other more general Galilean actions, producing purely second-order equations in the weak-field limit, now both for the Galileon and the metric perturbations.", "keyphrases": ["generalization", "kaluza-klein compactification", "galileon"]}
{"id": "1611.05178", "title": "Detecting the Neutrinos Mass Hierarchy from Cosmological Data", "abstract": "We propose a new parameterization to measure the neutrino mass hierarchy, namely \u0394=(m_3-m_1)/(m_1+m_3) which is dimensionless and varies in the range [-1,1]. Taking into account the results of neutrino oscillation experiments, \u0394 is the unique parameter for determining all the masses of neutrinos, and a positive (negative) sign of \u0394 denotes the normal (inverted) mass hierarchy. Adopting the currently available cosmic observations, we find that the normal mass hierarchy is slightly favored, and the mass of lightest neutrino is less than 0.030 eV for the normal mass hierarchy and 0.024 eV for the inverted mass hierarchy at 95% confidence level.", "keyphrases": ["neutrino mass", "hierarchy", "cosmology"]}
{"id": "1208.4667", "title": "Compact high-resolution spectrographs for large and extremely large telescopes: using the diffraction limit", "abstract": "As telescopes get larger, the size of a seeing-limited spectrograph for a given resolving power becomes larger also, and for ELTs the size will be so great that high resolution instruments of simple design will be infeasible. Solutions include adaptive optics (but not providing full correction for short wavelengths) or image slicers (which give feasible but still large instruments). Here we develop the solution proposed by Bland-Hawthorn and Horton: the use of diffraction-limited spectrographs which are compact even for high resolving power. Their use is made possible by the photonic lantern, which splits a multi-mode optical fiber into a number of single-mode fibers. We describe preliminary designs for such spectrographs, at a resolving power of R 50,000. While they are small and use relatively simple optics, the challenges are to accommodate the longest possible fiber slit (hence maximum number of single-mode fibers in one spectrograph) and to accept the beam from each fiber at a focal ratio considerably faster than for most spectrograph collimators, while maintaining diffraction-limited imaging quality. It is possible to obtain excellent performance despite these challenges. We also briefly consider the number of such spectrographs required, which can be reduced by full or partial adaptive optics correction, and/or moving towards longer wavelengths.", "keyphrases": ["spectrograph", "telescope", "single-mode fiber"]}
{"id": "0905.0821", "title": "Relativistic g-modes in rapidly rotating neutron stars", "abstract": "We study the g-modes of fast rotating stratified neutron stars in the general relativistic Cowling approximation, where we neglect metric perturbations and where the background models take into account the buoyant force due to composition gradients. This is the first paper studying this problem in a general relativistic framework. In a recent paper by Passamonti et al.(2009), a similar study was performed within the Newtonian framework, where the authors presented results about the onset of CFS-unstable g-modes and the close connection between inertial- and gravity-modes for sufficiently high rotation rates and small composition gradients. This correlation arises from the interplay between the buoyant force which is the restoring force for g-modes and the Coriolis force which is responsible for the existence of inertial modes. In our relativistic treatment of the problem, we find an excellent qualitatively agreement with respect to the Newtonian results.", "keyphrases": ["g-mode", "neutron star", "gravitational wave", "stellar oscillation", "rotational effect"]}
{"id": "1302.3842", "title": "Transporting non-Gaussianity from sub to super-horizon scales", "abstract": "We extend the `moment transport method' for calculating the statistics of inflationary perturbations to the quantum phase of evolution on sub-horizon scales. The quantum transport equations form a set of coupled ordinary differential equations for the evolution of quantum correlation functions during inflation, which are valid on sub- and super-horizon scales, and reduce to the known classical transport equations after horizon crossing. The classical and quantum equations follow directly from the field equations of cosmological perturbation theory. In this paper, we focus on how the evolution equations arise, and explore how transport methods relate to other approaches, and in particular how formal integral solutions to the transport equations connect to those of the In-In formalism.", "keyphrases": ["super-horizon scale", "transport method", "differential equation"]}
{"id": "1005.0174", "title": "Seeing, Wind and Outer Scale Effects on Image Quality at the Magellan Telescopes", "abstract": "We present an analysis of the science image quality obtained on the twin 6.5 metre Magellan telescopes over a 1.5 year period, using images of 10^5 stars. We find that the telescopes generally obtain significantly better image quality than the DIMM-measured seeing. This is qualitatively consistent with expectations for large telescopes, where the wavefront outer scale of the turbulence spectrum plays a significant role. However, the dominant effect is found to be wind speed with Magellan outperforming the DIMMs most markedly when the wind is strongest. Excluding data taken during strong wind conditions (>10 m/s), we find that the Magellan telescopes still significantly outperform the DIMM seeing, and we estimate the site to have L_0 25 m on average. We also report on the first detection of a negative bias in DIMM data. This is found to occur, as predicted, when the DIMM is affected by certain optical aberrations and the turbulence profile is dominated by the upper layers of the atmosphere.", "keyphrases": ["wind", "image quality", "telescope", "seeing"]}
{"id": "1312.0946", "title": "Inflationary Steps in the Planck Data", "abstract": "We extend and improve the modeling and analysis of large-amplitude, sharp inflationary steps for second order corrections required by the precision of the Planck CMB power spectrum and for arbitrary Dirac-Born-Infeld sound speed. With two parameters, the amplitude and frequency of the resulting oscillations, step models improve the fit by \u0394\u03c7^2 = -11.4. Evidence for oscillations damping before the Planck beam scale is weak: damping only improves the fit to \u0394\u03c7^2 = -14.0 for one extra parameter, if step and cosmological parameters are jointly fit, in contrast to analyses which fix the latter. Likewise, further including the sound speed as a parameter only marginally improves the fit to \u0394\u03c7^2 = -15.2 but has interesting implications for the lowest multipole temperature and polarization anisotropy. Since chance features in the noise can mimic these oscillatory features, we discuss tests from polarization power spectra, lensing reconstruction and squeezed and equilateral bispectra that should soon verify or falsify their primordial origin.", "keyphrases": ["inflationary step", "smooth power-law spectrum", "primordial power spectrum"]}
{"id": "2008.09621", "title": "No redshift evolution of non-repeating fast radio-burst rates", "abstract": "Fast radio bursts (FRBs) are millisecond transients of unknown origin(s) occurring at cosmological distances. Here we, for the first time, show time-integrated-luminosity functions and volumetric occurrence rates of non-repeating and repeating FRBs against redshift. The time-integrated-luminosity functions of non-repeating FRBs do not show any significant redshift evolution. The volumetric occurrence rates are almost constant during the past \u223c10 Gyr. The nearly-constant rate is consistent with a flat trend of cosmic stellar-mass density traced by old stellar populations. Our findings indicate that the occurrence rate of non-repeating FRBs follows the stellar-mass evolution of long-living objects with \u223cGyr time scales, favouring e.g. white dwarfs, neutron stars, and black holes, as likely progenitors of non-repeating FRBs. In contrast, the occurrence rates of repeating FRBs may increase towards higher redshifts in a similar way to the cosmic star formation-rate density or black hole accretion-rate density if the slope of their luminosity function does not evolve with redshift. Short-living objects with \u2272 Myr time scales associated with young stellar populations (or their remnants, e.g., supernova remnants, young pulsars, and magnetars) or active galactic nuclei might be favoured as progenitor candidates of repeating FRBs.", "keyphrases": ["redshift evolution", "non-repeating", "time-integrated-luminosity function"]}
{"id": "1501.04961", "title": "Unscreening Modified Gravity in the Matter Power Spectrum", "abstract": "Viable modifications of gravity that may produce cosmic acceleration need to be screened in high-density regions such as the Solar System, where general relativity is well tested. Screening mechanisms also prevent strong anomalies in the large-scale structure and limit the constraints that can be inferred on these gravity models from cosmology. We find that by suppressing the contribution of the screened high-density regions in the matter power spectrum, allowing a greater contribution of unscreened low densities, modified gravity models can be more readily discriminated from the concordance cosmology. Moreover, by variation of density thresholds, degeneracies with other effects may be dealt with more adequately. Specializing to chameleon gravity as a worked example for screening in modified gravity, employing N-body simulations of f(R) models and the halo model of chameleon theories, we demonstrate the effectiveness of this method. We find that a percent-level measurement of the clipped power at k < 0.3 h/Mpc can yield constraints on chameleon models that are more stringent than what is inferred from Solar System tests or distance indicators in unscreened dwarf galaxies. Finally, we verify that our method is also applicable to the Vainshtein mechanism.", "keyphrases": ["matter power spectrum", "anomaly", "gravity model"]}
{"id": "1807.09631", "title": "The determination of protoplanetary disk masses", "abstract": "In this article we review the methods used to determine the gas and dust masses of protoplanetary disks, with an emphasis on the lesser characterized total gas mass. Our review encompasses all the indirect tracers and the methodology that is be used to isolate the hidden H2 via dust, CO, and HD emission. We discuss the overall calibration of gaseous tracers which is based on decades of study of the dense phases of the interstellar medium. At present, disk gas masses determined via CO and HD are (in a few instances) different by orders of magnitude, hinting at either significant evolution in total disk mass or in the CO abundance . Either of these would represent a fundamental physical or chemical process that appears to dominate the system on million year timescales. Efforts to reconcile these differences using existing and future facilities are discussed.", "keyphrases": ["disk masse", "total gas mass", "planet formation"]}
{"id": "1704.07838", "title": "\"Non-cold\" dark matter at small scales: a general approach", "abstract": "Structure formation at small cosmological scales provides an important frontier for dark matter (DM) research. Scenarios with small DM particle masses, large momenta or hidden interactions tend to suppress the gravitational clustering at small scales. The details of this suppression depend on the DM particle nature, allowing for a direct link between DM models and astrophysical observations. However, most of the astrophysical constraints obtained so far refer to a very specific shape of the power suppression, corresponding to thermal warm dark matter (WDM), i.e., candidates with a Fermi-Dirac or Bose-Einstein momentum distribution. In this work we introduce a new analytical fitting formula for the power spectrum, which is simple yet flexible enough to reproduce the clustering signal of large classes of non-thermal DM models, which are not at all adequately described by the oversimplified notion of WDM. We show that the formula is able to fully cover the parameter space of sterile neutrinos (whether resonantly produced or from particle decay), mixed cold and warm models, fuzzy dark matter, as well as other models suggested by effective theory of structure formation (ETHOS). Based on this fitting formula, we perform a large suite of N-body simulations and we extract important nonlinear statistics, such as the matter power spectrum and the halo mass function. Finally, we present first preliminary astrophysical constraints, based on linear theory, from both the number of Milky Way satellites and the Lyman-\u03b1 forest. This paper is a first step towards a general and comprehensive modeling of small-scale departures from the standard cold DM model.", "keyphrases": ["dark matter", "neutrino", "small-scale departure"]}
{"id": "1207.2226", "title": "Luminosity Function of High-Mass X-ray Binaries and Anisotropy in the Distribution of Active Galactic Nuclei toward the Large Magellanic Cloud", "abstract": "In 2003-2012, the INTEGRAL observatory has performed long-term observations of the Large Magellanic Cloud (LMC). At present, this is one of the deepest hard X-ray (20-60 keV) surveys of extragalactic fields in which more than 20 sources of different natures have been detected. We present the results of a statistical analysis of the population of high-mass X-ray binaries in the LMC and active galactic nuclei (AGNs) observed in its direction. The hard X-ray luminosity function of high-mass X-ray binaries is shown to be described by a power law with a slope alpha 1.8, that in agreement with the luminosity function measurements both in the LMC itself, but made in the soft X-ray energy band, and in other galaxies. At the same time, the number of detected AGNs toward the LMC turns out to be considerably smaller than the number of AGNs registered in other directions, in particular, toward the source 3C 273. The latter confirms the previously made assumption that the distribution of matter in the local Universe is nonuniform.", "keyphrases": ["high-mass x-ray binary", "large magellanic cloud", "active galactic nucleus"]}
{"id": "1912.07500", "title": "The Universe acceleration from the Unimodular gravity view point: Background and linear perturbations", "abstract": "With the goal of studying the cosmological constant (CC) problem, we present an exhaustive analysis of unimodular gravity as a possible candidate to resolve the CC origin and with this, the current Universe acceleration. In this theory, a correction constant (CC-like) in the field equations sources the late cosmic acceleration. This constant is related to a new parameter, z_ini, which is interpreted as the redshift of CC-like emergence. By comparing with the CC value obtained from Planck and Supernovaes measurements, it is possible to estimate z_ini=11.15^+0.01_-0.02 and z_ini=11.43^+0.03_-0.06 respectively, which is close to the reionization epoch. Moreover, we use the observational Hubble data (OHD), Type Ia Supernovae (SnIa), Baryon Acoustic Oscillations (BAO) and the Cosmic Microwave Background Radiation (CMB) distance data to constrain the UG cosmological parameters. A Joint analysis (OHD+SnIa+BAO+CMB), results in z_ini=11.47^+0.074_-0.073 within 1\u03c3 confidence level consistent with our estimation from Planck and Supernovae measurements. We also include linear perturbations, starting with scalar and tensor perturbations and complementing with the perturbed Boltzmann equation for photons. We show that the 00 term in the UG field equations and the Boltzmann equation for photons contains corrections, meanwhile the other equations are similar as those obtained in standard cosmology.", "keyphrases": ["universe acceleration", "unimodular gravity", "cosmology"]}
{"id": "2106.09713", "title": "Cosmology at high redshift \u2013 a probe of fundamental physics", "abstract": "An observational program focused on the high redshift (2<z<6) Universe has the opportunity to dramatically improve over upcoming LSS and CMB surveys on measurements of both the standard cosmological model and its extensions. Using a Fisher matrix formalism that builds upon recent advances in Lagrangian perturbation theory, we forecast constraints for future spectroscopic and 21-cm surveys on the standard cosmological model, curvature, neutrino mass, relativistic species, primordial features, primordial non-Gaussianity, dynamical dark energy, and gravitational slip. We compare these constraints with those achievable by current or near-future surveys such as DESI and Euclid, all under the same forecasting formalism, and compare our formalism with traditional linear methods. Our Python code FishLSS - used to calculate the Fisher information of the full shape power spectrum, CMB lensing, the cross-correlation of CMB lensing with galaxies, and combinations thereof - is publicly available.", "keyphrases": ["high redshift", "neutrino mass", "primordial non-gaussianity"]}
{"id": "1110.2618", "title": "The Self-Accelerating Universe with Vectors in Massive Gravity", "abstract": "We explore the possibility of realising self-accelerated expansion of the Universe taking into account the vector components of a massive graviton. The effective action in the decoupling limit contains an infinite number of terms, once the vector degrees of freedom are included. These can be re-summed in physically interesting situations, which result in non-polynomial couplings between the scalar and vector modes. We show there are self-accelerating background solutions for this effective action, with the possibility of having a non-trivial profile for the vector fields. We then study fluctuations around these solutions and show that there is always a ghost, if a background vector field is present. When the background vector field is switched off, the ghost can be avoided, at the price of entering into a strong coupling regime, in which the vector fluctuations have vanishing kinetic terms. Finally we show that the inclusion of a bare cosmological constant does not change the previous conclusions and it does not lead to a ghost mode in the absence of a background vector field.", "keyphrases": ["massive gravity", "self-accelerating solution", "vector perturbation"]}
{"id": "1409.6817", "title": "Quantum field theory of relic nonequilibrium systems", "abstract": "In terms of the de Broglie-Bohm pilot-wave formulation of quantum theory, we develop field-theoretical models of quantum nonequilibrium systems which could exist today as relics from the very early universe. We consider relic excited states generated by inflaton decay, as well as relic vacuum modes, for particle species that decoupled close to the Planck temperature. Simple estimates suggest that, at least in principle, quantum nonequilibrium could survive to the present day for some relic systems. The main focus of this paper is to describe the behaviour of such systems in terms of field theory, with the aim of understanding how relic quantum nonequilibrium might manifest experimentally. We show by explicit calculation that simple perturbative couplings will transfer quantum nonequilibrium from one field to another (for example from the inflaton field to its decay products). We also show that fields in a state of quantum nonequilibrium will generate anomalous spectra for standard energy measurements. Possible connections to current astrophysical observations are briefly addressed.", "keyphrases": ["nonequilibrium", "quantum theory", "relic cosmological particle"]}
{"id": "1105.1603", "title": "Detecting the cosmic acceleration with current data", "abstract": "The deceleration parameter q as the diagnostic of the cosmological accelerating expansion is investigated. By expanding the luminosity distance to the fourth order of redshift and the so-called y-redshift in two redshift bins and fitting the SNIa data (Union2), the marginalized likelihood distribution of the current deceleration parameter shows that the cosmic acceleration is still increasing, but there might be a tendency that the cosmic acceleration will slow down in the near future. We also fit the Hubble evolution data together with SNIa data by expanding the Hubble parameter to the third order, showing that the present decelerating expansion is excluded within 2\u03c3 error. Further exploration on this problem is also approached in a non-parametrization method by directly reconstructing the deceleration parameter from the distance modulus of SNIa, which depends neither on the validity of general relativity nor on the content of the universe or any assumption regarding cosmological parameters. More accurate observation datasets and more effective methods are still in need to make a clear answer on whether the cosmic acceleration will keep increasing or not.", "keyphrases": ["cosmic acceleration", "deceleration parameter", "redshift"]}
{"id": "2012.05338", "title": "Effective field equations and scale-dependent couplings in gravity", "abstract": "A new set of field equations for a space-time dependent Newton's constant G(x) and cosmological constant \u039b(x) in the presence of matter is presented. We prove that it represents the most general mathematically consistent, physically plausible, set of evolution equations assuming at most second derivatives in the dynamical variables. In the new Einstein's equations, only \u039b-kinetic terms arise, while in the modified conservation equation, derivative terms of G also appear. As an application, this formalism is applied in the context of the Asymptotic Safety scenario to the early universe, assuming a perfect fluid with a radiation equation of state. Cosmological solutions are obtained for all types of spatial curvature, displaying a variety of interesting cosmic evolutions. As an indication of such behaviours, bouncing solutions, recollapsing solutions or non-singular expanding solutions with a transient acceleration era are discussed in details.", "keyphrases": ["field equation", "cosmological constant", "variable"]}
{"id": "1104.3629", "title": "The Primordial Curvature Perturbation from Vector Fields of General non-Abelian Groups", "abstract": "We consider the generation of primordial curvature perturbation by general non-Abelian vector fields without committing to a particular group. Self-interactions of non-Abelian fields make the field perturbation non-Gaussian. We calculate the bispectrum of the field perturbation using the in-in formalism at tree level. The bispectrum is dominated by the classical evolution of fields outside the horizon. In view of this we show that the dominant contribution can be obtained from the homogeneous classical equation of motion. Then we calculate the power spectrum of the curvature perturbation. The anisotropy in spectrum is suppressed by the number of fields. This makes it possible for vector fields to be responsible for the total curvature perturbation in the Universe without violating observational bounds on statistical anisotropy. The bispectrum of the curvature perturbation is also anisotropic. Finally we give an example of the end-of-inflation scenario in which the curvature perturbation is generated by vector gauge fields through varying gauge coupling constant(s), which in covariant derivatives couples the Higgs field to the vector fields. We find that reasonably large gauge groups may result in the observable anisotropy in the power spectrum of the curvature perturbation.", "keyphrases": ["primordial curvature perturbation", "vector field", "non-abelian field"]}
{"id": "1103.1882", "title": "Fast Magnetic Reconnection and Spontaneous Stochasticity", "abstract": "Magnetic field-lines in astrophysical plasmas are expected to be frozen-in at scales larger than the ion gyroradius. The rapid reconnection of magnetic flux structures with dimensions vastly larger than the gyroradius requires a breakdown in the standard Alfv\u00e9n flux-freezing law. We attribute this breakdown to ubiquitous MHD plasma turbulence with power-law scaling ranges of velocity and magnetic energy spectra. Lagrangian particle trajectories in such environments become \"spontaneously stochastic\", so that infinitely-many magnetic field-lines are advected to each point and must be averaged to obtain the resultant magnetic field. The relative distance between initial magnetic field lines which arrive to the same final point depends upon the properties of two-particle turbulent dispersion. We develop predictions based on the phenomenological Goldreich Sridhar theory of strong MHD turbulence and on weak MHD turbulence theory. We recover the predictions of the Lazarian Vishniac theory for the reconnection rate of large-scale magnetic structures. Lazarian Vishniac also invoked \"spontaneous stochasticity\", but of the field-lines rather than of the Lagrangian trajectories. More recent theories of fast magnetic reconnection appeal to microscopic plasma processes that lead to additional terms in the generalized Ohm's law, such as the collisionless Hall term. We estimate quantitatively the effect of such processes on the inertial-range turbulence dynamics and find them to be negligible in most astrophysical environments. For example, the predictions of the Lazarian-Vishniac theory are unchanged in Hall MHD turbulence with an extended inertial range, whenever the ion skin depth \u03b4_i is much smaller than the turbulent integral length or injection-scale L_i.", "keyphrases": ["spontaneous stochasticity", "magnetic field", "reconnection rate"]}
{"id": "1204.5294", "title": "Accelerating f(T) gravity models constrained by recent cosmological data", "abstract": "Generalised Teleparallel gravity, also referred to as f(T) gravity, has been recently proposed as an extended theory of gravitation able to give rise to an accelerated expansion in a matter only universe. The cosmic speed up is driven by an effective torsion fluid whose equation of state depend on the f(T) function entering the modified gravity Lagrangian. We focus on two particular choices for f(T) which share the nice property to emulate a phantom divide crossing as suggested by some recent data. We check their viability contrasting the predicted background dynamics to the Hubble diagram as traced by both Type Ia Supernovae (SNeIa) and Gamma Ray Bursts (GRBs), the measurement of the rate expansion H(z), the Baryon Acoustic Oscillations (BAOs) at different redshifts, and the Cosmic Microwave Background Radiation (CMBR) distance priors. Both f(T) models turn out to be in very good agreement with this large dataset so that we also investigate whether it is possible to discriminate among them relying on the different growth factors.", "keyphrases": ["cosmological data", "teleparallel gravity", "accelerated expansion"]}
{"id": "1311.4884", "title": "Lagrangian or Eulerian; Real or Fourier? Not All Approaches to Large-Scale Structure Are Created Equal", "abstract": "We present a pedagogical systematic investigation of the accuracy of Eulerian and Lagrangian perturbation theories of large-scale structure. We show that significant differences exist between them especially when trying to model the Baryon Acoustic Oscillations (BAO). We find that the best available model of the BAO in real space is the Zel'dovich Approximation (ZA), giving an accuracy of < 3 acoustic peak. All corrections to the ZA around the BAO scale are perfectly perturbative in real space. Any attempt to achieve better precision requires calibrating the theory to simulations because of the need to renormalize those corrections. In contrast, theories which do not fully preserve the ZA as their solution, receive O(1) corrections around the acoustic peak in real space at z=0, and are thus of suspicious convergence at low redshift around the BAO. As an example, we find that a similar accuracy of 3 achieved by Eulerian Standard Perturbation Theory (SPT) at linear order only at z 4. Thus even when SPT is perturbative, one needs to include loop corrections for z< 4 in real space. In Fourier space, all models perform similarly, and are controlled by the overdensity amplitude, thus recovering standard results. However, that comes at a price. Real space cleanly separates the BAO signal from non-linear dynamics. In contrast, Fourier space mixes signal from short mildly non-linear scales with the linear signal from the BAO to the level that non-linear contributions from short scales dominate. Therefore, one has little hope in constructing a systematic theory for the BAO in Fourier space.", "keyphrases": ["large-scale structure", "perturbation theory", "fourier space", "section"]}
{"id": "0907.1912", "title": "Dark Matter Astrophysics", "abstract": "These lectures are intended to provide a brief pedagogical review of dark matter for the newcomer to the subject. We begin with a discussion of the astrophysical evidence for dark matter. The standard weakly-interacting massive particle (WIMP) scenario\u2013the motivation, particle models, and detection techniques\u2013is then reviewed. We provide a brief sampling of some recent variations to the standard WIMP scenario as well as some alternatives (axions and sterile neutrinos). Exercises are provided for the reader.", "keyphrases": ["massive particle", "dark matter", "galactic rotation curve", "cosmic microwave background"]}
{"id": "1812.06986", "title": "A Global Analysis of Dark Matter Signals from 27 Dwarf Spheroidal Galaxies using 11 Years of Fermi-LAT Observations", "abstract": "We search for a dark matter signal in 11 years of Fermi-LAT gamma-ray data from 27 Milky Way dwarf spheroidal galaxies with spectroscopically measured J-factors. Our analysis includes uncertainties in J-factors and background normalisations and compares results from a Bayesian and a frequentist perspective. We revisit the dwarf spheroidal galaxy Reticulum II, confirming that the purported gamma-ray excess seen in Pass 7 data is much weaker in Pass 8, independently of the statistical approach adopted. We introduce for the first time posterior predictive distributions to quantify the probability of a dark matter detection from another dwarf galaxy given a tentative excess. A global analysis including all 27 dwarfs shows no indication for a signal in nine annihilation channels. We present stringent new Bayesian and frequentist upper limits on the dark matter cross section as a function of dark matter mass. The best-fit dark matter parameters associated with the Galactic Centre excess are excluded by at least 95 the frequentist/Bayesian framework in all cases. However, from a Bayesian model comparison perspective, dark matter annihilation within the dwarfs is not strongly disfavoured compared to a background-only model. These results constitute the highest exposure analysis on the most complete sample of dwarfs to date. Posterior samples and likelihood maps from this study are publicly available.", "keyphrases": ["dark matter signal", "fermi-lat", "annihilation cross section"]}
{"id": "1602.07835", "title": "Constraints on the Photon Mass with Fast Radio Bursts", "abstract": "Fast radio bursts (FRBs) are radio bursts characterized by millisecond durations, high Galactic latitude positions, and high dispersion measures. Very recently, the cosmological origin of FRB 150418 has been confirmed by <cit.>, and FRBs are now strong competitors as cosmological probes. The simple sharp feature of the FRB signal is ideal for them to probe some of the fundamental laws of physics. Here we show that by analyzing the delay time between different frequencies, the FRB data can place stringent upper limits on the rest mass of the photon. For FRB 150418 at z=0.492, one can potentially reach m_\u03b3\u2264 5.2 \u00d7 10^-47 g, which is 10^20 times smaller than the rest mass of electron, and is about 10^3 times smaller than that obtained using other astrophysical sources with the same method.", "keyphrases": ["photon mass", "cosmological origin", "physic"]}
{"id": "0906.0335", "title": "Twister quintessence scenario", "abstract": "We study generic solutions in a non-minimally coupled to gravity scalar field cosmology. It is shown that dynamics for both canonical and phantoms scalar fields with the potential can be reduced to the dynamical system from which the exact forms for an equation of the state parameter can be derived. We have found the stationary solutions of the system and discussed their stability. Within the large class of admissible solutions we have found a non-degenerate critical points and we pointed out multiple attractor type of trajectory travelling in neighborhood of three critical points at which we have the radiation dominating universe, the barotropic matter dominating state and finally the de Sitter attractor. We have demonstrated the stability of this trajectory which we call the twister solution. Discovered evolutional path is only realized if there exist the non-minimal coupling constant. We have found simple duality relations between twister solutions in phantom and canonical scalar fields in the radiation domination phase. For the twister trajectory we have found an oscillating regime of approaching the de Sitter attractor.", "keyphrases": ["non-minimal coupling", "field cosmology", "trajectory", "twister solution"]}
{"id": "1508.02147", "title": "Cold or Warm? Constraining Dark Matter with Primeval Galaxies and Cosmic Reionization after Planck", "abstract": "Dark matter constitutes the great majority of the matter content in the Universe, but its microscopic nature remains an intriguing mystery, with profound implications for particle physics, astrophysics and cosmology. Here we shed light on the longstanding issue of whether the dark matter is warm or cold by combining the measurements of the galaxy luminosity functions out to high redshifts z 10 from the Hubble Space Telescope with the recent cosmological data on the reionization history of the Universe from the Planck mission. We derive robust and tight bounds on the mass of warm dark matter particle, finding that the current data require it to be in the narrow range between 2 and 3 keV. In addition, we show that a mass not exceeding 3 keV is also concurrently indicated by astrophysical constraints related to the local number of satellites in Milky Way-sized galaxies, though it is in marginal tension with analysis of the Lyman-alpha forest. For warm dark matter masses above 3 keV as well as for cold dark matter, to satisfy the Planck constraints on the optical depth and not to run into the satellite problem would require invoking astrophysical processes that inhibit galaxy formation in halos with mass M_H< a few 10^8 M_sun, corresponding to a limiting UV magnitude M_UV -11. Anyway, we predict a downturn of the galaxy luminosity function at z 8 faintward of M_UV -12, and stress that its detailed shape is extremely informative both on particle physics and on the astrophysics of galaxy formation in small halos. These expectations will be tested via the Hubble Frontier Fields and with the advent of the James Webb Space Telescope, which will enable probing the very faint end of the galaxy luminosity function out to z 8-10.", "keyphrases": ["dark matter", "galaxy luminosity function", "way-sized galaxy"]}
{"id": "2001.07536", "title": "Resolving the H_0 tension with diffusion", "abstract": "The tension between the value of the Hubble constant H_0 determined from local supernovae data and the one inferred from the cosmic microwave background based on the \u039bCDM cosmological model may indicate the need for new physics. Here, we show that this `Hubble tension' can be resolved in models involving an effective energy flux from the matter sector into dark energy resulting naturally from a combination of unimodular gravity and an energy diffusion process. The scheme is one where dark energy has the standard equation of state w=-1. This proposal provides an alternative phenomenological paradigm accounting for the observations, while offering a general framework to study diffusion effects coming from novel fundamental physical processes.", "keyphrases": ["dark energy", "gravity", "tension\u2014as", "content", "low-redshift"]}
{"id": "1411.5889", "title": "Searching for Traces of Planck-Scale Physics with High Energy Neutrinos", "abstract": "High energy cosmic neutrino observations provide a sensitive test of Lorentz invariance violation, which may be a consequence of quantum gravity theories. We consider a class of non-renormalizable, Lorentz invariance violating operators that arise in an effective field theory description of Lorentz invariance violation in the neutrino sector inspired by Planck-scale physics and quantum gravity models. We assume a conservative generic scenario for the redshift distribution of extragalactic neutrino sources and employ Monte Carlo techniques to describe superluminal neutrino propagation, treating kinematically allowed energy losses of superluminal neutrinos caused by both vacuum pair emission and neutrino splitting. We consider EFTs with both non-renormalizable CPT-odd and non-renormalizable CPT-even operator dominance. We then compare the spectra derived using our Monte Carlo calculations in both cases with the spectrum observed by IceCube in order to determine the implications of our results regarding Planck-scale physics. We find that if the drop off in the neutrino flux above 2 PeV is caused by Planck scale physics, rather than by a limiting energy in the source emission, a potentially significant pileup effect would be produced just below the drop off energy in the case of CPT-even operator dominance. However, such a clear drop off effect would not be observed if the CPT-odd, CPT-violating term dominates.", "keyphrases": ["neutrino", "vacuum pair emission", "quantum-spacetime research"]}
{"id": "2007.11066", "title": "Revisiting Magnetogenesis during Inflation", "abstract": "We revisit the mechanism of primordial magnetogenesis during inflation by taking into account the dynamics of the stochastic noises of the electromagnetic perturbations. We obtain the associated Langevin and Fokker-Planck equations for the electromagnetic fields and solve them analytically. It is shown that while the backreactions of the electric field energy density may spoil inflation too early, but there are regions of parameter space where the usual decaying behavior of the magnetic fields are replaced by a mean-reverting process of stochastic dynamics. As a result, the magnetic fields settle down into an equilibrium state with the amplitude significantly larger than what is obtained in the absence of the stochastic noises. We show that magnetic fields with present time amplitude \u223c 10^-13 Gauss and coherent length Mpc can be generated while the backreactions of the electric field perturbations are under control.", "keyphrases": ["magnetogenesis", "electromagnetic perturbation", "primordial magnetic field"]}
{"id": "1804.05080", "title": "Infrared Resummation for Biased Tracers in Redshift Space", "abstract": "We incorporate the effects of redshift space distortions and non-linear bias in time-sliced perturbation theory (TSPT). This is done via a new method that allows to map cosmological correlation functions from real to redshift space. This mapping preserves a transparent infrared (IR) structure of the theory and provides us with an efficient tool to study non-linear infrared effects altering the pattern of baryon acoustic oscillations (BAO) in redshift space. We give an accurate description of the BAO by means of a systematic resummation of Feynman diagrams guided by well-defined power counting rules. This establishes IR resummation within TSPT as a robust and complete procedure and provides a consistent theoretical model for the BAO feature in the statistics of biased tracers in redshift space.", "keyphrases": ["resummation", "redshift space", "baryon"]}
{"id": "1108.1728", "title": "Extended LCDM: generalized non-minimal coupling for dark matter fluids", "abstract": "In this paper we discuss a class of models that address the issue of explaining the gravitational dynamics at the galactic scale starting from a geometric point of view. Instead of claiming the existence of some hidden coupling between dark matter and baryons, or abandoning the existence of dark matter itself, we consider the possibility that dark matter and gravity have some non trivial interaction able to modify the dynamics at astrophysical scales. This interaction is implemented assuming that dark matter gets non\u2013minimally coupled with gravity at suitably small scales and late times. After showing the predictions of the model in the Newtonian limit we also discuss the possible origin of it non-minimal coupling. This investigation seems to suggest that phenomenological mechanisms envisaged for the dark matter dynamics, such as the Bose\u2013Einstein condensation of dark matter halos, could be connected to this class of models.", "keyphrases": ["non-minimal coupling", "dark matter", "gravity"]}
{"id": "1208.0665", "title": "Generation of large-scale magnetic fields from inflation in teleparallelism", "abstract": "We explore the generation of large-scale magnetic fields from inflation in teleparallelism, in which the gravitational theory is described by the torsion scalar instead of the scalar curvature in general relativity. In particular, we examine the case that the conformal invariance of the electromagnetic field during inflation is broken by a non-minimal gravitational coupling between the torsion scalar and the electromagnetic field. It is shown that for a power-law type coupling, the magnetic field on 1 Mpc scale with its strength of \u223c 10^-9 G at the present time can be generated.", "keyphrases": ["large-scale magnetic field", "conformal invariance", "non-minimal gravitational coupling"]}
{"id": "1203.1252", "title": "Model selection applied to reconstruction of the Primordial Power Spectrum", "abstract": "The preferred shape for the primordial spectrum of curvature perturbations is determined by performing a Bayesian model selection analysis of cosmological observations. We first reconstruct the spectrum modelled as piecewise linear in logk between nodes in k-space whose amplitudes and positions are allowed to vary. The number of nodes together with their positions are chosen by the Bayesian evidence, so that we can both determine the complexity supported by the data and locate any features present in the spectrum. In addition to the node-based reconstruction, we consider a set of parameterised models for the primordial spectrum: the standard power-law parameterisation, the spectrum produced from the Lasenby Doran (LD) model and a simple variant parameterisation. By comparing the Bayesian evidence for different classes of spectra, we find the power-law parameterisation is significantly disfavoured by current cosmological observations, which show a preference for the LD model.", "keyphrases": ["primordial power spectrum", "curvature perturbation", "parameterisation"]}
{"id": "1811.02025", "title": "The origin of galaxy scaling laws in LCDM", "abstract": "It has long been recognized that tight relations link the mass, size, and characteristic velocity of galaxies. These scaling laws reflect the way in which baryons populate, cool, and settle at the center of their host dark matter halos; the angular momentum they retain in the assembly process; as well as the radial distribution and mass scalings of the dark matter halos. There has been steady progress in our understanding of these processes in recent years, mainly as sophisticated N-body and hydrodynamical simulation techniques have enabled the numerical realization of galaxy models of ever increasing complexity, realism, and appeal. These simulations have now clarified the origin of these galaxy scaling laws in a universe dominated by cold dark matter: these relations arise from the tight (but highly non-linear) relations between (i) galaxy mass and halo mass, (ii) galaxy size and halo characteristic radius; and (iii) from the self-similar mass nature of cold dark matter halo mass profiles. The excellent agreement between simulated and observed galaxy scaling laws is a resounding success for the LCDM cosmogony on the highly non-linear scales of individual galaxies.", "keyphrases": ["galaxy", "matter halo", "n-body"]}
{"id": "1302.3467", "title": "Note on Structure Formation from Cosmic String Wakes", "abstract": "The search for cosmic strings has been of renewed interest with the advent of precision cosmology. In this note we give a quantitative description of the nonlinear matter density fluctuations that can form from a scaling network of cosmic string wakes. Specifically, we compute the distribution of dark matter halos. These halos would possess strong correlations in position space that should have survived until today. We also discuss the challenges involved in their detection due to their small size and the complex dynamics of their formation.", "keyphrases": ["structure formation", "cosmic string", "string wake"]}
{"id": "1204.1784", "title": "Issues Concerning Loop Corrections to the Primordial Power Spectra", "abstract": "We expound ten principles in an attempt to clarify the debate over infrared loop corrections to the primordial scalar and tensor power spectra from inflation. Among other things we note that existing proposals for nonlinear extensions of the scalar fluctuation field \u03b6 introduce new ultraviolet divergences which no one understands how to renormalize. Loop corrections and higher correlators of these putative observables would also be enhanced by inverse powers of the slow roll parameter \u03f5. We propose an extension which should be better behaved.", "keyphrases": ["loop correction", "new ultraviolet divergence", "gauge"]}
{"id": "0912.3263", "title": "Probing star formation across cosmic time with absorption line systems", "abstract": "We present an empirical connection between cold gas in galactic halos and star formation. Using a sample of more than 8,500 MgII absorbers from SDSS quasar spectra, we report the detection of a 15 sigma correlation between the rest equivalent width W0 of MgII absorbers and the associated OII luminosity, an estimator of star formation rate. This correlation has interesting implications: using only observable quantities we show that MgII absorbers trace a substantial fraction of the global OII luminosity density and recover the overall star formation history of the Universe derived from classical emission estimators up to z 2. We then show that the distribution function of MgII rest equivalent widths, dN/dW0 inherits both its shape and amplitude from the OII luminosity function Phi(L). These distributions can be naturally connected, without any free parameter. Our results imply a high covering factor of cold gas around star forming galaxies: C>0.5, favoring outflows as the mechanism responsible for MgII absorption. We then argue that intervening MgII absorbers and blue-shifted MgII absorption seen in the spectra of star forming galaxies are essentially the same systems. These results not only shed light on the nature of MgII absorbers but also provide us with a new probe of star formation, in absorption, i.e. in a way which does not suffer from dust extinction and with a redshift-independent sensitivity. As shown in this analysis, such a tool can be applied in a noise-dominated regime, i.e. using a dataset for which emission lines are not detected in individual objects. This is of particular interest for high redshift studies.", "keyphrases": ["star formation", "cold gas", "redshift"]}
{"id": "1908.06234", "title": "Perturbation theory approach to predict the covariance matrices of the galaxy power spectrum and bispectrum in redshift space", "abstract": "In this paper, we predict the covariance matrices of both the power spectrum and the bispectrum, including full non-Gaussian contributions, redshift space distortions, linear bias effects and shot-noise corrections, using perturbation theory (PT). To quantify the redshift-space distortion effect, we focus mainly on the monopole and quadrupole components of both the power and bispectra. We, for the first time, compute the 5- and 6-point spectra to predict the cross-covariance between the power and bispectra, and the auto-covariance of the bispectrum in redshift space. We test the validity of our calculations by comparing them with the covariance matrices measured from the MultiDark-Patchy mock catalogues that are designed to reproduce the galaxy clustering measured from the Baryon Oscillation Spectroscopic Survey Data Release 12. We argue that the simple, leading-order perturbation theory works because the shot-noise corrections for the Patchy mocks are more dominant than other higher-order terms we ignore. In the meantime, we confirm some discrepancies in the comparison, especially of the cross-covariance. We discuss potential sources of such discrepancies. We also show that our PT model reproduces well the cumulative signal-to-noise of the power spectrum and the bispectrum as a function of maximum wavenumber, implying that our PT model captures successfully essential contributions to the covariance matrices.", "keyphrases": ["bispectrum", "redshift space", "perturbation theory"]}
{"id": "1908.01948", "title": "Imaging extended sources with the solar gravitational lens", "abstract": "We investigate the optical properties of the solar gravitational lens (SGL) with respect to an extended source located at a large but finite distance from the Sun. The static, spherically symmetric gravitational field of the Sun is modeled within the first post-Newtonian approximation of the general theory of relativity. We consider the propagation of monochromatic electromagnetic (EM) waves near the Sun. We develop, based on a Mie theory, a vector theory of diffraction that accounts for the refractive properties of the solar gravitational field. The finite distance to a point source can be accounted for using a rotation of the coordinate system to align its polar axis with the axis directed from the point source to the center of the Sun, which we call the optical axis. We determine the EM field and study the key optical properties of the SGL in all four regions formed behind the Sun by an EM wave diffracted by the solar gravity field: the shadow, geometric optics, and weak and strong interference regions. Extended sources can then be represented as collections of point sources. We present the power density of the signal received by a telescope in the image plane. Our discussion concludes with considering the implications for imaging with the SGL.", "keyphrases": ["extended source", "gravitational field", "telescope"]}
{"id": "1612.05860", "title": "Resolving Cosmological Singularities", "abstract": "We find a simple modification of the longitudinal mode in General Relativity which incorporates the idea of limiting curvature. In this case the singularities in contracting Friedmann and Kasner universes are avoided, and instead, the universe has a regular bounce which takes place during the time inversely proportional to the square root of the limiting curvature. Away from the bounce, corrections to General Relativity are negligible. In addition the non-singluar modification of General Relativity delivers for free a realistic candidate for Dark Matter.", "keyphrases": ["curvature", "dark matter", "mimetic gravity"]}
{"id": "2007.11363", "title": "Magnetic Flux Ropes in the Solar Corona: Structure and Evolution toward Eruption", "abstract": "Magnetic flux ropes are characterized by coherently twisted magnetic field lines, which are ubiquitous in magnetized plasmas. As the core structure of various eruptive phenomena in the solar atmosphere, flux ropes hold the key to understanding the physical mechanisms of solar eruptions, which impact the heliosphere and planetary atmospheres. Strongest disturbances in the Earth's space environments are often associated with large-scale flux ropes from the Sun colliding with the Earth's magnetosphere, leading to adverse, sometimes catastrophic, space-weather effects. However, it remains elusive as to how a flux rope forms and evolves toward eruption, and how it is structured and embedded in the ambient field. The present paper addresses these important questions by reviewing current understandings of coronal flux ropes from an observer's perspective, with emphasis on their structures and nascent evolution toward solar eruptions, as achieved by combining observations of both remote sensing and in-situ detection with modeling and simulation. It highlights an initiation mechanism for coronal mass ejections (CMEs) in which plasmoids in current sheets coalesce into a `seed' flux rope whose subsequent evolution into a CME is consistent with the standard model, thereby bridging the gap between microscale and macroscale dynamics.", "keyphrases": ["solar corona", "coronal mass ejection", "magnetic flux rope"]}
{"id": "1307.3547", "title": "Axions and the Galactic Angular Momentum Distribution", "abstract": "We analyze the behavior of axion dark matter before it falls into a galactic gravitational potential well. The axions thermalize sufficiently fast by gravitational self-interactions that almost all go to their lowest energy state consistent with the total angular momentum acquired from tidal torquing. That state is a state of rigid rotation on the turnaround sphere. It predicts the occurrence and detailed properties of the caustic rings of dark matter for which observational evidence had been found earlier. We show that the vortices in the axion Bose-Einstein condensate (BEC) are attractive, unlike those in superfluid ^4He and dilute gases. We expect that a large fraction of the vortices in the axion BEC join into a single big vortex along the rotation axis of the galaxy. The resulting enhancement of caustic rings explains the typical size of the rises in the Milky Way rotation curve attributed to caustic rings. We show that baryons and ordinary cold dark matter particles are entrained by the axion BEC and acquire the same velocity distribution. The resulting baryonic angular momentum distribution gives a good qualitative fit to the distributions observed in dwarf galaxies. We give estimates of the minimum fraction of dark matter that is axions.", "keyphrases": ["dark matter", "galaxy", "axion"]}
{"id": "1711.10524", "title": "MassiveNuS: Cosmological Massive Neutrino Simulations", "abstract": "The non-zero mass of neutrinos suppresses the growth of cosmic structure on small scales. Since the level of suppression depends on the sum of the masses of the three active neutrino species, the evolution of large-scale structure is a promising tool to constrain the total mass of neutrinos and possibly shed light on the mass hierarchy. In this work, we investigate these effects via a large suite of N-body simulations that include massive neutrinos using an analytic linear-response approximation: the Cosmological Massive Neutrino Simulations (MassiveNuS). The simulations include the effects of radiation on the background expansion, as well as the clustering of neutrinos in response to the nonlinear dark matter evolution. We allow three cosmological parameters to vary: the neutrino mass sum M_nu in the range of 0-0.6 eV, the total matter density Omega_m, and the primordial power spectrum amplitude A_s. The rms density fluctuation in spheres of 8 comoving Mpc/h (sigma_8) is a derived parameter as a result. Our data products include N-body snapshots, halo catalogues, merger trees, ray- traced galaxy lensing convergence maps for four source redshift planes between z_s=1-2.5, and ray-traced cosmic microwave background lensing convergence maps. We describe the simulation procedures and code validation in this paper. The data are publicly available at http://columbialensing.org.", "keyphrases": ["cosmic microwave background", "massivenus", "neutrino perturbation"]}
{"id": "1507.04363", "title": "Probing cosmology and gravity with redshift-space distortions around voids", "abstract": "Cosmic voids in the large-scale structure of the Universe affect the peculiar motions of objects in their vicinity. Although these motions are difficult to observe directly, the clustering pattern of their surrounding tracers in redshift space is influenced in a unique way. This allows to investigate the interplay between densities and velocities around voids, which is solely dictated by the laws of gravity. With the help of N-body simulations and derived mock-galaxy catalogs we calculate the average density fluctuations around voids identified with a watershed algorithm in redshift space and compare the results with the expectation from general relativity and the \u039bCDM model. We find linear theory to work remarkably well in describing the dynamics of voids. Adopting a Bayesian inference framework, we explore the full posterior of our model parameters and forecast the achievable accuracy on measurements of the growth rate of structure and the geometric distortion through the Alcock-Paczynski effect. Systematic errors in the latter are reduced from \u223c15% to \u223c5% when peculiar velocities are taken into account. The relative parameter uncertainties in galaxy surveys with number densities comparable to the SDSS MAIN (CMASS) sample probing a volume of 1h^-3 Gpc^3 yield \u03c3_f/b/(f/b).\u223c2% (20%) and \u03c3_D_AH/D_AH\u223c0.2% (2%), respectively. At this level of precision the linear-theory model becomes systematics dominated, with parameter biases that fall beyond these values. Nevertheless, the presented method is highly model independent; its viability lies in the underlying assumption of statistical isotropy of the Universe.", "keyphrases": ["gravity", "cosmic void", "redshift space"]}
