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we report on the implications for cosmic inflation of the 2018 release of the planck cosmic microwave background (cmb) anisotropy measurements. the results are fully consistent with those reported using the data from the two previous planck cosmological releases, but have smaller uncertainties thanks to improvements in the characterization of polarization at low and high multipoles. planck temperature, polarization, and lensing data determine the spectral index of scalar perturbations to be ns = 0.9649 ± 0.0042 at 68% cl. we find no evidence for a scale dependence of ns, either as a running or as a running of the running. the universe is found to be consistent with spatial flatness with a precision of 0.4% at 95% cl by combining planck with a compilation of baryon acoustic oscillation data. the planck 95% cl upper limit on the tensor-to-scalar ratio, r0.002 < 0.10, is further tightened by combining with the bicep2/keck array bk15 data to obtain r0.002 < 0.056. in the framework of standard single-field inflationary models with einstein gravity, these results imply that: (a) the predictions of slow-roll models with a concave potential, v″(ϕ) < 0, are increasingly favoured by the data; and (b) based on two different methods for reconstructing the inflaton potential, we find no evidence for dynamics beyond slow roll. three different methods for the non-parametric reconstruction of the primordial power spectrum consistently confirm a pure power law in the range of comoving scales 0.005 mpc-1 ≲ k ≲ 0.2 mpc-1. a complementary analysis also finds no evidence for theoretically motivated parameterized features in the planck power spectra. for the case of oscillatory features that are logarithmic or linear in k, this result is further strengthened by a new combined analysis including the planck bispectrum data. the new planck polarization data provide a stringent test of the adiabaticity of the initial conditions for the cosmological fluctuations. in correlated, mixed adiabatic and isocurvature models, the non-adiabatic contribution to the observed cmb temperature variance is constrained to 1.3%, 1.7%, and 1.7% at 95% cl for cold dark matter, neutrino density, and neutrino velocity, respectively. planck power spectra plus lensing set constraints on the amplitude of compensated cold dark matter-baryon isocurvature perturbations that are consistent with current complementary measurements. the polarization data also provide improved constraints on inflationary models that predict a small statistically anisotropic quadupolar modulation of the primordial fluctuations. however, the polarization data do not support physical models for a scale-dependent dipolar modulation. all these findings support the key predictions of the standard single-field inflationary models, which will be further tested by future cosmological observations. | planck 2018 results. x. constraints on inflation |
gaia is a cornerstone mission in the science programme of the europeanspace agency (esa). the spacecraft construction was approved in 2006, following a study in which the original interferometric concept was changed to a direct-imaging approach. both the spacecraft and the payload were built by european industry. the involvement of the scientific community focusses on data processing for which the international gaia data processing and analysis consortium (dpac) was selected in 2007. gaia was launched on 19 december 2013 and arrived at its operating point, the second lagrange point of the sun-earth-moon system, a few weeks later. the commissioning of the spacecraft and payload was completed on 19 july 2014. the nominal five-year mission started with four weeks of special, ecliptic-pole scanning and subsequently transferred into full-sky scanning mode. we recall the scientific goals of gaia and give a description of the as-built spacecraft that is currently (mid-2016) being operated to achieve these goals. we pay special attention to the payload module, the performance of which is closely related to the scientific performance of the mission. we provide a summary of the commissioning activities and findings, followed by a description of the routine operational mode. we summarise scientific performance estimates on the basis of in-orbit operations. several intermediate gaia data releases are planned and the data can be retrieved from the gaia archive, which is available through the gaia home page. http://www.cosmos.esa.int/gaia | the gaia mission |
we systematically review some standard issues and also the latest developments of modified gravity in cosmology, emphasizing on inflation, bouncing cosmology and late-time acceleration era. particularly, we present the formalism of standard modified gravity theory representatives, like f(r) , f(g) and f(t) gravity theories, but also several alternative theoretical proposals which appeared in the literature during the last decade. we emphasize on the formalism developed for these theories and we explain how these theories can be considered as viable descriptions for our universe. using these theories, we present how a viable inflationary era can be produced in the context of these theories, with the viability being justified if compatibility with the latest observational data is achieved. also we demonstrate how bouncing cosmologies can actually be described by these theories. moreover, we systematically discuss several qualitative features of the dark energy era by using the modified gravity formalism, and also we critically discuss how a unified description of inflation with dark energy era can be described by solely using the modified gravity framework. finally, we also discuss some astrophysical solutions in the context of modified gravity, and several qualitative features of these solutions. the aim of this review is to gather the different modified gravity techniques and form a virtual modified gravity "toolbox", which will contain all the necessary information on inflation, dark energy and bouncing cosmologies in the context of the various forms of modified gravity. | modified gravity theories on a nutshell: inflation, bounce and late-time evolution |
when surrounded by a transparent emission region, black holes are expected to reveal a dark shadow caused by gravitational light bending and photon capture at the event horizon. to image and study this phenomenon, we have assembled the event horizon telescope, a global very long baseline interferometry array observing at a wavelength of 1.3 mm. this allows us to reconstruct event-horizon-scale images of the supermassive black hole candidate in the center of the giant elliptical galaxy m87. we have resolved the central compact radio source as an asymmetric bright emission ring with a diameter of 42 ± 3 μas, which is circular and encompasses a central depression in brightness with a flux ratio ≳10:1. the emission ring is recovered using different calibration and imaging schemes, with its diameter and width remaining stable over four different observations carried out in different days. overall, the observed image is consistent with expectations for the shadow of a kerr black hole as predicted by general relativity. the asymmetry in brightness in the ring can be explained in terms of relativistic beaming of the emission from a plasma rotating close to the speed of light around a black hole. we compare our images to an extensive library of ray-traced general-relativistic magnetohydrodynamic simulations of black holes and derive a central mass of m = (6.5 ± 0.7) × 109 m ⊙. our radio-wave observations thus provide powerful evidence for the presence of supermassive black holes in centers of galaxies and as the central engines of active galactic nuclei. they also present a new tool to explore gravity in its most extreme limit and on a mass scale that was so far not accessible. | first m87 event horizon telescope results. i. the shadow of the supermassive black hole |
the european pulsar timing array (epta) and indian pulsar timing array (inpta) collaborations have measured a low-frequency common signal in the combination of their second and first data releases respectively, with the correlation properties of a gravitational wave background (gwb). such signal may have its origin in a number of physical processes including a cosmic population of inspiralling supermassive black hole binaries (smbhbs); inflation, phase transitions, cosmic strings and tensor mode generation by non-linear evolution of scalar perturbations in the early universe; oscillations of the galactic potential in the presence of ultra-light dark matter (uldm). at the current stage of emerging evidence, it is impossible to discriminate among the different origins. therefore, in this paper, we consider each process separately, and investigate the implications of the signal under the hypothesis that it is generated by that specific process. we find that the signal is consistent with a cosmic population of inspiralling smbhbs, and its relatively high amplitude can be used to place constraints on binary merger timescales and the smbh-host galaxy scaling relations. if this origin is confirmed, this is the first direct evidence that smbhbs merge in nature, adding an important observational piece to the puzzle of structure formation and galaxy evolution. as for early universe processes, the measurement would place tight constraints on the cosmic string tension and on the level of turbulence developed by first-order phase transitions. other processes would require non-standard scenarios, such as a blue-tilted inflationary spectrum or an excess in the primordial spectrum of scalar perturbations at large wavenumbers. finally, a uldm origin of the detected signal is disfavoured, which leads to direct constraints on the abundance of uldm in our galaxy. | the second data release from the european pulsar timing array: v. implications for massive black holes, dark matter and the early universe |
pulsar timing arrays aim to detect nanohertz-frequency gravitational waves (gws). a background of gws modulates pulsar arrival times and manifests as a stochastic process, common to all pulsars, with a signature spatial correlation. here we describe a search for an isotropic stochastic gravitational-wave background (gwb) using observations of 30 millisecond pulsars from the third data release of the parkes pulsar timing array (ppta), which spans 18 yr. using current bayesian inference techniques we recover and characterize a common-spectrum noise process. represented as a strain spectrum ${h}_{c}=a{(f/1{\mathrm{yr}}^{-1})}^{\alpha }$ , we measure $a={3.1}_{-0.9}^{+1.3}\times {10}^{-15}$ and α = -0.45 ± 0.20, respectively (median and 68% credible interval). for a spectral index of α = -2/3, corresponding to an isotropic background of gws radiated by inspiraling supermassive black hole binaries, we recover an amplitude of $a={2.04}_{-0.22}^{+0.25}\times {10}^{-15}$ . however, we demonstrate that the apparent signal strength is time-dependent, as the first half of our data set can be used to place an upper limit on a that is in tension with the inferred common-spectrum amplitude using the complete data set. we search for spatial correlations in the observations by hierarchically analyzing individual pulsar pairs, which also allows for significance validation through randomizing pulsar positions on the sky. for a process with α = -2/3, we measure spatial correlations consistent with a gwb, with an estimated false-alarm probability of p ≲ 0.02 (approx. 2σ). the long timing baselines of the ppta and the access to southern pulsars will continue to play an important role in the international pulsar timing array. | search for an isotropic gravitational-wave background with the parkes pulsar timing array |
we present the results of the search for an isotropic stochastic gravitational wave background (gwb) at nanohertz frequencies using the second data release of the european pulsar timing array (epta) for 25 millisecond pulsars and a combination with the first data release of the indian pulsar timing array (inpta). a robust gwb detection is conditioned upon resolving the hellings-downs angular pattern in the pairwise cross-correlation of the pulsar timing residuals. additionally, the gwb is expected to yield the same (common) spectrum of temporal correlations across pulsars, which is used as a null hypothesis in the gwb search. such a common-spectrum process has already been observed in pulsar timing data. we analysed (i) the full 24.7-year epta data set, (ii) its 10.3-year subset based on modern observing systems, (iii) the combination of the full data set with the first data release of the inpta for ten commonly timed millisecond pulsars, and (iv) the combination of the 10.3-year subset with the inpta data. these combinations allowed us to probe the contributions of instrumental noise and interstellar propagation effects. with the full data set, we find marginal evidence for a gwb, with a bayes factor of four and a false alarm probability of 4%. with the 10.3-year subset, we report evidence for a gwb, with a bayes factor of 60 and a false alarm probability of about 0.1% (≳3σ significance). the addition of the inpta data yields results that are broadly consistent with the epta-only data sets, with the benefit of better noise modelling. analyses were performed with different data processing pipelines to test the consistency of the results from independent software packages. the latest epta data from new generation observing systems show non-negligible evidence for the gwb. at the same time, the inferred spectrum is rather uncertain and in mild tension with the common signal measured in the full data set. however, if the spectral index is fixed at 13/3, the two data sets give a similar amplitude of (2.5 ± 0.7) × 10−15 at a reference frequency of 1 yr−1. further investigation of these issues is required for reliable astrophysical interpretations of this signal. by continuing our detection efforts as part of the international pulsar timing array (ipta), we expect to be able to improve the measurement of spatial correlations and better characterise this signal in the coming years. | the second data release from the european pulsar timing array. iii. search for gravitational wave signals |
desi (dark energy spectroscopic instrument) is a stage iv ground-based dark energy experiment that will study baryon acoustic oscillations (bao) and the growth of structure through redshift-space distortions with a wide-area galaxy and quasar redshift survey. to trace the underlying dark matter distribution, spectroscopic targets will be selected in four classes from imaging data. we will measure luminous red galaxies up to $z=1.0$. to probe the universe out to even higher redshift, desi will target bright [o ii] emission line galaxies up to $z=1.7$. quasars will be targeted both as direct tracers of the underlying dark matter distribution and, at higher redshifts ($ 2.1 < z < 3.5$), for the ly-$\alpha$ forest absorption features in their spectra, which will be used to trace the distribution of neutral hydrogen. when moonlight prevents efficient observations of the faint targets of the baseline survey, desi will conduct a magnitude-limited bright galaxy survey comprising approximately 10 million galaxies with a median $z\approx 0.2$. in total, more than 30 million galaxy and quasar redshifts will be obtained to measure the bao feature and determine the matter power spectrum, including redshift space distortions. | the desi experiment part i: science,targeting, and survey design |
the lux-zeplin experiment is a dark matter detector centered on a dual-phase xenon time projection chamber operating at the sanford underground research facility in lead, south dakota, usa. this letter reports results from lux-zeplin's first search for weakly interacting massive particles (wimps) with an exposure of 60 live days using a fiducial mass of 5.5 t. a profile-likelihood ratio analysis shows the data to be consistent with a background-only hypothesis, setting new limits on spin-independent wimp-nucleon, spin-dependent wimp-neutron, and spin-dependent wimp-proton cross sections for wimp masses above 9 gev /c2 . the most stringent limit is set for spin-independent scattering at 36 gev /c2 , rejecting cross sections above 9.2 ×10-48 cm at the 90% confidence level. | first dark matter search results from the lux-zeplin (lz) experiment |
machine learning (ml) encompasses a broad range of algorithms and modeling tools used for a vast array of data processing tasks, which has entered most scientific disciplines in recent years. this article reviews in a selective way the recent research on the interface between machine learning and the physical sciences. this includes conceptual developments in ml motivated by physical insights, applications of machine learning techniques to several domains in physics, and cross fertilization between the two fields. after giving a basic notion of machine learning methods and principles, examples are described of how statistical physics is used to understand methods in ml. this review then describes applications of ml methods in particle physics and cosmology, quantum many-body physics, quantum computing, and chemical and material physics. research and development into novel computing architectures aimed at accelerating ml are also highlighted. each of the sections describe recent successes as well as domain-specific methodology and challenges. | machine learning and the physical sciences* |
