Einstein static Universe in non-minimal kinetic coupled gravity

TL;DR

This paper investigates the stability of the Einstein static Universe within non-minimal kinetic coupled gravity, revealing conditions on initial size and coupling parameters that align with quantum cosmology and inflationary models.

Contribution

It provides a stability analysis of the Einstein static Universe in kinetic coupled gravity, identifying specific parameter conditions for stability and initial size constraints.

Findings

Stability depends on coupling parameters $$ and $$.

Initial size must be greater than Planck length for stability.

Small coupling parameter $$ is favored in inflation models.

Abstract

We study the stability of Einstein static Universe, with FLRW metric, by considering linear homogeneous perturbations in the kinetic coupled gravity. By taking linear homogeneous perturbations, we find that the stability of Einstein static Universe, in the kinetic coupled gravity with quadratic scalar field potential, for closed ($K=1$) isotropic and homogeneous FLRW Universe depends on the coupling parameters $\kappa$ and $\varepsilon$. Specifically, for $\kappa=L_P^2$ and $\varepsilon=1$ we find that the stability condition imposes the inequality $a_0>\sqrt{3}L_P$ on the initial size $a_0$ of the closed Einstein static Universe before the inflation. Such inequality asserts that the initial size of the Einstein static Universe must be greater than the Planck length $L_P$, in consistency with the quantum gravity and quantum cosmology requirements. In this way, we have determined the non-minimal coupling parameter $\kappa$ in the context of Einstein static Universe. Such a very small parameter is favored in the inflationary models constructed in the kinetic coupled gravity. We have also studied the stability against the vector and tensor perturbations and discussed on the acceptable values of the equation of state parameter.