Supersonic Electroweak Baryogenesis: Achieving Baryogenesis for Fast Bubble Walls

TL;DR

This paper introduces a novel electroweak baryogenesis mechanism that works with supersonic bubble walls by forming symmetric phase bubbles behind the wall, enabling baryon asymmetry generation under conditions previously thought unfavorable.

Contribution

It proposes a new baryogenesis mechanism for fast bubble walls involving symmetric phase bubbles, expanding the viable parameter space for electroweak baryogenesis.

Findings

Mechanism successfully generates sufficient baryon asymmetry.

Applicable to models with Higgs coupled to singlets.

Operates effectively with supersonic bubble expansion.

Abstract

Standard electroweak baryogenesis in the context of a first order phase transition is effective in generating the baryon asymmetry of the universe if the broken phase bubbles expand at subsonic speed, so that CP asymmetric currents can diffuse in front of the wall. Here we present a new mechanism for electroweak baryogenesis which operates for supersonic bubble walls. It relies on the formation of small bubbles of the symmetric phase behind the bubble wall, in the broken phase, due to the heating of the plasma as the wall passes by. We apply the mechanism to a model in which the Higgs field is coupled to several singlets, and find that enough baryon asymmetry is generated for reasonable values of the parameter space.