高自旋超形变带的代数模型研究

介绍高自旋超形变带的研究现状,提出一种可以统一描述超形变带的ΔI=4分岔现象、全同带现象等的代数模型,计算结果表明ΔI=4分岔现象可能起因于具有SO(5)(或SU(5))对称的微扰,全同带现象可能是产生超形变态的平均场具有超对称性的结果.     

126Cs的高自旋态能级结构

利用融合蒸发反应¹¹⁶Cd(¹⁴N,4n)¹²⁶Cs布居了¹²⁶Cs的高自旋态.观测到了100多条新的γ跃迁和相应的能级,建立了双奇核¹²⁶Cs由9个转动带构成的能级纲图.尝试性地指定了大部分能级的自旋和宇称以及各转动带的Nilsson单粒子组态.极大地丰富了已有的实验结果.     

自旋相干态变换和自旋-玻色模型的基于变分法的基态解析解

提出一种基于自旋相干态变换求解自旋-玻色模型基态的变分法, 并将其用于单原子模型, 得到旋波近似和非旋波近似情形下的解析基态能量和波函数, 特别是在光场与原子的弱、强耦合区域都与数值对角化结果符合得很好. 另外, 该方法也可以直接用于求解任意原子数的Dicke模型基态和相应的量子相变研究, 而通常基于Holstein-Primakoff变换的变分法, 原则上只适用于原子数趋于无穷的热力学极限情形. 关键词： 自旋相干态 变分法 J-C模型     

126I高自旋态的认定

利用重离子融合蒸发反应¹²²Sn(¹¹B,5n2p)布居了双奇核¹²⁶I的激发态,首次建立了具有集体带结构特征的能级纲图,其中包括20条新γ跃迁.所建能级纲图的核素归属指定得到了核反应¹²⁴Sn(⁷Li,5n)的交叉支持.简单讨论了所建带结构的可能组态.     

235, 237Np高自旋态的理论研究

锕系核的转动性质对于揭示$A \approx 250 $质量区原子核的顺排机制、对关联性质、能级结构等十分重要,研究这些核的高自旋结构一方面可以对现有的理论模型进行检验,另一方面有助于深入认识超重核。本工作采用基于推转壳模型的粒子数守恒方法研究了实验上观测到的$^{235}{\rm{Np}}$和$^{237}{\rm{Np}}$中转动带的性质,计算得到的转动惯量、角动量顺排等与实验符合。首先,通过描述转动谱的$ab$公式确定了$^{235}{\rm{Np}}$中观测到的转动带的带头自旋。随后,通过对比理论与实验上的转动惯量,确定了其组态为$\pi 5/2^-[523]$。此外,也讨论了高阶形变$\varepsilon_6^{}$对中子$j_{15/2}^{}$顺排的作用,探索了在计算中出现而在实验上未观测到中子$j_{15/2}^{}$顺排的原因,从而解释了$^{235, 237}{\rm{Np}}$的转动带中产生上弯的机制。最后,还讨论了$^{237}{\rm{Np}}$的转动带$\pi 5/2^-[523]$中出现旋称劈裂的原因,发现可能是由于这个转动带的两个旋称分支上弯以后高阶形变$\varepsilon_6^{}$不同所导致的。     

Ising自旋体系的非平衡动态相变

在平均场理论架构下, 以含时金兹堡-朗道和Glauber动力学这两类动态模型为基础，研究 了受外场和温度共同驱动的Ising自旋体系的非平衡动态相变.确定了界定动态无序(动态顺 磁相P)和动态有序(动态铁磁相F)转变的动态相界.并根据动态序参量Q和Binder参数U随系统 温度t(r₀)、驱动外场频率ω和振幅h₀的变化规律，就上述两类模 型的动态相界上是否存在区分连续动态转变和非连续动态转变的三临界点这一引发争议的问 题做出了进一步分析说明. 关键词： Ising自旋体系 非平衡动态相变 含时金兹堡-朗道模型 Glauber 动力学模型     

含Hopf项和Maxwell-Chern-Simons项O(3)非线性σ模型的分数自旋和分数统计性质

研究了（2＋1）维时空中含Hopf项和Maxwell-Chern-Simons(MCS)项的非线性σ模型的分数自旋性质.根据约束Hamilton系统的Faddeev-Senjanovic(FS)路径积分量子化方案,对该系统进行量子化，由量子Noether定理给出了量子守恒角动量，说明了在量子水平上该系统仍具有分数自旋的性质. 关键词： 约束Hamilton系统 分数自旋 O(3)σ模型     

