Covering by special Cantor sets.
On a Corson space of Todorčević
Partitions of compact Hausdorff spaces
Under the assumption that the real line cannot be covered by -many nowhere dense sets, it is shown that (a) no Čech-complete space can be partitioned into -many closed nowhere dense sets; (b) no Hausdorff continuum can be partitioned into -many closed sets; and (c) no compact Hausdorff space can be partitioned into -many closed -sets.
The Arkhangel’skiĭ–Tall problem: a consistent counterexample
We construct a consistent example of a normal locally compact metacompact space which is not paracompact, answering a question of A. V. Arkhangel’skiĭ and F. Tall. An interplay between a tower in P(ω)/Fin, an almost disjoint family in , and a version of an (ω,1)-morass forms the core of the proof. A part of the poset which forces the counterexample can be considered a modification of a poset due to Judah and Shelah for obtaining a Q-set by a countable support iteration.
The Arkhangel'skiĭ–Tall problem under Martin’s Axiom
We show that MA implies that normal locally compact metacompact spaces are paracompact, and that MA() implies normal locally compact metalindelöf spaces are paracompact. The latter result answers a question of S. Watson. The first result implies that there is a model of set theory in which all normal locally compact metacompact spaces are paracompact, yet there is a normal locally compact metalindelöf space which is not paracompact.
On a construction of perfectly normal spaces and its applications to dimension theory
Countable Toronto spaces
A space X is called an α-Toronto space if X is scattered of Cantor-Bendixson rank α and is homeomorphic to each of its subspaces of the same rank. We answer a question of Steprāns by constructing a countable α-Toronto space for each α ≤ ω. We also construct consistent examples of countable α-Toronto spaces for each .
Covering by special Cantor sets
This paper deals with questions of how many compact subsets of certain kinds it takes to cover the space of irrationals, or certain of its subspaces. In particular, given , we consider compact sets of the form , where for all, or for infinitely many, . We also consider “-splitting” compact sets, i.e., compact sets such that for any and , .
Correction to the paper: Covering by special Cantor sets
A game and its relation to netweight and D-spaces
We introduce a two player topological game and study the relationship of the existence of winning strategies to base properties and covering properties of the underlying space. The existence of a winning strategy for one of the players is conjectured to be equivalent to the space have countable network weight. In addition, connections to the class of D-spaces and the class of hereditarily Lindelöf spaces are shown.
Baireness of for ordered
We show that if is a subspace of a linearly ordered space, then is a Baire space if and only if is Choquet iff has the Moving Off Property.
Dugundji extenders and retracts on generalized ordered spaces
For a subspace A of a space X, a linear extender φ:C(A) → C(X) is called an -extender (resp. -extender) if φ(f)[X] is included in the convex hull (resp. closed convex hull) of f[A] for each f ∈ C(A). Consider the following conditions (i)-(vii) for a closed subset A of a GO-space X: (i) A is a retract of X; (ii) A is a retract of the union of A and all clopen convex components of X; (iii) there is a continuous -extender φ:C(A × Y) → C(X × Y), with respect to both the compact-open topology and...
On a perfect set theorem of A. H. Stone and N. N. Lusin’s constituents
Uniformization and anti-uniformization properties of ladder systems
Natural weakenings of uniformizability of a ladder system on ω₁ are considered. It is shown that even assuming CH all the properties may be distinct in a strong sense. In addition, these properties are studied in conjunction with other properties inconsistent with full uniformizability, which we call anti-uniformization properties. The most important conjunction considered is the uniformization property we call countable metacompactness and the anti-uniformization property we call thinness. The...
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