非合作博弈的轻微利他平衡点的存在性

在Marco和Morgan提出博弈论中一种新的解——轻微利他平衡的基础上,讨论了一类不连续博弈的轻微利他平衡点的存在性,进一步讨论了支付函数更弱情况(拟凹)的轻微利他平衡点的存在性.     

主从博弈的轻微利他平衡点

针对一个领导者的主从博弈问题,研究轻微利他平衡点的存在性问题.首先,基于非合作博弈Nash均衡的概念,给出了主从博弈轻微利他Nash均衡的定义;然后,应用非线性问题稳定性理论,证明了平衡点的存在性.     

多主从博弈的轻微利他平衡点问题

基于经典非合作博弈的Nash平衡点问题,结合利他主义的思想,研究了多主从博弈的轻微利他平衡点问题.通过利用Fan-Glicksberg不动点定理,对两个领导者的多主从博弈在轻微利他情况下的平衡点存在性进行了讨论和研究.     

轻微利他弱Pareto-Nash均衡

2008年,Marco和Morgan在正规型博弈中引入轻微利他均衡和友好均衡的概念.利用轻微利他的思想,研究多目标博弈.证明轻微利他弱Pareto-Nash均衡的存在性定理,进一步地讨论轻微利他弱Pareto-Nash均衡和本质均衡的关系.     

T-凸空间中Fan Ky点与Nash平衡点存在定理北大核心

充分利用KKM方法和经典的集值分析方法,在不具有线性结构的T-凸空间中,建立并证明了弱Fan Ky点存在引理,并借助该引理获得了两个Fan Ky点存在定理;最后,作为对Fan Ky点存在定理的应用,在T-凸策略空间中建立并证明了n人非合作博弈Nash平衡点存在定理.     

自反Banach空间中Ky Fan点的存在性

本文对自反Banach空间证明了一个Ky Fan点的存在性定理,作为它的应用,对非合作博弈的Nash平衡点及变分不等式的解给出了几个存在性定理.     

一类平面n＋2次系统的极限环

本文研究了一类生化反应模型证明了该系统当唯一正平衡点是不稳定奇点时，至少存在一个围绕此奇点的稳定极限环。当此平衡点是稳定奇点时，它是全局浙近稳定的。     

两类带有确定潜伏期的SEIS传染病模型的分析

通过研究两类带有确定潜伏期的SEIS传染病模型,发现对种群的常数输入和指数输入会使疾病的传播过程产生本质的差异．对于带有常数输入的情形,找到了地方病平衡点存在及局部渐近稳定的阈值,证明了地方病平衡点存在时一定局部渐近稳定,并且疾病一致持续存在．对于带有指数输入的情形,发现地方病平衡点当潜伏期充分小时是局部渐近稳定的,当潜伏期充分大时是不稳定的．     

有限理性与一类多主从博弈问题的良定性

利用Ky Fan不等式证明了一类多主从博弈平衡点的存在性,并且定义了此类多主从博弈的有限理性函数.在非线性问题的良定性的框架下,使用有限理性证明了此类多主从博弈问题是广义Had-amard良定的和广义Tykhonov良定的.     

具有染病年龄结构的SEIR流行病模型的稳定性

建立和研究了一类具有染病年龄结构的SEIR流行病模型.得到了该模型的基本再生数R0的表达式.证明了当R0<1时,无病平衡点E0不仅局部渐近稳定,而且全局吸引;当R0>1时,无病平衡点E0不稳定,此时存在稳定的地方病平衡点.     

Approximate equilibria for Bayesian games

In this paper the problem of the existence of approximate equilibria in mixed strategies is central. Sufficient conditions are given under which approximate equilibria exist for non-finite Bayesian games. Further one possible approach is suggested to the problem of the existence of approximate equilibria for the class of multicriteria Bayesian games.     

