Math 324

Algebraic Number Theory

General Information Schedule Homework

Schedule

We will spend the first few weeks of the course examining elementary number theory using the tools and viewpoint of abstract algebra. Such a perspective provides beautiful proofs of many simple facts together with a deeper understanding of fundamental results. From here, we will begin to think about the analog of the integers in fields extending the rationals. Our first step will be to analyze the Gaussian Integers and use their elegant structure to prove nontrivial theorems about the ordinary integers. Following up on that, we will study quadratic/cyclotomic extensions and examine the generalization of the integers in these settings. Unfortunately, we will discover that unique factorization and other essential properties can fail in these higher analogues. Toward the end of the course we will work to understand how to rectify the situation using more advanced ring theory.

Class Number Date Reading Brief Description
1 Monday, 1/23 1.1 - 1.4 Overview, Ideas and Techniques of Algebraic Number Theory
2 Wednesday, 1/25 (Algebra: 10.1 - 10.5, 11.1) Rings, Units, Integral Domains, Ideals, Divisibility, GCDs
3 Friday, 1/27 (Algebra: 2.2 - 2.5), 1.5 GCDs, Integer Primes, Fundamental Theorem of Arithmetic
4 Monday, 1/30 1.6, 1.7 Primes, Pythagorean Triples
5 Wednesday, 2/1 1.7, 2.1, 2.2 Pythagorean Triples, The Ring Z/nZ, Euler's Theorem and Fermat's Little Theorem
6 Friday, 2/3 2.3 Chinese Remainder Theorem
7 Monday, 2/6 2.4 Properites of the Euler Function
8 Wednesday, 2/8 2.5, 2.6 Wilson's Theorem, U(Z/pZ) is Cyclic
9 Friday, 2/10 2.7 Structure of U(Z/2^kZ)
10 Monday, 2/13 2.7 Structure of U(Z/p^kZ)
11 Wednesday, 2/15 2.7, 2.8 Structure of U(Z/nZ), When -1 is a Square Modulo p
12 Friday, 2/17 3.1, (Algebra: 11.1) Euclidean Domains, Gaussian Integers
13 Monday, 2/20 3.2 Principal Ideal Domains
14 Wednesday, 2/22 3.3 Noetherian Rings, Factorizations, UFDs
15 Friday, 2/24 3.4 Gaussian Integers, Sums of Squares
16 Monday, 2/27 3.4, 3.5 Gaussian Primes, Pythagorean Triples
17 Wednesday, 2/29 3.5, 3.6 Solving Diophantine Equations, Ideals and Quotients of the Gaussian Integers
18 Friday, 3/2 4.1, 4.2 Field Extensions, Algebraic and Transcendental Elements
19 Monday, 3/5 4.2 Algebraic and Transcendental Elements, Minimal Polynomials
20 Wednesday, 3/7 4.3 Irreducible Polynomials, Gauss' Lemma, Eisenstein's Criterion
21 Friday, 3/9 4.4, 4.5 Finite and Algebraic Extensions, Motivating Algebraic Integers
22 Monday, 3/12 4.5 Algebraic Integers
23 Wednesday, 3/14 5.1 Quadratic Number Fields
24 Friday, 3/16 5.2 The Ring of Integers in Quadratic Number Fields
- - - Spring Break
25 Monday, 4/2 - Class Canceled
26 Wednesday, 4/4 5.3 Norms and Units in Quadratic Number Fields
27 Friday, 4/6 5.3 Pell's Equation, Rational Approximations
28 Monday, 4/9 5.3 Pell's Equation, Units in Real Quadratic Number Fields
29 Wednesday, 4/11 5.3, 5.4 The Unit Group in Real Quadratic Number Fields, Factorizations
30 Friday, 4/13 5.4, 5.5 Euclidean Quadratic Number Fields, The Eisenstein Integers
31 Monday, 4/16 5.5 Fermat's Last Theorem for n = 3 (Sketch)
32 Wednesday, 4/18 6.1 Quadratic Residues, The Legendre Symbol
33 Friday, 4/20 6.2 Legendre Symbol, Primes Where 2 is a Quadratic Residue
34 Monday, 4/23 6.3 Quadratic Reciprocity
35 Wednesday, 4/25 7.1 Ideals as Missing Elements
36 Friday, 4/27 7.2 Dedekind Domains
37 Monday, 4/30 7.2, 7.3 Dedekind Domains, Factoring Ideals
38 Wednesday, 5/2 7.3 Unique Factorization of Ideals into Prime Ideals
39 Friday, 5/4 7.4 Class Groups
40 Monday, 5/7 8.1 Cyclotomic Polynomials
41 Wednesday, 5/9 8.1 Cyclotomic Polynomials
42 Friday, 5/11 8.1 Dirichlet's Theorem (Special Case), Ideals in Computable Rings