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the nanograv collaboration has recently observed first evidence of a gravitational wave background (gwb) in pulsar timing data. here we explore the possibility that this gwb is due to new physics, and show that the signal can be well fit also with peaked spectra like the ones expected from phase transitions (pts) or from the dynamics of axion like particles (alps) in the early universe. we find that a good fit to the data is obtained for a very strong pt at temperatures around 1 mev to 10 mev. for the alp explanation the best fit is obtained for a decay constant of $f \approx 5\times 10^{17}$ gev and an axion mass of $2\times 10^{-13}$ ev. we also illustrate the ability of ptas to constrain the parameter space of these models, and obtain limits which are already comparable to other cosmological bounds. | whispers from the dark side: confronting light new physics with nanograv data |
we present a joint cosmic shear analysis of the dark energy survey (des y3) and the kilo-degree survey (kids-1000) in a collaborative effort between the two survey teams. we find consistent cosmological parameter constraints between des y3 and kids-1000 which, when combined in a joint-survey analysis, constrain the parameter $s_8 = \sigma_8 \sqrt{\omega_{\rm m}/0.3}$ with a mean value of $0.790^{+0.018}_{-0.014}$. the mean marginal is lower than the maximum a posteriori estimate, $s_8=0.801$, owing to skewness in the marginal distribution and projection effects in the multi-dimensional parameter space. our results are consistent with $s_8$ constraints from observations of the cosmic microwave background by planck, with agreement at the $1.7\sigma$ level. we use a hybrid analysis pipeline, defined from a mock survey study quantifying the impact of the different analysis choices originally adopted by each survey team. we review intrinsic alignment models, baryon feedback mitigation strategies, priors, samplers and models of the non-linear matter power spectrum. | des y3 + kids-1000: consistent cosmology combining cosmic shear surveys |
we present the data release 14 quasar catalog (dr14q) from the extended baryon oscillation spectroscopic survey (eboss) of the sloan digital sky survey iv (sdss-iv). this catalog includes all sdss-iv/eboss objects that were spectroscopically targeted as quasar candidates and that are confirmed as quasars via a new automated procedure combined with a partial visual inspection of spectra, have luminosities mi [z = 2] < -20.5 (in a λ cdm cosmology with h0 = 70 km s-1 mpc-1, ω m =0.3, and ω λ = 0.7), and either display at least one emission line with a full width at half maximum larger than 500 km s-1 or, if not, have interesting/complex absorption features. the catalog also includes previously spectroscopically-confirmed quasars from sdss-i, ii, and iii. the catalog contains 526 356 quasars (144 046 are new discoveries since the beginning of sdss-iv) detected over 9376 deg2 (2044 deg2 having new spectroscopic data available) with robust identification and redshift measured by a combination of principal component eigenspectra. the catalog is estimated to have about 0.5% contamination. redshifts are provided for the mg ii emission line. the catalog identifies 21 877 broad absorption line quasars and lists their characteristics. for each object, the catalog presents five-band (u, g, r, i, z) ccd-based photometry with typical accuracy of 0.03 mag. the catalog also contains x-ray, ultraviolet, near-infrared, and radio emission properties of the quasars, when available, from other large-area surveys. the calibrated digital spectra, covering the wavelength region 3610-10 140 å at a spectral resolution in the range 1300 < r < 2500, can be retrieved from the sdss science archiver server. http://www.sdss.org/dr14/algorithms/qso_catalog | the sloan digital sky survey quasar catalog: fourteenth data release |
theories with higher order time derivatives generically suffer from ghost-like instabilities, known as ostrogradski instabilities. this fate can be avoided by considering ``degenerate'' lagrangians, whose kinetic matrix cannot be inverted, thus leading to constraints between canonical variables and a reduced number of physical degrees of freedom. in this work, we derive in a systematic way the degeneracy conditions for scalar-tensor theories that depend quadratically on second order derivatives of a scalar field. we thus obtain a classification of all degenerate theories within this class of scalar-tensor theories. the quartic horndeski lagrangian and its extension beyond horndeski belong to these degenerate cases. we also identify new families of scalar-tensor theories with the property that they are degenerate despite the nondegeneracy of the purely scalar part of their lagrangian. | degenerate higher derivative theories beyond horndeski: evading the ostrogradski instability |
during a cosmological first-order phase transition, particles of the plasma crossing the bubble walls can radiate a gauge boson. the resulting pressure cannot be computed perturbatively for large coupling constant and/or large supercooling. we resum the real and virtual emissions at all leading-log orders, both analytically and numerically using a monte-carlo simulation. we find that radiated bosons are dominantly soft and that the resulting retarding pressure on relativistic bubble walls is linear both in the lorentz boost and in the order parameter, up to a log. we further quantitatively discuss ir cut-offs, wall thickness effects, the impact of various approximations entering the calculation, and comment on the fate of radiated bosons that are reflected. | friction pressure on relativistic bubble walls |
astronomical observations reveal a major deficiency in our understanding of physics—the detectable mass is insufficient to explain the observed motions in a huge variety of systems given our current understanding of gravity, einstein's general theory of relativity (gr). this missing gravity problem may indicate a breakdown of gr at low accelerations, as postulated by milgromian dynamics (mond). we review the mond theory and its consequences, including in a cosmological context where we advocate a hybrid approach involving light sterile neutrinos to address mond's cluster-scale issues. we then test the novel predictions of mond using evidence from galaxies, galaxy groups, galaxy clusters, and the large-scale structure of the universe. we also consider whether the standard cosmological paradigm (λcdm) can explain the observations and review several previously published highly significant falsifications of it. our overall assessment considers both the extent to which the data agree with each theory and how much flexibility each has when accommodating the data, with the gold standard being a clear a priori prediction not informed by the data in question. our conclusion is that mond is favoured by a wealth of data across a huge range of astrophysical scales, ranging from the kpc scales of galactic bars to the gpc scale of the local supervoid and the hubble tension, which is alleviated in mond through enhanced cosmic variance. we also consider several future tests, mostly at scales much smaller than galaxies. | from galactic bars to the hubble tension: weighing up the astrophysical evidence for milgromian gravity |
we present a measurement of baryonic acoustic oscillations (baos) from lyα absorption and quasars at an effective redshift $z=2.33$ using the complete extended baryonic oscillation spectroscopic survey (eboss). the 16th and final eboss data release (sdss dr16) contains all data from eboss and its predecessor, the baryonic oscillation spectroscopic survey (boss), providing 210,005 quasars with zq > 2.10 that are used to measure lyα absorption. we measure the bao scale both in the autocorrelation of lyα absorption and in its cross-correlation with 341,468 quasars with redshift zq > 1.77. apart from the statistical gain from new quasars and deeper observations, the main improvements over previous work come from more accurate modeling of physical and instrumental correlations and the use of new sets of mock data. combining the bao measurement from the auto- and cross-correlation yields the constraints of the two ratios ${d}_{h}(z\,=2.33)/{r}_{d}=8.99\pm 0.19$ and ${d}_{m}(z=2.33)/{r}_{d}=37.5\pm 1.1$ , where the error bars are statistical. these results are within 1.5σ of the prediction of the flat-λcdm cosmology of planck (2016). the analysis code, picca, the catalog of the flux transmission field measurements, and the δχ2 surfaces are publicly available. | the completed sdss-iv extended baryon oscillation spectroscopic survey: baryon acoustic oscillations with lyα forests |
planck has mapped the microwave sky in temperature over nine frequency bands between 30 and 857 ghz and in polarization over seven frequency bands between 30 and 353 ghz in polarization. in this paper we consider the problem of diffuse astrophysical component separation, and process these maps within a bayesian framework to derive an internally consistent set of full-sky astrophysical component maps. component separation dedicated to cosmic microwave background (cmb) reconstruction is described in a companion paper. for the temperature analysis, we combine the planck observations with the 9-yr wilkinson microwave anisotropy probe (wmap) sky maps and the haslam et al. 408 mhz map, to derive a joint model of cmb, synchrotron, free-free, spinning dust, co, line emission in the 94 and 100 ghz channels, and thermal dust emission. full-sky maps are provided for each component, with an angular resolution varying between 7.´5 and 1deg. global parameters (monopoles, dipoles, relative calibration, and bandpass errors) are fitted jointly with the sky model, and best-fit values are tabulated. for polarization, the model includes cmb, synchrotron, and thermal dust emission. these models provide excellent fits to the observed data, with rms temperature residuals smaller than 4μk over 93% of the sky for all planck frequencies up to 353 ghz, and fractional errors smaller than 1% in the remaining 7% of the sky. the main limitations of the temperature model at the lower frequencies are internal degeneracies among the spinning dust, free-free, and synchrotron components; additional observations from external low-frequency experiments will be essential to break these degeneracies. the main limitations of the temperature model at the higher frequencies are uncertainties in the 545 and 857 ghz calibration and zero-points. for polarization, the main outstanding issues are instrumental systematics in the 100-353 ghz bands on large angular scales in the form of temperature-to-polarization leakage, uncertainties in the analogue-to-digital conversion, and corrections for the very long time constant of the bolometer detectors, all of which are expected to improve in the near future. | planck 2015 results. x. diffuse component separation: foreground maps |
this snowmass 2021 white paper describes the cosmic microwave background stage 4 project cmb-s4, which is designed to cross critical thresholds in our understanding of the origin and evolution of the universe, from the highest energies at the dawn of time through the growth of structure to the present day. we provide an overview of the science case, the technical design, and project plan. | snowmass 2021 cmb-s4 white paper |
gravitational waves from a first-order cosmological phase transition, at temperatures at the mev-scale, would arguably be the most exciting explanation of the common red spectrum reported by the nanograv collaboration, not the least because this would be direct evidence of physics beyond the standard model. here we perform a detailed analysis of whether such an interpretation is consistent with constraints on the released energy deriving from big bang nucleosynthesis and the cosmic microwave background. we find that a phase transition in a completely secluded dark sector with sub-horizon sized bubbles is strongly disfavoured with respect to the more conventional astrophysical explanation of the putative gravitational wave signal in terms of supermassive black hole binaries. on the other hand, a phase transition in a dark sector that subsequently decays, before the time of neutrino decoupling, remains an intriguing possibility to explain the data. from the model-building perspective, such an option is easily satisfied for couplings with the visible sector that are small enough to evade current collider and astrophysical constraints. the first indication that could eventually corroborate such an interpretation, once the observed common red spectrum is confirmed as a nhz gravitational wave background, could be the spectral tilt of the signal. in fact, the current data already show a very slight preference for a spectrum that is softer than what is expected from the leading astrophysical explanation. | does nanograv observe a dark sector phase transition? |
recent observations from several pulsar timing array (pta) collaborations have unveiled compelling evidence for a stochastic signal in the nanohertz band. this signal aligns remarkably with a gravitational wave (gw) background, potentially originating from the first-order color charge confinement phase transition. distinct quantum chromodynamics (qcd) matters, such as quarks or gluons, and diverse phase transition processes thereof can yield disparate gw energy density spectra. in this paper, employing the bayesian analysis on the nanograv 15-year data set, we explore the compatibility with the observed pta signal of the gw from phase transitions of various qcd matter scenarios in the framework of the holographic qcd. we find that the pta signal can be effectively explained by the gw from the confinement-deconfinement phase transition of pure quark systems in a hard wall model of the holographic qcd where the bubble dynamics, one important source of the gws, is of the jouguet detonations. notably, our analysis decisively rules out the plausibility of the pure gluon qcd-matter scenario and the non-runaway bubble dynamics model for the phase transition in explaining the observed pta signal. | nanograv hints for first-order confinement-deconfinement phase transition in different qcd-matter scenarios |
using the murchison widefield array (mwa), the low-frequency square kilometre array precursor located in western australia, we have completed the galactic and extragalactic all-sky mwa (gleam) survey, and present the resulting extragalactic catalogue, utilizing the first year of observations. the catalogue covers 24 831 square degrees, over declinations south of +30° and galactic latitudes outside 10° of the galactic plane, excluding some areas such as the magellanic clouds. it contains 307 455 radio sources with 20 separate flux density measurements across 72-231 mhz, selected from a time- and frequency-integrated image centred at 200 mhz, with a resolution of ≈2 arcmin. over the catalogued region, we estimate that the catalogue is 90 per cent complete at 170 mjy, and 50 per cent complete at 55 mjy, and large areas are complete at even lower flux density levels. its reliability is 99.97 per cent above the detection threshold of 5σ, which itself is typically 50 mjy. these observations constitute the widest fractional bandwidth and largest sky area survey at radio frequencies to date, and calibrate the low-frequency flux density scale of the southern sky to better than 10 per cent. this paper presents details of the flagging, imaging, mosaicking and source extraction/characterization, as well as estimates of the completeness and reliability. all source measurements and images are available online.1 this is the first in a series of publications describing the gleam survey results. | galactic and extragalactic all-sky murchison widefield array (gleam) survey - i. a low-frequency extragalactic catalogue |
