Black hole entropy from loop quantum gravity

We study the idea that the statistical entropy governing thermal interactions of a black hole with its exterior is determined by the microstates of the hole having distinct effects on the exterior, and over which a hole in a given macroscopic configuration thermally fluctuates. We argue that for a (macroscopically) Schwarzschild black hole this ensemble is formed by horizons with the same area. We compute the number of states in this ensemble from first principles using nonperturbative loop quantum gravity. We obtain a statistical entropy proportional to the area, as in the Bekenstein-Hawking formula.