paper

Black-bounce to traversable wormhole

arXiv:1812.07114 · doi:10.1088/1475-7516/2019/02/042

Abstract

So-called "regular black holes" are a topic currently of considerable interest in the general relativity and astrophysics communities. Herein we investigate a particularly interesting regular black hole spacetime described by the line element \[ ds^{2}=-\left(1-\frac{2m}{\sqrt{r^{2}+a^{2}}}\right)dt^{2}+\frac{dr^{2}}{1-\frac{2m}{\sqrt{r^{2}+a^{2}}}} +\left(r^{2}+a^{2}\right)\left(dθ^{2}+\sin^{2}θ\;dϕ^{2}\right). \] This spacetime neatly interpolates between the standard Schwarzschild black hole and the Morris-Thorne traversable wormhole; at intermediate stages passing through a black-bounce (into a future incarnation of the universe), an extremal null-bounce (into a future incarnation of the universe), and a traversable wormhole. As long as the parameter is non-zero the geometry is everywhere regular, so one has a somewhat unusual form of "regular black hole", where the "origin" can be either spacelike, null, or timelike. Thus this spacetime generalizes and broadens the class of "regular black holes" beyond those usually considered.

22 pages, 5 figures. One typo fixed; one reference added (for v2). 5 references added, explanation on the null energy condition rewritten for clarity (for v3)

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