Münster 2002 – scientific programme

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HK: Physik der Hadronen und Kerne

HK 2: Theory I

HK 2.7: Talk

Monday, March 11, 2002, 18:30–18:45, A

Thermodynamics of the chiral condensate — •Thomas M. Schwarz, Norbert Kaiser, and Wolfram Weise — Physik-Department, Technische Universität München.

We study the temperature and density dependence of the scalar quark condensate ⟨qq⟩ using effective field theory methods. Nucleons interact via perturbative chiral pion exchange and scalar plus vector four-point interactions. The latter are treated in relativistic mean field approximation giving rise to an effective nucleon mass M^∗ and an effective chemical potential µ^∗. Contributions from pion fluctuations at two-loop level are included in the self consistency equations for M^∗ and µ^∗. The strengths of the contact interactions are adjusted to the empirical nuclear matter saturation point and compressibility κ. From this we predict an effective nucleon mass of M^∗(ρ₀)≃ 0.8M. At a temperature T≃ 17 MeV a liquid-gas phase transition is observed. The dependence of the equation of state P(T,µ,m_π) on the pion mass allows to calculate deviations from the leading linear decrease in density of the quark condensate. We find that these are small below normal nuclear matter density, but substantial at higher densities. In a further step we include three-loop contributions from 2π-exchange.
Supported in part by BMBF and GSI.