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Annihilators of minus class groups of imaginary abelian fields

Cornelius Greither, Radan Kučera (2007)

Annales de l’institut Fourier

For certain imaginary abelian fields we find annihilators of the minus part of the class group outside the Stickelberger ideal. Depending on the exact situation, we use different techniques to do this. Our theoretical results are complemented by numerical calculations concerning borderline cases.

Annihilators of the class group of a compositum of quadratic fields

Jan Herman (2013)

Archivum Mathematicum

This paper is devoted to a construction of new annihilators of the ideal class group of a tamely ramified compositum of quadratic fields. These annihilators are produced by a modified Rubin’s machinery. The aim of this modification is to give a stronger annihilation statement for this specific type of fields.

Annulation du groupe des -classes généralisées d’une extension abélienne réelle de degré premier à

Georges Gras (1979)

Annales de l'institut Fourier

Soit un nombre premier impair. Soit K une extension abélienne réelle de Q de degré premier à et soit G son groupe de Galois; soit φ ( φ 1 ) un caractère -adique irréductible de K . Soit M la -extension abélienne maximale de K non ramifiée en dehors de et soit 𝒜 le Z [ G ] -module Gal ( M / K ) ; 𝒜 φ (la φ -composante de 𝒜 ) est un module fini sur l’anneau des entiers Z ψ ' de Q ψ ' (corps des valeurs sur Q d’un caractère ψ ' de degré 1 divisant φ ). On construit explicitement pour tout n 0 un élément 𝒮 n de Z ψ ' qui annule le module...

Another 80-dimensional extremal lattice

Mark Watkins (2012)

Journal de Théorie des Nombres de Bordeaux

We show that the unimodular lattice associated to the rank 20 quaternionic matrix group SL 2 ( F 41 ) S ˜ 3 GL 80 ( Z ) is a fourth example of an 80-dimensional extremal lattice. Our method is to use the positivity of the Θ -series in conjunction with an enumeration of all the norm 10 vectors. The use of Aschbacher’s theorem on subgroups of finite classical groups (reliant on the classification of finite simple groups) provides one proof that this lattice is distinct from the previous three, while computing the inner product...

Another look at real quadratic fields of relative class number 1

Debopam Chakraborty, Anupam Saikia (2014)

Acta Arithmetica

The relative class number H d ( f ) of a real quadratic field K = ℚ (√m) of discriminant d is defined to be the ratio of the class numbers of f and K , where K denotes the ring of integers of K and f is the order of conductor f given by + f K . R. Mollin has shown recently that almost all real quadratic fields have relative class number 1 for some conductor. In this paper we give a characterization of real quadratic fields with relative class number 1 through an elementary approach considering the cases when...

Anticyclotomic Iwasawa theory of CM elliptic curves

Adebisi Agboola, Benjamin Howard (2006)

Annales de l’institut Fourier

We study the Iwasawa theory of a CM elliptic curve E in the anticyclotomic Z p -extension of the CM field, where p is a prime of good, ordinary reduction for E . When the complex L -function of E vanishes to even order, Rubin’s proof of the two variable main conjecture of Iwasawa theory implies that the Pontryagin dual of the p -power Selmer group over the anticyclotomic extension is a torsion Iwasawa module. When the order of vanishing is odd, work of Greenberg show that it is not a torsion module. In...

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