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Almost disjoint refinement of families of subsets of $ {\bf N}$

Authors: Bohuslav Balcar and Peter Vojtáš
Journal: Proc. Amer. Math. Soc. 79 (1980), 465-470
MSC: Primary 04A20; Secondary 54A25, 54D40
MathSciNet review: 567994
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Abstract: Without any set-theoretic assumptions, we prove that every uniform ultrafilter on the set N of all natural numbers has a Comfort system, that is, an almost disjoint refinement. Moreover, we describe one type of ideal such that the family of all subsets of N that are not contained in it has an almost disjoint refinement.

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Keywords: Ultrafilter, almost disjoint family, $ {2^\omega }$-point, refinement
Article copyright: © Copyright 1980 American Mathematical Society

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