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Endomorphisms That Are the Sum of a Unit and a Root of a Fixed Polynomial

Published online by Cambridge University Press:  20 November 2018

W. K. Nicholson
Affiliation:
Department of Mathematics, University of Calgary, Calgary T2N 1N4, Canada e-mail: wknichol@ucalgary.ca
Y. Zhou
Affiliation:
Department of Mathematics, Memorial University of Newfoundland, St. John's A1C 5S7, Canada e-mail: zhou@math.mun.ca
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Abstract

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If $C=C\left( R \right)$ denotes the center of a ring $R$ and $g\left( x \right)$ is a polynomial in $C\left[ x \right]$, Camillo and Simón called a ring $g\left( x \right)$-clean if every element is the sum of a unit and a root of $g\left( x \right)$. If $V$ is a vector space of countable dimension over a division ring $D$, they showed that $\text{en}{{\text{d}}_{\,D}}V$ is $g\left( x \right)$-clean provided that $g\left( x \right)$ has two roots in $C\left( D \right)$. If $g\left( x \right)=x-{{x}^{2}}$ this shows that $\text{en}{{\text{d}}_{\,D}}V$ is clean, a result of Nicholson and Varadarajan. In this paper we remove the countable condition, and in fact prove that $\text{en}{{\text{d}}_{\,R}}M$ is $g\left( x \right)$-clean for any semisimple module $M$ over an arbitrary ring $R$ provided that $g\left( x \right)\in \left( x-a \right)\left( x-b \right)C\left[ x \right] $ where $a,b\in C$ and both $b$ and $b-a$ are units in $R$.

Type
Research Article
Copyright
Copyright © Canadian Mathematical Society 2006

References

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[3] Nicholson, W. K. and Varadarajan, K., Countable linear transformations are clean. Proc. Amer. Math. Soc. 126(1998), no. 1, 6164.Google Scholar