We consider linear systems in which some of the variables evolve on a much faster time scale than the remaining ones. By means of a systematic perturbation theory in the time-scale ratio we extract a reduced dynamics in terms of the slow variables only, valid after an initial transient period....

We consider linear dynamical systems with motions characterized by two different time-scales. In practice the dynamical matrix in the phenomenological equations of motion often exhibits a strong coupling of the slow and fast variables. It is shown on the basis of the Onsager symmetry relations...

We study thermodynamic systems near equilibrium described by both slow and fast variables. A reduced relaxation matrix for the slow variables can be obtained from the full relaxation matrix by a systematic elimination of the fast variables. When the full relaxation matrix possesses...