Diffraction radiation from a fast particle at a resonance frequency

Diffraction radiation generated by a fast particle moving past a dielectric wedge or past a homogeneous medium with the surface of arbitrary shape is considered at a frequency close to the natural frequency of the medium. The angular distribution of diffraction radiation is investigated as a function of the wedge angle and the shape of the surface.     

Electromagnetic radiation of a neutral fermi particle moving in an external field

The neutral particle has an anomalous magnetic moment; the motion in constant and homogeneous electric and magnetic fields is discussed. Photons can be emitted; the polarization is examined. It is shown that the emission is related to spin rotation.     

On wave radiation induced by a fast shock wave in an oblique magnetic field

The corrugation stability of the flat surface of a fast magnetohydrodynamic shock wave in a perfect monoatomic gas with a constant heat capacity is studied with numerical techniques. The magnetic field makes an arbitrary angle with the plane of discontinuity. It is shown that the shock wave remains stable only if it is strictly perpendicular to the magnetic field. At any other angle between the fast shock wave and magnetic field, the former may spontaneously radiate outwardly propagating magnetohydrodynamic waves under certain conditions. Incoming flow characteristics at which these waves are induced are determined.     

The external field effect on transient radiation of an ultrarelativistic particle

An external field determining the law of particle motion was shown to change the intensity of transient radiation in the ultrarelativistic case. The angular and frequency distribution of transient radiation in an external field was obtained. The possibility of determining the energy of an ultrarelativistic particle from the measured azimuthal asymmetry of particle transient radiation in an external field was discussed.     

Transition radiation from an ultrarelativistic particle in an external field at grazing emission angles

The effect of an external field on the transition radiation from an ultrarelativistic particle is considered at grazing emission angles. The angular and frequency distribution of transition radiation is found. It is shown that the external field substantially increases the angular asymmetry of transition radiation at grazing emission angles.     

Resonance radiation in electromagnetic wave scattering by a fast electron in the external magnetic field

The resonance radiation in Compton scattering of an electromagnetic wave by a fast relativistic electron moving in a given magnetic field is investigated with allowance for deceleration by the radiation. A general expression for the electric field of an arbitrarily polarized scattered wave is derived within the framework of small-perturbation theory. It is shown that the resonance peak in the scattering cross-section is caused by the small radiation friction. The dependence of the resonance line width on the characteristic parameters of the problem is examined. The scattering of a given polarized wave is considered, and the degree of linear polarization of the radiated wave under resonance is determined.Institute of Radiophysics and Electronics, Armenian Academy of Sciences, Erevan. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 38, No. 10, pp. 1001–1011, October, 1995.     

Surface superconductivity induced by an external electric field

A theory of surface superconductivity induced by an external electric field in superconducting semimetals, metals and semiconductors is presented. It is shown that the inhomogeneous surface superconducting state deeply penetrates into the bulk of the sample. The dependence of the critical surface temperature and magnetic field on the external electric field is calculated.     

Wigner elementary particle in an external homogeneous field

A covariant Hamiltonian is proposed which permits to describe in the Heisenberg picture the motion of a Wigner elementary particle in a homogeneous electromagnetic field. More precisely, at any time, the elementary particle is in a state associated with a given irreducible representation of the Poincaré group. As a remarkable result, the spin motion is shown to be governed by the Thomas-Bargmann-Michel-Telegdi equation. Also the Galilean limit is discussed.     

Spinning relativistic particle in an external electromagnetic field

The Hamiltonian formulation of the motion of a spinning relativistic particle in an external electromagnetic field is considered. The approach is based on the introduction of new coordinates and their conjugated momenta to describe the spin degrees of freedom together with an appropriate set of constraints in the Dirac formulation.     

