Isospin dependence of three-body force rearrangement contribution

Within the isospin-dependent Brueckner framework, we investigate the contribution of three-body force ( TBF) rearrangement to isospin symmetry potential as well as its momentum and density dependence. In particular, we investigate the TBF rearrangement effects on the isospin splitting of neutron and proton effective masses in neutron-rich nuclear matter. We show that the rearrangement contribution of TBF to neutron and proton single-particle potentials is repulsive and increases rapidly with increasing density and momentum. At low densities, the influence of the TBF rearrangement on symmetry potential is rather small, and the TBF rearrangement effect becomes more and more pronounced as the density rises. At high densities, the contribution of TBF rearrangement increases considerably the symmetry potential and modifies remarkably the momentum dependence of the symmetry potential. In both cases with and without including the TBF rearrangement contribution, the predicted neutron effective mass in neutron-rich matter is greater than the proton effective mass. The TBF rearrangement effect is to decrease remarkably both the proton and neutron effective masses, and reduce the magnitude of neutron-proton effective mass splitting in neutron-rich matter at high densities.

Improved BCS-type pairing for the relativistic mean-field theory

A density-dependent delta interaction (DDDI) is proposed in the formalism of BCS-type pairing correlations for exotic nuclei whose Fermi surfaces are close to the threshold of the unbound state. It provides the possibility to pick up those states whose wave functions are concentrated in the nuclear region by making the pairing matrix elements state dependent. On this basis, the energy level distributions, occupations, and ground-state properties are self-consistently studied in the RMF theory with deformation. Calculations are performed for the Sr isotopic chain. A good description of the total energy per nucleon, deformations, two-neutron separation energies and isotope shift from the proton drip line to the neutron drip line is found. Especially, by comparing the single-particle structure from the DDDI pairing interaction with that from the constant pairing interaction for a very neutron-rich nucleus it is demonstrated that the DDDI pairing method improves the treatment of the pairing in the continuum.

Microscopic three-body forces and kaon condensation in cold neutrino-trapped matter

We investigate the composition and the equation of state of the kaon condensed phase in neutrino-free and neutrino-trapped star matter within the framework of the Brueckner-Hartree-Fock approach with three-body forces. We find that neutrino trapping shifts the onset density of kaon condensation to a larger baryon density, and reduces considerably the kaon abundance. As a consequence, when kaons are allowed, the equation of state of neutrino-trapped star matter becomes stiffer than the one of neutrino free matter. The effects of different three-body forces are compared and discussed. Neutrino trapping turns out to weaken the role played by the symmetry energy in determining the composition of stellar matter, and thus reduces the difference between the results obtained by using different three-body forces.

Properties of proto-neutron star and effect of three-body forces

Within the Brueckner-Hartree-Fock framework, the equation of state and the properties of newborn neutron stars are investigated by adopting a realistic nucleon-nucleon interaction AV(18) supplemented with a microscopic three-body force or a phenomenological three-body force. The maximum mass of newborn neutron star and the proton fraction in the newborn beta-stable neutron-star matter are calculated. The neutrino-trapping and the three-body force effects are discussed, and the interplay between the effects of the trapped neutrino and the three-body force are especially explored. It is shown that neutrino trapping considerably affects the proton abundance and the equation of state of the newborn neutron star in both cases with and without the three-body forces. The effect of neutrino trapping remarkably enhances the proton abundance, and the contribution of the three-body force makes the equation of state of the newborn neutron star much stiffer at high densities and consequently increases the proton abundance strongly. The trapped neutrinos significantly reduce the influence of the three-body force on the proton abundance in newborn neutron stars.

