Vaidya spacetimes, black-bounces, and traversable wormholes

Abstract

We consider a non-static evolving version of the regular 'black-bounce'/traversable wormhole geometry recently introduced in Simpson and Visser (2019 J. Cosmol. Astropart. Phys. JCAP02(2019)042). We first re-write the static metric using Eddington-Finkelstein coordinates, and then allow the mass parameter m to depend on the null time coordinate (à la Vaidya). The spacetime metric is Here denotes suitably defined null time coordinates; representing time, while, (at least for), we allow. This spacetime is still simple enough to be tractable, and neatly interpolates between Vaidya spacetime, a black-bounce, and a traversable wormhole. We show how this metric can be used to describe several physical situations of particular interest, including a growing black-bounce, a wormhole to black-bounce transition, and the opposite black-bounce to wormhole transition.