Che-Yu Chen, "Joining black hole imaging and ringdown: A novel view of testing gravity"

Thursday 27 Aug 2026, 16:00 → 18:00 Asia/Seoul

Abstract: 

In geometric-optics limits, there exists a mapping connecting black hole images and eikonal black hole quasinormal modes (QNMs), where the latter characterize the ringdown phase in gravitational wave signals emitted by a perturbed black hole. More explicitly, the real part and imaginary part of the QNM frequencies correspond to the ring size and the detailed ring structure of the image, respectively. The explicit identification of such eikonal correspondence, however, relies a lot on the symmetry of the spacetime under consideration and, therefore, is highly non-trivial. After showing that such a correspondence may be violated in theories beyond GR, I will discuss how joining the observations of GW ringdown and images of black holes could test such a correspondence and constrain a class of modified theories of gravity in which the correspondence is broken. This kind of joint observation can open a novel window for testing gravity.