  In the past, the phase-space elementary cell of a non-quantized system was
set equal to the third power of the Planck constant; in fact, it is not a
necessary assumption. We discuss how the phase space volume, the number of
states and the elementary-cell volume of a system of non-interacting N
particles, changes when an interaction is switched on and the system becomes or
evolves to a system of correlated non-Boltzmann particles and derives the
appropriate expressions. Even if we assume that nowadays the volume of the
elementary cell is equal to the cube of the Planck constant, h^3, at least for
quantum systems, we show that there is a correspondence between different
values of h in the past, with important and, in principle, measurable
cosmological and astrophysical consequences, and systems with an effective
smaller (or even larger) phase-space volume described by non-extensive
generalized statistics.
