Abstract: Cosmological phase transitions that proceed via nucleation of bubbles are a possibility both in extensions of the Standard Model as well as in more general hidden sectors. I will discuss the dynamics of expanding vacuum bubbles in the presence of massive dark photons that gain mass across the interface - with a special focus on the benchmark where they furnish the dark matter. I will argue the existence of a transient relativistic regime during which the wall can be thought of as an (imperfect) mirror of longitudinal - but not transverse - vectors. This leads to a new source of pressure on the expanding interface that can prevent the accelerated expansion of the bubble walls. Instead, the energy released by the phase
transition goes into making the reflected dark photons relativistic. If subsequent interactions with the environment can be ignored, an observable contribution to Delta N_eff is possible for strong phase transitions. Our results highlight the potential interplay between the dark matter and the dynamics of phase transitions in the early universe, as well as the complementarity between gravitational wave detectors and CMB Stage-4 observatories.
Seminar: "Reflections on Bubble Walls" by R. Petrossian-Byrne, ICTP
22 mar 2023 , 14:30 - Venue: room 281, Department of Physics and Astronomy