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New York Journal of Mathematics
Volume 31 (2025), 91-125

  

Lenny Jones

Monogenic even octic polynomials and their Galois groups

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Published: January 8, 2025.
Keywords: monogenic, octic, Galois.
Subject [2020]: Primary 11R21, 11R32.

Abstract
A monic polynomial f(x) in Z[x] of degree N is called monogenic if f(x) is irreducible over Q and {1,θ,θ2, ... ,θN-1} is a basis for the ring of integers of Q(θ), where f(θ)=0. In a series of recent articles, complete classifications of the Galois groups were given for irreducible polynomials

F(x):=x8+ax4+b in Z[x]

and

G(x):=x8+ax6+bx4+ax2+1 in Z[x],

where a is not zero. In this article, for each Galois group G arising in these classifications, we either construct an infinite family of monogenic octic polynomials F(x) or G(x) having Galois group G, or we prove that at most a finite such family exists. In the finite family situations, we determine all such polynomials. Here, a "family" means that no two polynomials in the family generate isomorphic octic fields.

Acknowledgements

The author thanks the anonymous referee for a careful reading of this article, and for all the excellent suggestions.


Author information

Lenny Jones
Professor Emeritus
Department of Mathematics
Shippensburg University
Shippensburg, Pennsylvania 17257, USA

doctorlennyjones@gmail.com