Almost disjoint families on large underlying sets
نویسندگان
چکیده
We show that, for any poset P, the existence of a P-indestructible mad family F ⊆ [ω]א0 is equivalent to the existence of such a family over אn for some/all n ∈ ω. Under the very weak square principle ¤∗∗∗ ω1,μ of Fuchino and Soukup [7] and cf([μ]א0 ,⊆) = μ+ for all limit cardinals μ of cofinality ω, the equivalence for any proper poset P transfers to all cardinals. That is, under these assumptions, if P is a proper poset, then there is a P-indestructible mad family on ω if and only if there is a P-indestructible mad family on some/all infinite cardinals κ.
منابع مشابه
Almost disjoint families of connected sets
We investigate the question which (separable metrizable) spaces have a ‘large’ almost disjoint family of connected (and locally connected) sets. Every compact space of dimension at least 2 as well as all compact spaces containing an ‘uncountable star’ have such a family. Our results show that the situation for 1-dimensional compacta is unclear. 2004 Elsevier B.V. All rights reserved.
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