Thermalization of gluons with Bose-Einstein condensation

TL;DR

This paper investigates how gluons thermalize in a static medium, demonstrating the formation of Bose-Einstein condensates through kinetic theory and calculating associated timescales.

Contribution

It introduces a general scattering constraint for gluon condensation and demonstrates thermalization with Bose-Einstein condensation in a transport model.

Findings

Gluon overpopulation leads to Bose-Einstein condensation.

Condensation times scale inversely with energy density.

Entropy production coincides with condensation completion.

Abstract

We study the thermalization of gluons far from thermal equilibrium in relativistic kinetic theory. The initial distribution of gluons is assumed to resemble that in the early stage of ultrarelativistic heavy ion collisions. Only elastic scatterings in static, nonexpanding gluonic matter are considered. At first we show that the occurrence of condensation in the limit of vanishing particle mass requires a general constraint for the scattering matrix element. Then the thermalization of gluons with Bose-Einstein condensation is demonstrated in a transport calculation. We see a continuously increasing overpopulation of low energy gluons, followed by a decrease to the equilibrium distribution, when the condensation occurs. The times of the completion of the gluon condensation and of the entropy production are calculated. These times scale inversely with the energy density.