Inequalities for Casorati curvatures of submanifolds in real space forms

By using T. Oprea's optimization methods on submanifolds, we give another proof of the inequalities relating the normalized δ-Casorati curvature δc (n-1) for submanifolds in real space forms. Also, inequalities relating the normalized δ-Casorati curvature δC (n-1) for submanifolds in real space forms are obtained. Besides, we characterize a kind of Casorati ideal hypersurface of Euclidean 4-space. We also show that this kind of Casorati ideal hypersurface is rigid.