首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 93 毫秒
1.
In this paper the GYARMATI 's governing principle of dissipative processes is applied to a continuous material system with reversible polarization, magnetization and irreversible electric conduction phenomena due to finite electrical conductivity. After the general treatment of governing principle and MAXWELL 's field equations the forms of the balances of internal energy and entropy are determined. The main new results are the recovering of the electromagnetic field equations from the actual form of the governing principle and the verification of gauge invariance property of it.  相似文献   

2.
Analogs for Maxwell’s equations with fractional derivatives are obtained using the concepts of an effective current and the velocity of a charged particle in a medium. The calibration invariance is considered and a diffusion-wave equation is found and analyzed for scalar and vector potentials. It is shown that the stochastic nature of charged particle motion in a medium influences the dynamics of an electromagnetic field.  相似文献   

3.
We fulfill the detailed analysis of coupling the charged bosonic higher-spin fields to external constant electromagnetic field in first order in external field strength. Cubic interaction vertex of arbitrary massive and massless bosonic higher-spin fields with external field is found. Construction is based on deformation of free Lagrangian and free gauge transformations by terms linear in electromagnetic field strength. In massive case a formulation with Stueckelberg fields is used. We begin with the most general form of deformations for Lagrangian and gauge transformations, admissible by Lorentz covariance and gauge invariance and containing some number of arbitrary coefficients, and require the gauge invariance of the deformed theory in first order in strength. It yields the equations for the coefficients which are exactly solved. As a result, the complete interacting Lagrangian of arbitrary bosonic higher-spin fields with constant electromagnetic field in first order in electromagnetic strength is obtained. Causality of massive spin-2 and spin-3 fields propagation in the corresponding electromagnetic background is proved.  相似文献   

4.
Equations of motion for an electrically charged string with a current in an external electromagnetic field with regard to the first correction due to the self-action are derived. It is shown that the reparameterization invariance of the free action of the string imposes constraints on the possible form of the current. The effective equations of motion are obtained for an absolutely elastic charged string in the form of a ring (circle). Equations for the external electromagnetic fields that admit stationary states of such a ring are derived. Solutions to the effective equations of motion of an absolutely elastic charged ring in the absence of external fields as well as in an external uniform magnetic field are obtained. In the latter case, the frequency at which one can observe radiation emitted by the ring is evaluated. A model of an absolutely nonstretchable charged string with a current is proposed. The effective equations of motion are derived within this model, and a class of solutions to these equations is found.  相似文献   

5.
Equations of motion and energy-momentum tensors are obtained for a dissipative medium sustaining electromagnetic polarizations using a Lagrangian formalism. A previous work has been simplified by reducing the number of independent vector fields interacting with the sink modes. A relativistic formalism of the same is also suggested.  相似文献   

6.
A gauge-invariant Rarita-Schwinger theory of a massive spin-3/2 particle interacting with external electromagnetic, gravitational and dilaton fields is obtained by Kaluza-Klein reduction of a massless Rarita-Schwinger theory with graviational interaction. Fermionic gauge invariance serves to determine the background equations of motion. The couplings with external fields obtained by the Kaluza-Klein reduction are shown to lead to the absence of the classical Velo-Zwanziger problem and on quantizing using Dirac's procedure, the field anticommutators are found to be positive definite.  相似文献   

7.
The most complete nonrelativistic theory of dynamic fluctuation electromagnetic interactions between particles of various types (charges, dipoles, neutral atoms, nanoparticles) and the surfaces (flat or cylindrical) of a polarizable medium (the boundary of a solid) is reported for the first time. The theory is based on the application of the Maxwell equations and the formalism of fluctuation-dissipation relations. For a flat surface, effects of spatial dispersion are also taken into account. Papers of other authors are analyzed critically. The results of recent investigations in which dissipative fluctuational forces could be observed are considered briefly.  相似文献   

8.
The excitation and propagation of cylindrical electromagnetic waves in a nonlinear nondispersive medium are analyzed. It is assumed that the medium lacks a center of symmetry and that the dependence of the electric displacement on the electric field can be approximated by an exponential function. For this case, a method for integrating the system of the Maxwell equations is proposed. Exact solutions to a set of nonlinear electromagnetic field equations are obtained by this method. It is shown that nonlinear effects described by these solutions can become apparent under experimental conditions.  相似文献   

