Towards consistent black-to-white hole bounces from matter collapse

Understand

This article presents a new model-independent constraint for bouncing black hole geometries.

• Using the thin shell formalism, this constraint sets a bound on the minimal allowed radius of the time-like surface of the collapsing star at the bounce.
• It follows from this bound that the shell always bounces in an untrapped region or precisely on a trapping horizon.
• This constraint is of purely kinematical origin as it descends from the continuity of the metric between the geometries describing the interior and exterior of the collapsing object so that it is completely model-independent.