Self-consistent evolution of magnetic fields and chiral asymmetry in the early Universe

TL;DR

This paper investigates how quantum chiral anomaly influences the evolution of magnetic fields and lepton asymmetry in the early Universe's primordial plasma, revealing effects neglected in previous models.

Contribution

It introduces the impact of quantum chiral anomaly on magnetic field evolution and lepton asymmetry generation in the early Universe, extending previous understanding.

Findings

Chiral anomaly significantly affects magnetic field evolution at T > 10 MeV.

An asymmetry between left and right-chiral electrons develops in strong magnetic fields.

Lepton asymmetry can persist down to T ~ 10 MeV, influencing early Universe processes.

Abstract

We show that the evolution of magnetic fields in a primordial plasma, filled with Standard Model particles, at temperatures T > 10 MeV is strongly affected by the quantum chiral anomaly -- an effect that has been neglected previously. Although reactions equilibrating left and right-chiral electrons are in deep thermal equilibrium for T < 80 TeV, an asymmetry between these particle develops in the presence of strong magnetic fields. This results in magnetic helicity transfer from shorter to longer scales. This also leads to an effective generation of lepton asymmetry that may survive in the plasma down to temperatures T ~ 10 MeV, which may strongly affect many processes in the early Universe. Although we report our results for the Standard Model, they are likely to play an important role also in its extensions.