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We study some strong combinatorial properties of families. An ideal is Shelah-Steprāns if for every set there is an element of that either intersects every set in or contains infinitely many members of it. We prove that a Borel ideal is Shelah-Steprāns if and only if it is Katětov above the ideal . We prove that Shelah-Steprāns families have strong indestructibility properties (in particular, they are both Cohen and random indestructible). We also consider some other strong combinatorial properties of families. Finally, it is proved that it is consistent to have and no Shelah-Steprāns families of size .

生成讲解博客的中文版本

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