Quiver varieties and elliptic quantum groups

We define a sheafified elliptic quantum group for any symmetric Kac-Moody Lie algebra. This definition is naturally obtained from the elliptic cohomological Hall algebra of a preprojective algebra. The sheafified elliptic quantum group is an algebra object in a certain monoidal category of coherent sheaves on the colored Hilbert scheme of an elliptic curve. We show that the elliptic quantum group acts on the equivariant elliptic cohomology of Nakajima quiver varieties. This action is compatible with the action induced by Hecke correspondence, a construction similar to that of Nakajima. The elliptic Drinfeld currents are obtained as generating series of certain rational sections of the sheafified elliptic quantum group. We show that the Drinfeld currents satisfy the commutation relations of the dynamical elliptic quantum group studied by Felder and Gautam-Toledano Laredo.