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JOURNALS // Izvestiya Rossiiskoi Akademii Nauk. Seriya Matematicheskaya // Archive

Izv. RAN. Ser. Mat., 2021 Volume 85, Issue 5, Pages 132–151 (Mi im9070)

This article is cited in 3 papers

Arithmetic of certain $\ell$-extensions ramified at three places. II

L. V. Kuz'min

National Research Centre "Kurchatov Institute", Moscow

Abstract: Let $\ell$ be a regular odd prime, $k$ the $\ell$ th cyclotomic field and $K=k(\sqrt[\ell]{a})$, where $a$ is a positive integer. Under the assumption that there are exactly three places not over $\ell$ that ramify in $K_\infty/k_\infty$, we continue to study the structure of the Tate module (Iwasawa module) $T_\ell(K_\infty)$ as a Galois module. In the case $\ell=3$, we prove that for finite $T_\ell(K_\infty)$ we have $|T_\ell(K_\infty)|\,{=}\,\ell^r$ for some odd positive integer $r$. Under the same assumptions, if $\overline T_\ell(K_\infty)$ is the Galois group of the maximal unramified Abelian $\ell$-extension of $K_\infty$, then the kernel of the natural epimorphism $\overline T_\ell(K_\infty)\to T_\ell (K_\infty)$ is of order $9$. Some other results are obtained.

Keywords: Iwasawa theory, Tate module, extensions with restricted ramification.

UDC: 511.62

MSC: 11R23, 11R18

Received: 09.06.2020

DOI: 10.4213/im9070


 English version:
Izvestiya: Mathematics, 2021, 85:5, 953–971

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© Steklov Math. Inst. of RAS, 2024