Abstract
In this paper, driven by Behavioral applications to human dynamics, we consider the characterization of completeness in pseudo-quasimetric spaces in term of a generalization of Ekeland’s variational principle in such spaces, and provide examples illustrating significant improvements to some previously obtained results, even in complete metric spaces. At the behavioral level, we show that the completeness of a space is equivalent to the existence of traps, rather easy to reach (in a worthwhile way), but difficult (not worthwhile to) to leave. We first establish new forward and backward versions of Ekeland’s variational principle for the class of strict-decreasingly forward (resp. backward)-lsc functions in pseudo-quasimetric spaces. We do not require that the space under consideration either be complete or to enjoy the limit uniqueness property since, in a pseudo-quasimetric space, the collections of forward-limits and backward ones of a sequence, in general, are not singletons.
Similar content being viewed by others
Notes
Kelly (1963, p. 71) “The notion of a bitopological space used in relation to semi-continuous functions restores sufficient symmetry to enable one to use some of the existing techniques of continuous functions.”
It has been also defined a sequence as being bi-convergent if it is both forward- and backward-convergent, (i.e. if it convergent with respect to the pseudo-metric \(q^s\)).
Known also as bi-Cauchy, or Cauchy in two topologies
Recall that in Cobzaş (2013) a quasimetric satisfies the condition: \(q(x,y)=q(y,x)=0\) implies \(x=y\).
Left-complete
A quasimetric in the sense of Cobzaş (2011), Cobzaş is a pseuso-quasimetric satisfying \(q(x,y) = q(y,x) = 0 \Longrightarrow x=y\).
There are two versions of Ekeland’s variational principle with respect to each kind of completeness.
A quasimetric space enjoys the forward Hausdorff property, i.e. a sequence being forward-convergent has a unique forward-limit.
The Picard–Lindelöf theorem, which shows that ordinary differential equations have solutions, is essentially an application of the Banach fixed point theorem to a special sequence of functions which forms a fixed point iteration, constructing the solution to the equation. Solving an ODE in this way is called Picard iteration, Picard’s method, or the Picard iterative process.
The space in question is a metric space and thus there is no difference between two topologies.
The conjugate quasimetric of the one studied in Lin et al. (2011, Example 3.16).
Known as ‘left Hausdorff’ in the cited papers.
The topology \(\tau ({\overline{q}})\).
Cobzaş (2011, Remark 1.4) pointed out that the topology \(\tau (q)\) is regular under the assumptions made in the cited paper.
A quasimetric in the sense of Karapinar et al. is a pseudo-quasimetric defined in Definition 2 satisfying that \(x = y\) if and only if \(q(x,y) = q(y,x) = 0\).
References
Al-Homidan, S., Ansari, Q. H., & Yao, J.-C. (2008). Some generalizations of Ekeland-type variational principle with applications to equilibrium problems and fixed point theory. Nonlinear Analysis, Theory, Methods and Applications, 69(1), 126–139.
Ansari, Q. H. (2007). Vectorial form of Ekeland-type variational principle with applications to vector equilibrium problems and fixed point theory. Journal of Mathematical Analysis and Applications, 334(2), 561–575.
Ansari, Q. H. (2014). Ekeland’s variational principle and its extensions with applications. In S. Almezel, Q. H. Ansari, & M. A. Khamsi (Eds.), Topics in fixed point theory (pp. 65–100). Heidelberg: Springer.
Aydi, H., Karapınar, E., & Vetro, C. (2015). On Ekeland’s variational principle in partial metric spaces. Applied Mathematics and Information Sciences, 9, 257–262.
Bao, T. Q. (2015). Modelling, computation and optimization in information systems and management sciences. In L. T. Hoai An, P. D. Tao, & N. N. Thanh (Eds.), Vectorial Ekeland variational principles: A hybrid approach (pp. 513–525). Heidelberg: Springer.
Bao, T. Q., & Théra, M. A. (2015). On extended versions of Dancs-Hegedüs-Medvegyev’s fixed-point theorem. Optimization. doi:10.1080/02331934.2015.1113533.
Bao, T. Q., Mordukhovich, B. S., & Soubeyran, A. (2015a). Variational analysis in psychological modeling. Journal of Optimization Theory and Applications, 164, 290–315.
Bao, T. Q., Mordukhovich, B. S., & Soubeyran, A. (2015b). Fixed points and variational principles with applications to capability theory of wellbeing via variational rationality. Set-Valued Variational Analysis, 23, 375–398.
Bao, T. Q., Mordukhovich, B. S., & Soubeyran, A. (2015c). Minimal points, variational principles, and variable preferences in set optimization. Journal of Nonlinear Convex Analysis, 16, 1511–1537.
