Traversable asymptotically flat wormholes with short transit times
Abstract
We construct traverseable wormholes by starting with simple fourdimensional classical solutions respecting the null energy condition and containing a pair of oppositely charged black holes connected by a nontraverseable wormhole. We then consider the perturbative backreaction of bulk quantum fields in HartleHawking states. Our geometries have zero cosmological constant and are asymptotically flat except for a cosmic string stretching to infinity that is used to hold the black holes apart. Another cosmic string wraps the noncontractible cycle through the wormhole, and its quantum fluctuations provide the negative energy needed for traversability. Our setting is closely related to the nonperturbative construction of Maldacena, Milekhin, and Popov (MMP), but the analysis is complementary. In particular, we consider cases where backreaction slows, but fails to halt, the collapse of the wormhole interior, so that the wormhole is traverseable only at sufficiently early times. For nonextremal backgrounds, we find the integrated null energy along the horizon of the classical background to be exponentially small, and thus traversability to be exponentially fragile. Nevertheless, if there are no larger perturbations, and for appropriately timed signals, a wormhole with mouths separated by a distance d becomes traverseable with a minimum transit time . Thus is smaller than for the eternally traverseable MMP wormholes by more than a factor of 2, and approaches the value that, at least in higher dimensions, would be the theoretical minimum. For contrast we also briefly consider a ‘cosmological wormhole’ solution where the backreaction has the opposite sign, so that negative energy from quantum fields makes the wormhole harder to traverse.
 Publication:

Classical and Quantum Gravity
 Pub Date:
 December 2019
 DOI:
 10.1088/13616382/ab56e4
 arXiv:
 arXiv:1908.03273
 Bibcode:
 2019CQGra..36x5018F
 Keywords:

 High Energy Physics  Theory;
 General Relativity and Quantum Cosmology
 EPrint:
 23 pages, 5 figures