Essential spectra of quasisimilar -quasihyponormal operators.
Kim, An-Hyun, Kim, In Hyoun (2006)
Journal of Inequalities and Applications [electronic only]
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Kim, An-Hyun, Kim, In Hyoun (2006)
Journal of Inequalities and Applications [electronic only]
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Živković, Snežana (1997)
Publications de l'Institut Mathématique. Nouvelle Série
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Vladimir Rakočević (1997)
Studia Mathematica
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An operator in a Banach space is called upper (resp. lower) semi-Browder if it is upper (lower) semi-Fredholm and has a finite ascent (resp. descent). An operator in a Banach space is called semi-Browder if it is upper semi-Browder or lower semi-Browder. We prove the stability of the semi-Browder operators under commuting Riesz operator perturbations. As a corollary we get some results of Grabiner [6], Kaashoek and Lay [8], Lay [11], Rakočević [15] and Schechter [16].
Duggal, B.P. (2005)
International Journal of Mathematics and Mathematical Sciences
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Manuel González, Antonio Martinón (1991)
Extracta Mathematicae
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Let X and Y be infinite dimensional Banach spaces and let L(X,Y) be the class of all (linear continuous) operators acting between X and Y. Mil'man [5] introduced the isometry spectrum I(T) of T ∈ L(X,Y) in the following way: I(T) = {α ≥ 0: ∀ ε > 0, ∃M ∈ S∞(X), ∀x ∈ SM, | ||Tx|| - α | < ε}}, where S∞(X) is the set of all infinite dimensional closed subspaces of X and S...
L. A. Coburn, A. Lebow (1966)
Rendiconti del Seminario Matematico della Università di Padova
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Weis, L. W.
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Jaroslav Zemánek (1984)
Studia Mathematica
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Manuel González, Antonio Martinón (1993)
Extracta Mathematicae
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