Role of finite Larmor radius in chaotic regime of waves—particle interaction

The paper presents the discussion of the interaction of two electrostatic waves, propagating in a homogeneous magnetized plasma, with ions. The same case for two and three waves was already discussed in the paper of Misguich and Nakach [Phys. Rev. A, Vol. 44 (1991) 3869]. Contrary to their paper, we solve the dynamics not in the drift approximation, but in a full solution, using the Hamiltonian, which includes also a cyclotron motion of particles. We show that in a realistic regime, the full solution can cause stochastization of the dynamics in cases, when the drift approximation permits only regular dynamics. This work was supported by the Grant Agency of the Academy of Sciences of the Czech Republic, project No. A1043201.     

各向异性介质三维电磁响应模拟的Ho-GEBA算法

本文基于积分方程法研究并建立了一种模拟横向同性介质中任意各向异性异常 体三维电磁响应的高阶广义扩展Born近似(Ho-GEBA)算法. 首先利用逐次迭代技术给出积分方程的广义级数展开解, 为保证其收敛性, 引入一种各向异性条件下满足压缩映射的迭代算子. 然后利用异常体区域分解技术, 并结合扩展Born近似原理, 得到各向异性介质三维电磁响应的Ho-GEBA解. 为提高效率, 计算过程中采用并矢Green函数的解析表达式. 最后通过数值计算实例对比验证了本文算法的有效性. 关键词： 高阶广义扩展Born近似 积分方程 电磁模拟 解析Green函数     

A Study of Microwave Radiation Absorption in Ultrathin Conducting Films

Technical Physics - The interaction between microwave electromagnetic waves and conducting films with a nanometer thickness in the homogeneous region approximation and a structure consisting of...     

A transparent macroscopic sphere is cross-sectionally equivalent to a superposition of two quantum-like radial potentials

We consider two frameworks (i) the electromagnetic generalized Lorenz-Mie theory describing the interaction between an electromagnetic arbitrary shaped beam and a homogeneous, non-magnetic sphere, with an isotropic, linear, material and (ii) a quantum generalized Lorenz-Mie theory describing the interaction between a quantum eigen-arbitrary shaped beam and a quantum radial potential. For the time being, we restrict ourselves in this paper to elastic scattering cross-sections. We then demonstrate that a transparent macroscopic sphere in the first framework is equivalent to a superposition of two quantum-like radial potentials in the second framework. The restrictive meaning of “quantum-like” will be discussed when appropriate.     

Reflection of electromagnetic plane waves in a long-wavelength approximation from a multilayer system of anisotropic transparent films on non-absorbing isotropic medium

The reflection of s- and p-polarised electromagnetic plane waves from an N-layer system of anisotropic dielectric films upon transparent homogeneous substrate is investigated in the long-wavelength approximation. The analytical expressions are obtained for the amplitude reflection (transmission) coefficients, reflectances (transmittances), and ellipsometric angles of an anisotropic multilayer thin-film system. All analytical results are in agreement with the numerical solution of the reflection problem for anisotropic stratified medium. The possibilities of using obtained expressions for resolving the inverse problem for ultrathin anisotropic films upon isotropic substrates are discussed.     

Lattice Boltzmann model for three-dimensional decaying homogeneous isotropic turbulence

We implement a lattice Boltzmann method (LBM) for decaying homogeneous isotropic turbulence based on an analogous Galerkin filter and focus on the fundamental statistical isotropic property. This regularized method is constructed based on orthogonal Hermite polynomial space. For decaying homogeneous isotropic turbulence, this regularized method can simulate the isotropic property very well. Numerical studies demonstrate that the novel regularized LBM is a promising approximation of turbulent fluid flows, which paves the way for coupling various turbulent models with LBM.     

The Electromagnetic Analogue of Some Gravitational Perturbations in Cosmology

Recently attention has been drawn to the fact that perfect fluid tensor perturbations (with perturbed vorticity and acceleration vanishing) of isotropic cosmological models have a perturbed Weyl tensor with electric part satisfying a linear, homogeneous, third-order wave equation while the magnetic part satisfies a linear, homogeneous, second-order wave equation. We construct an analogous class of electromagnetic test fields in the isotropic cosmological models for which the electric vector satisfies a third-order, linear and homogeneous wave equation while the magnetic vector satisfies a second-order, linear and homogeneous wave equation. If the perfect fluid has an equation of state we give a simplified derivation of the authors' previous perturbation analysis describing gravitational waves carrying arbitrary information. We also present the analogous solutions of Maxwell's equations which contain electromagnetic waves conveying arbitrary information.     

Powerlike decreasing solutions of the Boltzmann equation for a Maxwell gas

We study the homogeneous, isotropic, nonlinear Boltzmann equation for a Maxwellian interaction. We show that solutions decreasing like inverse powers of the energy are physically acceptable both in the linearized and the quadratic problem. Because all moments may not exist, we introduce a generalized generating function and a finite differential system for generalized Sonine moments is derived. These new solutions may lead to small relaxation rates and justify in most cases the linear approximation.     

