Moduli of Vacua and Categorical representations David Ben-Zvi University of Texas at Austin Mathematics I will present some results on three-dimensional gauge theory from the point of view of extended topological field theory. In this setting a theory is specified by describing its collection of boundary conditions - in our case, a collection of categories (standing in for 2d TFTs) with a prescribed symmetry group G. We will apply ideas from Seiberg-Witten geometry to construct a new commutative algebra of symmetries for categorical representations (or line operators in the gauge theory) - a categorification of Kostant's ``Whittaker" description of the center of the enveloping algebra. (Joint with Sam Gunningham and David Nadler)