Showing papers in "Russian Physics Journal in 1990"

Physical nature of stages in plastic deformation

Abstract: In summary, the transition from one stage of plastic deformation to another is due to the phase transformations in the subsystem of deformation defects. These transformations are controlled by an internal parameter of the system, viz., the scalar dislocation density, whose value is determined by both the external force and processes retarding the shear and annihilation. The main structural level controlling this process is the level of the dislocation subsystem.

Relativistic polarization potential of a many-electron atom

Abstract: An effective approximate calculation of the exchange-polarization second-order diagrams in the Rayleigh-Schrodinger perturbation theory with the use of the relativistic Thomas-Fermi approximation is described and used to obtain a new relativistic expression for the effective two-particle polarization interaction potential in a many-electron atom.

Quantum electrodynamic theory of multiply charged ions

Abstract: A Rayleigh-Schrodinger perturbation theory is constructed within quantum electrodynamics so as to calculate energy levels nad transition probabilities in multiply charged ions. The basic features of the suggested model are renormalization and its relative simplicity. Renormalization is guaranteed by the fact that all interesting quantities (energy levels, transition probabilities, and cross sections of various processes) are expressed in terms of many-electron Green's functions, whose renormalization is achieved by standard methods. To demonstrate the simplicity of the suggested method, expressions are obtained for corrections to the ground state energy of a two-electron multiply charged ion due to two-photon exchange diagrams, whose derivation by other methods is, in our opinion, quite more complicated.

Gauge dynamic theory of defects in nonuniformly deformed media with a structure. Interface behavior

Abstract: Several problems of defect dynamics have been considered in the present study. In the future, along with a more detailed study of the problems touched upon, one can independently develop both a number of sections of this study (averaged equations for the various media, contact problems, and others), as well as direct numerical solution of the equations derived for specific mechanical problems. It is hoped that these studies will also be useful in the understanding of physical processes of plastic deformation and in its quantitative description in a number of specific cases.

New exact Schrödinger-equation solutions based on finite-dimensional matrices

Abstract: New exactly solvable models are found. The exact solutions pertain to low-lying states and are connected with the solution of the eigenvalue problem for three and five-diagonal matrices of special form. The solution can be described by introducing an effective spin Hamiltonian that is non-Hermitian in general but has real eigenvalues. The potentials obtained go over in various limiting cases into the Mathieu, Eckart, Peschl-Teller potential and into the effective potentials for anisotropic paramagnets.

Collisionless kinetic equations for massive particles with spins 1/2 and 0 in gravitational and electromagnetic fields

Abstract: We define a covariant and gauge-invariant generalization of the Wigner functions of particles with spins 1/2 and 0. The collisionless kinetic equations are obtained for these particles in external gravitational and electromagnetic fields in the quasiclassical approximation; also obtained are the momentum representations of the energy-momentum tensor, current, and spin tensor, taking into account the effects of the spin's interaction with the gravitational field an electromagnetic field. The following notation is used: e and m are the charge and mass of the particles; is Planck's constant; γμ(x) are the covariant-fixed Dirac matrices; σα,β=(1/4)[γα, γβ]: a(μbν)=(1/2) (a μ b ν +aνb μ); [A, B]=A·B − B·A; A,B=A·B+B·A; g(x)=det(g αβ(x));R α αμν=∂μΓ βν βν −...; the speed of light c=1.

Electrical properties of film heterojunctions of cadmium selenide and amorphous selenium

Abstract: Results are presented from a study of the volt-ampere characteristics of polycrystalline layers of cadmium selenide and amorphous layers of selenium, as well as the electrical and photoelectric characteristics of CdSe-Se heterojunctions. The experimental data and a theoretical examination of heterojunctions composed of a crystalline semiconductor and an amorphous semiconductor are used to propose an energy-band model for heterojunctions.

Magnetization processes of the first kind in the hexaferrite Co 0.62 Zn 1.38 W

Abstract: The magnetization curves M(H) and derivatives ∂2M/∂H2 of a polycrystalline textured specimen of the compound BaCo0.62Zn1.38Fe16O27 are investigated in the 100–300 K temperature range. It is shown that magnetization processes of the first kind are characteristic for this compound at temperatures below 220 K. The diagram of the magnetic state is analyzed in coordinates of the normalized anisotropy constants X=K2/K1 and Y=K3/K1. Temperature dependences of the three magnetic crystallographic anisotropy constants are computed on the basis of experimental data on the critical magnetization and the field, and hysteresis loop width.

Features of elastic phase interaction in the crystal Gd2(MoO4)3

Abstract: The elastic interaction of paraelastic-paraelectric (¯42m) and ferroelastic-improper ferroelectric (mm2) phases coexisting in a Gd2 (MoO4)3 crystal is investigated for a phase transition in the neighborhood of Tc=433 K. The energetic favorability of the monodomain state of the ferroelastic phase being formed is shown and the reasons for the impossibility of reaching the plane of zero mean strains on the phase interface boundary are analyzed.

