Aldo J. Lazar
We study Michael's lower semifinite topology and Fell's topology on the collection of all closed limit subsets of a topological space. Special attention is given to the subfamily of all maximal limit sets.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
继续探索
Recently, David S. Lipham has shown that if $X$ is an Erdős space factor then the Vietoris hyperspace $\mathcal{F}(X)$ of finite subsets of $X$ is an Erdős space factor. In this short note we prove that if $\mathfrak{E}$ denotes Erdős space then $\mathcal{F}(\mathfrak{E})$ is in fact homeomorphic to $\mathfrak{E}$.
For a topological space $X$, let $CL(X)$ be the set of all non-empty closed subset of $X$, and denote the set $CL(X)$ with the Vietoris topology by $(CL(X), \mathbb{V})$. In this paper, we mainly discuss the hyperspace $(CL(X), \mathbb{V})$ when $X$ is an infinite countable discrete space. As an application, we first prove that the hyperspace with the Vietoris topology on an infinite countable discrete space contains a closed copy of $n$-th power of Sorgenfrey line for each $n\in\mathbb{N}$. Then we investigate the tightness of the hyperspace $(CL(X), \mathbb{V})$, and prove that the tightness…
Let ${\rm Fin}(X)$ be the hyperspace consisting of non-empty finite subsets of a space $X$ endowed with the Vietoris topology. In this paper, we characterize a metrizable space $X$ whose hyperspace ${\rm Fin}(X)$ is homeomorphic to the linear subspace spanned by the canonical orthonormal basis of a non-separable Hilbert space.
For a regular space $X$, the hyperspace $(CL(X), τ_{F})$ (resp., $(CL(X), τ_{V})$) is the space of all nonempty closed subsets of $X$ with the Fell topology (resp., Vietoris topology). In this paper, we give the characterization of the space $X$ such that the hyperspace $(CL(X), τ_{F})$ (resp., $(CL(X), τ_{V})$) with a countable character of closed subsets. We mainly prove that $(CL(X), τ_F)$ has a countable character on each closed subset if and only if $X$ is compact metrizable, and $(CL(X), τ_F)$ has a countable character on each compact subset if and only if $X$ is locally compact and sepa…
Let $CLB_H(X)$ denote the hyperspace of closed bounded subsets of a metric space $X$, endowed with the Hausdorff metric topology. We prove, among others, that natural dense subspaces of $CLB_H(R^m)$ of all nowhere dense closed sets, of all perfect sets, of all Cantor sets and of all Lebesgue measure zero sets are homeomorphic to the Hilbert space $\ell_2$. Moreover, we investigate the hyperspace $CL_H(R)$ of all nonempty closed subsets of the real line $R$ with the Hausdorff (infinite-valued) metric. We show that a nonseparable component of $CL_H(R)$ is homeomorphic to the Hilbert space $\ell_…
Spectre operator, achievement sets and sets of P-sums in a hyperspace of compact sets
本文研究了在紧集超空间中，基于谱定义的算子S及其相关成就集和P-和集的性质，探讨了其在平面中的特性。
Let G be a compact group acting on a Banach space L by means of linear isometries. The action of G on L induces a natural continuous action on cc(L), the hyperspace of all compact convex subsets of L endowed with the Hausdorff metric topology. The main result of this paper states that the G-space cc(L) is a G-AE. Under some extra assumptions, this result can be extended to CB(L), the hyperspace of all closed and bounded convex subsets of L.
On hyperspaces of knots and planar simple closed curves
本文研究了 $\mathbb R^n$ 中简单闭曲线与纽结的 Vietoris 超空间，证明了这些超空间具有强局部可缩、弧连通及无穷维 Cantor 流形等拓扑性质，并阐明了特定子空间的绝对邻域收缩核属性。
Hyperspace Selections Avoiding Points
本文在连通空间中研究超空间选择，通过区分非空闭集与至多两点集上的选择，分别刻画紧可序空间和弱循环可序空间。
A continuum is a compact connected metric space. A non-empty closed subset $B$ of a continuum $X$ does not block $x\in X\setminus B$ provided that the union of all subcontinua of $X$ containing $x$ and contained in $X\setminus B$ is dense in $X$. We denote the collection of all non-empty closed subset $B$ of $X$ such that $B$ does not block each element of $X\setminus B$ by $NB(F_1(X))$. In this paper we show some properties of the hyperspace $NB(F_1(X))$. Particularly, we prove that the simple closed curve is the unique continuum $X$ such that $NB(F_1(X))=F_1(X)$, given a positive answer to a…
We characterize metric spaces $X$ whose hyperspaces $2^X$ or $Bd(X)$ of non-empty closed (bounded) subsets, endowed with the Hausdorff metric, are absolute [neighborhood] retracts.
