Faculty of Physics
M.V.Lomonosov Moscow State University
Theoretical and mathematical physics

## Foundations of possibility theory. Methods of optimal estimation and decision making. 5. Fuzzy elements, independence, and conditional distributions

### Yu.P. Pyt'ev

Moscow University Physics Bulletin 1998. N 2.

The notions of a fuzzy element, independence of fuzzy elements, conditional distribution, and of the integral conditional with respect to a fuzzy element have been defined and examined.

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## Spin correlations in synchrotron radiation

### A.V. Borisov$^1$, V.A. Vshivtsev$^1$, A.I. Ternov$^2$

Moscow University Physics Bulletin 1998. 53. N 2. P. 8

Correlation between the spin of a longitudinally polarized electron and the circular polarization of the emitted photon makes a contribution to synchrotron radiation power. A quasi-classical interpretation of this correlation as the interference of charge radiation and electron spin magnetic moment fields has been given.

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## Dimensional renormalization without nonintegral dimensions for vector and spinor fields

### D.A. Slavnov

Moscow University Physics Bulletin 1998. 53. N 2. P. 13

The hitherto constructed renormalization scheme for the generating functional of Green's functions has been generalized to vector and spinor fields. The scheme retains the mathematical means of dimensional regularization, but only positive integral dimensions are used in it for the case of vector and spinor fields.

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## Modulation of ionizing radiation as an excitation mechanism of plasma oscillations

### M.A. Drofa, L.S. Kuz'menkov, S.G. Maksimov

Moscow University Physics Bulletin 1998. 53. N 2. P. 17

It has been shown that modulation of the ionizing radiation intensity can serve as a mechanism of parametric excitation of the Langmuir oscillations in a plasma flow.

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Atomic and nuclear physics

## Analysis of the event in solar cosmic rays in June 1991 according to AES 'Granat' data

### G.P. Lyubimov, E.E. Grigorenko

Moscow University Physics Bulletin 1998. 53. N 2. P. 22

An intricate course of intensity growth in solar cosmic rays with intensities of 1-20 and more than 20 MeV has been analyzed. The event was caused by a sequence of six intense solar flares occurring in the same active region at solar latitudes from E65 to W69. This fact has determined an important role of the solar latitude effect on the propagation of solar cosmic rays and flare disturbances. The use of the "reflection" model has revealed the influence of solar flares on the modulation of solar cosmic and galactic cosmic ray streams.

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## Electron medium in a relativistic resonance surface wave generator

### V.I. Kanavets

Moscow University Physics Bulletin 1998. 53. N 2. P. 27

In this paper we discuss some special features of the interaction between the electron flow and the electromagnetic field in a relativistic single-section cavity surface wave generator in the range of $\pi$- frequencies.

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## Acoustooptic interaction in media with acoustic anisotropy

### V.B. Voloshinov, O.Yu. Makarov

Moscow University Physics Bulletin 1998. 53. N 2. P. 36

Diffraction of light by ultrasound in crystals with strongly anisotropic acoustic properties has been studied. It has been shown that acoustic anisotropy of crystals affects the acoustic frequency bandwidth of Bragg diffraction and the diffracted light intensity. Analysis of the acoustooptic interaction in gallium arsenide crystals reveals a significant change in the frequency bandwidth of diffraction for angles between the phase and group sound velocities greater than $\psi=\:$10-20$^о$ as compared to the acoustically isotropic case. The diffraction efficiency in GaAs differs from the isotropic case by more than 10%. With increasing acoustic beam walk-off, when $\psi>20$$^о$, this difference becomes even greater.

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Solid state physics

## Anomalies of longitudinal magnetoresistivity in $n$-InSb

### V.V. Ostroborodova, F. Terra Al-Saied

Moscow University Physics Bulletin 1998. 53. N 2. P. 43

Ohmic $V_x$ and Hall $V_{Hy}$ potentials of InSb single crystals as functions of the angle $\alpha$ between the current $J_x$ and magnetic induction $B_{zx}$ directions at 60-350 K in magnetic fields of 0.1-20 kG have been studied. A sharp decrease in $V_x$ between the potential contacts at $\alpha$ close to 0 (180$^\circ$) have been observed in a number of samples with intrinsic and impurity $n$-type conductivity. The nature of the effect is discussed in terms of "growth" deviations from stoichiometry and by the low-resistance inclusions with $n$-type conductivity caused by them.

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## Dependence of dielectric properties of polymethacrylate gels in low-polarity media on degree of ionization

### N.L. Sitnikova, I.A. Malyshkina, N.D. Gavrilova, O.E. Filippova, A.R. Khokhlov

Moscow University Physics Bulletin 1998. 53. N 2. P. 49

The dielectric dispersion of polymethacrylate gels with various degrees of ionization has been studied at frequencies $f$ of from 10 to 10$^5$ Hz. The permittivity of gels at low frequencies reached anomalously high values of 10$^7$-10$^8$ for gels swollen in methanol and 10$^4$ for dried gels, probably, as a result of the aggregation of ion pairs into multiplets with high polarizabilities. The $\lg\varepsilon'(f)$ curves of dried gels contained vertical shift regions evidencing the existence of ionic aggregates primarily of the same size. The ions in swollen gels occurred predominantly by ionic drift no matter what the degree of gel ionization. In dried gels, the character of ions transport changed from predominantly diffusion transport to ionic drift as the degree of ionization increased, probably, which testifies to a decrease in the distance between multiplets.

