The center of an algebra of operators
Anna Zappa (1978)
Colloquium Mathematicae
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Anna Zappa (1978)
Colloquium Mathematicae
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Milutin Dostanić (1994)
Publications de l'Institut Mathématique
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Abdelkader Benali, Mohammed Hichem Mortad (2014)
Bulletin of the Polish Academy of Sciences. Mathematics
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We are mainly concerned with the result of Kaplansky on the composition of two normal operators in the case in which at least one of the operators is unbounded.
Fernando Cobos, Luz M. Fernández-Cabrera, Antón Martínez (2005)
Studia Mathematica
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The paper establishes necessary and sufficient conditions for compactness of operators acting between general K-spaces, general J-spaces and operators acting from a J-space into a K-space. Applications to interpolation of compact operators are also given.
Beatriz Margolis (1972)
Annales Polonici Mathematici
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Galakhov, E. (1997)
Memoirs on Differential Equations and Mathematical Physics
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Ryotaro Sato (1976)
Colloquium Mathematicae
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Ryotaro Sato (1976)
Colloquium Mathematicae
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John B. Conway, Gabriel Prǎjiturǎ (2005)
Studia Mathematica
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For a scalar λ, two operators T and S are said to λ-commute if TS = λST. In this note we explore the pervasiveness of the operators that λ-commute with a compact operator by characterizing the closure and the interior of the set of operators with this property.
Sameer Chavan (2008)
Studia Mathematica
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We introduce and discuss a class of operators, to be referred to as operators close to isometries. The Bergman-type operators, 2-hyperexpansions, expansive p-isometries, and certain alternating hyperexpansions are main examples of such operators. We establish a few decomposition theorems for operators close to isometries. Applications are given to the theory of p-isometries and of hyperexpansive operators.
M. R. Dostanić (1989)
Matematički Vesnik
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Jaroslav Zemánek (2007)
Banach Center Publications
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Miroslav Sova (1982)
Časopis pro pěstování matematiky
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Chun Guang Li, Ting Ting Zhou (2014)
Studia Mathematica
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A bounded linear operator T acting on a Hilbert space is said to be polaroid if each isolated point in the spectrum is a pole of the resolvent of T. There are several generalizations of the polaroid property. We investigate compact perturbations of polaroid type operators. We prove that, given an operator T and ε > 0, there exists a compact operator K with ||K|| < ε such that T + K is polaroid. Moreover, we characterize those operators for which a certain polaroid type property...