CRITICAL-BEHAVIOR OF RANDOM-BOND POTTS MODELS

The effect of quenched impurities On systems undergoing first-order ph ase transitions is studied within the framework of the q-state Potts m odel. For large q a mapping to the random-field Ising model explains t he absence of any latent heat in 2D, and suggests that for d > 2 such systems exhibit a tricritical point with an exponent nu related to tho se of the random-field model by nu = nu(RF)/(2 - alpha(RF) - beta(RF)) In 2D we analyze the model using finite-size scaling and conformal in variance, and find a continuous transition with a ratio beta/nu which varies continuously with q, and a weakly varying exponent nu approxima te to 1. We find strong evidence for the multiscaling of the correlati on functions.