Classical stochastic approach to cosmology revisited

Abstract

The classical stochastic model of cosmology recently developed by us is reconsidered. In that approach the parameter $w$ defined by the equation of state $p=wρ$ was taken to be fluctuating with mean zero and we compared the theoretical probability distribution function(PDF) for the Hubble parameter with observational data corresponding to a universe with matter and vacuum energy. Eventhough qualitative agreement between the two was obtained, an attempt is herein made to introduce a more realistic assumption for the mean of $w$ and use it for the calculations. In the present theory the mean values of both $p$ and $w$ are taken to be nonzero. The theoretical and observational PDFs are compared for different epochs and values of the Hubble parameter. The corresponding values of the diffusion constant $D$ obtained are approximately constant. We use the scatter in the observed redshift-magnitude data of Type Ia supernova to place limits on the stochastic variation in expansion rate and consequently, on the stochastic variation of the equation of state.