On the number of components of the essential spectrum of one 2х2 operator matrix

Abstract

In this paper, a 2х2 block operator matrix H is considered as a bounded and self-adjointoperator in a Hilbert space. The location of the essential σess(H) of operator matrix H is described via the spectrum of the generalized Friedrichs model, i.e. the two- and three-particle branches of the essential spectrum σess(H) are singled out. We prove that the essential spectrum σess(H)  consists of no more than six segments (components).