Nonlinear $\sigma$-models in the Eddington-inspired Born-Infeld Gravity

TL;DR

This paper explores nonlinear sigma-models within Eddington-inspired Born-Infeld gravity, revealing that such models generally produce wormhole geometries, with some solutions being regular and geodesically complete depending on mass-charge relations.

Contribution

It introduces new solutions of nonlinear sigma-models in EiBI gravity, showing the emergence of wormholes and identifying conditions for regular, geodesically complete spacetimes.

Findings

Wormhole structures are a common feature in these models.

Certain solutions are regular everywhere and geodesically complete.

The properties depend on the mass and global charge relationship.

Abstract

In this paper we consider two different nonlinear $\sigma$-models minimally coupled to Eddington-inspired Born-Infeld gravity. We show that the resultant geometries represent minimal modifications with respect to those found in GR, though with important physical consequences. In particular, wormhole structures always arise, though this does not guarantee by itself the geodesic completeness of those space-times. In one of the models, quadratic in the canonical kinetic term, we identify a subset of solutions which are regular everywhere and are geodesically complete. We discuss characteristic features of these solutions and their dependence on the relationship between mass and global charge.