Non-singular G2 stiff fluid cosmologies

TL;DR

This paper investigates specific stiff fluid cosmological models, providing conditions under which these spacetimes are free of singularities, thereby demonstrating their abundance in such cosmologies.

Contribution

It introduces a practical criterion for geodesic completeness in Abelian diagonal orthogonally transitive stiff fluid spacetimes, enhancing understanding of non-singular cosmological solutions.

Findings

Non-singular spacetimes are common among stiff fluid cosmologies.

A sufficient, easy-to-apply condition for geodesic completeness is established.

The results support the prevalence of non-singular models in this class of spacetimes.

Abstract

In this paper we analyse Abelian diagonal orthogonally transitive spacetimes with spacelike orbits for which the matter content is a stiff perfect fluid. The Einstein equations are cast in a suitable form for determining their geodesic completeness. A sufficient condition on the metric of these spacetimes is obtained, that is fairly easy to check and to implement in exact solutions. These results confirm that non-singular spacetimes are abundant among stiff fluid cosmologies.