DBHF approach and thermodynamic consistency for nuclear matter calculations

Within the framework of Dirac Brueckner-Hartree-Fock (DBHF) approach, we calculate the energy per nucleon, the pressure, the nucleon self-energy, and the single-nucleon energy in the nuclear matter by adopting two different covariant representations for T-matrix. We mainly investigate the influence of different covariant representations on the satisfiable extent of the Hugenholtz-Van Hove (HVH) theorem in the nuclear medium in the framework of DBHF. By adopting the two different covariant representations of T-matrix, the predicted nucleon self-energy shows a quite different momentum and density dependence. Different covariant representations affect remarkably the satisfiable extent of the HVH theorem. By adopting the complete pseudo-vector representation of the T-matrix, HVH theorem is largely violated, which is in agreement with the result in the non-relativistic Brueckner-Hartree-Fock approach and reflects the importance of ground state correlations for single nucleon properties in nuclear medium, whereas by using the pseudoscalar representation, the ground state correlation cannot be shown. It indicates that the complete pseudo-vector presentation is more feasible than the pseudo-scalar one.

Three-body force rearrangement contribution to single nucleon potential in nuclear matter

Within the framework of microscopic Brueckner-Hatree-Fock, the contribution of the three-body force (TBF) rearrangement to the. single nucleon potential is calculated. The TBF rearrangement effects on the momentum and the density dependence of the single nucleon potential are investigated. The influence of the TBF rearrangement on the effective mass of nucleon is also discussed. It is shown that the rearrangement contribution of TBF is repulsive and momentum-dependent. The TBF rearrangement effect and its momentum dependence increase rapidly as increasing density and momentum. At high densities and high momenta, the repulsive rearrangement contribution reduces strongly the attraction of the single nucleon potential and enhances considerably the momentum dependence of the single nucleon potential.

Three-body force rearrangement effect on single particle properties in neutron-rich nuclear matter

We extend the Brueckner-Hartree-Fock (BHF) approach to include the three-body force (TBF) rearrangement contribution in calculating the neutron and proton single particle (s.p.) properties in isospin asymmetric nuclear matter. We investigate the TBF rearrangement effect on the momentum-dependence of neutron and proton s.p. potentials, the isospin splitting and especially its density dependence of the neutron and proton effective masses, and the isospin symmetry potential in neutron-rich nuclear matter by adopting the realistic Argonne V-18 two-body nucleon-nucleon interaction supplemented with a microscopic TBF. We find that at low densities, the TBF rearrangement effect is fairly weak, whereas the TBF induces a significant rearrangement effect on the s.p. properties at high densities and large momenta. The TBF rearrangement contribution to s.p. potential is shown to be repulsive, and it reduces considerably the attraction of the BHF s.p. potential. The repulsion from the TBF rearrangement turns out to be strongly momentum dependent at high densities and high momenta. As a consequence, it enhances remarkably the momentum dependence of the proton and neutron s.p. potentials and reduces the neutron and proton effective masses. At low densities, the TBF rearrangement effect on symmetry potential is almost negligible, while at high densities, it enlarges sizably the symmetry potential. At high enough densities, it may even change the high-momentum behavior of symmetry potential. In both cases, with and without including the TBF rearrangement contribution, the predicted neutron effective mass is larger than the proton one in neutron-rich matter within the BHF framework; i.e., the predicted isospin splitting of the proton and neutron effective masses in neutron-rich matter is such that m(n)(*)>= m(p)(*), in agreement with the recent Dirac-BHF predictions. The TBF rearrangement contribution reduces remarkably the magnitude of the proton-neutron effective mass splitting at high densities. At high enough densities, inclusion of the TBF rearrangement contribution even suppresses almost completely the effective mass splitting.

Single nucleon potential and effective mass with ground state correlations in hot nuclear matter

In the framework of the finite temperature Brueckner-Hartree-Fock approach including the contribution of the microscopic three-body force, the single nuclear potential and the nucleon effective mass in hot nuclear matter at various temperatures and densities have been calculated by using the hole-line expansion for mass operator, and the effects of the three-body forces and the ground state correlations on the single nucleon potential have been investigated. It is shown that both the ground state correlations and the three-body force affect considerably the density and temperature dependence of the single nucleon potential. The rearrangement correction in the single nucleon potential is repulsive and it reduces remarkably the attraction of the single nucleon potential in the low-momentum region. The rearrangement contribution due to the ground state correlations becomes smaller as the temperature rises up and becomes larger as the density increases. The effect of the three-body force on the ground state correlations is to reduce the contribution of rearrangement. At high densities, the single nucleon potential containing both the rearrangement correction and the contribution of the three-body force becomes more repulsive as the temperature increases.

