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this paper details the modeling pipeline and validates the baseline analysis choices of the des year 3 joint analysis of galaxy clustering and weak lensing (a so-called "3$\times$2pt" analysis). these analysis choices include the specific combination of cosmological probes, priors on cosmological and systematics parameters, model parameterizations for systematic effects and related approximations, and angular scales where the model assumptions are validated. we run a large number of simulated likelihood analyses using synthetic data vectors to test the robustness of our baseline analysis. we demonstrate that the des year 3 modeling pipeline, including the calibrated scale cuts, is sufficiently accurate relative to the constraining power of the des year 3 analyses. our systematics mitigation strategy accounts for astrophysical systematics, such as galaxy bias, intrinsic alignments, source and lens magnification, baryonic effects, and source clustering, as well as for uncertainties in modeling the matter power spectrum, reduced shear, and estimator effects. we further demonstrate excellent agreement between two independently-developed modeling pipelines, and thus rule out any residual uncertainties due to the numerical implementation. | dark energy survey year 3 results: multi-probe modeling strategy and validation |
the existence of a light or massive scalar field with a coupling to matter weaker than gravitational strength is a possible source of violation of the weak equivalence principle. we use the first results on the eötvös parameter by the microscope experiment to set new constraints on such scalar fields. for a massive scalar field of mass smaller than 10-12 ev (i.e., range larger than a few 1 05 m ), we improve existing constraints by one order of magnitude to |α |<10-11 if the scalar field couples to the baryon number and to |α |<10-12 if the scalar field couples to the difference between the baryon and the lepton numbers. we also consider a model describing the coupling of a generic dilaton to the standard matter fields with five parameters, for a light field: we find that, for masses smaller than 10-12 ev , the constraints on the dilaton coupling parameters are improved by one order of magnitude compared to previous equivalence principle tests. | microscope mission: first constraints on the violation of the weak equivalence principle by a light scalar dilaton |
a dark-energy, which behaves as the cosmological constant until a sudden phantom transition at very low redshift (z < 0.1), seems to solve the >4σ disagreement between the local and high-redshift determinations of the hubble constant, while maintaining the phenomenological success of the λ cold dark matter model with respect to the other observables. here, we show that such a hockey-stick dark energy cannot solve the h0 crisis. the basic reason is that the supernova absolute magnitude mb that is used to derive the local h0 constraint is not compatible with the mb that is necessary to fit supernova, baryon acoustic oscillation, and cosmic microwave background data, and this disagreement is not solved by a sudden phantom transition at very low redshift. we make use of this example to show why it is preferable to adopt in the statistical analyses the prior on mb as an alternative to the prior on h0. the three reasons are: (i) one avoids potential double counting of low-redshift supernovae, (ii) one avoids assuming the validity of cosmography, in particular, fixing the deceleration parameter to the standard model value q0 = -0.55, (iii) one includes in the analysis the fact that mb is constrained by local calibration, an information which would otherwise be neglected in the analysis, biasing both model selection and parameter constraints. we provide the priors on mb relative to the recent pantheon and des-sn3yr supernova catalogs. we also provide a gaussian joint prior on h0 and q0 that generalizes the prior on h0 by supernova h0 for the equation of state. | on the use of the local prior on the absolute magnitude of type ia supernovae in cosmological inference |
computing the properties of the bubble wall of a cosmological first order phase transition at electroweak scale is of paramount importance for the correct prediction of the baryon asymmetry of the universe and the spectrum of gravitational waves. by means of the semiclassical formalism we calculate the velocity and thickness of the wall using as theoretical framework the scalar singlet extension of the sm with a parity symmetry and the sm effective field theory supplemented by a dimension six operator. we use these solutions to carefully predict the baryon asymmetry and the gravitational wave signals. the singlet scenario can easily accommodate the observed asymmetry but these solutions do not lead to observable effects at future gravity wave experiments. in contrast the effective field theory fails at explaining the baryon abundance due to the strict constraints from electric dipole moment experiments, however, the strongest solutions we found fall within the sensitivity of the lisa experiment. we provide a simple analytical approximation for the wall velocity which only requires calculation of the strength and temperature of the transition and works reasonably well in all models tested. we find that generically the weak transitions where the fluid approximation can be used to calculate the wall velocity and verify baryogenesis produce signals too weak to be observed in future gravitational wave experiments. thus, we infer that gw signals produced by simple sm extensions visible in future experiments are likely to only result from strong transitions described by detonations with highly relativistic wall velocities. | electroweak bubble wall expansion: gravitational waves and baryogenesis in standard model-like thermal plasma |
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° < |b| < 20° 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° (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 ebreak = 2.1 ± 0.2 gev, and with spectra predicted by the self-annihilation of dark matter, implying in the case of b̄b final states a dark matter mass of mχ=49+6.4-5.4 gev. | background model systematics for the fermi gev excess |
we study the comoving curvature perturbation r in the single-field inflation models whose potential can be approximated by a piecewise quadratic potential v (φ ) by using the δ n formalism. we find a general formula for r (δ φ ,δ π ) , consisting of a sum of logarithmic functions of the field perturbation δ φ and the velocity perturbation δ π at the point of interest, as well as of δ π* at the boundaries of each quadratic piece, which are functions of (δ φ ,δ π ) through the equation of motion. each logarithmic expression has an equivalent dual expression, due to the second-order nature of the equation of motion for φ . we also clarify the condition under which r (δ φ ,δ π ) reduces to a single logarithm, which yields either the renowned "exponential tail" of the probability distribution function of r or a gumbel-distribution-like tail. | logarithmic duality of the curvature perturbation |
we derive the strongest constraint on the fraction of dark matter that can be composed of low mass primordial black holes by using the observation of the galactic center 511 kev γ -ray line. primordial black holes of masses ≲1015 kg will evaporate to produce e± pairs. the positrons will lose energy in the galactic center, become nonrelativistic, then annihilate with the ambient electrons. we derive robust and conservative bounds by assuming that the rate of positron injection via primordial black hole evaporation is less than what is required to explain the spi/integral observation of the galactic center 511 kev γ -ray line. depending on the primordial black hole mass function and other astrophysical uncertainties, these constraints are the most stringent in the literature and show that primordial black holes contribute to less than 1% of the dark matter density. our technique also probes part of the mass range which was completely unconstrained by previous studies. | primordial black holes as a dark matter candidate are severely constrained by the galactic center 511 kev γ -ray line |
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. | a note on inflation and the swampland |
we present the possibility that the seesaw mechanism with thermal leptogenesis can be tested using the stochastic gravitational background. achieving neutrino masses consistent with atmospheric and solar neutrino data, while avoiding nonperturbative couplings, requires right handed neutrinos lighter than the typical scale of grand unification. this scale separation suggests a symmetry protecting the right-handed neutrinos from getting a mass. thermal leptogenesis would then require that such a symmetry be broken below the reheating temperature. we enumerate all such possible symmetries consistent with these minimal assumptions and their corresponding defects, finding that in many cases, gravitational waves from the network of cosmic strings should be detectable. estimating the predicted gravitational wave background, we find that future space-borne missions could probe the entire range relevant for thermal leptogenesis. | testing the seesaw mechanism and leptogenesis with gravitational waves |
we point out two ways to search for low-mass axion dark matter using cosmic microwave background (cmb) polarization measurements. these appear, in particular, to be some of the most promising ways to directly detect fuzzy dark matter. axion dark matter causes rotation of the polarization of light passing through it. this gives rise to two novel phenomena in the cmb. first, the late-time oscillations of the axion field today cause the cmb polarization to oscillate in phase across the entire sky. second, the early-time oscillations of the axion field wash out the polarization produced at last scattering, reducing the polarized fraction (te and ee power spectra) compared to the standard prediction. since the axion field is oscillating, the common (static) "cosmic birefringence" search is not appropriate for axion dark matter. these two phenomena can be used to search for axion dark matter at the lighter end of the mass range, with a reach several orders of magnitude beyond current constraints. we set a limit from the washout effect using existing planck results, and find significant future discovery potential for cmb detectors searching in particular for the oscillating effect. | axion dark matter detection with cmb polarization |
the standard model higgs potential becomes unstable at large field values. after clarifying the issue of gauge dependence of the effective potential, we study the cosmological evolution of the higgs field in presence of this instability throughout inflation, reheating and the present epoch. we conclude that anti-de sitter patches in which the higgs field lies at its true vacuum are lethal for our universe. from this result, we derive upper bounds on the hubble constant during inflation, which depend on the reheating temperature and on the higgs coupling to the scalar curvature or to the inflaton. finally we study how a speculative link between higgs meta-stability and consistence of quantum gravity leads to a sharp prediction for the higgs and top masses, which is consistent with measured values. | the cosmological higgstory of the vacuum instability |
the abundance of primordial black holes (pbhs) in the mass range 0.1-103 msolar can potentially be tested by gravitational wave observations due to the large merger rate of pbh binaries formed in the early universe. to put the estimates of the latter on a firmer footing, we first derive analytical pbh merger rate for general pbh mass functions while imposing a minimal initial comoving distance between the binary and the pbh nearest to it, in order to pick only initial configurations where the binary would not get disrupted. we then study the formation and evolution of pbh binaries before recombination by performing n-body simulations. we find that the analytical estimate based on the tidally perturbed 2-body system strongly overestimates the present merger rate when pbhs comprise all dark matter, as most initial binaries are disrupted by the surrounding pbhs. this is mostly due to the formation of compact n-body systems at matter-radiation equality. however, if pbhs make up a small fraction of the dark matter, fpbh lesssim 10%, these estimates become more reliable. in that case, the merger rate observed by ligo imposes the strongest constraint on the pbh abundance in the mass range 2-160 msolar. finally, we argue that, even if most initial pbh binaries are perturbed, the present bh-bh merger rate of binaries formed in the early universe is larger than script o(10) gpc-3 yr-1 fpbh3. | formation and evolution of primordial black hole binaries in the early universe |
a key insight of the bootstrap approach to cosmological correlations is the fact that all correlators of slow-roll inflation can be reduced to a unique building block — the four-point function of conformally coupled scalars, arising from the exchange of a massive scalar. correlators corresponding to the exchange of particles with spin are then obtained by applying a spin-raising operator to the scalar-exchange solution. similarly, the correlators of massless external fields can be derived by acting with a suitable weight-raising operator. in this paper, we present a systematic and highly streamlined derivation of these operators (and their generalizations) using tools of conformal field theory. our results greatly simplify the theoretical foundations of the cosmological bootstrap program. | the cosmological bootstrap: weight-shifting operators and scalar seeds |
