 Award ID(s):
 2112540
 NSFPAR ID:
 10333907
 Date Published:
 Journal Name:
 Journal of High Energy Physics
 Volume:
 2022
 Issue:
 5
 ISSN:
 10298479
 Format(s):
 Medium: X
 Sponsoring Org:
 National Science Foundation
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A bstract We propose a new interacting dark sector model, Stepped Partially Acoustic Dark Matter (SPartAcous), that can simultaneously address the two most important tensions in current cosmological data, the H 0 and S 8 problems. As in the Partially Acoustic Dark Matter (PAcDM) scenario, this model features a subcomponent of dark matter that interacts with dark radiation at high temperatures, suppressing the growth of structure at small scales and thereby addressing the S 8 problem. However, in the SPartAcous model, the dark radiation includes a component with a light mass that becomes nonrelativistic close to the time of matterradiation equality. As this light component annihilates away, the remaining dark radiation heats up and its interactions with dark matter decouple. The heating up of the dark sector results in a steplike increase in the relative energy density in dark radiation, significantly reducing the H 0 tension, while the decoupling of dark matter and dark radiation ensures that the power spectrum at larger scales is identical to ΛCDM.more » « less

Context. Persistent tension between lowredshift observations and the cosmic microwave background radiation (CMB), in terms of two fundamental distance scales set by the sound horizon r d and the Hubble constant H 0 , suggests new physics beyond the Standard Model, departures from concordance cosmology, or residual systematics. Aims. The role of different probe combinations must be assessed, as well as of different physical models that can alter the expansion history of the Universe and the inferred cosmological parameters. Methods. We examined recently updated distance calibrations from Cepheids, gravitational lensing timedelay observations, and the tip of the red giant branch. Calibrating the baryon acoustic oscillations and type Ia supernovae with combinations of the distance indicators, we obtained a joint and selfconsistent measurement of H 0 and r d at low redshift, independent of cosmological models and CMB inference. In an attempt to alleviate the tension between latetime and CMBbased measurements, we considered four extensions of the standard ΛCDM model. Results. The sound horizon from our different measurements is r d = (137 ± 3 stat. ± 2 syst. ) Mpc based on absolute distance calibration from gravitational lensing and the cosmic distance ladder. Depending on the adopted distance indicators, the combined tension in H 0 and r d ranges between 2.3 and 5.1 σ , and it is independent of changes to the lowredshift expansion history. We find that modifications of ΛCDM that change the physics after recombination fail to provide a solution to the problem, for the reason that they only resolve the tension in H 0 , while the tension in r d remains unchanged. Prerecombination extensions (with early dark energy or the effective number of neutrinos N eff = 3.24 ± 0.16) are allowed by the data, unless the calibration from Cepheids is included. Conclusions. Results from timedelay lenses are consistent with those from distanceladder calibrations and point to a discrepancy between absolute distance scales measured from the CMB (assuming the standard cosmological model) and latetime observations. New proposals to resolve this tension should be examined with respect to reconciling not only the Hubble constant but also the sound horizon derived from the CMB and other cosmological probes.more » « less

Abstract In recent years discrepancies have emerged in measurements of the presentday rate of expansion of the universe H 0 and in estimates of the clustering of matter S 8 . Using the most recent cosmological observations we reexamine a novel model proposed to address these tensions, in which cold dark matter disintegrates into dark radiation. The disintegration process is controlled by its rate Q = αℋρ ddm , where α is a (constant) dimensionless parameter quantifying the strength of the disintegration mechanism and ℋ is the conformal Hubble rate in the spatially flat FriedmannLemaîtreRobertsonWalker universe and ρ ddm is the energy density of the disintegrating cold dark matter. We constrain this model with the latest 2018 Planck temperature and polarization data, showing that there is no evidence for α≠ 0 and that it cannot solve the H 0 tension below 3σ, clashing with the result obtained by analyzing the Planck 2015 temperature data. We also investigate two possible extensions of the model in which the dark energy equationofstate parameter w ≠ 1. In this case it is possible to combine Planck data with the SH0ES measurement, and we demonstrate that in both these models the H 0 tension is resolved at the 1σ level, but the condition w ≠ 1 exacerbates the S 8 tension. We also demonstrate that the addition of intermediateredshift data (from the Pantheon supernova type Ia dataset and baryon acoustic oscillations) weakens the effectiveness of all these models to address the H 0 and S 8 tensions.more » « less

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Abstract We present cosmological constraints from a gravitational lensing mass map covering 9400 deg^{2}reconstructed from measurements of the cosmic microwave background (CMB) made by the Atacama Cosmology Telescope (ACT) from 2017 to 2021. In combination with measurements of baryon acoustic oscillations and big bang nucleosynthesis, we obtain the clustering amplitude
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