gravitational lensing by massive objects along the line of sight to the source causes distortions of gravitational wave-signals; such distortions may reveal information about fundamental physics, cosmology and astrophysics. in this work, we have extended the search for lensing signatures to all binary black hole events from the third observing run of the ligo--virgo network. we search for repeated signals from strong lensing by 1) performing targeted searches for subthreshold signals, 2) calculating the degree of overlap amongst the intrinsic parameters and sky location of pairs of signals, 3) comparing the similarities of the spectrograms amongst pairs of signals, and 4) performing dual-signal bayesian analysis that takes into account selection effects and astrophysical knowledge. we also search for distortions to the gravitational waveform caused by 1) frequency-independent phase shifts in strongly lensed images, and 2) frequency-dependent modulation of the amplitude and phase due to point masses. none of these searches yields significant evidence for lensing. finally, we use the non-detection of gravitational-wave lensing to constrain the lensing rate based on the latest merger-rate estimates and the fraction of dark matter composed of compact objects. | search for gravitational-lensing signatures in the full third observing run of the ligo-virgo network |
this letter presents the results from pointlike neutrino source searches using ten years of icecube data collected between april 6, 2008 and july 10, 2018. we evaluate the significance of an astrophysical signal from a pointlike source looking for an excess of clustered neutrino events with energies typically above ∼1 tev among the background of atmospheric muons and neutrinos. we perform a full-sky scan, a search within a selected source catalog, a catalog population study, and three stacked galactic catalog searches. the most significant point in the northern hemisphere from scanning the sky is coincident with the seyfert ii galaxy ngc 1068, which was included in the source catalog search. the excess at the coordinates of ngc 1068 is inconsistent with background expectations at the level of 2.9 σ after accounting for statistical trials from the entire catalog. the combination of this result along with excesses observed at the coordinates of three other sources, including txs 0506 +056 , suggests that, collectively, correlations with sources in the northern catalog are inconsistent with background at 3.3 σ significance. the southern catalog is consistent with background. these results, all based on searches for a cumulative neutrino signal integrated over the 10 years of available data, motivate further study of these and similar sources, including time-dependent analyses, multimessenger correlations, and the possibility of stronger evidence with coming upgrades to the detector. | time-integrated neutrino source searches with 10 years of icecube data |
this study investigates the classical higgs inflation model with a modified higgs potential featuring a dip. we examine the implications of this modification on the generation of curvature perturbations, stochastic gravitational wave production, and the potential formation of primordial black holes (pbhs). unlike the classical model, the modified potential allows for enhanced power spectra and the existence of pbhs within a wide mass range $1.5\times10^{20}$ g -- $9.72\times10^{32}$ g. we identify parameter space regions that align with inflationary constraints and have the potential to contribute significantly to the observed dark matter content. additionally, the study explores the consistency of the obtained parameter space with cosmological constraints and discusses the implications for explaining the observed excess in gravitational wave signals, particularly in the nanograv experiment. overall, this investigation highlights the relevance of the modified higgs potential in the classical higgs inflation model, shedding light on the formation of pbhs, the nature of dark matter, and the connection to gravitational wave observations. | nanograv signal and pbh from the modified higgs inflation |
in this work we present several characteristic examples of theories of gravity and particle physics scenarios that may yield an observable energy spectrum of stochastic primordial gravitational waves, compatible with the 2023 nanograv observations. the resulting theories yield a flat or a peaklike energy spectrum, and we further seek the conditions which if hold true, the energy spectrum can be compatible with the recent nanograv stochastic gravitational wave detection. as we show, in most cases a blue tilted spectrum combined with a relatively low reheating temperature is needed, the scale of which is determined by whether the radiation domination era is ordinary or it is an abnormal radiation domination era. one intriguing higgs-axion model, which predicts short slow-roll eras for the axion field at the post-electroweak breaking epoch, which eventually change the total equation of state parameter at the reheating era, can explain the nanograv signal, if a blue tilted tensor spectral index inflationary era precedes the reheating era, and a reheating temperature of the order o (400 ) gev . this specific model produces an energy spectrum of primordial gravitational waves with a characteristic peak that is detectable from both the nanograv and future lisa experiment, but not from the future einstein telescope. | flat energy spectrum of primordial gravitational waves versus peaks and the nanograv 2023 observation |
the square kilometre array (ska) is a planned large radio interferometer designed to operate over a wide range of frequencies, and with an order of magnitude greater sensitivity and survey speed than any current radio telescope. the ska will address many important topics in astronomy, ranging from planet formation to distant galaxies. however, in this work, we consider the perspective of the ska as a facility for studying physics. we review four areas in which the ska is expected to make major contributions to our understanding of fundamental physics: cosmic dawn and reionisation; gravity and gravitational radiation; cosmology and dark energy; and dark matter and astroparticle physics. these discussions demonstrate that the ska will be a spectacular physics machine, which will provide many new breakthroughs and novel insights on matter, energy, and spacetime. | fundamental physics with the square kilometre array |
to date, 241 individual molecular species, composed of 19 different elements, have been detected in the interstellar and circumstellar medium by astronomical observations. these molecules range in size from two atoms to 70 and have been detected across the electromagnetic spectrum from centimeter wavelengths to the ultraviolet. this census presents a summary of the first detection of each molecular species, including the observational facility, wavelength range, transitions, and enabling laboratory spectroscopic work, as well as listing tentative and disputed detections. tables of molecules detected in interstellar ices, external galaxies, protoplanetary disks, and exoplanetary atmospheres are provided. a number of visual representations of these aggregate data are presented and briefly discussed in context. | 2021 census of interstellar, circumstellar, extragalactic, protoplanetary disk, and exoplanetary molecules |
we show that the recent nanograv result can be interpreted as a stochastic gravitational wave signal associated to formation of primordial black holes from high-amplitude curvature perturbations. the indicated amplitude and power of the gravitational wave spectrum agrees well with formation of primordial seeds for supermassive black holes. | did nanograv see a signal from primordial black hole formation? |
we review the current status of early dark energy (ede) models proposed to resolve the "hubble tension", the discrepancy between "direct" measurements of the current expansion rate of the universe and "indirect measurements" for which the values inferred rely on the λcdm cosmological model calibrated on early-universe data. ede refers to a new form of dark energy active at early times (typically a scalar-field), that quickly dilutes away at a redshift close to matter-radiation equality. the role of ede is to decrease the sound horizon by briefly contributing to the hubble rate in the pre-recombination era. we summarize the results of several analyses of ede models suggested thus far in light of recent cosmological data, including constraints from the canonical planck data, baryonic acoustic oscillations and type ia supernovae, and the more recent hints driven by cosmic microwave background observations using the atacama cosmology telescope. we also discuss potential challenges to ede models, from theoretical ones (a second "cosmic coincidence" problem in particular) to observational ones, related to the amplitude of clustering on scales of 8 h /mpc as measured by weak-lensing observables (the so-called s8 tension) and the galaxy power spectrum from boss analyzed through the effective field theory of large-scale structure. we end by reviewing recent attempts at addressing these shortcomings of the ede proposal. while current data remain inconclusive on the existence of an ede phase, we stress that given the signatures of ede models imprinted in the cmb and matter power spectra, next-generation experiments can firmly establish whether ede is the mechanism responsible for the hubble tension and distinguish between the various models suggested in the literature. | the ups and downs of early dark energy solutions to the hubble tension: a review of models, hints and constraints circa 2023 |
we report a correlation between the radial acceleration traced by rotation curves and that predicted by the observed distribution of baryons. the same relation is followed by 2693 points in 153 galaxies with very different morphologies, masses, sizes, and gas fractions. the correlation persists even when dark matter dominates. consequently, the dark matter contribution is fully specified by that of the baryons. the observed scatter is small and largely dominated by observational uncertainties. this radial acceleration relation is tantamount to a natural law for rotating galaxies. | radial acceleration relation in rotationally supported galaxies |
we measure weak lensing cosmic shear power spectra from the 3-year galaxy shear catalog of the hyper suprime-cam (hsc) subaru strategic program imaging survey. the shear catalog covers 416 deg2 of the northern sky, with a mean i -band seeing of 0.59 arcsec and an effective galaxy number density of 15 arcmin-2 within our adopted redshift range. with an i -band magnitude limit of 24.5 mag, and four tomographic redshift bins spanning 0.3 ≤zph≤1.5 based on photometric redshifts, we obtain a high-significance measurement of the cosmic shear power spectra, with a signal-to-noise ratio of approximately 26.4 in the multipole range 300 <ℓ<1800 . the accuracy of our power spectrum measurement is tested against realistic mock shear catalogs, and we use these catalogs to get a reliable measurement of the covariance of the power spectrum measurements. we use a robust blinding procedure to avoid confirmation bias, and model various uncertainties and sources of bias in our analysis, including point spread function systematics, redshift distribution uncertainties, the intrinsic alignment of galaxies and the modeling of the matter power spectrum. for a flat λ cdm model, we find s8≡σ8(ωm/0.3 )0.5=0.77 6-0.033+0.032, which is in excellent agreement with the constraints from the other hsc year 3 cosmology analyses, as well as those from a number of other cosmic shear experiments. this result implies a ∼2 σ -level tension with the planck 2018 cosmology. we study the effect that various systematic errors and modeling choices could have on this value, and find that they can shift the best-fit value of s8 by no more than ∼0.5 σ , indicating that our result is robust to such systematics. | hyper suprime-cam year 3 results: cosmology from cosmic shear power spectra |
the present rate of the expansion of our universe, the hubble constant, can be predicted from the cosmological model using measurements of the early universe, or more directly measured from the late universe. but as these measurements improved, a surprising disagreement between the two appeared. in 2019, a number of independent measurements of the late universe using different methods and data provided consistent results, making the discrepancy with the early universe predictions increasingly hard to ignore. | the expansion of the universe is faster than expected |
unidentified infrared emission bands are ubiquitous in many astronomical sources. these bands are widely, if not unanimously, attributed to collective emissions from polycyclic aromatic hydrocarbon (pah) molecules, yet no single species of this class has been identified in space. using spectral matched filtering of radio data from the green bank telescope, we detected two nitrile-group-functionalized pahs, 1- and 2-cyanonaphthalene, in the interstellar medium. both bicyclic ring molecules were observed in the tmc-1 molecular cloud. in this paper, we discuss potential in situ gas-phase pah formation pathways from smaller organic precursor molecules. | detection of two interstellar polycyclic aromatic hydrocarbons via spectral matched filtering |
sterile neutrinos are natural extensions to the standard model of particle physics in neutrino mass generation mechanisms. if they are relatively light, less than approximately 10 kev, they can alter cosmology significantly, from the early universe to the matter and radiation energy density today. here, we review the cosmological role such light sterile neutrinos can play from the early universe, including production of kev-scale sterile neutrinos as dark matter candidates, and dynamics of light ev-scale sterile neutrinos during the weakly-coupled active neutrino era. we review proposed signatures of light sterile neutrinos in cosmic microwave background and large scale structure data. we also discuss kev-scale sterile neutrino dark matter decay signatures in x-ray observations, including recent candidate ∼3.5 kev x-ray line detections consistent with the decay of a ∼7 kev sterile neutrino dark matter particle. | sterile neutrinos in cosmology |
we present constraints on the tensor-to-scalar ratio r using a combination of bicep/keck 2018 (bk18) and planck pr4 data allowing us to fit for r consistently with the six parameters of the λ cdm model. we discuss the sensitivity of constraints on r to uncertainties in the λ cdm parameters as defined by the planck data. in particular, we are able to derive a constraint on the reionization optical depth τ and thus propagate its uncertainty into the posterior distribution for r . while planck sensitivity to r is slightly lower than the current ground-based measurements, the combination of planck with bk18 and baryon-acoustic-oscillation data yields results consistent with r =0 and tightens the constraint to r <0.032 at 95% confidence. | improved limits on the tensor-to-scalar ratio using bicep and planck data |
recent pulsar timing array (pta) experiments have reported strong evidence of the stochastic gravitational wave background (sgwb). if interpreted as primordial gravitational waves (gws), the signal favors a strongly blue-tilted spectrum. consequently, the nonsingular cosmology, which is able to predict a strongly blue-tilted gw spectrum with nt≃2 on certain scales, offers a potential explanation for the observed sgwb signal. in this paper, we present a genesis-inflation model capable of explaining the sgwb signal observed by the pta collaborations while also overcoming the initial singularity problem associated with the inflationary cosmology. furthermore, our model predicts distinctive features in the sgwb spectrum, which might be examined by forthcoming space-based gravitational wave experiments. | pulsar timing array observations as possible hints for nonsingular cosmology |
