RESONANT BRANCH CUTS IN A GENERALIZED FRIEDRICHS MODEL

We study an example of a generalized Friedrichs model, in which a cont inuous-continuous coupling produces a pair of resonances as branch cut s of the analytic continuation of the reduced resolvent of the perturb ed Hamiltonian to the second sheet of the Riemann surface associated t o a transformation of the type w = z + alpha root z. To define the per turbation, we use the theory of self-adjoint extensions of symmetric o perators proposed by the group of St. Petersburg. (C) 1996 John Wiley & Sons, Inc.