Particle pumping driven by asymmetric unbiased external forces in a finite tube

Abstract

The transport of Brownian particles in a finite tube is investigated in the presence of asymmetric unbiased external forces. The system is embedded in a finite region and bounded by two particle reservoirs. It is found that the transport phenomena under asymmetric unbiased external forces exhibit peculiar behaviours. In a spatially symmetric tube, the particles can be pumped by asymmetric unbiased forces. Both spatial asymmetry of a tube and temporal asymmetry of unbiased external forces are the two driving factors for pumping particles from a reservoir at low concentration to one at the same or higher concentration. The interplay between these two factors can induce peculiar phenomena.