The Alexandrov-Toponogov comparison theorem for radial curvature

Abstract

We discuss the Alexandrov-Toponogov comparison theorem under the conditions of radial curvature of a pointed manifold (M,o) with reference surface of revolution. There are two obstructions to make the comparison theorem for a triangle one of whose vertices is a base point o. One is the cut points of another vertex of a comparison triangle in the reference surface of revolution. The other is the cut points of the base point o in M. We find a condition under which the omparison theorem is valid for any geodesic triangle with a vertex at o in M.