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Higher indescribability and derived topologies
Journal of Mathematical Logic ( IF 0.9 ) Pub Date : 2023-04-06 , DOI: 10.1142/s0219061323500010
Brent Cody 1
Affiliation  

We introduce reflection properties of cardinals in which the attributes that reflect are expressible by infinitary formulas whose lengths can be strictly larger than the cardinal under consideration. This kind of generalized reflection principle leads to the definitions of Lκ+,κ+-indescribability and Πξ1-indescribability of a cardinal κ for all ξ<κ+. In this context, universal Πξ1 formulas exist, there is a normal ideal associated to Πξ1-indescribability and the notions of Πξ1-indescribability yield a strict hierarchy below a subtle cardinal. Additionally, given a regular cardinal μ, we introduce a diagonal version of Cantor’s derivative operator and use it to extend Bagaria’s [Derived topologies on ordinals and stationary reflection, Trans. Amer. Math. Soc. 371(3) (2019) 1981–2002] sequence τξ:ξ<μ of derived topologies on μ to τξ:ξ<μ+. Finally, we prove that for all ξ<μ+, if there is a stationary set of α<μ that have a high enough degree of indescribability, then there are stationarily many α<μ that are nonisolated points in the space (μ,τξ+1).



中文翻译:

更高的不可描述性和派生拓扑

我们引入基数的反射属性,其中反射的属性可以通过无限公式来表达,无限公式的长度可以严格大于所考虑的基数。这种广义反射原理引出了以下定义Lκ+,κ+- 不可描述性和ΠΨ1- 红衣主教的难以形容κ对全部Ψ<κ+。在此背景下,普遍ΠΨ1公式存在,有一个正常的理想关联ΠΨ1- 不可描述性和概念ΠΨ1- 不可描述性产生了一个严格的等级制度,低于一个微妙的基数。此外,给定一个普通的枢机主教μ,我们引入了康托导数算子的对角版本,并用它来扩展 Bagaria 的[序数和平稳反射的导出拓扑,Trans。阿米尔。数学。苏克。 371(3)(2019)1981-2002]序列τΨΨ<μ的派生拓扑μτΨΨ<μ+。最后,我们证明对于所有Ψ<μ+,如果有一组平稳的α<μ具有足够高的不可描述性,那么有很多静止的α<μ是空间中的非孤立点μ,τΨ+1

更新日期:2023-04-06
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