Integration over homogenous spaces for classical Lie groups using iterated residues at infinity

Abstract: Using the Berline-Vergne integration formula for equivariant cohomology for torus actions, we prove that integrals over Grassmannians (classical, Lagrangian or orthogonal ones) of characteristic classes of the tautological bundle, can be expressed as iterated residues at infinity of some holomorphic functions of several variables. The results obtained for these cases, can be expressed as special cases of one formula, involving the Weyl group action on the characters of the natural representation of the torus.