{"id": "1207.5508", "title": "Magnitude Gap Statistics and the Conditional Luminosity Function", "abstract": "In a recent preprint, Hearin et al. (2012,H12) suggest that the halo mass-richness calibration of clusters can be improved by using the difference in the magnitude of the brightest and the second brightest galaxy (magnitude gap) as an additional observable. They claim that their results are at odds with the results from Paranjape Sheth (2012, PS12) who show that the magnitude distribution of the brightest and second brightest galaxies can be explained based on order statistics of luminosities randomly sampled from the total galaxy luminosity function. We find that a conditional luminosity function (CLF) for galaxies which varies with halo mass, in a manner which is consistent with existing observations, naturally leads to a magnitude gap distribution which changes as a function of halo mass at fixed richness, in qualitative agreement with H12. We show that, in general, the luminosity distribution of the brightest and the second brightest galaxy depends upon whether the luminosities of galaxies are drawn from the CLF or the global luminosity function. However, we also show that the difference between the two cases is small enough to evade detection in the small sample investigated by PS12. This shows that the luminosity distribution is not the appropriate statistic to distinguish between the two cases, given the small sample size. We argue in favor of the CLF (and therefore H12) based upon its consistency with other independent observations, such as the kinematics of satellite galaxies, the abundance and clustering of galaxies, and the galaxy-galaxy lensing signal from the Sloan Digital Sky Survey.", "keyphrases": ["conditional luminosity function", "richness", "magnitude gap"]}
{"id": "1804.01532", "title": "Planetary population synthesis", "abstract": "In stellar astrophysics, the technique of population synthesis has been successfully used for several decades. For planets, it is in contrast still a young method which only became important in recent years because of the rapid increase of the number of known extrasolar planets, and the associated growth of statistical observational constraints. With planetary population synthesis, the theory of planet formation and evolution can be put to the test against these constraints. In this review of planetary population synthesis, we first briefly list key observational constraints. Then, the work flow in the method and its two main components are presented, namely global end-to-end models that predict planetary system properties directly from protoplanetary disk properties and probability distributions for these initial conditions. An overview of various population synthesis models in the literature is given. The sub-models for the physical processes considered in global models are described: the evolution of the protoplanetary disk, the planets' accretion of solids and gas, orbital migration, and N-body interactions among concurrently growing protoplanets. Next, typical population synthesis results are illustrated in the form of new syntheses obtained with the latest generation of the Bern model. Planetary formation tracks, the distribution of planets in the mass-distance and radius-distance plane, the planetary mass function, and the distributions of planetary radii, semimajor axes, and luminosities are shown, linked to underlying physical processes, and compared with their observational counterparts. We finish by highlighting the most important predictions made by population synthesis models and discuss the lessons learned from these predictions - both those later observationally confirmed and those rejected.", "keyphrases": ["protoplanetary disk", "planetary population synthesis", "observed population", "material"]}
{"id": "1008.3330", "title": "Fast magnetic reconnection in the plasmoid-dominated regime", "abstract": "A conceptual model of resistive magnetic reconnection via a stochastic plasmoid chain is proposed. The global reconnection rate is shown to be independent of the Lundquist number. The distribution of fluxes in the plasmoids is shown to be an inverse square law. It is argued that there is a finite probability of emergence of abnormally large plasmoids, which can disrupt the chain (and may be responsible for observable large abrupt events in solar flares and sawtooth crashes). A criterion for the transition from magnetohydrodynamic to collisionless regime is provided.", "keyphrases": ["magnetic reconnection", "magnetohydrodynamic", "fast reconnection"]}
{"id": "2101.03740", "title": "Comparing early dark energy and extra radiation solutions to the Hubble tension with BBN", "abstract": "The shorten sound horizon scale at the recombination epoch by introducing extra energy components such as the extra radiation or early dark energy (EDE) is a simple approach to so-called the Hubble tension. We compare EDE models, an extra radiation model and an EDE and extra radiation co-existing model with paying attention to the fit to big bang nucleosynthesis (BBN). We find that a fit to BBN in EDE models also is somewhat poorer than that in the \u039bCDM model, because the increased inferred baryon asymmetry leads to smaller deuterium abundance. We find that an extra radiation-EDE co-existing model indicates the largest present Hubble parameter H_0 between models studied. We also the examine data sets dependence, whether we include BBN or not. The difference in an extra radiation model is 3.22 < N_eff < 3.49 (68 %) for data sets without BBN and 3.16 < N_eff < 3.40 (68 %) for data sets with BBN, and is so large that the 1\u03c3 border of the larger side becomes the 2\u03c3 border.", "keyphrases": ["early dark energy", "sound horizon scale", "gravitational theory"]}
{"id": "1402.5916", "title": "Renormalized Halo Bias", "abstract": "This paper provides a systematic study of renormalization in models of halo biasing. Building on work of McDonald, we show that Eulerian biasing is only consistent with renormalization if non-local terms and higher-derivative contributions are included in the biasing model. We explicitly determine the complete list of required bias parameters for Gaussian initial conditions, up to quartic order in the dark matter density contrast and at leading order in derivatives. At quadratic order, this means including the gravitational tidal tensor, while at cubic order the velocity potential appears as an independent degree of freedom. Our study naturally leads to an effective theory of biasing in which the halo density is written as a double expansion in fluctuations and spatial derivatives. We show that the bias expansion can be organized in terms of Galileon operators which aren't renormalized at leading order in derivatives. Finally, we discuss how the renormalized bias parameters impact the statistics of halos.", "keyphrases": ["higher-derivative contribution", "quartic order", "velocity potential", "bias expansion", "renormalization"]}
{"id": "1612.06891", "title": "Theoretical Challenges in Galaxy Formation", "abstract": "Numerical simulations have become a major tool for understanding galaxy formation and evolution. Over the decades the field has made significant progress. It is now possible to simulate the formation of individual galaxies and galaxy populations from well defined initial conditions with realistic abundances and global properties. An essential component of the calculation is to correctly estimate the inflow to and outflow from forming galaxies since observations indicating low formation efficiency and strong circum-glactic presence of gas are persuasive. Energetic 'feedback' from massive stars and accreting super-massive black holes - generally unresolved in cosmological simulations - plays a major role for driving galactic outflows, which have been shown to regulate many aspects of galaxy evolution. A surprisingly large variety of plausible sub-resolution models succeeds in this exercise. They capture the essential characteristics of the problem, i.e. outflows regulating galactic gas flows, but their predictive power is limited. In this review we focus on one major challenge for galaxy formation theory: to understand the underlying physical processes that regulate the structure of the interstellar medium, star formation and the driving of galactic outflows. This requires accurate physical models and numerical simulations, which can precisely describe the multi-phase structure of the interstellar medium on the currently unresolved few hundred parsecs scales of large scale cosmological simulations. Such models ultimately require the full accounting for the dominant cooling and heating processes, the radiation and winds from massive stars and accreting black holes, an accurate treatment of supernova explosions as well as the non-thermal components of the interstellar medium like magnetic fields and cosmic rays.", "keyphrases": ["galaxy formation", "star", "black hole", "cosmological simulation"]}
{"id": "0911.2438", "title": "The Architecture of the Cassini Division", "abstract": "The Cassini Division in Saturn's rings contains a series of eight named gaps, three of which contain dense ringlets. Observations of stellar occultations by the Visual and Infrared Mapping Spectrometer onboard the Cassini spacecraft have yielded 40 accurate and precise measurements of the radial position of the edges of all of these gaps and ringlets. These data reveal suggestive patterns in the shapes of many of the gap edges: the outer edges of the 5 gaps without ringlets are circular to within 1 km, while the inner edges of 6 of the gaps are eccentric, with apsidal precession rates consistent with those expected for eccentric orbits near each edge. Intriguingly, the pattern speeds of these eccentric inner gap edges, together with that of the eccentric Huygens ringlet,form a series with a characteristic spacing of 0.06 degrees/day. The two gaps with non-eccentric inner edges lie near first-order Inner Lindblad Resonances (ILRs) with moons. One such edge is close to the 5:4 ILR with Prometheus. The other resonantly confined edge is the outer edge of the B ring, which lies near the 2:1 Mimas ILR. Detailed investigation of the B-ring-edge data confirm the presence of an m=2 perturbation on the B-ring edge, but also suggest that this pattern moves or librates relative to Mimas. The B-ring edge also has an m=1 component that rotates around the planet at a rate close to the expected apsidal precession rate. The pattern speeds of the eccentric edges in the Cassini Division can potentially be generated from various combinations of the pattern speeds of structures observed on the edge of the B ring. We therefore suggest that the locations of most of the gaps in the Cassini Division may be determined by resonances involving a combination of perturbations from Mimas and the massive edge of the B ring.", "keyphrases": ["cassini division", "gap", "radial position"]}
{"id": "1206.2639", "title": "A 130 GeV photon line from dark matter annihilation in the NMSSM", "abstract": "In the Next-to-Minimal Supersymmetric Standard Model, neutralino dark matter can annihilate into a pair of photons through the exchange of a CP-odd Higgs boson in the s-channel. The CP-odd Higgs boson couples to two photons through a loop of dominantly higgsino-like charginos. We show that the parameter space of the NMSSM can accommodate simultaneously i) neutralino-like dark matter of a mass of about 130 GeV giving rise to a 130 GeV photon line; ii) an annihilation cross section of or larger than 10^-27cm^3s^-1; iii) a relic density in agreement with WMAP constraints; iv) a direct detection cross section compatible with bounds from XENON100, and v) a Standard Model like Higgs mass of about 125 GeV. However, the CP-odd Higgs mass has to lie accidentally close to 260 GeV.", "keyphrases": ["photon line", "dark matter", "annihilation cross section"]}
{"id": "1608.02525", "title": "Magnetically self-regulated formation of early protoplanetary discs", "abstract": "The formation of protoplanetary discs during the collapse of molecular dense cores is significantly influenced by angular momentum transport, notably by the magnetic torque. In turn, the evolution of the magnetic field is determined by dynamical processes and non-ideal MHD effects such as ambipolar diffusion. Considering simple relations between various timescales characteristic of the magnetized collapse, we derive an expression for the early disc radius, r \u2243 18 AU (\u03b7_ AD / 0.1 s)^2/9(B_z / 0.1 G) ^-4/9(M / 0.1 ) ^1/3, where M is the total disc plus protostar mass, \u03b7_AD is the ambipolar diffusion coefficient and B_z is the magnetic field in the inner part of the core. This is about significantly smaller than the discs that would form if angular momentum was conserved. The analytical predictions are confronted against a large sample of 3D, non-ideal MHD collapse calculations covering variations of a factor 100 in core mass, a factor 10 in the level of turbulence, a factor 5 in rotation, and magnetic mass-to-flux over critical mass-to-flux ratios 2 and 5. The disc radius estimates are found to agree with the numerical simulations within less than a factor 2. A striking prediction of our analysis is the weak dependence of circumstellar disc radii upon the various relevant quantities, suggesting weak variations among class-0 disc sizes. In some cases, we note the onset of large spiral arms beyond this radius.", "keyphrases": ["protoplanetary disc", "magnetic field", "magnetized collapse"]}
{"id": "1609.00707", "title": "Magnetic properties of Proxima Centauri b analogues", "abstract": "The discovery of a planet around the closest star to our Sun, Proxima Centauri, represents a quantum leap in the testability of exoplanetary models. Unlike any other discovered exoplanet, models of Proxima b could be contrasted against near future telescopic observations and far future in-situ measurements. In this paper we aim at predicting the planetary radius and the magnetic properties (dynamo lifetime and magnetic dipole moment) of Proxima b analogues (solid planets with masses of \u223c 1-3 M_\u2295, rotation periods of several days and habitable conditions). For this purpose we build a grid of planetary models with a wide range of compositions and masses. For each point in the grid we run the planetary evolution model developed in <cit.>. Our model assumes small orbital eccentricity, negligible tidal heating and earth-like radiogenic mantle elements abundances. We devise a statistical methodology to estimate the posterior distribution of the desired planetary properties assuming simple prior distributions for the orbital inclination and bulk composition. Our model predicts that Proxima b would have a mass 1.3\u2264 M_ p\u2264 2.3 M_\u2295 and a radius R_ p=1.4^+0.3_-0.2 R_\u2295. In our simulations, most Proxima b analogues develop intrinsic dynamos that last for \u22654 Gyr (the estimated age of the host star). If alive, the dynamo of Proxima b have a dipole moment M_ dip>0.32^\u00d7 2.3_\u00f7 2.9 M_ dip,\u2295. These results are not restricted to Proxima b but they also apply to earth-like planets having similar observed properties.", "keyphrases": ["planet", "composition", "magnetic property"]}
{"id": "1304.4226", "title": "Integrated Perturbation Theory and One-loop Power Spectra of Biased Tracers", "abstract": "General and explicit predictions from the integrated perturbation theory (iPT) for power spectra and correlation functions of biased tracers are derived and presented in the one-loop approximation. The iPT is a general framework of the nonlinear perturbation theory of cosmological density fields in presence of nonlocal bias, redshift-space distortions, and primordial non-Gaussianity. Analytic formulas of auto and cross power spectra of nonlocally biased tracers in both real and redshift spaces are derived and the results are comprehensively summarized. The main difference from previous formulas derived by the present author is to include effects of generally nonlocal Lagrangian bias and primordial non-Gaussianity, and the derivation method of the new formula is fundamentally different from the previous one. Relations to recent work on improved methods of nonlinear perturbation theory in literature are clarified and discussed.", "keyphrases": ["perturbation theory", "biased tracer", "correlation function"]}
{"id": "0912.0935", "title": "Cosmological implications of conformal field theory", "abstract": "Requiring all massless elementary fields to have conformal scaling symmetry removes a conflict between gravitational theory and the quantum theory of elementary particles and fields. Extending this postulate to the scalar field of the Higgs model, dynamical breaking of both gauge and conformal symmetries determines parameters for the interacting fields. In uniform isotropic geometry a modified Friedmann cosmic evolution equation is derived with nonvanishing cosmological constant. Parameters determined by numerical solution are consistent with empirical data for redshifts z\u2264 z_*=1090, including luminosity distances for observed type Ia supernovae and peak structure ratios in the cosmic microwave background (CMB). The theory does not require dark matter.", "keyphrases": ["scalar field", "cosmic evolution equation", "dark matter", "conformal higgs model"]}
{"id": "1312.6068", "title": "Atlas of three body mean motion resonances in the Solar System", "abstract": "We present a numerical method to estimate the strengths of arbitrary three body mean motion resonances between two planets in circular coplanar orbits and a massless particle in an arbitrary orbit. This method allows us to obtain an atlas of the three body resonances in the Solar System showing where are located and how strong are thousands of resonances involving all the planets from 0 to 1000 au. This atlas confirms the dynamical relevance of the three body resonances involving Jupiter and Saturn in the asteroid belt but also shows the existence of a family of relatively strong three body resonances involving Uranus and Neptune in the far Trans-Neptunian region and relatively strong resonances involving terrestrial and jovian planets in the inner planetary system. We calculate the density of relevant resonances along the Solar System resulting that the main asteroid belt is located in a region of the planetary system with the lowest density of three body resonances. The method also allows the location of the equilibrium points showing the existence of asymmetric librations (sigma different from 0 or 180 degrees). We obtain the functional dependence of the resonance's strength with the order of the resonance and the eccentricity and inclination of the particle's orbit. We identify some objects evolving in or very close to three body resonances with Earth-Jupiter, Saturn-Neptune and Uranus-Neptune apart from Jupiter-Saturn, in particular the NEA 2009 SJ18 is evolving in the resonance 1-1E-1J and the centaur 10199 Chariklo is evolving under the influence of the resonance 5-2S-2N.", "keyphrases": ["motion resonance", "solar system", "planet", "arbitrary orbit"]}
{"id": "1703.04585", "title": "Comment on \"Strong Evidence for the Normal Neutrino Hierarchy\"", "abstract": "In the preprint arxiv:1703.03425 \"strong evidence\" for the normal neutrino mass ordering is claimed. The authors obtain Bayesian odds of 42:1 in favour of the normal ordering. Their conclusion is based on adopting a flat logarithmic prior for the three neutrino masses. Such an assumption favours a hierarchical spectrum for the masses, which is much easier to accommodate for the normal mass ordering, and hence their prior assumption makes the inverted ordering much less likely a priori. We argue that the claimed \"evidence\" for normal ordering is almost entirely driven by the adopted prior and not due to the data itself.", "keyphrases": ["neutrino hierarchy", "mass ordering", "cosmology"]}
{"id": "2010.15119", "title": "QUBIC II: Spectro-Polarimetry with Bolometric Interferometry", "abstract": "Bolometric interferometry is a novel technique that has the ability to perform spectral imaging. A bolometric interferometer observes the sky in a wide frequency band and can reconstruct sky maps in several sub-bands within the physical band in post-processing of the data. This provides a powerful spectral method to discriminate between the cosmic microwave background (CMB) and astrophysical foregrounds. In this paper, the methodology is illustrated with examples based on the Q & U Bolometric Interferometer for Cosmology (QUBIC) which is a ground-based instrument designed to measure the B-mode polarization of the sky at millimeter wavelengths. We consider the specific cases of point source reconstruction and Galactic dust mapping and we characterize the point spread function as a function of frequency. We study the noise properties of spectral imaging, especially the correlations between sub-bands, using end-to-end simulations together with a fast noise simulator. We conclude showing that spectral imaging performance are nearly optimal up to five sub-bands in the case of QUBIC.", "keyphrases": ["bolometric interferometry", "sub-band", "qubic"]}
{"id": "1807.05435", "title": "Reionization in the dark and the light from Cosmic Microwave Background", "abstract": "We explore the constraints on the history of reionization from Planck 2015 Cosmic Microwave Background (CMB) data and we derive the forecasts for future CMB observations. We consider a class of monotonic histories of reionization as parametrized by two additional extra parameters with respect to the average optical depth used in the instantaneous reionization modeling. We investigate the degeneracies between the history of reionization and selected extensions of the standard cosmological model. In particular, we consider the degeneracies with the total mass of the neutrino sector and we discuss the possible correlation between the dark matter annihilation and the duration of reionization in the CMB. We use an extension to poly-reion model that was proposed in Hazra and Smoot, JCAP 1711, 028 (2017). We compare the constraints from Planck 2015 data with the predicted constraints from possible future CMB mission as LiteBIRD, and we also use the proposed CORE-like specifications as an example of what higher resolution can bring in addition. We find that the degeneracy between the average optical depth and the duration of reionization will be substantially removed by both concepts. Degeneracies between the reionization history and either the total neutrino mass and properties of dark matter annihilation will also be improved by future surveys. We find only marginal improvement in the constraints on reionization history for the higher resolution in the case of long duration of reionization.", "keyphrases": ["cosmic microwave background", "cosmological model", "neutrino sector"]}
{"id": "1810.04355", "title": "No low-frequency emission from extremely bright Fast Radio Bursts", "abstract": "We present the results of a coordinated campaign conducted with the Murchison Widefield Array (MWA) to shadow Fast Radio Bursts (FRBs) detected by the Australian Square Kilometre Array Pathfinder (ASKAP) at 1.4 GHz, which resulted in simultaneous MWA observations of seven ASKAP FRBs. We de-dispersed the 24 \u00d7 1.28 MHz MWA images across the 170-200 MHz band taken at 0.5 second time resolution at the known dispersion measures (DMs) and arrival times of the bursts and searched both within the ASKAP error regions (typically \u223c 10 arcmin \u00d7 10 arcmin), and beyond (4 deg \u00d7 4 deg). We identified no candidates exceeding a 5\u03c3 threshold at these DMs in the dynamic spectra. These limits are inconsistent with the mean fluence scaling of \u03b1=-1.8 \u00b1 0.3 (F_\u03bd\u221d\u03bd^\u03b1, where \u03bd is the observing frequency) that is reported for ASKAP events, most notably for the three high fluence (F_1.4 GHz\u2273 100 Jy ms) FRBs 171020, 180110 and 180324. Our limits show that pulse broadening alone cannot explain our non-detections, and that there must be a spectral turnover at frequencies above 200 MHz. We discuss and constrain parameters of three remaining plausible spectral break mechanisms: free-free absorption, intrinsic spectral turn-over of the radiative processes, and magnification of signals at ASKAP frequencies by caustics or scintillation. If free-free absorption were the cause of the spectral turnover, we constrain the thickness of the absorbing medium in terms of the electron temperature, T, to < 0.03 (T/10^4 K)^-1.35 pc for FRB 171020.", "keyphrases": ["fast radio bursts", "murchison widefield array", "non-detection"]}
{"id": "1204.4981", "title": "Probing Primordial Non-Gaussianity with Weak Lensing Minkowski Functionals", "abstract": "We study the cosmological information contained in the Minkowski Functionals (MFs) of weak gravitational lensing convergence maps. We show that the MFs provide strong constraints on the local type primordial non-Gaussianity parameter f_NL. We run a set of cosmological N-body simulations and perform ray-tracing simulations of weak lensing, to generate 100 independent convergence maps of 25 deg^2 field-of-view for f_NL = -100, 0 and 100. We perform a Fisher analysis to study the degeneracy among other cosmological parameters such as the dark energy equation of state parameter w and the fluctuation amplitude sigma_8. We use fully nonlinear covariance matrices evaluated from 1000 ray-tracing simulations. For the upcoming wide-field observations such as Subaru Hyper Suprime-Cam survey with the proposed survey area of 1500 deg^2, the primordial non-Gaussianity can be constrained with a level of f_NL 80 and w 0.036 by weak lensing MFs. If simply scaled by the effective survey area, a 20000 deg^2 lensing survey using Large Synoptic Survey Telescope will give constraints of f_NL 25 and w 0.013. We show that these constraints can be further improved by a tomographic method using source galaxies in multiple redshift bins.", "keyphrases": ["primordial non-gaussianity", "mfs", "cosmological parameter"]}
{"id": "1212.2541", "title": "Coupled three-form dark energy", "abstract": "Cosmology with a three-form field interacting with cold dark matter is considered. In particular, the mass of the dark matter particles is assumed to depend upon the amplitude of the three-form field invariant. In comparison to coupled scalar field quintessence, the new features include an effective pressure contribution to the field equations that manifests both in the background and perturbation level. The dynamics of the background is analyzed, and new scaling solutions are found. A simple example model leading to a de Sitter expansion without a potential is studied. The Newtonian limit of cosmological perturbations is derived, and it is deduced that the coupling can be very tightly constrained by the large-scale structure data. This is demonstrated with numerical solutions for a model with nontrivial coupling and a quadratic potential.", "keyphrases": ["dark energy", "three-form field", "cold dark matter", "cosmological perturbation"]}
{"id": "1002.1232", "title": "Large-scale inhomogeneities may improve the cosmic concordance of supernovae", "abstract": "We reanalyze the supernovae data from the Union Compilation including the weak lensing effects caused by inhomogeneities. We compute the lensing probability distribution function for each background solution described by the parameters Omega_M, Omega_L and w in the presence of inhomogeneities, approximately modeled with a single-mass population of halos. We then perform a likelihood analysis in the space of FLRW-parameters and compare our results with the standard approach. We find that the inclusion of lensing can move the best-fit model significantly towards the cosmic concordance of the flat LCDM model, improving the agreement with the constraints coming from the cosmic microwave background and baryon acoustic oscillations.", "keyphrases": ["cosmic concordance", "cosmological parameter", "matter distribution"]}
{"id": "0912.3005", "title": "On the Kennicutt-Schmidt relation of low-metallicity high-redshift galaxies", "abstract": "We present results of self-consistent, high-resolution cosmological simulations of galaxy formation at z 3. The simulations employ recently developed recipe for star formation based on the local abundance of molecular hydrogen, which is tracked self-consistently during the course of simulation. The phenomenological H2 formation model accounts for the effects of dissociating UV radiation of stars in each galaxy, as well as self-shielding and shielding of H2 by dust, and therefore allows us to explore effects of lower metallicities and higher UV fluxes prevalent in high redshift galaxies on their star formation. We compare stellar masses, metallicities, and star formation rates of the simulated galaxies to available observations of the Lyman Break Galaxies (LBGs) and find a reasonable agreement. We find that the Kennicutt-Schmidt (KS) relation exhibited by our simulated galaxies at z 3 is substantially steeper and has a lower amplitude than the z=0 relation at Sigma_gas < 100 Msun/pc^2. The predicted relation, however, is consistent with existing observational constraints for the z 3 Damped Lyman \u03b1 (DLA) and LBGs. Our tests show that the main reason for the difference from the local KS relation is lower metallicity of the ISM in high redshift galaxies. We discuss several implications of the metallicity-dependence of the KS relation for galaxy evolution and interpretation of observations.", "keyphrases": ["galaxy", "high-resolution cosmological simulation", "metallicity"]}
{"id": "2102.03809", "title": "Bayesian Evidence for Both Astrophysical and Primordial Black Holes: Mapping the GWTC-2 Catalog to Third-Generation Detectors", "abstract": "We perform a hierarchical Bayesian analysis of the GWTC-2 catalog to investigate the mixed scenario in which the merger events are explained by black holes of both astrophysical and primordial origin. For the astrophysical scenario we adopt the phenomenological model used by the LIGO/Virgo collaboration and we include the correlation between different parameters inferred from data, the role of the spins in both the primordial and astrophysical scenarios, and the impact of accretion in the primordial scenario. Our best-fit mixed model has a strong statistical evidence relative to the single-population astrophysical model, thus supporting the coexistence of populations of black-hole mergers of two different origins. In particular, our results indicate that the astrophysical mergers account for roughly four times the number of primordial black hole events and predict that third-generation detectors, such as the Einstein Telescope and Cosmic Explorer, should detect up to hundreds of mergers from primordial black hole binaries at redshift z\u227330.", "keyphrases": ["black hole", "third-generation detector", "primordial origin"]}
{"id": "1001.0139", "title": "Kepler Asteroseismology Program: Introduction and First Results", "abstract": "Asteroseismology involves probing the interiors of stars and quantifying their global properties, such as radius and age, through observationsof normal modes of oscillation. The technical requirements for conducting asteroseismology include ultra-high precision measured in photometry in parts per million, as well as nearly continuous time series over weeks to years, and cadences rapid enough to sample oscillations with periods as shortas a few minutes. We report on results from the first 43 days of observations in which the unique capabilities of Kepler in providing a revolutionary advance in asteroseismology are already well in evidence. The Kepler asteroseismology program holds intrinsic importance in supporting the core planetary search program through greatly enhanced knowledge of host star properties, and extends well beyond this to rich applications in stellar astrophysics.", "keyphrases": ["kepler asteroseismology program", "kepler photometry", "stellar activity", "secondary mission"]}
{"id": "1801.05745", "title": "Fast Generation of Covariance Matrices for Weak Lensing", "abstract": "Upcoming weak lensing surveys will probe large fractions of the sky with unprecedented accuracy. To infer cosmological constraints, a large ensemble of survey simulations are required to accurately model cosmological observables and their covariances. We develop a parallelized multi-lens-plane pipeline called UFalcon, designed to generate full-sky weak lensing maps from lightcones within a minimal runtime. It makes use of L-PICOLA, an approximate numerical code, which provides a fast and accurate alternative to cosmological N-Body simulations. The UFalcon maps are constructed by nesting 2 simulations covering a redshift-range from z=0.1 to 1.5 without replicating the simulation volume. We compute the convergence and projected overdensity maps for L-PICOLA in the lightcone or snapshot mode. The generation of such a map, including the L-PICOLA simulation, takes about 3 hours walltime on 220 cores. We use the maps to calculate the spherical harmonic power spectra, which we compare to theoretical predictions and to UFalcon results generated using the full N-Body code GADGET-2. We then compute the covariance matrix of the full-sky spherical harmonic power spectra using 150 UFalcon maps based on L-PICOLA in lightcone mode. We consider the PDF, the higher-order moments and the variance of the smoothed field variance to quantify the accuracy of the covariance matrix, which we find to be a few percent for scales \u2113\u223c 10^2 to 10^3. We test the impact of this level of accuracy on cosmological constraints using an optimistic survey configuration, and find that the final results are robust to this level of uncertainty. The speed and accuracy of our developed pipeline provides a basis to also include further important features such as masking, varying noise and will allow us to compute covariance matrices for models beyond \u039bCDM. [abridged]", "keyphrases": ["generation", "l-picola", "n-body simulation", "convergence map", "ufalcon package"]}
{"id": "1407.8502", "title": "Power spectrum tomography of dark matter annihilation with local galaxy distribution", "abstract": "Cross-correlating the gamma-ray background with local galaxy catalogs potentially gives stringent constraints on dark matter annihilation. We provide updated theoretical estimates of sensitivities to the annihilation cross section from gamma-ray data with Fermi telescope and 2MASS galaxy catalogs, by elaborating the galaxy power spectrum and astrophysical backgrounds, and adopting the Markov-Chain Monte Carlo simulations. In particular, we show that taking tomographic approach by dividing the galaxy catalogs into more than one redshift slice will improve the sensitivity by a factor of a few to several. If dark matter halos contain lots of bright substructures, yielding a large annihilation boost (e.g., a factor of \u223c100 for galaxy-size halos), then one may be able to probe the canonical annihilation cross section for thermal production mechanism up to masses of \u223c700 GeV. Even with modest substructure boost (e.g., a factor of \u223c10 for galaxy-size halos), on the other hand, the sensitivities could still reach a factor of three larger than the canonical cross section for dark matter masses of tens to a few hundreds of GeV.", "keyphrases": ["dark matter annihilation", "gamma-ray background", "redshift"]}
{"id": "2001.06518", "title": "Large Field Excursions from Dimensional (De)construction", "abstract": "An inflation model based on dimensional (de)construction of a massive gauge theory is proposed. The inflaton in this model is the \"zero-mode\" of a component of the massive gauge field in the (de)constructed extra dimensions. The inflaton potential originates from the gauge invariant Stueckelberg potential. At low energy, the field range of the inflaton is enhanced by a factor N^d/2 compared to the field range of the original fields in the model, where d is the number of the (de)constructed extra dimensions and N is the number of the lattice points in each (de)constructed dimension. This enhancement of the field range is used to achieve a trans-Planckian inflaton field excursion. The extension of the mechanism \u201cexcursions through KK modes\u201d to the case of (de)constructed extra dimensions is also studied. The burst of particle productions by this mechanism may have observable consequences in a region of the model parameter space.", "keyphrases": ["de)construction", "dimension", "lattice point"]}
{"id": "1203.1784", "title": "A New Equation of State for Dark Energy Model", "abstract": "A new parameterization for the dark energy equation of state(EoS) is proposed and some of its cosmological consequences are also investigated. This new parameterization is the modification of Efstathiou' dark energy EoS parameterization. w (z) is a well behaved function for z\u226b1 and has same behavior in z at low redshifts with Efstathiou' parameterization. In this parameterization there are two free parameter w_0 and w_a. We discuss the constraints on this model's parameters from current observational data. The best fit values of the cosmological parameters with 1\u03c3 confidence-level regions are: \u03a9_m=0.2735^+0.0171_-0.0163, w_0=-1.0537^+0.1432_-0.1511 and w_a=0.2738^+0.8018_-0.8288.", "keyphrases": ["parameterization", "efstathiou", "dark energy parameterisation"]}
{"id": "1110.2895", "title": "Cosmological bounds on pseudo Nambu-Goldstone bosons", "abstract": "We review the cosmological implications of a relic population of pseudo Nambu-Goldstone bosons (pNGB) with an anomalous coupling to two photons, often called axion-like particles (ALPs). We establish constraints on the pNGB mass and two-photon coupling by considering big bang nucleosynthesis, the physics of the cosmic microwave background, and the diffuse photon background. The bounds from WMAP7 and other large-scale-structure data on the effective number of neutrino species can be stronger than the traditional bounds from the primordial helium abundance. These bounds, together with those from primordial deuterium abundance, constitute the most stringent probes of early decays.", "keyphrases": ["nambu-goldstone boson", "axion-like particle", "big bang nucleosynthesis", "cosmology"]}
{"id": "1702.03314", "title": "Constraints on neutrino masses from Lyman-alpha forest power spectrum with BOSS and XQ-100", "abstract": "We present constraints on masses of active and sterile neutrinos. We use the one-dimensional Ly\u03b1-forest power spectrum from the Baryon Oscillation Spectroscopic Survey (BOSS) of the Sloan Digital Sky Survey (SDSS-III) and from the VLT/XSHOOTER legacy survey (XQ-100). In this paper, we present our own measurement of the power spectrum with the publicly released XQ-100 quasar spectra. Fitting Ly\u03b1 data alone leads to cosmological parameters in excellent agreement with the values derived independently from Planck 2015 Cosmic Microwave Background (CMB) data. Combining BOSS and XQ-100 Ly\u03b1 power spectra, we constrain the sum of neutrino masses to \u2211 m_\u03bd < 0.8 eV (95% C.L). With the addition of CMB data, this bound is tightened to \u2211 m_\u03bd < 0.14 eV (95% C.L.). With their sensitivity to small scales, Ly\u03b1 data are ideal to constrain \u039bWDM models. Using XQ-100 alone, we issue lower bounds on pure dark matter particles: m_X \u2273 2.08 keV (95% C.L.) for early decoupled thermal relics, and m_s \u2273 10.2 keV (95% C.L.) for non-resonantly produced right-handed neutrinos. Combining the 1D Ly\u03b1 forest power spectrum measured by BOSS and XQ-100, we improve the two bounds to m_X \u2273 4.17 keV and m_s \u2273 25.0 keV (95% C.L.). The 3 \u03c3 bound shows a more significant improvement, increasing from m_X \u2273 2.74 keV for BOSS alone to m_X \u2273 3.10 keV for the combined BOSS+XQ-100 data set. Finally, we include in our analysis the first two redshift bins (z=4.2 and z=4.6) of the power spectrum measured with the high-resolution HIRES/MIKE spectrographs. The addition of HIRES/MIKE power spectrum allows us to further improve the two limits to m_X \u2273 4.65 keV and m_s \u2273 28.8 keV (95% C.L.).", "keyphrases": ["neutrino masse", "forest power spectrum", "boss", "thermal relic", "warm dark matter"]}
{"id": "1404.0535", "title": "Eternal Universe", "abstract": "We discuss cosmological models for an eternal universe. Physical observables show no singularity from the infinite past to the infinite future. While the universe is evolving, there is no beginning and no end - the universe exists forever. The early state of inflation is described in two different, but equivalent pictures. In the freeze frame the universe emerges from an almost static state with flat geometry. After entropy production it shrinks and \"thaws\" slowly from a \"freeze state\" with extremely low temperature. The field transformation to the second \"big bang picture\" (Einstein frame) is singular. This \"field singularity\" is responsible for an apparent singularity of the big bang. Furthermore, we argue that past-incomplete geodesics do not necessarily indicate a singularity or beginning of the universe. Proper time ceases to be a useful concept for physical time if particles become massless. We propose to define physical time by counting the number of zeros of a component of the wave function. This counting is independent of the choice of coordinates and frames, and applies to massive and massless particles alike.", "keyphrases": ["singularity", "big bang picture", "physical time", "wave function", "eternal universe"]}
{"id": "1409.3708", "title": "Testing Gravity Theories Using Stars", "abstract": "Modified theories of gravity have received a renewed interest due to their ability to account for the cosmic acceleration. In order to satisfy the solar system tests of gravity, these theories need to include a screening mechanism that hides the modifications on small scales. One popular and well-studied theory is chameleon gravity. Our own galaxy is necessarily screened, but less dense dwarf galaxies may be unscreened and their constituent stars can exhibit novel features. In particular, unscreened stars are brighter, hotter and more ephemeral than screened stars in our own galaxy. They also pulsate with a shorter period. In this essay, we exploit these new features to constrain chameleon gravity to levels three orders of magnitude lower the previous measurements. These constraints are currently the strongest in the literature.", "keyphrases": ["star", "dwarf galaxy", "cosmology"]}
{"id": "1403.4089", "title": "Diffuse Neutrino Intensity from the Inner Jets of Active Galactic Nuclei: Impacts of External Photon Fields and the Blazar Sequence", "abstract": "We study high-energy neutrino production in inner jets of radio-loud active galactic nuclei (AGN), taking into account effects of external photon fields and the blazar sequence. We show that the resulting diffuse neutrino intensity is dominated by quasar-hosted blazars, in particular, flat spectrum radio quasars, and that PeV-EeV neutrino production due to photohadronic interactions with broadline and dust radiation is unavoidable if the AGN inner jets are ultrahigh-energy cosmic-ray (UHECR) sources. Their neutrino spectrum has a cutoff feature around PeV energies since target photons are due to Ly\u03b1 emission. Because of infrared photons provided by the dust torus, neutrino spectra above PeV energies are too hard to be consistent with the IceCube data unless the proton spectral index is steeper than 2.5, or the maximum proton energy is \u2272100 PeV. Thus, the simple model has difficulty in explaining the IceCube data. For the cumulative neutrino intensity from blazars to exceed \u223c10^-8 GeV cm^-2 s^-1 sr^-1, their local cosmic-ray energy generation rate would be \u223c10-100 times larger than the local UHECR emissivity, but is comparable to the averaged gamma-ray blazar emissivity. Interestingly, future detectors such as the Askaryan Radio Array can detect \u223c0.1-1 EeV neutrinos even in more conservative cases, allowing us to indirectly test the hypothesis that UHECRs are produced in the inner jets. We find that the diffuse neutrino intensity from radio-loud AGN is dominated by blazars with gamma-ray luminosity of \u227310^48 erg s^-1, and the arrival directions of their \u223c1-100 PeV neutrinos correlate with the luminous blazars detected by Fermi.", "keyphrases": ["inner jet", "spectrum radio quasar", "diffuse neutrino intensity"]}
{"id": "1706.04583", "title": "Cosmological constraints from a joint analysis of cosmic microwave background and spectroscopic tracers of the large-scale structure", "abstract": "The standard model of cosmology, \u039bCDM, is the simplest model that matches the current observations, but it relies on two hypothetical components, to wit, dark matter and dark energy. Future galaxy surveys and cosmic microwave background (CMB) experiments will independently shed light on these components, but a joint analysis that includes cross-correlations will be necessary to extract as much information as possible from the observations. In this paper, we carry out a multi-probe analysis based on pseudo-spectra and test it on publicly available data sets. We use CMB temperature anisotropies and CMB lensing observations from Planck as well as the spectroscopic galaxy and quasar samples of SDSS-III/BOSS, taking advantage of the large areas covered by these surveys. We build a likelihood to simultaneously analyse the auto and cross spectra of CMB lensing and tracer overdensity maps before running Monte-Carlo Markov Chains (MCMC) to assess the constraining power of the combined analysis. We then add the CMB temperature anisotropies likelihood and obtain constraints on cosmological parameters (H_0, \u03c9_b, \u03c9_c, ln10^10A_s, n_s and z_re) and galaxy biases. We demonstrate that the joint analysis can additionally constrain the total mass of neutrinos \u03a3 m_\u03bd as well as the dark energy equation of state w at once (for a total of eight cosmological parameters), which is impossible with either of the data sets considered separately. Finally, we discuss limitations of the analysis related to, e.g., the theoretical precision of the models, particularly in the non-linear regime.", "keyphrases": ["cosmic microwave background", "galaxy survey", "cross-correlation", "cosmological parameter"]}
{"id": "1709.02406", "title": "Active correction of aperture discontinuities - optimized stroke minimization I: a new adaptive interaction matrix algorithm", "abstract": "Future searches for biomarkers on habitable exoplanets will rely on telescope instruments that achieve extremely high contrast at small planet-to-star angular separations. Coronagraphy is a promising starlight suppression technique, providing excellent contrast and throughput for off-axis sources on clear apertures. However, the complexity of space- and ground-based telescope apertures goes on increasing over time, owing to the combination of primary mirror segmentation, secondary mirror, and support structures. These discontinuities in the telescope aperture limit the coronagraph performance. In this paper, we present ACAD-OSM, a novel active method to correct for the diffractive effects of aperture discontinuities in the final image plane of a coronagraph. Active methods use one or several deformable mirrors that are controlled with an interaction matrix to correct for the aberrations in the pupil. However, they are often limited by the amount of aberrations introduced by aperture discontinuities. This algorithm relies on the recalibration of the interaction matrix during the correction process to overcome this limitation. We first describe the ACAD-OSM technique and compare it to the previous active methods for the correction of aperture discontinuities. We then show its performance in terms of contrast and off-axis throughput for static aperture discontinuities (segmentation, struts) and for some aberrations evolving over the life of the instrument (residual phase aberrations, artifacts in the aperture, misalignments in the coronagraph design). This technique can now obtain the earth-like planet detection threshold of 10^(-10) contrast on any given aperture over at least a 10 designs.", "keyphrases": ["correction", "segmentation", "final image plane", "deformable mirror", "aberration"]}
{"id": "1804.00816", "title": "Classifying the Large Scale Structure of the Universe with Deep Neural Networks", "abstract": "We present the first application of deep neural networks to the semantic segmentation of cosmological filaments and walls in the Large Scale Structure of the Universe. Our results are based on a deep Convolutional Neural Network (CNN) with a U-Net architecture trained using an existing state-of-the-art manually-guided segmentation method. We successfully trained an tested an U-Net with a Voronoi model and an N-body simulation. The predicted segmentation masks from the Voronoi model have a Dice coefficient of 0.95 and 0.97 for filaments and mask respectively. The predicted segmentation masks from the N-body simulation have a Dice coefficient of 0.78 and 0.72 for walls and filaments respectively. The relatively lower Dice coefficient in the filament mask is the result of filaments that were predicted by the U-Net model but were not present in the original segmentation mask. Our results show that for a well-defined dataset such as the Voronoi model the U-Net has excellent performance. In the case of the N-body dataset the U-Net produced a filament mask of higher quality than the segmentation mask obtained from a state-of-the art method. The U-Net performs better than the method used to train it, being able to find even the tenuous filaments that the manually-guided segmentation failed to identify. The U-Net presented here can process a 512^3 volume in a few minutes and without the need of complex pre-processing. Deep CNN have great potential as an efficient and accurate analysis tool for the next generation large-volume computer N-body simulations and galaxy surveys.", "keyphrases": ["universe", "network", "filament"]}
{"id": "1707.01862", "title": "Plasmoid Instability in Forming Current Sheets", "abstract": "The plasmoid instability has revolutionized our understanding of magnetic reconnection in astrophysical environments. By preventing the formation of highly elongated reconnection layers, it is crucial in enabling the rapid energy conversion rates that are characteristic of many astrophysical phenomena. Most of the previous studies have focused on Sweet-Parker current sheets, which, however, are unattainable in typical astrophysical systems. Here, we derive a general set of scaling laws for the plasmoid instability in resistive and visco-resistive current sheets that evolve over time. Our method relies on a principle of least time that enables us to determine the properties of the reconnecting current sheet (aspect ratio and elapsed time) and the plasmoid instability (growth rate, wavenumber, inner layer width) at the end of the linear phase. After this phase the reconnecting current sheet is disrupted and fast reconnection can occur. The scaling laws of the plasmoid instability are not simple power laws, and depend on the Lundquist number (S), the magnetic Prandtl number (P_m), the noise of the system (\u03c8_0), the characteristic rate of current sheet evolution (1/\u03c4), as well as the thinning process. We also demonstrate that previous scalings are inapplicable to the vast majority of the astrophysical systems. We explore the implications of the new scaling relations in astrophysical systems such as the solar corona and the interstellar medium. In both these systems, we show that our scaling laws yield values for the growth rate, wavenumber, and aspect ratio that are much smaller than the Sweet-Parker based scalings.", "keyphrases": ["sheet", "reconnection", "plasmoid instability"]}
{"id": "1307.3559", "title": "Charting an Inflationary Landscape with Random Matrix Theory", "abstract": "We construct a class of random potentials for N >> 1 scalar fields using non-equilibrium random matrix theory, and then characterize multifield inflation in this setting. By stipulating that the Hessian matrices in adjacent coordinate patches are related by Dyson Brownian motion, we define the potential in the vicinity of a trajectory. This method remains computationally efficient at large N, permitting us to study much larger systems than has been possible with other constructions. We illustrate the utility of our approach with a numerical study of inflation in systems with up to 100 coupled scalar fields. A significant finding is that eigenvalue repulsion sharply reduces the duration of inflation near a critical point of the potential: even if the curvature of the potential is fine-tuned to be small at the critical point, small cross-couplings in the Hessian cause the curvature to grow in the neighborhood of the critical point.", "keyphrases": ["random matrix theory", "multifield inflation", "continuum limit"]}
{"id": "1309.7169", "title": "Numerical evaluation of the three-point scalar-tensor cross-correlations and the tensor bi-spectrum", "abstract": "Utilizing the Maldacena formalism and extending the earlier efforts to compute the scalar bi-spectrum, we construct a numerical procedure to evaluate the three-point scalar-tensor cross-correlations as well as the tensor bi-spectrum in single field inflationary models involving the canonical scalar field. We illustrate the accuracy of the adopted procedure by comparing the numerical results with the analytical results that can be obtained in the simpler cases of power law and slow roll inflation. We also carry out such a comparison in the case of the Starobinsky model described by a linear potential with a sudden change in the slope, which provides a non-trivial and interesting (but, nevertheless, analytically tractable) scenario involving a brief period of deviation from slow roll. We then utilize the code we have developed to evaluate the three-point correlation functions of interest (and the corresponding non-Gaussianity parameters that we introduce) for an arbitrary triangular configuration of the wavenumbers in three different classes of inflationary models which lead to features in the scalar power spectrum, as have been recently considered by the Planck team. We also discuss the contributions to the three-point functions during preheating in inflationary models with a quadratic minimum. We conclude with a summary of the main results we have obtained.", "keyphrases": ["three-point scalar-tensor cross-correlation", "tensor", "numerical procedure", "bispectrum"]}
{"id": "1704.05717", "title": "New structures of Power Density Spectra for four Kepler AGNs", "abstract": "Many nearby AGNs display a significant short-term variability. In this work we re-analyze photometric data of four active galactic nuclei observed by Kepler in order to study the flickering activity, having as main goal that of searching for multiple components in the power density spectra. We find that all four objects have similar characteristics, with two break frequencies at approximately log(f/Hz)=-5.2 and -4.7. We consider some physical phenomena whose characteristic time-scales are consistent with those observed, in particular mass accretion fluctuations in the inner geometrically thick disc (hot X-ray corona) and unstable relativistic Rayleigh-Taylor modes. The former is supported by detection of the same break frequencies in the Swift X-ray data of ZW229-15. We also discuss rms-flux relations, and we detect a possible typical linear trend at lower flux levels. Our findings support the hypothesis of a multiplicative character of variability, in agreement with the propagating accretion fluctuation model.", "keyphrases": ["power density spectra", "agns", "short-term variability"]}
