9,147 research outputs found
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
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
Recent thermodynamic results from lattice QCD analyzed within a quasi-particle model
The thermodynamic behavior of QCD matter at high temperature is currently
studied by lattice QCD theory. The main features are the fast rise of the
energy density around the critical temperature and the large
trace anomaly of the energy momentum tensor
which hints at a strongly interacting system. Such features can be accounted
for by employing a massive quasi-particle model with a temperature-dependent
bag constant. Recent lattice QCD calculations with physical quark masses by the
Wuppertal-Budapest group have shown a slower increase of and a
smaller peak with respect to previous results from the
hotQCD collaboration. We investigate the implications of such differences from
the point of view of a quasi-particle model, also discussing light and strange
quark number susceptibilities. Furthermore, we predict the impact of these
discrepancies on the temperature-dependence of the transport properties of
matter, like the shear and bulk viscosities.Comment: 18 pages, 9 figures; version accepted in Phys. Rev.D; calculation
with relaxation time \tau \sim g^4 ln g has been adde
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
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.
Additive manufacturing in the maritime industry: Impact on production processes, workers, and end-users
Additive Manufacturing (AM) technologies are revolutionising global production processes, offering substantial benefits to the maritime industry by eliminating the reliance on models and moulds. This shift toward a sustainable, zero-waste future presents significant opportunities and considerations for both workers and end-users.The adoption of automated 3D printing necessitates workforce retraining, with a focus on digital technology skills, reducing the reliance on manual labour. Proactive training programs are vital to equip operators for this evolving landscape. Additionally, studies are exploring occupational health-related aspects of 3D printing, assessing whether it could create a safer working environment compared to traditional manufacturing processes.AM customisation capabilities empower designers and engineers to prioritize human factors, enhancing user experience, comfort, and usability. This approach fosters innovations aligned with the preferences and needs of end-users.This paper aims to explore the impact of AM technologies on manufacturing processes and design freedom within the maritime industry, emphasizing opportunities for improved efficiency, sustainability, and adaptive design practices to meet the sector's dynamic needs
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