Warped AdS3 black holes

Three dimensional topologically massive gravity (TMG) with a negative cosmological constant -l(-2) and positive Newton constant G admits an AdS(3) vacuum solution for any value of the graviton mass mu. These are all known to be perturbatively unstable except at the recently explored chiral point mu l = 1. However we show herein that for every value of mu l not equal 3 there are two other (potentially stable) vacuum solutions given by SU(2, R) x U(1)-invariant warped AdS(3) geometries, with a timelike or spacelike U( 1) isometry. Critical behavior occurs at mu l = 3, where the warping transitions from a stretching to a squashing, and there are a pair of warped solutions with a null U(1) isometry. For mu l > 3, there are known warped black hole solutions which are asymptotic to warped AdS3. We show that these black holes are discrete quotients of warped AdS3 just as BTZ black holes are discrete quotients of ordinary AdS3. Moreover new solutions of this type, relevant to any theory with warped AdS3 solutions, are exhibited. Finally we note that the black hole thermodynamics is consistent with the hypothesis that, for mu l > 3, the warped AdS3 ground state of TMG is holographically dual to a 2D boundary CFT with central charges c(R) = 15(mu l)(2)+81/G mu((mu l)(2)+27) and c(L) = 12 mu l(2)/G((mu l)(2)+ 27).