Monte Carlo simulations are used to analyse the behavior of the extended Ashkin-Teller model in two dimensions from the ratio of the square of the second moment of the order parameter to its fourth moment. The critical surface in three dimensional parameter space is calculated in regions where...

We study the phase diagram of a generalization of the Ashkin-Teller model in two dimensions using the mean-field renormalization group (MFRG) theory. We calculate critical surfaces for this three-parameter Hamiltonian of the model using two different approaches, and we discuss the resulting...

We add a term to the original Ashkin-Teller Hamiltonian in order to reduce the degeneracy. It is shoen that a certain class of terms all lead to the same Hamiltonian. The phase diagram of the isotropic model is discussed in the framework of mean field theory. It exhibits a wealth of critical...