Fig. 2.

Intermediate states. Intermediate local configurations surrounding a candidate hole required in evaluation of the sum over particle removal paths that are used to empty the lattice (k = 4 and s = 3 in the example). The white circles are sites that have been emptied in previous steps, and the red disks are temporarily blocked particles along the perimeter edges. For each configuration, the arrows indicate allowed transitions (to be selected at random) involving the growth of one boundary line by one step. This process restores that local configuration to another intermediate state [ or ] with the indices k, s suitably revised. The process terminates (as a disconnected hole) when the local configuration makes a transition from outside of the class .