PROPERTIES OF RESONANT ACTIVATION PHENOMENA

The phenomenon of resonant activation of a Brownian particle over a fl uctuating barrier is revisited. We discuss the important distinctions between barriers that can fluctuate among ''up'' and ''down'' configur ations, and barriers that are always ''up'' but that can fluctuate amo ng different heights. A resonance as a function of the barrier fluctua tion rate is found in both cases, but the nature and physical descript ion of these resonances is quite distinct. The nature of the resonance s, the physical basis for the resonant behavior, and the importance of boundary conditions are discussed in some detail. We obtain analytic expressions for the escape time over the barrier that explicitly captu re the minima as a function of the barrier fluctuation rate, and show that our analytic results are in excellent agreement with numerical re sults.