Spin evolution of massive fermion in QED plasma

TL;DR

This paper investigates the spin evolution of a massive fermion in a hot QED plasma using quantum kinetic theory, deriving axial kinetic equations with collision effects, and analyzing diffusion and polarization phenomena.

Contribution

It introduces a detailed derivation of the axial kinetic equation including collision terms for massive fermions in QED plasma, highlighting relaxation and polarization effects.

Findings

Collision terms vanish at global equilibrium

Relaxation time operator is identified

Preliminary numerical analysis shows diffusion and polarization effects

Abstract

The dynamical evolution of spin of a massive probe fermion in a massless hot QED plasma at local equilibrium is investigated through the quantum kinetic theory. We consider the massive probe fermion undergoing 2-by-2 Coulomb scattering with the massless fermions in the medium. The axial kinetic equation is derived including the collision terms to the first order of gradients and leading logarithmic order of the coupling. The collision terms are vanishing at global equilibrium, around which the relaxation time can be extracted as an operator. We further decompose the axial kinetic equation into kinetic equations of axial-charge density as well as the transverse magnetic dipole moment, and illustrate the diffusion and polarization effect through preliminary numerical analysis.