Relativistic ponderomotive forces

The interaction of a relativistic classical electron with an inhomogeneous electromagnetic field is investigated. In second-order perturbation theory the motion is separated into fast and slow motions, and the relativistic Newtonian equation is averaged over the fast oscillations. The rate of change obtained for the slow component of the electron momentum is interpreted as a relativistic ponderomotive force. The result is generalized to the relativistic case of the wellknown expression for the Gaponov-Miller force acting on an electron at rest. The expressions obtained for the relativistic ponderomotive forces are very complicated in the general case. They simplify in the limit of a stationary field (pulses of long duration) and a small gradient. The most typical and simplest special case of an inhomogeneous field—a stationary plane-focused beam—is investigated. The main difference between relativistic ponderomotive forces and their nonrelativistic limit is they have multiple components. In addition to the usual force directed along the gradient of the field, the relativistic case is also characterized by force components that do not have the form of the gradient of a potential and are parallel to the wave vector and the direction of the field polarization. It is shown that when a relativistic electron travels in a direction close to the direction of the wave vector of a focused laser beam, these components can greatly exceed the gradient force. A force directed along the field polarization vector arises even when the gradient of the field in this direction is zero. Zh. éksp. Teor. Fiz. 116, 1198–1209 (October 1999)     

Motion of a particle in a static magnetic field and in the field of a electromagnetic plane wave

The solutions of the equations of motion of a charged particle in an external electromagnetic field consisting of a superposition of a constant uniform magnetic field and the field of a circularly polarized electromagnetic plane wave are presented as solutions of the Cauchy problem. The resonance case is studied. Zh. Tekh. Fiz. 67, 94–99 (February 1997)     

Quantum cryptography based on homodyne detection (vacuum-state cryptosystem)

A new protocol is proposed for quantum cryptography. The protocol is based on the use of a set of measurements which make it possible to reconstruct completely the density matrix — the information carrier — of a physical system. Such a protocol can be implemented by means of homodyne detection (well known in quantum optics) of an electromagnetic field. An example is given of a quantum cryptosystem in which the vacuum state of the photon field is used as one of two information states. Pis’ma Zh. éksp. Teor. Fiz. 66, No. 1, 64–68 (10 July 1997)     

Modeling of radar scattering conditions inside a circular hollow dielectric waveguide

A new ray representation of electromagnetic field inside a quasi — optical structure in the form of a circular hollow dielectric waveguide is suggested and confirms the possibility for the unusual application of such a waveguide as an off-beat microanechoic chamber for electromagnetic modeling in the near millimeter and submillimeter wave regions.     

Charge transfer states in GeO2-doped silicate fiber-optic waveguides and their role in second-harmonic generation

The concentration dependence of the broad-band luminescence arising in GeO₂-doped silicate fiber-optic waveguides is measured and interpreted. The spectra obtained show that electronic excitations of a new type that are absent in pure silicate glass — charge transfer excitons — arise in the doped system. Under the action of light an electron can be transferred both from a Ge center into the host and between Ge centers. Self-organization of these excitations in the field of a light wave (orientational ordering of their dipole moments) results in the appearance of a macroscopic electric field that destroys the initial centrosymmetry of the system and allows second-harmonic generation. Pis’ma Zh. éksp. Teor. Fiz. 68, No. 10, 737–740 (25 November 1998)     

Effect of a rapid increase in the strength of the gravitational field on the propagation of electromagnetic radiation

This article examines the shift in the frequency of an electromagnetic wave as it passes through a region of space in which the strength of the gravitational field increases rapidly. It is shown that charge or current in a region of space with a variable gravitational field radiates electromagnetic waves. Russian Federal Nuclear Center—VNIIEF. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 31–34, March, 1997.     

