IAS Fundamental Physics Seminar Series - A Nonlinear Voice from GW250114 Ringdown

Abstract
Extracting the rich spectrum of quasi-normal modes from gravitational-wave ringdown signals presents significant data analysis challenges, partly due to the challenge of isolating the ringdown phase from the preceding inspiral and merger. Various data analysis strategies have been developed to address this, including techniques such as gating and inpainting to isolate the ringdown contribution. In this talk, the speaker will first briefly review current observational evidence for ringdown from recent gravitational-wave events. He will then introduce his work: a novel data analysis framework that uses gating and inpainting to incorporate information from the pre-ringdown phase as an informed prior for ringdown analysis. Focusing on GW250114, the loudest event observed to date, the speaker will discuss how recent theoretical progress on calculating quadratic mode coupling ratios has enabled us to identify evidence for quadratic modes in this event and to perform tests of general relativity.