The notion of adequate function has been recently introduced in order to characterize the essentially strictly convex functions on a reflexive Banach space among the weakly lower semicontinuous ones. In this paper we reinforce this concept and show that a lower semicontinuous function is essentially firmly subdifferentiable if and only if it is strongly adequate.

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

Michel Volle

Dép. de Mathématiques, Université d'Avignon et des Pays de Vaucluse, 74 Rue Louis Pasteur, 84029 Avignon, France

Michel.Volle@univ-avignon.fr

Constantin Zălinescu

University Alexandru Ioan Cuza, Faculty of Mathematics, Iaşi, Romania
and: Institute of Mathematics O. Mayer, Iaşi, Romania

zalinesc@uaic.ro
  1. Y. I. Alber: Young-Fenchel transformation and some new characteristics of Banach spaces, in: Functions Spaces (Edwardsville, 2006), K. Jarosz (ed.), Contemp. Math. 435, Amer. Math. Soc., Providence (2007) 1–19.https://doi.org/10.1090/conm/435/08362Google Scholar
  2. E. Asplund: Fréchet differentiability of convex functions, Acta Math. 121 (1968) 31–47.https://doi.org/10.1007/BF02391908Google Scholar
  3. E. Asplund, R. T. Rockafellar: Gradients of convex functions, Trans. Amer. Math. Soc. 139 (1969) 443–467.https://doi.org/10.1090/S0002-9947-1969-0240621-XGoogle Scholar
  4. H. H. Bauschke, J. M. Borwein, P. L. Combettes: Essential smoothness, essential strict convexity, and Legendre functions in Banach spaces, Commun. Contemp. Math. 3 (2001) 615–647.https://doi.org/10.1142/S0219199701000524Google Scholar
  5. H. H. Bauschke, J. M. Borwein, P. L. Combettes: Bregman monotone optimization algorithms, SIAM J. Control Optim. 42 (2003) 596–636.https://doi.org/10.1137/S0363012902407120Google Scholar
  6. L. M. Bregman: The relaxation method for finding common points of convex sets and its application to the solution of problems in convex programming, USSR Comput. Math. Math. Phys. 7 (1967) 200–217.https://doi.org/10.1016/0041-5553(67)90040-7Google Scholar
  7. D. Butnariu, A. N. Iusem: Totally Convex Functions for Fixed Points Computation and Infinite Dimensional Optimization, Applied Optimization 40, Kluwer, Dordrecht (2000).https://doi.org/10.1007/978-94-011-4066-9Google Scholar
  8. D. Butnariu, A. N. Iusem, C. Zălinescu: On uniform convexity, total convexity and convergence of the proximal point and outer Bregman projection algorithms in Banach spaces, J. Convex Analysis 10 (2003) 35–61.https://doi.org/10.68381/jca1002Google Scholar
  9. D. Butnariu, E. Resmerita: Bregman distances, totally convex functions, and a method for solving operator equations in Banach spaces, Abstr. Appl. Anal. 2006 (2006) Art. ID 84919, 39 p.https://doi.org/10.1155/AAA/2006/84919Google Scholar
  10. A. L. Dontchev, T. Zolezzi: Well-Posed Optimization Problems, Springer, Berlin (1993).https://doi.org/10.1007/BFb0084195Google Scholar
  11. K. Fan, I. Glicksberg: Some geometric properties of the spheres in a normed linear space, Duke Math. J. 25 (1998) 553–568.https://doi.org/10.1215/S0012-7094-58-02550-XGoogle Scholar
  12. J. R. Giles: Convex Analysis with Application in the Differentiation of Convex Functions, Pitman, Boston (1982).Google Scholar
  13. R. B. Holmes: A Course on Optimization and Best Approximation, Lect. Notes Math. 257, Springer, Berlin (1972).https://doi.org/10.1007/BFb0059450Google Scholar
  14. M. Lassonde: Asplund spaces, Stegall variational principle and the RNP, Set-Valued Var. Anal. 17 (2009) 183–193.https://doi.org/10.1007/s11228-009-0111-6Google Scholar
  15. J. J. Moreau: Fonctionnelles Convexes, Collège de France, Paris (1967).Google Scholar
  16. E. Resmerita: On total convexity, Bregman projections and stability in Banach spaces, J. Convex Analysis 11 (2004) 1–16.https://doi.org/10.68381/jca11001Google Scholar
  17. R. T. Rockafellar: Convex Analysis, Princeton University Press, Princeton (1970).https://doi.org/10.1515/9781400873173Google Scholar
  18. T. Strömberg: Duality between Fréchet differentiability and strong convexity, Positivity 15 (2011) 527–536.https://doi.org/10.1007/s11117-010-0105-5Google Scholar
  19. M. Volle, J. B. Hiriart-Urruty: A characterization of essentially strictly convex functions in reflexive Banach spaces, Nonlinear Anal. 75 (2012) 1617–1622.https://doi.org/10.1016/j.na.2011.03.056Google Scholar
  20. C. Zălinescu: Convex Analysis in General Vector Spaces, World Scientific, River Edge (2002).https://doi.org/10.1142/5021Google Scholar

M. Volle, C. Zălinescu. “Strongly Adequate Functions on Banach Spaces.” Journal of Convex Analysis 20 (2013), No. 3, 655–668. https://doi.org/10.68381/jca20037