THERMODYNAMIC BETHE ANSATZ FOR RSOS SCATTERING THEORIES

Thermodynamic Bethe ansatz equations are suggested for RSOS scattering theories, which describe the scattering of kinks in the field theories, corresponding to the perturbations of the minimal CFT models M(p) by relevant operators PHI(1,3) with negative coupling constant. The equations turn to be of A(p-2) type with a special choice of the mass terms. For the M4 case (tricritical Ising) the equations are studied numerically. This gives high precision data for the Casimir energy of the finite-volume system. The analytic continuation in the coupling constant results in reasonable numerical data for positive values of coupling. The data support the interpretation of the positive-coupling field theory as the trajectory flowing from the tricritical Ising fixed-point to the critical Ising one.