Application of a coincidence index to some classes of impulsive control systems

We suggest the oriented coincidence index theory for pairs consisting of nonlinear zero-index Fredholm operators and multivalued maps which may be represented as compositions of multimaps with aspheric values. We consider, sequentially, finite dimensional, compact, and condensing cases. The theory developed is applied to the study of a feedback impulsive control system.     

Application of a coincidence index to some classes of impulsive control systems

We suggest the oriented coincidence index theory for pairs consisting of nonlinear zero-index Fredholm operators and multivalued maps which may be represented as compositions of multimaps with aspheric values. We consider, sequentially, finite dimensional, compact, and condensing cases. The theory developed is applied to the study of a feedback impulsive control system.     

A Unified Fixed Point Theory for Countably P -Concentrative Multimaps

New fixed point results and Leray-Schauder alternatives are presented for countably P -concentrative multimaps. The notion of an essential map is also introduced for a wide class of maps.     

Multivalent guiding function in a problem on existence of periodic solutions of some classes of differential inclusions

We propose to use the multivalent guiding function for the study of periodic solutions of some classes of differential inclusions. More precisely, we consider the periodic problem for nonlinear systems described by differential inclusions with both convex and nonconvex right-hand side. The latter include differential inclusions with a regular right-hand side. Note that the class of regular multimaps is wide enough. It includes, for example, bounded almost lower semicontinuous multimaps with compact values.     

Existence of Equilibria for Multivalued Mappings and Its Application to Vectorial Equilibria

In this paper, we apply a new fixed-point theorem and use various monotonicity and some coercivity conditions to establish equilibrium theorems for multimaps. As a simple consequence, we give a unified approach to vectorial equilibria for multimaps. We show that, from our results, some well-known classical results, such as the Ky Fan minimax inequality theorem and the Browder and Hartman-Stampacchia theorems concerning the existence for variational inequalities, can be derived easily.     

Viscosity approximation methods for nonexpansive multimaps in Banach spaces

We prove strong convergence of the viscosity approximation process for nonexpansive nonself multimaps. Furthermore, an explicit iteration process which converges strongly to a fixed point of multimap T is constructed. It is worth mentioning that, unlike other authors, we do not impose the condition ＂Tz = {z}＂ on the map T.     

Nielsen numbers of n-valued fiber maps

The Nielsen number for n-valued multimaps, defined by Schirmer, has been calculated only for the circle. A concept of n-valued fiber map on the total space of a fibration is introduced. A formula for the Nielsen numbers of n-valued fiber maps of fibrations over the circle reduces the calculation to the computation of Nielsen numbers of single-valued maps. If the fibration is orientable, the product formula for single-valued fiber maps fails to generalize, but a “semi-product formula" is obtained. In this way, the class of n-valued multimaps for which the Nielsen number can be computed is substantially enlarged. Dedicated, with gratitude, to Felix Browder who, long ago, encouraged and supported a young topologist’s interest in fixed point theory     

Fixed points of compact approachable multimaps in topological vector spaces

Applying the homotopy extension theorem for compact approachable vector fields with star-shaped values, we prove the existence of fixed points and eigenvalues of compact approachable multimaps in topological vector spaces. In particular, we give the Birkhoff-Kellogg Theorem for compact approachable multimaps with star-shaped values in normal spaces.     

Applications of Michael's selection theorems to fixed point theory

Applying some of Ernest Michael's selection theorems, from recent fixed point theorems on u.s.c. multimaps, we deduce generalizations of the classical Bolzano theorem, several fixed point theorems on multimaps defined on almost convex sets, almost fixed point theorems, coincidence theorems, and collectively fixed point theorems. These results are related mainly to Michael maps, that is, l.s.c. multimaps having nonempty closed convex values.     

Gap Continuity of Multimaps

We introduce a notion of continuity for multimaps (or set-valued maps) which is mild. It encompasses both lower semicontinuity and upper semicontinuity. We give characterizations and we consider some permanence properties. This notion can be used for various purposes. In particular, it is used for continuity properties of subdifferentials and of value functions in parametrized optimization problems. We also prove an approximate selection theorem.     

Strong convergence results for nonself multimaps in Banach spaces

We prove strong convergence theorems for multimaps under mild conditions, which include Browder's convergence theorem as well as Reich's convergence theorem. We thus provide a partial answer to Jung's question.

     

Fixed points of approximable maps

We present a simple proof of the Leray-Schauder type theorem for approximable multimaps given recently by Ben-El-Mechaiekh and Idzik. We apply this theorem to obtain a Schaefer type theorem, the Birkhoff-Kellogg type theorems, a Penot type theorem for non-self-maps, and quasi-variational inequalities, all related to compact closed approximable maps.

     

Fixed point theorems for generalized metrically inward maps

We prove fixed point results for multimaps satisfying a generalized metric (or an α-metric) inwardness condition. Our results extend, generalize or improve several known results.     

Gap Continuity of Multimaps

We introduce a notion of continuity for multimaps (or set-valued maps) which is mild. It encompasses both lower semicontinuity and upper semicontinuity. We give characterizations and we consider some permanence properties. This notion can be used for various purposes. In particular, it is used for continuity properties of subdifferentials and of value functions in parametrized optimization problems. We also prove an approximate selection theorem.      

Fixed point theorems for better admissible multimaps on almost convex sets

We obtain new fixed point theorems on multimaps in the class Bp defined on almost convex subsets of topological vector spaces. Our main results are applied to deduce various fixed point theorems, coincidence theorems, almost fixed point theorems, intersection theorems, and minimax theorems. Consequently, our new results generalize well-known works of Kakutani, Fan, Browder, Himmelberg, Lassonde, and others.     

Fixed point and approximation results for multimaps in S-KKM class

The paper discusses new fixed point and approximation theorems for multimaps in the class S-KKM.     

Comments on collectively fixed points in generalized convex spaces

Based on a Fan–Browder type fixed point theorem due to the author, we deduce new general collectively fixed point theorems for a family of Browder type multimaps defined on a product of generalized convex spaces.     

广义近似空间的粗糙同胚与拓扑同胚

对广义近似空间之间的映射引入并刻画了粗糙连续性和拓扑连续性,探讨了他们的性质及相互关系.证明了两个粗糙连续映射的复合还是粗糙连续的,每个粗糙连续的映射都是拓扑连续的.在此基础上引入了粗糙同胚性质和拓扑同胚性质的概念,证明了拓扑同胚性质均为粗糙同胚性质并考察了广义近似空间的诸如分离性、连通性、紧性等的粗糙同胚不变性和拓扑同胚不变性.     

Approximate selections of almost lower semicontinuous multimaps in C-spaces

We study the relations of almost lower semicontinuity, lower semicontinuity and other generalized lower semicontinuity; then we establish a new approximate selection theorem for almost lower semicontinuous multimaps with the generalized Zima type condition in C$C$-spaces. Our result unify and extend the approximate selection theorems in many published works.     

On the set of periodic intervals of an interval map

We investigate the closure of the set of periodic closed intervals for a continuous interval map with respect to Hausdorff metric. We prove that if a nondegenerate interval is limit of periodic ones then either a) it is periodic itself, or b) it is asymptotically degenerate, i.e. its diameter tends to 0 (when iterating under f). We present a continuous interval map for which case b) is possible.