Effective equation of state of hot and dense matter in nuclear collisions around FAIR energy

The chemical and thermal equilibration in the central zone of heavy-ion collisions at energies around FAIR is studied within two microscopic models. Two systems are utilized for the analysis: (i) central cubic cell of fixed volume V = 125 fm3 and (ii) expanding central area of uniformly distributed energy density. It is found that kinetic, thermal, and chemical equilibration of the expanding hadronic matter are nearly approached in both systems for the period of 10–18 fm/c. The expansion proceeds almost isentropically. The extracted equation of state (EOS) in P − ɛ plane has a linear dependence P = aɛ, where a ≡ c2s slightly increases with the collision energy from 0.12 to 0.145. Linear dependencies for the EOS are found also in T − μB and T − μS planes. The characteristic kinks observed in the last two phase diagrams are linked to inelastic freeze-out in the expanding fireball