Ising Disks

We introduce a dynamic model where the state space is the set of contractible cubical sets in the Euclidian space. The permissible state transitions, that is addition and removal of a cube to/from the set, is locally decidable. We prove that in the planar special case the state space is connected. We then define a continuous time Markov chain with a fugacity (tendency to grow) parameter. We prove that, on the plane, the Markov chain is irreducible (due to state connectivity), and is also ergodic if the fugacity is smaller than a threshold.