概率度量空间中一个新的不动点定理

概率度量空间中压缩型映象不动点定理的研究开始于1972年Schgal-Bharucha-Reid的工作[3]。以后不少人对概率度量空间中映象的不动点定理进一步讨论,特别是Istratescu的工作[4]把[3]中的结果作了重要的推广。最近张石生[2]对[3]、[4]中的结果作了进一步的推广,[2]中的结果包含了[3]、[4]的主要结果。 在此基础上,本文给出概率度量空间中压缩型映象的一个新的不动点定理。文中涉及的概念及引用的基本定理均见[1]。     

压缩型映象的几个不动点定理

非线性泛函分析中映象的不动点理论,近十多年来有了很大的发展。其中非扩张映象以及各种压缩型映象的不动点理论是讨论得很多的课题。(见[1]—[8]). 本文对现有的结果作一些推广。我们讨论了某些类压缩型映象的性质,并在不必有严格凸性的自反Opial空间,以及不必自反不必严格凸的某类*-Opial空间中,给出了它们的一些不动点定理。另外,我们还讨论了集合值压缩型映象的不动点定理。     

关于伪单调平衡问题和不动点问题的粘滞-次梯度方法

本文介绍了一个新的逼近伪单调平衡问题的解和广义渐近λ-严格伪压缩映象不动点的粘滞-次梯度方法,在Hilbert空间中建立了关于伪单调平衡问题和一簇广义渐近λ-严格伪压缩映象公共不动点的强收敛定理,并在收敛性分析中去掉了映象的一致Lipschitz连续性条件.     

有限簇伪压缩映象和单调映象广义迭代法的强收敛性

在Hilbert空间中,建立了一个关于有限簇伪压缩映象和单调映象的广义迭代方法,并在更弱的条件下证明了该方法所产生的序列强收敛到连续伪压缩映象不动点集和变分不等式解集的某个公共元.     

关于概率度量空间中压缩型映象对的不动点定理

Menger 1942 年提出概率度量空间的概念,近年来,Sehgal,Bharucha-Reid,Istratescu,林等对概率度量空间中压缩型映象不动点定理进行了研究。本文对概率度量空间压缩型映象对给出了几个新的不动点定理,这些结果统一和发展了[2,3,4]中的某些主要结果。     

广义平衡问题和渐近严格伪压缩映象的粘滞-投影方法

利用Meir-Keeler压缩映象,定义了一个关于广义平衡问题和渐近严格伪压缩映象的粘滞-投影方法,在Hilbert空间中建立逼近广义平衡问题的解和渐近严格伪压缩映象不动点的强收敛定理,并在收敛性分析中去掉了部分迭代控制条件和映象的渐近正则性等.     

Chebysev-中心和不动点定理

本文利用Chebysev—中心讨论了Banach空间Z中广义非扩张映象的不动点定理以及广义压缩映象不动点的迭代逼近。     

Banach空间中渐近非扩张映象不动点的迭代逼近问题

本文研究Banach空间中渐近非扩张映象和渐近伪压缩映象不动点的迭代逼近问题,本文结果是[4,5,7]中相应结果的发展和改进。     

P1—紧映象的多解结果及其应用

本文应用A-proper映象的不动点指数理论(见[4]、[7]),获得了P_I-紧映象的一个多解结果,它类似于全连续映象,k-集压缩映象,k∈[0,1),凝聚映象和半紧1-集压缩映象的相应结论,这里的证明方法不同于上述文献中相应定理的证明,结果改进了[9—10]、[12]、[14]中相应结论。 设F是具有完备投影逼近格式Γ={X_n,P_n}的Banach空间X中一闭凸集使得P_n(F)     

完备凸度量空间中(次)相容和集值广义非扩张映象的公共不动点定理

本文在完备凸度量空间中,利用集值和单值映象(次)相容的一些条件,建立了数值广义非扩张映象存在公共不动点的一个充要条件和一个充分条件.我们的结果改进、扩充和发展了文[2～7]中的主要结果.     

Kannan压缩映像的逆问题

称空间(X,d)上的自映像f为Kannan压缩映像,若对于,成立d(f(x),f(y))≤a{d(x,f(x))+d(y,f(y)}, 其中0<α<1/2。 Kannan压缩映像是Banach压缩映像的重要推广,特别在Banach压缩映像已被许多作者推广为形式多样的情况下(例如见[8],那里归纳出250个压缩映像定义),重要性尤其突出。本文通过对Kannan压缩映像逆问题的证明,把相当一部分形式不同的压缩映像统一归并为Kannan压缩映像。     

一类新的压缩条件及不动点

给出了一个一般的压缩条件，所给的压缩条件便于应用，同时还给出满足压缩条件的自映象不动点定理。     

m个d-空间之间复合映射的不动点

给出了m个d-空间之间复合映射在压缩和扩张条件下的几个不动点定理。     

Common fixed point theorems for maps under a contractive condition of integral type

Two common fixed point theorems for mapping of complete metric space under a general contractive inequality of integral type and satisfying minimal commutativity conditions are proved. These results extend and improve several previous results, particularly Theorem 4 of Rhoades [B.E. Rhoades, Two fixed point theorems for mappings satisfying a general contractive condition of integral type, Int. J. Math. Math. Sci. 63 (2003) 4007-4013] and Theorem 4 of Sessa [S. Sessa, On a weak commutativity condition of mappings in fixed point considerations, Publ. Inst. Math. (Beograd) (N.S.) 32 (46) (1982) 149-153].     

