Description of Isolated Macroscopic Systems inside Quantum Mechanics

For an isolated macrosystem classical state parameters c(t) are introduced inside a quantum mechanical treatment. By a suitable mathematical representation of the actual preparation procedure in the time interval [T, to] a statistical operator is constructed as a solution of the Liouvilleevon Neumann equation. exhibiting at time t the state parameters [(t’), to 5 t’ < t, and preparation parameters related to times T 5 t’ < to. Relation with Zubarev’s nonequilibrium statistical operator is discussed. A mechanism for memory loss is investigated and time evolution by a sernigroup is obtained for a restricted set of relevant observables, slowly varying on a suitable time scale.