in this work we revisit the construction of theories for a massive vector field with derivative self-interactions such that only the 3 desired polarizations corresponding to a proca field propagate. we start from the decoupling limit by constructing healthy interactions containing second derivatives of the stueckelberg field with itself and also with the transverse modes. the resulting interactions can then be straightforwardly generalized beyond the decoupling limit. we then proceed to a systematic construction of the interactions by using the levi-civita tensors. both approaches lead to a finite family of allowed derivative self-interactions for the proca field. this construction allows us to show that some higher order terms recently introduced as new interactions trivialize in 4 dimensions by virtue of the cayley-hamilton theorem. moreover, we discuss how the resulting derivative interactions can be written in a compact determinantal form, which can also be regarded as a generalization of the born-infeld lagrangian for electromagnetism. finally, we generalize our results for a curved background and give the necessary non-minimal couplings guaranteeing that no additional polarizations propagate even in the presence of gravity. | derivative self-interactions for a massive vector field |
dark matter (dm) could couple to particles in the standard model (sm) through a light vector mediator. in the limit of small coupling, this portal could be responsible for producing the observed dm abundance through a mechanism known as freeze-in. furthermore, the requisite dm-sm couplings provide a concrete benchmark for direct and indirect searches for dm. we present updated calculations of the relic abundance for dm produced by freeze-in through a light vector mediator. we identify an additional production channel: the decay of photons that acquire an in-medium plasma mass. these plasmon decays are a dominant channel for dm production for sub-mev dm masses, and including this channel leads to a significant reduction in the predicted signal strength for dm searches. accounting for production from both plasmon decays and annihilations of sm fermions, the dm acquires a highly nonthermal phase-space distribution which impacts the cosmology at later times; these cosmological effects will be explored in a companion paper. | making dark matter out of light: freeze-in from plasma effects |
we present the first cosmological parameter constraints using measurements of type ia supernovae (sne ia) from the dark energy survey supernova program (des-sn). the analysis uses a subsample of 207 spectroscopically confirmed sne ia from the first three years of des-sn, combined with a low-redshift sample of 122 sne from the literature. our “des-sn3yr” result from these 329 sne ia is based on a series of companion analyses and improvements covering sn ia discovery, spectroscopic selection, photometry, calibration, distance bias corrections, and evaluation of systematic uncertainties. for a flat λcdm model we find a matter density {{{ω }}}{{m}}=0.331+/- 0.038. for a flat wcdm model, and combining our sn ia constraints with those from the cosmic microwave background (cmb), we find a dark energy equation of state w=-0.978+/- 0.059, and {{{ω }}}{{m}}=0.321+/- 0.018. for a flat w 0 wa cdm model, and combining probes from sn ia, cmb and baryon acoustic oscillations, we find {w}0=-0.885+/- 0.114 and {w}a=-0.387 +/- 0.430. these results are in agreement with a cosmological constant and with previous constraints using sne ia (pantheon, jla). | first cosmology results using type ia supernovae from the dark energy survey: constraints on cosmological parameters |
astroparticle physics is undergoing a profound transformation, due to a series of extraordinary new results, such as the discovery of high-energy cosmic neutrinos with icecube, the direct detection of gravitational waves with ligo and virgo, and many others. this white paper is the result of a collaborative effort that involved hundreds of theoretical astroparticle physicists and cosmologists, under the coordination of the european consortium for astroparticle theory (eucapt). addressed to the whole astroparticle physics community, it explores upcoming theoretical opportunities and challenges for our field of research, with particular emphasis on the possible synergies among different subfields, and the prospects for solving the most fundamental open questions with multi-messenger observations. | eucapt white paper: opportunities and challenges for theoretical astroparticle physics in the next decade |
the low frequency array (lofar) is an ideal instrument to conduct deep extragalactic surveys. it has a large field of view and is sensitive to large-scale and compact emission. it is, however, very challenging to synthesize thermal noise limited maps at full resolution, mainly because of the complexity of the low-frequency sky and the direction dependent effects (phased array beams and ionosphere). in this first paper of a series, we present a new calibration and imaging pipeline that aims at producing high fidelity, high dynamic range images with lofar high band antenna data, while being computationally efficient and robust against the absorption of unmodeled radio emission. we apply this calibration and imaging strategy to synthesize deep images of the boötes and lockman hole fields at ~150 mhz, totaling ~80 and ~100 h of integration, respectively, and reaching unprecedented noise levels at these low frequencies of ≲30 and ≲23 μjy beam−1 in the inner ~3 deg2. this approach is also being used to reduce the lotss-wide data for the second data release. | the lofar two-meter sky survey: deep fields data release 1. i. direction-dependent calibration and imaging |
we combine new analysis of the stochastic gravitational wave background to be expected from cosmic strings with the latest pulsar timing array (pta) limits to give an upper bound on the energy scale of the possible cosmic string network, gμ < 1.5 ×10-11 at the 95% confidence level. we also show bounds from ligo and to be expected from lisa and bbo. current estimates for the gravitational wave background from supermassive black hole binaries are at the level where a pta detection is expected. but if ptas do observe a background soon, it will be difficult in the short term to distinguish black holes from cosmic strings as the source, because the spectral indices from the two sources happen to be quite similar. if ptas do not observe a background, then the limits on gμ will improve somewhat, but a string network with gμ substantially below 10-11 will produce gravitational waves primarily at frequencies too high for pta observation, so significant further progress will depend on intermediate-frequency observatories such as lisa, decigo and bbo. | new limits on cosmic strings from gravitational wave observation |
we study production of gravitational waves (gws) in strongly supercooled cosmological phase transitions in gauge theories. we extract from two-bubble lattice simulations the scaling of the gw source, and use it in many-bubble simulations in the thin-wall limit to estimate the resulting gw spectrum. we find that in presence of the gauge field the gw source decays with bubble radius as ∝r-3 after collisions. this leads to a gw spectrum that follows ωgw∝ω2.3 at low frequencies and ωgw∝ω-2.9 at high frequencies, marking a significant deviation from the popular envelope approximation. | gravitational waves from colliding vacuum bubbles in gauge theories |
we show that the excess in electron recoil events seen by the xenon1t experiment can be explained by a relatively low-mass luminous dark matter candidate. the dark matter scatters inelastically in the detector (or the surrounding rock) to produce a heavier dark state with a ∼2 - 3 kev mass splitting. this heavier state then decays within the detector, producing a peak in the electron recoil spectrum that is a good fit to the observed excess. we comment on the ability of future direct detection experiments to differentiate this model from other "beyond the standard model" scenarios and from possible tritium backgrounds, including the use of diurnal modulation, multichannel signals, etc., as possible distinguishing features of this scenario. | explaining the xenon1t excess with luminous dark matter |
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. | cosmology with cosmic shear observations: a review |
we present measurements of cosmic shear two-point correlation functions (tpcfs) from hyper suprime-cam subaru strategic program (hsc) first-year data, and derive cosmological constraints based on a blind analysis. the hsc first-year shape catalog is divided into four tomographic redshift bins ranging from $z=0.3$ to 1.5 with equal widths of $\delta z =0.3$ . the unweighted galaxy number densities in each tomographic bin are 5.9, 5.9, 4.3, and $2.4\:$ arcmin $^{-2}$ from the lowest to highest redshifts, respectively. we adopt the standard tpcf estimators, $\xi _\pm$ , for our cosmological analysis, given that we find no evidence of significant b-mode shear. the tpcfs are detected at high significance for all 10 combinations of auto- and cross-tomographic bins over a wide angular range, yielding a total signal-to-noise ratio of 19 in the angular ranges adopted in the cosmological analysis, $7^{\prime }<\theta <56^{\prime }$ for $\xi _+$ and $28^{\prime }<\theta <178^{\prime }$ for $\xi _-$ . we perform the standard bayesian likelihood analysis for cosmological inference from the measured cosmic shear tpcfs, including contributions from intrinsic alignment of galaxies as well as systematic effects from psf model errors, shear calibration uncertainty, and source redshift distribution errors. we adopt a covariance matrix derived from realistic mock catalogs constructed from full-sky gravitational lensing simulations that fully account for survey geometry and measurement noise. for a flat $\lambda$ cold dark matter model, we find $s\,_8 \equiv \sigma _8\sqrt{\omega _{\rm m}/0.3}=0.804_{-0.029}^{+0.032}$ , and $\omega _{\rm m}=0.346_{-0.100}^{+0.052}$ . we carefully check the robustness of the cosmological results against astrophysical modeling uncertainties and systematic uncertainties in measurements, and find that none of them has a significant impact on the cosmological constraints. | cosmological constraints from cosmic shear two-point correlation functions with hsc survey first-year data |
we compute and investigate four types of imprint of a stochastic background of primordial magnetic fields (pmfs) on the cosmic microwave background (cmb) anisotropies: the impact of pmfs on the cmb temperature and polarization spectra, which is related to their contribution to cosmological perturbations; the effect on cmb polarization induced by faraday rotation; the impact of pmfs on the ionization history; magnetically-induced non-gaussianities and related non-zero bispectra; and the magnetically-induced breaking of statistical isotropy. we present constraints on the amplitude of pmfs that are derived from different planck data products, depending on the specific effect that is being analysed. overall, planck data constrain the amplitude of pmfs to less than a few nanogauss, with different bounds that depend on the considered model. in particular, individual limits coming from the analysis of the cmb angular power spectra, using the planck likelihood, are b1 mpc < 4.4 ng (where b1 mpc is the comoving field amplitude at a scale of 1 mpc) at 95% confidence level, assuming zero helicity. by considering the planck likelihood, based only on parity-even angular power spectra, we obtain b1 mpc < 5.6 ng for a maximally helical field. for nearly scale-invariant pmfs we obtain b1 mpc < 2.0 ng and b1 mpc < 0.9 ng if the impact of pmfs on the ionization history of the universe is included in the analysis. from the analysis of magnetically-induced non-gaussianity, we obtain three different values, corresponding to three applied methods, all below 5 ng. the constraint from the magnetically-induced passive-tensor bispectrum is b1 mpc < 2.8 ng. a search for preferred directions in the magnetically-induced passive bispectrum yields b1 mpc < 4.5 ng, whereas the compensated-scalar bispectrum gives b1 mpc < 3 ng. the analysis of the faraday rotation of cmb polarization by pmfs uses the planck power spectra in ee and bb at 70 ghz and gives b1 mpc < 1380 ng. in our final analysis, we consider the harmonic-space correlations produced by alfvén waves, finding no significant evidence for the presence of these waves. together, these results comprise a comprehensive set of constraints on possible pmfs with planck data. | planck 2015 results. xix. constraints on primordial magnetic fields |
we search for signatures of gravitational lensing in the gravitational-wave signals from compact binary coalescences detected by advanced laser interferometer gravitational-wave observatory (ligo) and advanced virgo during o3a, the first half of their third observing run. we study: (1) the expected rate of lensing at current detector sensitivity and the implications of a non-observation of strong lensing or a stochastic gravitational-wave background on the merger-rate density at high redshift; (2) how the interpretation of individual high-mass events would change if they were found to be lensed; (3) the possibility of multiple images due to strong lensing by galaxies or galaxy clusters; and (4) possible wave-optics effects due to point-mass microlenses. several pairs of signals in the multiple-image analysis show similar parameters and, in this sense, are nominally consistent with the strong lensing hypothesis. however, taking into account population priors, selection effects, and the prior odds against lensing, these events do not provide sufficient evidence for lensing. overall, we find no compelling evidence for lensing in the observed gravitational-wave signals from any of these analyses. | search for lensing signatures in the gravitational-wave observations from the first half of ligo-virgo's third observing run |
we consider a real scalar singlet field which provides a strong first-order electroweak phase transition via its coupling to the higgs boson, and gives a c p violating contribution on the top quark mass via a dimension-6 operator. we study the correlation between the baryon-to-entropy ratio produced by electroweak baryogenesis, and the gravitational wave signal from the electroweak phase transition. we show that future gravitational wave experiments can test, in particular, the region of the model parameter space where the observed baryon-to-entropy ratio can be obtained even if the new physics scale, which is explicit in the dimension-6 operator, is high. | electroweak baryogenesis and gravitational waves from a real scalar singlet |
