Lectures on the ekeland variational principle with applications and detours (original) (raw)

1991, Acta Applicandae Mathematicae

AI-generated Abstract

This work presents a comprehensive overview of Ekeland's variational principle, detailing its applications across various fields of analysis. It includes foundational material, such as the concepts of lower semicontinuity, minimization of functionals, and duality mappings, alongside novel contributions like straightforward proofs and discussions on the geometry of Banach spaces. The notes aim to serve as an educational resource for students, linking theoretical concepts to practical applications, particularly in the realm of semilinear elliptic equations.

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Equivalent formulations of Ekeland's variational principle

Nonlinear Analysis: Theory, Methods & Applications, 2003

We prove that for some 0 ¡ and 0 ¡ 6 + ∞ a proper lower semicontinuous and bounded below function f on a metric space (X; d) satisÿes that for each x ∈ X with inf X f ¡ f(x) ¡ inf X f + there exists y ∈ X such that 0 ¡ d(x; y) 6 f(x) − f(y) i for each such x this inequality holds for some minimizer z of f. Similar conditions are shown to be su cient for f to possess minimizers, weak sharp minima and error bounds. A ÿxed point theorem is also established. Moreover, these results all turn out to be equivalent to the Ekeland variational principle, the Caristi-Kirk ÿxed point theorem and the Takahashi theorem.

Preface to “Optimization, Convex and Variational Analysis”

Set-Valued and Variational Analysis, 2021

This collection of works in the honor of professor Terry Rockafellar is a follow-up of the "Workshop on Optimization and Variational Analysis", dedicated to Terry's 85th birthday. The meeting, jointly organized by the CMM Center for Mathematical Modeling of the University of Chile (Chile) and the University of Perpignan (France), was held in Santiago on January 20-21, 2020. That workshop was one of the last meetings we could attend physically, before Coronavirus changed our lives in so many ways. Globetrotting has become virtual since then. Suddenly, the beauty of the world found itself flattened to a screen. Fortunately, some things have not changed: our admiration and appreciation for Terry's unique career has remained intact, as has the momentum to duly celebrate his birthday, through the edition of this special volume. We are very grateful to the authors and referees for their valuable contributions and careful work. The two volumes that make up the special issue in Terry's honor sample the tremendous breadth of subjects where Terry has made fruitful contributions. This special issue is a modest gift for someone who has gifted us with seminal textbooks, whose content has marked generations of researchers, influencing the way of doing mathematics when it involves "variations", regarding not only theory or analysis in optimization but also applications.

A comparison principle for minimizers

Comptes Rendus de l'Académie des Sciences - Series I - Mathematics, 2000

We give some conditions that ensure the validity of a Comparison principle for the minimizers of integral functionals, without assuming the validity of the Euler-Lagrange equation. We deduce a weak maximum principle for (possibly) degenerate elliptic equations and, together with a generalization of the bounded slope condition, the Lipschitz continuity of minimizers. To prove the main theorem we give a result on the existence of a representative of a given Sobolev function that is absolutely continuous along the trajectories of a suitable autonomous system. © 2000 Académie des sciences/Éditions scientifiques et médicales Elsevier SAS Un principe de comparaison pour les minima Résumé. Nous donnons des conditions qui assurent la validité d'un principe de comparaison pour les minimums d'une fonctionnelle intégrale qui ne satisfont pas nécessairement à l'équation d'Euler-Lagrange. Nous en déduisons un principe de maximum faible pour les équations elliptiques (éventuellement) dégénerées et, en généralisant la condition de la pente bornée, la Lipschitz continuité des minimums. La preuve du théorème principal se base sur l'éxistence d'un représentant d'une fonction de Sobolev donnée qui est absolument continu sur les trajectoires d'un système autonome convenable. © 2000 Académie des sciences/Éditions scientifiques et médicales Elsevier SAS Version française abrégée Nous fixons un ouvert borné Ω de R n. La fonction L(x, z, p) est définie dans Ω × R × R n et est une fonction dans W 1,q (Ω), q 1. La fonctionū est dans W 1,q (Ω) et on pose W 1,q u (Ω) =ū + W 1,q 0 (Ω). Dans cette partie nous nous référons aux hypothèses A, A , B et D du texte anglais qui suit. THÉORÈME PRINCIPAL 1 ([4]).-On suppose que (L,) satisfait à l'hypothèse B. Soit w un minimum de I(u) = Ω L x, u(x), ∇u(x) dx dans W 1,q u (Ω). Si w dans ∂Ω, alors w presque partout dans Ω. Note présentée par Haïm BRÉZIS.

Existence of Minimizers for NonLevel Convex Supremal Functionals

Siam Journal on Control and Optimization, 2014

The paper is devoted to determine necessary and sufficient conditions for existence of solutions to the problem inf ess sup x∈Ω f (∇u(x)) : u ∈ u0 + W 1,∞ 0 (Ω) , when the supremand f is not necessarily level convex. These conditions are obtained through a comparison with the related level convex problem and are written in terms of a differential inclusion involving the boundary datum. Several conditions of convexity for the supremand f are also investigated. Résumé Dans cet article onétudie des conditions nécessaires et suffisantes pour l'existence de solutions pour le problème de minimisation inf ess sup x∈Ω f (∇u(x)) : u ∈ u0 + W 1,∞ 0 (Ω) lorsque la fonction f n'est pas une fonction convexe par niveaux. La stratégie utilisée pour obtenir ces conditions est celle de comparer ce problème avec son problème relaxé. On obtient comme condition nécessaire et suffisante une inclusion différentielle sur la donnée au bord. Onétudie aussi plusieurs conditions de convexité.

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