Modern Algebra II

Math 627B
Course number: 22082
Spring 2016
Meeting TuTh 4:00-5:15
GMCS 305
San Diego State University
Last class: Thurs. May 5.
Final Exam: Tues. May. 10, 3:30 - 5:30.

Professor: Mike O'Sullivan
Web page:
Office: GMCS #579, ext. 594-6697
Office Hours: W. 3:00-5:00 Tu Th, 5:15-6:00
                         I'm in lots of meetings and I am traveling a bit this semester, so some of the Wednesday office hours will be cancelled. Please feel free to contact me by email with questions or to make an appointment.

Detailed Information

Additional notes on groups

Course Description

The goal of this course is to introduce the main theorems and standard examples in Galois theory. Along the way we will do some more advanced group theory (Sylow theorems, composition series, group extensions). We will focus on interesting examples of the Galois correspondence for finite fields, number fields and function fields.

The roots of Galois theory lead back to problems posed by the ancient Greeks and their predecessors. Greek geometers achieved remarkable constructions with ruler and compass, but a number of simple, nagging, problems remained unresolved until the Rennaisance. For example: Is it possible to trisect an arbitrary angle? Which regular polygons are constructible? In algebra, several civilizations investigated the solution of a quadratic equation (see MathWorld article ). The attempt to find a solution for higher degree equations was another project that occupied numerous mathematicians. The resolution of these ancient questions culminated in Galois' theory of fields. It is a delightful subject, and the modern treatment highlights the interplay between three key areas of algebra: groups, rings and fields.

The course begins with an introduction to classical problems and the link with field theory. We will then spend a few days on fundamental properties of polynomial rings: irreducibility, derivatives, and some related topics (including the abc conjecture). After rings we move to more advanced group theory. We will start with concrete constructions of groups: groups from rings, automorphism groups, semi-direct products, group extensions, group representations. Then we develop more theory: group actions, the Sylow theorems, composition series, solvable groups. At some point we return to field theory: the classification and structure of finite fields, the standard non-separable extension, normal and Galois extensions. We finish with Galois' theorem connecting field extensions to automorphism groups. We apply the theory to as many examples and classical problems as time allows.



I will assume that you have a solid understanding of the basics of groups, rings and fields (SDSU's Math 627A). The following fundamental topics play a recurring role so I suggest that you review them during the first weeks of the semester. See my notes for a concise presentation, see one of the texts above for more details.
  • Groups: Normal subgroups and the isomorphism theorems.
  • Commutative Rings: Ideals, homomorphisms, and quotient rings.
  • Fields: Field extensions. Adjoining a root of a polynomial. Splitting field of a polynomial.


    There will be several (6-8) homework assignments, two midterms and a final test. For each test, I will give you a very clear idea beforehand of the problems that will appear. The final grade will be weighted roughly as follows.
    Problem Sets 40%
    Midterms 15% each
    Final Exam 30%

    On homework and tests, your solutions should be understandable by a peer, so, not every detail has to be explained, provided a peer would know how to fill in the details. This is the art of exposition, knowing your audience and how to succinctly communicate essentials.

    You are encouraged to work together to solve problems, but you should write the solutions individually.