Multiphoton ionization of the hydrogen atom by a circularly polarized electromagnetic field

This paper examines the multiphoton ionization of the ground state of the hydrogen atom in the field of a circularly polarized intense electromagnetic wave. To describe the states of photoelectrons, quasiclassical wave functions are introduced that partially allow for the effect of an intense electromagnetic wave and that of the Coulomb potential. Expressions are derived for the angular and energy distributions of photoelectrons with energies much lower than the ionization potential of an unperturbed atom. It is found that, due to allowance for the Coulomb potential in the wave function of the final electron states, the transition probability near the ionization threshold tends to a finite value. In addition, the well-known selection rules for multiphoton transitions in a circularly polarized electromagnetic field are derived in a natural way. Finally, the results are compared with those obtained in the Keldysh-Faisal-Reiss approximation. Zh. éksp. Teor. Fiz. 116, 807–820 (September 1999)     

Structures and thermoelectric convection in cholesteric liquid crystals

The possibilities for excitation of electromagnetic field structures and convection cells, i.e., temperature and velocity structures, in a thermotropic cholesteric liquid crystal in the presence of flow are studied. Estimates are made and possible experiments for observing such structures are discussed. A special thermoelectric effect is investigated as the cause of these excitations — the influence of a heating-induced change in the pitch of the cholesteric helix of the molecules on the permittivity and the electric conductivity of the material. Fiz. Tverd. Tela (St. Petersburg) 41, 165–170 (January 1999)     

Propagation of a beam of gamma rays in the field of a monochromatic laser wave

The head-on propagation of a beam of γ grays through the field of a laser wave is investigated. The optical properties of the laser wave (as a medium) are described by the dielectric tensor. The refractive indices are determined, and the polarization characteristics of electromagnetic normal modes capable of propagating in such a medium are investigated. Relations are derived to describe the variation of the initial polarization and intensity of a γ-ray beam as it propagates in a laser field. The influence of laser intensity on the investigated process is discussed. Zh. éksp. Teor. Fiz. 112, 2016–2029 (December 1997)     

Motion of a particle in a static magnetic field and the field of a monochromatic electromagnetic plane wave

A solution of the equation of motion of a charged particle in an external electromagnetic field comprising a superposition of a uniform static magnetic field and the field of a monochromatic, elliptically polarized electromagnetic plane wave is obtained as the solution of a Cauchy problem. The resonance case is investigated. An analysis of the resulting solution is given. Zh. Tekh. Fiz. 69, 106–110 (May 1999)     

Kerr-Newman metric in deSitter background

In addition to the Kerr-Newman metric with cosmological constant several other metrics are presented giving Kerr-Newman type solutions of Einstein-Maxwell field equations in the background of deSitter universe. The electromagnetic field in all the solutions is assumed to be source-free. A new metric of what may be termed as an electrovac rotating de-Sitter space-time—a space-time devoid of matter but containing source-free electromagnetic field and a null fluid with twisting rays—has been presented. In the absence of the electromagnetic field, our solutions reduce to those discussed by Vaidya.     

Stationary soliton on a charged surface of liquid helium and hydrogen films

A change in the shape of a charged surface of liquid hydrogen and helium — the formation of a solitary wave (a positively charged hump for hydrogen and a negatively charged dimple for helium)-is observed in an electric field exceeding a critical value under conditions of total compensation of the applied field by the surface charge. Pis’ma Zh. éksp. Teor. Fiz. 65, No. 7, 547–552 (10 April 1997)     

Motion of an electronic wave packet in an electromagnetic field

An equation is derived for the matrix of the parameters of a small Gaussian wave packet moving in arbitrary fixed electromagnetic fields. The equation can be used to describe the evolution of wave packets in a wide class of vacuum devices. A simple example of the evolution of a packet in a constant magnetic field is studied. Pis’ma Zh. éksp. Teor. Fiz. 64, No. 8, 515–520 (25 October 1996)     

Total conversion of the polarization of electromagnetic waves during excitation of cyclotron polaritons in a two-dimensional electron system

The reflection of an electromagnetic wave from a two-dimensional (2D) electron system in a magnetic field is studied. It is predicted that a p (s) polarized incident wave will be totally converted into a reflected wave with the orthogonal polarization when cyclotron polaritons are excited in the 2D system. For a high electron density in the 2D system, the effect remains very substantial in magnitude even in the presence of electron scattering. Pis’ma Zh. éksp. Teor. Fiz. 70, No. 4, 247–252 (25 August 1999)     

