Weyl's Theorem for Algebraically (π, π)-Quasihyponormal Operators
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Salah Mecheri
Abstract
Let π΄ be a bounded linear operator acting on a Hilbert space π». The π΅-Weyl spectrum of π΄ is the set Οπ΅π€(π΄) of all β β β such that π΄ β βπΌ is not a π΅-Fredholm operator of index 0. Let πΈ(π΄) be the set of all isolated eigenvalues of π΄. Recently, in [Berkani and Arroud, J. Aust. Math. Soc. 76: 291β302, 2004] the author showed that if π΄ is hyponormal, then π΄ satisfies the generalized Weyl's theorem Οπ΅π€(π΄) = Ο(π΄) \ πΈ(π΄), and the π΅-Weyl spectrum Οπ΅π€(π΄) of π΄ satisfies the spectral mapping theorem. Lee [Han, Proc. Amer. Math. Soc. 128: 2291β2296, 2000] showed that Weyl's theorem holds for algebraically hyponormal operators. In this paper the above results are generalized to an algebraically (π, π)-quasihyponormal operator which includes an algebraically hyponormal operator.
Β© Heldermann Verlag
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Articles in the same Issue
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- Existence Theory for Perturbed Nonlinear Boundary Value Problems with Integral Boundary Conditions
- A Generalization of Bihari's Lemma for Discontinuous Functions and Its Application to the Stability Problem of Differential Equations with Impulse Disturbance
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