The European Physical Journal B

, 85:399

Overdamped motion of interacting particles in general confining potentials: time-dependent and stationary-state analyses

Regular Article

DOI: 10.1140/epjb/e2012-30671-3

Cite this article as:
Ribeiro, M., Nobre, F. & Curado, E. Eur. Phys. J. B (2012) 85: 399. doi:10.1140/epjb/e2012-30671-3

Abstract

By comparing numerical and analytical results, it is shown that a system of interacting particles under overdamped motion is very well described by a nonlinear Fokker-Planck equation, which can be associated with nonextensive statistical mechanics. The particle-particle interactions considered are repulsive, motivated by three different physical situations: (i) modified Bessel function, commonly used in vortex-vortex interactions, relevant for the flux-front penetration in disordered type-II superconductors; (ii) Yukawa-like forces, useful for charged particles in plasma, or colloidal suspensions; (iii) derived from a Gaussian potential, common in complex fluids, like polymer chains dispersed in a solvent. Moreover, the system is subjected to a general confining potential, φ(x) = (α|x|z)/z (α > 0, z > 1), so that a stationary state is reached after a sufficiently long time. Recent numerical and analytical investigations, considering interactions of type (i) and a harmonic confining potential (z = 2), have shown strong evidence that a q-Gaussian distribution, P(x,t), with q = 0, describes appropriately the particle positions during their time evolution, as well as in their stationary state. Herein we reinforce further the connection with nonextensive statistical mechanics, by presenting numerical evidence showing that: (a) in the case z = 2, different particle-particle interactions only modify the diffusion parameter D of the nonlinear Fokker-Planck equation; (b) for z ≠ 2, all cases investigated fit well the analytical stationary solution Pst(x), given in terms of a q-exponential (with the same index q = 0) of the general external potential φ(x). In this later case, we propose an approximate time-dependent P(x,t) (not known analytically for z ≠ 2), which is in very good agreement with the simulations for a large range of times, including the approach to the stationary state. The present work suggests that a wide variety of physical phenomena, characterized by repulsive interacting particles under overdamped motion, present a universal behavior, in the sense that all of them are associated with the same entropic form and nonlinear Fokker-Planck equation.

Keywords

Statistical and Nonlinear Physics 

Copyright information

© EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg 2012

Authors and Affiliations

  1. 1.Centro Brasileiro de Pesquisas FísicasRio de JaneiroBrazil
  2. 2.National Institute of Science and Technology for Complex SystemsRio de JaneiroBrazil