Abstract
For a prime number \(p\), the author shows that if two certain canonical finite quotients of a finitely generated Bloch–Kato pro-\(p\) group \(G\) coincide, then \(G\) has a very simple structure, i.e., \(G\) is a \(p\)-adic analytic pro-\(p\) group (see Theorem 1). This result has a remarkable Galois-theoretic consequence: if the two corresponding canonical finite extensions of a field \(F\)—with \(F\) containing a primitive \(p\)-th root of unity—coincide, then \(F\) is \(p\)-rigid (see Corollary 1). The proof relies only on group-theoretic tools, and on certain properties of Bloch–Kato pro-\(p\) groups.
Résumé
Étant donné un nombre premier \(p\), l’auteur montre que si \(G\) est un pro-\(p\) groupe de Bloch–Kato de type fini dont deux quotients finis canoniques coïncident, alors \(G\) admet une structure est très simple: c’est un pro-\(p\) groupe \(p\)-adique analytique (voir théorème 1). Ce résultat a une conséquence remarquable pour la théorie de Galois: si un corps \(F\) contient une racine primitive \(p\)-ième de l’unité et que ses deux extensions canoniques finies correspondantes coïncident, \(F\) est alors \(p\)-rigide (voir corollaire 1). La démonstration s’appuie sur des résultats de théorie des groupes et exploite certaines propriétés des pro-\(p\) groupes de Bloch–Kato.
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Acknowledgments
The author wishes to express his thanks to the referee for his/her valuable comments and remarks. Also, he is grateful to A. Chapman and D. Neftin for their interest and support, to D. Riley for the thoughtful discussions about the Zassenhaus filtration and restricted Lie algebras, and to S.K. Chebolu and J. Mináč for working with him on \(p\)-rigid fields.
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Dedicated to my maestri Th. Weigel and J. Mináč
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Quadrelli, C. Finite quotients of Galois pro-\(p\) groups and rigid fields. Ann. Math. Québec 39, 113–120 (2015). https://doi.org/10.1007/s40316-015-0027-5
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DOI: https://doi.org/10.1007/s40316-015-0027-5