DESCRIPTION OF ISOLATED MACROSCOPIC SYSTEMS INSIDE QUANTUM MECHANICS

For an isolated macrosystem classical state parameters (zeta)(t) are Aintroduced inside a quantum mechanical treatment. By a suitable Amathematical representation of the actual preparation procedure in the Atime interval [T,to] a statistical operator is constructed as a Asolution of the Liouville-von Neumann equation, exhibiting at time t the state parameters (zeta)(tʹ), to < tʹ< t, and preparation Aparameters related to times T < tʹ < to. Relation with Zubarevʹs Anonequilibrium statistical operator is discussed. A mechanism for Amemory loss is investigated and time evolution by a semigroup is Aobtained for a restricted set of relevant observables, slowly varying Aon a suitable time scale.