From 0 to 5000 in $2\times 10^{-24}$ seconds: Entropy production in relativistic heavy-ion collisions

TL;DR

This paper reviews entropy contributions in relativistic heavy-ion collisions, introduces a Husimi distribution-based framework for entropy growth calculation, and discusses how this approach can elucidate entropy production from first principles.

Contribution

It presents a novel quantum field theory framework using Husimi distributions to calculate entropy growth, especially during the early glasma phase of collisions.

Findings

Entropy from Husimi distribution shows linear growth with unstable modes.

Asymptotically matches Kolmogorov-Sina"i entropy.

Framework applicable to first-principles investigation of entropy production.

Abstract

We review what is known about the contributions to the final entropy from the different stages of a relativistic nuclear collision, including recent results on the decoherence entropy and the entropy produced during the hydrodynamic phase by viscous effects. We then present a general framework, based on the Husimi distribution function, for the calculation of entropy growth in quantum field theories, which is applicable to the earliest ("glasma") phase of the collision during which most of the entropy is generated. The entropy calculated from the Husimi distribution exhibits linear growth when the quantum field contains unstable modes and is asymptotically equal to the Kolmogorov-Sina\"i (KS) entropy. We outline how the approach can be used to investigate the problem of entropy production in a relativistic heavy-ion reaction from first principles.