Noncommutative $AdS^3$ with Quantized Cosmological Constant
  We examine a recent deformation of three-dimensional anti-deSitter gravity based on noncommutative Chern-Simons theory with gauge group $U(1,1)\times U(1,1)$. In addition to a noncommutative analogue of 3D gravity, the theory contains two addition gauge fields which decouple in the commutative limit. It is well known that the level is quantized in noncommutative Chern-Simons theory. Here it implies that the cosmological constant goes like minus one over an integer-squared. We construct the noncommutative $AdS^3$ vacuum by applying a Seiberg-Witten map from the commutative case. The procedure is repeated for the case of a conical space resulting from a massive spinning particle. 
A. Pinzul and A. Stern