Some remarks on higher derivations of finite rank in a field of a positive characteristic

H. Yanagihara
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引用次数: 0

Abstract

In this short note we give a generalization of an approximation theorem on iterated higher derivations given by F. K. Schmidt in a paper [_2J (see Satz 14). Our generalization is done by determining all the iterated higher derivations of finite rank in any field K of a positive characteristic p. The following result on a derivation d in K will play an essential role in the proof: if we have d = 0, then d~\a) = 0 if and only if a = d(β) for some β in K*\ We shall give a proof of this fact using the Jacobson-Bourbaki's theorem which asserts the existence of a 1 — 1 correspondence between subfields of finite codimension in a field K and certain subrings of the ring M(K) of endomorphisms of the additive group (K, +) . Lastly we shall be concerned with conditions for a purely inseparable extension K of finite degree over a field k to be a tensor product of simple extensions over k. These conditions will be given in terms of higher derivations in K.
正特征域上有限阶高导的若干注释
在这篇简短的笔记中,我们对F. K. Schmidt在一篇论文[j]中给出的关于迭代高阶导数的近似定理进行了推广。我们的推广是通过在任意域K中确定一个正特征p的所有有限阶的迭代高阶导数来完成的。关于K中的一个导数d的下列结果将在证明中起重要作用:如果我们有d = 0,则d~\a) = 0当且仅当K*\中某些β的a = d(β)。我们将利用雅克布森-布尔巴基定理证明这一事实,该定理断言域K中有限余维的子域与加性群(K, +)的自同态环M(K)的某些子域之间存在1 - 1对应关系。最后,我们将讨论域K上有限次的纯不可分扩展K是K上简单扩展的张量积的条件。这些条件将以K的高阶导数的形式给出。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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