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Analytic countably splitting families

Published online by Cambridge University Press:  12 March 2014

Otmar Spinas*
Affiliation:
Mathematisches Seminar, Christian-Albrechts-Universität Zu Kiel, Ludewig-Meyn-Straße 4, 24098 Kiel, Germany, E-mail: spinas@math.uni-kiel.de

Abstract

A family A(ω) is called countably splitting if for every countable F ⊆ [ω]ω, some element of A splits every member of F. We define a notion of a splitting tree, by means of which we prove that every analytic countably splitting family contains a closed countably splitting family. An application of this notion solves a problem of Blass. On the other hand we show that there exists an Fσ splitting family that does not contain a closed splitting family.

Type
Research Article
Copyright
Copyright © Association for Symbolic Logic 2004

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References

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