Crossover on fractal and branching structures of radial diffusion-limited growth in Laplace field of finite size

Two-dimensional off-lattice diffusion-limited clusters simulated in circula r boundary of finite size are studied by comparison with analytical solutio n in annular Laplace field and trajectory density of Brownian particles. Ra dial growth rate in annular field classifies into two different areas. The one is cluster size dominated area, and the other is the area dominated by distance from the boundary. Results clarify that the ordinary diffusion-lim ited aggregation (DLA) grows under the condition of size dominated area. Ra dial density, fractal dimension, and branching structure of cluster growing in the circular boundary of finite size support a crossover at similar to0 .37 that agrees with the analytical suggestion of 1/e = 0.368 for the ratio of cluster size to boundary radius. Fractal to non-fractal change on self- similarity and change from tip splitting to side branching on micro branchi ng structure characterize the morphological crossover of diffusion limited cluster.