Quantum Black Holes: A Survey

Black holes and their dynamical formation are well understood theoretically from analytical and numerical calculations in general relativity. There are two central observations associated with quantum theory that lead to the puzzle of what is a quantum black hole. The first is Hawking’s observation that quantum matter on a black hole spacetime, a hybrid quantum-classical setting, suggests that black holes are unstable, radiate like a black body, and eventually disappear; the second is that quantum theory should resolve the singularity at the center of a black hole. I review some of the approaches put forward to understand what is a quantum black hole, and how such an object might form from quantum gravitational collapse. The emphasis is on conveying insights gained from studying the quantization of model systems and effective semiclassical equations.