R e g u l a r p a p e r s

Theoretical and mathematical physics

Moscow University Physics Bulletin 1990. **45**. N 3. P. 5

The paper considers the possibility of applying the generalized Pauli-Willars regularization, with an additional condition imposed on the logarithms of auxiliary masses, to eliminate the ultraviolet divergence of correlation functions in the case of stochastic quantization of a scalar field. The equivalence of probability distributions in the regularized stochastic theory and in the Euclidean quantum field theory is established.

Show AbstractMoscow University Physics Bulletin 1990. **45**. N 3. P. 9

A method of stochastic quantization is proposed for field theories with indefinite Euclidean action, based on the introduction of a nonlocal kernel of a special form in the generalized Langevin equation. The method is applied to stochastic quantization of gravitation theories with Einstein's Lagrangian and of the $R^2$ gravity.

Show AbstractMoscow University Physics Bulletin 1990. **45**. N 3. P. 13

In the nonlinear two-dimensional model, whose action is the sum of actions of two Wess-Zumino-Witten models and of the interaction of a special kind between them, the classical energy-momentum tensor is expressed in terms of conserved currents. For the Virasoro algebra generated by the tensor to have a constant central charge in quantum theory, it is required that the theory by finite. It is shown by means of an explicit calculation of one- and two-loop counterterms that this is the case only for a special choice of parameters for which the model is gauge-invariant and is defined on a homogeneous space.

Show AbstractMoscow University Physics Bulletin 1990. **45**. N 3. P. 19

The chiral color model predicts the existence of axigluons, i.e. a color octet of massive axial-vector gauge bosons. In this connection, of interest in the decay of quarkonium into a gluon and a virtual axigluon, the latter disintegrating into a quark-antiquark pair. In this study, an expression has been found for the decay width of quarkonium S states. Calculations have been carried out for charmonium $J/\Psi$ and bottomonium $\Upsilon$ for different values of the axigluon mass.

Show AbstractMoscow University Physics Bulletin 1990. **45**. N 3. P. 23

An expression for the Cerenkov radiation power with consideration for the arbitrary electron and photon polarization is obtained which generalizes the results of previous studies. Various special cases are investigated. The polarization vector of the final electron is found, which is determined by the initial polarization and electron and photon momenta.

Show AbstractRadiophysics

Moscow University Physics Bulletin 1990. **45**. N 3. P. 27

Within the framework of single-velocity cold hydrodinamics, magnetic insulation in two-electrode systems of arbitrary cross-section is described for the case when the generators of the electrodes are parralel straight lines or straight lines intersecting at one point.

Show AbstractMoscow University Physics Bulletin 1990. **45**. N 3. P. 30

Variations of the radial profile of the current density for the tubular relativisttic electron beam (REB) in a long vacuum channel have been studied with the help of the sectional collector. In the experiments, the REB wall thickness was observed to increase with an increase in the transport channel length and a decrease in the guiding magnetic field. It has been shown that when a certain critical value of the magnetic field strength is exceeded, the REB wall thickness ceases to change along the drift channel length. The results obtained agree with the estimates made according to the theory of diocotron instability.

Show AbstractMoscow University Physics Bulletin 1990. **45**. N 3. P. 36

Simultaneous action of the continuous SHF and IR radiations affects the reflection coefficients of crystalline silicon due to alterations of both the temperature of the sample and the mobility and concentration of free charge carriers. Some theoretical and experimental results, as well as prospects for applying the effect in scientific studies, are considered.

Show AbstractOptics and spectroscopy

Moscow University Physics Bulletin 1990. **45**. N 3. P. 41

Absorption of radiation in the medium IR range by a periodic-profile metal surface has been investigated. The absorbed energy was measured by means of the opto-acoustic effect. Sharp and narrow absorption peaks were observed at light incidence angles corresponding to resonance excitation of surface electromagnetic waves by scattered radiation. A method of determining surface roughness and angular spectrum of laser radiation is proposed.

Show AbstractMoscow University Physics Bulletin 1990. **45**. N 3. P. 47

Algorithms of reproduction of a specified phase profile of a light beam by an elastic mirror have been considered. An effective procedure of phase approximation has been proposed based on the method of least squares and allowing the first- and second-order phase surfaces to be specified with a high accuracy using a small number of control channels. The effect of the phase corrector parameters on the quality of adaptive focusing in linear and nonlinear media has been analyzed on the basis of a numerical model of the adaptive mirror.

Show AbstractMoscow University Physics Bulletin 1990. **45**. N 3. P. 52

A solution has been found to the problem of selecting optimum parameters of the resonator and the pumped region in a solid-state ring laser with monochromatic end pumping with allowance for a non-uniform amplification and also for the astigmatism of the mirrors and other components of the resonator. It is demonstrated that the minimum lasing thresholds can be achieved through the use of resonators which are equivalent to a concentric resonator, with compensation for the mirrors' astigmatism. A method for calculating the optimum size of the pumped region is given.

