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Generalized KKM theorem on \(H\)-space with applications. (English) Zbl 0788.54048

An \(H\)-space is a pair \((X,(\Gamma_ A)_{A\in{\mathcal F}})\) consisting of a topological space \(X\) and a family \((\Gamma_ A)_{A\in{\mathcal F}}\) of nonempty contractible subsets of \(X\) indexed by the set \(\mathcal F\) of finite subsets of \(X\) such that \(\Gamma_ A\subset \Gamma_ B\) whenever \(A\subset B\). Let \((Y,(\Gamma_ A))\) be an \(H\)-space and \(X\) a nonempty set. A map \(F\) which assigns to \(x\in X\) a nonempty subset of \(Y\) is called a \(KKM\)-mapping if for each finite set \(\{x_ 1,\dots,x_ n\}\) in \(X\) there exists a finite set \(\{y_ 1,\dots,y_ n\}\subset Y\) such that \(\Gamma_{\{y_{i_ 1},\dots,y_{i_ k}\}} \subset\bigcup^ k_{j=1} F(x_{i_ j})\) whenever \(\{i_ 1,\dots,i_ k\} \subset \{1,\dots,n\}\). The authors prove the following KKM-type theorem: Let \(X\), \(Y\), \(F\) be as above and assume that either \(F(x)\) is closed relative to each compact subset of \(Y\) for all \(x\in X\) or that \(F(x)\) is open relative to each compact subset of \(Y\) for all \(x\in X\). If at least one \(F(x_ 0)\) is compact then \(\bigcap_{x\in X} F(x) \neq \emptyset\). It is then a routine matter to derive minimax and coincidence theorems from this result.
Reviewer: C.Fenske (Gießen)

MSC:

54H25 Fixed-point and coincidence theorems (topological aspects)
47H04 Set-valued operators
47H10 Fixed-point theorems

Citations:

Zbl 0788.54049
Full Text: DOI

References:

[1] Bardaro, C.; Ceppitelli, R., Some further generalizations of Knaster-Kuratowski-Mazurkiewicz theorem and minimax inequalities, J. Math. Anal. Appl., 132, 484-490 (1988) · Zbl 0667.49016
[2] Bardaro, C.; Ceppitelli, R., Applications of the generalized Knaster-Kuratowski-Mazurkiewicz theorem to variational inequalities, J. Math. Anal. Appl., 137, 46-58 (1989) · Zbl 0681.49010
[3] Ben-El-Mechaiekh, H.; Deguire, P.; Granas, A., Une alternative non linéaire en analyse convexe et applications, C. R. Acad. Sci. Paris, 295, 257-259 (1982) · Zbl 0521.47027
[4] Chang, Shih-sen; Chang, Yin, Generalized KKM theorem and variational inequalities, J. Math. Anal. Appl., 159, 208-223 (1991) · Zbl 0739.47026
[5] Dugundji, J.; Granas, A., KKM-maps and variational inequalities, Ann. Scuola Norm. Sup. Pisa, 5, 679-682 (1978) · Zbl 0396.47037
[6] Fan, K., A generalization of Tychonoff’s fixed point theorem, Math. Ann., 142, 305-310 (1961) · Zbl 0093.36701
[7] Fan, K., Some properties of convex sets related to fixed point theorems, Math. Ann., 266, 519-537 (1984) · Zbl 0515.47029
[8] Horvath, C., Points fixes et coïncidences pour les applications multivoques sans convexité, C. R. Acad. Sci. Paris, 296, 403-406 (1983) · Zbl 0527.54042
[9] Horvath, C., Some results on multivalued mappings and inequalities without convexity, (Nonlinear and Convex Analysis. Nonlinear and Convex Analysis, Lecture Notes in Pure and Appl. Math., Vol. 107 (1987), Dekker: Dekker New York) · Zbl 0619.55002
[10] Knaster, B.; Kuratowski, K.; Mazurkiewicz, S., Ein Beweis des Fixpunktsatzes für \(n\)-dimensionale Simplexe, Fund. Math., 14, 132-137 (1929) · JFM 55.0972.01
[11] Kim, W. K., Some applications of the Kakutani fixed point theorems, J. Math. Anal. Appl., 121, 119-122 (1987) · Zbl 0612.54055
[12] Kim, W. K., Some intersection theorems of the KKM-maps, Bull. Korean Math. Soc., 24, 139-144 (1987) · Zbl 0747.47038
[13] Ko, H.-M; Tan, K.-K, A coincidence theorem with applications to minimax inequalities and fixed point theorems, Tamkang J. Math., 17, 37-45 (1986) · Zbl 0613.47051
[14] Lassonde, M., On the use of KKM multifunctions in fixed point theory and related topics, J. Math. Anal. Appl., 97, 151-201 (1983) · Zbl 0527.47037
[15] Park, S., Generalizations of Ky Fan’s matching theorems and their applications, J. Math. Anal. Appl., 141, 164-176 (1989) · Zbl 0681.47028
[16] Simons, S., Two-function minimax theorems and variational inequalities for functions on compact and noncompact sets, with some comments on fixed point theorems, (Proc. Sympos. Pure Math., 45 (1986)), 377-392, Part 2
[17] Shih, M.-H; Tan, K.-K, A geometric property of convex sets with applications to minimax type inequalities and fixed point theorems, J. Austral. Math. Soc. Ser. A, 45, 169-183 (1988) · Zbl 0664.52001
[18] Takahashi, W., Fixed point, minimax and Hahn-Banach theorems, (Proc. Sympos. Pure Math., 45 (1986)), 419-427, Part 2 · Zbl 0636.47048
[19] Yen, C.-L, A minimax inequality and its applications to variational inequalities, Pacific J. Math., 97, 477-481 (1981) · Zbl 0493.49009
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