Dispersion in beam-plasma systems: III. Magnetic field induced pressure anisotropies

A treatment is given of linear waves in an homogeneous beam-plasma system in the presence of an external magnetic field. The pressure anisotropies generated by the magnetic field are also taken into account. The most general dispersion formula is then derived, using a low-temperature closure condition. The result is a coupling between all plasma waves, due to three causes: the external magnetic field, the pressure anisotropies and the beam velocities. Each of these phenomena can cause a coupling. Taken together, the coupling is intricate and complete. The only simplification comes from wave-vectors parallel to the zero-order magnetic field; then the waves are modified longitudinal and transverse waves.     

Dispersion in beam-plasma systems: II. External magnetic field

A treatment is given of linear waves in an homogeneous and infinite beam-plasma system in the presence of a uniform external magnetic field. A scalar pressure hypothesis is used to close the set of equations and enables the explicit derivation of the general dispersion formula. We emphasize the conclusion that even with scalar pressures the dispersion relation shows a general coupling between all waves present in the system. This coupling is due, in principal, more to the external magnetic field than to the presence of stream velocities, because part of that coupling disappears if and only if the external magnetic field vanishes or parallels the wavevector.     

Smooth massless limit of field theories. II

It is shown that the massless limit of any Fierz-Pauli field theory, in the external source approximation, is smooth under certain conditions on the sources. These conditions are no stronger than those that arise from the internal consistency of the massless field theory.     

The role of the polarization of a nonresonance external harmonic field in the dynamics of a nonautonomous spin oscillator

The results of an analysis of the action of a nonresonance external harmonic electromagnetic field on a quantum oscillator whose active medium is a two-level spin system, i.e. spin oscillator are briefly presented. The role of external field polarization in the dynamics of a nonautonomous spin oscillator is demonstrated. For the circular polarization of a nonresonance external field the shift of oscillation frequency of the spin oscillator is observed. For the linear polarization of a nonresonance external field the specific feature of spin oscillator synchronization at the third overtone of external field frequency is observed, along with an oscillation frequency shift.     

有偏压的光伏光折变晶体中的空间孤子

证明了有偏压的光伏光折变晶体中存在着明、暗稳态的空间孤子.它源于对外电场的非均匀空间屏蔽和光伏效应.与已报道的稳态光折变空间孤子相比,它具有不同的特性.当外电场为某一特定值时,用改变外电场的极性和旋转光的偏振方向可以实现明孤子与暗孤子的相互转换.当外电场足够强可以忽略光伏效应时,它类似于屏蔽孤子;当不存在外电场时,它类似于开路条件下的光伏孤子. 关键词：     

Random Ising model in the magnetic field at T = 0: I. The distribution of the effective fields

The integral equation for the distribution function of the effective fields in the random Ising model in the finite external field is solved exactly at zero temperature in the one-dimensional case for 1) dilute ferromagnet, 2) dilute antiferromagnet and 3) ±J model. The ground state characteristics of these systems are obtained. In particular the effective fields in the ±J model are shown to have a triangular distribution in the zero external field limit.     

两种外磁场形式对介质面次级电子倍增的抑制

利用自编1D3V PIC程序,数值研究了不同外加磁场方式对次级电子倍增抑制的物理过程,给出了次级电子数目、平均能量、密度、运动轨迹、渡越时间、介质表面静电场及沉积功率等物理量时空分布关系。模拟结果表明:不同方向外加磁场抑制次级电子倍增的机理有所不同。轴向外加磁场利用电子回旋运动干扰微波电场对电子加速过程,使其碰壁能量降低以达到抑制二次电子倍增的效果;横向外加磁场利用电子回旋漂移过程中,电子半个周期被推离介质表面（不发生次级电子倍增）,半个周期被推回介质表面（降低电子碰撞能量）的作用机理,达到抑制二次电子倍增的效果。讨论了横向磁场在回旋共振下,电子回旋同步加速导致回旋半径增大,电子能量持续增加的特殊过程。两种外加磁场方式都可以通过增加磁场达到进一步抑制次级电子倍增的目的。轴向外加磁场加载容易,但对磁场要求较高;横向外加磁场需要磁场较低,但加载较为困难。     

直流外电场诱导的MgI高里德堡态的混合

在直流外电场存在时,观察到MgI的经双光子禁戒跃迁3s~2 ~1S→3mp ~(1P)的多光子电离和倍频效应并解释为外电场引起的里德堡(Rydberg)态之间轨道角动量的混合.实验结果与理论解释一致.     

