Algebraic deformations arising from orbifolds with discrete torsion
  We develop methods for computing Hochschild cohomology groups and deformations of crossed product rings. We use these methods to find deformations of a ring associated to a particular orbifold with discrete torsion, and give a presentation of the center of the resulting deformed ring. This connects with earlier calculations by Vafa and Witten of chiral numbers and deformations of a similar orbifold. 
Andrei Caldararu, Anthony Giaquinto and Sarah Witherspoon