Dislocation problem for the Dirac operator

We consider the dislocation problem for the Dirac operator with a periodic potential on the real line. The dislocation is parameterized by a real parameter. For each parameter value, the absolutely continuous spectrum has a band structure and there are open gaps between spectral bands. We show that in each open gap there exist exactly two distinct “states” (eigenvalues or resonances) of the dislocated operator, such that they runs clockwise around the gap. These states are separated from each other by the Dirichlet eigenvalue and they make half as many revolutions as the Dirichlet eigenvalue does in unit time. We find asymptotic of this motion for the cases when a state is near the gaps boundary and collides with the Dirichlet eigenvalue.