the primordial black holes (pbhs) are a well-established probe for new physics in the very early universe. we discuss here the possibility of pbh agglomeration into clusters that may have several prominent observable features. the clusters can form due to closed domain walls appearance in the natural and hybrid inflation models whose subsequent evolution leads to pbh formation. the dynamical evolution of such clusters discussed here is of crucial importance. such a model inherits all the advantages of uniformly distributed pbhs, like possible explanation of supermassive black holes existence (origin of the early quasars), the binary black hole mergers registered by ligo/virgo through gravitational waves, which could provide ways to test the model in future, the contribution to reionization of the universe. if pbhs form clusters, they could alleviate or completely avoid existing constraints on the abundance of uniformly distributed to pbh, thus allowing pbh to be a viable dark matter candidate. most of the existing constraints on uniform pbh density should be re-considered to the case of pbh clustering. furthermore, unidentified cosmic gamma-ray point-like sources could be (partially) accounted. we conclude that models leading to pbh clustering are favored compared to models predicting the uniform distribution of pbhs. | clusters of primordial black holes |
we report the dark matter search results obtained using the full 132 ton·day exposure of the pandax-ii experiment, including all data from march 2016 to august 2018. no significant excess of events is identified above the expected background. upper limits are set on the spin-independent dark matter-nucleon interactions. the lowest 90% confidence level exclusion on the spin-independent cross section is 2.2 × 10-46 cm2 at a wimp mass of 30 gev/c2. * supported by a double top-class grant from shanghai jiao tong university, grants from national science foundation of china (11435008, 11525522, 11775141, 11755001), a grant from the ministry of science and technology of china (2016yfa0400301), the office of science and technology,shanghai municipal government (11dz2260700,16dz2260200, 18jc1410200) | results of dark matter search using the full pandax-ii exposure |
the recently released data by pulsar timing array (pta) collaborations have amassed substantial evidence corroborating the existence of a stochastic signal consistent with a gravitational-wave background at frequencies around the nanohertz regime. we investigate the situation in which the pta signal originates from scalar-induced gravitational waves (sigws), which serves as a valuable tool to probe the equation of state parameter w during the universe's early stages. the joint consideration of the pta data from the nanograv 15-year data set, ppta dr3, and epta dr2 yields that w = 0.60+0.32 -0.39 (median + 90% credible interval), indicating a period of condensate domination at the production of sigws is allowed by the data. moreover, the data also supports radiation domination (w = 1/3) within the 90% credible interval. we also impose an upper bound on the reheating temperature that t rh ≲ 0.2 gev and the constraint on w reveals valuable information on the inflationary potential and the dynamics at the end of inflation. | probing the equation of state of the early universe with pulsar timing arrays |
we present measurements of the e -mode (e e ) polarization power spectrum and temperature-e -mode (t e ) cross-power spectrum of the cosmic microwave background using data collected by spt-3g, the latest instrument installed on the south pole telescope. this analysis uses observations of a 1500 deg2 region at 95, 150, and 220 ghz taken over a four-month period in 2018. we report binned values of the e e and t e power spectra over the angular multipole range 300 ≤ℓ<3000 , using the multifrequency data to construct six semi-independent estimates of each power spectrum and their minimum-variance combination. these measurements improve upon the previous results of sptpol across the multipole ranges 300 ≤ℓ≤1400 for e e and 300 ≤ℓ≤1700 for t e , resulting in constraints on cosmological parameters comparable to those from other current leading ground-based experiments. we find that the spt-3g data set is well fit by a λ cdm cosmological model with parameter constraints consistent with those from planck and sptpol data. from spt-3g data alone, we find h0=68.8 ±1.5 km s−1 mpc−1 and σ8=0.789 ±0.016 , with a gravitational lensing amplitude consistent with the λ cdm prediction (al=0.98 ±0.12 ). we combine the spt-3g and the planck data sets and obtain joint constraints on the λ cdm model. the volume of the 68% confidence region in six-dimensional λ cdm parameter space is reduced by a factor of 1.5 compared to planck-only constraints, with no significant shifts in central values. we note that the results presented here are obtained from data collected during just half of a typical observing season with only part of the focal plane operable, and that the active detector count has since nearly doubled for observations made with spt-3g after 2018. | measurements of the e -mode polarization and temperature-e -mode correlation of the cmb from spt-3g 2018 data |
increasingly stringent limits from lhc searches for new physics, coupled with lack of convincing signals of weakly interacting massive particle (wimp) in dark matter searches, have tightly constrained many realizations of the standard paradigm of thermally produced wimps as cold dark matter. in this article, we review more generally both thermally and non-thermally produced dark matter (dm). one may classify dm models into two broad categories: one involving bosonic coherent motion (bcm) and the other involving wimps. bcm and wimp candidates need, respectively, some approximate global symmetries and almost exact discrete symmetries. supersymmetric axion models are highly motivated since they emerge from compelling and elegant solutions to the two fine-tuning problems of the standard model: the strong cp problem and the gauge hierarchy problem. we review here non-thermal relics in a general setup, but we also pay particular attention to the rich cosmological properties of various aspects of mixed susy/axion dark matter candidates which can involve both wimps and bcm in an interwoven manner. we also review briefly a panoply of alternative thermal and non-thermal dm candidates. | dark matter production in the early universe: beyond the thermal wimp paradigm |
the quijote simulations are a set of 44,100 full n-body simulations spanning more than 7000 cosmological models in the $\{{{\rm{\omega }}}_{{\rm{m}}},{{\rm{\omega }}}_{{\rm{b}}},h,{n}_{s},{\sigma }_{8},{m}_{\nu },w\}$ hyperplane. at a single redshift, the simulations contain more than 8.5 trillion particles over a combined volume of 44,100 ${\left({h}^{-1}\mathrm{gpc}\right)}^{3};$ each simulation follows the evolution of 2563, 5123, or 10243 particles in a box of 1 h-1 gpc length. billions of dark matter halos and cosmic voids have been identified in the simulations, whose runs required more than 35 million core hours. the quijote simulations have been designed for two main purposes: (1) to quantify the information content on cosmological observables and (2) to provide enough data to train machine-learning algorithms. in this paper, we describe the simulations and show a few of their applications. we also release the petabyte of data generated, comprising hundreds of thousands of simulation snapshots at multiple redshifts; halo and void catalogs; and millions of summary statistics, such as power spectra, bispectra, correlation functions, marked power spectra, and estimated probability density functions. | the quijote simulations |
we construct a holographic dark energy scenario based on kaniadakis entropy, which is a generalization of boltzmann-gibbs entropy that arises from relativistic statistical theory and is characterized by a single parameter k which quantifies the deviations from standard expressions, and we use the future event horizon as the infrared cutoff. we extract the differential equation that determines the evolution of the effective dark energy density parameter, and we provide analytical expressions for the corresponding equation-of-state and deceleration parameters. we show that the universe exhibits the standard thermal history, with the sequence of matter and dark-energy eras, while the transition to acceleration takes place at z ≈0.6 . concerning the dark-energy equation-of-state parameter we show that it can have a rich behavior, being quintessence-like, phantom-like, or experience the phantom-divide crossing in the past or in the future. finally, in the far future dark energy dominates completely, and the asymptotic value of its equation of state depends on the values of the two model parameters. | kaniadakis holographic dark energy and cosmology |
the third catalog of active galactic nuclei (agns) detected by the fermi-lat (3lac) is presented. it is based on the third fermi-lat catalog (3fgl) of sources detected between 100 mev and 300 gev with a test statistic greater than 25, between 2008 august 4 and 2012 july 31. the 3lac includes 1591 agns located at high galactic latitudes (| b| \gt 10^\circ ), a 71% increase over the second catalog based on 2 years of data. there are 28 duplicate associations, thus 1563 of the 2192 high-latitude gamma-ray sources of the 3fgl catalog are agns. most of them (98%) are blazars. about half of the newly detected blazars are of unknown type, i.e., they lack spectroscopic information of sufficient quality to determine the strength of their emission lines. based on their gamma-ray spectral properties, these sources are evenly split between flat-spectrum radio quasars (fsrqs) and bl lacs. the most abundant detected bl lacs are of the high-synchrotron-peaked (hsp) type. about 50% of the bl lacs have no measured redshifts. a few new rare outliers (hsp-fsrqs and high-luminosity hsp bl lacs) are reported. the general properties of the 3lac sample confirm previous findings from earlier catalogs. the fraction of 3lac blazars in the total population of blazars listed in bzcat remains non-negligible even at the faint ends of the bzcat-blazar radio, optical, and x-ray flux distributions, which hints that even the faintest known blazars could eventually shine in gamma-rays at lat-detection levels. the energy-flux distributions of the different blazar populations are in good agreement with extrapolation from earlier catalogs. | the third catalog of active galactic nuclei detected by the fermi large area telescope |
we present volume-averaged neutral hydrogen fractions $x_{\rm \hi}$ and ionized bubble radii $r_{\rm b}$ measured with ly$\alpha$ damping wing absorption of galaxies at the epoch of reionization. we combine jwst/nirspec spectra taken by ceers, go-1433, ddt-2750, and jades programs, and obtain a sample containing 26 bright uv-continuum ($m_{\rm uv}<-18.5~{\rm mag}$) galaxies at $7<z<12$. we construct 4 composite spectra binned by redshift, and find the clear evolution of softening break towards high redshift at the rest-frame $1216$ å, suggesting the increase of ly$\alpha$ damping wing absorption. we estimate ly$\alpha$ damping wing absorption in the galaxy spectra with realistic templates including ly$\alpha$ emission and circum-galactic medium absorptions. assuming the standard inside-out reionization picture having an ionized bubble with radius $r_b$ around a galaxy embedded in the intergalactic medium with $x_{\rm \hi}$, we obtain $x_{\rm \hi}$ ($r_{\rm b}$) values generally increasing (decreasing) from $x_{\rm \hi}={0.54}^{+0.13}_{-0.54}$ to ${0.94}^{+0.06}_{-0.41}$ ($\log r_{\rm b}={1.89}^{+0.49}_{-1.54}$ to ${-0.72}^{+1.57}_{-0.28}$ comoving mpc) at redshift $7.12^{+0.06}_{-0.08}$ to $10.28^{+1.12}_{-1.40}$. the redshift evolution of $x_{\rm \hi}$ indicates a moderately late reionization history consistent with the one previously suggested from the electron scattering of cosmic microwave background and the evolution of uv luminosity function with an escape fraction $f_{\rm esc}\sim 0.2$. our ${r_{\rm b}}$ measurements suggest that bubble sizes could be up to a few dex larger than the cosmic average values estimated by analytic calculations for a given $x_{\rm \hi}$, while our $r_{\rm b}$ measurements are roughly comparable with the values for merged ionized bubbles around bright galaxies predicted by recent numerical simulations. | jwst measurements of neutral hydrogen fractions and ionized bubble sizes at $z=7-12$ obtained with ly$\\alpha$ damping wing absorptions in 26 bright continuum galaxies |
the lofar two-metre sky survey (lotss) is a deep 120-168 mhz imaging survey that will eventually cover the entire northern sky. each of the 3170 pointings will be observed for 8 h, which, at most declinations, is sufficient to produce 5″ resolution images with a sensitivity of 100 μjy/beam and accomplish the main scientific aims of the survey, which are to explore the formation and evolution of massive black holes, galaxies, clusters of galaxies and large-scale structure. owing to the compact core and long baselines of lofar, the images provide excellent sensitivity to both highly extended and compact emission. for legacy value, the data are archived at high spectral and time resolution to facilitate subarcsecond imaging and spectral line studies. in this paper we provide an overview of the lotss. we outline the survey strategy, the observational status, the current calibration techniques, a preliminary data release, and the anticipated scientific impact. the preliminary images that we have released were created using a fully automated but direction-independent calibration strategy and are significantly more sensitive than those produced by any existing large-area low-frequency survey. in excess of 44 000 sources are detected in the images that have a resolution of 25″, typical noise levels of less than 0.5 mjy/beam, and cover an area of over 350 square degrees in the region of the hetdex spring field (right ascension 10h45m00s to 15h30m00s and declination 45°00'00″ to 57°00'00″). the catalogue (full table 3) is only available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?j/a+a/598/a104 | the lofar two-metre sky survey. i. survey description and preliminary data release |
this paper introduces colossus, a public, open-source python package for calculations related to cosmology, the large-scale structure (lss) of matter in the universe, and the properties of dark matter halos. the code is designed to be fast and easy to use, with a coherent, well-documented user interface. the cosmology module implements friedman-lemaitre-robertson-walker cosmologies including curvature, relativistic species, and different dark energy equations of state, and provides fast computations of the linear matter power spectrum, variance, and correlation function. the lss module is concerned with the properties of peaks in gaussian random fields and halos in a statistical sense, including their peak height, peak curvature, halo bias, and mass function. the halo module deals with spherical overdensity radii and masses, density profiles, concentration, and the splashback radius. to facilitate the rapid exploration of these quantities, colossus implements more than 40 different fitting functions from the literature. i discuss the core routines in detail, with particular emphasis on their accuracy. colossus is available at bitbucket.org/bdiemer/colossus. | colossus: a python toolkit for cosmology, large-scale structure, and dark matter halos |
