Multi-helicoidal Euclidean submanifolds of constant sectional curvature.
We classify locally the induced Riemannian metrics of all irreducible double-ruled hypersurfaces in .
We give a classification of minimal homothetical hypersurfaces in an (n+1)-dimensional Euclidean space. In fact, when n ≥ 3, a minimal homothetical hypersurface is a hyperplane, a quadratic cone, a cylinder on a quadratic cone or a cylinder on a helicoid.
We show that any real Kähler Euclidean submanifold with either non-negative Ricci curvature or non-negative holomorphic sectional curvature has index of relative nullity greater than or equal to . Moreover, if equality holds everywhere, then the submanifold must be a product of Euclidean hypersurfaces almost everywhere, and the splitting is global provided that is complete. In particular, we conclude that the only real Kähler submanifolds in that have either positive Ricci curvature or...