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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Duggal, B.P. (2005)
International Journal of Mathematics and Mathematical Sciences
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Bhagwati Prashad Duggal (2005)
Extracta Mathematicae
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A Banach space operator T belonging to B(X) is said to be hereditarily normaloid, T ∈ HN, if every part of T is normaloid; T ∈ HN is totally hereditarily normaloid, T ∈ THN, if every invertible part of T is also normaloid; and T ∈ CHN if either T ∈ THN or T - λI is in HN for every complex number λ. Class CHN is large; it contains a number of the commonly considered classes of operators. We study operators T ∈ CHN, and prove that the Riesz projection associated with a λ ∈ isoσ(T), T ∈...
Yusup Eshkabilov (2008)
Open Mathematics
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Let Ω= [a, b] × [c, d] and T 1, T 2 be partial integral operators in (Ω): (T 1 f)(x, y) = k 1(x, s, y)f(s, y)ds, (T 2 f)(x, y) = k 2(x, ts, y)f(t, y)dt where k 1 and k 2 are continuous functions on [a, b] × Ω and Ω × [c, d], respectively. In this paper, concepts of determinants and minors of operators E−τT 1, τ ∈ ℂ and E−τT 2, τ ∈ ℂ are introduced as continuous functions on [a, b] and [c, d], respectively. Here E is the identical operator in C(Ω). In addition, Theorems on the spectra...
Yang, Youngoh (1998)
International Journal of Mathematics and Mathematical Sciences
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S. Djordjević, B. Duggal (2000)
Studia Mathematica
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We show that p-hyponormal operators obey Weyl's and a-Weyl's theorem. Also, we show that the spectrum, Weyl spectrum, Browder spectrum and approximate point spectrum are continuous functions in the class of all p-hyponormal operators.
Abdelmoumen, Boulbeba, Baklouti, Hamadi (2009)
Journal of Inequalities and Applications [electronic only]
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Slaviša V. Đorđević (1998)
Matematički Vesnik
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Schôichi Ôta, Franciszek Hugon Szafraniec (2004)
Studia Mathematica
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The paper concerns operators of deformed structure like q-normal and q-hyponormal operators with the deformation parameter q being a positive number different from 1. In particular, an example of a q-hyponormal operator with empty spectrum is given, and q-hyponormality is characterized in terms of some operator inequalities.
Derek Kitson (2009)
Studia Mathematica
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We extend the notion of ascent and descent for an operator acting on a vector space to sets of operators. If the ascent and descent of a set are both finite then they must be equal and give rise to a canonical decomposition of the space. Algebras of operators, unions of sets and closures of sets are treated. As an application we construct a Browder joint spectrum for commuting tuples of bounded operators which is compact-valued and has the projection property.
F. Lombarkia, A. Bachir (2007)
Matematički Vesnik
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Vladimír Müller (1993)
Studia Mathematica
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We investigate relations between the spectra defined by Słodkowski [14] and higher Shilov boundaries of the Taylor spectrum. The results generalize the well-known relation between the approximate point spectrum and the usual Shilov boundary.
V. Rakočević (1984)
Matematički Vesnik
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