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1.
K. Alster 《Topology and its Applications》2009,156(7):1345-1347
We prove that if X is a paracompact space which has a neighborhood assignment x→Hx such that for each y∈X the closure of the set is compact then the products T×X, for every paracompact space T, and Xω are paracompact. The first result answers a problem of H. Junnila. 相似文献
2.
Udayan B. Darji 《Proceedings of the American Mathematical Society》1996,124(1):129-134
Suppose that is a sequence of differentiable functions defined on [0,1] which converges uniformly to some differentiable function , and converges pointwise to some function . Let . In this paper we characterize such sets under various hypotheses. It follows from one of our characterizations that can be the entire interval [0,1].
3.
A small Dowker space in ZFC 总被引:1,自引:0,他引:1
Zoltan T. Balogh 《Proceedings of the American Mathematical Society》1996,124(8):2555-2560
We construct a hereditarily normal topological space whose product with the unit interval is not normal. The space is -relatively discrete and has cardinality of the continuum .
4.
In this note we define a new topology on C(X),the set of all real-valued continuous functions on a Tychonoff space X.The new topology on C(X) is the topology having subbase open sets of both kinds:[f,C,ε[={g E C(X):|f(x)-g(x)| ε for every x∈C} and[U,r]~-={g∈C(X):g~(-1)(r)∩U≠φ},where f∈C(X),C∈KC(X)={nonempty compact subsets of X},ε 0,while U is an open subset of X and r∈R.The space C(X) equipped with the new topology T_(kh) which is stated above is denoted by C_(kh)(X).Denote X_0={x∈X:x is an isolated point of X} and X_c={x∈X:x has a compact neighborhood in X}.We show that if X is a Tychonoff space such that X_0=X_c,then the following statements are equivalent:(1) X_0 is G_δ-dense in X;(2) C_(kh)(X) is regular;(3) C_(kh)(X) is Tychonoff;(4) C_(kh)(X) is a topological group.We also show that if X is a Tychonoff space such that X_0=X_c and C_(kh)(X) is regular space with countable pseudocharacter,then X is σ-compact.If X is a metrizable hemicompact countable space,then C_(kh)(X) is first countable. 相似文献
5.
A. V. Arhangel'skii R. Z. Buzyakova 《Proceedings of the American Mathematical Society》1999,127(8):2449-2458
We prove that the cardinality of every first countable linearly Lindelöf Tychonoff space does not exceed , and every strongly discretely Lindelöf Tychonoff space of countable tightness is Lindelöf.
6.
设$u \in H(D), \ \phi$为$D$上的解析自映射,定义$H(D)$上的加权复合算子为$u C_{\phi}(f)=$$uf\circ\phi$, \ $f\in H(D)$.本文得到了从$A^{p}_{\alpha}$到$A^{\infty}(\varphi)\ (A_{0}^{\infty}(\varphi))$的加权复合算子$u C_{\phi}$的有界性和紧性的充要条件. 相似文献
7.
A linear space is Drake/Larson if it contains at least two lines and there are no lines of size 2, 3 or 6. The existence or nonexistence of such linear spaces on v points is known except for v=30. The purpose of this article is to settle the remaining case on thirty points in the negative. This result relies on a combination of parameter calculation and exhaustive computer search. © 2009 Wiley Periodicals, Inc. J Combin Designs 28: 48–70, 2010 相似文献
8.
Peter Nyikos Leszek Piatkiewicz 《Proceedings of the American Mathematical Society》1996,124(1):303-314
In 1975 E. K. van Douwen showed that if is a family of Hausdorff spaces such that all finite subproducts are paracompact, then for each element of the box product the -product is paracompact. He asked whether this result remains true if one considers uncountable families of spaces. In this paper we prove in particular the following result: Let be an infinite cardinal number, and let be a family of compact Hausdorff spaces. Let be a fixed point. Given a family of open subsets of which covers , there exists an open locally finite in refinement of which covers . We also prove a slightly weaker version of this theorem for Hausdorff spaces with ``all finite subproducts are paracompact" property. As a corollary we get an affirmative answer to van Douwen's question.
9.
