在中能重离子反应中核子的运动特征

在量子分子动力学模型框架下，研究了在中能重离子反应中单个核子的运动形态是规则的还是混沌的，它与反应系统的整体性质、反应机制是有关联的．在稳定的复合系统中，核子的运动显示出规则的行为．规则行为与混沌行为的并存反映了规则区域被不规则区域所包围的排斥极分岔特性，说明有中等质量碎片的局域稳定源存在．更多的不稳定轨道的出现则标志着这种局域稳定源的减少，有更多的核子及小集团发射．核子的混炖运动比核物质状态方程所标志的力学不稳定区域出现的时间更早．     

与核密度及温度相关的核子相对论微观光学势

在Walecka模型、热场动力学和相对论Dirac-Bruckner-Hartree-Fock计算结果基础上,研究了在不同核密度和各种温度情况下的核子相对论微观光学势及其相应的薛定谔等效势和平均自由程,计算结果表明,对于不同的温度,核子的薛定谔等效势与平均自由程随核密度变化较为敏感,而核温度对核子的薛定谔等效势和平均自由程的影响随着核密度的增加变大.     

核子相对论微观光学势、薛定谔等效势和平均自由程对核密度及温度的依赖关系

在Walecka模型的基础上,应用热动力学理论和Dirac-Bruckner-Hartree-Fock方法,研究了有限温度不同密度下核子相对论微观光学势及其相应的薛定谔等效势和平均自由程.计算结果表明,核子薛定谔等效势和平均自由程对核密度的依赖相当敏感,当核密度增大时对核密度的依赖变得更为敏感.     

A possible quark mechanism for the saturation of nuclear matter

A nuclear matter saturation mechanism based on the quark structure of the nucleon is proposed. Nuclear matter is described by nucleons and mesons but the meson field modifies the internal quark motion and this induces a saturation mechanism. Its possible relevance for nuclear physics is studied in a schematic model where it is the only active mechanism. Though caricatural, this model provides a rather satisfactory interpretation of the nuclear matter properties.     

THERMOSTATIC PROPERTIES OF ASYMMETRIC NUCLEAR MATTER AT LOW TEMPERATURE

The Küpper, Wegmnn, and Hilf's theory on the thermostatic properties of symmetric nuclear matter is extended to the asymmetric nuclear matter at low temperature less than 10 MeV. The numerical result shows that the entropy per nucleon s depends on the asymmetry δ weakly while the compressibility coefficient K depends on δ very strongly. At the neutron drip point the nucleon density n decreases while the asym-, metry ^δND increases linearly with T² at low temperature. The thermodynamic stability of the asymmetric nuclear matter is studied by means of the Gibbs-Duhem inequality.     

Nucleon currents between highly excited nuclei: (II). Influence of the relative motion

A finite-temperature Thomas-Fermi method has been used to study the nucleon flux between two hot semi-infinite slabs of nuclear matter in arbitrary relative motion. As an application, we estimate the imaginary part of the optical potential associated with nucléon transfer at the strong absorption radius. Analytical fits to the exact results are given for head-on and tangential collisions at zero temperature.     

Role of excited nuclear states in photoabsorption shadowing at medium energies

The effect of intranuclear motion of nucleons on the photoabsorption shadowing due to the conversion of a γ-ray photon into a vector meson in nuclear matter is analyzed. It is shown within the method of time-correlation functions that, in comparison with the results of the standard approach, the correction to the total photoabsorption cross section due to the nuclear shadowing is determined by two additional factors: the Fermi motion of nucleons in a nucleus and nucleon recoil.     

Transition to hot quark matter in relativistic heavy-ion collision

The nuclear matter-quark matter phase transition density is calculated as a function of temperature. The result suggests a transition to quark matter in heavy-ion collision at laboratory kinetic energies of a few GeV per nucleon. The transition may be inferred by observing a limiting temperature for the hadrons produced by the collision.     

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     

有限密度下的核子有效质量和EMC效应的一种可能解释

用热场动力学方法计算了核物质中核子有效质量随密度的变化关系.利用有限密度中核子质量的改变,在x重新标度模型的基础上,讨论了不同核的结构函数的比率R(x),与实验结果相符合.还考察了EMC效应和Brown—Rho猜测之间的关系.     

