Dynamics of a penta-hepta defect in a hexagonal pattern

When a layer of soap bubbles (diameter ~1mm) is placed on a flat glass substrate, a hexagonal pattern (or bubble raft) is automatically formed (see image below).   The soap bubble raft is known to be a good model that demonstrates the characteristic behavior of a 2D crystalline system. We use the bubble raft as a model system for studying defect motion in a 2D crystaline system, and results are compared with a theory based on the coupled Ginzburg-Landau  equations of  a nonequilibrium system(L. Tsimring, PRL, vol 74, 4201(1995).).