occupancy probabilities. Scaling relates the fractal dimension D to the cluster-tip occupancy
probabilities. These agree with the analytic probabilities near cusps of a lattice-symmetric
array of traps. On a two-dimensional square lattice D= 5 3, whereas D= 2 for the Eden
model, and D= 4 3 for the η= 2 dielectric breakdown model. D is not universal: D= 7 4 for the
two-dimensional triangular lattice. The square and triangular lattices bracket (±2.5%) …