等效的DBHF方法研究有限核性质

利用等效的Dirac Brueckner Hartree-Fock(DBHF)方法,即用密度相关的核子–介子耦合常数在相对论平均场近似下,考虑了重排列项,研究了有限核的性质.介子–核子耦合常数的密度相关性是由考虑了核子短程关联的DBHF方法来确定的,要求在每个密度下用相对论平均场方法得到的核子自能与用DBHF得到的自能一致.计算了核物质性质及有限核基态性质,并着重讨论了重排列项对Ca及Pb同位素链结果的影响.考虑重排列项作用后使计算的核电荷均方根半径增大,更好地符合实验值.     

温度相关的核子相对论微观光学势

本文将Walecka模型和热场动力学理论应用在核物质和有限核中,研究了核子在各种温度下的相对论微观光学势以及相应的薛定谔等效势和平均自由程.对于核物质,取核子的Hartree-Fock自能为光学势的实部,交换σ和ω介子的极化图为光学势的虚部.对于有限核的微观光学势通过定域密度近似获得.     

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.     

三体核力重排效应对核物质中单核子平均场的贡献

在微观多体Brueckner-Hartree-Fock理论框架内, 实现了三体核力对核物质中单核子势的重排贡献的计算, 研究了三体核力重排贡献对单核子平均势场的动量相关性和密度依赖性的影响. 另外, 还计算了核物质中核子的有效质量并着重讨论了三体核力重排效应的影响. 结果表明: 三体核力对单核子势的重排贡献具有排斥性, 而且三体核力的重排效应随动量和密度的增加而迅速增强; 在高密度和高动量区域这一排斥贡献具有很强的动量相关性并起到了减弱单核子势吸引性和增强单核子势动量相关性的重要作用, 有助于澄清非相对论性BHF平均势场在高密度和高动量区域吸引性过强和动量相关性过弱的问题.     

自洽的相对论微观光学位研究

在Dirac-Brueckner计算由于忽略负能态引起解的不唯一性可以根据Hugenholtz-Van Hove定理,要求核物质在饱和密度处每个核子的分离能等于费米能来给出限制.选取核子饱和结合能为E_B/A=－15.8MeV,自洽计算得到核物质的饱和密度k_f=1.41fm^－1以及有效质量为m*/m=0.52,核的不可压缩系数K=280MeV.利用热力学第一定律可以得到自洽的有效质量(实的标量位)和每个核子的平均结合能随核密度的分布,采用现实的核子-核子相互作用的Bonn位,解RBBG方程得到核在介质中的矢量位,它与动量的依赖关系是很弱的.用这种新的自洽的相对论微观光学位我们进一步讨论了核子-核散射的微分截面和自旋观测量.     

热核物质中基态关联修正下的单核子势和核子有效质量

以有限温度Brueckner-Hartree-Fock(BHF)方法为基础，利用质量算子的空穴线展开，计算了不同温度和密度下的核物质中单核子势和核子有效质量，特别是研究和讨论了基态关联效应和三体核力贡献对热核物质中单核子势的影响. 研究表明，基态关联和三体核力对单核子势的密度和温度依赖性均有重要影响. 基态关联导致的重排修正具有排斥性，大大减弱了低动量区域单核子势的吸引性，而且基态关联效应对单核子势的贡献随密度增大而增强，随温度升高而减弱. 三体核力对基态关联的影响是导致单核子势中重排项贡献减小. 在高密 关键词： 有限温度BHF方法 质量算子空穴线展开 重排修正 单核子势 有效质量     

低温核物质的性质与可能的夸克机制

本文用夸克袋模型来描述核子,并设核子内的夸克与标量和矢量介子场相耦合,考虑核子在核物质中的费米运动,计算了核物质内核子内禀特性随系统密度和温度的变化,给出了不同温度下单核子束缚能的变化曲线.     

四级交换图对相对论微观光学势的贡献

本文在Walecka介子-核子模型的基础上,在核物质中第一次研究了四级交换图对核子自能的虚部以及相对论微观光学势和Schrodinger等效势的贡献.     

