QCD thermodynamics is studied using a model which combines Polyakov loop dynamics with spontaneous chiral symmetry breaking and its restoration (the PNJL model). The input is fixed entirely by pure-gauge lattice QCD results and by pion properties in vacuum. Successful comparisons with results from thermal lattice QCD are achieved, including extrapolations to finite quark chemical potential. The phase diagram and selected susceptibilities for two quark flavors are investigated with inclusion of diquark degrees of freedom.
Using vector and axial-vector correlators within finite energy sum rules with inputs from a chiral quark model, coupled to the Polyakov loop, with nonlocal vector interactions, we extend our previous work to confirm the equivalence between the continuum threshold $s_0$ and the trace of the Polyakov loop $Φ$ as order parameters for the deconfinement transition at finite temperature $T$ and quark chemical potential $μ$. The obtained results are in agreement with our initial conclusion, where we showed that $s_0(T,μ)$ and $Φ(T,μ)$ provide the same information for the QCD deconfinement transition.
The SU(4) Polyakov linear sigma model (PLSM) is extended towards characterizing the chiral condensates, $σ_l$, $σ_s$ and $σ_c$ of light, strange and charm quarks, respectively and the deconfinement order-parameters $ϕ$ and $\barϕ$ at finite temperatures and densities (chemical potentials). The PLSM is considered to study the QCD equation of state in the presence of the chiral condensate of charm for different finite chemical potentials. The PLSM results are in a good agreement with the recent lattice QCD simulations. We conclude that, the charm condensate is likely not affected by the QCD phas…
We study the thermodynamics of QCD system under external magnetic field via the 2+1 flavor Polyakov-loop quark-meson model. To incorporate quantum and thermal fluctuations, the functional renormalization group approach is implemented in our work. Pressure, entropy density, magnetic susceptibility and other thermodynamic quantities are calculated and analyzed to investigate the effect of magnetic field on the QCD system. The calculated results are in reasonable agreement with lattice QCD simulations and perturbation theory. We then give an intuitive picture for the response of QCD system to the…
The SU($3$) Polyakov linear-sigma model (PLSM) in mean-field approximation is utilized in analyzing the chiral condensates $σ_u$, $σ_d$, $σ_s$ and the deconfinement order parameters $ϕ$, $\barϕ$, at finite isospin asymmetry. The bulk thermodynamics including pressure density, interaction measure, susceptibility, and second-order correlations with baryon, strange and electric charge quantum numbers are studied in thermal and dense medium. The PLSM results are confronted to the available lattice QCD calculations. The excellent agreement obtained strengthens the reliability of fixing the PLSM par…
We present a nonextensive version of the Polyakov-Nambu-Jona-Lasinio model which is based on the nonextentive statistical mechanics. This new statistics is characterized by a dimensionless nonextensivity parameter $q$ that accounts for all possible effects violating the assumptions of the Boltzmann-Gibbs (BG) statistics (when $q\rightarrow1$, it returns to the BG case). Based on the nonextensive Polyakov-Nambu-Jona-Lasinio model, we discussed the influence of the nonextensive effects on the QCD phase transition, especially on the location of the critical end point (CEP). A new and interesting …
A non-perturbative method of Field Correlators is applied to calculate the Polyakov loop dependence on temperature, $L(T)$, in the 2+1 flavor QCD with small quark masses, so the only relevant scale is the color-electric string tension $σ(T)$. Polyakov loop in the temperature range 100 MeV $\lesssim T\lesssim$ 400 MeV is expressed via the heavy-light meson mass that decreases with $T$ as $\sqrt{σ(T)}$. The latter is deduced from a gradually vanishing chiral condensate. The resulting $L(T)$ is in good agreement with recent lattice data.
Unquenching of the Polyakov-loop potential showed to be an important improvement for the description of the phase structure and thermodynamics of strongly-interacting matter at zero quark chemical potentials with Polyakov-loop extended chiral models. This work constitutes the first application of the quark backreaction on the Polyakov-loop potential at nonzero density. The observation is that it links the chiral and deconfinement phase transition also at small temperatures and large quark chemical potentials. The build up of the surface tension in the Polyakov-loop extended Quark-Meson model i…
Deconfinement and chiral restoration within the SU(3) Polyakov--Nambu--Jona-Lasinio and entangled Polyakov--Nambu--Jona-Lasinio models in an external magnetic field
We review theoretical aspects of quantum chromodynamics (QCD) at finite temperature. The most important physical variable to characterize hot QCD is the Polyakov loop, which is an approximate order parameter for quark deconfinement in a hot gluonic medium. Additionally to its role as an order parameter, the Polyakov loop has rich physical contents in both perturbative and non-perturbative sectors. This review covers a wide range of subjects associated with the Polyakov loop from topological defects in hot QCD to model building with coupling to the Polyakov loop.
We present a phase diagram for SU(3) lattice gauge theory with 695 MeV dynamical staggered fermions, in the plane of temperature and chemical potential, obtained from effective Polyakov line actions. The derivation is via the method of relative weights, and the effective theories are solved at finite chemical potential by mean field theory.
We discuss different aspects of the quark mass dependence of the chiral and deconfinement transitions. We make predictions for locating the deconfining critical point, by analyzing the $m_q$ dependence of the ratio of imaginary and real mass of the Polyakov loop. We then present an effective theory that allows the extraction of coupling constants from available lattice data for the temperature dependence of the chiral and Polyakov loop condensates at different quark masses.
Study of finite volume number density fluctuations in the SU(3) Polyakov loop extended Nambu-Jona-Lasinio model for the search of the QCD Critical Point
We apply the path optimization method to a QCD effective model with the Polyakov loop at finite density to circumvent the model sign problem. The Polyakov-loop extended Nambu--Jona-Lasinio model is employed as the typical QCD effective model and then the hybrid Monte-Carlo method is used to perform the path integration. To control the sign problem, the path optimization method is used with complexification of temporal gluon fields to modify the integral path in the complex space. We show that the average phase factor is well improved on the modified integral-path compared with that on the orig…
Dual meson condensates as possible order parameters for deconfinement are investigated in a Polyakov-loop enhanced linear sigma model of QCD at both zero and finite isospin chemical potential $μ_I$. We find that the rapid rise of the dual sigma condensate (corresponding to the dressed Polyakov-loop) with $T$ is driven by the chiral transition, no matter whether the Polyakov-loop dynamics is included or not. For $μ_I>m_π/2$, the dual sigma condensate shows abnormal thermal behavior which even decreases with $T$ below the melting temperature $T_c^{I_3}$ of pion superfluidity; On the other hand, …
Polyakov loops $L_a(T), a=3,8,...$ are shown to give the most important nonperturbative contribution to the thermodynamic potentials. Derived from the gluonic field correlators they enter as factors into free energy. It is shown in the $SU(3)$ case that $L_a (T)$ define to a large extent the behavior of the free energy and the trace anomaly $I(T)$, most sensitive to nonperturbative effects.
