内容简介
《代数几何入门(英文版)》旨在深层次讲述代数几何原理、20世纪的一些重要进展和数学实践中正在探讨的问题。该书的内容对于对代数几何不是很了解或了解甚少,但又想要了解代数几何基础的数学工作者是非常有用的。目次:仿射代数变量;代数基础;射影变量;Quasi射影变量;经典结构;光滑;双有理几何学;映射到射影空间。
读者对象:《代数几何入门(英文版)》适用于数学专业高年级本科生、研究生和与该领域有关的工作者。
内页插图
目录
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
精彩书摘
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.
现代代数几何的基石:理论与应用的桥梁 《现代代数几何导论》 本书旨在为读者提供一个全面且深入的现代代数几何的入门指南,系统地梳理了该领域的核心概念、关键理论框架及其在数学及其他相关科学中的广泛应用。代数几何,作为连接代数、几何和分析的强大工具,是现代数学的核心支柱之一,其影响力贯穿于数论、拓扑学、复分析乃至理论物理等多个领域。 本书的编排遵循由浅入深、逻辑严谨的原则,力求在保持数学严谨性的同时,提供清晰直观的几何洞察。我们假设读者已经具备扎实的抽象代数基础(如环、域、模的基本概念)以及微积分和基础拓扑学的知识,从而能够迅速进入代数几何的独特世界。 第一部分:预备知识与经典基础 本部分将构建读者理解现代代数几何所需的代数和几何框架。 第一章:域与多项式环的代数回顾 我们将从复习域扩张、伽罗瓦理论的基础概念开始,重点关注多项式环 $K[x_1, dots, x_n]$ 上的结构。深入探讨理想(Ideals)的概念,引入诺特环(Noetherian Rings)的性质,这是理解代数集合结构的关键。特别地,我们将详述希尔伯特零点定理(Hilbert’s Nullstellensatz)及其在将代数问题转化为几何问题中的核心地位。零点定理被视为连接代数与欧几里得空间中代数集之间的“字典”。 第二章:射影空间与代数集 本书将明确区分仿射空间(Affine Space) $mathbb{A}^n_K$ 和射影空间(Projective Space) $mathbb{P}^n_K$。射影空间因其完备性和处理“无穷远点”的能力,在现代代数几何中占据中心地位。我们将详细介绍如何通过齐次坐标来定义射影空间,并阐述齐次多项式与射影代数集之间的对应关系。本章还会探讨代数集的结构,如维数(Dimension)的定义,它通过多项式环的Krull维度来衡量几何对象的“大小”。 第三章:簇(Varieties)的几何结构 本章引入“簇”的概念,这是对代数集的更精细研究,特别是当我们将讨论转移到更抽象的代数结构时。我们将介绍不可约簇、有理映射(Rational Maps)和双有理几何(Birational Geometry)的初步概念。重点讨论曲线(Curves)作为最基础的非平凡对象,分析其光滑点(Smooth Points)与奇点(Singular Points)的区别,为后续引入切空间和微分结构打下基础。 第二部分:方案论(Schemes)的兴起与抽象化 现代代数几何的核心突破在于引入了“方案”(Scheme)的概念,它极大地推广了代数集的定义,使其能够处理具有“多重性”或定义在任意交换环上的几何对象。 第四章:预备层论与预层(Presheaves) 为了构建方案的理论,必须引入层论的语言。本章将介绍拓扑空间上的预层和层,特别是关于结构层的概念。通过局部地描述全局对象,层论提供了一种强大的工具来处理局部可积的几何信息。 第五章:环作为空间的体现:环谱(The Spectrum of a Ring) 这是本书最关键的章节之一。我们将定义环 $R$ 的谱 $ ext{Spec}(R)$,它由 $R$ 的素理想(Prime Ideals)构成。通过将每个素理想视为一个“点”,我们赋予了代数结构一个拓扑空间结构。随后,我们将构建结构层 $mathcal{O}_{ ext{Spec}(R)}$,从而定义出第一个也是最基本的方案——仿射方案(Affine Scheme)。本章将深入探讨素理想与极大理想(Maximal Ideals)在 $ ext{Spec}(R)$ 上的几何意义。 第六章:从代数集到方案的推广 本章致力于将前一部分的代数集概念提升到方案的语言下。我们将展示如何将任意交换环 $R$ 构造为一个方案 $X = ext{Spec}(R)$,并解释为什么方案论能够自然地处理代数几何中的各种奇点和退化现象。介绍如何定义方案之间的态射(Morphisms of Schemes),以及什么是“代数簇的概形化”(Generalization of Algebraic Varieties to Schemes)。 第七章:射影方案与概型(Projective Schemes) 如同在代数集中一样,射影空间在方案论中也至关重要。我们将定义齐次环(Graded Rings)及其方案 $ ext{Proj}(S)$,并将其作为射影空间的概形化。本章将对比 $ ext{Spec}$ 和 $ ext{Proj}$ 的性质,展示后者如何编码了更丰富的几何信息,尤其是在处理代数曲线和曲面的上同调理论时。 第三部分:局部性质、维数与光滑性 在方案的框架下,我们重新审视几何对象的局部性质,并引入更高级的代数工具来分析这些性质。 第八章:局部环与正则点 对方案的每个点 $p$,我们构造其局部环 $mathcal{O}_{X,p}$。本章详细分析局部环的性质,特别是其极大理想。我们将定义正则点(Regular Points)或光滑点,它们对应于局部环是正则局部环(Regular Local Ring)的点。这将通过分析局部环的“正则性”——即 Krull 维度等于其正则局部化中极大理想的最小生成元个数——来严格界定。 第九章:模(Sheaf of Modules)与向量丛(Vector Bundles) 向量丛(在代数几何中称为凝聚层,Coherent Sheaves)是研究几何对象上线性代数结构的基础。我们将从模的范畴出发,定义相干层,例如 $mathcal{O}_X$ 本身就是一个凝聚层。深入探讨局部自由层(Locally Free Sheaves)与向量丛的对应关系,这是连接代数与微分几何(或复分析)的关键桥梁。 第十章:同调代数与上同调(Cohomology) 本章将引入代数几何中不可或缺的工具——上同调理论。我们将首先概述链复形和导出函子的基本概念,然后重点关注层上同调(Sheaf Cohomology)。特别是对 $mathcal{O}_X$ 层的上同调 $H^i(X, mathcal{O}_X)$ 的计算,它直接衡量了全局截面与局部截面之间的“不匹配”程度。这为理解复流形上的塞尔上同调(Serre Cohomology)奠定了基础。 第四部分:特定空间与应用展望 第十一章:代数曲线的几何 将理论应用于一维对象——代数曲线。介绍曲线的亏格(Genus)的概念,并展示如何利用欧拉示性数和黎曼-罗赫定理(Riemann-Roch Theorem)来计算曲线上的线性系统。我们将详细阐述经典的平面三次曲线(如椭圆曲线)的几何特性和加法群结构。 第十二章:高维几何的初步探索 展望更高维度的情形,介绍卡拉比-丘流形(Calabi-Yau Manifolds)和 Fano 流形等重要的代数三维空间分类。简要介绍 Mori 计划和 BCDR 分类理论的宏伟蓝图,展示代数几何在解决复杂空间构造问题上的强大潜力。 本书的结构旨在培养读者从“几何想象”到“代数证明”的思维转换能力,为深入研究现代代数几何、代数拓扑或理论物理中的相关课题做好充分准备。