格点核子-核子势在核物质中的相对论效应(英文)

利用最新的格点核子-核子势研究了核物质中的相对论效应。通过此格点核子-核子势场,首先我们构建一个包括π介子,σ介子以及ω介子的单玻色子交换势。势场中的介子-核子耦合常数以及截断动量通过拟合格点核力得到的核子-核子散射相移确定。随后采用非常成功的第一性原理多体计算方法Brueckner-Hartree-Fock模型,计算了核物质的基本性质。发现对称核物质的状态方程以及饱和性质在非相对论框架和相对论框架中有很明显的区别。在格点核力中,该相对论效应对核物质的结合能提供吸引的贡献。这与采用传统的核力计算得到的结果是相反的。The relativistic effect in nuclear matter is investigated with the latest lattice nucleon-nucleon (NN) potential. A one-boson-exchange potential (OBEP) including three mesons, pion, σ meson and ω meson was constructed based on the lattice NN potential. The meson-nucleon coupling constants and cutoff momentums are determined by fitting the phase shifts of NN scattering from lattice NN potential. The properties of nuclear matter with this OBEP from lattice potential are calculated by one very successful ab initio many-body method, Brueckner-Hartree-Fock model. The equations of state and saturation properties of symmetric nuclear matter present very obvious different behaviors in non-relativistic and relativistic frameworks. The relativistic effect plays attractive contributions with the components of S and D waves in lattice NN potential, which is opposite comparing to the relativistic effect from the conventional NN potential.     

双折叠模型对相互作用势实部的计算

用双折叠模型计算了核核碰撞的相互作用势, 其中核子-核子相互作用势采用M3Y-Reid和M3Y-Paris形式, 交换部分考虑了有限力程的密度依赖的核子-核子相互作用, 程序用于重离子散射光学势实部的计算. 回顾了折叠模型的普遍特征和讨论了理论计算过程, 对各种类型的核子-核子相互作用下计算的相互作用势进行比较, 发现双折叠模型对大部分系统相互作用势的实部取得了满意的结果. 因此这个工作为重离子相互作用势的折叠计算提供了很好的方法.     

Some Aspects of Nuclear Structure in Relativistic Approach

The nucleon effective interaction in the nuclear medium is investigated in the framework of the DiracBrueckner-Hartree-Fock (DBHF) approach. A new decomposition of the Dirac structure of nucleon self-energy in the DBHF is adopted for asymmetric nuclear matter. The properties of finite nuclei are investigated with the nucleon effective interaction. The agreement with the experimental data is satisfactory. The relativistic microscopic optical potential in asymmetric nuclear matter is investigated in the DBHF approach. The proton scattering from nuclei is calculated and compared with the experimental data. A proper treatment of the resonant continuum for exotic nuclei is studied. The width effect of the resonant continuum on the pairing correlation is discussed. The quasiparticle relativistic random phase approximation based on the relativistic mean-field ground state in the response function formalism is also addressed.     

Some Aspects of Nuclear Structure in Relativistic Approach

The nucleon effective interaction in the nuclear medium is investigated in the framework of the DiracBrueckner-Hartree-Fock (DBHF) approach. A new decomposition of the Dirac structure of nucleon self-energy in the DBHF is adopted for asymmetric nuclear matter. The properties of finite nuclei are investigated with the nucleon effective interaction. The agreement with the experimental data is satisfactory. The relativistic microscopic optical potential in asymmetric nuclear matter is investigated in the DBHF approach. The proton scattering from nuclei is calculated and compared with the experimental data. A proper treatment of the resonant continuum for exotic nuclei is studied. The width effect of the resonant continuum on the pairing correlation is discussed. The quasiparticle relativistic random phase approximation based on the relativistic mean-field ground state in the response function formalism is also addressed.     

Isospin-dependent relativistic microscopic optical potential in the Dirac Brueckner-Hartree-Fock method

There is growing evidence to suggest that the binding energy of nucleon in nuclear matter comes from a cancellation between large Lorentz scalar and vector potentials[1,2]. The relativistic approach has been of a great success in describing not only the ground state properties of stable nuclei, but also those of exotic nuclei. In the relativistic frame, the spin-orbit coupling can be deduced automatically, which is usually given by hand in the non-relativistic approach. The relativistic method…     

Temperature-Dependent Imaginary Part of the Off-Shell Nucleon Self-Energy and the Second Order Correction of Real Part of the Nucleon Self-Energy

The imaginary part of the off-shell nucleon self-energy at finite temperature in nuclear matter, where the polarization and correlation contributions of exchanges of the meson are taken into account, is investigated based on Walecka's meson-nucleon model and thermofield dynamics. The second order correction of temperature-dependent real part of the nucleon self-energy is calculated in terms of the dispersion relation. The Schrodinger equivalent potential of relativistic microscopic optical potential of a nucleon at finite temperature in nuclear medium is also studied.     

