Symmetry Energy and Isovector Giant Dipole Resonance in Finite Nuclei

We study the relationship between the properties of the isovector giant dipole resonance of finite nuclei and the symmetry energy in the framework of the relativistic mean field theory with six different parameter sets of nonlinear effective Lagrangian. A strong linear correlation of excited energies of the dipole resonance in finite nuclei and symmetry energy at and below the saturation density is found. This linear correlation leads to the symmetry energy at the saturation density at the interval 33.0 MeV ≤ S（po） 〈37.0 MeV. The comparison to the present experimental data in the soft dipole mode of 132Sn constrains approximately the symmetry energy at p = 0,1 fm^-3 at the interval 21,2MeV- 22.5 MeV. It is proposed that a precise measurement of the soft dipole mode in neutron rich nuclei could set up an important constraint on the equation of state for asymmetric nuclear matter.     

基于有限核性质确定核物质对称能的密度依赖性

密度依赖的对称能作为核物质状态方程的同位旋相关部分,是当前核物理和天体物理两个领域共同关注的重要热点问题之一。人们在实验和理论两方面对此进行了大量的探索,然而由于问题的困难性,对其研究尚未达成共识。目前,研究对称能的方法有很多,其中包括微观和唯像核多体理论、重离子碰撞、原子核的巨共振等。近年来,低密对称能的研究已经取得了重要进展。本文综述了利用有限核的信息来约束核物质对称能的密度依赖性方面的研究工作,这一研究途径尽可能地降低了理论分析的模型依赖性。研究表明,208Pb对称能(系数)asym(A)等于参考密度ρA=0.55ρ0处的核物质对称能(系数)。这个关系将有限核与核物质的对称能联系了起来,借此可以探究亚饱和密度核物质对称能的密度依赖性,因此核心目标是准确确定208Pb对称能(系数)。我们通过重核β-衰变能和质量差来提取208Pb对称能(系数),进而约束亚饱和密度下核物质对称能的密度依赖行为。     

Probing Nuclear Symmetry Energy with Giant Dipole Resonances in Finite Nuclei

The relationship between the centroid energies of the isovector giant dipole resonance of finite nuclei and the symmetry energy has been studied.It is found the excitation energies of the dipole resonance in finite nuclei are correlated linearly with the symmetry energy at and below the saturation density.This linear correlation leads to the symmetry energy at the saturation density at the interval 33.0 MeV ≤ S(ρ_0) ≤ 37.0 MeV,and the symmetry energy at ρ=0.1 fm~(-3) at the interval 21.2-22.5 MeV.It is proposed that a precise measurement of the dipole mode in nuclei could set up an important constraint on the equation of state for nuclear matter.     

超重核的四面体对称性(英文)

基于反射不对称壳模型的投影位能面计算预言原子核310126 是继208Pb 之后的双幻核,其基态呈现出四面体形状。四面体对称性驱动的量子效应可以使基态的结合能,相较球形而言增加达13 MeV,这反映了在最重核的计算中,考虑四面体自由度的重要性。计算结果还表明,四面体对称性驱动的量子效应能够明显地增加裂变位垒,从而导致超重核合成几率的增加。     

原子核的赝自旋对称性近似

基于相对论平均场理论,讨论了Dirac方程中严格的赝自旋对称性,以及实际原子核中的近似赝自旋对称性.在严格的赝自旋对称性下,除赝自旋单态外,所有的态都有简并的赝自旋伙伴态,而且赝自旋双重态的径向量子数相同.以正常核²⁰⁸Pb和奇特核²⁶⁴Pb为例,分析了赝离心势和赝自旋–轨道耦合势的贡献,发现对于赝自旋单态,赝离心势恒为零;对赝自旋双重态,赝自旋–轨道耦合势的贡献很小,赝自旋对称性近似满足;但对于闯入态,相对于赝离心势,赝自旋–轨道耦合势的贡献很大,赝自旋对称性被完全破坏,也即闯入态不具有赝自旋伙伴态的可能原因.     

Finite Abnormal Nuclei

We solved the problem for both the normal and abnormal finite nuclei from a simple relativistic model,and found eritical mass numbers A₁=85 and A₂=165.Only nuclei with mass numbers A≥A₁ may bave bound abnormal states,and only abnormal nuclei with mass number A≥A₂ have binding energies larger than those of corresponding normal nuclei.Abnormal nuclei become unbound again if A>3310,because of the Coulomb repulsion.     

Mixed Symmetry Isomeric States in Nuclei

Mixed symmetry states are studied in the framework of the neutron-proton interacting boson model.It is found that some of the mixed symmetry states with moderate high spins change very fast with respect to the Majorana interaction.Under certain conditions,they become the yrast state or yrare state.These states are difficult to decay and become very stable.This study suggests that a possible new mode of isomers may exist due to the special nature in their proton and neutron degrees of freedom.     

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.     

Symmetry Reductions of Cauchy Problems for Fourth-Order Quasi-Linear Parabolic Equations

This paper is devoted to studying symmetry reduction of Cauchy problems for the fourth-order quasi-linear parabolic equations that admit certain generalized conditional symmetries （GCSs）. Complete group classification results are presented, and some examples are given to show the main reduction procedure.     

