In-Medium Nucleon-Nucleon Cross Section

Within the framework of Brueckner-Hartree-Fock method,the in-medium nucleonnucleon(NN)cross section is calculated.We base our investigation on a separable Paris potential for the NN interaction and a continuous choice for the single particle spectrum.It is found that the in-medium cross section is strongly modified by medium effect.In particular,with increasing of nuclear density,the cross sections decrease.This indicates a proper treatment of the density dependence of the in-medium NN cross sections is important.

Spin—Polarized States of Nuclear Matter

The equations of state of spin-polarized nuclear matter and pure neutron matter are studied in the framework of the Brueckner–Hartree–Fock theory including a three-body force. The energy per nucleon EA(δ) calculated in the full range of spin polarization for symmetric nuclear matter and pure neutron matter fulfills a parabolic law. In both the cases the spin-symmetry energy is calculated as a function of the baryonic density along with the related quantities such as the magnetic susceptibility and the Landau parameter G0. The main effect of the three-body force is to strongly reduce the degenerate Fermi gas magnetic susceptibility even more than the value with only two-body force. The equation of state is monotonically increasing with the density for all spin-aligned configurations studied here so that no any signature is found for a spontaneous transition to a ferromagnetic state.

Three—Body Force Effects on EOS of Asymmetric Nuclear Matter and Proton Fraction in Neutron Star Matter

The three-body force effects on the equation of state and its iso-spin dependence of asymmetric nuclear matter and on the proton fraction in neutron star matter have been investigated within Brueckner-Hartree-Fock approach by using a microscopic three-body force. It is shown that, even in the presence of the three-body force, the empirical parabolic law of the energy per nucleon vs. isospin asymmetry is fulfilled in the whole asymmetry range and also up to high density. The three-body force provides a strong enhancement of symmetry energy at high density in agreement with relativistic approaches. It also shows that the three-body force leads to a much more rapid increasing of symmetry energy with density in relatively high density region and to a much lower threshold density for the direct URCA process to occur in a neutron star as compared to the predictions adopting only pure two-body force.

Nucleon Effective Mass in Asymmetric Nuclear Matter within Extended Brueckner Approach

The on-shell properties of the nucleon effective mass in asymmetric nuclear matter are investigated in the framework of an extended Brueckner-Hartree-Fock (BHF) approach.The proton and neutron effective masses in neutron-rich nuclear matter are predicted by including both the effect of ground state correlations and the threebody force (TBF) rearrangement contribution.Within this framework,the neutron effective mass is predicted *to be larger than the proton one in neutron-rich nuclear matter,i.e.,m*n ≥ m*p.The effect of ground state correlations turns out to be dominated at low densities and it leads to a strong enhancement of the effective mass.The TBF rearrangement contribution becomes predominant over the effect of ground state correlations at high densities and it reduces remarkably the absolute magnitude of the isospin splitting of the neutron and proton effective masses in neutron-rich matter at high densities.

Three-body Force Effect from Different Elementary Processes and Relativistic Correction in Dirac-Brueckner Approach

Adopting the charge-dependent ArgonneV_(18) plus microscopic three-body forces,the equation of state(EOS) and single particle properties of symmetric nuclear matter have been investigated in Brueckner-Hartree-Fock(BHF) framework~[1].The microscopic three-body force

Effects of Microscopic Three-body Forces in Asymmetric Nuclear Matter

The efiects of microscopic three-body forces on the equatioil of state(EOS)and the single particle properties of isospin asymmetric nuclear matter have been studied within Brueckner-Hartree-Fock framework~[1]The microscopic three-body force model constructed from meson exchange current approach in Ref.~[2] has been extended to isospin asymmetric nuclear

Self-energy Effect on Superfluidity of Neutron Matter

In the present work,the self-energy effect on the superfluidity of neutron matter in the channel^1 So has been investigated in a generalized BCS theory.The ground-state correlations in the self-energy have been taken into account.The result of the calculated energy gap is shown in Fig.1~[1]in which,the solid line indicates

Three-body Force Effect on Proton Fraction in Neutron Star Matter

The three-body force ( TBF ) effect on the proton fraction in the β-stable neutron star matter has been investigated within the iso-spin dependent Brueckner Hartree-Fock ( BHF ) framework, by adopting the microscopic TBF based on a meson-exchange current model of interaction mediated by the excitation of NN couples and low-lying nucleon resonances The calculated proton fraction vs. baryon density is displayed

Equation of State of Spin-polarized Neutron Matter from BHF Approach

Within the spin-dependent Brueckner-Hatree-Fock framework, the equation of state ( EOS ) of the spin-polarized neutron matter has been investigated by adopting the realistic nucleon-nucleon interaction AV18 supplemented with the microscopic three-body force ( TBF ) based on the meson-exchange current method. The related physical quantities such as spin-symmetry energy, magnetic susceptibility and the Landau param-

Three-body Force Effects on Nuclear Pairing

In the present work, the influence of three-body force(TBF) on the 1S0 pairing in symmetric nuclear matter and pure neutron matter has been investigated. The energy gap is calculated within the standard BCS scheme. The AV18 force is adopted as the two-body realistic nucleon-nucleon interaction. The microscopic three-body force adopted in the present calculations is constructed from a meson-exchange current

1-14 Role of Nucleonic Fermi Surface Depletion in Neutron Star Cooling

The measurements on the neutron star surface temperature such as Cas A allow us to investigate the thermal evolution of NSs more deeply and hence grasp some crucial information and knowledge on the NS interior as well as some properties of dense nuclear matter[1;2].The Fermi surface depletion that comes from the nucleonic short-range correlation influences the level density of nucleons around the Fermi surface and controls many properties of Fermion systems related to particle-hole excitations around the Fermi energy.Thus,it affects the inputs of the neutron star cooling.

