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On power integral bases for certain pure number fields defined by x 18 - m

Lhoussain El Fadil (2022)

Commentationes Mathematicae Universitatis Carolinae

Let K = ( α ) be a number field generated by a complex root α of a monic irreducible polynomial f ( x ) = x 18 - m , m 1 , is a square free rational integer. We prove that if m 2 or 3 ( mod 4 ) and m ¬ 1 ( mod 9 ) , then the number field K is monogenic. If m 1 ( mod 4 ) or m 1 ( mod 9 ) , then the number field K is not monogenic.

On q-orders in primitive modular groups

Jacek Pomykała (2014)

Acta Arithmetica

We prove an upper bound for the number of primes p ≤ x in an arithmetic progression 1 (mod Q) that are exceptional in the sense that * p has no generator in the interval [1,B]. As a consequence we prove that if Q > e x p [ c ( l o g p ) / ( l o g B ) ( l o g l o g p ) ] with a sufficiently large absolute constant c, then there exists a prime q dividing Q such that ν q ( o r d p b ) = ν q ( p - 1 ) for some positive integer b ≤ B. Moreover we estimate the number of such q’s under suitable conditions.

On relative integral bases for unramified extensions

Kevin Hutchinson (1995)

Acta Arithmetica

0. Introduction. Since ℤ is a principal ideal domain, every finitely generated torsion-free ℤ-module has a finite ℤ-basis; in particular, any fractional ideal in a number field has an "integral basis". However, if K is an arbitrary number field the ring of integers, A, of K is a Dedekind domain but not necessarily a principal ideal domain. If L/K is a finite extension of number fields, then the fractional ideals of L are finitely generated and torsion-free (or, equivalently, finitely generated and...

On relative pure cyclic fields with power integral bases

Mohammed Sahmoudi, Mohammed Elhassani Charkani (2023)

Mathematica Bohemica

Let L = K ( α ) be an extension of a number field K , where α satisfies the monic irreducible polynomial P ( X ) = X p - β of prime degree belonging to 𝔬 K [ X ] ( 𝔬 K is the ring of integers of K ). The purpose of this paper is to study the monogenity of L over K by a simple and practical version of Dedekind’s criterion characterizing the existence of power integral bases over an arbitrary Dedekind ring by using the Gauss valuation and the index ideal. As an illustration, we determine an integral basis of a pure nonic field L with a...

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