Rotating traversable wormholes in Einstein-Maxwell theory

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.