we report observations from the hubble space telescope (hst) of cepheid variables in the host galaxies of 42 type ia supernovae (sne ia) used to calibrate the hubble constant (h 0). these include the complete sample of all suitable sne ia discovered in the last four decades at redshift z ≤ 0.01, collected and calibrated from ≥1000 hst orbits, more than doubling the sample whose size limits the precision of the direct determination of h 0. the cepheids are calibrated geometrically from gaia edr3 parallaxes, masers in ngc 4258 (here tripling that sample of cepheids), and detached eclipsing binaries in the large magellanic cloud. all cepheids in these anchors and sn ia hosts were measured with the same instrument (wfc3) and filters (f555w, f814w, f160w) to negate zero-point errors. we present multiple verifications of cepheid photometry and six tests of background determinations that show cepheid measurements are accurate in the presence of crowded backgrounds. the sne ia in these hosts calibrate the magnitude-redshift relation from the revised pantheon+ compilation, accounting here for covariance between all sn data and with host properties and sn surveys matched throughout to negate systematics. we decrease the uncertainty in the local determination of h 0 to 1 km s-1 mpc-1 including systematics. we present results for a comprehensive set of nearly 70 analysis variants to explore the sensitivity of h 0 to selections of anchors, sn surveys, redshift ranges, the treatment of cepheid dust, metallicity, form of the period-luminosity relation, sn color, peculiar-velocity corrections, sample bifurcations, and simultaneous measurement of the expansion history. our baseline result from the cepheid-sn ia sample is h 0 = 73.04 ± 1.04 km s-1 mpc-1, which includes systematic uncertainties and lies near the median of all analysis variants. we demonstrate consistency with measures from hst of the trgb between sn ia hosts and ngc 4258, and include them simultaneously to yield 72.53 ± 0.99 km s-1 mpc-1. the inclusion of high-redshift sne ia yields h 0 = 73.30 ± 1.04 km s-1 mpc-1 and q 0 = -0.51 ± 0.024. we find a 5σ difference with the prediction of h 0 from planck cosmic microwave background observations under λcdm, with no indication that the discrepancy arises from measurement uncertainties or analysis variations considered to date. the source of this now long-standing discrepancy between direct and cosmological routes to determining h 0 remains unknown. | a comprehensive measurement of the local value of the hubble constant with 1 km s-1 mpc-1 uncertainty from the hubble space telescope and the sh0es team |
we report constraints on spin-independent weakly interacting massive particle (wimp)-nucleon scattering using a 3.35 ×1 04 kg day exposure of the large underground xenon (lux) experiment. a dual-phase xenon time projection chamber with 250 kg of active mass is operated at the sanford underground research facility under lead, south dakota (usa). with roughly fourfold improvement in sensitivity for high wimp masses relative to our previous results, this search yields no evidence of wimp nuclear recoils. at a wimp mass of 50 gev c-2 , wimp-nucleon spin-independent cross sections above 2.2 ×10-46 cm2 are excluded at the 90% confidence level. when combined with the previously reported lux exposure, this exclusion strengthens to 1.1 ×10-46 cm2 at 50 gev c-2 . | results from a search for dark matter in the complete lux exposure |
the simplest λcdm model provides a good fit to a large span of cosmological data but harbors large areas of phenomenology and ignorance. with the improvement of the number and the accuracy of observations, discrepancies among key cosmological parameters of the model have emerged. the most statistically significant tension is the 4σ to 6σ disagreement between predictions of the hubble constant, h 0, made by the early time probes in concert with the 'vanilla' λcdm cosmological model, and a number of late time, model-independent determinations of h 0 from local measurements of distances and redshifts. the high precision and consistency of the data at both ends present strong challenges to the possible solution space and demands a hypothesis with enough rigor to explain multiple observations-whether these invoke new physics, unexpected large-scale structures or multiple, unrelated errors. a thorough review of the problem including a discussion of recent hubble constant estimates and a summary of the proposed theoretical solutions is presented here. we include more than 1000 references, indicating that the interest in this area has grown considerably just during the last few years. we classify the many proposals to resolve the tension in these categories: early dark energy, late dark energy, dark energy models with 6 degrees of freedom and their extensions, models with extra relativistic degrees of freedom, models with extra interactions, unified cosmologies, modified gravity, inflationary models, modified recombination history, physics of the critical phenomena, and alternative proposals. some are formally successful, improving the fit to the data in light of their additional degrees of freedom, restoring agreement within 1-2σ between planck 2018, using the cosmic microwave background power spectra data, baryon acoustic oscillations, pantheon sn data, and r20, the latest sh0es team riess, et al (2021 astrophys. j. 908 l6) measurement of the hubble constant (h 0 = 73.2 ± 1.3 km s-1 mpc-1 at 68% confidence level). however, there are many more unsuccessful models which leave the discrepancy well above the 3σ disagreement level. in many cases, reduced tension comes not simply from a change in the value of h 0 but also due to an increase in its uncertainty due to degeneracy with additional physics, complicating the picture and pointing to the need for additional probes. while no specific proposal makes a strong case for being highly likely or far better than all others, solutions involving early or dynamical dark energy, neutrino interactions, interacting cosmologies, primordial magnetic fields, and modified gravity provide the best options until a better alternative comes along. * in honor of the seminal work by e hubble [] | in the realm of the hubble tension-a review of solutions |
this book lays out the scientific goals to be addressed by the next-generation ground-based cosmic microwave background experiment, cmb-s4, envisioned to consist of dedicated telescopes at the south pole, the high chilean atacama plateau and possibly a northern hemisphere site, all equipped with new superconducting cameras. cmb-s4 will dramatically advance cosmological studies by crossing critical thresholds in the search for the b-mode polarization signature of primordial gravitational waves, in the determination of the number and masses of the neutrinos, in the search for evidence of new light relics, in constraining the nature of dark energy, and in testing general relativity on large scales. | cmb-s4 science book, first edition |
the 15 yr pulsar timing data set collected by the north american nanohertz observatory for gravitational waves (nanograv) shows positive evidence for the presence of a low-frequency gravitational-wave (gw) background. in this paper, we investigate potential cosmological interpretations of this signal, specifically cosmic inflation, scalar-induced gws, first-order phase transitions, cosmic strings, and domain walls. we find that, with the exception of stable cosmic strings of field theory origin, all these models can reproduce the observed signal. when compared to the standard interpretation in terms of inspiraling supermassive black hole binaries (smbhbs), many cosmological models seem to provide a better fit resulting in bayes factors in the range from 10 to 100. however, these results strongly depend on modeling assumptions about the cosmic smbhb population and, at this stage, should not be regarded as evidence for new physics. furthermore, we identify excluded parameter regions where the predicted gw signal from cosmological sources significantly exceeds the nanograv signal. these parameter constraints are independent of the origin of the nanograv signal and illustrate how pulsar timing data provide a new way to constrain the parameter space of these models. finally, we search for deterministic signals produced by models of ultralight dark matter (uldm) and dark matter substructures in the milky way. we find no evidence for either of these signals and thus report updated constraints on these models. in the case of uldm, these constraints outperform torsion balance and atomic clock constraints for uldm coupled to electrons, muons, or gluons. | the nanograv 15 yr data set: search for signals from new physics |
the european space agency's planck satellite, which was dedicated to studying the early universe and its subsequent evolution, was launched on 14 may 2009. it scanned the microwave and submillimetre sky continuously between 12 august 2009 and 23 october 2013, producing deep, high-resolution, all-sky maps in nine frequency bands from 30 to 857 ghz. this paper presents the cosmological legacy of planck, which currently provides our strongest constraints on the parameters of the standard cosmological model and some of the tightest limits available on deviations from that model. the 6-parameter λcdm model continues to provide an excellent fit to the cosmic microwave background data at high and low redshift, describing the cosmological information in over a billion map pixels with just six parameters. with 18 peaks in the temperature and polarization angular power spectra constrained well, planck measures five of the six parameters to better than 1% (simultaneously), with the best-determined parameter (θ*) now known to 0.03%. we describe the multi-component sky as seen by planck, the success of the λcdm model, and the connection to lower-redshift probes of structure formation. we also give a comprehensive summary of the major changes introduced in this 2018 release. the planck data, alone and in combination with other probes, provide stringent constraints on our models of the early universe and the large-scale structure within which all astrophysical objects form and evolve. we discuss some lessons learned from the planck mission, and highlight areas ripe for further experimental advances. | planck 2018 results. i. overview and the cosmological legacy of planck |
we present cosmological results from the final galaxy clustering data set of the baryon oscillation spectroscopic survey, part of the sloan digital sky survey iii. our combined galaxy sample comprises 1.2 million massive galaxies over an effective area of 9329 deg2 and volume of 18.7 gpc3, divided into three partially overlapping redshift slices centred at effective redshifts 0.38, 0.51 and 0.61. we measure the angular diameter distance dm and hubble parameter h from the baryon acoustic oscillation (bao) method, in combination with a cosmic microwave background prior on the sound horizon scale, after applying reconstruction to reduce non-linear effects on the bao feature. using the anisotropic clustering of the pre-reconstruction density field, we measure the product dmh from the alcock-paczynski (ap) effect and the growth of structure, quantified by fσ8(z), from redshift-space distortions (rsd). we combine individual measurements presented in seven companion papers into a set of consensus values and likelihoods, obtaining constraints that are tighter and more robust than those from any one method; in particular, the ap measurement from sub-bao scales sharpens constraints from post-reconstruction baos by breaking degeneracy between dm and h. combined with planck 2016 cosmic microwave background measurements, our distance scale measurements simultaneously imply curvature ωk = 0.0003 ± 0.0026 and a dark energy equation-of-state parameter w = -1.01 ± 0.06, in strong affirmation of the spatially flat cold dark matter (cdm) model with a cosmological constant (λcdm). our rsd measurements of fσ8, at 6 per cent precision, are similarly consistent with this model. when combined with supernova ia data, we find h0 = 67.3 ± 1.0 km s-1 mpc-1 even for our most general dark energy model, in tension with some direct measurements. adding extra relativistic species as a degree of freedom loosens the constraint only slightly, to h0 = 67.8 ± 1.2 km s-1 mpc-1. assuming flat λcdm, we find ωm = 0.310 ± 0.005 and h0 = 67.6 ± 0.5 km s-1 mpc-1, and we find a 95 per cent upper limit of 0.16 ev c-2 on the neutrino mass sum. | the clustering of galaxies in the completed sdss-iii baryon oscillation spectroscopic survey: cosmological analysis of the dr12 galaxy sample |
we report on a search for weakly interacting massive particles (wimps) using 278.8 days of data collected with the xenon1t experiment at lngs. xenon1t utilizes a liquid xenon time projection chamber with a fiducial mass of (1.30 ±0.01 ) t o n , resulting in a 1.0 ton yr exposure. the energy region of interest, [1.4 ,10.6 ] kevee ([4.9 ,40.9 ] kevnr ), exhibits an ultralow electron recoil background rate of [82-3+5(syst ) ±3 (stat ) ] events /(t o n yr kevee) . no significant excess over background is found, and a profile likelihood analysis parametrized in spatial and energy dimensions excludes new parameter space for the wimp-nucleon spin-independent elastic scatter cross section for wimp masses above 6 gev /c2, with a minimum of 4.1 ×10-47 cm2 at 30 gev /c2 and a 90% confidence level. | dark matter search results from a one ton-year exposure of xenon1t |
we present optical light curves, redshifts, and classifications for 365 spectroscopically confirmed type ia supernovae (sne ia) discovered by the pan-starrs1 (ps1) medium deep survey. we detail improvements to the ps1 sn photometry, astrometry, and calibration that reduce the systematic uncertainties in the ps1 sn ia distances. we combine the subset of 279 ps1 sne ia (0.03 < z < 0.68) with useful distance estimates of sne ia from the sloan digital sky survey (sdss), snls, and various low-z and hubble space telescope samples to form the largest combined sample of sne ia, consisting of a total of 1048 sne ia in the range of 0.01 < z < 2.3, which we call the “pantheon sample.” when combining planck 2015 cosmic microwave background (cmb) measurements with the pantheon sn sample, we find {{{ω }}}m=0.307+/- 0.012 and w=-1.026+/- 0.041 for the wcdm model. when the sn and cmb constraints are combined with constraints from bao and local h 0 measurements, the analysis yields the most precise measurement of dark energy to date: {w}0=-1.007+/- 0.089 and {w}a=-0.222+/- 0.407 for the {w}0{w}acdm model. tension with a cosmological constant previously seen in an analysis of ps1 and low-z sne has diminished after an increase of 2× in the statistics of the ps1 sample, improved calibration and photometry, and stricter light-curve quality cuts. we find that the systematic uncertainties in our measurements of dark energy are almost as large as the statistical uncertainties, primarily due to limitations of modeling the low-redshift sample. this must be addressed for future progress in using sne ia to measure dark energy. | the complete light-curve sample of spectroscopically confirmed sne ia from pan-starrs1 and cosmological constraints from the combined pantheon sample |
we update the constraints on the fraction of the universe that may have gone into primordial black holes (pbhs) over the mass range 10-5 to 1050 g. those smaller than ~1015 g would have evaporated by now due to hawking radiation, so their abundance at formation is constrained by the effects of evaporated particles on big bang nucleosynthesis, the cosmic microwave background (cmb), the galactic and extragalactic γ-ray and cosmic ray backgrounds and the possible generation of stable planck mass relics. pbhs larger than ~1015 g are subject to a variety of constraints associated with gravitational lensing, dynamical effects, influence on large-scale structure, accretion and gravitational waves. we discuss the constraints on both the initial collapse fraction and the current fraction of the dark matter (dm) in pbhs at each mass scale but stress that many of the constraints are associated with observational or theoretical uncertainties. we also consider indirect constraints associated with the amplitude of the primordial density fluctuations, such as second-order tensor perturbations and μ-distortions arising from the effect of acoustic reheating on the cmb, if pbhs are created from the high-σ peaks of nearly gaussian fluctuations. finally we discuss how the constraints are modified if the pbhs have an extended mass function, this being relevant if pbhs provide some combination of the dm, the ligo/virgo coalescences and the seeds for cosmic structure. even if pbhs make a small contribution to the dm, they could play an important cosmological role and provide a unique probe of the early universe. | constraints on primordial black holes |
we present the implications for cosmic inflation of the planck measurements of the cosmic microwave background (cmb) anisotropies in both temperature and polarization based on the full planck survey, which includes more than twice the integration time of the nominal survey used for the 2013 release papers. the planck full mission temperature data and a first release of polarization data on large angular scales measure the spectral index of curvature perturbations to be ns = 0.968 ± 0.006 and tightly constrain its scale dependence to dns/ dlnk = -0.003 ± 0.007 when combined with the planck lensing likelihood. when the planck high-ℓ polarization data are included, the results are consistent and uncertainties are further reduced. the upper bound on the tensor-to-scalar ratio is r0.002< 0.11 (95% cl). this upper limit is consistent with the b-mode polarization constraint r< 0.12 (95% cl) obtained from a joint analysis of the bicep2/keck array and planck data. these results imply that v(φ) ∝ φ2 and natural inflation are now disfavoured compared to models predicting a smaller tensor-to-scalar ratio, such as r2 inflation. we search for several physically motivated deviations from a simple power-law spectrum of curvature perturbations, including those motivated by a reconstruction of the inflaton potential not relying on the slow-roll approximation. we find that such models are not preferred, either according to a bayesian model comparison or according to a frequentist simulation-based analysis. three independent methods reconstructing the primordial power spectrum consistently recover a featureless and smooth pr(k) over the range of scales 0.008 mpc-1 ≲ k ≲ 0.1 mpc-1. at large scales, each method finds deviations from a power law, connected to a deficit at multipoles ℓ ≈ 20-40 in the temperature power spectrum, but at an uncompelling statistical significance owing to the large cosmic variance present at these multipoles. by combining power spectrum and non-gaussianity bounds, we constrain models with generalized lagrangians, including galileon models and axion monodromy models. the planck data are consistent with adiabatic primordial perturbations, and the estimated values for the parameters of the base λ cold dark matter (λcdm) model are not significantly altered when more general initial conditions are admitted. in correlated mixed adiabatic and isocurvature models, the 95% cl upper bound for the non-adiabatic contribution to the observed cmb temperature variance is | αnon - adi | < 1.9%, 4.0%, and 2.9% for cdm, neutrino density, and neutrino velocity isocurvature modes, respectively. we have tested inflationary models producing an anisotropic modulation of the primordial curvature power spectrum findingthat the dipolar modulation in the cmb temperature field induced by a cdm isocurvature perturbation is not preferred at a statistically significant level. we also establish tight constraints on a possible quadrupolar modulation of the curvature perturbation. these results are consistent with the planck 2013 analysis based on the nominal mission data and further constrain slow-roll single-field inflationary models, as expected from the increased precision of planck data using the full set of observations. | planck 2015 results. xx. constraints on inflation |
