Correlated Nucleon Pair Model and Microscopic Basis of Interacting Boson

An earlier work dealing with low-lying collective states in nuclei is revised and improved. Correlated and independent nucleon S and D pairs properly modified so that they behave approximately like bosons are constructed in terms of which a model space for lowlying collective states is defined, and a microscopic basis for IBM is thus set up. All dynamical variables can also be "bosonized", i.e., expressed in terms of these "bosons" but with statedependent coefficients or operators to incorporate their state dependence in model space.     

一种推广对力模型及在大形变核中的应用

总结了可描述大形变原子核运动的Nilsson平均场加推广的对力相互作用的可解模型.该模型在对力强度较弱的区域仍然以单体和两体相互作用为主.但随着对力强度的增加,高阶相互作用的修正将逐渐变得重要.通过对同位素154—171Yb奇偶质量差的数值拟合显示,该新模型可说明大形变核的运动规律.     

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.     

Validity of the Counting Schemes of Boson Number in the Interacting Boson Model and Regularities in Systematic Studiesfor Even-Even Nuclei

The E₂₁+, E₄₁+, E₆₁+, B(E2,0₁⁺ → 2₁⁺) systematics are presented by using the total np interaction V_Np and the ratio betwyn V_Np and the total pairing strength V_pair to have a richer understanding of the wel&known N_πN_V and N_nN_p/(N_n + N_p) schemes. The different counting schemes for effective bosoh numbers and some regularities uncovered in previous studies are tested by the figures of V_NP/V_pair schemes. The systematics in the V_NP/V_pair scheme suggest that-the N_nN_p/(N_n + N_p) scheme holds for A ≥ 100 even-even nudei.     

描述大形变核中对力的硬核Bose-Hubbard模型

讨论了一种描述大形变偶偶核邻近轨道对力相互作用近似的硬核Ｂｏｓｅ－Ｈｕｂｂａｒｄ模型．利用代数方法得到了该模型对激发谱和相应波函数的严格解．该结果可推广到具有任意自旋和有限格点的硬核Ｂｏｓｅ－Ｈｕｂｂａｒｄ和Ｆｅｒｍｉ－Ｈｕｂ－ｂａｒｄ模型中去．     

Nucleon Spin Content in a Relativistic Quark Potential Model Approach

Based on a relativistic quark model approach with an effective potential U(r) = (ac/2)(1 + γ0)r2, the spin content of the nucleon is investigated. Pseudo-scalar interaction between quarks and Goldstone bosons is employed to calculate the couplings between the Goldstone bosons and the nucleon. Different approaches to deal with the center of mass correction in the relativistic quark potential model approach are discussed.     

Duality in Interacting Particle Systems and Boson Representation

In the context of Markov processes, we show a new scheme to derive dual processes and a duality function based on a boson representation. This scheme is applicable to a case in which a generator is expressed by boson creation and annihilation operators. For some stochastic processes, duality relations have been known, which connect continuous time Markov processes with discrete state space and those with continuous state space. We clarify that using a generating function approach and the Doi-Peliti method, a birth-death process (or discrete random walk model) is naturally connected to a differential equation with continuous variables, which would be interpreted as a dual Markov process. The key point in the derivation is to use bosonic coherent states as a bra state, instead of a conventional projection state. As examples, we apply the scheme to a simple birth-coagulation process and a Brownian momentum process. The generator of the Brownian momentum process is written by elements of the SU(1,1) algebra, and using a boson realization of SU(1,1) we show that the same scheme is available.     

轻核中中子间的对相互作用和中子晕

选择Skyme势E作为两核子间唯象相互作用,在Hartree-Fock理论中结合粒子数守恒方法处理同类核子间的对相互作用,计算了Li和Be的丰中子同位素的结构,计算表明中子间的对相互作用和双中子晕之间存在紧密的联系.     

平均场加区分质子和中子的邻近轨道对力模型及对超铀区核的统一描述

利用严格可解的平均场加区分质子和中子的邻近轨道相互作用对力模型,对超铀区部分大形变核进行了统一的描述.计算了^227—233Th,^232—239U,^236—243Pu同位素和同中异质素²²⁸Ra-²²⁹Ac-²³⁰Th-²³¹Pa-²³²U,²³²Th-²³³Pa-²³⁴U-²³⁵Np-²³⁶Pu,²³⁶U-²³⁷Np-²³⁸Puv-²³⁹Am的结合能,对激发能和奇偶能差并与相应核的实验值进行了比较     

Energy Staggering in Ground Bands of 232Th and 236,238U Nuclei Using the Interacting Vector Boson Model

