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Remarks on star covering properties in pseudocompact spaces

Yan-Kui Song (2013)

Mathematica Bohemica

Let P be a topological property. A space X is said to be star P if whenever 𝒰 is an open cover of X , there exists a subspace A X with property P such that X = St ( A , 𝒰 ) , where St ( A , 𝒰 ) = { U 𝒰 : U A } . In this paper, we study the relationships of star P properties for P { Lindel ö f , compact , countablycompact } in pseudocompact spaces by giving some examples.

Remarks on the cardinality of a power homogeneous space

Angelo Bella (2005)

Commentationes Mathematicae Universitatis Carolinae

We provide a further estimate on the cardinality of a power homogeneous space. In particular we show the consistency of the formula | X | 2 π χ ( X ) for any regular power homogeneous ccc space.

Representing free Boolean algebras

Alan Dow, P. Nyikos (1992)

Fundamenta Mathematicae

Partitioner algebras are defined in [2] and are natural tools for studying the properties of maximal almost disjoint families of subsets of ω. In this paper we investigate which free algebras can be represented as partitioner algebras or as subalgebras of partitioner algebras. In so doing we answer a question raised in [2] by showing that the free algebra with 1 generators is represented. It was shown in [2] that it is consistent that the free Boolean algebra of size continuum is not a subalgebra...

Resolvability in c.c.c. generic extensions

Lajos Soukup, Adrienne Stanley (2017)

Commentationes Mathematicae Universitatis Carolinae

Every crowded space X is ω -resolvable in the c.c.c. generic extension V Fn ( | X | , 2 ) of the ground model. We investigate what we can say about λ -resolvability in c.c.c. generic extensions for λ > ω . A topological space is monotonically ω 1 -resolvable if there is a function f : X ω 1 such that { x X : f ( x ) α } d e n s e X for each α < ω 1 . We show that given a T 1 space X the following statements are equivalent: (1) X is ω 1 -resolvable in some c.c.c. generic extension; (2) X is monotonically ω 1 -resolvable; (3) X is ω 1 -resolvable in the Cohen-generic extension V Fn ( ω 1 , 2 ) ....

Rings of maps: sequential convergence and completion

Roman Frič (1999)

Czechoslovak Mathematical Journal

The ring B ( R ) of all real-valued measurable functions, carrying the pointwise convergence, is a sequential ring completion of the subring C ( R ) of all continuous functions and, similarly, the ring 𝔹 of all Borel measurable subsets of R is a sequential ring completion of the subring 𝔹 0 of all finite unions of half-open intervals; the two completions are not categorical. We study 0 * -rings of maps and develop a completion theory covering the two examples. In particular, the σ -fields of sets form an epireflective...

Rudin's Dowker space in the extension with a Suslin tree

Teruyuki Yorioka (2008)

Fundamenta Mathematicae

We introduce a generalization of a Dowker space constructed from a Suslin tree by Mary Ellen Rudin, and the rectangle refining property for forcing notions, which modifies the one for partitions due to Paul B. Larson and Stevo Todorčević and is stronger than the countable chain condition. It is proved that Martin's Axiom for forcing notions with the rectangle refining property implies that every generalized Rudin space constructed from Aronszajn trees is non-Dowker, and that the same can be forced...

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