scholarly journals (Strong) weak exhaustiveness and (strong uniform) continuity

Filomat ◽  
2010 ◽  
Vol 24 (4) ◽  
pp. 63-75 ◽  
Author(s):  
Agata Caserta ◽  
Maio Di ◽  
L'ubica Holá
Keyword(s):  
Uniform Convergence ◽  
Metric Spaces ◽  
Hausdorff Metric ◽  
Convergent Sequence ◽  
Uniform Continuity ◽  
Direct Image ◽  
Continuity Property ◽  
Property A ◽  
Sequence Of Functions

In this paper we continue, in the realm of metric spaces, the study of exhaustiveness and weak exhaustiveness at a point of a net of functions initiated by Gregoriades and Papanastassiou in 2008. We prove that exhaustiveness at every point of a net of pointwise convergent functions is equivalent to uniform convergence on compacta. We extend exhaustiveness-type properties to subsets. First, we introduce the notion of strong exhaustiveness at a subset B for sequences of functions and prove its equivalence with strong exhaustiveness at P0 (B) of the sequence of the direct image maps, where the hypersets are equipped with the Hausdorff metric. Furthermore, we show that the notion of strong-weak exhaustiveness at a subset is the proper tool to investigate when the limit of a pointwise convergent sequence of functions fulfills the strong uniform continuity property, a new pregnant form of uniform continuity discovered by Beer and Levi in 2009.

scholarly journals A characterization of the uniform convergence points set of some convergent sequence of functions

2021 ◽  
Vol 71 (2) ◽  
pp. 423-428
Author(s):  
Olena Karlova
Keyword(s):  
Uniform Convergence ◽  
Convergent Sequence ◽  
Normal Space ◽  
Disjoint Sequence ◽  
Isolated Points ◽  
Perfectly Normal Space ◽  
Set Of Points ◽  
Sequence Of Functions ◽  
Perfectly Normal

Abstract We characterize the uniform convergence points set of a pointwisely convergent sequence of real-valued functions defined on a perfectly normal space. We prove that if X is a perfectly normal space which can be covered by a disjoint sequence of dense subsets and A ⊆ X, then A is the set of points of the uniform convergence for some convergent sequence (fn ) n∈ω of functions fn : X → ℝ if and only if A is Gδ -set which contains all isolated points of X. This result generalizes a theorem of Ján Borsík published in 2019.

On Uniform Convergence of Continuous Functions and Topological Convergence of Sets

1983 ◽  
Vol 26 (4) ◽  
pp. 418-424 ◽  
Author(s):  
Gerald Beer
Keyword(s):  
Uniform Convergence ◽  
Metric Spaces ◽  
Hausdorff Metric ◽  
Related Result ◽  
Continuous Functions ◽  
Topological Convergence ◽  
The Relationship ◽  
Convergence Of Sets

AbstractLet X and Y be metric spaces. This paper considers the relationship between uniform convergence in C(X, Y) and topological convergence of functions in C(X, Y), viewed as subsets of X×Y. In general, uniform convergence in C(X, Y) implies Hausdorff metric convergence which, in turn, implies topological convergence, but if X and Y are compact, then all three notions are equivalent. If C([0, 1], Y) is nontrivial arid topological convergence in C(X, Y) implies uniform converger ce then X is compact. Theorem: Let X be compact and Y be loyally compact but noncompact. Then topological convergence in C(X, Y) implies uniform convergence if and only if X has finitely many components. We also sharpen a related result of Naimpally.

scholarly journals Metric Fourier Approximation of Set-Valued Functions of Bounded Variation

2021 ◽  
Vol 27 (2) ◽  
Author(s):  
Elena E. Berdysheva ◽  
Nira Dyn ◽  
Elza Farkhi ◽  
Alona Mokhov
Keyword(s):  
Fourier Series ◽  
Bounded Variation ◽  
Error Bounds ◽  
Metric Spaces ◽  
Hausdorff Metric ◽  
Dirichlet Kernel ◽  
Partial Sums ◽  
Functions Of Bounded Variation ◽  
Moduli Of Continuity ◽  
Fourier Approximation

AbstractWe introduce and investigate an adaptation of Fourier series to set-valued functions (multifunctions, SVFs) of bounded variation. In our approach we define an analogue of the partial sums of the Fourier series with the help of the Dirichlet kernel using the newly defined weighted metric integral. We derive error bounds for these approximants. As a consequence, we prove that the sequence of the partial sums converges pointwisely in the Hausdorff metric to the values of the approximated set-valued function at its points of continuity, or to a certain set described in terms of the metric selections of the approximated multifunction at a point of discontinuity. Our error bounds are obtained with the help of the new notions of one-sided local moduli and quasi-moduli of continuity which we discuss more generally for functions with values in metric spaces.

scholarly journals Property A for groups acting on metric spaces

2003 ◽  
Vol 130 (3) ◽  
pp. 239-251 ◽  
Author(s):  
Gregory C. Bell
Keyword(s):  
Metric Spaces ◽  
Property A

scholarly journals Statistical Convergence in Function Spaces

2011 ◽  
Vol 2011 ◽  
pp. 1-11 ◽  
Author(s):  
Agata Caserta ◽  
Giuseppe Di Maio ◽  
Ljubiša D. R. Kočinac
Keyword(s):  
Uniform Convergence ◽  
Statistical Convergence ◽  
Statistical Approach ◽  
Metric Spaces ◽  
Function Spaces ◽  
Strong Uniform Convergence ◽  
Convergence Of Sequences

We study statistical versions of several classical kinds of convergence of sequences of functions between metric spaces (Dini, Arzelà, and Alexandroff) in different function spaces. Also, we discuss a statistical approach to recently introduced notions of strong uniform convergence and exhaustiveness.

scholarly journals Quantitative nonlinear embeddings into Lebesgue sequence spaces

2016 ◽  
Vol 08 (01) ◽  
pp. 117-150
Author(s):  
Florent P. Baudier
Keyword(s):  
Group Theory ◽  
Positive Solution ◽  
Metric Spaces ◽  
Exact Formula ◽  
Geometric Group Theory ◽  
Sequence Spaces ◽  
Text Compression ◽  
Property A ◽  
Locally Compact ◽  
Strong Embeddability

In this paper fundamental nonlinear geometries of Lebesgue sequence spaces are studied in their quantitative aspects. Applications of this work are a positive solution to the strong embeddability problem from [Formula: see text] into [Formula: see text] ([Formula: see text]) and new insights on the coarse embeddability problem from [Formula: see text] into [Formula: see text], [Formula: see text]. Relevant to geometric group theory purposes, the exact [Formula: see text]-compression of [Formula: see text] is computed. Finally coarse deformation of metric spaces with property A and locally compact amenable groups is investigated.

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