共查询到20条相似文献,搜索用时 31 毫秒
1.
Ciprian Dariescu Marina-Aura Dariescu 《International Journal of Theoretical Physics》2008,47(10):2523-2532
The aim of the present work is to revisit the theory of the dipole radiation, within an SO(3,1)-gauge invariant formulation, by solving the Maxwell equations. Thus, we obtain the two interconnected components, A
B
, B=1,2, of the vector potential A, in terms of Hankel and Legendre polynomials. Finally, for the pure dipole-like radiation, the observables, regarded as phasors, the Umov–Poynting vector components and the well-known Larmor
formula for the effective radiated power are explicitly derived. 相似文献
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Bengt Eliasson 《Journal of computational physics》2003,190(2):501-522
The two-dimensional Vlasov–Maxwell system, for a plasma with mobile, magnetised electrons and ions, is investigated numerically. A previously developed method for solving the two-dimensional electrostatic Vlasov equation, Fourier transformed in velocity space, for mobile electrons and with ions fixed in space, is generalised to the fully electromagnetic, two-dimensional Vlasov–Maxwell system for mobile electrons and ions. Special attention is paid to the conservation of the divergences of the electric and magnetic fields in the Maxwell equations. The Maxwell equations are rewritten, by means of the Lorentz potentials, in a form which conserves these divergences. Linear phenomena are investigated numerically and compared with theory and with previous numerical results. 相似文献
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In this paper, we propose and analyze a method derived from a Nitsche approach for handling boundary conditions in the Maxwell equations. Several years ago, the Nitsche method was introduced to impose weakly essential boundary conditions in the scalar Laplace operator. Then, it has been worked out more generally and transferred to continuity conditions. We propose here an extension to vector div–curl problems. This allows us to solve the Maxwell equations, particularly in domains with reentrant corners, where the solution can be singular. We formulate the method for both the electric and magnetic fields and report some numerical experiments. 相似文献
6.
Joshua N. Goldberg 《Journal of Geometry and Physics》1992,8(1-4):163-171
The canonical formalism for a self-dual Maxwell field on a null plane is reviewed. After solution of the second class constraints, the transition to the quantum theory is carried out using a representation in which the self-dual Maxwell field is diagonal. The Gauss law constraint allows us to consider the physical state vectors to be holomorphic functionals of one complex function. Application of reality conditions allows us to define an inner product such that the Hermitean adjoint operators are identified with the classical complex conjugate operators. In going over to the Fourier expansion of the operators, we find that the inner product is formally convergent for positive frequency functionals and formally divergent for the negative frequency functionals. Following similar results of Ashtekar, Rovelli, and Smolin, negative frequency states are functional distributions identified with the helicity opposite to that of the positive frequency states. 相似文献
7.
In this paper we analyze the Cauchy problem for the Einstein–Maxwell equation in the case of non-characteristic initial hypersurface. To find the correct notions of characteristic and Cauchy data we introduce a complex, which we call the Einstein–Maxwell complex. Then the Cauchy problem acquires correctness in terms of an associated spectral sequence. We define a Cauchy data in such way that they allow us to reconstruct a cohomologously unique formal solution. 相似文献
8.
Unity‐Order Nonlinear Optical Index Change in Epsilon‐Near‐Zero Composite Materials of Gain Media and Metal Nanoparticles
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Kwang‐Hyon Kim 《Annalen der Physik》2018,530(4)
This work reports giant optical nonlinearity of active gain composites containing metal nanoparticles. In the epsilon‐near‐zero regime, the effective index of the composite strongly depends on the magnitude of host material's saturable gain and one can obtain unity‐order nonlinear optical index change for the pump with gain saturation intensity. For pump intensity of about 100 kW/cm2, the nonlinear refractive index (the refractive index change per unit pump intensity) reaches 10?5 cm2/W, which is 6–8 orders‐of‐magnitude larger than the records recently obtained in epsilon‐near‐zero bulk materials. If the gain value of the host medium is slightly larger than a critical value, such large optical nonlinearity can be obtained without loss or even accompanying with amplification. The proposed materials also have the advantage of wide tunability of operating wavelength range from visible to infrared by changing the gain value of the host and the shape parameters and filling factors of metal nanoparticles. 相似文献
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基于经典电动力学理论,从麦克斯韦方程组和麦克斯韦张量出发,推导出无工质微波推力器的推力计算方程. 应用有限元分析软件,计算了特定谐振模式下的特定圆台谐振腔在不同功率条件下的电磁场分布;根据推导出的理论计算公式,计算了不同功率条件下推力器的总推力. 计算结果表明:推力与功率成正比,而且磁场力决定着总推力的大小;圆台谐振腔消耗20–200 W电磁波功率时所产生的推力在20–250 mN范围内.
