  We discuss dense states of QCD matter formed in high-energy hadronic and
heavy-ion collisions from the point of view of statistical physics of
non-equilibrium processes. For this sake, we first propose a formulation of the
dynamical entropy of dense QCD states in the "saturation regime" leading to a
color glass condensate (CGC). The statistical physics description amounts to
describe the modification of the color correlation length with energy as a
compression process for which non equilibrium thermodynamic properties are
applicable. We derive an expression of the dynamical entropy in terms of the
rapidity evolution of the unintegrated gluon distributions in the colliding
nuclei, verifying suitable positivity and irreversibility properties. We extend
this approach to the initial pre-equilibrium (glasma) state of an heavy-ion
collision. It allows for a definition of the initial entropy before the
evolution towards the hydrodynamic regime as a function of the glasma
correlation length and an overlap parameter characterizing the low-momentum
spectrum of the glasma state. This initial entropy, by extension to the N=4 SYM
theory, is then matched as the key input parameter to the strong coupling
evaluation of thermalization towards the hydrodynamic regime based on the
AdS/CFT correspondence. It thus allows to cast a bridge between the weak and
strong coupling phases of an heavy-ion reaction.
