Time—Correlation—Function Expressions for Linear and Nonlinear Transport Coefficients

Construction of a statistical-mechanical ensemble to represent a system known to be out of equilibrium is discussed. The consequences of the temperature, velocity, and chemical potential fields are formal time-correlation-function expressions for both linear- and higher-order transport coefficients. Many different forms of correlation functions are equivalent, which permits choice of the most useful for a given purpose. Onsager-type reciprocal relations appear to exist for only the linear coefficients.