论文标题

在$ n $饱和的闭合图上

On $n$-saturated closed graphs

论文作者

Głab, Szymon, Gordinowicz, Przemysław

论文摘要

Geschke证明了$ 2^ω$上有3个饱和的clopen图,但是$ 2^ω$上的clopen图甚至没有4饱和的无限子图;但是,有$f_σ$图是$ω_1$ - 饱和。事实证明,$ 2^ω$(即$ω$)上没有封闭图。在本说明中,我们通过证明每$ n $都有$ n $饱和的封闭图$ 2^ω$来完成这张图片。关键引理基于概率论点。最终构造是有限图的反度。

Geschke proved that there is clopen graph on $2^ω$ which is 3-saturated, but the clopen graphs on $2^ω$ do not even have infinite subgraphs that are 4-saturated; however there is $F_σ$ graph that is $ω_1$-saturated. It turns out that there is no closed graph on $2^ω$ which is $ω$-saturated. In this note we complete this picture by proving that for every $n$ there is an $n$-saturated closed graph on the Cantor space $2^ω$. The key lemma is based on probabilistic argument. The final construction is an inverse limit of finite graphs.

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