# Simulations of Cold Electroweak Baryogenesis: Hypercharge U(1) and the creation of helical magnetic fields

## TL;DR

This paper presents numerical simulations of Cold Electroweak Baryogenesis including the full electroweak gauge group and CP-violation, revealing the impact on baryon asymmetry and magnetic fields, with implications for astrophysical observations.

## Contribution

First simulation including full SU(2)×U(1) gauge group and CP-violation in Cold Electroweak Baryogenesis, analyzing baryon asymmetry and magnetic helicity.

## Key findings

- Baryon asymmetry is reduced by a factor of three compared to SU(2)-only models.
- Magnetic helicity depends on CP-violation strength and quench time, not directly on baryon asymmetry.
- Primordial magnetic helicity signatures cannot definitively confirm electroweak baryogenesis.

## Abstract

We perform numerical simulations of Cold Electroweak Baryogenesis, including for the first time in the Bosonic sector the full electroweak gauge group SU(2)$\times$U(1) and CP-violation. We find that the maximum generated baryon asymmetry is reduced by a factor of three relative to the SU(2)-only model, but that the quench time dependence is very similar. In addition, we compute the magnitude of the helical magnetic fields, and find that it is proportional to the strength of CP-violation and dependent on quench time, but is not proportional to the magnitude of the baryon asymmetry as proposed in the literature. Astrophysical signatures of primordial magnetic helicity can therefore not in general be used as evidence that electroweak baryogenesis has taken place.