Long-term stable non-linear evolutions of ultracompact black hole mimickersConfirmed

by Seppe Staelens (University of Cambridge)

Thursday May 8, 2025, 1:00 p.m. → 2:30 p.m. America/Toronto

PI/4-400 - Space Room (Perimeter Institute for Theoretical Physics)

Ultracompact black hole mimickers formed through gravitational collapse under reasonable assumptions obtain light rings in pairs, where one is unstable and the other one is not. Stable light rings are believed to be a potential source for dynamical instability due to the trapping of massless perturbations, as their decay is relatively slow.

We study the stability of ultracompact boson stars admitting light rings combining a perturbative analysis with 3+1 numerical-relativity simulations with and without symmetry assumptions. We observe excellent agreement between all perturbative and numerical results which uniformly support the hypothesis that this family of black-hole mimickers is separated into stable and unstable branches by extremal-mass configurations. This separation includes, in particular, thin-shell boson stars with light rings located on the stable branch which we conclude to represent long-term stable black-hole mimickers. Our simulations suggest that the proposed mechanism may not be efficient after all to effectively destroy ultracompact black hole mimickers.