دانلود کتاب Undergraduate algebraic geometry

This book is intended to provide us with a short (135 pages), down to earth and fluently motivated introduction to algebraic geometry. And it does a great job. While the author does not clearly state his intentions in advance, I think it would be safe to assume that this is meant to accompany a more standard text on the subject (Hartshorne, Harris, Shafarevich, etc), and that the author’s main goal was to give the quickest possible route to the heart of the subject, making sure the reader stays interested throughout rather than that he is presented with the firmest logical structure. I would like to stress that despite of what I wrote so far, this book does present rigorous proofs and clear definitions.

The style is friendly, straightforward and unpretentious. Everything is well motivated, and one occasionally gets to hear the author’s personal perspective or view about a certain topic. I will quote two examples. When discussing the Zariski topology, the author writes “The Zariski topology may cause trouble to some students; since it is only being used as a language, and has almost no content, the difficulty is likely to be psychological rather than technical”. This was very calming for me to read, as I have been previously struggling with the “deep meaning” of the Zariski topology, and no book has had the honesty to tell me that I shouldn’t worry that much about it. As a second example of the author’s style, after a Q.E.D. in page 53 the author explains that “The proof of (b) is a typical algebraist’s proof: it’s logically very neat, but almost completely hides the content: the real point is that …”

Chapter 1 begins with the concrete example of conics, intended to motivate the later definitions of the projective plane. Next elliptic curves and their group law is discussed. The chapter ends with a brief survey of the genus of curves.

Chapter 2 is more technical; its purpose is to build the algebraic foundations needed for Hilbert’s Nullstellensatz. Among topics covered are Noetherian rings, Hilbert’s Basis Theorem, algebraic sets, the Zariski topology, prime ideals and a nice motivation for the Nullstellensatz. Next coordinate rings, morphisms, varieties and other standard topics are introduced.

Chapter 3, titled “Applications”, uses the previous material to discuss some nice geometric topics. I especially enjoyed the section on the 27 lines on a cubic surface.

I would highly recommend this book to anyone not very familiar with algebraic geometry; for instance, it could be a good reading to decide if you want to take a more serious study (e.g. a university course) of the subject. If I were to suggest only one text for someone who just wants to know what algebraic geometry is all about, it would definitely be this one.