内容简介
This book is intended as an introduction to fixed point theory and itsapplications. The topics treated range from fairly standard results (such asthe Principle of Contraction Mapping, Brouwers and Schauders fixedpoint theorems) to the frontier of what is known, but we have not tried toachieve maximal generality in all possible directions. We hope that thereferences quoted may be useful for this purpose.
The point of view adopted in this book is that of functional analysis; forthe readers more interested in the algebraic topological point of view wehave added some references at the end of the book. A knowledge offunctional analysis is not a prerequisite, although a knowledge of anintroductory course in functional analysis would be profitable. However,the book contains two introductory chapters, one on general topology andanother on Banach and Hilbert spaces.
内页插图
目录
Editors Preface
Foreword
CHAPTER 1. Topological Spaces and Topological Linear Spaces
1.1. Metric Spaces
1.2. Compactness in Metric Spaces. Measures of Noncompactness
1.3. Baire Category Theorem
1.4. Topological Spaces
1.5. Linear Topological Spaces. Locally Convex Spaces
CHAPTER 2. Hilbert spaces and Banach spaces
2.1. Normed Spaces. Banach Spaces
2.2. Hilbert Spaces
2.3. Convergence in X, X* and L(X)
2.4. The Adjoint of an Operator
2.5. Classes of Banach Spaces
2.6. Measures of Noncompactness in Banach Spaces
2.7. Classes of Special Operators on Banach Spaces
CHAPTER 3. The Contraction Principle
3.0. Introduction
3.1. The Principle of Contraction Mapping in Complete Metric Spaces
3.2. Linear Operators and Contraction Mappings
3.3. Some Generalizations of the Contraction Mappings
3.4. Hilberts Projective Metric and Mappings of Contractive Type
3.5. Approximate Iteration
3.6. A Converse of the Contraction Principle
3.7. Some Applications of the Contraction Principle
CHAPTER 4. Brouwers Fixed Point Theorem
4.0. Introduction
4.1. The Fixed Point Property
4.2. Brouwers Fixed Point theorem. Equivalent Formulations
4.3. Robbins Complements of Brouwers Theorem
4.4. The Borsuk-Ulam Theorem
4.5. An Elementary Proof of Brouwers Theorem
4.6. Some Examples
4.7. Some Applications of Brouwers Fixed Point Theorem
4.8. The Computation of Fixed Points. Scarfs Theorem
CHAPTER 5. Schauders Fixed Point Theorem and Some Generalizations
5.0. Introduction
5.1. The Schauder Fixed Point Theorem
5.2. Darbos Generalization of Schauders Fixed Point Theorem
5.3. Krasnoselskiis, Rothes and Altmans Theorems
5.4. Browders and Fans Generalizations of Schauders and Tychonoffs Fixed Point Theorem
5.5. Some Applications
CHAPTER 6. Fixed Point Theorems jbr Nonexpansive Mappings and Related Classes of Mappings
6.0. Introduction
6.1. Nonexpansive Mappings
6.2. The Extension of Nonexpansive Mappings
6.3. Some General Properties of Nonexpansive Mappings
6.4. Nonexpansive Mappings on Some Classes of Banach Spaces
6.5. Convergence of Iterations of Nonexpansive Mappings
6.6. Classes of Mappings Related to Nonexpansive Mappings
6.7. Computation of Fixed Points for Classes of Nonexpansive Mappings
6.8. A Simple Example of a Nonexpansive Mapping on a Rotund Space Without Fixed Points
CHAPTER 7. Sequences of Mappings and Fixed Points
