Resolvent Components of Completely Normal Elements and the Morgan-Mullen Conjecture
Abstract
We study completely normal elements of π½qn over π½q, that is, elements that are normal over every intermediate field, through partial Lagrange resolvents. In these coordinates, complete normality splits into independent components, in a way closely related to Hachenberger's decomposition theory. Our main tool is a structure theorem for the components; together with a finite computation, it shows that every component has weight (the sum of the probabilities that its conditions fail) at most 3/4, uniformly in n. Combined with the classical character-sum method, this gives an explicit sufficient criterion for the existence of a primitive completely normal element. We verify the criterion for all n>q except $70$ pairs (q,n), which we settle with explicit elements found by computer. Since the case nβ€ q is due to Garefalakis and Kapetanakis, this confirms the conjecture of Morgan and Mullen (1996) that every π½qn contains a primitive element that is completely normal over π½q. The same estimates give two further results. First, Hachenberger's conjectured lower bound (qβ1)n'q(paβ1)n' for the number of completely normal elements, where p is the characteristic and n=pan' with pnmid n', holds for all pairs (q,n); it was known for regular pairs. Second, primitivity and complete normality are asymptotically independent: as qnββ, the number of primitive completely normal elements is (1+o(1)) Ο(qnβ1)/(qnβ1) times the number of completely normal elements (for fixed n this was known). Our arguments for n>q and for both further results, including every computer-assisted step, are formalised in Lean 4 with Mathlib; the formalisation takes the case nβ€ q and an explicit bound of Rosser and Schoenfeld as axioms and relies on Lean's compiler and interpreter for the large computations.
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BibTeX
@misc{hellwig2026resolvent,
title = {{Resolvent Components of Completely Normal Elements and the Morgan-Mullen Conjecture}},
author = {Florian Hellwig},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.36534},
eprint = {2610.36534},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.36534},
}
RIS
TY - UNPB
TI - Resolvent Components of Completely Normal Elements and the Morgan-Mullen Conjecture
AU - Florian Hellwig
PY - 2026
DA - 2026/10/27
PB - arXiv
DO - 10.48550/arxiv.2610.36534
UR - https://arxiv.org/abs/2610.36534
AB - We study completely normal elements of π½_q^n over π½_q, that is, elements that are normal over every intermediate field, through partial Lagrange resolvents. In these coordinates, complete normality splits into independent components, in a way closely related to Hachenberger's decomposition theory. Our main tool is a structure theorem for the components; together with a finite computation, it shows that every component has weight (the sum of the probabilities that its conditions fail) at most 3/4, uniformly in n. Combined with the classical character-sum method, this gives an explicit sufficient criterion for the existence of a primitive completely normal element. We verify the criterion for all n>q except $70$ pairs (q,n), which we settle with explicit elements found by computer. Since the case nβ€ q is due to Garefalakis and Kapetanakis, this confirms the conjecture of Morgan and Mullen (1996) that every π½_q^n contains a primitive element that is completely normal over π½_q. The same estimates give two further results. First, Hachenberger's conjectured lower bound (qβ1)^n'q^(p^aβ1)n' for the number of completely normal elements, where p is the characteristic and n=p^an' with pnmid n', holds for all pairs (q,n); it was known for regular pairs. Second, primitivity and complete normality are asymptotically independent: as q^nββ, the number of primitive completely normal elements is (1+o(1)) Ο(q^nβ1)/(q^nβ1) times the number of completely normal elements (for fixed n this was known). Our arguments for n>q and for both further results, including every computer-assisted step, are formalised in Lean 4 with Mathlib; the formalisation takes the case nβ€ q and an explicit bound of Rosser and Schoenfeld as axioms and relies on Lean's compiler and interpreter for the large computations.
ER -