Inverse Electroweak Baryogenesis

TL;DR

This paper introduces a novel electroweak baryogenesis mechanism where baryon asymmetry arises from sphaleron processes during an inverse phase transition, allowing higher temperature scenarios and distinct signatures.

Contribution

It proposes a new baryogenesis mechanism involving equilibrium sphaleron responses during inverse electroweak phase transitions, independent of a first-order transition.

Findings

Baryon asymmetry generated during inverse phase transition.

Mechanism operates at higher temperatures than standard models.

Decouples baryon production from the strength of electroweak symmetry breaking.

Abstract

We propose a mechanism for baryogenesis in which the baryon asymmetry is generated as an equilibrium response of weak sphalerons in a region where electroweak sphaleron transitions remain unsuppressed, $h/T\lesssim 1$. A nonzero equilibrium baryon density arises in the presence of an approximately conserved global charge, carried either by new states with nonzero hypercharge, or by Standard Model fields themselves. The required global charge asymmetry is generated during a phase transition that changes the strength of electroweak symmetry breaking, but need not coincide with the final electroweak phase transition. In particular, the mechanism can operate during an inverse electroweak phase transition, where baryon number is produced behind the advancing wall, in contrast to conventional electroweak baryogenesis. Because baryon production is decoupled from a direct first-order electroweak phase transition, the scenario can be realized at parametrically higher temperatures than standard electroweak baryogenesis, thereby weakening current experimental constraints. This framework provides a qualitatively distinct route to electroweak baryogenesis, with different parametric dependence, phase-transition dynamics, and phenomenological signatures.