MULTICRITICAL 2-DIMENSIONAL VERTEX MODELS

We study the multicritical behavior of a class of two-dimensional ice-type vertex models on different lattices using renormalization-group theory. The models are classified by an integer m, with m = 2 corresponding to the known square lattice case. For m > 2, the specific-heat exponent is alpha = (m - 2)/(m - 1) with an upper critical dimensional confluent (lnt) 1/2 divergence for m = 3. The nature of the transition is similar to the mth-order multicritical point, yet the exponents are not those known from c < 1 conformal invariance. The models are anisotropic with nu(parallel-to) = 1 and nu(perpendicular-to) = 1/2. A few special features of the models are discussed.