1209.1400 (Thomas Vojta)

Monte-Carlo simulations of the clean and disordered contact process in
three dimensions    [PDF]

Thomas Vojta

We investigate the absorbing-state transition in the three-dimensional contact process with and without quenched disorder by means of large-scale Monte-Carlo simulations. In the clean case, we combine a reweighting technique with a careful extrapolation of the data to infinite time to determine with high accuracy the critical behavior in the three-dimensional directed percolation universality class. In the presence of quenched disorder, our data provide strong evidence for the transition being controlled by an exotic infinite-randomness critical point with activated (exponential) dynamical scaling. We determine the critical exponents of this transition and find them to be universal, i.e., independent of disorder strength. In the Griffiths region between the clean and disordered critical points, the dynamics is characterized by nonuniversal power laws. We relate our findings to a general classification of rare region effects at phase transitions with quenched disorder, and we compare them to results of other numerical methods.

View original: http://arxiv.org/abs/1209.1400