摘要

We investigate the differentiable pinching problem for compact immersed submanifolds of positive -th Ricci curvature, and prove that if is simply connected and the -th Ricci curvature of is bounded below by a quantity involving the mean curvature of and the curvature of the ambient manifold, then is diffeomorphic to the standard sphere . For the case where the ambient manifold is a space form with nonnegative constant curvature, we prove a differentiable sphere theorem without the assumption that the submanifold is simply connected. Motivated by a geometric rigidity theorem due to S. T. Yau and U. Simon, we prove a topological rigidity theorem for submanifolds in a space form.

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