Quantum kinetic theory for dynamical spin polarization from QED-type interaction

TL;DR

This paper develops a quantum kinetic theory framework to describe how massless electrons become spin-polarized through QED interactions in a thermal medium, incorporating quantum corrections and collision effects.

Contribution

It derives a novel axial kinetic equation with quantum corrections and relaxation-time approximation for dynamical spin polarization in electron plasmas.

Findings

Derived the axial kinetic equation with quantum corrections.

Identified the spin-polarization rate from spacetime gradients.

Simplified collision term into a relaxation-time form near equilibrium.

Abstract

We investigate the dynamical spin polarization of a massless electron probing an electron plasma in locally thermal equilibrium via the Moller scattering from the quantum kinetic theory. We derive an axial kinetic equation delineating the dynamical spin evolution in the presence of the collision term with quantum corrections up to $\mathcal{O}(\hbar)$ and the leading-logarithmic order in coupling by using the hard-thermal-loop (HTL) approximation, from which we extract the spin-polarization rate induced by the spacetime gradients of the medium. When the electron probe approaches local equilibrium, we further simplify the collision term into a relaxation-time expression. Our kinetic equation may be implemented in the future numerical simulations for dynamical spin polarization.