The Role of the Electron Mass in Damping Chiral Magnetic Instability in Supernova and Neutron Stars

TL;DR

This paper demonstrates that the nonzero electron mass prevents the generation of sufficient chiral charge density, thereby inhibiting the chiral magnetic instability that could generate large magnetic fields in neutron stars during supernova core collapse.

Contribution

It provides a detailed calculation showing electron mass effects suppress chiral charge buildup, challenging previous models of magnetic field generation in neutron stars.

Findings

Electron mass induces chirality violation via Rutherford scattering.

Chiral charge density remains too small for instability during core collapse.

Electron capture rates outpace chirality violation, preventing instability.

Abstract

We show that the nonzero electron mass plays a critical role in determining the magnetic properties of neutron stars, making it impossible to generate the chiral charge density needed to trigger a strong chiral magnetic instability during the core collapse of supernovae. This instability has been proposed as a plausible mechanism for generating extremely large helical magnetic fields in neutron stars at their birth; the mechanism relies on the generation of a large non-equilibrium chiral charge density via electron capture reactions that selectively deplete left-handed electrons during core-collapse and the early evolution of the protoneutron star. Our calculation shows that the electron chirality violation rate induced by Rutherford scattering, despite being suppressed by the smallness of the electron mass relative to the electron chemical potential, is still fast compared to the weak interaction electron capture rate. The resulting asymmetry between right and left-handed electron densities is therefore never able to attain an astrophysically relevant magnitude.