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A note on skew polynomial rings. (English) Zbl 0830.16019
The author considers the simplicity of a skew polynomial ring $$S_n = R[x_1,\dots, x_n; d_1, \dots, d_n]$$ where $$R$$ is a ring of prime characteristic $$p$$ and $$d_1, \dots, d_n$$ are commuting derivations of $$R$$. He establishes a sufficient condition, involving the derivations of the intermediate rings $$S_{i-1}$$ of the form $$\sum^m_{k = 0} c_k d^{p^k}_i$$, where each $$c_k \in \bigcap^n_{j = k} \text{ker} (d_j)$$, for the simplicity of $$S_n$$ and proves the necessity of a weaker condition. As the author points out, D. R. Malm [Pac. J. Math 132, 85-112 (1988; Zbl 0608.16005)] has given a necessary and sufficient condition, in terms of the derivations of $$R$$ of the form $$\sum^n_{i = 1} \sum^m_{k = 0} c_{ik} d^{p^k}_i$$, where each $$c_{ik} \in \bigcap^n_{j=1} \text{ker} (d_j)$$ and is central in $$R$$, for the simplicity of $$S_n$$.

##### MSC:
 16S36 Ordinary and skew polynomial rings and semigroup rings 16D25 Ideals in associative algebras 16W25 Derivations, actions of Lie algebras 16D60 Simple and semisimple modules, primitive rings and ideals in associative algebras
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