On the Dirac structure of the nucleon self-energy in nuclear matter

The relativistic structure of the self-energy of a nucleon in nuclear matter is investigated including the imaginary and real components which arise from the terms of first and second order in the NN interaction. A parameterized form of the Brueckner G-matrix is used for the NN interaction. The effects of the terms beyond the DBHF approximation on quasiparticle energies and the optical potential for nucleon-nucleus scattering are discussed.     

核子质量、 半径及夸克凝聚的核物质密度依赖性

简要介绍核物质中核子的质量、 半径及夸克凝聚的密度依赖关系基于QCD模型和QCD有效场论研究的现状, 并具体介绍整体色对称模型（GCM）的研究结果. GCM研究表明, 在小于临界密度的情况下, 核物质中核子的质量随核物质密度的增大而减小, 核子的半径和夸克凝聚随核物质密度的增大而增大. 当达到临界密度时, 核子质量减小为零, 核子半径变为无限大, 夸克凝聚突变为零, 进而提出一个核物质中手征对称性恢复的新机制. The status of the investigations on the nucleon mass, nucleon radius and quark condensate in the framework of QCD inspired models and QCD effective field theories is briefly reviewed. The results in the global color symmetry model (GCM) are described a little detailedly. The calculated results indicate that, before the maximal density is reached, the mass of a nucleon in nuclear matter decreases, the radius of a nucleon and the quark condensate increase very slowly, with the increase of the nuclear matter density. As the maximal nuclear matter density is reached, the mass of the nucleon vanishes gradually. The radius becomes infinite and the quark condensate vanishes suddenly. A new mechanism for the chiral symmetry restoration in nuclear matter is proposed.     

The nuclear symmetry energy from relativistic Brueckner-Hartree-Fock model

The microscopic mechanisms of the symmetry energy in nuclear matter are investigated in the framework of the relativistic Brueckner-Hartree-Fock (RBHF) model with a high-precision realistic nuclear potential, pvCDBonn A. The kinetic energy and potential contributions to symmetry energy are decomposed. They are explicitly expressed by the nucleon self-energies, which are obtained through projecting the G-matrices from the RBHF model into the terms of Lorentz covariants. The nuclear medium effects on the nucleon self-energy and nucleon-nucleon interaction in symmetry energy are discussed by comparing the results from the RBHF model and those from Hartree-Fock and relativistic Hartree-Fock models. It is found that the nucleon self-energy including the nuclear medium effect on the single-nucleon wave function provides a largely positive contribution to the symmetry energy, while the nuclear medium effect on the nucleon-nucleon interaction, i.e., the effective G-matrices provides a negative contribution. The tensor force plays an essential role in the symmetry energy around the density. The scalar and vector covariant amplitudes of nucleon-nucleon interaction dominate the potential component of the symmetry energy. Furthermore, the isoscalar and isovector terms in the optical potential are extracted from the RBHF model. The isoscalar part is consistent with the results from the analysis of global optical potential, while the isovector one has obvious differences at higher incident energy due to the relativistic effect.     

Correlations and the Dirac structure of the nucleon self-energy

The Dirac structure of the nucleon self-energy in symmetric nuclear matter as well as neutron matter is derived from a realistic meson exchange model for the nucleon-nucleon (NN) interaction. It is demonstrated that the effects of correlations on the effective NN interaction in the nuclear medium can be parameterized by means of an effective meson exchange. This analysis leads to a very intuitive interpretation of correlation effects and also provides an efficient parametrization of an effective interaction to be used in relativistic structure calculations for finite nuclei. Received: 29 January 2001 / Accepted: 5 May 2001     

Temperature Dependent Relativistic Microscopic Optical Potential and Mean Free Paths of Nucleons

The microscopic optical potential,mean free paths and Schrodinger equivalent potential of nucleons at finite temperature in nuclear matter are studied based on Walecka's model and thermo field dynamics.We let only the Hartree-Fock self-energy of nucleon represent to be the real part of the microscopic optical potential and the fourth order of meson exchange diagrams,i.e. the core polarization represent the imaginary part of microscopic optical potential in nuclear matter.The microscopic optical potential of finite nuclei is obtained with the local density approximation.