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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

Ern\'e weakened the concept of sobriety in order to extend the theory of sober spaces and locally hypercompact spaces to situations where directed joins were missing, and introduced and discussed three kinds of non-sober spaces: cut spaces,…

General Mathematics · Mathematics 2022-04-22 Xinpeng Wen , Xiaoquan Xu

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, 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, we provide a direct approach to $\mathbf{K}$-reflections of $T_0$ spaces. For a full subcategory $\mathbf{K}$ of the category of all $T_0$ spaces and a $T_0$ space $X$, let $\mathbf{K}(X)=\{A\subseteq X : A$ is closed and for…

General Topology · Mathematics 2019-11-27 Xiaoquan Xu

In this paper, for a full subcategory $\mathbf{K}$ of the category of all $T_0$ spaces with continuous mappings, we investigate the questions under what conditions the $\mathbf{K}$-reflection of a Scott space is still a Scott space and…

General Mathematics · Mathematics 2022-04-21 Xiaoquan Xu

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

For a $T_1$ space $X$, Zhao and Xi constructed a dcpo model $\hat{P}$, where $P$ is a bounded complete algebraic poset model of $X$. In this paper, we formulate the closed WD subsets of the maximal point space $\mathrm{Max}(\hat{P})$ and…

General Topology · Mathematics 2023-11-15 Siheng Chen , Qingguo Li

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 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

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

Using a construction derived from the descending central series of the free groups, we produce filtrations by infinite loop spaces of the classical infinite loop spaces $BSU$, $BU$, $BSO$, $BO$, $BSp$, $BGL_{\infty}(R)^{+}$ and…

Algebraic Topology · Mathematics 2017-03-22 Alejandro Adem , José Manuel Gómez , John A. Lind , Ulrike Tillmann

We show that the epireflective hull of the Q-Sierpinski space in the category Q-$TOP_0$ of $T_0$ Q-topological spaces is the category Q-SOB of Q-sober topological spaces.

Category Theory · Mathematics 2013-06-18 Sheo Kumar Singh , Arun K. Srivastava

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 short paper we combine the representability theorem introduced in [17, 18] with the theory of derived formal models introduced in [2] to prove the existence representability of the derived Hilbert space RHilb(X) for a separated…

Algebraic Geometry · Mathematics 2023-06-22 Jorge António , Mauro Porta

A word is cubefree if it contains no non-empty subword of the form xxx. A morphism h : Sigma^* -> Sigma^* is k-uniform if h(a) has length k for all a in Sigma. A morphism is cubefree if it maps cubefree words to cubefree words. We show that…

Combinatorics · Mathematics 2009-04-14 James Currie , Narad Rampersad

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

We say that a space X admits a homology exponent if there exists an exponent for the torsion subgroup of the integral homology. Our main result states if an H-space of finite type admits a homology exponent, then either it is, up to…

Algebraic Topology · Mathematics 2007-05-23 Alain Clement , Jerome Scherer

The main purpose of this study is to introduce the spaces $cs^{\lambda}, cs_0^{\lambda}$ and $bs^{\lambda}$ which are $BK-$spaces of non-absolute type. We prove that these spaces are linearly isomorphic to the spaces $cs, cs_0$ and $bs$,…

Functional Analysis · Mathematics 2013-07-23 Meltem Kaya , Hasan Furkan

The study of the sobriety of Scott spaces has got an relative long history in domain theory. Lawson and Hoffmann independently proved that the Scott space of every continuous directed complete poset (usually called domain) is sober.…

General Topology · Mathematics 2022-05-03 Hualin Miao , Xiaoyong Xi , Qingguo Li , Dongsheng Zhao
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