High intensity Compton scattering in a strong plane-wave field of general form

Photon emission by an electron embedded in a strong external field of general form is studied theoretically. The external field considered is a plane-wave electromagnetic field of any number of components, period and polarisation. Exact, Volkov solutions of the Dirac equation with the 4-potential of the general external field are obtained. The photon emission is considered in the usual perturbation theory using the Volkov solutions to represent the electron. An expression for the transition probability of this process is obtained after the usual spin and polarisation sums, trace calculation and phase space integration. The final transition probability in the general case contains a single sum over contributions from external field photons, an integration over one of the phase space components and the Fourier transforms of the Volkov phases. The validity of the general expression is established by considering specific external fields. Known specific analytic forms of the transition probability are obtained after substitution of the 4-potential for a circularly polarised and constant crossed external field. As an example usage of the general result for the transition probability, the case of two circularly polarised external fields separated by a phase difference is studied both analytically and numerically.     

External field in Landau theory of the weakly-first-order phase transition. Effect of uniaxial pressure on the orientational ordering in solid C70

The effect of the external conjugate field on a weakly discontinuous first-order phase transition is analyzed within Landau theory. The third-degree term in the Ginzburg-Landau expansion is shown to preserve the phase transition for some external fields, in contrast with the second-order case. The free-energy expansion is shown to correspond to a second-order phase transition under the influence of an “effective” external field that depends on both the temperature and the real field. The case of the orientational phase transition in solid C₇₀ is considered, and the transition thermoelastic phenomena caused by the coupling of order parameter with elastic strain are analyzed. It is shown that the uniaxial mechanical pressure along the direction of the 3-fold axis appears to be an external conjugate field for orientational ordering in crystalline C₇₀. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 8, 594–599 (25 April 1996) Published in English in the original Russian journal. Edited by Steve Torstveit.     

有限磁场中等离子体圆柱波导的传播特性

分析了有耗介质中等离子体圆柱波导在有限外加磁场中的传播特性.重点讨论了波导传播常数随等离子体参数、介质参数和外加磁场的变化.分析结果表明，有限强磁场中的等离子体波导的传播特性比无外磁场或外加磁场为无穷大时具有更强的控制能力. 关键词：     

On linear and non-linear hydromagnetic fluid motion generated by oscillating solid boundaries. Part I

In the present paper we start an investigation of the generation of second order vorticity (streaming) in an electric conducting, viscous and compressible fluid embedded in an external magnetic field. The equations used are those pertaining to the one-fluid model. First, fairly general equations for the generation of fluid vorticity as well as magnetic vorticity are derived. By using the method of successive approximations, the systems of equations of first and second order are developed. By the use of dimensional analysis the importance in the vorticity generation of the different generating terms is briefly investigated. Next the linear equations for two-dimensional problems are solved in the case of fluid motion above a flexible plate, vibrating in an external magnetic field.     

外电场下二氧化硫的分子结构及其特性

以6-311++g(3d, p)为基组, 采用B3P86方法研究了不同外电场(-0.04-0.04 a.u.)对SO₂分子基态的几何参数、电荷分布、能量、电偶极距、最高占据轨道(HOMO)能级、最低占据轨道(LUMO)能级及能隙的影响, 在优化构型的基础上, 采用含时密度泛函(TD-B3P86)方法研究了SO₂分子在外电场作用下前9个激发态的激发能、跃迁波长和振子强度. 研究表明: SO₂的几何参数与电场强度大小及方向均有明显的依赖关系. 电场由-0.04 a.u. 变化至0.04 a.u.时, 体系的总能量先增加后减小; 偶极矩先减小后增加; HOMO能级一直减小; LUMO能级先增加后减小; 能隙先增加后减小. 激发态的激发能、跃迁波长和振子强度与电场关联均较为复杂, 说明SO₂的激发特性易受外电场影响.     