{"id": "1502.03176", "title": "A unified picture of the post-merger dynamics and gravitational wave emission in neutron-star mergers", "abstract": "We introduce a classification scheme of the post-merger dynamics and gravitational-wave emission in binary neutron star mergers, after identifying a new mechanism by which a secondary peak in the gravitational-wave spectrum is produced. It is caused by a spiral deformation, the pattern of which rotates slower with respect to the double-core structure in center of the remnant. This secondary peak is typically well separated in frequency from the secondary peak produced by a nonlinear interaction between a quadrupole and a quasi-radial oscillation. The new mechanism allows for an explanation of low-frequency modulations seen in a number of physical characteristics of the remnant, such as the central lapse function, the maximum density and the separation between the two cores. We find empirical relations for both types of secondary peaks between their gravitational-wave frequency and the compactness of nonrotating individual neutron stars, that exist for fixed total binary masses. These findings are derived for equal-mass binaries without intrinsic neutron-star spin analyzing hydrodynamical simulations without magnetic field effects. Our classification scheme may form the basis for the construction of detailed gravitational-wave templates of the post-merger phase. We find that the quasi-radial oscillation frequency of the remnant decreases with the total binary mass. For a given merger event our classification scheme may allow to determine the proximity of the measured total binary mass to the threshold mass for prompt black hole formation, which can, in turn, yield an estimate of the maximum neutron-star mass.", "keyphrases": ["neutron star", "quasi-radial oscillation", "binary mass"]}
{"id": "0906.4757", "title": "Mimicking dark matter through a non-minimal gravitational coupling with matter", "abstract": "In this study one resorts to the phenomenology of models endowed with a non-minimal coupling between matter and geometry, in order to develop a mechanism through which dynamics similar to that due to the presence of dark matter is generated. As a first attempt, one tries to account for the flattening of the galaxy rotation curves as an effect of the non-(covariant) conservation of the energy-momentum tensor of visible matter. Afterwards, one assumes instead that this non-minimal coupling modifies the scalar curvature in a way that can be interpreted as a dark matter component (albeit with negative pressure). It is concluded that it is possible to mimic known dark matter density profiles through an appropriate power-law coupling f_2 = (R/R0)^n, with a negative index n \u2013 a fact that reflects the dominance of dark matter at large distances. The properties of the model are extensively discussed, and possible cosmological implications are addressed.", "keyphrases": ["dark matter", "non-minimal coupling", "gravity"]}
{"id": "1306.5800", "title": "Sensitivity of the High Altitude Water Cherenkov Detector to Sources of Multi-TeV Gamma Rays", "abstract": "The High Altitude Water Cherenkov (HAWC) observatory is an array of large water Cherenkov detectors sensitive to gamma rays and hadronic cosmic rays in the energy band between 100 GeV and 100 TeV. The observatory will be used to measure high-energy protons and cosmic rays via detection of the energetic secondary particles reaching the ground when one of these particles interacts in the atmosphere above the detector. HAWC is under construction at a site 4100 meters above sea level on the northern slope of the volcano Sierra Negra, which is located in central Mexico at 19 degrees N latitude. It is scheduled for completion in 2014. In this paper we estimate the sensitivity of the HAWC instrument to point-like and extended sources of gamma rays. The source fluxes are modeled using both unbroken power laws and power laws with exponential cutoffs. HAWC, in one year, is sensitive to point sources with integral power-law spectra as low as 5x10^-13 cm^-2 sec^-1 above 2 TeV (approximately 50 mCrab) over 5 sr of the sky. This is a conservative estimate based on simple event parameters and is expected to improve as the data analysis techniques are refined. We discuss known TeV sources and the scientific contributions that HAWC can make to our understanding of particle acceleration in these sources.", "keyphrases": ["altitude water cherenkov", "water cherenkov detector", "gamma ray"]}
{"id": "1205.3607", "title": "Lepton asymmetries and primordial hypermagnetic helicity evolution", "abstract": "The hypermagnetic helicity density at the electroweak phase transition (EWPT) exceeds many orders of magnitude the galactic magnetic helicity density. Together with previous magnetic helicity evolution calculations after the EWPT and hypermagnetic helicity conversion to the magnetic one at the EWPT, the present calculation completes the description of the evolution of this important topological feature of cosmological magnetic fields. It suggests that if the magnetic field seeding the galactic dynamo has a primordial origin, it should be substantially helical. This should be taken into account in scenarios of galactic magnetic field evolution with a cosmological seed.", "keyphrases": ["hypermagnetic helicity density", "electroweak phase transition", "lepton asymmetry", "baryogenesis"]}
{"id": "2006.00244", "title": "Hubble Sinks In The Low-Redshift Swampland", "abstract": "Local determinations of the Hubble constant H_0 favour a higher value than Planck based on CMB and \u039bCDM. Through a model-independent expansion, we show that low redshift (z \u2272 0.7) data comprising baryon acoustic oscillations (BAO), cosmic chronometers and Type Ia supernovae has a preference for Quintessence models that lower H_0 relative to \u039bCDM. In addition, we confirm that an exponential coupling to dark matter cannot alter this conclusion in the same redshift range. Our results leave open the possibility that a coupling in the matter-dominated epoch, potentially even in the dark ages, may yet save H_0 from sinking in the string theory Swampland.", "keyphrases": ["redshift", "quintessence model", "hubble"]}
{"id": "1205.5765", "title": "A shared frequency set between the historical mid-latitude aurora records and the global surface temperature", "abstract": "Herein we show that the historical records of mid-latitude auroras from 1700 to 1966 present oscillations with periods of about 9, 10-11, 20-21, 30 and 60 years. The same frequencies are found in proxy and instrumental global surface temperature records since 1650 and 1850, respectively and in several planetary and solar records. Thus, the aurora records reveal a physical link between climate change and astronomical oscillations. Likely, there exists a modulation of the cosmic ray flux reaching the Earth and/or of the electric properties of the ionosphere. The latter, in turn, have the potentiality of modulating the global cloud cover that ultimately drives the climate oscillations through albedo oscillations. In particular, a quasi 60-year large cycle is quite evident since 1650 in all climate and astronomical records herein studied, which also include an historical record of meteorite fall in China from 619 to 1943. These findings support the thesis that climate oscillations have an astronomical origin. We show that a harmonic constituent model based on the major astronomical frequencies revealed in the aurora records is able to forecast with a reasonable accuracy the decadal and multidecadal temperature oscillations from 1950 to 2010 using the temperature data before 1950, and vice versa. The existence of a natural 60-year modulation of the global surface temperature induced by astronomical mechanisms, by alone, would imply that at least 60-70 Moreover, the climate may stay approximately stable during the next decades because the 60-year cycle has entered in its cooling phase.", "keyphrases": ["aurora record", "global surface temperature", "climate", "60-year", "astronomical origin"]}
{"id": "1409.1598", "title": "Regulation of star formation in giant galaxies by precipitation, feedback, and conduction", "abstract": "The universe's largest galaxies reside at the centers of galaxy clusters and are embedded in hot gas that, if left unchecked, would cool prodigiously and create many more new stars than are actually observed. Cooling can be regulated by feedback from accretion of cooling gas onto the central black hole, but requires an accretion rate finely tuned to the thermodynamic state of the hot gas. Theoretical models in which cold clouds precipitate out of the hot gas via thermal instability and accrete onto the black hole exhibit the necessary tuning. We have recently presented observational evidence showing that the abundance of cold gas in the central galaxy increases rapidly near the predicted threshold for instability. Here we present observations showing that this threshold extends over a large range in cluster radius, cluster mass, and cosmic time, and incorporate the precipitation threshold into a comprehensive framework of theoretical models for the thermodynamic state of hot gas in galaxy clusters. According to that framework, precipitation regulates star formation in some giant galaxies, while thermal conduction prevents star formation in others, if it can compensate for radiative cooling and shut off precipitation.", "keyphrases": ["star formation", "thermal instability", "cold gas"]}
{"id": "2205.01049", "title": "High precision modeling of polarized signals: Moment expansion method generalized to spin-2 fields", "abstract": "The modeling and removal of foregrounds poses a major challenge to searches for signals from inflation using the cosmic microwave background (CMB). In particular, the modeling of CMB foregrounds including various spatial averaging effects introduces multiple complications that will have to be accounted for in upcoming analyses. In this work, we introduce the generalization of the intensity moment expansion to the spin-2 field of linear polarization: the spin-moment expansion. Within this framework, moments become spin-2 objects that are directly related to the underlying spectral parameters and polarization angle distribution functions. In obtaining the required expressions for the polarization modeling, we highlight the similarities and differences with the intensity moment methods. A spinor rotation in the complex plane with frequency naturally arises from the first order moment when the signal contains both spectral parameters and polarization angle variations. Additional dependencies are introduced at higher order, and we demonstrate how these can be accounted with several illustrative examples. Our new modeling of the polarized signals reveals to be a powerful tool to model the frequency dependence of the polarization angle. As such, it can be immediately applied to numerous astrophysical situations.", "keyphrases": ["generalization", "spin-2 field", "spectral parameter", "polarization angle"]}
{"id": "1809.03043", "title": "Fast Radio Burst 121102 Pulse Detection and Periodicity: A Machine Learning Approach", "abstract": "We report the detection of 72 new pulses from the repeating fast radio burst FRB 121102 in Breakthrough Listen C-band (4-8 GHz) observations at the Green Bank Telescope. The new pulses were found with a convolutional neural network in data taken on August 26, 2017, where 21 bursts have been previously detected. Our technique combines neural network detection with dedispersion verification. For the current application we demonstrate its advantage over a traditional brute-force dedis- persion algorithm in terms of higher sensitivity, lower false positive rates, and faster computational speed. Together with the 21 previously reported pulses, this observa- tion marks the highest number of FRB 121102 pulses from a single observation, total- ing 93 pulses in five hours, including 45 pulses within the first 30 minutes. The number of data points reveal trends in pulse fluence, pulse detection rate, and pulse frequency structure. We introduce a new periodicity search technique, based on the Rayleigh test, to analyze the time of arrivals, with which we exclude with 99 larger than 5.1 times the model-dependent time-stamp uncertainty. In particular, we rule out constant periods >10 ms in the barycentric arrival times, though intrinsic periodicity in the time of emission remains plausible.", "keyphrases": ["periodicity", "machine learning", "frb"]}
{"id": "1605.03834", "title": "Generalized dark energy interactions with multiple fluids", "abstract": "In the search for an explanation for the current acceleration of the Universe, scalar fields are the most simple and useful tools to build models of dark energy. This field, however, must in principle couple with the rest of the world and not necessarily in the same way to different particles or fluids. We provide the most complete dynamical system analysis to date, consisting of a canonical scalar field conformally and disformally coupled to both dust and radiation. We perform a detailed study of the existence and stability conditions of the systems and comment on constraints imposed on the disformal coupling from Big-Bang Nucleosynthesis and given current limits on the variation of the fine-structure constant.", "keyphrases": ["dark energy", "fluid", "scalar field"]}
{"id": "0909.2256", "title": "Moment transport equations for non-Gaussianity", "abstract": "We present a novel method for calculating the primordial non-Gaussianity produced by super-horizon evolution during inflation. Our method evolves the distribution of coarse-grained inflationary field values using a transport equation. We present simple evolution equations for the moments of this distribution, such as the variance and skewness. This method possesses some advantages over existing techniques. Among them, it cleanly separates multiple sources of primordial non-Gaussianity, and is computationally efficient when compared with popular alternatives, such as the \"delta N\" framework. We adduce numerical calculations demonstrating that our new method offers good agreement with those already in the literature. We focus on two fields and the fNL parameter, but we expect our method will generalize to multiple scalar fields and to moments of arbitrarily high order. We present our expressions in a field-space covariant form which we postulate to be valid for any number of fields.", "keyphrases": ["transport equation", "non-gaussianity", "super-horizon evolution", "moment"]}
{"id": "1807.05445", "title": "A note on Inflation and the Swampland", "abstract": "We provide some comments about the constraints on the inflationary models inferred from the two Swampland criteria which have been recently proposed. In particular we argue that, in the absence of any knowledge about the origin of the adiabatic curvature perturbations, within the slow-roll single field models of inflation there is no tension between the swampland criteria and the current lower bound on the tensor-to-scalar ratio.", "keyphrases": ["swampland", "single-field inflation", "swampland conjecture"]}
{"id": "1506.04808", "title": "Constraints on just enough inflation preceded by a thermal era", "abstract": "If the inflationary era is preceded by a radiation dominated era in which the inflaton too was in thermal equilibrium at some very early time then the CMB data places an upper bound on the comoving temperature of the (decoupled) inflaton quanta. In addition, if one considers models of \"just enough\" inflation, where the number of e-foldings of inflation is just enough to solve the horizon and flatness problems, then we get a lower bound on the Hubble parameter during inflation, H_ inf, which is in severe conflict with the upper bound from tensor perturbations. Alternatively, imposing the upper bound on H_ inf implies that such scenarios are compatible with the data only if the number of relativistic degrees of freedom in the thermal bath in the pre-inflationary Universe is extremely large (greater than 10^9 or 10^11). We are not aware of scenarios in which this can be satisfied.", "keyphrases": ["era", "thermal equilibrium", "pre-inflationary universe"]}
{"id": "1002.3912", "title": "Multiscale cosmology and structure-emerging Dark Energy: A plausibility analysis", "abstract": "Cosmological backreaction suggests a link between structure formation and the expansion history of the Universe. In order to quantitatively examine this connection, we dynamically investigate a volume partition of the Universe into over\u2013 and underdense regions. This allows us to trace structure formation using the volume fraction of the overdense regions \u03bb_ as its characterizing parameter. Employing results from cosmological perturbation theory and extrapolating the leading mode into the nonlinear regime, we construct a three\u2013parameter model for the effective cosmic expansion history, involving \u03bb__0, the matter density \u03a9_m^_0, and the Hubble rate H__0 of today's Universe. Taking standard values for \u03a9_m^_0 and H__0 as well as a reasonable value for \u03bb__0, that we derive from N\u2013body simulations, we determine the corresponding amounts of backreaction and spatial curvature. We find that the obtained values that are sufficient to generate today's structure also lead to a \u039bCDM\u2013like behavior of the scale factor, parametrized by the same parameters \u03a9_m^_0 and H__0, but without a cosmological constant. However, the temporal behavior of \u03bb_ does not faithfully reproduce the structure formation history. Surprisingly, however, the model matches with structure formation with the assumption of a low matter content, \u03a9_m^_0\u22483%, a result that hints to a different interpretation of part of the backreaction effect as kinematical Dark Matter. (truncated)", "keyphrases": ["dark energy", "cosmological constant", "present universe"]}
{"id": "1607.00817", "title": "Precise measurements of inflationary features with 21 cm observations", "abstract": "Future observations of 21 cm emission using HI intensity mapping will enable us to probe the large scale structure of the Universe over very large survey volumes within a reasonable observation time. We demonstrate that the three-dimensional information contained in such surveys will be an extremely powerful tool in searching for features that were imprinted in the primordial power spectrum and bispectrum during inflation. Here we focus on the \"resonant\" and \"step\" inflation models, and forecast the potential of upcoming 21 cm experiments to detect these inflationary features in the observable power- and bispectrum. We find that the full scale Tianlai experiment and the Square Kilometre Array (SKA) have the potential to improve on the sensitivity of current Cosmic Microwave Background (CMB) experiments by several orders of magnitude.", "keyphrases": ["inflationary feature", "anomaly", "large-scale structure"]}
{"id": "1612.06462", "title": "Updated Collider and Direct Detection Constraints on Dark Matter Models for the Galactic Center Gamma-Ray Excess", "abstract": "Utilizing an exhaustive set of simplified models, we revisit dark matter scenarios potentially capable of generating the observed Galactic Center gamma-ray excess, updating constraints from the LUX and PandaX-II experiments, as well as from the LHC and other colliders. We identify a variety of pseudoscalar mediated models that remain consistent with all constraints. In contrast, dark matter candidates which annihilate through a spin-1 mediator are ruled out by direct detection constraints unless the mass of the mediator is near an annihilation resonance, or the mediator has a purely vector coupling to the dark matter and a purely axial coupling to Standard Model fermions. All scenarios in which the dark matter annihilates through t-channel processes are now ruled out by a combination of the constraints from LUX/PandaX-II and the LHC.", "keyphrases": ["collider", "dark matter", "gamma-ray excess"]}
{"id": "1810.03575", "title": "Finite-time Singularities in Swampland-related Dark Energy Models", "abstract": "In this work we shall investigate the singularity structure of the phase space corresponding to an exponential quintessence dark energy model recently related to swampland models. The dynamical system corresponding to the cosmological system is an autonomous polynomial dynamical system, and by using a mathematical theorem we shall investigate whether finite-time singularities can occur in the dynamical system variables. As we demonstrate, the solutions of the dynamical system are non-singular for all cosmic times and this result is general, meaning that the initial conditions corresponding to the regular solutions, belong to a general set of initial conditions and not to a limited set of initial conditions. As we explain, a dynamical system singularity is not directly related to a physical finite-time singularity. Then, by assuming that the Hubble rate with functional form H(t)=f_1(t)+f_2(t)(t-t_s)^\u03b1, is a solution of the dynamical system, we investigate the implications of the absence of finite-time singularities in the dynamical system variables. As we demonstrate, Big Rip and a Type IV singularities can always occur if \u03b1<-1 and \u03b1>2 respectively. However, Type II and Type III singularities cannot occur in the cosmological system, if the Hubble rate we quoted is considered a solution of the cosmological system.", "keyphrases": ["dark energy", "singularity structure", "swampland model"]}
{"id": "1007.0006", "title": "Energy dependent neutrino flavor ratios from cosmic accelerators on the Hillas plot", "abstract": "We discuss neutrino fluxes and energy dependent flavor ratios of cosmic accelerators as a function of the size of the acceleration region and the magnetic field, which are the parameters of the Hillas plot. We assume that photohadronic interactions between Fermi accelerated protons and synchrotron photons from co-accelerated electrons (or positrons) lead to charged pion production. We include synchrotron cooling of the charged pions and successively produced muons, which then further decay into neutrinos, as well as the helicity dependence of the muon decays. Our photohadronic interaction model includes direct production, higher resonances, and high energy processes in order to model the neutrino flavor and neutrino-antineutrino ratios with sufficient accuracy. Since we assume that the sources are optically thin to neutron interactions, we include the neutrino fluxes from neutron decays. We classify the Hillas plot into regions with different characteristic flavor ratios over 20x24 orders of magnitude in R and B. In some examples with sizable magnetic fields, we recover neutron beam, pion beam, and muon damped beam as a function of energy. However, we also find anomalous or new sources, such as muon beam sources with a flavor ratio nu_e:nu_mu:nu_tau of 1:1:0 in energy regions where the synchrotron-damped muons pile up. We also discuss the use of the Glashow resonance to identify pgamma optically thin sources with a strong imbalance between pi^+ and pi^- production. We find that these can, in principle, be identified in most cases in spite of the pi^- contamination from high energy photohadronic processes and the mixing parameter uncertainties.", "keyphrases": ["cosmic accelerator", "co-accelerated electron", "muon"]}
{"id": "1801.06512", "title": "Haze Production in the Atmospheres of super-Earths and mini-Neptunes: Insights from the Lab", "abstract": "Numerous solar system atmospheres possess aerosols including the characteristic organic hazes of Titan and Pluto. Haze particles substantially impact atmospheric temperatures structures and may provide organic material to the surface of a world, thereby affecting its habitability. Observations of exoplanet atmospheres suggest the presence of aerosols, especially in cooler (<800 K), smaller (<0.3 times Jupiter's mass) exoplanets. It remains unclear if the aerosols muting the spectroscopic features of exoplanet atmospheres are condensate clouds or photochemical hazes, which is difficult to predict from theory alone. We present here the first laboratory haze simulation experiments for atmospheric compositions expected for super-Earths and mini-Neptunes. We explored temperatures from 300 to 600 K and a range of atmospheric metallicities (100x, 1000x, 10000x solar); all simulated atmospheres produced particles, and the cooler (300 and 400 K) 1000x solar metallicity (\"H2O-dominated\", CH4-rich) experiments exhibited haze production rates higher than our standard Titan simulation ( 10 mg/hr versus 7.4 mg/hr for Titan). However the particle production rates varied greatly, with measured rates as low as 0.04 mg/hr (100x solar metallicity, 600 K). Here we show that we should expect some, but not all, super-Earth and mini-Neptune atmospheres to possess a thick photochemically generated haze.", "keyphrases": ["atmosphere", "super-earths", "photochemical haze"]}
{"id": "1504.03322", "title": "Position-dependent correlation function from the SDSS-III Baryon Oscillation Spectroscopic Survey Data Release 10 CMASS Sample", "abstract": "We report on the first measurement of the three-point function with the position-dependent correlation function from the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS) Data Release 10 CMASS sample. This new observable measures the correlation between two-point functions of galaxy pairs within different subvolumes, \u03be\u0302( r, r_L), where r_L is the location of a subvolume, and the corresponding mean overdensities, \u03b4\u0305( r_L). This correlation, which we call the \"integrated three-point function\", i\u03b6(r)=\u27e8\u03be\u0302( r, r_L)\u03b4\u0305( r_L)\u27e9, measures a three-point function of two short- and one long-wavelength modes, and is generated by nonlinear gravitational evolution and possibly also by the physics of inflation. The i\u03b6(r) measured from the BOSS data lies within the scatter of those from the mock galaxy catalogs in redshift space, yielding a ten-percent-level determination of the amplitude of i\u03b6(r). The tree-level perturbation theory in redshift space predicts how this amplitude depends on the linear and quadratic nonlinear galaxy bias parameters (b_1 and b_2), as well as on the amplitude and linear growth rate of matter fluctuations (\u03c3_8 and f). Combining i\u03b6(r) with the constraints on b_1\u03c3_8 and f\u03c3_8 from the global two-point correlation function and that on \u03c3_8 from the weak lensing signal of BOSS galaxies, we measure b_2=0.41\u00b10.41 (68 assuming standard perturbation theory at the tree level and the local bias model.", "keyphrases": ["gravitational evolution", "position-dependent correlation function", "squeezed-limit bispectrum"]}
{"id": "1203.1803", "title": "Ultra-high energy particle collisions in a regular spacetime without blackholes or naked singularities", "abstract": "We investigate here the particle acceleration and collisions with extremely large center of mass energies in a perfectly regular spacetime containing neither singularity nor an event horizon. The ultra-high energy collisions of particles near the event horizon of extremal Kerr blackhole, and also in many other examples of extremal blackholes have been investigated and reported recently. We studied an analogous particle acceleration process in the Kerr and Reissner-Nordstrom spacetimes without horizon, containing naked singularities. Further to this, we show here that the particle acceleration and collision process is in fact independent of blackholes and naked singularities, and can happen in a fully regular spacetime containing neither of these. We derive the conditions on the general static spherically symmetric metric for such a phenomena to happen. We show that in order to have ultra-high energy collisions it is necessary for the norm of the timelike Killing vector to admit a maximum with a vanishingly small but a negative value. This is also a condition implying the presence of a surface with extremely large but nevertheless finite value of the redshift or blueshift. Conditions to have ultrahigh energy collisions and regular center imply the violation of strong energy condition near the center while the weak energy condition is respected in the region around the center. Thus the central region is surrounded by a dark energy fluid. Both the energy conditions are respected at the location where the high energy collisions take place. As a concrete example we then investigate the acceleration process in the spacetime geometry derived by Bardeen which is sourced by a non-liner self-gravitating magnetic monopole.", "keyphrases": ["regular spacetime", "high energy collision", "black hole"]}
{"id": "1809.01274", "title": "H0LiCOW - IX. Cosmographic analysis of the doubly imaged quasar SDSS 1206+4332 and a new measurement of the Hubble constant", "abstract": "We present a blind time-delay strong lensing (TDSL) cosmographic analysis of the doubly imaged quasar SDSS 1206+4332. We combine the relative time delay between the quasar images, Hubble Space Telescope imaging, the Keck stellar velocity dispersion of the lensing galaxy, and wide-field photometric and spectroscopic data of the field to constrain two angular diameter distance relations. The combined analysis is performed by forward modelling the individual data sets through a Bayesian hierarchical framework, and it is kept blind until the very end to prevent experimenter bias. After unblinding, the inferred distances imply a Hubble constant H_0 = 68.8^+5.4_-5.1 kms^-1Mpc^-1, assuming a flat Lambda cold dark matter cosmology with uniform prior on \u03a9_ m in [0.05, 0.5]. The precision of our cosmographic measurement with the doubly imaged quasar SDSS 1206+4332 is comparable with those of quadruply imaged quasars and opens the path to perform on selected doubles the same analysis as anticipated for quads. Our analysis is based on a completely independent lensing code than our previous three H0LiCOW systems and the new measurement is fully consistent with those. We provide the analysis scripts paired with the publicly available software to facilitate independent analysis. The consistency between blind measurements with independent codes provides an important sanity check on lens modelling systematics. By combining the likelihoods of the four systems under the same prior, we obtain H_0 = 72.5^+2.1_-2.3kms^-1Mpc^-1. This measurement is independent of the distance ladder and other cosmological probes.", "keyphrases": ["quasar sdss", "cosmological probe", "universe"]}
{"id": "2102.04619", "title": "An Ultra-High Time Resolution Cosmic Ray Detection Mode for the Murchison Widefield Array", "abstract": "The radio-wavelength detection of extensive air showers (EAS) initiated by cosmic-ray interactions in the Earth's atmosphere is a promising technique for investigating the origin of these particles and the physics of their interactions. The Low Frequency Array (LOFAR) and the Owens Valley Long Wavelength Array (OVRO-LWA) have both demonstrated that the dense cores of low frequency radio telescope arrays yield detailed information on the radiation ground pattern, which can be used to reconstruct key EAS properties and infer the primary cosmic-ray composition. Here, we demonstrate a new observation mode of the Murchison Widefield Array (MWA), tailored to the observation of the sub-microsecond coherent bursts of radiation produced by EAS. We first show how an aggregate 30.72 MHz bandwidth (3072x 10 kHz frequency channels) recorded at 0.1 ms resolution with the MWA's voltage capture system (VCS) can be synthesised back to the full bandwidth Nyquist resolution of 16.3 ns. This process, which involves `inverting' two sets of polyphase filterbanks, retains 90.5 timing and positional accuracy of this mode by resolving the location of a calibrator pulse to within 5 m. Finally, preliminary observations show that the rate of nanosecond radio-frequency interference (RFI) events is 0.1 Hz, much lower than that found at the sites of other radio telescopes that study cosmic rays. We conclude that the identification of cosmic rays at the MWA, and hence with the low-frequency component of the Square Kilometre Array, is feasible with minimal loss of efficiency due to RFI.", "keyphrases": ["cosmic ray", "murchison widefield array", "radio telescope array"]}
{"id": "0903.4158", "title": "Inflation from N-Forms and its stability", "abstract": "Anisotropic and isotropic slow-roll inflation supported by n-forms are sought. Canonical field strengths and their duals are taken into account, and they are allowed to have a potential and also, when necessary for slow-roll, a nonminimal curvature coupling. New isotropic solutions are found for three-forms. It is also shown that some n-form actions are equivalent to f(R) gravity and scalar field models with possible nonminimal couplings. Anisotropic solutions are found for two-forms, generalising vector inflation, however, also the two-form is unstable during inflation due to the nonminimal coupling to curvature. We also address the stability of the isotropic background solutions supported by a triad of vectors .", "keyphrases": ["three-form", "vector inflation", "universe", "form field"]}
{"id": "0910.1839", "title": "High Energy Electron Signals from Dark Matter Annihilation in the Sun", "abstract": "In this paper we discuss two mechanisms by which high energy electrons resulting from dark matter annihilations in or near the Sun can arrive at the Earth. Specifically, electrons can escape the sun if DM annihilates into long-lived states, or if dark matter scatters inelastically, which would leave a halo of dark matter outside of the sun. Such a localized source of electrons may affect the spectra observed by experiments with narrower fields of view oriented towards the sun, such as ATIC, differently from those with larger fields of view such as Fermi. We suggest a simple test of these possibilities with existing Fermi data that is more sensitive than limits from final state radiation. If observed, such a signal will constitute an unequivocal signature of dark matter.", "keyphrases": ["dark matter annihilation", "photon", "neutrino"]}
{"id": "1912.10255", "title": "Measuring the Hubble function with standard candle clustering", "abstract": "Supernova Ia magnitude surveys measure the dimensionless luminosity distance H_0D_L. However, from the distances alone one cannot obtain quantities like H(z) or the dark energy equation of state, unless further cosmological assumptions are imposed. Here we show that by measuring the power spectrum of density contrast and of peculiar velocities of supernovae one can estimate also H(z)/H_0 regardless of background or linearly perturbed cosmology and of galaxy-matter bias. This method, dubbed Clustering of Standard Candles (CSC) also yields the redshift distortion parameter \u03b2(k,z) and the biased matter power spectrum in a model-independent way. We forecast that an optimistic (pessimistic) LSST may be able to constrain H(z)/H_0 to 5-13 (9-40", "keyphrases": ["hubble function", "clustering", "velocity", "matter power spectrum"]}
{"id": "2103.01971", "title": "Astrophysics Cosmology from Line Intensity Mapping vs Galaxy Surveys", "abstract": "Line intensity mapping (LIM) proposes to efficiently observe distant faint galaxies and map the matter density field at high redshift. Building upon the formalism in the companion paper, we first highlight the degeneracies between cosmology and astrophysics in LIM. We discuss what can be constrained from measurements of the mean intensity and redshift-space power spectra. With a sufficient spectral resolution, the large-scale redshift-space distortions of the 2-halo term can be measured, helping to break the degeneracy between bias and mean intensity. With a higher spectral resolution, measuring the small-scale redshift-space distortions disentangles the 1-halo and shot noise terms. Cross-correlations with external galaxy catalogs or lensing surveys further break degeneracies. We derive requirements for experiments similar to SPHEREx, HETDEX, CDIM, COMAP and CONCERTO. We then revisit the question of the optimality of the LIM observables, compared to galaxy detection, for astrophysics and cosmology. We use a matched filter to compute the luminosity detection threshold for individual sources. We show that LIM contains information about galaxies too faint to detect, in the high-noise or high-confusion regimes. We quantify the sparsity and clustering bias of the detected sources and compare them to LIM, showing in which cases LIM is a better tracer of the matter density. We extend previous work by answering these questions as a function of Fourier scale, including for the first time the effect of cosmic variance, pixel-to-pixel correlations, luminosity-dependent clustering bias and redshift-space distortions.", "keyphrases": ["cosmology", "line intensity mapping", "astrophysic"]}
{"id": "2109.14647", "title": "Running Late: Testing Delayed Supermassive Black Hole Growth Models Against the Quasar Luminosity Function", "abstract": "Observations of massive galaxies at low redshift have revealed approximately linear scaling relations between the mass of a supermassive black hole (SMBH) and properties of its host galaxy. How these scaling relations evolve with redshift and whether they extend to lower-mass galaxies however remain open questions. Recent galaxy formation simulations predict a delayed, or \"two-phase\", growth of SMBHs: slow, highly intermittent BH growth due to repeated gas ejection by stellar feedback in low-mass galaxies, followed by more sustained gas accretion that eventually brings BHs onto the local scaling relations. The predicted two-phase growth implies a steep increase, or \"kink\", in BH-galaxy scaling relations at a stellar mass M_*\u223c5\u00d710^10 M_\u2299. We develop a parametric, semi-analytic model to compare different SMBH growth models against observations of the quasar luminosity function (QLF) at z\u223c0.5-4. We compare models in which the relation between SMBH mass and galaxy mass is purely linear versus two-phase models. The models are anchored to the observed galaxy stellar mass function, and the BH mass functions at different redshifts are consistently connected by the accretion rates contributing to the QLF. The best fits suggest that two-phase evolution is significantly preferred by the QLF data over a purely linear scaling relation. Moreover, when the model parameters are left free, the two-phase model fits imply a transition mass consistent with that predicted by simulations. Our analysis motivates further observational tests, including measurements of BH masses and AGN activity at the low-mass end, which could more directly test two-phase SMBH growth.", "keyphrases": ["quasar luminosity function", "stellar feedback", "bh-galaxy scaling relation"]}
{"id": "1912.00190", "title": "Can Non-standard Recombination Resolve the Hubble Tension?", "abstract": "The inconsistent Hubble constant values derived from cosmic microwave background (CMB) observations and from local distance-ladder measurements may suggest new physics beyond the standard \u039bCDM paradigm. It has been found in earlier works that, at least phenomenologically, non-standard recombination histories can reduce the \u2273 4\u03c3 Hubble tension to \u223c 2\u03c3. Following this path, we vary physical and phenomenological parameters in RECFAST, the standard code to compute ionization history of the universe, to explore possible physics beyond standard recombination. We find that the CMB constraint on the Hubble constant is sensitive to the Hydrogen ionization energy and 2s \u2192 1s two-photon decay rate, both of which are atomic constants, and is insensitive to other details of recombination. Thus, the Hubble tension is very robust against perturbations of recombination history, unless exotic physics modifies the atomic constants during the recombination epoch.", "keyphrases": ["hubble tension", "recombination history", "two-photon decay rate"]}
{"id": "1501.02809", "title": "Regular Black Hole Metric with Three Constants of Motion", "abstract": "According to the no-hair theorem, astrophysical black holes are uniquely characterized by their masses and spins and are described by the Kerr metric. Several parametric spacetimes which deviate from the Kerr metric have been proposed in order to test this theorem with observations of black holes in both the electromagnetic and gravitational-wave spectra. Such metrics often contain naked singularities or closed timelike curves in the vicinity of the compact objects that can limit the applicability of the metrics to compact objects that do not spin rapidly, and generally admit only two constants of motion. The existence of a third constant, however, can facilitate the calculation of observables, because the equations of motion can be written in first-order form. In this paper, I design a Kerr-like black hole metric which is regular everywhere outside of the event horizon, possesses three independent constants of motion, and depends nonlinearly on four free functions that parameterize potential deviations from the Kerr metric. This metric is generally not a solution to the field equations of any particular gravity theory, but can be mapped to known four-dimensional black hole solutions of modified theories of gravity for suitable choices of the deviation functions. I derive expressions for the energy, angular momentum, and epicyclic frequencies of a particle on a circular equatorial orbit around the black hole and compute the location of the innermost stable circular orbit. In addition, I write the metric in a Kerr-Schild-like form, which allows for a straightforward implementation of fully relativistic magnetohydrodynamic simulations of accretion flows in this metric. The properties of this metric make it a well-suited spacetime for strong-field tests of the no-hair theorem in the electromagnetic spectrum with black holes of arbitrary spin.", "keyphrases": ["black hole metric", "gravity", "hole solution", "non-kerr metric"]}
{"id": "1807.09796", "title": "Galaxy Two-Point Correlation Function in General Relativity", "abstract": "We perform theoretical and numerical studies of the full relativistic two-point galaxy correlation function, considering the linear-order scalar and tensor perturbation contributions and the wide-angle effects. Using the gauge-invariant relativistic description of galaxy clustering and accounting for the contributions at the observer position, we demonstrate that the complete theoretical expression is devoid of any long-mode contributions from scalar or tensor perturbations and it lacks the infrared divergences in agreement with the equivalence principle. By showing that the gravitational potential contribution to the correlation function converges in the infrared, our study justifies an IR cut-off (k_IR\u2264 H_0) in computing the gravitational potential contribution. Using the full gauge-invariant expression, we numerically compute the galaxy two-point correlation function and study the individual contributions in the conformal Newtonian gauge. We find that the terms at the observer position such as the coordinate lapses and the observer velocity (missing in the standard formalism) dominate over the other relativistic contributions in the conformal Newtonian gauge such as the source velocity, the gravitational potential, the integrated Sachs-Wolf effect, the Shapiro time-delay and the lensing convergence. Compared to the standard Newtonian theoretical predictions that consider only the density fluctuation and redshift-space distortions, the relativistic effects in galaxy clustering result in a few percent-level systematic errors beyond the scale of the baryonic acoustic oscillation. Our theoretical and numerical study provides a comprehensive understanding of the relativistic effects in the galaxy two-point correlation function, as it proves the validity of the theoretical prediction and accounts for effects that are often neglected in its numerical evaluation.", "keyphrases": ["two-point correlation function", "observer position", "theoretical prediction", "relativistic effect", "galaxy"]}
{"id": "1511.01537", "title": "Spectrum and Anisotropy of Turbulence from Multi-Frequency Measurement of Synchrotron Polarization", "abstract": "We consider turbulent synchrotron emitting media that also exhibits Faraday rotation and provide a statistical description of synchrotron polarization fluctuations. In particular, we consider these fluctuations as a function of the spatial separation of the direction of measurements and as a function of wavelength for the same line-of-sight. On the basis of our general analytical approach, we introduce several measures that can be used to obtain the spectral slopes and correlation scales of both the underlying magnetic turbulence responsible for emission and the spectrum of the Faraday rotation fluctuations. We show the synergetic nature of these measures and discuss how the study can be performed using sparsely sampled interferometric data. We also discuss how additional characteristics of turbulence can be obtained, including the turbulence anisotropy, the three dimensional direction of the mean magnetic field. We consider both cases when the synchrotron emission and Faraday rotation regions coincide and when they are spatially separated. Appealing to our earlier study in Lazarian and Pogosyan (2012) we explain that our new results are applicable to a wide range of spectral indexes of relativistic electrons responsible for synchrotron emission. We expect wide application of our techniques both with existing synchrotron data sets as well as with big forthcoming data sets from LOFAR and SKA.", "keyphrases": ["turbulence", "magnetic field", "synchrotron emission"]}
{"id": "1801.08609", "title": "First Cosmological Constraint on the Effective Theory of Dark Matter-Proton Interactions", "abstract": "We obtain the first cosmological constraints on interactions between dark matter and protons within the formalism of nonrelativistic effective field theory developed for direct detection. For each interaction operator in the effective theory, parametrized by different powers of the relative velocity of the incoming particles, we use the Planck 2015 cosmic microwave background (CMB) temperature, polarization, and lensing anisotropy to set upper limits on the scattering cross section for all dark matter masses above 15 keV. We find that for interactions associated with a stronger dependence on velocity, dark matter and baryons stay thermally coupled for longer, but the interaction strengths are suppressed at the low temperatures relevant for Planck observations and are thus less constrained. At the same time, cross sections with stronger velocity dependencies are more constrained in the limit of small dark matter mass. In all cases, the effect of dark matter-proton scattering is most prominent on small scales in the CMB power spectra and in the matter power spectrum, and we thus expect substantial improvement over the current limits with data from ground-based CMB experiments and galaxy surveys.", "keyphrases": ["baryon", "matter power spectrum", "first cosmological constraint"]}
{"id": "1207.1686", "title": "Large-mass neutron stars with hyperonization", "abstract": "Within a density-dependent relativistic mean-field model using in-medium meson-hadron coupling constants and meson masses, we explore effects of in-medium hyperon interactions on properties of neutron stars. It is found that the hyperonic constituents in large-mass neutron stars can not be simply ruled out, while the recently measured mass of the millisecond pulsar J1614-2230 can constrain significantly the in-medium hyperon interactions. Moreover, effects of nuclear symmetry energy on hyperonization in neutron stars are also discussed.", "keyphrases": ["in-medium hyperon interaction", "large-mass neutron star", "gravitational wave physics", "hyperon puzzle"]}
{"id": "1310.1996", "title": "Stellar Variability in the VVV survey", "abstract": "The Vista Variables in the V\u00eda L\u00e1ctea (VVV) ESO Public Survey is an ongoing time-series, near-infrared (IR) survey of the Galactic bulge and an adjacent portion of the inner disk, covering 562 square degrees of the sky, using ESO's VISTA telescope. The survey has provided superb multi-color photometry in 5 broadband filters (Z, Y, J, H, and K_s), leading to the best map of the inner Milky Way ever obtained, particularly in the near-IR. The main variability part of the survey, which is focused on K_s-band observations, is currently underway, with bulge fields having been observed between 31 and 70 times, and disk fields between 17 and 36 times. When the survey is complete, bulge (disk) fields will have been observed up to a total of 100 (60) times, providing unprecedented depth and time coverage. Here we provide a first overview of stellar variability in the VVV data, including examples of the light curves that have been collected thus far, scientific applications, and our efforts towards the automated classification of VVV light curves.", "keyphrases": ["vvv", "vista variables", "galactic bulge", "stellar variability"]}
{"id": "1607.04264", "title": "Evidence for the magnetar nature of 1E 161348-5055 in RCW 103", "abstract": "We report on the detection of a bright, short, structured X-ray burst coming from the supernova remnant RCW 103 on 2016 June 22 caught by the Swift/BAT monitor, and on the follow-up campaign made with Swift/XRT, Swift/UVOT and the optical/NIR GROND detector. The characteristics of this flash, such as duration, and spectral shape, are consistent with typical short bursts observed from soft gamma repeaters. The BAT error circle at 68 per cent confidence range encloses the point-like X-ray source at the centre of the nebula, 1E161348-5055. Its nature has been long debated due to a periodicity of 6.67 hr in X-rays, which could indicate either an extremely slow pulsating neutron star, or the orbital period of a very compact X-ray binary system. We found that 20 min before the BAT trigger, the soft X-ray emission of 1E161348-5055 was a factor of 100 higher than measured 2 yr earlier, indicating that an outburst had already started. By comparing the spectral and timing characteristics of the source in the two years before the outburst and after the BAT event, we find that, besides a change in luminosity and spectral shape, also the 6.67 hr pulsed profile has significantly changed with a clear phase shift with respect to its low-flux profile. The UV/optical/NIR observations did not reveal any counterpart at the position of 1E161348-5055. Based on these findings, we associate the BAT burst with 1E161348-5055, we classify it as a magnetar, and pinpoint the 6.67 hr periodicity as the magnetar spin period.", "keyphrases": ["magnetar", "short burst", "neutron star"]}
{"id": "1811.08889", "title": "Further refining the de Sitter swampland conjecture", "abstract": "We propose an alternative refined de Sitter conjecture. It is given by a natural condition on a combination of the first and second derivatives of the scalar potential. We derive our conjecture in the same weak coupling, semi-classical regime where the previous refined de Sitter conjecture was derived, using the same tools together with a few more assumptions that we discuss. We further test and constrain free parameters in our conjecture using data points of a classical type IIA supergravity setup. Interestingly, our conjecture easily accommodates slow-roll single field inflation with a concave potential, favored by observations. The standard quintessence potential is in tension with our new conjecture, and we thus propose a different type of quintessence model.", "keyphrases": ["refinement", "second derivative", "scalar potential"]}
{"id": "1103.6129", "title": "A new baryonic equation of state at sub-nuclear densities for core-collapse simulations", "abstract": "We calculate a new equation of state for baryons at sub-nuclear densities meant for the use in core-collapse simulations of massive stars. The abundance of various nuclei is obtained together with the thermodynamic quantities. The formulation is the NSE description and the liquid drop approximation of nuclei. The model free energy to minimize is calculated by relativistic mean field theory for nucleons and the mass formula for nuclei with the atomic number up to 1000. We have also taken into account the pasta phase, thanks to which the transition to uniform nuclear matter in our EOS occurs in the conventional manner: nuclei are not dissociated to nucleons but survive right up to the transition to uniform nuclear matter. We find that the free energy and other thermodynamical quantities are not very different from those given in the Shen's EOS, one of the standard EOS's that adopt the single nucleus approximation. The average mass is systematically different, on the other hand, which may have an important ramification to the rates of electron captures and coherent neutrino scatterings on nuclei in supernova cores. It is also interesting that the root mean square of the mass number is not very different from the average mass number, since the former is important for the evaluation of coherent scattering rates on nuclei but has been unavailable so far. The EOS table is currently under construction, which will include the weak interaction rates.", "keyphrases": ["core-collapse simulation", "nucleon", "mass number"]}
{"id": "1704.06455", "title": "Partial dust obscuration in active galactic nuclei as a cause of broad-line profile and lag variability, and apparent accretion disc inhomogeneities", "abstract": "The profiles of the broad emission lines of active galactic nuclei (AGNs) and the time delays in their response to changes in the ionizing continuum (\"lags\") give information about the structure and kinematics of the inner regions of AGNs. Line profiles are also our main way of estimating the masses of the supermassive black holes (SMBHs). However, the profiles often show ill-understood, asymmetric structure and velocity-dependent lags vary with time. Here we show that partial obscuration of the broad-line region (BLR) by outflowing, compact, dusty clumps produces asymmetries and velocity-dependent lags similar to those observed. Our model explains previously inexplicable changes in the ratios of the hydrogen lines with time and velocity, the lack of correlation of changes in line profiles with variability of the central engine, the velocity dependence of lags, and the change of lags with time. We propose that changes on timescales longer than the light-crossing time do not come from dynamical changes in the BLR, but are a natural result of the effect of outflowing dusty clumps driven by radiation pressure acting on the dust. The motion of these clumps offers an explanation of long-term changes in polarization. The effects of the dust complicate the study of the structure and kinematics of the BLR and the search for sub-parsec SMBH binaries. Partial obscuration of the accretion disc can also provide the local fluctuations in luminosity that can explain sizes deduced from microlensing.", "keyphrases": ["supermassive black hole", "dusty clump", "active galactic nucleus"]}
{"id": "1108.3688", "title": "Finite Width in out-of-Equilibrium Propagators and Kinetic Theory", "abstract": "We derive solutions to the Schwinger-Dyson equations on the Closed-Time-Path for a scalar field in the limit where backreaction is neglected. In Wigner space, the two-point Wightman functions have the curious property that the equilibrium component has a finite width, while the out-of equilibrium component has zero width. This feature is confirmed in a numerical simulation for scalar field theory with quartic interactions. When substituting these solutions into the collision term, we observe that an expansion including terms of all orders in gradients leads to an effective finite-width. Besides, we observe no breakdown of perturbation theory, that is sometimes associated with pinch singularities. The effective width is identical with the width of the equilibrium component. Therefore, reconciliation between the zero-width behaviour and the usual notion in kinetic theory, that the out-of-equilibrium contributions have a finite width as well, is achieved. This result may also be viewed as a generalisation of the fluctuation-dissipation relation to out-of-equilibrium systems with negligible backreaction.", "keyphrases": ["width", "kinetic theory", "pinch singularity"]}
{"id": "0909.4535", "title": "Non-Gaussianity from resonant curvaton decay", "abstract": "We calculate curvature perturbations in the scenario in which the curvaton field decays into another scalar field via parametric resonance. As a result of a nonlinear stage at the end of the resonance, standard perturbative calculation techniques fail in this case. Instead, we use lattice field theory simulations and the separate universe approximation to calculate the curvature perturbation as a nonlinear function of the curvaton field. For the parameters tested, the generated perturbations are highly non-Gaussian and not well approximated by the usual fNL parameterisation. Resonant decay plays an important role in the curvaton scenario and can have a substantial effect on the resulting perturbations.", "keyphrases": ["curvaton field", "parametric resonance", "non-gaussianity"]}
