On ultra-weak convergence in
Donald E. Myers (1976)
Annales Polonici Mathematici
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Donald E. Myers (1976)
Annales Polonici Mathematici
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Taras O. Banakh, Joanna Garbulińska-Wegrzyn (2020)
Commentationes Mathematicae Universitatis Carolinae
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We observe that the notion of an almost -universal based Banach space, introduced in our earlier paper [1]: Banakh T., Garbulińska-Wegrzyn J., The universal Banach space with a -suppression unconditional basis, Comment. Math. Univ. Carolin. 59 (2018), no. 2, 195–206, is vacuous for . Taking into account this discovery, we reformulate Theorem 5.2 from [1] in order to guarantee that the main results of [1] remain valid.
Taras O. Banakh, Joanna Garbulińska-Wegrzyn (2018)
Commentationes Mathematicae Universitatis Carolinae
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Using the technique of Fraïssé theory, for every constant , we construct a universal object in the class of Banach spaces possessing a normalized -suppression unconditional Schauder basis.
F. Albiac, C. Leránoz (2002)
Studia Mathematica
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We prove that the quasi-Banach spaces and (0 < p < 1) have a unique unconditional basis up to permutation. Bourgain, Casazza, Lindenstrauss and Tzafriri have previously proved that the same is true for the respective Banach envelopes and ℓ₁(ℓ₂). They used duality techniques which are not available in the non-locally convex case.
Madjid Eshaghi Gordji, Ali Jabbari, Abasalt Bodaghi (2019)
Mathematica Bohemica
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The generalized notion of weak amenability, namely -weak amenability, where are continuous homomorphisms on a Banach algebra , was introduced by Bodaghi, Eshaghi Gordji and Medghalchi (2009). In this paper, the -weak amenability on the measure algebra , the group algebra and the Segal algebra , where is a locally compact group, are studied. As a typical example, the -weak amenability of a special semigroup algebra is shown as well.
S. V. Konyagin, V. N. Temlyakov (2003)
Studia Mathematica
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We consider convergence of thresholding type approximations with regard to general complete minimal systems eₙ in a quasi-Banach space X. Thresholding approximations are defined as follows. Let eₙ* ⊂ X* be the conjugate (dual) system to eₙ; then define for ε > 0 and x ∈ X the thresholding approximations as , where . We study a generalized version of that we call the weak thresholding approximation. We modify the in the following way. For ε > 0, t ∈ (0,1) we set and consider...
Wolfgang Lusky (2003)
Studia Mathematica
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Let be a commuting approximating sequence of the Banach space X leaving the closed subspace A ⊂ X invariant. Then we prove three-space results of the following kind: If the operators Rₙ induce basis projections on X/A, and X or A is an -space, then both X and A have bases. We apply these results to show that the spaces and have bases whenever Λ ⊂ ℤ and ℤ∖Λ is a Sidon set.
Larry Kitchens, Charles Swartz (1974)
Colloquium Mathematicae
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S. Gabriyelyan, J. Kąkol, G. Plebanek (2016)
Studia Mathematica
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Following Banakh and Gabriyelyan (2016) we say that a Tychonoff space X is an Ascoli space if every compact subset of is evenly continuous; this notion is closely related to the classical Ascoli theorem. Every -space, hence any k-space, is Ascoli. Let X be a metrizable space. We prove that the space is Ascoli iff is a -space iff X is locally compact. Moreover, endowed with the weak topology is Ascoli iff X is countable and discrete. Using some basic concepts from probability...
Hamid Sadeghi (2019)
Archivum Mathematicum
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In this paper we investigate -weak character amenability of certain Banach algebras such as projective tensor product and Lau product , where and are two arbitrary Banach algebras and , the character space of . We also investigate -weak character amenability of abstract Segal algebras and module extension Banach algebras.
Sreela Gangopadhyay (1990)
Colloquium Mathematicae
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Aydin Sh. Shukurov (2014)
Colloquium Mathematicae
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It is well known that if φ(t) ≡ t, then the system is not a Schauder basis in L₂[0,1]. It is natural to ask whether there is a function φ for which the power system is a basis in some Lebesgue space . The aim of this short note is to show that the answer to this question is negative.
