Density fluctuations in the oscillatory phase of a nonclassical inflaton in the FRW universe

Abstract

The use of the coherent and squeezed state formalisms of quantum optics for a minimally coupled nonclassical inflaton in the FRW metric is studied, in the semiclassical theory of gravity. The leading order solutions to the semiclassical Einstein equations in the coherent, squeezed and squeezed vacuum states are obtained perturbatively and exhibit power law expansion behavior. The validity of the semiclassical theory is examined in the squeezed vacuum state in the oscillatory phase of the inflaton. The semiclassical theory in the oscillatory phase of the nonclassical inflaton holds only if the associated squeezing parameter is much smaller than unity. Quantum fluctuations of the inflaton are also examined in the coherent and squeezed state formalisms. © 2008 World Scientific Publishing Company.