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arXiv 1303.6533math.RA
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单环与度映射

Simple Rings and Degree Maps

Patrik Nystedt, Johan Öinert

摘要:

对于既不一定结合环也不一定酉环的扩张A/B,我们研究了A的单性与B的一个性质之间的联系,我们称之为A-单性。这意味着不存在满足AI \subseteq IA的B的非平凡理想I是A-不变的。当B是A的直和项时,我们证明了B的A-单性是A对一大类环扩张单性的必要条件。为了得到A的单纯性的充分条件,我们引入了A/B的度映射的概念.这意味着从A到非负整数集合的映射d满足以下两个条件(d1)如果a \in A,则d(a)=0当且仅当a=0;(d2)存在生成B作为环的B的子集X,使得对于A的每个非零理想I和每个非零\in I,存在非零a' \in I,其中d(a')\leq d(a)并且对于所有b \in X,d(a 'b-ba')< d(a)。证明了:如果B在A中的中心化子C是A-单环,C与A的理想的每个交都是A-不变的,ACA=A,且A/B存在一个度映射,则A是单环.我们将这些结果应用到各种类型的分次和过滤环,如斜群环,Ore扩张和Cayley-Dickson double。

英文摘要:

For an extension A/B of neither necessarily associative nor necessarily unital rings, we investigate the connection between simplicity of A with a property that we call A-simplicity of B. By this we mean that there is no non-trivial ideal I of B being A-invariant, that is satisfying AI \subseteq IA. We show that A-simplicity of B is a necessary condition for simplicity of A for a large class of ring extensions when B is a direct summand of A. To obtain sufficient conditions for simplicity of A, we introduce the concept of a degree map for A/B. By this we mean a map d from A to the set of non-negative integers satisfying the following two conditions (d1) if a \in A, then d(a)=0 if and only if a=0; (d2) there is a subset X of B generating B as a ring such that for each non-zero ideal I of A and each non-zero a \in I there is a non-zero a' \in I with d(a') \leq d(a) and d(a'b - ba') < d(a) for all b \in X. We show that if the centralizer C of B in A is an A-simple ring, every intersection of C with an ideal of A is A-invariant, ACA=A and there is a degree map for A/B, then A is simple. We apply these results to various types of graded and filtered rings, such as skew group rings, Ore extensions and Cayley-Dickson doublings.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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