DOES STOCHASTIC RESONANCE OCCUR IN PERIODIC POTENTIALS

The possibility of observing stochastic resonance (SR) in a periodic p otential without a static bias, driven by noise and an oscillating fie ld, is investigated in both limits of damping. It is shown from the ma trix continued fraction method that, although an underdamped Brownian particle moving in a periodic potential displays a dynamical resonance facilitated by noise, there is no conventional SR irrespective of dam ping. The reason such SR cannot be observed in an overdamped regime is demonstrated by a hopping model. Due to the unbound motion in the per iodic potential, transition probability decays algebraically and there is no persistent synchronized hopping. However, the noise-induced enh ancement of the diffusion constant related to escape rate enhancement exhibits an SR-like behavior. A comparison with the dynamics on a circ le as a different example of an unbound system is given.