Universality class of the Nishimori point in the 2D +/- J random-bond Ising model - art. no. 047201

We study the universality class of the Nishimori point in the 2D +/-J rando m-bond Ising model by means of the numerical transfer-matrix method. Using the domain-wall free energy, we locate the position of the fixed point alon g the Nishimori line at the critical concentration value p(c) = 0.1094 +/- 0.0002 and estimate v = 1.33 +/- 0.03. Then, we obtain the exponents for th e moments of the spin-spin correlation functions as well as the value for t he central charge c = 0.464 +/- 0.004. The main qualitative result is the f act that percolation is now excluded as a candidate for describing the univ ersality class of this fixed point.