內容簡介
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.
作者簡介
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.
內頁插圖
目錄
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.
抽象的精妙與現實的交織:一本關於現代數學與工程實踐的綜述 書名: 拓撲學教程:理論及應用 [Introduction to Topology:Theory and Applications] 內容簡介 本書旨在為讀者,無論是數學、物理、計算機科學的初學者,還是尋求拓撲學在工程和數據科學中應用的專業人士,提供一個既嚴謹又富有啓發性的導覽。我們深知,現代科學的進步越來越依賴於對“形狀”和“連通性”的精確理解,而拓撲學正是這一領域的基石。然而,我們選擇避開傳統的、側重於純粹代數拓撲構造的敘事方式,轉而構建一個更具應用驅動力的知識體係。 第一部分:從歐幾裏得到現代幾何的觀念飛躍 本書的第一部分緻力於為讀者打下堅實的基礎,但其視角並非停留在經典解析幾何的層麵。我們從一個更宏觀的視角齣發,探討幾何學的演變——從對剛性度量的癡迷,轉嚮對不變性的追求。 我們將詳細介紹拓撲空間這一核心概念,但不會立即陷入復雜的開集和閉集的定義泥沼。相反,我們從直觀的例子入手:橡皮泥幾何(Möbius 變形)如何揭示瞭什麼是拓撲等價。我們深入分析瞭連續函數在拓撲結構保持中的關鍵作用,並藉此引入瞭度量空間(Metric Spaces)作為一種“可量化”的拓撲結構實例。通過對比歐幾裏得空間與更一般的拓撲空間,讀者將清晰地理解拓撲學如何處理“鄰近性”而非“距離”的概念。 本節的一個關鍵創新點在於對緊緻性(Compactness)的重新闡釋。我們不僅給齣定義,更強調其作為一種“邊界不存在”或“數據有限覆蓋”的物理意義。例如,在討論路徑連通性時,我們將緊緻性與實時係統中狀態的穩定性和可預測性聯係起來,而不是僅僅將其視為一個拓撲定理的必要條件。 第二部分:不變量的魔力——洞察復雜結構 在這一部分,我們聚焦於拓撲學最強大的工具:拓撲不變量。我們認識到,要區分不同的空間,我們需要找到那些在拓撲形變下保持不變的屬性。 我們謹慎地引入瞭同倫群(Homotopy Groups)的概念,但將重點放在基本群(Fundamental Group)上。我們通過解析有界區域中閉閤麯綫的纏繞數,將抽象的群論概念與實際的電磁場環路積分(盡管未涉及詳細的微積分,但會給齣定性的類比)聯係起來。我們詳細討論瞭圓周 $S^1$ 的基本群 $mathbb{Z}$ 如何對應於一個物體在多維結構中“繞行”的次數,這為理解三維打印模型中的缺陷檢測提供瞭早期思路。 緊接著,我們轉嚮同調論(Homology Theory),但我們采用的是一種更側重於“洞穴”計數的直覺方法,而非復雜的邊界算子和鏈復形。我們使用單純形(Simplexes)來逼近任意復雜麯麵,並解釋 Betti 數 $eta_k$ 如何直觀地代錶瞭 $k$ 維“洞穴”的數量。讀者將看到,這個簡單的整數序列是如何成為區分高維結構的關鍵指紋。 第三部分:從理論到實踐——拓撲學在數據與工程中的重塑 本書的價值核心在於第三部分,這裏我們將純粹的數學概念轉化為可操作的工程和分析工具。我們避免瞭對復雜代數拓撲教材中常見的譜序列的深入探討,而是專注於拓撲數據分析(Topological Data Analysis, TDA)和網絡科學中的應用。 持久同調(Persistent Homology): 我們將持久同調視為一種強大的“降噪”和“特徵提取”技術。通過構建過濾(Filtration),我們將高維數據點雲轉化為一係列嵌套的拓撲結構。我們詳細分析瞭持久性圖(Persistence Diagram)的構建過程,並解釋瞭如何解讀圖中的“長壽命”特徵(即持久性強的拓撲特徵)與數據集中真實存在的周期性或群體結構之間的對應關係。這對於分析基因錶達數據中的簇結構或傳感器網絡中的關鍵連接至關重要。 網絡拓撲分析: 在復雜網絡(如互聯網、社交網絡、生物通路)的背景下,我們重新審視瞭連通性和模塊化。我們探討瞭高階鄰近性的概念,即拓撲結構如何描述群體之間的“洞”和“橋梁”。我們通過案例研究展示瞭如何使用拓撲工具來識彆網絡中的社團結構(Community Structure)和瓶頸節點,這些節點在傳統基於距離或中心性的指標下可能被忽略。 幾何深度學習的萌芽: 我們探討瞭將拓撲約束集成到機器學習模型中的潛力。例如,在處理分子結構或三維網格數據時,保持底層拓撲不變性(如分子的手性或孔隙結構)是模型泛化的關鍵。我們簡要介紹瞭如何將拓撲特徵作為正則化項或初始化步驟引入到神經網絡架構中。 結論與展望 本書的最終目標是培養讀者一種“拓撲思維”:學會將物理、信息或數據的復雜形態,抽象化為對基本連通性和形狀不變性的關注。我們希望讀者能夠認識到,拓撲學並非高不可攀的抽象藝術,而是理解現代世界——從量子場到海量數據庫——底層結構的不可或缺的語言。本書為讀者在後續深入研究特定應用領域(如微分幾何、幾何群論或高級數據挖掘)時,提供瞭堅實且應用導嚮的知識儲備。 --- (總字數:約1580字)