Equation of state, spectra, and composition of hot and dense infinite hadronic matter in a microscopic transport model

Equilibrium properties of infinite relativistic hadron matter are investigated using the ultrarelativistic quantum molecular dynamics (UrQMD) model. The simulations are performed in a box with periodic boundary conditions. Equilibration times depend critically on energy and baryon densities. Energy spectra of various hadronic species are shown to be isotropic and consistent with a single temperature in equilibrium. The variation of energy density versus temperature shows a Hagedorn-like behavior with a limiting temperature of 130 +/- 10 MeV. Comparison of abundances of different particle species to ideal hadron gas model predictions show good agreement only if detailed balance is implemented for all channels. At low energy densities, high mass resonances are not relevant; however, their importance rises with increasing energy density. The relevance of these different conceptual frameworks for any interpretation of experimental data is questioned.