Non-Abelian Boltzmann equation for mixing and decoherence

We consider particle oscillations and their damping in second-quantized form. We find that the damping or ``decoherence'' may be described by a Boltzmann-like collision integral with ``non-Abelian blocking factors'' (fermions). Earlier results are generalized in that the momentum degrees of freedom are included and that the mixing equations become intrinsically nonlinear at high densities.