we present an updated global fit of neutrino oscillation data in the simplest three-neutrino framework. in the present study we include up-to-date analyses from a number of experiments. concerning the atmospheric and solar sectors, besides the data considered previously, we give updated analyses of icecube deepcore and sudbury neutrino observatory data, respectively. we have also included the latest electron antineutrino data collected by the daya bay and reno reactor experiments, and the long-baseline t2k and noνa measurements, as reported in the neutrino 2020 conference. all in all, these new analyses result in more accurate measurements of θ13, θ12, δ m212 and |δ m312 |. the best fit value for the atmospheric angle θ23 lies in the second octant, but first octant solutions remain allowed at ∼ 2.4σ. regarding cp violation measurements, the preferred value of δ we obtain is 1.08π (1.58π) for normal (inverted) neutrino mass ordering. the global analysis still prefers normal neutrino mass ordering with 2.5σ statistical significance. this preference is milder than the one found in previous global analyses. these new results should be regarded as robust due to the agreement found between our bayesian and frequentist approaches. taking into account only oscillation data, there is a weak/moderate preference for the normal neutrino mass ordering of 2.00σ. while adding neutrinoless double beta decay from the latest gerda, cuore and kamland-zen results barely modifies this picture, cosmological measurements raise the preference to 2.68σ within a conservative approach. a more aggressive data set combination of cosmological observations leads to a similar preference for normal with respect to inverted mass ordering, namely 2.70σ. this very same cosmological data set provides 2σ upper limits on the total neutrino mass corresponding to σmν< 0.12 (0.15) ev in the normal (inverted) neutrino mass ordering scenario. the bounds on the neutrino mixing parameters and masses presented in this up-to-date global fit analysis include all currently available neutrino physics inputs. | 2020 global reassessment of the neutrino oscillation picture |
advanced virgo is the project to upgrade the virgo interferometric detector of gravitational waves, with the aim of increasing the number of observable galaxies (and thus the detection rate) by three orders of magnitude. the project is now in an advanced construction phase and the assembly and integration will be completed by the end of 2015. advanced virgo will be part of a network, alongside the two advanced ligo detectors in the us and geo hf in germany, with the goal of contributing to the early detection of gravitational waves and to opening a new window of observation on the universe. in this paper we describe the main features of the advanced virgo detector and outline the status of the construction. | advanced virgo: a second-generation interferometric gravitational wave detector |
we study whether the signal seen by pulsar timing arrays (ptas) may originate from gravitational waves (gws) induced by large primordial perturbations. such perturbations may be accompanied by a sizable primordial black hole (pbh) abundance. we improve existing analyses and show that pbh overproduction disfavors gaussian scenarios for scalar-induced gws at 2 σ and single-field inflationary scenarios, accounting for non-gaussianity, at 3 σ as the explanation of the most constraining nanograv 15-year data. this tension can be relaxed in models where non-gaussianities suppress the pbh abundance. on the flip side, the pta data does not constrain the abundance of pbhs. | recent gravitational wave observation by pulsar timing arrays and primordial black holes: the importance of non-gaussianities |
we present the first cosmology results from large-scale structure using the full 5000 deg2 of imaging data from the dark energy survey (des) data release 1. we perform an analysis of large-scale structure combining three two-point correlation functions (3 ×2 pt ): (i) cosmic shear using 100 million source galaxies, (ii) galaxy clustering, and (iii) the cross-correlation of source galaxy shear with lens galaxy positions, galaxy-galaxy lensing. to achieve the cosmological precision enabled by these measurements has required updates to nearly every part of the analysis from des year 1, including the use of two independent galaxy clustering samples, modeling advances, and several novel improvements in the calibration of gravitational shear and photometric redshift inference. the analysis was performed under strict conditions to mitigate confirmation or observer bias; we describe specific changes made to the lens galaxy sample following unblinding of the results and tests of the robustness of our results to this decision. we model the data within the flat λ cdm and w cdm cosmological models, marginalizing over 25 nuisance parameters. we find consistent cosmological results between the three two-point correlation functions; their combination yields clustering amplitude s8=0.77 6-0.017+0.017 and matter density ωm=0.33 9-0.031+0.032 in λ cdm , mean with 68% confidence limits; s8=0.77 5-0.024+0.026, ωm=0.35 2-0.041+0.035, and dark energy equation-of-state parameter w =-0.9 8-0.20+0.32 in w cdm . these constraints correspond to an improvement in signal-to-noise of the des year 3 3 ×2 pt data relative to des year 1 by a factor of 2.1, about 20% more than expected from the increase in observing area alone. this combination of des data is consistent with the prediction of the model favored by the planck 2018 cosmic microwave background (cmb) primary anisotropy data, which is quantified with a probability-to-exceed p =0.13 -0.48. we find better agreement between des 3 ×2 pt and planck than in des y1, despite the significantly improved precision of both. when combining des 3 ×2 pt data with available baryon acoustic oscillation, redshift-space distortion, and type ia supernovae data, we find p =0.34 . combining all of these datasets with planck cmb lensing yields joint parameter constraints of s8=0.81 2-0.008+0.008, ωm=0.30 6-0.005+0.004, h =0.68 0-0.003+0.004, and ∑mν<0.13 ev (95% c.l.) in λ cdm ; s8=0.81 2-0.008+0.008, ωm=0.30 2-0.006+0.006, h =0.68 7-0.007+0.006, and w =-1.03 1-0.027+0.030 in w cdm . | dark energy survey year 3 results: cosmological constraints from galaxy clustering and weak lensing |
monte carlo techniques, including mcmc and other methods, are widely used and generate sets of samples from a parameter space of interest that can be used to infer or plot quantities of interest. this note outlines methods used the python getdist package to calculate marginalized one and two dimensional densities using kernel density estimation (kde). many monte carlo methods produce correlated and/or weighted samples, for example produced by mcmc, nested, or importance sampling, and there can be hard boundary priors. getdist's baseline method consists of applying a linear boundary kernel, and then using multiplicative bias correction. the smoothing bandwidth is selected automatically following botev et al., based on a mixture of heuristics and optimization results using the expected scaling with an effective number of samples (defined to account for mcmc correlations and weights). two-dimensional kde use an automatically-determined elliptical gaussian kernel for correlated distributions. the package includes tools for producing a variety of publication-quality figures using a simple named-parameter interface, as well as a graphical user interface that can be used for interactive exploration. it can also calculate convergence diagnostics, produce tables of limits, and output in latex. | getdist: a python package for analysing monte carlo samples |
the standard λ cold dark matter (λcdm) cosmological model provides a good description of a wide range of astrophysical and cosmological data. however, there are a few big open questions that make the standard model look like an approximation to a more realistic scenario yet to be found. in this paper, we list a few important goals that need to be addressed in the next decade, taking into account the current discordances between the different cosmological probes, such as the disagreement in the value of the hubble constant h0, the σ8-s8 tension, and other less statistically significant anomalies. while these discordances can still be in part the result of systematic errors, their persistence after several years of accurate analysis strongly hints at cracks in the standard cosmological scenario and the necessity for new physics or generalisations beyond the standard model. in this paper, we focus on the 5.0 σ tension between the planck cmb estimate of the hubble constant h0 and the sh0es collaboration measurements. after showing the h0 evaluations made from different teams using different methods and geometric calibrations, we list a few interesting new physics models that could alleviate this tension and discuss how the next decade's experiments will be crucial. moreover, we focus on the tension of the planck cmb data with weak lensing measurements and redshift surveys, about the value of the matter energy density ωm, and the amplitude or rate of the growth of structure (σ8 , fσ8). we list a few interesting models proposed for alleviating this tension, and we discuss the importance of trying to fit a full array of data with a single model and not just one parameter at a time. additionally, we present a wide range of other less discussed anomalies at a statistical significance level lower than the h0-s8 tensions which may also constitute hints towards new physics, and we discuss possible generic theoretical approaches that can collectively explain the non-standard nature of these signals. finally, we give an overview of upgraded experiments and next-generation space missions and facilities on earth that will be of crucial importance to address all these open questions. | cosmology intertwined: a review of the particle physics, astrophysics, and cosmology associated with the cosmological tensions and anomalies |
the recently introduced swampland criterion for de sitter [17] can be viewed as a (hierarchically large) bound on the smallness of the slow roll parameter 𝜖v. this leads us to consider the other slow roll parameter ηv more closely, and we are lead to conjecture that the bound is not necessarily on 𝜖v, but on slow roll itself. a natural refinement of the de sitter swampland conjecture is therefore that slow roll is violated at o (1) in planck units in any uv complete theory. a corollary is that 𝜖v need not necesarily be o (1), if ηv≲-o (1 ) holds. we consider various tachyonic tree level constructions of de sitter in iia/iib string theory (as well as closely related models of inflation), which superficially violate [17], and show that they are consistent with this refined version of the bound. the phrasing in terms of slow roll makes it plausible why both versions of the conjecture run into trouble when the number of e-folds during inflation is high. we speculate that one way to evade the bound could be to have a large number of fields, like in n -flation. | bounds on slow roll and the de sitter swampland |
we present a measurement of the hubble constant (h0) and other cosmological parameters from a joint analysis of six gravitationally lensed quasars with measured time delays. all lenses except the first are analysed blindly with respect to the cosmological parameters. in a flat λ cold dark matter (λcdm) cosmology, we find $h_{0} = 73.3_{-1.8}^{+1.7}~\mathrm{km~s^{-1}~mpc^{-1}}$ , a $2.4{{\ \rm per\ cent}}$ precision measurement, in agreement with local measurements of h0 from type ia supernovae calibrated by the distance ladder, but in 3.1σ tension with planck observations of the cosmic microwave background (cmb). this method is completely independent of both the supernovae and cmb analyses. a combination of time-delay cosmography and the distance ladder results is in 5.3σ tension with planck cmb determinations of h0 in flat λcdm. we compute bayes factors to verify that all lenses give statistically consistent results, showing that we are not underestimating our uncertainties and are able to control our systematics. we explore extensions to flat λcdm using constraints from time-delay cosmography alone, as well as combinations with other cosmological probes, including cmb observations from planck, baryon acoustic oscillations, and type ia supernovae. time-delay cosmography improves the precision of the other probes, demonstrating the strong complementarity. allowing for spatial curvature does not resolve the tension with planck. using the distance constraints from time-delay cosmography to anchor the type ia supernova distance scale, we reduce the sensitivity of our h0 inference to cosmological model assumptions. for six different cosmological models, our combined inference on h0 ranges from ∼73 to 78 km s-1 mpc-1, which is consistent with the local distance ladder constraints. | h0licow - xiii. a 2.4 per cent measurement of h0 from lensed quasars: 5.3σ tension between early- and late-universe probes |
despite the remarkable success of the λ cold dark matter (λcdm) cosmological model, a growing discrepancy has emerged (currently measured at the level of ∼ 4 - 6 σ) between the value of the hubble constant h0 measured using the local distance ladder and the value inferred using the cosmic microwave background and galaxy surveys. while a vast array of λcdm extensions have been proposed to explain these discordant observations, understanding the (relative) success of these models in resolving the tension has proven difficult - this is a direct consequence of the fact that each model has been subjected to differing, and typically incomplete, compilations of cosmological data. in this review, we attempt to make a systematic comparison of seventeen different models which have been proposed to resolve the h0 tension (spanning both early- and late-universe solutions), and quantify the relative success of each using a series of metrics and a vast array of data combinations. owing to the timely appearance of this article, we refer to this contest as the "h0 olympics"; the goal being to identify which of the proposed solutions, and more broadly which underlying mechanisms, are most likely to be responsible for explaining the observed discrepancy (should unaccounted for systematics not be the culprit). this work also establishes a foundation of tests which will allow the success of novel proposals to be meaningfully "benchmarked". | the h0 olympics: a fair ranking of proposed models |
we present the science case, reference design, and project plan for the stage-4 ground-based cosmic microwave background experiment cmb-s4. | cmb-s4 science case, reference design, and project plan |
teleparallel gravity (tg) has significantly increased in popularity in recent decades, bringing attention to einstein's other theory of gravity. in this review, we give a comprehensive introduction to how teleparallel geometry is developed as a gauge theory of translations together with all the other properties of gauge field theory. this relates the geometry to the broader metric-affine approach to forming gravitational theories where we describe a systematic way of constructing consistent teleparallel theories that respect certain physical conditions such as local lorentz invariance. we first use tg to formulate a teleparallel equivalent of general relativity (gr) which is dynamically equivalent to gr but which may have different behaviors for other scenarios, such as quantum gravity. after setting this foundation, we describe the plethora of modified teleparallel theories of gravity that have been proposed in the literature. we attempt to connect them together into general classes of covariant gravitational theories. of particular interest, we highlight the recent proposal of a teleparallel analogue of horndeski gravity which offers the possibility of reviving all of the regular horndeski contributions. in the second part of the review, we first survey works in teleparallel astrophysics literature where we focus on the open questions in this regime of physics. we then discuss the cosmological consequences for the various formulations of tg. we do this at background level by exploring works using various approaches ranging from dynamical systems to noether symmetries, and more. naturally, we then discuss perturbation theory, firstly by giving a concise approach in which this can be applied in tg theories and then apply it to a number of important theories in the literature. finally, we examine works in observational and precision cosmology across the plethora of proposal theories. this is done using some of the latest observations and is used to tackle cosmological tensions which may be alleviated in teleparallel cosmology. we also introduce a number of recent works in the application of machine learning to gravity, we do this through deep learning and gaussian processes, together with discussions about other approaches in the literature. | teleparallel gravity: from theory to cosmology |
