Nonself-Adjoint Operators with Almost Hermitian Spectrum: Weak Annihilators

Author: Kiselev A. V.   Naboko S. N.  

Publisher: Springer Publishing Company

ISSN: 0016-2663

Source: Functional Analysis and Its Applications, Vol.38, Iss.3, 2004-07, pp. : 192-201

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Abstract

We consider nonself-adjoint nondissipative trace class additive perturbations l=a+iv of a bounded self-adjoint operator a in a Hilbert space h. The main goal is to study the properties of the singular spectral subspace n_i^0 of l corresponding to part of the real singular spectrum and playing a special role in spectral theory of nonself-adjoint nondissipative operators.To some extent, the properties of n_i^0 resemble those of the singular spectral subspace of a self-adjoint operator. Namely, we prove that l and the adjoint operator l^* are weakly annihilated by some scalar bounded outer analytic functions if and only if both of them satisfy the condition n_i^0=h. This is a generalization of the well-known Cayley identity to nonself-adjoint operators of the above-mentioned class.