Cosmic inventory of energy densities: issues and concerns

Abstract

The dynamics of our universe is characterised by the density parameters for cosmological constant (${\Omega }_V$), nonbaryonic darkmatter(${\Omega }_{\mathrm{wimp}}$), radiation (${\Omega }_R$) and baryons (${\Omega }_B$). To these parameters -- which describe the smooth background universe -- one needs to add at least another dimensionless number ($\sim 10^{-5}$) characterising the strength of primordial fluctuations in the gravitational potential, in order to ensure formation of structures by gravitational instability. I discuss several issues related to the description of the universe in terms of these numbers and argue that we do not yet have a fundamental understanding of these issues.

Based on the invited talk at the XIII Rencontres de Blois - Frontiers of the Universe, June 17-23,2001