Geodesic
A semifilter approach to selection principles
Commentationes Mathematicae Universitatis Carolinae, Tome 46 (2005) no. 3, pp. 525-539 Cet article a éte moissonné depuis la source Czech Digital Mathematics Library

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In this paper we develop the semifilter approach to the classical Menger and Hurewicz properties and show that the small cardinal $\frak g$ is a lower bound of the additivity number of the $\sigma$-ideal generated by Menger subspaces of the Baire space, and under $\frak u \frak g$ every subset $X$ of the real line with the property $\operatorname{Split} (\Lambda ,\Lambda )$ is Hurewicz, and thus it is consistent with ZFC that the property $\operatorname{Split} (\Lambda ,\Lambda )$ is preserved by unions of less than $\frak b$ subsets of the real line.
In this paper we develop the semifilter approach to the classical Menger and Hurewicz properties and show that the small cardinal $\frak g$ is a lower bound of the additivity number of the $\sigma$-ideal generated by Menger subspaces of the Baire space, and under $\frak u \frak g$ every subset $X$ of the real line with the property $\operatorname{Split} (\Lambda ,\Lambda )$ is Hurewicz, and thus it is consistent with ZFC that the property $\operatorname{Split} (\Lambda ,\Lambda )$ is preserved by unions of less than $\frak b$ subsets of the real line.
Classification : 03Axx, 03E17, 03E35, 54D20
Keywords: Menger property; Hurewicz property; property $\operatorname{Split}(\Lambda, \Lambda )$; semifilter; multifunction; small cardinals; additivity number 
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     title = {A semifilter approach to selection principles},
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Zdomsky, Lubomyr. A semifilter approach to selection principles. Commentationes Mathematicae Universitatis Carolinae, Tome 46 (2005) no. 3, pp. 525-539. http://geodesic.mathdoc.fr/item/CMUC_2005_46_3_a13/