Hawking's calculation of particle production by a black hole is based on the semi-classical limit of a fixed metric. This approximation can break down after a finite time as the black hole evolves due to back-reaction. Therefore, I shall argue that two far-reaching questions remain to be answered:
(1) How long is the semi-classical description valid?
(2) What happens after a potential breakdown?
In an attempt to answer them, I will subsequently present a simple analogue system, which shares quantum properties of a black hole such as its entropy. Numerical computations of non-perturbative time evolution reveal indications that (1) the semi-classical description can break down long before half of the mass is lost and that (2) evaporation slows down drastically at this point. This opens up a new window for small primordial black holes below 1015g as viable dark matter candidates. Detecting only a single one of them would greatly advance our understanding of quantum gravity.
Based on:
M. Michel, S. Zell, The Timescales of Quantum Breaking, Fortsch. Phys. 71 (2023) 2300163, arXiv:2306.09410.
G. Dvali, L. Eisemann, M. Michel, S. Zell, Black hole metamorphosis and stabilization by memory burden, Phys. Rev. D 102 (2020) 103523, arXiv:2006.00011.
