Superfluid nuclear matter in BCS theory and beyond

Medium polarization eflects are studied for 1S0 pairing in nuclear matter within BHF approach. The screening potential is calculated in the RPA limit, suitably renormalized to cure the low density mechanical instability of nuclear matter. The self-energy corrections are consistently included resulting in a strong depletion of the Fermi surface. The self-energy effects always lead to a quenching of the gap, whereas it is almost completely compensated by the anti-screening effect in nuclear matter.     

改进的核密度模型与强子-核Drell-Yan过程中的核效应

提出了改进的核密度模型，用唯象的方法找到了束缚核子内价夸克和海夸克的核效应的参数公式，其中利用了核密度与原子核的平均结合能之间的联系. 利用该模型所得到的束缚核子内部分子分布函数，对强子与核的Drell-Yan过程的核效应给出了满意的解释, 深化了对原子核内夸克分布受核效应影响的认识. 关键词： 核密度模型 核效应 强子-核Drell-Yan过程     

Higher order bulk characteristic parameters of asymmetric nuclear matter

The bulk parameters characterizing the energy of symmetric nuclear matter and the symmetry energy defined at normal nuclear density ρ0 provide important information on the equation of state (EOS) of isospin asymmetric nuclear matter. While significant progress has been made in determining some lower order bulk characteristic parameters, such as the energy E0(ρ0) and incompress ibility K0 of symmetric nuclear matter as well as the symmetry energy Esym(ρ0) and its slope parameter L, yet the higher order bulk ...     

一种处理原子核多体问题的有效方法

由二级散射矩阵元出发计算了核物质内强子的二级自能修正, 并且归纳了一种研究原子核多体问题的有效方法. 另外, 还讨论了各种密度相关的相对论多体方法之间的关系.     

Tensor optimized antisymmetrized molecular dynamics for relativistic nuclear matter

We apply a newly developed many-body theory, tensor optimized antisymmetrized molecular dynamics (TOAMD), to nuclear matter using a relativistic bare nucleon-nucleon interaction in the relativistic framework. It becomes evident that the tensor interaction plays an important role in nuclear many-body system due to the role of the pion in a strongly interacting system. We take the relativistic nuclear matter (RNM) wave function as a basic state and add tensor and short-range correlation operators in the form of pion and omega-meson correlation functions acting on the RNM wave function using the concept of TOAMD. We use the Monte Carlo (Metropolis) method based on the Gaussian integration and the second quantization method for antisymmetrization to calculate all the matrix elements of the many-body Hamiltonian. We write the whole formula of the TOAMD method for numerical calculations of the nuclear binding and saturation properties of nuclear matter using one-boson exchange potential.     

Effective-field theory and the nuclear many-body problem

We review many-body calculations of the equation of state of dilute neutron matter in the context of effective-field theories of the nucleon-nucleon interaction.     

Fractional exclusion statistics applied to relativistic nuclear matter

The effect of statistics of the quasiparticles in the nuclear matter at extreme conditions of density and temperature is evaluated in the relativistic mean-field model generalized to the framework of the fractional exclusion statistics (FES). In the model, the nucleons are described as quasiparticles obeying FES and the model parameters were chosen to reproduce the ground state properties of the isospin-symmetric nuclear matter. In this case, the statistics of the quasiparticles is related to the strengths of the nucleon-nucleon interaction mediated by the neutral scalar and vector meson fields. The relevant thermodynamic quantities were calculated as functions of the nucleons density, temperature and fractional exclusion statistics parameter α. It has been shown that at high temperatures and densities the thermodynamics of the system has a strong dependence on the statistics of the particles. The scenario in which the nucleon-nucleon interaction strength is independent of the statistics of particles was also calculated, but it leads in general to unstable thermodynamics.     

Nucleon sigma term and quark condensate in nuclear matter

We study the bound-nucleon sigma term and the quark condensate in nuclear matter. In the quark-meson coupling (QMC) model the nuclear correction to the sigma term is small and negative, i.e., it decelerates the decrease of the quark condensate in nuclear matter. However, the quark condensate in nuclear matter is controlled primarily by the scalar-isoscalar σ field. Compared to the leading term, it moderates the decrease more than that of the nuclear sigma term alone at densities around and larger than the normal nuclear-matter density.     

Study of various charged p-meson masses in asymmetric nuclear matter

We study the effective masses of p-mesons for different charged states in asymmetric nuclear matter (ANM) using the Quantum Hadrodynamics II model.The closed form analytical results are presented for the effective masses of p-mesons.We have shown that the different charged p-mesons have mass splitting similar to various charged pions.The effect of the Dirac sea is also examined, and it is found that this effect is very important and leads to a reduction of the different charged p-meson masses in ANM.     

