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we report a new search of weakly interacting massive particles (wimps) using the combined low background data sets in 2016 and 2017 from the pandax-ii experiment in china. the latest data set contains a new exposure of 77.1 live day, with the background reduced to a level of 0.8$\times10^{-3}$ evt/kg/day, improved by a factor of 2.5 in comparison to the previous run in 2016. no excess events were found above the expected background. with a total exposure of 5.4$\times10^4$ kg day, the most stringent upper limit on spin-independent wimp-nucleon cross section was set for a wimp with mass larger than 100 gev/c$^2$, with the lowest exclusion at 8.6$\times10^{-47}$ cm$^2$ at 40 gev/c$^2$. | dark matter results from 54-ton-day exposure of pandax-ii experiment |
the very large array sky survey (vlass) is a synoptic, all-sky radio sky survey with a unique combination of high angular resolution (≈2"5), sensitivity (a 1σ goal of 70 μjy/beam in the coadded data), full linear stokes polarimetry, time domain coverage, and wide bandwidth (2-4 ghz). the first observations began in 2017 september, and observing for the survey will finish in 2024. vlass will use approximately 5500 hr of time on the karl g. jansky very large array (vla) to cover the whole sky visible to the vla (decl. > -40°), a total of 33 885 deg 2 . the data will be taken in three epochs to allow the discovery of variable and transient radio sources. the survey is designed to engage radio astronomy experts, multi-wavelength astronomers, and citizen scientists alike. by utilizing an "on the fly" interferometry mode, the observing overheads are much reduced compared to a conventional pointed survey. in this paper, we present the science case and observational strategy for the survey, and also results from early survey observations. | the karl g. jansky very large array sky survey (vlass). science case and survey design |
recent measurements of the cosmic microwave background (cmb) anisotropies by planck provide a sensitive probe of dark matter annihilation during the cosmic dark ages, and specifically constrain the annihilation parameter feff⟨σ v ⟩/mχ. using new results (paper ii) for the ionization produced by particles injected at arbitrary energies, we calculate and provide feff values for photons and e+e- pairs injected at kev-tev energies; the feff value for any dark matter model can be obtained straightforwardly by weighting these results by the spectrum of annihilation products. this result allows the sensitive and robust constraints on dark matter annihilation presented by the planck collaboration to be applied to arbitrary dark matter models with s -wave annihilation. we demonstrate the validity of this approach using principal component analysis. as an example, we integrate over the spectrum of annihilation products for a range of standard model final states to determine the cmb bounds on these models as a function of dark matter mass, and demonstrate that the new limits generically exclude models proposed to explain the observed high-energy rise in the cosmic ray positron fraction. we make our results publicly available at http://nebel.rc.fas.harvard.edu/epsilon. | indirect dark matter signatures in the cosmic dark ages. i. generalizing the bound on s -wave dark matter annihilation from planck results |
we measure cosmic weak lensing shear power spectra with the subaru hyper suprime-cam (hsc) survey first-year shear catalog covering 137 deg2 of the sky. thanks to the high effective galaxy number density of ∼17 arcmin-2, even after conservative cuts such as a magnitude cut of i < 24.5 and photometric redshift cut of 0.3 ≤ z ≤ 1.5, we obtain a high-significance measurement of the cosmic shear power spectra in four tomographic redshift bins, achieving a total signal-to-noise ratio of 16 in the multipole range 300 ≤ ℓ ≤ 1900. we carefully account for various uncertainties in our analysis including the intrinsic alignment of galaxies, scatters and biases in photometric redshifts, residual uncertainties in the shear measurement, and modeling of the matter power spectrum. the accuracy of our power spectrum measurement method as well as our analytic model of the covariance matrix are tested against realistic mock shear catalogs. for a flat λ cold dark matter model, we find s 8≡ σ _8(ω _m/0.3)^α =0.800^{+0.029}_{-0.028} for α = 0.45 (s _8=0.780^{+0.030}_{-0.033} for α = 0.5) from our hsc tomographic cosmic shear analysis alone. in comparison with planck cosmic microwave background constraints, our results prefer slightly lower values of s8, although metrics such as the bayesian evidence ratio test do not show significant evidence for discordance between these results. we study the effect of possible additional systematic errors that are unaccounted for in our fiducial cosmic shear analysis, and find that they can shift the best-fit values of s8 by up to ∼0.6 σ in both directions. the full hsc survey data will contain several times more area, and will lead to significantly improved cosmological constraints. | cosmology from cosmic shear power spectra with subaru hyper suprime-cam first-year data |
local determinations of the hubble constant h0 favor a higher value than planck based on cosmic microwave background and λ cold dark matter (λ cdm ). through a model-independent expansion, we show that low redshift (z ≲0.7 ) data comprising baryon acoustic oscillations, cosmic chronometers, and type ia supernovae have a preference for quintessence models that lower h0 relative to λ cdm . in addition, we confirm that an exponential coupling to dark matter cannot alter this conclusion in the same redshift range. our results leave open the possibility that a coupling in the matter-dominated epoch, potentially even in the dark ages, may yet save h0 from sinking in the string theory swampland. | hubble sinks in the low-redshift swampland |
more than three-quarters of the baryonic content of the universe resides in a highly diffuse state that is difficult to detect, with only a small fraction directly observed in galaxies and galaxy clusters1,2. censuses of the nearby universe have used absorption line spectroscopy3,4 to observe the `invisible' baryons, but these measurements rely on large and uncertain corrections and are insensitive to most of the universe's volume and probably most of its mass. in particular, quasar spectroscopy is sensitive either to the very small amounts of hydrogen that exist in the atomic state, or to highly ionized and enriched gas4-6 in denser regions near galaxies7. other techniques to observe these invisible baryons also have limitations; sunyaev-zel'dovich analyses8,9 can provide evidence from gas within filamentary structures, and studies of x-ray emission are most sensitive to gas near galaxy clusters9,10. here we report a measurement of the baryon content of the universe using the dispersion of a sample of localized fast radio bursts; this technique determines the electron column density along each line of sight and accounts for every ionized baryon11-13. we augment the sample of reported arcsecond-localized14-18 fast radio bursts with four new localizations in host galaxies that have measured redshifts of 0.291, 0.118, 0.378 and 0.522. this completes a sample sufficiently large to account for dispersion variations along the lines of sight and in the host-galaxy environments11, and we derive a cosmic baryon density of ωb=0.051-0.025+0.021h70-1? (95 per cent confidence; h70 = h0/(70 km s-1 mpc-1) and h0 is hubble's constant). this independent measurement is consistent with values derived from the cosmic microwave background and from big bang nucleosynthesis19,20. | a census of baryons in the universe from localized fast radio bursts |
we present the first full release of a survey of the 150 mhz radio sky, observed with the giant metrewave radio telescope (gmrt) between april 2010 and march 2012 as part of the tifr gmrt sky survey (tgss) project. aimed at producing a reliable compact source survey, our automated data reduction pipeline efficiently processed more than 2000 h of observations with minimal human interaction. through application of innovative techniques such as image-based flagging, direction-dependent calibration of ionospheric phase errors, correcting for systematic offsets in antenna pointing, and improving the primary beam model, we created good quality images for over 95 percent of the 5336 pointings. our data release covers 36 900 deg2 (or 3.6 π steradians) of the sky between -53° and +90° declination (dec), which is 90 percent of the total sky. the majority of pointing images have a noise level below 5 mjy beam-1 with an approximate resolution of 25''×25'' (or 25''×25''/ cos(dec-19°) for pointings south of 19° declination). we have produced a catalog of 0.62 million radio sources derived from an initial, high reliability source extraction at the seven sigma level. for the bulk of the survey, the measured overall astrometric accuracy is better than two arcseconds in right ascension and declination, while the flux density accuracy is estimated at approximately ten percent. within the scope of the tgss alternative data release (tgss adr) project, the source catalog, as well as 5336 mosaic images (5°×5°) and an image cutout service, are made publicly available at the cds as a service to the astronomical community. next to enabling a wide range of different scientific investigations, we anticipate that these survey products will provide a solid reference for various new low-frequency radio aperture array telescopes (lofar, lwa, mwa, ska-low), and can play an important role in characterizing the epoch-of-reionisation (eor) foreground. the tgss adr project aims at continuously improving the quality of the survey data products. near-future improvements include replacement of bright source snapshot images with archival targeted observations, using new observations to fill the holes in sky coverage and replace very poor quality observational data, and an improved flux calibration strategy for less severely affected observational data. 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/a78 | the gmrt 150 mhz all-sky radio survey. first alternative data release tgss adr1 |
cosmic inflation provides a window to the highest energy densities accessible in nature, far beyond those achievable in any realistic terrestrial experiment. theoretical insights into the inflationary era and its observational probes may therefore shed unique light on the physical laws underlying our universe. this white paper describes our current theoretical understanding of the inflationary era, with a focus on the statistical properties of primordial fluctuations. in particular, we survey observational targets for three important signatures of inflation: primordial gravitational waves, primordial non-gaussianity and primordial features. with the requisite advancements in analysis techniques, the tremendous increase in the raw sensitivities of upcoming and planned surveys will translate to leaps in our understanding of the inflationary paradigm and could open new frontiers for cosmology and particle physics. the combination of future theoretical and observational developments therefore offer the potential for a dramatic discovery about the nature of cosmic acceleration in the very early universe and physics on the smallest scales. | inflation: theory and observations |
we present results from the search for a stochastic gravitational-wave background (gwb) as predicted by the theory of general relativity using six radio millisecond pulsars from the data release 2 (dr2) of the european pulsar timing array (epta) covering a timespan up to 24 yr. a gwb manifests itself as a long-term low-frequency stochastic signal common to all pulsars, a common red signal (crs), with the characteristic hellings-downs (hd) spatial correlation. our analysis is performed with two independent pipelines, enterprise, and temponest+fortytwo, which produce consistent results. a search for a crs with simultaneous estimation of its spatial correlations yields spectral properties compatible with theoretical gwb predictions, but does not result in the required measurement of the hd correlation, as required for gwb detection. further bayesian model comparison between different types of crss, including a gwb, finds the most favoured model to be the common uncorrelated red noise described by a power law with $a = 5.13_{-2.73}^{+4.20} \times 10^{-15}$ and $\gamma = 3.78_{-0.59}^{+0.69}$ (95 per cent credible regions). fixing the spectral index to γ = 13/3 as expected from the gwb by circular, inspiralling supermassive black hole binaries results in an amplitude of $a =2.95_{-0.72}^{+0.89} \times 10^{-15}$. we implement three different models, bayesephem, linimoss, and ephemgp, to address possible solar system ephemeris (sse) systematics and conclude that our results may only marginally depend on these effects. this work builds on the methods and models from the studies on the epta dr1. we show that under the same analysis framework the results remain consistent after the data set extension. | common-red-signal analysis with 24-yr high-precision timing of the european pulsar timing array: inferences in the stochastic gravitational-wave background search |
in this data release from the ongoing low-frequency array (lofar) two-metre sky survey we present 120-168 mhz images covering 27% of the northern sky. our coverage is split into two regions centred at approximately 12h45m +44°30' and 1h00m +28°00' and spanning 4178 and 1457 square degrees respectively. the images were derived from 3451 h (7.6 pb) of lofar high band antenna data which were corrected for the direction-independent instrumental properties as well as direction-dependent ionospheric distortions during extensive, but fully automated, data processing. a catalogue of 4 396 228 radio sources is derived from our total intensity (stokes i) maps, where the majority of these have never been detected at radio wavelengths before. at 6″ resolution, our full bandwidth stokes i continuum maps with a central frequency of 144 mhz have: a median rms sensitivity of 83 μjy beam−1; a flux density scale accuracy of approximately 10%; an astrometric accuracy of 0.2″; and we estimate the point-source completeness to be 90% at a peak brightness of 0.8 mjy beam−1. by creating three 16 mhz bandwidth images across the band we are able to measure the in-band spectral index of many sources, albeit with an error on the derived spectral index of > ± 0.2 which is a consequence of our flux-density scale accuracy and small fractional bandwidth. our circular polarisation (stokes v) 20″ resolution 120-168 mhz continuum images have a median rms sensitivity of 95 μjy beam−1, and we estimate a stokes i to stokes v leakage of 0.056%. our linear polarisation (stokes q and stokes u) image cubes consist of 480 × 97.6 khz wide planes and have a median rms sensitivity per plane of 10.8 mjy beam−1 at 4' and 2.2 mjy beam−1 at 20″; we estimate the stokes i to stokes q/u leakage to be approximately 0.2%. here we characterise and publicly release our stokes i, q, u and v images in addition to the calibrated uv-data to facilitate the thorough scientific exploitation of this unique dataset. the source catalogue is also available at the cds via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/j/a+a/659/a1 | the lofar two-metre sky survey. v. second data release |
this work and its companion paper, amon et al. [phys. rev. d 105, 023514 (2022), 10.1103/physrevd.105.023514], present cosmic shear measurements and cosmological constraints from over 100 million source galaxies in the dark energy survey (des) year 3 data. we constrain the lensing amplitude parameter s8≡σ8√{ωm/0.3 } at the 3% level in λ cdm : s8=0.75 9-0.023+0.025 (68% cl). our constraint is at the 2% level when using angular scale cuts that are optimized for the λ cdm analysis: s8=0.77 2-0.017+0.018 (68% cl). with cosmic shear alone, we find no statistically significant constraint on the dark energy equation-of-state parameter at our present statistical power. we carry out our analysis blind, and compare our measurement with constraints from two other contemporary weak lensing experiments: the kilo-degree survey (kids) and hyper-suprime camera subaru strategic program (hsc). we additionally quantify the agreement between our data and external constraints from the cosmic microwave background (cmb). our des y3 result under the assumption of λ cdm is found to be in statistical agreement with planck 2018, although favors a lower s8 than the cmb-inferred value by 2.3 σ (a p -value of 0.02). this paper explores the robustness of these cosmic shear results to modeling of intrinsic alignments, the matter power spectrum and baryonic physics. we additionally explore the statistical preference of our data for intrinsic alignment models of different complexity. the fiducial cosmic shear model is tested using synthetic data, and we report no biases greater than 0.3 σ in the plane of s8×ωm caused by uncertainties in the theoretical models. | dark energy survey year 3 results: cosmology from cosmic shear and robustness to modeling uncertainty |
