Directed Transport of Confined Brownian Particles with Torque
  We investigate the influence of an external magnetic field (torque) on the motion of Brownian particles confined in a channel geometry with varying width. Furthermore, the particles are driven by random fluctuations modeled by the Ornstein-Uhlenbeck process (OUP) with given correlation time $\tau_c$. The latter is implemented as both a thermal and a nonthermal process.   In contrast to the thermal OUP for the nonthermal process directed transport emerges, i.e. our setup now realizes a ratchet mechanism: Due to the assumed thermodynamic nonequilibrium situation random fluctuations are rectified. The transport quantities of the system are studied in detail with respect to the correlation time, the torque and the channel geometry. Eventually, the mechanism of the symmetry breaking is elucidated. 
Paul K. Radtke and Lutz Schimansky-Geier
physics.bio-ph cond-mat.stat-mech