  We investigate quantum decoherence in a class of models which interpolates
between expanding (inflation) and contracting (ekpyrosis) scenarios. For the
cases which result in a scale-invariant power spectrum, we find that ekpyrotic
universes lead to complete decoherence of the curvature perturbation before the
bounce. This is in stark contrast to the inflationary case, where recoherence
has been previously observed in some situations. Although the purity can be
computed for couplings of all sizes, we also study the purity perturbatively
and observe that late-time (secular growth) breakdown of perturbation theory
often occurs in these cases. Instead, we establish a simple yet powerful
late-time purity resummation which captures the exact evolution to a remarkable
level, while maintaining analytical control. We conclude that the cosmological
background plays a crucial role in the decoupling of the heavy fields during
inflation and alternatives.
