Gravitational perturbations of black holes in modified gravity theories using the METRICS approach

Gravitational-wave tests of general relativity have been mostly conducted in a model-independent and phenomenological way. To fully understand the physical origin of the deviations from the waveforms predicted by general relativity, which might be detected in the future, one needs to test general relativity in a model-specific way. One major obstacle to performing model-specific tests of gravity is that we have not fully understood the waveform generated by binary black holes coalescence in modified gravity, noticeable the waveform morphology during the merger and ringdown phases. In this talk, I will describe applying the recently developed METRICS (Metric pErTuRbations wIth speCtral methodS) approach to study the ringdown signals of black holes in alternative gravity theories, with a specific focus on dynamical Chern-Simons gravity.