Polarization of vacuum of quantum fields in the Aaronov-Bohm external field. II

A spinor field interacting with the Aaronov-Bohm external field is examined. Analytical expressions for the vacuum average components of the energy-momentum tensor are derived. Dependences of the components of energymomentum tensor of the spinor field in the vacuum state on the distance and field strength are investigated. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 3–8, April, 2006.     

QUANTUM FIELD THEORY IN EXTERNAL SOURCE:COHERENT STATE AND EIGENSTATES OF FIELDS

The real scalar field and the spinor field with external sources present are studied. The relationship between external sources and coherent states is given. In the case of real scalar field the eigenstates of field and its canonically conjugate field are derived in terms of coherent state and functional integration techniques. For a fermion field, it is demonstrated that Schwinger's external sources technique can lead to the spinor coherent states, with which we can also derive the eigenstates of fie3d operators and their conjugate field operators.The Yang-Feldman equation with the Grassmann sources is also obtained.     

Field-induced self-assembly: does size matter?

ABSTRACT

Simulated external electric fields are applied to polarisable species containing either a monodisperse of bidisperse distribution of polarisabilities. The magnitude of the external field and the polarisabilities are systematically varied. The application of an external field (of sufficient magnitude) is found to induce chain formation (as expected). The monodisperse systems are found to ‘self-assemble’ with larger induced dipole moments effectively clustering in chains as a result of significant dipole-induced dipole effects. The distribution of the chain lengths is characterised as a function of the applied field and the atom polarisability. For the bidisperse systems, the external field induces chain formation and a partial segregation, in which the more polarisable species preferentially form chains. The chain lengths are again determined as a function of field strength and the atom polarisabilities. Scaling behaviour is analysed.     

外加磁场对射频磁控溅射制备铝掺杂氧化锌薄膜影响的研究

利用射频磁控溅射法制备了铝掺杂氧化锌(AZO)透明导电薄膜,在传统的磁控溅射系统中引入外加磁场,研究了外加磁场对AZO薄膜沉积速率、形貌结构及光电特性的影响.研究结果表明,外加磁场后薄膜的沉积速率从不加磁场的13.04 nm/min提高到了19.93 nm/min;外加磁场后薄膜表面平整致密、颗粒大小均匀,结晶质量较高,而不加磁场薄膜表面形貌呈蠕虫状,薄膜质量较差.溅射时间为90 min时,外加磁场前后AZO薄膜方阻分别为30.74?/和12.88?/.外加磁场对薄膜可见光透过率影响不大,但使薄膜的吸收边蓝移现象更明显.运用ansys软件对磁控溅射二维磁场分布模拟后发现,外加磁场提高了靶上方横向磁场强度,改善了磁场分布的均匀性,加强了磁场对电子的磁控作用,提高了靶电流,是AZO薄膜的溅射速率、光电性能和形貌结构得到提高和优化的原因.     

The quantum relativistic two-body problem in time-dependent external potentials

A two-body system with scalar constituents of finite masses is described by a pair of coupled Klein-Gordon equations. The modification required for preserving compatibility in the presence of an external field is nontrivial but can be exactly carried out beyond the static case when the external potential admits a suitable invariance. The conditions ensuring this property are exhibited assuming that the external field is either electromagnetic or a pure spin-two tensor (like a weak gravitational field). Special attention is devoted to plane waves. A suitable superposition of linearly polarized waves permits to apply this method when the field is electromagnetic. Another example is given by an external spin-two field obeying the propagation equation with a mass term.