CLASSIFICATION OF QUANTUM FLUCTUATION IN INFLATIONARY UNIVERSE

We discuss the classicalization of a quantum state induced by an envir onment in the inflationary stage of the universe. The classicalization is necessary for the homogeneous ground state to become the inhomogen eous classical one accompanied with statistical fluctuations, which is a plausible candidate for the seeds of structure formation. Using sim ple models, we show that i) the two classicalization criteria, the cla ssical correlation and quantum decoherence, are simultaneously satisfi ed by the environment and that ii) the power spectrum of the resultant statistical fluctuations depends upon the details of the classicaliza tion process. In particular, the result ii) means that, taking into ac count the classicalization process, the inflationary scenario does not necessarily predict the unique spectrum which is usually believed.