Abstract
This paper provides necessary and sufficient conditions for the existence of solutions for some important problems from optimization and non-linear analysis by replacing two typical conditions—continuity and quasiconcavity with a unique condition, weakening topological vector spaces to arbitrary topological spaces that may be discrete, continuum, non-compact or non-convex. We establish a single condition, \(\gamma \)-recursive transfer lower semicontinuity, which fully characterizes the existence of \(\gamma \)-equilibrium of minimax inequality without imposing any restrictions on topological space. The result is then used to provide full characterizations of fixed point theorem, saddle point theorem, and KKM principle.
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References
Fan, K.: Minimax theorem. Proc. Nat. Acad. Sci. 39, 42–47 (1953)
Fan, K.: Minimax inequality and applications. In: Shisha, O. (eds.) Inequality, vol. III (pp. 103–113). Academic Press, New York (1972)
Fan, K.: Fixed point and related theorems for non-compact sets. In: Moeschlin, O., Pallaschke, D. (eds.) Game theory and related topics, pp. 151–156. North Holland, Amsterdam (1979)
Fan, K.: Some properties of convex sets related to fixed points theorems. Math. Ann. 266, 519–537 (1984)
Border, K.C.: Fixed point theorems with applications to economics and game theory. Cambridge University Press (1985)
Allen, G.: Variational inequalities, complementarity problems, and duality theorems. J. Math. Anal. Appl. 58, 1–10 (1977)
Ansari, Q.H., Lin, Y.C., Yao, J.C.: General KKM theorem with applications to minimax and variational inequalities. J. Optim. Theor. Appl. 104, 41–57 (2000)
Cain Jr., G.L., González, L.: The Knaster–Kuratowski–Mazurkiewicz theorem and abstract convexities. J. Math. Anal. Appl. 338, 563–571 (2008)
Chebbi, S.: Minimax inequality and equilibria with a generalized coercivity. J. Appl. Anal. 12, 117–125 (2006)
Chen, C.M.: KKM property and fixed point theorems in metric spaces. J. Math. Anal. Appl. 323, 1231–1237 (2005)
Choudhury, B.S., Kundu, A.: A coupled coincidence point result in partially ordered metric spaces for compatible mappings. Nonlinear Anal. Theor. Methods Appl. 73, 2524–2531 (2010)
Ding, X.P.: Generalized KKM type theorems in FC-spaces with applications (I). J. Glob. Optim. 36, 581–596 (2006)
Ding, X.P.: Generalized KKM type theorems in FC-spaces with applications (II). J. Glob. Optim. 38, 367–385 (2007)
Ding, X.P., Tan, K.K.: A minimax inequality with application to existence of equilibrium points and fixed point theorems. Colloq. Math. 63, 233–274 (1992)
Georgiev, P.G., Tanaka, T.: Vector-valued set-valued variants of Ky Fan’s inequality. J. Nonlinear Convex Anal. 1, 245–254 (2000)
Harjani, J., López, B., Sadarangani, K.: Fixed point theorems for mixed monotone operators and applications to integral equations. Nonlinear Anal. Theor. Methods Appl. 74, 1749–1760 (2011)
Iusem, A.N., Soca, W.: New existence results for equilibrium problems. Nonlinear Anal. Theor. Methods Appl. 54, 621–635 (2003)
Karamardian, S.: Generalized complementarity problem. J. Optim. Theory Appl. 8, 416–427 (1971)
Khanh, P.Q., Quan, N.H., Yao, J.C.: Generalized KKM-type theorems in GFC-spaces and applications. Nonlinear Anal. Theor. Methods Appl. 71, 1227–1234 (2009)
Kim, I.S., Park, S.: Saddle point theorems on generalized convex spaces. J. Inequal. Appl. 5, 397–405 (2000)
Lignola, M.B.: Ky Fan inequalities and Nash equilibrium points without semicontinuity and compactness. J. Optim. Theory Appl. 94, 137–145 (1997)
Lin, L.J., Chang, T.H.: S-KKM theorems, saddle points and minimax inequalities. Nonlinear Anal. Theor. Methods Appl. 34, 73–86 (1998)
Lin, L.J., Chen, H.L.: The study of KKM theorems with applications to vector equilibrium problems and implicit vector variational inequalities problems. J. Glob. Optim. 32, 135–157 (2005)
Lin, L.J., Huang, Y.J.: Generalized vector quasi-equilibrium problems with applications to common fixed point theorems and optimization problems. Nonlinear Anal. Theor. Methods Appl. 66, 1275–1289 (2007)
Lin, J., Tian, G.: Minimax inequality equivalent to the Fan–Knaster–Kuratowski–Mazurkiewicz theorem. Appl. Math. Optim. 28, 173–179 (1993)
Nessah, R., Tian, G.: Existence of solution of minimax inequalities, equilibria in games and fixed points without convexity and compactness assumptions. J. Optim. Theor. Appl. 157, 75–95 (2013)
