  When quarks and gluons are led to form a dense medium, like in high energy
or/and heavy-ion collisions, it is interesting to ask the question which are
the relevant degrees of freedom that Quantum Chromodynamics predict. The
present notes correspond to two lectures given at Zakopane in the (rainy)
summer of 2006, where this question is adressed concretely in two cases, one in
the regime of weak coupling, the other one at strong coupling. Each case
corresponds to the study of a dynamically important transient phase of quarks
and gluons expected to appear from Quantum Chromodynamics.
  In lecture I, we examine the dynamical phase space of gluon transverse
momenta near the so-called ``saturation'' phase including its fluctuation
pattern.
  In lecture II, we study the dynamics of strongly interacting gauge-theory
matter (modelling quark-gluon plasma) using the AdS/CFT duality between gauge
field theory at strong coupling and a gravitational background in Anti-de
Sitter space.
