Decoherence Problem in Ekpyrotic Phase
  Quantum decoherence and the transition to semiclassical behavior during
inflation has been extensively considered in the literature. In this paper, we
use a simple model to analyze the same process in ekpyrosis. Our result is that
the quantum to classical transition would not happen during an ekpyrotic phase
even for superhorizon modes, and therefore the fluctuations cannot be
interpreted as classical. This implies the prediction of scale-free power
spectrum in ekpyrotic/cyclic universe model requires more inspection.
