Soft hairy warped black hole entropy

TL;DR

This paper introduces new boundary conditions for warped black holes in topologically massive gravity, revealing soft hairy excitations and a simple entropy formula linked to horizon symmetries, supporting universality of this entropy law.

Contribution

It develops a general framework for asymptotic symmetries in Chern-Simons-like gravity theories and applies it to find novel boundary conditions with soft hairy excitations.

Findings

Boundary conditions allowing soft hairy excitations on warped black hole horizons.

Symmetry algebra comprising two u(1) current algebras.

Entropy formula $S=2\pi (J_0^+ + J_0^-)$ proven for non-maximally symmetric configurations.

Abstract

We reconsider warped black hole solutions in topologically massive gravity and find novel boundary conditions that allow for soft hairy excitations on the horizon. To compute the associated symmetry algebra we develop a general framework to compute asymptotic symmetries in any Chern-Simons-like theory of gravity. We use this to show that the near horizon symmetry algebra consists of two u(1) current algebras and recover the surprisingly simple entropy formula $S=2\pi (J_0^+ + J_0^-)$, where $J_0^\pm$ are zero mode charges of the current algebras. This provides the first example of a locally non-maximally symmetric configuration exhibiting this entropy law and thus non-trivial evidence for its universality.