we present the cosmological implications from final measurements of clustering using galaxies, quasars, and ly α forests from the completed sloan digital sky survey (sdss) lineage of experiments in large-scale structure. these experiments, composed of data from sdss, sdss-ii, boss, and eboss, offer independent measurements of baryon acoustic oscillation (bao) measurements of angular-diameter distances and hubble distances relative to the sound horizon, rd, from eight different samples and six measurements of the growth rate parameter, f σ8, from redshift-space distortions (rsd). this composite sample is the most constraining of its kind and allows us to perform a comprehensive assessment of the cosmological model after two decades of dedicated spectroscopic observation. we show that the bao data alone are able to rule out dark-energy-free models at more than eight standard deviations in an extension to the flat, λ cdm model that allows for curvature. when combined with planck cosmic microwave background (cmb) measurements of temperature and polarization, under the same model, the bao data provide nearly an order of magnitude improvement on curvature constraints relative to primary cmb constraints alone. independent of distance measurements, the sdss rsd data complement weak lensing measurements from the dark energy survey (des) in demonstrating a preference for a flat λ cdm cosmological model when combined with planck measurements. the combined bao and rsd measurements indicate σ8=0.85 ±0.03 , implying a growth rate that is consistent with predictions from planck temperature and polarization data and with general relativity. when combining the results of sdss bao and rsd, planck, pantheon type ia supernovae (sne ia), and des weak lensing and clustering measurements, all multiple-parameter extensions remain consistent with a λ cdm model. regardless of cosmological model, the precision on each of the three parameters, ωλ, h0, and σ8, remains at roughly 1%, showing changes of less than 0.6% in the central values between models. in a model that allows for free curvature and a time-evolving equation of state for dark energy, the combined samples produce a constraint ωk=-0.0022 ±0.0022 . the dark energy constraints lead to w0=-0.909 ±0.081 and wa=-0.4 9-0.30+0.35, corresponding to an equation of state of wp=-1.018 ±0.032 at a pivot redshift zp=0.29 and a dark energy task force figure of merit of 94. the inverse distance ladder measurement under this model yields h0=68.18 ±0.79 km s-1 mpc-1 , remaining in tension with several direct determination methods; the bao data allow hubble constant estimates that are robust against the assumption of the cosmological model. in addition, the bao data allow estimates of h0 that are independent of the cmb data, with similar central values and precision under a λ cdm model. our most constraining combination of data gives the upper limit on the sum of neutrino masses at ∑mν<0.115 ev (95% confidence). finally, we consider the improvements in cosmology constraints over the last decade by comparing our results to a sample representative of the period 2000-2010. we compute the relative gain across the five dimensions spanned by w , ωk, ∑mν, h0, and σ8 and find that the sdss bao and rsd data reduce the total posterior volume by a factor of 40 relative to the previous generation. adding again the planck, des, and pantheon sn ia samples leads to an overall contraction in the five-dimensional posterior volume of 3 orders of magnitude. | completed sdss-iv extended baryon oscillation spectroscopic survey: cosmological implications from two decades of spectroscopic surveys at the apache point observatory |
we present the fourth fermi large area telescope catalog (4fgl) of γ-ray sources. based on the first eight years of science data from the fermi gamma-ray space telescope mission in the energy range from 50 mev to 1 tev, it is the deepest yet in this energy range. relative to the 3fgl catalog, the 4fgl catalog has twice as much exposure as well as a number of analysis improvements, including an updated model for the galactic diffuse γ-ray emission, and two sets of light curves (one-year and two-month intervals). the 4fgl catalog includes 5064 sources above 4σ significance, for which we provide localization and spectral properties. seventy-five sources are modeled explicitly as spatially extended, and overall, 358 sources are considered as identified based on angular extent, periodicity, or correlated variability observed at other wavelengths. for 1336 sources, we have not found plausible counterparts at other wavelengths. more than 3130 of the identified or associated sources are active galaxies of the blazar class, and 239 are pulsars. | fermi large area telescope fourth source catalog |
we report on the first search for nuclear recoils from dark matter in the form of weakly interacting massive particles (wimps) with the xenonnt experiment, which is based on a two-phase time projection chamber with a sensitive liquid xenon mass of 5.9 ton. during the (1.09 ±0.03 ) ton yr exposure used for this search, the intrinsic 85k and 222rn concentrations in the liquid target are reduced to unprecedentedly low levels, giving an electronic recoil background rate of (15.8 ±1.3 ) events/ton yr kev in the region of interest. a blind analysis of nuclear recoil events with energies between 3.3 and 60.5 kev finds no significant excess. this leads to a minimum upper limit on the spin-independent wimp-nucleon cross section of 2.58 ×1047 cm2 for a wimp mass of 28 gev /c2 at 90% confidence level. limits for spin-dependent interactions are also provided. both the limit and the sensitivity for the full range of wimp masses analyzed here improve on previous results obtained with the xenon1t experiment for the same exposure. | first dark matter search with nuclear recoils from the xenonnt experiment |
we use the wide field camera 3 (wfc3) on the hubble space telescope (hst) to reduce the uncertainty in the local value of the hubble constant from 3.3% to 2.4%. the bulk of this improvement comes from new near-infrared (nir) observations of cepheid variables in 11 host galaxies of recent type ia supernovae (sne ia), more than doubling the sample of reliable sne ia having a cepheid-calibrated distance to a total of 19; these in turn leverage the magnitude-redshift relation based on ∼300 sne ia at z < 0.15. all 19 hosts as well as the megamaser system ngc 4258 have been observed with wfc3 in the optical and nir, thus nullifying cross-instrument zeropoint errors in the relative distance estimates from cepheids. other noteworthy improvements include a 33% reduction in the systematic uncertainty in the maser distance to ngc 4258, a larger sample of cepheids in the large magellanic cloud (lmc), a more robust distance to the lmc based on late-type detached eclipsing binaries (debs), hst observations of cepheids in m31, and new hst-based trigonometric parallaxes for milky way (mw) cepheids. we consider four geometric distance calibrations of cepheids: (i) megamasers in ngc 4258, (ii) 8 debs in the lmc, (iii) 15 mw cepheids with parallaxes measured with hst/fgs, hst/wfc3 spatial scanning and/or hipparcos, and (iv) 2 debs in m31. the hubble constant from each is 72.25 ± 2.51, 72.04 ± 2.67, 76.18 ± 2.37, and 74.50 ± 3.27 km s-1 mpc-1, respectively. our best estimate of h 0 = 73.24 ± 1.74 km s-1 mpc-1 combines the anchors ngc 4258, mw, and lmc, yielding a 2.4% determination (all quoted uncertainties include fully propagated statistical and systematic components). this value is 3.4σ higher than 66.93 ± 0.62 km s-1 mpc-1 predicted by λcdm with 3 neutrino flavors having a mass of 0.06 ev and the new planck data, but the discrepancy reduces to 2.1σ relative to the prediction of 69.3 ± 0.7 km s-1 mpc-1 based on the comparably precise combination of wmap+act+spt+bao observations, suggesting that systematic uncertainties in cmb radiation measurements may play a role in the tension. if we take the conflict between planck high-redshift measurements and our local determination of h 0 at face value, one plausible explanation could involve an additional source of dark radiation in the early universe in the range of δn eff ≈ 0.4-1. we anticipate further significant improvements in h 0 from upcoming parallax measurements of long-period mw cepheids. based on observations with the nasa/esa hubble space telescope, obtained at the space telescope science institute, which is operated by aura, inc., under nasa contract nas 5-26555. | a 2.4% determination of the local value of the hubble constant |
among swampland conditions, the distance conjecture characterizes the geometry of scalar fields and the de sitter conjecture constrains allowed potentials on it. we point out a connection between the distance conjecture and a refined version of the de sitter conjecture in any parametrically controlled regime of string theory by using bousso's covariant entropy bound. the refined version turns out to evade all counter-examples at scalar potential maxima that have been raised. we comment on the relation of our result to the dine-seiberg problem. | distance and de sitter conjectures on the swampland |
multiple theories have been proposed to describe the formation of black hole seeds in the early universe and to explain the emergence of very massive black holes observed in the first billion years after big bang. models consider different seeding and accretion scenarios, which require the detection and characterisation of black holes in the first few hundred million years after big bang to be validated. here we present an extensive analysis of the jwst-nirspec spectrum of gn-z11, an exceptionally luminous galaxy at z=10.6, revealing the detection of the [neiv]2423 and cii*1335 transitions (typical of active galactic nuclei, agn), as well as semi-forbidden nebular lines tracing gas densities higher than 10^9 cm-3, typical of the broad line region of agn. these spectral features indicate that gn-z11 hosts an accreting black hole. the spectrum also reveals a deep and blueshifted civ1549 absorption trough, tracing an outflow with velocity 800-1000 km/s, likely driven by the agn. assuming local virial relations, we derive a black hole mass of log(m_bh/msun) = 6.2 +- 0.3, accreting at about 5 times the eddington rate. these properties are consistent with both heavy seeds scenarios, or scenarios envisaging intermediate/light seeds experiencing episodic super-eddington phases. our finding naturally explains the high luminosity of gn-z11 and can also provide an explanation for its exceptionally high nitrogen abundance. | a small and vigorous black hole in the early universe |
the recently released data by pulsar timing array (pta) collaborations present strong evidence for a stochastic signal consistent with a gravitational-wave background. assuming this signal originates from scalar-induced gravitational waves, we jointly use the pta data from the nanograv 15-yr data set, ppta dr3, and epta dr2 to probe the small-scale non-gaussianity. we put the first-ever constraint on the non-gaussianity parameter, finding $|f_\mathrm{nl}|\lesssim 13.9$ for a lognormal power spectrum of the curvature perturbations. furthermore, we obtain $-13.9 \lesssim f_\mathrm{nl}\lesssim -0.1$ to prevent excessive production of primordial black holes. moreover, the multi-band observations with the space-borne gravitational-wave detectors, such as lisa/taiji/tianqin, will provide a complementary investigation of primordial non-gaussianity. our findings pave the way to constrain inflation models with pta data. | implications for the non-gaussianity of curvature perturbation from pulsar timing arrays |
we present results from an analysis of all data taken by the bicep2, keck array, and bicep3 cmb polarization experiments up to and including the 2018 observing season. we add additional keck array observations at 220 ghz and bicep3 observations at 95 ghz to the previous 95 /150 /220 ghz dataset. the q /u maps now reach depths of 2.8, 2.8, and 8.8 μ kcmb arcmin at 95, 150, and 220 ghz, respectively, over an effective area of ≈600 square degrees at 95 ghz and ≈400 square degrees at 150 and 220 ghz. the 220 ghz maps now achieve a signal-to-noise ratio on polarized dust emission exceeding that of planck at 353 ghz. we take auto- and cross-spectra between these maps and publicly available wmap and planck maps at frequencies from 23 to 353 ghz and evaluate the joint likelihood of the spectra versus a multicomponent model of lensed λ cdm +r +dust +synchrotron +noise . the foreground model has seven parameters, and no longer requires a prior on the frequency spectral index of the dust emission taken from measurements on other regions of the sky. this model is an adequate description of the data at the current noise levels. the likelihood analysis yields the constraint r0.05<0.036 at 95% confidence. running maximum likelihood search on simulations we obtain unbiased results and find that σ (r )=0.009 . these are the strongest constraints to date on primordial gravitational waves. | improved constraints on primordial gravitational waves using planck, wmap, and bicep/keck observations through the 2018 observing season |
we search for an isotropic stochastic gravitational-wave background (gwb) in the 12.5 yr pulsar-timing data set collected by the north american nanohertz observatory for gravitational waves. our analysis finds strong evidence of a stochastic process, modeled as a power law, with common amplitude and spectral slope across pulsars. under our fiducial model, the bayesian posterior of the amplitude for an f-2/3 power-law spectrum, expressed as the characteristic gw strain, has median 1.92 × 10-15 and 5%-95% quantiles of 1.37-2.67 × 10-15 at a reference frequency of ${f}_{\mathrm{yr}}=1\,{\mathrm{yr}}^{-1};$ the bayes factor in favor of the common-spectrum process versus independent red-noise processes in each pulsar exceeds 10,000. however, we find no statistically significant evidence that this process has quadrupolar spatial correlations, which we would consider necessary to claim a gwb detection consistent with general relativity. we find that the process has neither monopolar nor dipolar correlations, which may arise from, for example, reference clock or solar system ephemeris systematics, respectively. the amplitude posterior has significant support above previously reported upper limits; we explain this in terms of the bayesian priors assumed for intrinsic pulsar red noise. we examine potential implications for the supermassive black hole binary population under the hypothesis that the signal is indeed astrophysical in nature. | the nanograv 12.5 yr data set: search for an isotropic stochastic gravitational-wave background |
accordingly, by performing the 2-point correlation of hk (τ) which is proportional to the correlator of scalar source sk (τ), one can arrive at the power spectrum of igws during rd: | limits on scalar-induced gravitational waves from the stochastic background by pulsar timing array observations |
we describe the legacy planck cosmic microwave background (cmb) likelihoods derived from the 2018 data release. the overall approach is similar in spirit to the one retained for the 2013 and 2015 data release, with a hybrid method using different approximations at low (ℓ < 30) and high (ℓ ≥ 30) multipoles, implementing several methodological and data-analysis refinements compared to previous releases. with more realistic simulations, and better correction and modelling of systematic effects, we can now make full use of the cmb polarization observed in the high frequency instrument (hfi) channels. the low-multipole ee cross-spectra from the 100 ghz and 143 ghz data give a constraint on the λcdm reionization optical-depth parameter τ to better than 15% (in combination with the tt low-ℓ data and the high-ℓ temperature and polarization data), tightening constraints on all parameters with posterior distributions correlated with τ. we also update the weaker constraint on τ from the joint teb likelihood using the low frequency instrument (lfi) channels, which was used in 2015 as part of our baseline analysis. at higher multipoles, the cmb temperature spectrum and likelihood are very similar to previous releases. a better model of the temperature-to-polarization leakage and corrections for the effective calibrations of the polarization channels (i.e., the polarization efficiencies) allow us to make full use of polarization spectra, improving the λcdm constraints on the parameters θmc, ωc, ωb, and h0 by more than 30%, and ns by more than 20% compared to tt-only constraints. extensive tests on the robustness of the modelling of the polarization data demonstrate good consistency, with some residual modelling uncertainties. at high multipoles, we are now limited mainly by the accuracy of the polarization efficiency modelling. using our various tests, simulations, and comparison between different high-multipole likelihood implementations, we estimate the consistency of the results to be better than the 0.5 σ level on the λcdm parameters, as well as classical single-parameter extensions for the joint likelihood (to be compared to the 0.3 σ levels we achieved in 2015 for the temperature data alone on λcdm only). minor curiosities already present in the previous releases remain, such as the differences between the best-fit λcdm parameters for the ℓ < 800 and ℓ > 800 ranges of the power spectrum, or the preference for more smoothing of the power-spectrum peaks than predicted in λcdm fits. these are shown to be driven by the temperature power spectrum and are not significantly modified by the inclusion of the polarization data. overall, the legacy planck cmb likelihoods provide a robust tool for constraining the cosmological model and represent a reference for future cmb observations. | planck 2018 results. v. cmb power spectra and likelihoods |
we present an overview of the james webb space telescope (jwst) advanced deep extragalactic survey (jades), an ambitious program of infrared imaging and spectroscopy in the goods-s and goods-n deep fields, designed to study galaxy evolution from high redshift to cosmic noon. jades uses about 770 hours of cycle 1 guaranteed time largely from the near-infrared camera (nircam) and near-infrared spectrograph (nirspec) instrument teams. in goods-s, in and around the hubble ultra deep field and chandra deep field south, jades produces a deep imaging region of ~45 arcmin$^2$ with an average of 130 hrs of exposure time spread over 9 nircam filters. this is extended at medium depth in goods-s and goods-n with nircam imaging of ~175 arcmin$^2$ with an average exposure time of 20 hrs spread over 8-10 filters. in both fields, we conduct extensive nirspec multi-object spectroscopy, including 2 deep pointings of 55 hrs exposure time, 14 medium pointings of ~12 hrs, and 15 shallower pointings of ~4 hrs, targeting over 5000 hst and jwst-detected faint sources with 5 low, medium, and high-resolution dispersers covering 0.6-5.3 microns. finally, jades extends redward via coordinated parallels with the jwst mid-infrared instrument (miri), featuring ~9 arcmin$^2$ with 43 hours of exposure at 7.7 microns and twice that area with 2-6.5 hours of exposure at 12.8 microns for nearly 30 years, the goods-s and goods-n fields have been developed as the premier deep fields on the sky; jades is now providing a compelling start on the jwst legacy in these fields. | overview of the jwst advanced deep extragalactic survey (jades) |
