I will describe a remarkable symmetric monoidal category associated to a reductive group G, which acts centrally on any G-category. This construction quantizes the universal centralizer group scheme, together with its action on Hamiltonian G-spaces used by Ngo in his proof of the Fundamental Lemma. The category and its central action appear most naturally in a Langlands dual incarnation, which is phrased in terms of convolution on the affine Grassmannian, via work of Bezrukavnikov, Finkelberg and Mirkovic. This is joint work with David Ben-Zvi.
Vasily Pestun & Chris Elliott