Year: 2026
Type: preprint
Abstract: We consider a scenario in which a black hole is enclosed in a reflecting timelike cavity and linearly perturbed. For the resulting quasinormal spectra of gravitational, electromagnetic, and other perturbations, in conjunction with our arXiv:2606.11297, we establish a thermal product formula and derive a universal asymptotic expression for high quasinormal overtones. Both results hold in asymptotically flat, de Sitter, and Anti-de Sitter spacetimes (known previously). This spectral signature directly encodes information about the black hole interior and its singularity, and is, at least in principle, accessible to an observer outside the event horizon. We then propose a concrete observational setup in which accreting plasma plays the role of a partially transmissive mirror. For small, hypothetical, primordial black holes, we argue that one may thereby be able to extract concrete information about the black hole interior from electromagnetic waves in the radiowave spectrum.
Source: arXiv (Cornell University)
Authors: Grozdanov, Sašo, Movrin, Vita, Valach, Samuel
Institutions: University of Ljubljana, University of Edinburgh
Language: English
Subfield: Nuclear and High Energy Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7203613600