On operators with the same spectrum
Gh. Constantin (1975)
Matematički Vesnik
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Gh. Constantin (1975)
Matematički Vesnik
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Marcin Bownik, John Jasper (2015)
Bulletin of the Polish Academy of Sciences. Mathematics
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Given a finite set X⊆ ℝ we characterize the diagonals of self-adjoint operators with spectrum X. Our result extends the Schur-Horn theorem from a finite-dimensional setting to an infinite-dimensional Hilbert space analogous to Kadison's theorem for orthogonal projections (2002) and the second author's result for operators with three-point spectrum (2013).
Olli Hyvärinen, Ilmari Nieminen (2015)
Concrete Operators
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In this paperwe study both the spectra and the essential spectra ofweighted composition operators on Hardy spaces Hp(ⅅ), standard weighted Bergman spaces Apα(ⅅ) and weighted H∞1-type spaces when the symbols are of hyperbolic type
Albrecht Böttcher, Ilya M. Spitkovsky (1993)
Revista Matemática Iberoamericana
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We describe the spectrum and the essential spectrum and give an index formula for Wiener-Hopf integral operators with piecewise continuous symbols on the space L(R,ω) with a Muckenhoupt weight ω. Our main result says that the essential spectrum is a set resulting from the essential range of the symbol by joining the two endpoints of each jump by a certain sickle-shaped domain, whose shape is completely determined by the value of p and the behavior of the weight ω at the origin and at...
Gopal Datt, Deepak Kumar Porwal (2013)
Matematički Vesnik
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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.
Vasile Lauric (2018)
Czechoslovak Mathematical Journal
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The question whether a hyponormal weighted shift with trace class self-commutator is the compression modulo the Hilbert-Schmidt class of a normal operator, remains open. It is natural to ask whether Putinar's construction through which he proved that hyponormal operators are subscalar operators provides the answer to the above question. We show that the normal extension provided by Putinar's theory does not lead to the extension that would provide a positive answer to the question. ...
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.
J. Janas (1988)
Colloquium Mathematicae
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W. Młak (1990)
Annales Polonici Mathematici
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Benharrat, Mohammed, Messirdi, Bekkai (2011)
Serdica Mathematical Journal
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2010 Mathematics Subject Classification: 47A10. We show that the symmetric difference between the generalized Kato spectrum and the essential spectrum defined in [7] by sec(T) = {l О C ; R(lI-T) is not closed } is at most countable and we also give some relationship between this spectrum and the SVEP theory.
Bucur, Amelia (1996)
General Mathematics
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Aggour, M.M. (1996)
International Journal of Mathematics and Mathematical Sciences
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Bichegkuev, M. S. (2002)
Vladikavkazskiĭ Matematicheskiĭ Zhurnal
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Ptak Marek
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CONTENTS1. Introduction...................................................................................................52. N-tuples of linear transformations in finite-dimensional space......................83. Toeplitz operators on the polydisc and the unit ball....................................184. Subspaces of weighted shifts.....................................................................235. Joint spectra for N-tuples of operators........................................................276....
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.
Amila Appuhamy (2021)
Czechoslovak Mathematical Journal
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We study algebraic properties of two Toeplitz operators on the weighted Bergman space on the unit disk with harmonic symbols. In particular the product property and commutative property are discussed. Further we apply our results to solve a compactness problem of the product of two Hankel operators on the weighted Bergman space on the unit bidisk.
Svantje Janson (1992)
Mathematica Scandinavica
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