title: Anomalous field-induced growth of fluctuations in dynamics of a biased intruder moving in a quiescent medium.
abstract: We present exact results on the dynamics of a biased, by an external force F, intruder (BI) in a two-dimensional lattice gas of unbiased, randomly moving hard-core particles. Going beyond the usual analysis of the force-velocity relation, we study the probability distribution P(R(n)) of the BI displacement R(n) at time n. We show that despite the fact that the BI drives the gas to a nonequilibrium steady state, P(R(n)) converges to a Gaussian distribution as n→∞. We find that the variance σ(x)(2) of P(R(n)) along F exhibits a weakly superdiffusive growth σ(x)(2)~ν(1)nln(n), and a usual diffusive growth, σ(y)(2)~ν(2)n, in the perpendicular direction. We determine ν(1) and ν(2) exactly for arbitrary bias, in the lowest order in the density of vacancies, and show that ν(1)~|F|(2) for small bias, which signifies that superdiffusive behavior emerges beyond the linear-response approximation. We also present analytical arguments predicting a striking field-induced superdiffusive behavior σ(x)(2)~n(3/2) for two-dimensional stripes and three-dimensional capillaries, which is confirmed by Monte Carlo simulations.
authors.affiliation: Laboratoire de Physique Théorique de la Matière Condensée (UMR CNRS 7600), Université Pierre et Marie Curie (Paris 6), 4 Place Jussieu, 75252 Paris, France. benichou@lptmc.jussieu.fr
authors.forename: Olivier
authors.initials: O
authors.lastname: Bénichou
authors.forename: Carlos
authors.initials: C
authors.lastname: Mejía-Monasterio
authors.forename: Gleb
authors.initials: G
authors.lastname: Oshanin
mesh_terms: D003198:Computer Simulation; D004058:Diffusion; D005740:Gases / Q000737:chemistry*; D008956:Models, Chemical; D015233:Models, Statistical
chemical_list: D005740:Gases