Thermodynamics of irreversible processes in open systems

Abstract: The information-theory based description is given of irreversible processes in open systems interacting with the external environment. The amount of the information difference is expressed through the Kul'bak measure, for which a microscopic foundation is developed. New conditions are obtained for stability of evolution, and steady states of the systems are determined. Relationships are given for forces and fluxes in irreversible processes, and an expression is found for the total local production of information difference and for entropy.

Relaxation waves in plastic deformation

Abstract: Experimental study of distortion fields of plastically deformed solids performed on a wide range of materials including fine- and coarse-grain body- and face-centered polycrystals, as well as amorphous alloys reveals that in these materials plastic deformation develops in the form of waves having translational and rotational components. This fact is in accordance with the currently developed theory of a turbulent mechanical field, which also has translational and rotational components.

Noncrystallographic structural deformation levels in strongly excited systems

Abstract: Therefore, the analysis performed in the previous sections on the experimental data and results of modelling by the molecular dynamics method permits making a deduction on the possibility of the formation of strongly excited systems of noncrystallographic structural deformation levels during loading As an experimental investigation showed, for all the kinds of static loading utilized their origination is associated with the pre-fracture stages Crack propagation over the noncrystallographic interfacial boundaries of the fragments indicates this Under shockwave loading the macroflux motion with the grains is also a new, larger-scale dynamic deformation level (compared with the dislocation level)

A supersymmetric anharmonic oscillator

Abstract: We consider the supersymmetric model obtained from the Wess-Zumino model with interaction, with the help of a dimensional reduction. The solution is found of the corresponding classical problem with a precision up to terms of the third order of smallness. A quantum model of such a system is constructed. Its spectrum is found in the first and second order of perturbation theory. The supersymmetric finite-dimensional model under consideration proves to be extremely close to the usual anharmonic oscillator.

Calculation of the Shirokov effect for circular orbits in an axisymmetric static gravitational field

Abstract: In the post-Newtonian approximation of the metric theory of gravitation we calculate the frequencies of Shirokov oscillations for equatorial circular geodesics in an asymptotically flat static space-time which satisfies the conditions of axial symmetry and symmetry with respect to the plane of the equator.

Morphogenesis of distributions of microparticles by dimensions in the coarsening of dispersed systems

Abstract: For a wide class of dispersed systems, a basis is given for the possibility of a complete theoretical analysis of their evolution, owing to Ostwald coagulation of microparticles. Theoretical solutions are obtained to describe distributions of microparticles by dimensions with positive and negative asymmetry, kinetic dependences, and lifetimes of the microparticles of any given dimension, taking into account various mechanisms of their reactive interaction with the substance of the medium. In an example of change of the morphological indicators of experimental histograms of microparticles of Al3Mg2 under isothermal heating of the aluminum-magnesium alloy, their correspondence is shown to the nature of the transformation of the theoretical distribution functions.

Nonstationary Gödel-type cosmological model

Abstract: We construct a nonstationary, rotating, causal Godel-type cosmological model filled with a massless complex scalar field, an anisotropic fluid with distributed scalar field charge, and a radiation field, taking into account heat flow.

Z-dependences of atomic parameters of autoionization states of two-electron systems

Abstract: On the bais of two programs, calculations are carried out for energies, probabilities of radiative transitions and nonradiative decays, and lifetimes of levels of two-electron systems 2l.4l′. The results of the two calculations are compared for a wide range of Z. Possible channels of radiative transitions and nonradiative decays are discussed. Their relative contribution to the total probability is evaluated. This evaluation is compared with data obtained by calculations, on the basis of which a conclusion is made about the contribution of correlation and relativistic effects. The Z-dependences are investigated for each of the parameters under consideration. A comparison is made with the results of other calculations.

“Square root” of the Dirac equation in extended supersymmetry

Abstract: We discuss the possibility of extracting the “square root” from the Dirac equation in N-extended supersymmetry, with the aim of constructing a more fundamental dynamical theory. Although a “square root” of the Dirac operator can be defined in N-extended superspace for N≤2, it is not possible to construct with its help a new dynamical model that meets the standard requirements imposed on the theory.

A new method of calculating the spectrum and the self-consistent field of negative ions

Abstract: A new method is suggested for negative ion calculations, based on perturbation theory with a model zeroth approximation and a polarization potential formalism. The binding energy of an electron in an Na− ion is calculated as a test, and is found to agree with experiment.

