Brinkmann's theorem in general relativity

In the early 1920s Brinkmann made the first significant contribution to the study ofpp waves in general relativity. Reference to his original work and to the later work of Ehlers and Kundt is made in order to rectify and clarify statements made recently by McInnes.     

Field ionization processes in field ion microscopy

The processes of field ionization are considered by the time dependent perturbation theory. The metal wave function to be occupied by a tunneling electron from a monovalent atom is approximated by the tight-binding method. The system considered is hydrogen imaging a tungsten-type metal. The (001) crystallographic plane with an interatomic spacing of 3.16 Å and an externally applied electric field of 2.3 V/Å is considered for numerical results. Image formation mechanisms of field ion microscopy are qualitatively discussed.     

Quantum electrodynamics in a laser and the electron laser collision

Quantum electrodynamics in a laser is formulated, in which the electron–laser interaction is exactly considered, while the interaction of an electron and a single photon is considered by perturbation. The formulation is applied to the electron– laser collisions. The effect of coherence between photons in the laser is therefore fully considered in these collisions. The possibility of γ-ray laser generation by use of this kind of collision is discussed.     

Semi-statistical model for metals

Calculations of the cohesive energy, Wigner-Seitz radius and compressibility of some metals are performed by a semi-statistical method. Two regions are considered in the Wigner-Seitz cell, taken in the spherical approximation. In the internal region the electronic density is considered the same as in the free atom, while in the external region it is computed by means of the Thomas-Fermi-Dirac equation. In the calculation of energies, inhomogeneity and correlation corrections are considered.     

Light transmission in a finely divided scintillator

The propagation of scintillation light is considered for a granular detector bounded by surfaces differing in reflectivity. The optimal parameters of the detector are considered; a comparison is made with experiment.     

Pressure influence on the ferromagnetic resonance in ferrodielectrics

The pressure influence on the ferromagnetic resonance (FMR) is considered. Magnetostatic mode coupling caused by sample compression is taken into account by means of a perturbation theory. Two simple models are considered for strong coupling when perturbation theory works badly.     

Nonlinear sound waves upon collapse of a vortex dipole

Acoustic emission by a vortex dipole decreases the dipole energy and changes the vortex velocity distribution. A relative shift of the dipole component occurs. Earlier, such a process of acoustic instability of the vortex was considered as applied to the case of weak acoustic emission described by the wave equation. Features of acoustic instability upon emission of a strongly nonlinear sound by a vortex are considered in this work.     

一维三原子分子的振动

考虑三原子分子的振动问题,利用线性代数的化标准型理论,获得该振动系统简正频率的数学表达式,并讨论了几种特殊的情况.     

Calculation of the properties of a lens made of glass bricks by the equivalent-current method

The properties of a lens antenna are calculated by the equivalent-current method (second equivalence principle). A Luneberg lens formed by glass bricks is considered. The results of these calculations are compared with experimental data. The possibility is considered of applying the above theoretical method to calculating lens antennas where there is a random deviation of the dielectric constant from a preset distribution.     

Fractal structure of the acoustic signal excited in a liquid by an unstable laser radiation

Thermooptical excitation of sound in a liquid by a laser radiation with a harmonically modulated intensity randomly distributed over the beam cross-section is considered. The processes are considered to be statistically homogeneous. It is assumed that the spatial spectrum of the intensity fluctuations in a laser beam is described by a power (fractal) law. It is demonstrated that the acoustic field in a liquid has a fractal structure.     

Pair creation by a non-local potential

The probability of pair creation by a separable and non-local potential is considered following the Schwinger approach. It has been found that this probability is null. As a particular case, the separable δ-potential is considered and the probability is also found null.     

Influence of nonlinear interactions on the development of instability in hydrodynamic wave systems

The problem of the development of shear instability in a three-layer medium simulating the flow of a stratified incompressible fluid is considered. The hydrodynamic equations are solved by expanding the Hamiltonian in a small parameter. The equations for three interacting waves, one of which is unstable, have been derived and solved numerically. The three-wave interaction is shown to stabilize the instability. Various regimes of the system’s dynamics, including the stochastic ones dependent on one of the invariants in the problem, can arise in this case. It is pointed out that the instability development scenario considered differs from the previously considered scenario of a different type, where the three-wave interaction does not stabilize the instability. The interaction of wave packets is considered briefly.     

Numerical study of acoustic radiation dynamics of a Rankine vortex

The paper continues investigations of a fundamental problem important for understanding the nature of vortex flows: sound radiation by a perturbed Rankine vortex. Results of numerical simulation are presented for both quadrupole and higher-mode radiations. The structure and dynamics of tonal acoustic radiation generated by a vortex are considered in detail. The transition of a Rankine vortex to a perturbed state under small external perturbation is considered. Calculations are performed using the EBR scheme implemented by NOISEtte software.     

Role of cellulose crystallites in the polarization of a biopolymer composite: Wood in a nonuniform temperature field

Polarization phenomena caused by the presence of temperature gradients in a biopolymer such as wood are considered. It is shown that cellulose crystallites are centers of polarization in the fiber-forming part of the considered biocomposite. The relation for elementary polarization is obtained. It is proposed that the supermolecular structure of cellulose in samples of wood be studied by measuring the electric field characteristics of a thermal polarization nature.     

Thick brane solutions supported by two spinor fields

Stationary thick brane solutions supported by two spinor fields are considered. Two spinor fields are used here to exclude the off-diagonal components of the energy-momentum tensor of the spinor fields. The trapping of a test scalar field on the brane is also considered.     

The solid sphere model in studies of crystal stability

The possibility of employing the hard sphere model in studies of real, stable, inert-gas crystals is considered. On the basis of the firmly established phase transition criterion for a model system the stability curve of a real crystal is found, with attractive forces considered by first-order perturbation theory. The result obtained is compared with experiment.     

Relaxation between electrons and surface phonons of a homogeneously photoexcited metal film

The energy relaxation between the hot degenerate electrons of a homogeneously photoexcited metal film and the surface phonons (phonon wave vectors in two dimensions) is considered under Debye approximation. The state of electrons and phonons is described by equilibrium Fermi and Bose functions with different temperatures. Two cases for electron scattering by the metal surface, namely specular and diffuse scattering, are considered.     

Effect of phase-damped cavity on dynamics of tangles of a nondegenerate two-photon JC model

A two-mode cavity field coupled to a two-level atom and damped by the environment through a phase-damped process is considered. For a chosen initial state, the effects of phase damping on the purity loss of the global system and different bipartite partitions of the system (atom-two modes, mode-(atom-mode)) through the tangles are considered. In particular, the effect of phase damping on the amount of entanglement between atom and field is evaluated by the negativity.     

Rashba Effect in Presence of Time-Dependent Interaction

Rashba effect in presence of a time-dependent interaction has been considered.Then time-evolution of such a system has been studied by using Lewis–Riesenfeld dynamical invariant and unitary transformation method.So appropriate dynamical invariant and unitary transformation according the considered system have been constructed as well as some special cases have come into this article which are common in physics.     

Control over the instability wave in terms of the two-dimensional model of a nozzle edge

The problem of generation of an instability wave leaving the edge of a half-plane that separates an immobile medium from a moving medium is considered. It is assumed that the instability wave is initiated by an acoustic wave arriving from the moving medium. The possibility of suppressing the instability wave by another acoustic wave incident from the nonflowing medium is considered. It is shown that the suppression is always possible by adjusting the amplitude and phase of the control perturbation to the parameters of the instability wave.