Abstract: Gravitational waves from black hole binaries provide a unique opportunity to probe extreme gravitational phenomena, enabling precise tests of Einstein’s General Relativity (GR). In this talk, I will explore potential signatures of modified gravity in gravitational wave observations.
To systematically investigate black hole behavior in alternative theories, we employ the Parametrized Black Hole Quasinormal Modes (QNMs) formalism, a powerful approach that allows for efficient QNM calculations and the exploration of deviations from GR. Even in setups perturbatively close to GR, we uncover small but detectable deviations in QNM frequencies, suggesting the presence of modifications introduced by alternative gravity theories. This motivates a deeper analysis of linear perturbations, described by radial wave equations with potentials that encode the effects of modified gravity in spherically symmetric spacetimes.
Furthermore, I will highlight the significance of higher overtones, which dominate the early ringdown phase and exhibit heightened sensitivity to near-horizon physics. Our findings indicate that larger deviations from GR tend to manifest in the quasinormal frequencies of these higher overtones, making them key probes for testing gravity beyond Einstein’s theory. Finally, I will discuss recent advancements and challenges in identifying observational signatures of modified black holes, along with the prospects for detecting such deviations in future gravitational wave observations.