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Journal of Convex Analysis 26 (2019), No. 4, 1321--1336 Copyright Heldermann Verlag 2019 Convexity of the Distance Function to Convex Subsets of Riemannian Manifolds Solmaz Khajehpour School of Mathematics, Institute for Research in Fundamental Sciences, Tehran, Iran solmazkh114@ipm.ir Mohamad R. Pouryayevali Dept. of Mathematics, University of Isfahan, Isfahan, Iran pourya@math.ui.ac.ir A characterization of the proximal normal cone is obtained and a separation theorem for convex subsets of Riemannian manifolds is established. Moreover, the convexity of the distance function dS for a convex subset S in the cases where the boundary of S contains a geodesic segment, the boundary of S is C2 or the boundary of S is not regular is discussed. Furthermore, a nonsmooth version of positive semi-definiteness of the Hessian of convex functions on Riemannian manifolds is established. Keywords: Distance function, proximal normal cone, convexity, Riemannian manifold. MSC: 58C05, 53C21, 49J52 [ Fulltext-pdf (150 KB)] for subscribers only. |