[IP2I seminar] Gravitational waves - H. Roussille (ENS Lyon) - Testing General Relativity with the ringdown

jeudi 5 mars 2026, 11:00 → 12:00 Europe/Paris

Dirac/RdC-Amphithéâtre (IP2I)

The first detection of gravitational waves (GWs) from a binary black hole (BH) merger in 2015 marked the beginning of a new era for tests of General Relativity (GR): the strong gravity regime of this theory can now be tested through the direct observation of BHs. The last phase of the GW signal of a binary BH merger, called the ringdown, is made of a superposition of modes called the quasi-normal modes (QNMs): measuring these modes and comparing them with theoretical predictions constitutes the black hole spectroscopy program, which can now be realized thanks to recent observations with high signal-to-noise ratio such as GW250114. However, in order to constrain GR using GW QNM measurements, one needs to overcome the technical challenge of building theoretical predictions for beyond-GR theories. In this talk, I will show how such a computation can be performed in several modified gravity theories. I will explain why the computation is more difficult than in GR and present an algorithm that allows one to formulate a well-posed numerical problem for a broad class of theories beyond GR.

IP2I_seminars-poster_Roussille.pdf