The modified moment method and theory of nonlinear transport processes in gases: Third order cumulant approximation

By calculating the entropy production to the third order cumulant approximation within the framework of the modified moment method, we examine it for nonlinear transport processes and obtain nonlinear transport coefficients which include ’’Burnett-type’’ coefficients among them. The entropy production obtained has a mathematical form that can admit two minima, one at equilibrium and the other away from equilibrium. It therefore can have a region of decrease as the system is removed farther from equilibrium. This is a phenomenon not existent in linear theory or in the theory based on the first cumulant approximation in the modified moment method.