Virtual particle-antiparticle pair formation by a scalar particle bound in an external Coulomb field

A Hamiltonian variational Fock-space method is used to describe scalar massive particles in an external Coulomb field with strength f = Z. The use of an ansatz that includes a three-particle state in addition to a single-particle state built on the field-free vacuum enables one to highlight the role played by particle-antiparticle pair formation. Comparison is made with the Klein-Gordon equation in the Feshbach-Villars representation and it is shown explicitly how the virtual pair contribution corrects an O(f⁵) deficiency present in the energy spectrum of the naive Schrödinger-type single-particle equation.     

Invariance operator groups for a charged particle in an external electromagnetic field

In this paper a general group theoretical approach is given for the problem of a charged particle moving in an external electromagnetic field F. From a knowledge of the symmetry transformations of the field (Galilean or Poincaré), it is possible to explicitly construct groups of operators which commute with the operators of the equations of motion (classical, quantum mechanical, Klein-Gordon or Dirac) using the concept of compensating gauge transformations together with a uniquely chosen map π: F → A fixing the gauge of the potential A. Other choices of gauges give rise to isomorphic operator groups. The general structure of the possible symmetry groups of the fields is discussed and the corresponding invariance operator groups are explicitly given for (almost) arbitrary fields. The structure of these groups is then investigated and it is shown in particular that a large class of fields give rise to non-Type I groups, i.e. to groups which have (unitary continuous) representations whose corresponding von Neumann algebras have non-discrete factors. A general criterion for these pathological cases is given. As an application, we study the problem of a Bloch electron in arbitrary constant uniform electric and magnetic fields.     

Hall resistance anomalies induced by a radiation field

A study is made of the four-terminal Hall junction under the influence of a radiation field. The frequency of the radiation field is tuned to a transition between the energy of a bound state below a conduction subband and the Fermi energy of the incident electrons. Radiation-field-induced resonant dips of the Hall resistance are exhibited at low magnetic fields. Pis’ma Zh. éksp. Teor. Fiz. 66, No. 6, 403–408 (25 September 1997) Published in English in the original Russian journal. Edited by Steve Torstveit.     

Relativistic quantum particle in a homogeneous external field

The model of the relativistic quantum particle in a homogeneous external field is proposed. This model is realized in the one-dimensional relativistic configurational x-space and is described by the finite-difference equation. The momentum p-space in our case is the one-dimensional Lobachevsky space. We have found the wave functions and propagator for the model under study in both x- and p-representations.     

Pseudoscalar particle-photon interaction induced by an external magnetic field in an electron-positron plasma

The effective interaction of a pseudoscalar particle with a photon in a magnetized electron-positron plasma is investigated. The plasma and field contributions to the effective coupling between the pseudoscalar particle and the photon are calculated. The effective coupling is shown to be independent of the parameters of the medium and the particle 4-momentum in certain limiting cases.     

Density matrix for particle production processes in an external field

The general problem of finding the density matrices of particles and antiparticles produced by an external electromagnetic field fron an arbitrary initial state is solved. Expressions are obtained for the density matrices of particles and antiparticles produced from a state with given number of initial particles and from a state described by an initial grand canonical ensemble.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fiz., No. 6, pp. 77–81, June, 1980.     

Equation of motion of a particle in an external electromagnetic field in cylindrical coordinates

Translated from Isvetiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 34, No. 4, p. 435, April, 1991.     

Fast particle acceleration by radiation in a strong quantizing magnetic field

General Physics Institute, Academy of Sciences of the USSR. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Radiofizika, Vol. 31, No. 8, pp. 912–920, August, 1988.     

Angular distribution of transient radiation from an ultrarelativistic particle in a magnetic field

It is shown that a magnetic field acting on an ultrarelativistic charged particle escaping from a conductor changes the intensity of transient radiation. The angular and frequency distribution of transient radiation in the magnetic field is determined. The possibility of determining the energy of the ultrarelativistic particle from the change in the azimuthal asymmetry of transient radiation emitted by this particle in the magnetic field is discussed.