Energy budget of cosmological first-order phase transitions

Abstract

The study of the hydrodynamics of bubble growth in first-order phase\ntransitions is very relevant for electroweak baryogenesis, as the baryon\nasymmetry depends sensitively on the bubble wall velocity, and also for\npredicting the size of the gravity wave signal resulting from bubble\ncollisions, which depends on both the bubble wall velocity and the plasma fluid\nvelocity. We perform such study in different bubble expansion regimes, namely\ndeflagrations, detonations, hybrids (steady states) and runaway solutions\n(accelerating wall), without relying on a specific particle physics model. We\ncompute the efficiency of the transfer of vacuum energy to the bubble wall and\nthe plasma in all regimes. We clarify the condition determining the runaway\nregime and stress that in most models of strong first-order phase transitions\nthis will modify expectations for the gravity wave signal. Indeed, in this\ncase, most of the kinetic energy is concentrated in the wall and almost no\nturbulent fluid motions are expected since the surrounding fluid is kept mostly\nat rest.\n