8,168 research outputs found

### Effect of tensor force on density dependence of symmetry energy within the BHF Framework

The effect of tensor force on the density dependence of nuclear symmetry
energy has been investigated within the framework of the Brueckner-Hartree-Fock
approach. It is shown that the tensor force manifests its effect via the tensor
$^3SD_1$ channel. The density dependence of symmetry energy $E_{sym}$ turns out
to be determined essentially by the tensor force from the $\pi$ meson and
$\rho$ meson exchanges via the $^3SD_1$ coupled channel. Increasing the
strength of the tensor component due to the $\rho$-meson exchange tends to
enhance the repulsion of the equation of state of symmetric nuclear matter and
leads to reduction of symmetry energy. The present results confirm the dominant
role played by the tensor force in determining nuclear symmetry energy and its
density dependence within the microscopic BHF framework.Comment: 5 pages, 3 figure

### Three-body force effect on neutrino emissivities of neutron stars within the framework of the Brueckner-Hartree-Fock approach

The three-body force (TBF) effect on the neutrino emissivity in neutron star
matter and the total neutrino emissivity of neutron stars have been
investigated within the framework of the Brueckner-Hartree-Fock approach by
adopting the AV18 two-body interaction plus a microscopic TBF. The neutrino
emissivity from the direct Urca process turns out to be much larger than that
from the modified Urca process. Inclusion of the TBF reduces strongly the
density thresholds of the direct Urca processes involving electrons and muons.
The TBF effect on the total neutrino emissivity of neutron stars is shown to be
negligibly weak for neutron stars with small masses. For neutron stars with
large masses, the TBF effect becomes visible and inclusion of the TBF may
enhance the total neutrino emissivity by about 50% for neutron stars with a
given mass of $M=1.6M_{\odot}$.Comment: 7 pages, 3 figure

### Three-body force effect on the properties of nuclear matter under the gap and continuous choices within the BHF approach

We have calculated and compared the three-body force effects on the
properties of nuclear matter under the gap and continuous choices for the
self-consistent auxiliary potential within the Brueckner-Hartree-Fock approach
by adopting the Argonne $V18$ and the Bonn B two-body potentials plus a
microscopic three-body force (TBF). The TBF provides a strong repulsive effect
on the equation of state of nuclear matter at high densities for both the gap
and continuous choices. The saturation point turns out to be much closer to the
empirical value when the continuous choice is adopted. In addition, the
dependence of the calculated symmetry energy upon the choice of the
self-consistent auxiliary potential is discussed.Comment: 6 pages, 5 figure

### Angle-dependent Gap state in Asymmetric Nuclear Matter

We propose an axisymmetric angle-dependent gap (ADG) state with the broken
rotational symmetry in isospin-asymmetric nuclear matter. In this state, the
deformed Fermi spheres of neutrons and protons increase the pairing
probabilities along the axis of symmetry breaking near the average Fermi
surface. We find that the state possesses lower free energy and larger gap
value than the angle-averaged gap state at large isospin asymmetries. These
properties are mainly caused by the coupling of different m_{j} components of
the pairing gap. Furthermore, we find the transition from the ADG state to the
normal state is of second order and the ADG state vanishes at the critical
isospin asymmetry m_{j} where the angle-averaged gap vanishes.Comment: 23 pages, 7 figure

### Origin of symmetry energy in finite nuclei and density dependence of nuclear matter symmetry energy from measured alpha-decay energies

Based on the Skyrme energy density functional, the spatial distribution of
the symmetry energy of a finite nucleus is derived in order to examine whether
the symmetry energy of a finite nucleus originates from its interior or from
its surface. It is found that the surface part of a heavy nucleus contributes
dominantly to its symmetry energy compared to its inner part. The symmetry
energy coefficient $a_{\text{sym}}({A})$ is then directly extracted and the
ratio of the surface symmetry coefficient to the volume symmetry coefficient
$\kappa$ is estimated. Meanwhile, with the help of experimental alpha decay
energies, a macroscopic method is developed to determine the symmetry energy
coefficient of heavy nuclei. The resultant $a_{\text{sym}}({A})$ is used to
analyze the density dependence of the symmetry energy coefficient of nuclear
matter around the saturation density, and furthermore, the neutron skin
thickness of $^{208}\text{Pb}$ is deduced which is consistent with the pygmy
dipole resonance analysis. In addition, it is shown that the ratio $\kappa$
obtained from the macroscopic method is in agreement with that from the Skyrme
energy density functional. Thus the two completely different approaches may
validate each other to achieve more compelling results.Comment: 6 pages, 3 figures, to appear in Phys. Rev.

