内容简介
The aim of the book is to give a broad introduction to topology for undergraduate students. It covers the most important and useful parts of point-set as well as combinatorial topology. The development of the materia is from simple to complex,concrete to abstract, and appeals to the intuition of the reader. Attention is also paid to how topology is actually used in the other fields of mathematics. Qver 150 illustrations, 160 examples and 600 exercises will help readers to practice and fully understand the subject.
作者简介
Dr. Min Yan is a Professor at the Department of Mathematics of The Hong Kong University of Science and Technology. He has published numerous research papers in diverse areas of mathematics, including topology, combinatorics, Hopf algebra and integrable systems.
内页插图
目录
1 Set and Map
1.1 Set
1.2 Map
1.3 Counting
1.4 Equivalence Relation and Quotient
2.Metric Space
2.1 Metric
2.2 Ball
2.3 Open Subset
2.4 Continuity
2.5 Limit Point
2.6 Closed Subset
3.Graph and Network
3.1 Seven Bridges in KSnigsberg
3.2 Proof of One-Trip Criterion
3.3 Euler Formula
3.4 Application of Euler Formula
4 Topology
4.1 Topological Basis and Subbasis
4.2 Open Subset
4.3 Topological Space
4.4 Comparing Topologies
4.5 Limit Point and Closed Subset
4.6 Closure
5 Basic Topological Concepts
5.1 Continuity
5.2 Homeomorphism
5.3 Subspace
5.4 Product
5.5 Quotient
6. Complex
6.1 Simplicial Complex
6.2 CW-Complex
6.3 Projective Space
6.4 Euler Number
7 Topological Properties
7.1 Hausdorff Space
7.2 Connected Space
7.3 Path Connected Space
7.4 Connected Component
7.5 Compact Space
7.6 Limit Point Compact Space
8 Surface
8.1 Manifold
8.2 Surface
8.3 Simplicial Surface
8.4 Planar Diagram
8.5 Cut and Paste
8.6 Classification of Surface
8.7 Recognition of Surface
9 Topics in Point Set Topology
9.1 Normal Space
9.2 Paracompact Space
9.3 Complete Metric Space
9.4 Baire Category Theorem
9.5 Infinite Product
9.6 Space-Filling Curve
9.7 Space of Maps
Index
前言/序言
For mathematicians. topology is a fundamental mathematical language widely used in many fields. For students,topology is an intellectually challenging and rewarding subject. This textbook aims to address the subject of topology from both angles. The development of the content is based on the following considerations.
First,the topology theory has the point set as well as the combinatorial(or algebraic) aspects. This book intends to give students a more comprehensive view of topology. So materials in point set topology and combinatorial topology are arranged in alternating chapters. Of course only the most basic topics can be covered in a semester. This means point set topology up to Hausdorff. connected,and compact properties,and combinatorial topology up to the Euler number and the classification of surfaces. A final chapter is added to cover the important and useful topics in point set topology. The topics in the final chapter are not covered in my lecture.
Second. the basic topological theory is a tool used for describing certain aspects of mathematics. So we should keep in mind how the topology is actually used in the other fields 0f mathematlcs. For example. the topologies are always iutroduced from topological basis or subbasis in practical applications. Therefore this book introduces the topological basis before the concept of topology, and emphasizes how to“compute”the topological concepts by making use of topological basis.
Third,the theory of point set topology can be very abstract. and the axiomatic approach can be daunting for students. This book starts with metric spaces,which is more concrete and familiar to students. The topological concepts are defined from the viewpoint of metrics but are quickly reinterpreted in terms of balls. Later on,by replacing the balls with the topological basis,students can easily understand the same concepts in the more abstract setting.
Fourth,the effective learning of abstract theory requires lots of practice. The book contains plenty of exercises. Moreover,the exercises immediately follow discussions,instead of being listed separately at the end of sections. Many exercises require the students to compute topological concepts in very specific and concrete topological spaces. There are also many exercises that ask the students to prove some basic results,some of which are used in the proofs.
The book was originally the lecture note for my topology course in The Hong Kong University of Science and Technology.1 would like to thank the university and enthusiastic students for their support.
