关于W±介子磁矩的唯象分析和一种新的实验建议

本文第一部分唯象分析了W^&;#177;介子的磁矩,从顶角表达式得到它的裸磁矩、电四极矩后,再从有效拉氏量出发,指出了在什么情况下W介子有反常磁矩和反常电四极矩.第二部分与HERA的高能e+p对撞机相应,计算了圆偏振硬γ光与高能电子对碰的γ+e→w+v过程,得到了截面dσ（±）/dt,σ^±)和不对称系数A随能量的变化,指出可以通过这实验,确切地判断W介子的磁矩.     

轻子的束缚态波函数和反常磁矩

本文从Bethe-Salpeter方程出发讨论由费米子和标量玻色子组成的轻子束缚态波函数. 在组分粒子很重和内部运动为非相对论的假定下可以证明, 矢量相互作用能给出半径和反常磁矩都足够小的束缚态解, 但要求组分费米子质量远大于玻色子质量. 相反, 标量相互作用则只能给出半径和反常磁矩都很大的束缚态解.     

由于中子跃迁而产生的电多極内转换

本文讨论核子的反常磁矩对于内转换系数数值的影响。首先讨论了纵光子和标量光子在内转换过程中所起的作用。然后用对应的方法推导出具有反常磁矩的荷电粒子之间的推迟相互作用。又用量子电动力学推导推迟相互作用,得到完全相同的结果。这一推迟相互作用被用来计算内转换系数。结果指出:核子的反常磁矩对于磁多极内转换系数以及由于质子跃迁导致的电多极内转换系数的影响微不足道。但是和某些作者的结论相反,核子的反常磁矩对于由于中子跃迁而导致的电多极内转换系数产生显著的影响。讨论了计算中所用的规范问题,从而指出这些作者处理本问题时所引入的错误。     

反常磁矩对弱磁场弱相互作用费米气体热力学性质的影响

考虑费米子的反常磁矩, 运用赝势法和热力学理论, 导出弱磁场中弱相互作用费米气体自由能的解析式, 以此为基础给出高温和低温情况下系统热力学性质, 分析反常磁矩对热力学性质的影响机理. 研究表明: 反常磁矩对热力学性质的影响与温度相关, 而且这种影响随温度的上升在低温区是增大的, 在高温区是减小的; 对于系统的化学势、内能, 反常磁矩加强了磁场的影响, 弱化了相互作用的影响; 对于系统的热容量, 反常磁矩在低温区使其减小, 在高温区使其增加.     

Λ~0超子的磁矩

磁矩是基本粒子的一个重要的电磁性貭。大約三十年前斯特恩发現了貭子具有反常磁矩,后来发現中子也具有反常磁矩,并且把核子的磁矩测量得非常精确。此后核子反常磁矩就成了原子核构造理論的一个重要对象。虽然現在利用高能电子散射等方法对核子的电磁构造作了許多詳細的研究,可是理論所能給出的核子磁矩数值与实驗值比起来仍然很粗略。我們对超子的电磁性貭了解得非常少,从来还沒测量过任何一个超子的磁矩。由于指导理論的实驗资料这样缺乏,所以任何有关这方     

缪轻子反常磁矩和北京谱仪实验

最新的缪子反常磁矩实验测量结果与标准模型理论预言偏离4.2σ,提供了新物理存在的重要证据.然而要确认新物理的存在,实验和理论还需要进一步提高精度.运行在量子色动力学微扰与非微扰过渡能区的北京谱仪实验能够约束缪子反常磁矩理论计算中最重要的误差来源——强相互作用的修正.文章介绍了缪子反常磁矩的实验与理论现状,特别是北京谱仪...     

Weinberg-Salam模型中W±矢量中间玻色子的磁矩

本文讨论了Weinberg-Salam模型中W^±矢量中间玻色子(VIB)的磁矩问题. 首先在规范对称性没有自发破缺的假定下, 利用规范不变性得出正规顶角母泛函的方程, 求出三线VIB正规顶角满足的Ward-Takahashi恒等式, 证明了它的张量结构形式与裸的VIB三线耦合项相同, 因而表明这时W^±介子不存在反常磁矩及反常电四极矩. 对于有自发破缺的"实际"情况, 通过在标量场作用项中引入明显破缺项的办法,目对VIB的质量延拓问题完成整个讨论, 进而给出了上述结论在这时仍然成立的证明.     

