Abstract
We study the notion of finitely determined functions defined on a topological vector space E equipped with a biorthogonal system. We prove that, for real-valued convex functions defined on a Banach space with a Schauder basis, the notion of finitely determined function coincides with the classical continuity but outside the convex case there are many finitely determined nowhere continuous functions. This notion will be used to obtain a necessary and sufficient condition for a convex function to attain a minimum at some point. An application to the Karush–Kuhn–Tucker theorem will be given.
Similar content being viewed by others
References
Albiac, F., Kalton, N.J.: Topics in Banach space theory, 2nd edn. Springer International Publishing, Switzerland (2016)
Aliprentis, C.D., Border, K.C.: Infinite dimensional analysis. Springer Verlag, Berlin (1999)
Bachir, M.: Limited operators and differentiability, North-Western European. J. Math. 3, 63–73 (2017)
Barbu, V., Precupanu, T.: Convexity and optimization in Banach spaces, 2nd edn. D. Reidel Publishing Co., Dordrecht (1986)
Borwein, J., Vanderwerff, J.: Convex functions: constructions, characterizations and counterexamples. Cambridge University Press, Cambridge (2010)
Bourgain, J., Diestel, J.: Limited operators and strict cosingularity. Math. Nachr. 55–58 (1984)
Carrión, H., Galindo, P., Lourenco, M.L.: Banach spaces whose bounded sets are bounding in the bidual. Ann. Acad. Sci. Fenn. Math. 31(1), 61–70 (2006)
Diestel, J.: Sequences and series in Banach spaces. Graduate texts in mathematics. Springer Verlag, Tokyo (1984)
Dieudonné, J.: On biorthogonal systems. Michigan Math. J. 2(1), 7–20 (1953)
Enflo, P.: A counterexample to the approximation problem in Banach spaces. Acta Math. 130, 309–317 (1973)
Fabian, M., Habala, P., Hájek, P., Montesinos, V., Zizler, V.: Banach space theory: the basis for linear and nonlinear analysis. Springer, Canada (2011)
Fabian, M., Habala, P., Hayek, P., Santalucia, V., Montesinos, P.J., Zizler, V.: Functional analysis and infinite-dimensional geometry, in CMS Books in mathematics., vol. 8. Springer, New York (2001)
Kadets, M.I., Kadets, V.M.: Series in Banach spaces. Conditional and unconditional convergence, Basel-Boston-Berlin, Birkhäuser (1997)
Lu, H., Freund, R.M., Nesterov, Y.: Relatively smooth convex optimization by first-order methods, and applications. SIAM J. Optim. 28(1), 333–354 (2018)
Marchenko, V.: Isomorphic Schauder decompositions in certain Banach spaces. Cent. Eur. J. Math. 12(11), 1714–1732 (2014)
Moreau, J.-J.: Fonctionnelles convexes, Séminaire Jean Leray (Collège de France, Paris), N. 2, 1-108 (1966–1967)
Ovsepian, R., Pelczyński, A.: On the existence of a fundamental total and bounded biorthogonal sequence in every separable Banach space, and related constructions of uniformly bounded orthonormal systems in \({L}^2\). Stud. Math. 54, 149–159 (1975)
Phelps, R.R.: Convex functions, monotone operators and differentiability. Lecture notes in mathematics, vol. 1364. Springer-Verlag, Berlin (1993)
Taylor, A.B., Hendrickx, J.M., Glineur, F.: Smooth strongly convex interpolation and exact worst-case performance of first-order methods. Math. Program. 161, 307–345 (2017)
Yilmaz, Hasan: A generalization of multiplier rules for infinite-dimensional optimization problems. Optimization (2020). https://doi.org/10.1080/02331934.2020.1755863
Acknowledgements
The third author was supported by the grants CONICYT-PFCHA/Doctorado Nacional/2018-21181905, Monge Invitation Programme of École Polytechnique, FONDECYT 1171854 and CMM Grant AFB170001.
Author information
Authors and Affiliations
Corresponding author
Additional information
Communicated by Enrique A. Sanchez Perez.
The authors are grateful to the anonymous referee for these valuable remarks involving the following version of the paper.
This research has been conducted within the FP2M federation (CNRS FR 2036).
Rights and permissions
About this article
Cite this article
Bachir, M., Fabre, A. & Tapia-García, S. Finitely determined functions. Adv. Oper. Theory 6, 28 (2021). https://doi.org/10.1007/s43036-020-00125-y
Received:
Accepted:
Published:
DOI: https://doi.org/10.1007/s43036-020-00125-y
Keywords
- Schauder basis
- Convex optimization
- Finitely determined function
- Directional derivatives
- Karush–Kuhn–Tucker theorem