三体核力重排项的同位旋效应

在同位旋相关的Brueckner理论框架内, 研究了三体核力重排贡献对同位旋对称势及其动量相关性和密度依赖性的影响，特别是研究了三体核力重排效应对于非对称核物质中质子和中子有效质量同位旋劈裂的影响. 结果表明: 三体核力重排效应对质子和中子单核子势均具有排斥性，而且其贡献随动量和密度增加而迅速增大. 在低密度区域，三体核力重排贡献对同位旋对称势的影响相当小，然而随着密度的升高，三体核力重排效应的贡献显著增强. 在高密度区域，三体核力重排效应使得同位旋对称势明显增大，而且当密度足够高时，三体核力重排贡献甚至导致对称势的动量相关性质发生改变. 三体核力的重排效应对核子有效质量同位旋依赖性的影响是使高密度丰中子核物质中质子-中子有效质量同位旋劈裂的幅度显著减小.     

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     

热核物质中单核子势的重排项贡献和三体核力效应

在包含三体核力的有限温度Brueckner-Hartree-Fock理论方法基础上, 利用质量算子的空穴线展开, 研究了热核物质中基态关联所导致的对单核子势的重排修正项的密度和温度依赖性, 并讨论了三体核力对重排项的影响. 结果表明：单核子势的重排项贡献具有较强的密度和温度相关性, 重排项贡献随密度增加而增强并随温度升高而减弱. 在计算中引入三体核力会在一定程度上抑制基态空穴关联 效应, 从而导致单核子势的重排项贡献减小, 而且三体核力对重排项贡献的影响随密度增大而增强.     

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,它们的总贡献甚至在饱和密度附近也是不能忽略的     

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.     

非对称核物质中同位旋对称势的动量和密度依赖性

在Brueckner-Hartree-Fock理论框架内, 研究了同位旋非对称核物质中质子和中子单粒子势的动量相关性及其随同位旋非对称度的变化, 在此基础上计算了同位旋对称势, 并讨论了三体核力的影响. 结果表明同位旋对称势对于同位旋非对称度的依赖性很弱, 但对于动量和密度均有较强的依赖性. 当密度固定时, 同位旋对称势随动量增加而减小. 尽管三体核力对于质子和中子单粒子势的动量相关性有较大影响, 但对同位旋对称势的影响很小. 还与目前重离子碰撞输运理论模型中所使用的各种参数化的唯象对称势进行了比较.     

非对称核物质中质子和中子的1S0态超流性

利用Brueckner-Hartree-Fock和BCS理论方法,计算了非对称核物质中处于1S0态的质子和中子的对关联能隙,着重研究和讨论了能隙的同位旋依赖性和三体核力的影响.结果表明:随核物质的同位旋非对称度增大,中子1S0态超流相存在的密度范围逐渐缩小而且对关联能隙峰值稍有升高;质子1S0态超流相存在的密度范围迅速扩大而且对关联能隙峰值显著降低.三体核力对非对称核物质中1S0态中子超流性及其同位旋依赖性的影响相对较小,但对1S0态质子超流性具有重要影响,而且其效应随核子数密度增大而迅速增强.三体核力的主要作用是强烈地抑制了具有高非对称度的核物质中高密度区域的1S0态质子超流性,导致质子超流相存在的密度范围显著缩小.     

热核物质液气相变的临界温度和三体核力效应

通过引入微观三体核力, 扩展了有限温度Brueckner-Hartree-Fock方法. 利用这一扩展的理论模型, 研究了热核物质的状态方程和液气相变现象并计算了临界温度, 讨论了三体核力对液气相变临界点性质的影响并与Dirac-Brueckner-Hartree-Fock方法的理论预言进行了比较. 结果表明：三体核力对热核物质状态方程提供一个随密度和温度增大而增强的排斥贡献, 而且三体核力的排斥效应导致热核物质液气相变的临界温度明显降低.     

对称核物质中核子-核子散射截面的研究

在扩展的Brueckner-Hartree-Fock (BHF)理论框架下, 采用Argonne V₁₄ 两体相互作用势研究了对称核物质中核子-核子散射的总截面和微分截面, 分别讨论了三体核力(TBF)重排效应和基态关联效应对全同和非全同核子散射截面的影响。 计算表明: 低动量区域的基态关联效应会导致介质中核子-核子散射截面的增大; 而随着密度的增加,TBF重排效应的逐渐加强会减小介质中的核子-核子散射截面。 The nucleon nucleon cross sections in symmetric nuclear matter were investigated in the framework of the extended Brueckner-Hartree-Fock(BHF) approach with Argonne V₁₄ two body interaction. The influences of the ground state correlation and the rearrangement contribution of the three body force (TBF) on the cross section have been obtained and discussed separately for identical and non identical nucleon collisions. It is shown that the magnitudes of the cross section are increased by the effects of the ground state correlation in low momentum transfers,and are suppressed in medium with increasing density when the rearrangement contribution of the TBF force is considered.     

