8,593 research outputs found
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.Comment: 8 pages, 2 figures, reference added, typos corrected, version to
appear in Europhys. Let
Baryonic masses based on the NJL model
We employ the Nambu Jona--Lasinio model to determine the vacuum pressure on
the quarks in a baryon and hence their density inside. Then we estimate the
baryonic masses by implementing the local density approximation for the mean
field quark energies obtained in a uniform and isotropic system. We obtain a
fair agreement with the experimental masses.Comment: 17 pages, 3 figures. to be published on EPJ
Lattice QCD-based equations of state at vanishing net-baryon density
We present realistic equations of state for QCD matter at vanishing
net-baryon density which embed recent lattice QCD results at high temperatures
combined with a hadron resonance gas model in the low-temperature, confined
phase. In the latter, we allow an implementation of partial chemical
equilibrium, in which particle ratios are fixed at the chemical freeze-out, so
that a description closer to the experimental situation is possible. Given the
present uncertainty in the determination of the chemical freeze-out temperature
from first-principle lattice QCD calculations, we consider different values
within the expected range. The corresponding equations of state can be applied
in the hydrodynamic modeling of relativistic heavy-ion collisions at the LHC
and at the highest RHIC beam energies. Suitable parametrizations of our results
as functions of the energy density are also provided.Comment: Updated journal version with refined EoS-parametrization. July 2014.
8 pp. 4 figs. 3 parametrization-tables and weblink Ref. [45
Quark number susceptibilities: lattice QCD versus PNJL model
Quark number susceptibilities at finite quark chemical potential are
investigated in the framework of the Polyakov-loop-extended Nambu Jona-Lasinio
(PNJL) model. A detailed comparison is performed between the available lattice
data, extrapolated using a Taylor expansion around vanishing chemical
potential, and PNJL results consistently obtained from a Taylor series
truncated at the same order. The validity of the Taylor expansion is then
examined through a comparison between the full and truncated PNJL model
calculations.Comment: 8 pages, 2 figure
Mesonic correlation functions at finite temperature and density in the Nambu-Jona-Lasinio model with a Polyakov loop
We investigate the properties of scalar and pseudo-scalar mesons at finite
temperature and quark chemical potential in the framework of the
Nambu-Jona-Lasinio (NJL) model coupled to the Polyakov loop (PNJL model) with
the aim of taking into account features of both chiral symmetry breaking and
deconfinement. The mesonic correlators are obtained by solving the
Schwinger-Dyson equation in the RPA approximation with the Hartree (mean field)
quark propagator at finite temperature and density. In the phase of broken
chiral symmetry a narrower width for the sigma meson is obtained with respect
to the NJL case; on the other hand, the pion still behaves as a Goldstone
boson. When chiral symmetry is restored, the pion and sigma spectral functions
tend to merge. The Mott temperature for the pion is also computed.Comment: 24 pages, 9 figures, version to appear in Phys. Rev.
A PNJL model in 0+1 Dimensions
We formulate the Polyakov-Nambu-Jona-Lasinio (PNJL) model in 0+1 dimensions.
The thermodynamics captured by the partition function yields a bulk pressure,
as well as quark susceptibilities versus temperature that are similar to the
ones in 3+1 dimensions. Around the transition temperature the behavior in the
pressure and quark susceptibilities follows from the interplay between the
lowest Matsubara frequency and the Polyakov line. The reduction to the lowest
Matsubara frequency yields a matrix Model. In the presence of the Polyakov line
the UV part of the Dirac spectrum features oscillations when close to the
transition temperature.Comment: 18 pages, 13 figure
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