Fate of the Universe, Age of the Universe, Dark Matter, and the Decaying Vacuum Energy

Abstract

It is shown that in the cosmological models based on a vacuum energy decaying as a^{-2}, where a is the scale factor of the universe, the fate of the universe in regard to whether it will collapse in future or expand forever is determined not by the curvature constant k but by an effective curvature constant k_{eff}. It is argued that a closed universe with k=1 may expand forever, in other words simulate the expansion dynamics of a flat or an open universe because of the possibility that k_{eff}=0 or -1, respectively. Two such models, in one of which the vacuum does not interact with matter and in another of which it does, are studied. It is shown that the vacuum equation of state p_{vac}= -ρ_{vac} may be realized in a decaying vacuum cosmology provided the vacuum interacts wuth matter. The optical depths for gravitational lensing as a function of the matter density and other parameters in the models are calculated at a source redshift of 2. The age of the universe is discussed and shown to be compatible with the new Hipparcos lower limit of 11Gyr. The possibility that a time-varying vacuum energy may serve as dark matter is suggested.

AAS LaTex, 29 pages, published in the Astrophysical Journal, 520, 45, 1999

References in corpus (11)

• Measurements of the Cosmological Parameters Omega and Lambda from the First 7 Supernovae at z >= 0.35
• The Average Mass-to-Light Profile of Galaxy Clusters
• Big-Bang Nucleosynthesis and the Baryon Density of the Universe
• Younger and brighter - New distances to globular clusters based on Hipparcos parallax measurements of local subdwarfs
• Globular Cluster Ages and the Formation of the Galactic Halo
• Cosmology in a String-Dominated Universe
• Action Principle Solutions For Galaxy Motions Within 3000 Km/s
• CCD Photometry of the Globular Cluster M5. I. The Color-Magnitude Diagram and Luminosity Functions
• Gravitational Lensing Limits on Cold Dark Matter and Its Variants
• A Low-Density Closed Universe
• Implications For The Hubble Constant from the First Seven Supernovae at z >= 0.35

Cited by in corpus (6)

• Tachyons, Scalar Fields and Cosmology
• Median Statistics, H_0, and the Accelerating Universe
• Supernovae Ia Constraints on a Time-Variable Cosmological "Constant"
• Matter fields from a decaying background Lambda vacuum
• The Dyer-Roeder relation in a universe with particle production
• Flat Cosmology with Coupled Matter and Dark Energies