Set-valued Mappings Research Articles

A Modified Michael’s Selection Theorem with Application to Generalized Nash Equilibrium Problem

This paper provides a sufficient condition for the existence of solutions for generalized Nash equilibrium problems in the infinite-dimensional setting and with a countable (possibly infinite) number of players. The result has been achieved as a consequence of a modified version of Michael’s selection theorem that works even when the range space is not metrizable and the set-valued map has not closed values.

Stability for a Class of Differential Set-Valued Inverse Variational Inequalities in Finite Dimensional Spaces

In this paper, we introduce and study a new class of differential set-valued inverse variational inequalities in finite dimensional spaces. By applying a result on differential inclusions involving an upper semicontinuous set-valued mapping with closed convex values, we first prove the existence of Carathéodory weak solutions for differential set-valued inverse variational inequalities. Then, by the existence result, we establish the stability for the differential set-valued inverse variational inequality problem when the constraint set and the mapping are perturbed by two different parameters. The closedness and continuity of Carathéodory weak solutions with respect to the two different parameters are obtained.

Hölder continuity of solution maps to parametric set-valued Ky Fan inequalities

We first introduce notions of strong t-quasiconvexity and strong t-quasiconvex-likeness along with relaxed Hölder continuity with respect to an ordering cone of a set-valued map. Then, these new conditions are utilized to establish sufficient conditions for the non-emptiness of solution sets and the stability in the sense of Hölder continuity of solution maps to parametric set-valued Ky Fan inequalities. Our approach is different from the existing ones. At the end of the paper, we present an application of the main results to set-valued Nash equilibrium in games.

Choquet integrals of set-valued functions with respect to set-valued fuzzy measures

As powerful tools for modeling nondeterministic problems, Choquet integrals have attracted much attention in recent years. This study generalizes the existing set-valued Choquet integrals and formulates the theory of Choquet integrals with respect to set-valued fuzzy measures. First, a set-valued Choquet integral of a real-valued function is defined using the set of Choquet integrals of real-valued functions with respect to fuzzy measure selections of a set-valued fuzzy measure. The integrand is then extended to set-valued functions, after which various properties, convergence theorems, and set-valued Jensen's inequalities are obtained. Second, following how single-valued Choquet integrals are defined, an alternative set-valued Choquet integral of real-valued function is formulated using Aumann integrals. Through these steps, the existing set-valued Choquet integrals are covered.

An Algorithm Based on Unions of Nonexpansive Mappings in Metric Spaces

In this paper, we obtain two extensions of a recent result of Tam, which was proved for iterates of set-valued paracontracting operators in a finite-dimensional space. Our results are obtained for operators in an arbitrary metric space. In the first result, we study exact iterates of the set-valued mapping, while in the second one, we deal with its inexact iterates, taking computational errors into account. In a particular case of a Banach space, if all the operators are symmetric, then the set of all limit points of iterates is symmetric too.

On one inclusion with a mapping acting from a partially ordered set to a set with a reflexive binary relation

Set-valued mappings acting from a partially ordered space $X=(X,\leq)$ to a set $Y$ on which a reflexive binary relation $\vartheta$ is given (this relation is not supposed to be antisymmetric or transitive, i.e., $\vartheta$ is not an order in $Y$), are considered. For such mappings, analogues of the concepts of covering and monotonicity are introduced. These concepts are used to study the inclusion $F(x)\ni \tilde{y},$ where $F\colon X \rightrightarrows Y,$ $\tilde{y}\in Y.$ It is assumed that for some given $x_0 \in X,$ there exists $y_{0} \in F(x_{0})$ such that $(\tilde{y},y_{0}) \in \vartheta.$ Conditions for the existence of a solution $x\in X$ satisfying the inequality $x\leq x_0$ are obtained, as well as those for the existence of minimal and least solutions. The property of stability of solutions of the considered inclusion to changes of the set-valued mapping $F$ and of the element $\widetilde{y}$ is also defined and investigated. Namely, the sequence of “perturbed” inclusions $F_i(x)\ni \tilde{y}_i,$ $i\in \mathbb{N},$ is assumed, and the conditions of existence of solutions $x_i \in X$ such that for any increasing sequence of integers $\{i_n\}$ there holds $\sup_{n \in \mathbb{N}}\{x_{i_{n}}\}= x,$ where $x \in X$ is a solution of the initial inclusion, are derived.

