Speaker
Description
In many extensions of the Standard Model, the universe underwent one or several first order phase transitions. Such phase transitions proceed via the formation and collision of bubbles. The bubble collisions can source a stochastic gravitational wave background signal. In the case of the electroweak phase transition, the characteristic frequency would fall right in the sensitivity band of LISA. We can thus use data from gravitational wave experiments to probe physics beyond the standard model. In this talk, I will give an overview of the relevant contributions to the gravitational wave signal, and then focus on the contribution to the gravitational wave signal from sound waves.
Predictions of the gravitational wave spectrum typically rely on hydrodynamic lattice simulations of the scalar-plasma system. Hydrodynamic solutions of a single expanding bubble provide a bridge between the particle physics model and the hydrodynamic lattice simulation. Two relevant quantities in this computation are the bubble expansion velocity and the kinetic energy budget. I will discuss the computation of the bubble wall velocity, and present recent progress in the computation of this quantity, obtained in the limiting cases of local thermal equilibrium and a large enthalpy jump between the two phases.