Non-singular model universe from a perfect fluid scalar-metric cosmology

TL;DR

This paper investigates a non-singular emergent cosmology model using a perfect fluid scalar-metric framework, demonstrating stable static solutions and a future de Sitter attractor, suggesting a viable alternative to traditional inflation.

Contribution

It introduces a new static solution independent of free parameters and analyzes stability within a scalar-metric cosmology, supporting a non-singular emergent universe scenario.

Findings

Stable Einstein Static Universes found under classical perturbations.

Existence of a future de Sitter attractor in non-flat geometries.

A new static solution independent of model parameters.

Abstract

To seek for a singularity free model universe from a perfect fluid scalar-metric cosmology, we work in the "\emph{Emergent Cosmology}" (EC) paradigm which is a non-singular alternative for cosmological inflation. By using two methods including Linear Stability Theory and Effective Potential Formalism, we perform a classical analysis on the possible static solutions (that are called usually as Einstein Static Universes (ESU)in literature) in order to study EC paradigm in a FRW background. Our model contains a kinetic term of the scalar field minimally coupled to the background geometry without a potential term. The matter content of the model consists of a perfect fluid plus a cosmological constant $\Lambda$ as a separate source. In the framework of a local dynamical system analysis, we show that in the absence or presence of $\Lambda$, depending on some adopted values for the free parameters of the underlying cosmological model with flat and non-flat spatial geometries, one gets some static solutions which are viable under classical linear perturbations. By extending our study to a global dynamical system analysis, we show that in the presence of $\Lambda$ with non-flat spatial geometries there is a future global de Sitter attractor in this model. Following the second method, we derive a new static solution that represents a stable ESU but this time without dependence on the free parameters of the cosmological model at hand. As a whole, our analysis suggests the possibility of graceful realization of a non-singular EC paradigm (i.e. leaving the initial static phase and entering the inflation period as the universe is evolving) through either preserving or violation of the strong energy condition.