Show AbstractAcoustics and molecular physics

Moscow University Physics Bulletin 1990. **45**. N 3. P. 56

An approach to the solution of tomographic inverse problem of scattering by boundary acoustic inhomogeneities is briefly described using the extrapolated Richardson method. Results of the experimental verification of the theory that has been developed are presented.

Show AbstractMoscow University Physics Bulletin 1990. **45**. N 3. P. 61

The paper considers the problems of calculating nonlinear processes of harmonics boosting, front steepening, and destruction of a long monochromatic wave (with the formation of a shock wave) moving over a shallow-water plane shelf. The well-known theoretical method of simple waves is generalized to include the dissipation due to friction against the bottom. The destruction conditions are found, and the growth of harmonics in a tidal wave M2 propagating on the Siberian shelf is calculated.

Show AbstractAstronomy

Moscow University Physics Bulletin 1990. **45**. N 3. P. 66

The central part of the stellar globular cluster M15 has been investigated in search of the effects of gravitational focusing. The feasibility of this effect has been established by comparing the dispersion of the brightness of stars in the central part of the cluster, where this process more probable is, with the brightness of stars in a region distant from the center. The magnitudes of the dispersions have been estimated by the maximum likelihood method.

Show AbstractMoscow University Physics Bulletin 1990. **45**. N 3. P. 70

In the framework of the limited planar circular three-body problem it is shown that asteroids, which are unstable according to Hill, nevertheless can have stable orbits in the case of the first-order resonances. The limits and periods of changes in the eccentricities have been calculated for asteroids of the Hilda group.

Show AbstractSolid state physics

Moscow University Physics Bulletin 1990. **45**. N 3. P. 75

A correlation between the width of the phase transition region near the Curie points and the variance of the distribution function for hyperfine magnetic fields has been established on the basis of studies of the temperature dependence of magnetization and the distribution function of hyperfine magnetic fields on $^{57}Fe$ nuclei in rapidly quenched $Fe_{75}(Cr_xCo_{1-x})_{25}$ alloys.

Show AbstractMoscow University Physics Bulletin 1990. **45**. N 3. P. 79

The spectra of diffuse reflectivity of magnetic semiconductors $xCuCr_2S_4-(1-x)Cu_{0,5}Ga_{0,5}Cr_2S_4$ ($x$ = 0; 0.05; 0.1) have been investigated within the temperature range from 115 to 353 K. Based on the spectra obtained, a diagram of the energy band structure is proposed for these semiconductors, which is close to the band structure of a similar compound, $xCuCr_2S_4-(1-x)Cu_{0,5}In_{0,5}Cr_2S_4$.

Show AbstractMoscow University Physics Bulletin 1990. **45**. N 3. P. 84

The electron hopping relaxation in disordered organic semiconductors was analyzed within the framework of the diagonal-disorder model. The time variation of the electron concentration at the percolation level was found for different relaxation stages, the conditions for passing from dispersive to normal (Gaussian) transport were studied, and the dependence of the dispersion parameter on the temperature and the disorder degree was determined.

Show AbstractB r i e f r e p o r t s

Theoretical and mathematical physics

Moscow University Physics Bulletin 1990. **45**. N 3. P. 89

A new scheme is proposed for the description of massive gauge fields in which masses are induced by additional components of vector fields. By way of example, the scheme was applied to the gauge sector of the model of weak electric interactions.

Show AbstractAtomic and nuclear physics

Moscow University Physics Bulletin 1990. **45**. N 3. P. 92

This paper is devoted to studies of changes in the shape of a spectrum of highenergy gamma radiation as it travels through the photon field of a power spectrum (X-radiation in the active zone of compact gamma radiation sources). A relationship is established between the characteristics of the field and the gamma radiation spectrum.

Show AbstractRadiophysics

Moscow University Physics Bulletin 1990. **45**. N 3. P. 95

Mechanisms of mutual synchronization of coupled oscillators are analyzed for different types and magnitudes of the coupling. It is shown that mechanisms of transition from multifrequency to single-frequency operation of separate oscillators depend on the $Q$-factor and detuning of the coupling circuit.

Show AbstractMoscow University Physics Bulletin 1990. **45**. N 3. P. 98

This paper considers nonlinear interaction of a magnetized electron beam with a radiated wave in a dielectric waveguide at the stage of process saturation due to the capture of particles by the wave. The Compton mechanism of radiation excitation in devices of the Cerenkov emitter type is optimized on the basis of conservation laws and analysis of nonlinear solutions of the Vlasov kinetic equation. Beam density distributions corresponding to the maximum efficiency are presented.

Show AbstractSolid state physics

Moscow University Physics Bulletin 1990. **45**. N 3. P. 101

A method of theoretical description of recombination of hydrogen atoms on solid surfaces is proposed which is based on scattering theory for several quantum particles.

Show AbstractMoscow University Physics Bulletin 1990. **45**. N 3. P. 105

A completely self-consistent band structure calculation was performed for BaO. A theoretical energy dependence of the imaginary part of the permittivity function was obtained for the first time. The results obtained show satisfactory agreement with experimental data.

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