PSL septimic fields with a power basis
We give an infinite set of distinct monogenic septimic fields whose normal closure has Galois group .
We give an infinite set of distinct monogenic septimic fields whose normal closure has Galois group .
Given an algebraic number field and a finite group , we write for the subset of the locally free classgroup consisting of the classes of rings of integers in tame Galois extensions with . We determine , and show it is a subgroup of by means of a description using a Stickelberger ideal and properties of some cyclic codes, when contains a root of unity of prime order and , where is an elementary abelian group of order and is a cyclic group of order acting faithfully on...
Let be an extension of algebraic number fields, where is abelian over . In this paper we give an explicit description of the associated order of this extension when is a cyclotomic field, and prove that , the ring of integers of , is then isomorphic to . This generalizes previous results of Leopoldt, Chan Lim and Bley. Furthermore we show that is the maximal order if is a cyclic and totally wildly ramified extension which is linearly disjoint to , where is the conductor of .
We prove that any Galois extension of a commutative ring with a normal basis and abelian Galois group of odd order has a self-dual normal basis. We apply this result to get a very simple proof of nonexistence of normal bases for certain extensions which are of interest in number theory.
Let p be a rational prime, G a group of order p, and K a number field containing a primitive pth root of unity. We show that every tamely ramified Galois extension of K with Galois group isomorphic to G has a normal integral basis if and only if for every Galois extension L/K with Galois group isomorphic to G, the ring of integers in L is free as a module over the associated order . We also give examples, some of which show that this result can still hold without the assumption that K contains...
The Steinitz class of a number field extension is an ideal class in the ring of integers of , which, together with the degree of the extension determines the -module structure of . We denote by the set of classes which are Steinitz classes of a tamely ramified -extension of . We will say that those classes are realizable for the group ; it is conjectured that the set of realizable classes is always a group.In this paper we will develop some of the ideas contained in [7] to obtain some...