This article introduces strongly near proximity, which represents a new kind of proximity called \emph{almost proximity}. A main result in this paper is the introduction of a hit-and-miss topology on ${CL}(X)$, the hyperspace of nonempty closed subsets of $X$, based on the strongly near proximity.
This article introduces strongly far proximity, which is associated with Lodato proximity $δ$. A main result in this paper is the introduction of a hit-and-miss topology on $\mbox{CL}(X)$, the hyperspace of nonempty closed subsets of $X$, based on the strongly far proximity.
For a Hausdorff space $X$ we denote be $2^X$ the family of all closed subsets of $X$. In this paper we continue to research relationships between closure -type properties of hyperspaces over a space $X$ and covering properties of $X$. We investigate selectors for sequence of subsets of the space $2^{X}$ with the $Z^{+}$-topology and the upper Fell topology.
We study Vietoris hyperspaces of closed and closed final sets of Priestley spaces. We are particularly interested in Skula topologies. A topological space is \emph{Skula} if its topology is generated by differences of open sets of another topology. A compact Skula space is scattered and moreover has a natural well-founded ordering compatible with the topology, namely, it is a Priestley space. One of our main objectives is investigating Vietoris hyperspaces of general Priestley spaces, addressing the question when their topologies are Skula and computing the associated ordinal ranks. We apply o…
Given a metric continuum $X$, a nonempty proper closed subspace $B$ of $X$, does not block a point $p\in X\setminus B$ provided that the union of all subcontinua of $X$ containing $p$ and contained in $X\setminus B$ is a dense subset of $X$. The collection of all nonempty proper closed subspaces $B$ of $X$ such that $B$ does not block any element of $X\setminus B$ is denoted by $NB(F_{1}(X))$. In this paper we prove that for each completely metrizable and separable space $Z$, there exists a continuum $X$ such that $Z$ is homeomorphic to $NB(F_{1}(X))$. This answers a series of questions by Cam…
The hyperspace of k-dimensional closed convex sets
本文研究欧几里得空间中k维闭凸集超空间的拓扑结构，证明其与紧凸子集超空间均为Hilbert方体流形，并具有Grassmann流形上的纤维丛结构，同时确定了紧凸情形纤维的同胚类型。
It is shown that the hyperspace of all nonempty closed subsets $\Cld_{AW}(X)$ of a separable metric space $X$ endowed with the Attouch-Wets topology is homeomorphic to a separable Hilbert space if and only if the completion of $X$ is proper, locally connected and contains no bounded connected component, $X$ is topologically complete and not locally compact at infinity.
Hyperspaces of the double arrow
本文研究双箭空间与Sorgenfrey线的超空间齐性，证明双箭空间有限并闭区间空间非齐性，而收敛序列空间及Sorgenfrey线闭区间空间齐性，部分解决Arhangel'skiǐ问题。
Much of the structure in metric spaces that allows for the creation of fractals exists in more generalized non-metrizable spaces. In particular the same theorems regarding the behavior of compact sets can be proven in the more general framework of $β$-spaces. However in most $β$-spaces, a set being compact (and more generally being totally bounded) is so restrictive as to render all fractal examples completely uninteresting. In this paper we provide a generalization of compact sets, continuous functions, and all the related machinery necessary for fractals to be defined as the unique fixed set…
Modulo arithmetic of function spaces: Subset hyperspaces as quotients of function spaces
本文研究拓扑空间的子集超空间结构，将特定超空间刻画为函数空间的显式商，讨论相关紧子集超空间的可度量化，证明含Vietoris拓扑的超空间拓扑是含逐点收敛拓扑的函数空间拓扑的商。
Calibers of canonical hyperconnected spaces and their Vietoris hyperspaces
本文计算了特定超连通空间的尺度，并证明其与Vietoris超空间的尺度集合一致，为超空间理论提供了新结果。
On the Variety of Hyperspace Selections
本文研究Vietoris超空间连续选择点的集合$\mathcal{O}_{cs}(X)$的性质，证明其闭包是完全不连通子集，并在第一可数完全不连通空间中该集合是闭集。
It is shown that if a $T_2$ topological space $X$ contains a closed uncountable discrete subspace, then the spaces $(ω_1 + 1)^ω$ and $(ω_1 + 1)^{ω_1}$ embed into $(CL(X),τ_F)$, the hyperspace of nonempty closed subsets of $X$ equipped with the Fell topology. If $(X,d)$ is a non-separable perfect topological space, then $(ω_1 + 1)^ω$ and $(ω_1 + 1)^{ω_1}$ embed into $(CL(X),τ_{w(d)})$, the hyperspace of nonempty closed subsets of $X$ equipped with the Wijsman topology, giving a partial answer to the Question 3.4 in [CJ].
