Elliptic Dynamical Quantum Groups and Equivariant Elliptic Cohomology

We define an elliptic version of the stable envelope of Maulik and Okounkov for the equivariant elliptic cohomology of cotangent bundles of Grassmannians.It is a version of the construction proposed by Aganagic and Okounkov and is based on weight functions and shuffle products.We construct an action of the dynamical elliptic quantum group associated with gl 2 on the equivariant elliptic cohomology of the union of cotangent bundles of Grassmannians.The generators of the elliptic quantum groups act as difference operators on sections of admissible bundles, a notion introduced in this paper.