Particle clustering and Mott transitions in nuclear matter at finite temperature: (I). Method and general aspects

The thermodynamic state of nuclear matter as regards dependence on density and temperature is considered. Expressions for the association degree are derived describing the ratio of nuclear matter which is clustered to bound states. The problem of two nucleons imbedded in the surrounding nuclear matter is considered with the help of the Bethe-Goldstone equation for thermodynamic Green functions. The two-particle energy shift due to the effective nuclear matter hamiltonian is considered in a Hartree-Fock approximation, and a Mott density is obtained so that for densities of nuclear matter higher than the Mott density bound states cannot exist. With a simplified effective two-nucleon interaction the association degree is calculated as a function of the nucleon density and the temperature.     

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.     

Nuclear binding energy and symmetry energy of nuclear matter with modern nucleon–nucleon potentials

The binding energy of nuclear matter at zero temperature in the Brueckner–Hartree–Fock approximation with modern nucleon–nucleon potentials is studied. Both the standard and continuous choices of single particle energies are used. These modern nucleon–nucleon potentials fit the deuteron properties and are phase shifts equivalent. Comparison with other calculations is made. In addition we present results for the symmetry energy obtained with different potentials, which is of great importance in astrophysical calculation.     

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.     

核势和核子有效质量的同位旋相关性

在Dirac Brueckner Hartree-Fock (DBHF)理论框架下研究了核子光学势和核子有效质量的同位旋相关性. 非对称核物质的计算采用了DBHF的核子自能的Dirac结构的新的分解方法, 核子自能的实部是用G矩阵在Hartree-Fock近似下计算得到, 而虚部从极化图得到. 用核子的薛定谔等价势可以得到核子矢量有效质量. 研究表明考虑了核势的能量相关性在丰中子核物质情况下核子矢量有效质量比质子的大.     

Nucleon currents between highly excited nuclei

A finite temperature Thomas-Fermi method has been used to study the nucleon transfer between two hot slabs of symmetric nuclear matter. Special attention has been paid to temperature effects neglected in earlier calculations. As a result, closed and ready-to-use formulas for the exchange and transfer nucleon flux at zero relative momentum are given as a function of the temperature.     

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…     

Density dependence of nucleon radius and mass in the global color symmetry model of QCD with a sophisticated effective gluon propagator

Making use of the global color symmetry model (GCM) at finite chemical potential and with a sophisticated effective gluon propagator, the density dependence of the bag constant, the total energy and the radius of a nucleon in nuclear matter is investigated. A maximal nuclear matter density for the existence of the bag with three quarks confined within is given as about 8 times the normal nuclear matter density. The calculated results indicate that, before the maximal density is reached, the bag constant and the total energy of a nucleon decrease, and the radius of a nucleon increases, with the increasing of the nuclear matter density. As the maximal nuclear matter density is reached, the mass and the bag constant of the nucleon vanish and the radius becomes infinite suddenly. It manifests that a phase transition from nucleons to quarks takes place. Meanwhile, shortening the interaction range among quarks can induce the phase transition to happen easier.     

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.     

Charge-constrained coherent pion states produced in nuclear matter

In a recent article, Bloss, Hone and Scalapino have used a simplified model Hamiltonian and Keldysh field theoretic methods to approximately calculate the power radiated as Cherenkov charged pions whose emission is triggered when a fast nucleon traverses nuclear matter. The model used by these authors conserves charge by flipping the isospin state of the fast nucleon alone for each charged pion emitted. Since it is the nuclear matter excited by the fast nucleon which should be largely reponsible for emitting the Cherenkov charged pions, we investigate an alternate model that allows all the disturbed nuclear matter to change its charge state when a charged pion is emitted—as an idealization, the emitting matter is assumed to have an infinite number of charge states, in contrast to the two of the fast nucleon. This modified model is shown to be exactly solvable in terms of charge-constrained coherent pion states; the power radiated as charged pions is found to be approximately twice that calculated by Bloss et al. from their model.