Random Bond Potts Model: the Test of the Replica Symmetry Breaking

Averaged spin-spin correlation function squared $\overline{^{2}}$ is calculated for the ferromagnetic random bond Potts model. The technique being used is the renormalization group plus conformal field theory. The results are of the $\epsilon$ - expansion type fixed point calculation, $\epsilon$ being the deviation of the central charge (or the number of components) of the Potts model from the Ising model value. Calculations are done both for the replica symmetric and the replica symmetry broken fixed points. The results obtained allow for the numerical simulation tests to decide between the two different criticalities of the random bond Potts model.Comment: 50 pages, Latex, 2 eps figure

The third parafermionic chiral algebra with the symmetry Z_{3}

We have constructed the parafermionic chiral algebra with the principal parafermionic fields \Psi,\Psi^{+} having the conformal dimension \Delta_{\Psi}=8/3 and realizing the symmetry Z_{3}.Comment: 6 pages, no figur

Spin--spin critical point correlation functions for the 2D random bond Ising and Potts models

We compute the combined two and three loop order correction to the spin-spin correlation functions for the 2D Ising and q-states Potts model with random bonds at the critical point. The procedure employed is the renormalisation group approach for the perturbation series around the conformal field theories representing the pure models. We obtain corrections for the correlations functions which produce crossover in the amplitude but don't change the critical exponent in the case of the Ising model and which produce a shift in the critical exponent, due to randomness, in the case of the Potts model. Comparison with numerical data is discussed briefly.Comment: 10pp, latex, PAR--LPTHE 94/1

Randomly coupled minimal models

Using 1-loop renormalisation group equations, we analyze the effect of randomness on multi-critical unitary minimal conformal models. We study the case of two randomly coupled $M_p$ models and found that they flow in two decoupled $M_{p-1}$ models, in the infra-red limit. This result is then extend to the case with $M$ randomly coupled $M_p$ models, which will flow toward $M$ decoupled $M_{p-1}$.Comment: 12 pages, latex, 1 eps figures; new results adde

Renormalization group flows for the second ZNZ_{N} parafermionic field theory for N odd

Using the renormalization group approach, the Coulomb gas and the coset techniques, the effect of slightly relevant perturbations is studied for the second parafermionic field theory with the symmetry $Z_{N}$, for N odd. New fixed points are found and classified

Operator algebra of the SL(2) conformal field theories

Structure constants of Operator Algebras for the SL(2) degenerate conformal field theories are calculated.Comment: 10 pages, LaTeX2e, no figures, new refs and minor change

Coupled Minimal Models with and without Disorder

We analyse in this article the critical behavior of $M$ $q_1$-state Potts models coupled to $N$ $q_2$-state Potts models ($q_1,q_2\in [2..4]$) with and without disorder. The technics we use are based on perturbed conformal theories. Calculations have been performed at two loops. We already find some interesting situations in the pure case for some peculiar values of $M$ and $N$ with new tricritical points. When adding weak disorder, the results we obtain tend to show that disorder makes the models decouple. Therefore, no relations emerges, at a perturbation level, between for example the disordered $q_1\times q_2$-state Potts model and the two disordered $q_1,q_2$-state Potts models ($q_1\ne q_2$), despite their central charges are similar according to recent numerical investigations.Comment: 45 pages, Latex, 3 PS figure

Compatible associative products and trees

We compute dimensions of graded components for free algebras with two compatible associative products, and give a combinatorial interpretation of these algebras in terms of planar rooted trees.Comment: 19 pages, added a note on relation to other operad

Replica solution of the Random Energy Model

The alternative replica technique which involve summation over all integer momenta of the partition function and which does not require analytic continuation to non-integer values of the replica parameter $n$ is discussed. In terms of this technique (which does not involve any replica symmetry breaking "magic operations") rigorous solution for the average free energy of the Random Energy Model is recovered in a very simple way.Comment: 8 page