Rotating traversable wormholes in Einstein-Maxwell theory

TL;DR

This paper demonstrates that certain overcharged Kerr-Newman-NUT solutions in Einstein-Maxwell theory can be interpreted as traversable wormholes supported by cosmic strings, challenging the typical need for exotic matter.

Contribution

It reveals that these wormholes are supported by cosmic strings and analyzes their properties, including ergoregions and geodesic behavior, providing new insights into wormhole solutions in Einstein-Maxwell theory.

Findings

Wormholes are supported by cosmic strings violating null energy condition.

The solutions have ergoregions but no superradiance.

No closed circular null geodesics are present.

Abstract

It is well-known that traversable wormhole solutions to the Einstein equations require the existence of an exotic matter source violating the null energy condition. An apparent exception is the overcharged Kerr-Newman-NUT solution of the Einstein-Maxwell equations, which has all the properties of a geodesically complete, traversable wormhole spacetime. We show that the exotic matter sourcing this consists in two counter-rotating tensionless straight cosmic strings -- the Misner-Dirac strings -- which, as expected, violate the null energy condition. The wormhole possesses an ergoregion, but no superradiance. The geodesic motion in this spacetime is briefly discussed, and the absence of closed circular null geodesics is demonstrated.