2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/62527The Yamabe invariant Y(M) of a smooth compact manifold is roughly the supremum of the scalar curvatures of unit-volume constant-scalar-curvature Riemannian metrics g on M. (To be precise, one only considers those constant-scalar-curvature metrics which are Yamabe minimizers, but this technicality does not, e.g. affect the sign of the answer.) In this article, it is shown that many 4-manifolds M with Y(M) < 0 have have finite covering spaces \tilde{M} with Y(\tilde{M}) > 0.Source file for published version. Discussion expanded, minor errors corrected. 8 pages, LaTeX2eDifferential GeometryGeometric Topology53C27; 57R57text