Dresden 2009 – wissenschaftliches Programm
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DY: Fachverband Dynamik und Statistische Physik
DY 7: Statistical physics II (general)
DY 7.5: Vortrag
Dienstag, 24. März 2009, 10:45–11:00, HÜL 386
On the critical properties of DLA clusters — Lev Shchur1, Anton Menshutin1, and •Vladimir Vinokour2 — 1Landau Institute for Theoretical Physics, 142432 Chernogolovka, Russia — 2Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
We introduce variable size of the probe particles to estimate harmonic measure and extract fractal dimension of DLA clusters taking two limits, of vanishingly small probe particle size and of infinitely large size of a DLA cluster. We generate 1000 DLA clusters consisting of 50 million particles each using off-lattice killing-free algorithm developed in the early work. We found that effective fractal dimension D(N,b) measured using probe particles of size b and ensemble of the clusters of size N may be collapsed onto one curve as function of the variable b/Rdep, where Rdep is the radius of deposition. Thus, using smaller radius of the probe particles we get larger effective size of cluster. We extend our program and method for the case of clusters with the local anisotropy and investigate clusters with local symmetry of order 3 through 8. Results of simulation may be interpreted in the following way: i) there is strong repulsion between cluster branches for the local symmetry larger than 5, and all generated structures belongs to the one universality class of the off-lattice DLA with fractal dimension D=1.7104(5); 2) for symmetry lower than 5 structures seems to belong to the universality class of anisotropic fractals with D=3/2; 3) the case with 5 main branches is the marginal one - even lowest level of the noise reduction moves structures to the class of anisotropic fractals.