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M.V.Lomonosov Moscow State University
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Theoretical and mathematical physics

D.D. Sokolov

D.D. Sokolov

Discontinuous distributions of transport coefficients in mean-field electrodynamics

Moscow University Physics Bulletin 1997. 52. N 5. P. 1

An extension of the mean-field electrodynamics equations is proposed that enables discontinuous distributions of chirality to Ье described in its framework. А relation between the phenomena that take place at the jump surface of the magnetic diffusion coefficient and the time evolution of the magnetic moment is considered.

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Computer simulation of spontaneous decay of а three-particle cluster

Computer simulation of spontaneous decay of а three-particle cluster

О.А. Chichigina

Moscow University Physics Bulletin 1997. 52. N 5. P. 6

The spontaneous decay of а cluster of three identical atoms or molecules, whose interaction is described Ьу the Lennard-Jones potential, has been simulated. The mean cluster lifetime and decay curves have been produced for energy values higher than the maximum energy of а staЫe cluster but close to this value. The numerical data virtually coincide with analytical calculations obtained earlier on the basis of the dynamic theory.

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Classification of solutions of а special kind of nonlinear Schrodinger-type equations

Classification of solutions of а special kind of nonlinear Schrodinger-type equations

A.G. Kornienko, A.R. Frenkin, and G.A. Chizhov

Moscow University Physics Bulletin 1997. 52. N 5. P. 12

Classification has been made of solutions of unidimensional Schrodinger-type nonlinear equations in the form of solitary waves, obtained bу the quadrature method. Effective potentials for corresponding differential equations have been considered and the structure of the phase plane has been studied. Examples of nonstationary and oscillating solutions of these equations have been given.

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Sоmе nеw relations for the electromagnetic field tensor in pseudo-Riemannian space-time

Sоmе nеw relations for the electromagnetic field tensor in pseudo-Riemannian space-time

V.I. Grigor'ev and I.Р. Denisova

Moscow University Physics Bulletin 1997. 52. N 5. P. 17

Explicit expressions for powers ofthe electromagnetic field tensor in terms ofthe three lowest powers of this tensor, the metric tensor of the pseudo-Riemannian space-time and two independent invariants of the electromagnetic field have been obtained.

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Reconstruction of electron concentration profile for plasma layers of different size from radiosonde observation data

Reconstruction of electron concentration profile for plasma layers of different size from radiosonde observation data

V.E. Kunitsyn and I.А. Nesterov

Moscow University Physics Bulletin 1997. 52. N 5. P. 21

The impact ofthe layer size on the feasiЬility oflayer reconstruction is discussed. For high potentials with valleys, the reflection coefficient is shown to change abruptly within the narrow frequency intervals; outside these intervals the geometrical optics approximation is applicaЪle to а high precision. With increasing potential, the intervals width decreases rapidly (at an exponential rate), and the intervals bесоmе practically indiscernible, therefore, in actual practice, full information about the potential cannot bе obtained, which leads to an ambiguous solution of the inverse proЪlem.

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Regularized scaling factor method for calculatiпg molecнle force fields

Regularized scaling factor method for calculatiпg molecнle force fields

I.V. Kochikov, G.M. Kuramshina, A.V. Stepanova, and A.G. Yagola

Moscow University Physics Bulletin 1997. 52. N 5. P. 28

А regularizing algorithm has been implemented for calculating the force fields of polyatomic molecules. The algorithm is based on Pulay's method of scaling factors.

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Atomic and nuclear physics

Magnetic hyperfine fields AT^181Та nuclei in the laves phases RFe_2 (R = ТЬ, Но, Уb)

Magnetic hyperfine fields AT^181Та nuclei in the laves phases RFe_2 (R = ТЬ, Но, Уb)

А.А. Sorokin, В.А. Komissarova, G.K. Ryasnyi, S.I. Reiman, L.G. Shpin'kova, A.V. Tsvyashchenko, E.N. Shirani, L.N. Fomicheva, and A.S. Deпisova

Moscow University Physics Bulletin 1997. 52. N 5. P. 34

The method of ϒϒ-perturbed arigular correlations was used to measure magnetic hyperfine fields Вhf at the 181^Та nuclei in the Laves phases YbFe2, HoFe2, and TbFe2. At 300К the following Вhf(Та) values were oЬtained: 18.5 Т, 16.2 Т, and 12.1 Т, respectively. The experimental results are compared with the data obtained bу us earlier for other phases RFe2.

