Brane-Universes with Variable G and Lambda

Abstract

We investigate the cosmological consequences of a brane-world theory which incorporates time variations in the gravitational coupling G and the cosmological term Lambda. We analyze in detail the model where (dG/dt)/G ~ H and Lambda ~ H^2, which seems to be favored by observations. We show that these conditions single out models with flat space sections. We determine the behavior of the expansion scale factor, as well as, the variation of G, Lambda and H for different possible scenarios where the bulk cosmological constant can be zero, positive or negative. We demonstrate that the universe must recollapse, if it is embedded in an Anti-de Sitter five-dimensional bulk, which is the usual case in brane models. We evaluate the cosmological parameters, using some observational data, and show that we are nowhere near the time of recollapse. We conclude that the models with zero and negative bulk cosmological constant agree with the observed accelerating universe, while fitting simultaneously the observational data for the density and deceleration parameters. The age of the universe, even in the recollapsing case, is much larger than in the FRW universe.

Few comments added, references updated. To appear in Classical and Quantum Gravity

References in corpus (7)

• First Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Determination of Cosmological Parameters
• Cosmological Results from High-z Supernovae
• Brane-world models emerging from collisions of plane waves in 5D
• Problems of G and multidimensional models
• Gravitation and cosmology in a brane-universe
• Brane curvature and supernovae Ia observations
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Cited by in corpus (13)

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• Variable G and $\Lambda$: scalar-tensor versus RG-improved cosmology
• Transition from decelerated to accelerated cosmic expansion in braneworld universes
• Accelerated expansion from braneworld models with variable vacuum energy
• Lorentz violation and the speed of gravitational waves in brane-worlds
• Brane world solutions of perfect fluid in the background of a bulk containing dust or cosmological constant
• Anisotropic Brane Cosmology with Variable $G$ and $\Lambda$
• Lorentz violation and red shift of gravitational waves in brane-worlds
• Riemann Tensor of the Ambient Universe, the Dilaton and the Newton's Constant
• A Note on the Generalized Friedmann Equations for a Thick Brane
• Brane cosmology with variable tension