2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/106195We show an equivariant bordism principle for constructing metrics of positive scalar curvature that are invariant under a given group action. Furthermore, we develop a new codimension-2 surgery technique which removes singular strata from fixed point free $S^1$-manifolds while preserving equivariant positive scalar curvature. These results are applied to derive the following generalization of a result of Gromov and Lawson: Each closed fixed point free $S^1$-manifold of dimension at least 6 whose isotropy groups have odd order and whose union of maximal orbits is simply connected and not spin carries an $S^1$-invariant metric of positive scalar curvature.36 pages, 1 figure, minor changes; to appear in J. Reine Angew. MathGeometric TopologyDifferential Geometryprimary 53C23, 53C25, 57R85; secondary 57R65text