# Prerequisites for Atiyah Macdonald

I am currently doing a one semester course on groups and rings where we have learned about (so far):

Definitions of groups, subgroups, cyclic and normal subgroups, the symmetric group, homomorphisms, isomorphisms, The Correspondence Theorem, Product and Quotient Groups. As of yesterday's lecture we learned about the First Isomorphism Theorem and a little bit about rings.

By the end of the course we should have done rings, endomorphisms, The Orbit-Stabilizer Theorem and subjects which I am not sure about.

I am wondering if this would be sufficient to start Atiyah Macdonald; I have opened the first few pages and it looks hard. For those who have done it, what do you think are the prerequisites before doing this? Perhaps something like Herstein's Topics in Algebra?

Thanks.

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Algebra Prerequisites: A knowledge of the following results:

(1) The definition of ring, subring, ideal and quotient ring.

(2) The correspondence theorem in ring theory.

(3) The notion of a prime ideal, of a maximal ideal, and the facts that an ideal $I$ of a commutative ring $A$ is prime (resp. maximal) if and only if $R/I$ is an integral domain (resp. field).

In short, the first 4 pages of Atiyah and Macdonald should be in the nature of a review for you.

(4) An extensive knowledge of field theory and Galois theory; for example, in addition to the elements of Galois theory, you should probably be familiar with separable and inseparable extensions and transcendental extensions. (Chapter 5 on integral extensions of commutative rings is better appreciated if you have already studied the theory of algebraic extensions of fields. Transcendental extensions are discussed in the chapter on dimension theory. Finally, at least one result in chapter 9 (on Dedekind domains) and a few exercises in chapter 5 require a knowledge of separable and inseparable extensions in field theory.)

(5) I think the Jordan-H\"older theorem in group theory is alluded to at some point in the text. (The discussion of modules of finite length in chapter 6.)

Topology Prerequisites: A knowledge of the following results:

(1) The definition of a topological space, of open and closed sets, of a basis for a topology, of compact sets and Hausdorff spaces, of subspaces, and of continuous functions. (In the text itself, point-set topology is most prominent in the chapter on completions but you will need point-set topology for the exercises as well.)

(2) Urysohn's lemma is needed to solve exercise 4 in chapter 4 and at least one exercise in chapter 1 (on the characterization of the maximal spectrum of a commutative ring).

Summary: The most important prerequisites are point-set topology and the theory of fields. You can read chapters 1-4 of Atiyah and Macdonald with only (1)-(3) of the Algebra Prerequisites above and chapter 5 of Atiyah and Macdonald with a knowledge of algebraic and separable extensions of fields. Chapter 9 of Atiyah and Macdonald also requires a knowledge of separable extensions of fields and chapter 10 of Atiyah and Macdonald requires a knowledge of (1) of the Topology Prerequisites above.

However, in order to do the exercises in Atiyah and Macdonald (which are the most important part of the text, in my opinion), you will need all the prerequisites above. Point-set topology is an essential prerequisite in the exercises because many exercises discuss affine schemes. Also, the elements of Galois theory are needed in some exercises in chapter 5, for example.

I hope this helps!

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Thanks, by the way I think this would mean reading a lot on galois theory and things like that, which would mean at least Algebra II for me. –  fpqc Aug 30 '11 at 23:29
As for the topology prerequisites maybe Munkres can help to cover that... –  fpqc Aug 30 '11 at 23:31
@DBLim I think chapters 2 and 3 of Munkres' textbook should furnish more than enough preparation in regard to point-set topology. However, you probably do not need to wait until Algebra II to learn Galois theory (you could learn Galois theory in the summer). –  Amitesh Datta Aug 31 '11 at 0:15
+1 for mentioning the exercises. The amount of commutative algebra one learns from this small, slender, book, with its hundreds of exercises, has always fascinated me. Easily one of the best math books I've ever read. –  user641 Aug 31 '11 at 0:17
@Amitesh Datta Rudin's chapter 2 has some basic rudiments of topology... –  fpqc Aug 31 '11 at 0:39

You don't actually need a lot of abstract algebra knowledge before reading A-M. You will need to know the definitions of ideals, fields, and some basic group theory.

A-M is a hard book, and reading it is a pain, and so I cannot really recommend it for self-study. It is however a good book, one of the best I've read.

You could, for example, read it alongside Eisenbuds "Commutative Algebra with a view towards algebraic geometry", which is a really good (though enormous) book.

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That's what I've heard a lot of people say that A-M is very dry, what about this Eisenbud text? –  fpqc Aug 30 '11 at 23:30
@Lim: I wouldn't call A-M dry. It is "dense". Eisenbud is very vividly written with more examples than A-M and good exercises (his presentation is also more geometric). –  Fredrik Meyer Aug 30 '11 at 23:41
My god Eisenbud's is about 600 pages long! –  fpqc Aug 30 '11 at 23:43
@DBLim The prerequisites for reading Eisenbud's textbook are mostly subsumed in the appendices at the back of the book. However, you will need to spend at least a reasonable amount of time reading the appendices. For example, you will need to learn about free modules, projective modules, injective modules, complexes, the Tor and Ext functors and some multilinear algebra. The book also emphasizes computation (and has a chapter devoted to Grobner bases) but this is certainly not a bad thing (computational commutative algebra is very interesting). –  Amitesh Datta Aug 31 '11 at 0:04
@Amitesh: Well, I was merely offering an opposing opinion, from the point of view of an undergraduate mathematician with a more conventional background. Not everyone has had the benefit of learning so much, whether by their own efforts or otherwise, by the age of 16! –  Zhen Lin Aug 31 '11 at 3:55