Long-wavelength iteration scheme and scalar-tensor gravity

TL;DR

This paper develops a third-order long-wavelength iteration scheme for scalar-tensor gravity to analyze inhomogeneous and anisotropic cosmologies, examining the behavior of solutions near general relativity and specific cases like Brans-Dicke theory.

Contribution

It introduces a third-order iteration scheme for scalar-tensor cosmologies and explores the decay of anisotropies and inhomogeneities in specific models.

Findings

Third-order solutions are derived for scalar-tensor theories.

Conditions for decay of anisotropy and inhomogeneity are identified.

Analysis of Brans-Dicke coupling case shows specific behaviors.

Abstract

Inhomogeneous and anisotropic cosmologies are modeled withing the framework of scalar-tensor gravity theories. The inhomogeneities are calculated to third-order in the so-called long-wavelength iteration scheme. We write the solutions for general scalar coupling and discuss what happens to the third-order terms when the scalar-tensor solution approaches at first-order the general relativistic one. We work out in some detail the case of Brans-Dicke coupling and determine the conditions for which the anisotropy and inhomogeneity decay as time increases. The matter is taken to be that of perfect fluid with a barotropic equation of state.