Natural Cold Baryogenesis from Strongly Interacting Electroweak Symmetry Breaking

TL;DR

This paper proposes a natural mechanism for cold baryogenesis within strongly interacting electroweak symmetry breaking models, avoiding ad-hoc inflation assumptions and utilizing bubble collisions and CP violation to generate baryon asymmetry.

Contribution

It demonstrates that cold baryogenesis can occur without slow-roll inflation, using composite Higgs models with first-order phase transitions and effective operators that evade EDM constraints.

Findings

Baryogenesis can be achieved through bubble collisions during a first-order phase transition.

The mechanism does not require specific UV completions, only a stage of supercooling.

Effective dimension-six operators can induce CP violation without EDM constraints.

Abstract

The mechanism of "cold electroweak baryogenesis" has been so far unpopular because its proposal has relied on the ad-hoc assumption of a period of hybrid inflation at the electroweak scale with the Higgs acting as the waterfall field. We argue here that cold baryogenesis can be naturally realized without the need to introduce any slow-roll potential. Our point is that composite Higgs models where electroweak symmetry breaking arises via a strongly first-order phase transition provide a well-motivated framework for cold baryogenesis. In this case, reheating proceeds by bubble collisions and we argue that this can induce changes in Chern-Simons number, which in the presence of new sources of CP violation commonly lead to baryogenesis. We illustrate this mechanism using as a source of CP violation an effective dimension-six operator which is free from EDM constraints, another advantage of cold baryogenesis compared to the standard theory of electroweak baryogenesis. Our results are general as they do not rely on any particular UV completion but only on a stage of supercooling ended by a first-order phase transition in the evolution of the universe, which can be natural if there is nearly conformal dynamics at the TeV scale. Besides, baryon-number violation originates from the Standard Model only.