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We construct Menger subsets of the real line whose product is not Menger in the plane. In contrast to earlier constructions, our approach is purely combinatorial. The set theoretic hypothesis used in our construction is far milder than…

General Topology · Mathematics 2016-10-27 Piotr Szewczak , Boaz Tsaban

Menger's basis property is a generalization of $\sigma$-compactness and admits an elegant combinatorial interpretation. We introduce a general combinatorial method to construct non $\sigma$-compact sets of reals with Menger's property.…

General Topology · Mathematics 2010-11-02 Boaz Tsaban , Lubomyr Zdomsky

We show that even for subsets X of the real line which do not contain perfect sets, the Hurewicz property does not imply the property S1(Gamma,Gamma), asserting that for each countable family of open gamma-covers of X, there is a choice…

General Topology · Mathematics 2011-08-08 Dušan Repovš , Boaz Tsaban , Lyubomyr Zdomskyy

Using iterated Sacks forcing and topological games, we prove that the existence of a totally imperfect Menger set in the Cantor cube with cardinality continuum is independent from ZFC. We also analyze the structure of Hurewicz and consonant…

Logic · Mathematics 2025-10-28 Valentin Haberl , Piotr Szewczak , Lyubomyr Zdomskyy

We provide simplified solutions of Menger's and Hurewicz's problems and conjectures, concerning generalizations of sigma-compactness. The reader who is new to this field will find a self-contained treatment in Sections 1, 2, and 5. Sections…

General Topology · Mathematics 2017-03-10 Boaz Tsaban

We will show that, consistently, every uncountable set can be continuously mapped onto a non measure zero set, while there exists an uncountable set whose all continuous images into a Polish space are meager.

Logic · Mathematics 2007-05-23 Tomek Bartoszynski , Saharon Shelah

Hindman's celebrated Finite Sums Theorem, and its high-dimensional version due to Milliken and Taylor, are extended from covers of countable sets to covers of arbitrary topological spaces with Menger's classic covering property. The methods…

General Topology · Mathematics 2017-11-09 Boaz Tsaban

W. Hurewicz proved that analytic Menger sets of reals are $\sigma$-compact and that co-analytic completely Baire sets of reals are completely metrizable. It is natural to try to generalize these theorems to projective sets. This has…

General Topology · Mathematics 2018-03-12 Franklin D. Tall , Lyubomyr Zdomskyy

The Hurewicz property is a classical generalization of $\sigma$-compactness and Sierpi\'nski sets (whose existence follows from CH) are standard examples of non-$\sigma$-compact Hurewicz spaces. We show, solving a problem stated by Szewczak…

General Topology · Mathematics 2025-03-18 Witold Marciszewski , Roman Pol , Piotr Zakrzewski

In this paper we discuss what kind of constrains combinatorial covering properties of Menger, Scheepers, and Hurewicz impose on remainders of topological groups. For instance, we show that such a remainder is Hurewicz if and only it is…

General Topology · Mathematics 2016-06-10 Angelo Bella , Seçil Tokgöz , Lyubomyr Zdomskyy

Menger's conjecture that Menger spaces are /sigma-compact is false; it is true for analytic subspaces of Polish spaces and undecidable for more complex definable subspaces of Polish spaces. For non-metrizable spaces, analytic Menger spaces…

General Topology · Mathematics 2016-07-19 Franklin D. Tall

Using a dictionary translating a variety of classical and modern covering properties into combinatorial properties of continuous images, we get a simple way to understand the interrelations between these properties in ZFC and in the realm…

Logic · Mathematics 2010-11-02 Boaz Tsaban , Lyubomyr Zdomskyy

The theorem we prove is a slight strengthening of some results by Just, Miller, Scheepers and Szeptycki [JMSS]. We use the Michael technique instead of the combinatorial approach in the literature. Comments by the submitter: This short…

General Topology · Mathematics 2023-05-19 Jozef Chaber , Roman Pol

Hurewicz proved completely metrizable Menger spaces are /sigma-compact. We extend this to Cech-complete Menger spaces and consistently to projective Menger metrizable spaces. On the other hand, it is consistent that there is a co-analytic…

General Topology · Mathematics 2016-07-19 Franklin D. Tall , Secil Tokgoz

A subset of the Cantor cube is null-additive if its algebraic sum with any null set is null. We construct a set of cardinality continuum such that: all continuous images of the set into the Cantor cube are null-additive, it contains a…

General Topology · Mathematics 2021-07-08 Piotr Szewczak , Tomasz Weiss

We study the preservation of selective covering properties, including classic ones introduced by Menger, Hurewicz, Rothberger, Gerlits and Nagy, and others, under products with some major families of concentrated sets of reals. Our methods…

General Topology · Mathematics 2014-02-18 Arnold W. Miller , Boaz Tsaban , Lyubomyr Zdomskyy

The Continuum Hypothesis implies an Erd\"os-Sierpi\'nski like duality between the ideal of first category subsets of $\reals^{\naturals}$, and the ideal of countable dimensional subsets of $\reals^{\naturals}$. The algebraic sum of a…

General Topology · Mathematics 2009-01-22 Liljana Babinkostova , Marion Scheepers

A set of reals $X$ is $\mathfrak{b}$-concentrated if it has cardinality at least $\mathfrak{b}$ and it contains a countable set $D\subseteq X$ such that each closed subset of $X$ disjoint with $D$ has size smaller than $\mathfrak{b}$. We…

General Topology · Mathematics 2025-11-13 Valentin Haberl , Piotr Szewczak , Lyubomyr Zdomskyy

In this paper we consider some recent relative versions of Menger property called set strongly star Menger and set star Menger properties and the corresponding Hurewicz-type properties. In particular, using \cite {BMae}, we "easily" prove…

General Topology · Mathematics 2023-10-05 Maddalena Bonanzinga , Davide Giacopello , Fortunato Maesano

We work in the realm of sets of reals. We prove that in the Miller model and in a model constructed by Goldstern-Judah-Shelah all universally meager sets have size at most $\omega_1$. Some relations between combinatorial covering properties…

Logic · Mathematics 2025-12-18 Valentin Haberl , Piotr Szewczak , Lyubomyr Zdomskyy
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