20,898 research outputs found
Small radii of neutron stars as an indication of novel in-medium effects
At present, neutron star radii from both observations and model predictions
remain very uncertain. Whereas different models can predict a wide range of
neutron star radii, it is not possible for most models to predict radii that
are smaller than about 10 km, thus if such small radii are established in the
future they will be very difficult to reconcile with model estimates. By
invoking a new term in the equation of state that enhances the energy density,
but leaves the pressure unchanged we simulate the current uncertainty in the
neutron star radii. This new term can be possibly due to the exchange of the
weakly interacting light U-boson with appropriate in-medium parameters, which
does not compromise the success of the conventional nuclear models. The
validity of this new scheme will be tested eventually by more precise
measurements of neutron star radii.Comment: EPJA (2015) in pres
Neutron-skin thickness of finite nuclei in relativistic mean-field models with chiral limits
We study several structure properties of finite nuclei using relativistic
mean-field Lagrangians constructed according to the Brown-Rho scaling due to
the chiral symmetry restoration at high densities. The models are consistent
with current experimental constraints for the equations of state of symmetric
matter at both normal and supra-normal densities and of asymmetric matter at
sub-saturation densities. It is shown that these models can successfully
describe the binding energies and charge radii of finite nuclei. Compared to
calculations with usual relativistic mean-field models, these models give a
reduced thickness of neutron skin in ^{208}Pb between 0.17 fm and 0.21 fm. The
reduction of the predicted neutron skin thickness is found to be due to not
only the softening of the symmetry energy but also the scaling property of
meson required by the partial restoration of chiral symmetry.Comment: Accepted version to appear in PRC (2007
Stability of Two-Dimensional Soft Quasicrystals
The relative stability of two-dimensional soft quasicrystals is examined
using a recently developed projection method which provides a unified numerical
framework to compute the free energy of periodic crystal and quasicrystals.
Accurate free energies of numerous ordered phases, including dodecagonal,
decagonal and octagonal quasicrystals, are obtained for a simple model, i.e.
the Lifshitz-Petrich free energy functional, of soft quasicrystals with two
length-scales. The availability of the free energy allows us to construct phase
diagrams of the system, demonstrating that, for the Lifshitz-Petrich model, the
dodecagonal and decagonal quasicrystals can become stable phases, whereas the
octagonal quasicrystal stays as a metastable phase.Comment: 11 pages, 7 figure
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