Electroweak baryogenesis at high wall velocities

TL;DR

This paper quantitatively studies how electroweak baryogenesis efficiency varies with bubble wall velocity, showing it remains effective even at high speeds, especially in models with detectable gravitational waves.

Contribution

It derives new fluid equations for particle asymmetry transport without small-wall-velocity assumptions, clarifying baryogenesis behavior at high wall velocities.

Findings

Baryon asymmetry suppression is smooth across wall velocities.

Electroweak baryogenesis remains efficient at high wall speeds.

Comparison of transport equations highlights differences in modeling.

Abstract

It is widely believed that electroweak baryogenesis should be suppressed in strong phase transitions with fast-moving bubble walls, but this effect has never been quantitatively studied. We rederive fluid equations describing transport of particle asymmetries near the bubble wall without making the small-wall-velocity approximation. We show that the suppression of the baryon asymmetry is a smooth function of the wall speed and that there is no special behavior when crossing the sound speed barrier. Electroweak baryogenesis can thus be efficient also with strong detonations, generically associated with models with observably large gravitational waves. We also make a systematic and critical comparison of our improved transport equations to another one commonly used in the literature, based on the VEV-insertion formalism.