The initial fate of an anisotropic JBD universe

TL;DR

This paper investigates the early evolution of an anisotropic universe within Jordan-Brans-Dicke scalar-tensor cosmology, revealing conditions under which it transitions between singular and non-singular states depending on the coupling parameter.

Contribution

It provides a detailed analysis of how scalar field dynamics influence the initial fate of an anisotropic universe in scalar-tensor theories, highlighting the role of the coupling parameter .

Findings

Universe shows isotropic evolution despite initial anisotropy.

Initial state depends on the value of ; can start from or evolve towards singularities.

Different  ranges lead to distinct initial and final universe states.

Abstract

The dynamical effects on the scale factors due to the scalar $\phi$-field at the early stages of a supposedly anisotropic Universe expansion in the scalar-tensor cosmology of Jordan-Brans and Dicke is studied. This universe shows an {\sl isotropic} evolution and, depending on the value of the theorie's coupling parameter $\omega$, it can begin from a singularity if $\omega>0$ and after expanding shrink to another one; or, if $\omega <0$ and $-3/2< \omega\leq -4/3$, it can evolve from a flat spatially-infinite state to a non extended singularity; or, if $ -4/3 < \omega < 0$, evolve from an extended singularity to a non singular state and, at last, proceed towards a singularity.