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Reducibility of translates
of Dickson polynomials

Author: Gerhard Turnwald
Journal: Proc. Amer. Math. Soc. 126 (1998), 965-971
MSC (1991): Primary 12E10; Secondary 11T06
MathSciNet review: 1451832
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Abstract: Let $K$ be a field and $a,b\in K$. The Dickson polynomial $D_{n}(x,a)$ is characterized by the equation $D_{n}(x+(a/x),a)=x^{n}+ (a/x)^{n}$. We prove that $D_{n}(x,a)+b\in K[x]$ is reducible if and only if there is a prime $p|n$ such that $b=-D_{p}(c,a^{n/p})$ for some $c\in K$, or $n=4k$ and $b=4c^{4}-8a^{k}c^{2}+2a^{2k}$ for some $c\in K$. This result generalizes the well-known reducibility criterion for binomials; and it provides a reducibility criterion for $T_{n}(x)+c$ where $T_{n}(x)$ denotes the Chebyshev polynomial of degree $n$.

References [Enhancements On Off] (What's this?)

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Additional Information

Gerhard Turnwald
Affiliation: Mathematisches Institut, Universität Tübingen, Auf der Morgenstelle 10, D-72076 Tübingen, Germany

Keywords: Dickson polynomials, Chebyshev polynomials, binomials, reducibility
Received by editor(s): September 10, 1996
Communicated by: William W. Adams
Article copyright: © Copyright 1998 American Mathematical Society