Topology and its Applications ( IF 0.6 ) Pub Date : 2021-03-23 , DOI: 10.1016/j.topol.2021.107672 Liang-Xue Peng , Chun-Jie Ma , Li-Jun Wang
In the second part of this article, we show that if Z is a metacompact subspace of a GO-space X and is a family of open subsets of X such that then there exists a point-finite family of open subsets of X such that and . Thus every subspace Y of a GO-space X is metacompact in X if and only if Y is a metacompact subspace of X.
In the third part of this article, we get the following conclusions. We show that if is a GO-space and Z is a monotonically (countably) metacompact subspace of X, then Z is monotonically (countably) metacompact in X. By this conclusion we show that if is a GO-space with property such that the maximal dense in itself set Z of X is a monotonically (countably) metacompact subspace of X, then X is monotonically (countably) metacompact. This gives a partial answer to [8, Question].
In the fourth part of this article, we show that if X is in PIGO and X is a countable unions of D-spaces, then X is a D-space, where PIGO is the class of perfect images of GO-spaces.
In the last part of this article we point out that there is an error in the proof of Theorem 10 in (2018) [23]. Then we finally give a new proof for it.
中文翻译:
关于GO空间的(单调)超紧子空间及相关结论
在本文的第二部分中,我们证明了Z是GO空间X的超紧凑子空间,并且是X的开放子集的族,使得 然后有一个点有限的家庭 打开子集的X,使得 和 。因此,当且仅当Y是X的超紧致子空间时,GO空间X的每个子空间Y才是X中的超紧致。
在本文的第三部分,我们得出以下结论。我们证明,如果是一个GO-空间和ž是单调(可数)亚紧的子空间X,然后ž是单调(可数)亚紧X。根据这一结论,我们表明,如果 是一个具有属性的GO空间 使得在自身的最大密设置ž的X是单调(可数)亚紧的子空间X,那么X是单调(可数)亚紧。这给出了对[8,问题]的部分回答。
在这篇文章中的第四部分,我们证明,如果X是PIGO和X是可数工会d -spaces,那么X是d k空间,其中PIGO是类GO-空间的完美图像。
在本文的最后部分,我们指出(2018)[23]中的定理10的证明存在错误。然后,我们终于为其提供了新的证明。