共查询到20条相似文献,搜索用时 15 毫秒
1.
Sibe Mardeši? 《Topology and its Applications》2009,156(14):2326-2345
In 2003 the author has associated with every cofinite inverse system of compact Hausdorff spaces X with limit X and every simplicial complex K (possibly infinite) with geometric realization P=|K| a resolution R(X,K) of X×P, which consists of paracompact spaces. If X consists of compact polyhedra, then R(X,K) consists of spaces having the homotopy type of polyhedra. In two subsequent papers the author proved that R(X,K) is a covariant functor in each of its variables X and K. In the present paper it is proved that R(X,K) is a bifunctor. Using this result, it is proved that the Cartesian product X×Z of a compact Hausdorff space X and a topological space Z is a bifunctor SSh(Cpt)×Sh(Top)→Sh(Top) from the product category of the strong shape category of compact Hausdorff spaces SSh(Cpt) and the shape category Sh(Top) of topological spaces to the category Sh(Top). This holds in spite of the fact that X×Z need not be a direct product in Sh(Top). 相似文献
2.
Sibe Mardeši? 《Topology and its Applications》2007,155(1):1-32
In a previous paper the author has associated with every inverse system of compact Hausdorff spaces X with limit X and every simplicial complex K (possibly infinite) with geometric realization P=|K| a resolution RK(X) of X×P, which consists of paracompact spaces. If X consists of compact polyhedra, then RK(X) consists of spaces having the homotopy type of polyhedra. In the present paper it is proved that this construction is functorial. One of the consequences is the existence of a functor from the strong shape category of compact Hausdorff spaces X to the shape category of spaces, which maps X to the Cartesian product X×P. Another consequence is the theorem which asserts that, for compact Hausdorff spaces X, X′, such that X is strong shape dominated by X′ and the Cartesian product X′×P is a direct product in Sh(Top), then also X×P is a direct product in the shape category Sh(Top). 相似文献
3.
Yoshio Tanaka 《Topology and its Applications》2009,156(5):926-931
As is well known, every product of symmetric spaces need not be symmetric. For symmetric spaces X and Y, in terms of their balls, we give characterizations for the product X×Y to be symmetric under X and Y having certain k-networks, or Y being semi-metric. 相似文献
4.
《Quaestiones Mathematicae》2013,36(1-3):191-205
Abstract Examples are provided which demonstrate that in many cases topological products do not behave as they should. A new product for topological spaces is defined in a natural way by means of interior covers. In general this is no longer a topological space but can be interpreted as categorical product in a category larger than Top. For compact spaces the new product coincides with the old. There is a converse: For symmetric topological spaces X the following conditions are equivalent: (1) X is compact; (2) for each cardinal k the old and the new product Xk coincide; (3) for each compact Hausdorff space Y the old and the new product X x Y coincide. The new product preserves paracompactness, zero-dimensionality (in the covering sense), the Lindelöf property, and regular-closedness. With respect to the new product, a space is N-complete iff it is zerodimensional and R-complete. 相似文献
5.
Valentin G. Gutev 《Set-Valued Analysis》1993,1(3):247-260
Every open continuous mappingf from a metric space (X, d) onto a countable-dimensional metric spaceY admits a special type of factorization (Y×[0, 1] throughout), provided all fibers off are dense in itself and complete with respect tod. On this basis, an upper semi-continuous Cantor bouquet of disjoint usco selections for a class of 1.s.c. mappings between metrizable spaces is constructed. 相似文献
6.
The main result of the paper says that if X is a paracompact GO-space, meaning a subspace of a linearly ordered space and M a paracompact space satisfying the first axiom of countability such that X can be embedded in Mω1 then the product X×Y is paracompact for every paracompact space Y if and only if the first player of the G(DC,X) game, introduced by Telgarsky has a winning strategy. In particular we obtain that if X is paracompact GO-space of weight not greater than ω1 then the product X×Y is paracompact for every paracompact space Y if and only if the first player of the G(DC,X) game has a winning strategy. 相似文献
7.
