Diffusion on deterministic and quasirandom models of diffusion-limited aggregates. II. Anisotropic diffusion

In the preceding paper, we discuss the diffusion of a particle on deterministic and quasirandom fractal structures designed to mimic the properties of diffusion-limited aggregates. In this paper we deal with biased transport, that is, transport in the presence of an external field. Our method is based on a renormalization procedure that allows us to calculate the scaling properties relating distance and time as a function of the strength of the external field. We calculate hopping probabilities and mean first-passage times and show how these properties depend on the direction relative to the field and on the branching properties of the model.