Ordinal Decompositions and Extreme Selections
本文提出了两种基于特殊序数分解生成极值超空间选择的自然构造，利用“模一点闭开”集合简化论证并推导新结果。
For a given continuum $X$ and a natural number $n,$ we consider the hyperspace $F_n(X)$ of all nonempty subsets of $X$ with at most $n$ points, metrized by the Hausdorff metric. In this paper we show that if $X$ is a dendrite whose set of end points is closed, $n \in \mathbb{N}$ and $Y$ is a continuum such that the hyperspaces $F_n(X)$ and $F_n(Y)$ are homeomorphic, then $Y$ is a dendrite whose set of end points is closed.
Butterfly Points and Hyperspace Selections
本文通过局部性质刻画了Vietoris超空间的连续选择在全集上的取值点，证明其为强蝴蝶点当且仅当存在可数闭开基，并完全解决了作者先前的问题，同时给出了缺乏该性质时的更强选择。
It is shown that if a $T_2$ topological space contains an uncountable closed discrete set, then $ω_1 \times (ω_1 + 1)$ embeds as a closed subspace of $(CL(X),τ_F)$, the hyperspace of nonempty closed subsets of $X$ equipped with the Fell topology.
The quasi-metrizability of hyperspaces
本文研究了赋予不同拓扑的超空间的拟可度量性，分别给出了 Vietoris、局部有限和 Fell 拓扑下超空间拟可度量或可对称化的充要条件，并据此对相关猜想给出了否定回答。
Let $(X,ρ)$ be a metric space and $(CL(X),W_ρ)$ be the hyperspace of all nonempty closed subsets of $X$ equipped with the Wijsman topology. The Wijsman topology is one of the most important classical hyperspace topologies. We give a partial answer to a question posed in \cite{maio} whether the normality of $(CL(X),W_ρ)$ is equivalent to its metrizability. If $(X,ρ)$ is a linear metric space, then $(CL(X),W_ρ)$ is normal if and only if $(CL(X),W_ρ)$ is metrizable. Some further results concerning normality of the Wijsman topology on $CL(X)$ are also proved.
In 2017, Tkachuk isolated the closed discrete selection property while working on problems related to function spaces [15]. In this paper we will study the closed discrete selection property and the related games and strategies on $C_k(X)$. Clontz and Holshouser showed previously that the closed discrete selection game on $C_p(X)$ is equivalent to a modification of the point-open game on $X$. In this paper we show that the closed discrete selection game on $C_k(X)$ is equivalent to a modification of the compact-open game on $X$. We also connect discrete selection properties on $C_k(X)$ to a va…
On some convergence approach structures on hyperspaces
本文研究了超空间上收敛方法结构的上、下Kuratowski收敛及费尔拓扑，并证明了相关方法结构的性质与关系。
A Universal Quasi-Polish Space
本文构造了通用拟波兰空间Y，证明所有拟波兰空间均同胚于Y的闭子空间，其超空间F(Y)为拟波兰空间，且Y的波兰闭子空间集合是F(Y)的Π¹₁完全余解析非博雷尔子集。
Tietze extension does not always work in constructive mathematics if closed sets are defined as sequentially closed sets
本文通过离散度量空间上的不可扩张算法函数构造反例，证明在构造性数学中当闭集定义为序列闭集时 Tietze 扩张定理不成立。
Here we have studied the ideas of g*-closed sets, g^tou -sets and Lamda*-closed sets and investigate some of their properties in the spaces of A. D. Alexandroff [1]. We have also studied few separation axioms like T-omega/4,T-3omega/8, T-omega in Alexandroff spaces and have introduced a new separation axiom namely T-5omega/8 axiom in this space.
