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We introduce and study a new class of $T_0$ spaces, called open well-filtered spaces. The main results we proved include (1) every well-filtered space is an open well-filtered space; (2) every core-compact open well-filtered space is sober.…

General Topology · Mathematics 2023-06-22 Chong Shen , Xiaoyong Xi , Xiaoquan Xu , Dongsheng Zhao

Recently, Xu proposed a strongly well-filtered space in [24] and systematically investigated some of its properties and characterizations. In this paper, we introduce a new class of T0-spaces called S*-well-filtered spaces, which is…

General Topology · Mathematics 2026-01-19 Nana Han , Siheng Chen , Qingguo Li

The open well-filtered spaces were introduced by Shen, Xi, Xu and Zhao to answer the problem whether every core-compact well-filtered space is sober. In the current paper we explore further properties of open well-filtered spaces. One of…

General Topology · Mathematics 2025-02-25 Chong Shen , Xiaoyong Xi , Dongsheng Zhao

Based on topological Rudin's Lemma, we investigate two new kinds of sets - Rudin sets and well-filtered determined sets in $T_0$ topological spaces. Using such sets, we formulate and prove some new characterizations for well-filtered spaces…

General Topology · Mathematics 2019-11-27 Xiaoquan Xu , Dongsheng Zhao

We prove that a $T_0$ topological space is $\omega$-well-filtered if and only if it does not admit either the natural numbers with the cofinite topology or with the Scott topology as its closed subsets in the strong topology. Based on this,…

General Topology · Mathematics 2024-09-04 Hualin Miao , Xiaodong Jia , Ao Shen , Qingguo Li

In this paper, we mainly discuss some basic properties of Scott power spaces. For a $T_0$ space $X$, let $\mathsf{K}(X)$ be the poset of all nonempty compact saturated subsets of $X$ endowed with the Smyth order. It is proved that the Scott…

General Topology · Mathematics 2022-07-19 Xiaoquan Xu , Xinpeng Wen , Xiaoyong Xi

We prove that for every $T_0$ space $X$, there is a well-filtered space $W(X)$ and a continuous mapping $\eta_X: X\lra W(X)$ such that for any well-filtered space $Y$ and any continuous mapping $f: X\lra Y$ there is a unique continuous…

General Topology · Mathematics 2019-07-16 Guohua Wu , Xiaoyong Xi , Xiaoquan Xu , Dongsheng Zhao

In non-Hausdorff topology, many spaces exhibit significant separation properties, such as sober spaces, well-filtered spaces and d-spaces. These properties serve to fundamentally classify T0 topological spaces. In this paper, we introduce…

General Topology · Mathematics 2026-01-19 Xiangrui Li , Qingguo Li

We first introduce and study two new classes of subsets in $T_0$ spaces - Rudin sets and $\wdd$ sets lying between the class of all closures of directed subsets and that of irreducible closed subsets. Using such subsets, we define three new…

General Topology · Mathematics 2019-09-23 Xiaoquan Xu , Chong Shen , Xiaoyong Xi , Dongsheng Zhao

In this paper, we provide a uniform approach to $d$-spaces, sober spaces and well-filtered spaces, and develop a general framework for dealing with all these spaces. For a subset system H, the theory of H-sober spaces and super H-sober…

General Topology · Mathematics 2020-03-18 Xiaoquan Xu

A non-empty subset of a topological space is irreducible if whenever it is covered by the union of two closed sets, then already it is covered by one of them. Irreducible sets occur in proliferation: (1) every singleton set is irreducible,…

Logic in Computer Science · Computer Science 2016-10-04 Hadrian Andradi , Weng Kin Ho

In this paper, we highlight some open problems stated by Xu and Zhao. In particular, we focus on strong $d$-spaces and answer two open problems concerning strong $d$-spaces. One is about the product space of an arbitrary family of strong…

General Topology · Mathematics 2021-09-24 Mengjie Jin , Hualin Miao , Qingguo Li

We study two classes of spaces whose points are filters on partially ordered sets. Points in MF spaces are maximal filters, while points in UF spaces are unbounded filters. We give a thorough account of the topological properties of these…

General Topology · Mathematics 2014-12-15 Carl Mummert , Frank Stephan

We first introduce and study two new classes of subsets in $T_0$ spaces - $\omega$-Rudin sets and $\omega$-well-filtered determined sets lying between the class of all closures of countable directed subsets and that of irreducible closed…

General Topology · Mathematics 2019-12-02 Xiaoquan Xu , Chong Shen , Xiaoyong Xi , Dongsheng Zhaod

In this paper, we obtain some sufficient conditions for the D-completion of a T0 space to be the well-filterification of this space, the well-filterification of a T0 space to be the sobrification of this space and the D-completion of a T0…

General Topology · Mathematics 2021-01-14 Hualin Miao , Longchun Wang , Qingguo Li

Recently, J. D. Lawson encouraged the domain theory community to consider the scientific program of developing domain theory in the wider context of $T_0$-spaces instead of restricting to posets. In this paper, we respond to this calling by…

Logic in Computer Science · Computer Science 2017-09-12 Hadrian Andradi , Weng Kin Ho

In this thesis, we introduce the subject of D-spaces and some of its most important open problems which are related to well known covering properties. We then introduce a new approach for studying D-spaces and covering properties in…

General Topology · Mathematics 2025-04-17 Talal Alrawajfeh , Hasan Z. Hdeib

Recently, J. D. Lawson encouraged the domain theory community to consider the scientific program of developing domain theory in the wider context of $T_0$ spaces instead of restricting to posets. In this paper, we respond to this calling by…

Logic in Computer Science · Computer Science 2016-07-06 Hadrian Andradi , Weng Kin Ho

In this paper, the concepts of $K$-subset systems and $k$-well-filtered spaces are introduced, which provide another uniform approach to $d$-spaces, $s$-well-filtered spaces (i.e., $\mathcal{U}_{S}$-admissibility) and well-filtered spaces.…

General Topology · Mathematics 2023-06-22 Mengjie Jin , Qingguo Li

M. Escard\'o et al. asked whether the core compactly generated topology of a sober space is again sober and the sobrification of a core compactly generated space again core compactly generated. In this note, we answer the problem by…

General Topology · Mathematics 2023-05-02 Qingguo Li , Hualin Miao
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