內容簡介
《代數幾何入門(英文版)》旨在深層次講述代數幾何原理、20世紀的一些重要進展和數學實踐中正在探討的問題。該書的內容對於對代數幾何不是很瞭解或瞭解甚少,但又想要瞭解代數幾何基礎的數學工作者是非常有用的。目次:仿射代數變量;代數基礎;射影變量;Quasi射影變量;經典結構;光滑;雙有理幾何學;映射到射影空間。
讀者對象:《代數幾何入門(英文版)》適用於數學專業高年級本科生、研究生和與該領域有關的工作者。
內頁插圖
目錄
Notes for the Second Printing
Preface
Acknowledgments
Index of Notation
1 Affine Algebraic Varieties
1.1 Definition and Examples
1.2 The Zariski Topology
1.3 Morphisms of Affine Algebraic Varieties
1.4 Dimension
2 Algebraic Foundations
2.1 A Quick Review of Commutative Ring Theory
2.2 Hilberts Basis Theorem
2.3 Hilberts NuUstellensatz
2.4 The Coordinate Ring
2.5 The Equivalence of Algebra and Geometry
2.6 The Spectrum of a Ring
3 Projective Varieties
3.1 Projective Space
3.2 Projective Varieties
3.3 The Projective Closure of an Affine Variety
3.4 Morphisms of Projective Varieties
3.5 Automorphisms of Projective Space
4 Quasi-Projective Varieties
4.1 Quasi-Projective Varieties
4.2 A Basis for the Zariski Topology
4.3 Regular Functions
5 Classical Constructions
5.1 Veronese Maps
5.2 Five Points Determine a Conic
5.3 The Segre Map and Products of Varieties
5.4 Grassmannians
5.5 Degree
5.6 The Hilbert Function
6 Smoothness
6.1 The Tangent Space at a Point
6.2 Smooth Points
6.3 Smoothness in Families
6.4 Bertinis Theorem
6.5 The Gauss Mapping
7 Birational Geometry
7.1 Resolution of Singularities
7.2 Rational Maps
7.3 Birational Equivalence
7.4 Blowing Up Along an Ideal
7.5 Hypersurfaces
7.6 The Classification Problems
8 Maps to Projective Space
8.1 Embedding a Smooth Curve in Three-Space
8.2 Vector Bundles and Line Bundles
8.3 The Sections of a Vector Bundle
8.4 Examples of Vector Bundles
8.5 Line Bundles and Rational Maps
8.6 Very Ample Line Bundles
A Sheaves and Abstract Algebraic Varieties
A.1 Sheaves
A.2 Abstract Algebraic Varieties
References
Index
精彩書摘
The remarkable intuition of the turn-of-the-century algebraic geometerseventually began to falter as the subject grew beyond its somewhat shakylogical foundations. Led by David Hilbert, mathematical culture shiftedtoward a greater emphasis on rigor, and soon algebraic geometry fell outof favor as gaps and even some errors appeared in the subject. Luckily,the spirit and techniques of algebraic geometry were kept alive, primarilyby Italian mathematicians. By the mid-twentieth century, with the effortsof mathematicians such as David Hilbert and Emmy Noether, algebra wassufficiently developed so as to be able once again to support this beautifuland important subject. In the middle of the twentieth century, Oscar Zariski and Andr Weilspent a good portion of their careers redeveloping the foundations of alge-braic geometry on firm mathematical ground. This was not a mere processof filling in details left unstated before, but a revolutionary new approach,based on analyzing the algebraic properties of the set of all polynomial func-tions on an algebraic variety. These innovations revealed deep connectionsbetween previously separate areas of mathematics, such as number the-ory and the theory of Riemann surfaces, and eventually allowed AlexanderGrothendieck to carry algebraic geometry to dizzying heights of abstrac-tion in the last half of the century. This abstraction has simplified, unified,and greatly advanced the subject, and has provided powerful tools usedto solve difficult problems. Today, algebraic geometry touches nearly everybranch of mathematics. An unfortunate effect of this late-twentieth-century abstraction is that ithas sometimes made algebraic geometry appear impenetrable to outsiders.Nonetheless, as we hope to convey in this Invitation to Algebraic Geome-try, the main objects of study in algebraic geometry, affine and projectivealgebraic varieties, and the main research questions about them, are asinteresting and accessible as ever.
