Connections on moduli spaces and infinitesimal Hecke modifications

Abstract

Let X be a proper scheme and Z a prestack over X equipped with a flat connection. We give a local-to-global description of D-modules on the prestack S(Z) of flat sections of Z. Examples of S(Z) include the moduli stacks of principal G-bundles and de Rham local systems on X. We show that the category of D-modules is equivalent to the category of ind-coherent sheaves which are equivariant with respect to infinitesimal Hecke groupoids parametrized by finite subsets of X. We describe a number of applications to geometric representation theory and conformal field theory, including a derived enhancement of the Verlinde formula: the derived space of conformal blocks (a.k.a. chiral homology) of the WZW model is isomorphic to the cohomology of the corresponding line bundle on Bun_G, the moduli stack of G-bundles.