Isentropic thermodynamics in the PNJL model

We discuss the isentropic trajectories on the QCD phase diagram in the temperature and the quark chemical potential plane using the Nambu--Jona-Lasinio model with the Polyakov loop coupling (PNJL model). We impose a constraint on the strange quark chemical potential so that the strange quark density is zero, which is the case in the ultra relativistic heavy-ion collisions. We compare our numerical results with the truncated estimates by the Taylor expansion in terms of the chemical potential to quantify the reliability of the expansion used in the lattice QCD simulation. We finally discuss the strange quark chemical potential induced by the strangeness neutrality condition and relate it to the ratio of the Polyakov loop and the anti-Polyakov loop.Comment: 9 pages, 9 figure

QCD Thermodynamics from the Lattice

We review the current methods and results of lattice simulations of quantum chromodynamics at nonzero temperatures and densities. The review is intended to introduce the subject to interested nonspecialists and beginners. It includes a brief overview of lattice gauge theory, a discussion of the determination of the crossover temperature, the QCD phase diagram at zero and nonzero densities, the equation of state, some in-medium properties of hadrons including charmonium, and some plasma transport coefficients.Comment: 74 pp. 31 figs. To appear in the European Physical Journal A and Advances in Physics of Particles and Nuclei. Added references, corrected typos, and updated the discussion of the thermal heavy quark/antiquark potential. Added and updated references. Final versio

On the Parity Degeneracy of Baryons

The gross features of the observed baryon excitation spectrum below 2 GeV are well explained if the spectrum generating algebra of its intrinsic orbital angular momentum states is o(4)*su(2)_I. The spins of the resonances are obtained through the coupling of a Lorentz bi-spinor (1/2,0)+ (0,1/ 2) to a multiplet of the type (j,j) in its O(4)/O(3) reduction. The parities of the resonances follow from those of the O(3) members of the (j,j) multiplets. In this way relativistic SL(2,C) representations are constructed. For example, the first S11, P11, and D13 states with masses around 1500 MeV fit into the (1/2, 1/2)* [(1/2,0)+(0,1/2)] representation. The observed parities of the resonances correspond to natural parities of the (1/2,1/2) states. The second P11, S11, D13- together with the first P13, F15, D15, and (a predicted) F17 -resonances, centered around 1700 MeV, are organized into the (3/2,3/2)*[(1/2,0)+(0,1/2)] representation. I argue that the members of the (3/2,3/2) multiplet carry unnatural parities and that in this region chiral symmetry is restored. In the N(939)- N(1650) transition the chiral symmetry mode is changed, and therefore, a chiral phase transition is predicted to take place.Comment: 9 pages, LaTex, 1 figure; published in Mod.Phys.Lett. A12 (1997) 2373; minor misprints corrected, no statement change

Numerical Tests of the Improved Fermilab Action

Recently, the Fermilab heavy-quark action was extended to include dimension-six and -seven operators in order to reduce the discretization errors. In this talk, we present results of the first numerical simulations with this action (the OK action), where we study the masses of the quarkonium and heavy-light systems. We calculate combinations of masses designed to test improvement and compare results obtained with the OK action to their counterparts obtained with the clover action. Our preliminary results show a clear improvement.Comment: 7 pages, 3 figures, Talk presented at 28th International Symposium On Lattice Field Theory (Lattice 2010) 13-19 Jun 2010, Villasimius, Sardinia, Ital

Thermodynamics of the QCD plasma and the large-N limit

The equilibrium thermodynamic properties of the SU(N) plasma at finite temperature are studied non-perturbatively in the large-N limit, via lattice simulations. We present high-precision numerical results for the pressure, trace of the energy-momentum tensor, energy density and entropy density of SU(N) Yang-Mills theories with N=3, 4, 5, 6 and 8 colors, in a temperature range from 0.8T_c to 3.4T_c (where T_c denotes the critical deconfinement temperature). The results, normalized according to the number of gluons, show a very mild dependence on N, supporting the idea that the dynamics of the strongly-interacting QCD plasma could admit a description based on large-N models. We compare our numerical data with general expectations about the thermal behavior of the deconfined gluon plasma and with various theoretical descriptions, including, in particular, the improved holographic QCD model recently proposed by Kiritsis and collaborators. We also comment on the relevance of an AdS/CFT description for the QCD plasma in a phenomenologically interesting temperature range where the system, while still strongly-coupled, approaches a `quasi-conformal' regime characterized by approximate scale invariance. Finally, we perform an extrapolation of our results to the N to $\infty$ limit.Comment: 1+38 pages, 13 eps figures; v2: added reference

On Fluctuations of Conserved Charges : Lattice Results Versus Hadron Resonance Gas

We compare recent lattice results on fluctuations and correlations of strangeness, baryon number and electric charge obtained with p4 improved staggered action with the prediction of hadron resonance gas model. We show that hadron resonance gas can describe these fluctuations reasonably well if the hadron properties are as calculated on the lattice.Comment: 4 pages, LaTeX, uses jpconf.cls, to appear in the proceedings of 26th Winter Workshop on Nuclear Dynamic

Hot Quark Matter with an Axial Chemical Potential

We analyze the phase diagram of hot quark matter in presence of an axial chemical potential, $\mu_5$. The latter is introduced to mimic the chirality transitions induced, in hot Quantum Chromodynamics, by the strong sphaleron configurations. In particular, we study the curvature of the critical line at small $\mu_5$, the effects of a finite quark mass and of a vector interaction. Moreover, we build the mixed phase at the first order phase transition line, and draw the phase diagram in the chiral density and temperature plane. We finally compute the full topological susceptibility in presence of a background of topological charge.Comment: 12 pages, 7 figures. Few references added, short discussion included. Final version appearing on Phys. Rev.