非马尔科夫环境中各向异性海森堡自旋链的几何量子失协

本文主要在非马尔科夫环境中,在时变磁场和Dzyaloshinski—Moriya相互作用下,以最大纠缠态■作为信道,研究了具有各种参数的两比特海森堡XYZ模型的几何量子失协.通过在非马尔科夫环境中的量子态扩散方法模拟了系统的几何量子失协随时间的演化关系.根据数值模拟结果显示:环境关联系数γ、自旋耦合系数J和J_z、余弦磁场强度B、以及自旋—轨道相互作用都能影响系统几何量子失协的性质.当环境关联系数γ较小时,几何量子失协呈现出明显的上升趋势,可见非马尔科夫环境对系统的几何量子失协表现出积极的作用.同时较大的自旋耦合系数J和余弦磁场强度B对系统的几何量子失协也有积极的影响.     

一维扩展t-J模型中密度-自旋相互作用诱导的相分离

t-J模型是研究高温超导电性的重要理论模型之一. 最近的冷分子实验表明可用极性分子模拟t-J模型. 实验模拟的t-J模型除了引进长程的偶极相互作用外, 还引进了密度-自旋相互作用. 本文使用密度矩阵重整化群方法研究了密度-自旋相互作用对一维t-J 模型基态性质的影响. 选取了t-J模型基态相图中不同相区的三个点, 计算了不同密度-自旋相互作用强度下的粒子数和自旋的实空间分布,以及密度-密度关联函数和自旋-自旋关联函数与相应的结构因子. 计算结果表明, 密度-自旋相互作用强度较弱时, 对系统的性质不会产生定性影响;当其强度足够大时, 系统会进入相分离, 该相分离与传统t-J模型的相分离有很大区别.     

双能态自旋-晶格声子耦合量子隧道系统的非经典能态和量子相干耗散

采用关联表象变分波函数方案, 介入三个非经典关联效应, 求解有限温度双能态自旋-晶格声子耦合量子隧道系统的非经典态, 着重研究化解由于粒子自旋-单声子相互作用引起的量子涨落导致双能态系统的退相干性量子耗散. 这三个非经典关联效应是: 1) 声子位移-粒子自旋 (σ_z)间强非绝热关联; 2) 声子压缩态效应及其伴随发生的单声子相干态-声子压缩态两过程相干效应; 3) 由关联表象导致的声子位移(U_D)与声子压缩(U_S)的表象关联非绝热修正. 结果表明: 由于引入粒子自旋-双声子相互作用, 大幅度地增强了声子场压缩态, 特别是更进一步极大幅度地增强了非经典压缩-相干态效应. 因此, 由粒子自旋-单声子相互作用产生的Debye-Walle相干弹性散射效应导致量子隧道项(-Δ₀σ_x)的强烈指数衰减及其伴随严重的量子相干损失的极大幅度的抑制, 并且自旋-晶格声子耦合量子隧道系统的非经典态能量大幅度降低. 关键词： 非经典能态 量子隧穿相干损失 自旋-双声子相互作用 压缩相干态效应     

The Features of Low-Lying States of Ne3, Ar3 and Kr3

The methods for few-body physics are introduced to extract structures of low-lying states of threeatom clusters of neon, argon and krypton. Similarities among the states have been found, and accordingly a number of rotational bands have been identified. Each band is characterized by a specific mode of internal oscillation. The decisive effect of symmetry has been emphasized.     

约束哈密顿系统在相空间中的精确不变量与绝热不变量

研究小干扰力作用下约束哈密顿系统对称性的摄动问题.建立了非保守约束哈密顿系统的正则方程,在增广相空间中研究了系统的对称性与精确不变量.基于力学系统的高阶绝热不变量的概念,给出了系统的各阶绝热不变量的形式及存在条件,并建立了绝热不变量与对称变换之间的对应关系 关键词： 约束哈密顿系统 对称性 摄动 不变量     

原子核的反常宇称能谱研究

将具有负宇称的 fp 空间扩大到包含1g9/2 轨道, 采用修正的表面相互作用(MSDI), 对64Ge, 66Ge, 68Ge, 70Se, 72Se, 74Se, 76Kr 和 78Kr等偶偶核作了形变Hartree Fock计算, 得到了基态和一些激发态的解. 同时, 还用近似角动量投影形变Hartree Fock（PDHF）方法对偶偶核64Ge, 74Se和奇A核79Kr进行了能谱计算, 得到其正、 负宇称带的解, 计算结果与实验谱基本一致.Using modified surface delta interaction, enlarging the fp configuration space to include the 1g9/2 orbit with the abnormal parity, the deformed Hartree Fock calculations for the eight nuclei: 64Ge, 66Ge, 68Ge, 70Se, 72Se , 74Se, 76Kr and 78Kr are performed. The ground state and some particle hole excited configurations are obtained. The approximate angular momentum projected deformed Hartree Fock (PDHF) method is applied to even even nuclei 64Ge and 74Se and odd A nuclus 79Kr. Both of their normal and abnormal parity bands are obtained. The calculated energy spectra are consistent well with experimental spectra.     

