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Soft hairy warped black hole entropy. (English) Zbl 1387.83047
Summary: 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 $$\mathfrak{u} (1)$$ 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.

##### MSC:
 83C57 Black holes 83D05 Relativistic gravitational theories other than Einstein’s, including asymmetric field theories 83C05 Einstein’s equations (general structure, canonical formalism, Cauchy problems) 94A17 Measures of information, entropy 58J28 Eta-invariants, Chern-Simons invariants
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