A Two-Component Dark Matter Model and its Associated Gravitational Waves

We consider an extension of the Standard Model that accounts for the muon $g-2$ tension and neutrino masses and study in detail dark matter phenomenology. The model under consideration includes a WIMP and a FIMP scalar dark matter candidates and thus gives rise to two-component dark matter scenarios. We discuss different regimes and mechanisms of production, including the novel freeze-in semi-production, and show that the WIMP and FIMP together compose the observed relic density today. The presence of the extra scalar fields allows phase transitions of the first order. We examine the evolution of the vacuum state and discuss stochastic gravitational wave signals associated with the first-order phase transition. We show that the gravitational wave signals may be probed by future gravitational wave experiments which may serve as a complementary detection signal.
Comment: v1: 28 pages; v2: 28 pages, typos corrected, references updated; v3: 30 pages, references updated, typos corrected, discussion improved, accepted for publication in JHEP