English

A note on finite embedding problems with nilpotent kernel

Number Theory 2021-04-22 v3

Abstract

The first aim of this note is to fill a gap in the literature by proving that, given a global field KK and a finite set S\mathcal{S} of primes of KK, every finite split embedding problem GGal(L/K)G \rightarrow {\rm{Gal}}(L/K) over KK with nilpotent kernel has a solution Gal(F/K)G{\rm{Gal}}(F/K) \rightarrow G such that all primes in S\mathcal{S} are totally split in F/LF/L. We then apply this to inverse Galois theory over division rings. Firstly, given a number field KK of level at least 44, we show that every finite solvable group occurs as a Galois group over the division ring HKH_K of quaternions with coefficients in KK. Secondly, given a finite split embedding problem with nilpotent kernel over a finite field KK, we fully describe for which automorphisms σ\sigma of KK the embedding problem acquires a solution over the skew field of fractions K(T,σ)K(T, \sigma) of the twisted polynomial ring K[T,σ]K[T, \sigma].

Keywords

Cite

@article{arxiv.2011.07536,
  title  = {A note on finite embedding problems with nilpotent kernel},
  author = {Arno Fehm and François Legrand},
  journal= {arXiv preprint arXiv:2011.07536},
  year   = {2021}
}