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Extracting the equation of state from a microscopic non-equilibrium model

C. Spieles·A. Dumitru·S. A. Bass·M. Bleicher·J. Brachmann·M. Brandstetter·C. Ernst·L. Gerland·J. Konopka·S. Soff·H. Weber·L. A. Winckelmann·J. Maruhn·H. Stoecker·W. Greiner
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Abstract

We study the thermodynamic properties of infinite nuclear matter with the Ultrarelativistic Quantum Molecular Dynamics (URQMD), a semiclassical transport model, running in a box with periodic boundary conditions. It appears that the energy density rises faster than $T^4$ at high temperatures of $T\approx 200-300$~MeV. This indicates an increase in the number of degrees of freedom. Moreover, We have calculated direct photon production in Pb+Pb collisions at 160~GeV/u within this model. The direct photon slope from the microscopic calculation equals that from a hydrodynamical calculation without a phase transition in the equation of state of the photon source.

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C. Spieles, A. Dumitru, S. A. Bass, M. Bleicher, J. Brachmann, M. Brandstetter, C. Ernst, L. Gerland, J. Konopka, S. Soff, H. Weber, L. A. Winckelmann, J. Maruhn, H. Stoecker, W. Greiner. 1996-06-17. Extracting the equation of state from a microscopic non-equilibrium model. https://arxiv.org/abs/nucl-th/9606030

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