9.
傅景礼  陈本永  谢凤萍 《中国物理 B》2008,17(12):4354-4360
This paper focuses on studying Noether symmetries and conservation laws of the discrete mechanico-electricM systems with the nonconservative and the dissipative forces. Based on the invariance of discrete Hamilton action of the systems under the infinitesimal transformation with respect to the generalized coordinates, the generalized electrical quantities and time, it presents the discrete analogue of variational principle, the discrete analogue of Lagrange-Maxwell equations, the discrete analogue of Noether theorems for Lagrange Maxwell and Lagrange mechanico-electrical systems. Also, the discrete Noether operator identity and the discrete Noether-type conservation laws are obtained for these systems. An actual example is given to illustrate these results.  相似文献   

10.
We present a study of the effect of finite relaxation rates of media on the stability of dissipative solitons in single-mode fibers with longitudinal Bragg grating and nonlinear gain created by one active medium, and absorption created by one passive medium that gives the stability to solitons. The system of Maxwell–Bloch equations for this model is introduced. Based on the analysis of this system, it is shown that dissipative Bragg solitons are stable in the case when the active medium has greater relaxation rates than the passive medium.  相似文献   

11.
A technique for describing dissipative quantum systems that utilizes a fundamental Hamiltonian, which is composed of intrinsic operators of the system, is presented. The specific system considered is a capacitor (or free particle) that is coupled to a resistor (or dissipative medium). The microscopic mechanisms that lead to dissipation are represented by the standard Hamiltonian. Now dissipation is really a collective phenomenon of entities that comprise a macroscopic or mesoscopic object. Hence operators that describe the collective features of the dissipative medium are utilized to construct the Hamiltonian that represents the coupled resistor and capacitor. Quantization of the spatial gauge function is introduced. The magnetic energy part of the coupled Hamiltonian is written in terms of that quantized gauge function and the current density of the dissipative medium. A detailed derivation of the kinetic equation that represents the capacitor or free particle is presented. The partial spectral densities and functions related to spectral densities, which enter the kinetic equations as coefficients of commutators, are evaluated. Explicit expressions for the nonMarkoffian contribution in terms of products of spectral densities and related functions are given. The influence of all two-time correlation functions are considered. Also stated is a remainder term that is a product of partial spectral densities and which is due to higher order terms in the correlation density matrix. The Markoffian part of the kinetic equation is compared with the Master equation that is obtained using the standard generator in the axiomatic approach. A detailed derivation of the Master equation that represents the dissipative medium is also presented. The dynamical equation for the resistor depends on the spatial wavevector, and the influence of the free particle on the diagonal elements (in wavevector space) is stated.  相似文献   

12.
Gauge invariance of the electromagnetic vertex of bound state annihilation matrix elements is demonstrated by using Ward identities and Dyson equations. This problem is also discussed when potential assumption of the B-S kernel and the approximation of neglecting photon lines hung on closed fermion loop are considered. Under these two approximations, the simplified matrix element expression is given, which preserves the gauge invariance. The reliability of using zero point wave function approximation in cc, bb system is also discussed.  相似文献   

13.
We consider a conformal invariant formulation of quantum electrodynamics. Conformal invariance is achieved with a specific mathematical construction based on the indecomposable representations of the conformal group associated with the electromagnetic potential and current. As a corollary of this construction modified expressions for the 3-point Green functions are obtained which both contain transverse parts. They make it possible to formulate a conformal invariant skeleton perturbation theory. It is also shown that the Euclidean Maxwell equations in conformal electrodynamics are manifestations of its kinematical structure: in the case of the 3-point Green functions these equations follow (up to constants) from the conformal invariance while in the case of higher Green functions they are equivalent to the equality of the kernels of the partial wave expansions. This is the manifestation of the mathematical fact of a (partial) equivalence of the representations associated with the potential, current and the field tensor.  相似文献   

14.
耗散旋波介质中的色散关系   总被引:2,自引:2,他引:0  
崔元顺 《大学物理》2003,22(12):12-14
应用Maxwell经典电磁理论,结合旋波介质的本构关系,研究耗散旋波介质中光波的色散关系.结果表明,色散关系与介质电导率、旋波因子等因素密切相关.  相似文献   

