Thermalization of a nonequilibrium electron-positron-photon plasma

TL;DR

This paper investigates how a nonequilibrium electron-positron-photon plasma reaches thermal equilibrium through detailed analysis of binary and triple interactions, emphasizing the importance of inverse processes in the thermalization process.

Contribution

It provides a detailed numerical analysis of the thermalization process in a relativistic plasma, highlighting the critical role of inverse triple interactions for reaching equilibrium.

Findings

Binary interactions reach detailed balance in ~10^{-14} sec.

Triple interactions reach detailed balance in ~10^{-12} sec.

Neglecting inverse triple interactions prevents thermal equilibrium.

Abstract

Starting from a nonequilibrium configuration we analyse the essential role of the direct and the inverse binary and triple interactions in reaching an asymptotic thermal equilibrium in a homogeneous isotropic electron-positron-photon plasma. We focus on energies in the range 0.1--10 MeV. We numerically integrate the integro-partial differential relativistic Boltzmann equation with the exact QED collisional integrals taking into account all binary and triple interactions in the plasma. We show that first, when detailed balance is reached for all binary interactions on a timescale $t_{k}\lesssim10^{-14}$sec, photons and electron-positron pairs establish kinetic equilibrium. Successively, when triple interactions fulfill the detailed balance on a timescale $t_{eq}\lesssim10^{-12}$sec, the plasma reaches thermal equilibrium. It is shown that neglecting the inverse triple interactions prevents reaching thermal equilibrium. Our results obtained in the theoretical physics domain also find application in astrophysics and cosmology.