Primordial Cosmology in Mimetic Born-Infeld Gravity

TL;DR

This paper reformulates the EiBI model within the mimetic approach, demonstrating the existence of regular, non-singular primordial solutions like inflationary and bouncing universes, and addressing linear instabilities.

Contribution

It introduces a mimetic formulation of the EiBI model, revealing non-trivial vacuum solutions that are free of singularities and stable against linear instabilities.

Findings

Existence of regular primordial inflationary solutions

Presence of bouncing solutions avoiding singularities

Linear instabilities can be avoided in certain solutions

Abstract

The Eddington-inspired-Born-Infeld (EiBI) model is reformulated within the mimetic approach. In the presence of a mimetic field, the model contains non-trivial vacuum solutions which could be free of spacetime singularity because of the Born-Infeld nature of the theory. We study a realistic primordial vacuum universe and prove the existence of regular solutions, such as primordial inflationary solutions of de Sitter type or bouncing solutions. Besides, the linear instabilities present in the EiBI model are found to be avoidable for some interesting bouncing solutions in which the physical metric as well as the auxiliary metric are regular at the background level.