Subdiffusive transport close to thermal equilibrium: from the langevin equation to fractional diffusion.

Subdiffusion in the presence or absence of an external force field is established on the basis of an extension of conventional Langevin dynamics to include long-tailed trapping events. It is demonstrated how the presence of the trapping events leads to the macroscopic observation of fractional diffusion, described by a fractional Klein-Kramers equation.