Chiral gravity in three dimensions

Three dimensional Einstein gravity with negative cosmological constant -1/l(2) deformed by a gravitational Chern-Simons action with coefficient 1/mu is studied in an asymptotically AdS(3) spacetime. It is argued to violate unitary or positivity for generic mu due to negative-energy massive gravitons. However at the critical value mu l = 1, the massive gravitons disappear and BTZ black holes all have mass and angular momentum related by lM = J. The corresponding chiral quantum theory of gravity is conjectured to exist and be dual to a purely right-moving boundary CFT with central charges (c(L), c(R)) = (0, 3l/G).