Charmed Mesons in Nuclei with Heavy-Quark Spin Symmetry

We study the properties of charmed pseudoscalar and vector mesons in dense matter within a unitary meson–baryon coupled-channel model which incorporates heavy-quark spin symmetry. This is accomplished by extending the SU(3) Weinberg–Tomozawa Lagrangian to incorporate spin-flavor symmetry and implement a suitable flavor symmetry breaking. Several resonances with negative parity are generated dynamically by the s-wave interaction between pseudoscalar and vector meson multiplets with 1/2⁺ and 3/2⁺ baryons. Those states are then compared to experimental data as well as theoretical models. Next, Pauli-blocking effects and meson self-energies are introduced in a self-consistent manner to obtain the open-charm meson spectral functions in a dense nuclear environment. We finally discuss the formation of D-mesic nuclei.     

原子核反核子谱的自旋对称性

简要介绍原子核反核子谱的自旋对称性。通过分析包含标量势和矢量势的核子及反核子Dirac方程的性质,给出核子谱的赝自旋对称性和反核子谱的自旋对称性的起因。对于反核子双重态,除了它们的能量非常接近以外,它们的波函数也几乎严格地满足自旋对称性所要求的关系。     

Symmetry Reduction and Cauchy Problems for a Class of Fourth-Order Evolution Equations

We exploit higher-order conditional symmetry to reduce initial-value problems for evolution equations to Cauchy problems for systems of ordinary differential equations (ODEs). We classify a class of fourth-order evolution equations which admit certain higher-order generalized conditional symmetries (GCSs) and give some examples to show the main reduction procedure. These reductions cannot be derived within the framework of the standard Lie approach, which hints that the technique presented here is something essential for the dimensional reduction of evolution equations.     

Gas-Like Cluster States in Finite Nuclei

Gas-like α cluster states are investigated in ¹⁶O with the use of 4α OCM (orthogonality condition model) and GEM (Gauss expansion method). α-particle condensed state is found slightly above the 4α threshold as the ${0_6^+}$ state. The candidates of the ${\alpha + {^{12}{\rm C}(0_2^+)}}$ rotational states are also found at a few megaelectron volt above the condensate. The ${0_6^+}$ state is shown to have an analogue structure to the Hoyle state ${({^{12}{\rm C}}(0_2^+))}$ and its relation with the α+ Hoyle-like rotational states is also discussed.     

Relativistic Brueckner-Hartree-Fock Theory for Finite Nuclei

Starting with a bare nucleon-nucleon interaction,for the first time the full relativistic Brueckner-Hartree-Fock equations are solved for finite nuclei in a Dirac-Woods-Saxon basis.No free parameters are introduced to calculate the ground-state properties of finite nuclei.The nucleus ~(16)O is investigated as an example.The resulting groundstate properties,such as binding energy and charge radius,are considerably improved as compared with the non-relativistic Brueckner-Hartree-Fock results and much closer to the experimental data.This opens the door for ab initio covariant investigations of heavy nuclei.     

Symmetry Reduction and Cauchy Problems for a Class of Fourth-Order Evolution Equations

We exploit higher-order conditional symmetry to reduce initial-value problems for evolution equations to Cauchy problems for systems of ordinary differential equations （ODEs）. We classify a class of fourth-order evolution equations which admit certain higher-order generalized conditional symmetries （GCSs） and give some examples to show the main reduction procedure. These reductions cannot be derived within the framework of the standard Lie approach, which hints that the technique presented here is something essential for the dimensional reduction of evolution equations.     

原子核内光子的有效质量

研究了无限大核子费密气体和有限原子核内电磁场的性质.由于电荷密度算符的基态期待值在核子费密气体内不为零,电荷的U(1)定域规范对称性自发破缺.微扰计算光子的自能可知在核子费密气体内光子有效质量与质子的标量密度有关.在饱和密度ρ0=0.16fm^－3的正常核物质中,光子有效质量为5.42MeV;在²³⁸U原子核的表面处,光子有效质量约为2.0MeV.在这一问题中,这两种方法是等价的.同时文章指出正是由于原子核表面处有质量光子的两体衰变导致在低能²³⁸U+²³²Th重离子碰撞实验中正反电子对尖锐谱线的发现.     

Lifetime of Antibaryon Bound in Finite Nuclei

The study of finite nuclei containing antibaryon（s） in addition to nucleons is an interesting topic in nuclear physics. The calculation of the lifetime of an antibaryon embedded in a nucleus was performed in the framework of the standard quantum field theory. It was shown that the annihilation probability of the antibaryon in nuclei is strongly dependent on the effective masses of mesons involved in the annihilation channels. The contribution of the Dirac sea to the annihilation probability makes the lifetime of the antibaryon short. If the Dirac sea effect is neglected, the lifetime of the bound antibaryon tends to be longer with the nuclear density increasing. Particularly, when the nuclear density is larger than a critical value, the antibaryon may exist stably in a nucleus.