$T_0$ censorship of early dark energy and AdS vacua

TL;DR

This paper explores how early dark energy models compatible with the FIRAS CMB temperature measurement can influence the Hubble constant, proposing an AdS model that hints at an AdS phase near recombination with a higher H_0.

Contribution

It introduces an $ ext{alpha}$-attractor AdS model of early dark energy and analyzes its implications for the Hubble tension using MCMC methods.

Findings

EDE models can fit FIRAS data while increasing H_0.

Weak evidence for an AdS phase near recombination.

Best-fit models suggest H_0 around 73 km/s/Mpc.

Abstract

Present-day temperature $T_0$ of cosmic microwave background has been precisely measured by the FIRAS experiment. We identify that the early dark energy (EDE) (non-negligible around matter-radiation equality) scenario can remain compatible with the FIRAS result, while lifting the Hubble constant $H_0$. We perform Monte Carlo Markov chain analysis to confirm our observations. We also present an $\alpha$-attractor Anti-de Sitter (AdS) model of EDE, in which the AdS depth is consistently varied in the Monte Carlo Markov chain analysis. We found that our datasets weakly hinted the existence of an AdS phase near recombination with $H_0\sim 73$km/s/Mpc at 1$\sigma$ region in the best-fit model.