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arXiv 2012.12197math.GR
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关于无限群的扩张

On the spread of infinite groups

Charles Garnet Cox

摘要:

一个群是$\frac32$ -生成的,如果每个非平凡元素都是生成对的一部分。在2019年,Donoven和Harper证明了许多Thompson组是由$\frac32$生成的,并提出了五个问题。第一个问题是是否存在一个2-生成群,它的每个真商循环都不是$\frac32$ -生成的。这是一个自然的问题,鉴于有意义的工作证明,没有有限群有这个属性,但我们表明,有这样一个无限群。我们考虑的群是Houghton群$\text{FSym}(\mathbb{Z})\rtimes\mathbb{Z}$的有限指数子群族。然后,我们表明,前两组在我们的家庭是$\frac32$生成的,并调查这些群体的传播相关的概念。我们能够证明它们具有大于2的有限展度。因此,它们是第一个被证明具有有限正扩散的无限群,也是第一个被证明扩散大于2的无限群(除了$\mathbb{Z}$和塔斯基怪物,它们具有无限扩散)。

英文摘要:

A group is $\frac32$-generated if every non-trivial element is part of a generating pair. In 2019, Donoven and Harper showed that many Thompson groups are $\frac32$-generated and posed five questions. The first of these is whether there exists a 2-generated group with every proper quotient cyclic that is not $\frac32$-generated. This is a natural question given the significant work in proving that no finite group has this property, but we show that there is such an infinite group. The groups we consider are a family of finite index subgroups of the Houghton group $\text{FSym}(\mathbb{Z})\rtimes\mathbb{Z}$. We then show that the first two groups in our family are $\frac32$-generated, and investigate the related notion of spread for these groups. We are able to show that they have finite spread which is greater than 2. These are therefore the first infinite groups to be shown to have finite positive spread, and the first to be shown to have spread greater than 2 (other than $\mathbb{Z}$ and the Tarski monsters, which have infinite spread).

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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