Diffusion in a Rough Energy Landscape

We re-examine Zwanzig's model of diffusion in a rough energy landscape [PNAS (USA) 85, 2029 (1988)]. We interpret the one- dimensional coordinate as a mesoscopic degree of freedom of the system. It is shown that the fluctuating potential corresponds to a broken symmetry. The corresponding order parameter is associated with long- range elastic stress in the system. We derive a Landau-type expression for the free energy of the system from which the activation energy for barrier crossings can be obtained.