{"id": "1503.07522", "title": "A two-parameter criterion for classifying the explodability of massive stars by the neutrino-driven mechanism", "abstract": "Thus far, judging the fate of a massive star (either a neutron star (NS) or a black hole) solely by its structure prior to core collapse has been ambiguous. Our work and previous attempts find a non-monotonic variation of successful and failed supernovae with zero-age main-sequence mass, for which no single structural parameter can serve as a good predictive measure. However, we identify two parameters computed from the pre-collapse structure of the progenitor, which in combination allow for a clear separation of exploding and non-exploding cases with only few exceptions ( 1-2.5 investigated stellar models. One parameter is M4, defining the normalized enclosed mass for a dimensionless entropy per nucleon of s=4, and the other is mu4 = d(m/M_sun)/d(r/1000 km) at s=4, being the normalized mass-derivative at this location. The two parameters mu4 and M4*mu4 can be directly linked to the mass-infall rate, Mdot, of the collapsing star and the electron-type neutrino luminosity of the accreting proto-NS, L_nue M_ns*Mdot, which play a crucial role in the \"critical luminosity\" concept for the theoretical description of neutrino-driven explosions as runaway phenomenon of the stalled accretion shock. All models were evolved employing the approach of Ugliano et al. for simulating neutrino-driven explosions in spherical symmetry. The neutrino emission of the accretion layer is approximated by a gray transport solver, while the uncertain neutrino emission of the 1.1 M_sun proto-NS core is parametrized by an analytic model. The free parameters connected to the core-boundary prescription are calibrated to reproduce the observables of Supernova 1987A for five different progenitor models.", "keyphrases": ["massive star", "black hole", "core collapse"]}
{"id": "1406.1506", "title": "The Ellipticity Distribution of Ambiguously Blended Objects", "abstract": "Using overlapping fields with space-based Hubble Space Telescope (HST) and ground-based Subaru Telescope imaging we identify a population of blended galaxies that are blended to such a large degree that they are detected as single objects in the ground-based monochromatic imaging, which we label as 'ambiguous blends'. For deep imaging data, such as the depth targeted with the Large Synoptic Survey Telescope (LSST), the ambiguous blend population is both large (\u223c 14 from that of unblended objects in a way that will likely be important for the weak lensing measurements. Most notably, for a limiting magnitude of i \u223c 27 we find that ambiguous blending results in a 14 (or 12 neff) due to 1) larger intrinsic ellipticity dispersion, 2) a scaling with the galaxy number density N_gal that is shallower than 1/\u221a(N_gal). For the LSST Gold Sample (i < 25.3) there is a 7 7 noise, we find that the ellipticity distribution of ambiguous blends has an RMS 13 lensing surveys to constrain the ellipticity distribution of galaxies to better than a percent in order to mitigate cosmic shear multiplicative biases, the different ellipticity distribution of ambiguous blends could be a dominant systematic if unaccounted for.", "keyphrases": ["ellipticity distribution", "ambiguous blend", "bias"]}
{"id": "1609.04756", "title": "Dynamo Sensitivity in Solar Analogs with 50 Years of Ca II H K Activity", "abstract": "The Sun has a steady 11-year cycle in magnetic activity most well-known by the rising and falling in the occurrence of dark sunspots on the solar disk in visible bandpasses. The 11-year cycle is also manifest in the variations of emission in the Ca II H K line cores, due to non-thermal (i.e. magnetic) heating in the lower chromosphere. The large variation in Ca II H K emission allows for study of the patterns of long-term variability in other stars thanks to synoptic monitoring with the Mount Wilson Observatory HK photometers (1966-2003) and Lowell Observatory Solar-Stellar Spectrograph (1994-present). Overlapping measurements for a set of 27 nearby solar-analog (spectral types G0-G5) stars were used to calibrate the two instruments and construct time series of magnetic activity up to 50 years in length. Precise properties of fundamental importance to the dynamo are available from Hipparcos, the Geneva-Copenhagen Survey, and CHARA interferometry. Using these long time series and measurements of fundamental properties, we do a comparative study of stellar \"twins\" to explore the sensitivity of the stellar dynamo to small changes to structure, rotation, and composition. We also compare this sample to the Sun and find hints that the regular periodic variability of the solar cycle may be rare among its nearest neighbors in parameter space.", "keyphrases": ["dynamo", "solar variability", "solar-analog star"]}
{"id": "1211.5915", "title": "CMB Maximum Temperature Asymmetry Axis: Alignment with Other Cosmic Asymmetries", "abstract": "We use a global pixel based estimator to identify the axis of the residual Maximum Temperature Asymmetry (MTA) (after the dipole subtraction) of the WMAP 7 year Internal Linear Combination (ILC) CMB temperature sky map. The estimator is based on considering the temperature differences between opposite pixels in the sky at various angular resolutions (4 degrees-15 degrees and selecting the axis that maximizes this difference. We consider three large scale Healpix resolutions (N_side=16 (3.7 degrees), N_side=8 (7.3 degrees) and N_side=4 (14.7 degrees)). We compare the direction and magnitude of this asymmetry with three other cosmic asymmetry axes (\u03b1dipole, Dark Energy Dipole and Dark Flow) and find that the four asymmetry axes are abnormally close to each other. We compare the observed MTA axis with the corresponding MTA axes of 10^4 Gaussian isotropic simulated ILC maps (based on LCDM). The fraction of simulated ILC maps that reproduces the observed magnitude of the MTA asymmetry and alignment with the observed \u03b1dipole is in the range of 0.1 (depending on the resolution chosen for the CMB map). The corresponding magnitude+alignment probabilities with the other two asymmetry axes (Dark Energy Dipole and Dark Flow) are at the level of about 1 Topological Quintessence as a physical model qualitatively consistent with this coincidence of directions.", "keyphrases": ["maximum temperature asymmetry", "cosmic microwave background", "cosmological-scale axis"]}
{"id": "1011.4477", "title": "Next-to-leading resummations in cosmological perturbation theory", "abstract": "One of the nicest results in cosmological perturbation theory is the analytical resummaton of the leading corrections at large momentum, which was obtained by Crocce and Scoccimarro for the propagator. Using an exact evolution equation, we generalize this result, by showing that a class of next-to-leading corrections can also be resummed at all orders in perturbation theory. The new corrections modify the propagator by a few percent in the Baryonic Acoustic Oscillation range of scales, and therefore cannot be neglected in resummation schemes aiming at an accuracy compatible with future generation galaxy surveys. Similar tools can be employed to derive improved approximations for the Power Spectrum.", "keyphrases": ["cosmological perturbation theory", "propagator", "next-to-leading correction", "resummation scheme"]}
{"id": "2004.12382", "title": "General constraints on Horndeski wormhole throats", "abstract": "In this work, we consider the full Horndeski Lagrangian applied to wormhole geometries and present the full gravitational field equations. We analyse the general constraints imposed by the flaring-out conditions at the wormhole throat and consider a plethora of specific subclasses of the Horndeski Lagrangian, namely, quintessence/phantom fields, k-essence, scalar-tensor theories, covariant galileons, nonminimal kinetic coupling, kinetic gravity braiding, and the scalar-tensor representation of Gauss-Bonnet couplings, amongst others. The generic constraints analysed in this work serve as a consistency check of the main solutions obtained in the literature and draws out new avenues of research in considering applications of specific subclasses of the Horndeski theory to wormhole physics.", "keyphrases": ["wormhole throat", "full horndeski lagrangian", "wormhole geometry", "gravitational field equation"]}
{"id": "1304.6527", "title": "Obtaining the CMB anomalies with a bounce from the contracting phase to inflation", "abstract": "Recent Planck data show the anomalies of CMB fluctuations on large angular scales, which confirms the early observations by WMAP. We continue studying an inflationary model, in which before the slow roll inflation the universe is in a contracting phase, and fit the model with the Planck data. It is showed that this model may generate not only the power deficit at low-l, but also a large hemispherical power asymmetry in CMB. We also discuss the implication of the result to the eternal inflation scenario.", "keyphrases": ["cmb anomaly", "large angular scale", "universe", "pre-inflationary scenario", "initial singularity problem"]}
{"id": "1212.3329", "title": "Consistency Relations for the Conformal Mechanism", "abstract": "We systematically derive the consistency relations associated to the non-linearly realized symmetries of theories with spontaneously broken conformal symmetry but with a linearly-realized de Sitter subalgebra. These identities relate (N+1)-point correlation functions with a soft external Goldstone to N-point functions. These relations have direct implications for the recently proposed conformal mechanism for generating density perturbations in the early universe. We study the observational consequences, in particular a novel one-loop contribution to the four-point function, relevant for the stochastic scale-dependent bias and CMB mu-distortion.", "keyphrases": ["conformal mechanism", "universe", "consistency condition", "single-clock model"]}
{"id": "1103.0819", "title": "New Black Widows and Redbacks in the Galactic Field", "abstract": "There has recently been a large increase in the number of known eclipsing radio millisecond pulsars in the Galactic field, many of which are associated with Fermi gamma-ray sources. All are in tight binaries (P_b < 24hr) many of which are classical \"black widows\" with very low mass companions (M_c << 0.1 M_sol) but some are \"redbacks\" with probably non-degenerate low mass companions (M_c 0.2 M_sol). I review the new discoveries, briefly discuss the distance uncertainties and the implications for high-energy emission.", "keyphrases": ["redback", "galactic field", "binary"]}
{"id": "1512.02637", "title": "From Wires to Cosmology", "abstract": "We provide a statistical framework for characterizing stochastic particle production in the early universe via a precise correspondence to current conduction in wires with impurities. Our approach is particularly useful when the microphysics is uncertain and the dynamics are complex, but only coarse-grained information is of interest. We study scenarios with multiple interacting fields and derive the evolution of the particle occupation numbers from a Fokker-Planck equation. At late times, the typical occupation numbers grow exponentially which is the analog of Anderson localization for disordered wires. Some statistical features of the occupation numbers show hints of universality in the limit of a large number of interactions and/or a large number of fields. For test cases, excellent agreement is found between our analytic results and numerical simulations.", "keyphrases": ["wire", "cosmology", "impurity", "fokker-planck equation"]}
{"id": "1001.4817", "title": "Spectra of Magnetic Fields Injected during Baryogenesis", "abstract": "Helical magnetic fields are injected into the cosmic medium during cosmological baryogenesis and can potentially provide a useful probe of the early universe. We construct a model to study the injection process during a first order phase transition and to determine the power spectra of the injected magnetic field. By Monte Carlo simulations we evaluate the Fourier space symmetric and helical power spectra of the magnetic field at the time the phase transition completes. The spectra are peaked at the scale given by the inverse size of bubbles at percolation and with a comparable width. These injected magnetic fields set the initial conditions for further cosmological magneto-hydrodynamical evolution.", "keyphrases": ["magnetic field", "baryogenesis", "early universe", "phase transition"]}
{"id": "1404.6133", "title": "Gravitational Self-Force Correction to the Innermost Stable Circular Equatorial Orbit of a Kerr Black Hole", "abstract": "For a self-gravitating particle of mass \u03bcin orbit around a Kerr black hole of mass M >> \u03bc, we compute the O(\u03bc/M) shift in the frequency of the innermost stable circular equatorial orbit (ISCEO) due to the conservative piece of the gravitational self-force acting on the particle. Our treatment is based on a Hamiltonian formulation of the dynamics in terms of geodesic motion in a certain locally-defined effective smooth spacetime. We recover the same result using the so-called first law of binary black-hole mechanics. We give numerical results for the ISCEO frequency shift as a function of the black hole's spin amplitude, and compare with predictions based on the post-Newtonian approximation and the effective one-body model. Our results provide an accurate strong-field benchmark for spin effects in the general relativistic two-body problem.", "keyphrases": ["circular equatorial orbit", "black hole", "gravitational self-force"]}
{"id": "1508.07877", "title": "Stochastic Dynamics of Infrared Fluctuations in Accelerating Universe", "abstract": "We extend investigations of infrared dynamics in accelerating universes. In the presence of massless and minimally coupled scalar fields, physical quantities may acquire growing time dependences through quantum fluctuations at super-horizon scales. From a semiclassical viewpoint, it was proposed that such infrared effects are described by a Langevin equation. In de Sitter space, the stochastic approach has been proved to be equivalent to resummation of the growing time dependences at the leading power. In this paper, we make the resummation derivation of the Langevin equation in a general accelerating universe. We first consider an accelerating universe whose slow-roll parameter is constant, and then extend the background as the slow-roll parameter becomes time dependent. The resulting Langevin equation contains a white noise term and the coefficient of each term is modified by the slow-roll parameter. Furthermore we find that the semiclassical description of the scalar fields leads to the same stochastic equation as far as we adopt an appropriate time coordinate.", "keyphrases": ["universe", "scalar field", "stochastic equation"]}
{"id": "1609.00717", "title": "Very Massive Tracers and Higher Derivative Biases", "abstract": "Most of the upcoming cosmological information will come from analyzing the clustering of the Large Scale Structures (LSS) of the universe through LSS or CMB observations. It is therefore essential to be able to understand their behavior with exquisite precision. The Effective Field Theory of Large Scale Structures (EFTofLSS) provides a consistent framework to make predictions for LSS observables in the mildly non-linear regime. In this paper we focus on biased tracers. We argue that in calculations at a given order in the dark matter perturbations, highly biased tracers will underperform because of their larger higher derivative biases. A natural prediction of the EFTofLSS is therefore that by simply adding higher derivative biases, all tracers should perform comparably well. We implement this prediction for the halo-halo and the halo-matter power spectra at one loop, and the halo-halo-halo, halo-halo-matter, and halo-matter-matter bispectra at tree-level, and compare with simulations. We find good agreement with the prediction: for all tracers, we are able to match the bispectra up to k\u22430.17 h/Mpc at z=0 and the power spectra to a higher wavenumber.", "keyphrases": ["effective field theory", "biased tracer", "halo-matter power spectra", "bispectra", "wavenumber"]}
{"id": "1003.3486", "title": "The gravitational-wave memory effect", "abstract": "The nonlinear memory effect is a slowly-growing, non-oscillatory contribution to the gravitational-wave amplitude. It originates from gravitational waves that are sourced by the previously emitted waves. In an ideal gravitational-wave interferometer a gravitational-wave with memory causes a permanent displacement of the test masses that persists after the wave has passed. Surprisingly, the nonlinear memory affects the signal amplitude starting at leading (Newtonian-quadrupole) order. Despite this fact, the nonlinear memory is not easily extracted from current numerical relativity simulations. After reviewing the linear and nonlinear memory I summarize some recent work, including: (1) computations of the memory contribution to the inspiral waveform amplitude (thus completing the waveform to third post-Newtonian order); (2) the first calculations of the nonlinear memory that include all phases of binary black hole coalescence (inspiral, merger, ringdown); and (3) realistic estimates of the detectability of the memory with LISA.", "keyphrases": ["memory effect", "test masse", "lisa"]}
{"id": "1006.2484", "title": "Analytic calculations of the spectra of ultra high energy cosmic ray nuclei. II. The general case of background radiation", "abstract": "We discuss the problem of ultra high energy nuclei propagation in extragalactic background radiations. The present paper is the continuation of the accompanying paper I where we have presented three new analytic methods to calculate the fluxes and spectra of ultra high energy cosmic ray nuclei, both primary and secondary, and secondary protons. The computation scheme in this paper is based on the analytic solution of coupled kinetic equations, which takes into account the continuous energy losses due to the expansion of the universe and pair-production, together with photo-disintegration of nuclei. This method includes in the most natural way the production of secondary nuclei in the process of photo-disintegration of the primary nuclei during their propagation through extragalactic background radiations. In paper I, in order to present the suggested analytical schemes of calculations, we have considered only the case of the cosmic microwave background radiation, in the present paper we generalize this computation to all relevant background radiations, including infra-red and visible/ultra-violet radiations, collectively referred to as extragalactic background light. The analytic solutions allow transparent physical interpretation of the obtained spectra. Extragalactic background light plays an important role at intermediate energies of ultra high energy cosmic ray nuclei. The most noticeable effect of the extragalactic background light is the low-energy tail in the spectrum of secondary nuclei.", "keyphrases": ["background radiation", "proton", "photo-disintegration"]}
{"id": "1708.00633", "title": "Disintegrating Rocky Exoplanets", "abstract": "We discuss a new class of exoplanets that appear to be emitting a tail of dusty effluents. These disintegrating planets are found close to their host stars and have very hot, and likely molten, surfaces. The properties of the dust should provide a direct probe of the constituent material of these rocky bodies.", "keyphrases": ["exoplanet", "planet", "kepler"]}
{"id": "1705.11171", "title": "Association Of Supergranule Mean Scales with Solar Cycle Strengths and Total Solar Irradiance", "abstract": "We analyze the long-term behavior of supergranule scale parameter, in active and quiet regions (AR, QR), using the Kodaikanal digitized data archive. This database provides century-long daily full disc observations of the Sun in Ca-II K wavelength. In this paper, we study the distributions of the supergranular scales, over the whole data duration, which show identical shape in these two regimes. We found that the AR mean scale values are always higher than that of the QR for every solar cycle. The mean scale values are highly correlated with the sunspot number cycle amplitude and also with total solar irradiance (TSI) variations. Such correlation establishes the cycle-wise mean scale as a potential calibrator for the historical data reconstructions. We also see an upward trend in the mean scales, as already been reported in TSI. This may provide new input for climate forcing models. These results also give us insight into the different evolutionary scenarios of the supergranules in the presence of strong (AR) and weak (QR) magnetic fields.", "keyphrases": ["total solar irradiance", "sun", "supergranular scale"]}
{"id": "1507.07575", "title": "Encyclopaedia Curvatonis", "abstract": "We investigate whether the predictions of single-field models of inflation are robust under the introduction of additional scalar degrees of freedom, and whether these extra fields change the potentials for which the data show the strongest preference. We study the situation where an extra light scalar field contributes both to the total curvature perturbations and to the reheating kinematic properties. Ten reheating scenarios are identified, and all necessary formulas allowing a systematic computation of the predictions for this class of models are derived. They are implemented in the public library ASPIC, which contains more than 75 single-field potentials. This paves the way for a forthcoming full Bayesian analysis of the problem. A few representative examples are displayed and discussed.", "keyphrases": ["scalar field", "particle physics", "realistic model"]}
{"id": "1908.10189", "title": "MeV-scale reheating temperature and thermalization of oscillating neutrinos by radiative and hadronic decays of massive particles", "abstract": "From a theoretical point of view, there is a strong motivation to consider an MeV-scale reheating temperature induced by long-lived massive particles with masses around the weak scale, decaying only through gravitational interaction. In this study, we investigate lower limits on the reheating temperature imposed by big-bang nucleosynthesis assuming both radiative and hadronic decays of such massive particles. For the first time, effects of neutrino self-interactions and oscillations are taken into account in the neutrino thermalization calculations. By requiring consistency between theoretical and observational values of light element abundances, we find that the reheating temperature should conservatively be T_ RH\u2273 1.8 MeV in the case of the 100 radiative decay, and T_ RH\u2273 4-5 MeV in the case of the 100 hadronic decays for particle masses in the range of 10 GeV to 100 TeV.", "keyphrases": ["massive particle", "radiation-dominated epoch", "high temperature"]}
{"id": "1503.06539", "title": "Observational signatures of the theories beyond Horndeski", "abstract": "In the approach of the effective field theory of modified gravity, we derive the equations of motion for linear perturbations in the presence of a barotropic perfect fluid on the flat isotropic cosmological background. In a simple version of Gleyzes-Langlois-Piazza-Vernizzi (GLPV) theories, which is the minimum extension of Horndeski theories, we show that a slight deviation of the tensor propagation speed squared c_ t^2 from 1 generally leads to the large modification to the propagation speed squared c_ s^2 of a scalar degree of freedom \u03d5. This problem persists whenever the kinetic energy \u03c1_X of the field \u03d5 is much smaller than the background energy density \u03c1_m, which is the case for most of dark energy models in the asymptotic past. Since the scaling solution characterized by the constant ratio \u03c1_X/\u03c1_m is one way out for avoiding such a problem, we study the evolution of perturbations for a scaling dark energy model in the framework of GLPV theories in the Jordan frame. Provided the oscillating mode of scalar perturbations is fine-tuned so that it is initially suppressed, the anisotropic parameter \u03b7=-\u03a6/\u03a8 between the two gravitational potentials \u03a8 and \u03a6 significantly deviates from 1 for c_ t^2 away from 1. For other general initial conditions, the deviation of c_ t^2 from 1 gives rise to the large oscillation of \u03a8 with the frequency related to c_ s^2. In both cases, the model can leave distinct imprints for the observations of CMB and weak lensing.", "keyphrases": ["horndeski theory", "dark energy model", "gravitational potential", "observational signature"]}
{"id": "1710.05822", "title": "Evidence for Cocoon Emission from the Early Light Curve of SSS17a", "abstract": "Swope Supernova Survey 2017a (SSS17a) was discovered as the first optical counterpart to the gravitational wave event GW170817. Although its light curve on the timescale of weeks roughly matches the expected luminosity and red color of an r-process powered transient, the explanation for the blue emission from high velocity material over the first few days is not as clear. Here we show that the power-law evolution of the luminosity, temperature, and photospheric radius during these early times can be explained by cooling of shock heated material around the neutron star merger. This heating is likely from the interaction of the gamma-ray burst jet with merger debris, so-called cocoon emission. We summarize the properties of this emission and provide formulae that can be used to study future detections of shock cooling from merging neutron stars. This argues that optical transient surveys should search for such early, blue light if they wish to find off-axis gamma-ray bursts and double neutron star gravitational wave events as soon as possible after the merger.", "keyphrases": ["cocoon emission", "jet", "ejecta"]}
{"id": "1810.11007", "title": "Ginzburg-Landau Theory of Dark Energy: A Framework to Study Both Temporal and Spatial Cosmological Tensions Simultaneously", "abstract": "A dark energy model (DE) is proposed based on Ginzburg-Landau theory of phase transition (GLT). This model, GLTofDE, surprisingly provides a framework to study not only temporal tensions in cosmology e.g. H_0 tension but also spatial anomalies of CMB e.g. the hemispherical power asymmetry and quadrupole-octopole alignment. In the mean field (or Landau) approximation of GLTofDE, there is a spontaneously symmetry breaking exactly like the Higgs potential. We modeled this transition, phenomenologically, and showed that GLTofDE can resolve both the H_0 tension and Lyman-\u03b1 anomaly in a non-trivial way. According to \u03c7^2-analysis the transition happens at z_t=0.738\u00b10.028 while H_0=71.89\u00b10.93 km/s/Mpc and \u03a9^like_k=-0.225\u00b10.049 which are consistent with the latest H(z) reconstructions. In addition, the GLTofDE proposes a framework to address the CMB anomalies when it is considered beyond the mean field approximation. In this regime existence of a long wavelength mode is a typical consequence which is named the Goldstone mode in the case of continuous symmetries. This mode, which is an automatic byproduct in GLTofDE, makes cosmological constant, direction dependent. This means one side of the sky should be colder than the other side in agreement with what has been already observed in CMB. In addition between initial stochastic pattern and the final state with one long wavelength mode, we can observe smaller patches or protrusions of the biggest remaining patch in the simulation. Our simulations show these protrusions are few in numbers and will be evolved according to Alan-Cahn mechanism. These protrusions can give an additional effect on CMB which is the existence of aligned quadrupole-octopole mode and its direction should be orthogonal to the dipole direction. We conclude that GLTofDE is a fertile framework both theoretically and phenomenologically.", "keyphrases": ["ginzburg-landau theory", "dynamical dark energy", "low-redshift"]}
{"id": "1207.2439", "title": "Resolving the Radio Source Background: Deeper Understanding Through Confusion", "abstract": "We used the Karl G. Jansky Very Large Array (VLA) to image one primary beam area at 3 GHz with 8 arcsec FWHM resolution and 1.0 microJy/beam rms noise near the pointing center. The P(D) distribution from the central 10 arcmin of this confusion-limited image constrains the count of discrete sources in the 1 < S(microJy/beam) < 10 range. At this level the brightness-weighted differential count S^2 n(S) is converging rapidly, as predicted by evolutionary models in which the faintest radio sources are star-forming galaxies; and 96background originating in galaxies has been resolved into discrete sources. About 63 comes from star-forming galaxies that obey the far-infrared (FIR) / radio correlation and account for most of the FIR background at lambda = 160 microns. Our new data confirm that radio sources powered by AGNs and star formation evolve at about the same rate, a result consistent with AGN feedback and the rough correlation of black hole and bulge stellar masses. The confusion at centimeter wavelengths is low enough that neither the planned SKA nor its pathfinder ASKAP EMU survey should be confusion limited, and the ultimate source detection limit imposed by \"natural\" confusion is < 0.01 microJy at 1.4 GHz. If discrete sources dominate the bright extragalactic background reported by ARCADE2 at 3.3 GHz, they cannot be located in or near galaxies and most are < 0.03 microJy at 1.4 GHz.", "keyphrases": ["radio source", "confusion", "galaxy"]}
{"id": "1105.5649", "title": "Defrosting in an Emergent Galileon Cosmology", "abstract": "We study the transition from an Emergent Galileon condensate phase of the early universe to a later expanding radiation phase. This \"defrosting\" or \"preheating\" transition is a consequence of the excitation of matter fluctuations by the coherent Galileon condensate, in analogy to how preheating in inflationary cosmology occurs via the excitation of matter fluctuations through coupling of matter with the coherent inflaton condensate. We show that the \"minimal\" coupling of matter (modeled as a massless scalar field) to the Galileon field introduced by Creminelli, Nicolis and Trincherini in order to generate a scale-invariant spectrum of matter fluctuations is sufficient to lead to efficient defrosting, provided that the effects of the non-vanishing expansion rate of the universe are taken into account. If we neglect the effects of expansion, an additional coupling of matter to the Galileon condensate is required. We study the efficiency of the defrosting mechanism in both cases.", "keyphrases": ["universe", "inflationary cosmology", "galileon field"]}
{"id": "1306.2246", "title": "Element Abundances in Solar Energetic Particles and the Solar Corona", "abstract": "This is a study of abundances of the elements He, C, N, O, Ne, Mg, Si, S, Ar, Ca, and Fe in solar energetic particles (SEPs) in the 2 - 15 MeV amu-1 region measured on the Wind spacecraft during 54 large SEP events occurring between November 1994 and June 2012. The origin of most of the temporal and spatial variations in abundances of the heavier elements lies in rigidity-dependent scattering during transport of the particles away from the site of acceleration at shock waves driven out from the Sun by coronal mass ejections (CMEs). Variation in the abundance of Fe is correlated with the Fe spectral index, as expected from scattering theory but not previously noted. Clustering of Fe abundances during the \"reservoir\" period, late in SEP events, is also newly reported. Transport-induced enhancements in one region are balanced by depletions in another, thus, averaging over these variations produces SEP abundances that are energy independent, confirms previous SEP abundances in this energy region, and provides a credible measure of element abundances in the solar corona. These SEP-determined coronal abundances differ from those in the solar photosphere by a well-known function that depends upon the first ionization potential (FIP) or ionization time of the element.", "keyphrases": ["solar corona", "wind spacecraft", "heavy element"]}
{"id": "0909.2574", "title": "From Multiwavelength to Mass Scaling: Accretion and Ejection in Microquasars and AGN", "abstract": "A solid theoretical understanding of how inflowing, accreting plasma around black holes and other compact objects gives rise to outflowing winds and jets is still lacking, despite decades of observations. The fact that similar processes and morphologies are observed in both X-ray binaries as well as active galactic nuclei has led to suggestions that the underlying physics could scale with black hole mass, which could provide a new handle on the problem. In the last decade, simultaneous broadband campaigns of the fast-varying X-ray binaries particularly in their microquasar state have driven the development of, and in some cases altered, our ideas about the inflow/outflow connection in accreting black holes. Specifically the discovery of correlations between the radio, infrared and X-ray bands has revealed a remarkable connectivity between the various emission regions, and argued for a more holistic approach to tackling questions about accretion. This article reviews the recent major observational and theoretical advances that focus specifically on the relation between the two \"sides\" of the accretion process in black holes, with an emphasis on how new tools can be derived for comparisons across the mass scale.", "keyphrases": ["accretion", "black hole", "active galactic nucleus"]}
{"id": "1307.7938", "title": "Non-minimal Inflationary Attractors", "abstract": "Recently we identified a new class of (super)conformally invariant theories which allow inflation even if the scalar potential is very steep in terms of the original conformal variables. Observational predictions of a broad class of such theories are nearly model-independent. In this paper we consider generalized versions of these models where the inflaton has a non-minimal coupling to gravity with \u03be<0 different from its conformal value \u03be= -1/6. We show that these models exhibit attractor behavior. With even a slight increase of |\u03be| from |\u03be| = 0, predictions of these models for n_s and r rapidly converge to their universal model-independent values corresponding to conformal coupling \u03be= -1/6. These values of n_s and r practically coincide with the corresponding values in the limit of infinitely large negative \u03be.", "keyphrases": ["attractor", "non-minimal coupling", "inflationary model"]}
{"id": "1705.09292", "title": "Coannihilation without chemical equilibrium", "abstract": "Chemical equilibrium is a commonly made assumption in the freeze-out calculation of coannihilating dark matter. We explore the possible failure of this assumption and find a new conversion-driven freeze-out mechanism. Considering a representative simplified model inspired by supersymmetry with a neutralino- and sbottom-like particle we find regions in parameter space with very small couplings accommodating the measured relic density. In this region freeze-out takes place out of chemical equilibrium and dark matter self-annihilation is thoroughly inefficient. The relic density is governed primarily by the size of the conversion terms in the Boltzmann equations. Due to the small dark matter coupling the parameter region is immune to direct detection but predicts an interesting signature of disappearing tracks or displaced vertices at the LHC. Unlike freeze-in or superWIMP scenarios, conversion-driven freeze-out is not sensitive to the initial conditions at the end of reheating.", "keyphrases": ["chemical equilibrium", "simplified model", "relic density", "parameter region"]}
{"id": "1610.00047", "title": "Restrictions from Lorentz invariance violation on cosmic ray propagation", "abstract": "Lorentz Invariance Violation introduced as a generic modification to particle dispersion relations is used to study high energy cosmic ray attenuation processes. It is shown to reproduce the same physical effects for vacuum Cherenkov radiation, as in some particular models with spontaneous breaking of Lorentz symmetry. This approximation is also implemented for the study of photon decay in vacuum, where stringent limits to the violation scale are derived from the direct observation of very high energy cosmic ray photon events on gamma telescopes. Photo production processes by cosmic ray primaries on photon background are also addressed, to show that Lorentz violation may turn off this attenuation process at energies above a well defined secondary threshold.", "keyphrases": ["lorentz invariance violation", "vacuum cherenkov radiation", "photon decay"]}
{"id": "1510.04294", "title": "Three in one go: consequential angular momentum loss can solve major problems of CV evolution", "abstract": "The average white dwarf (WD) masses in cataclysmic variables (CVs) have been measured to significantly exceed those of single WDs, which is the opposite of what is theoretically expected. We present the results of binary population synthesis models taking into account consequential angular momentum loss (CAML) that is assumed to increase with decreasing WD mass. This approach can not only solve the WD mass problem, but also brings in agreement theoretical predictions and observations of the orbital period distribution and the space density of CVs. We speculate that frictional angular momentum loss following nova eruptions might cause such CAML and could thus be the missing ingredient of CV evolution.", "keyphrases": ["momentum loss", "dwarf", "nova eruption"]}
{"id": "1307.5873", "title": "Asymptotic freedom, asymptotic flatness and cosmology", "abstract": "Holographic RG flows in some cases are known to be related to cosmological solutions. In this paper another example of such correspondence is provided. Holographic RG flows giving rise to asymptotically-free \u03b2-functions have been analyzed in connection with holographic models of QCD. They are shown upon Wick rotation to provide a large class of inflationary models with logarithmically-soft inflaton potentials. The scalar spectral index is universal and depends only on the number of e-foldings. The ratio of tensor to scalar power depends on the single extra real parameter that defines this class of models. The Starobinsky inflationary model as well as the recently proposed models of T-inflation are members of this class. The holographic setup gives a completely new (and contrasting) view to the stability, naturalness and other problems of such inflationary models.", "keyphrases": ["cosmology", "holographic renormalization group", "quantum field theory"]}
{"id": "1001.3074", "title": "Accurate evolutions of unequal-mass neutron-star binaries: properties of the torus and short GRB engines", "abstract": "We present new results from accurate and fully general-relativistic simulations of the coalescence of unmagnetized binary neutron stars with various mass ratios. The evolution of the stars is followed through the inspiral phase, the merger and prompt collapse to a black hole, up until the appearance of a thick accretion disk, which is studied as it enters and remains in a regime of quasi-steady accretion. Although a simple ideal-fluid equation of state with \u0393=2 is used, this work presents a systematic study within a fully general relativistic framework of the properties of the resulting black-hole\u2013torus system produced by the merger of unequal-mass binaries. More specifically, we show that: (1) The mass of the torus increases considerably with the mass asymmetry and equal-mass binaries do not produce significant tori if they have a total baryonic mass M_tot > 3.7 M_sun; (2) Tori with masses M_tor 0.2 M_sun are measured for binaries with M_tot 3.4 M_sun and mass ratios q 0.75-0.85; (3) The mass of the torus can be estimated by the simple expression M_tor(q, M_tot) = [c_1 (1-q) + c_2](M_max-M_tot), involving the maximum mass for the binaries and coefficients constrained from the simulations, and suggesting that the tori can have masses as large as M_tor 0.35 M_sun for M_tot 2.8 M_sun and q 0.75-0.85; (4) Using a novel technique to analyze the evolution of the tori we find no evidence for the onset of non-axisymmetric instabilities and that very little, if any, of their mass is unbound; (5) Finally, for all the binaries considered we compute the complete gravitational waveforms and the recoils imparted to the black holes, discussing the prospects of detection of these sources for a number of present and future detectors.", "keyphrases": ["star", "black hole", "accretion disk"]}
{"id": "1103.2771", "title": "Asymmetric WIMP dark matter", "abstract": "In existing dark matter models with global symmetries the relic abundance of dark matter is either equal to that of anti-dark matter (thermal WIMP), or vastly larger, with essentially no remaining anti-dark matter (asymmetric dark matter). By exploring the consequences of a primordial asymmetry on the coupled dark matter and anti-dark matter Boltzmann equations we find large regions of parameter space that interpolate between these two extremes. Interestingly, this new asymmetric WIMP framework can accommodate a wide range of dark matter masses and annihilation cross sections. The present-day dark matter population is typically asymmetric, but only weakly so, such that indirect signals of dark matter annihilation are not completely suppressed. We apply our results to existing models, noting that upcoming direct detection experiments will constrain a large region of the relevant parameter space.", "keyphrases": ["relic abundance", "primordial asymmetry", "annihilation cross section"]}
{"id": "1806.05474", "title": "Non-Gaussianity from Axion-Gauge Fields Interactions during Inflation", "abstract": "We study the scalar-tensor-tensor non-Gaussian signal in an inflationary model comprising also an axion coupled with SU(2) gauge fields. In this set-up, metric fluctuations are sourced by the gauge fields already at the linear level providing an enhanced chiral gravitational waves spectrum. The same mechanism is at work in generating an amplitude for the three-point function that is parametrically larger than in standard single-field inflation.", "keyphrases": ["axion", "non-gaussianity", "primordial gravitational wave"]}
{"id": "2201.01300", "title": "The CAMELS project: public data release", "abstract": "The Cosmology and Astrophysics with MachinE Learning Simulations (CAMELS) project was developed to combine cosmology with astrophysics through thousands of cosmological hydrodynamic simulations and machine learning. CAMELS contains 4,233 cosmological simulations, 2,049 N-body and 2,184 state-of-the-art hydrodynamic simulations that sample a vast volume in parameter space. In this paper we present the CAMELS public data release, describing the characteristics of the CAMELS simulations and a variety of data products generated from them, including halo, subhalo, galaxy, and void catalogues, power spectra, bispectra, Lyman-\u03b1 spectra, probability distribution functions, halo radial profiles, and X-rays photon lists. We also release over one thousand catalogues that contain billions of galaxies from CAMELS-SAM: a large collection of N-body simulations that have been combined with the Santa Cruz Semi-Analytic Model. We release all the data, comprising more than 350 terabytes and containing 143,922 snapshots, millions of halos, galaxies and summary statistics. We provide further technical details on how to access, download, read, and process the data at <https://camels.readthedocs.io>.", "keyphrases": ["camels", "public data release", "cosmology", "astrophysics"]}
{"id": "1604.01722", "title": "CD-HPF: New Habitability Score Via Data Analytic Modeling", "abstract": "The search for life on the planets outside the Solar System can be broadly classified into the following: looking for Earth-like conditions or the planets similar to the Earth (Earth similarity), and looking for the possibility of life in a form known or unknown to us (habitability). The two frequently used indices, ESI and PHI, describe heuristic methods to score similarity/habitability in the efforts to categorize different exoplanets or exomoons. ESI, in particular, considers Earth as the reference frame for habitability and is a quick screening tool to categorize and measure physical similarity of any planetary body with the Earth. The PHI assesses the probability that life in some form may exist on any given world, and is based on the essential requirements of known life: a stable and protected substrate, energy, appropriate chemistry and a liquid medium. We propose here a different metric, a Cobb-Douglas Habitability Score (CDHS), based on Cobb-Douglas habitability production function (CD-HPF), which computes the habitability score by using measured and calculated planetary input parameters. The proposed metric, with exponents accounting for metric elasticity, is endowed with verifiable analytical properties that ensure global optima, and is scalable to accommodate finitely many input parameters. The model is elastic, does not suffer from curvature violations and, as we discovered, the standard PHI is a special case of CDHS. Computed CDHS scores are fed to K-NN (K-Nearest Neighbour) classification algorithm with probabilistic herding that facilitates the assignment of exoplanets to appropriate classes via supervised feature learning methods, producing granular clusters of habitability. The proposed work describes a decision-theoretical model using the power of convex optimization and algorithmic machine learning.", "keyphrases": ["habitability score", "exoplanet", "optima", "cd-hpf"]}
{"id": "2001.11420", "title": "Hints of dark energy anisotropic stress using Machine Learning", "abstract": "Recent analyses of the Planck data and quasars at high redshifts have suggested possible deviations from the flat \u039b cold dark matter model (\u039bCDM), where \u039b is the cosmological constant. Here we use machine learning methods to investigate any possible deviations from \u039bCDM at both low and high redshifts by using the latest cosmological data. Specifically, we apply the Genetic Algorithms to explore the nature of dark energy (DE) in a model independent fashion by reconstructing its equation of state w(z), the growth index of matter density perturbations \u03b3(z), the linear DE anisotropic stress \u03b7_DE(z) and the adiabatic sound speed c_s,DE^2(z) of DE perturbations. We find a \u223c2\u03c3 deviation of w(z) from -1 at high redshifts, the adiabatic sound speed is negative at the \u223c2.5\u03c3 level at z=0.1 and a \u223c2\u03c3 deviation of the anisotropic stress from unity at low redshifts and \u223c4 \u03c3 at high redshifts. These results hint towards either the presence of an non-adiabatic component in the DE sound speed or the presence of DE anisotropic stress, thus hinting at possible deviations from the \u039bCDM model.", "keyphrases": ["dark energy", "anisotropic stress", "hint"]}
{"id": "1011.3044", "title": "Cluster Mass Profiles from a Bayesian Analysis of Weak Lensing Distortion and Magnification Measurements: Applications to Subaru Data", "abstract": "We directly construct model-independent mass profiles of galaxy clusters from combined weak-lensing distortion and magnification measurements within a Bayesian statistical framework,which allows for a full parameter-space extraction of the underlying signal. This method applies to the full range of radius outside the Einstein radius, and recovers the absolute mass normalization. We apply our method to deep Subaru imaging of five high-mass (>10^15M_sun) clusters, A1689, A1703, A370, Cl0024+17, and RXJ1347-11, to obtain accurate profiles to beyond the virial radius (r_vir). For each cluster the lens distortion and magnification data are shown to be consistent with each other, and the total signal-to-noise ratio of the combined measurements ranges from 13 to 24 per cluster. We form a model-independent mass profile from stacking the clusters, which is detected at 37\u03c3 out to R 1.7r_vir. The projected logarithmic slope steepens from -1.01 \u00b10.09 at R 0.1r_vir to -1.92 \u00b10.51 at R 0.9r_vir. We also derive for each cluster inner strong-lensing based mass profiles from deep HST/ACS observations, which we show overlap well with the outer Subaru-based profiles and together are well described by a generalized form of the Navarro-Frenk-White profile, except for the ongoing merger RXJ1347-11, with modest variations in the central cusp slope (-dln\u03c1/dlnr < 0.9). The improvement here from adding the magnification measurements is significant, 30 measurements, compared with the lensing distortion signal.", "keyphrases": ["mass profile", "virial radius", "cluster"]}
{"id": "1001.0051", "title": "Lukewarm dark matter: Bose condensation of ultralight particles", "abstract": "We discuss the thermal evolution and Bose-Einstein condensation of ultra-light dark matter particles at finite, realistic cosmological temperatures. We find that if these particles decouple from regular matter before Standard model particles annihilate, their temperature will be about 0.9 K. This temperature is substantially lower than the temperature of CMB neutrinos and thus Big Bang Nucleosynthesis remains unaffected. In addition the temperature is consistent with WMAP 7-year+BAO+H0 observations without fine-tuning. We focus on particles of mass of m\u223c 10^-23 eV, which have Compton wavelengths of galactic scales. Agglomerations of these particles can form stable halos and naturally prohibit small scale structure. They avoid over-abundance of dwarf galaxies and may be favored by observations of dark matter distributions. We present numerical as well as approximate analytical solutions of the Friedmann-Klein-Gordon equations and study the cosmological evolution of this scalar field dark matter from the early universe to the era of matter domination. Today, the particles in the ground state mimic presureless matter, while the excited state particles are radiation like.", "keyphrases": ["dark matter", "bose-einstein condensation", "scalar field", "early universe"]}
{"id": "1603.06515", "title": "Collisionless Encounters and the Origin of the Lunar Inclination", "abstract": "The Moon is generally thought to have formed from the debris ejected by the impact of a planet-sized object with the proto-Earth towards the end of planetary accretion. Modeling of the impact process predicts that the lunar material was disaggregated into a circumplanetary disk and that lunar accretion subsequently placed the Moon in a near equatorial orbit. Forward integration of the lunar orbit from this initial state predicts a modern inclination at least an order of magnitude smaller than the lunar value, a long-standing discrepancy known as the lunar inclination problem. Here we show that the modern lunar orbit provides a sensitive record of gravitational interactions with Earth-crossing planetesimals not yet accreted at the time of the Moon-forming event. The excited lunar orbit can naturally be reproduced via interaction with a small quantity of mass (corresponding to 0.0075-0.015 ME eventually accreted to the Earth) carried by a few bodies, consistent with constraints and models of late accretion. While the process has a stochastic element, the observed value of the lunar inclination is among the most likely outcomes for a wide range of parameters. The excitation of the lunar orbit is most readily reproduced via collisionless encounters with strong tidal dissipation on the early Earth. This mechanism obviates the necessity of previously proposed (but idealized) excitation mechanisms and can constrain the planet formation context of the Moon-forming event and the pristineness of the dynamical state of the Earth-Moon system.", "keyphrases": ["lunar inclination", "planetesimal", "collisionless encounter"]}
{"id": "2001.10548", "title": "From galactic nuclei to the halo outskirts: tracing supermassive black holes across cosmic history and environments", "abstract": "We study the mass assembly and spin evolution of supermassive black holes (BHs) across cosmic time as well as the impact of gravitational recoil on the population of nuclear and wandering black holes (wBHs) by using the semi-analytical model LGalaxies run on top of Millennium merger trees. We track spin changes that BHs experience during both coalescence events and gas accretion phases. For the latter, we assume that spin changes are coupled with the bulge assembly. This assumption leads to predictions for the median spin values of z=0 BHs that depend on whether they are hosted by pseudobulges, classical bulges or ellipticals, being a 0.9, 0.7 and 0.4, respectively. The outcomes of the model display a good consistency with z<4 quasar luminosity functions and the z=0 BH mass function, spin values and black hole-bulge mass correlation. Regarding the wBHs, we assume that they can originate from both the disruption of satellite galaxies (orphan wBH) and ejections due to gravitational recoils (ejected wBH). The model points to a number density of wBHs that increases with decreasing redshift, although this population is always 2 dex smaller than the one of nuclear black holes. At all redshifts, wBHs are typically hosted in M_halo>10^13 M_\u2299 and M_stellar>10^10 M_\u2299, being orphan wBHs the dominant type. Besides, independently of redshift and halo mass, ejected wBHs inhabit the central regions (<0.3R_200) of the host DM halo, while orphan wBHs linger at larger scales (>0.5R_200). Finally, we find that gravitational recoils cause a progressive depletion of nuclear BHs with decreasing redshift and stellar mass. Moreover, ejection events lead to changes in the predicted local black hole-bulge relation, in particular for BHs in pseudobulges, for which the relation is flattened at M_bulge>10^10.2 M\u2299 and the scatter increase up to 3dex.", "keyphrases": ["supermassive black hole", "gravitational recoil", "bulge", "stellar mass"]}
{"id": "2203.12440", "title": "Joint analysis of DES Year 3 data and CMB lensing from SPT and Planck II: Cross-correlation measurements and cosmological constraints", "abstract": "Cross-correlations of galaxy positions and galaxy shears with maps of gravitational lensing of the cosmic microwave background (CMB) are sensitive to the distribution of large-scale structure in the Universe. Such cross-correlations are also expected to be immune to some of the systematic effects that complicate correlation measurements internal to galaxy surveys. We present measurements and modeling of the cross-correlations between galaxy positions and galaxy lensing measured in the first three years of data from the Dark Energy Survey with CMB lensing maps derived from a combination of data from the 2500 deg^2 SPT-SZ survey conducted with the South Pole Telescope and full-sky data from the Planck satellite. The CMB lensing maps used in this analysis have been constructed in a way that minimizes biases from the thermal Sunyaev Zel'dovich effect, making them well suited for cross-correlation studies. The total signal-to-noise of the cross-correlation measurements is 23.9 (25.7) when using a choice of angular scales optimized for a linear (nonlinear) galaxy bias model. We use the cross-correlation measurements to obtain constraints on cosmological parameters. For our fiducial galaxy sample, which consist of four bins of magnitude-selected galaxies, we find constraints of \u03a9_m = 0.272^+0.032_-0.052 and S_8\u2261\u03c3_8 \u221a(\u03a9_m/0.3)= 0.736^+0.032_-0.028 (\u03a9_m = 0.245^+0.026_-0.044 and S_8 = 0.734^+0.035_-0.028) when assuming linear (nonlinear) galaxy bias in our modeling. Considering only the cross-correlation of galaxy shear with CMB lensing, we find \u03a9_m = 0.270^+0.043_-0.061 and S_8 = 0.740^+0.034_-0.029. Our constraints on S_8 are consistent with recent cosmic shear measurements, but lower than the values preferred by primary CMB measurements from Planck.", "keyphrases": ["cosmological constraint", "galaxy", "cosmic microwave background"]}
{"id": "1212.1075", "title": "Clusters of galaxies and variation of the fine structure constant", "abstract": "We propose a new method to probe for variations in the fine structure constant alpha using clusters of galaxies, opening up a window on a new redshift range for such constraints. Hot clusters shine in the X-ray mainly due to bremsstrahlung, while they leave an imprint on the CMB frequency spectrum through the Sunyaev-Zel'dovich effect. These two physical processes can be characterized by the integrated Comptonization parameter Y_SZ DA^2 and its X-ray counterpart, the Y_X parameter. The ratio of these two quantities is expected to be constant from numerical simulations and current observations. We show that this fact can be exploited to constrain alpha, as the ratio of the two parameters depends on the fine structure constant as alpha^3.5. We determine current constraints from a combination of Planck SZ and XMM-Newton data, testing different models of variation of alpha. When fitting for a constant value of alpha, we find that current constraints are at the 1 comparable with current CMB constraints. We discuss strategies for further improving these constraints by almost an order of magnitude.", "keyphrases": ["galaxy", "fine structure", "x-ray counterpart", "spatial variation"]}
