Spontaneous Magnetogenesis at the Electroweak Phase Transition

TL;DR

This paper explores how spontaneous CP violation during the electroweak phase transition can generate intergalactic magnetic fields and baryon asymmetry, by coupling the Standard Model to an axion-like particle.

Contribution

It demonstrates a novel mechanism linking axion-like particles to magnetic field generation and baryogenesis during the electroweak phase transition.

Findings

Magnetic helicity fraction is proportional to axion velocity.

Electroweak phase transition can produce sizable intergalactic magnetic fields.

Small baryon asymmetry consistent with observations.

Abstract

Spontaneous CP violation during the electroweak phase transition can induce a twisting of the magnetic field configuration of Standard Model dumbbells, resulting in sizable intergalactic magnetic fields and a small baryon asymmetry, in agreement with observations. We demonstrate this by coupling the electroweak gauge group of the Standard Model to an axion-like particle with a non-vanishing velocity. Studying the resulting monopole, string and dumbbell configurations, we conclude that the helicity fraction of the magnetic fields generated at the electroweak phase transition is roughly given by the dimensionless axion velocity.