Slightly Altruistic Equilibria

We introduce a refinement concept for Nash equilibria (slightly altruistic equilibrium) defined by a limit process and which captures the idea of reciprocal altruism as presented in Binmore (Proceedings of the XV Italian Meeting on Game Theory and Applications, [2003]). Existence is guaranteed for every finite game and for a large class of games with a continuum of strategies. Results and examples emphasize the (lack of) connections with classical refinement concepts. Finally, it is shown that, under a pseudomonotonicity assumption on a particular operator associated to the game, it is possible, by selecting slightly altruistic equilibria, to eliminate those equilibria in which a player can switch to a strategy that is better for the others without leaving the set of equilibria. Part of the results in this paper have been presented at: First Spain, Italy, Netherlands Meeting on Game Theory, Maastricht, 2005; Fifth International ISDG Workshop, Segovia, 2005; GATE, Université Lumière Lyon 2, 2005; XXX AMASES Workshop, Trieste 2006; CSEF, Università di Salerno, 2006.     

Separable and low-rank continuous games

In this paper, we study nonzero-sum separable games, which are continuous games whose payoffs take a sum-of-products form. Included in this subclass are all finite games and polynomial games. We investigate the structure of equilibria in separable games. We show that these games admit finitely supported Nash equilibria. Motivated by the bounds on the supports of mixed equilibria in two-player finite games in terms of the ranks of the payoff matrices, we define the notion of the rank of an n-player continuous game and use this to provide bounds on the cardinality of the support of equilibrium strategies. We present a general characterization theorem that states that a continuous game has finite rank if and only if it is separable. Using our rank results, we present an efficient algorithm for computing approximate equilibria of two-player separable games with fixed strategy spaces in time polynomial in the rank of the game. This research was funded in part by National Science Foundation grants DMI-0545910 and ECCS-0621922 and AFOSR MURI subaward 2003-07688-1.     

Asymptotic Analysis of Linear Feedback Nash Equilibria in Nonzero-Sum Linear-Quadratic Differential Games

In this paper, we discuss nonzero-sum linear-quadratic differential games. For this kind of games, the Nash equilibria for different kinds of information structures were first studied by Starr and Ho. Most of the literature on the topic of nonzero-sum linear-quadratic differential games is concerned with games of fixed, finite duration; i.e., games are studied over a finite time horizon t _f. In this paper, we study the behavior of feedback Nash equilibria for t _f.In the case of memoryless perfect-state information, we study the so-called feedback Nash equilibrium. Contrary to the open-loop case, we note that the coupled Riccati equations for the feedback Nash equilibrium are inherently nonlinear. Therefore, we limit the dynamic analysis to the scalar case. For the special case that all parameters are scalar, a detailed dynamical analysis is given for the quadratic system of coupled Riccati equations. We show that the asymptotic behavior of the solutions of the Riccati equations depends strongly on the specified terminal values. Finally, we show that, although the feedback Nash equilibrium over any fixed finite horizon is generically unique, there can exist several different feedback Nash equilibria in stationary strategies for the infinite-horizon problem, even when we restrict our attention to Nash equilibria that are stable in the dynamical sense.     

利他扰动与Nash均衡点集的利他稳定性

引入了一个新的利他扰动.定义了KyFan点集的利他本质集,进一步证明在此扰动下,KyFan点集的利他本质连通区的存在性.证明了满足一定条件的n人非合作博弈中,Nash均衡点集至少存在一个利他本质连通区,而且Nash均衡点集的每一个本质集必是利他稳定集,Nash均衡点集的本质连通区也是利他本质集连通区.     

On the probability of existence of pure equilibria in matrix games

We examine the probability that a randomly chosen matrix game admits pure equilibria and its behavior as the number of actions of the players or the number of players increases. We show that, for zero-sum games, the probability of having pure equilibria goes to zero as the number of actions goes to infinity, but it goes to a nonzero constant for a two-player game. For many-player games, if the number of players goes to infinity, the probability of existence of pure equilibria goes to zero even if the number of actions does not go to infinity.This research was supported in part by NSF Grant CCR-92-22734.