Scalar-Tensor Bianchi VI Models

J A Belinchón

doi:10.1155/2013/491905

Abstract

We study how may vary the gravitational and the cosmological “constants,” ( and ) in several scalar-tensor theories with Bianchi III, , and symmetries. By working under the hypothesis of self-similarity we find exact solutions for two different theoretical models, which are the Jordan-Brans-Dicke (JBD) with and the usual JBD model with potential (that mimics the behaviour of . We compare both theoretical models, and some physical and geometrical properties of the solutions are also discussed putting special emphasis on the study of the isotropization of the solutions.

Highlights

Current observations of the large scale Cosmic Microwave Background (CMB) suggest to us that our physical universe is expanding in an accelerated way
We have reached the conclusion that the possible variation of the cosmological constant is better described within the JBDU theoretical framework, since with the JBDΛ model Λ usually vanishes
In the case of the Bianchi type VI0 we have found that the cosmological constant is zero, Λ = 0, but the solution is valid for all γ ∈ (−1/3, 1)

Summary

Introduction

Current observations of the large scale Cosmic Microwave Background (CMB) suggest to us that our physical universe is expanding in an accelerated way. We have several theoretical models that consider both constants as variable with respect to the cosmic time Such theories are modified general relativity (MGR), modified scalar cosmological models (MST), and several scalar-tensor theories (STT). In a recent paper [20], we have considered a family of scalar-tensor theories under the hypothesis of self-similarity They are the Jordan-Brans-Dicke model with a dynamical cosmological constant (JBDΛ) [21] and with a potential (JBDU) [19], which is equivalent to a time-dependent cosmological constant. For such theoretical models, we proved how must behave each physical quantity under the hypothesis of self-similarity.

Theoretical Models

The Metric

Solutions

Conclusions