title: Rare regions and Griffiths singularities at a clean critical point: the five-dimensional disordered contact process.
abstract: We investigate the nonequilibrium phase transition of the disordered contact process in five space dimensions by means of optimal fluctuation theory and Monte Carlo simulations. We find that the critical behavior is of mean-field type, i.e., identical to that of the clean five-dimensional contact process. It is accompanied by off-critical power-law Griffiths singularities whose dynamical exponent z' saturates at a finite value as the transition is approached. These findings resolve the apparent contradiction between the Harris criterion, which implies that weak disorder is renormalization-group irrelevant, and the rare-region classification, which predicts unconventional behavior. We confirm and illustrate our theory by large-scale Monte Carlo simulations of systems with up to 70(5) sites. We also relate our results to a recently established general relation between the Harris criterion and Griffiths singularities [Phys. Rev. Lett. 112, 075702 (2014)], and we discuss implications for other phase transitions.
authors.affiliation: Department of Physics, Missouri University of Science and Technology, Rolla, Missouri 65409, USA.
authors.forename: Thomas
authors.initials: T
authors.lastname: Vojta
authors.affiliation: Department of Physics and Astronomy, Washington State University, Pullman, Washington 99164, USA and Department of Physics, Missouri University of Science and Technology, Rolla, Missouri 65409, USA.
authors.forename: John
authors.initials: J
authors.lastname: Igo
authors.affiliation: Instituto de Física de São Carlos, Universidade de São Paulo, C.P. 369, São Carlos, São Paulo 13560-970, Brazil.
authors.forename: José A
authors.initials: JA
authors.lastname: Hoyos
mesh_terms: D009010:Monte Carlo Method; D044367:Phase Transition