Barrier-Controlled Non-Equilibrium Criticality in Random Organization

Random organization is a generic phenomenon found in many non-equilibrium systems, while the mechanism of the non-equilibrium criticality in these systems remains elusive. Here, by using computer simulation and theoretical analysis, we study the role of activation barrier on the criticality of non-equilibrium phase transitions in a random-organizing hard-sphere model. We find that at zero thermal noise, with increasing the activation barrier, the type of transition changes from a continuous conserved directed percolation into a discontinuous dynamic transition by crossing a tricritical point. A mean-field theory is proposed to explain this phenomenon, which suggests that the transition at finite thermal noise belongs to the Ising universality. Moreover, we obtain the tricritical exponents in the system which quantitatively agree with field theory simulations. This mechanism of the barrier-controlled criticality has many implications in dynamics of amorphous materials, chemical reactions and epidemic spreading.