反Tavis-Cummings模型中纠缠原子布居的时间演化

利用反Tavis-Cummings模型研究了初始处于纠缠态的两个全同二能级原子与单模二项式光场的相互作用.在强经典驱动和大失谐的情况下,原子与光场的相互作用可以转化为有效的Tavis-Cummings模型和反Tavis-Cummings模型.主要是研究了反Tavis-Cummings模型下纠缠原子布居的时间演化.结果表明,纠缠原子布居的时间演化和光场的强度以及光场的初始状态有关.     

高温超导体在对称和不对称外磁场中的悬浮力计算

在理想无限长直高温超导 -永磁导轨系统中 ,由于导轨磁场分布的不均匀性 ,超导体运动过程中所处外磁场有对称及不对称分布两种情况。原 Prigozhin模型假设超导体各向同性 ,但 YBCO高温超导体存在明显的各向异性。改进Prigozhin模型增加了原模型中的约束条件 ,考虑了这种各向异性。在对称外磁场中改进 Prigozhin模型的计算结果和原Prizhogin模型相同 ,因为原模型在对称外磁场中自然满足超导体各向异性。在不对称外磁场中计算结果和实验结果吻合较好 ,而原模型计算结果和实验结果差别较大。所以改进模型考虑了各向异性 ,适用于对称和不对称外磁场 ,能得到更准确的计算结果。     

The Thirring interaction in the two-dimensional axial–current–pseudoscalar derivative coupling model

We reexamine the two-dimensional model of massive fermions interacting with a massless pseudoscalar field via axial-current derivative coupling. The hidden Thirring interaction in the axial-derivative coupling model is exhibited compactly by performing a canonical field transformation on the Bose field algebra and the model is mapped into the Thirring model with an additional vector–current–scalar derivative interaction (Schroer–Thirring model). The Fermi field operator is rewritten in terms of the Mandelstam soliton operator coupled to a free massless scalar field. The charge sectors of the axial-derivative model are mapped into the charge sectors of the massive Thirring model. The complete bosonized version of the model is presented. The bosonized composite operators of the quantum Hamiltonian are obtained as the leading operators in the Wilson short distance expansions.     

外加静电场的聚焦激光脉冲真空加速电子方案

采用五阶修正的聚焦激光光场方程模拟研究了由Singh提出的在电子和激光脉冲作用尾部阶段施加外场的加速方案,将Singh方案中采用的外加磁场改成了外加电场,并且考虑了光束的纵向电场和光束衍射效应.模拟结果显示,电子可以从加速相位阶段被外场导入下一个加速相位阶段而不进入减速相位阶段,因此电子能获得比不加外场方案更高的净能增益. 关键词： 强激光 激光加速     

阵列波导光栅解复用器的标量传输理论及其简化模型

以波导本征模式场作输入光场,阐述了AWG中实际光场的传输数学模型,对输入场作高斯近似,阐述了光场传输的简化模型.通过简化模型与实际情况的比较,肯定了高斯近似简化模型在一定情况下的合理性.对于给定串扰要求,利用高斯近似模型可以决定最外层阵列波导坐标与衍射场光束束腰的比值,对实际器件设计来说有一定意义,但高斯简化模型在一定情况会引入较大误差,精确定量模拟AWG应采用实际光场标量传输模型.     

外加交变电场对光折变基频空间电荷场瞬态特性的影响

利用“跳跃模型”讨论外加交变电场（包括正弦和方波电场）对光折变基频空间电荷建立的影响,给出了空间电荷场基频分量随时间、外加交流电场振幅频率等变化的通解表达式。发现基频空间电荷场虎部和实部的振荡频率分别是外加交流电场振荡频率的两倍和一倍。当外加交变电场频率较大时光折变光栅是相移型的。这和基于“带导模型”给出的数值结果相符。     

囚禁粒子在热库型驻波场中的量子相干特性

研究囚禁粒子与热库型(热辐射)驻波场的相互作用,通过外加驱动场,分析置于热库型驻波场中的囚禁粒子约化密度算符非对角元的时间演化,得到囚禁粒子在热库型驻波场中的相干特性.当外加驱动场的时间演化满足一定条件时,可保持囚禁粒子的相干性.     

