The fundamental group of $S^1$-manifolds

2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/75249We address the problem of computing the fundamental group of a symplectic $S^1$-manifold for non-Hamiltonian actions on compact manifolds, and for Hamiltonian actions on non-compact manifolds with a proper moment map. We generalize known results for compact manifolds equipped with a Hamiltonian $S^1$-action. Several examples are presented to illustrate our main results.15 pages, 3 figuresSymplectic GeometryAlgebraic Topology53D05; 53D20; 57R19The fundamental group of $S^1$-manifoldstext