Math 4720 & 5210 (Spring 2024) Homepage

Advanced Topics in Modern Algebra:
Galois Theory

News & Announcements

5/03
Done! Great job all.

If you ever have any questions about this class, other math classes, or whatever, my door is open.

Stop by or email anytime - even just to say "Hi"!

Notes to future self:
• Maybe add a (small) 8th homework set.
• Differential algebra handouts could use some smoothing out.
    Add reference: "Computer Algebra" by Lamagna.
    See 7.11 "Risch DE"

4/19
Final Project & Presentation Guidelines and Suggested Topics:

Instead of a Final Exam, we will have a final "project" of sorts. Everyone should select a topic somehow related to this class (I have a few suggestions listed below). This should be something that we didn't cover or at least something we didn't cover in detail.

  • Pick and topic and clear it with me (in person or via email).
  • Study your topic.
  • Create a handout. This should be at least one page front and back.
    • Your classmates are your audience. Build off of background from class.
    • Let us know where to go for further reading somewhere in your handout.
      [Cite any valuable resources - like websites and textbooks - that you found.]
    • You might want to give a brief historical blurb.
    • Would worked out examples help us understand your topic? If so, include a few.
    • Is your topic about a "big theorem"? Include its proof or a sketch of its proof.
  • During the final exam period, everyone will give a brief presentation of their topic. Our class is small so everyone should have as much time as they need. Plan on having about 10 minutes.
  • Your presentation could use slides (like tex or powerpoint) or you could just use the board and your handout.
  • I can print off copies of your handout for you [if you send your handout to me in time].

My Fall 2020 MAT 2110 page has some sample slides.
Or Slides (.pdf) [Source: (.tex)] from a recent talk I gave.

Handout? Why not model after one of my monstrosities. For example:
Differential Algebra and Liouville's Theorem [Source: (.tex)]
Some differential Galois Theory [Source: (.tex)]

Suggested topics/ideas:
  • Symmetric Functions / Classical Galois Theory
  • Unsolvablity of a Generic Quintic
  • History of Solutions of Cubics, Quartics, etc.
  • Infinite Dimensional Issues
  • Transcendence Degrees / Algebraic Independence
  • Algebraic Integers / Algebraic Number Theory
  • Artin-Schreier Theorem
  • Artin-Wedderburn Theorem & Semisimple Rings
  • Wedderburn's Little Theorem
  • Dedekind Rings and Valuations
  • Group Actions & Sylow Theorems
  • Origami Constructability
  • Varieties, Radical Ideals, & Algebraic Geometry
  • Elliptic Curves
  • Applications like Cryptography

Selected Topics:
  • Alexia - Elliptic Curves
  • Gavin - Category Theory
  • Micah - Constructability
  • Sam - Origami Constructability
  • Brody - Risch Algorithm

4/17
Upcoming Handouts:
The Conjugate Trick [Maple source: (.mw)]
Differential Algebra and Liouville's Theorem [Source: (.tex)]
Some differential Galois Theory [Source: (.tex)]

3/26
Homework #7 [Source: (.tex)] is due Wednesday, April 3rd.

Upcoming Handouts:
The Alternating Group [Source: (.tex)]
Characters [Source: (.tex)]
Galois correspondence example [Source: (.tex)]

3/18
Homework #6 [Source: (.tex)] is due Monday, March 25th.

Forgotten Handouts:
Irreducibilty for Polynomials [Source: (.tex)]
Some Field Theory [Source: (.tex)]

3/01
Homework #5 [Source: (.tex)] is due Friday, March 8th.

Handout:
Transcendental Functions [Source: (.tex)]

2/23
Test #1 is Monday (February 26th).

To review I recommend looking over our homework answer keys. In addition old Rutgers Exams are full of good stuff to consider:
Exam #1 and Answer Key
Exam #2 and Answer Key

Most of Exam #1 looks like good review. Of course, some of the material is a little off topic. Also, be aware that some definitions (e.g. gcd is slightly different) & notations (e.g. M(F) for 2x2 matrices over F) may be a little different from ours. Exam #2 looks good as well. Generally I would down-play problems about matrices and Exam #2 8(b) is outside the scope of what we've done.

You can also check out old Math 4720/5210 (Abstract Algebra) exams:
Test #2
Final Exam

Test #2 is great stuff to look at. Although there's no answer key - but you can ask me. Ignore stuff about fields of fractions. Final Exam: 1,2(a)-(f),3,4,5(a),6,9 are relevant. Again, there's no key - but you can ask me.

2/19
Test #1 is Monday, February 26th.
(More information to come soon.)

2/12
Homework #4 [Source: (.tex)] is due Monday Wednesday, February 21st.

Oops! Forgot to post a link to our handout:
Chinese Remaindering [Source: (.tex)]
• [FORGOTTEN HANDOUT:] Irreducibilty for Polynomials [Source: (.tex)]
Possibly of interest:
Partial Fraction Decompositions

2/05
Homework #3 [Source: (.tex)] is due Monday, February 12th.

1/29
Handout:
Factorization Theory [Source: (.tex)]

In case we care, division with remainders in Maple examples (.mw)

Homework #2 [Source: (.tex)] is due Monday, February 5th.

1/24
Handout:
Isomorphism Theorems [Source: (.tex)]

1/19
Homework #1 [Source: (.tex)] is due Monday, January 29th.

1/17
Handouts:
Ring Definitions [Source: (.tex)]
Ring Examples [Source: (.tex)]

1/05
The 4720 syllabus, 5210 syllabus, tentative schedule, & ASULearn have been updated.

For some questionable history about Galois:
Stefanie (The Ballad of Galois).

MAT 4720-101 & 5210-101
"Advanced Topics in Modern Aglebra: Introduction to Galois Theory"
Everyone knows how to solve the quadratic equation. Although much more involved, there are also corresponding cubic and quartic equations. However, it turns out that no such "quintic formula" exists! This was first shown in the 1800's by Abel (and sort of by Ruffini in 1800). In the 1820's Galois developed a complete theory which explains exactly when a polynomial equation is "solvable".

This course will include a review of basic group and ring theory. We will cover some of the theory of vector spaces (linear algebra) and then study field extensions. This will then allow us to show the impossibility of obtaining certain compass-straightedge geometric constructions (eg. trisecting angles, doubling cubes, squaring circles). Next, we will develop the Galois correspondence relating field extensions to (Galois) groups of automorphisms and then show the impossibility of solving certain quintic equations.

If there is time, I also plan on sketching out some of "differential Galois theory" and discuss solvability of differential equations.

Meeting Times: Mondays, Wednesdays, & Fridays at 11-11:50am in Walker Hall room 308
Prerequisite details: MAT 3110. Although I will assume everyone has had an introductory course in modern algebra and linear algebra, I will take time to review necessary background material. I will assume that students are familiar with the definition of a ring, but not that they remember any substantial ring theory.

Our main text will be "Galois Theory" (2nd edition) by Joseph Rotman

For more details about "What is Galois theory?" I recommend the wikipedia article... https://en.wikipedia.org/wiki/Galois_theory ...or come talk to me!

If you have any questions specifically about this course, please feel free to contact Dr. Bill Cook at: cookwj@appstate.edu