Algebra/Number Theory Seminar

Genus numbers of cubic fields

Kevin, McGown, CSU, Chico

Wednesday, October 25th, 2017
12:00 PM - 1:00 PM
Hylan 1106A

The class number is among the most important invariants associated to a number field. Conjecturally, its behavior (at the “good” primes) is governed by the heuristics of Cohen-Lenstra-Martinet. By contrast, the genus number is supported at the “bad” primes, but is easier to understand. It is very natural to ask about the density of genus number one fields among all number fields of a fixed degree and signature. We do not impose the restriction that our fields are Galois, and consequently, the genus theory is a little more subtle. We prove that approximately 96.23% of cubic fields, ordered by discriminant, have genus number one. Finally, we show that a positive proportion of totally real cubic fields with genus number one fail to be norm-Euclidean. Time permitting, I will further discuss norm-Euclidean questions and the case of quintic fields. This is joint work with Amanda Tucker.

Event contact: dinesh dot thakur at rochester dot edu