GJC: Romeo Felice Rosato "Ringdown stability: greybody factors as stable gravitational-wave observables"

Tuesday 16 Jul 2024, 13:00 → 14:00 Europe/Rome

Sala Cortini (Fermi)

The quasinormal mode spectrum of black holes plays a crucial role in the modelling of postmerger ringdown signals. However, the spectrum is extremely sensitive to small deformations of the system and describes the linear response only in a certain (not precisely defined) timeframe after the merger. We argue here that the greybody factors, recently shown to describe the ringdown spectral amplitude at relatively high frequencies, are instead stable under small perturbations of the system and free of certain ambiguities that plague the quasinormal mode spectrum. Our analysis also unveils a nontrivial interplay: while certain ringdown quantities are dominated by the contribution of spectrally unstable quasinormal modes, these modes conspire to produce stable observables. Thus, we propose a complementary approach to ringdown studies, which circumvents some limitations of the standard quasinormal mode description.

Based on: https://arxiv.org/abs/2406.01692.