Generalized linearized hydrodynamic equations in the hard-sphere model are considered on the basis of N.N. Bogolubov’s approximate approach to the analysis of collective interactions. The generalized matrix of transfer coefficients is shown not to be self-adjoint when the finiteness of the two-particle interaction region is taken into account.
Show AbstractThe phase structure of a 2-dimensional Gross-Neveu model with a difermion channel of interaction is studied in the variables of the temperature and chemical potentials in the limit of a large number of field components $N\rightarrow\infty$.
Show AbstractThis paper describes a software package that is designed to simulate experiments to study photonucleon reactions by measuring residual activity. Calculations of the cross sections and yields of photonucleon reactions, the number of photonucleon reactions product-nuclei and their decay products, the spectrum of gamma rays produced in the irradiated sample, and the spectrum that is measured by the detector are described in detail. A comparison of the simulation results with the results of experiments is given.
Show AbstractAn expression for the neutrino luminosity of a degenerate electron gas in a strong magnetic field via plasmon decay to a neutrino pair due to electromagnetic neutrino moments is derived. The neutrino luminosity of the medium in an electromagnetic reaction channel is shown to be comparable with the luminosity in a weak channel. The relative upper bounds for the effective magnetic neutrino moment are obtained.
Show AbstractThe interaction of a shock wave with a turbulent air flow is investigated experimentally. The turbulence was created with the aid of a grid. On its reflection from a perforated disc the wave propagated through a turbulent flow. The Mach number of the incident shock was equal to 1.9–4, the Mach number of the reflected wave was equal to 1.6–2.5. We found the autocorrelation functions of pressure fluctuations and their phase diagrams. The turbulent length scale of pressure fluctuations behind the incident shock was determined. The appropriate quantity behind the reflected wave is less of an order as compared with the previous case. It is established that the pressure behind the reflected wave in the turbulent flow is 7–8% higher as compared with the pressure in the laminar flow, if other conditions are the same.
Show AbstractFluctuations in the plane-wave amplitude and positions of two rays that propagate in a medium with random inhomogeneities of dielectric permittivity are considered. The solution to the problem is based on the ray-diffusion method. The Einstein-Fokker equation is obtained for the density of probabilities of the distance between the rays and relative amplitude in the case where the initial distance between the rays is much smaller than the correlation radius of dielectric permittivity. A conditional probability density for the relative amplitude is obtained provided that the distribution of distances between the rays is described by a logarithmic normal law, which does not take amplitude fluctuations into account. Numerical analysis of the analytical solution is carried out for the propagation of short radio waves in the troposphere and ionosphere.
Show AbstractExplanations of contradictory results in some studies of the temporal characteristics of charging dielectric targets via the electron irradiation effect are given. Disagreement is caused by the difference in the times of the appearance of a quasi-equilibrium state of two main parameters of charging, namely, the complete coefficient of secondary electron emission and the surface electrostatic potential.
Show AbstractThe rotational spectrum of the absorption of the main isotope of sulfur dioxide ($^{32}$S$^{16}$O$_2$), which corresponds to the terahertz range of electromagnetic waves, namely 1–250 cm$^{-1}$ (0.1–10 THz), is studied. The consideration covers rotational transitions within all vibrational states whose Hamiltonian parameters are known from the literature: (000-000), (010-010), (100-100), (001-001), (020-020), (110-110), (011-011), (030-030), (120-120), (200-200), (002-002), (130-130), (103-103), (301-301), (101-101), (021-021), (210-210), (111-111), (201-201), (003-003), and (131-131). As a result, the absorption coefficient of $^{32}$S$^{16}$O$_2$ is calculated for a broad temperature range (300–1200 K) and the contribution of the rotational band of each vibrational state to the total absorption coefficient is evaluated.
Show AbstractA phenomenological model that describes the sequence of phase transitions in lawsonite is considered. A phase diagram of the model is constructed and theoretical temperature dependences of order parameters and inverse permittivity in low-symmetry phases are calculated. The comparison of theoretical curves with experimental results showed satisfactory qualitative agreement.
