Splitting fields of elements in arithmetic groups

TL;DR

This paper demonstrates that in large norm balls, the proportion of matrices with non-maximal Galois groups is negligible, extending results to elements in semisimple algebraic groups over number fields using advanced sieve and reduction techniques.

Contribution

It introduces a novel approach combining large sieve methods and reduction modulo primes to analyze Galois groups of elements in algebraic groups over number fields.

Findings

Non-maximal Galois groups are of lower order in norm balls

Results extend to elements in connected semisimple algebraic groups over number fields

Provides quantitative lattice point counting and non-concentration results

Abstract

We prove that the number of unimodular integral matrices in a norm ball whose characteristic polynomial has Galois group different than the full symmetric group is of strictly lower order of magnitude than the number of all such matrices in the ball, as the radius increases. More generally, we prove a similar result for the Galois groups associated with elements in any connected semisimple linear algebraic group defined and simple over a number field $F$. Our method is based on the abstract large sieve method developed by Kowalski, and the study of Galois groups via reductions modulo primes developed by Jouve, Kowalski and Zywina. The two key ingredients are a uniform quantitative lattice point counting result, and a non-concentration phenomenon for lattice points in algebraic subvarieties of the group variety, both established previously by the authors. The results answer a question posed by Rivin and by Jouve, Kowalski and Zywina, who have considered Galois groups of random products of elements in algebraic groups.