{"id": "1311.2468", "title": "Fundamental Particle Structure in the Cosmological Dark Matter", "abstract": "The nonbaryonic dark matter of the Universe is assumed to consist of new stable forms of matter. Their stability reflects symmetry of micro world and mechanisms of its symmetry breaking. Particle candidates for cosmological dark matter are lightest particles that bear new conserved quantum numbers. Dark matter particles may represent ideal gas of non-interacting particles. Self-interacting dark matter weakly or superweakly coupled to ordinary matter is also possible, reflecting nontrivial pattern of particle symmetry in the hidden sector of particle theory. In the early Universe the structure of particle symmetry breaking gives rise to cosmological phase transitions, from which macroscopic cosmological defects or primordial nonlinear structures can be originated. Primordial black holes (PBHs) can be not only a candidate for dark matter, but also represent a universal probe for super-high energy physics in the early Universe. Evaporating PBHs turn to be a source of even superweakly interacting particles, while clouds of massive PBHs can serve as a nonlinear seeds for galaxy formation. The observed broken symmetry of the three known families may provide a simultaneous solution for the problems of the mass of neutrino and strong CP violation in the unique framework of models of horizontal unification. The existence of new stable charged leptons and quarks is possible, hidden in elusive \"dark atoms\". Such possibility, strongly restricted by the constraints on anomalous isotopes of light elements, is not excluded in scenarios that predict stable double charged particles. The excessive -2 charged particles are bound in these scenarios with primordial helium in O-helium \"atoms\", maintaining specific nuclear-interacting form of the dark matter, which may provide an interesting solution for the puzzles of the direct dark matter searches. (abridged)", "keyphrases": ["cosmological dark matter", "universe", "matter particle", "primordial nonlinear structure"]}
{"id": "1912.01132", "title": "Big-Bang Nucleosynthesis After Planck", "abstract": "We assess the status of big-bang nucleosynthesis (BBN) in light of the final Planck data release and other recent developments, and in anticipation of future measurements. Planck data fix the cosmic baryon density to 0.9 precision, and determine the helium abundance and effective number of neutrinos with precision approaching that of astronomical and BBN determinations respectively. In addition, new high-redshift measurements give D/H to better precision than theoretical predictions, and new Li/H data reconfirm the lithium problem. We present new ^7 Be(n,p)^7 Li rates using new neutron capture measurements; we have also examined the effect of proposed changes in the d(p,\u03b3)^3 He rates. Using these results we perform a series of likelihood analyses. We assess BBN/CMB consistency, with attention to how our results depend on the choice of Planck data, as well as how the results depend on the choice of non-BBN, non-Planck data sets. Most importantly the lithium problem remains, and indeed is more acute given the very tight D/H observational constraints; new neutron capture data reveals systematics that somewhat increases uncertainty and thus slightly reduces but does not essentially change the problem. We confirm that d(p,\u03b3)^3 He theoretical rates brings D/H out of agreement and slightly increases 7Li; new experimental data are needed at BBN energies. Setting the lithium problem aside, we find the effective number of neutrino species at BBN is N_\u03bd = 2.86 \u00b1 0.15. Future CMB Stage-4 measurements promise substantial improvements in BBN parameters: helium abundance determinations will be competitive with the best astronomical determinations, and N_ eff will approach sensitivities capable of detecting the effects of Standard Model neutrino heating of the primordial plasma. (Abridged)", "keyphrases": ["nucleosynthesis", "neutrino specie", "early universe", "deuterium"]}
{"id": "0905.0255", "title": "Dynamical Scalar Degree of Freedom in Horava-Lifshitz Gravity", "abstract": "We investigate the linear cosmological perturbations of Ho\u0159ava-Lifshitz gravity in a FRW universe without any matter. Our results show that a new gauge invariant dynamical scalar mode emerges, due to the gauge transformation under the \"foliation-preserving\" diffeomorphism and \"projectability condition\", and it can produce a scale invariant power spectrum. In the infrared regime with \u03bb=1, the dynamical scalar degree of freedom turns to be a non-dynamical one at the linear order level.", "keyphrases": ["dynamical scalar degree", "gauge symmetry", "general relativity"]}
{"id": "1201.5029", "title": "PyCOOL - a Cosmological Object-Oriented Lattice code written in Python", "abstract": "There are a number of different phenomena in the early universe that have to be studied numerically with lattice simulations. This paper presents a graphics processing unit (GPU) accelerated Python program called PyCOOL that solves the evolution of scalar fields in a lattice with very precise symplectic integrators. The program has been written with the intention to hit a sweet spot of speed, accuracy and user friendliness. This has been achieved by using the Python language with the PyCUDA interface to make a program that is easy to adapt to different scalar field models. In this paper we derive the symplectic dynamics that govern the evolution of the system and then present the implementation of the program in Python and PyCUDA. The functionality of the program is tested in a chaotic inflation preheating model, a single field oscillon case and in a supersymmetric curvaton model which leads to Q-ball production. We have also compared the performance of a consumer graphics card to a professional Tesla compute card in these simulations. We find that the program is not only accurate but also very fast. To further increase the usefulness of the program we have equipped it with numerous post-processing functions that provide useful information about the cosmological model. These include various spectra and statistics of the fields. The program can be additionally used to calculate the generated curvature perturbation. The program is publicly available under GNU General Public License at https://github.com/jtksai/PyCOOL . Some additional information can be found from http://www.physics.utu.fi/tiedostot/theory/particlecosmology/pycool/ .", "keyphrases": ["early universe", "https://github.com/jtksai/pycool", "pycool"]}
{"id": "1504.06129", "title": "cosmoabc: Likelihood-free inference via Population Monte Carlo Approximate Bayesian Computation", "abstract": "Approximate Bayesian Computation (ABC) enables parameter inference for complex physical systems in cases where the true likelihood function is unknown, unavailable, or computationally too expensive. It relies on the forward simulation of mock data and comparison between observed and synthetic catalogues. Here we present cosmoabc, a Python ABC sampler featuring a Population Monte Carlo (PMC) variation of the original ABC algorithm, which uses an adaptive importance sampling scheme. The code is very flexible and can be easily coupled to an external simulator, while allowing to incorporate arbitrary distance and prior functions. As an example of practical application, we coupled cosmoabc with the numcosmo library and demonstrate how it can be used to estimate posterior probability distributions over cosmological parameters based on measurements of galaxy clusters number counts without computing the likelihood function. cosmoabc is published under the GPLv3 license on PyPI and GitHub and documentation is available at http://goo.gl/SmB8EX", "keyphrases": ["simulator", "scheme", "cosmoabc"]}
{"id": "1012.1305", "title": "No evidence for anomalously low variance circles on the sky", "abstract": "In a recent paper, Gurzadyan Penrose claim to have found directions on the sky centred on which are circles of anomalously low variance in the cosmic microwave background (CMB). These features are presented as evidence for a particular picture of the very early Universe. We attempted to repeat the analysis of these authors, and we can indeed confirm that such variations do exist in the temperature variance for annuli around points in the data. However, we find that this variation is entirely expected in a sky which contains the usual CMB anisotropies. In other words, properly simulated Gaussian CMB data contain just the sorts of variations claimed. Gurzadyan Penrose have not found evidence for pre-Big Bang phenomena, but have simply re-discovered that the CMB contains structure.", "keyphrases": ["sky", "noise", "cmb power spectrum"]}
{"id": "1309.7377", "title": "Flavor Oscillation Modes In Dense Neutrino Media", "abstract": "We study two-flavor neutrino oscillations in homogeneous neutrino gases in which neutrinos and anti-neutrinos are in nearly pure weak interaction states initially. We find that the monopole and dipole oscillation modes can trigger flavor instabilities in the opposite neutrino mass hierarchies in a nearly isotropic neutrino gas. For a class of simple neutrino systems we are able to identify the normal modes of neutrino oscillations in the linear regime. Our results provide new insights into the recently discovered multi-azimuthal angle (MAA) instability of neutrino oscillations in supernovae.", "keyphrases": ["axial symmetry", "neutrino-neutrino interaction", "flavor conversion", "multi-azimuthal-angle instability"]}
{"id": "1005.3287", "title": "Cosmological diagrammatic rules", "abstract": "A simple set of diagrammatic rules is formulated for perturbative evaluation of \u201cin-in\" correlators, as is needed in cosmology and other nonequilibrium problems. These rules are both intuitive, and efficient for calculational purposes.", "keyphrases": ["diagrammatic rule", "correlator", "in-in formalism"]}
{"id": "1203.0005", "title": "Dusty Planetary Systems", "abstract": "Extensive photometric stellar surveys show that many main sequence stars show emission at infrared and longer wavelengths that is in excess of the stellar photosphere; this emission is thought to arise from circumstellar dust. The presence of dust disks is confirmed by spatially resolved imaging at infrared to millimeter wavelengths (tracing the dust thermal emission), and at optical to near infrared wavelengths (tracing the dust scattered light). Because the expected lifetime of these dust particles is much shorter than the age of the stars (>10 Myr), it is inferred that this solid material not primordial, i.e. the remaining from the placental cloud of gas and dust where the star was born, but instead is replenished by dust-producing planetesimals. These planetesimals are analogous to the asteroids, comets and Kuiper Belt objects (KBOs) in our Solar system that produce the interplanetary dust that gives rise to the zodiacal light (tracing the inner component of the Solar system debris disk). The presence of these \"debris disks\" around stars with a wide range of masses, luminosities, and metallicities, with and without binary companions, is evidence that planetesimal formation is a robust process that can take place under a wide range of conditions. This chapter is divided in two parts. Part I discusses how the study of the Solar system debris disk and the study of debris disks around other stars can help us learn about the formation, evolution and diversity of planetary systems by shedding light on the frequency and timing of planetesimal formation, the location and physical properties of the planetesimals, the presence of long-period planets, and the dynamical and collisional evolution of the system. Part II reviews the physical processes that affect dust particles in the gas-free environment of a debris disk and their effect on the dust particle size and spatial distribution.", "keyphrases": ["dust", "asteroid", "solar system", "planet"]}
{"id": "1512.04787", "title": "Big-Bounce with Finite-time Singularity: The F(R) Gravity Description", "abstract": "An alternative to the Big Bang cosmologies is obtained by the Big Bounce cosmologies. In this paper, we study a bounce cosmology with a Type IV singularity occurring at the bouncing point, in the context of F(R) modified gravity. We investigate the evolution of the Hubble radius and we examine the issue of primordial cosmological perturbations in detail. As we demonstrate, for the singular bounce, the primordial perturbations originating from the cosmological era near the bounce, do not produce a scale invariant spectrum and also the short wavelength modes, after these exit the horizon, do not freeze, but grow linearly with time. After presenting the cosmological perturbations study, we discuss the viability of the singular bounce model, and our results indicate that the singular bounce must be combined with another cosmological scenario, or should be modified appropriately, in order that it leads to a viable cosmology. The study of the slow-roll parameters leads to the same result, indicating the singular bounce theory is unstable at the singularity point, for certain values of the parameters. We also conformally transform the Jordan frame singular bounce, and as we demonstrate, the Einstein frame metric leads to a Big Rip singularity. Therefore, the Type IV singularity in the Jordan frame, becomes a Big Rip singularity in the Einstein frame. Finally, we briefly study a generalized singular cosmological model, which contains two Type IV singularities, with quite appealing features.", "keyphrases": ["finite-time singularity", "cosmology", "singular bounce", "primordial perturbation"]}
{"id": "2102.01095", "title": "Confirmation of Asymmetric Iron Absorption in WASP-76b with HARPS", "abstract": "Hot Jupiters are predicted to have hot, clear daysides and cooler, cloudy nightsides. Recently, an asymmetric signature of iron absorption has been resolved in the transmission spectrum of WASP-76b using ESPRESSO on ESO's Very large Telescope. This feature is interpreted as being due to condensation of iron on the nightside, resulting in a different absorption signature from the evening than from the morning limb of the planet. It represents the first time that a chemical gradient has been observed across the surface of a single exoplanet. In this work, we confirm the presence of the asymmetric iron feature using archival HARPS data of four transits. The detection shows that such features can also be resolved by observing multiple transits on smaller telescopes. By increasing the number of planets where these condensation features are detected, we can make chemical comparisons between exoplanets and map condensation across a range of parameters for the first time.", "keyphrases": ["iron absorption", "wasp-76b", "exoplanet"]}
{"id": "1304.4473", "title": "Efficient sampling of fast and slow cosmological parameters", "abstract": "Physical parameters are often constrained from the data likelihoods using sampling methods. Changing some parameters can be much more computationally expensive (`slow') than changing other parameters (`fast parameters'). I describe a method for decorrelating fast and slow parameters so that parameter sampling in the full space becomes almost as efficient as sampling in the slow subspace when the covariance is well known and the distributions are simple. This gives a large reduction in computational cost when there are many fast parameters. The method can also be combined with a fast 'dragging' method proposed by Neal (2005) that can be more robust and efficient when parameters cannot be fully decorrelated a priori or have more complicated dependencies. I illustrate these methods for the case of cosmological parameter estimation using data likelihoods from the Planck satellite observations with dozens of fast nuisance parameters, and demonstrate a speed up by a factor of five or more. In more complicated cases, especially where the fast subspace is very fast but complex or highly correlated, the fast-slow sampling methods can in principle give arbitrarily large performance gains. The new samplers are implemented in the latest version of the publicly available CosmoMC code.", "keyphrases": ["sampling", "cost", "nuisance parameter"]}
{"id": "1204.5363", "title": "Is there a Size Difference between Red and Blue Globular Clusters?", "abstract": "Blue (metal-poor) globular clusters are observed to have half-light radii that are 20 this enhancement is not clear and differences in either the luminosity function or in the actual size of the clusters have been proposed. I analyze a set of dynamically self-consistent Monte Carlo globular cluster simulations to determine the origin of this enhancement. I find that my simulated blue clusters have larger half-light radii due to differences in the luminosity functions of metal-poor and metal-rich stars. I find that the blue clusters can also be physically larger, but only if they have a substantial number of black holes heating their central regions. In this case the difference between half-light radii is significantly larger than observed. I conclude that the observed difference in half-light radii between red and blue globular clusters is due to differences in their luminosity functions and that half-light radius is not a reliable proxy for cluster size.", "keyphrases": ["size difference", "blue cluster", "black hole"]}
{"id": "1401.8276", "title": "Local instabilities in magnetized rotational flows: A short-wavelength approach", "abstract": "We perform a local stability analysis of rotational flows in the presence of a constant vertical magnetic field and an azimuthal magnetic field with a general radial dependence. Employing the short-wavelength approximation we develop a unified framework for the investigation of the standard, the helical, and the azimuthal version of the magnetorotational instability, as well as of current-driven kink-type instabilities. Considering the viscous and resistive setup, our main focus is on the case of small magnetic Prandtl numbers which applies, e.g., to liquid metal experiments but also to the colder parts of accretion disks. We show that the inductionless versions of MRI that were previously thought to be restricted to comparably steep rotation profiles extend well to the Keplerian case if only the azimuthal field slightly deviates from its current-free (in the fluid) profile. We find an explicit criterion separating the pure azimuthal inductionless magnetorotational instability from the regime where this instability is mixed with the Tayler instability. We further demonstrate that for particular parameter configurations the azimuthal MRI originates as a result of a dissipation-induced instability of the Chandrasekhar's equipartition solution of ideal magnetohydrodynamics.", "keyphrases": ["rotational flow", "magnetic field", "accretion disk"]}
{"id": "2208.05432", "title": "The Gaia-ESO Public Spectroscopic Survey: Motivation, implementation, GIRAFFE data processing, analysis, and final data products", "abstract": "The Gaia-ESO Public Spectroscopic Survey is an ambitious project designed to obtain astrophysical parameters and elemental abundances for 100,000 stars, including large representative samples of the stellar populations in the Galaxy, and a well-defined sample of 60 (plus 20 archive) open clusters. We provide internally consistent results calibrated on benchmark stars and star clusters, extending across a very wide range of abundances and ages. This provides a legacy data set of intrinsic value, and equally a large wide-ranging dataset that is of value for homogenisation of other and future stellar surveys and Gaia's astrophysical parameters. This article provides an overview of the survey methodology, the scientific aims, and the implementation, including a description of the data processing for the GIRAFFE spectra. A companion paper (arXiv:2206.02901) introduces the survey results. Gaia-ESO aspires to quantify both random and systematic contributions to measurement uncertainties. Thus all available spectroscopic analysis techniques are utilised, each spectrum being analysed by up to several different analysis pipelines, with considerable effort being made to homogenise and calibrate the resulting parameters. We describe here the sequence of activities up to delivery of processed data products to the ESO Science Archive Facility for open use. The Gaia-ESO Survey obtained 202,000 spectra of 115,000 stars using 340 allocated VLT nights between December 2011 and January 2018 from GIRAFFE and UVES. The full consistently reduced final data set of spectra was released through the ESO Science Archive Facility in late 2020, with the full astrophysical parameters sets following in 2022.", "keyphrases": ["data product", "star", "gaia-eso survey"]}
{"id": "1606.04510", "title": "The Origin and Evolution of Saturn, with Exoplanet Perspective", "abstract": "Saturn formed beyond the snow line in the primordial solar nebula that made it possible for it to accrete a large mass. Disk instability and core accretion models have been proposed for Saturn's formation, but core accretion is favored on the basis of its volatile abundances, internal structure, hydrodynamic models, chemical characteristics of protoplanetary disk, etc. The observed frequency, properties and models of exoplanets provide additional supporting evidence for core accretion. The heavy elements with mass greater than 4He make up the core of Saturn, but are presently poorly constrained, except for carbon. The C/H ratio is super-solar, and twice that in Jupiter. The enrichment of carbon and other heavy elements in Saturn and Jupiter requires special delivery mechanisms for volatiles to these planets. In this chapter we will review our current understanding of the origin and evolution of Saturn and its atmosphere, using a multi-faceted approach that combines diverse sets of observations on volatile composition and abundances, relevant properties of the moons and rings, comparison with the other gas giant planet, Jupiter, analogies to the extrasolar giant planets, as well as pertinent theoretical models.", "keyphrases": ["saturn", "carbon", "planet"]}
{"id": "2009.04046", "title": "Fast neutrino flavor conversion, ejecta properties, and nucleosynthesis in newly-formed hypermassive remnants of neutron-star mergers", "abstract": "Neutrinos emitted in the coalescence of two neutron stars affect the dynamics of the outflow ejecta and the nucleosynthesis of heavy elements. In this work, we analyze the neutrino emission properties and the conditions leading to the growth of flavor instabilities in merger remnants consisting of a hypermassive neutron star and an accretion disk during the first 10 ms after the merger. The analyses are based on hydrodynamical simulations that include a modeling of neutrino emission and absorption effects via the \"Improved Leakage-Equilibration-Absorption Scheme\" (ILEAS). We also examine the nucleosynthesis of the heavy elements via the rapid neutron-capture process (r-process) inside the material ejected during this phase. The dominant emission of \u03bd\u0305_e over \u03bd_e from the merger remnant leads to favorable conditions for the occurrence of fast pairwise flavor conversions of neutrinos, independent of the chosen equation of state or the mass ratio of the binary. The nucleosynthesis outcome is very robust, ranging from the first to the third r-process peaks. In particular, more than 10^-5 M_\u2299 of strontium are produced in these early ejecta that may account for the GW170817 kilonova observation. We find that the amount of ejecta containing free neutrons after the r-process freeze-out, which may power early-time UV emission, is reduced by roughly a factor of 10 when compared to simulations that do not include weak interactions. Finally, the potential flavor equipartition between all neutrino flavors is mainly found to affect the nucleosynthesis outcome in the polar ejecta within \u2272 30^\u2218, by changing the amount of the produced iron-peak and first-peak nuclei, but it does not alter the lanthanide mass fraction therein.", "keyphrases": ["neutrino", "nucleosynthesis", "accretion disk"]}
{"id": "1009.4193", "title": "Observational constraints on the LLTB model", "abstract": "We directly compare the concordance LCDM model to the inhomogeneous matter-only alternative represented by LTB void models. To achieve a \"democratic\" confrontation we explore LLTB models with non-vanishing cosmological constant and perform a global likelihood analysis in the parameter space of cosmological constant and void radius. In our analysis we carefully consider SNe, Hubble constant, CMB and BAO measurements, marginalizing over spectral index, age of the universe and background curvature. We find that the LCDM model is not the only possibility compatible with the observations, and that a matter-only void model is a viable alternative to the concordance model only if the BAO constraints are relaxed. Moreover, we will show that the areas of the parameter space which give a good fit to the observations are always disconnected with the result that a small local void does not significantly affect the parameter extraction for LCDM models.", "keyphrases": ["lltb model", "observational result", "dark energy component"]}
{"id": "1207.1165", "title": "Stochastic Approach to Flat Direction during Inflation", "abstract": "We revisit the time evolution of a flat and non-flat direction system during inflation. In order to take into account quantum noises in the analysis, we base on stochastic formalism and solve coupled Langevin equations numerically. We focus on a class of models in which tree-level Hubble-induced mass is not generated. Although the non-flat directions can block the growth of the flat direction's variance in principle, the blocking effects are suppressed by the effective masses of the non-flat directions. We find that the fate of the flat direction during inflation is determined by one-loop radiative corrections and non-renormalizable terms as usually considered, if we remove the zero-point fluctuation from the noise terms.", "keyphrases": ["flat direction", "fluctuation", "scalar field"]}
{"id": "1802.04284", "title": "A Multi-Year Search For Transits Of Proxima Centauri. I: Light Curves Corresponding To Published Ephemerides", "abstract": "Proxima Centauri has become the subject of intense study since the radial-velocity discovery by Anglada-Escud\u00e9 et al. 2016 of a planet orbiting this nearby M-dwarf every 11.2 days. If Proxima Centauri b transits its host star, independent confirmation of its existence is possible, and its mass and radius can be measured in units of the stellar host mass and radius. To date, there have been three independent claims of possible transit-like event detections in light curve observations obtained by the MOST satellite (in 2014-15), the BSST telescope in Antarctica (in 2016), and the Las Campanas Observatory (in 2016). The claimed possible detections are tentative, due in part to the variability intrinsic to the host star, and in the case of the ground-based observations, also due to the limited duration of the light curve observations. Here, we present preliminary results from an extensive photometric monitoring campaign of Proxima Centauri, using telescopes around the globe and spanning from 2006 to 2017, comprising a total of 329 observations. Considering our data that coincide directly and/or phased with the previously published tentative transit detections, we are unable to independently verify those claims. We do, however, verify the previously reported ubiquitous and complex variability of the host star. We discuss possible interpretations of the data in light of the previous claims, and we discuss future analyses of these data that could more definitively verify or refute the presence of transits associated with the radial-velocity discovered planet.", "keyphrases": ["multi-year search", "planet", "transit search"]}
{"id": "1905.12618", "title": "Acoustic Dark Energy: Potential Conversion of the Hubble Tension", "abstract": "We discuss the ability of a dark fluid becoming relevant around the time of matter radiation equality to significantly relieve the tension between local measurements of the Hubble constant and CMB inference, within the \u039bCDM model. We show that the gravitational impact of acoustic oscillations in the dark fluid balance the effects on the CMB and result in an improved fit to CMB measurements themselves while simultaneously raising the Hubble constant. The required balance favors a model where the fluid is a scalar field that converts its potential to kinetic energy around matter radiation equality which then quickly redshifts away. We derive the requirements on the potential for this conversion mechanism and find that a simple canonical scalar with two free parameters for its local slope and amplitude robustly improves the fit to the combined data by \u0394\u03c7^2 \u2248 12.7 over \u039bCDM. We uncover the CMB polarization signatures that can definitively test this scenario with future data.", "keyphrases": ["scalar field", "acoustic dark energy", "matter-radiation equality", "universe"]}
{"id": "1406.0283", "title": "Magnetic Fields in the Milky Way", "abstract": "This chapter presents a review of observational studies to determine the magnetic field in the Milky Way, both in the disk and in the halo, focused on recent developments and on magnetic fields in the diffuse interstellar medium. I discuss some terminology which is confusingly or inconsistently used and try to summarize current status of our knowledge on magnetic field configurations and strengths in the Milky Way. Although many open questions still exist, more and more conclusions can be drawn on the large-scale and small-scale components of the Galactic magnetic field. The chapter is concluded with a brief outlook to observational projects in the near future.", "keyphrases": ["milky way", "strength", "magnetic field", "spiral arm"]}
{"id": "1506.08089", "title": "Realistic uncertainties on Hapke model parameters from photometric measurement", "abstract": "Hapke proposed a convenient and widely used analytical model to describe the spectro-photometry of granular materials. Using a compilation of the published data, Hapke (2012, Icarus, 221, 1079-1083) recently studied the relationship of b and c for natural examples and proposed the hockey stick relation (excluding b>0.5 and c>0.5). For the moment, there is no theoretical explanation for this relationship. One goal of this article is to study a possible bias due to the retrieval method. We expand here an innovative Bayesian inversion method in order to study into detail the uncertainties of retrieved parameters. On Emission Phase Function (EPF) data, we demonstrate that the uncertainties of the retrieved parameters follow the same hockey stick relation, suggesting that this relation is due to the fact that b and c are coupled parameters in the Hapke model instead of a natural phenomena. Nevertheless, the data used in the Hapke (2012) compilation generally are full Bidirectional Reflectance Diffusion Function (BRDF) that are shown not to be subject to this artifact. Moreover, the Bayesian method is a good tool to test if the sampling geometry is sufficient to constrain the parameters (single scattering albedo, surface roughness, b, c, opposition effect). We performed sensitivity tests by mimicking various surface scattering properties and various single image-like/disk resolved image, EPF-like and BRDF-like geometric sampling conditions. The second goal of this article is to estimate the favorable geometric conditions for an accurate estimation of photometric parameters in order to provide new constraints for future observation campaigns and instrumentations.", "keyphrases": ["brdf", "geometry", "realistic uncertainty"]}
{"id": "1503.06348", "title": "WIMP searches with gamma rays in the Fermi era: challenges, methods and results", "abstract": "The launch of the gamma-ray telescope Fermi Large Area Telescope (Fermi-LAT) started a pivotal period in indirect detection of dark matter. By outperforming expectations, for the first time a robust and stringent test of the paradigm of weakly interacting massive particles (WIMPs) is within reach. In this paper, we discuss astrophysical targets for WIMP detection and the challenges they present, review the analysis tools which have been employed to tackle these challenges, and summarize the status of constraints on and the claimed detections in the WIMP parameter space. Methods and results will be discussed in comparison to Imaging Air Cherenkov Telescopes. We also provide an outlook on short term and longer term developments.", "keyphrases": ["massive particle", "wimp search", "astrophysical environment"]}
{"id": "1105.3544", "title": "Unbound or Distant Planetary Mass Population Detected by Gravitational Microlensing", "abstract": "Since 1995, more than 500 exoplanets have been detected using different techniques, of which 11 were detected with gravitational microlensing. Most of these are gravitationally bound to their host stars. There is some evidence of free-floating planetary mass objects in young star-forming regions, but these objects are limited to massive objects of 3 to 15 Jupiter masses with large uncertainties in photometric mass estimates and their abundance. Here, we report the discovery of a population of unbound or distant Jupiter-mass objects, which are almost twice (1.8_-0.8^+1.7) as common as main-sequence stars, based on two years of gravitational microlensing survey observations toward the Galactic Bulge. These planetary-mass objects have no host stars that can be detected within about ten astronomical units by gravitational microlensing. However a comparison with constraints from direct imaging suggests that most of these planetary-mass objects are not bound to any host star. An abrupt change in the mass function at about a Jupiter mass favours the idea that their formation process is different from that of stars and brown dwarfs. They may have formed in proto-planetary disks and subsequently scattered into unbound or very distant orbits.", "keyphrases": ["gravitational microlensing", "mass object", "galactic bulge", "planet"]}
{"id": "1709.09193", "title": "New tracker models of dark energy", "abstract": "We describe a new class of dark energy (DE) models which behave like cosmological trackers at early times. These models are based on the \u03b1-attractor set of potentials, originally discussed in the context of inflation. The new models allow the current acceleration of the universe to be reached from a wide class of initial conditions. Prominent examples of this class of models are the potentials \u03c6 and cosh\u03c6. A remarkable feature of this new class of models is that they lead to large enough negative values of the equation of state at the present epoch, consistent with the observations of accelerated expansion of the universe, from a very large initial basin of attraction. They therefore avoid the fine tuning problem which afflicts many models of DE.", "keyphrases": ["tracker", "dark energy", "prominent example", "accelerated expansion"]}
{"id": "1309.6540", "title": "Supernovae as probes of cosmic parameters: estimating the bias from under-dense lines of sight", "abstract": "Correctly interpreting observations of sources such as type Ia supernovae (SNe Ia) require knowledge of the power spectrum of matter on AU scales - which is very hard to model accurately. Because under-dense regions account for much of the volume of the universe, light from a typical source probes a mean density significantly below the cosmic mean. The relative sparsity of sources implies that there could be a significant bias when inferring distances of SNe Ia, and consequently a bias in cosmological parameter estimation. While the weak lensing approximation should in principle give the correct prediction for this, linear perturbation theory predicts an effectively infinite variance in the convergence for ultra-narrow beams. We attempt to quantify the effect typically under-dense lines of sight might have in parameter estimation by considering three alternative methods for estimating distances, in addition to the usual weak lensing approximation. We find in each case this not only increases the errors in the inferred density parameters, but also introduces a bias in the posterior value.", "keyphrases": ["under-dense line", "universe", "cosmological parameter"]}
{"id": "1505.06585", "title": "Accelerating universe as a result of an adjustment mechanism", "abstract": "In this essay we propose that the theory of gravity's vacuum is described by a de Sitter geometry. Under this assumption we consider an adjustment mechanism able to screen any value of the vacuum energy of the matter fields. We discuss the most general scalar-tensor cosmological models with second order equations of motion that have a fixed de Sitter critical point for any kind of material content. These models give rise to interesting cosmological evolutions that we shall discuss.", "keyphrases": ["adjustment mechanism", "vacuum energy", "cosmological model"]}
{"id": "1511.07160", "title": "Detection of high frequency oscillations and damping from multi-slit spectroscopic observations of the corona", "abstract": "During the total solar eclipse of 11 July 2010, multi-slit spectroscopic observations of the solar corona were performed from Easter Island, Chile. To search for high-frequency waves, observations were taken at a high cadence in the green line at 5303 A due to [Fe xiv] and the red line at 6374 A due to [Fe x]. The data are analyzed to study the periodic variations in the intensity, Doppler velocity and line width using wavelet analysis. The data with high spectral and temporal resolution enabled us to study the rapid dynamical changes within coronal structures. We find that at certain locations each parameter shows significant oscillation with periods ranging from 6 - 25 s. For the first time, we could detect damping of high-frequency oscillations with periods of the order of 10 s. If the observed damped oscillations are due to magnetohydrodynamic (MHD) waves then they can contribute significantly in the heating of the corona. From a statistical study we try to characterize the nature of the observed oscillations while looking at the distribution of power in different line parameters.", "keyphrases": ["multi-slit spectroscopic observation", "solar eclipse", "coronal structure", "significant oscillation"]}
{"id": "1608.08234", "title": "The Cosmology Large Angular Scale Surveyor", "abstract": "The Cosmology Large Angular Scale Surveyor (CLASS) is a four telescope array designed to characterize relic primordial gravitational waves from inflation and the optical depth to reionization through a measurement of the polarized cosmic microwave background (CMB) on the largest angular scales. The frequencies of the four CLASS telescopes, one at 38 GHz, two at 93 GHz, and one dichroic system at 145/217 GHz, are chosen to avoid spectral regions of high atmospheric emission and span the minimum of the polarized Galactic foregrounds: synchrotron emission at lower frequencies and dust emission at higher frequencies. Low-noise transition edge sensor detectors and a rapid front-end polarization modulator provide a unique combination of high sensitivity, stability, and control of systematics. The CLASS site, at 5200 m in the Chilean Atacama desert, allows for daily mapping of up to 70% of the sky and enables the characterization of CMB polarization at the largest angular scales. Using this combination of a broad frequency range, large sky coverage, control over systematics, and high sensitivity, CLASS will observe the reionization and recombination peaks of the CMB E- and B-mode power spectra. CLASS will make a cosmic variance limited measurement of the optical depth to reionization and will measure or place upper limits on the tensor-to-scalar ratio, r, down to a level of 0.01 (95% C.L.).", "keyphrases": ["large angular scale", "gravitational wave", "reionization", "upper limit", "tensor-to-scalar ratio"]}
{"id": "1509.02538", "title": "Relativistic Mean-Field Models with Scaled Hadron Masses and Couplings: Hyperons and Maximum Neutron Star Mass", "abstract": "An equation of state of cold nuclear matter with an arbitrary isotopic composition is studied within a relativistic mean-field approach with hadron masses and coupling constants depending self-consistently on the scalar mean-field. All hadron masses decrease universally with the scalar field growth, whereas meson-nucleon coupling constants can vary differently. More specifically we focus on two modifications of the KVOR model studied previously. One extension of the model (KVORcut) demonstrates that the equation of state stiffens if the increase of the scalar-field magnitude with the density is bounded from above at some value for baryon densities above the saturation nuclear density. This can be realized if the nucleon vector-meson coupling constant changes rapidly as a function of the scalar field slightly above the desired value. The other version of the model (MKVOR) utilizes a smaller value of the nucleon effective mass at the nuclear saturation density and a saturation of the scalar field in the isospin asymmetric matter induced by a strong variation of the nucleon isovector-meson coupling constant as function of the scalar field. A possibility of hyperonization of the matter in neutron star interiors is incorporated. Our equations of state fulfill majority of known empirical constraints including the pressure-density constraint from heavy-ion collisions, direct Urca constraint, gravitational-baryon mass constraint for the pulsar J0737-3039B, and the constraint on the maximum mass of the neutron stars.", "keyphrases": ["hadron masse", "scalar field", "hyperon puzzle", "gravitational wave physics", "nearby pulsar"]}
{"id": "1808.00415", "title": "Probing Oort clouds around Milky Way stars with CMB surveys", "abstract": "Long-period comets observed in our solar system are believed to originate from the Oort cloud, which is estimated to extend from roughly a few thousand to 10^5 AU from the Sun. Despite many theoretical arguments for its existence, no direct observations of the cloud have been reported. Here, we explore the possibility of measuring Oort clouds around other stars through their emission at submillimeter wavelengths. Observations with the 545 and 857 GHz bands of the Planck satellite are well matched to the expected temperatures of Oort cloud bodies (on the order of 10 K). By correlating the Planck maps with catalogs of stars observed by the Gaia mission, we are able to constrain interesting regions of the exo-Oort cloud parameter space, placing limits on the total mass and the minimum size of grains in the cloud. We compare our measurements with known debris disk systems \u2013 in the case of Vega and Fomalhaut we find a significant excess that is in agreement with measurements from Herschel. We use the measurements around Fomalhaut to constrain a possible exo-Oort cloud of that system. We explore an observed excess around the brightest and nearest stars in our sample as arising from possible exo-Oort clouds or other extended sources of thermal emission. We argue that future CMB surveys and targeted observations with far-infrared and millimeter wavelength telescopes have the potential to detect exo-Oort clouds or other extended sources of thermal emission beyond \u223c 1000 AU from the parent stars.", "keyphrases": ["cmb survey", "other star", "thermal emission"]}
{"id": "1510.00893", "title": "Gravitational waves from dark matter collapse in a star", "abstract": "We investigate the collapse of clusters of weakly interacting massive particles (WIMPs) in the core of a Sun-like star and the possible formation of mini-black holes and the emission of gravitational waves. When the number of WIMPs is small, thermal pressure balances the WIMP cluster's self gravity. If the number of WIMPs is larger than a critical number, thermal pressure cannot balance gravity and the cluster contracts. If WIMPs are collisionless and bosonic, the cluster collapses directly to form a mini-black hole. For fermionic WIMPs, the cluster contracts until it is sustained by Fermi pressure, forming a small compact object. If the fermionic WIMP mass is smaller than 4\u00d7 10^2 GeV, the radius of the compact object is larger than its Schwarzschild radius and Fermi pressure temporally sustains its self gravity, halting the formation of a black hole. If the fermionic WIMP mass is larger than 4\u00d7 10^2 GeV, the radius is smaller than its Schwarzschild radius and the compact object becomes a mini-black hole. If the WIMP mass is 1 TeV, the size of the black hole will be approximately 2.5 cm and ultra high frequency gravitational waves will be emitted during black hole formation. The central frequency f_c of ringdown gravitational waves emitted from the black hole will be approximately 2 GHz. To detect the ringdown gravitational waves, the detector's noise must be below \u221a(S_h(f_c))\u2248 10^-30/\u221a( Hz).", "keyphrases": ["sun-like star", "mini-black hole", "gravitational wave"]}
{"id": "1708.08842", "title": "Fast Automated Analysis of Strong Gravitational Lenses with Convolutional Neural Networks", "abstract": "Quantifying image distortions caused by strong gravitational lensing and estimating the corresponding matter distribution in lensing galaxies has been primarily performed by maximum likelihood modeling of observations. This is typically a time and resource-consuming procedure, requiring sophisticated lensing codes, several data preparation steps, and finding the maximum likelihood model parameters in a computationally expensive process with downhill optimizers. Accurate analysis of a single lens can take up to a few weeks and requires the attention of dedicated experts. Tens of thousands of new lenses are expected to be discovered with the upcoming generation of ground and space surveys, the analysis of which can be a challenging task. Here we report the use of deep convolutional neural networks to accurately estimate lensing parameters in an extremely fast and automated way, circumventing the difficulties faced by maximum likelihood methods. We also show that lens removal can be made fast and automated using Independent Component Analysis of multi-filter imaging data. Our networks can recover the parameters of the Singular Isothermal Ellipsoid density profile, commonly used to model strong lensing systems, with an accuracy comparable to the uncertainties of sophisticated models, but about ten million times faster: 100 systems in approximately 1s on a single graphics processing unit. These networks can provide a way for non-experts to obtain lensing parameter estimates for large samples of data. Our results suggest that neural networks can be a powerful and fast alternative to maximum likelihood procedures commonly used in astrophysics, radically transforming the traditional methods of data reduction and analysis.", "keyphrases": ["convolutional neural networks", "lens", "astronomy"]}
{"id": "1807.10380", "title": "The FIRST Classifier: Compact and Extended Radio Galaxy Classification using Deep Convolutional Neural Networks", "abstract": "Upcoming surveys with new radio observatories such as the Square Kilometer Array will generate a wealth of imaging data containing large numbers of radio galaxies. Different classes of radio galaxies can be used as tracers of the cosmic environment, including the dark matter density field, to address key cosmological questions. Classifying these galaxies based on morphology is thus an important step toward achieving the science goals of next generation radio surveys. Radio galaxies have been traditionally been classified as Fanaroff-Riley (FR) I and II, although some exhibit more complex 'bent' morphologies arising from environmental factors or intrinsic properties. In this work we present the FIRST Classifier, an on-line system for automated classification of Compact and Extended radio sources. We developed the FIRST Classifier based on a trained Deep Convolutional Neural Network Model to automate the morphological classification of compact and extended radio sources observed in the FIRST radio survey. Our model achieved an overall accuracy of 97 galaxies respectively. The current version of the FIRST classifier is able to predict the morphological class for a single source or for a list of sources as Compact or Extended (FRI, FRII and BENT).", "keyphrases": ["first classifier", "convolutional neural network", "astronomical object"]}
{"id": "1611.05912", "title": "Collisional super-Penrose process and Wald inequalities", "abstract": "We consider collision of two massive particles in the equatorial plane of an axially symmetric stationary spacetime that produces two massless particles afterwards. It is implied that the horizon is absent but there is a naked singularity or another potential barrier that makes possible the head-on collision. The relationship between the energy in the center of mass frame E_c.m. and the Killing energy E measured at infinity is analyzed. It follows immediately from the Wald inequalities that unbounded E is possible for unbounded E_c.m. only. This can be realized if the spacetime is close to the threshold of the horizon formation. Different types of spacetimes (black holes, naked singularities, wormholes) correspond to different possible relations between E_c.m. and E. We develop a general approach that enables us to describe the collision process in the frames of the stationary observer and ZAMO (zero angular momentum observer). The escape cone and escape fraction are derived. A simple explanation of the existence of the bright spot is given. For the particular case of the Kerr metric, our results agree with the previous ones found in M. Patil, T. Harada, K. Nakao, P.S. Joshi, and M. Kimura, Phys. Rev. D 93, 104015 (2016).", "keyphrases": ["wald inequality", "naked singularity", "black hole"]}
{"id": "2103.09729", "title": "Implication of the Hubble tension for the primordial Universe in light of recent cosmological data", "abstract": "In prerecombination resolutions of the Hubble tension, such as early dark energy, new physics before recombination shifts the values of relevant cosmological parameters so that the models can fit with cosmic microwave background and baryon acoustic oscillations observations as well as \u039bCDM does. In this paper, we clarify how the parameter shifts are related with \u03b4 H_0, particularly we find the shift of primordial scalar spectral index scales as \u03b4 n_s\u2243 0.4\u03b4 H_0 H_0 by performing the Monte Carlo Markov chain analysis with the Planck2018+BAO+Pantheon+R19+Keck Array/BICEP dataset. A novel point of our result is that if the current H_0 measured locally is correct, complete resolution of the Hubble tension seems to be pointing to a scale invariant Harrison-Zeldovich spectrum, i.e. n_s= 1 for H_0\u223c 73km/s/Mpc.", "keyphrases": ["universe", "primordial scalar perturbation", "scale-invariant harrison-zeldovich spectrum"]}
{"id": "1901.08308", "title": "Determining the Dominant Acceleration Mechanism during Relativistic Magnetic Reconnection in Large-scale Systems", "abstract": "While a growing body of research indicates that relativistic magnetic reconnection is a prodigious source of particle acceleration in high-energy astrophysical systems, the dominant acceleration mechanism remains controversial. Using a combination of fully kinetic simulations and theoretical analysis, we demonstrate that Fermi-type acceleration within the large-scale motional electric fields dominates over direct acceleration from non-ideal electric fields within small-scale diffusion regions. This result has profound implications for modeling particle acceleration in large-scale astrophysical problems, since it opens up the possiblity of modeling the energetic spectra without resolving microscopic diffusion regions.", "keyphrases": ["relativistic magnetic reconnection", "particle acceleration", "non-ideal electric field", "high energy"]}
{"id": "1409.6549", "title": "A Relativistic view on large scale N-body simulations", "abstract": "We discuss the relation between the output of Newtonian N-body simulations on scales that approach or exceed the particle horizon to the description of General Relativity. At leading order, the Zeldovich approximation is correct on large scales, coinciding with the General Relativistic result. At second order in the initial metric potential, the trajectories of particles deviate from the second order Newtonian result and hence the validity of 2LPT initial conditions should be reassessed when used in very large simulations. We also advocate using the expression for the synchronous gauge density as a well behaved measure of density fluctuations on such scales.", "keyphrases": ["large scale", "simulation", "general relativity", "newtonian result"]}
{"id": "2205.05892", "title": "Full-Shape Galaxy Power Spectra and the Curvature Tension", "abstract": "With recent evidence for a possible \"curvature tension\" among early and late universe cosmological probes, Effective Field Theories of Large Scale Structure (EFTofLSS) have emerged as a promising new framework to generate constraints on \u03a9_k that are independent of both CMB measurements, and some of the assumptions of flatness that enter into other large-scale structure analyses. In this work we use EFTofLSS to simultaneously constrain measurements from the 6dFGS, BOSS, and eBOSS catalogues, representing the most expansive full-shape investigation of curvature to date. Fitting the full-shape data with a BBN prior on \u03a9_b h^2 and fixed n_s, we measure \u03a9_k = -0.089^+0.049_-0.046, corresponding to a \u223c 2 \u03c3 preference for curvature. We argue that this result cannot be biased towards flatness by assumptions in the fitting methodology. Using the Bayesian evidence ratio our full-shape data assigns betting odds of 2:1 in favour of curvature, indicating present measurements remain broadly compatible with both flat and curved cosmological models. When our full-shape sample is combined with Planck 2018 CMB measurements, we break the geometric degeneracy and recover a joint fit on \u03a9_k of -0.0041^+0.0026_-0.0021. Using the suspiciousness statistic (built on the standard Bayes factor), we find evidence for a moderate tension between Planck 2018 and our suite of full-shape measurements, at a significance of 1.76 ^+0.14_-0.11\u03c3 (p \u223c 0.08 \u00b1 0.02). These results demonstrate the usefulness of full-shape clustering measurements as a CMB independent probe of curvature in the ongoing curvature tension debate.", "keyphrases": ["curvature tension", "field theories", "large scale structure"]}
{"id": "1909.08192", "title": "Scattering-Induced Disk Polarization By Millimeter-Sized Grains", "abstract": "Spatially resolved (sub)millimeter polarization has been detected by ALMA in an increasing number of disks around young stellar objects. The majority of the observations show polarization patterns that are consistent with self-scattering, especially at ALMA Band 7. The inferred sizes of the grains are typically of order 100 microns, which is very different from the millimeter size commonly inferred from the dust opacity index beta. In an effort to resolve this discrepancy, we first introduced the so-called \"Coplanar Isotropic Radiation Field\" approximation, which enables the computation of the (signed) polarization fraction analytically. With an oft-adopted dust composition (used, e.g., by DSHARP), we find that models with big dust grains produce very small polarization with reversed orientation, which hasn't been observed. The semi-analytic results are validated through Monte Carlo radiative transfer simulations. In these models, the \"correct\" polarization orientation and the small beta index are mutually exclusive. To resolve this tension, we explore a wide range of dust models, parameterized by their complex refractive index. We find that both the fraction of the polarization and whether it is reversed or not depend on the refractive index in a complex way, and this dependence is mapped out on an n-k plane for a representative dust size distribution (MRN with amax=3mm) and wavelength of 870 microns. In particular, refractory organics dust grains produce reversed polarization, whereas grains of the same size but made of absorptive carbonaceous materials can produce a percent-level polarization that is not reversed; the latter may alleviate the tension between the grain sizes inferred from the scattering-induced polarization and the opacity index beta. We conclude that scattering-induced polarization has the potential to probe not only the sizes of the grains but also their composition.", "keyphrases": ["polarization pattern", "dust grain", "refractive index", "small spectral index"]}
