Near horizon soft hair as microstates of three dimensional black holes

We provide the first explicit proposal for all microstates of generic black holes in three dimensions (of Bañados-Teitelboim-Zanelli type): black hole microstates, termed “horizon fluff,” are a particular class of near horizon soft hairs which have zero energy as measured by the horizon observer and cannot be distinguished by observers at a finite distance from the horizon. These states are arranged in orbits of the two-dimensional conformal algebra associated with the asymptotic black hole geometry. We count these microstates using the Hardy-Ramanujan formula for the number of partitions of a given integer into non-negative integers, recovering the Bekenstein-Hawking entropy. We discuss possible extensions of our black hole microstate construction to astrophysical Kerr-type black holes.