The Three-Dimensional Noncommutative Nonlinear Sigma Model in Superspace

We study the superspace formulation of the noncommutative nonlinear supersymmetric O(N) invariant sigma-model in 2+1 dimensions. We prove that the model is renormalizable to all orders of 1/N and explicitly verify that the model is asymptotically free.Comment: 16 pages, 5 figures, Revte

A Consistent Noncommutative Field Theory: the Wess-Zumino Model

We show that the noncommutative Wess-Zumino model is renormalizable to all orders of perturbation theory. The noncommutative scalar potential by itself is non-renormalizable but the Yukawa terms demanded by supersymmetry improve the situation turning the theory into a renormalizable one. As in the commutative case, there are neither quadratic nor linear divergences. Hence, the IR/UV mixing does not give rise to quadratic infrared poles.Comment: 22 pages, 7 figures. Added references. Typos correcte

Poisson Algebra of Diffeomorphism Generators in a Spacetime Containing a Bifurcation

In this article we will analyze the possibility of a nontrivial central extension of the Poisson algebra of the diffeomorphism generators, which respect certain boundary conditions on the black hole bifurcation. The origin of a possible central extension in the algebra is due to the existence of boundary terms in the in the canonical generators. The existence of such boundary terms depend on the exact boundary conditions one takes. We will check two possible boundary conditions i.e. fixed bolt metric and fixed surface gravity. In the case of fixed metric the the action acquires a boundary term associated to the bifurcation but this is canceled in the Legendre transformation and so absent in the canonical generator and so in this case the possibility of a nontrivial central extension is ruled out. In the case of fixed surface gravity the boundary term in the action is absent but present in the Hamiltonian. Also in this case we will see that there is no nontrivial central extension, also if there exist a boundary term in the generator.Comment: LaTex 20 pages, some misprints corrected, 2 references added. Accepted for publication on Phys. Rev.