An effective thermodynamic potential from the instanton vacuum with the Polyakov loop
School of Physics, Korea Institute for Advanced Study, Seoul 130-722, Republic of Korea
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In this talk, we report our recent studies on an effective thermodynamic potential (Ωeff) at finite temperature (T ≠ 0) and zero quark-chemical potential (μR = 0), using the singular-gauge instanton solution and Matsubara formula for Nc = 3 and Nf = 2 in the chiral limit, i.e. mq = 0. The momentum-dependent constituent-quark mass is computed as a function of T, together with the Harrington-Shepard caloron solution in the large-Nc limit. In addition, we take into account the imaginary quark-chemical potential μI ≡ A4, identified as the traced Polyakov-loop (Φ) as an order parameter for the ℤ(Nc) symmetry, characterizing the confinement (intact) and deconfinement (spontaneously broken) phases. As a consequence, we observe the crossover of the chiral (χ) order parameter σ2 and Φ. It also turns out that the critical temperature for the deconfinement phase transition, Tcℤ is lowered by about (5 ~10)% in comparison to the case with the constant constituent-quark mass. This behavior can be understood by considerable effects from the partial chiral restoration and nontrivial QCD vacuum on the Φ. Numerical results show that the crossover transitions occur at (Tcχ, Tcℤ) ≈ (216, 227) MeV.
© Owned by the authors, published by EDP Sciences, 2012