Resonances while surmounting a fluctuating barrier

Electronic analog experiments on escape over a fluctuating potential barrie r are performed for the case when the fluctuations are caused by Ornstein-U hlenbeck noise (OUN). In its dependence on the relation between the two OUN parameters (the correlation time tau and noise strength Q) the nonmonotoni c variation of the mean escape time las a function of tau can exhibit eithe r a minimum (resonant activation), or a maximum (inhibition of activation), or both these effects. The possible resonant nature of these features is d iscussed. We claim that lis not a good quantity to describe the resonanceli ke character of the problem. Independently of the specific relation between the OUN parameters, the resonance manifests itself as a maximal lowering o f the potential barrier juring the escape event, and it appears for tau of the order of the relaxation time toward the metastable state.