前言/序言
These notes grew out of a course at the University of Jyvaskyla in Jan-uary 1996 as part of Finlands new graduate school in mathematics. The course was suggested by Professor Karl Astala, who asked me to give a series of ten two-hour lectures entitled "Algebraic Geometry for Analysts." The audience consisted mainly of two groups of mathematicians: Ph.D. students from the Universities of Jyvaskyla and Helsinki, and mature mathemati-cians whose research and training were quite far removed from algebra.Finland has a rich tradition in classical and topological analysis, and it was primarily in this tradition that my audience was educated, although there were representatives of another well-known Finnish school, mathematical logic.
I tried to conduct a course that would be accessible to everyone, but that would take participants beyond the standard course in algebraic ge-ometry. I wanted to convey a feeling for the underlying algebraic principles of algebraic geometry. But equally important, I wanted to explain some of algebraic geometrys major achievements in the twentieth century, as well as some of the problems that occupy its practitioners today. With such ambitious goals, it was necessary to omit many proofs and sacrifice some rigor.
In light of the background of the audience, few algebraic prerequisites were presumed beyond a basic course in linear algebra. On the other hand,the language of elementary point-set topology and some basic facts from complex analysis were used freely, as was a passing familiarity with the definition of a manifold.
My sketchy lectures were beautifully written up and massaged into this text by Lauri Kahanpaa and Pekka Kekallainen. This was a Herculean effort,no less because of the excellent figures Lauri created with the computer.Extensive revisions to the Finnish text were carried out together with Lauri and Pekka; later Will Traves joined in to help with substantial revisions to the English version. What finally resulted is this book, and it would not have been possible without the valuable contributions of all members of our four-author team.
This book is intended for the working or the aspiring mathematician who is unfamiliar with algebraic geometry but wishes to gain an appreciation of its foundations and its goals with a minimum of prerequisites. It is not in-tended to compete with such comprehensive introductions as Hartshornes or Shafarevichs texts, to which we freely refer for proofs and rigor. Rather,we hope that at least some readers will be inspired to undertake more se-rious study of this beautiful subject. This book is, in short, An Invitation to Algebraic Geometry.
