轻子、夸克的磁矩和跃迁矩

根据轻子、夸克的亚结构理论和在亚夸克模型中的组合波函数,计算了轻子、夸克的磁矩,自旋s=1/2→s=3/2的跃迁矩。     

自旋S＝3／2的轻子激发态

若轻子由3个自旗为1／2的亚夸克组成，则除了存在自旋S1／2的轻子基态外，在受激情况下，也将出现S＝3／2的激发态，两者的质量差与亚夸克构成轻子的对称性质及亚夸克与双夸克的相互作用密切相关。     

轻子结构模型和夸克——轻子对称

假定组成轻子和夸克的味亚夸克可以用规范群SU_L(2)(?)SU_R(2)(?)UY_W=5-l(1)表示;并引入同位旋I.C——旋.t——旋二重态的概念,它们分别定义为:I_3~-=(u+d)/2,C_3~-=(C+S)/2,t_3~-=(t+b)/2;弱超荷为y_W=B-l.则能进一步地解释轻子——夸克对称的物理根源:说明三代轻子二重态,三代夸克二重态中所呈现的质量分裂发生较大差异的原因;消除超荷y_w的多值性而导致破坏轻子、夸克左旋、右旋对称性的困难;本模型也自然地给出了重轻子哀变的三μ事例.     

轻子-夸克质量谱

根据SU(2)_L(?)SU(2)_R(?)U(1)_Y_W=B-l规范对称性,从我们的亚夸克模型得到轻子和夸克量子数,可将轻子-夸克质量谱公式归纳为:m_i=m_e{|(u-d)|+|(c-s+t-b)|(3/2)α~(-1)}Q~2/|B-l|~3(n-c+s-t+b)~4     

轻子,夸克的磁矩和跃迁矩

根据轻子、夸克的亚结构理论和在亚夸克模型中的组合波函数,计算了轻子、夸克的磁矩,自旋ｓ＝１／２→ｓ＝３／２的跃迁矩。     

亚介子和轻子的位势模型

本文在亚夸克模型的基础上,采用B——S方程,讨论了由一对正、反亚夸克构成的两体束缚态亚介子,如果引入库仑型势,深方位势,线性势和诣振子势的速加位势,则可得到符合实验事实的能谱。本文又推广了W.Krolikowski的费米子——玻色子两体相对论性束缚态方程,并用它讨论了轻子结构。如果引入矢量库仑型势和标量线性势的迭加,则其相应激发态的能级差可达数百GeV,从而为至今没有发现3/2自旋或更高自旋的轻子、以及尚未找到轻子的径向激发态等事实,给出了一种可能的解释。本文还指出,所用位势概有“非静态”特征。     

夸克和“色”荷的电荷二分量理论

本文通过对夸克电荷及其自旋分量的分析,发现夸克的自旋应为1/6 h,为解释这一异乎寻常的结论,本文提出了夸克的轻子一“色”荷复合模型.从而使强子运动学和动力学有了统一的说明.     

粲重子的磁矩

把计算磁矩的Gerasimov公式用于亚夸克模型,可以得到亚夸克qi(i=1,2,3,4)、b、g的磁矩。设亚夸克磁矩服从独立可加性法则,则导出夸克的磁矩与夸克——极子模型获得的结果相同。在考虑到夸克自旋的情况下,据夸克组成粲重子的波函数计算出粲重子的磁矩,其结果恰好与S,Iwao以及G,Dattoli等人从其它方法所导出的结果一致。     

编内、"编外"粒子的超对称性和SUf(3)表示

据焦一宫提出的夸克、轻子的亚克三体结构模型和推广后的Preon模型，讨论了超对称性的数学和物理基础，分析了编内费米子和“编外”玻色子间具有的正、反两界粒子一一对应的超对称关系，且正、反两界粒子分别满足SUf（3）群和SUf(3）亚群对称，从而人为最近观测到的质量m^′＞50mp的奇异粒子是“编外”轻子型夸克q^′及q^-′的复合态H′（q′,q^-′），发现l^--q共振是“编外”玻色子中存在“反轻子型夸克”Sc^ 2/3(bc,g^-）的必然结果，可能是对亚夸克物理的有力支持。     

