Time evolution of hot and dense nuclear matter produced in central gold-gold collisions at energies between \(E_{lab} = 10\) and 160 AGeV is studied within two transport string models, UrQMD and QGSM. In contrast to the previous studies, here we investigate the macroscopic characteristics of the system before the state of chemical and thermal equilibrium is attained. For all energies in question two interesting observations are made for times starting already from \(t \ge 1\) fm/c. (1) The matter in the cell expands almost isentropically with nearly constant entropy per baryon. (2) Pressure in the cell appears to be very close to the pressure calculated for equilibrated hadron gas with the same values of energy density, baryon density and strangeness density. The pressure linearly depends on the energy density, \(P = a(\sqrt{s}) \varepsilon \). Therefore, both observations endorses the formal application of relativistic hydrodynamics from the very early stages of heavy-ion collisions, despite of the fact that the matter in the fireball is out of equilibrium.

在两个输电串模型UrQMD和QGSM中研究了中心金金碰撞在能量（E_ {lab} = 10 \）和160 AGeV之间产生的热核和密核物质的时间演化。与以前的研究相比，这里我们研究了达到化学和热平衡状态之前系统的宏观特征。对于所有有疑问的能量，已经从\（t \ ge 1 \）  fm / c开始进行了两个有趣的观察。。（1）细胞中的物质几乎等熵地膨胀，每个重子的熵几乎恒定。（2）在相同的能量密度，重子密度和奇异密度值下，电池中的压力似乎非常接近于平衡的强子气体所计算出的压力。压力线性地取决于能量密度\（P = a（\ sqrt {s}）\ varepsilon \）。因此，尽管火球中的物质是不平衡的，但这两个观点都支持从重离子碰撞的早期阶段就相对论流体力学的正式应用。