NotationsThroughout the paper T will denote a compact, connected abelian Lie group, and t its Lie algebra. The integral lattice Λ ⊂ t is defined as the kernel of exp : t → T , and the real weight lattice Λ * ⊂ t * is defined by : Λ * := hom(Λ, 2πZ). Every µ ∈ Λ * defines a 1-dimensional T -representation, denoted by C µ , where t = exp X acts by t µ := e i µ,X . We denote by R(T ) the ring of characters of finite-dimensional Trepresentations. We denote by R −∞ (T ) the set of generalized characters of T . Anhas at most polynomial growth. The symplectic manifolds are oriented by their Liouville volume forms. If (Z, o Z ) is an oriented submanifold of an oriented manifold (M, o M ), we take on the fibers of the normal bundle N of Z in M , the orientation o N satisfying o M = o Z · o N .
Duistermaat-Heckman measuresLet (M, Ω) be a symplectic manifold of dimension 2n equipped with an Hamiltonian action of a torus T , with Lie algebra t. The moment map Φ : M → t * satisfies the relations Ω(X M , −) + d Φ, X = 0, X ∈ t. We assume in this section that Φ is proper, and that the generic stabiliser Γ M of T on M is finite.The Duistermaat-Heckman measure DH(M) is defined as the pushforward by Φ of the Liouville volume form Ω n n! on M . For every f ∈ C ∞ (t * ) with compact support one has t * DH(M)(a)f (a) = M f (Φ) Ω n n! . In other terms DH(M)(a) = M δ(a − Φ) Ω n n! . We can define DH(M) in terms of equivariant forms as follows. Let A(M ) be the space of differential forms on M with complex coefficients. We denote by A −∞ temp (t, M ) the space of tempered generalized functions over t with values in A(M ), and by M −∞ temp (t * , M ) the space of tempered distributions over t * with values in A(M ). Let F : A −∞ temp (t, M ) → M −∞ temp (t * , M ) be the Fourier transform normalized by the condition that F (X → e i ξ,X ) is equal to the Dirac distribution a → δ(a − ξ).Let Ω t (X) = Ω − Φ, X be the equivariant symplectic form. We have then F (e −iΩt ) = e −iΩ δ(a − Φ) and so (2.1) DH(M) = (i) n M