手征SU(3)夸克模型的Σ-N相互作用及4ΣHe结合能的计算

利用SU（3）夸克模型,采用共振群方法得到非定域Σ-N相互作用势以及Σ超子与3He壳心核的相互作用势,并用于4ΣHe基态结合能的计算.计算结果表明SU（3）夸克模型不仅能较好地描述Σ-P散射,而且由其计算的Σ4He结合能也与实验值吻合得很好.同时,研究结果也表明在同位旋T=1/2的条件下,只有自旋S=1对Σ4He结合能有贡献,S=0则没有.     

Υ（1S,2S）→B_c~*lν_e半轻衰变

基于高亮度的重味物理实验中对Υ(nS)测量潜在的前景,在标准模型中详细研究了以树图贡献为主的Υ(1S,2S)→B_c~*lν_e半轻衰变,给出这些衰变过程的分支比,轻子极化不对称和前后不对称,以及一些重要的比值R_(Υ(nS))~((L))和F_(Υ(nS))~L(n=1,2)．最终的数据结果表明Υ(1S,2S)→B_c~*lν_e半轻衰变有较大的分支比,且量级为10~(-10)～10~(-9),有望被实验观测到．     

混自旋σ=3/2和S=2与σ=3/2和S=5/2Ising系统基态性质的比较

研究了混自旋σ=3/2和S=2与混自旋σ=3/2和S=5/2两种Ising系统的基态性质.根据能量最低原理,通过比较各种可能基态构型的基态能,确定出了系统的基态相图.并得到了基态能Eg随DA/(zJ)和DB/(zJ)的变化规律.结果表明,对于混自旋σ=3/2和S=2 Ising系统可存在无序相,而对于混自旋σ=3/2和S=5/2 Ising系统只存在有序相.两种系统的基态能均随着DA/(zJ),DB/(zJ)值的变大而线性升高,但不同区域的斜率不同.DA/(zJ),DB/(zJ)值越大,基态能升高得越慢.此外发现对于混自旋σ=3/2和S=2 Ising系统存在4种构型共存点(0.5,0.5),...     

格点稀疏Ising自旋玻璃

本文扩展自旋玻璃的SK模型,分别计算了S=1/2和S=1的格点稀疏lsing自旋玻璃的热力学参量。     

Y(nS)→B_c■■_■半轻衰变

基于高亮度的重味物理实验产生大量Y介子.在标准模型中详细地研究了以树图贡献为主的Y(n S)→B_c■■_■(n=1,2,3)半轻衰变,给出了这些衰变过程的分支比,比值RY(nS),轻子自旋不对称和前后不对称.最终的数值结果表明,所有的Y(nS)→B_c■■_■的半轻衰变均有较大的分支比,且量级为10-10~10-9.因此,这些过程均有望被LHC和Supper KEKB/Belle-II实验所观测到.     

伊辛自旋梯的磁化平台和热力学性质研究

利用传递矩阵方法严格求解了混自旋S=1和S=3/2组成的伊辛自旋梯,考察了系统的磁化过程及外磁场下各向异性对系统热力学性质的影响.发现系统最近邻为铁磁性交换作用,链间次近邻为反铁磁性作用时,系统的磁化强度在m=1/4和m=3/4处出现磁化平台现象,与量子模型中的磁化平台可能出现的位置一致.系统的磁比热和磁化率曲线中出现了新颖的双峰现象.     

反铁磁系统(S=5/2)中外磁场诱导的相变

讨论了在外磁场下自旋为S＝5／2的反铁磁三角晶格的静态磁化率与8温度的关系，当不存在磁场时，磁化率曲线在温度TN1处出现一个峰，加上外磁场时磁化率曲线又在TN2处出现一谷，在TN2处的相变是由外磁场诱导的，磁化率与外磁场的变化曲线存在一个连续区，对应实验上磁化率的1／3（S＝1／2）或1／2（S＝1）平台。     

量子海森堡自旋玻璃的Almeida-Thouless不稳定性

分析了量子海森堡自旋玻璃稳态Replica对称解的稳定性,获得了著名的Almeida-Thouless(AT)和Gabay-Toulouse(GT)相变条件,通过数值计算得到了不同自旋值的AT临界相图,并讨论了与其它理论的关联.     

