Smooth reheating and dark matter via non-Abelian gauge theory

TL;DR

This paper explores how a dark non-Abelian gauge sector can facilitate reheating after inflation and produce dark matter relics, with the dynamics constrained by cosmological and particle physics bounds.

Contribution

It introduces a model linking dark gauge fields, reheating, and dark matter production via confinement and portal interactions, with detailed phenomenological constraints.

Findings

Dark sector forms a heat bath after inflation.

Glueball states can be stable dark matter candidates.

Parameter space exists where both reheating and dark matter abundance are achieved.

Abstract

We demonstrate how a dark sector can provide a crucial link between a vacuum-dominated early universe and the later radiation-dominated epoch. As an example, we consider a feeble axion-like coupling of dark non-Abelian gauge fields with a single inflaton. In this scenario, a dark heat bath emerges at the end of inflation. As the dark sector cools down, its gauge fields confine into composite glueball states. The reheating of the visible sector is realized through portal interactions. After confinement, discrete symmetries protect part of the glueball states that form relic dark matter, while the others keep decaying into Standard Model degrees of freedom. The dark relic abundance depends mostly on the departure from equilibrium dynamics after the phase transition, constraining the confinement scale of the dark sector. Moreover, indirect detection and Big-Bang nucleosynthesis set bounds on the scale of portal interactions. We show that in a narrow but non-vanishing region of the parameter space, the correct dark matter abundance and sufficient reheating temperature are simultaneously reached.