we develop a general approach to distill symbolic representations of a learned deep model by introducing strong inductive biases. we focus on graph neural networks (gnns). the technique works as follows: we first encourage sparse latent representations when we train a gnn in a supervised setting, then we apply symbolic regression to components of the learned model to extract explicit physical relations. we find the correct known equations, including force laws and hamiltonians, can be extracted from the neural network. we then apply our method to a non-trivial cosmology example-a detailed dark matter simulation-and discover a new analytic formula which can predict the concentration of dark matter from the mass distribution of nearby cosmic structures. the symbolic expressions extracted from the gnn using our technique also generalized to out-of-distribution data better than the gnn itself. our approach offers alternative directions for interpreting neural networks and discovering novel physical principles from the representations they learn. | discovering symbolic models from deep learning with inductive biases |
we report a reanalysis of a near-pristine absorption system, located at a redshift {z}abs}=2.52564 toward the quasar q1243+307, based on the combination of archival and new data obtained with the hires echelle spectrograph on the keck telescope. this absorption system, which has an oxygen abundance [o/h] = -2.769 ± 0.028 (≃1/600 of the solar abundance), is among the lowest metallicity systems currently known where a precise measurement of the deuterium abundance is afforded. our detailed analysis of this system concludes, on the basis of eight d i absorption lines, that the deuterium abundance of this gas cloud is {log}}10({{d}}/{{h}})=-4.622+/- 0.015, which is in very good agreement with the results previously reported by kirkman et al., but with an improvement on the precision of this single measurement by a factor of ∼3.5. combining this new estimate with our previous sample of six high precision and homogeneously analyzed d/h measurements, we deduce that the primordial deuterium abundance is {log}}10{({{d}}/{{h}})}{{p}}=-4.5974+/- 0.0052 or, expressed as a linear quantity, {10}5{({{d}}/{{h}})}{{p}}=2.527+/- 0.030; this value corresponds to a one percent determination of the primordial deuterium abundance. combining our result with a big bang nucleosynthesis (bbn) calculation that uses the latest nuclear physics input, we find that the baryon density derived from bbn agrees to within 2σ of the latest results from the planck cosmic microwave background data. based on observations collected at the w.m. keck observatory which is operated as a scientific partnership among the california institute of technology, the university of california, and the national aeronautics and space administration. the observatory was made possible by the generous financial support of the w.m. keck foundation. | one percent determination of the primordial deuterium abundance |
we present limits on spin-independent dark matter-nucleon interactions using a 10.6 g si athermal phonon detector with a baseline energy resolution of σe=3.86 ±0.04 (stat )-0.00+0.19(syst ) ev . this exclusion analysis sets the most stringent dark matter-nucleon scattering cross-section limits achieved by a cryogenic detector for dark matter particle masses from 93 to 140 mev /c2 , with a raw exposure of 9.9 g d acquired at an above-ground facility. this work illustrates the scientific potential of detectors with athermal phonon sensors with ev-scale energy resolution for future dark matter searches. | light dark matter search with a high-resolution athermal phonon detector operated above ground |
high-energy cosmic-ray electrons and positrons (cres), which lose energy quickly during their propagation, provide a probe of galactic high-energy processes and may enable the observation of phenomena such as dark-matter particle annihilation or decay. the cre spectrum has been measured directly up to approximately 2 teraelectronvolts in previous balloon- or space-borne experiments, and indirectly up to approximately 5 teraelectronvolts using ground-based cherenkov γ-ray telescope arrays. evidence for a spectral break in the teraelectronvolt energy range has been provided by indirect measurements, although the results were qualified by sizeable systematic uncertainties. here we report a direct measurement of cres in the energy range 25 gigaelectronvolts to 4.6 teraelectronvolts by the dark matter particle explorer (dampe) with unprecedentedly high energy resolution and low background. the largest part of the spectrum can be well fitted by a ‘smoothly broken power-law’ model rather than a single power-law model. the direct detection of a spectral break at about 0.9 teraelectronvolts confirms the evidence found by previous indirect measurements, clarifies the behaviour of the cre spectrum at energies above 1 teraelectronvolt and sheds light on the physical origin of the sub-teraelectronvolt cres. | direct detection of a break in the teraelectronvolt cosmic-ray spectrum of electrons and positrons |
we present a detailed exposition on the prospects of the formation of primordial black holes (pbhs) during slow roll (sr) to ultra slow roll (usr) sharp transitions in the framework of single-field inflation. we use an effective field theory (eft) approach in order to keep the analysis model-independent and applicable to both the canonical and non-canonical cases. we show in detail how renormalizing the power spectrum to one loop order in p(x,ϕ) theories severely limits the prospects for pbh formation in a single-field inflationary framework. we demonstrate that for the allowed range of effective sound speed, 1 < cs < 1.17, the consistency of one-loop corrected power spectrum leaves a small window for black hole masses, m pbh~𝒪(102-103)gm to have sufficient e-foldings, δ𝒩total ~ 𝒪(54-59) for inflation. we confirm that adding an sr regime after usr before the end of inflation does not significantly alter our conclusions. our findings for sharp transition strictly rule out the possibility of generating large masses of pbhs from all possible models of single field inflation (canonical and non-canonical). our results are at least valid for the situation where constraints from the loop effects are computed using either late-time (lt) or adiabatic-wave function (af) scheme followed by power spectrum (ps) renormalization schemes. | quantum loop effects on the power spectrum and constraints on primordial black holes |
we present an overview of scenarios where the observed dark matter (dm) abundance consists of feebly interacting massive particles (fimps), produced nonthermally by the so-called freeze-in mechanism. in contrast to the usual freeze-out scenario, frozen-in fimp dm interacts very weakly with the particles in the visible sector and never attained thermal equilibrium with the baryon-photon fluid in the early universe. instead of being determined by its annihilation strength, the dm abundance depends on the decay and annihilation strengths of particles in equilibrium with the baryon-photon fluid, as well as couplings in the dm sector. this makes frozen-in dm very difficult but not impossible to test. in this review, we present the freeze-in mechanism and its variations considered in the literature (dark freeze-out and reannihilation), compare them to the standard dm freeze-out scenario, discuss several aspects of model building, and pay particular attention to observational properties and general testability of such feebly interacting dm. | the dawn of fimp dark matter: a review of models and constraints |
the north american nanohertz observatory for gravitational waves has recently reported strong evidence for a stochastic common-spectrum process affecting the pulsar timing residuals in its 12.5-year data set. we demonstrate that this process admits an interpretation in terms of a stochastic gravitational-wave background emitted by a cosmic-string network in the early universe. we study stable nambu-goto strings in dependence of their tension g μ and loop size α and show that the entire viable parameter space will be probed by an array of future experiments. | has nanograv found first evidence for cosmic strings? |
the event horizon telescope (eht) collaboration has recently released the first image of a black hole (bh), opening a new window onto tests of general relativity in the strong field regime. in this paper, we derive constraints on the nature of m87* (the supermassive object at the center of the galaxy m87), exploiting the fact that its shadow appears to be highly circular, and using measurements of its angular size. we first consider the simple case where m87* is assumed to be a kerr bh. we find that the inferred circularity of m87* excludes kerr bhs with observation angle θobs≳4 5 ° for dimensionless rotational parameter 0.95 ≲a*≤1 whereas the observation angle is unbounded for a*≲0.9 . we then consider the possibility that m87* might be a superspinar, i.e., an object described by the kerr solution and spinning so fast that it violates the kerr bound by having |a*|>1 . we find that, within certain regions of parameter space, the inferred circularity and size of the shadow of m87* do not exclude the possibility that this object might be a superspinar. | testing the rotational nature of the supermassive object m87* from the circularity and size of its first image |
speed matters. how the masses and spins of new particles active during inflation can be read off from the statistical properties of primordial density fluctuations is well understood. however, not when the propagation speeds of the new degrees of freedom and of the curvature perturbation differ, which is the generic situation in the effective field theory of inflationary fluctuations. here we use bootstrap techniques to find exact analytical solutions for primordial 2-,3- and 4-point correlators in this context. we focus on the imprints of a heavy relativistic scalar coupled to the curvature perturbation that propagates with a reduced speed of sound cs, hence strongly breaking de sitter boosts. we show that akin to the de sitter invariant setup, primordial correlation functions can be deduced by acting with suitable weight-shifting operators on the four-point function of a conformally coupled field induced by the exchange of the massive scalar. however, this procedure requires the analytical continuation of this seed correlator beyond the physical domain implied by momentum conservation. we bootstrap this seed correlator in the extended domain from first principles, starting from the boundary equation that it satisfies due to locality. we further impose unitarity, reflected in cosmological cutting rules, and analyticity, by demanding regularity in the collinear limit of the four-point configuration, in order to find the unique solution. equipped with this, we unveil that heavy particles that are lighter than h/cs leave smoking gun imprints in the bispectrum in the form of resonances in the squeezed limit, a phenomenon that we call the low speed collider. we characterise the overall shape of the signal as well as its unusual logarithmic mass dependence, both vividly distinct from previously identified signatures of heavy fields. eventually, we demonstrate that these features can be understood in a simplified picture in which the heavy field is integrated out, albeit in a non-standard manner resulting in a single-field effective theory that is non-local in space. nonetheless, the latter description misses the non-perturbative effects of spontaneous particle production, well visible in the ultra-squeezed limit in the form of the cosmological collider oscillations, and it breaks down for masses of order the hubble scale, for which only our exact bootstrap results hold. | cosmological bootstrap in slow motion |
active galactic nuclei (agn) are energetic astrophysical sources powered by accretion onto supermassive black holes in galaxies, and present unique observational signatures that cover the full electromagnetic spectrum over more than twenty orders of magnitude in frequency. the rich phenomenology of agn has resulted in a large number of different "flavours" in the literature that now comprise a complex and confusing agn "zoo". it is increasingly clear that these classifications are only partially related to intrinsic differences between agn and primarily reflect variations in a relatively small number of astrophysical parameters as well the method by which each class of agn is selected. taken together, observations in different electromagnetic bands as well as variations over time provide complementary windows on the physics of different sub-structures in the agn. in this review, we present an overview of agn multi-wavelength properties with the aim of painting their "big picture" through observations in each electromagnetic band from radio to γ -rays as well as agn variability. we address what we can learn from each observational method, the impact of selection effects, the physics behind the emission at each wavelength, and the potential for future studies. to conclude, we use these observations to piece together the basic architecture of agn, discuss our current understanding of unification models, and highlight some open questions that present opportunities for future observational and theoretical progress. | active galactic nuclei: what's in a name? |
we present a comprehensive review of kev-scale sterile neutrino dark matter, collecting views and insights from all disciplines involved—cosmology, astrophysics, nuclear, and particle physics—in each case viewed from both theoretical and experimental/observational perspectives. after reviewing the role of active neutrinos in particle physics, astrophysics, and cosmology, we focus on sterile neutrinos in the context of the dark matter puzzle. here, we first review the physics motivation for sterile neutrino dark matter, based on challenges and tensions in purely cold dark matter scenarios. we then round out the discussion by critically summarizing all known constraints on sterile neutrino dark matter arising from astrophysical observations, laboratory experiments, and theoretical considerations. in this context, we provide a balanced discourse on the possibly positive signal from x-ray observations. another focus of the paper concerns the construction of particle physics models, aiming to explain how sterile neutrinos of kev-scale masses could arise in concrete settings beyond the standard model of elementary particle physics. the paper ends with an extensive review of current and future astrophysical and laboratory searches, highlighting new ideas and their experimental challenges, as well as future perspectives for the discovery of sterile neutrinos. | a white paper on kev sterile neutrino dark matter |
