We generalize the
well-known Gauchman theorem for closed minimal submanifolds in a unit sphere, and
prove that if M is an n-dimensional closed submanifold of parallel mean curvature in
Sn+p and if σ(u) ≤ for any unit vector u ∈ TM, where σ(u) = ∥h(u,u)∥2, and
h is the second fundamental form of M, then either σ(u) ≡ H2 and M is
a totally umbilical sphere, or σ(u) ≡. Moreover, we give a geometrical
classification of closed submanifolds with parallel mean curvature satisfying
σ(u) ≡.
Keywords
closed submanifolds, rigidity theorem, parallel mean
curvature