同位旋非对称核物质性质与扩展的BHF方法 (Ⅰ)同位旋相关的扩展的BHF方法

通过引进基态关联和同位旋自由度的区分 ,推广了Brueckner Hartree Fock理论方法 ,并应用于同位旋非对称核物质 ,系统地研究了在整个同位旋自由度范围内核物质的状态方程和单粒子特性及其同位旋效应 .还研究了微观三体核力对同位旋非对称核物质性质及其同位旋效应的影响 ,定量讨论了三体力效应与相对论性平均场理论及Dirac Brueckner方法的联系 .主要给出了同位旋相关的Brueckner Hartree

同位旋非对称核物质性质与扩展的BHF方法(Ⅱ)状态方程、对称能以及三体核力效应

在同位旋相关的BHF理论框架内 ,研究了微观三体核力对非对称核物质状态方程和原子核对称能的影响 .结果表明 :即使引进了微观三体核力后 ,核物质结合能随同位旋非对称度的变化关系仍然能够在整个同位旋自由度范围内(0≤β≤ 1) 相当精确地满足二次方规律 .在核物质饱和密度 ρ0 =0 .17fm- 3处 ,三体核力对于对称能Esym的影响很小 ,考虑三体核力后得到的对称能为 30 .71MeV ,与其经验值符合得很好 ;对于高密度核物质 ,由于三体核力效应 ,对称能明显增大 ,而且三体核力使对称能随密度的增大要比不考虑三体核力情况下的计算结果陡得多 .同时还给出了对称能的密度依赖关系的一个简单的参数化形式 .

核物质中的三体核力效应和相对论效应

在BHF理论框架内 ,利用两体现实核力和微观三体核力研究了核物质状态方程 ,仔细计算和分析了核介质中不同的基本微观过程导致的三体核力对核物质状态方程的贡献 ,与相对论DBHF方法的计算进行了比较 .结果表明 ,DBHF方法中包含的对核物质状态方程的主要相对论修正来自于核介质中伴随着自由核子 -反核子对虚激发中间过程对核子相互作用中标量σ介子交换过程介质修正效应所导致的三体核力 ,而来自于其他的基本微观过程的三体核力对核物质状态方程的贡献并不能完全相互抵消 。

The spin-isospin decomposition of the nuclear symmetry energy from low to high density

The energy per particle BA in nuclear matter is calculated up to high baryon density in the whole isospin asymmetry range from symmetric matter to pure neutron matter.The results,obtained in the framework of the Brueckner-Hartree-Fock approximation with two-and three-body forces,confirm the well-known parabolic dependence on the asymmetry parameterβ=(N?Z)/A(β^2 law)that is valid in a wide density range.To investigate the extent to which this behavior can be traced back to the properties of the underlying interaction,aside from the mean field approximation,the spin-isospin decomposition of BA is performed.Theoretical indications suggest that theβ^2 law could be violated at higher densities as a consequence of the three-body forces.This raises the problem that the symmetry energy,calculated according to theβ^2 law as a difference between BA in pure neutron matter and symmetric nuclear matter,cannot be applied to neutron stars.One should return to the proper definition of the nuclear symmetry energy as a response of the nuclear system to small isospin imbalance from the Z=N nuclei and pure neutron matter.

β-稳定核物质

在相对论平均场近似下,从有效的拉氏量密度出发研究了液-汽相变并推广到β-稳定核物质和纯中子物质.结果表明,在使用Bonn势参数的基础上,用Brown-Rho质量标度描述介质效应,所得到的改进的相对论平均场有效模型可以合理地描述核物质的饱和性质和液-汽相变行为.将该模型用来研究β-稳定核物质和纯中子物质时,预言了β-稳定核物质和纯中子物质的性质.

同位旋非对称核物质性质与扩展的BHF方法(Ⅲ)HVH定理与费米能量

在扩展的同位旋相关的Brueckner—Hartree—Fock理论框架内,在整个同位旋自由度范围内研究了质量算子的空穴线展开中不同等级近似下非对称核物质中Hugenholtz—Van Hove定理的满足程度,并计算了中子和质子的费米能量.结果表明为了使Hugenholtz-Van Hove定理达到令人满意的满足程度,需要同时考虑质量算子中的重排贡献和重正修正,从而指出了基态关联对于非对称核物质中单粒子性质的重要性.