Bounds on the bubble wall velocity
Wen-Yuan Ai (Vienna, OAW)

The terminal bubble wall velocity in a first-order phase transition (FOPT) is a critical parameter that influences not only the gravitational wave power spectrum but also a wide range of FOPT-related phenomena, including baryogenesis and dark matter production. However, precise computation of this velocity remains challenging. In this talk, I will discuss how to establish bounds on bubble wall velocities using two straightforward approximations: the local thermal equilibrium (LTE) approximation and the ballistic approximation. We perform numerical calculations both for a model-independent analysis and within an example model, the singlet-extended Standard Model.