  Entropy production in non-Abelian gauge theory is discussed in the limit of
vanishing classical fields. Based on the Kadanoff-Baym equation with the
leading order self-energy in the temporal axial gauge, the kinetic entropy is
introduced and is proven to increase for a given self-energy. Numerical
simulation of the Kadanoff-Baym equation for the non-Abelian gauge theory is
performed in 2+1 dimensions. Starting from anisotropic distribution in momentum
space, relaxation to isotropic distribution proceeds and the entropy is
produced due to off-shell scattering of massive transverse polarization mode as
expected from the proof of the H-theorem.