Quantum Field Formalism for the Electromagnetic Interaction of Composite Particles in a Nonrelativistic Gauge Model

A classical nonrelativistic U(1) × U(1) gauge field model for the electromagnetic interaction of composite particles is proposed and the quantum formalism is constructed. This gauge model containing a Chern–Simons U(1) field and the electromagnetic U(1) field can be coupled to both a bosonic or a fermionic matter field. We explicitly consider the second case, a composite fermion system in the presence of an electromagnetic field, and we carry out the canonical quantization by the Dirac method. The path integral approach is developed and the Feynman rules are established. A simplified model is considered. As an alternative path integral method, the BRST formalism for this gauge model is also treated.     

Tavis-Cummings模型中原子间偶极相互作用对场熵演化特性的影响

研究了单模辐射场与耦合双原子相互作用系统场熵的演化特性,讨论了原子间偶极相互作用对场熵演化特性的影响.研究结果表明,当原子间偶极偶极相互作用不太强时,场熵的时间演化行为与单光子JC模型相似;当原子间偶极偶极相互作用足够强时,场熵的时间演化行为与双光子JC模型相似 关键词： 单模辐射场 耦合双原子 场熵演化     

Multi-pole dark energy

A scalar field with a pole in its kinetic term is often used to study cosmological inflation; it can also play the role of dark energy, which is called the pole dark energy model. We propose a generalized model where the scalar field may have two or even multiple poles in the kinetic term, and we call it the multi-pole dark energy. We find that the poles can place some restrictions on the values of the original scalar field with a non-canonical kinetic term. After the transformation to the canonical form, we get a flat potential for the transformed scalar field even if the original field has a steep one. The late-time evolution of the universe is obtained explicitly for the two pole model, while dynamical analysis is performed for the multiple pole model. We find that it does have a stable attractor solution, which corresponds to the universe dominated by the potential of the scalar field.     

An anisotropic magnetized viscous fluid cosmological model in general relativity

We investigate the behavior of a magnetic field in a viscous fluid cosmological model where the free gravitational field is of Petrov type D and the coefficient of shear viscosity is proportional to the rate of expansion in the model. Also discussed are the behavior of the model when the magnetic field tends to zero and some other physical properties.     

Modeling of Focused Acoustic Field of a Concave Multi-annular Phased Array Using Spheroidal Beam Equation

A theoretical model of focused acoustic field for a multi-annular phased array on concave spherical surface is proposed.In this model,the source boundary conditions of the spheroidal beam equation(SBE) for multi-annular phased elements are studied.Acoustic field calculated by the dynamic focusing model of SBE is compared with numerical results of the O'Neil and Khokhlov-Zabolotskaya-Kuznetsov(KZK) model,respectively.Axial dynamic focusing and the harmonic effects are presented.The results demonstrate that the dynamic focusing model of SBE is good valid for a concave multi-annular phased array with a large aperture angle in the linear or nonlinear field.     

用于制作光纤光栅的Talbot干涉仪的分析与建模

对用于制作光纤光栅的Talbot干涉仪进行了分析.当考虑准分子激光器的空间相干性和时间相干性时,几何光学中的光线法并不能给出Talbot干涉仪干涉场的真实强度分布情况,而通过光的电磁理论,则可以提供对干涉场的详细描述.基于电磁理论,建立了一个Talbot干涉仪干涉场计算模型,并首次将Talbot干涉仪的反射镜转角作为模型计算参数加以考虑,随后进行了一系列的计算.计算结果显示了干涉场的分布,同时表明空间相干性对Talbot干涉仪的近场干涉和远场干涉影响都很大,其中远场干涉对空间相干性的要求更严格,且对于远场干涉,反射镜转角的影响不可忽视.     

