Number Theory II

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Lectures: Lars Kindler
Mondays, 10am-2pm (with a break), SR005, Arnimallee 3

Exercises: Lei Zhang
Wednesdays, 10am-12pm, SR005/A3, Arnimallee 3

Official website in course registry

Please send questions and comments to kindler - at -
or come to office 112A, Arnimallee 3

Prerequisites: Lecture "Algebra I" or roughly equivalent knowledge, i.e. familiarity with basic notions of algebra and commutative algebra.


This course gives an introduction to algebraic number theory. The main objects of study are number fields, i.e. finite extensions of the field of rational numbers. To a number field $K$ we will attach its ring of integers $\mathcal{O}_K$. The ring $\mathcal{O}_K$ is a Dedekind domain and we will see that one of its invariants is the class number $h_K$, which measures "how far" $\mathcal{O}_K$ is away from being a unique factorization domain.
We will also study finite extensions $K\subset L$ of number fields, and how the prime ideals behave in the associated extension $\mathcal{O}_K\subset \mathcal{O}_L$ of Dedekind domains.

Here is a rough outline of the course (subject to change):
  1. Rings of integers
  2. Basic properties of Dedekind domains
  3. Minkowski's theory and finiteness of the class number
  4. Dirichlet's Unit Theorem
  5. Extensions of Dedekind domains and ramification theory
  6. Absolute values and completions, local fields


This course will mainly follow:

Summary of what happened so far (pdf)


Problem set 1 (due April 22)
Problem set 2 (due April 27)
Problem set 3 (due May 4)
Problem set 4 (due May 11)
Problem set 5 (due May 18)
Problem set 6 (due May 26)
Problem set 7 (due June 8)
Problem set 8 (due June 15)
Problem set 9 (due June 22)
Problem set 10 (due June 29)
Problem set 11 (due July 6)