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On spaces with point-countable k -systems

Iwao Yoshioka (2004)

Commentationes Mathematicae Universitatis Carolinae

This paper deals with the behavior of M -spaces, countably bi-quasi- k -spaces and singly bi-quasi- k -spaces with point-countable k -systems. For example, we show that every M -space with a point-countable k -system is locally compact paracompact, and every separable singly bi-quasi- k -space with a point-countable k -system has a countable k -system. Also, we consider equivalent relations among spaces entried in Table 1 in Michael’s paper [15] when the spaces have point-countable k -systems.

On spaces with the property of weak approximation by points

Angelo Bella (1994)

Commentationes Mathematicae Universitatis Carolinae

A sufficient condition that the product of two compact spaces has the property of weak approximation by points (briefly WAP) is given. It follows that the product of the unit interval with a compact WAP space is also a WAP space.

On star covering properties related to countable compactness and pseudocompactness

Marcelo D. Passos, Heides L. Santana, Samuel G. da Silva (2017)

Commentationes Mathematicae Universitatis Carolinae

We prove a number of results on star covering properties which may be regarded as either generalizations or specializations of topological properties related to the ones mentioned in the title of the paper. For instance, we give a new, entirely combinatorial proof of the fact that Ψ -spaces constructed from infinite almost disjoint families are not star-compact. By going a little further we conclude that if X is a star-compact space within a certain class, then X is neither first countable nor separable....

On -starcompact spaces

Yan-Kui Song (2006)

Czechoslovak Mathematical Journal

A space X is -starcompact if for every open cover 𝒰 of X , there exists a Lindelöf subset L of X such that S t ( L , 𝒰 ) = X . We clarify the relations between -starcompact spaces and other related spaces and investigate topological properties of -starcompact spaces. A question of Hiremath is answered.

On 𝒞 -starcompact spaces

Yan-Kui Song (2008)

Mathematica Bohemica

A space X is 𝒞 -starcompact if for every open cover 𝒰 of X , there exists a countably compact subset C of X such that St ( C , 𝒰 ) = X . In this paper we investigate the relations between 𝒞 -starcompact spaces and other related spaces, and also study topological properties of 𝒞 -starcompact spaces.

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