Thermal evolution of dark matter and gravitational-wave production in the early universe from a symplectic glueball model

TL;DR

This paper explores a dark matter model based on a symplectic gauge group, analyzing its phase transition, thermal evolution, gravitational wave production, and relic abundance in the early universe, offering a novel alternative to SU(N) gauge theories.

Contribution

It introduces a symplectic gauge group dark matter model with a first-order phase transition, detailing its thermodynamics and potential gravitational wave signals, expanding beyond traditional SU(N) models.

Findings

Determined the equation of state near the phase transition.

Evaluated the latent heat associated with the transition.

Discussed gravitational wave spectra and relic abundance implications.

Abstract

The hypothesis that dark matter could be a bound state of a strongly coupled non-Abelian gauge theory is theoretically appealing and has a variety of interesting phenomenological implications. In particular, an interpretation of dark matter as the lightest glueball state in the spectrum of a dark Yang-Mills theory, possibly coupled to the visible sector only through gravitational interactions, has been discussed quite extensively in the literature, but most of previous work has been focused on dark SU(N) gauge theories. In this article, we consider an alternative model, based on a symplectic gauge group, which has a first-order confinement/deconfinement phase transition at a finite critical temperature. We first determine the equation of state of this theory, focusing on temperatures close to the transition, and evaluating the associated latent heat. Then we discuss the evolution of this dark-matter model in the early universe, commenting on the mechanisms by which it could indirectly interact with the visible sector, on the spectrum of gravitational waves it could produce, and on the relic abundances it would lead to. Our discussion includes an extensive review of relevant literature, a number of comments on similarities and differences between our model and dark SU(N) gauge theories, as well as some possible future extensions of the present study.