Show AbstractThe influence of heating after sharp cooling to −60°C on the low-frequency dielectric response of erbium formate crystallohydrate is investigated. Such research has been performed previously for objects of different chemical natures and structural organizations (in colemanite, diglycinenitrate, triglycinetellurate crystals, and several polymers with water). There is one structural fragment in these substances, viz., a weak hydrogen bond O...H-O that is 0.26–0.29 nm in length. A common feature of these measurements is a sharp increase of dielectric permittivity of the orders at frequencies of 0.1–4 Hz close to 0°C, upon heating after sharp cooling, and decay in the region of 40°C. To explain similar phenomena one can use the deformation model of the double minimum potential in the field of the thermoelastic stresses and other molecular fields.
Show AbstractThe existence of two forms of unipolar gas-breakdown discharge that depend on the pulse-repetition frequency and the polarity of high-voltage pulses is experimentally revealed. These two forms differ in their intensities, the distribution of luminescence on the discharge length, and their volt-ampere characteristics. The transition from one discharge form to another proceeds in a narrow frequency range and is caused by the breakdown of the near-electrode layer in some critical field under the inclusion of ion-electron emission process. The transition frequency increases with the growth of the gas pressure and a decrease of the pulse amplitude. The development of discharge instability and the hysteresis of its parameters are observed in the transition area.
Show AbstractEffect of heavy (Pb$^{2+}$, Cs$^+$) and light (Na$^+$) metal ions on the molecular-dynamic characteristics of type-I collagen in aqueous solution was studied using the method of dynamic light scattering. It was found that the dependence of the translational diffusion coefficient D$_t$ from pH solutions has a nonlinear form with a pronounced extremum close to the isoelectric point of the protein (pI 6.0). For pure aqueous solution of protein there is a maximum of D t in isoelectric point. For collagen solutions with the addition of heavy-metal salts the minimum of D$_t$ was observed near the isoelectric point. This fenomenon is connected with the formation of protein nanoclusters in solution. With concentration of heavy metal ions increasing translational diffusion coefficient Dt decreases, which shows on increasing of aggregation effect. The addition of sodium ions in aqueous solution of collagen containing heavy metal ions sharp decreasing of the translational diffusion of molecules is observed. That can be connected with the rise of scattering particles masses.
Show AbstractThe apparent motions of extragalactic ICRF sources are considered. Computer simulation of apparent motions is carried out assuming that they are stochastic and uncorrelated, while the position angle of the velocity for each source has a uniform distribution. We calculate the vector amplitudes of spherical harmonics and show that the corresponding spectrum has the form of “white noise.” In addition, we discuss observational data and calculate their angular spectra. Preliminary conclusions on the origin of the observed multipolar harmonics in the velocity angular spectrum are given.
Show AbstractThe effect of radio-telescope characteristics on the precision of pulsar timing is studied. We found a definite correlation between the accuracy of long-term pulsar time-series data, instrumental uncertainties of arrival-time timing, and pulsar-flux density. This correlation suggests that modern radio telescopes are still not sensitive enough to investigate the noise that is intrinsic to pulsars or the noise that is due to the propagation of the pulsar signal toward the solar system in the interstellar medium. The next-generation radio telescope, the Square Kilometer Array (SKA), is estimated to have an instrumental uncertainty that will be low enough to be insignificant and not affect the quality of pulsar-timing data.
Show AbstractAn expression that explicitly describes variations in the internal energy of the plasma that flows through a discontinuity is derived based on the complete system of boundary conditions for the MHD equations on the discontinuity surface. The dependence of the plasma heating on the magnetic field density and configuration in the vicinity of the discontinuity surface (i.e., on the MHD flow type) is studied. The conditions of plasma heating at discontinuities in a self-consistent analytical model of magnetic reconnection are discussed.
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