this paper presents the high frequency instrument (hfi) data processing procedures for the planck 2018 release. major improvements in mapmaking have been achieved since the previous planck 2015 release, many of which were used and described already in an intermediate paper dedicated to the planck polarized data at low multipoles. these improvements enabled the first significant measurement of the reionization optical depth parameter using planck-hfi data. this paper presents an extensive analysis of systematic effects, including the use of end-to-end simulations to facilitate their removal and characterize the residuals. the polarized data, which presented a number of known problems in the 2015 planck release, are very significantly improved, especially the leakage from intensity to polarization. calibration, based on the cosmic microwave background (cmb) dipole, is now extremely accurate and in the frequency range 100-353 ghz reduces intensity-to-polarization leakage caused by calibration mismatch. the solar dipole direction has been determined in the three lowest hfi frequency channels to within one arc minute, and its amplitude has an absolute uncertainty smaller than 0.35 μk, an accuracy of order 10−4. this is a major legacy from the planck hfi for future cmb experiments. the removal of bandpass leakage has been improved for the main high-frequency foregrounds by extracting the bandpass-mismatch coefficients for each detector as part of the mapmaking process; these values in turn improve the intensity maps. this is a major change in the philosophy of "frequency maps", which are now computed from single detector data, all adjusted to the same average bandpass response for the main foregrounds. end-to-end simulations have been shown to reproduce very well the relative gain calibration of detectors, as well as drifts within a frequency induced by the residuals of the main systematic effect (analogue-to-digital convertor non-linearity residuals). using these simulations, we have been able to measure and correct the small frequency calibration bias induced by this systematic effect at the 10−4 level. there is no detectable sign of a residual calibration bias between the first and second acoustic peaks in the cmb channels, at the 10−3 level. | planck 2018 results. iii. high frequency instrument data processing and frequency maps |
we show that polar materials are excellent targets for direct detection of sub-gev dark matter due to the presence of gapped optical phonons as well as acoustic phonons with high sound speed. we take the example of gallium arsenide (gaas), which has the properties needed for experimental realization, and where many results can be estimated analytically. we find gaas has excellent reach to dark photon absorption, can completely cover the freeze-in benchmark for scattering via an ultralight dark photon, and is competitive with other proposals to detect sub-mev dark matter scattering off nuclei. | detection of light dark matter with optical phonons in polar materials |
the observation of the global 21 cm signal produced by neutral hydrogen gas in the intergalactic medium (igm) during the dark ages, cosmic dawn, and epoch of reionization requires measurements with extremely well-calibrated wideband radiometers. we describe the design and characterization of the mapper of the igm spin temperature (mist), which is a new ground-based, single-antenna, global 21 cm experiment. the design of mist was guided by the objectives of avoiding systematics from an antenna ground plane and cables around the antenna, as well as maximizing the instrument's on-sky efficiency and portability for operations at remote sites. we have built two mist instruments, which observe in the range 25-105 mhz. for the 21 cm signal, this frequency range approximately corresponds to redshifts 55.5 > z > 12.5, encompassing the dark ages and cosmic dawn. the mist antenna is a horizontal blade dipole of 2.42 m in length, 60 cm in width, and 52 cm in height above the ground. this antenna operates without a metal ground plane. the instruments run on 12 v batteries and have a maximum power consumption of 17 w. the batteries and electronics are contained in a single receiver box located under the antenna. we present the characterization of the instruments using electromagnetic simulations and lab measurements. we also show sample sky measurements from recent observations at remote sites in california, nevada, and the canadian high arctic. these measurements indicate that the instruments perform as expected. detailed analyses of the sky measurements are left for future work. | mapper of the igm spin temperature (mist): instrument overview |
within the friedmann-lemaître-robertson-walker (flrw) framework, the hubble constant $h_0$ is an integration constant. thus, mathematical consistency demands that $h_0$ is also observationally a constant. building on earlier results, we demonstrate redshift evolution of flat $\lambda$cdm cosmological parameters $(h_0, \omega_{m})$ in pantheon+ supernove (sn) in the redshift range $0 < z \lesssim 2.26$. we compare the whole sn sample and the sn sample split into low and high redshift subsamples demarcated by redshift $z_{\textrm{split}}$. we show that $z_{\textrm{split}}=1$ has a marginal bayesian preference through the akaike information criterion for evolution in $h_0$ (also $\omega_m)$ compared to the whole sample. such evolution is strictly forbidden in flrw models. through mock analysis, we estimate the evolution as a $ 1.4 \sigma$ effect ($p=0.08$), and the presence of $\omega_m >1$ best fits, indicative of negative dark energy (de) density, beyond $z_{\textrm{split}} =1$ as $1.3 \sigma$ ($p=0.1$) to $1.9 \sigma$ effects $(p=0.026$) depending on the criteria. finally, using complementary profile distributions we confirm a robust $> 2 \sigma$ shift in $h_0$ for sn with $z > 1$. | negative dark energy density from high redshift pantheon+ supernovae |
the violation of the null energy condition (nec) is closely related to potential solutions for the cosmological singularity problem and may therefore play a crucial role in the very early universe. we explore a novel approach to generate primordial black holes (pbhs) via the violation of the nec in a single-field inflationary scenario. in our scenario, the universe transitions from a first slow-roll inflation stage with a hubble parameter h = hinf1 to a second slow-roll inflation stage with h = hinf2 > hinf1, passing through an intermediate stage of nec violation. the resulting primordial scalar power spectrum is naturally enhanced by the nec violation at a certain wavelength. as a result, pbhs with masses and abundances of observational interest can be produced in our scenario. we also examine the phenomenological signatures of scalar-induced gravitational waves (sigws). our work highlights the significance of utilizing a combination of pbhs, sigws, and primordial gravitational waves as a powerful probe for exploring the nec violation during inflation. | primordial black holes from null energy condition violation during inflation |
strong evidence for a gravitational-wave background (gwb) has been reported in the nano-hertz band. interpreting the origin of this background to be scalar-induced gravitational waves (sigws), we explore the equation of state (eos) of the early universe by performing bayes parameter inferences across the big-bang nucleosynthesis (bbn), cosmic microwave background (cmb), and pulsar timing array (pta) joint observations for the first time. assuming a monochromatic power spectrum for primordial curvature perturbations, we obtain the spectral amplitude $a\sim10^{-3}-10^{-1}$ and spectral peak frequency $f_\ast\sim10^{-7}-10^{-6}$ hz. we find that the radiation domination with eos $w=1/3$ is compatible with the current observational data, the kination domination with eos $w=1$ is not forbidden, while the early matter domination with eos $w=0$ is excluded at more than $2\sigma$ confidence level. these results can be tested with future observations. | exploring the equation of state of the early universe: insights from bbn, cmb, and pta observations |
we use a formalism that describes electron ejections from graphenelike targets by dark matter (dm) scattering for general forms of scalar and spin-1/2 dm-electron interactions in combination with state-of-the-art density functional calculations to produce predictions and reach estimates for various possible carbon-based detector designs. our results indicate the importance of a proper description of the target electronic structure. in addition, we find a strong dependence of the predicted observed signal for different dm candidate masses and interaction types on the detailed geometry and design of the detector. combined with directional background vetoing, these dependencies will enable the identification of dm particle properties once a signal has been established. | direct searches for general dark matter-electron interactions with graphene detectors: part ii. sensitivity studies |
evidence for a low-frequency stochastic gravitational-wave background has recently been reported based on analyses of pulsar timing array data. the most likely source of such a background is a population of supermassive black hole binaries, the loudest of which may be individually detected in these data sets. here we present the search for individual supermassive black hole binaries in the nanograv 15 yr data set. we introduce several new techniques, which enhance the efficiency and modeling accuracy of the analysis. the search uncovered weak evidence for two candidate signals, one with a gravitational-wave frequency of ~4 nhz, and another at ~170 nhz. the significance of the low-frequency candidate was greatly diminished when hellings-downs correlations were included in the background model. the high-frequency candidate was discounted due to the lack of a plausible host galaxy, the unlikely astrophysical prior odds of finding such a source, and since most of its support comes from a single pulsar with a commensurate binary period. finding no compelling evidence for signals from individual binary systems, we place upper limits on the strain amplitude of gravitational waves emitted by such systems. at our most sensitive frequency of 6 nhz, we place a sky-averaged 95% upper limit of 8 × 10-15 on the strain amplitude. we also calculate an exclusion volume and a corresponding effective radius, within which we can rule out the presence of black hole binaries emitting at a given frequency. | the nanograv 15 yr data set: bayesian limits on gravitational waves from individual supermassive black hole binaries |
we present an initial design study for ldmx, the light dark matter experiment, a small-scale accelerator experiment having broad sensitivity to both direct dark matter and mediator particle production in the sub-gev mass region. ldmx employs missing momentum and energy techniques in multi-gev electro-nuclear fixed-target collisions to explore couplings to electrons in uncharted regions that extend down to and below levels that are motivated by direct thermal freeze-out mechanisms. ldmx would also be sensitive to a wide range of visibly and invisibly decaying dark sector particles, thereby addressing many of the science drivers highlighted in the 2017 us cosmic visions new ideas in dark matter community report. ldmx would achieve the required sensitivity by leveraging existing and developing detector technologies from the cms, hps and mu2e experiments. in this paper, we present our initial design concept, detailed geant-based studies of detector performance, signal and background processes, and a preliminary analysis approach. we demonstrate how a first phase of ldmx could expand sensitivity to a variety of light dark matter, mediator, and millicharge particles by several orders of magnitude in coupling over the broad sub-gev mass range. | light dark matter experiment (ldmx) |
we observed the afterglow of the extremely bright grb221009a (dichiara et al., gcn 32632; kennea & williams, gcn 32635; bissaldi et al., gcn 32637; veres et al., gcn 32636; lesage et al., gcn 32642) with x-shooter at eso's ut3 of the very large telescope (paranal, chile). the observations started at 00:49:58.9 ut (11.55 hr after the gbm trigger and 10.66 hr after the bat trigger). the observation consisted of 4x600s with a spectral coverage between 3000 and 21000 aa. we detect a very red continuum with absorption features that correspond to caii, cai and naid at a redshift of z = 0.151. we also detect multiple features due to the milky way's interstellar medium, due to the large galactic column density of material along this line of sight. at this redshift the event has an isotropic equivalent energy of eiso=2x10^54 erg (using the gbm fluence reported in gcn 32642), barring saturation effects in the fermi/gbm fluence. this is within the upper end of grb energetics. further follow-up is strongly encouraged. we acknowledge the excellent support provided by the paranal staff, in particular a. escorza and zahed wahhaj. | grb 221009a: redshift from x-shooter/vlt |
active galactic nuclei (agns) represent the growth phases of the supermassive black holes in the center of almost every galaxy. powerful, highly ionized winds, with velocities â¼0.1-0.2c, are a common feature in x-ray spectra of luminous agns, offering a plausible physical origin for the well-known connections between the hole and properties of its host. observability constraints suggest that the winds must be episodic and detectable only for a few percent of their lifetimes. the most powerful wind feedback, establishing the m⊙ relation, is probably not directly observable at all. the m⊙ relation signals a global change in the nature of agn feedback. at black hole masses below m⊙ feedback is confined to the immediate vicinity of the hole. at the m⊙ mass, it becomes much more energetic and widespread and can drive away much of the bulge gas as a fast molecular outflow. | powerful outflows and feedback from active galactic nuclei |
we present a catalog of galaxy clusters selected via their sunyaev-zel'dovich (sz) effect signature from 2500 deg2 of south pole telescope (spt) data. this work represents the complete sample of clusters detected at high significance in the 2500 deg2 spt-sz survey, which was completed in 2011. a total of 677 (409) cluster candidates are identified above a signal-to-noise threshold of ξ = 4.5 (5.0). ground- and space-based optical and near-infrared (nir) imaging confirms overdensities of similarly colored galaxies in the direction of 516 (or 76%) of the ξ > 4.5 candidates and 387 (or 95%) of the ξ > 5 candidates; the measured purity is consistent with expectations from simulations. of these confirmed clusters, 415 were first identified in spt data, including 251 new discoveries reported in this work. we estimate photometric redshifts for all candidates with identified optical and/or nir counterparts; we additionally report redshifts derived from spectroscopic observations for 141 of these systems. the mass threshold of the catalog is roughly independent of redshift above z ~ 0.25 leading to a sample of massive clusters that extends to high redshift. the median mass of the sample is m 500c(ρcrit) ∼ 3.5× 1014 m_⊙ h70-1, the median redshift is z med = 0.55, and the highest-redshift systems are at z > 1.4. the combination of large redshift extent, clean selection, and high typical mass makes this cluster sample of particular interest for cosmological analyses and studies of cluster formation and evolution. | galaxy clusters discovered via the sunyaev-zel'dovich effect in the 2500-square-degree spt-sz survey |
hawking evaporation of black holes in the early universe is expected to copiously produce all kinds of particles, regardless of their charges under the standard model gauge group. for this reason, any fundamental particle, known or otherwise, could be produced during the black hole lifetime. this certainly includes dark matter (dm) particles. this paper improves upon previous calculations of dm production from primordial black holes (pbh) by consistently including the greybody factors, and by meticulously tracking a system of coupled boltzmann equations. we show that the initial pbh densities required to produce the observed relic abundance depend strongly on the dm spin, varying in about ∼2 orders of magnitude between a spin-2 and a scalar dm in the case of nonrotating pbhs. for kerr pbhs, we have found that the expected enhancement in the production of bosons reduces the initial fraction needed to explain the measurements. we further consider indirect production of dm by assuming the existence of additional and unstable degrees of freedom emitted by the evaporation, which later decay into the dm. for a minimal setup where there is only one heavy particle, we find that the final relic abundance can be increased by at most a factor of ∼4 for a scalar heavy state and a schwarzschild pbh, or by a factor of ∼4.3 for a spin-2 particle in the case of a kerr pbh. | primordial black hole evaporation and dark matter production. i. solely hawking radiation |
