The Hilbert transform in weighted spaces of integrable vector-valued functions
T. M. Wolniewicz (1987)
Colloquium Mathematicae
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T. M. Wolniewicz (1987)
Colloquium Mathematicae
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G. Corach, G. Fongi, A. Maestripieri (2013)
Studia Mathematica
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We study A-projections, i.e. operators on a Hilbert space 𝓗 which act as projections when a seminorm is considered in 𝓗. The A-projections were introduced by Mitra and Rao (1974) for finite-dimensional spaces. We relate this concept to the theory of compatibility between positive operators and closed subspaces of 𝓗. We also study the relationship between weighted least squares problems and compatibility.
Maria Nowak, Renata Rososzczuk (2014)
Annales UMCS, Mathematica
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We consider Hilbert spaces which are counterparts of the de Branges-Rovnyak spaces in the context of the weighted Bergman spaces A2α, −1 < α < ∞. These spaces have already been studied in [8], [7], [5] and [1]. We extend some results from these papers
G. Peskir, D. Schneider, M. Weber (1996)
Mathematica Scandinavica
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Jarno Talponen (2010)
Studia Mathematica
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We characterize Hilbert spaces among Banach spaces in terms of transitivity with respect to nicely behaved subgroups of the isometry group. For example, the following result is typical: If X is a real Banach space isomorphic to a Hilbert space and convex-transitive with respect to the isometric finite-dimensional perturbations of the identity, then X is already isometric to a Hilbert space.
Minghua Lin (2013)
Studia Mathematica
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Let A, B be positive operators on a Hilbert space with 0 < m ≤ A, B ≤ M. Then for every unital positive linear map Φ, Φ²((A + B)/2) ≤ K²(h)Φ²(A ♯ B), and Φ²((A+B)/2) ≤ K²(h)(Φ(A) ♯ Φ(B))², where A ♯ B is the geometric mean and K(h) = (h+1)²/(4h) with h = M/m.
Guessous, Mohamed (1997)
Journal of Convex Analysis
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G. Greaves (1985)
Banach Center Publications
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Zbigniew Burdak, Wiesław Grygierzec (2020)
Annales Universitatis Paedagogicae Cracoviensis. Studia Mathematica
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The n-tuples of commuting Hilbert space contractions are considered. We give a model of a commuting lifting of one contraction and investigate conditions under which a commuting lifting theorem holds for an n-tuple. A series of such liftings leads to an isometric dilation of the n-tuple. The method is tested on some class of triples motivated by Parrotts example. It provides also a new proof of the fact that a positive definite n-tuple has an isometric dilation.
İlker Eryilmaz (2012)
Colloquium Mathematicae
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The boundedness, compactness and closedness of the range of weighted composition operators acting on weighted Lorentz spaces L(p,q,wdμ) for 1 < p ≤ ∞, 1 ≤ q ≤ ∞ are characterized.
Jan Stochel (1990)
Studia Mathematica
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Paweł Wójcik (2017)
Annales Mathematicae Silesianae
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In this expository paper, we present a new and easier proof of the Polar Decomposition Theorem. Unlike in classical proofs, we do not use the square root of a positive matrix. The presented proof is accessible to a broad audience.
Antonio Avantaggiati, Paola Loreti (2009)
Bollettino dell'Unione Matematica Italiana
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In this paper we obtain a more general inequality with respect to a well known inequality due to Gagliardo (see [4], [5]). The inequality contained in [4], [5] has been extended to weighted spaces, obtained as cartesian product of measurable spaces. As application, we obtain a first order weighted Sobolev inequality. This generalize a previous result obtained in [2].
Geraldo Soares De Souza (1990)
Colloquium Mathematicae
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B. E. Rhoades (1975)
Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti
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G. H. Constantin ha definito una classe di operatori di Cesàro-Hilbert-Schmidt. In questa Nota l'Autore trova la corrispondente proprietà per una più generale classe di operatori di Hilbert-Schmidt (G. H. S.).
Migórski, S. (1995)
Journal of Applied Mathematics and Stochastic Analysis
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Elke Wolf (2012)
Annales Universitatis Mariae Curie-Sklodowska, sectio A – Mathematica
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We study when a weighted composition operator acting between different weighted Bergman spaces is bounded, resp. compact.
Javier Carrillo-Alanís (2013)
Studia Mathematica
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We study the behaviour of the Rademacher functions in the weighted Cesàro spaces Ces(ω,p), for ω(x) a weight and 1 ≤ p ≤ ∞. In particular, the case when the Rademacher functions generate in Ces(ω,p) a closed linear subspace isomorphic to ℓ² is considered.
Zahra Kamali, Bahram Khani Robati, Karim Hedayatian (2011)
Czechoslovak Mathematical Journal
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In this paper, we discuss the hypercyclicity, supercyclicity and cyclicity of the adjoint of a weighted composition operator on a Hilbert space of analytic functions.
Eberhard Gerlach (1971)
Annales de l'institut Fourier
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A general theorem on Hilbert subspaces of dually nuclear spaces is proved, from which all previous results of K. Maurin and the writer on regularity of generalized eigenfunctions follow as simple corollaries. In addition some supplements to L. Schwartz’s work on Hilbert subspaces in spaces of smooth functions are given.
Elke Wolf (2012)
Annales UMCS, Mathematica
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We study when a weighted composition operator acting between different weighted Bergman spaces is bounded, resp. compact.