EXACT EFFECTIVE POTENTIAL FOR A SCALAR SOURCE COUPLED TO THE SINE-GORDON MODEL - TEST OF EFFECTIVE POTENTIALS FOR COMPOSITE NUCLEONS

Bethe ansatz methods are used to obtain an exact expression for the energy density for a system consisting of the (1+1)-dimensional sine-Gordon model coupled to an external scalar source. This method exploits the equivalence between the sine-Gordon model and the massive Thirring model. These calculations allow one to test various loop-expansion approximations to the effective potential for the scalar. Such calculations are of relevance to fundamental issues regarding quantum hadrodynamics. © 1990 The American Physical Society.