much of the structure of cosmological correlators is controlled by their singularities, which in turn are fixed in terms of flat-space scattering amplitudes. an important challenge is to interpolate between the singular limits to determine the full correlators at arbitrary kinematics. this is particularly relevant because the singularities of correlators are not directly observable, but can only be accessed by analytic continuation. in this paper, we study rational correlators — including those of gauge fields, gravitons, and the inflaton — whose only singularities at tree level are poles and whose behavior away from these poles is strongly constrained by unitarity and locality. we describe how unitarity translates into a set of cutting rules that consistent correlators must satisfy, and explain how this can be used to bootstrap correlators given information about their singularities. we also derive recursion relations that allow the iterative construction of more complicated correlators from simpler building blocks. in flat space, all energy singularities are simple poles, so that the combination of unitarity constraints and recursion relations provides an efficient way to bootstrap the full correlators. in many cases, these flat-space correlators can then be transformed into their more complex de sitter counterparts. as an example of this procedure, we derive the correlator associated to graviton compton scattering in de sitter space, though the methods are much more widely applicable. | linking the singularities of cosmological correlators |
we show that the seesaw mechanisms that exhibit right-handed neutrino mass-dependent nonstandard postinflationary cosmology make blue-tilted inflationary gravitational waves (gws) compatible with the recent findings of nanohertz stochastic gw background by the pulsar-timing arrays (ptas) for high reheating temperatures. the right-handed neutrino (rhn) mass scale has to be o (gev ) . remarkably, such a scenario produces a correlated signature testable by the future ligo run. in addition to contributing to the active neutrino masses, o (gev ) rhns generate baryon asymmetry of the universe via low scale leptogenesis. they can be searched for in collider experiments. therefore, the recent detection by ptas is not only exciting for gws in the nanohertz range, it paves the way to test and constrain well-studied mechanisms, such as seesaws, with a low frequency and a correlated measurement of high-frequency gw spectral features, complementary to particle physics searches. | fingerprints of gev scale right-handed neutrinos on inflationary gravitational waves and pta data |
we provide a review on the state-of-the-art of gravitational waves induced by primordial fluctuations, so-called induced gravitational waves. we present the intuitive physics behind induced gravitational waves and we revisit and unify the general analytical formulation. we then present general formulas in a compact form, ready to be applied. this review places emphasis on the open possibility that the primordial universe experienced a different expansion history than the often assumed radiation dominated cosmology. we hope that anyone interested in the topic will become aware of current advances in the cosmology of induced gravitational waves, as well as becoming familiar with the calculations behind. | scalar induced gravitational waves review |
we present the first event-horizon-scale images and spatiotemporal analysis of sgr a* taken with the event horizon telescope in 2017 april at a wavelength of 1.3 mm. imaging of sgr a* has been conducted through surveys over a wide range of imaging assumptions using the classical clean algorithm, regularized maximum likelihood methods, and a bayesian posterior sampling method. different prescriptions have been used to account for scattering effects by the interstellar medium toward the galactic center. mitigation of the rapid intraday variability that characterizes sgr a* has been carried out through the addition of a "variability noise budget" in the observed visibilities, facilitating the reconstruction of static full-track images. our static reconstructions of sgr a* can be clustered into four representative morphologies that correspond to ring images with three different azimuthal brightness distributions and a small cluster that contains diverse nonring morphologies. based on our extensive analysis of the effects of sparse (u, v)-coverage, source variability, and interstellar scattering, as well as studies of simulated visibility data, we conclude that the event horizon telescope sgr a* data show compelling evidence for an image that is dominated by a bright ring of emission with a ring diameter of ~50 μas, consistent with the expected "shadow" of a 4 × 106 m ⊙ black hole in the galactic center located at a distance of 8 kpc. | first sagittarius a* event horizon telescope results. iii. imaging of the galactic center supermassive black hole |
atmospheric aerosols and their effect on clouds are thought to be important for anthropogenic radiative forcing of the climate, yet remain poorly understood. globally, around half of cloud condensation nuclei originate from nucleation of atmospheric vapours. it is thought that sulfuric acid is essential to initiate most particle formation in the atmosphere, and that ions have a relatively minor role. some laboratory studies, however, have reported organic particle formation without the intentional addition of sulfuric acid, although contamination could not be excluded. here we present evidence for the formation of aerosol particles from highly oxidized biogenic vapours in the absence of sulfuric acid in a large chamber under atmospheric conditions. the highly oxygenated molecules (homs) are produced by ozonolysis of α-pinene. we find that ions from galactic cosmic rays increase the nucleation rate by one to two orders of magnitude compared with neutral nucleation. our experimental findings are supported by quantum chemical calculations of the cluster binding energies of representative homs. ion-induced nucleation of pure organic particles constitutes a potentially widespread source of aerosol particles in terrestrial environments with low sulfuric acid pollution. | ion-induced nucleation of pure biogenic particles |
1. inflation: theory and observations; 2. inflation in effective field theory; 3. elements of string theory; 4. what is string inflation?; 5. examples of string inflation; 6. conclusions and outlook; appendix a. mathematical preliminaries; appendix b. the effective theory of inflation; appendix c. primordial perturbations from inflation. | inflation and string theory |
we use 26 ×106 galaxies from the dark energy survey (des) year 1 shape catalogs over 1321 deg2 of the sky to produce the most significant measurement of cosmic shear in a galaxy survey to date. we constrain cosmological parameters in both the flat λ cdm and the w cdm models, while also varying the neutrino mass density. these results are shown to be robust using two independent shape catalogs, two independent photo-z calibration methods, and two independent analysis pipelines in a blind analysis. we find a 3.5% fractional uncertainty on σ8(ωm/0.3 )0.5=0.78 2-0.027+0.027 at 68% c.l., which is a factor of 2.5 improvement over the fractional constraining power of our des science verification results. in w cdm , we find a 4.8% fractional uncertainty on σ8(ωm/0.3 )0.5=0.77 7-0.038+0.036 and a dark energy equation-of-state w =-0.9 5-0.39+0.33. we find results that are consistent with previous cosmic shear constraints in σ8—ωm, and we see no evidence for disagreement of our weak lensing data with data from the cosmic microwave background. finally, we find no evidence preferring a w cdm model allowing w ≠-1 . we expect further significant improvements with subsequent years of des data, which will more than triple the sky coverage of our shape catalogs and double the effective integrated exposure time per galaxy. | dark energy survey year 1 results: cosmological constraints from cosmic shear |
the recent planck legacy 2018 release has confirmed the presence of an enhanced lensing amplitude in cosmic microwave background power spectra compared with that predicted in the standard λ cold dark matter model, where λ is the cosmological constant. a closed universe can provide a physical explanation for this effect, with the planck cosmic microwave background spectra now preferring a positive curvature at more than the 99% confidence level. here, we further investigate the evidence for a closed universe from planck, showing that positive curvature naturally explains the anomalous lensing amplitude, and demonstrating that it also removes a well-known tension in the planck dataset concerning the values of cosmological parameters derived at different angular scales. we show that since the planck power spectra prefer a closed universe, discordances higher than generally estimated arise for most of the local cosmological observables, including baryon acoustic oscillations. the assumption of a flat universe could therefore mask a cosmological crisis where disparate observed properties of the universe appear to be mutually inconsistent. future measurements are needed to clarify whether the observed discordances are due to undetected systematics, or to new physics or simply are a statistical fluctuation. | planck evidence for a closed universe and a possible crisis for cosmology |
the planck full mission cosmic microwave background (cmb) temperature and e-mode polarization maps are analysed to obtain constraints on primordial non-gaussianity (ng). using three classes of optimal bispectrum estimators - separable template-fitting (ksw), binned, and modal - we obtain consistent values for the primordial local, equilateral, and orthogonal bispectrum amplitudes, quoting as our final result from temperature alone ƒlocalnl = 2.5 ± 5.7, ƒequilnl= -16 ± 70, , and ƒorthonl = -34 ± 32 (68% cl, statistical). combining temperature and polarization data we obtain ƒlocalnl = 0.8 ± 5.0, ƒequilnl= -4 ± 43, and ƒorthonl = -26 ± 21 (68% cl, statistical). the results are based on comprehensive cross-validation of these estimators on gaussian and non-gaussian simulations, are stable across component separation techniques, pass an extensive suite of tests, and are consistent with estimators based on measuring the minkowski functionals of the cmb. the effect of time-domain de-glitching systematics on the bispectrum is negligible. in spite of these test outcomes we conservatively label the results including polarization data as preliminary, owing to a known mismatch of the noise model in simulations and the data. beyond estimates of individual shape amplitudes, we present model-independent, three-dimensional reconstructions of the planck cmb bispectrum and derive constraints on early universe scenarios that generate primordial ng, including general single-field models of inflation, axion inflation, initial state modifications, models producing parity-violating tensor bispectra, and directionally dependent vector models. we present a wide survey of scale-dependent feature and resonance models, accounting for the "look elsewhere" effect in estimating the statistical significance of features. we also look for isocurvature ng, and find no signal, but we obtain constraints that improve significantly with the inclusion of polarization. the primordial trispectrum amplitude in the local model is constrained to be 𝓰localnl = (-0.9 ± 7.7 ) x 104(68% cl statistical), and we perform an analysis of trispectrum shapes beyond the local case. the global picture that emerges is one of consistency with the premises of the λcdm cosmology, namely that the structure we observe today was sourced by adiabatic, passive, gaussian, and primordial seed perturbations. | planck 2015 results. xvii. constraints on primordial non-gaussianity |
cosmological first-order phase transitions (1stopts) are said to be strongly supercooled when the nucleation temperature is much smaller than the critical temperature. these are often encountered in theories that admit a nearly scale-invariant potential, for which the bounce action decreases only logarithmically with temperature. during supercooled 1stopts the equation of state of the universe undergoes a rapid and drastic change, transitioning from vacuum-domination to radiation-domination. the statistical variations in bubble nucleation histories imply that distinct causal patches percolate at slightly different times. patches which percolate the latest undergo the longest vacuum-domination stage and as a consequence develop large over-densities triggering their collapse into primordial black holes (pbhs). we derive an analytical approximation for the probability of a patch to collapse into a pbh as a function of the 1stopt duration, $\beta^{-1}$, and deduce the expected pbh abundance. we find that 1stopts which take more than $12\%$ of a hubble time to complete ($\beta/h \lesssim 8$) produce observable pbhs. their abundance is independent of the duration of the supercooling phase, in agreement with the de sitter no hair conjecture. | primordial black holes from supercooled phase transitions |
we investigate the potential for the elisa space-based interferometer to detect the stochastic gravitational wave background produced by strong first-order cosmological phase transitions. we discuss the resulting contributions from bubble collisions, magnetohydrodynamic turbulence, and sound waves to the stochastic background, and estimate the total corresponding signal predicted in gravitational waves. the projected sensitivity of elisa to cosmological phase transitions is computed in a model-independent way for various detector designs and configurations. by applying these results to several specific models, we demonstrate that elisa is able to probe many well-motivated scenarios beyond the standard model of particle physics predicting strong first-order cosmological phase transitions in the early universe. | science with the space-based interferometer elisa. ii: gravitational waves from cosmological phase transitions |
direct dark matter detection experiments based on a liquid xenon target are leading the search for dark matter particles with masses above ∼5 gev /c2, but have limited sensitivity to lighter masses because of the small momentum transfer in dark matter-nucleus elastic scattering. however, there is an irreducible contribution from inelastic processes accompanying the elastic scattering, which leads to the excitation and ionization of the recoiling atom (the migdal effect) or the emission of a bremsstrahlung photon. in this letter, we report on a probe of low-mass dark matter with masses down to about 85 mev /c2 by looking for electronic recoils induced by the migdal effect and bremsstrahlung using data from the xenon1t experiment. besides the approach of detecting both scintillation and ionization signals, we exploit an approach that uses ionization signals only, which allows for a lower detection threshold. this analysis significantly enhances the sensitivity of xenon1t to light dark matter previously beyond its reach. | search for light dark matter interactions enhanced by the migdal effect or bremsstrahlung in xenon1t |
we study the fundamentals of quantum field theory on a rigid de sitter space. we show that the perturbative expansion of late-time correlation functions to all orders can be equivalently generated by a non-unitary lagrangian on a euclidean ads geometry. this finding simplifies dramatically perturbative computations, as well as allows us to establish basic properties of these correlators, which comprise a euclidean cft. we use this to infer the analytic structure of the spectral density that captures the conformal partial wave expansion of a late-time four-point function, to derive an ope expansion, and to constrain the operator spectrum. generically, dimensions and ope coefficients do not obey the usual cft notion of unitarity. instead, unitarity of the de sitter theory manifests itself as the positivity of the spectral density. this statement does not rely on the use of euclidean ads lagrangians and holds non-perturbatively. we illustrate and check these properties by explicit calculations in a scalar theory by computing first tree-level, and then full one- loop-resummed exchange diagrams. an exchanged particle appears as a resonant feature in the spectral density which can be potentially useful in experimental searches. | analyticity and unitarity for cosmological correlators |
