Field theories and orbifold cohomology

I will describe a dimensional reduction procedure for 1-dimensional supersymmetric Euclidean field theories over an orbifold.  As a basic application, we obtain a geometric interpretation of the equivariant Chern character for finite group actions.  I will also explain how twisted K-theory fits into this picture: a gerbe with connection gives rise to a 1-dimensional twist, and 0-dimensional field theories twisted by the dimensionally reduced twist represent classes in (twisted) complexified K-theory.