The Kerr/CFT Correspondence

Abstract

Quantum gravity in the region very near the horizon of an extreme Kerr black hole (whose angular momentum and mass are related by \(J = GM^2\)) is considered. It is shown that consistent boundary conditions exist, for which the asymptotic symmetry generators form one copy of the Virasoro algebra with central charge \(c_L = 12J/\hbar\). This implies that the near-horizon quantum states can be identified with those of (a chiral half of) a two-dimensional conformal field theory (CFT). Moreover, in the extreme limit, the Frolov-Thorne vacuum state reduces to a thermal density matrix with dimensionless temperature \(T_L = 1/2\pi\) and conjugate energy given by the zero mode generator, \(L_0\), of the Virasoro algebra. Assuming unitarity, the Cardy formula then gives a microscopic entropy \(S_{micro} = 2\pi J/\hbar\) for the CFT, which reproduces the macroscopic Bekenstein-Hawking entropy \(S_{macro} = Area/4\hbar G\). The results apply to any consistent unitary quantum theory of gravity with a Kerr solution. We accordingly conjecture that extreme Kerr black holes are holographically dual to a chiral two-dimensional conformal field theory with central charge \(c_L = 12J/\hbar\), and, in particular, that the near-extreme black hole GRS 1915+105 is approximately dual to a CFT with \(c_L\sim 2 \times 10^{79}\).