Journal of the European Mathematical Society
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Published online: 2008-09-30
Scales, fields, and a problem of HurewiczBoaz Tsaban and Lyubomyr Zdomskyy (1) Weizmann Institute of Science, Rehovot, Israel
(2) Weizmann Institute of Science, Rehovot, Israel
Menger's basis property is a generalization of $\sigma$-comp\-actness and admits an elegant combinatorial interpretation. We introduce a general combinatorial method to construct non $\sigma$-compact sets of reals with Menger's property. Special instances of these constructions give known counterexamples to conjectures of Menger and Hurewicz. We obtain the first explicit solution to the Hurewicz 1927 problem, that was previously solved by Chaber and Pol on a dichotomic basis. The constructed sets generate nontrivial subfields of the real line with strong combinatorial properties, and most of our results can be stated in a Ramsey-theoretic manner. Since we believe that this paper is of interest to a diverse mathematical audience, we have made a special effort to make it self-contained and accessible.
Keywords: Menger property, Hurewicz property, filter covers, topological groups, selection principles
Tsaban Boaz, Zdomskyy Lyubomyr: Scales, fields, and a problem of Hurewicz. J. Eur. Math. Soc. 10 (2008), 837-866. doi: 10.4171/JEMS/132