Periodic Hamiltonian flows on four dimensional manifolds

Abstract

We classify the periodic Hamiltonian flows on compact four dimensional symplectic manifolds up to isomorphism of Hamiltonian S^1 spaces. Additionally, we show that all these spaces are Kaehler, that every such space is obtained from a simple model by a sequence of symplectic blowups, and that if the fixed points are isolated then the space is a toric variety.

71 pages, LaTeX. The paper is essentially rewritten (following an excellent referee report): I clarified statements, simplified proofs, added missing details, and corrected a false proof of a true statement, which is currently in Appendix C