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 dSd_S for a convex subset S in the cases where the boundary of S contains a geodesic segment, the boundary of S is C2C^2 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.

Contact details are reproduced from the original publication and may be historical.

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
  1. T. Aubin: Nonlinear Analysis on Riemannian Manifolds. Monge-Ampère Equations, Springer, New York (1982).https://doi.org/10.1007/978-1-4612-5734-9Google Scholar
  2. F. H. Clarke, Yu. S. Ledyaev, R. J. Stern, P. R. Wolenski: Nonsmooth Analysis and Control Theory, Graduate Texts in Mathematics 178, Springer, New York (1998).Google Scholar
  3. H. Federer: Curvature Measures, Trans. Amer. Math. Soc. 93(3) (1959) 418–491.https://doi.org/10.1090/S0002-9947-1959-0110078-1Google Scholar
  4. G. De Philippis, A. Figalli: The Monge-Ampère equation and its link to optimal transportation, Bull. Amer. Math. Soc. 51(4) (2014) 527–580.https://doi.org/10.1090/S0273-0979-2014-01459-4Google Scholar
  5. M. P. do Carmo: Riemannian Geometry, Mathematical Theory and its Applications, Birkhäuser, Boston (1992).https://doi.org/10.1007/978-1-4757-2201-7Google Scholar
  6. A. Gray: Tubes, Birkhäuser, Boston (2004).https://doi.org/10.1007/978-3-0348-7966-8Google Scholar
  7. R. E. Greene: A genealogy of noncompact manifolds of nonnegative curvature: history and logic, in: Comparison Geometry, K. Grove and P. Petersen (eds.), Math. Sci. Res. Inst. Publ. 30, Cambridge University Press, Cambridge (1997) 99–134.https://doi.org/10.1017/9781009701891.005Google Scholar
  8. R. E. Greene, K. Shiohama: Convex functions on complete noncompact manifolds: topological structure, Invent. Math. 63(1) (1981) 129–157.https://doi.org/10.1007/BF01389196Google Scholar
  9. M. Gromov: Metric Structures for Riemannian and Non-Riemannian spaces, Birkhäuser, Boston (2007).Google Scholar
  10. B. Guan, Y. Y. Li: Monge-Ampère equations on Riemannian manifolds, J. Differential Equations 132(1) (1996) 126–139.https://doi.org/10.1006/jdeq.1996.0174Google Scholar
  11. S. Hosseini, M. R. Pouryayevali: On the metric projection onto prox-regular subsets of Riemannian manifolds, Proc. Amer. Math. Soc. 141(1) (2013) 233–244.https://doi.org/10.1090/S0002-9939-2012-11828-3Google Scholar
  12. S. Khajehpour, M. R. Pouryayevali: Viscosity solutions of second order partial differential equations with boundary conditions on Riemannian manifolds, Nonlinear Analysis 146 (2016) 211–232.https://doi.org/10.1016/j.na.2016.08.020Google Scholar
  13. A. Kristály, V. D. Rădulescu, C. Varga: Variational Principles in Mathematical Physics, Geometry, and Economics: Qualitative Analysis of Nonlinear Equations and Unilateral Problems, Cambridge University Press, Cambridge (2010).https://doi.org/10.1017/CBO9780511760631Google Scholar
  14. C. Li, J. C. Yao: Variational inequalities for set-valued vector fields on Riemannian manifolds: convexity of the solution set and the proximal point algorithm, SIAM J. Control Optim. 50(4) (2012) 2486–2514.https://doi.org/10.1137/110834962Google Scholar
  15. M. R. Pouryayevali, H. Radmanesh: Sets with the unique footpoint property and φ-convex subsets of Riemannian manifolds, J. Convex Analysis 26(2) (2019) 617–633.https://doi.org/10.68381/jca26033Google Scholar
  16. T. Sakai: Riemannian Geometry, Translations of Math. Monographs 149, American Mathematical Society, Providence (1996).https://doi.org/10.1090/mmono/149Google Scholar
  17. R. Walter: On the metric projection onto convex sets in Riemannian spaces, Arch. Math. 25(1) (1974) 91–98.https://doi.org/10.1007/BF01238646Google Scholar
  18. S. T. Yau: Non-existence of continuous convex functions on certain Riemannian manifolds, Math. Ann. 207(4) (1974) 269–270.https://doi.org/10.1007/BF01351342Google Scholar

S. Khajehpour, M. R. Pouryayevali. “Convexity of the Distance Function to Convex Subsets of Riemannian Manifolds.” Journal of Convex Analysis 26 (2019), No. 4, 1321–1336. https://doi.org/10.68381/jca26069