Implicit Implementation of Nonsmooth Controllers to Nonsmooth Actuators

This article presents an approach to implement a sliding-mode position controller to a plant equipped with a nonsmooth actuator. The actuator is modeled as a set-valued function from the control input and the velocity to the actuator force, which is motivated by quasi-static characteristics of hydraulic actuators shown in a previous study. The implementation of the sliding-mode controller is performed with the implicit discretization of the nominal plant model and the controller, which copes with the difficulties caused by the set-valuedness, such as numerical chattering. Stability analyses both in the continuous-time and discrete-time domains are presented. Simulation results illustrate the theoretical findings.

Common fixed-point results of fuzzy mappings and applications on stochastic Volterra integral equations

The objective of the present research is to establish and prove some new common fuzzy fixed-point theorems for fuzzy set-valued mappings involving Θ-contractions in a complete metric space. For this purpose, a novel integral-type contraction condition is applied to obtain these results. In this way, several useful and classical results have been generalized. Moreover, a concrete example is created to furnish our results. An application to stochastic Volterra integral equations has been given to enhance the validity of our results.

Set-valued equilibrium problems based on the concept of null set with applications

In this paper, by means of the null set defined by Wu (J Math Anal Appl. 2019;472:1741–1761), we introduce a set-valued equilibrium problem based on the null set, where the objective mapping takes values in a hyperspace equipped with a convex cone. Moreover, we obtain new existence results for set-valued equilibrium problems defined on compact or noncompact sets. Some applications are given to set optimization problems, to a set-valued variational inequality, to saddle point theorems for set-valued mappings, and to a generalized noncooperative game.

Directional derivatives and subdifferentials for set-valued maps applied to set optimization

Directional derivatives and subdifferentials for set-valued maps applied to set optimization

Generalized Differentiation and Duality in Infinite Dimensions under Polyhedral Convexity

This paper addresses the study and applications of polyhedral duality in locally convex topological vector (LCTV) spaces. We first revisit the classical Rockafellar’s proper separation theorem for two convex sets one of which is polyhedral and then present its LCTV extension replacing the relative interior by its quasi-relative interior counterpart. Then we apply this result to derive enhanced calculus rules for normals to convex sets, coderivatives of convex set-valued mappings, and subgradients of extended-real-valued functions under certain polyhedrality requirements in LCTV spaces by developing a geometric approach. We also establish in this way new results on conjugate calculus and duality in convex optimization with relaxed qualification conditions in polyhedral settings. Our developments contain significant improvements to a number of existing results obtained by Ng and Song (Nonlinear Anal. 55, 845–858, 12).

On continuity of set-valued mappings

We will show that under certain circumstances upper and lower quasi-continuity implies continuity. We also extend Fort's theorem for upper quasi-continuous mappings, by showing that every upper quasi-continuous mapping from a Baire space into compact subsets of a regular locally metrizable space is continuous at points of a dense Gδ subset of X.

On the Accuracy of the Model Predictive Control Method

The paper investigates the accuracy of the model predictive control (MPC) method for finding on-line approximate optimal feedback control for Bolza-type problems on a fixed finite horizon. The predictions for the dynamics, the state measurements, and the solution of the auxiliary open-loop control problems that appear at every step of the MPC method may be inaccurate. The main result provides an error estimate of the MPC-generated solution compared with the optimal open-loop solution of the “ideal” problem, where all predictions and measurements are exact. The technique of proving the estimate involves an extension of the notion of strong metric subregularity of set-valued maps and utilization of a specific new metric in the control space, which makes the proof nonstandard. The result is specialized for two problem classes: coercive problems and affine problems.

