37,844 research outputs found
Modification of nucleon properties in nuclear matter and finite nuclei
We present a model for the description of nuclear matter and finite nuclei,
and at the same time, for the study of medium modifications of nucleon
properties. The nucleons are described as nontopological solitons which
interact through the self-consistent exchange of scalar and vector mesons. The
model explicitly incorporates quark degrees of freedom into nuclear many-body
systems and provides satisfactory results on the nuclear properties. The
present model predicts a significant increase of the nucleon radius at normal
nuclear matter density. It is very interesting to see the nucleon properties
change from the nuclear surface to the nuclear interior.Comment: 22 pages, 10 figure
Neutron star matter in the quark-meson coupling model in strong magnetic fields
The effects of strong magnetic fields on neutron star matter are investigated
in the quark-meson coupling (QMC) model. The QMC model describes a nuclear
many-body system as nonoverlapping MIT bags in which quarks interact through
self-consistent exchange of scalar and vector mesons in the mean-field
approximation. The results of the QMC model are compared with those obtained in
a relativistic mean-field (RMF) model. It is found that quantitative
differences exist between the QMC and RMF models, while qualitative trends of
the magnetic field effects on the equation of state and composition of neutron
star matter are very similar.Comment: 16 pages, 4 figure
Possible dibaryons in the quark cluster model
In the framework of RGM, the binding energy of one channel
() and are studied in the
chiral SU(3) quark cluster model. It is shown that the binding energies of the
systems are a few tens of MeV. The behavior of the chiral field is also
investigated by comparing the results with those in the SU(2) and the extended
SU(2) chiral quark models. It is found that the symmetry property of the
system makes the contribution of the relative kinetic energy
operator between two clusters attractive. This is very beneficial for forming
the bound dibaryon. Meanwhile the chiral-quark field coupling also plays a very
important role on binding. The S-wave phase shifts and the corresponding
scattering lengths of the systems are also given.Comment: LeTex with 2 ps figure
Measurement of a Sign-Changing Two-Gap Superconducting Phase in Electron-Doped Ba(Fe_{1-x}Co_x)_2As_2 Single Crystals using Scanning Tunneling Spectroscopy
Scanning tunneling spectroscopic studies of (x =
0.06, 0.12) single crystals reveal direct evidence for predominantly two-gap
superconductivity. These gaps decrease with increasing temperature and vanish
above the superconducting transition . The two-gap nature and the slightly
doping- and energy-dependent quasiparticle scattering interferences near the
wave-vectors and are consistent with
sign-changing -wave superconductivity. The excess zero-bias conductance and
the large gap-to- ratios suggest dominant unitary impurity scattering.Comment: 4 pages, 4 figures. Paper accepted for publication in Physical Review
Letters. Contact author: Nai-Chang Yeh ([email protected]
Resolvent Estimates in L^p for the Stokes Operator in Lipschitz Domains
We establish the resolvent estimates for the Stokes operator in
Lipschitz domains in , for . The result, in particular, implies that the Stokes operator in a
three-dimensional Lipschitz domain generates a bounded analytic semigroup in
for (3/2)-\varep < p< 3+\epsilon. This gives an affirmative answer to a
conjecture of M. Taylor.Comment: 28 page. Minor revision was made regarding the definition of the
Stokes operator in Lipschitz domain
Quark mean field model with density dependent couplings for finite nuclei
The quark mean field model, which describes the nucleon using the constituent
quark model, is applied to investigate the properties of finite nuclei. The
couplings of the scalar and vector mesons with quarks are made density
dependent through direct coupling to the scalar field so as to reproduce the
relativistic Brueckner-Hartree-Fock results of nuclear matter. The present
model provides satisfactory results on the properties of spherical nuclei, and
predicts an increasing size of the nucleon as well as a reduction of the
nucleon mass in the nuclear environmentComment: 8 pages, REVTeX, 8 ps figures, accepted for publication in Phys. Rev.
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