Anomalous diffusion induced by combining non-Stokesian friction with nonlinear binding

Abstract

We investigate nonequilibrium physical processes governed by a combination of non-Stokesian friction and nonlinear binding, within a framework where the fluctuation–dissipation theorem remains valid. Two distinct models are examined: a non-stationary Langevin equation and a system exhibiting non-Markovian dynamics, the both can induce the limitation of thermal diffusion: ballistic diffusion. In the first case, this behavior arises when the friction decays inversely with time, while in the second case, it results from a lack of low-frequency components in the driving noise. Then, we demonstrate that a logarithmic potential, acting as a weak binding force, can transition ballistic diffusion into full-scale anomalous diffusion. The effective temperature of the system deviates from the equilibrium value and exhibits nonmonotonic variation with the depth of the potential. Moreover, we study the noise-enhanced stability effect of the metastable state. This work highlights the critical impact of ergodicity breaking and underscores the peculiar role of nonlinear potentials in shaping dynamical behavior.