{"id": "1301.7424", "title": "Three-dimensional Spontaneous Magnetic Reconnection", "abstract": "Magnetic reconnection is best known from observations of the Sun where it causes solar flares. Observations estimate the reconnection rate a small, but non-negligible fraction of the Alfv\u00e9n speed, so-called fast reconnection. Until recently, the prevailing pictures of reconnection were referring to either resistivity or plasma microscopic effects, which was contradictory to the observed rates. The alternative picture was either reconnection due to the stochasticity of magnetic field lines in turbulence or the tearing instability of the thin current sheet. In this paper I simulated long-term three-dimensional nonlinear evolution of a thin, planar current sheet subject to fast oblique tearing instability using direct numerical simulations of resistive-viscous MHD. The late-time evolution resembles generic turbulence with -5/3 power spectrum and scale-dependent anisotropy, so I conclude that the tearing-driven reconnection becomes turbulent reconnection. The turbulence is local in scale, so microscopic diffusivity should not affect large-scale quantities. This is confirmed by convergence of the reconnection rate towards \u223c 0.015 v_A with increasing Lundquist number. In this spontaneous reconnection with mean field and without driving the dissipation rate per unit area also converge to \u223c 0.006 \u03c1 v_A^3, the dimensionless constants 0.015 and 0.006 are governed only by self-driven nonlinear dynamics of the sheared magnetic field. Remarkably, this also means that thin current sheet has a universal fluid resistance depending only on its length to width ratio and to v_A/c.", "keyphrases": ["magnetic reconnection", "reconnection", "turbulence", "current sheet"]}
{"id": "2005.02895", "title": "Generating PBHs and small-scale GWs in two-field models of inflation", "abstract": "Primordial black holes (PBHs) generated by gravitational collapse of large primordial overdensities can be a fraction of the observed dark matter. In this paper, we introduce a mechanism to produce a large peak in the primordial power spectrum (PPS) in two-field inflationary models characterized by two stages of inflation based on a large non-canonical kinetic coupling. This mechanism is generic to several two-field inflationary models, due to a temporary tachyonic instability of the isocurvature perturbations at the transition between the two stages of inflation. We numerically compute the primordial perturbations from largest scales to the small scales corresponding to that of PBHs using an extension of BINGO (BI-spectra and Non-Gaussianity Operator). Moreover we numerically compute the stochastic background of gravitational waves (SBGW) produced by second order scalar perturbations within frequencies ranging from nano-Hz to KHz that covers the observational scales corresponding to Pulsar Timing Arrays, Square Kilometer Array to that of Einstein telescope. We discuss the prospect of its detection by these proposed and upcoming gravitational waves experiments.", "keyphrases": ["two-field model", "primordial black hole", "curvature perturbation"]}
{"id": "1510.04429", "title": "Relativistic virial relation for cosmological structures", "abstract": "Starting with the relativistic Boltzmann equation for a system of particles defined by a distribution function, we have derived the virial relation for a spherical structure within an expanding background in the context of general relativity. This generalized form of the virial relation is then applied to the static case of a spherically symmetric structure to see the difference in the simplest case to the Newtonian relation. A relativistic Mass-Temperature relation for this simple case is also derived which can be applied to compact objects in astrophysics. Our general virial relation is then applied to the non-static case of a structure within an expanding universe where an extra term, usually missed in studies of structures in the presence of the dark energy, appears.", "keyphrases": ["virial relation", "cosmological structure observable", "exact relativistic calculation", "einstein equation", "second order perturbation"]}
{"id": "1709.00834", "title": "How does the cosmic web impact assembly bias?", "abstract": "The mass, accretion rate and formation time of dark matter haloes near proto-filaments (identified as saddle points of the potential) are analytically predicted using a conditional version of the excursion set approach in its so-called \"upcrossing\" approximation. The model predicts that at fixed mass, mass accretion rate and formation time vary with orientation and distance from the saddle, demonstrating that assembly bias is indeed influenced by the tides imposed by the cosmic web. Starved, early forming haloes of smaller mass lie preferentially along the main axis of filaments, while more massive and younger haloes are found closer to the nodes. Distinct gradients for distinct tracers such as typical mass and accretion rate occur because the saddle condition is anisotropic, and because the statistics of these observables depend on both the conditional means and their covariances. The theory is extended to other critical points of the potential field. The response of the mass function to variations of the matter density field (the so-called large scale bias) is computed, and its trend with accretion rate is shown to invert along the filament. The signature of this model should correspond at low redshift to an excess of reddened galactic hosts at fixed mass along preferred directions, as recently reported in spectroscopic and photometric surveys and in hydrodynamical simulations. The anisotropy of the cosmic web emerges therefore as a significant ingredient to describe jointly the dynamics and physics of galaxies, e.g. in the context of intrinsic alignments or morphological diversity.", "keyphrases": ["cosmic web", "assembly bias", "formation time", "halo"]}
{"id": "0901.2858", "title": "QPOs from Random X-ray Bursts around Rotating Black Holes", "abstract": "We continue our earlier studies of quasi-periodic oscillations (QPOs) in the power spectra of accreting, rapidly-rotating black holes that originate from the geometric \"light echoes\" of X-ray flares occurring within the black hole ergosphere. Our present work extends our previous treatment to three-dimensional photon emission and orbits to allow for arbitrary latitudes in the positions of the distant observers and the X-ray sources in place of the mainly equatorial positions and photon orbits of the earlier consideration. Following the trajectories of a large number of photons we calculate the response functions of a given geometry and use them to produce model light curves which we subsequently analyze to compute their power spectra and autocorrelation functions. In the case of an optically-thin environment, relevant to advection-dominated accretion flows, we consistently find QPOs at frequencies of order of kHz for stellar-mass black hole candidates while order of mHz for typical active galactic nuclei ( 10^7 Msun) for a wide range of viewing angles (30 to 80deg) from X-ray sources predominantly concentrated toward the equator within the ergosphere. As in our previous treatment, here too, the QPO signal is produced by the frame-dragging of the photons by the rapidly-rotating black hole, which results in photon \"bunches\" separated by constant time-lags, the result of multiple photon orbits around the hole. Our model predicts for various source/observer configurations the robust presence of a new class of QPOs, which is inevitably generic to curved spacetime structure in rotating black hole systems.", "keyphrases": ["quasi-periodic oscillation", "x-ray source", "qpos"]}
{"id": "1711.01730", "title": "Gravitational lensing by exotic objects", "abstract": "This paper reviews a phenomenological approach to the gravitational lensing by exotic objects such as the Ellis wormhole lens, where exotic lens objects may follow a non-standard form of the equation of state or may obey a modified gravity theory. A gravitational lens model is proposed in the inverse powers of the distance, such that the Schwarzschild lens and exotic lenses can be described in a unified manner as a one parameter family. As observational implications, the magnification, shear, photo-centroid motion and time delay in this lens model are discussed.", "keyphrases": ["exotic object", "gravity theory", "exotic lense"]}
{"id": "1710.07579", "title": "Modeling GW170817 based on numerical relativity and its implications", "abstract": "Gravitational-wave observation together with a large number of electromagnetic observations shows that the source of the latest gravitational-wave event, GW170817, detected primarily by advanced LIGO, is the merger of a binary neutron star. We attempt to interpret this observational event based on our results of numerical-relativity simulations performed so far paying particular attention to the optical and infra-red observations. We finally reach a conclusion that this event is described consistently by the presence of a long-lived hypermassive or supramassive neutron star as the merger remnant, because (i) significant contamination by lanthanide elements along our line of sight to this source can be avoided by the strong neutrino irradiation from it and (ii) it could play a crucial role to produce an ejecta component of appreciable mass with fast motion in the post-merger phase. We also point out that (I) the neutron-star equation of state has to be sufficiently stiff (i.e., the maximum mass of cold spherical neutron stars, M_max, has to be appreciably higher than 2M_sun in order that a long-lived massive neutron star can be formed as the merger remnant for the binary systems of GW170817, for which the initial total mass is > 2.73M_sun and (II) no detection of relativistic optical counterpart suggests a not-extremely high value of M_max approximately as 2.15-2.25M_sun.", "keyphrases": ["numerical relativity", "merger remnant", "total mass", "black hole"]}
{"id": "1106.5019", "title": "Late and early time phenomenology of Higgs-dependent cutoff", "abstract": "The analysis of theories with non-minimal coupling of Higgs field to gravity revealed that they enter into strong coupling regime above certain Higgs-dependent cutoff, which may be considerably below the Planck scale. Assuming that the effective theory, complementing the Standard Model or its minimal extension\u2013the nuMSM\u2013contains a set of higher dimensional operators suppressed by the Higgs-dependent cutoff, we analyse the reheating of the Universe after the Higgs inflation. We show that extra terms do not spoil the Higgs inflation, but can lead to baryogenesis and to warm sterile neutrino dark matter production at the reheating stage of the Universe expansion. They can also result in neutrino mass generation and proton decay.", "keyphrases": ["higgs-dependent cutoff", "higgs inflation", "sterile neutrino"]}
{"id": "1205.2758", "title": "Non-Gaussianities in the Cosmological Perturbation Spectrum due to Primordial Anisotropy II", "abstract": "We continue to investigate possible signatures of a pre-inflationary anisotropic phase in two-point and three point correlation functions of the curvature perturbation for high-momentum modes which exit the horizon well after isotropization. The late time dynamics of these modes is characterized by a non-Bunch Davies vacuum state which encodes all the information about initial anisotropy in the background space-time. We observe that, unlike the non-planar momenta, there exist regimes of planar momenta for which scale invariance of the power spectrum is strongly broken. This regime of planar momenta gives rise to enhanced non-Gaussianity in certain squeezed triangle configurations, although the enhancement of the f_NL parameter is limited by the breakdown of linear perturbation theory at \"exact planarity\". Finally, we demonstrate that for the range of planar modes for which scale invariance of the power spectrum is preserved, non-Gaussianity in the curvature perturbation spectrum is naturally constrained to be extremely small.", "keyphrases": ["high-momentum mode", "initial anisotropy", "non-gaussianitie"]}
{"id": "0909.2159", "title": "Equilibrium thermodynamics in modified gravitational theories", "abstract": "We show that it is possible to obtain a picture of equilibrium thermodynamics on the apparent horizon in the expanding cosmological background for a wide class of modified gravity theories with the Lagrangian density f(R, \u03d5, X), where R is the Ricci scalar and X is the kinetic energy of a scalar field \u03d5. This comes from a suitable definition of an energy momentum tensor of the \"dark\" component that respects to a local energy conservation in the Jordan frame. In this framework the horizon entropy S corresponding to equilibrium thermodynamics is equal to a quarter of the horizon area A in units of gravitational constant G, as in Einstein gravity. For a flat cosmological background with a decreasing Hubble parameter, S globally increases with time, as it happens for viable f(R) inflation and dark energy models. We also show that the equilibrium description in terms of the horizon entropy S is convenient because it takes into account the contribution of both the horizon entropy \u015c in non-equilibrium thermodynamics and an entropy production term.", "keyphrases": ["apparent horizon", "gravity theory", "energy momentum tensor", "dark energy model", "equilibrium thermodynamic"]}
{"id": "1910.03566", "title": "Strong Lensing Time Delay Constraints on Dark Energy: a Forecast", "abstract": "Measurements of time delays between multiple quasar images produced by strong lensing are reaching a sensitivity that makes them a promising cosmological probe. Future surveys will provide significantly more measurements, reaching unprecedented depth in redshift, making strong lensing time delay (SLTD) observations competitive with other background probes. We forecast constraints on the nature of dark energy from upcoming SLTD surveys, simulating future catalogues with different numbers of lenses distributed up to redshift z\u223c 1 and focusing on cosmological parameters such as the Hubble constant H_0 and parametrisations of the dark energy equation of state. We also explore the impact of our ability to precisely model the lens mass profile and its environment, on the forecasted constraints. We find that in the most optimistic cases, SLTD will constrain H_0 at the level of \u223c 0.1%, while the CPL equation of state parameters, w_0 and w_a, can be determined with errors \u03c3_w_0\u223c 0.05 and \u03c3_w_a\u223c 0.3, respectively. Furthermore, we investigate the bias introduced when a wrong cosmological model is assumed for the analysis. We find that the value of H_0 could be biased up to 10 \u03c3, assuming a perfect knowledge of the lens profile, when a \u039bCDM model is used to analyse data that really belong to a wCDM cosmology with w=-0.9. Based on these findings, we identify a consistency check of the assumed cosmological model in future SLTD surveys, by splitting the dataset in several redshift bins. Depending on the characteristics of the survey, this could provide a smoking gun for dark energy.", "keyphrases": ["lensing time delay", "dark energy", "cosmological parameter", "lens mass profile"]}
{"id": "0907.1278", "title": "Color Magnetic Flux Tubes in Dense QCD", "abstract": "QCD is expected to be in the color-flavor locking phase in high baryon density, which exhibits color superconductivity. The most fundamental topological objects in the color superconductor are non-Abelian vortices which are topologically stable color magnetic flux tubes. We present numerical solutions of the color magnetic flux tube for diverse choices of the coupling constants. We also analytically study its asymptotic profiles and find that they are different from the case of usual superconductors. We propose the width of color magnetic fluxes and find that it is larger than naive expectation of the Compton wave length of the massive gluon when the gluon mass is larger than the scalar mass.", "keyphrases": ["numerical solution", "diverse choice", "vortex", "non-abelian vortex"]}
{"id": "1107.2642", "title": "Inflation and primordial non-Gaussianities of \"generalized Galileons\"", "abstract": "We set up cosmological perturbation theory and study the cosmological implications of the so-called \u201cgeneralized Galileon\u201d developed in <cit.>. This is the most general scalar field theory whose Lagrangian contains derivatives up to second order while keeping second order equations of motion, and contains as sub-cases k-inflation, G-inflation and many other models. We calculate the power spectrum of the primordial curvature perturbation, finding a modification of the usual consistency relation of the tensor-to-scalar ratio in k-inflation or perfect fluid models. Finally we also calculate the bispectrum, which contains no new shapes beyond those of k-inflation.", "keyphrases": ["generalized galileon", "scalar field", "cosmological application"]}
{"id": "1610.02748", "title": "Mars sedimentary rock erosion rates constrained using crater counts, with applications to organic matter preservation and to the global dust cycle", "abstract": "Small-crater counts on Mars light-toned sedimentary rock are often inconsistent with any isochron; these data are usually plotted then ignored. We show (using an 18-HiRISE-image, >10^4 crater dataset) that these non-isochron crater counts are often well-fit by a model where crater production is balanced by crater obliteration via steady exhumation. For these regions, we fit erosion rates. We infer that Mars light-toned sedimentary rocks typically erode at 10^2 nm/yr, when averaged over 10 km^2 scales and 10^7-10^8 yr timescales. Crater-based erosion-rate determination is consistent with independent techniques, but can be applied to nearly all light-toned sedimentary rocks on Mars. Erosion is swift enough that radiolysis cannot destroy complex organic matter at some locations (e.g. paleolake deposits at SW Melas), but radiolysis is a severe problem at other locations (e.g. Oxia Planum). The data suggest that the relief of the Valles Marineris mounds is currently being reduced by wind erosion, and that dust production on Mars <3 Gya greatly exceeds the modern reservoir of mobile dust.", "keyphrases": ["rock", "erosion rate", "crater count"]}
{"id": "1411.1679", "title": "An introduction to the physics of Cartan gravity", "abstract": "A distance can be measured by monitoring how much a wheel has rotated when rolled without slipping. This simple idea underlies the mathematics of Cartan geometry. The Cartan-geometric description of gravity consists of a SO(1,4) gauge connection A^AB(x) and a symmetry-breaking field V^A(x). The clear similarity with symmetry-broken Yang-Mills theory suggests strongly the existence of a new field in nature: the gravitational Higgs field V^A. By treating V^A as a genuine dynamical field we arrive at a natural generalization of General Relativity with a wealth of new phenomenology and with General Relativity reproduced exactly in the limit where V^2 tends to a positive constant. We show that in regions wherein V^2(x) varies, but has a definite sign, the Cartan-geometric formulation is a form of a scalar-tensor theory. A specific choice of action yields the Peebles-Ratra quintessence model whilst more general actions are shown to exhibit propagation of torsion. Regions where the sign of V^2 changes correspond to a change in signature of the geometry; a simple choice of action with FRW symmetry yields, without any additional ad hoc assumptions, a classical analogue of the Hartle-Hawking no-boundary proposal. Solutions from more general actions are discussed. A gauge prescription for coupling matter to gravity is described and matter actions are presented which reduce to standard ones in the limit V^2\u2192 const. It becomes clear that Cartan geometry may function as a novel platform for inspiring and exploring modified theories of gravity with applications to dark energy, black holes, and early-universe cosmology. We end by listing a set of open problems.", "keyphrases": ["introduction", "cartan geometry", "cosmology", "antisymmetric tensor field"]}
{"id": "1303.3839", "title": "Localized Features in Non-Gaussianity from Heavy Physics", "abstract": "We discuss the possibility that we could obtain some hints of the heavy physics during inflation by analyzing local features of the primordial bispectrum. A heavy scalar field could leave large signatures in the primordial spectra through the parametric resonance between its background oscillation and the fluctuations. Since the duration of the heavy-mode oscillations is finite, the effect of the resonance is localized in momentum space. In this paper, we show that the bispectrum is amplified when such a resonance occurs, and that the peak amplitude of the feature can be O(10^1-2), or as large as O(10^5) depending on the type of interactions. In particular, the resonance can give large contributions in finitely squeezed configurations, while the bispectrum cannot be large in the exact squeezed limit. We also find that there is a relation between the scales at which the features appear in the bispectrum and the power spectrum, and that the feature in the bispectrum can be much larger than that in the power spectrum. If correlated features are observed at characteristic scales in the primordial spectra, it will indicate the presence of heavy degrees of freedom. By analyzing these features, we may be able to obtain some information on the physics behind inflation.", "keyphrases": ["heavy physics", "bispectrum", "resonance", "oscillation", "local feature"]}
{"id": "0903.2052", "title": "Numerical Tests of Fast Reconnection in Weakly Stochastic Magnetic Fields", "abstract": "We study the effects of turbulence on magnetic reconnection using 3D numerical simulations. This is the first attempt to test a model of fast magnetic reconnection in the presence of weak turbulence proposed by Lazarian Vishniac (1999). This model predicts that weak turbulence, generically present in most of astrophysical systems, enhances the rate of reconnection by reducing the transverse scale for reconnection events and by allowing many independent flux reconnection events to occur simultaneously. As a result the reconnection speed becomes independent of Ohmic resistivity and is determined by the magnetic field wandering induced by turbulence. To quantify the reconnection speed we use both an intuitive definition, i.e. the speed of the reconnected flux inflow, as well as a more sophisticated definition based on a formally derived analytical expression. Our results confirm the predictions of the Lazarian Vishniac model. In particular, we find that Vrec Pinj^(1/2), as predicted by the model. The dependence on the injection scale for some of our models is a bit weaker than expected, i.e. l^(3/4), compared to the predicted linear dependence on the injection scale, which may require some refinement of the model or may be due to the effects like finite size of the excitation region. The reconnection speed was found to depend on the expected rate of magnetic field wandering and not on the magnitude of the guide field. In our models, we see no dependence on the guide field when its strength is comparable to the reconnected component. More importantly, while in the absence of turbulence we successfully reproduce the Sweet-Parker scaling of reconnection, in the presence of turbulence we do not observe any dependence on Ohmic resistivity, confirming that our reconnection is fast.", "keyphrases": ["turbulence", "magnetic reconnection", "numerical simulation", "reconnection rate"]}
{"id": "1709.04474", "title": "Illuminating Low-Surface-Brightness Galaxies with the Hyper Suprime-Cam Survey", "abstract": "We present a catalog of extended low-surface-brightness galaxies (LSBGs) identified in the Wide layer of the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP). Using the first \u223c200 deg^2 of the survey, we have uncovered 781 LSBGs, spanning red (g-i\u22650.64) and blue (g-i<0.64) colors and a wide range of morphologies. Since we focus on extended galaxies (r_eff=2.5-14^''), our sample is likely dominated by low-redshift objects. We define LSBGs to have mean surface brightnesses \u03bc\u0305_eff(g)>24.3 mag arcsec^-2, which allows nucleated galaxies into our sample. As a result, the central surface brightness distribution spans a wide range of \u03bc_0(g)=18-27.4 mag arcsec^-2, with 50 respectively. Furthermore, the surface brightness distribution is a strong function of color, with the red distribution being much broader and generally fainter than that of the blue LSBGs, and this trend shows a clear correlation with galaxy morphology. Red LSBGs typically have smooth light profiles that are well-characterized by single-component S\u00e9rsic functions. In contrast, blue LSBGs tend to have irregular morphologies and show evidence for ongoing star formation. We crossmatch our sample with existing optical, HI, and ultraviolet catalogs to gain insight into the physical nature of the LSBGs. We find that our sample is diverse, ranging from dwarf spheroidals and ultra-diffuse galaxies in nearby groups to gas-rich irregulars to giant LSB spirals, demonstrating the potential of the HSC-SSP to provide a truly unprecedented view of the LSBG population.", "keyphrases": ["galaxy", "hyper suprime-cam", "view", "lsbg catalog"]}
{"id": "1607.00878", "title": "Athena Wide Field Imager Key Science Drivers", "abstract": "The Wide Field Imager (WFI) is one of two instruments for the Advanced Telescope for High-ENergy Astrophysics (Athena). In this paper we summarise three of the many key science objectives for the WFI - the formation and growth of supermassive black holes, non-gravitational heating in clusters of galaxies, and spin measurements of stellar mass black holes - and describe their translation into the science requirements and ultimately instrument requirements. The WFI will be designed to provide excellent point source sensitivity and grasp for performing wide area surveys, surface brightness sensitivity, survey power, and absolute temperature and density calibration for in-depth studies of the outskirts of nearby clusters of galaxies and very good high-count rate capability, throughput, and low pile-up, paired with very good spectral resolution, for detailed explorations of bright Galactic compact objects.", "keyphrases": ["growth", "outskirt", "good spectral resolution", "detailed exploration"]}
{"id": "0903.1037", "title": "PAMELA, DAMA, INTEGRAL and Signatures of Metastable Excited WIMPs", "abstract": "Models of dark matter with GeV scale force mediators provide attractive explanations of many high energy anomalies, including PAMELA, ATIC, and the WMAP haze. At the same time, by exploiting the MeV scale excited states that are automatically present in such theories, these models naturally explain the DAMA/LIBRA and INTEGRAL signals through the inelastic dark matter (iDM) and exciting dark matter (XDM) scenarios, respectively. Interestingly, with only weak kinetic mixing to hypercharge to mediate decays, the lifetime of excited states with delta < 2 m_e is longer than the age of the universe. The fractional relic abundance of these excited states depends on the temperature of kinetic decoupling, but can be appreciable. There could easily be other mechanisms for rapid decay, but the consequences of such long-lived states are intriguing. We find that CDMS constrains the fractional relic population of 100 keV states to be < 10^-2, for a 1 TeV WIMP with sigma_n = 10^-40 cm^2. Upcoming searches at CDMS, as well as xenon, silicon, and argon targets, can push this limit significantly lower. We also consider the possibility that the DAMA excitation occurs from a metastable state into the XDM state, which decays via e+e- emission, which allows lighter states to explain the INTEGRAL signal due to the small kinetic energies required. Such models yield dramatic signals from down-scattering, with spectra peaking at high energies, sometimes as high as 1 MeV, well outside the usual search windows. Such signals would be visible at future Ar and Si experiments, and may be visible at Ge and Xe experiments. We also consider other XDM models involving 500 keV metastable states, and find they can allow lighter WIMPs to explain INTEGRAL as well.", "keyphrases": ["wimp", "high energy", "excited state"]}
{"id": "1806.04763", "title": "Constraining strangeness in dense matter with GW170817", "abstract": "Particles with strangeness content are predicted to populate dense matter, modifying the equation of state of matter inside neutron stars as well as their structure and evolution. In this work, we show how the modeling of strangeness content in dense matter affects the properties of isolated neutrons stars and the tidal deformation in binary systems. For describing nucleonic and hyperonic stars we use the many-body forces model (MBF) at zero temperature, including the \u03d5 mesons for the description of repulsive hyperon-hyperon interactions. Hybrid stars are modeled using the MIT Bag Model with vector interaction (vMIT) in both Gibbs and Maxwell constructions, for different values of bag constant and vector interaction couplings. A parametrization with a Maxwell construction, which gives rise to third family of compact stars (twin stars), is also investigated. We calculate the tidal contribution that adds to the post-Newtonian point-particle corrections, the associated love number for sequences of stars of different composition (nucleonic, hyperonic, hybrid and twin stars), and determine signatures of the phase transition on the gravitational waves in the accumulated phase correction during the inspirals among different scenarios for binary systems. On the light of the recent results from GW170817 and the implications for the radius of \u223c1.4 M_\u2299 stars, our results show that hybrid stars can only exist if a phase transition takes place at low densities close to saturation.", "keyphrases": ["dense matter", "hyperon puzzle", "nearby pulsar"]}
{"id": "1710.05452", "title": "Swope Supernova Survey 2017a (SSS17a), the Optical Counterpart to a Gravitational Wave Source", "abstract": "On 2017 August 17, the Laser Interferometer Gravitational-wave Observatory (LIGO) and the Virgo interferometer detected gravitational waves emanating from a binary neutron star merger, GW170817. Nearly simultaneously, the Fermi and INTEGRAL telescopes detected a gamma-ray transient, GRB 170817A. 10.9 hours after the gravitational wave trigger, we discovered a transient and fading optical source, Swope Supernova Survey 2017a (SSS17a), coincident with GW170817. SSS17a is located in NGC 4993, an S0 galaxy at a distance of 40 megaparsecs. The precise location of GW170817 provides an opportunity to probe the nature of these cataclysmic events by combining electromagnetic and gravitational-wave observations.", "keyphrases": ["neutron star merger", "optical afterglow", "merger gw170817", "host galaxy"]}
{"id": "1607.00322", "title": "HATS-19b, HATS-20b, HATS-21b: Three Transiting Hot-Saturns Discovered by the HATSouth Survey", "abstract": "We report the discovery by the HATSouth exoplanet survey of three hot-Saturn transiting exoplanets: HATS-19b, HATS-20b, and HATS-21b. The planet host HATS-19 is a slightly evolved V = 13.0 G0 star with [Fe/H] = 0.240, a mass of 1.303 Msun, and a radius of 1.75 Rsun. HATS-19b is in an eccentric orbit (e = 0.30) around this star with an orbital period of 4.5697 days and has a mass of 0.427 Mjup and a highly inflated radius of 1.66 Rjup. The planet HATS-20b has a Saturn-like mass and radius of 0.273 Mjup and 0.776 Rjup respectively. It orbits the V = 13.8 G9V star HATS-20 (Ms = 0.910 Msun; Rs = 0.892 Rsun) with a period of 3.7993 days. Finally, HATS-21 is a V = 12.2 G4V star with [Fe/H] = 0.300, a mass of 1.080 Msun, and a radius of 1.021 Rsun. Its accompanying planet HATS-21b has a 3.5544-day orbital period, a mass of 0.332 Mjup, and a moderately inflated radius of 1.123 Rjup. With the addition of these three very different planets to the growing sample of hot-Saturns, we re-examine the relations between the observed giant planet radii, stellar irradiation, and host metallicity. We find a significant positive correlation between planet equilibrium temperature and radius, and a weak negative correlation between host metallicity and radius. To assess the relative influence of various physical parameters on observed planet radii, we train and fit models using Random Forest regression. We find that for hot-Saturns (0.1 < Mp < 0.5 Mjup), the planetary mass and equilibrium temperature play dominant roles in determining radii. For hot-Jupiters (0.5 < Mp < 2.0 Mjup), the most important parameter is equilibrium temperature alone. Finally, for irradiated higher-mass planets (Mp > 2.0 Mjup), we find that equilibrium temperature dominates in influence, with smaller contributions from planet mass and host metallicity.", "keyphrases": ["hats-21b", "exoplanet", "equilibrium temperature", "planetary mass"]}
{"id": "1803.02837", "title": "Primordial Black Holes from String Inflation", "abstract": "We present a single-field string inflationary model which allows for the generation of primordial black holes in the low mass region where they can account for a significant fraction of the dark matter abundance. The potential is typical of type IIB fibre inflation models and features a plateau at CMB scales and a near inflection point at large distance scales where the power spectrum is enhanced due to a period of ultra slow-roll. The tunability of the underlying parameters is guaranteed by scanning through the string landscape and their stability against quantum corrections is ensured by an effective shift symmetry.", "keyphrases": ["primordial black hole", "inflaton field", "string theory"]}
{"id": "0909.0001", "title": "Omniscopes: Large Area Telescope Arrays with only N log N Computational Cost", "abstract": "We show that the class of antenna layouts for telescope arrays allowing cheap analysis hardware (with correlator cost scaling as N log N rather than N^2 with the number of antennas N) is encouragingly large, including not only previously discussed rectangular grids but also arbitrary hierarchies of such grids, with arbitrary rotations and shears at each level. We show that all correlations for such a 2D array with an n-level hierarchy can be efficiently computed via a Fast Fourier Transform in not 2 but 2n dimensions. This can allow major correlator cost reductions for science applications requiring exquisite sensitivity at widely separated angular scales, for example 21cm tomography (where short baselines are needed to probe the cosmological signal and long baselines are needed for point source removal), helping enable future 21cm experiments with thousands or millions of cheap dipole-like antennas. Such hierarchical grids combine the angular resolution advantage of traditional array layouts with the cost advantage of a rectangular Fast Fourier Transform Telescope. We also describe an algorithm for how a subclass of hierarchical arrays can efficiently use rotation synthesis to produce global sky maps with minimal noise and a well-characterized synthesized beam.", "keyphrases": ["antenna", "grid", "fast fourier transform", "omniscope"]}
{"id": "1305.5422", "title": "Wide-Field InfraRed Survey Telescope-Astrophysics Focused Telescope Assets WFIRST-AFTA Final Report", "abstract": "The Astro2010 Decadal Survey recommended a Wide Field Infrared Survey Telescope (WFIRST) as its top priority for a new large space mission. As conceived by the decadal survey, WFIRST would carry out a dark energy science program, a microlensing program to determine the demographics of exoplanets, and a general observing program utilizing its ultra wide field. In October 2012, NASA chartered a Science Definition Team (SDT) to produce, in collaboration with the WFIRST Project Office at GSFC and the Program Office at JPL, a Design Reference Mission (DRM) for an implementation of WFIRST using one of the 2.4-m, Hubble-quality mirror assemblies recently made available to NASA. This DRM builds on the work of the earlier WFIRST SDT, reported by Green et al. (2012). The 2.4-m primary mirror enables a mission with greater sensitivity and higher angular resolution than the 1.3-m and 1.1-m designs considered previously, increasing both the science return of the primary surveys and the capabilities of WFIRST as a Guest Observer facility. The option of adding an on-axis, coronagraphic instrument would enable imaging and spectroscopic studies of planets around nearby stars. This document presents the final report of the SDT.", "keyphrases": ["telescope", "angular resolution", "planet", "space-based mission", "galaxy survey"]}
{"id": "1903.10136", "title": "The Virgo Overdensity Explained", "abstract": "We suggest that the Virgo Overdensity (VOD) of stars in the stellar halo is the result of a radial dwarf galaxy merger that we call the Virgo Radial Merger. Because the dwarf galaxy passed very near to the Galactic center, the debris has a large range of energies but nearly zero L_z angular momentum. The debris appears to extend from 5 to 50 kpc from the Sun in the Virgo region. We connect different parts of this merger debris to the Perpendicular and Parallel Streams (the Virgo Stellar Stream is associated with either or both of these streams), the Hercules-Aquila Cloud (HAC), and possibly the Eridanus Phoenix Overdensity (EriPhe). This radial merger can explain the majority of the observed moving groups of RR Lyrae and blue horizontal branch stars that have previously been identified in Virgo. This merger also produces debris in the Solar neighborhood similar to that identified as the Gaia-Enceladus or it Gaia-sausage merger. Orbits are provided for components of the Virgo Radial Merger progenitor and for debris that appears to be related to the Cocytos Stream, which was also recovered in the Virgo region.", "keyphrases": ["virgo overdensity", "vod", "debris", "hac", "solar neighborhood"]}
{"id": "1012.3460", "title": "Reconciling the local void with the CMB", "abstract": "In the standard cosmological model, the dimming of distant Type Ia supernovae is explained by invoking the existence of repulsive `dark energy' which is causing the Hubble expansion to accelerate. However this may be an artifact of interpreting the data in an (oversimplified) homogeneous model universe. In the simplest inhomogeneous model which fits the SNe Ia Hubble diagram without dark energy, we are located close to the centre of a void modelled by a Lema\u00edtre-Tolman-Bondi metric. It has been claimed that such models cannot fit the CMB and other cosmological data. This is however based on the assumption of a scale-free spectrum for the primordial density perturbation. An alternative physically motivated form for the spectrum enables a good fit to both SNe Ia (Constitution/Union2) and CMB (WMAP 7-yr) data, and to the locally measured Hubble parameter. Constraints from baryon acoustic oscillations and primordial nucleosynthesis are also satisfied.", "keyphrases": ["void", "dark energy", "such model", "density perturbation"]}
{"id": "2202.05867", "title": "Photodissociation and X-Ray Dominated Regions", "abstract": "The radiation from stars and active galactic nuclei (AGN) creates photodissociation regions (PDRs) and X-ray dominated regions (XDRs), where the chemistry or heating are dominated by far-ultraviolet (FUV) radiation or X-ray radiation, respectively. PDRs include a wide range of environments from the diffuse interstellar medium to dense star-forming regions. XDRs are found in the center of galaxies hosting AGN, in protostellar disks, and in the vicinity of X-ray binaries. In this review, we describe the dominant thermal, chemical, and radiation transfer processes in PDRs and XDRs, as well as a brief description of models and their use to analyze observations. We then present recent results from Milky Way, nearby extragalactic, and high-redshift observations. Several important results are: \u2219 Velocity resolved PDR lines reveal the kinematics of the neutral atomic gas and provide constraints on the stellar feedback process. Their interpretation is, however, in dispute as observations suggest a prominent role for stellar winds while they are much less important in theoretical models. \u2219 A significant fraction of molecular mass resides in CO-dark gas especially in low-metallicity/highly irradiated environments. \u2219 The CO ladder and CI/CII ratios can determine if FUV or X-rays dominate the ISM heating of extragalactic sources. \u2219 With ALMA, PDR and XDR tracers are now routinely detected on galactic scales over cosmic time. This makes it possible to link the star formation history of the Universe to the evolution of the physical and chemical properties of the gas.", "keyphrases": ["radiation", "star", "interstellar medium", "stellar feedback process", "photo-dissociation regions"]}
{"id": "1612.04493", "title": "Non-thermal particle acceleration in collisionless relativistic electron-proton reconnection", "abstract": "Magnetic reconnection in relativistic collisionless plasmas can accelerate particles and power high-energy emission in various astrophysical systems. Whereas most previous studies focused on relativistic reconnection in pair plasmas, less attention has been paid to electron-ion plasma reconnection, expected in black hole accretion flows and relativistic jets. We report a comprehensive particle-in-cell numerical investigation of reconnection in an electron-ion plasma, spanning a wide range of ambient ion magnetizations \u03c3_i, from the semirelativistic regime (ultrarelativistic electrons but nonrelativistic ions, 0.001<<\u03c3_i<<1) to the fully relativistic regime (both species are ultrarelativistic, \u03c3_i>>1). We investigate how the reconnection rate, electron and ion plasma flows, electric and magnetic field structures, electron/ion energy partitioning, and nonthermal particle acceleration depend on \u03c3_i. Our key findings are: (1) the reconnection rate is about 0.1 of the Alfvenic rate across all regimes; (2) electrons can form concentrated moderately relativistic outflows even in the semirelativistic, small-\u03c3_i regime; (3) while the released magnetic energy is partitioned equally between electrons and ions in the ultrarelativistic limit, the electron energy fraction declines gradually with decreased \u03c3_i and asymptotes to about 0.25 in the semirelativistic regime; (4) reconnection leads to efficient nonthermal electron acceleration with a \u03c3_i-dependent power-law index, p(\u03c3_i) \u2243const+0.7 \u03c3_i^-1/2. These findings are important for understanding black hole systems and lend support to semirelativistic reconnection models for powering nonthermal emission in blazar jets, offering a natural explanation for the spectral indices observed in these systems.", "keyphrases": ["particle acceleration", "high-energy emission", "relativistic reconnection", "electron-ion plasma"]}
{"id": "1907.02330", "title": "Reconstructing large-scale structure with neutral hydrogen surveys", "abstract": "Upcoming 21-cm intensity surveys will use the hyperfine transition in emission to map out neutral hydrogen in large volumes of the universe. Unfortunately, large spatial scales are completely contaminated with spectrally smooth astrophysical foregrounds which are orders of magnitude brighter than the signal. This contamination also leaks into smaller radial and angular modes to form a foreground wedge, further limiting the usefulness of 21-cm observations for different science cases, especially cross-correlations with tracers that have wide kernels in the radial direction. In this paper, we investigate reconstructing these modes within a forward modeling framework. Starting with an initial density field, a suitable bias parameterization and non-linear dynamics to model the observed 21-cm field, our reconstruction proceeds by combining the likelihood of a forward simulation to match the observations (under given modeling error and a data noise model) with the Gaussian prior on initial conditions and maximizing the obtained posterior. For redshifts z=2 and 4, we are able to reconstruct 21cm field with cross correlation, r_c > 0.8 on all scales for both our optimistic and pessimistic assumptions about foreground contamination and for different levels of thermal noise. The performance deteriorates slightly at z=6. The large-scale line-of-sight modes are reconstructed almost perfectly. We demonstrate how our method also reconstructs baryon acoustic oscillations, outperforming standard methods on all scales. We also describe how our reconstructed field can provide superb clustering redshift estimation at high redshifts, where it is otherwise extremely difficult to obtain dense spectroscopic samples, as well as open up cross-correlation opportunities with projected fields (e.g. lensing) which are restricted to modes transverse to the line of sight.", "keyphrases": ["neutral hydrogen survey", "large spatial scale", "density field", "high redshift", "area"]}
{"id": "0909.4699", "title": "Circular dichroism, magnetic knots and the spectropolarimetry of the Cosmic Microwave Background", "abstract": "When the last electron-photon scattering takes place in a magnetized environment, the degree of circular polarization of the outgoing radiation depends upon the magnetic field strength. After deriving the scattering matrix of the process, the generalized radiative transfer equations are deduced in the presence of the relativistic fluctuations of the geometry and for all the four brightness perturbations. The new system of equations is solved under the assumption that the incident radiation is not polarized. The induced V-mode polarization is analyzed both analytically and numerically. The corresponding angular power spectra are calculated and compared with the measured (or purported) values of the linear polarizations (i.e. E-mode and B-mode) as they arise in the concordance model and in its neighboring extensions. Possible connections between the V-mode polarization of the Cosmic Microwave background and the topological properties of the magnetic flux lines prior to equality are outlined and briefly explored in analogy with the physics of magnetized sun spots.", "keyphrases": ["cosmic microwave background", "circular polarization", "magnetic field", "brightness perturbation"]}
{"id": "1507.02685", "title": "SCORCH I: The Galaxy-Halo Connection in the First Billion Years", "abstract": "SCORCH (Simulations and Constructions of the Reionization of Cosmic Hydrogen) is a new project to study the Epoch of Reionization (EoR). In this first paper, we probe the connection between observed high-redshift galaxies and simulated dark matter halos to better understand the abundance and evolution of the primary source of ionizing radiation. High-resolution N-body simulations are run to quantify the abundance of dark matter halos as a function of mass M, accretion rate \u1e40, and redshift z. A new fit for the halo mass function dn/dM is \u2248 20% more accurate at the high-mass end where bright galaxies are expected to reside. A novel approach is used to fit the halo accretion rate function dn/d\u1e40 in terms of the halo mass function. Abundance matching against the observed galaxy luminosity function is used to estimate the luminosity-mass relation and the luminosity-accretion-rate relation. The inferred star formation efficiency is not monotonic with M nor \u1e40, but reaches a maximum value at a characteristic mass \u223c 2 \u00d7 10^11 M_\u2299 and a characteristic accretion rate \u223c 6 \u00d7 10^2M_\u2299/ yr at z \u2248 6. We find a universal EoR luminosity-accretion-rate relation and construct a fiducial model for the galaxy luminosity function. The Schechter parameters evolve such that \u03d5_\u22c6 decreases, M_\u22c6 is more positive (fainter), and \u03b1 is more negative (steeper) at higher redshifts. We forecast for the upcoming James Webb Space Telescope and show that with apparent magnitude limit m_ AB\u2248 31 (32), it can observe \u2273 11 (24) unlensed galaxies per square degree per unit redshift at least down to M_\u22c6 at z \u2272 13(14).", "keyphrases": ["reionization", "redshift", "scorch"]}
{"id": "1804.09679", "title": "The distinguishing signature of Magnetic Penrose Process", "abstract": "In this Letter, we wish to point out that the distinguishing feature of Magnetic Penrose process (MPP) is its super high efficiency exceeding 100% (which was established in mid 1980s for discrete particle accretion) of extraction of rotational energy of a rotating black hole electromagnetically for a magnetic field of milli Gauss order. Another similar process, which is also driven by electromagnetic field, is Blandford-Znajek mechanism (BZ), which could be envisaged as high magnetic field limit MPP as it requires threshold magnetic field of order 10^4G. Recent simulation studies of fully relativistic magnetohydrodynamic flows have borne out super high efficiency signature of the process for high magnetic field regime; viz BZ. We would like to make a clear prediction that similar simulation studies of MHD flows for low magnetic field regime, where BZ would be inoperative, would also have super efficiency.", "keyphrases": ["magnetic penrose process", "mpp", "high efficiency", "black hole", "magnetic field"]}
{"id": "1805.02699", "title": "Deep learning from 21-cm tomography of the Cosmic Dawn and Reionization", "abstract": "The 21-cm power spectrum (PS) has been shown to be a powerful discriminant of reionization and cosmic dawn astrophysical parameters. However, the 21-cm tomographic signal is highly non-Gaussian. Therefore there is additional information which is wasted if only the PS is used for parameter recovery. Here we showcase astrophysical parameter recovery directly from 21-cm images, using deep learning with convolutional neural networks (CNN). Using a database of 2D images taken from 10,000 21-cm lightcones (each generated from different cosmological initial conditions), we show that a CNN is able to recover parameters describing the first galaxies: (i) Tvir , their minimum host halo virial temperatures (or masses) capable of hosting efficient star formation; (ii) \u03b6 , their typical ionizing efficiencies; (iii) LX/SFR , their typical soft-band X-ray luminosity to star formation rate; and (iv) E0 , the minimum X-ray energy capable of escaping the galaxy into the IGM. For most of their allowed ranges, log Tvir and log LX/SFR are recovered with < 1 uncertainty, while \u03b6 and E0 are recovered within 10 results are roughly comparable to the accuracy obtained from Monte Carlo Markov Chain sampling of the PS with 21CMMC for the two mock observations analyzed previously, although we caution that we do not yet include noise and foreground contaminants in this proof-of-concept study.", "keyphrases": ["cosmic dawn", "convolutional neural network", "slice"]}
{"id": "1204.3781", "title": "Gravitational waves from color-magnetic `mountains' in neutron stars", "abstract": "Neutron stars may harbour the true ground state of matter in the form of strange quark matter. If present, this type of matter is expected to be a color superconductor, a consequence of quark pairing with respect to the color/flavor degrees of freedom. The stellar magnetic field threading the quark core becomes a color-magnetic admixture and, in the event that superconductivity is of type II, leads to the formation of color-magnetic vortices. In this Letter we show that the volume-averaged color-magnetic vortex tension force should naturally lead to a significant degree of non-axisymmetry in systems like radio pulsars. We show that gravitational radiation from such color-magnetic `mountains' in young pulsars like the Crab and Vela could be observable by the future Einstein Telescope, thus becoming a probe of paired quark matter in neutron stars. The detectability threshold can be pushed up toward the sensitivity level of Advanced LIGO if we invoke an interior magnetic field about a factor ten stronger than the surface polar field.", "keyphrases": ["neutron star", "color superconductor", "magnetic field", "pulsar"]}
{"id": "1609.09290", "title": "Sonneberg plate photometry for Boyajian's Star in two passbands", "abstract": "The F3 main sequence star KIC 8462852 (Boyajian's Star) showed deep (up to 20 mission. A 0.164 mag (16 the analysis of photographic plates from the Harvard Observatory. We have gathered an independent set of historic plates from Sonneberg Observatory, Germany, covering the years 1934-1995. With 861 magnitudes in B, and 397 magnitudes in V, we find the star to be of constant brightness within 0.03 mag per century (3 best 119 plates. Results are supported by data from Sternberg Observatory, Moscow, which show the star as constant between 1895 and 1995. The previously claimed century-long dimming is inconsistent with our results at the 5-sigma level, however the recently reported modest dimming of 3 not inconsistent with our data. We find no periodicities or shorter trends within our limits of 5 Oct 1978.", "keyphrases": ["star", "sonneberg observatory", "constant brightness"]}
{"id": "1311.6324", "title": "Non-standard Models and the Sociology of Cosmology", "abstract": "I review some theoretical ideas in cosmology different from the standard \"Big Bang\": the quasi-steady state model, the plasma cosmology model, non-cosmological redshifts, alternatives to non-baryonic dark matter and/or dark energy, and others. Cosmologists do not usually work within the framework of alternative cosmologies because they feel that these are not at present as competitive as the standard model. Certainly, they are not so developed, and they are not so developed because cosmologists do not work on them. It is a vicious circle. The fact that most cosmologists do not pay them any attention and only dedicate their research time to the standard model is to a great extent due to a sociological phenomenon (the \"snowball effect\" or \"groupthink\"). We might well wonder whether cosmology, our knowledge of the Universe as a whole, is a science like other fields of physics or a predominant ideology.", "keyphrases": ["cosmology", "cosmologist", "standard model", "sociological phenomenon", "snowball effect"]}
{"id": "1408.4788", "title": "CLASS: The Cosmology Large Angular Scale Surveyor", "abstract": "The Cosmology Large Angular Scale Surveyor (CLASS) is an experiment to measure the signature of a gravita-tional-wave background from inflation in the polarization of the cosmic microwave background (CMB). CLASS is a multi-frequency array of four telescopes operating from a high-altitude site in the Atacama Desert in Chile. CLASS will survey 70% of the sky in four frequency bands centered at 38, 93, 148, and 217 GHz, which are chosen to straddle the Galactic-foreground minimum while avoiding strong atmospheric emission lines. This broad frequency coverage ensures that CLASS can distinguish Galactic emission from the CMB. The sky fraction of the CLASS survey will allow the full shape of the primordial B-mode power spectrum to be characterized, including the signal from reionization at low \u2113. Its unique combination of large sky coverage, control of systematic errors, and high sensitivity will allow CLASS to measure or place upper limits on the tensor-to-scalar ratio at a level of r=0.01 and make a cosmic-variance-limited measurement of the optical depth to the surface of last scattering, \u03c4.", "keyphrases": ["cosmic microwave background", "array", "reionization", "upper limit"]}
{"id": "1108.0020", "title": "Bayesian Methods for Analysis and Adaptive Scheduling of Exoplanet Observations", "abstract": "We describe work in progress by a collaboration of astronomers and statisticians developing a suite of Bayesian data analysis tools for extrasolar planet (exoplanet) detection, planetary orbit estimation, and adaptive scheduling of observations. Our work addresses analysis of stellar reflex motion data, where a planet is detected by observing the \"wobble\" of its host star as it responds to the gravitational tug of the orbiting planet. Newtonian mechanics specifies an analytical model for the resulting time series, but it is strongly nonlinear, yielding complex, multimodal likelihood functions; it is even more complex when multiple planets are present. The parameter spaces range in size from few-dimensional to dozens of dimensions, depending on the number of planets in the system, and the type of motion measured (line-of-sight velocity, or position on the sky). Since orbits are periodic, Bayesian generalizations of periodogram methods facilitate the analysis. This relies on the model being linearly separable, enabling partial analytical marginalization, reducing the dimension of the parameter space. Subsequent analysis uses adaptive Markov chain Monte Carlo methods and adaptive importance sampling to perform the integrals required for both inference (planet detection and orbit measurement), and information-maximizing sequential design (for adaptive scheduling of observations). We present an overview of our current techniques and highlight directions being explored by ongoing research.", "keyphrases": ["adaptive scheduling", "planet", "velocity", "importance"]}
