Spectral Concentration and Virtual Poles. II

Abstract

Spectral concentration at an isolated eigenvalue of finite multiplicity of the selfadjoint operator <!-- MATH ${H_\varepsilon } = {T_\varepsilon } + {A_\varepsilon }{B_\varepsilon }$ --> is shown to arise from a pole of an analytic continuation of <!-- MATH ${A_\varepsilon }{({H_\varepsilon } - z)^{ - 1}}{B_\varepsilon }$ --> . An application to quantum mechanical barrier penetration is given.