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Generating the group of nonzero elements of a quadratic extension of \(\mathbb{F}_p\). (English) Zbl 07803496

Summary: It is well known that if \(\mathbb{F}\) is a finite field then \(\mathbb{F}^{\ast}\), the set of nonzero elements of \(\mathbb{F}\), is a cyclic group. In this paper we will assume \(\mathbb{F} = \mathbb{F}_p\) (the finite field with \(p\) elements, \(p\) a prime) and \(\mathbb{F}_{p^2}\) is a quadratic extension of \(\mathbb{F}_p\). In this case, the groups \(\mathbb{F}^{\ast}_p\) and \(\mathbb{F}^{\ast}_{p^2}\) have orders \(p-1\) and \(p^2 -1\) respectively. We will provide necessary and sufficient conditions for an element \(u\in \mathbb{F}^{\ast}_{p^2}\) to be a generator. Specifically, we will prove \(u\) is a generator of \(\mathbb{F}^{\ast}_{p^2}\) if and only if \(N(u)\) generates \(\mathbb{F}^{\ast}_p\) and \(\frac{u^2}{N(u)}\) generates \(Ker\, N\), where \(N : \mathbb{F}^{\ast}_{p^2} \rightarrow \mathbb{F}^{\ast}_p\) denotes the norm map.

MSC:

11T30 Structure theory for finite fields and commutative rings (number-theoretic aspects)
11A07 Congruences; primitive roots; residue systems
12F05 Algebraic field extensions

References:

[1] Lorenzo-Robledo, Álvaro, Number Theory and Geometry An Introduction to Arithmetic Geometry, Pure and Applied Undergraduate Texts, Vol. 35, American Mathematical Society, Providence, RI, 2019. · Zbl 1432.11002
[2] Conrad, K., Trace and Norm, online at kconrad.math.uconn.edu/blurbs/galoistheory/tracenorm.pdf.
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