广义Minimax不等式及不动点定理

最近,许多作者推广了著名的Ky Fan的minimax不等式.本文提出了T-对角凸凹性条件,发展了这一方面的主要结果.其次,我们讨论了一些不动点问题,推广了Fan-Glicksberg不动点定理.     

Fixed Points,Continuous Selections,and Existence of Solution of Optimization-Related Problems

We propose a definition of a generalized type of Knaster–Kuratowski–Mazurkiewicz (KKM) mappings, called a weak T-KKM mapping, and a corresponding weak KKM property. A new extension of the Fan–Glicksberg fixed-point theorem is established. Sufficient conditions for the existence of a continuous selection, a fixed point of a composition, and a coincidence point are also provided. Then, we use the obtained results to study the existence of solutions to various optimization-related problems. Discussions and detailed examples are included as well to compare our results with existing ones and to explain their advantages in many situations.     

没有紧性, 连续性和凹性的多准则对策的帕雷多平衡*

在本文中利用作者得到的一极小极大不等式,对不具有紧性,连续性和四性的多准则对策在拓扑矢量空间和自反Banach空间内证明了某些帕雷多平衡存在定理。     

Generic Well-Posedness of Constrained Variational Problems Without Convexity Assumptions

In our previous work, a generic well-posedness result (with respect to variations of the integrand of the integral functional) without the convexity condition was established for a class of optimal control problems satisfying the Cesari growth condition. In this paper, we extend this generic well-posedness result to classes of constrained variational problems in which the values at the endpoints and constraint maps are also subject to variations.     

The Study of Minimax Inequalities, Abstract Economics and Applications to Variational Inequalities and Nash Equilibria

In this survey, a new minimax inequality and one equivalent geometricform are proved. Next, a theorem concerning the existence of maximalelements for an LC-majorized correspondence is obtained.By the maximal element theorem, existence theorems of equilibrium point fora noncompact one-person game and for a noncompact qualitative game withLC-majorized correspondences are given. Using the lastresult and employing 'approximation approach', we prove theexistence of equilibria for abstract economies in which the constraintcorrespondence is lower (upper) semicontinuous instead of having lower(upper) open sections or open graphs in infinite-dimensional topologicalspaces. Then, as the applications, the existence theorems of solutions forthe quasi-variational inequalities and generalized quasi-variationalinequalities for noncompact cases are also proven. Finally, with theapplications of quasi-variational inequalities, the existence theorems ofNash equilibrium of constrained games with noncompact are given. Our resultsinclude many results in the literature as special cases.     

非紧L-凸度量空间中的一个新的不动点定理及其对极大极小不等式和鞍点的应用

In this paper,a new fixed point theorem is established in noncompact complete Lconvex metric spaces.As applications,a maximal element theorem,a minimax inequality and a saddle point theorem are obtained.     

Inequalities for Fixed Points of Holomorphic Functions

Cowen and Pommerenke obtained inequalities for fixed pointsof holomorphic and univalent functions in [1]. There was onlyone case where their inequality was not the best possible. Byan entirely new method, we will establish a sharp improvementto this case and provide simple proofs to their main resultsin [1]     

Existence of Equilibrium in Generalized Games with Abstract Convexity Structure

The aim of this paper is to prove the existence of equilibrium for generalized games or abstract economies in contexts where the convexity conditions on strategy spaces and preference correspondences are relaxed and an arbitrary number of agents is considered. The results are based on a fixed-point theorem in which the convexity condition on sets and images of correspondences is replaced by a general notion of abstract convexity, called mc-spaces, generalizing the notions of simplicial convexity, H-spaces, and G-convex spaces.     

A Fixed Point Theorem and Some Generalized Ky Fan's Minimax Inequalities

In this paper, we establish a fixed point theorem for set-valued mapping on a topological vector space without "local convexity". And we also establish some generalized Ky Fan's minimax inequalities for set-value vector mappings, which are the generalization of some previous results.     

Ky Fan Inequalities and Nash Equilibrium Points without Semicontinuity and Compactness

In this paper, a Ky Fan inequality without compactness and semicontinuity assumptions is proved. The inequality is next applied in order to obtain existence results for Nash equilibrium points for two-person games in topological vector spaces and in reflexive Banach spaces.     

