论文标题

可衡量的半群动作的复发

Recurrence for measurable semigroup actions

论文作者

Blank, Michael

论文摘要

我们研究有限生成的可测量图的自由半群的复发点集的定性特性。在单个发电机的情况下,经典的繁殖性复发定理表明,这些属性与不变度度量的存在密切相关。奇怪的是,但事实证明,几乎所有要点都是复发的,而有一组徘徊的正(无变形)度量。对于一般的半群,关于所有发电机的常见不变度度量的假设看起来有些不自然(尽管被广泛使用)。取而代之的是,我们为此问题提供了抽象条件(保守性类型),并提出了复发性属性的较弱版本。从技术上讲,该问题将减少为特殊构建的马尔可夫过程的复发分析。详细研究了从半群生成器到整个半群的继承的问题,反之亦然,我们证明这种继承可能是相当意外的。

We study qualitative properties of the set of recurrent points of finitely generated free semigroups of measurable maps. In the case of a single generator the classical Poincare recurrence theorem shows that these properties are closely related to the presence of an invariant measure. Curious, but otherwise it turns out to be possible that almost all points are recurrent, while there is an wandering set of positive (non-invariant) measure. For a general semigroup the assumption about the common invariant measure for all generators looks somewhat unnatural (despite being widely used). Instead we give abstract conditions (of conservativity type) for this problem and propose a weaker version of the recurrent property. Technically, the problem is reduced to the analysis of the recurrence of a specially constructed Markov process. Questions of inheritance of the recurrence property from the semigroup generators to the entire semigroup and vice versa are studied in detail and we demonstrate that this inheritance might be rather unexpected.

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