Siye Wu

Non-orientable surfaces and S-duality

In this talk, I explain the role of non-orientable surfaces in twisted N=4 supersymmetric Yang-Mills theory in 4 dimensions whose compactification along orientable surfaces yields mirror symmetry and geometric Langlands program as studied by Kapustin and Witten. I relate the discrete electric and magnetic fluxes of 't Hooft in 4 dimensions to the topology of moduli spaces.