Here we have investigated some aspects of $sλ$-closed sets on separation axioms including $s T_{2\frac{1}{2}} $ and $s T_{3\frac{1}{2}} $ axioms and on compactness in generalized topological spaces
We use convergence theory as the framework for studying H-closed spaces and H-sets in topological spaces. From this viewpoint, it becomes clear that the property of being H-closed and the property of being an H-set in a topological space are pretopological notions. Additionally, we define a version of H-closedness for pretopological spaces and investigate the properties of such a space.
The purpose of this paper is to continue studying the properties of $γ$-regular open sets introduced and explored in [6]. The concept of $γ$-closed spaces have also been defined and discussed.
On $a$-locally closed sets
本文借助 Ekici 的 $a$-开集提出 $a$-局部闭集概念，研究其性质与刻画，并阐明其与已有各类局部闭集的关系。
The aim of this note is to show that every subset of a given topological space is the intersection of a preopen and a preclosed set, therefore $β$-locally closed, and that every topological space is $β$-submaximal.
Here we have studied the ideas of $ sg_λ,sλ$ and $ sβ_λ$-closed sets and investigated some of their properties in generalized topological spaces. We have also studied some low separation axioms namely $ sλT_\frac{1}{4} $, $ sλT_\frac{3}{8} $, $ sλT_\frac{1}{2} $ axioms and their mutual relations with $ sλT_0 $ and $sλT_1 $ axioms.
Here we have introduced the ideas of $ (j-i)sg_κ^*$-closed sets and a semi generalized closed set in a bispace; $ i,j=1,2; i\not=j $ and then have studied on pairwise semi $T_0 $-axiom, pairwise semi $T_1 $-axiom and pairwise semi $T_ω$-axiom. We have investigated some of their topological properties and also established a relation among these axioms under some additional conditions.
Here we have introduced and studied the idea of $ Ig^*$-closed set with respect to an ideal and investigated some of its properties in Alexandroff spaces. We have also introduced $ Ig^*$-$T_0 $ axiom, $ Ig^*$-$T_1$ axiom, $ Ig^*$-$T_ω$ axiom and explored a relation among them
Closed sets in a generalization of the Alexandrov cube
本文继续研究由收敛 λ_ls 诱导的拓扑，重点利用极小元素族刻画闭集和闭包算子，并特别关注满足可数链条件的完备布尔代数。
Here we have studied the idea of semi Lamda*-closed sets and investigate some of their properties in spaces considered by A. D. Alexandroff [1]. We have introduced some new separation axioms namely semi-Tw/4, , semi-T3w/8, semi-T5w/8, and their inter-relation with semi-T0 and semi-T1. We have shown that under certain conditions these axioms are equivalent.
It is proved that -- consistently -- there can be no ccc closed P-sets in the remainder space omega^* .
Porosities of the sets of attractors
本文研究 $[0,1]$ 上迭代函数系统吸引子族与弱迭代函数系统吸引子族的差异，证明 $A[0,1]$ 不是 $σ$-强孔隙的，并证明 $A_w[0,1]\setminus A[0,1]$ 在超空间 $K([0,1])$ 中稠密。
Families of unconditionally $τ$-closed and $τ$-algebraic sets in a group are defined, which are natural generalizations of unconditionally closed and algebraic sets defined by Markov. A sufficient condition for the coincidence of these families is found. In particular, it is proved that these families coincide in any group of cardinality at most $τ$. This result generalizes both Markov's theorem on the coincidence of unconditionally closed and algebraic sets in a countable group (as is known, they may be different in an uncountable group) and Podewski's theorem on the topologizablity of any un…
We prove that the countable product of lines contains a Borel linear subspace $L\ne\mathbb R^ω$ that cannot be covered by countably many closed Haar-meager sets. This example is applied to studying the interplay between various classes of ``large'' sets and Kuczma--Ger classes in the topological vector spaces $\mathbb R^n$ for $n\le ω$.
扫码添加微信好友，提出您的宝贵建议 👇
💡 备注请填写：网站反馈
发表机构由 AI 从论文文本抽取，如发现错误，欢迎反馈修正建议。