MORPHOLOGICAL TRANSITIONS OF DIFFUSION-LIMITED AGGREGATE UNDER OUTWARD RADIAL DRIFT

We carried out computer simulations to grow Diffusion Limited Aggregat es (DLAs) with the diffusing particles subject to outward radial drift u that varies as the power law (u = ar(b);b = 0,1,-1) with the distan ce r from the seed of the aggregate. We found that a morphological tra nsition from DLA structure to single branch structure occurs if the dr ift strength is strong enough, Such morphological transition is relate d to the probability for the random walkers to get to the inner part o f the aggregate. For b = -1, the aggregates grow from a single branch structure to a ramified structure with dimension close to that of the ordinary DLA. The recovery of the DLA structure is confirmed for b = - 2.