Thin-Shell Black Bounce

Abstract

A recently proposed class of black-bounce solutions sourced by anisotropic fluids, whose exterior reproduces the Reissner-Nordström geometry all the way down to a minimal-area bounce, was put forward by Lessa and Olmo. In this work, we show that this solution conceals a thin-shell structure precisely at the bounce. Motivated by this observation, we construct a new class of black-bounce solutions with static, spherical symmetry featuring the emergence of a minimal-area bounce supported by a thin shell. This nontrivial topological structure is shown to arise from the degeneracy of the metric at the bounce, where the inverse metric becomes ill-defined, leading to curvature tensors with distributional discontinuities precisely at that point. As a consequence, a delta-function thin shell of energy-condition-violating matter is necessarily present at the bounce. To generate such solutions, we draw on proposals from quantum gravity that predict the existence of a fundamental minimum length scale, employing energy density profiles that encode these quantum-gravitational effects in an effective manner, replacing the point-like description of matter at minimal-length scales with a smeared one. We consider two well-motivated profiles, of Lorentzian and Gaussian type, to generate a novel class of solutions exhibiting the features of either regular black holes or wormholes, whose center conceals a thin-shell bounce. In addition, we investigate the thermodynamics of these compact objects.