A black hole in an expanding universe can only hold a limited number of energy levels unlike one in a flat universe.
This analytic treatment shows that the expansion of the universe fundamentally changes how black holes trap energy. In a flat universe, a black hole can theoretically support an infinite spectrum of bound-state resonances. This study proves that when you add the expansion of space, that spectrum suddenly becomes finite. This discovery reveals that the large-scale shape of the cosmos dictates the behavior of the most dense objects in it. It helps physicists understand how black holes will evolve as the universe continues to grow.
Bound-State Resonances of Schwarzschild-de Sitter Black Holes: Analytic Treatment
arXiv · 2604.27377
Inspired by Mashhoon's framework connecting black hole quasi-normal modes (QNMs) to bound-state resonances in inverted potentials, V$\ddot{\text{o}}$lkel's recent numerical analysis of asymptotically flat Schwarzschild black holes revealed a counterintuitive phenomenon: highly excited bound states rapidly delocalize, become extremely weakly bound, and exhibit wavefunctions highly sensitive to far-field perturbations. This challenges the conventional interpretation of QNMs as localized excitation