Quasinormal modes of black holes and black branes

TLDR

Quasinormal modes are dissipative eigenmodes that arise from perturbations of black holes or branes, requiring non‑Hermitian eigenvalue analyses, and are used in gauge‑gravity duality to extract transport coefficients and in gravitational‑wave astronomy to measure black‑hole parameters and test general relativity. This review introduces recent developments in the study of quasinormal modes. It surveys recent theoretical and computational methods for analyzing quasinormal spectra of black holes and branes.

Abstract

Quasinormal modes are eigenmodes of dissipative systems. Perturbations of classical gravitational backgrounds involving black holes or branes naturally lead to quasinormal modes. The analysis and classification of the quasinormal spectra require solving non-Hermitian eigenvalue problems for the associated linear differential equations. Within the recently developed gauge-gravity duality, these modes serve as an important tool for determining the near-equilibrium properties of strongly coupled quantum field theories, in particular their transport coefficients, such as viscosity, conductivity and diffusion constants. In astrophysics, the detection of quasinormal modes in gravitational wave experiments would allow precise measurements of the mass and spin of black holes as well as new tests of general relativity. This review is meant as an introduction to the subject, with a focus on the recent developments in the field.