Let ℓ be a rational prime, K be a number field that contains a primitive ℓth root of unity, L an abelian extension of K whose degree over K, [L:K], is divisible by ℓ, a prime ideal of K whose ideal class has order ℓ in the ideal class group of K, and $a_{}$ any generator of the principal ideal ${}^{\ell }$. We will call a prime ideal of K ’reciprocal to ’ if its Frobenius element generates $Gal(K\left(\sqrt[\ell ]{a_{}}\right)/K)$ for every choice of $a_{}$. We then show that becomes principal in L if and only if every reciprocal prime is not a norm inside...

In the previous paper [15], we determined the structure of the Galois groups $\text{Gal}(K_{ur}/K)$ of the maximal unramified extensions $K_{ur}$ of imaginary quadratic number fields $K$ of conductors $\leqq 1000$ under the Generalized Riemann Hypothesis (GRH) except for 23 fields (these are of conductors $\geqq 723$) and give a table of $\text{Gal}(K_{ur}/K)$. We update the table (under GRH). For 19 exceptional fields $K$ of them, we determine $\text{Gal}(K_{ur}/K)$. In particular, for $K=𝐐\left(\sqrt{-856}\right)$, we obtain $\text{Gal}(K_{ur}/K)\cong \widetilde{S_4}\times C_5\text{and}{K}_{ur}=K_4$, the fourth Hilbert class field of $K$. This is the first example of a number field whose...

We determine the structures of the Galois groups Gal$(K_{ur}/K)$ of the maximal unramified extensions $K_{ur}$ of imaginary quadratic number fields $K$ of conductors $\leqq 420(\leqq 719$ under the Generalized Riemann Hypothesis). For all such $K$, $K_{ur}$ is $K$, the Hilbert class field of $K$, the second Hilbert class field of $K$, or the third Hilbert class field of $K$. The use of Odlyzko’s discriminant bounds and information on the structure of class groups obtained by using the action of Galois groups on class groups is essential. We also use class...

The Gauss-Schering Lemma is a classical formula for the Legendre symbol commonly used in elementary proofs of the quadratic reciprocity law. In this paper we show how the Gauss Schering Lemma may be generalized to give a formula for a $2$-cocycle corresponding to a higher metaplectic extension of GL${}_n/k$ for any global field $k$. In the case that $k$ has positive characteristic, our formula gives a complete construction of the metaplectic group and consequently an independent proof of the power reciprocity...

Soient $k$ une extension quadratique imaginaire de $\mathbf{Q}$ et $A$ son anneau des entiers. Lorsque 3 est décomposé dans $k$, nous démontrons que les anneaux d’entiers de certains corps de classe de rayon de $k$ sont monogènes sur l’anneau des entiers du corps de classes de rayon 3. Des générateurs de “monogénéite” sont obtenus a l’aide de fonctions elliptiques qui paramétrisent un modèle de Deuring de la courbe elliptique associée au réseau $A$.