Reformulation of the Representation of Transport Coefficients Using the Autocorrelation-Function Formalism and the Linear-Trajectory Approximation

The linear-transport coefficients are exactly described in terms of the ``generalized force'' autocorrelation function. For weakly coupled systems these formal expressions take simple forms equivalent to the results obtained from other approaches. In addition, the linear-trajectory method is described for the case of strongly interacting systems, and an elementary analysis of the transport coefficients at finite frequency is given (see Appendix B).