An improved proximity force approximation for electrostatics

A quite straightforward approximation for the electrostatic interaction between two perfectly conducting surfaces suggests itself when the distance between them is much smaller than the characteristic lengths associated with their shapes. Indeed, in the so called “proximity force approximation” the electrostatic force is evaluated by first dividing each surface into a set of small flat patches, and then adding up the forces due two opposite pairs, the contributions of which are approximated as due to pairs of parallel planes. This approximation has been widely and successfully applied in different contexts, ranging from nuclear physics to Casimir effect calculations. We present here an improvement on this approximation, based on a derivative expansion for the electrostatic energy contained between the surfaces. The results obtained could be useful for discussing the geometric dependence of the electrostatic force, and also as a convenient benchmark for numerical analyses of the tip–sample electrostatic interaction in atomic force microscopes.     

Acoustic and radar scattering from directional seas

The small-slope approximation is applied to predict acoustic and electromagnetic scattering from directional seas. Results are presented for the scatter of high-frequency fields from fetch-limited seas for which the wavenumber spectrum is isotropic at high wavenumbers but highly directional near the spectral peak. Monostatic backscatter is found to display an upwind-crosswind dependence for a broad range of scattering angles due solely to the directionality of the large-scale waves.     

Effects of long-range interaction on critical and multicritical behavior of compressible disordered systems

A field-theoretic approach is applied to describe behavior of weakly disordered, isotropic elastic compressible systems with long-range interactions directly in the three-dimensional space for various values of the long-range interaction parameter a. A renormalization-group procedure is applied separately for a > 2 and a ≤ 2 directly in the three-dimensional space. Renormalization-group equations are analyzed in the two-loop approximation, and critical and tricritical points are determined. It is shown that long-range effects are not important when a ≤ 2, whereas they play a key role in the opposite case of a > 2. Critical exponents characterizing the system are obtained for various values of the long-range interaction parameter. Behavior of homogeneous and disordered systems characterized by two fluctuating order parameters is also described.     

Fluctuation-electromagnetic interaction of a moving neutral particle with a condensed-medium surface: relativistic approach

A relativistic theory of the fluctuation-electromagnetic interaction of a moving small particle with a flat boundary of a homogeneous isotropic polarizable medium is presented for the first time with a maximum degree of completeness. The theory is based on the dipole approximation of fluctuation-electromagnetic theory. Fundamental relativistic expressions are derived for conservative and dissipative forces and heating power of a particle. These expressions reduce to earlier nonrelativistic results in particular cases. The results obtained in other approaches and experimental studies of fluctuation-electromagnetic interactions are critically analyzed.     

Stability of the accelerated expansion in nonlinear electrodynamics

This paper is devoted to the phase space analysis of an isotropic and homogeneous model of the universe by taking a noninteracting mixture of the electromagnetic and viscous radiating fluids whose viscous pressure satisfies a nonlinear version of the Israel–Stewart transport equation. We establish an autonomous system of equations by introducing normalized dimensionless variables. In order to analyze the stability of the system, we find corresponding critical points for different values of the parameters. We also evaluate the power-law scale factor whose behavior indicates different phases of the universe in this model. It is concluded that the bulk viscosity as well as electromagnetic field enhances the stability of the accelerated expansion of the isotropic and homogeneous model of the universe.     

Acoustic and radar scattering from directional seas

Abstract

The small-slope approximation is applied to predict acoustic and electromagnetic scattering from directional seas. Results are presented for the scatter of high-frequency fields from fetch-limited seas for which the wavenumber spectrum is isotropic at high wavenumbers but highly directional near the spectral peak. Monostatic backscatter is found to display an upwind-crosswind dependence for a broad range of scattering angles due solely to the directionality of the large-scale waves.     

Generation of stable bright pulse and the dark soliton interaction in nonlinear left-handed materials

In homogeneous and isotropic nonlinear left-handed materials (LHMs), using the split step Fourier transform method, we demonstrate that two dark electromagnetic solitons which are the solutions of coupled nonlinear Schrödinger equations (CNLS) move along a line toward each other, when the distance between them down to a certain value, the interaction of the two dark solitons can produce a stable bright electromagnetic pulse that behaves like a bright soliton. Although our mathematical analysis shows that the new generated stable bright pulse is not an exact solution of the CNLS, it can propagate steadily in the nonlinear LHMs. And this unusual phenomenon can also be observed in our numerical simulation results by another method.     

Irregular dielectric or permeable bodies in an external field

An integral equation is derived for the electrostatic potential ψ that arises when a uniform dielectric body of arbitrary shape is placed in an applied electrostatic field. By expansion of ψ in a certain basic set, the integral equation becomes a set of linear equations for the expansion coefficients, and it is often practical to solve the set by truncation. As a test, the equations are applied to the problem of a spheroid in a uniform field, and they easily yield the standard results that are usually derived by introducing spheroidal harmonics. Either the integral equation or the equivalent linear equations can be solved in an iterative approximation (the analog of the Born approximation) when the dielectric constant of the body is not too far from unity. For bodies that differ from spherical or cylindrical ones by a small parameter λ, perturbation formulae are derived that solve the equations in powers of λ. The problem of a homogeneous permeable body of arbitrary shape in an external magnetostatic field is reducible to the dielectric problem, but in addition an alternate integral equation for the magnetic problem is discussed.