Within the framework of general relativity, we explore the interior of the Schwarzschild black hole before complete collapse occurs, finding that the exterior is perfectly compatible with a source much more complex than a pointlike mass. We provide a set of inner geometries for singular and regular black holes that smoothly joint the Schwarzschild exterior at the horizon $r=h=2\mathcal{M}$, and which can therefore be regarded as suitable initial conditions for collapse. In particular, the regular solutions might be an alternative to the Schwarzschild black hole as the final stage of gravitational collapse, and thus useful to study the validity of general relativity in environments of high curvature.

• Received 9 February 2024
• Accepted 18 April 2024

DOI:https://doi.org/10.1103/PhysRevD.109.104032