Generating Seed magnetic field \`a la Chiral Biermann battery

TL;DR

This paper proposes a novel mechanism for generating seed magnetic fields in the early universe using inhomogeneous chiral plasma, extending the Biermann battery concept through chiral anomaly effects.

Contribution

It introduces a new seed magnetic field generation mechanism based on inhomogeneous chiral plasma and chiral anomaly, applicable during different cosmological epochs.

Findings

Seed magnetic fields range from a few nG to hundreds of nG.

The mechanism depends on inhomogeneities in chiral chemical potential and temperature.

Generation varies with the epoch of the universe.

Abstract

Cosmological and astrophysical observations indicate the presence of magnetic field over all scales. In order to explain these magnetic fields, it is assumed that there exists a seed magnetic field that gets amplified by dynamos. These seed fields may have been produced during inflation, at phase transitions, or some turbulent phase of the early universe. One well-known mechanism to get the seed field is the Biermann battery, which was originally discussed in the context of generation in an astrophysical object. Requirements for this mechanism to work are (i) non-zero gradient of the electron number density and pressure, (ii) they are non-parallel to each other. In the present article, we propose a similar mechanism to generate the seed field but in inhomogeneous chiral plasma. Our mechanism works, in presence of chiral anomaly, by the virtue of inhomogeneity in the chiral chemical potential and temperature. We will discuss various scenarios where inhomogeneities in the chemical potential and temperature can arise. We found that, depending on the epoch of generation, the strength of the seed magnetic fields varies from a few nano-Gauss (nG) to a few hundred nG.