CRITICAL-BEHAVIOR OF A 19-VERTEX MODEL WITH FULL FRUSTRATION

We apply the singular value decomposition method to matrices made from eigenvectors of the transfer matrix of a 19-vertex model on a square lattice with full frustration. The conformal anomaly c is estimated to be close to 3/2. This result suggests that the 19-vertex model with f ull frustration has a single transition due to two kinds of degrees of freedom, each of which has U(1) symmetry and Z(2) symmetry. Moreover, we find that the value of index eta is Smaller than that at the Berez inskii-Kosterlitz-Thouless (BKT) transition by considering a logarithm ic correction to the finite size analysis. This result for eta suggest s that there is another universality class which is different from tha t of either the Onsager type or the BKT type. [S0163-1829(98)02941-5].