953 research outputs found
Kaons and pions in strange quark matter
The behavior of kaons and pions in strange quark matter in weak equilibrium,
is investigated within the SU(3) Nambu-Jona-Lasinio [NJL] model. This work
focuses a region of high densities where the behavior of mesons has not been
explored in the framework of this model. It is found that above the density
where strange valence quarks appear in the medium, , a
change of behavior of different observables is observed indicating a tendency
to the restoration of flavor symmetry. In particular, the splitting between
charge multiplets, decrease and
the low energy modes with quantum numbers of , which
are excitations of the Fermi sea, are less relevant than for lower densities.Comment: 10 pages, 3 figures included; revised version, some changes in the
discussio
Thermal Abelian monopoles as selfdual dyons
The properties of the thermal Abelian monopoles are studied in the
deconfinement phase of the SU(2) gluodynamics. To remove effects of Gribov
copies the simulated annealing algorithm is applied to fix the maximally
Abelian gauge. To study monopole profile we complete the first computations of
excess of the nonabelian action density as a function of the distance from the
center of the thermal Abelian monopole. We have found that starting from the
distances 2 lattice spacings the chromoelectric and chromomagnetic
action densities created by monopole are equal to each other, from what we draw
a conclusion that monopole is a dyon. Furthermore, we find that the
chromoelectric and chromomagnetic fields decrease exponentially with increasing
distance. These findings were confirmed for different temperatures in the range
.Comment: 4 pages, 3 figure
Nonlocal Polyakov-Nambu-Jona-Lasinio model with wavefunction renormalization at finite temperature and chemical potential
We study the phase diagram of strongly interacting matter in the framework of
a non-local SU(2) chiral quark model which includes wave function
renormalization and coupling to the Polyakov loop. Both non-local interactions
based on the frequently used exponential form factor, and on fits to the quark
mass and renormalization functions obtained in lattice calculations are
considered. Special attention is paid to the determination of the critical
points, both in the chiral limit and at finite quark mass. In particular, we
study the position of the Critical End Point as well as the value of the
associated critical exponents for different model parameterizations.Comment: v.2_August 2010, 26 pp, 8 fi
A predictive formulation of the Nambu--Jona-Lasinio model
A novel strategy to handle divergences typical of perturbative calculations
is implemented for the Nambu--Jona-Lasinio model and its phenomenological
consequences investigated. The central idea of the method is to avoid the
critical step involved in the regularization process, namely the explicit
evaluation of divergent integrals. This goal is achieved by assuming a
regularization distribution in an implicit way and making use, in intermediary
steps, only of very general properties of such regularization. The finite parts
are separated of the divergent ones and integrated free from effects of the
regularization. The divergent parts are organized in terms of standard objects
which are independent of the (arbitrary) momenta running in internal lines of
loop graphs. Through the analysis of symmetry relations, a set of properties
for the divergent objects are identified, which we denominate consistency
relations, reducing the number of divergent objects to only a few ones. The
calculational strategy eliminates unphysical dependencies of the arbitrary
choices for the routing of internal momenta, leading to ambiguity-free, and
symmetry-preserving physical amplitudes. We show that the imposition of scale
properties for the basic divergent objects leads to a critical condition for
the constituent quark mass such that the remaining arbitrariness is removed.
The model become predictive in the sense that its phenomenological consequences
do not depend on possible choices made in intermediary steps. Numerical results
are obtained for physical quantities at the one-loop level for the pion and
sigma masses and pion-quark and sigma-quark coupling constants.Comment: 38 pages, 1 figure, To appear in Phy.Rev.
Nonlocality effects on Color Spin Locking condensates
We consider the color spin locking (CSL) phase of two-flavor quark matter at
zero temperature for nonlocal instantaneous, separable interactions. We employ
a Lorentzian-type form factor allowing a parametric interpolation between the
sharp (Nambu-Jona-Lasinio (NJL) model) and very smooth (e.g. Gaussian) cut-off
models for systematic studies of the influence on the CSL condensate the
deviation from the NJL model entails. This smoothing of the NJL model form
factor shows advantageous features for the phenomenology of compact stars: (i)
a lowering of the critical chemical potential for the onset of the chiral phase
transition as a prerequisite for stability of hybrid stars with extended quark
matter cores and (ii) a reduction of the smallest pairing gap to the order of
100 keV, being in the range of values interesting for phenomenological studies
of hybrid star cooling evolution.Comment: 8 pages, 8 figures, 1 table, accepted for publication in Phys.Rev.
Are There Diquarks in the Nucleon?
This work is devoted to the study of diquark correlations inside the nucleon.
We analyze some matrix elements which encode information about the
non-perturbative forces, in different color anti-triplet diquark channels. We
suggest a lattice calculation to check the quark-diquark picture and clarify
the role of instanton-mediated interactions. We study in detail the physical
properties of the 0+ diquark, using the Random Instanton Liquid Model. We find
that instanton forces are sufficiently strong to form a diquark bound-state,
with a mass of ~500 MeV, which is compatible with earlier estimates. We also
compute its electro-magnetic form factor and find that the diquark is a broad
object, with a size comparable with that of the proton.Comment: Final version, accepted for publication on Phys. Rev.
Eddy current speed sensor with magnetic shielding
This paper presents the design and analysis of a new eddy current speed sensor with ferromagnetic shielding. Aluminum and solid iron are considered for the moving part. One excitation coil and two antiserially connected pick up coils are shielded by a thin steel lamination. 3D time stepping finite element analysis is used to analyze the sensor performance with different magnetic materials and compare with experimental results. The compactness, simplicity and excellent linearity with different magnetic materials for the moving part show uniqueness of the proposed speed sensor. The shielding increases sensitivity and reduces the influence of close ferromagnetic objects and interferences on the sensor performance
Transformer position sensor for a pneumatic cylinder
A novel transformer-based sensor for a pneumatic cylinder enables measurements of the piston position to be made through a thick conductive cylinder. Unlike existing industrial solutions, which are mainly based on a moving magnet, our sensors do not require modifications to the parts inside the cylinder
Static Potentials and the Magnetic Component of QCD Plasma near
Static quark-anti-quark potential encodes important information on the
chromodynamical interaction between color charges, and recent lattice results
show its very nontrivial behavior near the deconfinement temperature . In
this paper we study such potential in the framework of the ``magnetic
scenario'' for the near Tc QCD plasma, and particularly focus on the linear
part (as quantified by its slope, the tension) in the potential as well as the
strong splitting between the free energy and internal energy. By using an
analytic ``ellipsoidal bag'' model, we will quantitatively relate the free
energy tension to the magnetic condensate density and relate the internal
energy tension to the thermal monopole density. By converting the lattice
results for static potential into density for thermal monopoles we find the
density to be very large around Tc and indicate at quantum coherence, in good
agreement with direct lattice calculation of such density. A few important
consequences for heavy ion collisions phenomenology will also be discussed.Comment: 10 pages, 6 figure
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