On nonmeasurable unions

For a Polish space X and a σ-ideal I of subsets of X which has a Borel base we consider families A of sets in I with the union ⋃ A not in I. We determine several conditions on A which imply the existence of a subfamily A ′ of A whose union ⋃ A ′ is not in the σ-field generated by the Borel sets on X...

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Published inTopology and its applications Vol. 154; no. 4; pp. 884 - 893
Main Authors Cichoń, Jacek, Morayne, Michał, Rałowski, Robert, Ryll-Nardzewski, Czesław, Żeberski, Szymon
Format Journal Article
LanguageEnglish
Published Elsevier B.V 15.02.2007
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Summary:For a Polish space X and a σ-ideal I of subsets of X which has a Borel base we consider families A of sets in I with the union ⋃ A not in I. We determine several conditions on A which imply the existence of a subfamily A ′ of A whose union ⋃ A ′ is not in the σ-field generated by the Borel sets on X and I. Main examples are X = R and I being the ideal of sets of Lebesgue measure zero or the ideal of sets of the first Baire category.
ISSN:0166-8641
1879-3207
DOI:10.1016/j.topol.2006.09.013