Cosmological Constraints on Thermal Friction of Axion Dark Matter

TL;DR

This study explores how thermal friction in axion dark matter affects cosmological observations, aiming to address tensions in Hubble constant and large-scale structure measurements by analyzing multiple datasets.

Contribution

It introduces a thermal friction model for axion dark matter and demonstrates its partial effectiveness in alleviating large-scale structure tension using cosmological data.

Findings

Partial alleviation of large-scale structure tension.

Lower $ ext{S}_8$ value compared to $ ext{Λ}$CDM.

Lower $ ext{χ}^2_{tot}$ indicating better fit.

Abstract

In this paper, we investigate the process in which axion dark matter undergoes thermal friction, resulting in energy injection into dark radiation, with the aim of mitigating the Hubble tension and large-scale structure tension. In the early universe, this scenario led to a rapid increase in the energy density of dark radiation; in the late universe, the evolution of axion dark matter is similar to that of cold dark matter, with this scenario resembling decaying dark matter and serving to ease the large-scale structure tension. We employ cosmological observational data, including cosmic microwave background (CMB), baryon acoustic oscillation (BAO), supernova data (SNIa), $H_0$ measurement from SH0ES, and $S_8$ from the Dark Energy Survey Year-3 (DES), to study and analyze this model. Our results indicate that the thermal friction model offers partial alleviation of the large-scale structure tension, while its contribution on alleviating Hubble tension can be ignored. The new model yields the value of $S_8$ is $0.795\pm 0.011$ at a 68% confidence level, while the $\Lambda$CDM model yields a result of $0.8023\pm 0.0085$. In addition, the new model exhibits a lower $\chi^2_\mathrm{tot}$ value, with a difference of -2.60 compared to the $\Lambda$CDM model. Additionally, we incorporate Lyman-$\alpha$ data to re-constrain the new model and find a slight improvement in the results, with the values of $H_0$ and $S_8$ being $68.76^{+0.39}_{-0.35}$ km/s/Mpc and $0.791\pm 0.011$ at a 68% confidence level, respectively.