Restoring cosmological concordance with axion-like early dark energy and dark matter characterized by a constant equation of state?

TL;DR

This paper explores an extended axion-like early dark energy model with a constant dark matter equation of state to address the Hubble tension, finding it reduces the tension but worsens the $S_8$ tension.

Contribution

It introduces a novel extension of the axion-like EDE model by incorporating dark matter with a constant EoS, and constrains it using comprehensive cosmological data.

Findings

Reduces Hubble tension to about 1.4σ

Worsens $S_8$ tension similar to previous models

Maintains viability of EDE in alleviating Hubble tension

Abstract

The Hubble tension persists as a challenge in cosmology. Even early dark energy (EDE) models, initially considered the most promising for alleviating the Hubble tension, fall short of addressing the issue without exacerbating other tensions, such as the $S_8$ tension. Considering that a negative dark matter (DM) equation of state (EoS) parameter is conducive to reduce the value of $\sigma_8$ parameter, we extend the axion-like EDE model in this paper by replacing the cold dark matter (CDM) with DM characterized by a constant EoS $w_{\rm dm}$ (referred as WDM hereafter). We then impose constraints on this axion-like EDE extension model, along with three other models: the axion-like EDE model, $\Lambda$WDM, and $\Lambda$CDM. These constraints are derived from a comprehensive analysis incorporating data from the Planck 2018 cosmic microwave background (CMB), baryon acoustic oscillations (BAO), the Pantheon compilation, as well as a prior on $H_0$ (i.e., $H_0=73.04\pm1.04$, based on the latest local measurement by Riess et al.) and a Gaussianized prior on $S_8$ (i.e., $S_8=0.766\pm0.017$, determined through the joint analysis of KID1000+BOSS+2dLenS). We find that although the new model maintains the ability to alleviate the Hubble tension to $\sim$ 1.4$\sigma$, it still exacerbate the $S_8$ tension to a level similar to that of the axion-like EDE model.