Essential spectrum of pseudodifferential operators and exponential estimates of it solutions

The main aim of the talk is the relations between the location of the essential spectrum and the exponential decay of solutions of pseudodifferential operators perturbed by singular potentials. For a solution of this problem we apply the limit operators method.
We give applications to the calculation of relations between essential spectra and exponential estimates of the decay behavior of eigenfunctions of Schrödinger, Dirac and Klein-Gordon operators.