we show that a combined analysis of cosmic microwave background anisotropy power spectra obtained by the planck satellite and luminosity distance data simultaneously excludes a flat universe and a cosmological constant at 99% confidence level. these results hold separately when combining planck with three different data sets: the two determinations of the hubble constant from riess et al. and freedman et al., and the pantheon catalog of high-redshift type ia supernovae. we conclude that either the lambda cold dark matter model needs to be replaced by a different paradigm, or else there are significant but still undetected systematics. our result calls for new observations and stimulates the investigation of alternative theoretical models and solutions. | investigating cosmic discordance |
in this paper, we investigated the effect of dark matter on the weak deflection angle by black holes at the galactic center. we consider three known dark matter density profiles such as the cold dark matter, scalar field dark matter, and the universal rotation curve from the burkert profile. to achieve this goal, we used how the positional angles are measured by the ishihara et al. method based on the gauss-bonnet theorem on the optical metric. with the help of the non-asymptotic form of the gauss-bonnet theorem, the longitudinal angle difference is also calculated. first, we find the emergence of apparent divergent terms on the said profiles, which indicates that the spacetime describing the black hole-dark matter combination is non-asymptotic. we showed that these apparent divergent terms vanish when the distance of the source and receiver are astronomically distant from the black hole. using the current observational data in the milky way and m87 galaxies, we find interesting behaviors of how the weak deflection angle varies with the impact parameter, which gives us some hint on how dark matter interacts with the null particles for each dark matter density profile. we conclude that since these deviations are evident near the dark matter core radius, the weak deflection angle offers a better alternative for dark matter detection than using the deviation from the black hole shadow. with the dark matter profiles explored in this study, we find that the variation of the values for weak deflection angle strongly depends on the dark matter mass on a particular profile. | dark matter effect on the weak deflection angle by black holes at the center of milky way and m87 galaxies |
in this paper, we study a possible early universe source for the recent observation of a stochastic gravitational wave background at the nanograv pulsar timing array. the source is a tachyonic instability in a dark gauge field induced by an axion-like particle (alp), a known source for gravitational waves. we find that relative to the previous analysis with the nanograv 12.5-year data set, the current 15-year data set favors parameter space with a relatively larger axion mass and decay constant. this favored parameter space is heavily constrained by $\delta n_{\rm eff}$ and overproduction of alp dark matter. while there are potential mechanisms for avoiding the second problem, evading the $\delta n_{\rm eff}$ constraint remains highly challenging. in particular, we find that the gravitational wave magnitude is significantly suppressed with respect to the gauge boson dark radiation, which implies that successfully explaining the nanograv observation requires a large additional dark radiation, violating the cosmological constraints. | challenges in interpreting the nanograv 15-year data set as early universe gravitational waves produced by alp induced instability |
recently, multiple pulsar timing array collaborations have presented compelling evidence for a stochastic signal at nanohertz frequencies, potentially originating from cosmic strings. cosmic strings are linear topological defects that can arise during phase transitions in the early universe or as fundamental strings in superstring theory. this paper focuses on investigating the detection capabilities of taiji, a planned space-based gravitational wave detector, for the gravitational wave background generated by cosmic strings. by analyzing simulated taiji data and utilizing comprehensive bayesian parameter estimation techniques, we demonstrate a significant improvement in precision compared to the nanograv 15-year data, surpassing it by an order of magnitude. this highlights the enhanced measurement capabilities of taiji. consequently, taiji can serve as a valuable complementary tool to pulsar timing arrays in validating and exploring the physics of cosmic strings in the early universe. | prospects for taiji to detect a gravitational-wave background from cosmic strings |
general relativity predicts that gravitational waves propagate at the speed of light. although ground-based gravitational-wave detectors have successfully constrained the velocity of gravitational waves in the high-frequency range, extending this constraint to the lower frequency range remains a challenge. in this work, we utilize the deviations in the overlap reduction function for a gravitational-wave background within pulsar timing arrays to investigate the velocity of gravitational waves in the nanohertz frequency band. by analyzing the nanograv 15-year data set, we obtain a well-constrained lower bound for the velocity of gravitational waves that $v \gtrsim 0.87\,c$, where $c$ is the speed of light. | constraints on the velocity of gravitational waves from nanograv 15-year data set |
dark matter (dm) particles with mass in the sub-gev range are an attractive alternative to heavier weakly interacting massive particles, but direct detection of such light particles is challenging. if, however, dm-nucleus scattering leads to ionization of the recoiling atom, the resulting electron may be detected even if the nuclear recoil is unobservable. we demonstrate that including this effect significantly enhances direct detection sensitivity to sub-gev dm. existing experiments set world-leading limits, and future experiments may probe the cross sections relevant for thermal freeze-out. | directly detecting sub-gev dark matter with electrons from nuclear scattering |
persisting tensions between high-redshift and low-redshift cosmological observations suggest the dark energy sector of the universe might be more complex than the positive cosmological constant of the λcdm model. motivated by string theory, wherein symmetry considerations make consistent ads backgrounds (i.e., maximally-symmetric spacetimes with a negative cosmological constant) ubiquitous, we explore a scenario where the dark energy sector consists of two components: a negative cosmological constant, with a dark energy component with equation of state wϕ on top. we test the consistency of the model against low-redshift baryon acoustic oscillation and type ia supernovae distance measurements, assessing two alternative choices of distance anchors: the sound horizon at baryon drag determined by the planck collaboration and the hubble constant determined by the sh0es program. we find no evidence for a negative cosmological constant and mild indications for an effective phantom dark energy component on top. a model comparison analysis reveals that the λcdm model is favoured over our negative cosmological constant model. while our results are inconclusive, should low-redshift tensions persist with future data, it would be worth reconsidering and further refining our toy negative cosmological constant model by considering realistic string constructions. | revisiting a negative cosmological constant from low-redshift data |
current cosmological data exhibit discordance between indirect and some direct inferences of the present-day expansion rate h0 . early dark energy (ede), which briefly increases the cosmic expansion rate prior to recombination, is a leading scenario for resolving this "hubble tension" while preserving a good fit to cosmic microwave background (cmb) data. however, this comes at the cost of changes in parameters that affect structure formation in the late-time universe, including the spectral index of scalar perturbations ns. here, we present the first constraints on axionlike ede using data from the lyman-α forest, i.e., absorption lines imprinted in background quasar spectra by neutral hydrogen gas along the line of sight. we consider two independent measurements of the one-dimensional ly α forest flux power spectrum from the sloan digital sky survey (sdss eboss) and from the mike/hires and x-shooter spectrographs. we combine these with a baseline dataset comprised of planck cmb data and baryon acoustic oscillation (bao) measurements. combining the eboss ly α data with the cmb and bao dataset reduces the 95% confidence level (c.l.) upper bound on the maximum fractional contribution of ede to the cosmic energy budget fede from 0.07 to 0.03 and constrains h0=67.9-0.4+0.4 km /s /mpc (68% c.l.), with maximum a posteriori value h0=67.9 km /s /mpc . similar results are obtained for the mike/hires and x-shooter ly α data. our ly α -based ede constraints yield h0 values that are in >4 σ tension with the sh0es distance-ladder measurement and are driven by the preference of the ly α forest data for ns values lower than those required by ede cosmologies that fit planck cmb data. taken at face value, the ly α forest severely constrains canonical ede models that could resolve the hubble tension. | canonical hubble-tension-resolving early dark energy cosmologies are inconsistent with the lyman-α forest |
we compute the decay spectrum for dark matter (dm) with masses above the scale of electroweak symmetry breaking, all the way to the planck scale. for an arbitrary hard process involving a decay to the unbroken standard model, we determine the prompt distribution of stable states including photons, neutrinos, positrons, and antiprotons. these spectra are a crucial ingredient in the search for dm via indirect detection at the highest energies as being probed in current and upcoming experiments including icecube, hawc, cta, and lhaaso. our approach improves considerably on existing methods, for instance, we include all relevant electroweak interactions. | dark matter spectra from the electroweak to the planck scale |
we show that the minimal type-i seesaw mechanism can successfully account for the observed dark matter abundance in the form of a kev sterile neutrino. this population can be produced by the decay of the heavier neutral leptons, with masses above the electroweak mass scale, while they are in thermal equilibrium in the early universe (freeze-in). moreover, the implementation of the relevant phenomenological constraints (relic abundance, indirect detection and structure formation) on this model automatically selects a region of the parameter space featuring an approximate lepton number symmetry. | freeze-in dark matter within the seesaw mechanism |
we discuss cosmic domain walls described by a tension redshifting with the expansion of the universe. these melting domain walls emit gravitational waves with the low-frequency spectral shape ωg w∝f2 corresponding to the spectral index γ =3 favored by the recent nanograv 15 yrs data. we discuss a concrete high-energy physics scenario leading to such a melting domain wall network in the early universe. this scenario involves a feebly coupled scalar field, which can serve as a promising dark matter candidate. we identify parameters of the model matching the gravitational wave characteristics observed in the nanograv data. the dark matter mass is pushed to the ultralight range below 10-11−10-12 ev which is accessible through planned observations thanks to the effects of superradiance of rotating black holes. | nanograv spectral index γ =3 from melting domain walls |
releasing the 12.5-year pulsar timing array data, the north american nanohertz observatory for gravitational waves (nanograv) has recently reported the evidence for a stochastic common-spectrum which would herald the detection of a stochastic gravitational wave background (sgwb) for the first time. we investigate if the signal could be generated from the end of a $\sim 10$ mev but still phenomenologically viable double-field inflation when the field configuration settles to its true vacuum. during the double-field inflation at such scales, bubbles of true vacuum that can collapse to ligo mass and heavier primordial black holes form. we show that only when this process happens with a first-order phase transition, the produced gravitational wave spectrum can match with the nanograv acclaimed sgwb signal. we show that the produced gravitational wave spectrum matches the nanograv sgwb signal only when this process happens through a first-order phase transition. using latticeeasy, we also examine the previous observation in the literature that by lowering the scale of preheating, despite the shift of the peak frequency of the gravitational wave profile to smaller values, the amplitude of the sgwb could be kept almost constant. we notice that this observation breaks down at the preheating scale, $m\lesssim 10^{-14}~m_{{}_{\rm pl}}$. | nanograv signal from the end of inflation and the ligo mass and heavier primordial black holes |
gravitational waves are expected to be radiated by supermassive black hole binaries formed during galaxy mergers. a stochastic superposition of gravitational waves from all such binary systems would modulate the arrival times of pulses from radio pulsars. using observations of millisecond pulsars obtained with the parkes radio telescope, we constrained the characteristic amplitude of this background, ac,yr, to be <1.0 × 10-15 with 95% confidence. this limit excludes predicted ranges for ac,yr from current models with 91 to 99.7% probability. we conclude that binary evolution is either stalled or dramatically accelerated by galactic-center environments and that higher-cadence and shorter-wavelength observations would be more sensitive to gravitational waves. | gravitational waves from binary supermassive black holes missing in pulsar observations |
