to be merged with geometric Langlands program
The conjectured geometric Langlands correspondence asserts that for a reductive group there is an equivalence of derived categories of D-modules on the moduli stack of -principal bundles over a given curve, and quasi-coherent sheaves on the moduli space of -local systems
for the Langlands dual group?.
This equivalence is a certain limit of the more general quantum geometric Langlands correspondence that identifies twisted -modules on both sides.
The Kapustin-Witten TQFT (KapustinWitten 2007) is supposed to exhibit geometric Langlands duality as a special case of S-duality.
geometric Langlands correspondence
A classical survey is
Notes on two introductory lecture talks are here:
An interpretation of the geometric Langlands correspondence as describing S-duality of certain twisted reduction of super Yang-Mills theory was given in
An exposition of the relation to S-duality and electro-magnetic duality is in