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Investigating monogenity in a family of cyclic sextic fields

István Gaál

TL;DR

The paper investigates monogenity in a parametric family of cyclic sextic fields K = LM, where L is a totally real cubic field and M = Q(i) is imaginary quadratic, derived from Jones' sextic polynomials. By leveraging a relative index form I_{K/M}(γ) and a secondary factor J(γ), the authors reduce the problem to cubic Thue equations over L and a norm/linear-factor condition; they implement a Maple-based algorithm to search for generators of power integral bases across parameter values n. The main findings show monogenic instances for a small set of n in a bounded range, with explicit generators and integral bases, while a larger parameter set yields no generators within the search bound, illustrating both the method's effectiveness and its computational limits. The work provides the first non-trivial application of this approach to a parametric family of sextic fields and demonstrates practical feasibility for obtaining explicit generators in this class.

Abstract

L. Jones characterized among others monogenity of a family of cyclic sextic polynomials. Our purpose is to study monogenity of the family of corresponding sextic number fields. This also provides the first non-trivial application of the used method, emphasizing its efficiency.

Investigating monogenity in a family of cyclic sextic fields

TL;DR

The paper investigates monogenity in a parametric family of cyclic sextic fields K = LM, where L is a totally real cubic field and M = Q(i) is imaginary quadratic, derived from Jones' sextic polynomials. By leveraging a relative index form I_{K/M}(γ) and a secondary factor J(γ), the authors reduce the problem to cubic Thue equations over L and a norm/linear-factor condition; they implement a Maple-based algorithm to search for generators of power integral bases across parameter values n. The main findings show monogenic instances for a small set of n in a bounded range, with explicit generators and integral bases, while a larger parameter set yields no generators within the search bound, illustrating both the method's effectiveness and its computational limits. The work provides the first non-trivial application of this approach to a parametric family of sextic fields and demonstrates practical feasibility for obtaining explicit generators in this class.

Abstract

L. Jones characterized among others monogenity of a family of cyclic sextic polynomials. Our purpose is to study monogenity of the family of corresponding sextic number fields. This also provides the first non-trivial application of the used method, emphasizing its efficiency.
Paper Structure (6 sections, 8 theorems, 32 equations)

This paper contains 6 sections, 8 theorems, 32 equations.

Key Result

Lemma 1

$f(x)$ is irreducible for all $n\in{\mathbb Z}$, and is monogenic exactly for $n=-2,-1,0,1$.

Theorems & Definitions (8)

  • Lemma 1
  • Lemma 2
  • Lemma 3
  • Lemma 4
  • Lemma 5
  • Lemma 6
  • Theorem 7
  • Theorem 8