after a decade and a half of research motivated by the accelerating universe, theory and experiment have reached a certain level of maturity. the development of theoretical models beyond λ or smooth dark energy, often called modified gravity, has led to broader insights into a path forward, and a host of observational and experimental tests have been developed. in this review we present the current state of the field and describe a framework for anticipating developments in the next decade. we identify the guiding principles for rigorous and consistent modifications of the standard model, and discuss the prospects for empirical tests. we begin by reviewing recent attempts to consistently modify einstein gravity in the infrared, focusing on the notion that additional degrees of freedom introduced by the modification must "screen" themselves from local tests of gravity. we categorize screening mechanisms into three broad classes: mechanisms which become active in regions of high newtonian potential, those in which first derivatives of the field become important, and those for which second derivatives of the field are important. examples of the first class, such as f(r) gravity, employ the familiar chameleon or symmetron mechanisms, whereas examples of the last class are galileon and massive gravity theories, employing the vainshtein mechanism. in each case, we describe the theories as effective theories and discuss prospects for completion in a more fundamental theory. we describe experimental tests of each class of theories, summarizing laboratory and solar system tests and describing in some detail astrophysical and cosmological tests. finally, we discuss prospects for future tests which will be sensitive to different signatures of new physics in the gravitational sector. the review is structured so that those parts that are more relevant to theorists vs. observers/experimentalists are clearly indicated, in the hope that this will serve as a useful reference for both audiences, as well as helping those interested in bridging the gap between them. | beyond the cosmological standard model |
we present measurements of the properties of the central radio source in m87 using event horizon telescope data obtained during the 2017 campaign. we develop and fit geometric crescent models (asymmetric rings with interior brightness depressions) using two independent sampling algorithms that consider distinct representations of the visibility data. we show that the crescent family of models is statistically preferred over other comparably complex geometric models that we explore. we calibrate the geometric model parameters using general relativistic magnetohydrodynamic (grmhd) models of the emission region and estimate physical properties of the source. we further fit images generated from grmhd models directly to the data. we compare the derived emission region and black hole parameters from these analyses with those recovered from reconstructed images. there is a remarkable consistency among all methods and data sets. we find that >50% of the total flux at arcsecond scales comes from near the horizon, and that the emission is dramatically suppressed interior to this region by a factor >10, providing direct evidence of the predicted shadow of a black hole. across all methods, we measure a crescent diameter of 42 ± 3 μas and constrain its fractional width to be <0.5. associating the crescent feature with the emission surrounding the black hole shadow, we infer an angular gravitational radius of gm/dc 2 = 3.8 ± 0.4 μas. folding in a distance measurement of 16.8-0.7+0.8 mpc gives a black hole mass of m=6.5+/- 0.2| stat+/- 0.7| sys× 109 m⊙. this measurement from lensed emission near the event horizon is consistent with the presence of a central kerr black hole, as predicted by the general theory of relativity. | first m87 event horizon telescope results. vi. the shadow and mass of the central black hole |
the observation of gw170817 and its electromagnetic counterpart implies that gravitational waves travel at the speed of light, with deviations smaller than a few ×10-15 . we discuss the consequences of this experimental result for models of dark energy and modified gravity characterized by a single scalar degree of freedom. to avoid tuning, the speed of gravitational waves must be unaffected not only for our particular cosmological solution but also for nearby solutions obtained by slightly changing the matter abundance. for this to happen, the coefficients of various operators must satisfy precise relations that we discuss both in the language of the effective field theory of dark energy and in the covariant one, for horndeski, beyond horndeski, and degenerate higher-order theories. the simplification is dramatic: of the three functions describing quartic and quintic beyond horndeski theories, only one remains and reduces to a standard conformal coupling to the ricci scalar for horndeski theories. we show that the deduced relations among operators do not introduce further tuning of the models, since they are stable under quantum corrections. | dark energy after gw170817 and grb170817a |
this white paper summarizes the workshop "u.s. cosmic visions: new ideas in dark matter" held at university of maryland on march 23-25, 2017. | us cosmic visions: new ideas in dark matter 2017: community report |
a number of challenges to the standard λcdm model have been emerging during the past few years as the accuracy of cosmological observations improves. in this review we discuss in a unified manner many existing signals in cosmological and astrophysical data that appear to be in some tension (2 σ or larger) with the standard λcdm model as specified by the cosmological principle, general relativity and the planck18 parameter values. in addition to the well-studied 5 σ challenge of λcdm (the hubble h0 tension) and other well known tensions (the growth tension, and the lensing amplitude al anomaly), we discuss a wide range of other less discussed less-standard signals which appear at a lower statistical significance level than the h0 tension some of them known as 'curiosities' in the data) which may also constitute hints towards new physics. for example such signals include cosmic dipoles (the fine structure constant α, velocity and quasar dipoles), cmb asymmetries, bao ly α tension, age of the universe issues, the lithium problem, small scale curiosities like the core-cusp and missing satellite problems, quasars hubble diagram, oscillating short range gravity signals etc. the goal of this pedagogical review is to collectively present the current status (2022 update) of these signals and their level of significance, with emphasis on the hubble tension and refer to recent resources where more details can be found for each signal. we also briefly discuss theoretical approaches that can potentially explain some of these signals. | challenges for λcdm: an update |
the desi legacy imaging surveys (http://legacysurvey.org/) are a combination of three public projects (the dark energy camera legacy survey, the beijing-arizona sky survey, and the mayall z-band legacy survey) that will jointly image ≈14,000 deg2 of the extragalactic sky visible from the northern hemisphere in three optical bands (g, r, and z) using telescopes at the kitt peak national observatory and the cerro tololo inter-american observatory. the combined survey footprint is split into two contiguous areas by the galactic plane. the optical imaging is conducted using a unique strategy of dynamically adjusting the exposure times and pointing selection during observing that results in a survey of nearly uniform depth. in addition to calibrated images, the project is delivering a catalog, constructed by using a probabilistic inference-based approach to estimate source shapes and brightnesses. the catalog includes photometry from the grz optical bands and from four mid-infrared bands (at 3.4, 4.6, 12, and 22 μm) observed by the wide-field infrared survey explorer satellite during its full operational lifetime. the project plans two public data releases each year. all the software used to generate the catalogs is also released with the data. this paper provides an overview of the legacy surveys project. | overview of the desi legacy imaging surveys |
the nanograv 15 yr data set shows evidence for the presence of a low-frequency gravitational-wave background (gwb). while many physical processes can source such low-frequency gravitational waves, here we analyze the signal as coming from a population of supermassive black hole (smbh) binaries distributed throughout the universe. we show that astrophysically motivated models of smbh binary populations are able to reproduce both the amplitude and shape of the observed low-frequency gravitational-wave spectrum. while multiple model variations are able to reproduce the gwb spectrum at our current measurement precision, our results highlight the importance of accurately modeling binary evolution for producing realistic gwb spectra. additionally, while reasonable parameters are able to reproduce the 15 yr observations, the implied gwb amplitude necessitates either a large number of parameters to be at the edges of expected values or a small number of parameters to be notably different from standard expectations. while we are not yet able to definitively establish the origin of the inferred gwb signal, the consistency of the signal with astrophysical expectations offers a tantalizing prospect for confirming that smbh binaries are able to form, reach subparsec separations, and eventually coalesce. as the significance grows over time, higher-order features of the gwb spectrum will definitively determine the nature of the gwb and allow for novel constraints on smbh populations. | the nanograv 15 yr data set: constraints on supermassive black hole binaries from the gravitational-wave background |
we report constraints on light dark matter (dm) models using ionization signals in the xenon1t experiment. we mitigate backgrounds with strong event selections, rather than requiring a scintillation signal, leaving an effective exposure of (22 ±3 ) tonne day. above ∼0.4 keve e , we observe <1 event/(tonne day keve e) , which is more than 1000 times lower than in similar searches with other detectors. despite observing a higher rate at lower energies, no dm or cevns detection may be claimed because we cannot model all of our backgrounds. we thus exclude new regions in the parameter spaces for dm-nucleus scattering for dm masses mχ within 3 - 6 gev /c2 , dm-electron scattering for mχ>30 mev /c2 , and absorption of dark photons and axionlike particles for mχ within 0.186 - 1 kev /c2 . | light dark matter search with ionization signals in xenon1t |
very recently pulsar timing array (pta) collaborations have independently reported the evidence for a stochastic gravitational-wave background (sgwb), which can unveil the formation of primordial seeds of inhomogeneities in the early universe. with the sgwb parameters inferred from ptas data, we can make a prediction of the primordial black hole (pbh) clusters from the domain walls of axion-like particles (alps). these primordial seeds can naturally provide a solution to the early active galactic nuclei (agn) formation indicated by james webb space telescope (jwst). besides, the mass of alp is also constrained, $m_a \sim 10^{-15}-10^{-14}$ ev, within the reach of upcoming cavity experiments. | footprints of axion-like particle in pulsar timing array data and jwst observations |
a kavli institute for theoretical physics workshop in july 2019 directed attention to the hubble constant discrepancy. new results showed that it does not appear to depend on the use of any one method, team or source. proposed solutions focused on the pre-recombination era. | tensions between the early and late universe |
the event horizon telescope (eht) has mapped the central compact radio source of the elliptical galaxy m87 at 1.3 mm with unprecedented angular resolution. here we consider the physical implications of the asymmetric ring seen in the 2017 eht data. to this end, we construct a large library of models based on general relativistic magnetohydrodynamic (grmhd) simulations and synthetic images produced by general relativistic ray tracing. we compare the observed visibilities with this library and confirm that the asymmetric ring is consistent with earlier predictions of strong gravitational lensing of synchrotron emission from a hot plasma orbiting near the black hole event horizon. the ring radius and ring asymmetry depend on black hole mass and spin, respectively, and both are therefore expected to be stable when observed in future eht campaigns. overall, the observed image is consistent with expectations for the shadow of a spinning kerr black hole as predicted by general relativity. if the black hole spin and m87’s large scale jet are aligned, then the black hole spin vector is pointed away from earth. models in our library of non-spinning black holes are inconsistent with the observations as they do not produce sufficiently powerful jets. at the same time, in those models that produce a sufficiently powerful jet, the latter is powered by extraction of black hole spin energy through mechanisms akin to the blandford-znajek process. we briefly consider alternatives to a black hole for the central compact object. analysis of existing eht polarization data and data taken simultaneously at other wavelengths will soon enable new tests of the grmhd models, as will future eht campaigns at 230 and 345 ghz. | first m87 event horizon telescope results. v. physical origin of the asymmetric ring |
multiple pulsar-timing-array collaborations have reported strong evidence for the existence of a gravitational-wave background. we study physical implications of this signal for cosmology, assuming that it is attributed to scalar-induced gravitational waves. by incorporating primordial non-gaussianity $f_{\mathrm{nl}}$, we specifically examine the nature of primordial curvature perturbations and primordial black holes. we find that the signal allows for a primordial non-gaussianity $f_{\mathrm{nl}}$ in the range of $-4.1\lesssim f_{\mathrm{nl}} \lesssim 4.1$ (68\% confidence intervals) and a mass range for primordial black holes $m_{\mathrm{pbh}}$ spanning from $\sim10^{-5}m_{\odot}$ to $\sim10^{-2}m_{\odot}$. furthermore, we find that the signal favors a negative non-gaussianity, which can suppress the abundance of primordial black holes. we also demonstrate that the anisotropies of scalar-induced gravitational waves serve as a powerful tool to probe the non-gaussianity $f_{\mathrm{nl}}$. we conduct a comprehensive analysis of the angular power spectrum within the nano-hertz band. looking ahead, we anticipate that future projects, such as the square kilometre array, will have the potential to measure these anisotropies and provide further insights into the primordial universe. | implications of pulsar timing array data for scalar-induced gravitational waves and primordial black holes: primordial non-gaussianity $f_{\\mathrm{nl}}$ considered |
in recent years, several pulsar timing array collaborations have reported first hints for a stochastic gravitational wave background at nano-hertz frequencies. here we elaborate on the possibility that this signal comes from new physics that leads to the generation of a primordial stochastic gravitational wave background. we propose a set of simple but concrete models that can serve as benchmarks for gravitational waves sourced by cosmological phase transitions, domain wall networks, cosmic strings, axion dynamics, or large scalar fluctuations. these models are then confronted with pulsar timing data and with cosmological constraints. with only a limited number of free parameters per model, we are able to identify viable regions of parameter space and also make predictions for future astrophysical and laboratory tests that can help with model identification and discrimination. | primordial gravitational waves in the nano-hertz regime and pta data — towards solving the gw inverse problem |
we present the first event horizon telescope (eht) images of m87, using observations from april 2017 at 1.3 mm wavelength. these images show a prominent ring with a diameter of ∼40 μas, consistent with the size and shape of the lensed photon orbit encircling the “shadow” of a supermassive black hole. the ring is persistent across four observing nights and shows enhanced brightness in the south. to assess the reliability of these results, we implemented a two-stage imaging procedure. in the first stage, four teams, each blind to the others’ work, produced images of m87 using both an established method (clean) and a newer technique (regularized maximum likelihood). this stage allowed us to avoid shared human bias and to assess common features among independent reconstructions. in the second stage, we reconstructed synthetic data from a large survey of imaging parameters and then compared the results with the corresponding ground truth images. this stage allowed us to select parameters objectively to use when reconstructing images of m87. across all tests in both stages, the ring diameter and asymmetry remained stable, insensitive to the choice of imaging technique. we describe the eht imaging procedures, the primary image features in m87, and the dependence of these features on imaging assumptions. | first m87 event horizon telescope results. iv. imaging the central supermassive black hole |
we discuss the interpretation of the detected signal by pulsar timing array (pta) observations as a gravitational wave background (gwb) of cosmological origin. we combine nanograv 15-years and epta-dr2new data sets and confront them against backgrounds from supermassive black hole binaries (smbhbs) and cosmological signals from inflation, cosmic (super)strings, first-order phase transitions, gaussian and non-gaussian large scalar fluctuations, and audible axions. we find that scalar-induced, and to a lesser extent audible axion and cosmic superstring signals, provide a better fit than smbhbs. these results depend, however, on modeling assumptions, so further data and analysis are needed to reach robust conclusions. independently of the signal origin, the data strongly constrain the parameter space of cosmological signals, for example, setting an upper bound on primordial non-gaussianity at pta scales as $|f_{nl}| \lesssim 2.34$ at 95\% cl. | cosmological background interpretation of pulsar timing array data |
