Nonsingular electrovacuum solutions with dynamically generated cosmological constant

TL;DR

This paper explores static, spherically symmetric solutions in a modified Palatini gravity theory with nonlinear electrodynamics, resulting in nonsingular, asymptotically de Sitter wormhole spacetimes with a dynamically generated cosmological constant.

Contribution

It introduces a nonlinear electromagnetic extension in Palatini gravity that generates a cosmological constant and replaces singularities with wormholes in electrovacuum solutions.

Findings

Solutions are asymptotically de Sitter.

Wormhole topology replaces central singularity.

Conditions for nonsingular, non-traversable wormholes are identified.

Abstract

We consider static spherically symmetric configurations in a Palatini extension of General Relativity including $R^2$ and Ricci-squared terms, which is known to replace the central singularity by a wormhole in the electrovacuum case. We modify the matter sector of the theory by adding to the usual Maxwell term a nonlinear electromagnetic extension which is known to implement a confinement mechanism in flat space. One feature of the resulting theory is that the non-linear electric field leads to a dynamically generated cosmological constant. We show that with this matter source the solutions of the model are asymptotically de Sitter and possess a wormhole topology. We discuss in some detail the conditions that guarantee the absence of singularities and of traversable wormholes.