Black hole entropy and soft hair

A set of infinitesimal Virasoro (L) circle times Virasoro (R) diffeomorphisms are presented which act non-trivially on the horizon of a generic Kerr black hole with spin J. The covariant phase space formalism provides a formula for the Virasoro charges as surface integrals on the horizon. Integrability and associativity of the charge algebra are shown to require the inclusion of Wald-Zoupas' counterterms. A counterterm satisfying the known consistency requirement is constructed and yields central charges c(L) = c(R) = 12J. Assuming the existence of a quantum Hilbert space on which these charges generate the symmetries, as well as the applicability of the Cardy formula, the central charges reproduce the macroscopic area-entropy law for generic Kerr black holes.