Electrodynamics in a linearly accelarated system

The frequency of electromagnetic radiation measured by a linearly accelerated observer is discussed from both classical and quantum points of view. It is shown that the Doppler principle is valid only in the eikonal limit. An alternative measure of frequency is considered and its limitations are critically examined.     

Electrodynamics in a linearly accelerated system

The frequency of electromagnetic radiation measured by a linearly accelerated observer is discussed from both classical and quantum points of view. It is shown that the Doppler principle is valid only in the eikonal limit. An alternative measure of frequency is considered and its limitations are critically examined.     

Electrodynamics and thermodynamics of a paramagnetic system in a metallic resonator

The well-known problem of the phase transition in a two-level system coupled with the radiation field of a resonator is considered subject to the conduction electrons of the resonator walls. It is shown that the conduction electrons are important for consideration of the high-frequency properties of the system to cut off the frequency spectrum of the radiation field at the plasma frequency. In the vicinity of the phase transition the conduction electrons lead to the damping of the soft mode.     

Dissipative structures in a continuous medium

Institute of Mining, Siberian Branch, Russian Academy of Sciences, Novosibirsk. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 94–104, April, 1992.     

Electrodynamics in a model with induced geometry

It is shown that electrodynamics can be consistently introduced in a classical field model involving induced geometry.     

Thermodynamics of a continuous medium with electric and magnetic dipoles

The thermodynamics of an electrically charged, multicomponent fluid with spontaneous electric and magnetic dipoles is analysed in the presence of electromagnetic fields. Taking into account the chemical composition of the current densities and stress tensors leads to three types of irreversible terms: scalars, vectors and pseudo-vectors. The scalar terms account for chemical reactivities, the vectorial terms account for transport and the pseudo-vectorial terms account for relaxation. The linear phenomenological relations, derived from the irreversible evolution, describe notably the Lehmann and electric Lehmann effects, the Debye relaxation of polar molecules and the Landau-Lifshitz relaxation of the magnetisation. This formalism accounts for the thermal and electric magnetisation accumulations and magnetisation waves. It also predicts that a temperature gradient affects the dynamics of magnetic vortices and drives magnetisation waves.     

Atomic radiative transition probabilities in a continuous medium

A simple quantization procedure is applied to the electromagnetic radiation field in a nondissipative, weakly dispersive continuous medium. The resulting operator expressions for the electric and magnetic field strengths are used to study the influence of the dielectric and magnetic properties of the medium on the Einstein coefficients for spontaneous and stimulated radiative transitions of single atoms or molecules embedded in the medium. The expressions obtained are consistent with detailed-balance considerations.     

The Milne problem in a continuous stochastic planar medium with Gaussian statistics

The Milne problem of radiative transfer in a planar medium, with isotropic scattering is considered. The medium is assumed to be continuous stochastic medium, with fluctuations described as Gaussian field. Pomraning-Eddington method is used to obtain an explicit form for the radiation energy density in the deterministic case. It depends on two random variables, namely the optical space variable and the optical thickness of the medium. The Gaussian joint probability density function of these two random variables is defined and used to find the ensemble-averaged energy density and the linear extrapolation distance. It is shown that the statistical nature of the medium leads to two quite different solutions of the Milne problem. Numerical results are implemented for the sake of clarification.     

Electrodynamics of a convective cloud

An attempt has been made to describe analytically the electrodynamics of a convective cloud on the basis of a one-dimensional convective cell with solid gas rotation. The cloud electrification is due to the interaction between heavy (large raindrops and particles of hail) and light (microparticles of water and ice) particles. As a result, the particles acquire unlike electric charges. The large-scale electric field in the cloud is stipulated by boundary effects and influences considerably the motion of the heavy fraction of aerosol particles. A scenario is proposed for the development of an intracloud charge, by which the large-scale electric field does not reach the breakdown value, staying at the level of the corona discharge field, while an increase in the irregular component of the electric field is continued and achieves the breakdown value in the small-scale electric cells induced by analogues of plasma beam instabilities. The basic electric discharge occurs against the background of multiple discharges inside the cell which provide for the leader lightning channel. Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 40, Nos. 1–2, pp. 123–137, January–February, 1997.     

Specific features of neutron propagation in a medium with a helical magnetic structure

The features of neutron motion in a noncoplanar magnetic field have been considered in the example of a specific magnetization distribution in the form of a conical helix. The neutron reflectances for holmium crystals have been calculated. It is shown that, in the case of noncoplanar distribution of magnetic field in a crystal, the spin-flip neutron reflectance has an additional singularity.     

Method for designing an arbitrary continuous refracting surface with specified property of wavefronts conversion

A method is proposed for designing an arbitrary continuous refracting surface that can realize conversion between two specified distributions of wavefront. Optimization technique is avoided by solving a partial differential equation governing the surface-profile function. This equation is obtained using the property of congruence and the law of refraction, and its solution in this special case is found to be the same as that obtained in wavefront conjugation. A method based on finding the local coefficients of the surface is developed to solve the equation numerically, and an example is given to illustrate its feasibility.     

Photonic crystals with a specified bandgap width

A new method is proposed for the production of photonic crystals with a thoroughly controlled photonic bandgap. The method is based on the synthesis of an A_1?x B _x photonic crystal with controlled parameter x based on two isostructural A and B photonic crystals such that the photonic bandgap of the A crystal is smaller and that of the B crystal is greater than the required bandgap. The method is exemplified in a (100 ? x) mol % SiO₂?x mol % ZnO inverse opal, in which the relative stop-band width monotonically increases with parameter x.     

Propagation of surface acoustic waves in a piezoelectric medium with a periodic groove structure

A system of equations is formulated to describe the propagation of surface acoustic waves in a piezoelectric substrate whose surface has a periodic structure formed by transverse grooves. Dependences of the reflection coefficient and the wave velocity on the geometry of the periodic structure (the width and the depth of the grooves) are obtained in a wide range of variation of these parameters for five different orientations in various piezoelectric crystals (quartz, lithium niobate, lithium tantalate, and langasite).