the hubble tension can be significantly eased if there is an early component of dark energy that becomes active around the time of matter-radiation equality. early dark energy models suffer from a coincidence problem—the physics of matter-radiation equality and early dark energy are completely disconnected, so some degree of fine-tuning is needed in order for them to occur nearly simultaneously. in this letter, we propose a natural explanation for this coincidence. if the early dark energy scalar couples to neutrinos then it receives a large injection of energy around the time that neutrinos become nonrelativistic. this is precisely when their temperature is of order of their mass, which, coincidentally, occurs around the time of matter-radiation equality. neutrino decoupling therefore provides a natural trigger for early dark energy by displacing the field just before matter-radiation equality. we discuss various theoretical aspects of this proposal, potential observational signatures, and future directions for its study. | early dark energy from massive neutrinos as a natural resolution of the hubble tension |
the event horizon telescope (eht) collaboration recently published the first images of the supermassive black holes in the cores of the messier 87 and milky way galaxies. these observations have provided a new means to study supermassive black holes and probe physical processes occurring in the strong-field regime. we review the prospects of future observations and theoretical studies of supermassive black hole systems with the next-generation event horizon telescope (ngeht), which will greatly enhance the capabilities of the existing eht array. these enhancements will open up several previously inaccessible avenues of investigation, thereby providing important new insights into the properties of supermassive black holes and their environments. this review describes the current state of knowledge for five key science cases, summarising the unique challenges and opportunities for fundamental physics investigations that the ngeht will enable. | fundamental physics opportunities with the next-generation event horizon telescope |
a group of massive galaxies at redshifts of $z\gtrsim 7$ have been recently detected by the james webb space telescope (jwst), which were unexpected to form at such early time within the standard big bang cosmology. in this work, we propose that this puzzle can be explained by the presence of some primordial black holes (pbhs) with mass of $\sim 1000 m_\odot$. these pbhs act as seeds for early galaxies formation with masses of $\sim 10^{8}-10^{10}~m_\odot$ at high redshift, hence accounting for the jwst observations. we use a hierarchical bayesian inference framework to constrain the pbh mass distribution models, and find that the lognormal model with the $m_{\rm c}\sim 750m_\odot$ is preferred over other hypotheses. these rapidly growing bhs are expected to have strong radiation and may appear as the high-redshift compact objects, similar to those recently discovered by jwst. | rapidly growing primordial black holes as seeds of the massive high-redshift jwst galaxies |
we present a bayesian population modeling method to analyze the abundance of galaxy clusters identified by the south pole telescope (spt) with a simultaneous mass calibration using weak gravitational lensing data from the dark energy survey (des) and the hubble space telescope (hst). we discuss and validate the modeling choices with a particular focus on a robust, weak-lensing-based mass calibration using des data. for the des year 3 data, we report a systematic uncertainty in weak-lensing mass calibration that increases from 1\% at $z=0.25$ to 10\% at $z=0.95$, to which we add 2\% in quadrature to account for uncertainties in the impact of baryonic effects. we implement an analysis pipeline that joins the cluster abundance likelihood with a multi-observable likelihood for the sz, optical richness, and weak-lensing measurements for each individual cluster. we validate that our analysis pipeline can recover unbiased cosmological constraints by analyzing mocks that closely resemble the cluster sample extracted from the spt-sz, sptpol~ecs, and sptpol~500d surveys and the des year~3 and hst-39 weak-lensing datasets. this work represents a crucial prerequisite for the subsequent cosmological analysis of the real dataset. | spt clusters with des and hst weak lensing. i. cluster lensing and bayesian population modeling of multi-wavelength cluster datasets |
global cosmic strings are predicted in many motivated extensions to the standard model of particle physics, with close connections to axion dark matter physics. recent studies suggest that, although subdominant relative to goldstone emission, gravitational wave (gw) signals from global strings can be detectable with current and planned gw detectors such as ligo, lisa, decigo/bbo, et/ce and aedge/aion, as well as pulsar timing arrays such as ppta, nanograv and ska. this work is an extensive, updated study on gws from a global cosmic string network, taking into account of the most recent developments related to the subject. the main analysis is based on the analytical velocity-dependent one-scale (vos) model calibrated with recent simulation results, which provides a generic protocol for such calculations with details given. we also demonstrate how the gw signal can be influenced with variations to the baseline model: this includes considering the uncertainties of model parameters and the potential deviation from the conventional vos model prediction (i.e. the scaling behavior) as suggested by some of the recent simulation results. furthermore, we investigated in detail the effect of a non-standard cosmology (e.g. early matter domination or kination) or new particle species on the gw signals from global strings. we demonstrate that the frequency spectrum of gw background from global cosmic strings can be used to probe the cosmic history prior to the big bang nucleosynthesis (bbn) (i.e. the primordial dark age) up to a temperature of t ∼ 108 gev. | gravitational waves from global cosmic strings and cosmic archaeology |
the time evolution of primordial fluctuations conceals a wealth of insights into the high-energy physics at play during the earliest moments of our universe, which is ultimately encoded in late-time spatial correlation functions. however, the conventional procedure to compute them is technically challenging, and a complete dictionary mapping the landscape of inflationary theories and the corresponding observable signatures is not yet available. in this paper, we develop a framework to compute tree-level cosmological correlators based on following their time evolution from their origin as quantum zero-point fluctuations to the end of inflation. from first principles, the structure of the bulk time evolution imposes a set of universal differential equations in time satisfied by equal-time correlators. we automatise the process of systematically solving these equations. this allows us to accurately capture all physical effects and obtain exact results in theories formulated at the level of inflationary fluctuations that include any number of degrees of freedom with arbitrary dispersion relations and masses, coupled through any time-dependent interactions. we then illustrate the power of this formalism by exploring the phenomenology of cosmological correlators emerging from the interaction with a massive scalar field. we study both the size and the shape dependence of non-gaussianities in the entire parameter space, including the strong mixing regime. we present novel characteristics of cosmological collider signals in (would be) single-, double-, and triple-exchange three-point correlators. in the presence of primordial features, we show that soft limits of cosmological correlators offer a new possibility to probe the inflationary landscape. finally, we provide templates to search for in future cosmological surveys. | the cosmological flow: a systematic approach to primordial correlators |
recently, pulsar timing array experiments reported the observation of a stochastic gravitational wave background in the nanohertz range frequency band. we show that such a signal can be originated from a cosmological first-order phase transition (pt) within a well-motivated heavy (visible) qcd axion model. considering the peccei-quinn symmetry breaking at the tev scale in the scenario, we find a supercooled pt, in the parameter space of the model, prolonging the pt with the reheating temperature at the gev scale. | heavy qcd axion model in light of pulsar timing arrays |
our work highlights the crucial role played by the equation of state (eos) parameter $w$ within the context of single field inflation with multiple sharp transitions (msts) to untangle the current state of the pbh overproduction issue. we examine the situation for a broad interval of eos parameter that remains most favourable to explain the recent data released by the pulsar timing array (pta) collaboration. our analysis yields the interval, $0.2 \leq w \leq 1/3$, to be the most acceptable window from the sigw interpretation of the pta signal and where sizeable pbhs abundance, $f_{\rm pbh} \in (10^{-3},1)$, is observed. we also obtain $w=1/3$, radiation-dominated era, to be the best scenario to explain the early stages of the universe and address the overproduction problem. within the range of $1 \leq c_{s} \leq 1.17$, we construct a regularized-renormalized-resummed scalar power spectrum whose amplitude obeys the perturbativity criterion while being substantial enough to generate eos dependent scalar induced gravitational waves ($w$-sigws) consistent with nanograv-15 data. working for both $c_{s} = 1\;{\rm and}\;1.17$, we find the $c_{s}=1.17$ case more favourable for generating large mass pbhs, $m_{\rm pbh}\sim {\cal o}(10^{-6}-10^{-3})m_{\odot}$, as potential dark matter candidates with substantial abundance after constraints coming from microlensing experiments. | untangling pbh overproduction in $w$-sigws generated by pulsar timing arrays for mst-eft of single field inflation |
understanding the co-evolution of supermassive black holes (smbhs) and their host systems requires a comprehensive census of active galactic nuclei (agn) behavior across a wide range of redshift, luminosity, obscuration level and galaxy properties. we report significant progress with jwst towards this goal from the systematic mid-infrared instrument legacy extragalactic survey (smiles). based on comprehensive sed analysis of 3273 miri-detected sources, we identify 217 agn candidates over a survey area of $\sim$34 arcmin$^2$, including a primary sample of 111 agns in normal massive galaxies ($m_{*}>10^{9.5}~m_\odot$) at $z\sim$0--4, an extended sample of 86 agn {\it candidates} in low-mass galaxies ($m_{*}<10^{9.5}~m_\odot$) and a high-$z$ sample of 20 agn {\it candidates} at $z\sim$4--8.4. notably, about 80\% of our miri-selected agn candidates are new discoveries despite the extensive pre-jwst agn searches. even among the massive galaxies where the previous agn search is believed to be thorough, 34\% of the miri agn identifications are new, highlighting the impact of obscuration on previous selections. by combining our results with the efforts at other wavelengths, we build the most complete agn sample to date and examine the relative performance of different selection techniques. we find the obscured agn fraction increases from $l_{\rm agn, bol}\sim10^{10}~l_\odot$ to $10^{11}~l_\odot$ and then drops towards higher luminosity. additionally, the obscured agn fraction gradually increases from $z\sim0$ to $z\sim4$ with most high-$z$ agns obscured. we discuss how agn obscuration, intrinsic sed variations, galaxy contamination, survey depth and selection techniques complicate the construction of a complete agn sample. | agn selection and demographics: a new age with jwst/miri |
the detection of the stochastic gravitational wave background by nanograv imposes constraints on the mass of compact cores of ultralight dark matter, also known as "solitons", surrounding supermassive black holes found at the centers of large galaxies. the strong dynamical friction between the rotating black holes and the solitons competes with gravitational wave emission, resulting in a suppression of the characteristic strain in the nhz frequency range. our findings rule out solitons arising from the condensation of ultralight dark matter particles with masses ranging from $1.3\times 10^{-21}$ ev to $1.4\times 10^{-20}$ ev. | bounds on ultralight dark matter from nanograv |
the hubble parameter $h_0$, is not a univocally-defined quantity: it relates redshifts to distances in the near universe, but is also a key parameter of the $\lambda$cdm standard cosmological model. as such, $h_0$ affects several physical processes at different cosmic epochs, and multiple observables. we have counted more than a dozen $h_0$'s which are expected to agree if a) there are no significant systematics in the data and their interpretation and b) the adopted cosmological model is correct. with few exceptions (proverbially confirming the rule) these determinations do not agree at high statistical significance; their values cluster around two camps: the low (68 km/s/mpc) and high (73 km/s/mpc) camp. it appears to be a matter of anchors: the shape of the universe expansion history agrees with the model, it is the normalizations that disagree. beyond systematics in the data/analysis, if the model is incorrect there are only two viable ways to "fix" it: by changing the early time ($z\gtrsim 1100$) physics and thus the early time normalization, or by a global modification, possibly touching the model's fundamental assumptions (e.g., homogeneity, isotropy, gravity). none of these three options has the consensus of the community. the research community has been actively looking for deviations from $\lambda$cdm for two decades; the one we might have found makes us wish we could put the genie back in the bottle. | a tale of many $h_0$ |
we discuss a possible extension of calculations of the bending angle of light in a static, spherically symmetric and asymptotically flat spacetime to a nonasymptotically 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 nonasymptotically flat spacetimes to suggest finite-distance corrections: the kottler (schwarzschild-de sitter) solution to the einstein equation and an exact solution in weyl conformal gravity. | gravitational bending angle of light for finite distance and the gauss-bonnet theorem |
much like ordinary matter, dark matter might consist of elementary particles, and weakly interacting massive particles are one of the prime suspects. during the past decade, the sensitivity of experiments trying to directly detect them has improved by three to four orders of magnitude, but solid evidence for their existence is yet to come. we overview the recent progress in direct dark matter detection experiments and discuss future directions. | current status of direct dark matter detection experiments |