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Radiophysics

Dispersion properties of planar shielded waveguides with Kerr's dielectric

Dispersion properties of planar shielded waveguides with Kerr's dielectric

A.F. Aleksandrov and V.A. Kubarev

Moscow University Physics Bulletin 1997. 52. N 5. P. 39

Propagation of electromagnetic waves in waveguides completely or partially filled witli а Kerr-type medium with positive nonlinearity is considered. Dispersion relations have been obtained and dispersion characteristics have been studied. It is shown that the dependence of wave retardation on its intensity is Kerr in nature with а certain effective nonlinearity coefficient.

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lncoherent signal accumulation in gravity-wave experiment

lncoherent signal accumulation in gravity-wave experiment

М.Р. Vinogradov, A.V. Gusev, and V.K. Milyukov

Moscow University Physics Bulletin 1997. 52. N 5. P. 44

An incoherent accumulator of gravity radiation bursts has been synthesized on the basis of the generalized maximum likelihood criterion for an integrated data processing system. А technique has been developed for estimating the probability of errors of the first kind for а non-Gaussian approximation of the source statistics.

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Optics and spectroscopy

Effect of anti-Stokes component on tl1e gain of stimulated Rama11 scattering in plasma

Effect of anti-Stokes component on tl1e gain of stimulated Rama11 scattering in plasma

0.М. Bilak and S.Yu. Nikitin

Moscow University Physics Bulletin 1997. 52. N 5. P. 49

The authors have calculated the correction to the gain of stimulated Raman scattering (SRS) in а homogeneous plasma due to the effect of the anti-Stokes scattering component. It has been shown that for conditions close to those of laser fusion synthesis this correction does not exceed а few percent and is independent of the pumping intensity.

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Nonreciprocal effects in ring Raman lasers

Nonreciprocal effects in ring Raman lasers

N.V. Kravtsov апd N.I. Naumkin

Moscow University Physics Bulletin 1997. 52. N 5. P. 55

The initiation of amplitude and frequency nonreciprocity in а pulsed ring Raman laser with compressed hydrogen has been studied experimentally. The character and magnitude of nonreciprocal effects have been shown to depend on the density of radiation power in the laser resonator. The observed effects are analyzed on the assumption of spatial nonuniformity of the nonlinear medium and the formation of а wave front reversal mirror.

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Acoustics and molecular physics

Propagation of wide-band acoustic pulses in unidirectional fibrous

Propagation of wide-band acoustic pulses in unidirectional fibrous

А.А. Karabutov, I.М. Kershtein, I.М. Pelivanov, апd N.V. Podymova

Moscow University Physics Bulletin 1997. 52. N 5. P. 60

Propagation of acoustic videopulses in unidirectional fibrous graphite-epoxy composites is studied. The immersion technique with thermooptical ultrasound excitation is used. Experiments have shown that the mechanical properties of such media can bе described bу the orthotropic model. ln the frequency range of from 1 to 15 MHz, frequency dispersion of phase velocity has not been observed independently of the direction of ultrasound propagation in the composite.

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Solid state physics

Spin-torsional interactions in magnetic substances

Spin-torsional interactions in magnetic substances

S.A. Istomin and R.N. Kuz'min

Moscow University Physics Bulletin 1997. 52. N 5. P. 66

А Lagrangian has been constructed and а system of dynamic equations has been derived that describe an elastic ferromagnet under the action of external magnetic and torsional fields. It has been shown that an external torsional field affects the mechanical state of magnetics and their magnetization. Analysis of the equations has revealed some features inherent in the spin-torsional interaction in magnetics. А feasiЬle experiment has been proposed for detecting spin-torsional interactions in magnetic substances. The range of admissiЫe values of the spin-torsional interaction constant has been estimated.

