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A Dark Sector to Restore Cosmological Concordance | | Itamar J. Allali
; Mark P. Hertzberg
; Fabrizio Rompineve
; | | Date: |
26 Apr 2021 | | Abstract: | We develop a new phenomenological model that addresses current tensions
between observations of the early and late Universe. Our scenario features: (i)
a decaying dark energy fluid, which undergoes a transition at $z sim 5,000$,
to raise today’s value of the Hubble parameter -- addressing the $H_0$ tension,
and (ii) an ultra-light axion, which starts oscillating at $zsim 16,000$, to
suppress the matter power spectrum -- addressing the $S_8$ tension. Our Markov
Chain Monte Carlo analyses show that such a Dark Sector model fits a
combination of early time datasets slightly better than the $Lambda$CDM model,
while reducing both the $H_0$ and $S_8$ tensions to $lesssim 3sigma$ level.
Combined with measurements from cosmic shear surveys, we find that the
discrepancy on $S_8$ is reduced to the $1.4sigma$ level, and the value of
$H_0$ is further raised. Adding local supernovae measurements, we find that the
$H_0$ and $S_8$ tensions are reduced to the $1.5sigma$ and $1.1sigma$ level
respectively, with a significant improvement $Deltachi^2simeq -17$ compared
to the $Lambda$CDM model. We discuss a possible particle physics realization
of this model, with a dark confining gauge sector and its associated axion,
although embedding the full details within microphysics remains an urgent open
question. Our scenario will be decisively probed with future CMB surveys. | | Source: | arXiv, 2104.12798 | | Services: | Forum | Review | PDF | Favorites | |
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