Rotating traversable wormholes in Einstein-Maxwell theory

Understand

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.