Zobrazeno 1 - 10
of 57
pro vyhledávání: '"Wei-Feng Xuan"'
Autor:
Wei-Feng Xuan
Publikováno v:
Mathematica Bohemica, Vol 145, Iss 1, Pp 15-18 (2020)
We say that a space $X$ has the discrete countable chain condition (DCCC for short) if every discrete family of nonempty open subsets of $X$ is countable. A space $X$ has a zeroset diagonal if there is a continuous mapping $f X^2 \rightarrow[0,1]$ wi
Externí odkaz:
https://doaj.org/article/02f42e41dd124910a8dc5844cae0dd7b
Autor:
Wei-Feng Xuan, Yan-Kui Song
Publikováno v:
Mathematica Bohemica, Vol 144, Iss 2, Pp 113-123 (2019)
We study relationships between separability with other properties in semi-stratifiable spaces. Especially, we prove the following statements: (1) If $X$ is a semi-stratifiable space, then $X$ is separable if and only if $X$ is $DC(ømega_1)$; (2) If
Externí odkaz:
https://doaj.org/article/f2cc79951685420b9fc2eb45d36a6b5b
Autor:
Wei-Feng Xuan
Publikováno v:
Mathematica Bohemica, Vol 142, Iss 4, Pp 445-448 (2017)
A topological space $X$ is said to be star Lindelöf if for any open cover $\mathcal U$ of $X$ there is a Lindelöf subspace $A \subset X$ such that $øperatorname{St}(A, \mathcal U)=X$. The "extent" $e(X)$ of $X$ is the supremum of the cardinalities
Externí odkaz:
https://doaj.org/article/3d7169ade4f54e4ba71bdc6ddf1601b4
Autor:
Wei-Feng Xuan, Wei-Xue Shi
Publikováno v:
Mathematica Bohemica, Vol 141, Iss 4, Pp 457-461 (2016)
A topological space $X$ has a rank 2-diagonal if there exists a diagonal sequence on $X$ of rank $2$, that is, there is a countable family $\{\mathcal U_n n\inømega\}$ of open covers of $X$ such that for each $x \in X$, $\{x\}=\bigcap\{{\rm St}^2(x,
Externí odkaz:
https://doaj.org/article/af0bb4ab8da148d1a39684e3a11f575a
Autor:
Yan-Kui Song1 songyankui@njnu.edu.cn, Wei-Feng Xuan2 wfxuan@nau.edu.cn
Publikováno v:
Matematicki Vesnik. Dec2023, Vol. 75 Issue 4, p296-302. 7p.
Autor:
Yan-Kui Song, Wei-Feng Xuan
Publikováno v:
Quaestiones Mathematicae; Vol. 46 No. 1 (2023); 73-83
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 in
Externí odkaz:
https://explore.openaire.eu/search/publication?articleId=doi_dedup___::f06235121c37befd447c45ed8ecf8b38
https://www.ajol.info/index.php/qm/article/view/243025
https://www.ajol.info/index.php/qm/article/view/243025
Autor:
Wei-Feng Xuan1 wfxuan@nau.edu.cn, Yan-Kui Song2 songyankui@njnu.edu.cn, Wei-Xue Shi3 wxshi@nju.edu.cn
Publikováno v:
Bulletin of the Belgian Mathematical Society - Simon Stevin. May2020, Vol. 27 Issue 1, p61-69. 9p.
Autor:
Yan-Kui Song, Wei-Feng Xuan
Publikováno v:
Quaestiones Mathematicae; Vol. 44 No. 12 (2021); 1773–1781
In this paper, we show the following statements:(1) There exists a pseudocompact star Lindelöf Tychonoff space which is not star σ-compact.(2) There exists a Tychonoff pseudocompact star countable (hence, star Lindelöf) space having a pseudocompac
Externí odkaz:
https://explore.openaire.eu/search/publication?articleId=doi_dedup___::b9a90def8fa643d3e5c73d45233e6e5d
https://www.ajol.info/index.php/qm/article/view/224177
https://www.ajol.info/index.php/qm/article/view/224177
Autor:
Yan-Kui Song, Wei-Feng Xuan
Publikováno v:
Studia Scientiarum Mathematicarum Hungarica. 57:139-146
In this paper, we prove that if X is a space with a regular Gδ-diagonal and X2 is star Lindelöf then the cardinality of X is at most 2c. We also prove that if X is a star Lindelöf space with a symmetric g-function such that {g2(n, x): n ∈ ω} =
Externí odkaz:
https://explore.openaire.eu/search/publication?articleId=doi_________::5cbca4797bf3a1e0da4d5591a0c72108
https://doi.org/10.1556/012.2020.57.2.1462
https://doi.org/10.1556/012.2020.57.2.1462
Autor:
Yan-Kui Song1, Wei-Feng Xuan2
Publikováno v:
Bulletin of the Belgian Mathematical Society - Simon Stevin. Nov2019, Vol. 26 Issue 4, p527-534. 8p.