THE BOUNDARY SINE-GORDON THEORY - CLASSICAL AND SEMICLASSICAL ANALYSIS

We consider the sine-Gordon model on a half-line, with an additional p otential term of the form -M cos[1/2 beta(phi - phi(0))] at the bounda ry. We compute the classical time delay for general values of M, beta and phi(0) using tau-function methods and show that in the classical l imit the method of images still works, despite the non-linearity of th e problem. We also perform a semi-classical analysis, and find agreeme nt with the exact quantum S-matrix conjectured by Ghoshal and Zamolodc hikov.