Spin- and isospin-polarized states of nuclear matter in the Dirac-Brueckner-Hartree-Fock model

Spin-polarized isospin asymmetric nuclear matter is studied within the Dirac-Brueckner-Hartree-Fock approach. After a brief review of the formalism, we present and discuss the self-consistent single-particle potentials at various levels of spin and isospin asymmetry. We then move to predictions of the energy per particle, also under different conditions of isospin and spin polarization. Comparison with the energy per particle in isospin symmetric or asymmetric unpolarized nuclear matter shows no evidence for a phase transition to a spin ordered state, neither ferromagnetic nor antiferromagnetic.Comment: 8 pages, 6 figure

International Legal Review of the Relationship between International Tax Law and National Tax Sovereignty: Theoretical Foundation and Development Practices

By examining their theoretical basis and exercising practice relationship between national sovereignty and international tax law, it is demonstrated that the international tax law results from the coordination to exercise national sovereignty in the international law. Given the modern connotation of national sovereignty and exercising practices of international tax treaties in the international law, it is reasoned that “the international tax treaty is a kind of limitation or mitigation to national tax sovereignty” is a false pseudo-proposition; International tax regime has been established on the international law level and constitutes a part of customary international law, which is of great significance; No country has the law-making capacity or its national interest dives in the international law to change the existing international tax regime. Taking account of the exercise of the national tax sovereignty under the backdrop of the latest development practices in international tax law, it can be found that international tax cooperation makes the exercise of national tax sovereignty increase other than decrease; Countries’ intensive actions to safeguard their own international taxation interests strengthen the exercise of their national tax sovereignty; New international tax topics, such as Carbon tariff and environmental taxes, will accelerate law-making revolution of international law in the field of international tax law, and thus makes the exercise of national tax sovereignty to be unified.preprin

Ionizing radiation fluctuations and large-scale structure in the Lyman-alpha forest

We investigate the large-scale inhomogeneities of the hydrogen ionizing radiation field in the Universe at redshift z=3. Using a raytracing algorithm, we simulate a model in which quasars are the dominant sources of radiation. We make use of large scale N-body simulations of a LambdaCDM universe, and include such effects as finite quasar lifetimes and output on the lightcone, which affects the shape of quasar light echoes. We create Lya forest spectra that would be generated in the presence of such a fluctuating radiation field, finding that the power spectrum of the Lya forest can be suppressed by as much as 15 % for modes with k=0.05-1 Mpc/h. This relatively small effect may have consequences for high precision measurements of the Lya power spectrum on larger scales than have yet been published. We also investigate another radiation field probe, the cross-correlation of quasar positions and the Lya forest. For both quasar lifetimes which we simulate (10^7 yr and 10^8 yr), we expect to see a strong decrease in the Lya absorption close to other quasars (the ``foreground'' proximity effect). We then use data from the Sloan Digital Sky Survey First Data Release to make an observational determination of this statistic. We find no sign of our predicted lack of absorption, but instead increased absorption close to quasars. If the bursts of radiation from quasars last on average < 10^6 yr, then we would not expect to be able to see the foreground effect. However, the strength of the absorption itself seems to be indicative of rare objects, and hence much longer total times of emission per quasar. Variability of quasars in bursts with timescales > 10^4yr and < 10^6 yr could reconcile these two facts.Comment: Submitted to ApJ, 21 pages, 17 postscript figures, emulateapj.st

Extended quark mean-field model for neutron stars

We extend the quark mean-field (QMF) model to strangeness freedom to study the properties of hyperons ($\Lambda,\Sigma,\Xi$) in infinite baryon matter and neutron star properties. The baryon-scalar meson couplings in the QMF model are determined self-consistently from the quark level, where the quark confinement is taken into account in terms of a scalar-vector harmonic oscillator potential. The strength of such confinement potential for $u,d$ quarks is constrained by the properties of finite nuclei, while the one for $s$ quark is limited by the properties of nuclei with a $\Lambda$ hyperon. These two strengths are not same, which represents the SU(3) symmetry breaking effectively in the QMF model. Also, we use an enhanced $\Sigma$ coupling with the vector meson, and both $\Sigma$ and $\Xi$ hyperon potentials can be properly described in the model. The effects of the SU(3) symmetry breaking on the neutron star structures are then studied. We find that the SU(3) breaking shifts earlier the hyperon onset density and makes hyperons more abundant in the star, in comparisons with the results of the SU(3) symmetry case. However, it does not affect much the star's maximum mass. The maximum masses are found to be $1.62 M_{\odot}$ with hyperons and $1.88 M_{\odot}$ without hyperons. The present neutron star model is shown to have limitations on explaining the recently measured heavy pulsar.Comment: 7 pages, 7 figures, Phys. Rev. C (2014) accepte

Nuclear Three-body Force Effect on a Kaon Condensate in Neutron Star Matter

We explore the effects of a microscopic nuclear three-body force on the threshold baryon density for kaon condensation in chemical equilibrium neutron star matter and on the composition of the kaon condensed phase in the framework of the Brueckner-Hartree-Fock approach. Our results show that the nuclear three-body force affects strongly the high-density behavior of nuclear symmetry energy and consequently reduces considerably the critical density for kaon condensation provided that the proton strangeness content is not very large. The dependence of the threshold density on the symmetry energy becomes weaker as the proton strangeness content increases. The kaon condensed phase of neutron star matter turns out to be proton-rich instead of neutron-rich. The three-body force has an important influence on the composition of the kaon condensed phase. Inclusion of the three-body force contribution in the nuclear symmetry energy results in a significant reduction of the proton and kaon fractions in the kaon condensed phase which is more proton-rich in the case of no three-body force. Our results are compared to other theoretical predictions by adopting different models for the nuclear symmetry energy. The possible implications of our results for the neutron star structure are also briefly discussed.Comment: 15 pages, 5 figure

Spin Polarized Asymmetric Nuclear Matter and Neutron Star Matter Within the Lowest Order Constrained Variational Method

In this paper, we calculate properties of the spin polarized asymmetrical nuclear matter and neutron star matter, using the lowest order constrained variational (LOCV) method with the $AV_{18}$, $Reid93$, $UV_{14}$ and $AV_{14}$ potentials. According to our results, the spontaneous phase transition to a ferromagnetic state in the asymmetrical nuclear matter as well as neutron star matter do not occur.Comment: 21 pages, 11 figure

Isospin dependence of nucleon emission and radial flow in heavy-ion collisions induced by high energy radioactive beams

Using an isospin- and momentum-dependent transport model we study the emission of free nucleons and the nuclear radial flow in central heavy-ion collisions induced by high energy radioactive beams. The midrapidity neutron/proton ratio and its transverse momentum dependence are found very sensitive to the high density behavior of nuclear symmetry energy. The nuclear radial flow, however, depends only weakly on the symmetry energy.Comment: 13 pages including 6 figures, submitted to Phys. Rev.