© The London Mathematical Society
Intersection Cohomology of Symplectic Quotients by Circle Actions
Department of Mathematics, Seoul National University Seoul 151-747, Korea kiem{at}math.snu.ac.kr
Christ's College, University of Cambridge Cambridge, CB2 3BU, United Kingdom jw301{at}cam.ac.uk
Received 2 December 2003. Revision received 30 March 2004.
Let T = U(1) and M be a Hamiltonian T-space with proper moment map µ : M
R. When 0 is not a regular value of µ, the symplectic quotient X = µ1(0)/T is a singular stratified space. A description is provided of the middle perversity intersection cohomology of X as a subspace of the equivariant cohomology
. The approach is sheaf theoretic.