Relaxation through an asymmetric fluctuating potential barrier.

We revise the problem of thermally activated crossing of a fluctuating potential barrier, laying stress on the asymmetry of the barrier. Considering as a working model a paradigmatic triangular dichotomously varying potential landscape we find an atypical dependence of the mean first-passage time on the correlation time tau of fluctuations. Namely, in the range of small tau an additional maximum appears.

Transient multimodality in the presence of potential fluctuations.

When a stochastic system evolves from its unstable state the phenomenon of transient multimodality may appear, namely for a period of time, probability distribution develops a larger number of maxima than it possesses in the initial and in the stationary states. We investigate the influence of potential fluctuations generated by a Gaussian white noise on this effect. Some general conditions which suffice for the occurrence of noise induced transient multimodality are presented.

Kinetic models for stochastically modified ionic channels.

Ionic channels form pores in biomembranes. These pores are large macromolecular structures. Due to thermal fluctuations of countless degrees-of-freedom of the biomembrane material, the actual form of the pores is permanently subject to modification.

Mean escape time over a fluctuating barrier.

An approximate method for studying activation over a fluctuating barrier of potential is proposed. It involves considering separately the slow and fast components of barrier fluctuations, and it applies for any value of their correlation time tau. It gives exact results for the limiting values tau-->0 and tau--> infinity, and the agreement with numerics in between is also excellent, both for dichotomic and Gaussian barrier perturbations.

Resonances while surmounting a fluctuating barrier.

Electronic analog experiments on escape over a fluctuating potential barrier are performed for the case when the fluctuations are caused by Ornstein-Uhlenbeck noise (OUN). In its dependence on the relation between the two OUN parameters (the correlation time tau and noise strength Q) the nonmonotonic variation of the mean escape time T as a function of tau can exhibit either a minimum (resonant activation), or a maximum (inhibition of activation), or both these effects. The possible resonant nature of these features is discussed.