Energy budget of cosmological first-order phase transitions

Abstract

The study of the hydrodynamics of bubble growth in first-order phasetransitions is very relevant for electroweak baryogenesis, as thebaryon asymmetry depends sensitively on the bubble wall velocity, andalso for predicting the size of the gravity wave signal resulting frombubble collisions, which depends on both the bubble wall velocity andthe plasma fluid velocity. We perform such study in different bubbleexpansion regimes, namely deflagrations, detonations, hybrids (steadystates) and runaway solutions (accelerating wall), without relying ona specific particle physics model. We compute the efficiency of thetransfer of vacuum energy to the bubble wall and the plasma in allregimes. We clarify the condition determining the runaway regime andstress that in most models of strong first-order phase transitionsthis will modify expectations for the gravity wave signal. Indeed, inthis case, most of the kinetic energy is concentrated in the wall andalmost no turbulent fluid motions are expected since the surroundingfluid is kept mostly at rest.