Soon-Yeong Chung Dohan Kim Sungjin Lee 《Proceedings of the American Mathematical Society》1997,125(11):3229-3234
We give an elementary proof of the equivalence of the original definition of Schwartz and our characterization for the Schwartz space . The new proof is based on the Landau inequality concerning the estimates of derivatives. Applying the same method, as an application, we give a better symmetric characterization of the Beurling-Björck space of test functions for tempered ultradistributions with respect to Fourier transform without conditions on derivatives.
10.
Warren B. Moors 《Proceedings of the American Mathematical Society》2006,134(7):2161-2163
In this paper we prove that the product of a Baire space with a metrizable hereditarily Baire space is again a Baire space. This answers a recent question of J. Chaber and R. Pol.
11.
12.
Menachem Kojman Saharon Shelah 《Proceedings of the American Mathematical Society》1998,126(8):2459-2465
The existence of a Dowker space of cardinality and weight is proved in ZFC using pcf theory.
13.
Warren B. Moors Sivajah Somasundaram 《Proceedings of the American Mathematical Society》2003,131(2):647-654
A topological space is said to belong to the class of Stegall (weakly Stegall) spaces if for every Baire (complete metric) space and minimal usco , is single-valued at some point of . In this paper we show that under some additional set-theoretic assumptions that are equiconsistent with the existence of a measurable cardinal there is a Banach space whose dual, equipped with the weak topology, is in the class of weakly Stegall spaces but not in the class of Stegall spaces. This paper also contains an example of a compact space such that belongs to the class of weakly Stegall spaces but does not.
14.
P. Szewczak 《Topology and its Applications》2011,158(2):177-182
In [3] R. Telgársky (1975) asked: does the first player have a winning strategy in the game G(F,X×X) if the first player has a winning strategy in the game G(F,X)? I give a positive answer to this question and prove that this result is also true for spaces where the first player has a winning strategy in game G(K,X) where K=1, F, C, for σC if X is P-space and for DC if X is collectionwise-normal space. The last result is related to the Telgársky's (1983) conjecture discussed in [1]. These results are not true for infinite product of spaces. 相似文献
15.
L. Brian Lawrence 《Proceedings of the American Mathematical Society》1996,124(2):627-632
We give an example as indicated in the title where the weight (i.e., the minimum cardinality of a base for the topology) of the product is the smallest uncountable cardinal.
16.
为了从采样值稳定和惟一地重建信号f(x),函数在采样集{xj,j=∈Z}上的采样值{f(xj),j∈Z}要满足A||f||L^p^p≤∑j∈Z|f(xj)|^p≤B||f||L^p^p.本文研究在平移不变空间V^p[φ]中使上式成立的条件,在几种情况下,得到了使上式成立的采样条件,并建立了由采样值重建f(x)的重建算法,该算法比一般的迭代重建算法收敛更快. 相似文献
17.
Camillo Costantini 《Proceedings of the American Mathematical Society》1998,126(11):3393-3396
We prove the following two results. 1) There exists a non-separable complete metric space whose Wijsman hypertopology is not Cech-complete. 2) There exist a non-separable metrizable space and two compatible metrics on it, such that the collections of the Borel sets generated by the relative Wijsman hypertopologies do not coincide.
18.
Dechao Zheng 《Transactions of the American Mathematical Society》1998,350(4):1595-1618
By making use of -harmonic function theory, we characterize commuting Toeplitz operators with bounded pluriharmonic symbols on the Bergman space of the unit ball or on the Hardy space of the unit sphere in -dimensional complex space.
19.
Wolfgang Knirsch 《Mathematische Nachrichten》2004,265(1):15-23
On weighted spaces with strictly plurisubharmonic weightfunctions the canonical solution operator of and the ‐Neumann operator are bounded. In this paper we find a class of strictly plurisubharmonic weightfunctions with certain growth conditions, so that they are Hilbert‐Schmidt operators between weighted spaces with different weightfunctions, if they are restricted to forms with holomorphic coefficients. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
20.
Lixin Cheng Mariá n Fabian 《Proceedings of the American Mathematical Society》2001,129(12):3539-3541
This paper shows that the product of a Gâteaux differentiability space and a separable Banach space is again a Gâteaux differentiability space.