In 1975 Hagopian proved that continua X and Y are atriodic and hereditarily unicoherent when the product X×Y is disk-like. In this paper, under the same condition, we prove that X and Y are contractible with respect to every ANR and X and Y are tree-like continua in ClassHW. 相似文献
8.
Ioana Ghenciu 《Quaestiones Mathematicae》2018,41(6):811-828
In this paper we study equivalent formulations of the DP? Pp (1 < p < ∞). We show that X has the DP? Pp if and only if every weakly-p-Cauchy sequence in X is a limited subset of X. We give su?cient conditions on Banach spaces X and Y so that the projective tensor product X ?π Y, the dual (X ?? Y)? of their injective tensor product, and the bidual (X ?π Y)?? of their projective tensor product, do not have the DP Pp, 1 < p < ∞. We also show that in some cases, the projective and the injective tensor products of two spaces do not have the DP? Pp, 1 < p < ∞. 相似文献
9.
LetC(X,Y) be the space of continuous functions from a metric space (X,d) to a metric space (Y, e).C(X, Y) can be thought as subset of the hyperspaceCL(X×Y) of closed and nonempty subsets ofX×Y by identifying each element ofC(X,Y) with its graph. We considerC(X,Y) with the topology inherited from the Wijsman topology induced onCL(X×Y) by the box metric ofd ande. We study the relationships between the Wijsman topology and the compact-open topology onC(X,Y) and also conditions under which the Wijsman topology coincide with the Fell topology. Sufficient conditions under which the
compactopen topology onC(X,Y) is weaker than the Wijsman topology are given (IfY is totally bounded, then for every metric spaceX the compactopen topology onC(X,Y) is weaker than the Wijsman topology and the same is true forX locally connected andY rim-totally bounded). We prove that a metric spaceX is boundedly compact iff the Wijsman topology onC(X, ℝ) is weaker than the compact-open topology. We show that ifX is a σ-compact complete metric space andY a compact metric space, then the Wijsman topology onC(X,Y) is Polish. 相似文献
10.
K. Alster 《Topology and its Applications》2009,156(8):1545-1553
R. Telgarsky conjectured that if X is a paracompact space then the product X×Y is paracompact for every paracompact space Y if and only if the first player of the G(DC,X) game, introduced by R. Telgarsky, see [R. Telgarsky, Spaces defined by topological games, Fund. Math. 88 (1975) 193-223], has a winning strategy. The paper contains some results supporting this conjecture. 相似文献
11.
Haruto Ohta 《Topology and its Applications》1982,13(2):155-165
We generalize and refine results from the author's paper [18]. For a completely regular Hausdorff space X, υX denotes the Hewitt realcompactification of X. It is proved that if υ(X×Y)=υX×υY for any metacompact subparacompact (or m-paracompact) space Y, then X is locally compact. A P(n)-space is a space in which every intersection of less than n open sets is open. A characterization of those spaces X such that υ (X×Y = υX×υY for any (metacompact) P(n)-space Y is also obtained. 相似文献
12.
Functoriality of the standard resolution of the Cartesian product of a compactum and a polyhedron II
Sibe Mardeši? 《Topology and its Applications》2008,155(15):1708-1719
In 2003 the author has associated with every cofinite inverse system of compact Hausdorff spaces X with limit X and every simplicial complex K (possibly infinite) with geometric realization P=|K| a resolution R(X,K) of X×P, which consists of paracompact spaces. If X consists of compact polyhedra, then R(X,K) consists of spaces having the homotopy type of polyhedra. In a subsequent paper, published in 2007, the author proved that R(X,K) is a covariant functor in the first variable. In the present paper it is proved that R(X,K) is a covariant functor also in the second variable. 相似文献
13.
