Quasinormal modes of black holes with general spin in dynamical Chern-Simons gravity

The success of the LIGO-Virgo-KAGRA collaboration has enabled tests of Einstein's theory of general relativity (GR) in the strong-gravity regime. A key test involves measuring the quasinormal modes (QNMs) emitted during the ringdown phase of binary black hole mergers. Within GR, a black hole's QNM spectrum is entirely determined by its mass, spin, and charge. However, in beyond-Einstein theories, the QNM spectrum also depends on the coupling constants of the theory and the properties of additional non-metric fields. Calculating beyond-Einstein QNMs was historically challenging, but recent advances in the modified Teukolsky formalism have made this task more feasible. In previous years, we demonstrated how to use this formalism to compute QNMs in dynamical Chern-Simons (dCS) gravity within the slow-rotation approximation. In this talk, I will briefly review those results, highlighting their consistency with other approaches. We will then show how to generalize our procedures to dCS black holes with a general spin. Our findings include the radial equations governing the Weyl scalars Psi0 and Psi4, as well as the dCS scalar field. Finally, we apply the eigenvalue perturbation method to compute the QNM spectrum in this broader context.