Cosmic inventory of energy densities : issues and concerns

Abstract

The dynamics of our universe is characterised by the density parameters for cos- mological constant (ΩV ), nonbaryonic darkmatter(Ωwimp), radiation (ΩR) and baryons (ΩB). To these parameters — which describe the smooth background universe — one needs to add at least another dimensionless number (∼ 10−5) characterising the strength of primordial fluctuations in the gravitational potential, in order to ensure formation of structures by gravi- tational 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