arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1012.5784math.GR
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可序群

Orderable groups

Cristóbal Rivas

摘要:

在第一章中,我们给出了基本的背景和符号。我们还给出了序的Conrad性质的一个新的刻画。在第二章中,我们使用Conradian性质的新刻画给出了(仅)允许n个Conradian序的群的分类§2.1。利用这种分类,我们推出了一个Conradian序空间的结构定理§2.2。此外,通过研究给定序的共轭逼近的可能性,我们能够给出群上左序空间的结构定理§2.3。在第三章中,我们证明了,对于具有1000个Conradian序的群,具有孤立的左序等价于只有1000个左序。第四章证明了$n\geq2$生成元上的自由群的左序空间在自由群的自然作用下有一个稠密轨道,从而给出了至少两个生成元上的自由群的左序空间无孤立点的新证明。在第五章中,我们描述了Thompson群$\efe$的双序空间。我们表明,这个空间包含八个孤立点连同四个典型的副本的康托尔集。

英文摘要:

In Chapter 1 we give the basic background and notations. We also give a new characterization of the Conrad property for orderings. In Chapter 2, we use the new characterization of the Conradian property to give a classification of groups admitting (only) finitely many Conradian orderings §2.1. Using this classification we deduce a structure theorem for the space of Conradian orderings §2.2. In addition, we are able to give a structure theorem for the space of left-orderings on a group by studying the possibility of approximating a given ordering by its conjugates §2.3. In Chapter 3 we show that, for groups having finitely many Conradian orderings, having an isolated left-ordering is equivalent to having only finitely many left-orderings. In Chapter 4, we prove that the space of left-orderings of the free group on $n\geq2$ generators have a dense orbit under the natural action of the free group on it. This gives a new proof of the fact that the space of left-orderings of the free group in at least two generators have no isolated point. In Chapter 5, we describe the space of bi-orderings of the Thompson's group $\efe$. We show that this space contains eight isolated points together with four canonical copies of the Cantor set.

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