the strong discrepancy between local and early-time (inverse distance ladder) estimates of the hubble constant h0 could be pointing towards new physics beyond the concordance λ cdm model. several attempts to address this tension through new physics rely on extended cosmological models, featuring extra free parameters beyond the six λ cdm parameters. however, marginalizing over additional parameters has the effect of broadening the uncertainties on the inferred parameters (including h0), and it is often the case that within these models the h0 tension is addressed due to larger uncertainties rather than a genuine shift in the central value of h0. in this paper i consider an alternative viewpoint: what happens if a physical theory is able to fix the extra parameters to a specific set of nonstandard values? in this case, the degrees of freedom of the model are reduced with respect to the standard case where the extra parameters are free to vary. focusing on the dark energy equation of state w and the effective number of relativistic species neff, i find that physical theories able to fix w ≈-1.3 or neff≈3.95 would lead to an estimate of h0 from cosmic microwave background, baryon acoustic oscillation, and type ia supernovae data in perfect agreement with the local distance ladder estimate, without broadening the uncertainty on the former. these two nonstandard models are, from a model-selection perspective, strongly disfavored with respect to the baseline λ cdm model. however, models that predict neff≈3.45 would be able to bring the tension down to 1.5 σ while only being weakly disfavored with respect to λ cdm , whereas models that predict w ≈-1.1 would be able to bring the tension down to 2 σ (at the cost of the preference for λ cdm being definite). finally, i estimate dimensionless multipliers relating variations in h0 to variations in w and neff, which can be used to swiftly repeat the analysis of this paper in light of future more precise local distance ladder estimates of h0, should the tension persist. as a caveat, these results were obtained from the 2015 planck data release, but these findings would be qualitatively largely unaffected were i to use more recent data. | new physics in light of the h0 tension: an alternative view |
in the light of the evidence of a gravitational wave background from the nanograv 15yr data set, we reconsider the split majoron model as a new physics extension of the standard model able to generate a needed contribution to solve the current tension between the data and the standard interpretation in terms of inspiraling supermassive black hole massive binaries. in the split majoron model the seesaw right-handed neutrinos acquire majorana masses from spontaneous symmetry breaking of global $u(1)_{b-l}$ in a strong first order phase transition of a complex scalar field occurring above the electroweak scale. the final vacuum expectation value couples to a second complex scalar field undergoing a low scale phase transition occurring after neutrino decoupling. such a coupling enhances the strength of this second low scale first order phase transition and can generate a sizeable primordial gravitational wave background contributing to the nanograv 15yr signal. some amount of extra-radiation is generated after neutron-to-proton ration freeze-out but prior to nucleosynthesis. this can be either made compatible with current upper bound from primordial deuterium measurements or even be used to solve a potential deuterium problem. moreover, the free streaming length of light neutrinos can be suppressed by their interactions with the resulting majoron background and this mildly ameliorates existing cosmological tensions. thus cosmological observations nicely provide independent motivations for the model. | the split majoron model confronts the nanograv signal |
we discuss the ability of a dark fluid becoming relevant around the time of matter-radiation equality to significantly relieve the tension between local measurements of the hubble constant and cosmic microwave background (cmb) inference, within the λ cdm model. we show that the gravitational impact of acoustic oscillations in the dark fluid balance the effects on the cmb and result in an improved fit to cmb measurements themselves while simultaneously raising the hubble constant. the required balance favors a model where the fluid is a scalar field that converts its potential to kinetic energy around matter-radiation equality, which then quickly redshifts away. we derive the requirements on the potential for this conversion mechanism and find that a simple canonical scalar with two free parameters for its local slope and amplitude robustly improves the fit to the combined data by δ χ2≈12.7 over λ cdm . we uncover the cmb polarization signatures that can definitively test this scenario with future data. | acoustic dark energy: potential conversion of the hubble tension |
the data recently released by the north american nanohertz observatory for gravitational waves provides compelling evidence supporting the existence of a stochastic signal that aligns with a gravitational-wave background. we show this signal can be the scalar-induced gravitational waves from the higgs inflation model with the parametric amplification mechanism. such a gravitational-wave background naturally predicts the substantial existence of planet-mass primordial black holes, which can be planet 9 in our solar system and the lensing objects for the ultrashort-timescale microlensing events observed by the optical gravitational lensing experiment. the future observations of stochastic gravitational wave background by pulsar timing arrays and planet-mass primordial black holes provide such a possibility to give further confirmations on higgs inflation, which unifies two fundamental aspects of theoretical physics, particle physics and cosmology. | exploring the nanograv signal and planet-mass primordial black holes through higgs inflation |
we present two new lagrangian methods for hydrodynamics, in a systematic comparison with moving-mesh, smoothed particle hydrodynamics (sph), and stationary (non-moving) grid methods. the new methods are designed to simultaneously capture advantages of both sph and grid-based/adaptive mesh refinement (amr) schemes. they are based on a kernel discretization of the volume coupled to a high-order matrix gradient estimator and a riemann solver acting over the volume `overlap'. we implement and test a parallel, second-order version of the method with self-gravity and cosmological integration, in the code gizmo:1 this maintains exact mass, energy and momentum conservation; exhibits superior angular momentum conservation compared to all other methods we study; does not require `artificial diffusion' terms; and allows the fluid elements to move with the flow, so resolution is automatically adaptive. we consider a large suite of test problems, and find that on all problems the new methods appear competitive with moving-mesh schemes, with some advantages (particularly in angular momentum conservation), at the cost of enhanced noise. the new methods have many advantages versus sph: proper convergence, good capturing of fluid-mixing instabilities, dramatically reduced `particle noise' and numerical viscosity, more accurate sub-sonic flow evolution, and sharp shock-capturing. advantages versus non-moving meshes include: automatic adaptivity, dramatically reduced advection errors and numerical overmixing, velocity-independent errors, accurate coupling to gravity, good angular momentum conservation and elimination of `grid alignment' effects. we can, for example, follow hundreds of orbits of gaseous discs, while amr and sph methods break down in a few orbits. however, fixed meshes minimize `grid noise'. these differences are important for a range of astrophysical problems. | a new class of accurate, mesh-free hydrodynamic simulation methods |
all attempts to directly detect particle dark matter (dm) scattering on nuclei suffer from the partial or total loss of sensitivity for dm masses in the gev range or below. we derive novel constraints from the inevitable existence of a subdominant, but highly energetic, component of dm generated through collisions with cosmic rays. subsequent scattering inside conventional dm detectors, as well as neutrino detectors sensitive to nuclear recoils, limits the dm-nucleon scattering cross section to be below 10-31 cm2 for both spin-independent and spin-dependent scattering of light dm. | novel direct detection constraints on light dark matter |
we present cluster counts and corresponding cosmological constraints from the planck full mission data set. our catalogue consists of 439 clusters detected via their sunyaev-zeldovich (sz) signal down to a signal-to-noise ratio of 6, and is more than a factor of 2 larger than the 2013 planck cluster cosmology sample. the counts are consistent with those from 2013 and yield compatible constraints under the same modelling assumptions. taking advantage of the larger catalogue, we extend our analysis to the two-dimensional distribution in redshift and signal-to-noise. we use mass estimates from two recent studies of gravitational lensing of background galaxies by planck clusters to provide priors on the hydrostatic bias parameter, (1-b). in addition, we use lensing of cosmic microwave background (cmb) temperature fluctuations by planck clusters as an independent constraint on this parameter. these various calibrations imply constraints on the present-day amplitude of matter fluctuations in varying degrees of tension with those from the planck analysis of primary fluctuations in the cmb; for the lowest estimated values of (1-b) the tension is mild, only a little over one standard deviation, while it remains substantial (3.7σ) for the largest estimated value. we also examine constraints on extensions to the base flat λcdm model by combining the cluster and cmb constraints. the combination appears to favour non-minimal neutrino masses, but this possibility does little to relieve the overall tension because it simultaneously lowers the implied value of the hubble parameter, thereby exacerbating the discrepancy with most current astrophysical estimates. improving the precision of cluster mass calibrations from the current 10%-level to 1% would significantly strengthen these combined analyses and provide a stringent test of the base λcdm model. | planck 2015 results. xxiv. cosmology from sunyaev-zeldovich cluster counts |
we investigate the explicit role of negative local non-gaussianity, $f_{\rm nl}$, in suppressing the abundance of primordial black holes (pbhs) in the single-field model of galileon inflation. pbh formation requires significantly enhancing the scalar power spectrum, which greatly affects their abundance. the associated frequencies in the nhz regime are also sensitive to the generation of scalar-induced gravitational waves (sigws) which may explain the current data from the pulsar timing arrays (ptas). our analysis using the threshold statistics on the compaction function demonstrates that galileon theory not only avoids pbh overproduction using the curvature perturbation enhancements that give $f_{\rm nl} \sim {\cal o}(-6)$, but also generates sigws that conform well with the pta data. | primordial non-gaussianity as a saviour for pbh overproduction in sigws generated by pulsar timing arrays for galileon inflation |
a supermassive black hole, obscured by cosmic dust, powers the nearby active galaxy ngc 1068. neutrinos, which rarely interact with matter, could provide information on the galaxy's active core. we searched for neutrino emission from astrophysical objects using data recorded with the icecube neutrino detector between 2011 and 2020. the positions of 110 known gamma-ray sources were individually searched for neutrino detections above atmospheric and cosmic backgrounds. we found that ngc 1068 has an excess of 79−20+22 neutrinos at tera–electron volt energies, with a global significance of 4.2σ, which we interpret as associated with the active galaxy. the flux of high-energy neutrinos that we measured from ngc 1068 is more than an order of magnitude higher than the upper limit on emissions of tera–electron volt gamma rays from this source. | evidence for neutrino emission from the nearby active galaxy ngc 1068 |
we review the paradigm of holographic dark energy (hde), which arises from a theoretical attempt of applying the holographic principle (hp) to the dark energy (de) problem. making use of the hp and the dimensional analysis, we derive the general formula of the energy density of hde. then, we describe the properties of hde model, in which the future event horizon is chosen as the characteristic length scale. we also introduce the theoretical explorations and the observational constraints for this model. next, in the framework of hde, we discuss various topics, such as spatial curvature, neutrino, instability of perturbation, time-varying gravitational constant, inflation, black hole and big rip singularity. in addition, from both the theoretical and the observational aspects, we introduce the interacting holographic dark energy scenario, where the interaction between dark matter and hde is taken into account. furthermore, we discuss the hde scenario in various modified gravity (mg) theories, such as brans-dicke theory, braneworld theory, scalar-tensor theory, horava-lifshitz theory, and so on. besides, we introduce the attempts of reconstructing various scalar-field de and mg models from hde. moreover, we introduce other de models inspired by the hp, in which different characteristic length scales are chosen. finally, we make comparisons among various hp-inspired de models, by using cosmological observations and diagnostic tools. | holographic dark energy |
the recent results from the pulsar timing array (pta) collaborations show the first evidence for the detection of a stochastic background of gravitational waves at the nhz frequencies. this discovery has profound implications for the physics of both the late and the early universe. in fact, together with the interpretation in terms of supermassive black hole binaries, many sources in the early universe can provide viable explanations as well. in this paper, we study the gravitational wave background sourced by a network of axion-like-particle (alp) domain walls at temperatures around the qcd crossover, where the qcd-induced potential provides the necessary bias to annihilate the network. remarkably, this implies a peak amplitude at frequencies around the sensitivity range of ptas. we extend previous analysis by taking into account the unavoidable friction on the network stemming from the topological coupling of the alp to qcd in terms of gluon and pion reflection off the domain walls at high and low temperatures, respectively. we identify the regions of parameter space where the network annihilates in the scaling regime ensuring compatibility with the pta results, as well as those where friction can be important and a more detailed study around the qcd crossover is required. | axionic domain walls at pulsar timing arrays: qcd bias and particle friction |
new results are reported from the operation of the pico-60 dark matter detector, a bubble chamber filled with 52 kg of c3 f8 located in the snolab underground laboratory. as in previous pico bubble chambers, pico -60 c 3f8 exhibits excellent electron recoil and alpha decay rejection, and the observed multiple-scattering neutron rate indicates a single-scatter neutron background of less than one event per month. a blind analysis of an efficiency-corrected 1167-kg day exposure at a 3.3-kev thermodynamic threshold reveals no single-scattering nuclear recoil candidates, consistent with the predicted background. these results set the most stringent direct-detection constraint to date on the weakly interacting massive particle (wimp)-proton spin-dependent cross section at 3.4 ×10-41 cm2 for a 30 -gev c-2 wimp, more than 1 order of magnitude improvement from previous pico results. | dark matter search results from the pico -60 c 3f8 bubble chamber |
the cosmic evolution survey (cosmos) has become a cornerstone of extragalactic astronomy. since the last public catalog in 2015, a wealth of new imaging and spectroscopic data have been collected in the cosmos field. this paper describes the collection, processing, and analysis of these new imaging data to produce a new reference photometric redshift catalog. source detection and multiwavelength photometry are performed for 1.7 million sources across the 2 deg2 of the cosmos field, ~966,000 of which are measured with all available broadband data using both traditional aperture photometric methods and a new profile-fitting photometric extraction tool, the farmer, which we have developed. a detailed comparison of the two resulting photometric catalogs is presented. photometric redshifts are computed for all sources in each catalog utilizing two independent photometric redshift codes. finally, a comparison is made between the performance of the photometric methodologies and of the redshift codes to demonstrate an exceptional degree of self-consistency in the resulting photometric redshifts. the i < 21 sources have subpercent photometric redshift accuracy and even the faintest sources at 25 < i < 27 reach a precision of 5%. finally, these results are discussed in the context of previous, current, and future surveys in the cosmos field. compared to cosmos2015, it reaches the same photometric redshift precision at almost one magnitude deeper. both photometric catalogs and their photometric redshift solutions and physical parameters will be made available through the usual astronomical archive systems (eso phase 3, ipac-irsa, and cds). | cosmos2020: a panchromatic view of the universe to z∼10 from two complementary catalogs |
