Quantum mechanics and general relativity are among the most precisely tested theories in physics, yet a complete quantum theory of gravity remains elusive. A natural starting point, Feynman’s path integral over spacetime geometries, is easy to write down but difficult to make sense of. In this colloquium, I will argue that, in quantum gravity, black holes can play the role the harmonic oscillator plays in quantum mechanics: a simple, controllable system in which the theory can be tested. Building on ideas from statistical mechanics and open quantum systems, I will show how, for long-wavelength perturbations of black holes, the gravitational path integral can be made precise as an effective theory of dissipative hydrodynamics.
Página personal
