Including the fermion vacuum fluctuations in the (2+1) flavor Polyakov quark-meson model

Abstract

We consider the (2 + 1) flavor Polyakov Quark Meson Model and study the effect of including fermion vacuum fluctuations on the thermodynamics and phase diagram. The resulting model predictions are compared to the recent QCD lattice simulations by the HotQCD and Wuppertal-Budapest collaborations. The variation of the thermodynamic quantities across the phase transition region becomes smoother. This results in better agreement with the lattice data. Depending on the value of the mass of the sigma meson, including the vacuum term results in either pushing the critical end point into higher values of the chemical potential or excluding the possibility of a critical end point altogether.

Chiral Phase Transition Scenarios from the Vector Meson Extended Polyakov Quark Meson Model

“…Since the larger is the sigma mass compared to the mass of its chiral partner (the pion) the larger is the temperature at which m f 0 approaches m π in the chiral symmetry restoration, one would expect that a large m f 0 mass results in a large pseudocritical temperature (T c ) at zero baryochemical potentials. On the other hand it is a common expectation that the chiral phase transition is of first order as a function the baryochemical potential (µ B ) at T = 0, and since with increasing m f 0 mass the transition weakens, at some point it is possible that the transition becomes crossover [5,6]. This suggest that for a good thermodynamic description a small m f 0 mass is needed, and indeed as it turns out our approach supports this requirement.…”

Implications of the fermion vacuum term in the extended SU(3) quark meson model on compact star properties

“…It is interesting to note that the grand canonical potential remains unaffected by the choice of the renormalization scale parameter Λ r . This is easily seen in the SU(2) case [39] and has also been shown for the SU(3) case for m σ = 400 MeV [28,42]. To compare our results with [42], the renormalization scale parameter is set to Λ r = 200 MeV.…”

“…We have studied the SU(3) quark meson model including the fermion vacuum term and have determined the vacuum parameters for different values of the sigma meson mass m σ . The whole potential is independent on any renormalization scale [28,31,42,43]. For all scalar meson masses in the eMFA a crossover transition in the condensates is found.…”

“…For that purpose we determine the vacuum parameters for different sigma meson masses m σ . The dependence of the vacuum parameters on the renormalization scale parameter Λ r cancels with the dependence of the additional fermion vacuum term Ω vac qq (Λ r ) in the grand potential, so that the whole grand potential is independent on the renormalization scale parameter Λ r [28,31,42,43]. The resulting equations of state (EoSs) are investigated and subsequently used to solve the Tolman-Oppenheimer-Volkoff (TOV) equations [44] for various parameters of the model, that is the sigma meson mass m σ , the repulsive vector coupling * zacchi@astro.uni-frankfurt.de † schaffner@astro.uni-frankfurt.de constant g ω and the vacuum pressure constant B 1/4 .…”

Quark number susceptibility: Revisited with fluctuation-dissipation theorem in mean field theories

“…Another well-known formulation to study the strongly interacting matter in nonperturbative regime is the quark meson (QM) model and its Polyakov loop extended version (PQM), which is used to explore the phase transition and phase diagram of QCD [112][113][114][115][116][117] as well as quark number susceptibility [118][119][120][121][122][123][124].…”