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On the structure of Borel ideals in-between the ideals ED and Fin ⊗ Fin in the Katětov order
Annals of Pure and Applied Logic ( IF 0.6 ) Pub Date : 2021-04-15 , DOI: 10.1016/j.apal.2021.102976
Pratulananda Das , Rafał Filipów , Szymon Gła̧b , Jacek Tryba

For a family Fωω we define the ideal I(F) on ω×ω to be the ideal generated by the family{Aω×ω:fFn(|{k:(n,k)A}|f(n))}. Using ideals of the form I(F), we show that the structure of Borel ideals in-between two well known Borel idealsED={Aω×ω:mn(|{k:(n,k)A}|<m))} andFinFin={Aω×ω:n(|{k:(n,k)A}|<0))} in the Katětov order is fairly complicated. Namely, there is a copy of P(ω)/Fin in-between ED and FinFin, and consequently there are increasing and decreasing chains of length b and antichains of size c.



中文翻译:

关于理想之间的Borel理想的结构 ED 和Kat⊗tov秩序中的Fin⊗Fin

对于一个家庭 Fωω 我们定义理想 一世Fω×ω 成为家庭的理想{一种ω×ωFFñ|{ķñķ一种}|Fñ} 使用形式的理想 一世F,我们证明了两个著名的Borel理想之间的Borel理想的结构ED={一种ω×ωñ|{ķñķ一种}|<}={一种ω×ωñ|{ķñķ一种}|<0}卡捷夫(Katětov)的命令相当复杂。即,有一个副本Pω/ 中间的 ED,因此长度的链条增加和减少 b 和大小的反链 C

更新日期:2021-04-19
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