2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/66733We calculate geometric and homotopical (or stable) bordism rings associated to semi-free $S^1$ actions on complex manifolds, giving explicit generators for the geometric theory. The classification of semi-free actions with isolated fixed points up to cobordism complements similar results from symplectic geometry.11 pagesAlgebraic Topology57R85text