2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/108980We show that a given $x:M^n\to \bar{M}^{n+1}=I\times_ϕF^{n}$ closed spacelike hypersurface with constant mean curvature $H$ and warping function $ϕ$ satisfying ϕ''\geq \ma\{Hϕ'',0\}$ is either minimal or a spacelike slice $\{t_{o}\}\times F$ for some $t_{o}\in I$.10 pagesDifferential Geometry53C50text