Archive For Mathematical Logic ( IF 0.3 ) Pub Date : 2022-12-04 , DOI: 10.1007/s00153-022-00859-x Vera Fischer 1 , Corey Bacal Switzer 1
We study \(\kappa \)-maximal cofinitary groups for \(\kappa \) regular uncountable, \(\kappa = \kappa ^{<\kappa }\). Revisiting earlier work of Kastermans and building upon a recently obtained higher analogue of Bell’s theorem, we show that:
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(1)
Any \(\kappa \)-maximal cofinitary group has \({<}\kappa \) many orbits under the natural group action of \(S(\kappa )\) on \(\kappa \).
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(2)
If \(\mathfrak {p}(\kappa ) = 2^\kappa \) then any partition of \(\kappa \) into less than \(\kappa \) many sets can be realized as the orbits of a \(\kappa \)-maximal cofinitary group.
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(3)
For any regular \(\lambda > \kappa \) it is consistent that there is a \(\kappa \)-maximal cofinitary group which is universal for groups of size \({<}2^\kappa = \lambda \). If we only require the group to be universal for groups of size \(\kappa \) then this follows from \(\mathfrak {p}(\kappa ) = 2^\kappa \).
中文翻译:
$$\kappa $$ -最大共尾群的结构
我们研究\(\kappa \) -正则不可数的\(\kappa \)最大共有限群,\(\kappa = \kappa ^{<\kappa }\)。回顾卡斯特曼斯的早期工作并基于最近获得的贝尔定理的更高模拟,我们证明:
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(1)
任何\(\kappa \)最大共陪群在 \(\kappa \)上\(S(\kappa )\)的自然群作用下都有\({<} \kappa \ ) 个轨道。
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(2)
如果\(\mathfrak {p}(\kappa ) = 2^\kappa \)则将\(\kappa \)划分为少于\(\kappa \)个集合可以实现为\( \kappa \) -最大共尾群。
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(3)
对于任何正则\(\lambda > \kappa \) ,一致的是存在一个\(\kappa \)最大共穷群,该群对于大小为\({<}2^\kappa = \lambda \) 的群是通用的。如果我们只要求该群对于大小为\(\kappa \)的群是通用的,那么这可以从\(\mathfrak {p}(\kappa ) = 2^\kappa \)得出。