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The Smallest Pisot Element in the Field of Formal Power Series Over a Finite Field

Published online by Cambridge University Press:  20 November 2018

A. Chandoul
Affiliation:
Faculté des Sciences de Sfax, BP 1171, Sfax 3000, Tunisia e-mail: [email protected]@[email protected]
M. Jellali
Affiliation:
Faculté des Sciences de Sfax, BP 1171, Sfax 3000, Tunisia e-mail: [email protected]@[email protected]
M. Mkaouar
Affiliation:
Faculté des Sciences de Sfax, BP 1171, Sfax 3000, Tunisia e-mail: [email protected]@[email protected]
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Abstract.

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Dufresnoy and Pisot characterized the smallest Pisot number of degree $n\,\ge \,3$ by giving explicitly its minimal polynomial. In this paper, we translate Dufresnoy and Pisot’s result to the Laurent series case. The aim of this paper is to prove that the minimal polynomial of the smallest Pisot element $\left( \text{SPE} \right)$ of degree $n$ in the field of formal power series over a finite field is given by $P\left( Y \right)\,=\,{{Y}^{n}}\,-\,\alpha X{{Y}^{n-1}}\,-{{\alpha }^{n}}$ where $\alpha $ is the least element of the finite field ${{\mathbb{F}}_{q}}\backslash \left\{ 0 \right\}$ (as a finite total ordered set). We prove that the sequence of SPEs of degree $n$ is decreasing and converges to $\alpha X$. Finally, we show how to obtain explicit continued fraction expansion of the smallest Pisot element over a finite field.

Type
Research Article
Copyright
Copyright © Canadian Mathematical Society 2013

References

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