Free circle actions with contractible orbits on symplectic manifolds
Abstract
Description
We prove that closed symplectic four-manifolds do not admit any smooth free circle actions with contractible orbits, without assuming that the actions preserve the symplectic forms. In higher dimensions such actions by symplectomorphisms do exist, and we give explicit examples based on a construction of Fernandez, Gray and Morgan. We also prove that the only compact complex surfaces admitting free circle actions with contractible orbits are primary Hopf surfaces.
proof of Prop. 1 clarified, to appear in Mathematische Zeitschrift
proof of Prop. 1 clarified, to appear in Mathematische Zeitschrift