we present the catalog of ∼31,500 extragalactic h i line sources detected by the completed arecibo legacy fast alfa (alfalfa) survey out to z < 0.06, including both high signal-to-noise ratio (>6.5) detections and ones of lower quality that coincide in both position and recessional velocity with galaxies of known redshift. we review the observing technique, data reduction pipeline, and catalog construction process, focusing on details of particular relevance to understanding the catalog’s compiled parameters. we further describe and make available the digital h i line spectra associated with the cataloged sources. in addition to the extragalactic h i line detections, we report nine confirmed oh megamasers (ohms) and 10 ohm candidates at 0.16 < z < 0.22 whose oh line signals are redshifted into the alfalfa frequency band. because of complexities in data collection and processing associated with the use of a feed-horn array on a complex single-dish antenna in the terrestrial radio frequency interference environment, we also present a list of suggestions and caveats for consideration by users of the alfalfa extragalactic catalog for future scientific investigations. | the arecibo legacy fast alfa survey: the alfalfa extragalactic h i source catalog |
we present the temperature and polarization angular power spectra of the cmb measured by the atacama cosmology telescope (act) from 5400 deg2 of the 2013-2016 survey, which covers >15000 deg2 at 98 and 150 ghz. for this analysis we adopt a blinding strategy to help avoid confirmation bias and, related to this, show numerous checks for systematic error done before unblinding. using the likelihood for the cosmological analysis we constrain secondary sources of anisotropy and foreground emission, and derive a "cmb-only" spectrum that extends to l=4000. at large angular scales, foreground emission at 150 ghz is ~1% of tt and ee within our selected regions and consistent with that found by planck. using the same likelihood, we obtain the cosmological parameters for λcdm for the act data alone with a prior on the optical depth of τ=0.065±0.015. λcdm is a good fit. the best-fit model has a reduced χ2 of 1.07 (pte=0.07) with h0=67.9±1.5 km/s/mpc. we show that the lensing bb signal is consistent with λcdm and limit the celestial eb polarization angle to ψp =-0.07o±0.09o. we directly cross correlate act with planck and observe generally good agreement but with some discrepancies in te. all data on which this analysis is based will be publicly released. | the atacama cosmology telescope: a measurement of the cosmic microwave background power spectra at 98 and 150 ghz |
we propose the use of silicon carbide (sic) for direct detection of sub-gev dark matter. sic has properties similar to both silicon and diamond but has two key advantages: (i) it is a polar semiconductor which allows sensitivity to a broader range of dark matter candidates; and (ii) it exists in many stable polymorphs with varying physical properties and hence has tunable sensitivity to various dark matter models. we show that sic is an excellent target to search for electron, nuclear and phonon excitations from scattering of dark matter down to 10 kev in mass, as well as for absorption processes of dark matter down to 10 mev in mass. combined with its widespread use as an alternative to silicon in other detector technologies and its availability compared to diamond, our results demonstrate that sic holds much promise as a novel dark matter detector. | silicon carbide detectors for sub-gev dark matter |
we test the statistical isotropy and gaussianity of the cosmic microwave background (cmb) anisotropies using observations made by the planck satellite. our results are based mainly on the full planck mission for temperature, but also include some polarization measurements. in particular, we consider the cmb anisotropy maps derived from the multi-frequency planck data by several component-separation methods. for the temperature anisotropies, we find excellent agreement between results based on these sky maps over both a very large fraction of the sky and a broad range of angular scales, establishing that potential foreground residuals do not affect our studies. tests of skewness, kurtosis, multi-normality, n-point functions, and minkowski functionals indicate consistency with gaussianity, while a power deficit at large angular scales is manifested in several ways, for example low map variance. the results of a peak statistics analysis are consistent with the expectations of a gaussian random field. the "cold spot" is detected with several methods, including map kurtosis, peak statistics, and mean temperature profile. we thoroughly probe the large-scale dipolar power asymmetry, detecting it with several independent tests, and address the subject of a posteriori correction. tests of directionality suggest the presence of angular clustering from large to small scales, but at a significance that is dependent on the details of the approach. we perform the first examination of polarization data, finding the morphology of stacked peaks to be consistent with the expectations of statistically isotropic simulations. where they overlap, these results are consistent with the planck 2013 analysis based on the nominal mission data and provide our most thorough view of the statistics of the cmb fluctuations to date. | planck 2015 results. xvi. isotropy and statistics of the cmb |
we present the cosmological analysis of the configuration-space anisotropic clustering in the completed sloan digital sky survey iv extended baryon oscillation spectroscopic survey (eboss) data release 16 galaxy sample. this sample consists of luminous red galaxies (lrgs) spanning the redshift range 0.6 < $z$ < 1, at an effective redshift of $z$ eff = 0.698. it combines 174 816 eboss and 202 642 boss lrgs. we extract and model the baryon acoustic oscillation (bao) and redshift-space distortion (rsd) features from the galaxy two-point correlation function to infer geometrical and dynamical cosmological constraints. the adopted methodology is extensively tested on a set of realistic simulations. the correlations between the inferred parameters from the bao and full-shape correlation function analyses are estimated. this allows us to derive joint constraints on the three cosmological parameter combinations: dm( $z$ )/rd, dh( $z$ )/rd, and fσ8( $z$ ), where dm is the comoving angular diameter distance, dh is the hubble distance, rd is the comoving bao scale, f is the linear growth rate of structure, and σ8 is the amplitude of linear matter perturbations. after combining the results with those from the parallel power spectrum analysis of gil-marin et al., we obtain the constraints: dm/rd = 17.65 ± 0.30, dh/rd = 19.77 ± 0.47, and fσ8 = 0.473 ± 0.044. these measurements are consistent with a flat lambda cold dark matter model with standard gravity. | the completed sdss-iv extended baryon oscillation spectroscopic survey: measurement of the bao and growth rate of structure of the luminous red galaxy sample from the anisotropic correlation function between redshifts 0.6 and 1 |
cosmic neutrinos provide a unique window into the otherwise hidden mechanism of particle acceleration in astrophysical objects. the icecube collaboration recently reported the likely association of one high-energy neutrino with a flare from the relativistic jet of an active galaxy pointed towards the earth. however a combined analysis of many similar active galaxies revealed no excess from the broader population, leaving the vast majority of the cosmic neutrino flux unexplained. here we present the likely association of a radio-emitting tidal disruption event, at2019dsg, with a second high-energy neutrino. at2019dsg was identified as part of our systematic search for optical counterparts to high-energy neutrinos with the zwicky transient facility. the probability of finding any coincident radio-emitting tidal disruption event by chance is 0.5%, while the probability of finding one as bright in bolometric energy flux as at2019dsg is 0.2%. our electromagnetic observations can be explained through a multizone model, with radio analysis revealing a central engine, embedded in a uv photosphere, that powers an extended synchrotron-emitting outflow. this provides an ideal site for petaelectronvolt neutrino production. assuming that the association is genuine, our observations suggest that tidal disruption events with mildly relativistic outflows contribute to the cosmic neutrino flux. | a tidal disruption event coincident with a high-energy neutrino |
in the framework of metric-affine gravity, we consider the role of the boundary term in symmetric teleparallel gravity assuming f(q, b) models where f is a smooth function of the non-metricity scalar q and the related boundary term b. starting from a variational approach, we derive the field equations and compare them with respect to those of f(q) gravity in the limit of b →0 . it is possible to show that f (q ,b )=f (q -b ) models are dynamically equivalent to f(r) gravity as in the case of teleparallel f (b ~-t ) gravity (where b ≠b ~ ). furthermore, conservation laws are derived. in this perspective, considering boundary terms in f(q) gravity represents the last ingredient towards the extended geometric trinity of gravity, where f(r), f (t ,b ~) , and f(q, b) can be dealt under the same standard. in this perspective, we discuss also the gibbons-hawking-york boundary term of general relativity comparing it with b in f(q, b) gravity. | the role of the boundary term in f(q, b) symmetric teleparallel gravity |
the difference from 4 to 6 σ in the hubble constant (h0) between the values observed with the local (cepheids and supernovae ia, sne ia) and the high-z probes (cosmic microwave background obtained by the planck data) still challenges the astrophysics and cosmology community. previous analysis has shown that there is an evolution in the hubble constant that scales as f(z)=h0/(1+z)η, where h0 is h0(z=0) and η is the evolutionary parameter. here, we investigate if this evolution still holds by using the sne ia gathered in the pantheon sample and the baryon acoustic oscillations. we assume h0=70kms‑1mpc‑1 as the local value and divide the pantheon into three bins ordered in increasing values of redshift. similar to our previous analysis but varying two cosmological parameters contemporaneously (h0, ω0m in the λcdm model and h0, wa in the w0wacdm model), for each bin we implement a markov-chain monte carlo analysis (mcmc) obtaining the value of h0 assuming gaussian priors to restrict the parameters spaces to values we expect from our prior knowledge of the current cosmological models and to avoid phantom dark energy models with w<‑1. subsequently, the values of h0 are fitted with the model f(z). our results show that a decreasing trend with η∼10‑2 is still visible in this sample. the η coefficient reaches zero in 2.0 σ for the λcdm model up to 5.8 σ for w0wacdm model. this trend, if not due to statistical fluctuations, could be explained through a hidden astrophysical bias, such as the effect of stretch evolution, or it requires new theoretical models, a possible proposition is the modified gravity theories, f(r). this analysis is meant to further cast light on the evolution of h0 and it does not specifically focus on constraining the other parameters. this work is also a preparatory to understand how the combined probes still show an evolution of the h0 by redshift and what is the current status of simulations on grb cosmology to obtain the uncertainties on the ω0m comparable with the ones achieved through sne ia. | on the evolution of the hubble constant with the sne ia pantheon sample and baryon acoustic oscillations: a feasibility study for grb-cosmology in 2030 |
we investigate modified theories of gravity in the context of teleparallel geometries. it is well known that modified gravity models based on the torsion scalar are not invariant under local lorentz transformations while modifications based on the ricci scalar are. this motivates the study of a model depending on the torsion scalar and the divergence of the torsion vector. we derive the teleparallel equivalent of f (r ) gravity as a particular subset of these models and also show that this is the unique theory in this class that is invariant under local lorentz transformation. furthermore one can show that f (t ) gravity is the unique theory admitting second-order field equations. | modified teleparallel theories of gravity |
in this paper, we describe the system design and capabilities of the australian square kilometre array pathfinder (askap) radio telescope at the conclusion of its construction project and commencement of science operations. askap is one of the first radio telescopes to deploy phased array feed (paf) technology on a large scale, giving it an instantaneous field of view that covers$31\,\textrm{deg}^{2}$at$800\,\textrm{mhz}$. as a two-dimensional array of 36$\times$12 m antennas, with baselines ranging from 22 m to 6 km, askap also has excellent snapshot imaging capability and 10 arcsec resolution. this, combined with 288 mhz of instantaneous bandwidth and a unique third axis of rotation on each antenna, gives askap the capability to create high dynamic range images of large sky areas very quickly. it is an excellent telescope for surveys between 700 and$1800\,\textrm{mhz}$and is expected to facilitate great advances in our understanding of galaxy formation, cosmology, and radio transients while opening new parameter space for discovery of the unknown. | australian square kilometre array pathfinder: i. system description |
we show that one-loop corrections to the large-scale power spectrum from small-scale modes in non-slow-roll dynamics are always negligible, namely they are volume suppressed by the ratio of the short to long distance scales. one-loop contributions proportional to the long wavelength tree-level power spectrum, and not sharing this suppression, appear only when considering a subset of vertexes, but they cancel exactly when all relevant interactions are taken into account. we prove the previous statement in two different ways, i.e. by using two equivalent forms of the interaction hamiltonian. contributions from boundary terms to equal time correlators are included when necessary. | absence of one-loop effects on large scales from small scales in non-slow-roll dynamics |
we propose a mellin space approach to the evaluation of late-time momentum-space correlation functions of quantum fields in (d + 1)-dimensional de sitter space. the mellin-barnes representation makes manifest the analytic structure of late-time correlators and, more generally, provides a convenient general d framework for the study of conformal correlators in momentum space. in this work we focus on tree-level correlation functions of general scalars as a prototype, including n-point contact diagrams and 4-point exchanges. for generic scalars, both the contact and exchange diagrams are given by (generalised) hypergeometric functions, which reduce to existing expressions available in the literature for d = 3 and external scalars which are either simultaneously conformally coupled or massless. this approach can also be used for the perturbative bulk evaluation of momentum space boundary correlators in (d + 1)-dimensional anti-de sitter space (witten diagrams). | a mellin space approach to cosmological correlators |
