Vol 62, No 1 (2019)

Possible types of stationary states and waves in linear media separated by a nonlinear interface are analyzed. The mathematical formulation of the model is reduced to a one-dimensional boundary value problem for the nonlinear Schrödinger equation. The nonlinearity of the equation in the form of an arbitrary function of the desired field is taken into account only inside the waveguide. It is shown that there are stationary states of three types for different ranges of propagation constant values. The dispersion dependences of the propagation constant as functions of the parameters of the medium and the interface have explicitly been obtained for stationary states of all types, and conditions of their existence have been indicated. It is shown that total wave transition through the interface is possible. It has been established that the total transition of wave through the interface with nonzero parameters can occur only if the nonlinear response of the medium is taken into account.

The constrained Hamiltonian formalism for the extended higher derivative Chern–Simons theory of an arbitrary finite order is considered. It is shown that the n-th order theory admits an (n–1)-parametric series of conserved tensors. It is clarified that this theory admits a series of canonically non-equivalent Hamiltonian formulations, where a zero-zero component of any conserved tensor can be chosen as a Hamiltonian. The canonical Ostrogradski Hamiltonian is included into this series. An example of interactions with a charged scalar field is also given, which preserve the selected representative of the series of Hamiltonian formulations.

Decay channels of the Higgs boson H into a gauge boson and a longitudinally polarized fermion-antifermion pair \( H\to Z\overline{ff} \) and \( H\to Z\overline{f{f}^{\prime }} \) have been investigated within the framework of the Minimal Supersymmetric Standard Model. Analytical expressions for the corresponding decay widths have been obtained and their dependence on the masses of the Higgs bosons are examined.

Spontaneous disturbance of gauge symmetry in cosmology, including that in cosmological models with rotation, has been investigated in a number of studies. In this work, a spontaneous disturbance of the gauge symmetry of a complex scalar field is considered within the general relativity theory in cosmological models with Bianchi III and VIII metrics.

This work investigates the interaction of an axial vector-meson with nucleons in the AdS/QCD soft wall model. The axial vector fields have been determined inside the anti-de Sitter (AdS) space with the help of gauge fields with left and right chiral symmetries. In addition, a pseudoscalar field has been introduced inside the AdS space to break the chiral symmetry. A Lagrangian for these fields has been introduced inside the AdS space and the profile functions which are solutions of the equation of motion have been found. In accordance with AdS/CFT, the interaction constant of the axial vector-meson with the nucleons has been obtained as an integral over the additional dimension. The main task of this work was to find numerical values of the interaction constant of the axial vector-meson with the nucleons in the AdS/QCD soft wall model. With the help of the computer program Mathematica 7, these values were determined. A comparison of the theoretical and experimental data has revealed significant agreement of the results.

In this paper we investigate the influence of the light pressure on the motion stability of near-Earth space objects whose orbital semi-major axes change from 8000 to 42400 km. The orbital evolution of each object with area-to-mass ratio in the range from 1 to 70 m²/kg has been considered. In addition, values of the area-tomass ratio have been investigated at which the objects from various zones of the near-Earth space depart from their orbits under the influence of the light pressure and then fall to the Earth.

The density functional theory is used to study the nonlinear screening properties of a two-dimensional electron gas in a strong magnetic field. The Kohn-Sham equations for two-dimensional electrons are solved numerically. It is shown that at low electron densities, two electrons are localized on impurities and the wave functions of these electrons do not overlap with the wave functions of other electrons. The phase diagram of the metal – insulator transition in a magnetic field is constructed.

The paper deals with the grown tin telluride (SnTe) single crystals сontaining extrinsic stacking faults (SFs) and their alloyed ohmic contacts of the 57Bi–43Sn eutectic alloy in the temperature range of 77–300 K. It is found that at a low concentration, SFs decrease the hole concentration and increase the electrical resistivity of specimens when they occupy vacancies in the Sn sublattice. At a high concentration, SFs create new current carriers, thereby decreasing the specific resistance of specimens. The ohmic contact resistance is rather low, and the current flows mainly through metallic shunts.

Results of theoretical and experimental studies of exciplex of a zinc complex Zn(DFP-SAMQ)₂ with the hole-transporting layer of NPD are presented. It is shown that at least three different arrangements of Zn(DFP-SAMQ)₂ and NPD molecules in the excited state result in the long-wavelength charge-transfer emission bands. At the same time, such systems are unstable in the ground state.

Method of modeling optoacoustic signals initiated by a laser pulse in composites transparent matrix – metal nanoparticles taking into account melting processes has been developed and tested. The method consists in calculating the function of pressure sources depending on time and coordinate and its convolution with the Green’s function of the one-dimensional wave equation. Testing has been performed for composites of pentaerythritol tetranitrate with 50 nm radius aluminum nanoparticles that are important for practical applications. The melting is characterized by an increase in the specific volume and leads to an increase in the amplitude of the maximum of the source function and the appearance of the area of its negative values. The dependences have been calculated of the effective growth constant of the optoacoustic signal and its amplitude on the pulse energy density that must be taken into account in this method. The results are important for the development of methods of nondestructive testing and prediction of functioning of photonic devices and optical detonators containing nanoparticles.

A model of the thermo-field electron emission from the metal cathode with a thin insulating surface film at temperatures of 200–400 K is developed. An expression for the film emission efficiency in the gas discharge is obtained. The efficiency is equal to the fraction of electrons emitted into the film from the metal substrate, which enter the discharge volume and increase the effective secondary-electron emission yield of the cathode. It is shown that the thermo-field mechanism of electron emission influences noticeably the ignition voltage of the low-current discharge with such cathode at rather low temperatures exceeding the room temperature by less than 100 K.

Using the Monte Carlo method, the influence of vacancy concentration on the structural-phase states and energy characteristics is investigated by the example of an intermetallic compound NiAl in the course of its heating and cooling. According to the analysis, the availability and concentration of vacancies are important factors in the pre-transitional low-stability structural-phase states prior to transformation. On the one hand, neither the vacancies nor their concentration affect the temperature ranges of structural-phase transformations, on the other hand, they essentially influence both the pre-transitional low-stability structural-phase states and the rate of diffusion processes. The temperature behavior of the short-range order parameter suggests that the higher the vacancy concentration (i.e., system’s defectiveness), the higher the temperatures at which the tendencies for increasing atomic ordering would be manifested due to intensified diffusion. This, in turn, evidences of a higher starting structural transformation temperature with an increase in the number of defects in the alloy during cooling. An analysis of the temperature curves of the long-range order parameter of the NiAl intermetallide allows making a conclusion that an increased vacancy concentration (i.e., the alloy’s defectiveness) gives rise to a logical result – decreased long-range ordering in the system in the region of low-stability pre-transitional states and increased starting transformation temperature.

We present results of simulation of time dependences of the Bi₁₂SiO₂₀ crystal transmission coefficient with harmonic wavelength modulation of probe radiation. The possibility for estimation of the spectral position of the Gaussian curves descriptive of the probability of intracenter transitions that contribute to the extrinsic absorption in sillenite-type crystals is analyzed. It has been shown that the amplitude of the second Fourier harmonic in the expansion of the time dependence of the transmission coefficient of the sample under investigation peaks near the central wavelengths of the intracenter transitions.

An interpretation of the Bethe approximation based on the method of averaging over local exchange fields taking into account the correlation of neighboring spins is proposed. Based on this interpretation, an approximate method of analysis of Ising magnetics with nonmagnetic dilution is constructed. In the approximation considered, percolation thresholds and dependences of the Curie temperature on the concentration of magnetic atoms for lattices with different coordination numbers are calculated.