Generalized Hartree-Fock theory and the Hubbard model

The familiar unrestricted Hartree-Fock variational principles is generalized to include quasi-free states. As we show, these are in one-to-one correspondence with the one-particle density matrices and these, in turn, provide a convenient formulation of a generalized Hartree-Fock variational principle, which includes the BCS theory as a special case. While this generalization is not new, it is not well known and we begin by elucidating it. The Hubbard model, with its particle-hole symmetry, is well suited to exploring this theory because BCS states for the attractive model turn into usual HF states for the repulsive model. We rigorously determine the true, unrestricted minimizers for zero and for nonzero temperature in several cases, notably the half-filled band. For the cases treated here, we can exactly determine all broken and unbroken spatial and gauge symmetries of the Hamiltonian.Dedicated to Philippe Choquard on his 65th birthday.     

Feature of Energy Spectra of Four-Identical-Particle Systems in 2D Space

A comparison has been made between features of low-lying states of a four-electron dot and a 2-dimensional four-alpha-particle system. A series of qualitative features are revealed to be identical. We stress the importance of quantum mechanical symmetries in the understanding of quantum mechanical few-body systems.     

QQqq Four-Quark Bound States in Chiral SU(3) Quark Model

The possibility of QQqq heavy-light four-quark bound states has been analyzed by means of the chiral SU(3) quark model, where Q is the heavy quark (c or b) and q is the light quark (u, d, or s). We obtain a bound state for the bbnn configuration with quantum number J^P=1⁺,I=0 and for the ccnn (J^P=1⁺,I=0) configuration, which is not bound but slightly above the D^*D^* threshold (n is u or d quark). Meanwhile, we also conclude that a weakly bound state in bbnn system can also be found without considering the chiral quark interactions between the two light quarks, yet its binding energy is weaker than that with the chiral quark interactions.     

Skyrme Hartree-Fock模型对中等质量超形变超核的研究（英文）

采用Skyrme Hartree-Fock 模型和微观的核子-超子相互作用对Ar 同位素和40Ca 及相应超核的超形变态进行了研究,计算结果表明,基态的Λ 超子分离能比激发态的大。这一结果与反对称化分子动力学模型的结果一致,而与相对论平均场的结果相反。这区别主要来源于不同模型中不同的相互作用导致的核心核及相应超核密度分布的不同。The superdeformed (SD) states in medium heavy hypernuclei with core nuclei of Ar isotopes and 40Ca are studied in the frame of Skyrme Hartree-Fock (SHF)+ BCS model together with a microscopic ΛN interaction. The calculation indicates that the Λ separation energy S_Λ of ground state is larger than that of SD state. The result is consistent with the antisymmetrized molecular dynamics (AMD) calculation, but inconsistent with that of relativistic mean field (RMF). The difference comes from the different interaction and density distribution in the core nuclei and the corresponding hypernuclei.     

手征SU(3)夸克模型的六夸克集团态的研究

用手征SU(3)夸克模型分析了(Os)6组态的六夸克态能量,结果表明手征SU(3)介子场可以对某些高奇异数的态提供较强的吸引作用,这为进一步讨论是否有可能存在窄宽度的六夸克态提供了有用的信息.     

Detailed Description of Mixed Symmetry States in 94Mo Using Interacting Boson Model

We have investigated the low-lying collective states and electromagnetic transitions in 94Mo within the framework of the interacting boson model. The influence of model parameters on the energy levels and electromagnetic properties has been investigated. The analysis of the obtained results and the parameter values predict that the 23+state is the lowest mixed symmetry state with pure F = Fmax - 1 in this nucleus. The calculated results predicate that the 25+ (two-Q-phonon) mixed symmetry state is closed to the J = 2+ at 2.870 MeV in the experimental data, and the 2.965 MeV state is the lowest mixed symmetry with J = 3+.