It is argued that the dynamics of an isolated system, due to the concrete
procedure by which it is separated from the environment, has a non-Hamiltonian
contribution. By a unified quantum field theoretical treatment of typical
subdynamics, e.g., hydrodynamics, kinetic theory, master equation for a
particle interacting with matter, we look for the structure of this more
general dynamics.Comment: 16 pages, latex, no figures, to appear in the Proceedings of the
Third International Conference on Quantum Communication & Measurement 1996
(Hakone, Japan