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Nombre d'extensions abéliennes sur Q

Artur Travesa (1990)

Journal de théorie des nombres de Bordeaux

The aim of this paper is to give the numbers of abelian number fields with given degree and ramification indices. We describe, also, an algorithm to compute all these fields.

Non-existence and splitting theorems for normal integral bases

Cornelius Greither, Henri Johnston (2012)

Annales de l’institut Fourier

We establish new conditions that prevent the existence of (weak) normal integral bases in tame Galois extensions of number fields. This leads to the following result: under appropriate technical hypotheses, the existence of a normal integral basis in the upper layer of an abelian tower K L forces the tower to be split in a very strong sense.

Nonvanishing of a certain Bernoulli number and a related topic

Humio Ichimura (2013)

Acta Arithmetica

Let p = 1 + 2 e + 1 q be an odd prime number with q an odd integer. Let δ (resp. φ) be an odd (resp. even) Dirichlet character of conductor p and order 2 e + 1 (resp. order d φ dividing q), and let ψₙ be an even character of conductor p n + 1 and order pⁿ. We put χ = δφψₙ, whose value is contained in K = ( ζ ( p - 1 ) p ) . It is well known that the Bernoulli number B 1 , χ is not zero, which is shown in an analytic way. In the extreme cases d φ = 1 and q, we show, in an algebraic and elementary manner, a stronger nonvanishing result: T r n / 1 ( ξ B 1 , χ ) 0 for any pⁿth root ξ...

Note à propos d'une conjecture de H.J. Godwin sur les unités des corps cubiques

Marie-Nicole Gras (1980)

Annales de l'institut Fourier

On démontre, à partir de résultats de H.J. Godwin, H. Brunotte et F. Halter-Koch, le théorème suivant : soit K un corps cubique cyclique de conducteur m dont le groupe de Galois G est engendré par σ ; soit E le groupe des unités de norme 1.Soit ϵ E , ϵ 1 , telle que 𝒮 ( ϵ ) = 1 2 [ ( ϵ - ϵ σ ) 2 + ( ϵ σ - ϵ σ 2 ) 2 + ( ϵ σ 2 - ϵ ) 2 ] soit minimum. Alors ϵ est un Z [ G ] -générateur de E .

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