Tan, K.K.: G-KKM theorems, minimax inequalities and saddle points. Nonlinear Anal. Theor. Methods Appl. 30, 4151–4160 (1997)
Tian, G.: Generalizations of the FKKM theorem and Ky-Fan minimax inequality, with applications to maximal elements, price equilibrium, and complementarity. J. Math. Anal. Appl. 170, 457–471 (1992)
Tian, G.: Generalized KKM theorem and minimax inequalities and their applications. J. Optim. Theor. Appl. 83, 375–389 (1994)
Tian, G., Zhou, J.: Quasi-Variational inequalities with non-compact sets. J. Math. Anal. Appl. 160, 583–595 (1991)
Tian, G., Zhou, J.: The maximum theorem and the existence of Nash equilibrium of (generalized) games without lower semicontinuities. J. Math. Anal. Appl. 166, 351–364 (1992)
Tian, G., Zhou, Z.: Quasi-inequalities without the concavity assumption. J. Math. Anal. Appl. 172, 289–299 (1993)
Yuan, X.Z.: KKM principal, Ky Fan minimax inequalities and fixed point theorems. Nonlinear World 2, 131–169 (1995)
Yuan, X.Z.: The study of minimax inequalities and applications to economies and variational inequalities. Mem. Am. Math. Soc. 132(625), 1–140 (1998)
Zhou, J., Chen, G.: Diagonal convexity conditions for problems in convex analysis and quasi-variational inequalities. J. Math. Anal. Appl. 132, 213–225 (1988)
Sonnenschein, H.: Demand theory without transitive preferences, with application to the theory of competitive equilibrium. In: Chipman, J., Hurwicz, L., Richter, M.K., Sonnenschein, H. (eds.) Preferences, utility, and demand. Harcourt Brace Jovanovich, New York (1971)
Shafer, W., Sonnenschein, H.: Equilibrium in abstract economies without ordered preferences. J. Math. Econ. 2, 345–348 (1975)
Baye, M.R., Tian, G., Zhou, J.: Characterizations of the existence of equilibria in games with discontinuous and nonquasiconcave payoffs. Rev. Econ. Stud. 60, 935–948 (1993)
Tarski, A.: A lattice-theoretical fixpoint theorem and its applications. Pacific J. Math. 5, 285–309 (1955)
Halpern, B.: Fixed-point theorems for outward maps. Doctoral Thesis, U.C.L.A. (1965)
Halpern, B.: Fixed point theorems for set-valued maps in infinite dimensional spaces. Math. Ann. 189, 87–98 (1970)
Halpern, B., Bergman, G.: A fixed-point theorem for inward and outward maps. Trans. Am. Math. Soc. 130(2), 353–358 (1968)
Reich, S.: Fixed points in locally convex spaces. Mathematische Zeitschrift 125, 17–31 (1972)
Istrăţescu, V.I.: Fixed point theory. D. Reidel Publishing Company (1981)
Tian, G.: Fixed points theorems for mappings with non-compact and non-convex domains. J. Math. Anal. Appl. 158, 161–167 (1991)
Knaster, B., Kuratowski, C., Mazurkiewicz, S.: ein beweis des fixpunktsatze \(n\) demensionale simpliexe. Fund. Math. 14, 132–137 (1929)
Tian, G.: Necessary and sufficient conditions for maximization of a class of preference relations. Rev. Econ. Stud. 60, 949–958 (1993)
Tian, G., Zhou, J.: Transfer continuities, generalizations of the Weierstrass and maximum theorems: a full characterization. J. Math. Econ. 24, 281–303 (1995)
Zhou, J.X., Tian, G.: Transfer method for characterizing the existence of maximal elements of binary relations on compact or noncompact sets. SIAM J. Optim. 2, 360–375 (1992)
Rodríguez-Palmero, C., García-Lapresta, J.L.: Maximal elements for irreflexive binary relations on compact sets. Math. Soc. Sci. 43, 55–60 (2002)
Tian, G.: On the existence of equilibria in games with arbitrary strategy spaces and preferences. J. Math. Econ. 60, 9–16 (2015)
Tian, G.: On the existence of price equilibrium in economies with excess demand functions. Econ. Theor. Bull. 4, 5–16 (2016)
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I shall thank an anonymous referee for helpful comments and suggestions. Financial support from the National Natural Science Foundation of China (NSFC-71371117) and the Key Laboratory of Mathematical Economics (SUFE) at Ministry of Education of China is gratefully acknowledged.
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Tian, G. Full characterizations of minimax inequality, fixed point theorem, saddle point theorem, and KKM principle in arbitrary topological spaces. J. Fixed Point Theory Appl. 19, 1679–1693 (2017). https://doi.org/10.1007/s11784-016-0314-z
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DOI: https://doi.org/10.1007/s11784-016-0314-z