Non-Hamiltonian actions with isolated fixed points

IAS/Columbia University/Bendersky-Gitler Symplectic Geometry Seminar
Topic:Non-Hamiltonian actions with isolated fixed points
Speaker:Sue Tolman
Affiliation:University of Illinois at Urbana-Champaign
Date:Friday, March 20
Time/Room:2:45pm - 3:45pm/Jadwin A10, Princeton University

Let a circle act symplectically on a closed symplectic manifold $M$. If the action is Hamiltonian, we can pass to the reduced space; moreover, the fixed set largely determines the cohomology and Chern classes of $M$. In particular, symplectic circle actions with no fixed points are never Hamiltonian. This leads to the following important question: What conditions force a symplectic action with fixed points to be Hamiltonian? Frankel proved that Kahler circle actions with fixed points on Kahler manifolds are always Hamiltonian. In contrast, McDuff constructed a non-Hamiltonian symplectic circle action with fixed tori. Despite significant additional research, the following question is still open: Does there exists a non-Hamiltonian symplectic circle action with isolated fixed points? The main goal of this talk is to answer this question by constructing a non-Hamiltonian symplectic circle action with exactly 32 fixed points on a closed six-dimensional symplectic manifold. In part, joint with Jordan Watts.