On -starcompact spaces.
Absolutely strongly star-Hurewicz spaces
A space X is absolutely strongly star-Hurewicz if for each sequence (Un :n ∈ℕ/ of open covers of X and each dense subset D of X, there exists a sequence (Fn :n ∈ℕ/ of finite subsets of D such that for each x ∈X, x ∈St(Fn; Un) for all but finitely many n. In this paper, we investigate the relationships between absolutely strongly star-Hurewicz spaces and related spaces, and also study topological properties of absolutely strongly star-Hurewicz spaces.
Remarks on absolutely star countable spaces
We prove the following statements: (1) every Tychonoff linked-Lindelöf (centered-Lindelöf, star countable) space can be represented as a closed subspace in a Tychonoff pseudocompact absolutely star countable space; (2) every Hausdorff (regular, Tychonoff) linked-Lindelöf space can be represented as a closed G δ-subspace in a Hausdorff (regular, Tychonoff) absolutely star countable space; (3) there exists a pseudocompact absolutely star countable Tychonoff space having a regular closed subspace which...
Remarks on Star-Hurewicz Spaces
A space X is star-Hurewicz if for each sequence (𝒰ₙ: n ∈ ℕ) of open covers of X there exists a sequence (𝓥ₙ: n ∈ ℕ) such that for each n, 𝓥ₙ is a finite subset of 𝒰ₙ, and for each x ∈ X, x ∈ St(⋃ 𝓥ₙ,𝒰ₙ) for all but finitely many n. We investigate the relationship between star-Hurewicz spaces and related spaces, and also study topological properties of star-Hurewicz spaces.
Spaces with large relative extent
In this paper, we prove the following statements: (1) For every regular uncountable cardinal , there exist a Tychonoff space and a subspace of such that is both relatively absolute star-Lindelöf and relative property (a) in and , but is not strongly relative star-Lindelöf in and is not star-Lindelöf. (2) There exist a Tychonoff space and a subspace of such that is strongly relative star-Lindelöf in (hence, relative star-Lindelöf), but is not absolutely relative star-Lindelöf...
On -starcompact spaces
A space is -starcompact if for every open cover of there exists a Lindelöf subset of such that We clarify the relations between -starcompact spaces and other related spaces and investigate topological properties of -starcompact spaces. A question of Hiremath is answered.
Remarks on discretely absolutely star-Lindelöf spaces
Spaces with large star cardinal number
In this paper, we prove the following statements: (1) For any cardinal , there exists a Tychonoff star-Lindelöf space such that . (2) There is a Tychonoff discretely star-Lindelöf space such that does not exist. (3) For any cardinal , there exists a Tychonoff pseudocompact -starcompact space such that .
Remarks on strongly star-Menger spaces
A space is strongly star-Menger if for each sequence of open covers of , there exists a sequence of finite subsets of such that is an open cover of . In this paper, we investigate the relationship between strongly star-Menger spaces and related spaces, and also study topological properties of strongly star-Menger spaces.
Remarks on star countable discrete closed spaces
In this paper, we prove the following statements: (1) There exists a Tychonoff star countable discrete closed, pseudocompact space having a regular-closed subspace which is not star countable. (2) Every separable space can be embedded into an absolutely star countable discrete closed space as a closed subspace. (3) Assuming , there exists a normal absolutely star countable discrete closed space having a regular-closed subspace which is not star countable.
Remarks on star covering properties in pseudocompact spaces
Let be a topological property. A space is said to be star if whenever is an open cover of , there exists a subspace with property such that , where In this paper, we study the relationships of star properties for in pseudocompact spaces by giving some examples.
A note on spaces with countable extent
Let be a topological property. A space is said to be star P if whenever is an open cover of , there exists a subspace with property such that . In this note, we construct a Tychonoff pseudocompact SCE-space which is not star Lindelöf, which gives a negative answer to a question of Rojas-Sánchez and Tamariz-Mascarúa.
Closed subsets of absolutely star-Lindelöf spaces II
In this paper, we prove the following two statements: (1) There exists a discretely absolutely star-Lindelöf Tychonoff space having a regular-closed subspace which is not CCC-Lindelöf. (2) Every Hausdorff (regular, Tychonoff) linked-Lindelöf space can be represented in a Hausdorff (regular, Tychonoff) absolutely star-Lindelöf space as a closed subspace.
Embedding into discretely absolutely star-Lindelöf spaces
A space is if for every open cover of and every dense subset of , there exists a countable subset of such that is discrete closed in and , where . We show that every Hausdorff star-Lindelöf space can be represented in a Hausdorff discretely absolutely star-Lindelöf space as a closed subspace.
Absolute countable compactness of products and topological groups
In this paper, we generalize Vaughan's and Bonanzinga's results on absolute countable compactness of product spaces and give an example of a separable, countably compact, topological group which is not absolutely countably compact. The example answers questions of Matveev [8, Question 1] and Vaughan [9, Question (1)].
On -starcompact spaces
A space is if for every open cover of there exists a countably compact subset of such that In this paper we investigate the relations between -starcompact spaces and other related spaces, and also study topological properties of -starcompact spaces.
Subspaces of cs-starcompact spaces
Some topological properties weaker than Lindelofness
A note on discretely absolutely star-Lindelöf spaces
A note on star compact spaces with a -diagonal
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