题 目：The photon sphere and response functions in AdS/CFT
报告人：孙昊宇，University of Texas at Austin
时 间：2024年1月26号（星期五）15:00
地 点：腾讯会议：545-826-527
邀请人：周思益
报告摘要：We demonstrate that the photon sphere plays a surprising role in the holography for small AdS-Schwarzschild black holes. A precise formula is derived to show how a black hole amplifies or attenuates an oscillating source dual to boundary operators across the bulk. We estimate the quasi-normal modes of small black holes at large angular momenta $l$. The lowest mode matches the phase transition for the massless scalar fields and the null geodesics, which are identified with the short-lived excitations of the black hole at large $l$. This sharpens the conjecture by Hashimoto that the photon sphere seen by a boundary observer is the spatial Fourier transform of the response function. The conjecture agrees excellently with numerics after certain long-lived excitations -- associated with geodesics connecting boundary points, predicted by Festuccia and Liu -- are removed from the response, which is then controlled by the short-lived excitations of the black hole.
Haoyu Sun received his bachelor degrees in physics, math, and microbial biology from in 2014, and PhD in physics in 2020, both from UC Berkeley. He is now a postdoc at UT Austin, associated with the Ultra-Quantum Matter Simons Collaboration. He will move to Georgia Tech as a research scientist this fall. His main interests lie in string theory, holography, and their intersections with geometric topology and condensed matter physics.