Three dimensional Eddington--inspired Born--Infeld gravity: solutions

TL;DR

This paper explores solutions in three-dimensional Eddington-inspired Born-Infeld gravity, including cosmological models and static solutions, revealing conditions for singular and non-singular universes and spacetimes.

Contribution

It provides new analytical and numerical solutions in 3D EiBI gravity for various matter contents and curvature, highlighting conditions for singularity and regularity.

Findings

For >0, solutions are generally singular except in specific open universe cases.

For <0, non-singular cosmological solutions are found.

Static solutions with certain matter contents are non-singular for <0 and include de Sitter, anti-de Sitter, and flat spacetimes.

Abstract

Three dimensional Eddington-inspired Born--Infeld gravity is studied with the goal of finding new solutions. Beginning with cosmology, we obtain analytical and numerical solutions for the scale factor, a(t), in spatially flat (k=0) and spatially curved (k=+1,-1) Friedmann-Roberston-Walker universes with (i) pressureless dust (P=0) and (ii) perfect fluid (P=\rho/2), as matter sources. When the theory parameter \kappa>0, our cosmological solutions are generically singular (except for the open universe, with a specific condition). On the other hand, for \kappa<0 we do find non-singular cosmologies. We then move on towards finding static, circularly symmetric line elements with matter obeying (i) p=0 and (ii) p=\rho/2. For p=0, the solution found is nonsingular for \kappa<0 with the matter--stress--energy representing inhomogeneous dust. For p=\rho/2 we obtain nonsingular solutions, for all \kappa, and discuss some interesting characteristics of these solutions. Finally, we look at the rather simple p=-\rho case where the solutions are either de Sitter or anti-de Sitter or flat spacetime.