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An elementary operator with log-hyponormal, p-hyponormal entries
Authors:BP Duggal
Institution:8 Redwood Grove, Northfield Avenue, Ealing, London W5 4SZ, United Kingdom
Abstract:A Hilbert space operator AB(H) is p-hyponormal, A∈(p-H), if |A|2p?|A|2p; an invertible operator AB(H) is log-hyponormal, A∈(?-H), if log(TT)?log(TT). Let dAB=δAB or ?AB, where δABB(B(H)) is the generalised derivation δAB(X)=AX-XB and ?ABB(B(H)) is the elementary operator ?AB(X)=AXB-X. It is proved that if A,B∈(?-H)∪(p-H), then, for all complex λ, View the MathML source, the ascent of (dAB-λ)?1, and dAB satisfies the range-kernel orthogonality inequality ‖X‖?‖X-(dAB-λ)Y‖ for all X∈(dAB-λ)-1(0) and YB(H). Furthermore, isolated points of σ(dAB) are simple poles of the resolvent of dAB. A version of the elementary operator E(X)=A1XA2-B1XB2 and perturbations of dAB by quasi-nilpotent operators are considered, and Weyl’s theorem is proved for dAB.
Keywords:Primary 47B47  47B10  47A10  47B40
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