we summarize the properties and initial data release of the jades origins field (jof), which will soon be the deepest imaging field yet observed with the james webb space telescope (jwst). this field falls within the goods-s region about 8' south-west of the hubble ultra deep field (hudf), where it was formed initially in cycle 1 as a parallel field of hudf spectroscopic observations within the jwst advanced deep extragalactic survey (jades). this imaging will be greatly extended in cycle 2 program 3215, which will observe the jof for 5 days in six medium-band filters, seeking robust candidates for z>15 galaxies. this program will also include ultra-deep parallel nirspec spectroscopy (up to 104 hours on-source, summing over the dispersion modes) on the hudf. cycle 3 observations from program 4540 will add 20 hours of nircam slitless spectroscopy to the jof. with these three campaigns, the jof will be observed for 380 open-shutter hours with nircam using 15 imaging filters and 2 grism bandpasses. further, parts of the jof have deep 43 hr miri observations in f770w. taken together, the jof will soon be one of the most compelling deep fields available with jwst and a powerful window into the early universe. this paper presents the second data release from jades, featuring the imaging and catalogs from the year 1 jof observations. | the jades origins field: a new jwst deep field in the jades second nircam data release |
we derive cosmological constraints using a galaxy cluster sample selected from the 2500 deg2 spt-sz survey. the sample spans the redshift range 0.25 < z < 1.75 and contains 343 clusters with sz detection significance ξ > 5. the sample is supplemented with optical weak gravitational lensing measurements of 32 clusters with 0.29 < z < 1.13 (from magellan and hubble space telescope) and x-ray measurements of 89 clusters with 0.25 < z < 1.75 (from chandra). we rely on minimal modeling assumptions: (i) weak lensing provides an accurate means of measuring halo masses, (ii) the mean sz and x-ray observables are related to the true halo mass through power-law relations in mass and dimensionless hubble parameter e(z) with a priori unknown parameters, and (iii) there is (correlated, lognormal) intrinsic scatter and measurement noise relating these observables to their mean relations. we simultaneously fit for these astrophysical modeling parameters and for cosmology. assuming a flat νλcdm model, in which the sum of neutrino masses is a free parameter, we measure ωm = 0.276 ± 0.047, σ 8 = 0.781 ± 0.037, and σ 8(ωm/0.3)0.2 = 0.766 ±0.025. the redshift evolutions of the x-ray y x-mass and m gas-mass relations are both consistent with self-similar evolution to within 1σ. the mass slope of the y x-mass relation shows a 2.3σ deviation from self-similarity. similarly, the mass slope of the m gas-mass relation is steeper than self-similarity at the 2.5σ level. in a νwcdm cosmology, we measure the dark energy equation-of-state parameter w = -1.55 ± 0.41 from the cluster data. we perform a measurement of the growth of structure since redshift z ∼ 1.7 and find no evidence for tension with the prediction from general relativity. this is the first analysis of the spt cluster sample that uses direct weak-lensing mass calibration and is a step toward using the much larger weak-lensing data set from des. we provide updated redshift and mass estimates for the spt sample. | cluster cosmology constraints from the 2500 deg2 spt-sz survey: inclusion of weak gravitational lensing data from magellan and the hubble space telescope |
a flat friedmann-robertson-walker universe dominated by a cosmological constant (λ) and cold dark matter (cdm) has been the working model preferred by cosmologists since the discovery of cosmic acceleration1,2. however, tensions of various degrees of significance are known to be present among existing datasets within the λcdm framework3-11. in particular, the lyman-α forest measurement of the baryon acoustic oscillations (bao) by the baryon oscillation spectroscopic survey3 prefers a smaller value of the matter density fraction ωm than that preferred by cosmic microwave background (cmb). also, the recently measured value of the hubble constant, h0 = 73.24 ± 1.74 km s-1 mpc-1 (ref. 12), is 3.4σ higher than the 66.93 ± 0.62 km s-1 mpc-1 inferred from the planck cmb data7. in this work, we investigate whether these tensions can be interpreted as evidence for a non-constant dynamical dark energy. using the kullback-leibler divergence13 to quantify the tension between datasets, we find that the tensions are relieved by an evolving dark energy, with the dynamical dark energy model preferred at a 3.5σ significance level based on the improvement in the fit alone. while, at present, the bayesian evidence for the dynamical dark energy is insufficient to favour it over λcdm, we show that, if the current best-fit dark energy happened to be the true model, it would be decisively detected by the upcoming dark energy spectroscopic instrument survey14. | dynamical dark energy in light of the latest observations |
we study the imprints of massive particles with spin on cosmological correlators. using the framework of the effective field theory of inflation, we classify the couplings of these particles to the goldstone boson of broken time translations and the graviton. we show that it is possible to generate observable non-gaussianity within the regime of validity of the effective theory, as long as the masses of the particles are close to the hubble scale and their interactions break the approximate conformal symmetry of the inflationary background. we derive explicit shape functions for the scalar and tensor bispectra that can serve as templates for future observational searches. | non-gaussianity as a particle detector |
we review inflationary cosmology in modified gravity such as r2 gravity with its extensions in order to generalize the starobinsky inflation model. in particular, we explore inflation realized by three kinds of effects: modification of gravity, the quantum anomaly, and the r2 term in loop quantum cosmology. it is explicitly demonstrated that in these inflationary models, the spectral index of scalar modes of the density perturbations and the tensor-to-scalar ratio can be consistent with the planck results. bounce cosmology in f(r) gravity is also explained. | inflationary cosmology in modified gravity theories |
we assess the status of big-bang nucleosynthesis (bbn) in light of the final planck data release and other recent developments, and in anticipation of future measurements. planck data from the recombination era fix the cosmic baryon density to 0.9% precision, and now damping tail measurements determine the helium abundance and effective number of neutrinos with precision approaching that of astronomical and bbn determinations respectively. all three parameters are related by bbn . in addition, new high-redshift measurements give d/h to better precision than theoretical predictions, and new li/h data reconfirm the lithium problem. we present new 7be(n,p)7li rates using new neutron capture measurements; we have also examined the effect of proposed changes in the d(p,γ)3he rates. using these results we perform a series of likelihood analyses. we assess bbn/cmb consistency, with attention to how our results depend on the choice of planck data, as well as how the results depend on the choice of non-bbn, non-planck data sets. most importantly the lithium problem remains, and indeed is more acute given the very tight d/h observational constraints; new neutron capture data reveals systematics that somewhat increases uncertainty and thus slightly reduces but does not essentially change the problem. we confirm that d(p,γ)3he theoretical rates brings d/h out of agreement and slightly increases 7li new experimental data are needed at bbn energies. setting the lithium problem aside, we find the effective number of neutrino species at bbn is nν = 2.86 ± 0.15. future cmb stage\nobreakdash-4 measurements promise substantial improvements in bbn parameters: helium abundance determinations will be competitive with the best astronomical determinations, and neff will approach sensitivities capable of detecting the effects of standard model neutrino heating of the primordial plasma. | big-bang nucleosynthesis after planck |
we show an inconsistence of the novel 4d einstein-gauss-bonnet gravity by considering a quantum tunneling process of vacua. based on standard semiclassical techniques, we find a nonperturbative way to the study of the vacuum decay rate of the theory. we analytically compute all allowed cases in the parameter space. it turns out, without exception, that the theory either encounters a disastrous divergence of vacuum decay rate, or exhibits a confusing complex value of vacuum decay rate, or involves an instability (a large vacuum mixing). these suggest a strong possibility that the theory, at least the vacuum of the theory, is either unphysical or unstable, or has no well-defined limit as d → 4. | vacua in novel 4d einstein-gauss-bonnet gravity: pathology and instability? |
we present a modified cosmological scenario that arises from the application of non-extensive thermodynamics with varying exponent. we extract the modified friedmann equations, which contain new terms quantified by the non-extensive exponent, possessing standard λ cdm cosmology as a subcase. concerning the universe evolution at late times we obtain an effective dark energy sector, and we show that we can acquire the usual thermal history, with the successive sequence of matter and dark-energy epochs, with the effective dark-energy equation-of-state parameter being in the quintessence or in the phantom regime. the interesting feature of the scenario is that the above behaviors can be obtained even if the explicit cosmological constant is set to zero, namely they arise purely from the extra terms. additionally, we confront the model with supernovae type ia and hubble parameter observational data, and we show that the agreement is very good. concerning the early-time universe we obtain inflationary de sitter solutions, which are driven by an effective cosmological constant that includes the new terms of non-extensive thermodynamics. this effective screening can provide a description of both inflation and late-time acceleration with the same parameter choices, which is a significant advantage. | modified cosmology from extended entropy with varying exponent |
we report constraints on sub-gev dark matter particles interacting with electrons from the first underground operation of damic-m detectors. the search is performed with an integrated exposure of 85.23 g days, and exploits the subelectron charge resolution and low level of dark current of damic-m charge-coupled devices (ccds). dark-matter-induced ionization signals above the detector dark current are searched for in ccd pixels with charge up to 7 e-. with this dataset we place limits on dark matter particles of mass between 0.53 and 1000 mev /c2 , excluding unexplored regions of parameter space in the mass ranges [1.6 ,1000 ] mev /c2 and [1.5 ,15.1 ] mev /c2 for ultralight and heavy mediator interactions, respectively. | first constraints from damic-m on sub-gev dark-matter particles interacting with electrons |
we present a comprehensive analysis of the $\lambda_{\rm s}$cdm model, which explores the recent conjecture suggesting a rapid transition of the universe from anti-de sitter vacua to de sitter vacua (viz., the cosmological constant switches sign from negative to positive) at redshift ${z_\dagger\sim 2}$, inspired by the graduated dark energy (gde) model. our analysis shows that, predicting $z_\dagger\approx1.7$, $\lambda_{\rm s}$cdm simultaneously addresses the major cosmological tensions of the standard $\lambda$cdm model, viz., the hubble constant $h_0$, the type ia supernovae absolute magnitude $m_{\rm b}$, and the growth parameter $s_8$ tensions, along with other less significant tensions such as the bao lyman-$\alpha$ discrepancy. | $\\lambda_{\\rm s}$cdm model: a promising scenario for alleviation of cosmological tensions |
the stochastic signal detected by nanograv, ppta, epta, and cpta can be explained by the scalar-induced gravitational waves. in order to determine the scalar-induced gravitational waves model that best fits the stochastic signal, we employ both single- and double-peak parameterizations for the power spectrum of the primordial curvature perturbations, where the single-peak scenarios include the δ-function, box, lognormal, and broken power law model, and the double-peak scenario is described by the double lognormal form. using bayesian inference, we find that there is no significant evidence for or against the single-peak scenario over the double-peak model, with log (bayes factors) among these models ln ℬ < 1. therefore, we cannot distinguish the different shapes of the power spectrum of the primordial curvature perturbation with the current sensitivity of pulsar timing arrays. | constraints on primordial curvature power spectrum with pulsar timing arrays |
models where dark matter and dark energy interact with each other have been proposed to solve the coincidence problem. we review the motivations underlying the need to introduce such interaction, its influence on the background dynamics and how it modifies the evolution of linear perturbations. we test models using the most recent observational data and we find that the interaction is compatible with the current astronomical and cosmological data. finally, we describe the forthcoming data sets from current and future facilities that are being constructed or designed that will allow a clearer understanding of the physics of the dark sector. | dark matter and dark energy interactions: theoretical challenges, cosmological implications and observational signatures |
self-interacting dark matter (sidm) arises generically in scenarios for physics beyond the standard model that have dark sectors with light mediators or strong dynamics. the self-interactions allow energy and momentum transport through halos, altering their structure and dynamics relative to those produced by collisionless dark matter. sidm models provide a promising way to explain the diversity of galactic rotation curves, and they form a predictive and versatile framework for interpreting astrophysical phenomena related to dark matter. this review provides a comprehensive explanation of the physical effects of dark matter self-interactions in objects ranging from galactic satellites (dark and luminous) to clusters of galaxies and the large-scale structure. the second major part describes the methods used to constrain sidm models including current constraints, with the aim of advancing tests with upcoming galaxy surveys. this part also provides a detailed review of the unresolved small-scale structure formation issues and concrete ways to test simple sidm models. the review is rounded off by a discussion of the theoretical motivation for self-interactions, degeneracies with baryonic and gravitational effects, extensions to the single-component elastic-interactions sidm framework, and future observational and theoretical prospects. | astrophysical tests of dark matter self-interactions |
