Generic two-phase coexistence, relaxation kinetics, and interface propagation in the quadratic contact process: simulation studies.
The quadratic contact process is formulated as an adsorption-desorption model on a two-dimensional square lattice. It involves random adsorption at empty sites and correlated desorption requiring diagonally adjacent pairs of empty neighbors. We assess the model behavior utilizing kinetic Monte Carlo simulations. One finds generic two-phase coexistence between a low-coverage active steady state and a completely covered or "poisoned" absorbing steady state; i.e., both states are stable over a finite range of adsorption rates or "pressures." This behavior is in marked contrast to that for equilibrium phase separation. For spatially homogeneous systems, we provide a comprehensive characterization of the kinetics of relaxation to the steady states. We analyze rapid poisoning for higher pressures above an effective spinodal point terminating a metastable active state, nucleation-mediated poisoning in the metastable region, the dynamics of poisoned droplets within the two-phase coexistence region, and behavior reminiscent of bootstrap percolation dynamics for lower pressures. For spatially inhomogeneous systems, we analyze the propagation of planar interfaces between active and absorbing states, fully characterizing an orientation dependence which underlies the generic two-phase coexistence.
Ames Laboratory, U.S. DOE and Departments of Physics & Astronomy and Mathematics, Iowa State University, Ames, Iowa 50011, USA.
Xiaofang
X
Guo
Da-Jiang
DJ
Liu
J W
JW
Evans