This article presents an approach to the theory of open manifolds of nonnegative sectional curvature via the calculus of nonsmooth functions. This analytical approach makes possible a very compact development of the by now classical theory. The article also gives a summary of the historical development of the subject of open manifolds of nonnegative sectional curvature and of related topics. So...

In this paper, we study closed four-dimensional manifolds. particular, show that under various new pinching curvature conditions (for example, the sectional is no more than 5/6 of smallest Ricci eigenvalue) then manifold definite. If restricting to a metric with harmonic Weyl tensor, it must be self-dual or anti-self-dual same conditions. Similarly, if an Einstein metric, either complex project...

In this short communication, we announce results from our research on the structure of complete noncompact oriented weakly stable minimal hypersurfaces in a manifold of nonnegative sectional curvature. In particular, a complete oriented weakly stable minimal hypersurface in Rm, m > or = 4, must have only one end; any complete noncompact oriented weakly stable minimal hypersurface has only one e...

In this paper, we prove a general maximum principle for the time dependent Lichnerowicz heat equation on symmetric tensors coupled with the Ricci flow on complete Riemannian manifolds. As an application we construct complete manifolds with bounded nonnegative sectional curvature of dimension greater than or equal to four such that the Ricci flow does not preserve the nonnegativity of the sectio...