Abstract :
The wave function for the matter field fluctuations in the infrared sector is studied within the framework of inflationary cosmology. These fluctuations are described by a coarse-grained field which takes into account only the modes with wavelength much bigger than the size of the Hubble horizon. The case of a power-law expanding universe is considered and it is found that the relevant phase-space (φcg,Pφcg) remains coherent under certain circumstances. In this case the classical stochastic treatment for matter field fluctuations is not valid, however, for p>4.6, the system loses its coherence and a classical stochastic approximation is allowed.
