Hurewicz test sets for generalized separation and reduction

• Autores: Tamás Mátrai
• Localización: Mathematical proceedings of the Cambridge Philosophical Society, ISSN 0305-0041, Vol. 143, Nº 2, 2007, págs. 407-417
• Idioma: inglés
• DOI: 10.1017/s0305004107000436
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• Resumen

  • We prove a Hurewicz-type theorem for generalized separation: we present a method which allows us to test if for a sequence of Borel sets (Ai)i > ? satisfying there is a sequence (Bi)i < ? of ?0? sets such that or not. We also prove an analogous result for generalized reduction. The results of the paper are motivated by a Hurewicz-type theorem of A. Louveau and J. Saint Raymond on ordinary separation of analytic sets.