层子模型中的不具有SU6对称的波函数及其应用

本文在层子模型的基础上,用[2]中给出的基态介子、重子波函数的一般形式,在一些假定下,构造了不具有 SU₆对称性的介子、重子波函数;用这些波函数去解释介子、重子的电磁、弱作用性质,得到许多与实验相符合的结果.这种不具有 SU₆对称性的（（1⁺）/2）重子波函数可以给出质子的反常磁矩,而不需要在层子的等效电磁作用哈密顿量中引入层子反常磁矩项,也可以较好地解释中子的磁矩.     

铁磁金属的表面阻抗与自旋波共振

本文计算了铁磁金属在平行磁场中的表面阻抗。计算中考虑了交换作用所引起的磁化率空间色散及趋肤效应的反常性。分别讨论了磁矩的两种边界条件m=0和(?m)/(?n)=0。同时研究了导电电子在表面散射性质的影响。利用Азбель-Канер在迴旋共振理论中的方法,计算了考虑电导率旋磁性条件下的表面阻抗。     

弱作用对轻子电磁性质的影响

讨论了弱作用对轻子电磁性质的影响。对于中间玻色子和轻子及电磁场的相互作用应用了Stueckelberg-Matthews的矢量场理论,给出了矢量准确到e,G的一次方的矩阵元。得到的轻子反常磁矩的修正项是不发散的,并与中间玻色子的质量无关。计算中不存在出现于Зельдовнч的工作中的不唯一性。     

Detecting topological order through a continuous quantum phase transition

We study a continuous quantum phase transition that breaks a Z2 symmetry. We show that the transition is described by a new critical point which does not belong to the Ising universality class, despite the presence of well-defined symmetry-breaking order parameter. The new critical point arises since the transition not only breaks the Z2 symmetry, it also changes the topological or quantum order in the two phases across the transition. We show that the new critical point can be identified in experiments by measuring critical exponents. So measuring critical exponents and identifying new critical points is a way to detect new topological phases and a way to measure topological or quantum orders in those phases.     

Structural phase transition in pyrene - how does it occur?

The phase transition in pyrene crystal has been studied by a continuous differential optical transmittance measurement. The result suggests that the transition around 120 K is of the first order structural transition and occurs domain by domain which are formed temporarily in the crystal. In some crystals the phase transition does not occur around 120 K but only a variation of the lattice constants occurs.     

Dynamic mechanical characterization of relaxations in poly(oxymethylene), miscible blends,and oriented filaments

Multifrequency dynamic mechanical analysis (DMA) data were obtained for molded poly(oxymethylene) (POM) and its blends from-150°C to 150°C. Because of the high crystallinity, the assignment of the glass transition in POM has been controversial in the literature. Low and high glass transition temperature (T _g) phenolated compounds, including poly(vinyl phenol), were found to be miscible with POM. The shift of the β transition in the POM blends favors an assignment of the β transition detected at ?3°C(1 Hz), not the ?80°C γ transition, as the T _g in semicrystalline POM because the latter is invariant with diluent. The peak at the β transition in pure POM is weak and can only be seen clearly by DMA measurements on samples that have not “aged” at ambient temperature. This is further evidence that the β transition arises from a cooperative glass-transition-like motion. The γ transition is not influenced by aging because it is due to a concerted localized main chain motion. The β transition of an oriented POM filament can be seen in the DMA flexural loss spectrum at-18°C (1 Hz), but not in a tensile loss spectrum. The broad a relaxation was detected at about 110°C (1 Hz) in molded POM and its blends, while it was shifted to about 135°C in the higher crystallinity, oriented system. The α peak is also independent of diluent, consistent with a crystalline origin for this transition, as was proposed earlier.     

Hall-effect and metal-nonmetal transition in copper-argon and lead-argon systems

Summary Hall-effect measurements have been made to find out the type of transition from metal to nonmetal in copper-argon and lead-argon films prepared at helium temperature. The Hall measurements indicate that the transition from metal to nonmetal is a new-type transition. Such a metal-nonmetal transition in metal-argon systems may be attributed to the combined effect of electron correlation intermediated by phase transition. To speed up publication, the authors of this paper have agreed to not receive the proofs for correction.     

Study of neutron irradiation effect on Morin transition in hematite

It is established by Mössbauer spectroscopy and slow neutron diffraction that temperature range of Morin transition in hematite changes depending on neutron irradiation dose, and above some critical values the transition is not observed at all. A fraction of iron ions with high-temperature orientation of moments which cause the sample weak-ferromagnetic characteristics decreases with temperature fall but does not disappear completely, and near 4 K it even rises. It is established that radiation defects causing the changes in Morin transition disappear at annealing of hematite on air at temperatures of 400–500 K.     

