Timelike hypersurfaces of Minkowski ۴-space with proper mean curvature vector

In this paper, we study timelike hypersurfaces of the Minkowski ۴-pace with ۱-proper second meancurvature vector eld. The second mean curvature vector eld is ۱-proper if it is an eigenvector of theCheng-Yau operator. we prove that these hypersurfaces have constant scalar curvature. As a classi cationresult, we show that such a hypersurface has to be nite type or ۱-minimal.