Fundamental group of Symp ( M , ω ) with no circle action Jarek Kędra — 2009 Archivum Mathematicum We show that π 1 ( Symp ( M , ω ) ) can be nontrivial for M that does not admit any symplectic circle action.
Homotopy properties of Hamiltonian group actions. Kȩdra, Jarek; McDuff, Dusa — 2005 Geometry & Topology