Classes of operators satisfying a-Weyl's theorem

In this article Weyl's theorem and a-Weyl's theorem on Banach spaces are related to an important property which has a leading role in local spectral theory: the single-valued extension theory. We show that if T has SVEP then Weyl's theorem and a-Weyl's theorem for T* are equivalent, and analogously, if T* has SVEP then Weyl's theorem and a-Weyl's theorem for T are equivalent. From this result we deduce that a-Weyl's theorem holds for classes of operators for which the quasi-nilpotent part H 0(λI-T) is equal to ker (λI -T)p for some p ∈ ℕ and every λ ∈ ℂ, and for algebraically paranormal operators on Hilbert spaces. We also improve recent results established by Curto and Han, Han and Lee, and Oudghiri

Local spectral theory for operators R and S satisfying RSR = R^2

We study some local spectral properties for bounded operators R, S, RS and SR in the case that R and S satisfy the operator equation RSR =R^2. Among other results, we prove that S, R, SR and RS share Dunford's property (C) when RSR = R^2and SRS =S^2peerReviewe

Property (w) and perturbations

A bounded linear operator T ∈ L(X) defined on a Banach space X satisfies property (w), a variant of Weyl’s theorem, if the complement in the approximate point spectrum σa(T ) of the Weyl essential approximate spectrum σwa(T ) coincides with the set of all isolated points of the spectrum which are eigenvalues of finite multiplicity. In this note, we study the stability of property (w), for a bounded operator T acting on a Banach space, under perturbations by finite rank operators, by nilpotent operator and quasi-nilpotent operators commuting with T

Property (gb) through local spectral theory

Property (gb) for a bounded linear operator T on a Banach space X means that the points c of the approximate point spectrum for which c I-T is upper semi B-Weyl are exactly the poles of the resolvent. In this paper we shall give several characterizations of property (gb). These characterizations are obtained by using typical tools from local spectral theory. We also show that property (gb) holds for large classes of operators and prove the stability of property (gb) under some commuting perturbations

Further Properties of an Operator Commuting with an Injective Quasi-Nilpotent Operator

In (Aiena et al., Math. Proc. R. Irish Acad. 122A(2):101–116, 2022), it has been shown that a bounded linear operator T ∈ L(X), defined on an infinite-dimensional complex Banach space X, for which there exists an injective quasi-nilpotent operator that commutes with it, has a very special structure of the spectrum. In this paper, we show that we have much more: if a such quasi-nilpotent operator does exist, then some of the spectra of T originating from B-Fredholm theory coalesce. Further, the spectral mapping theorem holds for all the B-Weyl spectra. Finally, the generalized version of Weyl type theorems hold for T assuming that T is of polaroid type. Our results apply to the operators that belong to the commutant of Volterra operators

Polaroid type operators under quasi-affinities

AbstractIn this paper we study the preservation of some polaroid conditions under quasi-affinities. As a consequence, we derive several results concerning the preservation of Weyl type theorems and generalized Weyl type theorems under quasi-affinities

A unifying approach to Weyl type theorems for Banach space operators

Weyl type theorems have been proved for a considerably large number of classes of operators. In this paper, by introducing the class of quasi totally hereditarily normaloid operators, we obtain a theoretical and general framework from which Weyl type theorems may be promptly established for many of these classes of operators. This framework also entails Weyl type theorems for perturbations f(T+K), where K is algebraic and commutes with T, and f is an analytic function, defined on an open neighborhood of the spectrum of $T+K, such that f is non constant on each of the components of its domain

Local spectral theory for operators R and S satisfying RSR =R2

We study some local spectral properties for bounded operators R, S, RS and SR in the case that R and S satisfy the operator equation RSR = R2. Among other results, we prove that S, R, SR and RS share Dunford?s property (C) when RSR = R2 and SRS = SSupported in part by MICINN (Spain), Grant MTM2013-45643