高温超导块脉冲磁化实验研究与理论模拟

通过磁化熔融织构超导块材俘获远高于常规永磁体的磁场,可以用于磁分离、制作电机等,如何磁化是其中关键技术问题之一.脉冲磁化目前被认为是最有前景的超导块材的磁化方式之一.我们通过霍尔元件测量脉冲磁化过程中超导块材表面磁场的变化,并运用磁通蠕动流动模型和幂指数模型分别描述脉冲磁化过程,理论与实验相比较,结果表明磁通蠕动流动模型能够更好地描述脉冲磁化,热量的产生、局域的温升直接关系到俘获磁场的大小,通过合理的铁轭设置和利用多脉冲磁化技术有助于提高最终的磁化效果.     

Entropy evolution of field interacting with V-type three-level atom via intensity-dependent coupling

The entropy evolution property of a single-mode light field interacting with V-type three-level atoms via intensity-dependent coupling has been studied, and the influence of detuning of light field and initial photon number on entropy evolution of field is discussed. It is found that if detuning is relatively small and initial light field weak, the time-evolution behavior of field entropy is similar to that of Jaynes–Cummings model with single-photon transition, but in case of sufficient large detuning and strong initial light field, the time-evolution behavior of field entropy is similar to the periodic one of field entropy of Jaynes–Cummings model with two-photon transition.     

Scalars coupled to fermions in 0+1 dimensions

A model of a Bose field coupled to a Fermi field is presented which shows interesting features that might arise in higher dimensional field theories. The model is partly analytically soluble. The remaining, part is investigated using a computer solution and some analytic approximations.     

Phase diagram and critical properties of the asymmetric Mattis model

We extend the well-known Mattis model to the case of asymmetric bond distributions. Although the partition function is identical with that of the pure ferromagnetic Ising model (FIM) when the external field is absent, the response to the external field is nontrivial even at zero field. There are some exact relations between the present model and the FIM in the correlation functions, from which the phase diagram and critical exponents can be determined. Multicritical behavior and some other interesting phenomena typical for a random system are demonstrated by this model.     

Mimicking the LCDM model with stealths

We present a new cosmological model that mimics the Lambda Cold Dark Matter by using a stealth field. This kind of field is characterized as not coupling directly to gravity; however, it is connected to the underlying matter content of the universe model. As is well known, stealth fields do not back-react on the space-time; however, their mimicry skills show how this field and its self-interaction potential determines the cosmic evolution. We show the study of the simplest model that can be developed with the stealth field.     

近场条件下的扫描成象方程

本文考察了传统(远场)扫描成象方程,发现它们在近场条件下不成立.通过引入一个探测效率因子,我们建立了对近场条件与远场条件都成立的统一的扫描成象方程.同时我们还分别采用标量Kirchhof模型和矢量Bethe-Bouwkamp模型对探测效率因子进行了计算,计算结果表明它们都与探针孔径成正比,但后者的分布要比前者宽约6倍.     

Reciprocity principle-based model for shielding effectiveness prediction of a rectangular cavity with a covered aperture

According to the reciprocity principle, we propose an efficient model to compute the shielding effectiveness of a rectangular cavity with apertures covered by conductive sheet against an external incident electromagnetic wave. This problem is converted into another problem of solving the electromagnetic field leakage from the cavity when the cavity is excited by an electric dipole placed within it. By the combination of the unperturbed cavity field and the transfer impedance of the sheet, the tangential electric field distribution on the outer surface of the sheet is obtained. Then, the field distribution is regarded as an equivalent surface magnetic current source responsible for the leakage field. The validation of this model is verified by a comparison with the circuital model and the full-wave simulations. This time-saving model can deal with arbitrary aperture shape, various wave propagation and polarization directions, and the near-field effect.