we present the data release and data reduction process for the epoch 1 nircam observations for the cosmic evolution early release science survey (ceers). these data consist of nircam imaging in six broadband filters (f115w, f150w, f200w, f277w, f356w and f444w) and one medium-band filter (f410m) over four pointings, obtained in parallel with primary ceers miri observations. we reduced the nircam imaging with the jwst calibration pipeline, with custom modifications and reduction steps designed to address additional features and challenges with the data. here we provide a detailed description of each step in our reduction and a discussion of future expected improvements. our reduction process includes corrections for known prelaunch issues such as 1/f noise, as well as in-flight issues including snowballs, wisps, and astrometric alignment. many of our custom reduction processes were first developed with prelaunch simulated nircam imaging over the full 10 ceers nircam pointings. we present a description of the creation and reduction of this simulated data set in the appendix. we provide mosaics of the real images in a public release, as well as our reduction scripts with detailed explanations to allow users to reproduce our final data products. these represent one of the first official public data sets released from the directors discretionary early release science (dd-ers) program. | ceers epoch 1 nircam imaging: reduction methods and simulations enabling early jwst science results |
chirality—the geometric property of objects that do not coincide with their mirror image—is found in nature, for example, in molecules, crystals, galaxies and life forms. in quantum field theory, the chirality of a massless particle is defined by whether the directions of its spin and motion are parallel or antiparallel. although massless chiral fermions—weyl fermions—were predicted 90 years ago, their existence as fundamental particles has not been experimentally confirmed. however, their analogues have been observed as quasiparticles in condensed matter systems. in addition to weyl fermions1-4, theorists have proposed a number of unconventional (that is, beyond the standard model) chiral fermions in condensed matter systems5-8, but direct experimental evidence of their existence is still lacking. here, by using angle-resolved photoemission spectroscopy, we reveal two types of unconventional chiral fermion—spin-1 and charge-2 fermions—at the band-crossing points near the fermi level in cosi. the projections of these chiral fermions on the (001) surface are connected by giant fermi arcs traversing the entire surface brillouin zone. these chiral fermions are enforced at the centre or corner of the bulk brillouin zone by the crystal symmetries, making cosi a system with only one pair of chiral nodes with large separation in momentum space and extremely long surface fermi arcs, in sharp contrast to weyl semimetals, which have multiple pairs of weyl nodes with small separation. our results confirm the existence of unconventional chiral fermions and provide a platform for exploring the physical properties associated with chiral fermions. | observation of unconventional chiral fermions with long fermi arcs in cosi |
we consider the production of secondary gravity waves in galileon inflation with an ultra-slow roll (usr) phase and show that the spectrum of scalar-induced gravitational waves (sigws) in this case is consistent with the recent nanograv 15-year data and with sensitivities of other ground and space-based missions, lisa, bbo, decigo, ce, et, hlvk (consists of aligo, avirgo, and kagra), and hlv(03). thanks to the non-renormalization property of galileon theory, the amplitude of the large fluctuation is controllable at the sharp transitions between sr and usr regions. we show that the behaviour of the gw spectrum, when one-loop effects are included in the scalar power spectrum, is preserved under a shift of the sharp transition scale with peak amplitude $\omega_{\rm gw}h^2\sim {\cal o}(10^{-6})$, and hence it can cover a wide range of frequencies within ${\cal o}(10^{-9}{\rm hz} - 10^{7}{\rm hz})$. an analysis of the allowed mass range for primordial black holes (pbhs) is also performed, where we find that mass values ranging from ${\cal o}(1m_{\odot} - 10^{-18}m_{\odot})$ can be generated over the corresponding allowed range of low and high frequencies. | scalar induced gravity waves from ultra slow-roll galileon inflation |
the exomol database (www.exomol.com) provides extensive line lists of molecular transitions which are valid over extended temperatures ranges. the status of the current release of the database is reviewed and a new data structure is specified. this structure augments the provision of energy levels (and hence transition frequencies) and einstein $a$ coefficients with other key properties, including lifetimes of individual states, temperature-dependent cooling functions, landé $g$-factors, partition functions, cross sections, $k$-coefficients and transition dipoles with phase relations. particular attention is paid to the treatment of pressure broadening parameters. the new data structure includes a definition file which provides the necessary information for utilities accessing exomol through its application programming interface (api). prospects for the inclusion of new species into the database are discussed. | the exomol database: molecular line lists for exoplanet and other hot atmospheres |
recently, the cdf collaboration has reported the precise measurement of the w boson mass, mw = 80433.5 ± 9.4 mev , based on 8.8 fb-1 of √{ s } = 1.96 tev p p bar collision data from the cdf ii detector at the fermilab tevatron. this is about 7σ away from the standard model prediction, mwsm = 80357 ± 6 mev . such a large discrepancy may be partially due to exotic particles that radiatively alter the relation between the w and z boson masses. in this letter, we study singlet extensions of the standard model focusing on the shift of the w boson mass since they are accidentally flavor and cp safe without changing the standard model structure. in the minimal extension with a real singlet field, using the bounds from the electroweak oblique parameters, b meson decays, lep, and lhc, we find that the w boson mass shift is at most a few mev, and therefore it does not alleviate the tension between the cdf ii result and the sm prediction. we then examine how much various bounds are relaxed when the singlet is allowed to decay invisibly, and find that the increase of the w boson mass does not exceed 5 mev due to the bound from the higgs signal strength. we also discuss phenomenological and cosmological implications of the singlet extensions such as the muon g - 2 anomaly, axion/hidden photon dark matter, and self-interacting dark radiation as a possible alleviation of the hubble tension. | singlet extensions and w boson mass in light of the cdf ii result |
the standard λ cold dark matter cosmological model provides a wonderful fit to current cosmological data, but a few statistically significant tensions and anomalies were found in the latest data analyses. while these anomalies could be due to the presence of systematic errors in the experiments, they could also indicate the need for new physics beyond the standard model. in this letter of interest we focus on the tension between planck data and weak lensing measurements and redshift surveys, in the value of the matter energy density ωm and the amplitude σ8 (or the growth rate fσ8) of cosmic structure. we list a few promising models for solving this tension, and discuss the importance of trying to fit multiple cosmological datasets with complete physical models, rather than fitting individual datasets with a few handpicked theoretical parameters. | cosmology intertwined iii: fσ8 and s8 |
understanding the reason for the observed accelerated expansion of the universe represents one of the fundamental open questions in physics. in cosmology, a classification has emerged among physical models for this acceleration, distinguishing between dark energy and modified gravity. in this review, we provide a brief overview of models in both categories as well as their phenomenology and characteristic observable signatures in cosmology. we also introduce a rigorous distinction between dark energy and modified gravity based on the strong and weak equivalence principles. | dark energy versus modified gravity |
we analyze cosmic superstring models in light of nanograv 15-year pulsar timing data. a good fit is found for a string tension g μ ∼10-12- 10-11 and a string intercommutation probability p ∼10-3- 10-1. extrapolation to higher frequencies assuming standard big bang cosmology is compatible at the 68% cl with the current ligo/virgo/kagra upper limit on a stochastic gravitational wave background in the 10 to 100 hz range. the superstring interpretation of the nanograv data would be robustly testable by future experiments even in modified cosmological scenarios. | cosmic superstrings revisited in light of nanograv 15-year data |
supermassive black hole binaries source gravitational waves measured by pulsar timing arrays. the frequency spectrum of this stochastic background is predicted more precisely than its amplitude. we argue that dark matter friction can suppress the spectrum around nhz frequencies, where it is measured, allowing to derive robust and significant bounds on the dark matter density, which, in turn, controls indirect detection signals from galactic centers. a precise spectrum of gravitational waves would translate in a tomography of the dm density profile, potentially probing dm particle-physics effects that induce a characteristic dm density profile, such as dm annihilations or de broglie wavelength. | probing the dark matter density with gravitational waves from super-massive binary black holes |
deploying \textit{multiple sharp transitions} (msts) under a unified framework, we investigate the formation of primordial black holes (pbhs) and the production of scalar induced gravitational waves (sigws) by incorporating one-loop corrected renormalized-resummed scalar power spectrum. with effective sound speed parameter, $1 \leq c_s \leq 1.17$, the direct consequence is the generation of pbh masses spanning $m_{\rm pbh}\sim{\cal o}(10^{-31}m_{\odot}- 10^{4}m_{\odot})$, thus evading well known \textit{no-go theorem} on pbh mass. our results align coherently with the extensive nanograv 15-year data and the sensitivities outlined by other terrestrial and space-based experiments (e.g.: lisa, hlvk, bbo, hlv(o3), etc.). | evading no-go for pbh formation and production of sigws using multiple sharp transitions in eft of single field inflation |
this article is intended to review the recent developments in the horndeski theory and its generalization, which provide us with a systematic understanding of scalar-tensor theories of gravity as well as a powerful tool to explore astrophysics and cosmology beyond general relativity. this review covers the generalized galileons, (the rediscovery of) the horndeski theory, cosmological perturbations in the horndeski theory, cosmology with a violation of the null energy condition, degenerate higher-order scalar-tensor theories and their status after gw170817, the vainshtein screening mechanism in the horndeski theory and beyond, and hairy black hole solutions. | horndeski theory and beyond: a review |
we demonstrate that the recently announced signal for a stochastic gravitational wave background (sgwb) from pulsar timing array (pta) observations, if attributed to new physics, is compatible with primordial gw production due to axion-gauge dynamics during inflation. more specifically we find that axion-$u(1)$ models may lead to sufficient particle production to explain the signal while simultaneously source some fraction of sub-solar mass primordial black holes (pbhs) as a signature. moreover there is a parity violation in gw sector, hence the model suggests chiral gw search as a concrete target for future. we further analyze the axion-$su(2)$ coupling signatures and find that in the low/mild backreaction regime, it is incapable of producing pta evidence and the tensor-to-scalar ratio is low at the peak, hence it overproduces scalar perturbations and pbhs. | axion-gauge dynamics during inflation as the origin of pulsar timing array signals and primordial black holes |
the last decade has seen unprecedented effort in dark matter model building at all mass scales coupled with the design of numerous new detection strategies. transformative advances in quantum technologies have led to a plethora of new high-precision quantum sensors and dark matter detection strategies for ultralight ($<10\,$ev) bosonic dark matter that can be described by an oscillating classical, largely coherent field. this white paper focuses on searches for wavelike scalar and vector dark matter candidates. | new horizons: scalar and vector ultralight dark matter |
big bang nucleosynthesis (bbn) describes the production of the lightest nuclides via a dynamic interplay among the four fundamental forces during the first seconds of cosmic time. a brief overview of the essentials of this physics is given, and new calculations presented of light-element abundances through 6li and 7li, with updated nuclear reactions and uncertainties including those in the neutron lifetime. fits are provided for these results as a function of baryon density and of the number of neutrino flavors nν. recent developments are reviewed in bbn, particularly new, precision planck cosmic microwave background (cmb) measurements that now probe the baryon density, helium content, and the effective number of degrees of freedom neff. these measurements allow for a tight test of bbn and cosmology using cmb data alone. our likelihood analysis convolves the 2015 planck data chains with our bbn output and observational data. adding astronomical measurements of light elements strengthens the power of bbn. a new determination of the primordial helium abundance is included in our likelihood analysis. new d/h observations are now more precise than the corresponding theoretical predictions and are consistent with the standard model and the planck baryon density. moreover, d/h now provides a tight measurement of nν when combined with the cmb baryon density and provides a 2 σ upper limit nν<3.2 . the new precision of the cmb and d/h observations together leaves d/h predictions as the largest source of uncertainties. future improvement in bbn calculations will therefore rely on improved nuclear cross-section data. in contrast with d/h and 4he, 7li predictions continue to disagree with observations, perhaps pointing to new physics. this paper concludes with a look at future directions including key nuclear reactions, astronomical observations, and theoretical issues. | big bang nucleosynthesis: present status |
the glass-jwst early release science (hereafter glass-jwst-ers) program will obtain and make publicly available the deepest extragalactic data of the ers campaign. it is primarily designed to address two key science questions, namely, "what sources ionized the universe and when?" and "how do baryons cycle through galaxies?", while also enabling a broad variety of first look scientific investigations. in primary mode, it will obtain niriss and nirspec spectroscopy of galaxies lensed by the foreground hubble frontier field cluster, abell 2744. in parallel, it will use nircam to observe two fields that are offset from the cluster center, where lensing magnification is negligible, and which can thus be effectively considered blank fields. in order to prepare the community for access to this unprecedented data, we describe the scientific rationale, the survey design (including target selection and observational setups), and present pre-commissioning estimates of the expected sensitivity. in addition, we describe the planned public releases of high-level data products, for use by the wider astronomical community. | the glass-jwst early release science program. i. survey design and release plans |
