Where are the BTZ Black Hole Degrees of Freedom?

Abstract

Previous derivations of the BTZ black hole entropy from a dual conformal description place the degrees of freedom at spatial infinity. Here it is shown for the non-rotating case that a dual conformal description exists at any location around the black hole, a result that has a strong physical appeal considering that in 2+1 dimensions there are no propagating degrees of freedom in the classical theory. Two copies of the central charge of $3\ell/2G$ are recovered, and the microcanonical Cardy formula yields the correct Bekenstein-Hawking entropy.