Mon, 03 Nov 2025
16:00
C3

Abelian number fields with restricted ramification and rational points on stacks

Julie Tavernier
(University of Bath)
Abstract

A conjecture by Malle gives a prediction for the number of number fields of bounded discriminant. In this talk I will give an asymptotic formula for the number of abelian number fields of bounded height whose ramification type has been restricted to lie in a given subset of the Galois group and provide an explicit formula for the leading constant. I will then describe how counting these number fields can be viewed as a problem of counting rational points on the stack BG and how the existence of such number fields is controlled by a Brauer-Manin obstruction. No prior knowledge of stacks is needed for this talk!

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Many people think mathematics lives on the dark side. 

Turns out they were right.

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