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arXiv · 2006.06461

Disforming the Kerr metric

Timothy Anson·Eugeny Babichev·Christos Charmousis·Mokhtar Hassaine
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Abstract

Starting from a recently constructed stealth Kerr solution of higher order scalar tensor theory involving scalar hair, we analytically construct disformal versions of the Kerr spacetime with a constant degree of disformality and a regular scalar field. While the disformed metric has only a ring singularity and asymptotically is quite similar to Kerr, it is found to be neither Ricci flat nor circular. Non-circularity has far reaching consequences on the structure of the solution. As we approach the rotating compact object from asymptotic infinity we find a static limit ergosurface similar to the Kerr spacetime with an enclosed ergoregion. However, the stationary limit of infalling observers is found to be a timelike hypersurface. A candidate event horizon is found in the interior of this stationary limit surface. It is a null hypersurface generated by a null congruence of light rays which are no longer Killing vectors. Under a mild regularity assumption, we find that the candidate surface is indeed an event horizon and the disformed Kerr metric is therefore a black hole quite distinct from the Kerr solution.

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Timothy Anson, Eugeny Babichev, Christos Charmousis, Mokhtar Hassaine. 2020-06-11. Disforming the Kerr metric. https://doi.org/10.1007/jhep01(2021)018

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