Speaker
Description
The bubble wall velocity is a key parameter controlling the phenomenology of first-order phase transitions, including the emission of gravitational waves. In this talk, I will discuss how the heating of the primordial plasma around the time of percolation can strongly reduce the velocity of the bubble walls that are still expanding. Such slow-down, first observed in numerical simulations, has been shown to induce a large suppression of the gravitational-wave emission, highlighting the need for incorporating it in the theoretical framework. By modeling the late-time evolution of the bubbles as shrinking droplets of false vacuum, I will show how the terminal wall velocity can actually be predicted from first principles, finding remarkable agreement with all available numerical simulations. This opens the way to a novel characterization of the gravitational waves from first order phase transitions that combines such heating effects with other geometrical inputs such as the size of the shocks in the fluid.