Mass inflation and thin shells in quasitopological gravity
Phys. Rev. D 114, 044061 – Published 20 August, 2026
DOI: https://doi.org/10.1103/ddgs-4ggp
Abstract
We study the null junction conditions in (resummed) quasitopological gravity theories, showing that no null thin shells exist within the realms of standard distributional theory for the pure gravity regular black hole solutions we have analyzed. This implies that the usual derivation of the mass inflation instability, which makes use of null thin shells, is not applicable in these theories. The problem of stability of inner horizons of regular black holes in quasitopological gravity is hence still open and must be addressed with a more refined analysis, which does not rely on thin shells or the vacuum condition.