現代代數幾何的基石:理論與應用的橋梁 《現代代數幾何導論》 本書旨在為讀者提供一個全麵且深入的現代代數幾何的入門指南,係統地梳理瞭該領域的核心概念、關鍵理論框架及其在數學及其他相關科學中的廣泛應用。代數幾何,作為連接代數、幾何和分析的強大工具,是現代數學的核心支柱之一,其影響力貫穿於數論、拓撲學、復分析乃至理論物理等多個領域。 本書的編排遵循由淺入深、邏輯嚴謹的原則,力求在保持數學嚴謹性的同時,提供清晰直觀的幾何洞察。我們假設讀者已經具備紮實的抽象代數基礎(如環、域、模的基本概念)以及微積分和基礎拓撲學的知識,從而能夠迅速進入代數幾何的獨特世界。 第一部分:預備知識與經典基礎 本部分將構建讀者理解現代代數幾何所需的代數和幾何框架。 第一章:域與多項式環的代數迴顧 我們將從復習域擴張、伽羅瓦理論的基礎概念開始,重點關注多項式環 $K[x_1, dots, x_n]$ 上的結構。深入探討理想(Ideals)的概念,引入諾特環(Noetherian Rings)的性質,這是理解代數集閤結構的關鍵。特彆地,我們將詳述希爾伯特零點定理(Hilbert’s Nullstellensatz)及其在將代數問題轉化為幾何問題中的核心地位。零點定理被視為連接代數與歐幾裏得空間中代數集之間的“字典”。 第二章:射影空間與代數集 本書將明確區分仿射空間(Affine Space) $mathbb{A}^n_K$ 和射影空間(Projective Space) $mathbb{P}^n_K$。射影空間因其完備性和處理“無窮遠點”的能力,在現代代數幾何中占據中心地位。我們將詳細介紹如何通過齊次坐標來定義射影空間,並闡述齊次多項式與射影代數集之間的對應關係。本章還會探討代數集的結構,如維數(Dimension)的定義,它通過多項式環的Krull維度來衡量幾何對象的“大小”。 第三章:簇(Varieties)的幾何結構 本章引入“簇”的概念,這是對代數集的更精細研究,特彆是當我們將討論轉移到更抽象的代數結構時。我們將介紹不可約簇、有理映射(Rational Maps)和雙有理幾何(Birational Geometry)的初步概念。重點討論麯綫(Curves)作為最基礎的非平凡對象,分析其光滑點(Smooth Points)與奇點(Singular Points)的區彆,為後續引入切空間和微分結構打下基礎。 第二部分:方案論(Schemes)的興起與抽象化 現代代數幾何的核心突破在於引入瞭“方案”(Scheme)的概念,它極大地推廣瞭代數集的定義,使其能夠處理具有“多重性”或定義在任意交換環上的幾何對象。 第四章:預備層論與預層(Presheaves) 為瞭構建方案的理論,必須引入層論的語言。本章將介紹拓撲空間上的預層和層,特彆是關於結構層的概念。通過局部地描述全局對象,層論提供瞭一種強大的工具來處理局部可積的幾何信息。 第五章:環作為空間的體現:環譜(The Spectrum of a Ring) 這是本書最關鍵的章節之一。我們將定義環 $R$ 的譜 $ ext{Spec}(R)$,它由 $R$ 的素理想(Prime Ideals)構成。通過將每個素理想視為一個“點”,我們賦予瞭代數結構一個拓撲空間結構。隨後,我們將構建結構層 $mathcal{O}_{ ext{Spec}(R)}$,從而定義齣第一個也是最基本的方案——仿射方案(Affine Scheme)。本章將深入探討素理想與極大理想(Maximal Ideals)在 $ ext{Spec}(R)$ 上的幾何意義。 第六章:從代數集到方案的推廣 本章緻力於將前一部分的代數集概念提升到方案的語言下。我們將展示如何將任意交換環 $R$ 構造為一個方案 $X = ext{Spec}(R)$,並解釋為什麼方案論能夠自然地處理代數幾何中的各種奇點和退化現象。介紹如何定義方案之間的態射(Morphisms of Schemes),以及什麼是“代數簇的概形化”(Generalization of Algebraic Varieties to Schemes)。 第七章:射影方案與概型(Projective Schemes) 如同在代數集中一樣,射影空間在方案論中也至關重要。我們將定義齊次環(Graded Rings)及其方案 $ ext{Proj}(S)$,並將其作為射影空間的概形化。本章將對比 $ ext{Spec}$ 和 $ ext{Proj}$ 的性質,展示後者如何編碼瞭更豐富的幾何信息,尤其是在處理代數麯綫和麯麵的上同調理論時。 第三部分:局部性質、維數與光滑性 在方案的框架下,我們重新審視幾何對象的局部性質,並引入更高級的代數工具來分析這些性質。 第八章:局部環與正則點 對方案的每個點 $p$,我們構造其局部環 $mathcal{O}_{X,p}$。本章詳細分析局部環的性質,特彆是其極大理想。我們將定義正則點(Regular Points)或光滑點,它們對應於局部環是正則局部環(Regular Local Ring)的點。這將通過分析局部環的“正則性”——即 Krull 維度等於其正則局部化中極大理想的最小生成元個數——來嚴格界定。 第九章:模(Sheaf of Modules)與嚮量叢(Vector Bundles) 嚮量叢(在代數幾何中稱為凝聚層,Coherent Sheaves)是研究幾何對象上綫性代數結構的基礎。我們將從模的範疇齣發,定義相乾層,例如 $mathcal{O}_X$ 本身就是一個凝聚層。深入探討局部自由層(Locally Free Sheaves)與嚮量叢的對應關係,這是連接代數與微分幾何(或復分析)的關鍵橋梁。 第十章:同調代數與上同調(Cohomology) 本章將引入代數幾何中不可或缺的工具——上同調理論。我們將首先概述鏈復形和導齣函子的基本概念,然後重點關注層上同調(Sheaf Cohomology)。特彆是對 $mathcal{O}_X$ 層的上同調 $H^i(X, mathcal{O}_X)$ 的計算,它直接衡量瞭全局截麵與局部截麵之間的“不匹配”程度。這為理解復流形上的塞爾上同調(Serre Cohomology)奠定瞭基礎。 第四部分:特定空間與應用展望 第十一章:代數麯綫的幾何 將理論應用於一維對象——代數麯綫。介紹麯綫的虧格(Genus)的概念,並展示如何利用歐拉示性數和黎曼-羅赫定理(Riemann-Roch Theorem)來計算麯綫上的綫性係統。我們將詳細闡述經典的平麵三次麯綫(如橢圓麯綫)的幾何特性和加法群結構。 第十二章:高維幾何的初步探索 展望更高維度的情形,介紹卡拉比-丘流形(Calabi-Yau Manifolds)和 Fano 流形等重要的代數三維空間分類。簡要介紹 Mori 計劃和 BCDR 分類理論的宏偉藍圖,展示代數幾何在解決復雜空間構造問題上的強大潛力。 本書的結構旨在培養讀者從“幾何想象”到“代數證明”的思維轉換能力,為深入研究現代代數幾何、代數拓撲或理論物理中的相關課題做好充分準備。