  There is a solution to the problem of asymptotic completeness in many body
scattering theory that offers a specific view of the quantum unitary dynamics
which allows for the straightforward introduction of local time for every, at
least approximately closed, many-particle system. In this approach, Time
appears as a hidden classical parameter of the unitary dynamics of a
many-particle system. We show that a closed many-particle system can exhibit
behavior that is characteristic for open quantum systems and there is no need
for the "state collapse" or environmental influence. On the other hand, closed
few-particle systems bear high quantum coherence. This local time scheme
encompasses concepts including "emergent time", "relational time" as well as
the "hybrid system" models with possibly induced gravitational uncertainty of
time.