we study for the first time the gravitational waves generated during the collapse of domain walls, incorporating the potential bias in the lattice simulations. the final stages of domain wall collapse are crucial for the production of gravitational waves, but have remained unexplored due to computational difficulties. as a significant application of this new result, we show that the observed nanograv, epta, ppta, and cpta data, which indicate stochastic gravitational waves in the nanohertz regime, can be attributed to axion domain walls coupled to qcd. in our model, non-perturbative effects of qcd induce a temperature-dependent bias around the qcd crossover, inducing the rapid collapse of the domain walls. we use sophisticated lattice simulations that account for the temperature-dependent bias to measure the gravitational waves resulting from the domain wall annihilation. we also discuss the future prospects for accelerator-based searches for the axion and the potential for the formation and detection of primordial black holes. | gravitational waves from domain wall collapse, and application to nanohertz signals with qcd-coupled axions |
the simons observatory (so) is a new cosmic microwave background experiment being built on cerro toco in chile, due to begin observations in the early 2020s. we describe the scientific goals of the experiment, motivate the design, and forecast its performance. so will measure the temperature and polarization anisotropy of the cosmic microwave background in six frequency bands centered at: 27, 39, 93, 145, 225 and 280 ghz. the initial configuration of so will have three small-aperture 0.5-m telescopes and one large-aperture 6-m telescope, with a total of 60,000 cryogenic bolometers. our key science goals are to characterize the primordial perturbations, measure the number of relativistic species and the mass of neutrinos, test for deviations from a cosmological constant, improve our understanding of galaxy evolution, and constrain the duration of reionization. the small aperture telescopes will target the largest angular scales observable from chile, mapping ≈ 10% of the sky to a white noise level of 2 μk-arcmin in combined 93 and 145 ghz bands, to measure the primordial tensor-to-scalar ratio, r, at a target level of σ(r)=0.003. the large aperture telescope will map ≈ 40% of the sky at arcminute angular resolution to an expected white noise level of 6 μk-arcmin in combined 93 and 145 ghz bands, overlapping with the majority of the large synoptic survey telescope sky region and partially with the dark energy spectroscopic instrument. with up to an order of magnitude lower polarization noise than maps from the planck satellite, the high-resolution sky maps will constrain cosmological parameters derived from the damping tail, gravitational lensing of the microwave background, the primordial bispectrum, and the thermal and kinematic sunyaev-zel'dovich effects, and will aid in delensing the large-angle polarization signal to measure the tensor-to-scalar ratio. the survey will also provide a legacy catalog of 16,000 galaxy clusters and more than 20,000 extragalactic sources. | the simons observatory: science goals and forecasts |
we present cosmological results from a combined analysis of galaxy clustering and weak gravitational lensing, using 1321 deg2 of griz imaging data from the first year of the dark energy survey (des y1). we combine three two-point functions: (i) the cosmic shear correlation function of 26 million source galaxies in four redshift bins, (ii) the galaxy angular autocorrelation function of 650,000 luminous red galaxies in five redshift bins, and (iii) the galaxy-shear cross-correlation of luminous red galaxy positions and source galaxy shears. to demonstrate the robustness of these results, we use independent pairs of galaxy shape, photometric-redshift estimation and validation, and likelihood analysis pipelines. to prevent confirmation bias, the bulk of the analysis was carried out while "blind" to the true results; we describe an extensive suite of systematics checks performed and passed during this blinded phase. the data are modeled in flat λ cdm and w cdm cosmologies, marginalizing over 20 nuisance parameters, varying 6 (for λ cdm ) or 7 (for w cdm ) cosmological parameters including the neutrino mass density and including the 457 ×457 element analytic covariance matrix. we find consistent cosmological results from these three two-point functions and from their combination obtain s8≡σ8(ωm/0.3 )0.5=0.77 3-0.020+0.026 and ωm=0.26 7-0.017+0.030 for λ cdm ; for w cdm , we find s8=0.78 2-0.024+0.036, ωm=0.28 4-0.030+0.033, and w =-0.8 2-0.20+0.21 at 68% c.l. the precision of these des y1 constraints rivals that from the planck cosmic microwave background measurements, allowing a comparison of structure in the very early and late universe on equal terms. although the des y1 best-fit values for s8 and ωm are lower than the central values from planck for both λ cdm and w cdm , the bayes factor indicates that the des y1 and planck data sets are consistent with each other in the context of λ cdm . combining des y1 with planck, baryonic acoustic oscillation measurements from sdss, 6df, and boss and type ia supernovae from the joint lightcurve analysis data set, we derive very tight constraints on cosmological parameters: s8=0.802 ±0.012 and ωm=0.298 ±0.007 in λ cdm and w =-1.0 0-0.04+0.05 in w cdm . upcoming dark energy survey analyses will provide more stringent tests of the λ cdm model and extensions such as a time-varying equation of state of dark energy or modified gravity. | dark energy survey year 1 results: cosmological constraints from galaxy clustering and weak lensing |
we present an expanded sample of 75 milky way cepheids with hubble space telescope (hst) photometry and gaia edr3 parallaxes, which we use to recalibrate the extragalactic distance ladder and refine the determination of the hubble constant. all hst observations were obtained with the same instrument (wfc3) and filters (f555w, f814w, f160w) used for imaging of extragalactic cepheids in type ia supernova (sn ia) hosts. the hst observations used the wfc3 spatial scanning mode to mitigate saturation and reduce pixel-to-pixel calibration errors, reaching a mean photometric error of 5 millimags per observation. we use new gaia edr3 parallaxes, greatly improved since dr2, and the period-luminosity (p-l) relation of these cepheids to simultaneously calibrate the extragalactic distance ladder and to refine the determination of the gaia edr3 parallax offset. the resulting geometric calibration of cepheid luminosities has 1.0% precision, better than any alternative geometric anchor. applied to the calibration of sne ia, it results in a measurement of the hubble constant of 73.0 ± 1.4 km s-1 mpc-1, in good agreement with conclusions based on earlier gaia data releases. we also find the slope of the cepheid p-l relation in the milky way, and the metallicity dependence of its zero-point, to be in good agreement with the mean values derived from other galaxies. in combination with the best complementary sources of cepheid calibration, we reach 1.8% precision and find h0 = 73.2 ± 1.3 km s-1 mpc-1, a 4.2σ difference with the prediction from planck cmb observations under λcdm. we expect to reach ∼1.3% precision in the near term from an expanded sample of ∼40 sne ia in cepheid hosts. | cosmic distances calibrated to 1% precision with gaia edr3 parallaxes and hubble space telescope photometry of 75 milky way cepheids confirm tension with λcdm |
high energy collisions at the high-luminosity large hadron collider (lhc) produce a large number of particles along the beam collision axis, outside of the acceptance of existing lhc experiments. the proposed forward physics facility (fpf), to be located several hundred meters from the atlas interaction point and shielded by concrete and rock, will host a suite of experiments to probe standard model (sm) processes and search for physics beyond the standard model (bsm). in this report, we review the status of the civil engineering plans and the experiments to explore the diverse physics signals that can be uniquely probed in the forward region. fpf experiments will be sensitive to a broad range of bsm physics through searches for new particle scattering or decay signatures and deviations from sm expectations in high statistics analyses with tev neutrinos in this low-background environment. high statistics neutrino detection will also provide valuable data for fundamental topics in perturbative and non-perturbative qcd and in weak interactions. experiments at the fpf will enable synergies between forward particle production at the lhc and astroparticle physics to be exploited. we report here on these physics topics, on infrastructure, detector, and simulation studies, and on future directions to realize the fpf's physics potential. | the forward physics facility at the high-luminosity lhc |
in this paper, we propose a new swampland condition, the trans-planckian censorship conjecture (tcc), based on the idea that in a consistent quantum theory of gravity sub-planckian quantum fluctuations should remain quantum and never become larger than the hubble horizon and freeze in an expanding universe. applied to the case of scalar fields, it leads to conditions that are similar to the refined ds swampland conjecture. for large field ranges, tcc is stronger than the ds swampland conjecture but it is weaker for small field ranges. in particular for asymptotic regions of field space, tcc leads to a bound |v ' |≥2/√{(d -1 )(d -2 ) }v , which is consistent with all known cases in string theory. like the ds swampland conjecture, the tcc forbids long-lived meta-stable ds spaces, but it does allow sufficiently short-lived ones. | trans-planckian censorship and the swampland |
we report on the neutrino mass measurement result from the first four-week science run of the karlsruhe tritium neutrino experiment katrin in spring 2019. beta-decay electrons from a high-purity gaseous molecular tritium source are energy analyzed by a high-resolution mac-e filter. a fit of the integrated electron spectrum over a narrow interval around the kinematic end point at 18.57 kev gives an effective neutrino mass square value of (-1.0-1.1+0.9) ev2. from this, we derive an upper limit of 1.1 ev (90% confidence level) on the absolute mass scale of neutrinos. this value coincides with the katrin sensitivity. it improves upon previous mass limits from kinematic measurements by almost a factor of 2 and provides model-independent input to cosmological studies of structure formation. | improved upper limit on the neutrino mass from a direct kinematic method by katrin |
context. gaia early data release 3 (gaia edr3) contains astrometry and photometry results for about 1.8 billion sources based on observations collected by the european space agency gaia satellite during the first 34 months of its operational phase.aims: in this paper, we focus on the photometric content, describing the input data, the algorithms, the processing, and the validation of the results. particular attention is given to the quality of the data and to a number of features that users may need to take into account to make the best use of the gaia edr3 catalogue.methods: the processing broadly followed the same procedure as for gaia dr2, but with significant improvements in several aspects of the blue and red photometer (bp and rp) preprocessing and in the photometric calibration process. in particular, the treatment of the bp and rp background has been updated to include a better estimation of the local background, and the detection of crowding effects has been used to exclude affected data from the calibrations. the photometric calibration models have also been updated to account for flux loss over the whole magnitude range. significant improvements in the modelling and calibration of the gaia point and line spread functions have also helped to reduce a number of instrumental effects that were still present in dr2.results: gaia edr3 contains 1.806 billion sources with g-band photometry and 1.540 billion sources with gbp and grp photometry. the median uncertainty in the g-band photometry, as measured from the standard deviation of the internally calibrated mean photometry for a given source, is 0.2 mmag at magnitude g = 10-14, 0.8 mmag at g ≈ 17, and 2.6 mmag at g ≈ 19. the significant magnitude term found in the gaia dr2 photometry is no longer visible, and overall there are no trends larger than 1 mmag mag−1. using one passband over the whole colour and magnitude range leaves no systematics above the 1% level in magnitude in any of the bands, and a larger systematic is present for a very small sample of bright and blue sources. a detailed description of the residual systematic effects is provided. overall the quality of the calibrated mean photometry in gaia edr3 is superior with respect to dr2 for all bands. passband table is only available at the cds via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/j/a+a/649/a3 | gaia early data release 3. photometric content and validation |
we present measurements of the cosmic microwave background (cmb) lensing potential using the final planck 2018 temperature and polarization data. using polarization maps filtered to account for the noise anisotropy, we increase the significance of the detection of lensing in the polarization maps from 5σ to 9σ. combined with temperature, lensing is detected at 40σ. we present an extensive set of tests of the robustness of the lensing-potential power spectrum, and construct a minimum-variance estimator likelihood over lensing multipoles 8 ≤ l ≤ 400 (extending the range to lower l compared to 2015), which we use to constrain cosmological parameters. we find good consistency between lensing constraints and the results from the planck cmb power spectra within the λcdm model. combined with baryon density and other weak priors, the lensing analysis alone constrains σ8ωm0.25 = 0.589 ± 0.020 (1σ errors). also combining with baryon acoustic oscillation data, we find tight individual parameter constraints, σ8 = 0.811 ± 0.019, h0 = 67.9-1.3+1.2 km s-1 mpc-1, and ωm = 0.303-0.018+0.016. combining with planck cmb power spectrum data, we measure σ8 to better than 1% precision, finding σ8 = 0.811 ± 0.006. cmb lensing reconstruction data are complementary to galaxy lensing data at lower redshift, having a different degeneracy direction in σ8 - ωm space; we find consistency with the lensing results from the dark energy survey, and give combined lensing-only parameter constraints that are tighter than joint results using galaxy clustering. using the planck cosmic infrared background (cib) maps as an additional tracer of high-redshift matter, we make a combined planck-only estimate of the lensing potential over 60% of the sky with considerably more small-scale signal. we additionally demonstrate delensing of the planck power spectra using the joint and individual lensing potential estimates, detecting a maximum removal of 40% of the lensing-induced power in all spectra. the improvement in the sharpening of the acoustic peaks by including both cib and the quadratic lensing reconstruction is detected at high significance. | planck 2018 results. viii. gravitational lensing |
the main objectives of the km3net collaboration are (i) the discovery and subsequent observation of high-energy neutrino sources in the universe and (ii) the determination of the mass hierarchy of neutrinos. these objectives are strongly motivated by two recent important discoveries, namely: (1) the high-energy astrophysical neutrino signal reported by icecube and (2) the sizable contribution of electron neutrinos to the third neutrino mass eigenstate as reported by daya bay, reno and others. to meet these objectives, the km3net collaboration plans to build a new research infrastructure consisting of a network of deep-sea neutrino telescopes in the mediterranean sea. a phased and distributed implementation is pursued which maximises the access to regional funds, the availability of human resources and the synergistic opportunities for the earth and sea sciences community. three suitable deep-sea sites are selected, namely off-shore toulon (france), capo passero (sicily, italy) and pylos (peloponnese, greece). the infrastructure will consist of three so-called building blocks. a building block comprises 115 strings, each string comprises 18 optical modules and each optical module comprises 31 photo-multiplier tubes. each building block thus constitutes a three-dimensional array of photo sensors that can be used to detect the cherenkov light produced by relativistic particles emerging from neutrino interactions. two building blocks will be sparsely configured to fully explore the icecube signal with similar instrumented volume, different methodology, improved resolution and complementary field of view, including the galactic plane. one building block will be densely configured to precisely measure atmospheric neutrino oscillations. | letter of intent for km3net 2.0 |
aspects of primordial black holes, i.e. black holes formed in the early universe, are reviewed. special emphasis is put on their formation, their r{ô}le as dark matter candidates and their manifold signatures, particularly through gravitational waves. | primordial black holes |
we present the third fermi large area telescope (lat) source catalog (3fgl) of sources in the 100 mev-300 gev range. based on the first 4 yr of science data from the fermi gamma-ray space telescope mission, it is the deepest yet in this energy range. relative to the second fermi lat catalog, the 3fgl catalog incorporates twice as much data, as well as a number of analysis improvements, including improved calibrations at the event reconstruction level, an updated model for galactic diffuse γ-ray emission, a refined procedure for source detection, and improved methods for associating lat sources with potential counterparts at other wavelengths. the 3fgl catalog includes 3033 sources above 4σ significance, with source location regions, spectral properties, and monthly light curves for each. of these, 78 are flagged as potentially being due to imperfections in the model for galactic diffuse emission. twenty-five sources are modeled explicitly as spatially extended, and overall 238 sources are considered as identified based on angular extent or correlated variability (periodic or otherwise) observed at other wavelengths. for 1010 sources we have not found plausible counterparts at other wavelengths. more than 1100 of the identified or associated sources are active galaxies of the blazar class; several other classes of non-blazar active galaxies are also represented in the 3fgl. pulsars represent the largest galactic source class. from source counts of galactic sources we estimate that the contribution of unresolved sources to the galactic diffuse emission is ∼3% at 1 gev. | fermi large area telescope third source catalog |
