1999/06/30 by Arbab I. Arbab
Physics and Astronomy · #gr-qc
published as Grav.Cosmol. 8 (2002) 227-231 · A revised version, 8 pages Latex, submitted to Gravitation and Cosmology
arxiv created 2001/05/24 · arxiv updated 2009/11/30
We have considered a cosmological model with a cosmological constant of the form Λ=3α( R2)/(R2)+\bt( R)/(R) α, \bt=\rm const. The cosmological constant is found to decrease as t-2 and the rate of particle creation is smaller than the Steady State value. We have found that this behavior gives \fracΛPlΛp=10120 where ΛPl is the value of Λ at Planck time. Solutions with \bt=3α in the radiation dominated era and \bt=6α in the matter dominated era are equivalent to the FRW results. We have found an inflationary solution of the de-Sitter type with \bt=3-3α. Some problems of the Standard Model may be resolved with the presence of the above cosmological constant in the Einstein's equation. Since observations suggest a contribution of the vacuum energy density in the range 0.40<ΩΛ<0.76, one gets 4<β<12. If α=0 the minimum age of the universe is found to be Hp-1 (Hp is the present Hubble constant) with β=∞.