Bao, T. Q., Khanh, P. Q., & Soubeyran, A. (2016). Variational principles with generalized distances and the modelization of organizational change. Optimization, 65, 2049–2066.
Cobzaş, S. (2011). Completeness in quasi-metric spaces and Ekeland variational principle. Topology and its Applications, 158, 1073–1084.
Cobzaş, S. (2013). Functional analysis in asymmetric normed spaces. Frontiers in mathematics. Basel: Birkhäuser/Springer Basel AG.
Cobzaş, S. (2016). Fixed points and completeness in metric and in generalized metric spaces, pp. 1–71. arXiv:1508.05173v4.
Dancs, S., Hegedüs, M., & Medvegyev, P. (1983). A general ordering and fixed-point principle in complete metric space. Acta Scientiarum Mathematicarum (Szeged), 46, 381–388.
Ekeland, I. (1972). Sur les problèmes variationnels. Comptes rendus de l’Académie des Sciences Sér. A-B, 275, 1057–1059.
Ekeland, I., & Turnbull, T. (1983). Infinite-dimensional optimization and convexity. Chicago lectures in mathematics. Chicago, IL: University of Chicago Press.
Filip, A.-D. (2011). Fixed point theory in Kasahara spaces. Babeş-Bolyai University, Thesis (Ph.D.)-Babeş-Bolyai University, Cluj-Napoca, Romania.
Gierz, G., Hofmann, K. H., Keimel, K., Lawson, J. D., Mislove, M., & Scott, D. S. (2003). Continuous lattices and domains. Encyclopedia of mathematics and its applications. Cambridge: Cambridge University Press.
Goubault-Larrecq, J. (2013). Non-Hausdorff topology and domain theory: Selected topics in point-set topology. New Mathematical Monographs, Vol. 22. Cambridge: Cambridge University Press.
Karapinar, E., & Romaguera, S. (2015). On the weak form of Ekeland’s variational principle in quasi-metric spaces. Topology and its Applications, 184, 54–60.
Kelley, J. L. (1975). General topology, 2nd ed. Graduate Texts in Mathematics, Vol. 27. New York: Springer.
Kelly, J. C. (1963). Proceedings London Mathematical Society. Bitopological Spaces, 13, 71–89.
Khanh, P. Q., & Quy, D. N. (2013). Versions of Ekeland’s variational principle involving set perturbations. Journal of Global Optimization, 57, 951–968.
Kirk, W. A., & Saliga, L. M. (2001). The Brézis–Browder order principle and extensions of Caristi’s theorem. Nonlinear Analysis, 47, 2765–2778.
Lin, L.-J., Wang, S.-Y., & Ansari, Q. H. (2011). Critical point theorems and Ekeland type variational principle with applications. Fixed Point Theory and Applications, Art. ID, 914624, 1–21.
Megginson, R. E. (1998). An introduction to Banach space theory. Graduate Texts in Mathematics, Vol. 183. New York: Springer.
Reilly, I. L., & Subrahmanyam, P. V. (1982). Cauchy sequences in quasipseudometric spaces. Monatshefte für Mathematik, 93, 127–140.
Soubeyran, A. (2009). Variational rationality, a theory of individual stability and change: Worthwhile and ambidextry behaviors. Preprint at GREQAM, Aix-Marseille University.
Soubeyran, A. (2010). Variational rationality and the “unsatisfied man” : Routines and the course pursuit between aspirations, beliefs. Preprint at GREQAM. Aix-Marseille University.
Soubeyran, A. (2016). Variational rationality. Part 1. Worthwhile stay and change approach-avoidance human dynamics ending in traps. Preprint at GREQAM, Aix-Marseille University.
Sullivan, F. (1981). A characterization of complete metric spaces. Proceedings of the American Mathematical Society, 83, 345–346.
Ume, J. S. (2002). A minimization theorem in quasi-metric spaces and its applications. International Journal of Mathematics and Mathematical Sciences, 31, 443–447.
Wilson, W. A. (1931a). On quasi-metric spaces. American Journal of Mathematics, 53, 675–684.
Wilson, W. A. (1931b). On semi-metric spaces. American Journal of Mathematics, 53, 361–373.
Acknowledgements
The contribution of the first author was completed while visiting Aix-Marseille University with a GREQAM-AMSE grant.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Bao, T.Q., Cobzaş, S. & Soubeyran, A. Variational principles, completeness and the existence of traps in behavioral sciences. Ann Oper Res 269, 53–79 (2018). https://doi.org/10.1007/s10479-016-2368-0
Published:
Issue Date:
DOI: https://doi.org/10.1007/s10479-016-2368-0