Resonance spectra of caged black holes

Understand

Recent numerical studies of the coupled Einstein-Klein-Gordon system in a cavity have provided compelling evidence that {\it confined} scalar fields generically collapse to form black holes.

• Motivated by this intriguing discovery, we here use analytical tools in order to study the characteristic resonance spectra of the confined fields.
• These discrete resonant frequencies are expected to dominate the late-time dynamics of the coupled black-hole-field-cage system.
• We consider caged Reissner-Nordstr\"om black holes whose confining mirrors are placed in the near-horizon region $x_{\text{m}}\equiv (r_{\text{m}}-r_+)/r_+\ll\tau\equiv (r_+-r_-)/r_+$ (here $r_{\text{m}}$ is the radius of the confining mirror and $r_{\pm}$ are the radii of the black-hole horizons).