  While the issues of dissipation, fluctuations, noise and decoherence in open
quantum systems (with autocratic divide) analyzed via Langevin dynamics are
familiar subjects, the treatment of corresponding issues in closed quantum
systems is more subtle, as witnessed by Boltzmann's explanation of dissipation
in a macroscopic system made up of many equal constituents (a democratic
system). How to extract useful physical information about a closed democratic
system with no obvious ways to distinguish one constituent from another, nor
the existence of conservation laws governing certain special kinds of
variables, e.g., the hydrodynamic variables -- this is the question we raise in
this essay. Taking the inspirations from Boltzmann and Langevin, we study a)
how a hierarchical order introduced to a closed democratic system -- defined
either by substance or by representation, and b) how hierarchical
coarse-graining, executed in a specific order, can facilitate our understanding
in how macro-behaviors arise from micro-dynamics. We give two examples in: a)
the derivation of correlation noises in the BBGKY hierarchy and how using a
Boltzmann-Langevin equation one can study the decoherence of the lower order
correlations; and b) the derivation of quantum fluctuation forces by ordered
coarse-grainings of the relevant variables in the medium, the quantum field and
the internal degrees of freedom of an atom.