we present the first limits on inelastic electron-scattering dark matter and dark photon absorption using a prototype supercdms detector having a charge resolution of 0.1 electron-hole pairs (cdms hvev, a 0.93 g cdms high-voltage device). these electron-recoil limits significantly improve experimental constraints on dark matter particles with masses as low as 1 mev /c2 . we demonstrate a sensitivity to dark photons competitive with other leading approaches but using substantially less exposure (0.49 g d). these results demonstrate the scientific potential of phonon-mediated semiconductor detectors that are sensitive to single electronic excitations. | first dark matter constraints from a supercdms single-charge sensitive detector |
lux-zeplin (lz) is a next-generation dark matter direct detection experiment that will operate 4850 feet underground at the sanford underground research facility (surf) in lead, south dakota, usa. using a two-phase xenon detector with an active mass of 7 tonnes, lz will search primarily for low-energy interactions with weakly interacting massive particles (wimps), which are hypothesized to make up the dark matter in our galactic halo. in this paper, the projected wimp sensitivity of lz is presented based on the latest background estimates and simulations of the detector. for a 1000 live day run using a 5.6-tonne fiducial mass, lz is projected to exclude at 90% confidence level spin-independent wimp-nucleon cross sections above 1.4 ×10-48 cm2 for a 40 gev /c2 mass wimp. additionally, a 5 σ discovery potential is projected, reaching cross sections below the exclusion limits of recent experiments. for spin-dependent wimp-neutron(-proton) scattering, a sensitivity of 2.3 ×10-43 cm2 (7.1 ×10-42 cm2) for a 40 gev /c2 mass wimp is expected. with underground installation well underway, lz is on track for commissioning at surf in 2020. | projected wimp sensitivity of the lux-zeplin dark matter experiment |
past studies have identified a spatially extended excess of ∼1-3 gev gamma rays from the region surrounding the galactic center, consistent with the emission expected from annihilating dark matter. we revisit and scrutinize this signal with the intention of further constraining its characteristics and origin. by applying cuts to the fermi event parameter ctbcore, we suppress the tails of the point spread function and generate high resolution gamma-ray maps, enabling us to more easily separate the various gamma-ray components. within these maps, we find the gev excess to be robust and highly statistically significant, with a spectrum, angular distribution, and overall normalization that is in good agreement with that predicted by simple annihilating dark matter models. for example, the signal is very well fit by a 36-51 gev dark matter particle annihilating to b b ¯ with an annihilation cross section of σv =(1 - 3) × 10-26cm3 / s (normalized to a local dark matter density of 0.4 gev /cm3). furthermore, we confirm that the angular distribution of the excess is approximately spherically symmetric and centered around the dynamical center of the milky way (within ∼ 0.05∘ of sgr a∗), showing no sign of elongation along the galactic plane. the signal is observed to extend to at least ≃ 10∘ from the galactic center, which together with its other morphological traits disfavors the possibility that this emission originates from previously known or modeled pulsar populations. | the characterization of the gamma-ray signal from the central milky way: a case for annihilating dark matter |
recently, pulsar timing array (pta) collaborations have detected a stochastic gravitational wave background (sgwb) at nano-hz frequencies, with domain wall networks (dws) proposed as potential sources. to be cosmologically viable, they must annihilate before dominating the universe energy budget, thus generating a sgwb. while sub-horizon dws shrink and decay rapidly, causality requires dws with super-horizon size to continue growing until they reach the hubble horizon. those entering the latest can be heavier than a hubble patch and collapse into primordial black holes (pbhs). by applying percolation theory, we pioneer an estimation of the pbh abundance originating from dw networks. we conduct a bayesian analysis of the pta signal, interpreting it as an outcome of sgwb from dw networks, accounting for pbh overproduction as a prior. we included contributions from supermassive black hole binaries along with their astrophysical priors. our findings indicate that dws, as the proposed source of the pta signal, result in the production of pbhs about ten times heavier than the sun. the binary mergers occurring within these pbhs generate a second sgwb in the kilo-hz domain which could be observable in on-going or planned earth-based interferometers if the correlation length of the dw network is greater than approximately 60$\%$ than the cosmic horizon, $l \gtrsim 0.6 t$. | domain wall interpretation of the pta signal confronting black hole overproduction |
we propose a new method towards distinguishing the dirac versus majorana nature of neutrino masses from the spectrum of gravitational waves (gws) associated with neutrino mass genesis. motivated by the principle of generating small neutrino masses without tiny yukawa couplings, we assume generic seesaw mechanisms for both majorana and dirac neutrino masses. for majorana neutrinos, we further assume a spontaneously broken gauged $u(1)_{b-l}$ symmetry, independently of the type of majorana seesaw mechanism, which gives a cosmic string induced gw signal flat over a wide range of frequencies. for dirac neutrinos, we assume the spontaneous breaking of a $z_2$ symmetry, the minimal symmetry choice associated with all dirac seesaw mechanisms, which is softly broken, generating a peaked gw spectrum from the annihilation of the resulting domain walls. in fact, the gw spectra for all types of dirac seesaws with such a broken $z_2$ symmetry are identical, subject to a mild caveat. as an illustrative example, we study the simplest respective type-i seesaw mechanisms, and show that the striking difference in the shapes of the gw spectra can help differentiate between these dirac and majorana seesaws, complementing results of neutrinoless double beta decay experiments. we also discuss detailed implications of the recent nanograv data for majorana and dirac seesaw models. | towards distinguishing dirac from majorana neutrino mass with gravitational waves |
we review the advanced version of the kklt construction and pure $d=4$ de sitter supergravity, involving a nilpotent multiplet, with regard to various conjectures that de sitter state cannot exist in string theory. we explain why we consider these conjectures problematic and not well motivated, and why the recently proposed alternative string theory models of dark energy, ignoring vacuum stabilization, are ruled out by cosmological observations at least at the $3\sigma$ level, i.e. with more than $99.7\%$ confidence. | the landscape, the swampland and the era of precision cosmology |
in 2017 april, the event horizon telescope (eht) observed the near-horizon region around the supermassive black hole at the core of the m87 galaxy. these 1.3 mm wavelength observations revealed a compact asymmetric ring-like source morphology. this structure originates from synchrotron emission produced by relativistic plasma located in the immediate vicinity of the black hole. here we present the corresponding linear-polarimetric eht images of the center of m87. we find that only a part of the ring is significantly polarized. the resolved fractional linear polarization has a maximum located in the southwest part of the ring, where it rises to the level of ∼15%. the polarization position angles are arranged in a nearly azimuthal pattern. we perform quantitative measurements of relevant polarimetric properties of the compact emission and find evidence for the temporal evolution of the polarized source structure over one week of eht observations. the details of the polarimetric data reduction and calibration methodology are provided. we carry out the data analysis using multiple independent imaging and modeling techniques, each of which is validated against a suite of synthetic data sets. the gross polarimetric structure and its apparent evolution with time are insensitive to the method used to reconstruct the image. these polarimetric images carry information about the structure of the magnetic fields responsible for the synchrotron emission. their physical interpretation is discussed in an accompanying publication. | first m87 event horizon telescope results. vii. polarization of the ring |
we present full-sky maps of the cosmic microwave background (cmb) and polarized synchrotron and thermal dust emission, derived from the third set of planck frequency maps. these products have significantly lower contamination from instrumental systematic effects than previous versions. the methodologies used to derive these maps follow closely those described in earlier papers, adopting four methods (commander, nilc, sevem, and smica) to extract the cmb component, as well as three methods (commander, gnilc, and smica) to extract astrophysical components. our revised cmb temperature maps agree with corresponding products in the planck 2015 delivery, whereas the polarization maps exhibit significantly lower large-scale power, reflecting the improved data processing described in companion papers; however, the noise properties of the resulting data products are complicated, and the best available end-to-end simulations exhibit relative biases with respect to the data at the few percent level. using these maps, we are for the first time able to fit the spectral index of thermal dust independently over 3° regions. we derive a conservative estimate of the mean spectral index of polarized thermal dust emission of βd = 1.55 ± 0.05, where the uncertainty marginalizes both over all known systematic uncertainties and different estimation techniques. for polarized synchrotron emission, we find a mean spectral index of βs = -3.1 ± 0.1, consistent with previously reported measurements. we note that the current data processing does not allow for construction of unbiased single-bolometer maps, and this limits our ability to extract co emission and correlated components. the foreground results for intensity derived in this paper therefore do not supersede corresponding planck 2015 products. for polarization the new results supersede the corresponding 2015 products in all respects. | planck 2018 results. iv. diffuse component separation |
we consider a simple spherical model consisting of a schwarzschild black hole of mass m and a dark matter of mass δm around it. the general formula for the radius of black-hole shadow has been derived in this case. it is shown that the change of the shadow is not negligible, once the effective radius of the dark matter halo is of order ∼√{ 3 mδm }. for this to happen, for example, for the galactic black hole, the dark matter must be concentrated near the black hole. for small deviations from the schwarzschild limit, the dominant contribution into the size of a shadow is due to the dark matter under the photon sphere, but at larger deviations, the matter outside the photon sphere cannot be ignored. | shadow of a black hole surrounded by dark matter |
the recent observations by pulsar timing array (pta) experiments suggest the existence of stochastic gravitational wave background in the nano-hz range. it can be a hint for the new physics and cosmic string is one of the promising candidates. in this paper, we study the implication of the pta result for cosmic strings and dark photon dark matter produced by the decay of cosmic string loops. it can simultaneously explain the pta result and present dark matter abundance for the dark photon mass m ∼10-7-10-5ev. implications for the gravitational wave detection with multi-frequency bands are also discussed. | nanohertz gravitational waves from cosmic strings and dark photon dark matter |
recently, the pulsar timing array (pta) collaborations have reported the evidence for a stochastic gravitational wave background (sgwb) at nano-hertz band. the spectrum of inflationary gravitational wave (igw) is unknown, which might exhibit different power law at different frequency-bands, thus if the pta signal is primordial, it will be significant to explore the underlying implications of current pta and cmb data on igw. in this paper, we perform a joint markov chain monte carlo analysis for a broken power-law spectrum of igw with the nanograv 15-year and bicep/keck 2018 data. it is found that though the bestfit spectral tilt of igw at pta band is $n^\text{pta}_\text{t} =2.42^{+0.32}_{-0.91}$, at cmb band the bestfit is $n^\text{cmb}_\text{t} =0.55^{+0.37}_{-0.10}$ while a detectable amplitude of $r$ with $n^\text{cmb}_\text{t} \simeq 0$ is still compatible. the implication of our results for inflation is also discussed. | broken blue-tilted inflationary gravitational waves: a joint analysis of nanograv 15-year and bicep/keck 2018 data |
euclid is a mission of the european space agency that is designed to constrain the properties of dark energy and gravity via weak gravitational lensing and galaxy clustering. it will carry out a wide area imaging and spectroscopy survey (the euclid wide survey: ews) in visible and near-infrared bands, covering approximately 15 000 deg2 of extragalactic sky in six years. the wide-field telescope and instruments are optimised for pristine point spread function and reduced stray light, producing very crisp images. this paper presents the building of the euclid reference survey: the sequence of pointings of ews, deep fields, and calibration fields, as well as spacecraft movements followed by euclid as it operates in a step-and-stare mode from its orbit around the lagrange point l2. each ews pointing has four dithered frames; we simulated the dither pattern at the pixel level to analyse the effective coverage. we used up-to-date models for the sky background to define the euclid region-of-interest (roi). the building of the reference survey is highly constrained from calibration cadences, spacecraft constraints, and background levels; synergies with ground-based coverage were also considered. via purposely built software, we first generated a schedule for the calibrations and deep fields observations. on a second stage, the roi was tiled and scheduled with ews observations, using an algorithm optimised to prioritise the best sky areas, produce a compact coverage, and ensure thermal stability. the result is the optimised reference survey rsd_2021a, which fulfils all constraints and is a good proxy for the final solution. the current ews covers ≈14 500 deg2. the limiting ab magnitudes (5σ point-like source) achieved in its footprint are estimated to be 26.2 (visible band ie) and 24.5 (for near infrared bands ye, je, he); for spectroscopy, the hα line flux limit is 2 × 10−16 erg−1 cm−2 s−1 at 1600 nm; and for diffuse emission, the surface brightness limits are 29.8 (visible band) and 28.4 (near infrared bands) mag arcsec−2. | euclid preparation. i. the euclid wide survey |
deriving the expansion history of the universe is a major goal of modern cosmology. to date, the most accurate measurements have been obtained with type ia supernovae (sne) and baryon acoustic oscillations (bao), providing evidence for the existence of a transition epoch at which the expansion rate changes from decelerated to accelerated. however, these results have been obtained within the framework of specific cosmological models that must be implicitly or explicitly assumed in the measurement. it is therefore crucial to obtain measurements of the accelerated expansion of the universe independently of assumptions on cosmological models. here we exploit the unprecedented statistics provided by the baryon oscillation spectroscopic survey (boss, [1-3]) data release 9 to provide new constraints on the hubble parameter h(z) using the cosmic chronometers approach. we extract a sample of more than 130000 of the most massive and passively evolving galaxies, obtaining five new cosmology-independent h(z) measurements in the redshift range 0.3 < z < 0.5, with an accuracy of ~11-16% incorporating both statistical and systematic errors. once combined, these measurements yield a 6% accuracy constraint of h(z = 0.4293) = 91.8 ± 5.3 km/s/mpc. the new data are crucial to provide the first cosmology-independent determination of the transition redshift at high statistical significance, measuring zt = 0.4 ± 0.1, and to significantly disfavor the null hypothesis of no transition between decelerated and accelerated expansion at 99.9% confidence level. this analysis highlights the wide potential of the cosmic chronometers approach: it permits to derive constraints on the expansion history of the universe with results competitive with standard probes, and most importantly, being the estimates independent of the cosmological model, it can constrain cosmologies beyond—and including—the λcdm model. | a 6% measurement of the hubble parameter at z~0.45: direct evidence of the epoch of cosmic re-acceleration |
