Bubble wall dynamics at the electroweak phase transition

TL;DR

This paper presents a novel, comprehensive solution to the linearized Boltzmann equation for top quarks during a first-order electroweak phase transition, revealing significant differences from traditional fluid approximation results.

Contribution

It introduces the first full solution of the Boltzmann equation for top quarks in this context, avoiding the fluid approximation and capturing plasma density perturbations more accurately.

Findings

Results differ significantly from fluid approximation models.

Sizable differences in the friction acting on the bubble wall.

Qualitative and quantitative deviations from previous approaches.

Abstract

First order phase transitions could play a major role in the early universe, providing important phenomenological consequences, such as the production of gravitational waves and the generation of baryon asymmetry. An important aspect that determines the properties of the phase transition is the dynamics of the true-vacuum bubbles, which is controlled by the density perturbations in the hot plasma. We study this aspect presenting, for the first time, the full solution of the linearized Boltzmann equation for the top quark species coupled to the Higgs field during a first-order electroweak phase transition. Our approach, differently from the traditional one based on the fluid approximation, does not rely on any ansatz and can fully capture the density perturbations in the plasma. We find that our results significantly differ from the ones obtained in the fluid approximation (including its extensions and modifications), both at the qualitative and quantitative level. In particular sizable differences are found for the friction acting on the bubble wall.