We extend earlier work [M.R. Burke, N.D. Macheras, K. Musia?, W. Strauss, Category product densities and liftings, Topology Appl. 153 (2006) 1164-1191] of the authors on the existence of category liftings in the product of two topological spaces X and Y such that X×Y is a Baire space. For given densities ρ, σ on X and Y, respectively, we introduce two ‘Fubini type’ products ρ⊙σ and ρ?σ on X×Y. We present a necessary and sufficient condition for ρ⊙σ to be a density. Provided (X,Y) and (Y,X) have the Kuratowski-Ulam property, we prove for given category liftings ρ, σ on the factors the existence of a category lifting π on the product, dominating the density ρ?σ and such that
14.
《Quaestiones Mathematicae》2013,36(3):215-228
Abstract A categorical characterization of the category Haus of Hausdorft topological spaces within the category Top of topological spaces is given. A notion of a Hausdorff nearness space is then introduced and it is proved that the resulting subcategory Haus Near of the category Near of nearness spaces fulfills exactly the same characterization as derived for Haus in Top. Properties of Haus Near and relations to other important sub-categories of Near are studied. 相似文献
15.
Alessandro Berarducci Dikran Dikranjan Jan Pelant 《Topology and its Applications》2009,156(7):1422-1437
A metric space X is straight if for each finite cover of X by closed sets, and for each real valued function f on X, if f is uniformly continuous on each set of the cover, then f is uniformly continuous on the whole of X. A locally connected space is straight iff it is uniformly locally connected (ULC). It is easily seen that ULC spaces are stable under finite products. On the other hand the product of two straight spaces is not necessarily straight. We prove that the product X×Y of two metric spaces is straight if and only if both X and Y are straight and one of the following conditions holds:
- (a)
- both X and Y are precompact;
- (b)
- both X and Y are locally connected;
- (c)
- one of the spaces is both precompact and locally connected.
16.
The relations between zero-dimensional homogeneous spaces and h-homogeneous ones are investigated. We suggest an indication of h -homogeneity for a homogeneous zero-dimensional paracompact space and its modification for a topological group. We describe some cases when the product X×Y is an h-homogeneous space provided X is h-homogeneous and Y is homogeneous. 相似文献
17.
Jonathan David Farley 《Order》1996,13(1):65-98
The category of bounded distributive lattices with order-preserving maps is shown to be dually equivalent to the category of Priestley spaces with Priestley multirelations. The Priestley dual space of the ideal lattice L
of a bounded distributive lattice L is described in terms of the dual space of L. A variant of the Nachbin-Stone-ech compactification is developed for bitopological and ordered spaces. Let X be a poset and Y an ordered space; X
Y
denotes the poset of continuous order-preserving maps from Y to X with the discrete topology. The Priestley dual of L
P
is determined, where P is a poset and L a bounded distributive lattice. 相似文献
18.
Jose L. Blasco 《Topology and its Applications》1983,16(2):117-121
F.B. Jones has proved that for many different topological properties P if there exists a non-normal space with property P then there exists a non-completely regular space Y with property P. In this paper we study the topological structure of the space Y and we characterize the topological spaces with a similar structure to that possessed by Y. 相似文献
19.
Věra Trnková 《Applied Categorical Structures》2007,15(5-6):621-631
Solving the problem stated in Sichler and Trnková, Topol. Its Appl., 142: 159–179, 2004, we construct metrics μ, ν on a set P such that the spaces X=(P,μ) and Y=(P,ν) have the same monoid of all continuous selfmaps, the space Y is coconnected (in the sense that every continuous map Y×Y→Y depends on at most one coordinate) while X is not. Also, properties of the forgetful functors Metr → Unif → Top are investigated for the “simultaneous variant” of the
above problem.
Supported by the Grant Agency of Czech Republic under grant 201/06/0664 and by the project of Ministry of Education of Czech
Republic MSM 0021620839. 相似文献
20.
In this paper we investigate two main problems. One of them is the question on the existence of category liftings in the product of two topological spaces. We prove, that if X×Y is a Baire space, then, given (strong) category liftings ρ and σ on X and Y, respectively, there exists a (strong) category lifting π on the product space such that π is a product of ρ and σ and satisfies the following section property: