Non-singular flat universes in braneworld and Loop Quantum Cosmology

TL;DR

This paper investigates non-singular flat universes within braneworld and Loop Quantum Cosmology frameworks, demonstrating how specific matter and scalar field configurations can avoid initial singularities and produce emergent, bouncing, or cyclic cosmologies.

Contribution

It introduces new models of non-singular universes in braneworld and LQC, analyzing their dynamics and inflationary behavior without violating energy conditions.

Findings

Initial singularity is generally avoided in studied models.

Enhanced slow-roll inflation scenarios compared to standard cosmology.

Existence of bouncing and cyclic universe solutions.

Abstract

In this paper we take matter source with non-linear Equation of state (EoS) that has produced non-singular Emergent cosmology for spatially flat universe in General Relativity and minimally coupled scalar field with two different potentials that produce an inflationary emergent universe for positive spatial curvature in the relativistic context. We study all these three cases both in the context of Randall-Sundrum braneworld and effective Loop quantum cosmology (LQC) for zero spatial curvature that is observationally favoured and in the absence of any effective cosmological constant term. We solve the modified Friedmann equation in each case to obtain the time evolution of the scale factor and use it to check whether the initial singularity can be averted. In almost all the cases we find the initial singularity is absent. We study the nature of the slow roll inflation in the cases where we obtain inflationary emergent universes. The inflationary scenario is found to be improved than in a standard relatvistic context and we compare the improved scenario for both the braneworld and LQC models. Interestingly, we also obtain bouncing and cyclic universes from our analysis in some cases. We find that the initial singularity can be averted for a spatially flat universe with specific choice of matter EoS or scalar field potential, which do not violate the Null Energy condition in most cases, taking into account effective high energy (curvature) corrections with or without extra dimensions.