Circle, sphere, and drop packings

We studied the geometrical and topological rules underlying the dispositions and the size distribution of nonoverlapping, polydisperse circle packings. We found that the size distribution of circles of radii R that densely cover a plane follows the power law N(R) proportional to R-a. We obtained an approximate expression that relates the exponent a to the average coordination number and to the packing strategy. In the case of disordered packings (where the circles have random sizes and positions) we found the upper bound alpha(max) = 2. The results that were obtained for circle packing were extended to packing of spheres and hyperspheres in spaces of arbitrary dimension D. We found that the size distribution of dense packed polydisperse D spheres, follows, as in the two-dimensional case, a power law, where the exponent alpha depends on the packing strategy. In particular, in the case of disordered packing, we obtained the upper bound alpha(max) = D. Circle covering generated by computer simulations gives size distributions that are in agreement with these analytical predictions. Tin drops generated by vapor deposition on a hot substrate form breath figures where the drop-size distributions are power laws with exponent alpha similar or equal to 2. We pointed out the similarity between these structures and the circle packings. Despite the complicated mechanism of formation of these structures, we showed that it is possible to describe the drop arrangements, the size distribution, and the evolution at constant coverage, in terms of maximum packing of circles regulated by coalescence.