Radiation bursts from particles in the field of compact, impenetrable, astrophysical objects

The radiation emitted by charged, scalar particles in a Schwarzschild field with maximal acceleration corrections is calculated classically and in the tree approximation of quantum field theory. In both instances the particles emit radiation that has characteristics similar to those of gamma-ray bursters.     

The itinerant electron metamagnetism for ScCo2, YCo2 and LuCo2

Electronic structure of d-electrons under external magnetic field is calculated for ScCo₂, YCo₂ and LuCo₂ in the self-consistent tight-binding approximation and the field dependence of the induced moment is estimated in the Hartree-Fock approximation. The critical field of the metamegnetic transition for these compounds is evaluated at 0 K.     

Structure of a nonparaxial gaussian beam near the focus: III. Stability,eigenmodes, and vortices

Exact analytical structurally stable solutions of the Maxwell equations for singular mode beams propagating in free space or a uniform isotropic medium are obtained. Approximate boundary conditions are chosen in the form of the requirement that in the paraxial approximation the fields of nonparaxial mode beams in the waist plane are transformed into the fields of eigenmodes and vortices of weakly guiding optical fibers with the axial symmetry of refractive index. It is shown that optical vortices, in spite of a rather complex structure of field distribution, do not experience substantial changes in the beam form and reproduce, in general features, the field of paraxial vortices. Linear perturbations of the characteristic parameters of mode beams do not change the structure of their electromagnetic field. Nonparaxial singular beams have one more important property, in addition to the fact that the structure of these beams in the paraxial approximation is similar to the structure of the fields of eigenmodes in a fiber. The propagation constants of eigenmodes of a fiber exactly coincide (in the first approximation of perturbation theory) with the projection of the wave vector of a mode beam on the optical axis (an analog of the propagation constant). The possibility of the paraxial transition for nonparaxial mode beams with arbitrary values of azimuthal and radial indices is shown. The properties of nonparaxial modes are illustrated by numerous examples. The solutions obtained and the results of their analysis can be used for exact matching optical fibers and laser beams in various applications.     

Accurate Treatment of Tunnel Ionization,Induced by a Constant Electric Field,From a Power-Law Singular Potential

The tunnel ionization, induced by a weak electrostatic field, of a particle bound in an attractive one-dimensional power-law singular potential is analysed. An accurate approximation applicable for the general case of non-fractional power exponent is suggested.     

Correlation effects,image charge effects and finite size in the macro-ion-electrolyte system: A field-theoretic approach

We consider a model of a macro-ion surrounded by small ions of an electrolyte solution. The finite size of ionic charge distributions of ions, and image charge effects are considered. From such a model it is possible to construct a statistical field theory with a single fluctuating field and derive physical interpretations for both the mean field and two-point correlation function. For point-like charges, at the level of a Gaussian (or saddle point) approximation, we recover the standard Poisson-Boltzmann equation. However, to include ionic correlation effects, as well as image charge effects of individual ions, we must go beyond this. From the field theory considered, it is possible to construct self-consistent approximations. We consider the simplest of these, namely the Hartree approximation. The Hartree equations take the form of two coupled equations. One is a modified Poisson-Boltzmann equation; the other describes both image charge effects on the individual ions, as well as correlations. Such equations are difficult to solve numerically, so we develop an (a WKB-like) approximation for obtaining approximate solutions. This, we apply to a uniformly charged rod in univalent electrolyte solution, for point like ions, as well as for extended spherically symmetric distributions of ionic charge on electrolyte ions. The solutions show how correlation effects and image charge effects modify the Poisson-Boltzmann result. Finite-size charge distributions of the ions reduce both the effects of correlations and image charge effects. For point charges, we test the WKB approximation by calculating a leading-order correction from the exact Hartree result, showing that the WKB-like approximation works reasonably well in describing the full solution to the Hartree equations. From these solutions, we also calculate an effective charge compensation parameter in an analytical formula for the interaction of two charged cylinders. Electronic supplementary material  Supplementary material in the form of a doc file available from the journal web page at and are accessible for authorised users.     

A conformai,symmetry broken model for gravity

Starting from Padmanabhan's fully conformally invariant action, we obtain gravity as a spontaneously broken theory. Newton's constant and the cosmological constant follow from the breakdown of the conformal symmetry at the tree approximation. For small oscillation of the scalar field about the fundamental state, the matter field degenerates into two decoupled fields.     

Theoretical investigations of the vapour-liquid equilibrium and dielectric properties of dipolar Yukawa fluids in an external field

In a low field approximation, using the dipolar Yukawa fluid model (in mean spherical approximation as a reference system) a consistent field-dependent free energy expression is proposed for the calculation of the vapour-liquid equilibrium of polar fluids in an applied electric field. A perturbation theory high field approximation expression of the free energy is also proposed to study the field-dependent properties of fluids. In the high field approximation, equations for the field-dependent polarization and for the nonlinear dielectric constant (or Piekara constant) are also predicted. It has been discussed that our approximations are appropriate to describe the vapour-liquid-like phase equilibria and the magnetization curves of magnetic fluids.     

Unified derivation of soliton, polaron and soliton lattice solutions in polyacetylene

The trans-(CH)_x polyacetylene system is studied in the framework of mean field approximation. In this paper it is shown that the phonon field satisfies a differential equation, which admits as solutions, besides the well-known solutions. found by other authors, many others.     