Calculation of the coupling constants of many-electron atoms with external fields using expansions in a discrete basis of sturmian-type virtual orbitals

Abstract: Based on a generalization of the method of Sturmian expansions to the case of many-electron systems, a fundamentally new approach was developed for the construction of a complete set of intermediate states in many-body perturbation theory thereby avoiding integration over states of the continuous spectrum. A complete system of eigenfunctions of the generalized eigenvalue problem for the one-electron Hartree-Fock equation with a factor before the energy operator and fixed values of the Lagrange multipliers is used as a basis of single-particle virtual orbitals for an initial approximation to the eigenfunctions of the Hartree-Fock self-consistent field method. In the case of bound states, the spectrum of the effective operator is purely discrete, thus permitting one to completely eliminate integration over continuum virtual orbitals in applying methods of many-body perturbation theory to atomic and molecular calculations for a number of cases. As a consequence, one manages to avoid a number of the technical difficulties associated with inclusion of such states. The possibilities of the developed approach are illustrated in application to the investigation of the interaction of many-electron atoms with external fields.

Numerical solution of classical equations of motion for a field in the infrared region

Abstract: A numerical study is carried out of equations of motion for the classical Yang-Mills fields described by a nonstandard Arbuzov-Alekseev Lagrangian.

Barrier layers as resonators on deep centers

Abstract: A response is given to the paper of L. S. Barman and A. A. Lebedev (Izv. Vyssh. Uchebn. Zaved. SSSR, Fiz., No. 12, 88–90 (1989)), and it is shown that the arguments given there are not satisfactory. New experimental data have been obtained for n+-p junctions in Si, where square reverse-bias pulses U < Ures are observed to shift the DLTS peaks. Here Ures is the magnitude of the pulse for which all activation-drift processes become activation-transit processes and the barrier layer operates as a freshly prepared resonator on deep centers (see the paper by P. T. Oreshkin, Elektronnaya Tekhnika, Ser. 3, Mikroelektronika, No. 4 (128), 12–20 (1988).

Structural deformation and fracture levels of polycrystals under different kinds of loading

Abstract: A survey is given in this paper of the researches [3-12] devoted to the systematic investigation of the turning deformation modes and their associated structural deformation levels of polycrystals Results of investigations executed on identical materials (lead and alloys with it as base) but for different kinds of loading, active deformation of one sign, creep, and sign-variable loading, are considered

Group analysis of the nonlinear electrodynamics equations

Abstract: The symmetry of the Maxwell equations is investiated in this paper in a nonlinear isotropic medium without currents and charges. A group-theoretic classification is given of the material equations and partially invariant solutions. Exact solutions of the Maxwell equations are found.

Electron sink at a probe in the conditions of a collisional near-probe space-charge layer

Abstract: On the basis of the concept of the sink effect, the dependence of the electron currents on the retaining potential is calculated for probes of arbitrary form, both in the presence of a magnetic field and in its absence. The focus is on the calculation of currents in the conditions of the collisional near-probe space-charge layer. It is shown that, in the case where the layer thickness is small in comparison with the probe radius, expressions obtained within the frame-work of sink-effect theory (when the layer is assumed to be noncollisional) may be used to calculate the current in such conditions. It is also shown that, instead of the requirement λ ≫ rD for use of the standard method of determining the plasma parameters, satisfaction of the less stringent requirement λe ≫ rD is adequate; λe is the energy relaxation length of the electrons.

Probability of creation of pseudoscalar mesons in the field of a flat electromagnetic wave

Abstract: The probability of creation of pseudoscalar particles (π0-meson and Higgs boson) by a lepton in the field of flat elliptically polarized electromagnetic wave is considered Polarization and spin effects are studied

Elastic and inelastic scattering of electrons by aligned light nuclei

Abstract: The contribution to the elastic and inelastic scattering cross sections, Δ, due to alignment of nuclei having axial symmetry was calculated for scattering of unpolarized, ultra-relativistic electrons by7Li atoms. This contribution turned out to be on the order of magnitude of the cross section σ0 previously calculated in the absence of nuclear alignment. For various nuclear orientations, the ratios Δ/σo were calculated as a function of the momentum transfer q, which may be useful, for example, in increasing the reliability of identification of quantum numbers of nuclear states and multipole transitions. In contrast with the expression for σo, the expression for Δ contains cross products of reduced matrix elements (RME), along with the squares of their moduli. This permits one, having previously experimentally found σ0 and Δ under various kinematical conditions but for fixed q (the RME depend only on q), to obtain a system of equations for the RME and the statistical tensor g2, which characterizes the degree of alignment of the nuclear target, along with the separation of the parallel and perpendicular cross sections as in the case of unaligned nuclei. Having solved the system of equations, one finds g2 both in terms of the moduli of the RME of each multipole transition individually, and also in terms of their relative phases. The additional information thus obtained for each nuclear transition may serve as a more strict criterion for checking models of nuclei used in calculations than measurement of σ0 alone.