You can find more information about the tool itself, but also about the Bartis Widom analysis method using the following links:Introducing the workhorse of Stochastic SimulationBartis Widom Analysis MethodReferencesA:I don't think that anybody here actually implements the master equation itself.Instead, a lot of people work with the Langevin equation which describes the time evolution of the position of a particle. A Langevin equation is essentially the Newton equation, where the acceleration is constantly applied (this is known as white noise). The basic idea of Langevin is that the interaction between the particle and its environment induces random forces, a much better description of reality than Newton's equations. The random forces are normally drawn from a Gaussian distribution, and they cause the particle's position to fluctuate about a mean position.The mean position is known as the probability density function, and is calculated by solving the Fokker-Planck equation, which is essentially the transport equation with an extra term for the random forces.This plot is for a single classical system, which means that it is much easier to implement, but can only provide us with an average over time. Since the interactions of a system are determined by its probability density function, the rate at which a classical system does a certain reaction is determined by how fast it has a high probability in that region.The Fokker-Planck equation has a Master equation form, and if we solve this equation using the method of successive approximations, we can determine the probability density function for any time.This plot is for a single system, where the system has several states, and transitions between these states are forbidden. Since we are not interested in the time evolution of this system, we are only interested in the steady state. Like the Fokker-Planck equation, the Master equation for this system can be reduced to a Fokker-Planck equation. This is easy to see, since we only have two variables and no derivatives. This Master equation has two steady states, representing the probabilities of being in the upper and lower states, and has a neat property that the transition rate between these states is a constant independent of time.Looking for a good book on the economics of the Roman Empire? Well, a shiny new hardcover edition of The Fall of the Roman Empire has just been released.The Rise of the Roman Empire by Edward Luttwak (£34.99, 08929e5ed8