RENORMALIZATION-GROUP CALCULATION OF CORRELATION-FUNCTIONS FOR THE 2DRANDOM BOND ISING AND POTTS MODELS

We find the crossover behaviour of the disorder averaged spin-spin cor relation function for the 2D Ising and 3-state Potts model with random bonds at the critical point. The procedure employed is the renormalis ation approach of the perturbation series around the conformal field t heories representing the pure models. We obtain a crossover in the amp litude for the correlation function for the Ising model, which does no t change the critical exponent, and a shift in the critical exponent p roduced by randomness in the case of the Potts model. A comparison wit h numerical data is discussed briefly.