English

Existence of normal elements with prescribed norms

Number Theory 2024-12-23 v1

Abstract

For each positive integer nn, let Fqn\mathbb F_{q^n} be the unique nn-degree extension of the finite field Fq\mathbb F_q with qq elements, where qq is a prime power. It is known that for arbitrary qq and nn, there exists an element βFqn\beta\in \mathbb F_{q^n} such that its Galois conjugates β,βq,,βqn1\beta, \beta^q, \ldots, \beta^{q^{n-1}} form a basis for Fqn\mathbb F_{q^n} as an Fq\mathbb F_q-vector space. These elements are called normal and they work as additive generators of finite fields. On the other hand, the multiplicative group Fqn\mathbb F_{q^n}^* is cyclic and any generator of this group is a primitive element. Many past works have dealt with the existence of primitive and normal elements with specified properties, including the existence of primitive elements whose traces over intermediate extensions are prescribed. Inspired by the latter, in this paper we explore the existence of normal elements whose norms over intermediate extensions are prescribed. We combine combinatorial and number-theoretic ideas and obtain both asymptotic and concrete results. In particular, we completely solve the problem in the case where only one intermediate extension is considered.

Keywords

Cite

@article{arxiv.2412.15384,
  title  = {Existence of normal elements with prescribed norms},
  author = {Arthur Fernandes and Daniel Panario and Lucas Reis},
  journal= {arXiv preprint arXiv:2412.15384},
  year   = {2024}
}
R2 v1 2026-06-28T20:43:04.757Z