the cresst experiment is a direct dark matter search which aims to measure interactions of potential dark matter particles in an earth-bound detector. with the current stage, cresst-iii, we focus on a low energy threshold for increased sensitivity towards light dark matter particles. in this manuscript we describe the analysis of one detector operated in the first run of cresst-iii (05/2016-02/2018) achieving a nuclear recoil threshold of 30.1ev. this result was obtained with a 23.6g cawo$_4$ crystal operated as a cryogenic scintillating calorimeter in the cresst setup at the laboratori nazionali del gran sasso (lngs). both the primary phonon/heat signal and the simultaneously emitted scintillation light, which is absorbed in a separate silicon-on-sapphire light absorber, are measured with highly sensitive transition edge sensors operated at ~15mk. the unique combination of these sensors with the light element oxygen present in our target yields sensitivity to dark matter particle masses as low as 160mev/c$^2$. | first results from the cresst-iii low-mass dark matter program |
the xenon1t experiment at the laboratori nazionali del gran sasso (lngs) is the first wimp dark matter detector operating with a liquid xenon target mass above the ton-scale. out of its 3.2 t liquid xenon inventory, 2.0 t constitute the active target of the dual-phase time projection chamber. the scintillation and ionization signals from particle interactions are detected with low-background photomultipliers. this article describes the xenon1t instrument and its subsystems as well as strategies to achieve an unprecedented low background level. first results on the detector response and the performance of the subsystems are also presented. | the xenon1t dark matter experiment |
recently, aligo announced the first direct detections of gravitational waves, a direct manifestation of the propagating degrees of freedom of gravity. the detected signals gw150914 and gw151226 have been used to examine the basic properties of these gravitational degrees of freedom, particularly setting an upper bound on their mass. it is timely to review what the mass of these gravitational degrees of freedom means from the theoretical point of view, particularly taking into account the recent developments in constructing consistent massive gravity theories. apart from the gw150914 mass bound, a few other observational bounds have been established from the effects of the yukawa potential, modified dispersion relation, and fifth force that are all induced when the fundamental gravitational degrees of freedom are massive. these different mass bounds are reviewed, how they stand in the wake of recent theoretical developments and how they compare to the bound from gw150914 are examined. | graviton mass bounds |
we critically examine the magnitude of theoretical uncertainties in perturbative calculations of fist-order phase transitions, using the standard model effective field theory as our guide. in the usual daisy-resummed approach, we find large uncertainties due to renormalisation scale dependence, which amount to two to three orders-of-magnitude uncertainty in the peak gravitational wave amplitude, relevant to experiments such as lisa. alternatively, utilising dimensional reduction in a more sophisticated perturbative approach drastically reduces this scale dependence, pushing it to higher orders. further, this approach resolves other thorny problems with daisy resummation: it is gauge invariant which is explicitly demonstrated for the standard model, and avoids an uncontrolled derivative expansion in the bubble nucleation rate. | theoretical uncertainties for cosmological first-order phase transitions |
cosmography can be considered as a sort of a model-independent approach to tackle the dark energy/modified gravity problem. in this review, the success and the shortcomings of the λcdm model, based on general relativity (gr) and standard model of particles, are discussed in view of the most recent observational constraints. the motivations for considering extensions and modifications of gr are taken into account, with particular attention to f(r) and f(t) theories of gravity where dynamics is represented by curvature or torsion field, respectively. the features of f(r) models are explored in metric and palatini formalisms. we discuss the connection between f(r) gravity and scalar-tensor theories highlighting the role of conformal transformations in the einstein and jordan frames. cosmological dynamics of f(r) models is investigated through the corresponding viability criteria. afterwards, the equivalent formulation of gr (teleparallel equivalent general relativity (tegr)) in terms of torsion and its extension to f(t) gravity is considered. finally, the cosmographic method is adopted to break the degeneracy among dark energy models. a novel approach, built upon rational padé and chebyshev polynomials, is proposed to overcome limits of standard cosmography based on taylor expansion. the approach provides accurate model-independent approximations of the hubble flow. numerical analyses, based on monte carlo markov chain integration of cosmic data, are presented to bound coefficients of the cosmographic series. these techniques are thus applied to reconstruct f(r) and f(t) functions and to frame the late-time expansion history of the universe with no a priori assumptions on its equation-of-state. a comparison between the λcdm cosmological model with f(r) and f(t) models is reported. | extended gravity cosmography |
we present a detailed investigation of a subdominant oscillating scalar field ["early dark energy" (ede)] in the context of resolving the hubble tension. consistent with earlier work, but without relying on fluid approximations, we find that a scalar field frozen due to hubble friction until log10(zc)∼3.5 , reaching ρede(zc)/ρtot∼10 % and diluting faster than matter afterwards, can bring cosmic microwave background (cmb), baryonic acoustic oscillations, supernovae luminosity distances, and the late-time estimate of the hubble constant from the sh0es collaboration into agreement. a scalar field potential that scales as v (ϕ )∝ϕ2 n with 2 ≲n ≲3.4 around the minimum is preferred at the 68% confidence level, and the planck polarization places additional constraints on the dynamics of perturbations in the scalar field. in particular, the data prefer a potential that flattens at large field displacements. a markov-chain monte carlo analysis of mock data shows that the next-generation cmb observations (i.e., cmb-s4) can unambiguously detect the presence of the ede at a very high significance. this projected sensitivity to the ede dynamics is mainly driven by improved measurements of the e -mode polarization. we also explore new observational signatures of ede scalar field dynamics: (i) we find that depending on the strength of the tensor-to-scalar ratio, the presence of the ede might imply the existence of isocurvature perturbations in the cmb. (ii) we show that a strikingly rapid, scale-dependent growth of ede field perturbations can result from parametric resonance driven by the anharmonic oscillating field for n ≈2 . this instability and ensuing potentially nonlinear, spatially inhomogeneous, dynamics may provide unique signatures of this scenario. | oscillating scalar fields and the hubble tension: a resolution with novel signatures |
frb 121102 is the only known repeating fast radio burst source. here we analyze a wide-frequency-range (1-8 ghz) sample of high signal-to-noise, coherently dedispersed bursts detected using the arecibo and green bank telescopes. these bursts reveal complex time-frequency structures that include subbursts with finite bandwidths. the frequency-dependent burst structure complicates the determination of a dispersion measure (dm); we argue that it is appropriate to use a dm metric that maximizes frequency-averaged pulse structure, as opposed to peak signal-to-noise, and find dm = 560.57 ± 0.07 pc cm-3 at mjd 57,644. after correcting for dispersive delay, we find that the subbursts have characteristic frequencies that typically drift lower at later times in the total burst envelope. in the 1.1-1.7 ghz band, the ∼0.5-1 ms subbursts have typical bandwidths ranging from 100 to 400 mhz, and a characteristic drift rate of ∼200 mhz ms-1 toward lower frequencies. at higher radio frequencies, the subburst bandwidths and drift rate are larger, on average. while these features could be intrinsic to the burst emission mechanism, they could also be imparted by propagation effects in the medium local to the source. comparison of the burst dms with previous values in the literature suggests an increase of δdm ∼ 1-3 pc cm-3 in 4 yr; though, this could be a stochastic variation as opposed to a secular trend. this implies changes in the local medium or an additional source of frequency-dependent delay. overall, the results are consistent with previously proposed scenarios in which frb 121102 is embedded in a dense nebula. | frb 121102 bursts show complex time-frequency structure |
we outline the experimental concept and key scientific capabilities of aion (atom interferometer observatory and network), a proposed experimental programme using cold strontium atoms to search for ultra-light dark matter, to explore gravitational waves in the mid-frequency range between the peak sensitivities of the lisa and ligo/virgo/ kagra/indigo/einstein telescope/cosmic explorer experiments, and to probe other frontiers in fundamental physics. aion would complement other planned searches for dark matter, as well as probe mergers involving intermediate-mass black holes and explore early-universe cosmology. aion would share many technical features with the magis experimental programme, and synergies would flow from operating aion in a network with this experiment, as well as with other atom interferometer experiments such as miga, zaiga and elgar. operating aion in a network with other gravitational wave detectors such as ligo, virgo and lisa would also offer many synergies. | aion: an atom interferometer observatory and network |
we present a novel theory of gravity by considering an extension of symmetric teleparallel gravity. this is done by introducing, in the framework of the metric-affine formalism, a new class of theories where the nonmetricity q is nonminimally coupled to the matter lagrangian. more specifically, we consider a lagrangian of the form l ∼f1(q )+f2(q )lm , where f1 and f2 are generic functions of q , and lm is the matter lagrangian. this nonminimal coupling entails the nonconservation of the energy-momentum tensor, and consequently the appearance of an extra force. the formulation of the gravity sector in terms of the q instead of the curvature may result in subtle improvements of the theory. in the context of nonminimal matter couplings, we are therefore motivated to explore whether the new geometrical formulation in terms of the q , when implemented also in the matter sector, would allow more universally consistent and viable realizations of the nonminimal coupling. furthermore, we consider several cosmological applications by presenting the evolution equations and imposing specific functional forms of the functions f1(q ) and f2(q ), such as power-law and exponential dependencies of the nonminimal couplings. cosmological solutions are considered in two general classes of models, and found to feature accelerating expansion at late times. | coupling matter in modified q gravity |
we present constraints on the masses of extremely light bosons dubbed fuzzy dark matter (fdm) from lyman-α forest data. extremely light bosons with a de broglie wavelength of ∼1 kpc have been suggested as dark matter candidates that may resolve some of the current small scale problems of the cold dark matter model. for the first time, we use hydrodynamical simulations to model the lyman-α flux power spectrum in these models and compare it to the observed flux power spectrum from two different data sets: the xq-100 and hires/mike quasar spectra samples. after marginalization over nuisance and physical parameters and with conservative assumptions for the thermal history of the intergalactic medium (igm) that allow for jumps in the temperature of up to 5000 k, xq-100 provides a lower limit of 7.1 ×10-22 ev , hires/mike returns a stronger limit of 14.3 ×10-22 ev , while the combination of both data sets results in a limit of 20 ×10-22 ev (2 σ c.l.). the limits for the analysis of the combined data sets increases to 37.5 ×10-22 ev (2 σ c.l.) when a smoother thermal history is assumed where the temperature of the igm evolves as a power law in redshift. light boson masses in the range 1 - 10 ×10-22 ev are ruled out at high significance by our analysis, casting strong doubts that fdm helps solve the "small scale crisis" of the cold dark matter models. | first constraints on fuzzy dark matter from lyman-α forest data and hydrodynamical simulations |
several pulsar timing array (pta) collaborations, including nanograv, epta, ppta, and cpta, have announced the evidence for a stochastic signal consistent with a stochastic gravitational wave background (sgwb). supermassive black hole binaries (smbhbs) are supposed to be the most promising gravitational-wave (gw) sources for this signal. in this paper, we use the nanograv 15-year data set to constrain the parameter space in an astro-informed formation model for smbhbs. our results prefer a large turn-over eccentricity of the smbhb orbit when gws begin to dominate the smbhb evolution. furthermore, the sgwb spectrum is extrapolated to the space-borne gw detector frequency band by including inspiral-merge-cutoff phases of smbhbs, indicating that the sgwb from smbhbs should be detected by lisa, taiji and tianqin in the near future. | implications for the supermassive black hole binaries from the nanograv 15-year data set |
if even a relatively small number of black holes were created in the early universe, they will constitute an increasingly large fraction of the total energy density as space expands. it is thus well-motivated to consider scenarios in which the early universe included an era in which primordial black holes dominated the total energy density. within this context, we consider hawking radiation as a mechanism to produce both dark radiation and dark matter. if the early universe included a black hole dominated era, we find that hawking radiation will produce dark radiation at a level δ n eff ∼ 0 .03 - 0 .2 for each light and decoupled species of spin 0, 1/2, or 1. this range is well suited to relax the tension between late and early-time hubble determinations, and is within the reach of upcoming cmb experiments. the dark matter could also originate as hawking radiation in a black hole dominated early universe, although such dark matter candidates must be very heavy ( m dm ≳ 1011 gev) if they are to avoid exceeding the measured abundance. | dark radiation and superheavy dark matter from black hole domination |
we present evidence for a suppressed growth rate of large-scale structure during the dark-energy-dominated era. modeling the growth rate of perturbations with the "growth index" γ , we find that current cosmological data strongly prefer a higher growth index than the value γ =0.55 predicted by general relativity in a flat lambda cold dark matter cosmology. both the cosmic microwave background data from planck and the large-scale structure data from weak lensing, galaxy clustering, and cosmic velocities separately favor growth suppression. when combined, they yield γ =0.63 3-0.024+0.025 , excluding γ =0.55 at a statistical significance of 3.7 σ . the combination of f σ8 and planck measurements prefers an even higher growth index of γ =0.63 9-0.025+0.024, corresponding to a 4.2 σ tension with the concordance model. in planck data, the suppressed growth rate offsets the preference for nonzero curvature and fits the data equally well as the latter model. a higher γ leads to a higher matter fluctuation amplitude s8 inferred from galaxy clustering and weak lensing measurements, and a lower s8 from planck data, effectively resolving the s8 tension. | evidence for suppression of structure growth in the concordance cosmological model |
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