15.
非完整系统的形式不变性与Hojman守恒量   总被引:5,自引:0,他引:5       下载免费PDF全文
罗绍凯  郭永新  梅凤翔 《物理学报》2004,53(8):2413-2418
研究非完整力学系统的形式不变性导致的非Noether守恒量——Hojman守恒量. 在时间不变的特殊无限小变换下,给出非完整系统形式不变性的确定方程、约束限制方程和附加限制方程,提出并定义弱(强)形式不变性的概念. 研究特殊形式不变性导致特殊Lie对称性的条件,由系统的特殊形式不变性,得到相应完整系统的Hojman守恒量以及非完整系统的弱Hojman守恒量和强Hojman守恒量. 给出两个经典例子说明结果的应用. 关键词: 分析力学 非完整系统 形式不变性 非Noether守恒量 Hojman守恒量  相似文献   

16.
汪会波  罗孝阳  董建峰 《物理学报》2015,64(15):154102-154102
基于麦克斯韦方程组在不同坐标系下具有形式不变性以及变换光学理论, 通过设计材料的本构参数(介电常数和磁导率)来引导电磁波的传播, 提出了具有电磁透明和电磁聚集两种功能的新型电磁器件-椭圆形透明聚集器的设计方法. 电磁波透明体不会阻挡电磁波的传播并且能够与斗篷内部进行交互; 电磁波聚集器是当电磁波入射到该装置上时, 电磁波能够被设计的装置按照要求集中到一个区域或者一个点, 实现电磁波能量的集中. 本文利用压缩变换和扩展变换推导出了这种电磁器件中各层的相对介电常数和相对磁导率的张量表达式, 并利用基于有限元算法的电磁仿真软件对该电磁器件进行了全波仿真验证, 得到了入射波从各个不同方向入射时磁场z 分量的分布图, 仿真结果证实了该设计方法和电磁参数的正确性. 最后还讨论了电磁器件存在损耗时的情况, 当损耗逐渐增大时, 器件的功能在一定程度上受到了削弱. 本文的设计方法为其他新型电磁器件的设计提供了一种新的思路.  相似文献   

17.
The behavior of a quasi-monochromatic nonlinear wave near a caustic is considered. Nonlinear ordinary differential equations for a dispersive dissipative medium with a cubic or quadratic nonlinearity are derived. For the latter medium, nonstationary equations describing it near the caustic are presented with allowance for the dissipative dispersive terms. These equations yield ordinary ones for quasi-monochromatic waves. The amplitude of the second harmonic is expressed in terms of the squared amplitude of the first harmonic. The amplitude of the second harmonic, as well as the solution as a whole, increases near the caustic.  相似文献   

18.
A canonical relativistic formulation is introduced to quantize electromagnetic field in the presence of a polarizable and magnetizable moving medium. The medium is modeled by a continuum of the second rank antisymmetric tensors in a phenomenological way. The covariant wave equation for the vector potential and the covariant constitutive equation of the medium are obtained as the Euler-Lagrange equations using the Lagrangian of the total system. A fourth rank tensor which couples the electromagnetic field and the medium is introduced. The susceptibility tensor of the medium is obtained in terms of this coupling tensor. The noise polarization tensor is calculated in terms of both the coupling tensor and the ladder operators of the tensors modeling the medium.  相似文献   

19.
王华英  赵中华  刘琳 《大学物理》2004,23(6):8-10,28
讨论了磁各向异性理想介质中平面电磁波的一般特性,继而推证了这种介质中平面波的对偶关系,导出了磁晶体中的“菲涅耳方程”,并利用此方程分析了这种理想介质中的平面波的结构、传播及其偏振特性.  相似文献   

20.
It is shown by a dissipative generalization of the dynamic gage theory of crystalline media that the symmetric part of the plastic distortion tensor of an elastoplastic medium is suppressed in the low-frequency limit due to the high energy of the elastic stresses present in the medium. Full displacements and plastic rotations are the only motions excited at low frequencies, so that a crystalline medium turns out to be equivalent to a Cosserat continuum. The equations of motion of this continuum are obtained as a low-frequency approximation of the complete equations of dynamic gage theory.Institute of Strength Physics and Materials Research. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 37–43, April, 1994.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号