Stability of essential B-spectra of unbounded linear operators and applications

Abstract

In this paper, we study the stability of some essential B-spectra of closed linear operators on a Banach space X, under polynomially finite rank operators and we give the characterization of some essential B-spectra of a $$2\times 2$$ of unbounded matrix operator acting in the product of Banach spaces $$X\times Y$$ . Then, using the functional calculus, we prove that a spectral mapping type theorem holds for these essential B-spectra. As an application, we study the effect of the functional calculus on the class of meromorphic operators, and on the class of isoloid operators with sable sign index, satisfying generalized Weyl theorem.