the rapid askap continuum survey (racs) is the first large-area survey to be conducted with the full 36-antenna australian square kilometre array pathfinder (askap) telescope. racs will provide a shallow model of the askap sky that will aid the calibration of future deep askap surveys. racs will cover the whole sky visible from the askap site in western australia and will cover the full askap band of 700–1800 mhz. the racs images are generally deeper than the existing nrao vla sky survey and sydney university molonglo sky survey radio surveys and have better spatial resolution. all racs survey products will be public, including radio images (with$\sim$15 arcsec resolution) and catalogues of about three million source components with spectral index and polarisation information. in this paper, we present a description of the racs survey and the first data release of 903 images covering the sky south of declination$+41^\circ$made over a 288-mhz band centred at 887.5 mhz. | the rapid askap continuum survey i: design and first results |
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 ∼ 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 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-α forest are outlined. constraints from radio and γ-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. | the origin, evolution and signatures of primordial magnetic fields |
recent rapid progress in time domain surveys makes it possible to detect various types of explosive transients in the universe in large numbers, some of which will be gravitationally lensed into multiple images. although a large number of strongly lensed distant galaxies and quasars have already been discovered, strong lensing of explosive transients opens up new applications, including improved measurements of cosmological parameters, powerful probes of small scale structure of the universe, and new observational tests of dark matter scenarios, thanks to their rapidly evolving light curves as well as their compact sizes. in particular, compact sizes of emitting regions of these transient events indicate that wave optics effects play an important role in some cases, which can lead to totally new applications of these lensing events. recently we have witnessed first discoveries of strongly lensed supernovae, and strong lensing events of other types of explosive transients such as gamma-ray bursts, fast radio bursts, and gravitational waves from compact binary mergers are expected to be observed soon. in this review article, we summarize the current state of research on strong gravitational lensing of explosive transients and discuss future prospects. | strong gravitational lensing of explosive transients |
primordial black holes may have formed in the radiative era of the early universe from the collapse of large enough amplitude perturbations of the metric. these correspond to non linear energy density perturbations characterized by an amplitude larger than a certain threshold, measured when the perturbations reenter the cosmological horizon. the process of primordial black hole formation is studied here within spherical symmetry, using the gradient expansion approximation in the long wavelength limit, where the pressure gradients are small, and the initial perturbations are functions only of a time-independent curvature profile. in this regime it is possible to understand how the threshold for primordial black hole formation depends on the shape of the initial energy density profile, clarifying the relation between local and averaged measures of the perturbation amplitude. although there is no universal threshold for primordial black hole formation, the averaged mass excess of the perturbation depends on the amplitude of the energy density peak, and it is possible to formulate a well-defined criterion to establish when a cosmological perturbation is able to form a black hole in terms of one of these two key quantities. this gives understanding of how the abundance of primordial black holes depends on the shape of the inflationary power spectrum of cosmological perturbations. | threshold for primordial black holes: dependence on the shape of the cosmological perturbations |
models for light dark matter particles with masses below 1 gev/c^2 are a natural and well-motivated alternative to so-far unobserved weakly interacting massive particles. gram-scale cryogenic calorimeters provide the required detector performance to detect these particles and extend the direct dark matter search program of cresst. a prototype 0.5 g sapphire detector developed for the ν -cleus experiment has achieved an energy threshold of e_{th}=(19.7± 0.9) ev. this is one order of magnitude lower than for previous devices and independent of the type of particle interaction. the result presented here is obtained in a setup above ground without significant shielding against ambient and cosmogenic radiation. although operated in a high-background environment, the detector probes a new range of light-mass dark matter particles previously not accessible by direct searches. we report the first limit on the spin-independent dark matter particle-nucleon cross section for masses between 140 and 500 mev/c^2. | results on mev-scale dark matter from a gram-scale cryogenic calorimeter operated above ground |
detection of electron recoils by dark matter (dm) may reveal the structure of the dark sector. we consider a scenario where a heavier dm particle inelastically scatters off an electron and is converted into a lighter dm particle. a small mass difference between the two dm particles is transferred into electron recoil energy. we investigate the dm-electron interaction mediated by a massive dark photon and evaluate the inelastic dm scattering rate, taking account of the atomic structure. it is found that the scattering rate is significantly enhanced because of the small mass splitting, which allows for a small momentum transfer matched with the size of the electron wave function. we show that there exists a viable parameter space which explains the excess of electron recoil events around 2-3 kev recently reported by the xenon1t experiment. | inelastic dark matter electron scattering and the xenon1t excess |
we present rest-frame optical emission-line flux ratio measurements for five z > 5 galaxies observed by the james webb space telescope near-infared spectrograph (nirspec) in the smacs 0723 early release observations. we add several quality-control and post-processing steps to the nirspec pipeline reduction products in order to ensure reliable relative flux calibration of emission lines that are closely separated in wavelength, despite the uncertain absolute spectrophotometry of the current version of the reductions. compared to z ~ 3 galaxies in the literature, the z > 5 galaxies have similar [o iii]λ5008/hβ ratios, similar [o iii]λ4364/hγ ratios, and higher (~0.5 dex) [ne iii]λ3870/[o ii]λ3728 ratios. we compare the observations to mappings v photoionization models and find that the measured [ne iii]λ3870/[o ii]λ3728, [o iii]λ4364/hγ, and [o iii]λ5008/hβ emission-line ratios are consistent with an interstellar medium (ism) that has very high ionization ( $\mathrm{log}(q)\simeq 8-9$ , units of cm s-1), low metallicity (z/z ⊙ ≲ 0.2), and very high pressure ( $\mathrm{log}(p/k)\simeq 8-9$ , units of cm-3). the combination of [o iii]λ4364/hγ and [o iii]λ(4960 + 5008)/hβ line ratios indicate very high electron temperatures of $4.1\lt \mathrm{log}({t}_{e}/{\rm{k}})\lt 4.4$ , further implying metallicities of z/z ⊙ ≲ 0.2 with the application of low-redshift calibrations for "te -based" metallicities. these observations represent a tantalizing new view of the physical conditions of the ism in galaxies at cosmic dawn. | the physical conditions of emission-line galaxies at cosmic dawn from jwst/nirspec spectroscopy in the smacs 0723 early release observations |
observations of the submillimetre emission from galactic dust, in both total intensity i and polarization, have received tremendous interest thanks to the planck full-sky maps. in this paper we make use of such full-sky maps of dust polarized emission produced from the third public release of planck data. as the basis for expanding on astrophysical studies of the polarized thermal emission from galactic dust, we present full-sky maps of the dust polarization fraction p, polarization angle ψ, and dispersion function of polarization angles 𝒮. the joint distribution (one-point statistics) of p and nh confirms that the mean and maximum polarization fractions decrease with increasing nh. the uncertainty on the maximum observed polarization fraction, pmax = 22.0-1.4+3.5% at 353 ghz and 80' resolution, is dominated by the uncertainty on the galactic emission zero level in total intensity, in particular towards diffuse lines of sight at high galactic latitudes. furthermore, the inverse behaviour between p and 𝒮 found earlier is seen to be present at high latitudes. this follows the 𝒮 ∝ p-1 relationship expected from models of the polarized sky (including numerical simulations of magnetohydrodynamical turbulence) that include effects from only the topology of the turbulent magnetic field, but otherwise have uniform alignment and dust properties. thus, the statistical properties of p, ψ, and 𝒮 for the most part reflect the structure of the galactic magnetic field. nevertheless, we search for potential signatures of varying grain alignment and dust properties. first, we analyse the product map 𝒮 × p, looking for residual trends. while the polarization fraction p decreases by a factor of 3-4 between nh = 1020 cm-2 and nh = 2 × 1022 cm-2, out of the galactic plane, this product 𝒮 × p only decreases by about 25%. because 𝒮 is independent of the grain alignment efficiency, this demonstrates that the systematic decrease in p with nh is determined mostly by the magnetic-field structure and not by a drop in grain alignment. this systematic trend is observed both in the diffuse interstellar medium (ism) and in molecular clouds of the gould belt. second, we look for a dependence of polarization properties on the dust temperature, as we would expect from the radiative alignment torque (rat) theory. we find no systematic trend of 𝒮 × p with the dust temperature td, whether in the diffuse ism or in the molecular clouds of the gould belt. in the diffuse ism, lines of sight with high polarization fraction p and low polarization angle dispersion 𝒮 tend, on the contrary, to have colder dust than lines of sight with low p and high 𝒮. we also compare the planck thermal dust polarization with starlight polarization data in the visible at high galactic latitudes. the agreement in polarization angles is remarkable, and is consistent with what we expect from the noise and the observed dispersion of polarization angles in the visible on the scale of the planck beam. the two polarization emission-to-extinction ratios, rp/p and rs/v, which primarily characterize dust optical properties, have only a weak dependence on the column density, and converge towards the values previously determined for translucent lines of sight. we also determine an upper limit for the polarization fraction in extinction, pv/e(b - v), of 13% at high galactic latitude, compatible with the polarization fraction p ≈ 20% observed at 353 ghz. taken together, these results provide strong constraints for models of galactic dust in diffuse gas. | planck 2018 results. xii. galactic astrophysics using polarized dust emission |
we investigate the observational consequences of a novel class of stable interacting dark energy (ide) models, featuring interactions between dark matter (dm) and dark energy (de). in the first part of our work, we start by considering two ide models which are known to present early-time linear perturbation instabilities. applying a transformation depending on the dark energy equation of state (eos) to the dm-de coupling, we then obtain two novel stable ide models. subsequently, we derive robust and accurate constraints on the parameters of these models, assuming a constant eos wx for the de fluid, in light of some of the most recent publicly available cosmological data. these include cosmic microwave background (cmb) temperature and polarization anisotropy measurements from the planck satellite, a selection of baryon acoustic oscillation measurements, supernovae type-ia luminosity distance measurements from the jla sample, and measurements of the hubble parameter up to redshift 2 from cosmic chronometers. our analysis displays a mild preference for the de fluid residing in the phantom region (wx<-1), with significance up to 95% confidence level, while we obtain new upper limits on the coupling parameter between the dark components. the preference for a phantom de suggests a coupling function 0q<, thus a scenario where energy flows from the de to the dm . we also examine the possibility of addressing the h0 and σ8 tensions, finding that only the former can be partially alleviated. finally, we perform a bayesian model comparison analysis to quantify the possible preference for the two ide models against the standard concordance λcdm model, finding that the latter is always preferred with the strength of the evidence ranging from positive to very strong. | tale of stable interacting dark energy, observational signatures, and the h0 tension |
we present details of numerical simulations of the gravitational radiation produced by a first order thermal phase transition in the early universe. we confirm that the dominant source of gravitational waves is sound waves generated by the expanding bubbles of the low-temperature phase. we demonstrate that the sound waves have a power spectrum with a power-law form between the scales set by the average bubble separation (which sets the length scale of the fluid flow lf) and the bubble wall width. the sound waves generate gravitational waves whose power spectrum also has a power-law form, at a rate proportional to lf and the square of the fluid kinetic energy density. we identify a dimensionless parameter ω∼gw characterizing the efficiency of this "acoustic" gravitational wave production whose value is 8 π ω∼gw≃0.8 ±0.1 across all our simulations. we compare the acoustic gravitational waves with the standard prediction from the envelope approximation. not only is the power spectrum steeper (apart from an initial transient) but the gravitational wave energy density is generically larger by the ratio of the hubble time to the phase transition duration, which can be 2 orders of magnitude or more in a typical first order electroweak phase transition. | numerical simulations of acoustically generated gravitational waves at a first order phase transition |
