共查询到20条相似文献,搜索用时 93 毫秒
1.
2.
3.
4.
5.
主要借助于紧覆盖映射、闭映射和商映射讨论了局部紧Lindel(o)f空间的像空间,推导出具有某些特定性质的k系空间的一些刻画,引入强k系的概念给出了局部紧Lindel(o)f空间和仿紧局部紧空间的一种新的等价刻画. 相似文献
6.
给出代数L-domain和强core紧空间以及连续L-domain和core紧空间的刻画。 相似文献
7.
8.
9.
10.
11.
利用拓扑博弈G(DC,X)的理论,推广了关于meso-紧空间有限乘积性质并得到如下结果:(1)如果(V)i∈ω,Yi是正则DC-like的meso-紧空间,则∏iωYi是meso-紧的;(2)如果(V)i∈ω,Yi是正则C-散射meso-紧的P-空间,则∏i∈ωYi是meso-紧的. 相似文献
12.
In the paper [properties defined with semi-continuous functions and some related spaces',Houston J.Math.,2015,41(3):1097–1106] properties(U L)~(wl)_m,(U L)~K_m and(U L)_m were defined and it was shown that spaces having these properties coincide with countably paracompact spaces,countably mesocompact spaces and countably metacompact spaces,respectively.In this paper,we continue with the study on the relationship between properties defined with real-valued functions and some covering properties.Some characterizations of countably compact spaces and pseudo-compact spaces in terms of real-valued functions are obtained. 相似文献
13.
关于submeso紧空间的映射定理 总被引:4,自引:0,他引:4
证明了在正则空间中闭Lindelof映射保持且逆保持submeso紧性,这改进了林寿关于正则空间完备映射保持且逆保持submeso紧性这一结果;同时我们引用一个反例说明原象空间的正则性是必要的. 相似文献
14.
In Riemannian spaces, locally Desarguesian spaces have constant curvature and are therefore locally symmetric. This does not hold for Finsler spaces, so that locally Desarguesian spaces represent a generalization other than the obvious one we studied previously of (certain) Riemannian symmetric spaces. In this paper we discuss them in detail; as an example of the results obtained we mention that a simply connected locally Desarguesian space without conjugate points is globally Desarguesian. Applications are then given to spaces which are locally symmetric in a wider sense. We also study (and in Minkowski spaces determine exactly) the properties of functions which measure the distance of a point from those on a line. 相似文献
15.
Valerio Capraro 《Expositiones Mathematicae》2013,31(4):334-349
We define the isoperimetric constant for any locally finite metric space and we study the property of having isoperimetric constant equal to zero. This property, called Small Neighborhood property, clearly extends amenability to any locally finite space. Therefore, we start making a comparison between this property and other notions of amenability for locally finite metric spaces that have been proposed by Gromov, Lafontaine and Pansu, by Ceccherini-Silberstein, Grigorchuk and de la Harpe and by Block and Weinberger. We discuss possible applications of the property SN in the study of embedding a metric space into another one. In particular, we propose three results: we prove that a certain class of metric graphs that are isometrically embeddable into Hilbert spaces must have the property SN. We also show, by a simple example, that this result is not true replacing property SN with amenability. As a second result, we prove that many spaces with uniform bounded geometry having a bi-lipschitz embedding into Euclidean spaces must have the property SN. Finally, we prove a Bourgain-like theorem for metric trees: a metric tree with uniform bounded geometry and without property SN does not have bi-lipschitz embeddings into finite-dimensional Hilbert spaces. 相似文献
16.
A normed space is paracomplete if it admits a new norm, stronger than the initial one, that makes it complete. Here we give
a characterization of paracomplete normed spaces. As a consequence, we show that operators on paracomplete spaces have compact
spectrum in the algebra of all operators, and that the class of paracomplete spaces is not stable under ℓ2-sums. Moreover, we give characterizations for the closed Fredholm operators on paracomplete spaces and for the almost semi-Fredholm
operators of Harte on normed spaces. 相似文献
17.
In this article we study a construction of compactly supported frame expansions for decomposition spaces of Triebel-Lizorkin
type and for the associated modulation spaces. This is done by showing that finite linear combinations of shifts and dilates
of a single function with sufficient decay in both direct and frequency space can constitute a frame for Triebel-Lizorkin
type spaces and the associated modulation spaces. First, we extend the machinery of almost diagonal matrices to Triebel-Lizorkin
type spaces and the associated modulation spaces. Next, we prove that two function systems which are sufficiently close have
an almost diagonal “change of frame coefficient” matrix. Finally, we approximate to an arbitrary degree an already known frame
for Triebel-Lizorkin type spaces and the associated modulation spaces with a single function with sufficient decay in both
direct and frequency space. 相似文献
18.
In this paper we study Banach spaces that admit weighted Chebyshev centres for finite sets. Such spaces have been extensively studied recently by Veselý using the approach of finitely intersecting balls. Following his approach we exhibit large classes of Banach spaces that have this property. Certain stability results for spaces of vector valued continuous and Bochner integrable functions are also obtained. 相似文献
19.
Francisco García Arenas Miguel Angel Sánchez-Granero 《Mediterranean Journal of Mathematics》2012,9(4):709-728
In this paper we use fractal structures to study self-similar sets and self-similar symbolic spaces. We show that these spaces have a natural fractal structure, justifying the name of fractal structure, and we characterize self-similar symbolic spaces in terms of fractal structures. We prove that self-similar symbolic spaces can be characterized in a similar way, in the form, to the definition of classical self-similar sets by means of iterated function systems. We also study when a self-similar symbolic space is a self-similar set. Finally, we study relations between fractal structures with “pieces” homeomorphic to the space and different concepts of self-homeomorphic spaces. Along the paper, we propose several methods in order to construct self-similar sets and self-similar symbolic spaces from a geometrical approach. This allows to construct these kind of spaces in a very easy way. 相似文献
20.
Straight spaces are spaces for which a continuous map defined on the space which is uniformly continuous on each set of a finite closed cover is then uniformly continuous on the whole space. Previously, straight spaces have been studied in the setting of metric spaces. In this paper, we present a study of straight spaces in the more general setting of nearness spaces. In a subcategory of nearness spaces somewhat more general than uniform spaces, we relate straightness to uniform local connectedness. We investigate category theoretic situations involving straight spaces. We prove that straightness is preserved by final sinks, in particular by sums and by quotients, and also by completions. 相似文献