we describe the 2017 release of the spectral synthesis code cloudy, summarizing the many improvements to the scope and accuracy of the physics which have been made since the previous release. exporting the atomic data into external data files has enabled many new large datasets to be incorporated into the code. the use of the complete datasets is not realistic for most calculations, so we describe the limited subset of data used by default, which predicts significantly more lines than the previous release of cloudy. this version is nevertheless faster than the previous release, as a result of code optimizations. we give examples of the accuracy limits using small models, and the performance requirements of large complete models. we summarize several advances in the h- and he-like iso-electronic sequences and use our complete collisional-radiative models to establish the densities where the coronal and local thermodynamic equilibrium approximations work. | the 2017 release cloudy |
the einstein telescope (et), a proposed european ground-based gravitational-wave detector of third-generation, is an evolution of second-generation detectors such as advanced ligo, advanced virgo, and kagra which could be operating in the mid 2030s. et will explore the universe with gravitational waves up to cosmological distances. we discuss its main scientific objectives and its potential for discoveries in astrophysics, cosmology and fundamental physics. | science case for the einstein telescope |
we present the first direct-detection search for sub-gev dark matter using a new ∼2 -gram high-resistivity skipper ccd from a dedicated fabrication batch that was optimized for dark matter searches. using 24 days of data acquired in the minos cavern at the fermi national accelerator laboratory, we measure the lowest rates in silicon detectors of events containing one, two, three, or four electrons, and achieve world-leading sensitivity for a large range of sub-gev dark matter masses. data taken with different thicknesses of the detector shield suggest a correlation between the rate of high-energy tracks and the rate of single-electron events previously classified as "dark current." we detail key characteristics of the new skipper ccds, which augur well for the planned construction of the ∼100 -gram sensei experiment at snolab. | sensei: direct-detection results on sub-gev dark matter from a new skipper ccd |
we study constraints imposed by two proposed string swampland criteria on cosmology. these criteria involve an upper bound on the range traversed by scalar fields as well as a lower bound on |∇ϕ v | / v when v > 0. we find that inflationary models are generically in tension with these two criteria. applying these same criteria to dark energy in the present epoch, we find that specific quintessence models can satisfy these bounds and, at the same time, satisfy current observational constraints. assuming the two swampland criteria are valid, we argue that the universe will undergo a phase transition within a few hubble times. these criteria sharpen the motivation for future measurements of the tensor-to-scalar ratio r and the dark energy equation of state w, and for tests of the equivalence principle for dark matter. | on the cosmological implications of the string swampland |
we present a joint cosmological analysis of weak gravitational lensing observations from the kilo-degree survey (kids-1000), with redshift-space galaxy clustering observations from the baryon oscillation spectroscopic survey (boss) and galaxy-galaxy lensing observations from the overlap between kids-1000, boss, and the spectroscopic 2-degree field lensing survey. this combination of large-scale structure probes breaks the degeneracies between cosmological parameters for individual observables, resulting in a constraint on the structure growth parameter s8 = σ8√(ωm/0.3) = 0.766-0.014+0.020, which has the same overall precision as that reported by the full-sky cosmic microwave background observations from planck. the recovered s8 amplitude is low, however, by 8.3 ± 2.6% relative to planck. this result builds from a series of kids-1000 analyses where we validate our methodology with variable depth mock galaxy surveys, our lensing calibration with image simulations and null-tests, and our optical-to-near-infrared redshift calibration with multi-band mock catalogues and a spectroscopic-photometric clustering analysis. the systematic uncertainties identified by these analyses are folded through as nuisance parameters in our cosmological analysis. inspecting the offset between the marginalised posterior distributions, we find that the s8-difference with planck is driven by a tension in the matter fluctuation amplitude parameter, σ8. we quantify the level of agreement between the cosmic microwave background and our large-scale structure constraints using a series of different metrics, finding differences with a significance ranging between ∼3σ, when considering the offset in s8, and ∼2σ, when considering the full multi-dimensional parameter space. | kids-1000 cosmology: multi-probe weak gravitational lensing and spectroscopic galaxy clustering constraints |
we present constraints on cosmological parameters from the pantheon+ analysis of 1701 light curves of 1550 distinct type ia supernovae (sne ia) ranging in redshift from z = 0.001 to 2.26. this work features an increased sample size from the addition of multiple cross-calibrated photometric systems of sne covering an increased redshift span, and improved treatments of systematic uncertainties in comparison to the original pantheon analysis, which together result in a factor of 2 improvement in cosmological constraining power. for a flat λcdm model, we find ω m= 0.334 ± 0.018 from sne ia alone. for a flat w 0cdm model, we measure w 0 = -0.90 ± 0.14 from sne ia alone, h 0 = 73.5 ± 1.1 km s-1 mpc-1 when including the cepheid host distances and covariance (sh0es), and w 0 = $-{0.978}_{-0.031}^{+0.024}$ when combining the sn likelihood with planck constraints from the cosmic microwave background (cmb) and baryon acoustic oscillations (bao); both w 0 values are consistent with a cosmological constant. we also present the most precise measurements to date on the evolution of dark energy in a flat w 0 wa cdm universe, and measure wa= $-{0.1}_{-2.0}^{+0.9}$ from pantheon+ sne ia alone, h 0 = 73.3 ± 1.1 km s-1 mpc-1 when including sh0es cepheid distances, and wa= $-{0.65}_{-0.32}^{+0.28}$ when combining pantheon+ sne ia with cmb and bao data. finally, we find that systematic uncertainties in the use of sne ia along the distance ladder comprise less than one-third of the total uncertainty in the measurement of h 0 and cannot explain the present "hubble tension" between local measurements and early universe predictions from the cosmological model. | the pantheon+ analysis: cosmological constraints |
we analyse the planck full-mission cosmic microwave background (cmb) temperature and e-mode polarization maps to obtain constraints on primordial non-gaussianity (ng). we compare estimates obtained from separable template-fitting, binned, and optimal modal bispectrum estimators, finding consistent values for the local, equilateral, and orthogonal bispectrum amplitudes. our combined temperature and polarization analysis produces the following final results: fnllocal = -0.9 ± 5.1; fnlequil = -26 ± 47; and fnlortho = -38 ± 24 (68% cl, statistical). these results include low-multipole (4 ≤ ℓ < 40) polarization data that are not included in our previous analysis. the results also pass an extensive battery of tests (with additional tests regarding foreground residuals compared to 2015), and they are stable with respect to our 2015 measurements (with small fluctuations, at the level of a fraction of a standard deviation, which is consistent with changes in data processing). polarization-only bispectra display a significant improvement in robustness; they can now be used independently to set primordial ng constraints with a sensitivity comparable to wmap temperature-based results and they give excellent agreement. in addition to the analysis of the standard local, equilateral, and orthogonal bispectrum shapes, we consider a large number of additional cases, such as scale-dependent feature and resonance bispectra, isocurvature primordial ng, and parity-breaking models, where we also place tight constraints but do not detect any signal. the non-primordial lensing bispectrum is, however, detected with an improved significance compared to 2015, excluding the null hypothesis at 3.5σ. beyond estimates of individual shape amplitudes, we also present model-independent reconstructions and analyses of the planck cmb bispectrum. our final constraint on the local primordial trispectrum shape is gnllocal = (-5.8 ± 6.5) × 104 (68% cl, statistical), while constraints for other trispectrum shapes are also determined. exploiting the tight limits on various bispectrum and trispectrum shapes, we constrain the parameter space of different early-universe scenarios that generate primordial ng, including general single-field models of inflation, multi-field models (e.g. curvaton models), models of inflation with axion fields producing parity-violation bispectra in the tensor sector, and inflationary models involving vector-like fields with directionally-dependent bispectra. our results provide a high-precision test for structure-formation scenarios, showing complete agreement with the basic picture of the λcdm cosmology regarding the statistics of the initial conditions, with cosmic structures arising from adiabatic, passive, gaussian, and primordial seed perturbations. | planck 2018 results. ix. constraints on primordial non-gaussianity |
the dark energy plus cold dark matter (λcdm) cosmological model has been a demonstrably successful framework for predicting and explaining the large-scale structure of the universe and its evolution with time. yet on length scales smaller than ∼1 mpc and mass scales smaller than ∼1011m⊙, the theory faces a number of challenges. for example, the observed cores of many dark matter-dominated galaxies are both less dense and less cuspy than naïvely predicted in λcdm. the number of small galaxies and dwarf satellites in the local group is also far below the predicted count of low-mass dark matter halos and subhalos within similar volumes. these issues underlie the most well-documented problems with λcdm: cusp/core, missing satellites, and too-big-to-fail. the key question is whether a better understanding of baryon physics, dark matter physics, or both is required to meet these challenges. other anomalies, including the observed planar and orbital configurations of local group satellites and the tight baryonic/dark matter scaling relations obeyed by the galaxy population, have been less thoroughly explored in the context of λcdm theory. future surveys to discover faint, distant dwarf galaxies and to precisely measure their masses and density structure hold promising avenues for testing possible solutions to the small-scale challenges going forward. observational programs to constrain or discover and characterize the number of truly dark low-mass halos are among the most important, and achievable, goals in this field over the next decade. these efforts will either further verify the λcdm paradigm or demand a substantial revision in our understanding of the nature of dark matter. | small-scale challenges to the λcdm paradigm |
over the past decade, the disparity between the value of the cosmic expansion rate determined directly from measurements of distance and redshift and that determined instead from the standard lambda cold dark matter (λcdm) cosmological model, calibrated by measurements from the early universe, has grown to a level of significance requiring a solution. proposed systematic errors are not supported by the breadth of available data (and unknown errors are untestable by lack of definition). simple theoretical explanations for this hubble tension that are consistent with the majority of the data have been surprisingly hard to come by, but in recent years, attention has focused increasingly on models that alter the early or pre-recombination physics of λcdm as the most feasible. here, we describe the nature of this tension and emphasize recent developments on the observational side. we then explain why early-universe solutions are currently favored and the constraints that any such model must satisfy. we discuss one workable example, early dark energy, and describe how it can be tested with future measurements. given an assortment of more extended recent reviews on specific aspects of the problem, the discussion is intended to be fairly general and understandable to a broad audience. | the hubble tension and early dark energy |
pulsar timing arrays (ptas) have reported evidence for a stochastic gravitational wave (gw) background at nhz frequencies, possibly originating in the early universe. we show that the spectral shape of the low-frequency (causality) tail of gw signals sourced at temperatures around $t\gtrsim 1$ gev is distinctively affected by confinement of strong interactions (qcd), due to the corresponding sharp decrease in the number of relativistic species. bayesian analyses in the nanograv 15 years and the previous international pta datasets reveal a significant improvement in the fit with respect to cubic power-law spectra, previously employed for the causality tail. this suggests that the inclusion of standard model effects on gws can have a potentially decisive impact on model selection. | footprints of the qcd crossover on cosmological gravitational waves at pulsar timing arrays |
we introduce the illustristng project, a new suite of cosmological magnetohydrodynamical simulations performed with the moving-mesh code arepo employing an updated illustris galaxy formation model. here we focus on the general properties of magnetic fields and the diffuse radio emission in galaxy clusters. magnetic fields are prevalent in galaxies, and their build-up is closely linked to structure formation. we find that structure formation amplifies the initial seed fields (10-14 comoving gauss) to the values observed in low-redshift galaxies (1-10 {μ g}). the magnetic field topology is closely connected to galaxy morphology such that irregular fields are hosted by early-type galaxies, while large-scale, ordered fields are present in disc galaxies. using two simple models for the energy distribution of relativistic electrons we predict the diffuse radio emission of 280 clusters with a baryonic mass resolution of 1.1× 107 {m_{⊙}}, and generate mock observations for very large array (vla), low-frequency array (lofar), australian square kilometre array pathfinder (askap), and square kilometre array (ska). our simulated clusters show extended radio emission, whose detectability correlates with their virial mass. we reproduce the observed scaling relations between total radio power and x-ray emission, m500, and the sunyaev-zel'dovich y500 parameter. the radio emission surface brightness profiles of our most massive clusters are in reasonable agreement with vla measurements of coma and perseus. finally, we discuss the fraction of detected extended radio haloes as a function of virial mass and source count functions for different instruments. overall our results agree encouragingly well with observations, but a refined analysis requires a more sophisticated treatment of relativistic particles in large-scale galaxy formation simulations. | first results from the illustristng simulations: radio haloes and magnetic fields |
although the dark matter is usually assumed to be made up of some form of elementary particle, primordial black holes (pbhs) could also provide some of it. however, various constraints restrict the possible mass windows to 1016–1017 g, 1020–1024 g, and 10–103m⊙. the last possibility is contentious but of special interest in view of the recent detection of black hole mergers by ligo/virgo. pbhs might have important consequences and resolve various cosmological conundra even if they account for only a small fraction of the dark matter density. in particular, those larger than 103m⊙ could generate cosmological structures through the seed or poisson effect, thereby alleviating some problems associated with the standard cold dark matter scenario, and sufficiently large pbhs might provide seeds for the supermassive black holes in galactic nuclei. more exotically, the planck-mass relics of pbh evaporations or stupendously large black holes bigger than 1012m⊙ could provide an interesting dark component. | primordial black holes as dark matter: recent developments |
we create a sample of spectroscopically identified galaxies with z < 0.2 from the sloan digital sky survey (sdss) data release 7 (dr7), covering 6813 deg2. galaxies are chosen to sample the highest mass haloes, with an effective bias of 1.5, allowing us to construct 1000 mock galaxy catalogues (described in paper ii), which we use to estimate statistical errors and test our methods. we use an estimate of the gravitational potential to `reconstruct' the linear density fluctuations, enhancing the baryon acoustic oscillation (bao) signal in the measured correlation function and power spectrum. fitting to these measurements, we determine dv(zeff = 0.15) = (664 ± 25)(rd/rd, fid) mpc; this is a better than 4 per cent distance measurement. this `fills the gap' in bao distance ladder between previously measured local and higher redshift measurements, and affords significant improvement in constraining the properties of dark energy. combining our measurement with other bao measurements from baryon oscillation spectroscopic survey and 6-degree field galaxy redshift survey galaxy samples provides a 15 per cent improvement in the determination of the equation of state of dark energy and the value of the hubble parameter at z = 0 (h0). our measurement is fully consistent with the planck results and the λ cold dark matter concordance cosmology, but increases the tension between planck+bao h0 determinations and direct h0 measurements. | the clustering of the sdss dr7 main galaxy sample - i. a 4 per cent distance measure at z = 0.15 |
multiple pulsar timing array (pta) collaborations recently announced the evidence of common-spectral processes caused by gravitational waves (gws). these can be the stochastic gw background and its origin may be astrophysical and/or cosmological. we interpret it as the gws induced by the primordial curvature perturbations and discuss their implications on primordial black holes (pbhs). we show that the newly released data suggest pbhs much lighter than the sun ($\mathcal{o}(10^{-4}) \, m_\odot$) in contrast to what was expected from the previous pta data releases. | the detected stochastic gravitational waves and subsolar-mass primordial black holes |
