Review of analytic results on quasinormal modes of black holes (2504.05014v1)

Abstract: We present a concise review of known analytic results for quasinormal modes of black holes and related spacetimes. Our emphasis is on those regimes where the perturbation equations admit exact or perturbative solutions, providing insights complementary to numerical or semi-analytic approaches. We discuss solvable cases in lower-dimensional spacetimes, algebraically special modes, and exact results in higher-curvature gravity theories. Particular attention is given to the eikonal regime and its correspondence with null geodesics, as well as to beyond-eikonal approximations based on inverse multipole expansions in parametrized metrics. We review analytic solutions obtained in the near-extremal limit of Schwarzschild - de Sitter black holes, in the regime of large field mass, and in pure de Sitter and anti - de Sitter spacetimes, where boundary conditions play a crucial role. While not exhaustive, this overview highlights the diversity of techniques and physical insights made possible by analytic treatments of quasinormal spectra.