非对称核物质中质子和中子的1S0态超流性

利用Brueckner-Hartree-Fock和BCS理论方法，计算了非对称核物质中处于¹S₀态的质子和中子的对关联能隙，着重研究和讨论了能隙的同位旋依赖性和三体核力的影响.结果表明：随核物质的同位旋非对称度增大，中子¹S₀态超流相存在的密度范围逐渐缩小而且对关联能隙峰值稍有升高；质子¹S₀态超流相存在的密度范围迅速扩大而且对关联能隙峰值显著降低.三体核力对非对称核物质中¹S₀态中子超流性及其同位旋依赖性的影响相对较小，但对¹S₀态质子超流性具有重要影响，而且其效应随核子数密度增大而迅速增强.三体核力的主要作用是强烈地抑制了具有高非对称度的核物质中高密度区域的¹S₀态质子超流性，导致质子超流相存在的密度范围显著缩小. 关键词： 同位旋非对称核物质 质子和中子超流性 三体核力 BCS理论     

Nucleon effective mass in symmetric nuclearmatter from the extended Brueckner-Hartree-Fock approach

We have calculated the nucleon effective mass in symmetric nuclear matter within the framework of the Brueckner-Bethe-Goldstone (BBG) theory, which has been extended to include both the contributions from the ground-state correlation effect and the three-body force (TBF) rearrangement effect. The effective mass is predicted by including the ground-state correlation effect and the TBF rearrangement effect, and we discuss the momentum dependence and the density dependence of the effective mass. It is shown that the effect of ground state correlations plays an important role at low densities, while the TBF-induced rearrangement effect becomes predominant at high densities.     

Decomposition of the equation of state of asymmetric nuclear matter into different spin-isospin channels

We investigate the equation of state of asymmetric nuclear matter and its isospin dependence in various spin-isospin ST channels within the framework of the Brueckner-Hartree-Fock approach extended to include a microscopic three-body force (TBF). It is shown that the potential energy per nucleon in the isospin-singlet T=0 channel is mainly determined by the contribution from the tensor SD coupled channel. At high densities, the TBF effect on the lsospin-triplet T=1 channel contribution turns out to be much larger than that on the T=0 channel contribution. At low densities around and below the normal nuclear matter density, the isospin dependence is found to come essentially from the isospin-singlet SD channel and the isospin-triplet T=1 component is almost independent of isospin asymmetry. As the density increases, the T=1 channel contribution becomes sensitive to the isospin asymmetry and at high enough densities its isospin dependence may even become more pronounced than that of the T=0 contribution. The present results may provide some microscopic constraints for improving effective nucleon-nucleon interactions in a nuclear medium and for constructing new functionals of effective nucleon-nucleon interaction based on microscopic many-body theories.     

Symmetry energy,unstable nuclei and neutron star crusts

We present an upgraded review of our microscopic investigation on the single-particle properties and the EOS of isospin asymmetric nuclear matter within the framework of the Brueckner theory extended to include a microscopic three-body force. We pay special attention to the discussion of the three-body force effect and the comparison of our results with the predictions by other ab initio approaches. Three-body force is shown to be necessary for reproducing the empirical saturation properties of symmetric nuclear matter within nonrelativistic microscopic frameworks, and also for extending the hole-line expansion to a wide density range. The three-body force effect on nuclear symmetry energy is repulsive, and it leads to a significant stiffening of the density dependence of symmetry energy at supra-saturation densities. Within the Brueckner approach, the three-body force affects the nucleon s.p. potentials primarily via its rearrangement contribution which is strongly repulsive and momentum-dependent at high densities and high momenta. Both the rearrangement contribution induced by the three-body force and the effect of ground-state correlations are crucial for predicting reliably the single-particle properties within the Brueckner framework.     

Decomposition of the equation of state of asymmetric nuclear matter into different spin-isospin channels

We investigate the equation of state of asymmetric nuclear matter and its isospin dependence in various spin-isospin ST channels within the framework of the Brueckner-Hartree-Fock approach extended to include a microscopic three-body force（TBF） . It is shown that the potential energy per nucleon in the isospinsinglet T = 0 channel is mainly determined by the contribution from the tensor SD coupled channel. At high densities,the TBF effect on the isospin-triplet T = 1 channel contribution turns out to be much larger than that on the T =0 channel contribution. At low densities around and below the normal nuclear matter density,the isospin dependence is found to come essentially from the isospin-singlet SD channel and the isospin-triplet T = 1 component is almost independent of isospin asymmetry. As the density increases,the T = 1 channel contribution becomes sensitive to the isospin asymmetry and at high enough densities its isospin dependence may even become more pronounced than that of the T = 0 contribution. The present results may provide some microscopic constraints for improving effective nucleon-nucleon interactions in a nuclear medium and for constructing new functionals of effective nucleon-nucleon interaction based on microscopic many-body theories.     

Three-body force effect on the properties of nuclear matter under the gap and continuous choices within the BHF approach

We have calculated and compared the three-body force effects on the properties of nuclear matter under the gap and continuous choices for the self-consistent auxiliary potential within the Brueckner-Hartree-Fock approach by adopting the Argonne V₁₈ and the Bonn B two-body potentials plus a microscopic three-body force (TBF). The TBF provides a strong repulsive effect on the equation of state of nuclear matter at high densities for both the gap and continuous choices. The saturation point turns out to be much closer to the empirical value when the continuous choice is adopted. In addition, the dependence of the calculated symmetry energy upon the choice of the self-consistent auxiliary potential is discussed.