Phase transitions and gravitational waves in a non-abelian vector dark matter scenario

TL;DR

This paper explores a non-abelian vector dark matter model with a dark SU(2) gauge group, analyzing phase transitions and gravitational wave signals, identifying parameter regions compatible with dark matter relic density and detectable gravitational waves.

Contribution

It introduces a dark SU(2) gauge extension with a custodial symmetry, analyzing phase transitions and gravitational wave signals, and identifying detectable signals consistent with dark matter constraints.

Findings

Certain parameter regions produce gravitational waves detectable by future space-based detectors.

The model can account for the observed dark matter relic density.

Strong phase transitions are achievable within the model's parameter space.

Abstract

We study a scenario where the Standard Model is extended by a SU(2) gauge group in the dark sector. The three associated dark gauge bosons are stabilised via a custodial symmetry triggered by an additional dark SU(2) scalar doublet, thus making them viable dark-matter candidates. After considering the most recent constraints for this model, we analyse the phase transition dynamics and compute the power spectrum of resulting stochastic gravitational-wave background. Finally, we find regions of the parameter space yielding the observed dark-matter relic density while also leading to strong enough phase transition with an associated gravitational-wave signal reaching the sensitivity of future space-based gravitational-wave detector, such as LISA, DECIGO, BBO, TianQin or Taiji.