  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.