{"id": "1812.00847", "title": "Rescuing Quartic and Natural Inflation in the Palatini Formalism", "abstract": "When considered in the Palatini formalism, the Starobinsky model does not provide us with a mechanism for inflation due to the absence of a propagating scalar degree of freedom. By (non)\u2013minimally coupling scalar fields to the Starobinsky model in the Palatini formalism we can in principle describe the inflationary epoch. In this article, we focus on the minimally coupled quartic and natural inflation models. Both theories are excluded in their simplest realization since they predict values for the inflationary observables that are outside the limits set by the Planck data. However, with the addition of the R^2 term and the use of the Palatini formalism, we show that these models can be rendered viable.", "keyphrases": ["palatini formalism", "inflationary model", "non-minimal coupling", "gravity"]}
{"id": "1801.02778", "title": "Statistically Anisotropic Tensor Modes from Inflation", "abstract": "We consider the inflationary universe with a spectator scalar field coupled to a U(1) gauge field and calculate curvature perturbation and gravitational waves (GWs). We find that the sourced GWs can be larger than the one from vacuum fluctuation and they are statistically anisotropic as well as linearly polarized. The GW power spectrum acquires higher multipole moments as \ud835\udcab_h \u221d (1-cos^2\u03b8+cos^4\u03b8-cos^6\u03b8) irrespective of the model parameters.", "keyphrases": ["scalar field", "gravitational wave", "anisotropic inflation"]}
{"id": "1102.1060", "title": "Polycyclic aromatic hydrocarbons in the dwarf galaxy IC 10", "abstract": "Infrared observations from the Spitzer Space Telescope archive are used to study the dust component of the interstellar medium in the IC 10 irregular galaxy. Dust distribution in the galaxy is compared to the distributions of H\u03b1 and [SII] emission, neutral hydrogen and CO clouds, and ionizing radiation sources. The distribution of polycyclic aromatic hydrocarbons (PAH) in the galaxy is shown to be highly non-uniform with the mass fraction of these particles in the total dust mass reaching 4 regions and correlate well with atomic and molecular gas. This pattern suggests that PAHs form in the dense interstellar gas. We propose that the significant decrease of the PAH abundance at low metallicity is observed not only globally (at the level of entire galaxies), but also locally (at least, at the level of individual HII regions). We compare the distribution of the PAH mass fraction to the distribution of high-velocity features, that we have detected earlier in wings of H\u03b1 and SII lines, over the entire available galaxy area. No conclusive evidence for shock destruction of PAHs in the IC 10 galaxy could be found.", "keyphrases": ["aromatic hydrocarbon", "galaxy", "mass fraction", "metallicity"]}
{"id": "1405.1447", "title": "Understanding higher-order nonlocal halo bias at large scales by combining the power spectrum with the bispectrum", "abstract": "Understanding the relation between underlying matter distribution and biased tracers such as galaxy or dark matter halo is essential to extract cosmological information from ongoing or future galaxy redshift surveys. At sufficiently large scales such as the BAO scale, a standard approach for the bias problem on the basis of the perturbation theory (PT) is to assume the `local bias' model in which the density field of biased tracers is deterministically expanded in terms of matter density field at the same position. The higher-order bias parameters are then determined by combining the power spectrum with higher-order statistics such as the bispectrum. As is pointed out by recent studies, however, nonlinear gravitational evolution naturally induces nonlocal bias terms even if initially starting only with purely local bias. As a matter of fact, previous works showed that the second-order nonlocal bias term, which corresponds to the gravitational tidal field, is important to explain the characteristic scale-dependence of the bispectrum. In this paper we extend the nonlocal bias term up to third order, and investigate whether the PT-based model including nonlocal bias terms can simultaneously explain the power spectrum and the bispectrum of simulated halos in N-body simulations. We show that the power spectrum, including density and momentum, and the bispectrum between halo and matter in N-body simulations can be simultaneously well explained by the model including up to third-order nonlocal bias terms up to k 0.1h/Mpc. Also, the results seem in a good agreement with theoretical predictions of a simple coevolution picture, although the agreement is not perfect. These demonstration clearly shows a failure of the local bias model even at such large scales, and we conclude that nonlocal bias terms should be consistently included in order to model statistics of halos. [abridged]", "keyphrases": ["bispectrum", "biased tracer", "galaxy", "matter halo", "perturbation theory"]}
{"id": "2002.11707", "title": "Can Late Dark Energy Transitions Raise the Hubble constant?", "abstract": "Late times dark energy transitions at redshifts z \u226a 0.1 can raise the predicted value of the Hubble constant to the SH0ES value, 74.03\u00b1 1.42 (km s^-1 Mpc^-1) or more, while providing an equally good fit as \u039bCDM at 67.73 \u00b1 0.41 to higher redshift data, in particular from the cosmic microwave background and baryon acoustic oscillations. These models however do not fully resolve the true source of tension between the distance ladder and high redshift observations: the local calibration of supernovae luminosities well out into the Hubble flow. When tested in this manner by transferring the SH0ES calibration to the Pantheon supernovae dataset, the ability of such transitions to raise the Hubble constant is reduced to 69.17 \u00b1 1.09. Such an analysis should also be used when testing any dynamical dark energy model which can produce similarly fine features in redshift or local void models.", "keyphrases": ["dark energy", "energy transition", "late time", "baryon acoustic oscillation", "gravitational theory"]}
{"id": "2112.13198", "title": "Field sources for Simpson-Visser space-times", "abstract": "Simpson-Visser (SV) space-times are the simplest globally regular modifications of the Schwarzschild, Reissner-Nordstrom and other blak-hole solutions of general relativity. They smoothly interpolate between these black holes and traversable wormholes. After a brief presentation of the Schwarzschild-like and Reissner-Nordstrom-like SV geometries, including their Carter-Penrose diagrams, we show that any static, spherically symmetric SV metric can be obtained as an exact solution to the Einstein field equations sourced by a combination of a minimally coupled phantom scalar field with a nonzero potential V(\u03d5) and a magnetic field in the framework of nonlinear electrodynamics with the Lagrangian \u2112(\u2131), \u2131 = F_\u03bc\u03bd F^\u03bc\u03bd (in standard notations). Explicit forms of V(\u03d5) and \u2112(\u2131) are presented for the cases of Schwarzschild-like and Reissner-Nordstrom-like SV metrics.", "keyphrases": ["static", "scalar field", "electrodynamic", "field source"]}
{"id": "0802.4452", "title": "Analytic calculations of the spectra of ultra-high energy cosmic ray nuclei. I. The case of CMB radiation", "abstract": "We present a systematic study of different methods for the analytic calculation of ultra-high energy nuclei diffuse spectra. Nuclei propagating in the intergalactic space are photo-disintegrated and decrease their Lorentz factor due to the interaction with cosmic microwave background and extragalactic background light. We calculate the evolution trajectories in the backward time, that describe how atomic mass number A and Lorentz factor \u0393 change with redshift z. Three methods of spectra calculations are investigated and compared: (i) trajectory method, (ii) kinetic equation combined with trajectory calculations and (iii) coupled kinetic equations. We believe that these three methods exhaust at least the principal possibilities for any analytic solution of the problem. In the most straightforward method (i) only trajectory calculations are used to connect the observed nuclei flux with the production rate of primary (accelerated) nuclei A_0. In the second method (ii) the flux (space density) of primary nuclei, and secondary nuclei and protons are calculated with the help of kinetic equation and trajectories are used only to determine the generation rates of these nuclei. The third method (iii) consists in solving the complete set of coupled kinetic equations, written starting with primary nuclei A_0, then for A_0-1 etc down to the A of interest. The solution of the preceding equation gives the generation rate for the one which follows. An important element of the calculations for all methods is the systematic use of Lorentz factor instead of energy. We consider here the interaction of nuclei only with the cosmic microwave background, this case is particularly suitable for understanding the physical results.", "keyphrases": ["analytic calculation", "high energy", "astrophysical background", "observed spectrum"]}
{"id": "0904.0472", "title": "Generalised DBI-Quintessence", "abstract": "We investigate the phase space of a quintessence theory governed by a generalised version of the DBI action, using a combination of numeric and analytic methods. The additional degrees of freedom lead to a vastly richer phase space structure, where the field covers the full equation of state parameter space; -1 \u2264\u03c9\u2264 1. We find many non-trivial solution curves to the equations of motion which indicate that DBI quintessence is an interesting candidate for a viable k-essence model.", "keyphrases": ["k-essence", "dbi-essence", "hessence"]}
{"id": "1302.6882", "title": "Selecting microscopic Equations of State", "abstract": "We compare a set of equations of state derived within microscopic many-body approaches, and study their predictions as far as phenomenological data on nuclei from heavy ion collisions, and astrophysical observations on neutron stars are concerned. We find that all the data, taken together, put strong constraints not easy to be fulfilled accurately. However, no major discrepancies are found among the selected equations of state and with respect to the data. The results provide an estimate of the uncertainty on the theoretical prediction at a microscopic level of the nuclear equation of state.", "keyphrases": ["large masse", "particle density", "nucleonic degree"]}
{"id": "1807.11742", "title": "Fifth force constraints from galaxy warps", "abstract": "Intra-galaxy signals contain a wealth of information on fundamental physics, both the dark sector and the nature of gravity. While so far largely unexplored, such probes are set to rise dramatically in importance as upcoming surveys provide data of unprecedented quantity and quality on galaxy structure and dynamics. In this paper, we use warping of stellar disks to test the chameleon- or symmetron-screened fifth forces which generically arise when new fields couple to matter. We take r-band images of mostly late-type galaxies from the Nasa Sloan Atlas and develop an automated algorithm to quantify the degree of U-shaped warping they exhibit. We then forward-model the warp signal as a function of fifth-force strength \u0394 G/G_N and range \u03bb_C, and the gravitational environments and internal properties of the galaxies, including full propagation of the non-Gaussian uncertainties. Convolving this fifth-force likelihood function with a Gaussian describing astrophysical and observational noise and then constraining \u0394 G/G_N and \u03bb_C by Markov Chain Monte Carlo, we find the overall likelihood to be significant increased (\u0394log(\u2112) \u2243 20) by adding a screened fifth force with \u03bb_C \u2243 2 Mpc, \u0394 G/G_N \u2243 0.01. The variation of \u0394log(\u2112) with \u03bb_C is quantitatively as expected from the correlation of the magnitude of the fifth-force field with the force's range, and a similar model without screening achieves no increase in likelihood over the General Relativistic case \u0394 G=0. Although these results are in good agreement with a previous analysis of the same model using offsets between galaxies' stellar and gas mass centroids (Desmond et al. 2018), we caution that the effects of confounding baryonic and dark matter physics must be thoroughly investigated for the results of the inference to be unambiguous.", "keyphrases": ["galaxy", "offset", "fifth force"]}
{"id": "0910.0811", "title": "Exoplanet Chemistry", "abstract": "The terrestrial and gas-giant planets in our solar system may represent some prototypes for planets around other stars; the exoplanets because most stars have similar overall elemental abundances as our sun. The solar system planets represent at least four chemical planet types, depending on the phases that make them: Terrestrial-like planets made of rock (metal plus silicates), Plutonian planets made of rock and ice, Neptunian giant planets of rocky, icy with low H and He contents, and Jovian gas-giant planets of rocky, icy planets with near-solar H and He contents. The planetary compositions are linked to the chemical fractionation in the planetary accretion disks. Chemical tracers of these fractionations are described. Many known exoplanets are gas-giant planets with up to several Jupiter-masses and their atmospheric chemistry is compared to that of brown dwarfs. Exoplanets in close orbits around their host stars may resemble hot brown dwarfs (L-dwarfs). Planets receiving less radiation form their host may compare more to the methane-rich T dwarfs. The cloud layers resulting from condensation of oxides, metal, sulfides, and salts in these hot and cool gas giant planets and their chemical tracers are described.", "keyphrases": ["chemistry", "composition", "atmospheric chemistry", "exoplanet"]}
{"id": "1606.06627", "title": "Relativistic Stars in Beyond Horndeski Theories", "abstract": "This work studies relativistic stars in beyond Horndeski scalar-tensor theories that exhibit a breaking of the Vainshtein mechanism inside matter, focusing on a model based on the quartic beyond Horndeski Lagrangian. We self-consistently derive the scalar field profile for static spherically symmetric objects in asymptotically de Sitter space-time and show that the Vainshtein breaking branch of the solutions is the physical branch thereby resolving several ambiguities with non-relativistic frameworks. The geometry outside the star is shown to be exactly Schwarzschild-de Sitter and therefore the PPN parameter \u03b2_ PPN=1, confirming that the external screening works at the post-Newtonian level. The Tolman-Oppenheimer-Volkoff (TOV) equations are derived and a new lower bound on the Vainshtein breaking parameter \u03a5_1>-4/9 is found by requiring the existence of static spherically symmetric stars. Focusing on the unconstrained case where \u03a5_1<0, we numerically solve the TOV equations for polytropic and realistic equations of state and find stars with larger radii at fixed mass. Furthermore, the maximum mass can increase dramatically and stars with masses in excess of 3M_\u2299 can be found for relatively small values of the Vainshtein breaking parameter. We re-examine white dwarf stars and show that post-Newtonian corrections are important in beyond Horndeski theories and therefore the bounds coming from previous analyses should be revisited.", "keyphrases": ["horndeski theory", "scalar-tensor theory", "post-newtonian correction", "relativistic star", "gravity"]}
{"id": "2101.12471", "title": "Effective metric outside bootstrapped Newtonian sources", "abstract": "We determine the complete space-time metric from the bootstrapped Newtonian potential generated by a static spherically symmetric source in the surrounding vacuum. This metric contains post-Newtonian parameters which can be further used to constrain the complete underlying dynamical theory. For values of the post-Newtonian parameters within experimental bounds, the reconstructed metric appears very close to the Schwarzschild solution of General Relativity in the whole region outside the event horizon. The latter is however larger in size for the same value of the mass compared to the Schwarzschild case.", "keyphrases": ["bootstrapped newtonian potential", "vacuum", "general relativity"]}
{"id": "2009.14157", "title": "Core-Collapse Supernova Explosion Theory", "abstract": "Most supernova explosions accompany the death of a massive star. These explosions give birth to neutron stars and black holes and eject solar masses of heavy elements. However, determining the mechanism of explosion has been a half-century journey of great complexity. In this paper, we present our perspective of the status of this theoretical quest and the physics and astrophysics upon which its resolution seems to depend. The delayed neutrino-heating mechanism is emerging as a robust solution, but there remain many issues to address, not the least of which involves the chaos of the dynamics, before victory can unambiguously be declared. It is impossible to review in detail all aspects of this multi-faceted, more-than-half-century-long theoretical quest. Rather, we here map out the major ingredients of explosion and the emerging systematics of the observables with progenitor mass, as we currently see them. Our discussion will of necessity be speculative in parts, and many of the ideas may not survive future scrutiny. Some statements may be viewed as informed predictions concerning the numerous observables that rightly exercise astronomers witnessing and diagnosing the supernova Universe. Importantly, the same explosion in the inside, by the same mechanism, can look very different in photons, depending upon the mass and radius of the star upon explosion. A 10^51-erg (one \"Bethe\") explosion of a red supergiant with a massive hydrogen-rich envelope, a diminished hydrogen envelope, no hydrogen envelope, and, perhaps, no hydrogen envelope or helium shell all look very different, yet might have the same core and explosion evolution.", "keyphrases": ["explosion", "star", "black hole", "core-collapse supernovae"]}
{"id": "1308.6186", "title": "Cosmological Parameter Estimation with Large Scale Structure Observations", "abstract": "We estimate the sensitivity of future galaxy surveys to cosmological parameters, using the redshift dependent angular power spectra of galaxy number counts, C_\u2113(z_1,z_2), calculated with all relativistic corrections at first order in perturbation theory. We pay special attention to the redshift dependence of the non-linearity scale and present Fisher matrix forecasts for Euclid-like and DES-like galaxy surveys. We compare the standard P(k) analysis with the new C_\u2113(z_1,z_2) method. We show that for surveys with photometric redshifts the new analysis performs significantly better than the P(k) analysis. For spectroscopic redshifts, however, the large number of redshift bins which would be needed to fully profit from the redshift information, is severely limited by shot noise. We also identify surveys which can measure the lensing contribution and we study the monopole, C_0(z_1,z_2).", "keyphrases": ["large scale", "galaxy survey", "angular power spectra", "cosmological parameter"]}
{"id": "1709.02473", "title": "Bispectrum Supersample Covariance", "abstract": "Modes with wavelengths larger than the survey window can have significant impact on the covariance within the survey window. The supersample covariance has been recognized as an important source of covariance for the power spectrum on small scales, and it can potentially be important for the bispectrum covariance as well. In this paper, using the response function formalism, we model the supersample covariance contributions to the bispectrum covariance and the cross covariance between the power spectrum and the bispectrum. The supersample covariances due to the long wavelength density and tidal perturbations are investigated, and the tidal contribution is a few orders of magnitude smaller than the density one because in configuration space the bispectrum estimator involves angular averaging and the tidal response function is anisotropic. The impact of the super-survey modes is quantified using numerical measurements with periodic box and subbox setups. For the matter bispectrum, the ratio between the supersample covariance correction and the small scale covariance, which can be computed using a periodic box, is roughly an order of magnitude smaller than that for the matter power spectrum. This is because for the bispectrum, the small scale non-Gaussian covariance is significantly larger than that for the power spectrum. For the cross covariance, the supersample covariance is as important as for the power spectrum covariance. The supersample covariance prediction with the halo model response function is in good agreement with numerical results.", "keyphrases": ["covariance", "super-sample mode", "ssc"]}
{"id": "2010.15795", "title": "Tidal Love Numbers of Kerr Black Holes", "abstract": "The open question of whether a Kerr black hole can become tidally deformed or not has profound implications for fundamental physics and gravitational-wave astronomy. We consider a Kerr black hole embedded in a weak and slowly varying, but otherwise arbitrary, multipolar tidal environment. By solving the static Teukolsky equation for the gauge-invariant Weyl scalar \u03c8_0, and by reconstructing the corresponding metric perturbation in an ingoing radiation gauge, for a general harmonic index \u2113, we compute the linear response of a Kerr black hole to the tidal field. This linear response vanishes identically for a Schwarzschild black hole and for an axisymmetric perturbation of a spinning black hole. For a nonaxisymmetric perturbation of a spinning black hole, however, the linear response does not vanish, and it contributes to the Geroch-Hansen multipole moments of the perturbed Kerr geometry. As an application, we compute explicitly the rotational black hole tidal Love numbers that couple the induced quadrupole moments to the quadrupolar tidal fields, to linear order in the black hole spin, and we introduce the corresponding notion of tidal Love tensor. Finally, we show that those induced quadrupole moments are closely related to the well-known physical phenomenon of tidal torquing of a spinning body interacting with a tidal gravitational environment.", "keyphrases": ["love number", "black hole", "tidal field"]}
{"id": "1809.07409", "title": "New Scalar Field Quartessence", "abstract": "We propose a cosmological scenario involving a scalar field, \u03c6, that is a source of Dark Matter as well as of Dark Energy. Besides \u03c6, the Lagrangian of the field theory envisaged in our scenario contains a second field \u03c7, for simplicity assumed to be a scalar, too. For fixed values of \u03c7, the potential term decays exponentially at large positive values of \u03c6. While \u03c6 is not coupled to Standard Model fields, \u03c7 is assumed to be coupled to them, and the Green functions of \u03c7 depend on the cosmological redshift in the expanding universe. We assume that the term in the Lagrangian coupling \u03c7 to \u03c6 is such that, at redshifts z larger than some critical redshift z_c, \u03c6 is trapped near \u03c6=0, and oscillations of \u03c6 about \u03c6=0 describing massive scalar particles give rise to Dark Matter. At redshifts below z_c, the field \u03c6 is no longer trapped near the origin and starts to `roll' towards large field values. A homogenous component of \u03c6 emerges that acts as Dark Energy. Within over-dense regions, such as galaxies and galaxy clusters, the redshifting of \u03c7 stops, and \u03c6 therefore remains trapped near \u03c6=0 as long as z_c is smaller than the redshift when structures on galactic scales decouple from the Hubble flow. Thus, at the present time, \u03c6 describes both Dark Energy and Dark Matter.", "keyphrases": ["scalar field", "dark matter", "dark energy"]}
{"id": "1502.07301", "title": "Cosmic Strings and the Origin of Globular Clusters", "abstract": "We hypothesize that cosmic string loops are the seeds about which globular clusters accrete. Fixing the cosmic string tension by demanding that the peak in the distribution of masses of objects accreting onto string loops agrees with the peak in the observed mass distribution of globular clusters in our Milky Way galaxy, we then compute the expected number density and mass function of globular clusters, and compare with observations. Our hypothesis naturally explains why globular clusters are the oldest and most dense objects in a galaxy, and why they are found in the halo of the galaxy.", "keyphrases": ["globular cluster", "cosmic string loop", "mass distribution"]}
{"id": "1101.0026", "title": "An Ignoble Approach to Large Field Inflation", "abstract": "We study an inflationary model developed by Kaloper and Sorbo, in which the inflaton is an axion with a sub-Planckian decay constant, whose potential is generated by mixing with a topological 4-form field strength. This gives a 4d construction of \"axion monodromy inflation\": the axion winds many times over the course of inflation and draws energy from the 4-form. The classical theory is equivalent to chaotic inflation with a quadratic inflaton potential. Such models can produce \"high scale\" inflation driven by energy densities of the order of (10^16 GeV)^4, which produces primordial gravitational waves potentially accessible to CMB polarization experiments. We analyze the possible corrections to this scenario from the standpoint of 4d effective field theory, identifying the physics which potentially suppresses dangerous corrections to the slow-roll potential. This yields a constraint relation between the axion decay constant, the inflaton mass, and the 4-form charge. We show how these models can evade the fundamental constraints which typically make high-scale inflation difficult to realize. Specifically, the moduli coupling to the axion-four-form sector must have masses higher than the inflationary Hubble scale (10^14 GeV). There are also constraints from states that become light due to multiple windings of the axion, as happens in explicit string theory constructions of this scenario. Further, such models generally have a quantum-mechanical \"tunneling mode\" in which the axion jumps between windings, which must be suppressed. Finally, we outline possible observational signatures.", "keyphrases": ["axion", "effective field theory", "fundamental constraint", "high-scale inflation", "flux"]}
{"id": "1012.4238", "title": "Higgs G-inflation", "abstract": "A new class of inflation models within the context of G-inflation is proposed, in which the standard model Higgs boson can act as an inflaton thanks to Galileon-like non-linear derivative interaction. The generated primordial density perturbation is shown to be consistent with the present observational data. We also make a general discussion on potential-driven G-inflation models, and find a new consistency relation between the tensor-to-scalar ratio r and the tensor spectral index n_T, r = -32 \u221a(6)n_T / 9, which is crucial in discriminating the present models from standard inflation with a canonical kinetic term.", "keyphrases": ["g-inflation", "new class", "derivative interaction", "tensor-to-scalar ratio"]}
{"id": "1902.08820", "title": "Variations of Infinite Derivative Modified Gravity", "abstract": "We consider nonlocal modified Einstein gravity without matter, where nonlocal term has the form P(R) F() Q(R). For this model, in this paper we give the derivation of the equations of motion in detail. This is not an easy task and presented derivation should be useful to a researcher who wants to investigate nonlocal gravity. Also, we present the second variation of the related Einstein-Hilbert modified action and basics of gravity perturbations.", "keyphrases": ["cosmological constant", "differentiable function", "ricci scalar"]}
{"id": "1407.4693", "title": "A cluster finding algorithm based on the multiband identification of red sequence galaxies", "abstract": "We present a new algorithm, CAMIRA, to identify clusters of galaxies in wide-field imaging survey data. We base our algorithm on the stellar population synthesis model to predict colours of red-sequence galaxies at a given redshift for an arbitrary set of bandpass filters, with additional calibration using a sample of spectroscopic galaxies to improve the accuracy of the model prediction. We run the algorithm on 11960 deg^2 of imaging data from the Sloan Digital Sky Survey (SDSS) Data Release 8 to construct a catalogue of 71743 clusters in the redshift range 0.1<z<0.6 with richness after correcting for the incompleteness of the richness estimate greater than 20. We cross-match the cluster catalogue with external cluster catalogues to find that our photometric cluster redshift estimates are accurate with low bias and scatter, and that the corrected richness correlates well with X-ray luminosities and temperatures. We use the publicly available Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS) shear catalogue to calibrate the mass-richness relation from stacked weak lensing analysis. Stacked weak lensing signals are detected significantly for 8 subsamples of the SDSS clusters divided by redshift and richness bins, which are then compared with model predictions including miscentring effects to constrain mean halo masses of individual bins. We find the richness correlates well with the halo mass, such that the corrected richness limit of 20 corresponds to the cluster virial mass limit of about 1 \u00d710^14 M_Sun/h for the SDSS DR8 cluster sample.", "keyphrases": ["cluster", "red-sequence galaxy", "redshift range"]}
{"id": "1412.0145", "title": "Observational constraints to a unified cosmological model", "abstract": "We propose a phenomenological unified model for dark matter and dark energy based on an equation of state parameter w that scales with the arctan of the redshift. The free parameters of the model are three constants: \u03a9_b0, \u03b1 and \u03b2. Parameter \u03b1 dictates the transition rate between the matter dominated era and the accelerated expansion period. The ratio \u03b2 / \u03b1 gives the redshift of the equivalence between both regimes. Cosmological parameters are fixed by observational data from Primordial Nucleosynthesis (PN), Supernovae of the type Ia (SNIa), Gamma-Ray Bursts (GRB) and Baryon Acoustic Oscillations (BAO). The calibration of the 138 GRBs events is performed using the 580 SNIa of the Union2.1 data set and a new set of 79 high-redshift GRBs is obtained. The various sets of data are used in different combinations to constraint the parameters through statistical analysis. The unified model is compared to the \u039bCDM model and their differences are emphasized.", "keyphrases": ["phenomenological unified model", "cosmological parameter", "supernovae"]}
{"id": "1805.07165", "title": "The universal rotation curve of low surface brightness galaxies IV: the interrelation between dark and luminous matter", "abstract": "We investigate the properties of the baryonic and the dark matter components in low surface brightness (LSB) disc galaxies, with central surface brightness in the B band \u03bc_0 \u2265 23 mag arcsec^-2. The sample is composed by 72 objects, whose rotation curves show an orderly trend reflecting the idea of a universal rotation curve (URC) similar to that found in the local high surface brightness (HSB) spirals in previous works. This curve relies on the mass modelling of the coadded rotation curves, involving the contribution from an exponential stellar disc and a Burkert cored dark matter halo. We find that the dark matter is dominant especially within the smallest and less luminous LSB galaxies. Dark matter halos have a central surface density \u03a3 _0 \u223c 100 M_\u2299 pc^-2, similar to galaxies of different Hubble types and luminosities. We find various scaling relations among the LSBs structural properties which turn out to be similar but not identical to what has been found in HSB spirals. In addition, the investigation of these objects calls for the introduction of a new luminous parameter, the stellar compactness C_* (analogously to a recent work by Karukes & Salucci), alongside with the optical radius and the optical velocity in order to reproduce the URC. Furthermore, a mysterious entanglement between the properties of the luminous and the dark matter emerges.", "keyphrases": ["low surface brightness", "galaxy", "dark matter"]}
{"id": "1001.0010", "title": "Minimal Inflation", "abstract": "Using the universal X superfield that measures in the UV the violation of conformal invariance we build up a model of multifield inflation. The underlying dynamics is the one controlling the natural flow of this field in the IR to the Goldstino superfield once SUSY is broken. We show that flat directions satisfying the slow roll conditions exist only if R-symmetry is broken. Naturalness of our model leads to scales of SUSY breaking of the order of 10^11-13 Gev, a nearly scale-invariant spectrum of the initial perturbations and negligible gravitational waves. We obtain that the inflaton field is lighter than the gravitino by an amount determined by the slow roll parameter eta. The existence of slow-roll conditions is directly linked to the values of supersymmetry and R-symmetry breaking scales. We make cosmological predictions of our model and compare them to current data.", "keyphrases": ["universe", "superfield", "goldstino", "minimal-inflation", "low energy"]}
{"id": "1304.3903", "title": "When Matter Matters", "abstract": "We study a recently proposed scenario for the early universe: Subluminal Galilean Genesis. We prove that without any other matter present in the spatially flat Friedmann universe, the perturbations of the Galileon scalar field propagate with a speed at most equal to the speed of light. This proof applies to all cosmological solutions \u2013 to the whole phase space. However, in a more realistic situation, when one includes any matter which is not directly coupled to the Galileon, there always exists a region of phase space where these perturbations propagate superluminally, indeed with arbitrarily high speed. We illustrate our analytic proof with numerical computations. We discuss the implications of this result for the possible UV completion of the model.", "keyphrases": ["galileon", "phase space", "high speed"]}
{"id": "2102.03780", "title": "CNN Architecture Comparison for Radio Galaxy Classification", "abstract": "The morphological classification of radio sources is important to gain a full understanding of galaxy evolution processes and their relation with local environmental properties. Furthermore, the complex nature of the problem, its appeal for citizen scientists and the large data rates generated by existing and upcoming radio telescopes combine to make the morphological classification of radio sources an ideal test case for the application of machine learning techniques. One approach that has shown great promise recently is Convolutional Neural Networks (CNNs). Literature, however, lacks two major things when it comes to CNNs and radio galaxy morphological classification. Firstly, a proper analysis of whether overfitting occurs when training CNNs to perform radio galaxy morphological classification using a small curated training set is needed. Secondly, a good comparative study regarding the practical applicability of the CNN architectures in literature is required. Both of these shortcomings are addressed in this paper. Multiple performance metrics are used for the latter comparative study, such as inference time, model complexity, computational complexity and mean per class accuracy. As part of this study we also investigate the effect that receptive field, stride length and coverage has on recognition performance. For the sake of completeness, we also investigate the recognition performance gains that we can obtain by employing classification ensembles. A ranking system based upon recognition and computational performance is proposed. MCRGNet, Radio Galaxy Zoo and ConvXpress (novel classifier) are the architectures that best balance computational requirements with recognition performance.", "keyphrases": ["recognition performance", "radio galaxy zoo", "computational requirement", "cnns"]}
{"id": "1504.03610", "title": "Two-portal Dark Matter", "abstract": "We propose a renormalizable dark matter model in which a fermionic dark matter (DM) candidate communicates with the standard model particles through two distinct portals: Higgs and vector portals. The dark sector is charged under a U(1)' gauge symmetry while the standard model has a leptophobic interaction with the dark vector boson. The leading contribution of DM-nucleon elastic scattering cross section begins at one-loop level. The model meets all the constraints imposed by direct detection experiments provided by LUX and XENON100, observed relic abundance according to WMAP and Planck, and the invisible Higgs decay width measured at the LHC. It turns out that the dark matter mass in the viable parameter space can take values from a few GeV up to 1 TeV. This is a new feature which is absent in the models with only one portal. In addition, we can find in the constrained regions of the parameter space a DM mass of \u223c 34 GeV annihilating into b quark pair, which explains the Fermi-LAT gamma-ray excess.", "keyphrases": ["dark matter", "standard model", "dark sector"]}
{"id": "1204.3433", "title": "Dynamics of a lattice Universe", "abstract": "We find a solution to Einstein field equations for a regular toroidal lattice of size L with equal masses M at the centre of each cell; this solution is exact at order M/L. Such a solution is convenient to study the dynamics of an assembly of galaxy-like objects. We find that the solution is expanding (or contracting) in exactly the same way as the solution of a Friedman-Lema\u00eetre-Robertson-Walker Universe with dust having the same average density as our model. This points towards the absence of backreaction in a Universe filled with an infinite number of objects, and this validates the fluid approximation, as far as dynamics is concerned, and at the level of approximation considered in this work.", "keyphrases": ["universe", "einstein field equation", "toroidal lattice"]}
{"id": "1407.7979", "title": "Large-Scale Structure Observables in General Relativity", "abstract": "We review recent studies that rigorously define several key observables of the large-scale structure of the Universe in a general relativistic context. Specifically, we consider i) redshift perturbation of cosmic clock events; ii) distortion of cosmic rulers, including weak lensing shear and magnification; iii) observed number density of tracers of the large-scale structure. We provide covariant and gauge-invariant expressions of these observables. Our expressions are given for a linearly perturbed flat Friedmann-Robertson-Walker metric including scalar, vector, and tensor metric perturbations. While we restrict ourselves to linear order in perturbation theory, the approach can be straightforwardly generalized to higher order.", "keyphrases": ["redshift-space distortion", "matter density fluctuation", "velocity effect", "magnification bias"]}
{"id": "1308.1019", "title": "Variable gravity Universe", "abstract": "For variable gravity models the strength of gravity, as measured by Newton's \u201cconstant\u201d or the Planck mass, depends on the value of a scalar field, the cosmon. We discuss two simple four-parameter models with a quadratic or constant cosmon potential. They are compatible with all presently available cosmological observations, including inflation. The inflaton and the scalar field of quintessence are the same cosmon field. Dark Energy constitutes a small, almost constant fraction of the energy density during the radiation and matter dominated epochs (Early Dark Energy). In the present epoch we witness a transition to a new Dark Energy dominated epoch. Our models are free of a big bang singularity. The stability of solutions generates an arrow of time. Our picture of the Universe is unusual, with a shrinking or static scale factor, while the masses of particles increase and the size of atoms shrinks. The evolution of the universe can be very slow for all cosmological epochs including inflation, with typical time scale 10^10 yr, and in sharp contrast to the usual big bang picture. The map to the equivalent Einstein frame with constant particle masses and expanding scale factor can be singular at the big bang.", "keyphrases": ["energy density", "big bang picture", "massive neutrino matter"]}
{"id": "1811.02586", "title": "Spectator Dark Matter", "abstract": "The observed dark matter abundance in the Universe can be fully accounted for by a minimally coupled spectator scalar field that was light during inflation and has sufficiently strong self-coupling. In this scenario, dark matter was produced during inflation by amplification of quantum fluctuations of the spectator field. The self-interaction of the field suppresses its fluctuations on large scales, and therefore avoids isocurvature constraints. The scenario does not require any fine-tuning of parameters. In the simplest case of a single real scalar field, the mass of the dark matter particle would be in the range 1 GeV\u2272 m\u2272 10^8 GeV, depending on the scale of inflation, and the lower bound for the quartic self-coupling is \u03bb\u2273 0.45.", "keyphrases": ["dark matter", "scalar field", "spectator field", "matter particle", "era"]}
{"id": "2006.11019", "title": "Relativistic Corrections to the Growth of Structure in Modified Gravity", "abstract": "We present a method to introduce relativistic corrections including linear dark energy perturbations in Horndeski theory into Newtonian simulations based on the N-body gauge approach. We assume that standard matter species (cold dark matter, baryons, photons and neutrinos) are only gravitationally-coupled with the scalar field and we then use the fact that one can include modified gravity effects as an effective dark energy fluid in the total energy-momentum tensor. In order to compute the scalar field perturbations, as well as the cosmological background and metric perturbations, we use the Einstein-Boltzmann code . As an example, we study the impact of relativistic corrections on the matter power spectrum in k-essence, a subclass of Horndeski theory, including the effects of massless and massive neutrinos. For massive neutrinos with \u2211 m_\u03bd = 0.1 eV, the corrections due to relativistic species (photons, neutrinos and dark energy) can introduce a maximum deviation of approximately 7% to the power spectrum at k \u223c 10^-3 Mpc^-1 at z=0, for a scalar field with sound speed c_s^2\u223c 0.013 during matter domination epoch. Our formalism makes it possible to test beyond \u039bCDM models probed by upcoming large-scale structure surveys on very large scales.", "keyphrases": ["n-body gauge approach", "gravity effect", "large scale"]}
{"id": "1308.4131", "title": "The Baryon Cycle of Dwarf Galaxies: Dark, Bursty, Gas-Rich Polluters", "abstract": "We present results from a fully cosmological, very high-resolution, LCDM \"zoom-in\" simulation of a group of seven field dwarf galaxies with present-day virial masses in the range M_vir=4.4e8-3.6e10 Msun. The simulation includes a blastwave scheme for supernova feedback, a star formation recipe based on a high gas density threshold, metal-dependent radiative cooling, a scheme for the turbulent diffusion of metals and thermal energy, and a uniform UV background that modifies the ionization and excitation state of the gas. The properties of the simulated dwarfs are strongly modulated by the depth of the gravitational potential well. All three halos with M_vir < 1e9 Msun are devoid of stars, as they never reach the density threshold for star formation of 100 atoms/cc. The other four, M_vir > 1e9 Msun dwarfs have blue colors, low star formation efficiencies, high cold gas to stellar mass ratios, and low stellar metallicities. Their bursty star formation histories are characterized by peak specific star formation rates in excess of 50-100 1/Gyr, far outside the realm of normal, more massive galaxies, and in agreement with observations of extreme emission-line starbursting dwarfs by the Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey. Metal-enriched galactic outflows produce sub-solar effective yields and pollute with heavy elements a Mpc-size region of the intergalactic medium, but are not sufficient to completely quench star formation activity and are not ubiquitous in our dwarfs. Within the limited size of the sample, our simulations appear to simultaneously reproduce the observed stellar mass and cold gas content, resolved star formation histories, stellar kinematics, and metallicities of field dwarfs in the Local Volume.", "keyphrases": ["field dwarf galaxy", "present-day virial masse", "cold gas content"]}
{"id": "1702.01646", "title": "Bar formation in the Milky Way type galaxies", "abstract": "Many barred galaxies, possibly including the Milky Way, have cusps in the centres. There is a widespread belief, however, that usual bar instability taking place in bulgeless galaxy models is impossible for the cuspy models, because of the presence of the inner Lindblad resonance for any pattern speed. At the same time there are numerical evidences that the bar instability can form a bar. We analyse this discrepancy, by accurate and diverse N-body simulations and using the calculation of normal modes. We show that bar formation in cuspy galaxies can be explained by taking into account the disc thickness. The exponential growth time is moderate for typical current disc masses (about 250 Myr), but considerably increases (factor 2 or more) upon substitution of the live halo and bulge with a rigid halo/bulge potential; meanwhile pattern speeds remain almost the same. Normal mode analysis with different disc mass favours a young bar hypothesis, according to which the bar instability saturated only recently.", "keyphrases": ["bar instability", "different disc mass", "young bar hypothesis"]}
{"id": "1802.04816", "title": "Cosmic Curvature Tested Directly from Observations", "abstract": "Cosmic spatial curvature is a fundamental geometric quantity of the Universe. We investigate a model independent, geometric approach to measure spatial curvature directly from observations, without any derivatives of data. This employs strong lensing time delays and supernova distance measurements to measure the curvature itself, rather than just testing consistency with flatness. We define two curvature estimators, with differing error propagation characteristics, that can crosscheck each other, and also show how they can be used to map the curvature in redshift slices, to test constancy of curvature as required by the Robertson-Walker metric. Simulating realizations of redshift distributions and distance measurements of lenses and sources, we estimate uncertainties on the curvature enabled by next generation measurements. The results indicate that the model independent methods, using only geometry without assuming forms for the energy density constituents, can determine the curvature at the \u223c6\u00d710^-3 level.", "keyphrases": ["spatial curvature", "universe", "independent method"]}
{"id": "1005.1203", "title": "An Improved Calculation of the Non-Gaussian Halo Mass Function", "abstract": "The abundance of collapsed objects in the universe, or halo mass function, is an important theoretical tool in studying the effects of primordially generated non-Gaussianities on the large scale structure. The non-Gaussian mass function has been calculated by several authors in different ways, typically by exploiting the smallness of certain parameters which naturally appear in the calculation, to set up a perturbative expansion. We improve upon the existing results for the mass function by combining path integral methods and saddle point techniques (which have been separately applied in previous approaches). Additionally, we carefully account for the various scale dependent combinations of small parameters which appear. Some of these combinations in fact become of order unity for large mass scales and at high redshifts, and must therefore be treated non-perturbatively. Our approach allows us to do this, and to also account for multi-scale density correlations which appear in the calculation. We thus derive an accurate expression for the mass function which is based on approximations that are valid over a larger range of mass scales and redshifts than those of other authors. By tracking the terms ignored in the analysis, we estimate theoretical errors for our result and also for the results of others. We also discuss the complications introduced by the choice of smoothing filter function, which we take to be a top-hat in real space, and which leads to the dominant errors in our expression. Finally, we present a detailed comparison between the various expressions for the mass functions, exploring the accuracy and range of validity of each.", "keyphrases": ["halo mass function", "perturbative expansion", "non-gaussianitie"]}
{"id": "1308.3393", "title": "Cosmology with matter diffusion", "abstract": "We construct a viable cosmological model based on velocity diffusion of matter particles. In order to ensure the conservation of the total energy-momentum tensor in the presence of diffusion, we include a cosmological scalar field \u03d5 which we identify with the dark energy component of the Universe. The model is characterized by only one new degree of freedom, the diffusion parameter \u03c3. The standard \u039bCDM model can be recovered by setting \u03c3=0. If diffusion takes place (\u03c3 >0) the dynamics of the matter and of the dark energy fields are coupled. We argue that the existence of a diffusion mechanism in the Universe can serve as a theoretical motivation for interacting models. We constrain the background dynamics of the diffusion model with Supernovae, H(z) and BAO data. We also perform a perturbative analysis of this model in order to understand structure formation in the Universe. We calculate the impact of diffusion both on the CMB spectrum, with particular attention to the integrated Sachs-Wolfe signal, and on the matter power spectrum P(k). The latter analysis places strong constraints on the magnitude of the diffusion mechanism but does not rule out the model.", "keyphrases": ["cosmological model", "scalar field", "dark energy", "diffusion model"]}
{"id": "1208.1344", "title": "Cosmological Perturbations from the Standard Model Higgs", "abstract": "We propose that the Standard Model (SM) Higgs is responsible for generating the cosmological perturbations of the universe by acting as an isocurvature mode during a de Sitter inflationary stage. In view of the recent ATLAS and CMS results for the Higgs mass, this can happen if the Hubble rate during inflation is in the range (10^10- 10^14) GeV (depending on the SM parameters). Implications for the detection of primordial tensor perturbations through the B-mode of CMB polarization via the PLANCK satellite are discussed. For example, if the Higgs mass value is confirmed to be m_h=125.5 GeV and m_t, \u03b1_s are at their central values, our mechanism predicts tensor perturbations too small to be detected in the near future. On the other hand, if tensor perturbations will be detected by PLANCK through the B-mode of CMB, then there is a definite relation between the Higgs and top masses, making the mechanism predictive and falsifiable.", "keyphrases": ["universe", "primordial higgs condensate", "primordial perturbation", "new physics", "inflationary fluctuation"]}
{"id": "1501.05316", "title": "Composition of the Fermi-LAT isotropic gamma-ray background intensity: Emission from extragalactic point sources and dark matter annihilations", "abstract": "A new estimation of the isotropic diffuse gamma-ray background (IGRB) observed by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope (Fermi) has been presented for 50 months of data, in the energy range 100 MeV-820 GeV and for different modelings of the Galactic foreground. We attempt here the interpretation of the Fermi-LAT IGRB data in terms of the gamma-ray unresolved emission from different extragalactic populations. We find very good fits to the experimental IGRB, obtained with theoretical predictions for the emission from active galactic nuclei and star-forming galaxies. In addition, we probe a possible emission coming from the annihilation of weakly interacting dark matter (DM) particles in the halo of our Galaxy. We set stringent limits on its annihilation cross section into gamma rays, which are about the thermal relic value for a wide range of DM masses. We also identify regions in the DM mass and annihilation cross section parameter space which can significantly improve the fit to the IGRB data. Our analysis is conducted within the different IGRB data sets obtained from different models for the Galactic emission, which is shown to add a significant ambiguity on the IGRB interpretation.", "keyphrases": ["gamma-ray background", "star-forming galaxy", "active galactic nucleus"]}
{"id": "1910.01105", "title": "Parametrising non-linear dark energy perturbations", "abstract": "In this paper, we quantify the non-linear effects from k-essence dark energy through an effective parameter \u03bc that encodes the additional contribution of a dark energy fluid or a modification of gravity to the Poisson equation. This is a first step toward quantifying non-linear effects of dark energy/modified gravity models in a more general approach. We compare our N-body simulation results from k-evolution with predictions from the linear Boltzmann code , and we show that for the k-essence model one can safely neglect the difference between the two potentials, \u03a6 -\u03a8, and short wave corrections appearing as higher order terms in the Poisson equation, which allows us to use single parameter \u03bc for characterizing this model. We also show that for a large k-essence speed of sound the results are sufficiently accurate, while for a low speed of sound non-linearities in matter and in the k-essence field are non-negligible. We propose a tanh-based parameterisation for \u03bc, motivated by the results for two cases with low (c_s^2=10^-7) and high (c_s^2=10^-4) speed of sound, to include the non-linear effects based on the simulation results. This parametric form of \u03bc can be used to improve Fisher forecasts or Newtonian N-body simulations for k-essence models.", "keyphrases": ["dark energy", "gravity", "k-evolution"]}
{"id": "1112.0728", "title": "Constraining Thawing Dark Energy using Galaxy Cluster Number Counts", "abstract": "We study the formation of galaxy clusters in the presence of thawing class of scalar field dark energy. We consider cases where the scalar field has canonical as well non canonical kinetic term in its action. We also consider various form for the potential of the scalar field e.g, linear, quadratic, inverse quadratic, exponential as well as Pseudo-Nambu-Goldstone Boson (PNGB) type. Moreover we investigate situation where dark energy is homogeneous as well as the situation where dark energy takes part in virialization process. We use the Sheth-Tormen formalism while calculating the number density of galaxy clusters. Our results show that cluster number density for different dark energy models have significant deviation from the corresponding value for the \u039bCDM case. The deviation is more for higher redshifts. Moreover the tachyon type scalar field with linear potential has the highest deviation from the \u039bCDM case. For the total cluster number counts, different dark energy models can have substantial deviation from \u039bCDM and this deviation is most significant around z \u223c 0.5 for all the models we considered. We also constrain thawing class of models using the presently available data for number counts of massive X-ray clusters. The results show that current cluster data is not suitable enough for constraining potentials for the thawing scalar fields as well as for other cosmological parameters like n_s. But one can get significant constraint for the parameter \u03c3_8 and a lower bound on \u03a9_m0.", "keyphrases": ["dark energy", "galaxy cluster", "number density"]}
