Entropy production in classical Yang-Mills theory from Glasma initial conditions

TL;DR

This paper investigates entropy production in classical Yang-Mills fields starting from glasma-like initial conditions, revealing significant entropy generation linked to chaotic dynamics and Lyapunov spectra stabilization.

Contribution

It extends previous work by analyzing glasma-like initial conditions, demonstrating entropy production and chaos in classical Yang-Mills dynamics.

Findings

Entropy increases with noisy initial conditions

Large number of positive Lyapunov exponents early on

Spectrum stabilizes indicating steady-state dynamics

Abstract

We study the thermalization process in classical Yang-Mills (CYM) field theory starting from noisy glasma-like initial conditions by investigating the initial-value sensitivity of trajectories. Kunihiro et al. linked entropy generation to the Kolmogorov-Sinai entropy, which gives the entropy production rate in classical chaotic systems, calculated numerically for CYM fields starting from purely random initial field configurations. In contrast, we here study glasma-like initial conditions. For small random fluctuations we obtain qualitatively similar results while no entropy increase is observed when such fluctuations are absent. We analyze the intermediate time Lyapunov spectrum for several time windows and calculate the Kolmogorov-Sinai entropy. We find a large number of positive Lyapunov exponents at the early stages of time evolution. Also for later times their number is a sizeable fraction of the total number of degrees of freedom. The spectrum of positive Lyapunov exponents at first changes rapidly, but then stabilizes, indicating that the dynamics of the gauge fields approaches a steady state. Thus we conclude that also for glasma-like initial conditions a significant amount of entropy is produced by classical gluon field dynamics.