Einstein Static Universe in Rastall Theory of Gravity

TL;DR

This paper demonstrates that in Rastall gravity, the Einstein static universe can be stable against various perturbations and may exist eternally, potentially resolving the big bang singularity.

Contribution

It shows the stability of the Einstein static universe in Rastall gravity and explores conditions for its eternal existence, a novel insight into early universe models.

Findings

The Einstein static universe is stable with perfect fluid and vacuum energy.

Stability depends on the coupling parameter in Rastall theory.

The model suggests a universe that can avoid the big bang singularity.

Abstract

We investigate stability of the Einstein static solution against homogeneous scalar, vector and tensor perturbations in the context of Rastall theory of gravity. We show that this solution in the presence of perfect fluid and vacuum energy originating from conformally-invariant fields is stable. Using the fix point method and taking linear homogeneous perturbations, we find that the scale factor of Einstein static universe for closed deformed isotropic and homogeneous FLRW universe depends on the coupling parameter $\lambda$ between the energy-momentum tensor and the gradient of Ricci scalar. Thus, in the present model and in presence of vacuum energy, our universe can stay at the Einstein static state past-eternally, which means that the big bang singularity may be resolved successfully in the context of Einstein static universe in Rastall theory.