Ricci-positive metrics on connected sums of products with arbitrarily many spheres

Abstract

In this paper we construct Ricci-positive metrics on the connected sum of products of arbitrarily many spheres provided the dimensions of all but one sphere in each summand are at least 3. There are two new technical theorems required to extend previous results on sums of products of two spheres. The first theorem is a gluing construction for Ricci-positive manifolds with corners generalizing a gluing construction of Perelman for Ricci-positive manifolds with boundaries. Our construction gives a sufficient condition for gluing together two Ricci-positive manifolds with corners along isometric faces so that the resulting smooth manifold with boundary will be Ricci-positive and have convex boundary. The second theorem claims that one can deform the boundary of a Ricci-positive Riemannian manifold with convex boundary along a Ricci-positive isotopy while preserving Ricci-positivity and boundary convexity.