weak gravitational lensing, the deflection of light by mass, is one of the best tools to constrain the growth of cosmic structure with time and reveal the nature of dark energy. i discuss the sources of systematic uncertainty in weak lensing measurements and their theoretical interpretation, including our current understanding and other options for future improvement. these include long-standing concerns such as the estimation of coherent shears from galaxy images or redshift distributions of galaxies selected on the basis of photometric redshifts, along with systematic uncertainties that have received less attention to date because they are subdominant contributors to the error budget in current surveys. i also discuss methods for automated systematics detection using survey data of the 2020s. the goal of this review is to describe the current state of the field and what must be done so that if weak lensing measurements lead toward surprising conclusions about key questions such as the nature of dark energy, those conclusions will be credible. | weak lensing for precision cosmology |
scattering amplitudes at weak coupling are highly constrained by lorentz invariance, locality and unitarity, and depend on model details only through coupling constants and particle content. in this paper, we develop an understanding of inflationary correlators which parallels that of flat-space scattering amplitudes. specifically, we study slow-roll inflation with weak couplings to extra massive particles, for which all correlators are controlled by an approximate conformal symmetry on the boundary of the spacetime. after classifying all possible contact terms in de sitter space, we derive an analytic expression for the four-point function of conformally coupled scalars mediated by the tree-level exchange of massive scalars. conformal symmetry implies that the correlator satisfies a pair of differential equations with respect to spatial momenta, encoding bulk time evolution in purely boundary terms. the absence of unphysical singularities completely fixes this correlator. a spin-raising operator relates it to the correlators associated with the exchange of particles with spin, while weight-shifting operators map it to the four-point function of massless scalars. we explain how these de sitter four-point functions can be perturbed to obtain inflationary three-point functions. we reproduce many classic results in the literature and provide a complete classification of all inflationary three- and four-point functions arising from weakly broken conformal symmetry. the inflationary bispectrum associated with the exchange of particles with arbitrary spin is completely characterized by the soft limit of the simplest scalar-exchange four-point function of conformally coupled scalars and a series of contact terms. finally, we demonstrate that the inflationary correlators contain flat-space scattering amplitudes via a suitable analytic continuation of the external momenta. | the cosmological bootstrap: inflationary correlators from symmetries and singularities |
we present results from large-scale numerical simulations of a first order thermal phase transition in the early universe, in order to explore the shape of the acoustic gravitational wave and the velocity power spectra. we compare the results with the predictions of the recently proposed sound shell model. for the gravitational wave power spectrum, we find that the predicted k-3 behavior, where k is the wave number, emerges clearly for detonations. the power spectra from deflagrations show similar features, but exhibit a steeper high-k decay and an extra feature not accounted for in the model. there are two independent length scales: the mean bubble separation and the thickness of the sound shell around the expanding bubble of the low temperature phase. it is the sound shell thickness which sets the position of the peak of the power spectrum. the low wave number behavior of the velocity power spectrum is consistent with a causal k3, except for the thinnest sound shell, where it is steeper. we present parameters for a simple broken power law fit to the gravitational wave power spectrum for wall speeds well away from the speed of sound where this form can be usefully applied. we examine the prospects for the detection, showing that a lisa-like mission has the sensitivity to detect a gravitational wave signal from sound waves with an rms fluid velocity of about 0.05 c , produced from bubbles with a mean separation of about 10-2 of the hubble radius. the shape of the gravitational wave power spectrum depends on the bubble wall speed, and it may be possible to estimate the wall speed, and constrain other phase transition parameters, with an accurate measurement of a stochastic gravitational wave background. | shape of the acoustic gravitational wave power spectrum from a first order phase transition |
we propose a new broadband search strategy for ultralight axion dark matter that interacts with electromagnetism. an oscillating axion field induces transitions between two quasidegenerate resonant modes of a superconducting cavity. in two broadband runs optimized for high and low masses, this setup can probe unexplored parameter space for axionlike particles covering 15 orders of magnitude in mass, including astrophysically long-ranged fuzzy dark matter. | heterodyne broadband detection of axion dark matter |
the discrepancy in measurements of the hubble constant indicates new physics in dark energy, dark matter, or both. drawing inspiration from string theory, where axions interact with the other moduli fields, including the dilaton, here we demonstrate that the dynamics of an interacting dilaton and axion naturally realizes the proposal of early dark energy. in this setup, stabilization of the dilaton is in part due to the axion, and in the early universe the dilaton contributes to dark energy. the combined axion-dilaton system is destabilized when the hubble constant falls below the mass of the axion, triggering a phase of fast-roll evolution of the dilaton wherein its equation of state is w = 1, and the early dark energy redshifts away as a-6. | axion-dilaton destabilization and the hubble tension |
we review the production of gravitational waves by an electroweak first-order phase transition. the resulting signal is a good candidate for detection at next-generation gravitational wave detectors, such as lisa. detection of such a source of gravitational waves could yield information about physics beyond the standard model that is complementary to that accessible to current and near-future collider experiments. we summarize efforts to simulate and model the phase transition and the resulting production of gravitational waves. this article is part of the theo murphy meeting issue `higgs cosmology'. | gravitational waves from a first-order electroweak phase transition: a brief review |
the nanograv collaboration for the pulsar timing array (pta) observation recently announced evidence of an isotropic stochastic process, which may be the first detection of the stochastic gravitational-wave (gw) background. we discuss the possibility that the signal is caused by the second-order gws associated with the formation of solar-mass primordial black holes (pbhs). this possibility can be tested by future interferometer-type gw observations targeting the stochastic gws from merger events of solar-mass pbhs as well as by updates of pta observations. | solar-mass primordial black holes explain nanograv hint of gravitational waves |
cosmological models in which dark matter consists of cold elementary particles predict that the dark halo population should extend to masses many orders of magnitude below those at which galaxies can form1-3. here we report a cosmological simulation of the formation of present-day haloes over the full range of observed halo masses (20 orders of magnitude) when dark matter is assumed to be in the form of weakly interacting massive particles of mass approximately 100 gigaelectronvolts. the simulation has a full dynamic range of 30 orders of magnitude in mass and resolves the internal structure of hundreds of earth-mass haloes in as much detail as it does for hundreds of rich galaxy clusters. we find that halo density profiles are universal over the entire mass range and are well described by simple two-parameter fitting formulae4,5. halo mass and concentration are tightly related in a way that depends on cosmology and on the nature of the dark matter. for a fixed mass, the concentration is independent of the local environment for haloes less massive than those of typical galaxies. haloes over the mass range of 10-3 to 1011 solar masses contribute about equally (per logarithmic interval) to the luminosity produced by dark matter annihilation, which we find to be smaller than all previous estimates by factors ranging up to one thousand3. | universal structure of dark matter haloes over a mass range of 20 orders of magnitude |
the pseudo-cℓ is an algorithm for estimating the angular power and cross-power spectra that is very fast and in realistic cases also nearly optimal. the algorithm can be extended to deal with contaminant deprojection and e/b purification, and can therefore be applied in a wide variety of scenarios of interest for current and future cosmological observations. this paper presents namaster, a public, validated, accurate, and easy-to-use software package that, for the first time, provides a unified framework to compute angular cross-power spectra of any pair of spin-0 or spin-2 fields, contaminated by an arbitrary number of linear systematics and requiring b- or e-mode purification, both on the sphere or in the flat-sky approximation. we describe the mathematical background of the estimator, including all the features above, and its software implementation in namaster. we construct a validation suite that aims to resemble the types of observations that next-generation large-scale structure and ground-based cosmic microwave background experiments will face, and use it to show that the code is able to recover the input power spectra in the most complex scenarios with no detectable bias. namaster can be found at https://github.com/lsstdesc/namaster, and is provided with comprehensive documentation and a number of code examples. | a unified pseudo-cℓ framework |
astrophysical and cosmological observations currently provide the only robust, empirical measurements of dark matter. future observations with large synoptic survey telescope (lsst) will provide necessary guidance for the experimental dark matter program. this white paper represents a community effort to summarize the science case for studying the fundamental physics of dark matter with lsst. we discuss how lsst will inform our understanding of the fundamental properties of dark matter, such as particle mass, self-interaction strength, non-gravitational couplings to the standard model, and compact object abundances. additionally, we discuss the ways that lsst will complement other experiments to strengthen our understanding of the fundamental characteristics of dark matter. more information on the lsst dark matter effort can be found at https://lsstdarkmatter.github.io/ . | probing the fundamental nature of dark matter with the large synoptic survey telescope |
we compare the science capabilities of different elisa mission designs, including four-link (two-arm) and six-link (three-arm) configurations with different arm lengths, low-frequency noise sensitivities and mission durations. for each of these configurations we consider a few representative massive black hole formation scenarios. these scenarios are chosen to explore two physical mechanisms that greatly affect elisa rates, namely (i) black hole seeding, and (ii) the delays between the merger of two galaxies and the merger of the black holes hosted by those galaxies. we assess the elisa parameter estimation accuracy using a fisher matrix analysis with spin-precessing, inspiral-only waveforms. we quantify the information present in the merger and ringdown by rescaling the inspiral-only fisher matrix estimates using the signal-to-noise ratio from nonprecessing inspiral-merger-ringdown phenomenological waveforms, and from a reduced set of precessing numerical relativity/post-newtonian hybrid waveforms. we find that all of the elisa configurations considered in our study should detect some massive black hole binaries. however, configurations with six links and better low-frequency noise will provide much more information on the origin of black holes at high redshifts and on their accretion history, and they may allow the identification of electromagnetic counterparts to massive black hole mergers. | science with the space-based interferometer elisa: supermassive black hole binaries |
we report the first results of darkside-50, a direct search for dark matter operating in the underground laboratori nazionali del gran sasso (lngs) and searching for the rare nuclear recoils possibly induced by weakly interacting massive particles (wimps). the dark matter detector is a liquid argon time projection chamber with a (46.4 ± 0.7) kg active mass, operated inside a 30 t organic liquid scintillator neutron veto, which is in turn installed at the center of a 1 kt water cherenkov veto for the residual flux of cosmic rays. we report here the null results of a dark matter search for a (1422 ± 67) kgd exposure with an atmospheric argon fill. this is the most sensitive dark matter search performed with an argon target, corresponding to a 90% cl upper limit on the wimp-nucleon spin-independent cross section of 6.1 ×10-44 cm2 for a wimp mass of 100 gev /c2. | first results from the darkside-50\u2005dark matter experiment at laboratori nazionali del gran sasso |
