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.
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.
Svantje Janson (1992)
Mathematica Scandinavica
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E. Wolf (2009)
RACSAM
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