Universality of the triplet contact process with diffusion

The one-dimensional triplet contact process with diffusion (TCPD) model has been studied using fast multispin GPU Monte Carlo simulations. In particular, the particle density p and the density of pairs of neighboring particles pp have been monitored as a function of time. Mean field predictions for the time evolution of these observables at the critical point are rho similar to t(-delta) and rho(p) similar to t(-delta p) with delta = 1/3 and delta(p) = 2/3. We observe that in the vicinity of the critical point of the model, the ratio rho(p)/rho tends to a constant, which shows that the one-dimensional TCPD model is not described by mean field behavior. Furthermore, our long simulations allow us to conclude that the mean field prediction of the exponent delta is almost certainly not correct either. Since the crossover to the critical regime is extremely slow for the TCPD model, we are unable to pinpoint a precise value for delta, although we find as an upper bound delta <0.32.