On directed Barabási-Albert networks with two and seven neighbours selected by each added site, the Ising model was seen not to show a spontaneous magnetisation. Instead, the decay time for flipping of the magnetisation followed an Arrhenius law for Metropolis and Glauber algorithms, but for Wolff cluster flipping the magnetisation decayed exponentially with time. On these networks the Majority-vote model with noise is now studied through Monte Carlo simulations. However, in this model, the order-disorder phase transition of the order parameter is well defined in this system. We calculate the value of the critical noise parameter q c for several values of connectivity z of the directed Barabási-Albert network. The critical exponentes β/ν, γ/ν and 1/ν were calculated for several values of z.Keywords:Monte Carlo simulation,vote , networks, nonequilibrium.
IntroductionIt has been argued that nonequilibrium stochastic spin systems on regular square lattice with up-down symmetry fall in the universality class of the equilibrium Ising model [1]. This conjecture was found in several models that do not obey detailed balance [2,3,4]. Campos et al.[5] investigated the majority-vote model on small-world network by rewiring the two dimensional square lattice. These small-world networks, aside from presenting quenched disorder, also posses long-range interactions. They found that the critical exponents γ/ν and β/ν are different from the Ising model and depend on the rewiring probability. However, it was not evident that the exponent change was due to the disordered nature of the network or due to the presence of long-range interactions. Lima et al.[6] studied the majority-vote model on Voronoi-Delaunay random lattices with periodic boundary conditions. These lattices posses natural quenched disorder in their conecctions. They showed that presence of quenched connectivity disorder is enough to alter the exponents β/ν and γ/ν from the pure model and therefore that is a relevant term to such non-equilibrium phase-transition. Sumour and Shabat [7,8]