Impact of Cosmological Phase Transitions on Dark Matter Phenomenology

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As electroweak-scale dark matter (DM) continues to stubbornly evade experimental detection, the possibility that the DM abundance in the Universe is not determined by thermal freeze-out, but by some alternative mechanism, is becoming more and more appealing. We propose here to investigate in particular novel scenarios in which the dynamics of DM in the early Universe, and thus its abundance today, is influenced by cosmological phase transitions. The vacuum expectation values (vevs) of scalar fields can change abruptly during a phase transition, thereby breaking or restoring the symmetry that stabilizes DM particles. Moreover, by affecting particle masses, scalar field vevs can determine whether or not DM decay or annihilation processes are kinematically allowed. Based on a preliminary proof-of-principle study, we plan to develop theoretical models implementing this mechanism for setting the DM abundance,and to explore their phenomenology in terrestrial, astrophysical, and cosmological experiments. Moreover, we plan to connect DM phenomenology to electroweak baryogenesis by exploiting the fact that the scenarios under consideration often feature strong first order phase transitions. Finally, we plan to study the interplay between DM phenomenology and the gravitational wave signals of phase transitions in the early Universe.