Universe Driven by Perfect Fluid in Eddington-inspired Born-Infeld Gravity

TL;DR

This paper explores how Eddington-inspired Born-Infeld gravity alters the early universe's evolution with perfect fluids, potentially avoiding singularities and reducing anisotropy compared to general relativity.

Contribution

It demonstrates that in this gravity theory, the universe can avoid initial singularities and exhibit de Sitter-like states for pressureless matter, differing from predictions of general relativity.

Findings

Initial singularity is avoided for $w>0$.

For $w=0$, the universe approaches a de Sitter state.

Anisotropy remains mild without developing curvature singularities.

Abstract

We investigate the evolution of the Universe filled with barotropic perfect fluid in Eddington-inspired Born-Infeld gravity. We consider both the isotropic and the anisotropic universe. At the early stage when the energy density is high, the evolution is modified considerably compared with that in general relativity. For the equation-of-state parameter $w>0$, the initial singularity is not accompanied as it was discovered for radiation in earlier work. More interestingly, for pressureless dust ($w=0$), the initial state approaches a de Sitter state. This fact opens a new possibility of singularity-free nature of the theory. The anisotropy is mild, and does not develop curvature singularities in spacetime contrary to general relativity.