Effect of three-body interaction on hot asymmetric nuclear matter

The properties of hot asymmetric nuclear matter are studied in the framework of the finite temperature Brueckner－Hartree－Fock theory that is extended to include the contribution of microscopic three-body forces. We give the variation of the critical temperature with the asymmetry parameter and show the effect brought by this three-body repulsive potential on the value of the critical asymmetry of the phase transition for asymmetric nuclear matter. Owing to the additional repulsion provided by three-body forces, this value decreases. In addition, the domain of mechanical instability for hot nuclear matter is also indicated, which gradually shrinks with increasing asymmetry and temperature.     

DBHF方法和热力学自洽性

采用Dirac Brueckner-Hartree-Fock理论方法, 计算了零温核物质中每核子的结合能、压强和单核子能量, 着重讨论了不同的T矩阵协变表示对核物质中Hugenholtz-Van Hove(HVH)定理满足程度的影响. 结果表明: 不同的协变表示对核子自能各分量的动量相关性和密度依赖性均有重要影响, 进而对核介质中HVH定理的满足程度产生重要影响. 在完全的膺矢量表示下, HVH定理遭到了相当大程度的破坏, 从而体现出基态关联效应对单核子性质的重要性, 并与非相对论BHF理论方法得到的结论一致, 因而完全的膺矢量表示要优于膺标量表示.     

A phenomenological equation of state for isospin asymmetric nuclear matter

A phenomenological momentum-independent(MID) model is constructed to describe the equation of state(EOS) for isospin asymmetric nuclear matter,especially the density dependence of the nuclear symmetry energy Esym(ρ).This model can reasonably describe the general properties of the EOS for symmetric nuclear matter and the symmetry energy predicted by both the sophisticated isospin and momentum dependent MDI model and the Skyrme-Hartree-Fock approach.We find that there exists a nicely linear correlation betwee...     

高密核物质中核子的运动对于K介子的等效质量和能量的影响

本文对比分析了目前用于研究K介子产生与演化的不同动力学模型中,高温高密核物质中K⁺介子和K^-介子的等效质量和它所感受到的平均场.所得结果显示:在关于K介子的一般的平均场理论中,所定义的K⁺介子的等效质量随着核物质密度的增大而增加, K^-介子的等效质量随着核物质密度的增大而减小;但在K介子演化的协变动力学模型中,所采用的K⁺介子和K^-介子等效质量是随着核物质密度的增大都是减小的 关键词： 高密核物质 K介子 等效质量 核子运动     

Infinite nuclear matter model and a new mass formula for atomic nuclei

The ground-state energy of an atomic nucleus with asymmetryβ is considered to be equivalent to the energy of a perfect sphere made up of the infinite nuclear matter of the same asymmetry plus a residual energyη called the local energy,η represents the energy due to shell, deformation, diffuseness and exchange Coulomb effect etc. Using this picture and the generalized Hugenholtz- Van Hove theorem of many-body theory a new mass formula has been developed. Based on this, a mass table containing the mass excesses of 3481 nuclei in the range 18 ⩽A ⩽ 267 has been made. This mass formula is compared with other mass models.     

Saturation of nuclear matter and realistic interactions

In this communication we study symmetric nuclear matter for the Brueckner-Hartree-Fock approach, using two realistic nucleon-nucleon interactions (CD-Bonn and Bonn C). The single-particle energy is calculated self-consistently from the real on-shell self-energy. The relation between different expressions for the pressure is studied in cold nuclear matter. For best calculations the self-energy is calculated with the inclusion of hole-hole (hh) propagation. The effects of hh contributions and a self-consistent treatment within the framework of the Green function approach are investigated. Using two different methods, namely, G-matrix and bare potential, the hh term is calculated. We found that using G-matrix brought about non-negligible contribution to the self-energy, but this difference is very small and can be ignored if compared with the large contribution coming from particle-particle term. The contribution of the hh term leads to a repulsive contribution to the Fermi energy which increases with density. For extended Brueckner-Hartree-Fock approach the Fermi energy at the saturation point fulfills the Hugenholtz-Van Hove relation.     

Quark-clustering in cold quark matter

Quarks are proposed to be grouped together to make quark-clusters due to the strong interaction in cold quark matter at a few nuclear densities, because a weakly coupling treatment of the interaction between quarks there would be inadequate. Cold quark matter is then conjectured to be in solid state (i.e., forming a crystal structure) if the inter-cluster potential is deep enough to localize clusters in lattice. Such a solid state of cold quark matter would be very necessary for us to understand different manifestations of pulsar-like compact stars, and could not be ruled by first principles.     

Quark-clustering in cold quark matter

Quarks are proposed to be grouped together to make quark-clusters due to the strong interaction in cold quark matter at a few nuclear densities,because a weakly coupling treatment of the interaction between quarks there would be inadequate.Cold quark matter is then conjectured to be in solid state （i.e.,forming a crystal structure） if the inter-cluster potential is deep enough to localize clusters in lattice.Such a solid state of cold quark matter would be very necessary for us to understand different manifestations of pulsar-like compact stars,and could not be ruled by first principles.