2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/72505We prove a surgery formula for the renormalized Euler characteristic of Ozsvath and Szabo. Equality between this Euler cahracteristic and the Seiberg-Witten invariant follows for rational homology three-spheres.11 pages, sign conventions explainedGeometric Topology57R58; 57Q10; 57R57; 53D40text