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

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 stabilized 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 analyze the phase transition dynamics and compute the power spectrum of the resulting stochastic gravitational-wave background. Finally, we find regions of the parameter space yielding the observed dark-matter relic density while also leading to a strong enough phase transition with an associated gravitational-wave signal reaching the sensitivity of a future space-based gravitational-wave detector, such as LISA, DECIGO, BBO, TianQin, or Taiji.