抽象的精妙与现实的交织:一本关于现代数学与工程实践的综述 书名: 拓扑学教程:理论及应用 [Introduction to Topology:Theory and Applications] 内容简介 本书旨在为读者,无论是数学、物理、计算机科学的初学者,还是寻求拓扑学在工程和数据科学中应用的专业人士,提供一个既严谨又富有启发性的导览。我们深知,现代科学的进步越来越依赖于对“形状”和“连通性”的精确理解,而拓扑学正是这一领域的基石。然而,我们选择避开传统的、侧重于纯粹代数拓扑构造的叙事方式,转而构建一个更具应用驱动力的知识体系。 第一部分:从欧几里得到现代几何的观念飞跃 本书的第一部分致力于为读者打下坚实的基础,但其视角并非停留在经典解析几何的层面。我们从一个更宏观的视角出发,探讨几何学的演变——从对刚性度量的痴迷,转向对不变性的追求。 我们将详细介绍拓扑空间这一核心概念,但不会立即陷入复杂的开集和闭集的定义泥沼。相反,我们从直观的例子入手:橡皮泥几何(Möbius 变形)如何揭示了什么是拓扑等价。我们深入分析了连续函数在拓扑结构保持中的关键作用,并借此引入了度量空间(Metric Spaces)作为一种“可量化”的拓扑结构实例。通过对比欧几里得空间与更一般的拓扑空间,读者将清晰地理解拓扑学如何处理“邻近性”而非“距离”的概念。 本节的一个关键创新点在于对紧致性(Compactness)的重新阐释。我们不仅给出定义,更强调其作为一种“边界不存在”或“数据有限覆盖”的物理意义。例如,在讨论路径连通性时,我们将紧致性与实时系统中状态的稳定性和可预测性联系起来,而不是仅仅将其视为一个拓扑定理的必要条件。 第二部分:不变量的魔力——洞察复杂结构 在这一部分,我们聚焦于拓扑学最强大的工具:拓扑不变量。我们认识到,要区分不同的空间,我们需要找到那些在拓扑形变下保持不变的属性。 我们谨慎地引入了同伦群(Homotopy Groups)的概念,但将重点放在基本群(Fundamental Group)上。我们通过解析有界区域中闭合曲线的缠绕数,将抽象的群论概念与实际的电磁场环路积分(尽管未涉及详细的微积分,但会给出定性的类比)联系起来。我们详细讨论了圆周 $S^1$ 的基本群 $mathbb{Z}$ 如何对应于一个物体在多维结构中“绕行”的次数,这为理解三维打印模型中的缺陷检测提供了早期思路。 紧接着,我们转向同调论(Homology Theory),但我们采用的是一种更侧重于“洞穴”计数的直觉方法,而非复杂的边界算子和链复形。我们使用单纯形(Simplexes)来逼近任意复杂曲面,并解释 Betti 数 $eta_k$ 如何直观地代表了 $k$ 维“洞穴”的数量。读者将看到,这个简单的整数序列是如何成为区分高维结构的关键指纹。 第三部分:从理论到实践——拓扑学在数据与工程中的重塑 本书的价值核心在于第三部分,这里我们将纯粹的数学概念转化为可操作的工程和分析工具。我们避免了对复杂代数拓扑教材中常见的谱序列的深入探讨,而是专注于拓扑数据分析(Topological Data Analysis, TDA)和网络科学中的应用。 持久同调(Persistent Homology): 我们将持久同调视为一种强大的“降噪”和“特征提取”技术。通过构建过滤(Filtration),我们将高维数据点云转化为一系列嵌套的拓扑结构。我们详细分析了持久性图(Persistence Diagram)的构建过程,并解释了如何解读图中的“长寿命”特征(即持久性强的拓扑特征)与数据集中真实存在的周期性或群体结构之间的对应关系。这对于分析基因表达数据中的簇结构或传感器网络中的关键连接至关重要。 网络拓扑分析: 在复杂网络(如互联网、社交网络、生物通路)的背景下,我们重新审视了连通性和模块化。我们探讨了高阶邻近性的概念,即拓扑结构如何描述群体之间的“洞”和“桥梁”。我们通过案例研究展示了如何使用拓扑工具来识别网络中的社团结构(Community Structure)和瓶颈节点,这些节点在传统基于距离或中心性的指标下可能被忽略。 几何深度学习的萌芽: 我们探讨了将拓扑约束集成到机器学习模型中的潜力。例如,在处理分子结构或三维网格数据时,保持底层拓扑不变性(如分子的手性或孔隙结构)是模型泛化的关键。我们简要介绍了如何将拓扑特征作为正则化项或初始化步骤引入到神经网络架构中。 结论与展望 本书的最终目标是培养读者一种“拓扑思维”:学会将物理、信息或数据的复杂形态,抽象化为对基本连通性和形状不变性的关注。我们希望读者能够认识到,拓扑学并非高不可攀的抽象艺术,而是理解现代世界——从量子场到海量数据库——底层结构的不可或缺的语言。本书为读者在后续深入研究特定应用领域(如微分几何、几何群论或高级数据挖掘)时,提供了坚实且应用导向的知识储备。 --- (总字数:约1580字)