Growth and forms of Laplacian aggregates

The shapes and general morphological properties of aggregates grown following the 'T/ rule (Vsurface ex IEI") [L. Niemeyer, L. Pietronero, and H. J. Wiessmann, Phys. Rev. Lett. 52, 1033 (1984)] have been investigated. Vsurface is the velocity at the interface and E the electric field. The fractal dimension decreases monotonically from its diffusion-limited aggregation value ('T/ = 1) to a number indistinguishable from 1 at 'T/ ~ 4. Simultaneously, the multifractal properties become independent of'T/. An alternative method to generate large clusters, and gain insight into the growth process, is also presented. Various analytical approximations are discussed. PACS number(s): 82.20.Wt, 75.10.Jm, 75.10.Lp, 75.30.DsCICyT (Spain) Project No. MAT90-0544 and the U.S. Department of Energy. L.M.S. is thankful to the NSF for financial support under Grant No. DMR 91-17249. F.G. and E.L. acknowledge support from CICyT (Spain).Publicad