The first renormalization-group approach for irreversible growth models of randomly branched aggregates is presented. The main result is that the Witten-Sander diffusionlimited aggregation model, a discrete version of a dendritic growth model, is in a different universality class than "equilibrium" lattice animals. Also calculated is the fractal dimension for the Witten-Sander model and the Eden model (a model developed for the study of biological structures).

• Received 22 November 1982

DOI:https://doi.org/10.1103/PhysRevLett.50.686