GYRAC: a compact, cyclic electron accelerator

The concept of the gyro-resonant accelerator (GYRAC), which is based on cyclotron resonance in a magnetic field that is increasing slowly in time, is presented. Previously published work shows that this results in an autoresonance in which the wave provides a synchronous acceleration of the electrons. Using a simple model makes it possible to design a particularly compact, cyclic electron accelerator; in a cavity with a 1-m radius and final magnetic field of 5 T, electron energy reaches 680 MeV, giving rise to synchrotron radiation of 1 keV. Assuming uniform fields and rescaling time, a Hamiltonian system is arrived at which has one degree of freedom and which, in first-order approximation is time independent. In a second-order approximation, a slow damping of the autoresonant oscillation is found. A paraxial model for beam and fields allows evaluation of the charge effects-the GYRAC then resembles the betatron. These results are illustrated by numerical three-dimensional simulations     

Optical characterization of weakly absorbing PP,PE, and PP/PE films

The interaction between a solitary electromagnetic wave and a narrow layer with an increased electron concentration in a semiconductor superlattice in a preset uniform alternating electric field directed along the superlattice axis is investigated. The model of the electron energy spectrum in the superlattice is chosen in the strong coupling approximation taking into account the second harmonic. It is shown that, for certain relations between the amplitude and frequency of the alternating electric field, a solitary electromagnetic wave approaching the layer with an increased electron concentration can be trapped by this layer.     

Adiabatic expansions of green's functions in electromagnetic and gravitational fields. Radiative corrections

A solution of Maxwell's equations is constructed that describes a homogeneous electromagnetic field in a curved space-time in the lowest adiabatic approximation in the curvature. The Green's function for Dirac particles in this field is constructed to the same accuracy. It is shown that in the case of a super strong magnetic field the main approximation is the two-dimensional approximation, moreover, the gravitational correction is determined by a single component of the curvature tensor R₁₂₃₀. The mass operator of the electron is calculated in this approximation.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 32–38, February, 1986.     

Gluon transport equations,plasma oscillations,and screening

The gluon transport equations (Phys. Lett. 177B (1986) 402) are reconsidered to derive a consistent semiclassical limit. Introducing the color current of gluon fluctuations around a classical mean field, we calculate the color permeability function of a collisionless gluon plasma in linear response approximation. The dispersion relations and electric screening length agree with one-loop high temperature QCD results. We find no magnetic screening atO(g ²) and predict transverse magnetic plasma oscillations similar to electric ones. The extension to include particle production by a mean color field is shortly described.     

Scalar Approximation of Super-Gaussian Beams

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On the effective medium model for particles with a complex structure

We consider a generalization of the effective medium approximation to the case of matrices containing macroscopically inhomogeneous particles with an arbitrary structure (cermet topology). The form of the result is determined to a considerable extent by the heuristic choice of effective cells used to estimate the field and induction values averaged over the volume. The simplest choice of a particle in an unperturbed field as a cell leads to the Maxwell–Garnett approximation, while the self-consistent effective medium approximation corresponds to the replacement of the unperturbed field by the mean field. As an example, we describe particles with a shell, as well as statistically anisotropic media with a single preferred direction.     

Calculations of total ionization cross sections of Ne,Ar, Kr,and Xe atoms in the born approximation allowing for electron perturbations in the continuous spectrum

Electron impact ionization cross sections of Ne, Ar, Kr, and Xe atoms are numerically calculated. The electron perturbation in the continuous spectrum in the target field is taken into account. The matrix elements are calculated in many-electron, nonrelativistic approximation with allowance for the superposition of configurations and relaxation effect. The radial part of the electron wave function in the continuum is calculated by solving the single-configuration Hartree-Fock equation. The wave functions of electrons in the continuum are orthogonalized with respect to the core orbital functions. The calculated cross sections are compared to the experimental data and calculations made using the plane-wave Born approximation and that involving generalized oscillator strengths.     

Surface tension in field theory at finite temperature: Semiclassical fermionic plus bosonic contributions

We compute, within the one loop approximation, the temperature dependent surface tension for a model involving a scalar field coupled to a fermionic field. The fermionic and bosonic contributions have been computed in this approximation by evaluating explicitly the determinants in the presence of a domain wall.     

Quasi-static field of an elementary electric dipole in a moving,isotropic, warm plasma

We have investigated the field of an elementary electric dipole in a medium moving at nonrelativistic velocities. We used a quasi-static approximation and a hydrodynamic model of the plasma, taking into account the thermal motion of the electrons. The plasma is assumed to be isotropic, uniform, and infinite. We demonstrate that the intrinsic spatial dispersion of the medium (in the associated reference frame) produces a change in the plasma wave part of the source field.Kirovskii State Teachers Institute. Translated from Izvestiya Vysshikh Uchebnykh Zavedeni Radiofizika, No. 10, pp. 1227–1236, October, 1994.     

虚光子过程对“两个二能级原子-单模光场”相互作用系统场熵演化特性的影响

利用全量子理论,研究了非旋波近似下两个二能级原子与单模光场相互作用过程中受激场场熵的演化规律,通过与旋波近似下的相应结果进行比较,进一步揭示出非旋波近似条件下虚光子过程对场熵演化特性的影响.