Chiral Symmetry Restoration at Finite Temperature in the Linear Sigma--Model

الأصل · EN

The temperature behaviour of meson condensates <σ₀> and <σ₈> is calculated in the SU(3)× SU(3)-linear sigma model. The couplings of the Lagrangian are fitted to the physical π,K,η,η' masses, the pion decay constant and a O+(I=0) scalar mass of mσ=1.5 GeV. The quartic terms of the mesonic interaction are converted to a quadratic term with the help of a Hubbard-Stratonovich transformation. Effective mass terms are generated this way, which are treated self-consistently to leading order of a 1/N-expansion. We calculate the light < q q> and strange < s s>-quark condensates using PCAC relations between the meson masses and condensates. For a cut-off value of 1.5 GeV we find a first-order chiral transition at a critical temperature Tc 161 MeV. At this temperature the spontaneously broken subgroup SU(2)× SU(2) is restored. Entropy density, energy density and pressure are calculated for temperatures up to and slightly above the critical temperature. To our surprise we find some indications for a reduced contribution from strange mesons for T≥ Tc.