Observing Quantum Gravity in Extremely Cold Horizons

Recent developments have revealed that black holes near extremality exhibit large quantum fluctuations in their geometry, marking a controllable breakdown of semiclassical quantum field theory in curved spacetime. In this talk, I will discuss how these fluctuations can be revealed through scattering waves off the black hole. In particular, we find that extremely cold black holes become transparent to low-frequency light or gravitational radiation. Although such signatures are extraordinarily hard to detect, they provide concrete signatures of quantum gravity at play in near-extremal regimes.