On tamely ramified infinite Galois extensions

Fuente: arXiv
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Auteurs principaux: Hajir, Farshid, Larsen, Michael, Maire, Christian, Ramakrishna, Ravi
Format: Preprint
Publié: 2024
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author Hajir, Farshid
Larsen, Michael
Maire, Christian
Ramakrishna, Ravi
author_facet Hajir, Farshid
Larsen, Michael
Maire, Christian
Ramakrishna, Ravi
contents For a number field $K$, we consider $K^{\rm ta}$ the maximal tamely ramified algebraic extension of~$K$, and its Galois group $G^{\rm ta}_K= Gal(K^{ta}/K)$. Choose a prime $p$ such that $μ_p \not \subset K$. Our guiding aim is to characterize the finitely generated pro-$p$ quotients of~$G^{\rm ta}$. We give a {unified point of view} by introducing the notion of {\it stably inertially generated} pro-$p$ groups~$G$, for which linear groups are archetypes. This key notion {is compatible} with local {\it tame liftings} as used in the Scholz-Reichardt Theorem. We realize every finitely generated pro-$p$ group~$G$ which is stably inertially generated as a quotient of $G^{\rm ta}$. Further examples of groups that we realize as quotients of $G^{\rm ta}$ include congruence subgroups of special linear groups over ${\mathbb Z}_p[[ T_1,\cdots, T_n ]]$. Finally, we give classes of groups which cannot be realized as quotients of $G^{\rm ta}_{\mathbb Q}$.
format Preprint
id arxiv_https___arxiv_org_abs_2401_05927
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle On tamely ramified infinite Galois extensions
Hajir, Farshid
Larsen, Michael
Maire, Christian
Ramakrishna, Ravi
Number Theory
11F80, 11R37, 11R32
For a number field $K$, we consider $K^{\rm ta}$ the maximal tamely ramified algebraic extension of~$K$, and its Galois group $G^{\rm ta}_K= Gal(K^{ta}/K)$. Choose a prime $p$ such that $μ_p \not \subset K$. Our guiding aim is to characterize the finitely generated pro-$p$ quotients of~$G^{\rm ta}$. We give a {unified point of view} by introducing the notion of {\it stably inertially generated} pro-$p$ groups~$G$, for which linear groups are archetypes. This key notion {is compatible} with local {\it tame liftings} as used in the Scholz-Reichardt Theorem. We realize every finitely generated pro-$p$ group~$G$ which is stably inertially generated as a quotient of $G^{\rm ta}$. Further examples of groups that we realize as quotients of $G^{\rm ta}$ include congruence subgroups of special linear groups over ${\mathbb Z}_p[[ T_1,\cdots, T_n ]]$. Finally, we give classes of groups which cannot be realized as quotients of $G^{\rm ta}_{\mathbb Q}$.
title On tamely ramified infinite Galois extensions
topic Number Theory
11F80, 11R37, 11R32
url https://arxiv.org/abs/2401.05927