7.0. Introduction
7.1. Convergence of Fixed Points for Contractions or Related Mappings
7.2. Sequences of Mappings and Measures of Noncompactness
CHAPTER 8. Duality Mappings amt Monotome Operators
8.0. Introduction
8.1. Duality Mappings
8.2. Monotone Mappings and Classes of Nonexpansive Mappings
8.3. Some Surjectivity Theorems on Real Banach Spaces
8.4. Some Surjectivity Theorems in Complex Banach Spaces
8.5. Some Surjectivity Theorems in Locally Convex Spaces
8.6. Duality Mappings and Monotonicity for Set-Valued Mappings
8.7. Some Applications
CHAPTER 9. Families of Mappings and Fixed Points
9.0. Introduction
9.1. Markovs and Kakutanis Results
9.2. The RylI-Nardzewski Fixed Point Theorem
9.3. Fixed Points for Families of Nonexpansive Mappings
9.4. lnvariant Means on Semigroups and Fixed Point for Families of Mappings
CHAPTER 10. Fixed Points and Set-Valued Mappings
10.0 Introduction
10.1 The Pompeiu-Hausdorff Metric
10.2. Continuity for Set-Valued Mappings
10.3. Fixed Point Theorems for Some Classes of Set-valued Mappings
10.4. Set-Valued Contraction Mappings
10.5. Sequences of Set-Valued Mappings and Fixed Points
CHAPTER 11. Fixed Point Theorems for Mappings on PM-Spaces
11.0. Introduction
11.1. PM-Spaces
11.2. Contraction Mappings in PM-Spaces
11.3. Probabilistic Measures of Noncompactness
11.4. Sequences of Mappings and Fixed Points
CHAPTER 12. The Topological Degree
12.0.Introduction
12.1. The Topological Degree in Finite-Dimensional Spaces
12.2. The Leray-Schauder Topological Degree
12.3. Lerays Example
12.4. The Topological Degree for k-Set Contractions
12.5. The Uniqueness Problem for the Topological Degree
I2.6. The Computation of the Topological Degree
12.7. Some Applications of the Topological Degree
BIBLIOGRAPHY
INDEX
前言/序言
This book is intended as an introduction to fixed point theory and itsapplications. The topics treated range from fairly standard results (such asthe Principle of Contraction Mapping, Brouwers and Schauders fixedpoint theorems) to the frontier of what is known, but we have not tried toachieve maximal generality in all possible directions. We hope that thereferences quoted may be useful for this purpose.
The point of view adopted in this book is that of functional analysis; forthe readers more interested in the algebraic topological point of view wehave added some references at the end of the book. A knowledge offunctional analysis is not a prerequisite, although a knowledge of anintroductory course in functional analysis would be profitable. However,the book contains two introductory chapters, one on general topology andanother on Banach and Hilbert spaces. As a special feature of these chapterswe note the study of measures of noncompactness; first in the case of metricspaces, and second in the case of Banach spaces.