montepython is a parameter inference package for cosmology. we present the latest development of the code over the past couple of years. we explain, in particular, two new ingredients both contributing to improve the performance of metropolis-hastings sampling: an adaptation algorithm for the jumping factor, and a calculation of the inverse fisher matrix, which can be used as a proposal density. we present several examples to show that these features speed up convergence and can save many hundreds of cpu-hours in the case of difficult runs, with a poor prior knowledge of the covariance matrix. we also summarize all the functionalities of montepython in the current release, including new likelihoods and plotting options. | montepython 3: boosted mcmc sampler and other features |
xenonnt is a dark matter direct detection experiment, utilizing 5.9 t of instrumented liquid xenon, located at the infn laboratori nazionali del gran sasso. in this work, we predict the experimental background and project the sensitivity of xenonnt to the detection of weakly interacting massive particles (wimps). the expected average differential background rate in the energy region of interest, corresponding to (1, 13) kev and (4, 50) kev for electronic and nuclear recoils, amounts to 12.3 ± 0.6 (kev t y)-1 and (2.2± 0.5)× 10-3 (kev t y)-1, respectively, in a 4 t fiducial mass. we compute unified confidence intervals using the profile construction method, in order to ensure proper coverage. with the exposure goal of 20 t y, the expected sensitivity to spin-independent wimp-nucleon interactions reaches a cross-section of 1.4×10-48 cm2 for a 50 gev/c2 mass wimp at 90% confidence level, more than one order of magnitude beyond the current best limit, set by xenon1t . in addition, we show that for a 50 gev/c2 wimp with cross-sections above 2.6×10-48 cm2 (5.0×10-48 cm2) the median xenonnt discovery significance exceeds 3σ (5σ). the expected sensitivity to the spin-dependent wimp coupling to neutrons (protons) reaches 2.2×10-43 cm2 (6.0×10-42 cm2). | projected wimp sensitivity of the xenonnt dark matter experiment |
the curvature parameter tension between planck 2018, cosmic microwave background (cmb) lensing, and baryon acoustic oscillation (bao) data is measured using the suspiciousness statistic to be 2.5 - 3 σ . conclusions regarding the spatial curvature of the universe which stem from the combination of these data should therefore be viewed with suspicion. without cmb lensing or bao, planck 2018 has a moderate preference for closed universes, with bayesian betting odds of over 50 ∶1 against a flat universe and over 2000 ∶1 against an open universe. | curvature tension: evidence for a closed universe |
pulsar timing array experiments probe the presence of possible scalar or pseudoscalar ultralight dark matter particles through decade-long timing of an ensemble of galactic millisecond radio pulsars. with the second data release of the european pulsar timing array, we focus on the most robust scenario, in which dark matter interacts only gravitationally with ordinary baryonic matter. our results show that ultralight particles with masses 10-24.0 ev ≲m ≲10-23.3 ev cannot constitute 100% of the measured local dark matter density, but can have at most local density ρ ≲0.3 gev /cm3 . | second data release from the european pulsar timing array: challenging the ultralight dark matter paradigm |
we present new constraints on sub-gev dark-matter particles scattering off electrons based on 6780.0 kg d of data collected with the darkside-50 dual-phase argon time projection chamber. this analysis uses electroluminescence signals due to ionized electrons extracted from the liquid argon target. the detector has a very high trigger probability for these signals, allowing for an analysis threshold of three extracted electrons, or approximately 0.05 kevee. we calculate the expected recoil spectra for dark matter-electron scattering in argon and, under the assumption of momentum-independent scattering, improve upon existing limits from xenon10 for dark-matter particles with masses between 30 and 100 mev /c2 . | constraints on sub-gev dark-matter-electron scattering from the darkside-50 experiment |
in a six-year program started in 2014 july, the extended baryon oscillation spectroscopic survey (eboss) will conduct novel cosmological observations using the boss spectrograph at apache point observatory. these observations will be conducted simultaneously with the time domain spectroscopic survey (tdss) designed for variability studies and the spectroscopic identification of erosita sources (spiders) program designed for studies of x-ray sources. in particular, eboss will measure with percent-level precision the distance-redshift relation with baryon acoustic oscillations (bao) in the clustering of matter. eboss will use four different tracers of the underlying matter density field to vastly expand the volume covered by boss and map the large-scale-structures over the relatively unconstrained redshift range 0.6 < z < 2.2. using more than 250,000 new, spectroscopically confirmed luminous red galaxies at a median redshift z = 0.72, we project that eboss will yield measurements of the angular diameter distance da(z) to an accuracy of 1.2% and measurements of h(z) to 2.1% when combined with the z > 0.6 sample of boss galaxies. with ∼195,000 new emission line galaxy redshifts, we expect bao measurements of da(z) to an accuracy of 3.1% and h(z) to 4.7% at an effective redshift of z = 0.87. a sample of more than 500,000 spectroscopically confirmed quasars will provide the first bao distance measurements over the redshift range 0.9 < z < 2.2, with expected precision of 2.8% and 4.2% on da(z) and h(z), respectively. finally, with 60,000 new quasars and re-observation of 60,000 boss quasars, we will obtain new lyα forest measurements at redshifts z > 2.1 these new data will enhance the precision of da(z) and h(z) at z > 2.1 by a factor of 1.44 relative to boss. furthermore, eboss will provide improved tests of general relativity on cosmological scales through redshift-space distortion measurements, improved tests for non-gaussianity in the primordial density field, and new constraints on the summed mass of all neutrino species. here, we provide an overview of the cosmological goals, spectroscopic target sample, demonstration of spectral quality from early data, and projected cosmological constraints from eboss. | the sdss-iv extended baryon oscillation spectroscopic survey: overview and early data |
we present the all-sky planck catalogue of sunyaev-zeldovich (sz) sources detected from the 29 month full-mission data. the catalogue (psz2) is the largest sz-selected sample of galaxy clusters yet produced and the deepest systematic all-sky surveyof galaxy clusters. it contains 1653 detections, of which 1203 are confirmed clusters with identified counterparts in external data sets, and is the first sz-selected cluster survey containing >103 confirmed clusters. we present a detailed analysis of the survey selection function in terms of its completeness and statistical reliability, placing a lower limit of 83% on the purity. using simulations, we find that the estimates of the sz strength parameter y5r500are robust to pressure-profile variation and beam systematics, but accurate conversion to y500 requires the use of prior information on the cluster extent. we describe the multi-wavelength search for counterparts in ancillary data, which makes use of radio, microwave, infra-red, optical, and x-ray data sets, and which places emphasis on the robustness of the counterpart match. we discuss the physical properties of the new sample and identify a population of low-redshift x-ray under-luminous clusters revealed by sz selection. these objects appear in optical and sz surveys with consistent properties for their mass, but are almost absent from rosat x-ray selected samples. | planck 2015 results. xxvii. the second planck catalogue of sunyaev-zeldovich sources |
fast radio bursts (frbs) are short pulses observed in the radio band from cosmological distances1. one class of models invokes soft gamma-ray repeaters (sgrs), or magnetars, as the sources of frbs2. some radio pulses have been observed from some magnetars3, but no frb-like events have been detected in association with any magnetar burst, including one giant flare4. recently, a pair of frb-like bursts (termed frb 200428) separated by 29 milliseconds were detected from the general direction of the galactic magnetar sgr j1935+2154 (refs. 5,6). here, we report the detection of a non-thermal x-ray burst in the 1-250 kev energy band with the insight-hxmt satellite7, which we identify as having been emitted from sgr j1935+2154. the burst showed two hard peaks with a separation of 34 milliseconds, broadly consistent with that of the two bursts in frb 200428. the delay time between the double radio peak and the x-ray peaks is about 8.62 s, fully consistent with the dispersion delay of frb 200428. we thus identify the non-thermal x-ray burst to be associated with frb 200428, whose high-energy counterpart is the two hard x-ray peaks. our results suggest that the non-thermal x-ray burst and frb 200428 share the same physical origin in an explosive event from sgr j1935+2154. | hxmt identification of a non-thermal x-ray burst from sgr j1935+2154 and with frb 200428 |
the wide field infrared survey telescope (wfirst) is a 2.4m space telescope with a 0.281 deg^2 field of view for near-ir imaging and slitless spectroscopy and a coronagraph designed for > 10^8 starlight suppresion. as background information for astro2020 white papers, this article summarizes the current design and anticipated performance of wfirst. while wfirst does not have the uv imaging/spectroscopic capabilities of the hubble space telescope, for wide field near-ir surveys wfirst is hundreds of times more efficient. some of the most ambitious multi-cycle hst treasury programs could be executed as routine general observer (go) programs on wfirst. the large area and time-domain surveys planned for the cosmology and exoplanet microlensing programs will produce extraordinarily rich data sets that enable an enormous range of archival research (ar) investigations. requirements for the coronagraph are defined based on its status as a technology demonstration, but its expected performance will enable unprecedented observations of nearby giant exoplanets and circumstellar disks. wfirst is currently in the preliminary design and technology completion phase (phase b), on schedule for launch in 2025, with several of its critical components already in production. | the wide field infrared survey telescope: 100 hubbles for the 2020s |
the first direct measurement of gravitational waves by the ligo and virgo collaborations has opened up new avenues to explore our universe. this white paper outlines the challenges and gains expected in gravitational-wave searches at frequencies above the ligo/virgo band, with a particular focus on ultra high-frequency gravitational waves (uhf-gws), covering the mhz to ghz range. the absence of known astrophysical sources in this frequency range provides a unique opportunity to discover physics beyond the standard model operating both in the early and late universe, and we highlight some of the most promising gravitational sources. we review several detector concepts that have been proposed to take up this challenge, and compare their expected sensitivity with the signal strength predicted in various models. this report is the summary of the workshop "challenges and opportunities of high-frequency gravitational wave detection" held at ictp trieste, italy in october 2019, that set up the stage for the recently launched ultra-high-frequency gravitational wave (uhf-gw) initiative. | challenges and opportunities of gravitational-wave searches at mhz to ghz frequencies |
when ultralight axion dark matter encounters a static magnetic field, it sources an effective electric current that follows the magnetic field lines and oscillates at the axion compton frequency. we propose a new experiment to detect this axion effective current. in the presence of axion dark matter, a large toroidal magnet will act like an oscillating current ring, whose induced magnetic flux can be measured by an external pickup loop inductively coupled to a squid magnetometer. we consider both resonant and broadband readout circuits and show that a broadband approach has advantages at small axion masses. we estimate the reach of this design, taking into account the irreducible sources of noise, and demonstrate potential sensitivity to axionlike dark matter with masses in the range of 10-14-10-6 e v . in particular, both the broadband and resonant strategies can probe the qcd axion with a gut-scale decay constant. | broadband and resonant approaches to axion dark matter detection |
we present , a general-purpose bayesian analysis code aimed at models with complex internal interdependencies. without the need for specific code by the user, interdependencies between different stages of a model pipeline are exploited for sampling efficiency: intermediate results are automatically cached, and parameters are grouped in blocks according to their dependencies and optimally sorted, taking into account their individual computational costs, so as to minimize the cost of their variation during sampling, thanks to a novel algorithm. cobaya allows exploration of posteriors using a range of monte carlo samplers, and also has functions for maximization and importance-reweighting of monte carlo samples with new priors and likelihoods. cobaya is written in python in a modular way that allows for extendability, use of calculations provided by external packages, and dynamical reparameterization without modifying its source. it can exploit hybrid openmp/mpi parallelization, and has sub-millisecond overhead per posterior evaluation. though cobaya is a general purpose statistical framework, it includes interfaces to a set of cosmological boltzmann codes and likelihoods (the latter being agnostic with respect to the choice of the former), and automatic installers for external dependencies. | cobaya: code for bayesian analysis of hierarchical physical models |
the evolution of the content of heavy elements in galaxies, the relative chemical abundances, their spatial distribution, and how these scale with various galactic properties, provide unique information on the galactic evolutionary processes across the cosmic epochs. in recent years major progress has been made in constraining the chemical evolution of galaxies and inferring key information relevant to our understanding of the main mechanisms involved in galaxy evolution. in this review we provide an overview of these various areas. after an overview of the methods used to constrain the chemical enrichment in galaxies and their environment, we discuss the observed scaling relations between metallicity and galaxy properties, the observed relative chemical abundances, how the chemical elements are distributed within galaxies, and how these properties evolve across the cosmic epochs. we discuss how the various observational findings compare with the predictions from theoretical models and numerical cosmological simulations. finally, we briefly discuss the open problems and the prospects for major progress in this field in the nearby future. | de re metallica: the cosmic chemical evolution of galaxies |
we present an up-to-date global analysis of data coming from neutrino oscillation and non-oscillation experiments, as available in april 2018, within the standard framework including three massive and mixed neutrinos. we discuss in detail the status of the three-neutrino (3 ν) mass-mixing parameters, both known and unknown. concerning the latter, we find that: normal ordering (no) is favored over inverted ordering (io) at 3 σ level; the dirac cp phase is constrained within ∼ 15% (∼ 9%) uncertainty in no (io) around nearly-maximal cp-violating values; the octant of the largest mixing angle and the absolute neutrino masses remain undetermined. we briefly comment on other unknowns related to theoretical and experimental uncertainties (within 3 ν) or possible new states and interactions (beyond 3 ν). | current unknowns in the three-neutrino framework |