The ΔI=2 and ΔI=4 staggering parameters of transition energies E_γ for normally deformed positive parity ground bands in ²³²Th and ^236,238U nuclei are studied in framework of the symplectic extension of the interacting vector boson model. The model parameters are obtained from the fitting procedure between the calculated excitation energies and the corresponding experimental ones. The staggering parameters represent the finite difference approximations to higher order derivatives dⁿE_γ/d Iⁿ of the γ -ray transition energies in a ΔI=2 and ΔI=4 bands, which yielding multipoint formulae. The first order derivative (two-point formula) provides us with information about the dynamical moment of inertia. The staggering oscillation for the fourth order derivative (five-point formula) is about 0.5 KeV and is even larger than that in superdeformed bands. The quite similarity in dynamical moments of inertia of the isotopes ^236,238U up to high spin states indicate that the phenomenon of identical bands is not restricted to superdeformed bands.     

Isoscalar and Isovector Giant Resonances in Closed Shells Nuclei and Bulk Properties of Nuclear Matter

Physics of Atomic Nuclei - Centroid energies, $$E_{\textrm{CEN}}$$ , of the isoscalar ( $$T=0$$ ) and isovector ( $$T=1$$ ) giant resonances of multipolarities $$L_{m}=0$$ –3 in...     

Approach to Equilibrium in a Microscopic Model of Friction

We consider the time evolution of a disk under the action of a constant force and interacting with a free gas in the mean-field approximation. Letting V₀>0 be the initial velocity of the disk and V_∞>0 its equilibrium velocity, namely the one for which the external field is balanced by the friction force exerted by the background, we show that, if V_∞−V₀ is positive and sufficiently small, then the disk reaches V_∞ with the power law t^−(d+2), d=1,2,3 being the dimension of the physical space. The reason for this behavior is the long tail memory due to recollisions. Any Markovian approximation (or simply neglecting the recollisions) yields an exponential approach to equilibrium.     

一个微观两参数核模型和它对超铀区核Yrast线的应用

基于费米子动力学对称模型提出了一个两参数模型.数值计算显示此模型能很好地符合超铀区核Yrast线能谱.     

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.     

Fine Structure of Beta Decay Strength Function and Anisotropy of Isovector Nuclear Dencity Component Oscillations in Deformed Nuclei

The experimental measurement data on the fine structure of beta-decay strength function S_β(E) in spherical, transitional, and deformed nuclei are analyzed. Modern high-resolution nuclear spectroscopy methods made it possible to identify the splitting of peaks in S_β(E) for deformed nuclei. By analogy with splitting of the peak of E1 giant dipole resonance (GDR) in deformed nuclei, the peaks in S_β(E) are split into two components from the axial nuclear deformation. In this report, the fine structure of S_β(E) is discussed. Splitting of the peaks connected with the oscillations of neutrons against protons (E1GDR), of proton holes against neutrons (peaks in S_β(E) of β⁺/EC-decay), and of protons against neutron holes (peaks in S_β(E) of β^–-decay) is discussed.     

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.     

Electronic Spectroscopies of the Mixed Valence Ce Compounds:A Slave Boson Approach to the Impurity Model

A slave boson approach to the electronic spectroscopies for the mixed valence Cecompounds in the impurity model is presented. Three valence configurations of Ceion (f⁰, f¹ and f²) are considered so the framework of the theorv can be used for culculating both XPS and BIS. The spectrum under mean field approximation is presented.     

Momentum Distribution of a Fragment and Nucleon Removal Cross Section in the Reaction of Halo Nuclei

Recently the research on the halo structure of drip-line nuclei has shown some interesting properties of the existence of one or more halo nucleons. In the framework of few-body Glauber model, the momentum distribution of a fragment and nucleon removal cross section in the reaction of halo nuclei is presented and extended to nuclei having more than one halo nucleons. The reaction mechanism is treated with and without taking account of the final-state interaction. The wave function of removal halo nucleons in the continuum state is modified by imposing an orthogonal condition to the bound state. An analytical expression of the longitudinal momentum distribution of the fragment is derived when the bound state wave function of halo nucleons is taken as a Gaussian-type function. This is useful in the further investigation on the structure of halo nuclei.     

Momentum Distribution of a Fragment and Nucleon Removal Cross Section in the Reaction of Halo Nuclei

Recently the research on the halo structure of drip-line nuclei has shown some interesting properties of the existence of one or more halo nucleons. In the framework of few-body Glauber model, the momentum distribution of a fragment and nucleon removal cross section in the reaction of halo nuclei is presented and extended to nuclei having more than one halo nucleons. The reaction mechanism is treated with and without taking account of the final-state interaction. The wave function of removal halo nucleons in the continuum state is modified by imposing an orthogonal condition to the bound state. An analytical expression of the longitudinal momentum distribution of the fragment is derived when the bound state wave function of halo nucleons is taken as a Gaussian-type function. This is useful in the further investigation on the structure of halo nuclei.