16607491
The NJL model and strange quark matter
The stability of strange-quark matter is studied within the Nambu Jona-Lasinio model with three different parameter sets. The model Lagrangian contains 4-fermion (with and without vector interaction) and 6-fermion terms; the minimum energy per baryon number as a function of the strangeness fraction of the system is compared to the masses of hyperons having the same strangeness fraction, and coherently calculated in the same version of the model, and for the same parameter set. The results show that in none of the different parameter sets strangelets are stable, and in some cases a minimum in the energy per baryon does not even exist.
16977039
The Role of Color-Magnetic Monopoles in a Gluonic Plasma
Abstract The role of color-magnetic monopoles in a pure gauge plasma at high temperature T > 2 T c is considered. In this temperature regime, monopoles can be considered heavy, rare objects embedded into matter consisting mostly of the usual “electric” quasiparticles, quarks and gluons. The gluon-monopole scattering is found to hardly influence thermodynamic quantities, yet it produces a large transport cross section, significantly exceeding that for pQCD gluon-gluon scattering up to quite high T. This mechanism keeps viscosity small enough for hydrodynamics to work at LHC.
56465034
The chiral and deconfinement crossover transitions: PNJL model beyond mean field ∗
Abstract The Polyakov loop extended Nambu and Jona-Lasinio model (PNJL model) in a mean field framework shows astonishingly good agreement with lattice QCD calculations which needs to be better understood. The present work reports on further developments concerning both Polyakov loop and mesonic fluctuations beyond mean field approximation. Corrections beyond mean field are of special interest for the thermal expectation values of the Polyakov loop 〈 Φ 〉 and its conjugate 〈 Φ ∗ 〉 , which differ once the quark chemical potential is non-zero. Mesonic fluctuations are also considered with emphasis on the role of pionic modes.
119349228
Stability of strange quark matter in the MIT bag model and in the Color Dielectric Model
We utilize the MIT bag model and two different versions of the Color Dielectric Model in order to study the properties of strange matter, and to discuss the stability of strangelets. We also investigate the effect of the introduction of perturbative gluons. The MIT bag model and the Double Minimum version of the Color Dielectric Model allow the existence of strangelets, while the Single Minimum version excludes this possibility.
14960863
Polyakov loop, diquarks, and the two-flavor phase diagram
An updated version of the PNJL model is used to study the thermodynamics of N{sub f}=2 quark flavors interacting through chiral four-point couplings and propagating in a homogeneous Polyakov loop background. Previous PNJL calculations are extended by introducing explicit diquark degrees of freedom and an improved effective potential for the Polyakov loop field. The mean field equations are treated under the aspect of accommodating group theoretical constraints and issues arising from the fermion sign problem. The input is fixed exclusively by selected pure-gauge lattice QCD results and by pion properties in vacuum. The resulting (T,{mu}) phase diagram is studied with special emphasis on the critical point, its dependence on the quark mass and on Polyakov loop dynamics. We present successful comparisons with lattice QCD thermodynamics expanded to finite chemical potential {mu}.
55793321
The QCD equation of state with dynamical quarks
The present paper concludes our investigation on the QCD equation of state with 2 + 1 staggered flavors and one-link stout improvement. We extend our previous study [JHEP01 (2006) 089] by choosing even finer lattices. Lattices with Nt=6, 8 and 10 are used, and the continuum limit is approached by checking the results at Nt= 12. A Symanzik improved gauge and a stout-link improved staggered fermion action is utilized. We use physical quark masses, that is, for the lightest staggered pions and kaons we fix the mπ/fK and mK/fK ratios to their experimental values. The pressure, the interaction measure, the energy and entropy density and the speed of sound are presented as functions of the temperature in the range 100 ... 1000MeV. We give estimates for the pion mass dependence and for the contribution of the charm quark. We compare our data to the equation of state obtained by the “hotQCD” collaboration.
15615236
Mesons in marginally deformed AdS/CFT
We study the embedding of spacetime filling D7-branes in β-deformed backgrounds which, according to the AdS/CFT dictionary, corresponds to flavoring β-deformed = 4 super Yang-Mills. We consider supersymmetric and more general non-supersymmetric three parameter deformations. The equations of motion for quadratic fluctuations of a probe D7-brane wrapped on a deformed three-sphere exhibit a non-trivial coupling between scalar and vector modes induced by the deformation. Nevertheless, we manage to solve them analytically and find that the mesonic mass spectrum is discrete, with a mass gap and a Zeeman-like splitting occurs. Finally we propose the action for the dual field theory as obtained by -product deformation of super Yang-Mills with fundamental matter.