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Totally hereditarily normaloid operators and Weyl's theorem for an elementary operator
Authors:BP Duggal
Institution:a 8 Redwood Grove, Northfields Avenue, Ealing, London W5 4SZ, England, UK
b Catholic University of Rio de Janeiro, 22453-900 Rio de Janeiro, RJ, Brazil
Abstract:A Hilbert space operator TB(H) is hereditarily normaloid (notation: THN) if every part of T is normaloid. An operator THN is totally hereditarily normaloid (notation: TTHN) if every invertible part of T is normaloid. We prove that THN-operators with Bishop's property (β), also THN-contractions with a compact defect operator such that View the MathML source and non-zero isolated eigenvalues of T are normal, are not supercyclic. Take A and B in THN and let dAB denote either of the elementary operators in B(B(H)): ΔAB and δAB, where ΔAB(X)=AXBX and δAB(X)=AXXB. We prove that if non-zero isolated eigenvalues of A and B are normal and View the MathML source, then dAB is an isoloid operator such that the quasi-nilpotent part H0(dABλ) of dABλ equals −1(dABλ)(0) for every complex number λ which is isolated in σ(dAB). If, additionally, dAB has the single-valued extension property at all points not in the Weyl spectrum of dAB, then dAB, and the conjugate operator View the MathML source, satisfy Weyl's theorem.
Keywords:Hilbert space  Totally hereditarily normaloid operators  Weyl's theorems  Single-valued extension property
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