高超声速边界层中由粗糙元引起强制转捩的机理

由大粗糙元引起的高超声速边界层强制转捩在航天技术中有实际应用, 因而近年来受到人们的广泛关注.虽然目前导致该转捩过程的内在机理尚不完全清楚, 但有一点是明确的, 即粗糙元的尾迹流场中存在强对流不稳定性.文章的出发点是研究这种对流不稳定模态是如何触发转捩的.首先通过CFD方法, 计算出高超声速边界层中粗糙元的尾迹流场, 并对其进行二维稳定性分析.结果发现, 在传统不稳定Tollmien-Schlichting(T-S)模态出现的临界Reynolds数之前, 存在高增长率的无黏不稳定模态, 表现为对称的余弦模态和反对称的正弦模态.然后对该不稳定模态在粗糙元尾迹流中的演化进行了模拟, 验证了二维稳定性分析的结果, 并考察了非平行性效应的影响.最后通过直接数值模拟, 研究由这些不稳定模态触发转捩的全过程.结果表明, 对流不稳定模态确实是导致边界层转捩的关键机制.该转捩过程的特点是, 局部湍斑首先在不稳定模态特征函数的峰值附近出现, 然后向全流场扩散.就文章研究的工况而言, 余弦和正弦模态的相互作用对转捩的影响并不明显, 且后者在转捩过程中起主导作用.      

Excluded volume reduced mechanical stability for an intrinsically curved biopolymer

We find that the excluded volume interaction (EVI) can accelerate an abrupt transition in extension for an intrinsically curved two-dimensional semiflexible biopolymer. It makes the transition much sharper, reduces the critical force remarkably, and the larger the persistent length or the intrinsic curvature, the larger the reduction in critical force. The transition is caused by a collective change in bending angles associated with removing cusps owing to thermal fluctuation. Our results reveal that EVI can excite a cooperative behavior, straighten more bonds simultaneously so cause a sharper transition. The transition is dominated by the mechanical force because the specific heat does not divergence. Our findings suggest that an intrinsically curved biopolymer can act as a switch or sensor in some biological processes.     

Periodic saddle-splay Freedericksz transition in nematic liquid crystals

By use of a local stability criterion recently introduced, we predict the existence of a periodic saddle-splay Freedericksz (PSSF) transition that adds to the existing class of classical Freedericksz transitions driven in a nematic cell by an external field. Occurrence of the PSSF transition requires a saddle-splay elastic constant with a large enough magnitude and different anchoring strengths at the plates confining the nematic cell. Otherwise, either the PSSF transition does not occur at all, or it requires a field higher than that associated with the classical aperiodic splay Freedericksz (ASF) transition, in which case it is not observable. Here, we determine the threshold field for which the PSSF precedes the ASF transition, as well as the structure of the destabilizing mode.     

Superconducting properties of long TiN wires

The low-temperature transport properties of titanium nitride wires with the width comparable with or much larger than the superconducting coherence length are studied experimentally. It is shown that the reduction of the width of wires does not affect the transport properties at the temperatures above the superconducting transition temperature and electron transport in this temperature range is determined by quantum contributions to the conductivity from weak localization and electron–electron interaction. It is established that the reduction of the width of wires does not change the superconducting transition temperature but completely suppresses the topological Berezinskii–Kosterlitz–Thouless transition. It is found that the threshold magnetic field increases with a decrease in the width of wires.     

The evolution of the molecular relaxation parameters described by the Cole–Cole model at the isotropic-nematic phase transition*

This paper presents the dielectric properties of the isotropic liquid and nematic phase at the phase transition. One strong molecular relaxation is observed in both phases. It is interpreted as related to the relaxation around a short molecular axis, due to the fact that molecules possess a strong longitudinal dipole moment. In the isotropic liquid the relaxation is described by the Debye model, while after entering the nematic phase (at cooling) relaxation becomes described by the Cole–Cole model. The distribution parameter of the Cole–Cole model changes from 0.05 (10 degrees above the temperature of the Iso-N transition) to 0.09 (exactly at the phase transition Iso-N), and finally, it reaches 0.35 (10 degrees below the Iso-N transition). Additionally, we observe that ion contribution to the dielectric response is not influenced by the phase transition. All relaxation parameters are discussed within the context of the phase transition phenomena.