Aydin Sh. Shukurov (2012)
Colloquium Mathematicae
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A necessary condition for Kostyuchenko type systems and system of powers to be a basis in (1 ≤ p < +∞) spaces is obtained. In particular, we find a necessary condition for a Kostyuchenko system to be a basis in (1 ≤ p < +∞).
Artur Michalak (2014)
Bulletin of the Polish Academy of Sciences. Mathematics
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We say that a function f from [0,1] to a Banach space X is increasing with respect to E ⊂ X* if x* ∘ f is increasing for every x* ∈ E. A function is separately increasing if it is increasing in each variable separately. We show that if X is a Banach space that does not contain any isomorphic copy of c₀ or such that X* is separable, then for every separately increasing function with respect to any norming subset there exists a separately increasing function such that the sets of...
Eva Matoušková, Simeon Reich (2003)
Studia Mathematica
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A Banach space X is reflexive if and only if every bounded sequence xₙ in X contains a norm attaining subsequence. This means that it contains a subsequence for which is attained at some f in the dual unit sphere . A Banach space X is not reflexive if and only if it contains a normalized sequence xₙ with the property that for every , there exists such that . Combining this with a result of Shafrir, we conclude that every infinite-dimensional Banach space contains an unbounded...
Mahdi Dehghani, Mohammad B. Dehghani, Mohammad S. Moshtaghioun (2020)
Commentationes Mathematicae Universitatis Carolinae
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We introduce and study two new classes of Banach spaces, the so-called sequentially Right Banach spaces of order , and those defined by the dual property, the sequentially Right Banach spaces of order for . These classes of Banach spaces are characterized by the notions of -limited sets in the corresponding dual space and subsets of the involved Banach space, respectively. In particular, we investigate whether the injective tensor product of a Banach space and a reflexive Banach...
B. Cascales, I. Namioka, J. Orihuela (2003)
Studia Mathematica
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A topological space (T,τ) is said to be fragmented by a metric d on T if each non-empty subset of T has non-empty relatively open subsets of arbitrarily small d-diameter. The basic theorem of the present paper is the following. Let (M,ϱ) be a metric space with ϱ bounded and let D be an arbitrary index set. Then for a compact subset K of the product space the following four conditions are equivalent: (i) K is fragmented by , where, for each S ⊂ D, . (ii) For each countable subset...
Salvador García-Ferreira, Y. F. Ortiz-Castillo (2015)
Commentationes Mathematicae Universitatis Carolinae
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Let be the subspace of consisting of all weak -points. It is not hard to see that is a pseudocompact space. In this paper we shall prove that this space has stronger pseudocompact properties. Indeed, it is shown that is a -pseudocompact space for all .
Stanisław Szufla (1989)
Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti
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For the integral equation (1) below we prove the existence on an interval of a solution with values in a Banach space , belonging to the class , . Further, the set of solutions is shown to be a compact one in the sense of Aronszajn.
Sergey V. Astashkin, Lech Maligranda (2014)
Banach Center Publications
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Geometric structure of Cesàro function spaces , where I = [0,1] and [0,∞), is investigated. Among other matters we present a description of their dual spaces, characterize the sets of all q ∈ [1,∞] such that contains isomorphic and complemented copies of -spaces, show that Cesàro function spaces fail the fixed point property, give a description of subspaces generated by Rademacher functions in spaces .
Abderrahman Retbi (2024)
Mathematica Bohemica
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We introduce and study the disjoint weak -convergent operators in Banach lattices, and we give a characterization of it in terms of sequences in the positive cones. As an application, we derive the domination and the duality properties of the class of positive disjoint weak -convergent operators. Next, we examine the relationship between disjoint weak -convergent operators and disjoint -convergent operators. Finally, we characterize order bounded disjoint weak -convergent operators...
Paolo Terenzi
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There exists a universal control sequence of increasing positive integers such that: Every infinite-dimensional separable Banach space X has a biorthogonal system xₙ,xₙ* with ||xₙ|| = 1 and ||xₙ*|| < K for each n such that, for each x ∈ X, where π(n) is a permutation of n which depends on x but is uniformly controlled by , that is, for each m.