Solving the Banach fixed point principle for nonlinear contractions in probabilistic metric spaces

The probabilistic version of the classical Banach Contraction Principle was proved in 1972 by Sehgal and Bharucha-Reid [V.M. Sehgal, A.T. Bharucha-Reid, Fixed points of contraction mappings on PM spaces. Math. Syst. Theory 6, 97–102]. Their fixed point theorem is further generalized by many authors. In the intervening years many others have proved the probabilistic versions of the other known metric fixed point theorems. However, the problem to prove the probabilistic versions of the very important generalization of the Banach Contraction Principle, obtained in 1969 by Boyd and Wong [D.W. Boyd, J.S.W. Wong, On nonlinear contractions, Proc. Am. Math. Soc. 20 (1969) 458–464], who proved the fixed point theorem for a self-mapping of a metric space, satisfying the very general nonlinear contractive condition, is unsolved in these days. Similarly, as in the metric space case, to prove a fixed point theorem for a mapping, satisfying the general probabilistic nonlinear contractive condition, it was necessary to find a new approach, substantially different from the previous technique for cases where a mapping satisfies the probabilistic linear contraction condition, introduced by Sehgal and Bharucha-Reid and further used by many authors. So, the problem to obtain a truthful probabilistic version of the Banach fixed point principle for general nonlinear contractions existed unsolved for over 35 years. We have solved this problem in this paper.     

Fixed Points of Mappings Satisfying a Weakly Contractive Type Condition

In this paper, we discuss a fixed point theorem for mappings derived by a pair of mappings satisfying weak(k, k/) contractive type condition on the tensor product spaces. Let X and Y be Banach spaces and T_1 : X γ Y → X and T_2: X γ Y → Y be two operators which satisfy weak(k, k/) contractive type condition. Using T_1 and T_2, we construct an operator T on X γ Y and show that T has a unique fixed point in a closed and bounded subset of X γ Y.We derive an iteration scheme converging to this unique fixed point of T. Conversely, using a weakly contractive mapping T, we construct a pair of mappings(T_1, T_2) satisfying weak(k, k/)contractive type condition on X γ Y and from this pair, we also obtain two self mappings S_1 and S_2 on X and Y respectively with unique fixed points.     

Common fixed points for discontinuous mappings in fuzzy metric spaces

In this paper we prove some common fixed point theorems for fuzzy contraction respect to a mapping, which satisfies a condition of weak compatibility. We deduce also fixed point results for fuzzy contractive mappings in the sense of Gregori and Sapena. The authors are supported by Università degli Studi di Palermo, R. S. ex 60%.     

多分支自相似集的自仿嵌入

本文研究了一类多分支自相似集的自仿嵌入.利用压缩映射的不动点,在一定条件下,证明了若一个自相似集能自仿嵌入到另一个自相似集中,则它们对应的迭代函数系的压缩比满足某种代数性质.     

A common fixed point theorem for weakly compatible mappings in symmetric spaces satisfying a contractive condition of integral type

In this paper, we proved a common fixed point theorem for weakly compatible mappings in symmetric spaces satisfying a contractive condition of integral type and a property (E.A) introduced in [M. Aamri, D. El Moutawakil, Some new common fixed point theorems under strict contractive conditions, J. Math. Anal. Appl. 270 (2002) 181-188]. Our theorem generalizes Theorem 2.2 of [M. Aamri, D. El Moutawakil, Common fixed points under contractive conditions in symmetric spaces, Appl. Math. E-Notes 3 (2003) 156-162] and Theorem 2 of [M. Aamri, D. El Moutawakil, Some new common fixed point theorems under strict contractive conditions, J. Math. Anal. Appl. 270 (2002) 181-188].     

Common fixed point theorems of Gregus type for weakly compatible mappings satisfying generalized contractive conditions

We prove a common fixed point theorem of Gregus type for four mappings satisfying a generalized contractive condition in metric spaces using the concept of weak compatibility which generalizes theorems of [I. Altun, D. Turkoglu, B.E. Rhoades, Fixed points of weakly compatible mappings satisfying a general contractive condition of integral type, Fixed Point Theory Appl. 2007 (2007), article ID 17301; A. Djoudi, L. Nisse, Gregus type fixed points for weakly compatible mappings, Bull. Belg. Math. Soc. 10 (2003) 369-378; A. Djoudi, A. Aliouche, Common fixed point theorems of Gregus type for weakly compatible mappings satisfying contractive conditions of integral type, J. Math. Anal. Appl. 329 (1) (2007) 31-45; P. Vijayaraju, B.E. Rhoades, R. Mohanraj, A fixed point theorem for a pair of maps satisfying a general contractive condition of integral type, Int. J. Math. Math. Sci. 15 (2005) 2359-2364; X. Zhang, Common fixed point theorems for some new generalized contractive type mappings, J. Math. Anal. Appl. 333 (2) (2007) 780-786]. We prove also a common fixed point theorem which generalizes Theorem 3.5 of [H.K. Pathak, M.S. Khan, T. Rakesh, A common fixed point theorem and its application to nonlinear integral equations, Comput. Math. Appl. 53 (2007) 961-971] and common fixed point theorems of Gregus type using a strict generalized contractive condition, a property (E.A) and a common property (E.A).