Superradiance and instability of the charged Myers-Perry black holes in the G\"{o}del Universe

TL;DR

This paper investigates scalar field perturbations of charged rotating black holes in a G"odel universe, revealing superradiant instabilities caused by boundary conditions that confine the perturbations, similar to effects seen in AdS space.

Contribution

It demonstrates the existence of superradiant unstable modes in 5D charged G"odel black holes, highlighting the role of boundary conditions in black hole stability analysis.

Findings

Superradiant modes lead to instability in G"odel black holes.

Confining boundary conditions cause energy extraction and growth of perturbations.

Instability mechanism is analogous to that in AdS black holes.

Abstract

We consider scalar field perturbations of the asymptotically G\"odel 5-dimensional charged rotating black holes with two equal angular momenta. It is shown that the spectrum of proper oscillations of the perturbation includes superradiant unstable modes. The reason for the instability is the confining Dirichlet boundary condition at the asymptotically far region of the G\"odel Universe. The confining box makes superradiant modes extract rotational energy from the black hole and, after repeated reflections from the black hole, grow unboundedly. A similar instability takes place for rotating black holes in the asymptotically anti-de Sitter (AdS) space-time.