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arXiv 1705.02809math.GRcs.FL
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L系统在群论中的应用

Applications of L systems to group theory

Laura Ciobanu, Murray Elder, Michal Ferov

摘要:

L系统通过合并并行重写来概括上下文无关语法,并生成严格包含在索引语言类中的语言,如EDT 0 L和ET 0 L。在本文中,我们表明,许多自然出现在群论,并被称为索引或上下文敏感的语言,实际上是ET 0 L,在许多情况下EDT 0 L。例如,两个生成元上的自由群中的基元语言,三维流形或轨道流形的基本群的Bridson-Gilman标准形,Grigorchuk群的余字问题等都可以由L系统生成。为了补充自由群中原语的结果,我们证明了秩高于2的自由群中原语和原语集的语言是上下文敏感的。我们还表明存在中等增长的EDT 0 L和ET 0 L语言。

英文摘要:

L systems generalise context-free grammars by incorporating parallel rewriting, and generate languages such as EDT0L and ET0L that are strictly contained in the class of indexed languages. In this paper we show that many of the languages naturally appearing in group theory, and that were known to be indexed or context-sensitive, are in fact ET0L and in many cases EDT0L. For instance, the language of primitives in the free group on two generators, the Bridson-Gilman normal forms for the fundamental groups of 3-manifolds or orbifolds, and the co-word problem of Grigorchuk's group can be generated by L systems. To complement the result on primitives in free groups, we show that the language of primitives, and primitive sets, in free groups of rank higher than two is context-sensitive. We also show the existence of EDT0L and ET0L languages of intermediate growth.

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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