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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,mπ) 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.