Primordial magnetic field from chiral plasma instability with sourcing

TL;DR

This paper explores how a source of chirality can enable the chiral plasma instability to generate primordial magnetic fields at lower temperatures than previously thought, with analytical and numerical analysis of the resulting magnetic helicity.

Contribution

It introduces the idea that a chirality source can sustain CPI-driven magnetic field growth below 80 TeV, challenging prior assumptions.

Findings

Chirality source enables CPI below 80 TeV.

Predictions for magnetic field helicity are derived.

Numerical simulations support analytical results.

Abstract

In an electron-positron plasma, an imbalance in the number of right- and left-chiral particles can lead to the growth of a helical magnetic field through a phenomenon called the chiral plasma instability (CPI). In the early universe, scattering reactions that violate chirality come into thermal equilibrium when the plasma cools below a temperature of approximately $80 \, \mathrm{TeV}$. Since these reactions tend to relax any pre-existing chiral asymmetry to zero as the system approaches equilibrium, the standard lore is that primordial magnetogenesis via the CPI is not viable below $80 \, \mathrm{TeV}$. In this work, we propose that the presence of a source for chirality can allow the CPI to operate even below $80 \, \mathrm{TeV}$, we explore the implications of this scenario, and we derive predictions for the resultant magnetic field helicity using a combination of analytical methods and direct numerical simulation.