Duration of classicality in highly degenerate interacting Bosonic
  systems
  We study sets of oscillators that have high quantum occupancy and that
interact by exchanging quanta. It is shown by analytical arguments and
numerical simulation that such systems obey classical equations of motion only
on time scales of order their relaxation time $\tau$ and not longer than that.
The results are relevant to the cosmology of axions and axion-like particles.
