BOUND-STATE IN A ONE-DIMENSIONAL QUANTUM SINE-GORDON MODEL

The impurity problem ina one-dimensional quantum sine-Gordon model is studied in this paper. We use an analytic self-consistent theory to de rive the excitation spectrum of the global sine-Gordon model, and then to study the bound state induced by local impurity. We give the condi tions where an impurity level exists within the global gap of the exci tation spectrum and show the possibility of the existence of a thresho ld value about the model parameter.