We prove several versions of "quantization commutes with reduction" for
circle actions on manifolds that are not symplectic. Instead, these manifolds
possess a weaker structure, such as a spin^c structure. Our theorems work
whenever the quantization data and the reduction data are compatible; this
condition always holds if we start from a presymplectic (in particular,
symplectic) manifold.Comment: LaTeX 2e, 28 page