Two-electron-one-photon M1 and E2 transitions between the states of the 2p(3) and 2s(2)2p odd configurations for B-like ions with 18 <= Z <= 92

Two-electron-one-photon (TEOP) M1 and E2 transition energies, line strengths and transition probabilities between the states of the 2p(3) and 2s(2)2p odd configurations for B-like ions with 18 <= Z <= 92 have been calculated using the GRASP2K package based on the multiconfiguration Dirac-Hartree-Fock (MCDHF) method. Employing active-space techniques to expand the configuration list, we have systematically considered the valence, core-valence and core-core electron correlation effects. Breit interaction and quantum electrodynamical (QED) effects were also included to correct atomic state wavefunctions and the corresponding energies. Influences of electron correlation, Breit interaction and QED effects on transition energies and line strengths of the TEOP M1 and E2 transitions were analysed in detail. The present results were also compared with other theoretical and experimental values.

Nucleon Superfluidity in Asymmetric Nuclear Matter and Neutron Star Matter

We have investigate the nucleon superfluidity in asymmetric nuclear matter and neutron star matter by using the Brueckner-Hartree-Fock approach and the BCS theory. We have predicted the isospin-asymmetry dependence of the nucleon superfluidity in asymmetric nuclear matter and discussed particularly the effect of microscopic three-body forces. It has been shown that the three-body force leads to a strong suppression of the proton S-1(0) superfluidity in beta -stable neutron star matter. Whereas the microscopic three-body force is found to enhance remarkably the (PF2)-P-3 neutron superfluidity in neutron star matter and neutron stars.

The effect of hyperfine interaction on the lifetime of the 3s3p P-3(2) level of Mg-like ions

On the basis of previous work, the hyperfine-induced 3s3p P-3(2) -> 3s(2) S-1(0) E1 transition probabilities of Mg-like ions were further calculated using the GRASP2K package based on the multiconfiguration Dirac-Hartree-Fock method. The contribution to the lifetime of the P-3(2) level from the 3s3p P-3(2) -> 3s(2) S-1(0) hyperfine-induced E1, 3s3p P-3(2) -> 3s3p P-3(1) M1, 3s3p P-3(2) -> 3s(2) S-1(0) M2 and 3s3p P-3(2) -> 3s3p P-3(0,1) E2 transition was discussed in detail. It was found that hyperfine interaction has an obvious effect on the lifetime at the beginning of the Mg-like isoelectronic sequence.

NUCLEON-NUCLEON CROSS SECTIONS IN ISOSPIN ASYMMETRIC NUCLEAR MATTER

The in medium nucleon-nucleon (N N) cross sections in isospin asymmetric nuclear matter at various densities are investigated in the frame work of Brueckner-Hartree-Fock theory with the Bonn B two-body nucleon-nucleon inter action supplemented with a new version microscopic three-body force (TBF). The TBF depresses the amplitude of cross sections at high density region. At low densities, the proton-proton and neutron-neutron cross sections decrease while the proton-neutron one increases as the asymmetry increases. But the sensitivity of the N N cross sections to the isospin a symmetry are reduced with the increasing density.

中子及中子星物质中的3PF2态超流性和微观三体核力效力效应

本论文介绍了当前中子及中子星物质中超流性研究的背景及现状、核多体理论Brueckner-Hartree-Fock及同位旋相关的Brueckner-Hartree-Fock方法，以及利用BHF和BCS理论计算中子及中子星物质中的对关联能隙方法。系统计算并描述了中子及中子星物质中子的3PF2态超流性，并重点考虑了利用介子交换流方法建立的微观三体核力所产生的影响。 我们的研究结果表明：三体核力对中子物质中3PF2态中子超流性有强烈的增强效应。 当在BCS能隙方程中采用自由粒子能谱近似时，三体核力使相应的对关联能隙峰值增加了77%(由0.64MeV增大到1.13MeV)；当采用自洽BHF单粒子能谱时，三体核力导致相应的对关联能隙峰值由0.22MeV增大到0.50MeV，增加了约127%。 三体核力使中子星物质中3PF2态中子超流能隙随着密度的增大而单调递增。当采用自洽BHF单粒子能谱时不考虑三体核力时，对关联能隙峰值在密度约1.9fm-3时有峰值0.19MeV。而在这个两体力导致的能隙的峰值密度，三体核力导致相应的对关联能隙由0.19MeV增大到0.36MeV

