This working group treats collective dynamics of the strong interaction under conditions of extreme density in terms of energy and/or baryonic matter. It concerns extraordinary conditions only met in the early stages of the universe in cosmology, in astrophysical objects or at hadron colliders. In one word, this work aims at the experimental and theoretical exploration of the phase diagram of nuclear matter within the French community in all its principal regions (quark-gluon plasma, hadronic gas, ultra-relativistic nuclear matter, ordinary nuclear matter, …) but also the transition between these different regions.
We can start with the idea of different phase diagram domains that are typically described with a certain degree of success via quasi-stationary thermodynamic equations and by dynamics which correspond to relativistic ideal or weakly viscous hydrodynamics. The task is hence to understand how this collectivity emerges from elementary collisions governed by QCD and how this collectivity evolves as function of external conditions (partonic deconfinement, less or more advanced, chiral symmetry restoration, more or less complete).