The Einstein static universe in Scalar-Fluid theories

TL;DR

This paper explores the stability of Einstein static universe solutions within Scalar-Fluid theories, revealing configurations stable against inhomogeneous perturbations but unstable against homogeneous ones, with implications for emergent universe models.

Contribution

It introduces a new framework for analyzing Einstein static universes in Scalar-Fluid theories and assesses their stability properties under various perturbations.

Findings

Stable against inhomogeneous perturbations

Unstable against homogeneous perturbations

Potential applications to emergent universe scenarios

Abstract

A new Lagrangian framework has recently been proposed to describe interactions between relativistic perfect fluids and scalar fields. In this paper we investigate the Einstein static universe in this new class of theories, which have been named Scalar-Fluid theories. The stability of the static solutions to both homogeneous and inhomogeneous perturbations is analysed deriving the relevant cosmological perturbation equations at the linear order. We can find several configurations corresponding to an Einstein static universes which are stable against inhomogeneous perturbations, but unstable against homogeneous perturbations. This shows the possible applications of Scalar-Fluid theories to the inflationary emergent universe scenario.