the hubble constant (h0) tension between type ia supernovae (sne ia) and planck measurements ranges from 4 to 6σ. to investigate this tension, we estimate h0 in the λcdm and ${w}_{0}{w}_{a}$ cdm (cold dark matter) models by dividing the pantheon sample, the largest compilation of sne ia, into 3, 4, 20, and 40 bins. we fit the extracted h0 values with a function mimicking the redshift evolution: $g{(z)={h}_{0}(z)={\tilde{h}}_{0}/(1+z)}^{\alpha }$ , where α indicates an evolutionary parameter and ${\tilde{h}}_{0}={h}_{0}$ at z = 0. we set the absolute magnitude of sne ia so that ${h}_{0}\,=73.5\,\mathrm{km}\,{{\rm{s}}}^{-1}\,{\mathrm{mpc}}^{-1}$ , and we fix fiducial values for ${{\rm{\omega }}}_{0m}^{{\rm{\lambda }}\mathrm{cdm}}=0.298$ and ${{\rm{\omega }}}_{0m}^{{w}_{0}{w}_{a}\mathrm{cdm}}=0.308$ . we find that h0 evolves with redshift, showing a slowly decreasing trend, with α coefficients consistent with zero only from 1.2 to 2.0σ. although the α coefficients are compatible with zero in 3σ, this however may affect cosmological results. we measure locally a variation of ${h}_{0}(z=0)-{h}_{0}(z=1)=0.4\,\mathrm{km}\,{{\rm{s}}}^{-1}\,{\mathrm{mpc}}^{-1}$ in three and four bins. extrapolating ${h}_{0}(z)$ to z = 1100, the redshift of the last scattering surface, we obtain values of h0 compatible in 1σ with planck measurements independent of the cosmological models and number of bins we investigated. thus, we have reduced the h0 tension in the range from 54% to 72% for both cosmological models. if the decreasing trend of ${h}_{0}(z)$ is real, it could be due to astrophysical selection effects or to modified gravity. | on the hubble constant tension in the sne ia pantheon sample |
the recent determination of the local value of the hubble constant by riess et al., 2016 (hereafter r16) is now 3.3 sigma higher than the value derived from the most recent cmb anisotropy data provided by the planck satellite in a λcdm model. here we perform a combined analysis of the planck and r16 results in an extended parameter space, varying simultaneously 12 cosmological parameters instead of the usual 6. we find that a phantom-like dark energy component, with effective equation of state w = -1.29-0.12+0.15 at 68% c.l. can solve the current tension between the planck dataset and the r16 prior in an extended λcdm scenario. on the other hand, the neutrino effective number is fully compatible with standard expectations. this result is confirmed when including cosmic shear data from the cfhtlens survey and cmb lensing constraints from planck. however, when bao measurements are included we find that some of the tension with r16 remains, as also is the case when we include the supernova type ia luminosity distances from the jla catalog. | reconciling planck with the local value of h0 in extended parameter space |
we present the final sloan digital sky survey iv (sdss-iv) quasar catalog from data release 16 of the extended baryon oscillation spectroscopic survey (eboss). this catalog comprises the largest selection of spectroscopically confirmed quasars to date. the full catalog includes two subcatalogs (the current versions are dr16q_v4 and dr16q_superset_v3 at https://data.sdss.org/sas/dr16/eboss/qso/dr16q/): a "superset" of all sdss-iv/eboss objects targeted as quasars containing 1,440,615 observations and a quasar-only catalog containing 750,414 quasars, including 225,082 new quasars appearing in an sdss data release for the first time, as well as known quasars from sdss-i/ii/iii. we present automated identification and redshift information for these quasars alongside data from visual inspections for 320,161 spectra. the quasar-only catalog is estimated to be 99.8% complete with 0.3%-1.3% contamination. automated and visual inspection redshifts are supplemented by redshifts derived via principal component analysis and emission lines. we include emission-line redshifts for hα, hβ, mg ii, c iii], c iv, and lyα. identification and key characteristics generated by automated algorithms are presented for 99,856 broad absorption-line quasars and 35,686 damped lyman alpha quasars. in addition to sdss photometric data, we also present multiwavelength data for quasars from the galaxy evolution explorer, ukidss, the wide-field infrared survey explorer, first, rosat/2rxs, xmm-newton, and gaia. calibrated digital optical spectra for these quasars can be obtained from the sdss science archive server. | the sloan digital sky survey quasar catalog: sixteenth data release |
the lofar two-metre sky survey (lotss) is an ongoing sensitive, high-resolution 120-168 mhz survey of the entire northern sky for which observations are now 20% complete. we present our first full-quality public data release. for this data release 424 square degrees, or 2% of the eventual coverage, in the region of the hetdex spring field (right ascension 10h45m00s to 15h30m00s and declination 45°00'00″ to 57°00'00″) were mapped using a fully automated direction-dependent calibration and imaging pipeline that we developed. a total of 325 694 sources are detected with a signal of at least five times the noise, and the source density is a factor of ∼10 higher than the most sensitive existing very wide-area radio-continuum surveys. the median sensitivity is s144 mhz = 71 μjy beam-1 and the point-source completeness is 90% at an integrated flux density of 0.45 mjy. the resolution of the images is 6″ and the positional accuracy is within 0.2″. this data release consists of a catalogue containing location, flux, and shape estimates together with 58 mosaic images that cover the catalogued area. in this paper we provide an overview of the data release with a focus on the processing of the lofar data and the characteristics of the resulting images. in two accompanying papers we provide the radio source associations and deblending and, where possible, the optical identifications of the radio sources together with the photometric redshifts and properties of the host galaxies. these data release papers are published together with a further ∼20 articles that highlight the scientific potential of lotss. lotss.the catalogue is available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?j/a+a/622/a1 | the lofar two-metre sky survey. ii. first data release |
we summarize our understanding of millisecond radio bursts from an extragalactic population of sources. fast radio bursts (frbs) occur at an extraordinary rate, thousands per day over the entire sky with radiation energy densities at the source about ten billion times larger than those from galactic pulsars. we survey frb phenomenology, source models and host galaxies, coherent radiation models, and the role of plasma propagation effects in burst detection. the frb field is guaranteed to be exciting: new telescopes will expand the sample from the current ∼80 unique burst sources (and only a few secure localizations and redshifts) to thousands, with burst localizations that enable host-galaxy redshifts emerging directly from interferometric surveys. frbs are now established as an extragalactic phenomenon. only a few sources are known to repeat. despite the failure to redetect other frbs, they are not inconsistent with all being repeaters. frb sources may be new, exotic kinds of objects or known types in extreme circumstances. many inventive models exist, ranging from alien spacecraft to cosmic strings, but those concerning compact objects and supermassive black holes have gained the most attention. a rapidly rotating magnetar is a promising explanation for frb 121102 along with the persistent source associated with it, but alternative source models are not ruled out for it or other frbs. frbs are powerful tracers of circumsource environments, “missing baryons” in the intergalactic medium (igm), and dark matter. the relative contributions of host galaxies and the igm to propagation effects have yet to be disentangled, so dispersion measure distances have large uncertainties. | fast radio bursts: an extragalactic enigma |
we use 47 gravitational wave sources from the third ligo-virgo-kamioka gravitational wave detector gravitational wave transient catalog (gwtc-3) to estimate the hubble parameter h(z), including its current value, the hubble constant h 0. each gravitational wave (gw) signal provides the luminosity distance to the source, and we estimate the corresponding redshift using two methods: the redshifted masses and a galaxy catalog. using the binary black hole (bbh) redshifted masses, we simultaneously infer the source mass distribution and h(z). the source mass distribution displays a peak around 34 m ⊙, followed by a drop-off. assuming this mass scale does not evolve with the redshift results in a h(z) measurement, yielding ${h}_{0}={68}_{-8}^{+12}\,\mathrm{km}\ \,\ {{\rm{s}}}^{-1}\,{\mathrm{mpc}}^{-1}$ (68% credible interval) when combined with the h 0 measurement from gw170817 and its electromagnetic counterpart. this represents an improvement of 17% with respect to the h 0 estimate from gwtc-1. the second method associates each gw event with its probable host galaxy in the catalog glade+, statistically marginalizing over the redshifts of each event's potential hosts. assuming a fixed bbh population, we estimate a value of ${h}_{0}={68}_{-6}^{+8}\,\mathrm{km}\ \,\ {{\rm{s}}}^{-1}\,{\mathrm{mpc}}^{-1}$ with the galaxy catalog method, an improvement of 42% with respect to our gwtc-1 result and 20% with respect to recent h 0 studies using gwtc-2 events. however, we show that this result is strongly impacted by assumptions about the bbh source mass distribution; the only event which is not strongly impacted by such assumptions (and is thus informative about h 0) is the well-localized event gw190814. | constraints on the cosmic expansion history from gwtc-3 |
we report a detection of the baryon acousticoscillation (bao) feature in the flux-correlation function of the lyα forest of high-redshift quasars with a statistical significance of five standard deviations. the study uses 137 562 quasars in the redshift range 2.1 ≤ z ≤ 3.5 from the data release 11 (dr11) of the baryon oscillation spectroscopic survey (boss) of sdss-iii. this sample contains three times the number of quasars used in previous studies. the measured position of the bao peak determines the angular distance, da(z = 2.34) and expansion rate, h(z = 2.34), both on a scale set by the sound horizon at the drag epoch, rd. we find da/rd = 11.28 ± 0.65(1σ)+2.8-1.2 (2σ) and dh/rd = 9.18 ± 0.28(1σ) ± 0.6(2σ) where dh = c/h. the optimal combination, ~dh0.7da0.3/rd is determined with a precision of ~2%. for the value rd = 147.4 mpc, consistent with the cosmic microwave background power spectrum measured by planck, we find da(z = 2.34) = 1662 ± 96(1σ) mpc and h(z = 2.34) = 222 ± 7(1σ) km s-1 mpc-1. tests with mock catalogs and variations of our analysis procedure have revealed no systematic uncertainties comparable to our statistical errors. our results agree with the previously reported bao measurement at the same redshift using the quasar-lyα forest cross-correlation. the autocorrelation and cross-correlation approaches are complementary because of the quite different impact of redshift-space distortion on the two measurements. the combined constraints from the two correlation functions imply values of da/rd that are 7% lower and 7% higher for dh/rd than the predictions of a flat λcdm cosmological model with the best-fit planck parameters. with our estimated statistical errors, the significance of this discrepancy is ≈2.5σ. appendices are available in electronic form at http://www.aanda.org | baryon acoustic oscillations in the lyα forest of boss dr11 quasars |
the diffuse galactic γ -ray emission, mainly produced via interactions between cosmic rays and the interstellar medium and/or radiation field, is a very important probe of the distribution, propagation, and interaction of cosmic rays in the milky way. in this letter, we report the measurements of diffuse γ rays from the galactic plane between 10 tev and 1 pev energies, with the square kilometer array of the large high altitude air shower observatory (lhaaso). diffuse emissions from the inner (15 ° <l <12 5 ° , |b |<5 ° ) and outer (125 ° <l <23 5 ° , |b |<5 ° ) galactic plane are detected with 29.1 σ and 12.7 σ significance, respectively. the outer galactic plane diffuse emission is detected for the first time in the very- to ultra-high-energy domain (e >10 tev ). the energy spectrum in the inner galaxy regions can be described by a power-law function with an index of -2.99 ±0.04 , which is different from the curved spectrum as expected from hadronic interactions between locally measured cosmic rays and the line-of-sight integrated gas content. furthermore, the measured flux is higher by a factor of ∼3 than the prediction. a similar spectrum with an index of -2.99 ±0.07 is found in the outer galaxy region, and the absolute flux for 10 ≲e ≲60 tev is again higher than the prediction for hadronic cosmic ray interactions. the latitude distributions of the diffuse emission are consistent with the gas distribution, while the longitude distributions show clear deviation from the gas distribution. the lhaaso measurements imply that either additional emission sources exist or cosmic ray intensities have spatial variations. | measurement of ultra-high-energy diffuse gamma-ray emission of the galactic plane from 10 tev to 1 pev with lhaaso-km2a |
according to the weak equivalence principle, all bodies should fall at the same rate in a gravitational field. the microscope satellite, launched in april 2016, aims to test its validity at the 10-15 precision level, by measuring the force required to maintain two test masses (of titanium and platinum alloys) exactly in the same orbit. a nonvanishing result would correspond to a violation of the equivalence principle, or to the discovery of a new long-range force. analysis of the first data gives δ (ti ,pt )=[-1 ±9 (stat)±9 (syst)]×10-15 (1 σ statistical uncertainty) for the titanium-platinum eötvös parameter characterizing the relative difference in their free-fall accelerations. | microscope mission: first results of a space test of the equivalence principle |
we report on the discovery of eight repeating fast radio burst (frb) sources found using the canadian hydrogen intensity mapping experiment (chime) telescope. these sources span a dispersion measure (dm) range of 103.5-1281 pc cm-3. they display varying degrees of activity: six sources were detected twice, another three times, and one 10 times. these eight repeating frbs likely represent the bright and/or high-rate end of a distribution of infrequently repeating sources. for all sources, we determine sky coordinates with uncertainties of ∼10‧. frb 180916.j0158+65 has a burst-averaged dm = 349.2 ± 0.3 pc cm-3 and a low dm excess over the modeled galactic maximum (as low as ∼20 pc cm-3) this source also has a faraday rotation measure (rm) of -114.6 ± 0.6 rad m-2, which is much lower than the rm measured for frb 121102. frb 181030.j1054+73 has the lowest dm for a repeater, 103.5 ± 0.3 pc cm-3, with a dm excess of ∼70 pc cm-3. both sources are interesting targets for multi-wavelength follow-up due to their apparent proximity. the dm distribution of our repeater sample is statistically indistinguishable from that of the first 12 chime/frb sources that have not yet repeated. we find, with 4σ significance, that repeater bursts are generally wider than those of chime/frb bursts that have not repeated, suggesting different emission mechanisms. many of our repeater events show complex morphologies that are reminiscent of the first two discovered repeating frbs. the repetitive behavior of these sources will enable interferometric localizations and subsequent host galaxy identifications. | chime/frb discovery of eight new repeating fast radio burst sources |
supercdms snolab will be a next-generation experiment aimed at directly detecting low-mass particles (with masses ≤10 gev /c2 ) that may constitute dark matter by using cryogenic detectors of two types (hv and izip) and two target materials (germanium and silicon). the experiment is being designed with an initial sensitivity to nuclear recoil cross sections ∼1 ×10-43 cm2 for a dark matter particle mass of 1 gev /c2 , and with capacity to continue exploration to both smaller masses and better sensitivities. the phonon sensitivity of the hv detectors will be sufficient to detect nuclear recoils from sub-gev dark matter. a detailed calibration of the detector response to low-energy recoils will be needed to optimize running conditions of the hv detectors and to interpret their data for dark matter searches. low-activity shielding, and the depth of snolab, will reduce most backgrounds, but cosmogenically produced <mml:mmultiscripts>h 3 </mml:mmultiscripts> and naturally occurring <mml:mmultiscripts>si 32 </mml:mmultiscripts> will be present in the detectors at some level. even if these backgrounds are 10 times higher than expected, the science reach of the hv detectors would be over 3 orders of magnitude beyond current results for a dark matter mass of 1 gev /c2 . the izip detectors are relatively insensitive to variations in detector response and backgrounds, and will provide better sensitivity for dark matter particles with masses ≳5 gev /c2 . the mix of detector types (hv and izip), and targets (germanium and silicon), planned for the experiment, as well as flexibility in how the detectors are operated, will allow us to maximize the low-mass reach, and understand the backgrounds that the experiment will encounter. upgrades to the experiment, perhaps with a variety of ultra-low-background cryogenic detectors, will extend dark matter sensitivity down to the "neutrino floor," where coherent scatters of solar neutrinos become a limiting background. | projected sensitivity of the supercdms snolab experiment |