介子-重子的对称性、夸克和新的粒子模型

按照衰变和结构,介子应与轻子统一.引入新的组合量子数F’=|B+I-S|,则基态介子-重子量子数等距并统一.提出了重味强子的寿命公式和等比关系.讨论了量子数三角形和四面体.对夸克模型,可能微粒子运动产生出现具有对称性的幻夸克.探讨了两体模型和亚夸克.最后提出粒子三代结构等的新模型.按照Occam剃刀原则,粒子基本结构只应该有光子、电子和质子.     

Magnetic and non-magnetic phases of a quantum spin liquid

A quantum spin-liquid phase is an intriguing possibility for a system of strongly interacting magnetic units in which the usual magnetically ordered ground state is avoided owing to strong quantum fluctuations. It was first predicted theoretically for a triangular-lattice model with antiferromagnetically coupled S = 1/2 spins. Recently, materials have become available showing persuasive experimental evidence for such a state. Although many studies show that the ideal triangular lattice of S = 1/2 Heisenberg spins actually orders magnetically into a three-sublattice, non-collinear 120° arrangement, quantum fluctuations significantly reduce the size of the ordered moment. This residual ordering can be completely suppressed when higher-order ring-exchange magnetic interactions are significant, as found in nearly metallic Mott insulators. The layered molecular system κ-(BEDT-TTF)(2)Cu(2)(CN)(3) is a Mott insulator with an almost isotropic, triangular magnetic lattice of spin-1/2 BEDT-TTF dimers that provides a prime example of a spin liquid formed in this way. Despite a high-temperature exchange coupling, J, of 250 K (ref. 6), no obvious signature of conventional magnetic ordering is seen down to 20 mK (refs 7, 8). Here we show, using muon spin rotation, that applying a small magnetic field to this system produces a quantum phase transition between the spin-liquid phase and an antiferromagnetic phase with a strongly suppressed moment. This can be described as Bose-Einstein condensation of spin excitations with an extremely small spin gap. At higher fields, a second transition is found that suggests a threshold for deconfinement of the spin excitations. Our studies reveal the low-temperature magnetic phase diagram and enable us to measure characteristic critical properties. We compare our results closely with current theoretical models, and this gives some further insight into the nature of the spin-liquid phase.     

Quantum oscillations in a molecular magnet

The term 'molecular magnet' generally refers to a molecular entity containing several magnetic ions whose coupled spins generate a collective spin, S (ref. 1). Such complex multi-spin systems provide attractive targets for the study of quantum effects at the mesoscopic scale. In these molecules, the large energy barriers between collective spin states can be crossed by thermal activation or quantum tunnelling, depending on the temperature or an applied magnetic field. There is the hope that these mesoscopic spin states can be harnessed for the realization of quantum bits--'qubits', the basic building blocks of a quantum computer--based on molecular magnets. But strong decoherence must be overcome if the envisaged applications are to become practical. Here we report the observation and analysis of Rabi oscillations (quantum oscillations resulting from the coherent absorption and emission of photons driven by an electromagnetic wave) of a molecular magnet in a hybrid system, in which discrete and well-separated magnetic clusters are embedded in a self-organized non-magnetic environment. Each cluster contains 15 antiferromagnetically coupled S = 1/2 spins, leading to an S = 1/2 collective ground state. When this system is placed into a resonant cavity, the microwave field induces oscillatory transitions between the ground and excited collective spin states, indicative of long-lived quantum coherence. The present observation of quantum oscillations suggests that low-dimension self-organized qubit networks having coherence times of the order of 100 micros (at liquid helium temperatures) are a realistic prospect.