“KMI colloquium” 11th Jun. (Wed)  17：00 – 18 : 00
Speaker: Naritaka Oshita (Hakubi Center for Advanced Research/YITP, Kyoto University)
Title: Chords of a black hole ringing: Probing extreme gravity with gravitational-wave observations
Place: ES635 & ZOOM

Abstract: As musical instruments resonate with their characteristic vibrational modes, black holes also ring with their distinctive tones. These tones are known as quasi-normal modes (QNMs), and their frequencies are uniquely determined by the black hole’s mass and spin. After the merger of a binary black hole system, the remnant black hole exhibits its free oscillations, emitting gravitational waves known as the ringdown signal. The ringdown contains multiple QNMs, and it is expected that black hole spectroscopy—resolving these modes individually—will enable precision tests of gravity in the strong-field regime.
In this colloquium, I will present an overview of black hole perturbation studies from both theoretical and observational perspectives. I will then introduce recent progress in ringdown modeling based on the universal excitability of QNMs and the black hole S-matrix, and will discuss its implications for probing strong gravity.