Residual Non-Abelian Dark Matter and Dark Radiation

TL;DR

This paper introduces a non-Abelian dark sector model where dark gauge bosons serve as both dark matter and dark radiation, potentially resolving cosmological tensions and affecting structure formation.

Contribution

It presents a novel non-Abelian dark sector model with spontaneous symmetry breaking, linking dark matter and dark radiation in a unified framework.

Findings

Massless gauge bosons act as dark radiation, alleviating Hubble tension.

Massive gauge bosons serve as vector dark matter candidates.

Interaction between dark matter and dark radiation suppresses matter power spectrum.

Abstract

We propose a novel particle physics model in which vector dark matter (VDM) and dark radiation (DR) originate from the same non-Abelian dark sector. We show an illustrating example where dark $SU(3)$ is spontaneously broken into $SU(2)$ subgroup by the nonzero vacuum expectation value of a complex scalar in fundamental representation of $SU(3)$. The massless gauge bosons associated with the residual unbroken $SU(2)$ constitute DR and help to relieve the tension in Hubble constant measurements between $\textit{Planck}$ and Hubble Space Telescope. In the meantime, massive dark gauge bosons associated with the broken generators are VDM candidates. Intrinsically, this non-Abelian VDM can interact with non-Abelian DR in the cosmic background, which results in a suppressed matter power spectrum and leads to a smaller $\sigma_8$ for structure formation.