Monte-Carlo simulations of the smeared phase transition in a contact process with extended defects

TL;DR

This paper uses Monte-Carlo simulations to show that extended defects in a contact process cause the phase transition to smear, with rare regions undergoing independent transitions, significantly altering the critical behavior.

Contribution

It demonstrates how spatially correlated quenched disorder leads to smeared phase transitions in nonequilibrium systems, supported by simulation and theoretical comparison.

Findings

Disorder correlations dramatically enhance impurity effects

Sharp phase transition is destroyed by smearing

Rare regions undergo independent phase transitions

Abstract

We study the nonequilibrium phase transition in a contact process with extended quenched defects by means of Monte-Carlo simulations. We find that the spatial disorder correlations dramatically increase the effects of the impurities. As a result, the sharp phase transition is completely destroyed by smearing. This is caused by effects similar to but stronger than the usual Griffiths phenomena, viz., rare strongly coupled spatial regions can undergo the phase transition independently from the bulk system. We determine both the stationary density in the vicinity of the smeared transition and its time evolution, and we compare the simulation results to a recent theory based on extremal statistics.