Chapter 3 contains a detailed account of the Contraction Principle,perhaps the best known fixed point theorem. Many generalizations of theContraction Principle are also included. We note here the connectionbetween ideas from projective geometry and contractive mappings. Afterpresenting some ways to compute the fixed points for contractivemappings, we discuss several applications in various areas. Chapter 4 presents Brouwers fixed point theorem, perhaps the mostimportant fixed point theorem. After some historical notes concerningopinions about Brouwers proof- which have been influential for the futureof the fixed point theory (Alexander and Birkhoff and Kellogg)-wepresent many proofs of this theorem of Brouwer, of interest to differentcategories of readers. Thus we present an elementary one, which requiresonly elementary properties of polynomials and continuous functions;another uses differential forms; still another uses differential topology; andone relies on combinatorial topology. These different proofs may be used indifferent ways to compute the fixed points for mappings. In this connection,some algorithms for the computation of fixed points are given.
《不动点理论导论(英文版)》图书简介 书名: 《不动点理论导论(英文版)》 (Fixed Point Theory: An Introduction) 导论:不动点理论的深远影响与核心概念 不动点理论,作为数学分析和拓扑学的一个核心分支,其重要性已远远超越了理论研究的范畴,深入到众多应用科学的基石之中。从经济学中的均衡分析到物理学中的稳定态研究,再到计算机科学中的算法收敛性证明,不动点理论提供了一种强有力的工具,用以论证特定方程或映射在给定空间中必然存在“不动点”——即输入与输出完全相同的点。 本书《不动点理论导论(英文版)》正是为有志于深入探索这一迷人领域的读者精心编纂的入门性教材。它旨在系统而清晰地介绍不动点理论的基本概念、经典定理及其在数学及相关学科中的应用,为初学者构建坚实的理论基础,同时为资深研究者提供一个结构化的回顾平台。 本书的叙述风格力求严谨而不失启发性,内容组织遵循从基础到深入、从经典到现代的逻辑脉络。我们专注于清晰地阐述数学直觉与严格证明之间的桥梁,确保读者不仅理解“定理为什么成立”,更能掌握“如何运用这些定理”。 第一部分:基础奠定——度量空间与拓扑结构 不动点理论的根基深深植根于拓扑学和泛函分析之中。因此,本书的第一部分将详尽回顾和巩固读者对这些基础概念的理解。 1.1 度量空间的基础 我们将从度量空间的定义入手,这是不动点理论中最常用且最直观的背景空间。内容涵盖开集、闭集、完备性(至关重要的一环,特别是巴拿赫空间)、紧致性以及连续性的度量空间定义。我们强调完备性的重要性,因为它是许多核心不动点定理(如巴拿赫压缩映射定理)得以成立的必要前提。 1.2 拓扑空间简介 为了将理论推广到更抽象的背景,我们简要介绍了拓扑空间的概念,包括邻域、开集、闭集、Hausdorff空间等基本拓扑性质。这部分内容旨在为后续更抽象的不动点存在性证明做铺垫。 1.3 连续映射与收敛性 连续映射的定义及其在度量空间上的性质是研究迭代过程和极限行为的关键。我们将讨论一致收敛性与点收敛性,并引入函数空间的概念,为处理函数空间上的不动点问题打下基础。 第二部分:经典基石——三大核心不动点定理 本书的核心内容集中在不动点理论中三座最著名、应用最广泛的里程碑式定理上。我们不仅详细阐述这些定理的陈述,更着重于剖析其证明的关键步骤和内在逻辑。 2.1 巴拿赫压缩映射定理(Banach Fixed Point Theorem) 作为不动点理论的“入门钥匙”,压缩映射定理在构造性证明中占据核心地位。我们将详细讨论压缩映射的定义、完备度量空间上的唯一不动点存在性证明,并深入分析其实际应用,例如证明常微分方程(ODE)的局部解的存在性(通过皮卡迭代法)。我们还将讨论该定理的误差估计及其在数值分析中的重要性。 2.2 布劳威尔不动点定理(Brouwer Fixed Point Theorem) 布劳威尔定理将不动点理论提升到了更抽象的拓扑层面。我们介绍二维和三维情况下的直观几何意义,随后转向 $n$ 维标准单纯形 $Delta^n$ 上的证明。本书将采用拓扑学中更易于理解的证明思路(例如基于奇偶性的论证或与度函数相关的概念),以期帮助读者掌握这一非构造性定理的精髓。该定理在经济学(如瓦尔拉斯均衡)中的应用将被着重讨论。 2.3 庞加莱旋转向量定理(Poincaré Fixed Point Theorem)及其推广 虽然不如前两者那样常用,但庞加莱定理在特定几何背景下具有重要意义。本章节将介绍在紧致凸集上的映射不动点问题,并自然过渡到更具包容性的舍弗定理。 第三部分:泛化与扩展——更广阔的函数空间 在奠定了度量空间上的基础后,本书将视野扩展到更抽象、更强大的函数空间,特别是赋范线性空间和更一般的一致凸巴拿赫空间。 3.1 舍弗不动点定理(Schauder Fixed Point Theorem) 舍弗定理是布劳威尔定理在无限维空间中的推广,它在处理偏微分方程(PDE)的解的存在性问题中起着决定性作用。我们将讨论在凸紧集上的连续映射不动点存在性,并分析该定理在形式化证明中所涉及的拓扑工具,如紧集、分离性等。 3.2 不动点理论在凸优化中的应用 我们将探讨不动点理论与变分不等式、均衡问题之间的密切关系。特别是对Kakutani不动点定理的介绍,它在非合作博弈论和经济均衡模型中提供了强有力的理论支持。 3.3 更一般的拓扑不动点理论 为了完成理论的闭环,本书将简要介绍不动点理论在更一般拓扑结构下的结果,包括一些基于吸引性(Contractive-like mappings)的概念,以及如何利用不动点理论来分析迭代过程的稳定性。 第四部分:应用聚焦——不动点理论的实践价值 理论的价值在于其应用性。本书的最后一部分将聚焦于不动点理论如何在具体的数学分支中发挥作用。 4.1 常微分方程(ODEs) 详细展示皮卡-林德勒夫(Picard-Lindelöf)定理的证明如何直接依赖于巴拿赫压缩映射定理,并讨论柯西问题解的存在性与唯一性。 4.2 积分方程与泛函分析 讨论如何将某些线性与非线性积分方程转化为函数空间上的不动点问题,并利用舍弗定理证明这些方程的解的存在性。 4.3 经济学与博弈论 深入探讨布劳威尔定理和Kakutani定理在证明市场均衡、纳什均衡存在性中的关键作用,展示不动点理论如何成为现代经济学分析的数学骨架。 结论与展望 《不动点理论导论(英文版)》旨在成为一本结构完整、内容丰富的学习指南。通过对经典定理的深入剖析和对现代应用的恰当介绍,本书力求使读者不仅掌握不动点理论的工具箱,更能体会到这一数学领域跨越多个学科的普适之美和强大力量。本书的编写遵循数学教材的最高标准,注重概念的清晰界定和证明的逻辑严密性,确保读者在学习过程中获得扎实的理论功底和开阔的应用视野。