Anomalous diffusion of particles with inertia in external potentials.

Recently a new type of Kramers-Fokker-Planck equation has been proposed [Friedrich, R.; Jenko, F.; Baule, A.; Eule, S. Phys. Rev. Lett. 2006, 96, 230601] describing anomalous diffusion in external potentials. In the present paper, the explicit cases of a harmonic potential and a velocity-dependent damping are incorporated. Exact relations for moments for these cases are presented, and the asymptotic behavior for long times is discussed. Interestingly, the bounding potential and the additional damping by itself lead to a subdiffusive behavior. While acting together, the particle becomes localized for long periods of time.