DBHF方法和核物质的性质

基于Dirac-Brueckner-Hartree-Fock（DBHF）方法的输入量是由NN散射和氘核数据确定的自由NN势，没有可调参数，这样可自洽地求解核物质的性质；同时，它给出的核物质的饱和性质（核物质的饱和能量和饱和密度）明显符合经验值。在论文的第一部分中，我们采用DBHF方法来计算研究了核物质性质的一系列物理量在核介质中的变化行为以及不同的T矩阵协变表示对这种行为的影响，譬如核物质中的自能，单粒子能量，核状态方程以及核物质的热力学自洽性等。同时从DBHF方法中给出的两核子的有效相互作用T矩阵出发，我们可以直接得出介质中核子-核子反应的总截面和微分截面，作为输运理论输入量的介质中的截面，对重离子碰撞中的各物理量有重要影响。论文的第二部分是计算研究同位旋非对称核物质的性质。作为通向研究有限核的一个中间过程，非对称核物质的研究对丰中子核物理以及核天体物理具有重要的意义。我们首先将对称的DBHF方法推广到非对称的情况，然后基于非对称的DBHF方法计算研究非对称核物质的性质，特别是不同定义的非相对论有效质量和Dirac有效质量在非对称核物质中的劈裂效应

中能重离子碰撞中的同位旋效应及非对称核物质的状态方程研究

本论文介绍了放射性核束物理研究的现状以及当前常用的几种同位旋相关的重离子微观输运理论，系统描述了非对称核物质的状态方程、中能重离子碰撞中的同位旋效应以及中子星的性质。基于 Hartree-Fock 理论和扩展的 Skyrme 相互作用，在核物质近似下得到了一个非相对论性的密度、温度和同位旋相关的核物质状态方程 (IEOS)。系统研究了核物质状态方程的同位旋效应。讨论了核子的平均场、核物质的不可压缩系数、核子的有效质量以及核物质临界温度的同位旋相关性，并且给出了核物质饱笔点处的饱和密度、不可压缩系数以及单核子结合能的抛物线规律。同时，探讨了对称能的温度和密度相关性，给出了零温度时对称能的解析表达式，并提出了对称能温度相关性的抛物线规律，发现对称能随着温度的升高而减小。另外，基于以上的同位旋相关的核物质状态方程，对 ALADIN's Caloric Curve 给出了一种静态解释。在传统量子分子动力学 (QMD) 模型的基础上，通过在相互作用平均场、两体碰撞、泡利阻塞、初始化以及碎片构造过程中适当地考虑同位旋自由度，得到了一个同位旋相关的 QMD 模型 (IQMD 模型)。利用IQMD模型系统研究了中能重离子碰撞中的同位旋效应。例如，中能重离子碰撞中同位旋自由度的弛豫、重离子碰撞中核子前平衡发射的同位旋效应、重离子碰撞中的集体流（包括直接流、转动流、挤出流和径向流）及其同位旋相关性、原子核多重碎裂的同位旋效应及其消失、重离子碰撞中的化学不稳定性以及中能重离子碰撞中如何选取事件的碰撞参数及其同位旋效应等。同样，在传统的 Boltzmann-Langevin 方程中适当地考虑同位旋自由度，得到了同位旋相关的Boltzmann-Langevin方程 (IBLE)，利用IBLE研究了 ~(19)Na的产生截面。另外，利用IQMD模型探讨了多重碎裂的"neck" 机制以及重离子碰撞中局域势的有限程效应。基于前面给出的非相对论的核物质状态方程，系统研究了中子星的性质，如中子星的化学组份、质量、结合能、半径、密度剖面、转动惯量及表面红移等。结果表明，使用一些常用的 Skyrme 势参数能够给出与天文学观测相一致的结果。