APPROXIMATION OF POSITIONAL IMPULSE CONTROLS FOR DIFFERENTIAL INCLUSIONS

Nonlinear control systems presented as differential inclusions with positional impulse controls are investigated. By such a control we mean some abstract operator with the Dirac function concentrated at each time. Such a control ("running impulse"), as a generalized function, has no meaning and is formalized as a sequence of correcting impulse actions on the system corresponding to a directed set of partitions of the control interval. The system responds to such control by discontinuous trajectories, which form a network of so-called "Euler's broken lines." If, as a result of each such correction, the phase point of the object under study is on some given manifold (hypersurface), then a slip-type effect is introduced into the motion of the system, and then the network of "Euler's broken lines" is called an impulse-sliding mode. The paper deals with the problem of approximating impulse-sliding modes using sequences of continuous delta-like functions. The research is based on Yosida's approximation of set-valued mappings and some well-known facts for ordinary differential equations with impulses.

On Newton's method for solving generalized equations

In this paper, we study the convergence properties of a Newton-type method for solving generalized equations under a majorant condition. To this end, we use a contraction mapping principle. More precisely, we present semi-local convergence analysis of the method for generalized equations involving a set-valued map, the inverse of which satisfying the Aubin property. Our analysis enables us to obtain convergence results under Lipschitz, Smale and Nesterov-Nemirovski's self-concordant conditions.

"On certain boundary value problems associated to some fractional integro-differential inclusions"

"Two classes of fractional integro-differential inclusions with certain boundary conditions are studied. The existence of solutions is established in the case when the set-valued map has nonconvex values."

On a fractional differential inclusion involving a generalized Caputo type derivative with certain fractional integral boundary conditions

We study a class of fractional differential inclusions defined by Caputo-Katugampola fractional derivativeinvolving a nonconvex set-valued map in the presence of certain fractional integral boundary conditions.Using a technique developed by Filippov we establish an existence result for the problem considered underthe hypothesis that the set-valued map is Lipschitz in the state variable. Also, based on a result concerningthe arcwise connectedness of the fixed point set of a class of set-valued contractions, we prove the arcwiseconnectedness of the solution set of the problem considered. The paper is the first in literature which containssuch kind of results in the framework of the problem studied.

Viability for functional differential inclusions without convexity

The aim of this paper is to prove the existence result of viable solutions for the differential inclusion x ̇(t)ϵF(t,T(t)x) where F is a set-valued map with closed graph. We consider the case when the constraint is moving.

Weak epigraphical solutions to Hamilton-Jacobi-Bellman equations on infinite horizon

In this paper we show a uniqueness result for weak epigraphical solutions of Hamilton-Jacobi-Bellman (HJB) equations on infinite horizon for a class of lower semicontinuous functions vanishing at infinity. Weak epigraphical solutions of HJB equations, with time-measurable data and fiber-convex, turn out to be viscosity solutions – in the classical sense – whenever they are locally Lipschitz continuous. Here we extend the notion of locally absolutely continuous tubes to set-valued maps with continuous epigraph of locally bounded variations. This new notion fits with the lack of uniform lower bound of the Fenchel transform of the Hamiltonian with respect to the fiber. Controllability assumptions are considered.

Fixed points of single-valued and multi-valued mappings in sb-metric spaces

In this paper, we have established some fixed point theorems in the context of strong b-metric spaces. For this purpose, Ciric type contraction for single-valued mapping and Nadler’s type Banach and Chatterjea contractions for set-valued mappings are applied to obtain fixed point and common fixed points. A simple and different technique has been used to obtain the results. Our results unify, extend and generalize the existence of corresponding present and conventional results existing in the literature of fixed point theory.