不动点在讨论驻点存在性问题中的应用

本文通过建立不动点与驻点之间的关系，从而利用不动点的存在性来确定函数驻点的存在性。     

Existence and Uniqueness of Open-Loop Stackelberg Equilibria in Linear-Quadratic Differential Games

We present existence and uniqueness results for a hierarchical or Stackelberg equilibrium in a two-player differential game with open-loop information structure. There is a known convexity condition ensuring the existence of a Stackelberg equilibrium, which was derived by Simaan and Cruz (Ref. 1). This condition applies to games with a rather nonconflicting structure of their cost criteria. By another approach, we obtain here new sufficient existence conditions for an open-loop equilibrium in terms of the solvability of a terminal-value problem of two symmetric Riccati differential equations and a coupled system of Riccati matrix differential equations. The latter coupled system appears also in the necessary conditions, but contrary to the above as a boundary-value problem. In case that the convexity condition holds, both symmetric equations are of standard type and admit globally a positive-semidefinite solution. But the conditions apply also to more conflicting situations. Then, the corresponding Riccati differential equations may be of H-type. We obtain also different uniqueness conditions using a Lyapunov-type approach. The case of time-invariant parameters is discussed in more detail and we present a numerical example.     

A New Existence Theorem of Maximal Elements in Non-Compact H-Spaces with Applications to Minimax Inequalities and Variational Inequalities

We give a new existence theorem of maximal elements in non-compact H-spaces. As applications, two extended versions of Fan-Yen minimax inequality are obtained and the existence problems of solutions of variational inequalities and quasi-variational inequalities are studied.     

On the Probability of Existence of Pure Equilibria in Matrix Games

In a recent paper (Ref. 1), Papavassilopoulos obtained results on the probability of the existence of pure equilibrium solutions in stochastic matrix games. We report a similar result, but where the payoffs are drawn from a finite set of numbers N. In the limiting case, as N tends to infinity, our result and that of Papavassilopoulos are identical. We also cite similar results obtained independently by others, some of which were already independently brought to the notice of Papavassilopoulos by Li Calzi as reported in Papavassilopoulos (Ref. 2). We cite a much earlier result obtained by Goldman (Ref. 3). We also cite our related work (Ref. 4), in which we derive the conditions for the existence of mixed strategy equilibria in two-person zero-sum games.     

On the Existence of Solutions for Fully Nonlinear Elliptic Equations Under Relaxed Convexity Assumptions

We establish the existence and uniqueness of solutions of fully nonlinear elliptic second-order equations like H(v, Dv, D ² v, x) = 0 in smooth domains without requiring H to be convex or concave with respect to the second-order derivatives. Apart from ellipticity nothing is required of H at points at which |D ² v| ≤K, where K is any given constant. For large |D ² v| some kind of relaxed convexity assumption with respect to D ² v mixed with a VMO condition with respect to x are still imposed. The solutions are sought in Sobolev classes.     

The Existence of Zeros of Multivalued Functionals,Coincidence Points,and Fixed Points in $$f$$ -Quasimetric Spaces

Mathematical Notes - The notion of a $$lambda$$ -generalized-search multivalued functional on an $$f$$ -quasimetric space is introduced. An existence theorem for zeros of such functionals is...     

Nonemptiness and Compactness of Solution Sets to Weakly Homogeneous Generalized Variational Inequalities

Journal of Optimization Theory and Applications - In this paper, we deal with the weakly homogeneous generalized variational inequality, which provides a unified setting for several special...     

Generic Existence of Fixed Points for Set-Valued Mappings

We first consider a complete metric space of nonexpansive set-valued mappings acting on a closed convex subset of a Banach space with a nonempty interior, and show that a generic mapping in this space has a fixed point. We then establish analogous results for two complete metric spaces of set-valued mappings with convex graphs.     

On Existence of Nash Equilibria of Games with Constraints on Multistrategies

In this paper, sufficient conditions are given, which are less restrictivethan those required by the Arrow–Debreu–Nash theorem, on theexistence of a Nash equilibrium of an n-player game {₁, . . . , Y_n,f₁, . . . , f_n} in normal form with a nonempty closedconvex constraint C on the set Y=i Y_i of multistrategies. Theith player has to minimize the function fi with respect to the ithvariable. We consider two cases.In the first case, Y is a real Hilbert space and the loss function class isquadratic. In this case, the existence of a Nash equilibrium is guaranteedas a simple consequence of the projection theorem for Hilbert spaces. In thesecond case, Y is a Euclidean space, the loss functions are continuous, andf_i is convex with respect to the ith variable. In this case, the techniqueis quite particular, because the constrained game is approximated with asequence of free games, each with a Nash equilibrium in an appropriatecompact space X. Since X is compact, there exists a subsequence of theseNash equilibrium points which is convergent in the norm. If thelimit point is in C and if the order of convergence is greater than one,then this is a Nash equilibrium of the constrained game.