Theory of superfluidity of nuclear matter based on the Fermi-liquid approach

This paper discusses how an electromagnetic field consisting of a superposition of a constant magnetic field and a field of laser type can affect nuclear beta decay. In general it is not assumed that the intensities of the two types of fields are small compared to the characteristic field H _cr*=β ₁ H _cr, where H _cr=m ² c ³/eℏ and the quantity β ₁ depends on the energy liberated in the decay and the configuration of the electromagnetic field. For nonrelativistic decays the quantity β ₁ is found to be of the same order as the maximum kinetic energy of an electron referenced to its rest energy β ₁∼I≪1. It is assumed that the frequency of the wave field satisfies ℏω/mc ²⩽I. The behavior of the probability for the process is studied over a wide range of the fundamental parameters that characterize the fields. Corresponding asymptotic expressions are derived in the “weak”-and “strong”-field regimes. Also discussed are so-called interference corrections to the unperturbed decay probability, which cannot in principle be studied by the methods of perturbation theory. It is shown that the times and distances that are important in generating these contributions exceed the parameters of the unperturbed processes, just as in the case of a plane-wave field previously investigated in detail by Nikishov and Ritus. However, in contrast to the case of a pure wave field, when a system is simultaneously subjected to a constant magnetic field and a wave field, the degree to which these characteristic regions are enlarged can depend not only on the intensities of the electromagnetic fields but also on their rates of change, even in the limit in which the wave field is slowly varying. Zh. éksp. Teor. Fiz. 111, 3–24 (January 1997)     

Electronic spectrum of a two-dimensional Fibonacci lattice

The electronic spectrum and wave functions of a new quasicrystal structure—a two-dimensional Fibonacci lattice—are investigated in the tight-binding approximation using the method of the level statistics. This is a self-similar structure consisting of three elementary structural units. The “central” and “nodal” decoration of this structure are examined. It is shown that the electronic energy spectrum of a two-dimensional Fibonacci lattice contains a singular part, but in contrast to a one-dimensional Fibonacci lattice the spectrum does not contain a hierarchical gap structure. The measure of allowed states (Lebesgue measure) of the spectrum is different from zero, and for “central” decoration it is close to 1. The character of the localization of the wave functions is investigated, and it is found that the wave functions are “critical.” Zh. éksp. Teor. Fiz. 116, 1834–1842 (November 1999)     

Linear topological defects in electromagnetic vector fields

An analysis is made of the topological structure of an electromagnetic vector field near the point where the amplitude of the field vanishes. Linear topological defects in the form of dislocations of the wave front and disclinations are studied. It is shown that the polarization of the field near a zero of the amplitude differs from the initial value. The structural stability of the amplitude zeros is studied. Zh. Tekh. Fiz. 68, 122–124 (January 1998)     

Electromagnetic excitation of infrasound in a conducting medium

A comparative analysis is made of the mechanisms of interaction between the electromagnetic fields of a global resonator and hydrodynamic and acoustic disturbances in a conducting medium. A universal boundary condition at the interface between air and the conducting medium, which takes into account the motion of the electrolyte, is obtained in an explicit analytical form to calculate the long-wavelength electromagnetic fields. The intensity of the electromagnetic field excited by a vertical hydroacoustic wave is estimated together with the efficiency of excitation of infrasonic oscillations of a conducting medium in the field of a global resonator. Zh. Tekh. Fiz. 68, 80–83 (January 1998)     

Effect of pulsed excitation of a bounded medium on a plane electromagnetic wave

An analysis is made of the transformation of a plane monochromatic electromagnetic wave in response to a temporal change in the permittivity and conductivity of a semibounded medium. The change in the parameters of the medium takes the form of a rectangular pulse of arbitrary duration and amplitude. The detailed structure of the electric field and its evolutional redistribution are determined. The asymptotic formation of a backward wave is demonstrated, whose amplitude may exceed that of the primary wave for parameters typical of a semiconductor. Zh. Tekh. Fiz. 69, 84–92 (August 1999)     

Anisotropic momentum transfer in low-dimensional electron systems in a magnetic field

In low-dimensional systems with an asymmetric quantizing potential, an asymmetric electron energy spectrum ε(p)≠ε(−p), where p is the electron momentum, arises in the presence of a magnetic field. A consequence of such an energy spectrum is that momentum transfer to the electron system in mutually opposite directions in the presence of an external perturbation is different. Therefore, in the presence of a standing electromagnetic wave momentum is transferred from the wave to the electrons, which gives rise to a new type of electromotive force. Pis’ma Zh. éksp. Teor. Fiz. 66, No. 8, 551–555 (25 October 1997)