Equivariant Cohomology and the Duistermaat-Heckman Theorem

Another famous and spectacular theorem in the theory of Hamiltonian torus actions is the Duistermaat-Heckman Theorem [44] (as we have learned since that time, similar results had been proved by Karasev [81] in 1981). This theorem has two versions, both asserting, once again, the importance of linear phenomena in the theory.