Primitive elements with prescribed traces
| Autor: | Booker, Andrew R., Cohen, Stephen D., Leong, Nicol, Trudgian, Tim |
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| Rok vydání: | 2021 |
| Předmět: | |
| Druh dokumentu: | Working Paper |
| Popis: | Given a prime power $q$ and a positive integer $n$, let $\mathbb{F}_{q^{n}}$ denote the finite field with $q^n$ elements. Also let $a,b$ be arbitrary members of the ground field $\mathbb{F}_{q}$. We investigate the existence of a non-zero element $\xi \in \mathbb{F}_{q^{n}}$ such that $\xi+ \xi^{-1}$ is primitive and $T(\xi)=a, T(\xi^{-1})=b$, where $T(\xi)$ denotes the trace of $\xi$ in $\mathbb{F}_{q}$. This was a question intended to be addressed by Cao and Wang in 2014. Their work dealt instead with another problem already in the literature. Our solution deals with all values of $n \geq 5$. A related study involves the cubic extension $\mathbb{F}_{q^{3}}$ of $\mathbb{F}_{q}$. We show that if $q\geq 8\cdot 10^{12}$ then, for any $a\in \mathbb{F}_{q}$ we can find a primitive element $\xi \in \mathbb{F}_{q^{3}}$ such that $\xi + \xi^{-1}$ is also a primitive element of $\mathbb{F}_{q^{3}}$, and for which the trace of $\xi$ is equal to $a$. The improves a result of Cohen and Gupta. Along the way we prove a hybridised lower bound on prime divisors in various residue classes, which may be of interest to related existence questions. Comment: 13 pages; revised version |
| Databáze: | arXiv |
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