Vol 106, No 2 (2017)

We examine the role of the large-scale anisotropy of the high-energy cosmic ray distribution in a search for the heavy decaying dark matter (DM) signal. Using recent anisotropy measurements from the extensive air shower (EAS) observatories, we constrain the lifetime of the DM particles with masses 10⁷ ≤ M_X ≤ 10¹⁶ GeV. These constraints appear to be weaker than that obtained with the high-energy gamma-ray limits. We also estimate the desired precision level for the anisotropy measurements to discern the decaying DM signal marginally allowed by the gamma-ray limits and discuss the prospects of the DM search with the modern EAS facilities.

The differential cross sections of the (p, p′) inelastic reaction on nuclei ¹²C, ²⁸Si, ⁴⁰Ca, and ⁵⁶Fe at the initial proton energy of 1 GeV were measured over a wide range of the scattered proton momenta at a laboratory angle of Θ = 21°. Scattered protons were detected by means of the magnetic spectrometer equipped with a polarimeter based on multiwire proportional chambers. Momentum intervals were observed in which the ratios of the scattering cross sections off the nuclei do not depend on the scattered proton momentum (i.e., scaling).

The characteristics of gold nanoparticles coated with silicon dioxide containing embedded dye molecules are experimentally investigated at room and liquid-nitrogen temperatures. The origin of the observed narrowing of the luminescence line upon cooling is discussed. Model analysis of the nanosystem under study indicates that the observed behavior cannot be related to the temperature dependence of individual parameters of the components of the medium. The effect is explained by the occurrence of nonlinear feedback that leads to the enhancement of phase synchronization between the polarizations of the active transitions in the dye molecules and plasmons. This effect is an analog of plasmon polariton superradiance.

Phase transitions and critical properties in the antiferromagnetic Heisenberg model on a layered cubic lattice with allowance for intralayer next nearest neighbor interactions have been studied using the replica Monte Carlo algorithm. The character of phase transitions has been analyzed using the histogram method and the Binder cumulant method. It has been found that a transition from the collinear to paramagnetic phase in the model under study occurs as a second order phase transition. The statistical critical exponents of the specific heat α, susceptibility γ, order parameter β, and correlation radius ν, as well as the Fisher index η, have been calculated using the finite-size scaling theory. It has been shown that the three-dimensional Heisenberg model on the layered cubic lattice with allowance for the next nearest neighbor interaction belongs to the same universality class of the critical behavior as the antiferromagnetic Heisenberg model on a layered triangular lattice.

The effect of a magnetic field on the processes of relaxation of the defect structure relaxation in a triglycine sulfate (TGS) ferroelectric (nonmagnetic) crystal has been observed for the first time. The atomic-force microscopy study has shown that the application of a static weak magnetic field (2 T, 20 min) significantly changes the size distribution of defect nanoclusters characteristic of TGS. Previously known macroscopic aftereffects of the magnetic field in TGS (slow relaxation of the dielectric susceptibility, symmetrization of P–E dielectric hysteresis loops, etc.) can be explained by the redistribution of pinning centers of domain walls caused by the magnetically induced reconfiguration of the defect structure.

The main zero-dimensional defects in graphane, a completely hydrogenated single-layer graphene, having the chair-type conformation have been numerically simulated. The hydrogen and carbon−hydrogen vacancies, Stone–Wales defect, and “transmutation defect” resulting from the simultaneous hoppings of two hydrogen atoms between the neighboring carbon atoms have been considered. The energies of formations of these defects have been calculated and their effect on the electronic structure, phonon spectra, and Young modulus has been studied.

The contribution of higher orders of relativistic quantum perturbation theory to the differential cross section for the merging of three X-ray photons into one photon in the field of a multielectron atom has been studied in the Tamm–Dankov approximation. It has been shown that higher orders do not change the physical results obtained in the leading (second) order of perturbation theory.

The possibility of controlling interference in two spaced fiber Mach–Zehnder interferometers and maintaining a nearly ideal visibility has been demonstrated for the one-way quantum cryptography system directly in the key distribution process through a communication channel with a length of 50 km. It has been shown that the deviation of the visibility from ideal is certainly due to the detected difference between the numbers of 0’s and 1’s in the raw (sifted) key. For this reason, an interferometer can be balanced only in the quasi-singlephoton mode without the interruption of the process of key distribution by using the difference between the numbers of 0’s and 1’s in the raw key as an indicator of an error. The proposed approach reduces the balancing time and, furthermore, does not require additional exchanges through an open communication channel.

The spectrum of coherent transition radiation has been recorded with the use of a Martin–Puplett interferometer. It has been shown that the spectrum includes monochromatic lines that are caused by the modulation of an electron beam with the frequency of an accelerating radio-frequency field ν_RF and correspond to resonances at ν_k = kν_RFk ≤ 10. To determine the length of an electron bunch from the measurement of the spectrum from a single bunch, it is necessary to use a spectrometer with the resolution Δν_sp > ν_RF.