On the phase diagram of the Nambu–Jona‐Lasinio Lagrangian

International audienceThe (Polyakov) Nambu–Jona‐Lasinio approach is an effective theory for low energies, which shares with Quantumchromodynamics the global symmetries. This approach is easy to handle and allows for analytical results for many of the observables that are of interest for the studies of ultrarelativistic heavy ion collisions but also for the merger and collisions of neutron stars. It allows in particular to study the density and temperature dependence of quark masses and of the masses of mesons and baryons as well as the chiral phase transition. In recent times, this transition came in the focus of interest because it is expected that the upcoming experiments at the Fair (Germany) and Nuclotron‐based Ion Collider fAcility (Russia) facilities will observe a Quark‐Gluon‐Plasma at finite baryon chemical potential