### Symbolic Dynamics of the Diamagnetic Kepler Problem Without Involving Bounces

Without involving bounce events, a Poincar\'e section associated with the
axes is found to give a map on the annulus for the diamagnetic Kepler problem.
Symbolic dynamics is then established based on the lift of the annulus map. The
correspondence between the coding derived from this axis Poincar\'e section is
compared with the coding based on bounces. Symmetry is used to reduce the
symbolic dynamics. By means of symbolic dynamics the admissibility of periodic
orbits is analyzed, and the symmetry of orbits discussed

### Constraints on neutron skin thickness in 208Pb and density-dependent symmetry energy

Accurate knowledge about the neutron skin thickness $\Delta R_{np}$ in
$^{208}$Pb has far-reaching implications for different communities of nuclear
physics and astrophysics. Yet, the novel Lead Radius Experiment (PREX) did not
yield stringent constraint on the $\Delta R_{np}$ recently. We employ a more
practicable strategy currently to probe the neutron skin thickness of
$^{208}$Pb based on a high linear correlation between the $\Delta R_{np}$ and
$J-a_{\text{sym}}$, where $J$ and $a_{\text{sym}}$ are the symmetry energy
(coefficient) of nuclear matter at saturation density and of $^{208}$Pb. An
accurate $J-a_{\text{sym}}$ thus places a strong constraint on the $\Delta
R_{np}$. Compared with the parity-violating asymmetry $A_{\text{PV}}$ in the
PREX, the reliably experimental information on the $J-a_{\text{sym}}$ is much
more easily available attributed to a wealth of measured data on nuclear masses
and on decay energies. The density dependence of the symmetry energy is also
well constrained with the $J-a_{\text{sym}}$. Finally, with a `tomoscan'
method, we find that one just needs to measure the nucleon densities in
$^{208}$Pb starting from $R_{m} = 7.61\pm0.04$ fm to obtain the $\Delta R_{np}$
in hadron scattering experiments, regardless of its interior profile that is
hampered by the strong absorption.Comment: 13 pages, 4 figure

### Magnetization of neutron star matter

The magnetization of neutron star matter in magnetic fields is studied by
employing the FSUGold interaction. It is found that the magnetic
susceptibilities of the charged particles (proton, electron and muon) can be
larger than that of neutron. The effects of the anomalous magnetic moments
(AMM) of each component on the magnetic susceptibility are examined in detail.
It is found that the proton and electron AMM affect their respective magnetic
susceptibility evidently in strong magnetic fields. In addition, they are the
protons instead of the electrons that contribute most significantly to the
magnetization of the neutron star matter in a relative weak magnetic field, and
the induced magnetic field due to the magnetization can be appear to be very
large. Finally, the effect of the density-dependent symmetry energy on the
magnetization is discussed.Comment: 6 pages, 3 figure

### Density-dependent symmetry energy at subsaturation densities from nuclear mass differences

We extract the mass-dependent symmetry energy coefficients
$a_{\text{sym}}({A})$ with the nuclear mass differences reducing the
uncertainties as far as possible. The estimated $a_{\text{sym}}({A})$ of
$^{208}\text{Pb}$ is $22.4\pm 0.3$ MeV, which is further used to analyze the
density-dependent nuclear matter symmetry energy at subsaturation densities.
The slope parameter of the symmetry energy at the saturation density $\rho_{0}$
is $L=50.0\pm15.5$ MeV. Furthermore, it is found that, at the density of
$\rho=0.69\rho_{0}=0.11$fm$^{-3}$, the symmetry energy
$S(\rho=0.11\text{fm}^{-3})=25.98\pm0.01$ MeV and the correspondingly slope
parameter is $L=49.6\pm6.2$ MeV, which are consistent with other independent
analysis.Comment: 4 pages, 1 figur

### Symmetry energy at subsaturation densities and the neutron skin thickness of 208Pb

The mass-dependent symmetry energy coefficients $a_{sym}(A)$ has been
extracted by analysing the heavy nuclear mass differences reducing the
uncertainties as far as possible in our previous work. Taking advantage of the
obtained symmetry energy coefficient $a_{sym}(A)$ and the density profiles
obtained by switching off the Coulomb interaction in $^{208}\text{Pb}$, we
calculated the slope parameter $L_{0.11}$ of the symmetry energy at the density
of $0.11\text{fm}^{-3}$. The calculated $L_{0.11}$ ranges from 40.5 MeV to 60.3
MeV. The slope parameter $L_{0.11}$ of the symmetry energy at the density of
$0.11\text{fm}^{-3}$ is also calculated directly with Skyrme interactions for
nuclear matter and is found to have a fine linear relation with the neutron
skin thickness of $^{208}\text{Pb}$, which is the difference of the neutron and
proton rms radii of the nucleus. With the linear relation the neutron skin
thickness $\Delta R_{np}$ of $^{208}\text{Pb}$ is predicted to be 0.15 - 0.21
fm.Comment: 5 pages, 2 figure

- β¦