Periodic driving in a two-dimensional Brownian ratchet

Brownian dynamics on a fixed potential landscape generates no steady-state current, but currents can be obtained by periodically switching between multiple landscapes. Even more interesting than the existence of such ratcheted currents is that the direction of the current can depend on the frequency of the switching. I will present numerical work on the behavior of current reversals in a two-dimensional system. I will discuss our efforts to make sense of the system by conditioning a time-periodic Markov process for a coarse-grained model. Interestingly, the low-frequency asymmetry between leftward and rightward motion appears at the level of typical events, but the high-frequency asymmetry only emerges for atypical events.