关键词:
电磁波
麦克斯韦张量 相似文献
11.
熵的概念来自物理学研究,但是它的应用早已超过物理学的范畴,对许多自然科学领域产生了重要的影响,本文研究生命现象中的熵,期望对丰富熵的内涵从而理解生命过程能有所裨益。 相似文献
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We show that the excitation threshold for the on-set of superradiance in the Λ-system depends on the initial state of coherence between the atomic lower levels. Furthermore, we find the characteristics of the superradiant radiation as function of the degree of excitation, the atomic relaxation times, the incoming seed-field area and the local field correction term. 相似文献
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We show that the rate of convergence towards the self-similar solution of certain linearized versions of the fast diffusion
equation can be related to the number of moments of the initial datum that are equal to the moments of the self-similar solution
at a fixed time. As a consequence, we find an improved rate of convergence to self-similarity in terms of a Fourier based
distance between two solutions. The results are based on the asymptotic equivalence of a collisional kinetic model of Boltzmann
type with a linear Fokker-Planck equation with nonconstant coefficients, and make use of methods first applied to the reckoning
of the rate of convergence towards equilibrium for the spatially homogeneous Boltzmann equation for Maxwell molecules. 相似文献
14.
The interaction between bulk and dynamic domain wall in the presence of a linear/non-linear electromagnetism make energy density, tension and pressure on the wall all variables, depending on the wall position. In Lee et al. (2009) [1] this fact seems to be ignored. 相似文献
15.
The Lagrangian and Hamiltonian formulations of electromagnetism are reviewed and the Maxwell equations are obtained from the Hamiltonian for a system of many electric charges. It is shown that three of the equations which were obtained from the Hamiltonian, namely the Lorentz force law and two Maxwell equations, can be obtained as well from a set of postulated Poisson brackets. It is shown how the results derived from these brackets can be used to reconstruct the original Lagrangian for the theory aided by some reasoning based on physical concepts. 相似文献
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Gas mixtures can reach the Maxwell's specter shape in case of low‐ionized mono‐atomic mixtures in the weak electric field. The parameters pertaining to the Maxwell spectrum of free electrons' gas straightforwardly settle on the insulating characteristics of the examined gas mixture at the fundamental level. In this paper, a condition for breakdown has been accomplished taking as a starting point the ionization coefficients derived accordingly, as well as the conditions for breakdown in keeping with the Townsend mechanism. The dc breakdown voltage value of noble gases mixture has been measured in the experimental part of the paper. The hypothesis that the free‐electron gas spectrum is unique in the noble gas mixture and is of Maxwell's type has been verified. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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W. B. Bonnor 《General Relativity and Gravitation》2006,38(6):1063-1067
I consider stationary axially symmetric solutions of the Einstein–Maxwell equations. These show that, in general, time-independent electric and magnetic fields acting together cause rotational effects in the spacetime. An electric charge placed on the axis of a magnetic dipole induces a region of closed timelike curves. 相似文献
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In the present study, using the Fourier analysis method and considering the Bianchi-type I spacetime, we investigate the dynamics of photon in the torsion gravity, and show that the free-space Maxwell equations give the same results. Furthermore, we also discuss the harmonic oscillator behavior of the solutions. 相似文献
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Recently, a simple solution of the vacuum Einstein–Maxwell field equations was given describing a plane electromagnetic shock wave sharing its wave front with a plane gravitational impulse wave. We present here an exact solution of the vacuum Einstein–Maxwell field equations describing the head-on collision of such a wave with a plane gravitational impulse wave. The solution has the Penrose–Khan solution and a solution obtained by Griffiths as separate limiting cases. 相似文献