C -field cosmological model for barotropic fluid distribution with bulk viscosity and decaying vacuum energy (Λ) in FRW space-time

摘要

A solution of Einstein's field equations that admits barotropic fluid distribution and a negative-energy massless scalar creation field as a source in the presence of bulk viscosity and time-dependent vacuum energy density (Λ) is investigated. It is shown that a cosmological model based on this solution satisfies observational tests and is thus a viable alternative to the standard Big Bang model. The present model is free from real singularity and particle horizon. The creation field increases with time, which matches the result as obtained by Hoyle and Narlikar (Proc. Roy. Soc. A, 282, 178 (1964)). The vacuum energy density, Λ ～ t~(-2), matches the result as obtained by Bertolami (Nuovocim. B, 93, 36 (1986)). The spatial volume increases exponentially with time. Thus the model has an inflationary scenario. The deceleration parameter q < 0 indicating that the model represents accelerating expansion of the universe. The presence of the creation field prevents matter density from vanishing and it remains constant for large t. We also observe that bulk viscosity slows down the rate of decrease of volume expansion.