Stability of warped AdS3 vacua of topologically massive gravity

AdS(3) vacua of topologically massive gravity (TMG) have been shown to be perturbatively unstable for all values of the coupling constant except the chiral point mu l = 1. We study the possibility that the warped vacua of TMG, which exist for all values of mu, are stable under linearized perturbations. In this paper, we show that spacelike warped AdS(3) vacua with Compere-Detournay boundary conditions are indeed stable in the range mu l > 3. This is precisely the range in which black hole solutions arise as discrete identifications of the warped AdS(3) vacuum. The situation somewhat resembles chiral gravity: although negative energy modes do exist, they are all excluded by the boundary conditions, and the perturbative spectrum solely consists of boundary ( pure large gauge) gravitons.