Horizon Fluffs: Near Horizon Soft Hairs as Microstates of Generic AdS3 Black Holes

Abstract

In [1] the horizon fluffs proposal is put forward to identify microstates of generic non-extremal three-dimensional Banados-Teitelboim-Zanelli (BTZ) black holes. The proposal is that black hole microstates, which were dubbed as horizon fluffs, are states labelled by the conserved charges associated with non-trivial diffeomorphisms on the near horizon geometry and these states are not in the coadjoint orbits of the asymptotic Virasoro algebra at the Brown-Henneaux central charge, associated with the BTZ black holes. It is also known that AdS3 Einstein gravity has more general black hole solutions than the BTZ family which are generically described by two periodic, but otherwise arbitrary, holomorphic and anti-holomorphic functions. We show that these general AdS3 black holes which are typically conformal descendants of the BTZ black holes and are characterised by the associated Virasoro coadjoint orbits, appear as coherent states in the asymptotic symmetry algebra corresponding to the black hole family. We apply the horizon fluffs proposal to these generic AdS3 black holes and identify the corresponding microstates. We then perform microstate counting and compute the entropy. The entropy appears to be an orbit invariant quantity, providing an important check for the horizon fluffs proposal.

Figures (1)

• Figure 1: A schematic diagram of the near horizon Hilbert spaces ${\mathcal{H}}_{\mathcal{N}\mathcal{H}}$, Asymptotic black hole Hilbert space is ${\mathcal{H}}_{\mathcal{B}\mathcal{H}}$ (green region) and the Hilbert space of horizon fluffs (black hole microstates) is $\mathcal{H}_\mathcal{F}$ (red region). Intersection of $\mathcal{H}_{\mathcal{B}\mathcal{H}}$ and $\mathcal{H}_\mathcal{F}$ is the vacuum state $|0\rangle$ or $|0;0\rangle_{_{\mathcal{B}\mathcal{H}}}$