Transport in ratchet-type systems

Diffusion motion of overdamped Brownian particles in a spatially periodic asymmetrical potential and driven by a zero-mean time-periodic external force and zero-mean Gaussian white noise is considered. The influence of asymmetry of the spatial potential, amplitude of the driving force and intensity of the noise on an average translocation velocity of particles is analyzed. The adiabatic approximation for calculation o f a stationary particle current is used and verified by comparison with results obtained from computer simulations of the process considered

Barrier crossing and transport activated by kangaroo fluctuations

We study barrier crossing of Brownian particles in a bistable symmetric potential and transport of Brownian particles in spatially periodic structures, driven by both kangaroo fluctuations and thermal equilibrium noise of zero mean values. We consider exponentially and algebraically correlated kangaroo fluctuations. Starting with the full Newton-Langevin equation for the Brownian particle and by introducing scaling as well as dimensionless variables, we show that the equation is very well approximated by overdamped dynamics in which inertial effects can be neglected. We analyze properties of selected macroscopic characteristics of the system such as the mean first passage time (MFPT) of particles from one minimum of the bistable potential to the other and mean stationary velocity of particles moving in a spatially periodic potential. In dependence upon statistics of kangaroo fluctuations and temperature of the system, macroscopic characteristics exhibit distinctive non-monotonic behavior. Accordingly, there exist optimal statistics of fluctuations optimizing macroscopic characteristics

Simulations of localized dissipative structures in excitable media by an ensemble of Brownian walkers

The effective method of simulation of stochastic excitable media by en ensemble of Brownian particles is presented. The system studied is a variant of Rinzel-Keller model with global inhibition. The formation, time evolution, and statistical properties of localized structures — spots — are investigated

Control of transport characteristics in two coupled Josephson junctions

We report on a theoretical study of transport properties of two coupled Josephson junctions and compare two scenarios for controlling the currentvoltage characteristics when the system is driven by an external biased DC current and unbiased AC current consisting of one harmonic. In the first scenario, only one junction is subjected to both DC and AC currents. In the second scenario the signal is split — one junction is subjected to the DC current while the other is subjected to the AC current. We study DC voltages across both junctions and find diversity of anomalous transport regimes for the first and second driving scenarios