Let G be a finite abelian group, it is a difficult and unsolved problem to find a number field F whose ideal class group is isomorphic to G. In [WAS], Corollary 3.9 and in [COR], Theorem 2, it is proved that every finite abelian group is isomorphic to a factor group of the ideal class group of some
On the Ideal Class Group Problem for Global Fields
โ Scribed by Marc Perret
- Publisher
- Elsevier Science
- Year
- 1999
- Tongue
- English
- Weight
- 116 KB
- Volume
- 77
- Category
- Article
- ISSN
- 0022-314X
No coin nor oath required. For personal study only.
โฆ Synopsis
We prove that any finite abelian group is the ideal class group of the ring of S-integers of some global field of given characteristic.
1999 Academic Press
Nous prouvons que tout groupe abe lien fini est groupe des classes d'ide aux de l'anneau des S-entiers d'un corps global de caracte ristique donne .
1999 Academic Press
Theorem 1. Let G be a finite abelian group. Then there exist a number field K and a finite set S of places containing the archimedian one, such that G is equal to the ideal class group Cl(O K, S ) of the ring of S-integers O S of K.
๐ SIMILAR VOLUMES
Let p be a fixed prime number. By a p-extension of fields, we understand a Galois extension with pro-p Galois group. If k is a number field, let k ลฝฯฑ. be the maximal unramified p-extension of k s k ลฝ0. , and put ลฝ ลฝฯฑ. . ร ลฝ i. 4 ลฝ . ลฝ 0 .
In this note we prove an analogue of the classical Riemann-Hurwitz formula for the minus part of the p-rank of S-ideal class groups of algebraic CM-fields. The result is an improvement of Kida's formula for the cyclotomic Z p -extension.
We use bifurcation theory to study positive, negative, and sign-changing solutions for several classes of boundary value problems, depending on a real parameter . We show the existence of infinitely many points of pitchfork bifurcation, and study global properties of the solution curves.
Focusing on a particular case, we will show that one can explicitly determine the quartic fields \(\mathbf{K}\) that have ideal class groups of exponent \(\leqslant 2\), provided that \(\mathbf{K} / \mathbf{Q}\) is not normal, provided that \(\mathbf{K}\) is a quadratic extension of a fixed imaginar
We show by a counterexample that Perret's conjecture on in"nite class "eld towers for global function "elds is wrong, and so Perret's method of in"nite rami"ed class "eld towers in the asymptotic theory of global function "elds with many rational places breaks down.