new physics in the neutrino sector might be necessary to address anomalies between different neutrino oscillation experiments. intriguingly, it also offers a possible solution to the discrepant cosmological measurements of h0 and σ8. we show here that delaying the onset of neutrino free streaming until close to the epoch of matter-radiation equality can naturally accommodate a larger value for the hubble constant h0=72.3 ±1.4 km s-1 mpc-1 and a lower value of the matter fluctuations σ8=0.786 ±0.020 , while not degrading the fit to the cosmic microwave background (cmb) damping tail. we achieve this by introducing neutrino self-interactions in the presence of a nonvanishing sum of neutrino masses. without explicitly incorporating additional neutrino species, this strongly interacting neutrino cosmology prefers neff=4.02 ±0.29 , which has interesting implications for particle model building and neutrino oscillation anomalies. we show that the absence of the neutrino free-streaming phase shift on the cmb can be compensated for by shifting the values of several cosmological parameters, hence providing an important caveat to the detections made in the literature. due to their impact on the evolution of the gravitational potential at early times, self-interacting neutrinos and their subsequent decoupling leave a rich structure on the matter power spectrum. in particular, we point out the existence of a novel localized feature appearing on scales entering the horizon at the onset of neutrino free streaming. while the interacting neutrino cosmology provides a better global fit to current cosmological data, we find that traditional bayesian analyses penalize the model as compared to the standard cosmological scenario due to the relatively narrow range of neutrino interaction strengths that is favored by the data. the model we present illustrates desirable cosmological impacts to simultaneously resolve the hubble constant and matter clustering tensions rather than proposing a viable particle model. our analysis shows that it is possible to find radically different cosmological models that nonetheless provide excellent fits to the data, hence providing an impetus to thoroughly explore alternate cosmological scenarios. | neutrino puzzle: anomalies, interactions, and cosmological tensions |
we report direct-detection constraints on light dark matter particles interacting with electrons. the results are based on a method that exploits the extremely low levels of leakage current of the damic detector at snolab of 2 - 6 ×10-22a cm -2 . we evaluate the charge distribution of pixels that collect <10 e- for contributions beyond the leakage current that may be attributed to dark matter interactions. constraints are placed on so-far unexplored parameter space for dark matter masses between 0.6 and 100 mev c-2 . we also present new constraints on hidden-photon dark matter with masses in the range 1.2 - 30 ev c-2 . | constraints on light dark matter particles interacting with electrons from damic at snolab |
pulsar timing arrays gathered evidence of the presence of a gravitational wave background around nhz frequencies. if the gravitational wave background was induced by large and gaussian primordial fluctuations, they would then produce too many sub-solar mass primordial black holes. we show that if at the time of gravitational wave generation the universe was dominated by a canonical scalar field, with the same equation of state as standard radiation but a higher propagation speed of fluctuations, one can explain the gravitational wave background with a primordial black hole counterpart consistent with observations. lastly, we discuss possible ways to test this model with future gravitational wave detectors. | scalar-induced gravitational wave interpretation of pta data: the role of scalar fluctuation propagation speed |
this paper describes the recommended solar forcing dataset for cmip6 and highlights changes with respect to cmip5. the solar forcing is provided for radiative properties, namely total solar irradiance (tsi), solar spectral irradiance (ssi), and the f10.7 index as well as particle forcing, including geomagnetic indices ap and kp, and ionization rates to account for effects of solar protons, electrons, and galactic cosmic rays. this is the first time that a recommendation for solar-driven particle forcing has been provided for a cmip exercise. the solar forcing datasets are provided at daily and monthly resolution separately for the cmip6 preindustrial control, historical (1850-2014), and future (2015-2300) simulations. for the preindustrial control simulation, both constant and time-varying solar forcing components are provided, with the latter including variability on 11-year and shorter timescales but no long-term changes. for the future, we provide a realistic scenario of what solar behavior could be, as well as an additional extreme maunder-minimum-like sensitivity scenario. this paper describes the forcing datasets and also provides detailed recommendations as to their implementation in current climate models.for the historical simulations, the tsi and ssi time series are defined as the average of two solar irradiance models that are adapted to cmip6 needs: an empirical one (nrltsi2-nrlssi2) and a semi-empirical one (satire). a new and lower tsi value is recommended: the contemporary solar-cycle average is now 1361.0 w m-2. the slight negative trend in tsi over the three most recent solar cycles in the cmip6 dataset leads to only a small global radiative forcing of -0.04 w m-2. in the 200-400 nm wavelength range, which is important for ozone photochemistry, the cmip6 solar forcing dataset shows a larger solar-cycle variability contribution to tsi than in cmip5 (50 % compared to 35 %).we compare the climatic effects of the cmip6 solar forcing dataset to its cmip5 predecessor by using time-slice experiments of two chemistry-climate models and a reference radiative transfer model. the differences in the long-term mean ssi in the cmip6 dataset, compared to cmip5, impact on climatological stratospheric conditions (lower shortwave heating rates of -0.35 k day-1 at the stratopause), cooler stratospheric temperatures (-1.5 k in the upper stratosphere), lower ozone abundances in the lower stratosphere (-3 %), and higher ozone abundances (+1.5 % in the upper stratosphere and lower mesosphere). between the maximum and minimum phases of the 11-year solar cycle, there is an increase in shortwave heating rates (+0.2 k day-1 at the stratopause), temperatures ( ∼ 1 k at the stratopause), and ozone (+2.5 % in the upper stratosphere) in the tropical upper stratosphere using the cmip6 forcing dataset. this solar-cycle response is slightly larger, but not statistically significantly different from that for the cmip5 forcing dataset.cmip6 models with a well-resolved shortwave radiation scheme are encouraged to prescribe ssi changes and include solar-induced stratospheric ozone variations, in order to better represent solar climate variability compared to models that only prescribe tsi and/or exclude the solar-ozone response. we show that monthly-mean solar-induced ozone variations are implicitly included in the sparc/ccmi cmip6 ozone database for historical simulations, which is derived from transient chemistry-climate model simulations and has been developed for climate models that do not calculate ozone interactively. cmip6 models without chemistry that perform a preindustrial control simulation with time-varying solar forcing will need to use a modified version of the sparc/ccmi ozone database that includes solar variability. cmip6 models with interactive chemistry are also encouraged to use the particle forcing datasets, which will allow the potential long-term effects of particles to be addressed for the first time. the consideration of particle forcing has been shown to significantly improve the representation of reactive nitrogen and ozone variability in the polar middle atmosphere, eventually resulting in further improvements in the representation of solar climate variability in global models. | solar forcing for cmip6 (v3.2) |
over recent decades, cosmological simulations of galaxy formation have been instrumental in advancing our understanding of structure and galaxy formation in the universe. these simulations follow the nonlinear evolution of galaxies, modelling a variety of physical processes over an enormous range of time and length scales. a better understanding of the relevant physical processes, improved numerical methods and increased computing power have led to simulations that can reproduce a large number of the observed galaxy properties. modern simulations model dark matter, dark energy and ordinary matter in an expanding space-time starting from well-defined initial conditions. the modelling of ordinary matter is most challenging due to the large array of physical processes affecting this component. cosmological simulations have also proven useful to study alternative cosmological models and their impact on the galaxy population. this technical review presents a concise overview of the methodology of cosmological simulations of galaxy formation and their different applications. | cosmological simulations of galaxy formation |
we review the topic of 4d einstein-gauss-bonnet (4degb) gravity, which has been the subject of considerable interest over the past two years. our review begins with a general introduction to lovelock's theorem, and the subject of gauss-bonnet terms in the action for gravity. these areas are of fundamental importance for understanding modified theories of gravity, and inform our subsequent discussion of recent attempts to include the effects of a gauss-bonnet term in four space-time dimensions by re-scaling the appropriate coupling parameter. we discuss the mathematical complexities involved in implementing this idea, and review recent attempts at constructing well-defined, self-consistent theories that enact it. we then move on to consider the gravitational physics that results from these theories, in the context of black holes, cosmology, and weak-field gravity. we show that 4degb gravity exhibits a number of interesting phenomena in each of these areas. | the 4d einstein-gauss-bonnet theory of gravity: a review |
we perform a comprehensive cosmological study of the h0 tension between the direct local measurement and the model-dependent value inferred from the cosmic microwave background. with the recent measurement of h0 this tension has raised to more than 3 σ. we consider changes in the early time physics without modifying the late time cosmology. we also reconstruct the late time expansion history in a model independent way with minimal assumptions using distance measurements from baryon acoustic oscillations and type ia supernovae, finding that at z < 0.6 the recovered shape of the expansion history is less than 5% different than that of a standard λcdm model. these probes also provide a model insensitive constraint on the low-redshift standard ruler, measuring directly the combination rsh where h0 = h × 100 mpc-1km/s and rs is the sound horizon at radiation drag (the standard ruler), traditionally constrained by cmb observations. thus rs and h0 provide absolute scales for distance measurements (anchors) at opposite ends of the observable universe. we calibrate the cosmic distance ladder and obtain a model-independent determination of the standard ruler for acoustic scale, rs. the tension in h0 reflects a mismatch between our determination of rs and its standard, cmb-inferred value. without including high-l planck cmb polarization data (i.e., only considering the ``recommended baseline" low-l polarisation and temperature and the high l temperature data), a modification of the early-time physics to include a component of dark radiation with an effective number of species around 0.4 would reconcile the cmb-inferred constraints, and the local h0 and standard ruler determinations. the inclusion of the ``preliminary" high-l planck cmb polarisation data disfavours this solution. | the trouble with h0 |
we report the detection of new binary black hole merger events in the publicly available data from the second observing run of advanced ligo and advanced virgo (o2). the mergers were discovered using the new search pipeline described in venumadhav et al. [phys. rev. d 100, 023011 (2019), 10.1103/physrevd.100.023011] and are above the detection thresholds as defined in abbott et al. (ligo scientific and virgo collaborations) [phys. rev. x 9, 031040 (2019)., 10.1103/physrevx.9.031040]. three of the mergers (gw170121, gw170304, gw170727) have inferred probabilities of being of astrophysical origin pastro>0.98 . the remaining three (gw170425, gw170202, gw170403) are less certain, with pastro ranging from 0.5 to 0.8. the newly found mergers largely share the statistical properties of previously reported events, with the exception of gw170403, the least secure event, which has a highly negative effective spin parameter χeff. the most secure new event, gw170121 (pastro>0.99 ), is also notable due to its inferred negative value of χeff, which is inconsistent with being positive at the ≈95.8 % confidence level. the new mergers nearly double the sample of gravitational wave events reported from o2 and present a substantial opportunity to explore the statistics of the binary black hole population in the universe. the number of detected events is not surprising since we estimate that the detection volume of our pipeline may be larger than that of other pipelines by as much as a factor of 2 (with significant uncertainties in the estimate). the increase in volume is larger when the constituent detectors of the network have very different sensitivities, as is likely to be the case in current and future runs. | new binary black hole mergers in the second observing run of advanced ligo and advanced virgo |
this letter reports on a cavity haloscope search for dark matter axions in the galactic halo in the mass range 2.81 - 3.31 μ ev . this search utilizes the combination of a low-noise josephson parametric amplifier and a large-cavity haloscope to achieve unprecedented sensitivity across this mass range. this search excludes the full range of axion-photon coupling values predicted in benchmark models of the invisible axion that solve the strong c p problem of quantum chromodynamics. | extended search for the invisible axion with the axion dark matter experiment |
we present a tomographic cosmic shear analysis of the kilo-degree survey (kids) combined with the vista kilo-degree infrared galaxy survey. this is the first time that a full optical to near-infrared data set has been used for a wide-field cosmological weak lensing experiment. this unprecedented data, spanning 450 deg2, allows us to significantly improve the estimation of photometric redshifts, such that we are able to include robustly higher-redshift sources for the lensing measurement, and - most importantly - to solidify our knowledge of the redshift distributions of the sources. based on a flat λcdm model we find s8 ≡ σ8 ωm/0.3 = 0.737+0.040-0.036 in a blind analysis from cosmic shear alone. the tension between kids cosmic shear and the planck-legacy cmb measurements remains in this systematically more robust analysis, with s8 differing by 2.3σ. this result is insensitive to changes in the priors on nuisance parameters for intrinsic alignment, baryon feedback, and neutrino mass. kids shear measurements are calibrated with a new, more realistic set of image simulations and no significant b-modes are detected in the survey, indicating that systematic errors are under control. when calibrating our redshift distributions by assuming the 30-band cosmos-2015 photometric redshifts are correct (following the dark energy survey and the hyper suprime-cam survey), we find the tension with planck is alleviated. the robust determination of source redshift distributions remains one of the most challenging aspects for future cosmic shear surveys. data products from this analysis are available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/j/a+a/633/a69 and at http://kids.strw.leidenuniv.nl | kids+viking-450: cosmic shear tomography with optical and infrared data |
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