the nanograv pulsar timing array experiment reported evidence for a stochastic common-spectrum process affecting pulsar timing residuals in its 12.5-yr data set, which might be interpreted as the first detection of a stochastic gravitational wave background (sgwb). i examine whether the nanograv signal might be explained by an inflationary sgwb, focusing on the implications for the tensor spectral index nt and the tensor-to-scalar ratio r. explaining nanograv while complying with upper limits on r from bicep2/keck array and planck requires $r \gtrsim {\cal o}(10^{-6})$ in conjunction with an extremely blue tensor spectrum, 0.7 ≲ nt ≲ 1.3. after discussing models, which can realize such a blue spectrum, i show that this region of parameter space can be brought in agreement with big bang nucleosynthesis constraints for a sufficiently low reheating scale, $t_{\rm rh} \lesssim 100\, {\rm gev} \!-\! 1\, {\rm tev}$ . with the important caveat of having assumed a power-law parametrization for the primordial tensor spectrum, an inflationary interpretation of the nanograv signal is therefore not excluded. | implications of the nanograv results for inflation |
ultracompact dark matter (dm) minihalos at masses at and below 10-12 m⊙ arise in axion dm models where the peccei-quinn (pq) symmetry is broken after inflation. the minihalos arise from density perturbations that are generated from the nontrivial axion self-interactions during and shortly after the collapse of the axion-string and domain-wall network. we perform high-resolution simulations of this scenario starting at the epoch before the pq phase transition and ending at matter-radiation equality. we characterize the spectrum of primordial perturbations that are generated and comment on implications for efforts to detect axion dm. we also measure the dm density at different simulated masses and argue that the correct dm density is obtained for ma=25.2 ±11.0 μ ev . | early-universe simulations of the cosmological axion |
some gamma-ray bursts (grbs) have a tera–electron volt (tev) afterglow, but the early onset of this has not been observed. we report observations with the large high altitude air shower observatory (lhaaso) of the bright grb 221009a, which serendipitously occurred within the instrument’s field of view. more than 64,000 photons >0.2 tev were detected within the first 3000 seconds. the tev flux began several minutes after the grb trigger and then rose to a peak ~10 seconds later. this was followed by a decay phase, which became more rapid ~650 seconds after the peak. we interpret the emission using a model of a relativistic jet with half-opening angle of ~0.8°. this is consistent with the core of a structured jet and could explain the high isotropic energy of this grb. | a tera-electron volt afterglow from a narrow jet in an extremely bright gamma-ray burst. |
there are currently several existing and proposed experiments designed to probe sub-gev dark matter (dm) using electron ionization in various materials. the projected signal rates for these experiments assume that this ionization yield arises only from dm scattering directly off electron targets, ignoring secondary ionization contributions from dm scattering off nuclear targets. we investigate the validity of this assumption and show that if sub-gev dm couples with comparable strength to both protons and electrons, as would be the case for a dark photon mediator, the ionization signal from atomic scattering via the migdal effect scales with the atomic number z and 3-momentum transfer q as z2q2. the result is that the migdal effect is always subdominant to electron scattering when the mediator is light, but that migdal-induced ionization can dominate over electron scattering for heavy mediators and dm masses in the hundreds of mev range. we put these two ionization processes on identical theoretical footing, address some theoretical uncertainties in the choice of atomic wave functions used to compute rates, and discuss the implications for dm scenarios where the migdal process dominates, including for xenon10, xenon100, and the recent xenon1t results on light dm scattering. | electron ionization via dark matter-electron scattering and the migdal effect |
mapping nearby galaxies at apache point observatory (manga) is an optical fiber-bundle integral-field unit (ifu) spectroscopic survey that is one of three core programs in the fourth-generation sloan digital sky survey (sdss-iv). with a spectral coverage of 3622-10354 å and an average footprint of ∼500 arcsec2 per ifu the scientific data products derived from manga will permit exploration of the internal structure of a statistically large sample of 10,000 low-redshift galaxies in unprecedented detail. comprising 174 individually pluggable science and calibration ifus with a near-constant data stream, manga is expected to obtain ∼100 million raw-frame spectra and ∼10 million reduced galaxy spectra over the six-year lifetime of the survey. in this contribution, we describe the manga data reduction pipeline algorithms and centralized metadata framework that produce sky-subtracted spectrophotometrically calibrated spectra and rectified three-dimensional data cubes that combine individual dithered observations. for the 1390 galaxy data cubes released in summer 2016 as part of sdss-iv data release 13, we demonstrate that the manga data have nearly poisson-limited sky subtraction shortward of ∼8500 å and reach a typical 10σ limiting continuum surface brightness μ = 23.5 ab arcsec-2 in a five-arcsecond-diameter aperture in the g-band. the wavelength calibration of the manga data is accurate to 5 km s-1 rms, with a median spatial resolution of 2.54 arcsec fwhm (1.8 kpc at the median redshift of 0.037) and a median spectral resolution of σ = 72 km s-1. | the data reduction pipeline for the sdss-iv manga ifu galaxy survey |
this voyage 2050 paper highlights the unique science opportunities using spectral distortions of the cosmic microwave background (cmb). cmb spectral distortions probe many processes throughout the history of the universe, delivering novel information that complements past, present and future efforts with cmb anisotropy and large-scale structure studies. precision spectroscopy, possible with existing technology, would not only provide key tests for processes expected within the cosmological standard model but also open an enormous discovery space to new physics. this offers unique scientific opportunities for furthering our understanding of inflation, recombination, reionization and structure formation as well as dark matter and particle physics. a dedicated experimental approach could open this new window to the early universe in the decades to come, allowing us to turn the long-standing upper distortion limits obtained with cobe/firas some 25 years ago into clear detections of the expected standard distortion signals and also challenge our current understanding of the laws of nature. | new horizons in cosmology with spectral distortions of the cosmic microwave background |
the giant radio array for neutrino detection (grand) is a planned large-scale observatory of ultra-high-energy (uhe) cosmic particles, with energies exceeding 108 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 10000 radio antennas deployed over 10000 km2. 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. | the giant radio array for neutrino detection (grand): science and design |
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 1011 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. | a cosmological signature of the sm higgs instability: gravitational waves |
the region around the galactic center (gc) is now well established to be brighter at energies of a few gev than what is expected from conventional models of diffuse gamma-ray emission and catalogs of known gamma-ray sources. we study the gev excess using 6.5 yr of data from the fermi large area telescope. we characterize the uncertainty of the gc excess spectrum and morphology due to uncertainties in cosmic-ray source distributions and propagation, uncertainties in the distribution of interstellar gas in the milky way, and uncertainties due to a potential contribution from the fermi bubbles. we also evaluate uncertainties in the excess properties due to resolved point sources of gamma rays. the gc is of particular interest, as it would be expected to have the brightest signal from annihilation of weakly interacting massive dark matter (dm) particles. however, control regions along the galactic plane, where a dm signal is not expected, show excesses of similar amplitude relative to the local background. based on the magnitude of the systematic uncertainties, we conservatively report upper limits for the annihilation cross-section as a function of particle mass and annihilation channel. | the fermi galactic center gev excess and implications for dark matter |
the fermi large area telescope (lat) has provided the most detailed view to date of the emission toward the galactic center (gc) in high-energy γ-rays. this paper describes the analysis of data taken during the first 62 months of the mission in the energy range 1-100 gev from a 15° × 15° region about the direction of the gc. specialized interstellar emission models (iems) are constructed to enable the separation of the γ-ray emissions produced by cosmic ray particles interacting with the interstellar gas and radiation fields in the milky way into that from the inner ∼1 kpc surrounding the gc, and that from the rest of the galaxy. a catalog of point sources for the 15° × 15° region is self-consistently constructed using these iems: the first fermi-lat inner galaxy point source catalog (1fig). the spatial locations, fluxes, and spectral properties of the 1fig sources are presented, and compared with γ-ray point sources over the same region taken from existing catalogs. after subtracting the interstellar emission and point-source contributions a residual is found. if templates that peak toward the gc are used to model the positive residual the agreement with the data improves, but none of the additional templates tried account for all of its spatial structure. the spectrum of the positive residual modeled with these templates has a strong dependence on the choice of iem. | fermi-lat observations of high-energy gamma-ray emission toward the galactic center |
one of the primary limiting sources of systematic uncertainty in forthcoming weak lensing measurements is systematic uncertainty in the quantitative relationship between the distortions due to gravitational lensing and the measurable properties of galaxy images. we present a statistically principled, general solution to this problem. our technique infers multiplicative shear calibration parameters by modifying the actual survey data to simulate the effects of a known shear. it can be applied to any shear estimation method based on weighted averages of galaxy shape measurements, which includes all methods used to date for shear estimation with real data. use of the real images mitigates uncertainty due to unknown galaxy morphology, which is a serious concern for calibration of shear estimates based on image simulations. we test our results on simulated images from the great3 challenge, and show that the method eliminates calibration biases for several different shape measurement techniques at the level of precision measurable with the great3 simulations (a few tenths of a percent). | metacalibration: direct self-calibration of biases in shear measurement |
the disagreement between direct late-time measurements of the hubble constant from the sh0es collaboration, and early-universe measurements based on the λcdm 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. | the hubble tension in light of the full-shape analysis of large-scale structure data |
we revisit the impact of early dark energy (ede) on galaxy clustering using boss galaxy power spectra, analyzed using the effective field theory (eft) of large-scale structure (lss) and anisotropies of the cosmic microwave background (cmb) from planck. recent studies found that these data place stringent constraints on the maximum abundance of ede allowed in the universe. we argue here that their conclusions are a consequence of their choice of priors on the ede parameter space, rather than any disagreement between the data and the model. for example, when considering eft-lss, cmb, and high-redshift supernovae data we find the ede and λ cdm models can provide statistically indistinguishable fits (δ χ2=0.12 ) with a relatively large value for the maximum fraction of energy density in the ede (fede=0.09 ) and hubble constant (h0=71 km /s /mpc ) in the ede model. moreover, we demonstrate that the constraining power added from the inclusion of eft-lss traces to the potential tension between the power-spectrum amplitudes as derived from boss and from planck that arises even within the context of λ cdm . until this is better understood, caution should be used when interpreting eft -boss +p l a n c k constraints to models beyond λ cdm . these findings suggest that ede still provides a potential resolution to the hubble tension and that it is worthwhile to test the predictions of ede with future datasets and further study its theoretical possibilities. | early dark energy is not excluded by current large-scale structure data |
we discuss several low-energy backgrounds to sub-gev dark-matter searches, which arise from high-energy particles of cosmic or radioactive origin that interact with detector materials. we focus, in particular, on cherenkov radiation, transition radiation, and luminescence or phonons from electron-hole pair recombination and show that these processes are an important source of backgrounds at both current and planned detectors. we perform detailed analyses of these backgrounds at several existing and proposed experiments based on a wide variety of detection strategies and levels of shielding. we find that a large fraction of the observed single-electron events in the sensei 2020 run originate from cherenkov photons generated by high-energy events in the skipper charge coupled device and from recombination photons generated in a phosphorus-doped layer of the same instrument. in a supercdms hvev 2020 run, cherenkov photons produced in printed-circuit boards located near the sensor likely explain the origin of most of the events containing 2-6 electrons. at supercdms snolab, radioactive contaminants inside the cirlex located inside or on the copper side walls of their detectors produce many cherenkov photons, which could dominate the low-energy backgrounds. for the edelweiss experiment, cherenkov or luminescence backgrounds are subdominant to their observed event rate but could still limit the sensitivity of their future searches. we also point out that cherenkov radiation, transition radiation, and recombination could be a significant source of backgrounds at future experiments aiming to detect dark matter via scintillation or phonon signals. we also discuss the implications of our results for the development of superconducting qubits and low-threshold searches for coherent neutrino scattering. fortunately, several design strategies to mitigate these backgrounds can be implemented, such as minimizing nonconductive materials near the target, implementing active and passive shielding, and using multiple nearby detectors. | sources of low-energy events in low-threshold dark-matter and neutrino detectors |
