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On the Laczkovich-Komjáth property of sigma-ideals
Authors:Marek Balcerzak  Szymon G?a?b
Institution:a Institute of Mathematics, ?ód? Technical University, ul. Wólczañska 215, 93-005 ?ód?, Poland
b Mathematical Institute, Polish Academy of Sciences, ?niadeckich 8, 00-956 Warszawa, Poland
Abstract:Komjáth in 1984 proved that, for each sequence (An) of analytic subsets of a Polish space X, if lim supnHAn is uncountable for every HωN] then ?nGAn is uncountable for some GωN]. This fact, by our definition, means that the σ-ideal X]?ω has property (LK). We prove that every σ-ideal generated by X/E has property (LK), for an equivalence relation EX2 of type Fσ with uncountably many equivalence classes. We also show the parametric version of this result. Finally, the invariance of property (LK) with respect to various operations is studied.
Keywords:54H05  03E15  28A05
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