Anisotropic Scalar-Tensor Cosmologies

Abstract

We examine homogeneous but anisotropic cosmologies in scalar-tensor gravity theories, including Brans-Dicke gravity. We present a method for deriving solutions for any isotropic perfect fluid with a barotropic equation of state ($p\propto \rho$) in a spatially flat (Bianchi type~I) cosmology. These models approach an isotropic, general relativistic solution as the expansion becomes dominated by the barotropic fluid. All models that approach general relativity isotropize except for the case of a maximally stiff fluid. For stiff fluid or radiation or in vacuum we are able to give solutions for arbitrary scalar-tensor theories in a number of anisotropic Bianchi and Kantowski-Sachs metrics. We show how this approach can also be used to derive solutions from the low-energy string effective action. We discuss the nature, and possibly avoidance of, the initial singularity where both shear and non-Einstein behavior is important.

30 pages, LaTeX, four uuencoded postscript figures

References in corpus (7)

• The String Dilaton and a Least Coupling Principle
• Extended Gravity Theories and the Einstein-Hilbert Action
• Low energy effective string cosmology
• Massless Fileds in Scalar-Tensor Cosmologies
• Homogeneous Conformal String Backgrounds
• Inflationary Attractors and Perturbation Spectra in Generally Coupled Gravity
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