we have used flux-transmission correlations in lyα forests to measure the imprint of baryon acoustic oscillations (bao). the study uses spectra of 157 783 quasars in the redshift range 2.1 ≤ z ≤ 3.5 from the sloan digital sky survey (sdss) data release 12 (dr12). besides the statistical improvements on our previous studies using sdss dr9 and dr11, we have implemented numerous improvements in the analysis procedure, allowing us to construct a physical model of the correlation function and to investigate potential systematic errors in the determination of the bao peak position. the hubble distance, dh = c/h(z), relative to the sound horizon is dh(z = 2.33) /rd = 9.07 ± 0.31. the best-determined combination of comoving angular-diameter distance, dm, and the hubble distance is found to be dh0.7dm0.3 /rd = 13.94 ± 0.35. this value is 1.028 ± 0.026 times the prediction of the flat-λcdm model consistent with the cosmic microwave background (cmb) anisotropy spectrum. the errors include marginalization over the effects of unidentified high-density absorption systems and fluctuations in ultraviolet ionizing radiation. independently of the cmb measurements, the combination of our results and other bao observations determine the open-λcdm density parameters to be ωm = 0.296 ± 0.029, ωλ = 0.699 ± 0.100 and ωk = -0.002 ± 0.119. | measurement of baryon acoustic oscillation correlations at z = 2.3 with sdss dr12 lyα-forests |
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 trh gtrsim 1.8 mev in the case of the 100% radiative decay, and trh gtrsim 4-5 mev in the case of the 100% hadronic decays for particle masses in the range of 10 gev to 100 tev. | mev-scale reheating temperature and thermalization of oscillating neutrinos by radiative and hadronic decays of massive particles |
the cosmos-legacy survey is a 4.6 ms chandra program that has imaged 2.2 deg2 of the cosmos field with an effective exposure of ≃ 160 ks over the central 1.5 deg2 and of ≃ 80 ks in the remaining area. the survey is the combination of 56 new observations obtained as an x-ray visionary project with the previous c-cosmos survey. we describe the reduction and analysis of the new observations and the properties of 2273 point sources detected above a spurious probability of 2 × 10-5. we also present the updated properties of the c-cosmos sources detected in the new data. the whole survey includes 4016 point sources (3814, 2920 and 2440 in the full, soft, and hard band). the limiting depths are 2.2 × 10-16, 1.5 × 10-15, and 8.9 × 10-16 {\text{erg cm}}-2 {{{s}}}-1 in the 0.5-2, 2-10, and 0.5-10 kev bands, respectively. the observed fraction of obscured active galactic nuclei with a column density >1022 cm-2 from the hardness ratio (hr) is ∼50{}-16+17%. given the large sample we compute source number counts in the hard and soft bands, significantly reducing the uncertainties of 5%-10%. for the first time we compute number counts for obscured (hr > -0.2) and unobscured (hr < -0.2) sources and find significant differences between the two populations in the soft band. due to the unprecedent large exposure, cosmos-legacy area is three times larger than surveys at similar depths and its depth is three times fainter than surveys covering similar areas. the area-flux region occupied by cosmos-legacy is likely to remain unsurpassed for years to come. | the chandra cosmos legacy survey: overview and point source catalog |
the cosmicflows database of galaxy distances that in the second edition contained 8188 entries is now expanded to 17,669 entries. the major additions are 2257 distances that we have derived from the correlation between galaxy rotation and luminosity with photometry at 3.6 μ {{m}} obtained with the spitzer space telescope and 8885 distances based on the fundamental plane methodology from the six degree field galaxy survey collaboration. there are minor augmentations to the tip of the red giant branch and type ia supernova compilations. a zero-point calibration of the supernova luminosities gives a value for the hubble constant of 76.2+/- 3.4+/- 2.7 (± rand. ± sys.) km s-1 mpc-1. alternatively, a restriction on the peculiar velocity monopole term representing global infall/outflow implies {h}0=75+/- 2 km s-1 mpc-1. | cosmicflows-3 |
these lectures on the cosmological constant problem were prepared for the x mexican school on gravitation and mathematical physics. the problem itself is explained in detail, emphasising the importance of radiative instability and the need to repeatedly fine tune as we change our effective description. weinberg's no go theorem is worked through in detail. i review a number of proposals including linde's universe multiplication, coleman's wormholes, the fat graviton, and sled, to name a few. large distance modifications of gravity are also discussed, with causality considerations pointing towards a global modification as being the most sensible option. the global nature of the cosmological constant problem is also emphasized, and as a result, the sequestering scenario is reviewed in some detail, demonstrating the cancellation of the standard model vacuum energy through a global modification of general relativity. | lectures on the cosmological constant problem |
we investigate primordial perturbations and non-gaussianities in the hořava-lifshitz theory of gravitation. in the uv limit, the scalar perturbation in the hořava theory is naturally scale-invariant, ignoring the details of the expansion of the universe. one may thus relax the exponential inflation and the slow-roll conditions for the inflaton field. as a result, it is possible that the primordial non-gaussianities, which are " slow-roll suppressed" in the standard scenarios, become large. we calculate the non-gaussianities from the bispectrum of the perturbation and find that the equilateral-type non-gaussianity is of the order of unity, while the local-type non-gaussianity remains small, as in the usual single-field slow-roll inflation model in general relativity. our result is a new constraint on hořava-lifshitz gravity. | primordial perturbations and non-gaussianities in hořava-lifshitz gravity |
we derive efficiency factors for the production of gravitational waves through bubble collisions and plasma-related sources in strong phase transitions, and find the conditions under which the bubble collisions can contribute significantly to the signal. we use lattice simulations to clarify the dependence of the colliding bubbles on their initial state. we illustrate our findings in two examples, the standard model with an extra |h|6 interaction and a classically scale-invariant u(1)b-l extension of the standard model. the contribution to the gw spectrum from bubble collisions is found to be negligible in the |h|6 model, whereas it can play an important role in parts of the parameter space in the scale-invariant u(1)b-l model. in both cases the sound-wave period is much shorter than a hubble time, suggesting a significant amplification of the turbulence-sourced signal. we find, however, that the peak of the plasma-sourced spectrum is still produced by sound waves with the slower-falling turbulence contribution becoming important off-peak. | gravitational wave energy budget in strongly supercooled phase transitions |
measuring the morphological parameters of galaxies is a key requirement for studying their formation and evolution. surveys such as the sloan digital sky survey have resulted in the availability of very large collections of images, which have permitted population-wide analyses of galaxy morphology. morphological analysis has traditionally been carried out mostly via visual inspection by trained experts, which is time consuming and does not scale to large (≳104) numbers of images. although attempts have been made to build automated classification systems, these have not been able to achieve the desired level of accuracy. the galaxy zoo project successfully applied a crowdsourcing strategy, inviting online users to classify images by answering a series of questions. unfortunately, even this approach does not scale well enough to keep up with the increasing availability of galaxy images. we present a deep neural network model for galaxy morphology classification which exploits translational and rotational symmetry. it was developed in the context of the galaxy challenge, an international competition to build the best model for morphology classification based on annotated images from the galaxy zoo project. for images with high agreement among the galaxy zoo participants, our model is able to reproduce their consensus with near-perfect accuracy (>99 per cent) for most questions. confident model predictions are highly accurate, which makes the model suitable for filtering large collections of images and forwarding challenging images to experts for manual annotation. this approach greatly reduces the experts' workload without affecting accuracy. the application of these algorithms to larger sets of training data will be critical for analysing results from future surveys such as the large synoptic survey telescope. | rotation-invariant convolutional neural networks for galaxy morphology prediction |
we combine dark energy survey year 1 clustering and weak lensing data with baryon acoustic oscillations and big bang nucleosynthesis experiments to constrain the hubble constant. assuming a flat λcdm model with minimal neutrino mass (∑mν = 0.06 ev), we find h_0=67.4^{+1.1}_{-1.2} {km s^{-1} mpc^{-1}} (68 per cent cl). this result is completely independent of hubble constant measurements based on the distance ladder, cosmic microwave background anisotropies (both temperature and polarization), and strong lensing constraints. there are now five data sets that: (a) have no shared observational systematics; and (b) each constrains the hubble constant with fractional uncertainty at the few-per cent level. we compare these five independent estimates, and find that, as a set, the differences between them are significant at the 2.5σ level (χ2/dof = 24/11, probability to exceed = 1.1 per cent). having set the threshold for consistency at 3σ, we combine all five data sets to arrive at h_0=69.3^{+0.4}_{-0.6} {km s^{-1} mpc^{-1}}. | dark energy survey year 1 results: a precise h0 estimate from des y1, bao, and d/h data |
since the expansion of the universe was first established by edwin hubble and georges lemaître about a century ago, the hubble constant h0 which measures its rate has been of great interest to astronomers. besides being interesting in its own right, few properties of the universe can be deduced without it. in the last decade, a significant gap has emerged between different methods of measuring it, some anchored in the nearby universe, others at cosmological distances. the sh0es team has found h0=73.2 ±1.3 kms-1mpc-1 locally, whereas the value found for the early universe by the planck collaboration is h0=67.4 ±0.5 kms-1mpc-1 from measurements of the cosmic microwave background. is this gap a sign that the well-established λ cdm cosmological model is somehow incomplete? or are there unknown systematics? and more practically, how should humble astronomers pick between competing claims if they need to assume a value for a certain purpose? in this article, we review results and what changes to the cosmological model could be needed to accommodate them all. for astronomers in a hurry, we provide a buyer's guide to the results, and make recommendations. | a buyer's guide to the hubble constant |
the inspiral phase of gravitational waves emitted by spinless compact binary systems is derived through the fourth-and-a-half post-newtonian (4.5pn) order beyond quadrupole radiation, and the leading amplitude mode (ℓ,m )=(2 ,2 ) is obtained at 4pn order. we also provide the radiated flux, as well as the phase in the stationary phase approximation. rough numerical estimates for the contribution of each pn order are provided for typical systems observed by current and future gravitational wave detectors. | gravitational-wave phasing of quasicircular compact binary systems to the fourth-and-a-half post-newtonian order |
since 2012 august voyager 1 has been observing the local interstellar energy spectra of galactic cosmic-ray nuclei down to 3 mev nuc-1 and electrons down to 2.7 mev. the h and he spectra have the same energy dependence between 3 and 346 mev nuc-1, with a broad maximum in the 10-50 mev nuc-1 range and a h/he ratio of 12.2 ± 0.9. the peak h intensity is ∼15 times that observed at 1 au, and the observed local interstellar gradient of 3-346 mev h is -0.009 ± 0.055% au-1, consistent with models having no local interstellar gradient. the energy spectrum of electrons (e - + e +) with 2.7-74 mev is consistent with e -1.30±0.05 and exceeds the h intensity at energies below ∼50 mev. propagation model fits to the observed spectra indicate that the energy density of cosmic-ray nuclei with >3 mev nuc-1 and electrons with >3 mev is 0.83-1.02 ev cm-3 and the ionization rate of atomic h is in the range of 1.51-1.64 × 10-17 s-1. this rate is a factor >10 lower than the ionization rate in diffuse interstellar clouds, suggesting significant spatial inhomogeneity in low-energy cosmic rays or the presence of a suprathermal tail on the energy spectrum at much lower energies. the propagation model fits also provide improved estimates of the elemental abundances in the source of galactic cosmic rays. | galactic cosmic rays in the local interstellar medium: voyager 1 observations and model results |
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