2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/73460We obtain a priori estimates for solutions to the prescribed scalar curvature equation on $S^3$. The usual non-degeneracy assumption on the curvature function is replaced by a new condition, which is necessary and sufficient for the existence of a priori estimates, when the curvature function is a positive Morse function.36 pagesAnalysis of PDEsDifferential Geometry35J60; 35J20; 55C21A priori estimates for the scalar curvature equation on $S^3$text