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Indices isotypiques des éléments cyclotomiques.
Tatiana Beliaeva 1, Jean-Robert Belliard ( ) 2, 3
(2009-12-04)

Given $F$ a real abelian field, $p$ an odd prime and $\chi$ any Dirichlet character of $F$ we give a method for computing the $\chi$-index $\displaystyle \left (H^1(G_S,\mathbb{Z}_p(r))^\chi: C^F(r)^\chi\right)$ where the Tate twist $r$ is an odd integer $r\geq 3$, the group $C^F(r)$ is the group of higher circular units, $G_S$ is the Galois group over $F$ of the maximal $S$ ramified algebraic extension of $F$, and $S$ is the set of places of $F$ dividing $p$. This $\chi$-index can now be computed in terms only of elementary arithmetic of finite fields $\FM_\ell$. Our work generalizes previous results by Kurihara who used the assumption that the order of $\chi$ divides $p-1$.
1:  Institut de Recherche Mathématique Avancée (IRMA)
CNRS : UMR7501 – Université de Strasbourg
2:  Laboratoire de Mathématiques (LM-Besançon)
CNRS : UMR6623 – Université de Franche-Comté
3:  Institut de Mathématiques de Bordeaux (IMB)
CNRS : UMR5251 – Université Sciences et Technologies - Bordeaux I – Université Victor Segalen - Bordeaux II
Mathematics/Number Theory
Galois cohomologie – Iwasawa theory – cyclotomic fields.
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