Isotropisation of flat homogeneous Bianchi type I model with a non minimally coupled and massive scalar field

TL;DR

This paper investigates how flat homogeneous Bianchi type I cosmological models evolve towards isotropy when involving a non-minimally coupled, massive scalar field, extending previous minimally coupled analyses.

Contribution

It generalizes previous isotropisation results to include non-minimally coupled scalar fields, applying conformal transformations to connect different coupling scenarios.

Findings

Isotropisation occurs in non-minimally coupled models under certain conditions.

Results apply to Brans-Dicke and low energy string theories.

The approach extends previous minimally coupled scalar field analyses.

Abstract

In previous works, we studied the isotropisation of Bianchi class A models with a minimally coupled scalar field. In this paper, we extend these results to the case of a non minimally coupled one. We first make the calculations in the Einstein frame where the scalar field is minimally coupled to the curvature but non minimally coupled to the perfect fluid. Then, we use a conformal transformation to generalise our results to a scalar field non minimally coupled to the curvature. Universe isotropisation for the Brans-Dicke and low energy string theories are studied.