Quantum Gravity Seminar: Roberto Emparan

Speaker: Roberto Emparan (ICREA & Barcelona U.)

Spacetime coordinates: Wed @ 14:30, Auditorium A

Zoom Link: https://ucph-ku.zoom.us/j/9295289933?omn=67282578176

Title: Quantum Cross-section of Near-extremal Black Holes

Abstract: Is it possible to observe large, controllable quantum fluctuations of the spacetime geometry? We will explore how to probe the quantum throat of a near-extremal black hole, where the dynamics are governed by the Schwarzian theory. To this end, we study the scattering of a low-frequency wave of a massless scalar field off the black hole and calculate the absorption cross-section. In the semiclassical regime, we recover the universal result that the cross-section equals the horizon area. However, in the regime where quantum fluctuations dominate, we find that the absorption cross-section exceeds the semiclassical prediction, since quantum fluctuations greatly enhance absorption transitions between black hole states. We conclude that a measurement showing an enhanced absorption cross-section serves as a clear signature of the large quantum fluctuations in the geometry.