Testing the horizon of black holes with gravitational waves

Elisa Maggio, Max Planck Institute of Gravitational Physics (AEI)

Gravitational waves open the possibility to investigate the nature of compact objects and probe the existence of horizons in black holes. This is of particular interest given some quantum-gravity models which predict the presence of horizonless and singularity-free compact objects. Such exotic compact objects can emit a different gravitational-wave signal relative to the black hole case. In this talk, I derive the characteristic oscillation frequencies of horizonless compact objects in the ringdown. Finally, I describe how parametrised tests on general relativity can allow for tests of the black hole paradigm.