the self-interacting dark matter (sidm) paradigm offers a potential solution to small-scale structure problems faced by the collision-less cold dark matter. this framework incorporates self-interactions among dark matter particles, typically mediated by a particle with a mev-scale mass. recent evidences of nano-hertz gravitational waves from pulsar timing arrays (ptas) such as nanograv, cpta, epta, and ppta suggest the occurrence of a first-order phase transition (fopt) at a mev-scale temperature. considering the close proximity between these two scales, we propose that the mediator mass in the sidm model originates from the spontaneous breaking of a $u(1)'$ symmetry, which is driven by the fopt indicated by pta data. consequently, the alignment of these two scales is believed to be deeply connected by the same underlying physics. by extensively exploring the parameter space, remarkably, we find that the parameter space favored by sidm just provides an explanation for the pta data. | self-interacting dark matter implied by nano-hertz gravitational waves |
pulsar timing arrays offer a probe of the low-frequency gravitational wave spectrum (1-100 nhz), which is intimately connected to a number of markers that can uniquely trace the formation and evolution of the universe. we present the dataset and the results of the timing analysis from the second data release of the european pulsar timing array (epta). the dataset contains high-precision pulsar timing data from 25 millisecond pulsars collected with the five largest radio telescopes in europe, as well as the large european array for pulsars. the dataset forms the foundation for the search for gravitational waves by the epta, presented in associated papers. we describe the dataset and present the results of the frequentist and bayesian pulsar timing analysis for individual millisecond pulsars that have been observed over the last ~25 yr. we discuss the improvements to the individual pulsar parameter estimates, as well as new measurements of the physical properties of these pulsars and their companions. this data release extends the dataset from epta data release 1 up to the beginning of 2021, with individual pulsar datasets with timespans ranging from 14 to 25 yr. these lead to improved constraints on annual parallaxes, secular variation of the orbital period, and shapiro delay for a number of sources. based on these results, we derived astrophysical parameters that include distances, transverse velocities, binary pulsar masses, and annual orbital parallaxes. | the second data release from the european pulsar timing array. i. the dataset and timing analysis |
we present the results of a search for continuous gravitational wave signals (cgws) in the second data release (dr2) of the european pulsar timing array (epta) collaboration. the most significant candidate event from this search has a gravitational wave frequency of 4-5 nhz. such a signal could be generated by a supermassive black hole binary (smbhb) in the local universe. we present the results of a follow-up analysis of this candidate using both bayesian and frequentist methods. the bayesian analysis gives a bayes factor of 4 in favor of the presence of the cgw over a common uncorrelated noise process, while the frequentist analysis estimates the p-value of the candidate to be 1%, also assuming the presence of common uncorrelated red noise. however, comparing a model that includes both a cgw and a gravitational wave background (gwb) to a gwb only, the bayes factor in favour of the cgw model is only 0.7. therefore, we cannot conclusively determine the origin of the observed feature, but we cannot rule it out as a cgw source. we present results of simulations that demonstrate that data containing a weak gravitational wave background can be misinterpreted as data including a cgw and vice versa, providing two plausible explanations of the epta dr2 data. further investigations combining data from all pta collaborations will be needed to reveal the true origin of this feature. | the second data release from the european pulsar timing array iv. search for continuous gravitational wave signals |
we introduce a new class of scalar-tensor theories of gravity that extend horndeski, or "generalized galileon," models. despite possessing equations of motion of higher order in derivatives, we show that the true propagating degrees of freedom obey well-behaved second-order equations and are thus free from ostrogradski instabilities, in contrast to standard lore. remarkably, the covariant versions of the original galileon lagrangians—obtained by direct replacement of derivatives with covariant derivatives—belong to this class of theories. these extensions of horndeski theories exhibit an uncommon, interesting phenomenology: the scalar degree of freedom affects the speed of sound of matter, even when the latter is minimally coupled to gravity. | new class of consistent scalar-tensor theories |
this letter reports the results from a haloscope search for dark matter axions with masses between 2.66 and 2.81 μ ev . the search excludes the range of axion-photon couplings predicted by plausible models of the invisible axion. this unprecedented sensitivity is achieved by operating a large-volume haloscope at subkelvin temperatures, thereby reducing thermal noise as well as the excess noise from the ultralow-noise superconducting quantum interference device amplifier used for the signal power readout. ongoing searches will provide nearly definitive tests of the invisible axion model over a wide range of axion masses. | search for invisible axion dark matter with the axion dark matter experiment |
the existence of dark matter as evidenced by numerous indirect observations is one of the most important indications that there must be physics beyond the standard model of particle physics. this article reviews the concepts of direct detection of dark matter in the form of weakly interacting massive particles in ultra-sensitive detectors located in underground laboratories, discusses the expected signatures, detector concepts, and how the stringent low-background requirements are achieved. finally, it summarizes the current status of the field and provides an outlook on the years to come. | direct detection of wimp dark matter: concepts and status |
this report, based on the dark sectors workshop at slac in april 2016, summarizes the scientific importance of searches for dark sector dark matter and forces at masses beneath the weak-scale, the status of this broad international field, the important milestones motivating future exploration, and promising experimental opportunities to reach these milestones over the next 5-10 years. | dark sectors 2016 workshop: community report |
we review recent trends in inflationary dynamics in the context of viable modified gravity theories. after providing a general overview of the inflationary paradigm emphasizing on what problems hot big bang theory inflation solves, and a somewhat introductory presentation of single-field inflationary theories with minimal and non-minimal couplings, we review how inflation can be realized in terms of several string-motivated models of inflation, which involve gauss–bonnet couplings of the scalar field, higher-order derivatives of the scalar field, and some subclasses of viable horndeski theories. we also present and analyze inflation in the context of chern–simons theories of gravity, including various subcases and generalizations of string-corrected modified gravities, which also contain chern–simons correction terms, with the scalar field being identified with the invisible axion, which is the most viable to date dark matter candidate. we also provide a detailed account of vacuum f(r) gravity inflation, and also inflation in f(r,ϕ) and kinetic-corrected f(r,ϕ) theories of gravity. at the end of the review, we discuss the technique for calculating the overall effect of modified gravity on the waveform of the standard general relativistic gravitational wave form. | recent advances in inflation |
we report the first dark matter search results from xenon1t, a ∼2000 -kg -target-mass dual-phase (liquid-gas) xenon time projection chamber in operation at the laboratori nazionali del gran sasso in italy and the first ton-scale detector of this kind. the blinded search used 34.2 live days of data acquired between november 2016 and january 2017. inside the (1042 ±12 )-kg fiducial mass and in the [5 ,40 ] kevnr energy range of interest for weakly interacting massive particle (wimp) dark matter searches, the electronic recoil background was (1.93 ±0.25 )×10-4 events /(kg ×day ×kevee) , the lowest ever achieved in such a dark matter detector. a profile likelihood analysis shows that the data are consistent with the background-only hypothesis. we derive the most stringent exclusion limits on the spin-independent wimp-nucleon interaction cross section for wimp masses above 10 gev /c2 , with a minimum of 7.7 ×10-47 cm2 for 35 -gev /c2 wimps at 90% c.l. | first dark matter search results from the xenon1t experiment |
this paper characterizes the actual science performance of the james webb space telescope (jwst), as determined from the six month commissioning period. we summarize the performance of the spacecraft, telescope, science instruments, and ground system, with an emphasis on differences from pre-launch expectations. commissioning has made clear that jwst is fully capable of achieving the discoveries for which it was built. moreover, almost across the board, the science performance of jwst is better than expected; in most cases, jwst will go deeper faster than expected. the telescope and instrument suite have demonstrated the sensitivity, stability, image quality, and spectral range that are necessary to transform our understanding of the cosmos through observations spanning from near-earth asteroids to the most distant galaxies. | the science performance of jwst as characterized in commissioning |
early dark energy (ede) that behaves like a cosmological constant at early times (redshifts z ≳3000 ) and then dilutes away like radiation or faster at later times can solve the hubble tension. in these models, the sound horizon at decoupling is reduced resulting in a larger value of the hubble parameter h0 inferred from the cosmic microwave background (cmb). we consider two physical models for this ede, one involving an oscillating scalar field and another a slowly rolling field. we perform a detailed calculation of the evolution of perturbations in these models. a markov chain monte carlo search of the parameter space for the ede parameters, in conjunction with the standard cosmological parameters, identifies regions in which h0 inferred from planck cmb data agrees with the sh0es local measurement. in these cosmologies, current baryon acoustic oscillation and supernova data are described as successfully as in the cold dark matter model with a cosmological constant, while the fit to planck data is slightly improved. future cmb and large-scale-structure surveys will further probe this scenario. | early dark energy can resolve the hubble tension |
the european space agency's planck satellite, which is dedicated to studying the early universe and its subsequent evolution, was launched on 14 may 2009. it scanned the microwave and submillimetre sky continuously between 12 august 2009 and 23 october 2013. in february 2015, esa and the planck collaboration released the second set of cosmology products based ondata from the entire planck mission, including both temperature and polarization, along with a set of scientific and technical papers and a web-based explanatory supplement. this paper gives an overview of the main characteristics of the data and the data products in the release, as well as the associated cosmological and astrophysical science results and papers. the data products include maps of the cosmic microwave background (cmb), the thermal sunyaev-zeldovich effect, diffuse foregrounds in temperature and polarization, catalogues of compact galactic and extragalactic sources (including separate catalogues of sunyaev-zeldovich clusters and galactic cold clumps), and extensive simulations of signals and noise used in assessing uncertainties and the performance of the analysis methods. the likelihood code used to assess cosmological models against the planck data is described, along with a cmb lensing likelihood. scientific results include cosmological parameters derived from cmb power spectra, gravitational lensing, and cluster counts, as well as constraints on inflation, non-gaussianity, primordial magnetic fields, dark energy, and modified gravity, and new results on low-frequency galactic foregrounds. | planck 2015 results. i. overview of products and scientific results |
in this work, we present a quintessential interpretation of having a blue-tilted tensor power spectrum for canonical single-field slow-roll inflation to explain the recently observed nanogracv 15-year signal of gravitational waves (gw). we formulate the complete semi-classical description of cosmological perturbation theory in terms of scalar and tensor modes using the non-bunch davies initial condition. we found that the existence of the blue tilt ($n_t$) within the favoured range $1.2<n_t<2.5$ can be explained in terms of a newly derived consistency relation. further, we compute a new field excursion formula using the non-bunch davies initial condition, that validates the requirement of effective field theory in the sub-planckian regime, $|\delta\phi|\ll m_{\rm pl}$ for the allowed value of the tensor-to-scalar ratio, $r<0.06$ from cmb observations. in our study, we refer to this result as anti lyth bound as it violates the well-known lyth bound originally derived for bunch davies initial condition. further, we study the behaviour of the spectral density of gw and the associated abundance with the frequency, which shows that within the frequency domain $10^{-9}{\rm hz}<f<10^{-7}{\rm hz}$ the outcome obtained from our analysis is completely consistent with the nanogracv 15-year signal. also, we found that the behaviour of gw spectra satisfies the cmb constraints at the low frequency, $f_*\sim 7.7\times 10^{-17}{\rm hz}$ corresponding to the pivots scale wave number, $k_*\sim 0.05{\rm mpc}^{-1}$. finally, the sharp falling behaviour of the gw spectra within the frequency domain $10^{-7}{\rm hz}<f<1{\rm hz}$ validates our theory in the comparatively high-frequency regime as well. | single field inflation in the light of nanograv 15-year data: quintessential interpretation of blue tilted tensor spectrum through non-bunch davies initial condition |
the event horizon telescope (eht) is a very long baseline interferometry (vlbi) array that comprises millimeter- and submillimeter-wavelength telescopes separated by distances comparable to the diameter of the earth. at a nominal operating wavelength of ∼1.3 mm, eht angular resolution (λ/d) is ∼25 μas, which is sufficient to resolve nearby supermassive black hole candidates on spatial and temporal scales that correspond to their event horizons. with this capability, the eht scientific goals are to probe general relativistic effects in the strong-field regime and to study accretion and relativistic jet formation near the black hole boundary. in this letter we describe the system design of the eht, detail the technology and instrumentation that enable observations, and provide measures of its performance. meeting the eht science objectives has required several key developments that have facilitated the robust extension of the vlbi technique to eht observing wavelengths and the production of instrumentation that can be deployed on a heterogeneous array of existing telescopes and facilities. to meet sensitivity requirements, high-bandwidth digital systems were developed that process data at rates of 64 gigabit s-1, exceeding those of currently operating cm-wavelength vlbi arrays by more than an order of magnitude. associated improvements include the development of phasing systems at array facilities, new receiver installation at several sites, and the deployment of hydrogen maser frequency standards to ensure coherent data capture across the array. these efforts led to the coordination and execution of the first global eht observations in 2017 april, and to event-horizon-scale imaging of the supermassive black hole candidate in m87. | first m87 event horizon telescope results. ii. array and instrumentation |
we consider the constraints from supernova 1987a on particles with small couplings to the standard model. we discuss a model with a fermion coupled to a dark photon, with various mass relations in the dark sector; millicharged particles; dark-sector fermions with inelastic transitions; the hadronic qcd axion; and an axion-like particle that couples to standard model fermions with couplings proportional to their mass. in the fermion cases, we develop a new diagnostic for assessing when such a particle is trapped at large mixing angles. our bounds for a fermion coupled to a dark photon constrain small couplings and masses ≲ 200 mev, and do not decouple for low fermion masses. they exclude parameter space that is otherwise unconstrained by existing accelerator-based and direct-detection searches. in addition, our bounds are complementary to proposed laboratory searches for sub-gev dark matter, and do not constrain several benchmark-model targets in parameter space for which the dark matter obtains the correct relic abundance from interactions with the standard model. for a millicharged particle, we exclude charges between 10-9-few×10-6 in units of the electron charge, also for masses ≲ 200 mev; this excludes parameter space to higher millicharges and masses than previous bounds. for the qcd axion and an axion-like particle, we apply several updated nuclear physics calculations and include the energy dependence of the optical depth to accurately account for energy loss at large couplings. these corrections allow us to rule out a hadronic axion of mass between 0.1 and a few hundred ev, or equivalently to put a bound on the scale of peccei-quinn symmetry breaking between a few×104 and 108 gev, closing the hadronic axion window. for an axion-like particle, our bounds disfavor decay constants between a few×105 gev up to a few×108 gev, for a mass ≲ 200 mev. in all cases, our bounds differ from previous work by more than an order of magnitude across the entire parameter space. we also provide estimated systematic errors due to the uncertainties of the progenitor. | supernova 1987a constraints on sub-gev dark sectors, millicharged particles, the qcd axion, and an axion-like particle |
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