An energy function and its application to the periodic behavior of k-reversible processes

We consider the graph dynamical systems known as k-reversible processes. In such processes, each vertex in the graph has one of two possible states at each discrete time step. Each vertex changes its state between the current time and the next if and only if it currently has at least k neighbors in a state different than its own. For such processes, we present a monotonic function similar to the decreasing energy functions used to study threshold networks. Using this new function, we show an alternative proof for the maximum period length in a k-reversible process and provide better upper bounds on the transient length in both the general case and the case of trees.