{"id": "1209.2509", "title": "The First Stars", "abstract": "The first stars to form in the Universe \u2013 the so-called Population III stars \u2013 bring an end to the cosmological Dark Ages, and exert an important influence on the formation of subsequent generations of stars and on the assembly of the first galaxies. Developing an understanding of how and when the first Population III stars formed and what their properties were is an important goal of modern astrophysical research. In this review, I discuss our current understanding of the physical processes involved in the formation of Population III stars. I show how we can identify the mass scale of the first dark matter halos to host Population III star formation, and discuss how gas undergoes gravitational collapse within these halos, eventually reaching protostellar densities. I highlight some of the most important physical processes occurring during this collapse, and indicate the areas where our current understanding remains incomplete. Finally, I discuss in some detail the behaviour of the gas after the formation of the first Population III protostar. I discuss both the conventional picture, where the gas does not undergo further fragmentation and the final stellar mass is set by the interplay between protostellar accretion and protostellar feedback, and also the recently advanced picture in which the gas does fragment and where dynamical interactions between fragments have an important influence on the final distribution of stellar masses.", "keyphrases": ["star", "end", "fragmentation", "simulation"]}
{"id": "1204.5892", "title": "Models of Interacting Dark Energy", "abstract": "Any non-gravitational coupling between dark matter and dark energy modifies the cosmological dynamics. Interactions in the dark sector are considered to be relevant to address the coincidence problem. Moreover, in various models the observed accelerated expansion of the Universe is a pure interaction phenomenon. Here we review recent approaches in which a coupling between both dark components is crucial for the evolution of the Universe.", "keyphrases": ["coincidence problem", "universe", "dark energy model"]}
{"id": "1603.08864", "title": "Scaling laws in chiral hydrodynamic turbulence", "abstract": "We study the turbulent regime of chiral (magneto)hydrodynamics for charged and neutral matter with chirality imbalance. We find that the chiral magnetohydrodynamics for charged plasmas possesses a unique scaling symmetry, only without fluid helicity under the local charge neutrality. We also find a different type of unique scaling symmetry in the chiral hydrodynamics for neutral matter with fluid helicity in the inertial range. We show that these symmetries dictate the self-similar inverse cascade of the magnetic and kinetic energies. Our results imply the possible inverse energy cascade in core-collapse supernovae due to the chiral transport of neutrinos.", "keyphrases": ["chiral magnetohydrodynamic", "scaling symmetry", "neutrino"]}
{"id": "0903.3844", "title": "Statistical dynamo theory: Mode excitation", "abstract": "We compute statistical properties of the lowest-order multipole coefficients of the magnetic field generated by a dynamo of arbitrary shape. To this end we expand the field in a complete biorthogonal set of base functions, viz. B = sum_k a^k(t) b^k(r). We consider a linear problem and the statistical properties of the fluid flow are supposed to be given. The turbulent convection may have an arbitrary distribution of spatial scales. The time evolution of the expansion coefficients a^k(t) is governed by a stochastic differential equation from which we infer their averages <a^k>, autocorrelation functions <a^k(t) a^k*(t+tau)>, and an equation for the cross correlations <a^k a^l*>. The eigenfunctions of the dynamo equation (with eigenvalues lambda_k) turn out to be a preferred set in terms of which our results assume their simplest form. The magnetic field of the dynamo is shown to consist of transiently excited eigenmodes whose frequency and coherence time is given by Im(lambda_k) and -1/(Re lambda_k), respectively. The relative r.m.s. excitation level of the eigenmodes, and hence the distribution of magnetic energy over spatial scales, is determined by linear theory. An expression is derived for <|a^k|^2> / <|a^0|^2> in case the fundamental mode b^0 has a dominant amplitude, and we outline how this expression may be evaluated. It is estimated that <|a^k|^2>/<|a^0|^2> 1/N where N is the number of convective cells in the dynamo. We show that the old problem of a short correlation time (or FOSA) has been partially eliminated. Finally we prove that for a simple statistically steady dynamo with finite resistivity all eigenvalues obey Re(lambda_k) < 0.", "keyphrases": ["statistical property", "multipole coefficient", "magnetic field"]}
{"id": "1603.02698", "title": "Masses, Radii, and Equation of State of Neutron Stars", "abstract": "We summarize our current knowledge of neutron star masses and radii. Recent instrumentation and computational advances have resulted in a rapid increase in the discovery rate and precise timing of radio pulsars in binaries in the last few years, leading to a large number of mass measurements. These discoveries show that the neutron star mass distribution is much wider than previously thought, with 3 known pulsars now firmly in the 1.9-2.0 Msun mass range. For radii, large, high quality datasets from X-ray satellites as well as significant progress in theoretical modeling led to considerable progress in the measurements, placing them in the 9.9-11.2 km range and shrinking their uncertainties due to a better understanding of the sources of systematic errors. The combination of the massive neutron star discoveries, the tighter radius measurements, and improved laboratory constraints of the properties of dense matter has already made a substantial impact on our understanding of the composition and bulk properties of cold nuclear matter at densities higher than that of the atomic nucleus, a major unsolved problem in modern physics.", "keyphrases": ["neutron star", "pulsar", "dense matter", "electromagnetic spectrum"]}
{"id": "1812.07581", "title": "Stellar Accelerations and the Galactic Gravitational Field", "abstract": "Typical stars in the Milky Way galaxy have velocities of hundreds of kilometres per second and experience gravitational accelerations of \u223c 10^-10 m s^-2, resulting in velocity changes of a few centimetres per second over a decade. Measurements of these accelerations would permit direct tests of the applicability of Newtonian dynamics on kiloparsec length scales and could reveal significant small scale inhomogeneities within the galaxy, as well increasing the sensitivity of measurements of the overall mass distribution of the galaxy. Noting that a reasonable extrapolation of progress in exoplanet hunting spectrographs suggests that centimetre per second level precision will be attainable in the coming decade(s), we explore the possibilities such measurements would create. We consider possible confounding effects, including apparent accelerations induced by stellar motion and reflex velocities from planetary systems, along with possible strategies for their mitigation. If these issues can be satisfactorily addressed it will be possible to use high precision measurements of changing stellar velocities to perform a \"blind search\" for dark matter, make direct tests of theories of non-Newtonian gravitational dynamics, detect local inhomogeneities in the dark matter density, and greatly improve measurements of the overall properties of the galaxy.", "keyphrases": ["star", "gravitational acceleration", "dark matter"]}
{"id": "1111.2305", "title": "New Q-ball Solutions in Gauge-Mediation, Affleck-Dine Baryogenesis and Gravitino Dark Matter", "abstract": "Affleck-Dine (AD) baryogenesis along a d=6 flat direction in gauge-mediated supersymmetry-breaking (GMSB) models can produce unstable Q-balls which naturally have field strength similar to the messenger scale. In this case a new kind of Q-ball is formed, intermediate between gravity-mediated and gauge-mediated type. We study in detail these new Q-ball solutions, showing how their properties interpolate between standard gravity-mediated and gauge-mediated Q-balls as the AD field becomes larger than the messenger scale. It is shown that E/Q for the Q-balls can be greater than the nucleon mass but less than the MSSM-LSP mass, leading to Q-ball decay directly to Standard Model fermions with no MSSM-LSP production. More significantly, if E/Q is greater than the MSSM-LSP mass, decaying Q-balls can provide a natural source of non-thermal MSSM-LSPs, which can subsequently decay to gravitino dark matter without violating nucleosynthesis constraints. The model therefore provides a minimal scenario for baryogenesis and gravitino dark matter in the gauge-mediated MSSM, requiring no new fields.", "keyphrases": ["gravitino", "dark matter", "gauge-mediated q-balls"]}
{"id": "0904.2784", "title": "On The Maximum Mass of Stellar Black Holes", "abstract": "We present the spectrum of compact object masses: neutron stars and black holes that originate from single stars in different environments. In particular, we calculate the dependence of maximum black hole mass on metallicity and on some specific wind mass loss rates (e.g., Hurley et al. and Vink et al.). Our calculations show that the highest mass black holes observed in the Galaxy M_bh = 15 Msun in the high metallicity environment (Z=Zsun=0.02) can be explained with stellar models and the wind mass loss rates adopted here. To reach this result we had to set Luminous Blue Variable mass loss rates at the level of about 0.0001 Msun/yr and to employ metallicity dependent Wolf-Rayet winds. With such winds, calibrated on Galactic black hole mass measurements, the maximum black hole mass obtained for moderate metallicity (Z=0.3 Zsun=0.006) is M_bh,max = 30 Msun. This is a rather striking finding as the mass of the most massive known stellar black hole is M_bh = 23-34 Msun and, in fact, it is located in a small star forming galaxy with moderate metallicity. We find that in the very low (globular cluster-like) metallicity environment the maximum black hole mass can be as high as M_bh,max = 80 Msun (Z=0.01 Zsun=0.0002). It is interesting to note that X-ray luminosity from Eddington limited accretion onto an 80 Msun black hole is of the order of about 10^40 erg/s and is comparable to luminosities of some known ULXs. We emphasize that our results were obtained for single stars only and that binary interactions may alter these maximum black hole masses (e.g., accretion from a close companion). This is strictly a proof-of-principle study which demonstrates that stellar models can naturally explain even the most massive known stellar black holes.", "keyphrases": ["black hole", "star", "stellar wind"]}
{"id": "1403.6462", "title": "Cosmological parameter fittings with the BICEP2 data", "abstract": "Combining the latest Planck, Wilkinson Microwave Anisotropy Probe (WMAP), and baryon acoustic oscillation (BAO) data, we exploit the recent cosmic microwave background (CMB) B-mode power spectra data released by the BICEP2 collaboration to constrain the cosmological parameters of the \u039bCDM model, esp. the primordial power spectra parameters of the scalar and the tensor modes, n_s,\u03b1_s, r, n_t. We obtained constraints on the parameters for a lensed \u039bCDM model using the Markov Chain Monte Carlo (MCMC) technique, the marginalized 68% bounds are r = 0.1043\u00b1_0.0914^0.0307, n_s = 0.9617\u00b1_0.0061^ 0.0061, \u03b1_s = -0.0175\u00b1_0.0097^0.0105, n_t = 0.5198\u00b1_0.4579^0.4515. We found that a blue tilt for n_t is favored slightly, but it is still well consistent with flat or even red tilt. Our r value is slightly smaller than the one obtained by the BICEP team, as we allow n_t as a free parameter without imposing the single-field slow roll inflation consistency relation. If we impose this relation, r=0.2130\u00b1_0.0609^0.0446. For most other parameters, the best fit values and measurement errors are not altered much by the introduction of the BICEP2 data.", "keyphrases": ["free parameter", "cosmological model", "tensor spectrum"]}
{"id": "1506.07306", "title": "Fine Tuning May Not Be Enough", "abstract": "We argue that the fine tuning problems of scalar-driven inflation may be worse than is commonly believed. The reason is that reheating requires the inflaton to be coupled to other matter fields whose vacuum fluctuations alter the inflaton potential. The usual response has been that even more fine-tuning of the classical potential V(\u03c6) can repair any damage done in this way. We point out that the effective potential in de Sitter background actually depends in a complicated way upon the dimensionless combination of \u03c6/H. We also show that the factors of H which occur in de Sitter do not even correspond to local functionals of the metric for general geometries, nor are they Planck-suppressed.", "keyphrases": ["sitter", "complicated way", "local functional", "counterterm"]}
{"id": "1207.0751", "title": "Magnetic Fields from QCD Phase Transitions", "abstract": "We study the evolution of QCD phase transition-generated magnetic fields in freely decaying MHD turbulence of the expanding Universe. We consider a magnetic field generation model that starts from basic non-perturbative QCD theory and predicts stochastic magnetic fields with an amplitude of the order of 0.02 \u03bcG and small magnetic helicity. We employ direct numerical simulations to model the MHD turbulence decay and identify two different regimes: \"weakly helical\" turbulence regime, when magnetic helicity increases during decay, and \"fully helical\" turbulence, when maximal magnetic helicity is reached and an inverse cascade develops. The results of our analysis show that in the most optimistic scenario the magnetic correlation length in the comoving frame can reach 10 kpc with the amplitude of the effective magnetic field being 0.007 nG. We demonstrate that the considered model of magneto-genesis can provide the seed magnetic field for galaxies and clusters.", "keyphrases": ["turbulence", "universe", "helicity", "magnetic field"]}
{"id": "1905.09476", "title": "Modified Gravity (MOG) fits to observed radial acceleration of SPARC galaxies", "abstract": "The equation of motion in the generally covariant modified gravity (MOG) theory leads, for weak gravitational fields and non-relativistic motion, to a modification of Newton's gravitational acceleration law. In addition to the metric g_\u03bc\u03bd, MOG has a vector field \u03d5_\u03bc that couples with gravitational strength to all baryonic matter. The gravitational coupling strength is determined by the MOG parameter \u03b1, while parameter \u03bc is the small effective mass of \u03d5_\u03bc. The MOG acceleration law has been demonstrated to fit a wide range of galaxies, galaxy clusters and the Bullet Cluster and Train Wreck Cluster mergers. For the SPARC sample of rotationally supported spiral and irregular galaxies, McGaugh et al. [24] (MLS) have found a radial acceleration relation (RAR) that relates accelerations derived from galaxy rotation curves to Newtonian accelerations derived from galaxy mass models. Using the same SPARC galaxy data, mass models independently derived from that data, and MOG parameters \u03b1 and \u03bc that run with galaxy mass, we demonstrate that adjusting galaxy parameters within \u00b1 1-sigma bounds can yield MOG predictions consistent with the given rotational velocity data. Moreover, the same adjusted parameters yield a good fit to the RAR of MLS, with the RAR parameter a_0=(5.4\u00b1 .3)\u00d7 10^-11 m/s^2.", "keyphrases": ["gravity", "baryonic matter", "galaxy rotation curve"]}
{"id": "1502.02979", "title": "Magnetar superconductivity versus magnetism: neutrino cooling processes", "abstract": "We describe the microphysics, phenomenology, and astrophysical implication of a B-field induced unpairing effect that may occur in magnetars, if the local B-field in the core of a magnetar exceeds a critical value H_c2. Using the Ginzburg-Landau theory of superconductivity, we derive the H_c2 field for proton condensate taking into the correction (\u2264 30%) which arises from its coupling to the background neutron condensate. The density dependence of pairing of proton condensate implies that H_c2 is maximal at the crust-core interface and decreases towards the center of the star. As a consequence, magnetar cores with homogenous constant fields will be partially superconducting for \"medium-field\" magnetars (10^15\u2264 B\u2264 5 \u00d7 10^16 G) whereas \"strong-field\" magnetars (B>5\u00d7 10^16 G) will be void of superconductivity. The neutrino emissivity of a magnetar's core changes in a twofold manner: (i) the B-field assisted direct Urca process is enhanced by orders of magnitude, because of the unpairing effect in regions where B\u2265 H_c2; (ii) the Cooper-pair breaking processes on protons vanish in these regions and the overall emissivity by the pair-breaking processes is reduced by a factor of only a few.", "keyphrases": ["superconductivity", "proton condensate", "neutrino emissivity"]}
{"id": "0712.1118", "title": "Understanding the WMAP Cold Spot mystery", "abstract": "The first and third year data releases from the WMAP provide evidence of an anomalous Cold Spot (CS) at galactic latitude b=-57deg and longitude l=209deg. We have examined the properties of the CS in some detail in order to assess its cosmological significance. We have performed a cluster analysis of the local extrema in the CMB signal to show that the CS is actually associated with a large group of extrema rather than just one. In the light of this we have re-examined the properties of the WMAP ILC and co-added \"cleaned\" WCM maps, which have previously been used for the analysis of the properties of the signal in the vicinity of the CS. These two maps have remarkably similar properties on equal latitude rings for |b|>30deg, as well as in the vicinity of the CS. We have also checked the idea that the CMB signal has a non-Gaussian tail, localized in the low multipole components of the signal. For each ring we apply a linear filter with characteristic scale R, dividing the CMB signal in two parts: the filtered part, with characteristic scale above that of the filter R, and the difference between the initial and filtered signal. Using the filter scale as a variable, we can maximize the skewness and kurtosis of the smoothed signal and minimize these statistics for the difference between initial and filtered signal. We have discovered that the shape of the CS is formed primarily by the components of the CMB signal represented by multipoles between 10<=L<=20, with a corresponding angular scale about 5-10 degs. This signal leads to modulation of the whole CMB sky, clearly seen at |b|>30deg in both the ILC and WCM maps, rather than a single localized feature. After subtraction of this modulation, the remaining part of the CMB signal appears to be consistent with statistical homogeneity and Gaussianity.", "keyphrases": ["cold spot", "vicinity", "gaussianity"]}
{"id": "1201.0768", "title": "IR Divergences in Inflation and Entropy Perturbations", "abstract": "We study leading order perturbative corrections to the two point correlation function of the scalar field describing the curvature perturbation in a slow-roll inflationary background, paying particular attention to the contribution of entropy mode loops. We find that the infrared divergences are worse than in pure de Sitter space: they are power law rather than logarithmic. The validity of perturbation theory and thus of the effective field theory of cosmological perturbations leads to stringent constraints on the coupling constants describing the interactions, in our model the quartic self-interaction coupling constant of the entropy field. If the self coupling constant is larger than some critical value which depends in particular on the duration of the inflationary phase, then perturbation theory breaks down. Our analysis may have implications for the stability of de Sitter space: the quantum effects which lead to an instability of de Sitter space will be larger in magnitude in the presence of entropy fluctuations.", "keyphrases": ["entropy perturbation", "scalar field", "infrared divergence"]}
{"id": "1008.3143", "title": "Optimal Time-Series Selection of Quasars", "abstract": "We present a novel method for the optimal selection of quasars using time-series observations in a single photometric bandpass. Utilizing the damped random walk model of Kelly et al. (2009), we parameterize the ensemble quasar structure function in Sloan Stripe 82 as a function of observed brightness. The ensemble model fit can then be evaluated rigorously for and calibrated with individual light curves with no parameter fitting. This yields a classification in two statistics \u2014 one describing the fit confidence and one describing the probability of a false alarm \u2014 which can be tuned, a priori, to achieve high quasar detection fractions (99 acceptable rate of false alarms. We establish the typical rate of false alarms due to known variable stars as <3 we increase the sample of potential quasars relative to those known in Stripe 82 by as much as 29 2.5<z<3, where selection by color is extremeley inefficient. This represents 1875 new quasars in a 290 deg^2 field. The observed rates of both quasars and stars agree well with the model predictions, with >99 the expected variability profile. We discus the utility of the method at high-redshift and in the regime of noisy and sparse data. Our time series selection complements well independent selection based on quasar colors and has strong potential for identifying high redshift quasars for BAO and other cosmology studies in the LSST era.", "keyphrases": ["selection", "quasar", "time-series observation"]}
{"id": "0906.1198", "title": "Calibrating the Baryon Oscillation Ruler for Matter and Halos", "abstract": "We characterize the nonlinear evolution of the baryon acoustic feature as traced by the dark matter and halos, using a combination of perturbation theory and N-body simulations. We confirm that the acoustic peak traced by the dark matter is both broadened and shifted as structure forms, and that this shift is well described by second-order perturbation theory. These shifts persist for dark matter halos, and are a simple function of halo bias, with the shift (mostly) increasing with increasing bias. Extending our perturbation theory results to halos with simple two parameter bias models (both in Lagrangian and Eulerian space) quantitatively explains the observed shifts. In particular, we demonstrate that there are additional terms that contribute to the shift that are absent for the matter. At z=0 for currently favored cosmologies, the matter shows shifts of 0.5 halos shift it by 0.5 factor at higher redshifts. These results are easily generalized to galaxies within the halo model, where we show that simple galaxy models show marginally larger shifts than the correspondingly biased halos, due to the contribution of satellites in high mass halos. While our focus here is on real space, our results make specific predictions for redshift space. For currently favored cosmological models, we find that the shifts for halos at z=0 increase by 0.3 these theoretical systematics are smaller than the statistical precision of upcoming surveys, even if one ignored the corrections discussed here. Simple modeling, along the lines discussed here, has the potential to reduce these systematics to below the levels of cosmic variance limited surveys.", "keyphrases": ["baryon", "galaxy", "cosmological model"]}
{"id": "1212.1416", "title": "Lepton asymmetry growth in the symmetric phase of an electroweak plasma with hypermagnetic fields versus its washing out by sphalerons", "abstract": "We study lepton asymmetry evolution in plasma of the early Universe before the electroweak phase transition (EWPT) accounting for chirality flip processes via Higgs decays (inverse decays) entering equilibrium at temperatures below T_RL 10 TeV, T_EW < T < T_RL. We solve appropriate kinetic equations for leptons and Higgs bosons taking into account the lepton number violation due to Abelian anomalies for right and left electrons and neutrinos in the self-consistent hypercharge field obeying Maxwell equations modified by the contribution of the Standard Model of electroweak interactions. The violation of left lepton numbers and the corresponding violation of the baryon number due to sphaleron processes in symmetric phase is taken into account as well. Assuming the Chern-Simons wave configuration of the seed hypercharge field, we get the estimates of baryon and lepton asymmetries evolved from the primordial right electron asymmetry existing alone as partial asymmetry at T > T_RL. One finds a strong dependence of the asymmetries on the Chern-Simons wave number. We predict a nonzero chiral asymmetry \u0394\u03bc= \u03bc_e_R - \u03bc_e_L \u22600 in this scenario evolved down to the EWPT moment that can be used as an initial value for the Maxwellian field evolution after EWPT.", "keyphrases": ["electroweak phase transition", "left lepton doublet", "baryogenesis"]}
{"id": "1610.10051", "title": "Cosmological constraints on exotic injection of electromagnetic energy", "abstract": "We compute cosmic microwave background (CMB) anisotropy constraints on exotic forms of energy injection in electromagnetic (e.m.) channels over a large range of timescales. These constraints are very powerful around or just after recombination, although CMB keeps some sensitivity e.g. to decaying species with lifetimes as long as 10^25s. We review here complementary with CMB spectral distortions and primordial nucleosynthesis bounds, which dominate at earlier timescales. For the first time, we describe the effects of the e.m. energy injection on the CMB power spectra as a function of the injection epoch, using the lifetime of a decaying particle as proxy. We identify a suitable on-the-spot approximation. Our results are of interest not only for early universe relics constituting (a fraction of) the dark matter, but also for other exotic injection of e.m. radiation. For illustration, we apply our formalism to: i) Primordial black holes of mass \u2208 [10^13.5,10^16.8] g, showing that the constraints are comparable to the ones obtained from gamma-ray background studies and even dominate below \u223c 10^14g. ii) To a peculiar mass-mixing range in the sterile neutrino parameter space, complementary to other astrophysical and laboratory probes. iii) Finally, we provide a first estimate of the room for improvement left for forthcoming 21 cm experiments, comparing it with the reach of proposed CMB spectral distortion (PiXiE) and CMB angular power spectrum (CORE) missions. We show that the best and most realistic opportunity to look for this signal (or to improve over current constraints) in the 21 cm probe is to focus on the Cosmic Dawn epoch, 15\u2272 z\u227230, where the qualitatively unambiguous signature of a spectrum in emission can be expected for models that evade all current constraints.", "keyphrases": ["energy injection", "early universe", "dark matter", "black hole"]}
{"id": "1403.6403", "title": "The Observational Status of Simple Inflationary Models: an Update", "abstract": "We provide an update on five relatively well motivated inflationary models in which the inflaton is a Standard Model singlet scalar field. These include i) the textbook quadratic and quartic potential models but with additional couplings of the inflaton to fermions and bosons, which enable reheating and also modify the naive predictions for the scalar spectral index n_s and r, ii) models with Higgs and Coleman-Weinberg potentials, and finally iii) a quartic potential model with non-minimal coupling of the inflaton to gravity. For n_s values close to 0.96, as determined by the WMAP9 and Planck experiments, most of the considered models predict r\u22730.02. The running of the scalar spectral index, quantified by |d n_s/dln k|, is predicted in these models to be of order 10^-4\u201310^-3.", "keyphrases": ["inflationary model", "gravity", "chaotic inflation", "standard cosmology", "simple model"]}
{"id": "1402.5163", "title": "The K2 Mission: Characterization and Early results", "abstract": "The K2 mission will make use of the Kepler spacecraft and its assets to expand upon Kepler's groundbreaking discoveries in the fields of exoplanets and astrophysics through new and exciting observations. K2 will use an innovative way of operating the spacecraft to observe target fields along the ecliptic for the next 2-3 years. Early science commissioning observations have shown an estimated photometric precision near 400 ppm in a single 30 minute observation, and a 6-hour photometric precision of 80 ppm (both at V=12). The K2 mission offers long-term, simultaneous optical observation of thousands of objects at a precision far better than is achievable from ground-based telescopes. Ecliptic fields will be observed for approximately 75-days enabling a unique exoplanet survey which fills the gaps in duration and sensitivity between the Kepler and TESS missions, and offers pre-launch exoplanet target identification for JWST transit spectroscopy. Astrophysics observations with K2 will include studies of young open clusters, bright stars, galaxies, supernovae, and asteroseismology.", "keyphrases": ["kepler", "spacecraft", "star"]}
{"id": "1003.4513", "title": "On the Dynamics and Evolution of Gravitational Instability-Dominated Disks", "abstract": "We derive the evolution equations describing a thin axisymmetric disk of gas and stars with an arbitrary rotation curve that is kept in a state of marginal gravitational instability and energy equilibrium due to the balance between energy released by accretion and energy lost due to decay of turbulence. Rather than adopt a parameterized alpha prescription, we instead use the condition of marginal gravitational instability to self-consistently determine the position- and time-dependent transport rates. We show that there is a steady-state configuration for disks dominated by gravitational instability, and that this steady state persists even when star formation is taken into account if the accretion rate is sufficiently large. For disks in this state we analytically determine the velocity dispersion, surface density, and rates of mass and angular momentum transport as a function of the gas mass fraction, the rotation curve, and the rate of external accretion onto the disk edge. We show that disks that are initially out of steady state will evolve into it on the viscous timescale of the disk, which is comparable to the orbital period if the accretion rate is high. Finally, we discuss the implications of these results for the structure of disks in a broad range of environments, including high redshift galaxies, the outer gaseous disks of local galaxies, and accretion disks around protostars.", "keyphrases": ["star", "marginal gravitational instability", "energy equilibrium", "orbital period"]}
{"id": "2102.03724", "title": "Testing Fundamental Physics with Astrophysical Transients", "abstract": "Explosive astrophysical transients at cosmological distances can be used to place precision tests of the basic assumptions of relativity theory, such as Lorentz invariance, the photon zero-mass hypothesis, and the weak equivalence principle (WEP). Signatures of Lorentz invariance violations (LIV) include vacuum dispersion and vacuum birefringence. Sensitive searches for LIV using astrophysical sources such as gamma-ray bursts, active galactic nuclei, and pulsars are discussed. The most direct consequence of a nonzero photon rest mass is a frequency dependence in the velocity of light propagating in vacuum. A detailed representation of how to obtain a combined severe limit on the photon mass using fast radio bursts at different redshifts through the dispersion method is presented. The accuracy of the WEP has been well tested based on the Shapiro time delay of astrophysical messengers traveling through a gravitational field. Some caveats of Shapiro delay tests are discussed. In this article, we review and update the status of astrophysical tests of fundamental physics.", "keyphrases": ["fundamental physic", "lorentz invariance violation", "photon mass"]}
{"id": "1609.03022", "title": "Escape probability of the super-Penrose process", "abstract": "We consider a head-on collision of two massive particles that move in the equatorial plane of an extremal Kerr black hole, which results in the production of two massless particles. Focusing on a typical case, where both of the colliding particles have zero angular momenta, we show that a massless particle produced in such a collision can escape to infinity with arbitrarily large energy in the near-horizon limit of the collision point. Furthermore, if we assume that the emission of the produced massless particles is isotropic in the center-of-mass frame but confined to the equatorial plane, the escape probability of the produced massless particle approaches 5/12 and almost all escaping massless particles have arbitrarily large energy at infinity and an impact parameter approaching 2GM/c^2, where M is the mass of the black hole.", "keyphrases": ["black hole", "infinity", "escape probability"]}
{"id": "1406.0319", "title": "Observed galaxy number counts on the lightcone up to second order: II. Derivation", "abstract": "We present a detailed derivation of the observed galaxy number over-density on cosmological scales up to second order in perturbation theory. We include all relativistic effects that arise from observing on the past lightcone. The derivation is in a general gauge, and applies to all dark energy models (including interacting dark energy) and many modified gravity models. The result will be important for accurate cosmological parameter estimation, including non-Gaussianity, since all projection effects need to be taken into account. It also offers the potential for new probes of General Relativity, dark energy and modified gravity. This paper accompanies Paper I which presents the key results for the concordance model in Poisson gauge.", "keyphrases": ["projection effect", "galaxy clustering", "bispectrum", "second-order relativistic description", "correction"]}
{"id": "1609.04081", "title": "Hubble trouble or Hubble bubble?", "abstract": "The recent analysis of low-redshift supernovae (SN) has increased the apparent tension between the value of H_0 estimated from low and high redshift observations such as the cosmic microwave background (CMB) radiation. At the same time other observations have provided evidence of the existence of local radial inhomogeneities extending in different directions up to a redshift of about 0.07. About 40% of the Cepheids used for SN calibration are directly affected because are located along the directions of these inhomogeneities. We derive a new simple formula relating directly the luminosity distance to the monopole of the density contrast, which does not involve any metric perturbation. We then use it to develop a new inversion method to reconstruct the monopole of the density field from the deviations of the redshift uncorrected observed luminosity distance respect to the \u039b CDM prediction based on cosmological parameters obtained from large scale observations. The inversion method confirms the existence of inhomogeneities whose effects were not previously taken into account because the 2M++ density field maps used to obtain the peculiar velocity for redshift correction were for z\u2264 0.06, which is not a sufficiently large scale to detect the presence of inhomogeneities extending up to z=0.07. The inhomogeneity does not affect the high redshift luminosity distance because the volume averaged density contrast tends to zero asymptotically, making the value of H_0^CMB obtained from CMB observations insensitive to any local structure. The inversion method can provide a unique tool to reconstruct the density field at high redshift where only SN data is available, and in particular to normalize correctly the density field respect to the average large scale density of the Universe.", "keyphrases": ["apparent tension", "hubble parameter", "outer denser region"]}
{"id": "1308.6406", "title": "Updating constraints on inflationary features in the primordial power spectrum with the Planck data", "abstract": "We present new constraints on possible features in the primordial inflationary density perturbations power spectrum in light of the recent Cosmic Microwave Background Anisotropies measurements from the Planck satellite. We found that the Planck data hints for the presence of features in two different ranges of angular scales, corresponding to multipoles 10< l <60 and 150< l < 300, with a decrease in the best fit chi^2 value with respect to the featureless \"vanilla\" LCDM model of Delta chi^2 around 9 in both cases.", "keyphrases": ["primordial power spectrum", "inflationary model", "smooth power-law spectrum"]}
{"id": "1712.03444", "title": "The dipole anisotropy of AllWISE galaxies", "abstract": "We determine the dipole in the WISE galaxy catalogue. After reducing star contamination to <0.1 close to the Galactic plane, we eliminate low redshift sources to suppress the non-kinematic, clustering dipole. We remove sources within \u00b15 of the super-galactic plane, as well as those within 1\u201d of 2MRS sources at redshift z < 0.03. We enforce cuts on the source angular extent to preferentially select distant ones. As we progress along these steps, the dipole converges in direction to within 5 of the CMB dipole and its magnitude also progressively reduces but stabilises at \u223c0.012, corresponding to a velocity >1000 km/s if it is solely of kinematic origin. However, previous studies have shown that only \u223c70 inferred from the CMB dipole is due to sources at z < 0.03. We examine the Dark Sky simulations to quantify the prevalence of such environments and find that <2.1 bulk flow (> 240 km/s extending to z > 0.03) that we do. We construct mock catalogues in the neighbourhood of such peculiar observers in order to mimic our final galaxy selection and quantify the residual clustering dipole. After subtracting this the remaining dipole is 0.0048 \u00b1 0.0022, corresponding to a velocity of 420 \u00b1 213 km/s which is consistent with the CMB. However the sources (at z > 0.03) of such a large clustering dipole remain to be identified.", "keyphrases": ["catalogue", "bulk flow", "observer"]}
{"id": "1407.4748", "title": "Perturbative Quantum Gravity Comes of Age", "abstract": "I argue that cosmological data from the epoch of primordial inflation is catalyzing the maturation of quantum gravity from speculation into a hard science. I explain why quantum gravitational effects from primordial inflation are observable. I then review what has been done, both theoretically and observationally, and what the future holds. I also discuss what this tells us about quantum gravity.", "keyphrases": ["quantum", "gravitational effect", "precision cosmology"]}
{"id": "2006.14866", "title": "Cataloging the radio-sky with unsupervised machine learning: a new approach for the SKA era", "abstract": "We develop a new analysis approach towards identifying related radio components and their corresponding infrared host galaxy based on unsupervised machine learning methods. By exploiting PINK, a self-organising map algorithm, we are able to associate radio and infrared sources without the a priori requirement of training labels. We present an example of this method using 894,415 images from the FIRST and WISE surveys centred towards positions described by the FIRST catalogue. We produce a set of catalogues that complement FIRST and describe 802,646 objects, including their radio components and their corresponding AllWISE infrared host galaxy. Using these data products we (i) demonstrate the ability to identify objects with rare and unique radio morphologies (e.g. 'X'-shaped galaxies, hybrid FR-I/FR-II morphologies), (ii) can identify the potentially resolved radio components that are associated with a single infrared host and (iii) introduce a \"curliness\" statistic to search for bent and disturbed radio morphologies, and (iv) extract a set of 17 giant radio galaxies between 700-1100 kpc. As we require no training labels, our method can be applied to any radio-continuum survey, provided a sufficiently representative SOM can be trained.", "keyphrases": ["machine learning method", "infrared source", "astronomical survey"]}
{"id": "1402.3286", "title": "More on Universal Superconformal Attractors", "abstract": "We define a general class of superconformal inflationary attractor models studied in our previous papers [1,2], which include, among others, inflationary models of 'induced gravity' which were argued to retain perturbative unitarity up to the Planck scale [3]. The choice of the function f(\u03d5) in superconformal attractors for the models introduced in [3] is f(\u03d5)= \u03d5^n - \u03be^-1. We present both superconformal and supergravity versions of these models, which were derived in [1,2] for arbitrary f(\u03d5), together with the universal conditions required for stabilization of the extra three moduli present in the superconformal attractors, in addition to the inflaton.", "keyphrases": ["attractor", "gravity", "scalar-tensor theory"]}
{"id": "1508.06342", "title": "Phases of New Physics in the CMB", "abstract": "Fluctuations in the cosmic neutrino background are known to produce a phase shift in the acoustic peaks of the cosmic microwave background. It is through the sensitivity to this effect that the recent CMB data has provided a robust detection of free-streaming neutrinos. In this paper, we revisit the phase shift of the CMB anisotropy spectrum as a probe of new physics. The phase shift is particularly interesting because its physical origin is strongly constrained by the analytic properties of the Green's function of the gravitational potential. For adiabatic fluctuations, a phase shift requires modes that propagate faster than the speed of fluctuations in the photon-baryon plasma. This possibility is realized by free-streaming relativistic particles, such as neutrinos or other forms of dark radiation. Alternatively, a phase shift can arise from isocurvature fluctuations. We present simple models to illustrate each of these effects. We then provide observational constraints from the Planck temperature and polarization data on additional forms of radiation. We also forecast the capabilities of future CMB Stage IV experiments. Whenever possible, we give analytic interpretations of our results.", "keyphrases": ["free-streaming neutrino", "photon-baryon plasma", "relativistic particle", "cmb experiment"]}
{"id": "1605.08761", "title": "CMB-lensing beyond the Born approximation", "abstract": "We investigate the weak lensing corrections to the cosmic microwave background temperature anisotropies considering effects beyond the Born approximation. To this aim, we use the small deflection angle approximation, to connect the lensed and unlensed power spectra, via expressions for the deflection angles up to third order in the gravitational potential. While the small deflection angle approximation has the drawback to be reliable only for multipoles \u2113\u2272 2500, it allows us to consistently take into account the non-Gaussian nature of cosmological perturbation theory beyond the linear level. The contribution to the lensed temperature power spectrum coming from the non-Gaussian nature of the deflection angle at higher order is a new effect which has not been taken into account in the literature so far. It turns out to be the leading contribution among the post-Born lensing corrections. On the other hand, the effect is smaller than corrections coming from non-linearities in the matter power spectrum, and its imprint on CMB lensing is too small to be seen in present experiments.", "keyphrases": ["gravitational potential", "non-gaussian nature", "bispectrum"]}
{"id": "1410.7392", "title": "Relativistic simulations of black hole-neutron star coalescence: the jet emerges", "abstract": "We perform magnetohydrodynamic simulations in full general relativity (GRMHD) of a binary black hole-neutron star on a quasicircular orbit that undergoes merger. The binary mass ratio is 3:1, the black hole initial spin parameter a/m=0.75 (m is the black hole Christodoulou mass) aligned with the orbital angular momentum, and the neutron star is an irrotational \u0393=2 polytrope. About two orbits prior to merger (at time t=t_B), we seed the neutron star with a dynamically weak interior dipole magnetic field that extends into the stellar exterior. At t=t_B the exterior has a low-density atmosphere with constant plasma parameter \u03b2\u2261 P_ gas/P_ mag. Varying \u03b2 at t_B in the exterior from 0.1 to 0.01, we find that at a time \u223c 4000 M\u223c 100(M_ NS/1.4M_\u2299)ms [M is the total (ADM) mass] following the onset of accretion of tidally disrupted debris, magnetic winding above the remnant black hole poles builds up the magnetic field sufficiently to launch a mildly relativistic, collimated outflow - an incipient jet. The duration of the accretion and the lifetime of the jet is \u0394 t\u223c 0.5(M_ NS/1.4M_\u2299)s. Our simulations furnish the first explicit examples in GRMHD which show that a jet can emerge following a black hole - neutron star merger.", "keyphrases": ["black hole", "gamma-ray burst", "relativistic jet"]}
{"id": "1410.1407", "title": "Trojan resonant dynamics, stability, and chaotic diffusion, for parameters relevant to exoplanetary systems", "abstract": "We investigate the dynamics of small trojan exoplanets in domains of secondary resonances within the tadpole domain of motion. We consider the limit of a massless trojan companion of a giant planet. Without other planets, this is a case of the elliptic restricted three body problem (ERTBP). The presence of more planets (the restricted multi-planet problem, RMPP) induces new direct and indirect secular effects on the trojan's dynamics. In the theoretical part of this paper, we develop a Hamiltonian formalism in action-angle variables, which allows to treat in a unified way resonant dynamics and secular effects on the trojan body in both the ERTBP or the RMPP. Our formalism leads to a decomposition of the Hamiltonian in two parts, H=H_b+H_sec. H_b, called the basic model, describes resonant dynamics in the short-period (epicyclic) and synodic (libration) degrees of freedom. H_sec contains only terms depending on slow (secular) angles. H_b is formally identical in the ERTBP and the RMPP, apart from a re-definition of angular variables. An important physical consequence is that the slow chaotic diffusion proceeds in both the ERTBP and the RMPP by a qualitatively similar dynamical mechanism better approximated by the paradigm of `modulational diffusion'. In the numerical part, we focus on the ERTBP for making a numerical demonstration of the chaotic diffusion process along resonances. Using color stability maps, we provide a survey of the resonant web for characteristic mass parameters of the primary, in which the secondary resonances from 1:5 to 1:12 (ratio of the short over the synodic period) and their resonant multiplets appear. We give numerical examples of diffusion of weakly chaotic orbits in the resonant web. We make a statistics of the escaping times in the resonant domain, and find power-law tails of the distribution of escaping times for slowly diffusing chaotic orbits.", "keyphrases": ["resonant dynamic", "multi-planet problem", "trojan"]}
{"id": "1204.6047", "title": "Gamma-ray Lines in the Fermi Data: is it a Bubble?", "abstract": "Recently, tentative evidence for an excess of gamma rays at energies around 130 GeV has been reported from analyses of data from the Fermi Large Area Telescope (LAT). The excess is potentially of great interest, as it could be associated with the pair-annihilation of Galactic dark matter and the subsequent production of monochromatic or internal bremsstrahlung gamma rays. The 130 GeV excess appears when an optimized selection of the target region of interest is employed, a procedure that depends upon the assumed dark matter density profile. For the profiles producing an appreciable signal, these target regions vastly overlap with the region corresponding to the so-called \"Fermi bubbles\". We argue that the tentative evidence for a line feature is likely due to hard photons in the Fermi bubbles regions, where the gamma-ray spectrum contains a spectral break in the energy range of interest (100-150 GeV). Although the origin of this broken power-law is unclear, it is probably related to standard astrophysical processes and not to dark matter annihilation. A broken power-law provides as good a fit as a line \"excess\", even within small energy windows, and a significantly better fit for large energy windows.", "keyphrases": ["fermi bubble", "matter annihilation", "astrophysical origin"]}
{"id": "1308.0013", "title": "Failed Supernovae Explain the Compact Remnant Mass Function", "abstract": "One explanation for the absence of higher mass red supergiants (16.5 Msun < M < 25Msun) as the progenitors of Type IIP supernovae (SNe) is that they die in failed SNe creating black holes. Simulations show that such failed SNe still eject their hydrogen envelopes in a weak transient, leaving a black hole with the mass of the star's helium core (5-8Msun). Here we show that this naturally explains the typical masses of observed black holes and the gap between neutron star and black hole masses without any fine-tuning of the SN mechanism beyond having it fail in a mass range where many progenitor models have density structures that make the explosions more likely to fail. There is no difficulty including this 20 the progenitor mass function. And, other than patience, there is no observational barrier to either detecting these black hole formation events or limiting their rates to be well below this prediction.", "keyphrases": ["red supergiant", "black hole", "neutron star"]}
{"id": "1002.3928", "title": "Large scale directional anomalies in the WMAP 5yr ILC map", "abstract": "We study the alignments of the low multipoles of CMB anisotropies with specific directions in the sky (i.e. the dipole, the north Ecliptic pole, the north Galactic pole and the north Super Galactic pole). Performing 10^5 random extractions we have found that: 1) separately quadrupole and octupole are mildly orthogonal to the dipole but when they are considered together, in analogy to <cit.>, we find an unlikely orthogonality at the level of 0.8 with the dipole at 99.1\u2113=5are mildly orthogonal to the dipole but when we consider only maps that show exactly the same correlation among the multipoles as in the observed WMAP 5yr ILC, these multipole vectors are unlikely orthogonal to the dipole at99.7", "keyphrases": ["few issue", "cmb anomaly", "orientation", "multipole moment"]}
{"id": "1701.03928", "title": "Asteroseismic constraints on Asymmetric Dark Matter: Light particles with an effective spin-dependent coupling", "abstract": "So far, direct detection searches have come empty handed in their quest for Dark Matter (DM). Meanwhile, asteroseismology arises as a complementary tool to study DM, as its accumulation in a star can enhance energy transport, by providing a conduction mechanism, producing significant changes in the stellar structure during the course of the star's evolution. The stellar core, particularly affected by the presence of DM, can be investigated through precise asteroseismic diagnostics. We modelled three stars including DM energy transport: the Sun, a slightly less massive and much older star, KIC 7871531 (0.85 M_\u2299, 9.41 Gyr), and a more massive and younger one, KIC 8379927 (1.12 M_\u2299, 1.82 Gyr). We considered both the case of Weakly Interactive Massive Particles, albeit with a low annihilation, and the case of Asymmetric DM for which the number of trapped particles in the star can be much greater. By analysing these models with asteroseismic separation ratios weighted towards the core, we found indications limiting the effective spin-dependent DM-proton coupling for masses of a few GeV. This independent result is very close to the most recent and most stringent direct detection DM constraints.", "keyphrases": ["stellar structure", "asteroseismic diagnostic", "effective spin-dependent dm-proton"]}
{"id": "0902.3452", "title": "Galaxy Satellites and the Weak Equivalence Principle", "abstract": "Numerical simulations of the effect of a long-range scalar interaction (LRSI) acting only on nonbaryonic dark matter, with strength comparable to gravity, show patterns of disruption of satellites that can agree with what is seen in the Milky Way. This includes the symmetric Sagittarius stellar stream. The exception presented here to the Kesden and Kamionkowski demonstration that an LRSI tends to produce distinctly asymmetric streams follows if the LRSI is strong enough to separate the stars from the dark matter before tidal disruption of the stellar component, and if stars dominate the mass in the luminous part of the satellite. It requires that the Sgr galaxy now contains little dark matter, which may be consistent with the Sgr stellar velocity dispersion, for in the simulation the dispersion at pericenter exceeds virial. We present other examples of simulations in which a strong LRSI produces satellites with large mass-to-light ratio, as in Draco, or free streams of stars, which might be compared to \"orphan\" streams.", "keyphrases": ["milky way", "orphan", "scalar field", "relevant model"]}
{"id": "1911.04441", "title": "Characterizing Exoplanet Habitability", "abstract": "Habitability is a measure of an environment's potential to support life, and a habitable exoplanet supports liquid water on its surface. However, a planet's success in maintaining liquid water on its surface is the end result of a complex set of interactions between planetary, stellar, planetary system and even Galactic characteristics and processes, operating over the planet's lifetime. In this chapter, we describe how we can now determine which exoplanets are most likely to be terrestrial, and the research needed to help define the habitable zone under different assumptions and planetary conditions. We then move beyond the habitable zone concept to explore a new framework that looks at far more characteristics and processes, and provide a comprehensive survey of their impacts on a planet's ability to acquire and maintain habitability over time. We are now entering an exciting era of terrestiral exoplanet atmospheric characterization, where initial observations to characterize planetary composition and constrain atmospheres is already underway, with more powerful observing capabilities planned for the near and far future. Understanding the processes that affect the habitability of a planet will guide us in discovering habitable, and potentially inhabited, planets.", "keyphrases": ["life", "surface", "planet"]}
{"id": "1101.4520", "title": "Almost Birkhoff Theorem in General Relativity", "abstract": "We extend Birkhoff's theorem for almost LRS-II vacuum spacetimes to show that the rigidity of spherical vacuum solutions of Einstein's field equations continues even in the perturbed scenario.", "keyphrases": ["rigidity", "spherical vacuum solution", "einstein", "field equation"]}
{"id": "2009.10106", "title": "Constraints on the curvature of the Universe and dynamical dark energy from the Full-shape and BAO data", "abstract": "We present limits on the parameters of the o\u039bCDM, w_0CDM, and w_0 w_aCDM models obtained from the joint analysis of the full-shape, baryon acoustic oscillations (BAO), big bang nucleosynthesis (BBN) and supernovae data. Our limits are fully independent of the data on the cosmic microwave background (CMB) anisotropies, but rival the CMB constraints in terms of parameter error bars. We find the spatial curvature consistent with a flat universe \u03a9_k=-0.043_-0.036^+0.036 (68% C.L.); the dark-energy equation of state parameter w_0 is measured to be w_0=-1.031_-0.048^+0.052 (68% C.L.), consistent with a cosmological constant. This conclusion also holds for the time-varying dark energy equation of state, for which we find w_0=-0.98_-0.11^+0.099 and w_a=-0.33_-0.48^+0.63 (both at 68% C.L.). The exclusion of the supernovae data from the analysis does not significantly weaken our bounds. This shows that using a single external BBN prior, the full-shape and BAO data can provide strong CMB-independent constraints on the non-minimal cosmological models.", "keyphrases": ["baryon", "total neutrino mass", "supernovae redshift-distance"]}