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## Iron corrosion in natural anaerobic high-humidity conditions

### A.A. Novakova, N.D. Manyurova, T.S. Gendler

Moscow University Physics Bulletin 1998. 53. N 2. P. 56

A fragment of an archaeological iron spear extracted from an unearthing in North Osetia, where it had been exposed to soil corrosion in humid conditions for 19 centuries, has been studied for its chemical and structural composition. With the aid of a comprehensive technique involving X-ray diffraction analysis, M$\stackrel{..}{o}$ssbauer spectroscopy, and thermomagnetic analysis the following compounds have been found as the main corrosion products: superparamagnetic hoetite {$\alpha$-FeOOH), hydrohoetite {FeOOH$\cdot n$H$_2$O), and iron sulfides (pyrite FeS$_2$ and pyrrhotine Fe$_7$S$_8$).

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## On superparamagnetic-type paraprocess

### V.I. Nikolaev, T.A. Bushina, Kim Eng Chan

Moscow University Physics Bulletin 1998. 53. N 2. P. 62

Distinctive features of the paraprocess in superparamagnetic particles have been explored within the formalism of the molecular field theory using Langevin's model. In particular, it has been demonstrated that at the Curie temperature and under magnetic fields $H$ not exceeding (by the order of magnitude) the "characteristic field" value $H'=kT_C/\mu_0$ (where $\mu_0$ is the particle magnetic moment at absolute saturation and $T_C$ is the Curie temperature), the magnetization of an ensemble of superparamagnetic particles is proportional to $H^3$ irrespective of the scatter of their sizes (and the moment $\mu_0$).

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Geophysics

## Reconstruction of turbidity current velocity profile from distribution of suspended particles concentration

### B.I. Samolyubov, L. V. Silaeva

Moscow University Physics Bulletin 1998. 53. N 2. P. 67

A technique has been developed for reconstructing the velocity profile of turbidity current from the distribution of suspended particles concentration. The reconstructed velocity profiles agree well with direct measurement data obtained in the ocean, in reservoirs, and with a laboratory model.

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Theoretical and mathematical physics

## Covariant quark bag and vector anomaly

### K.A. Sveshnikov, I.O. Cherednikov

Moscow University Physics Bulletin 1998. 53. N 2. P. 72

An explicit covariant formalism for hybrid chiral quark bag models in 1 + 1 dimensions has been formulated. Within the suggested approach, the effect of fermionic charge flow through the interphase boundary is a direct corollary to field equations and boundary conditions.

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## Adaptive regularizing algorithms for solving ill-posed problems

### A.S. Leonov$^1$, A.G. Yagola$^2$

Moscow University Physics Bulletin 1998. 53. N 2. P. 75

A new class of stable methods for solving linear ill-posed problems is suggested. The methods take into account information about sourcewise representability of the sought normal pseudosolution. They are optimal in the order of accuracy and have such a special additional feature as adaptivity.

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## Radiative decay of a massive neutrino in a magnetized electron-positron gas

### V.Ch. Zhukovskii, P.A. Eminov, K.G. Levchenko, V.A. Vshivtsev

Moscow University Physics Bulletin 1998. 53. N 2. P. 78

The probability of radiative decay of the massive Dirac neutrino $\nu_i\to\nu_j+\gamma$ in a magnetized electron-positron gas has been calculated. A considerable enhancement of the decay rate in the case of a superstrong magnetic field as compared to the free process in matter has been demonstrated to take place.

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Optics and spectroscopy

## Stability of laser array in-phase generation in cylindrical Talbot cavity

### V.P. Kandidov, A.V. Kondrat'ev

Moscow University Physics Bulletin 1998. 53. N 2. P. 81

The in-phase generation mode of a closed laser array in a cylindrical Talbot cavity has been shown to be stable with respect to small perturbations in the form of higher-order collective modes.

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Solid state physics

## Relaxation of microstresses in a deformed Pd-Er alloy after electrolytic saturation with hydrogen

### V.M. Avdyukhina, A.A. Katsnel'son, N.A. Prokof'ev, G.P. Revkevich

Moscow University Physics Bulletin 1998. 53. N 2. P. 84

Lattice parameters of a deformed Pd-Er alloy have been measured prior to saturating the sample hydrogen with subsequent degassing. Oriented microstresses were found to change partially during degassing. These changes had a nonmonotone character.

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## Nonmonotone kinetics of $\alpha$-Si:H film conductivity variations under illumination at elevated temperature

### I.A. Kurova, N.N. Ormont

Moscow University Physics Bulletin 1998. 53. N 2. P. 87

Light intensity effect on the kinetics of dark conductivity ($\sigma_d$) variations during and after illumination has been studied for $\alpha$-Si:H films undoped and weakly doped with boron. The observed kinetics was nonmonotone at high and monotone at low light intensities. The influence oflight intensity on the kinetics of $\sigma_d$ variations can be explained by the formation and thermal annealing of photoinduced broken bonds and impurity activation and deactivation not involving light annealing of broken bonds.

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