A CRITICAL ISING-MODEL IN A MAGNETIC-FIELD

Generalising ideas developed by Owczarek and Baxter and by Pasquier, w e establish an equivalence between restricted solid-on-solid models an d loop models. Application to the O(n) model leads to a new family of solvable A-D-E models. For the models related to the classical A(L) al gebra we present an off-critical extension and show that the A3 model thus obtained can be viewed as a critical spin-1 Ising model in a magn etic field. For this Ising model we calculate the critical exponent de lta = 15 without the use of scaling relations.