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Influence of ferroelectric phase transition on Langmuir- Blodgett film adsorption properties

Influence of ferroelectric phase transition on Langmuir- Blodgett film adsorption properties

N.L. Levshin, S.G. Yudin, and А.Р. Diankina

Moscow University Physics Bulletin 1997. 52. N 5. P. 71

Adsorption isotherms of water molecules and hexane on the surface of polar Langmuir-Blodgett films (VDF/TrFE} have been obtained bу the method of piezoresonance quartz balance at several measurement temperatures. The ferroelectric phase transition of the first kind in the film was found to influence the adsorption capacity of the adsorbent.

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Theoretical and mathematical physics

Oscillatory disintegration of small-amplitude magnetohydrodynamic shock waves

Oscillatory disintegration of small-amplitude magnetohydrodynamic shock waves

S.A. Markovskii

Moscow University Physics Bulletin 1997. 52. N 5. P. 75

А new scenario of time evolution of small-amplitude trans-Alfvenic shock waves is suggested. The scenario is the oscillatory disintegration, i.e., the mutually reversible transformation into an Alfven discontinuity. Simultaneously, shock and self-similar waves are emitted and contact discontinuities occur. Thus, а nonevolutionary shock wave cannot exist as а steady flow.

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Influence of polarization potential on probaЬilities of free-free electron transitions

Influence of polarization potential on probaЬilities of free-free electron transitions

N.Yu. Dobrolyubov, V.D. Kukin, and V.S. Rostovskii

Moscow University Physics Bulletin 1997. 52. N 5. P. 78

А method for evaluating the matrix element of an electric dipole transition between the states of the continuous spectrum with regard to the existence of an atom of Coulomb and polarization potentials in the exterior region has been considered. Recurrent formulas for evaluating the contribution of the integral over the domain outside the atom to the matrix element with the use of the values of the radial wave functions and their first derivatives on the boundary have been obtained.

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Relation for nonlocality parameters of gluon and four-quark condensates of QCD from finiteenergy sum rules

Relation for nonlocality parameters of gluon and four-quark condensates of QCD from finiteenergy sum rules

D.V. Meshcheryakov and V.B. Tverskoi

Moscow University Physics Bulletin 1997. 52. N 5. P. 81

In the framework of the finite-energy sum rules method а relation has been obtained for the nonlocality parameters of the four-quark and gluon condensates of QCD.

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Neutrino pair production bу virtual photon in external magnetic field

Neutrino pair production bу virtual photon in external magnetic field

V.Ch. Zhukovskii, А.Е. Grigoruk, K.G. Levchenko, and Р.А. Eminov

Moscow University Physics Bulletin 1997. 52. N 5. P. 83

Production of а massive neutrino-antineutrino pair bу а virtual polarized photon in the Weinberg-Salam model with mixing has been studied. The rate of the neutrino pair production bу photons with various polarizations at values of the magnetic field strength lower than critical has been found.

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Solid state physics

On magnetic moment of Cr^{3+} ion in ferrites-chromites with spinel structure

On magnetic moment of Cr^{3+} ion in ferrites-chromites with spinel structure

A.N. Goryaga, L.G. Antoshina, and E.N. Kukudzhanova

Moscow University Physics Bulletin 1997. 52. N 5. P. 86

The behaviour ofthe paramagnetic susceptibllity ofa series offerrites-chromites samples with а high content of Cr$^{3+}$ ions has been studied. The experimental value of the Curie-Weiss constant has been found to bе much smaller than the theoretical one on the basis of the obtained results and making use of the results of NMR study in the compound MgO with an admixture of Cr$^{3+}$ ions. For the first time the authors have made а proposal that the understated values of the experimental magnetic moments of ferrites-chromites with а high content of chromium ions may also bе due, together with other reasons, to а decrease in the magnetic moment of Cr$^{3+}$ $({t^3}_{2g},{e^0}_g)$ ions because of the transfer of the spin density from О$^{2-}$ ions to the vacant eg-orbltals of Cr$^{3+}$ ions.

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