Before revision:  This model is solvable using the theory of branching processes and the mean-field approximation  and displays a power-law cascade-size distribution-similar to the empirically observed one-over a wide range of parameters .
After revision:  This model is solvable using the theory of branching processes and the mean-field approximation . For a wide range of parameters, the system is in a critical state and displays a power-law cascade-size distribution-similar to the empirically observed one-over a wide range of parameters .