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

## On meaningful interpretation of possibility and necessity

### Yu.P. Pyt'ev

Moscow University Physics Bulletin 1999. 54. N 5. P. 1

The relativity principle in theory of possibilities has been stated. According to this principle, only those aspects of the possibility-theoretic model are meaningful that do not change under scaling.

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## Stability of magnetic field inversion regions in spiral galaxies

### A.A. Bykov, V.Yu. Popov

Moscow University Physics Bulletin 1999. 54. N 5. P. 7

In some spiral galaxies, the so-called magnetic field inversion regions are observed inside which the field direction is opposite to that in the adjoining regions. Under the differential rotation, the inversion regions should be expected to elongate, to become thinner, and to disappear eventually. It is shown in this paper that the existence of stable inversion regions can be accounted for by modulations of the generation saturation level in spiral arms.

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## Equation for plasma and space charge boundary layer with regard to ion collisions

### S.A. Dvinin, V.A. Dovzhenko, A.A. Kuzovnikov

Moscow University Physics Bulletin 1999. 54. N 5. P. 12

The integro-differential equation proposed in this paper generalizes the equation for a plasma and the Langmuir-Tonks layer and takes into account possible charge exchange between ions and neutral atoms in a discharge. This equation allows us to consider adequately the transition of a discharge from a mean free path of ions to diffusion in pure gases. Numerical solutions of the equation are presented.

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## Distribution of absolute maximum of correlated stationary Gaussian sequence

### A.V. Gusev

Moscow University Physics Bulletin 1999. 54. N 5. P. 16

The distribution function of an absolute maximum of the correlated stationary Gaussian sequence has been calculated. The final formula includes the Owen functions $T(c,a)$ tabulated for a wide range of possible values of the arguments $c$ and $a$. The main results are specified for computing abnormal errors in the search for the "astro-gravitational correlation".

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Optics and spectroscopy

## Multiple light scattering by aggregating spheroid ensembles. Application to erythrocyte aggregation problem

### V.V. Lopatin, A.V. Priezzhev

Moscow University Physics Bulletin 1999. 54. N 5. P. 21

A method has been proposed for calculating characteristics of multiple light scattering by aggregating spheroid ensembles. This method is used for the case of spontaneous aggregation of red blood cells (erythrocytes) in blood to determine 1l:he appropriate scattering indicatrices and the relationship of the intensity of backscattered light versus aggregation time. The results obtained have been compared with experimental data.

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## Analysis of a collective generation model of laser arrays with diffraction coupling

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

Moscow University Physics Bulletin 1999. 54. N 5. P. 27

The dynamic model for laser arrays with diffraction coupling has been used to develop a technique for studying a transient process when changing over from spontaneous radiation of individual channels to collective generation. The nature and time of the transient process depend on the relationship between the selectivity factor of the system and the extent by which the gain increment exceeds the generation threshold. It is shown that the traditional dynamic model of collective generation provides the results that contradict the experimental evidence.

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Solid state physics

## Influence of polar Langmuir-Blodgett films on slow states of silicon surface

### N.L. Levshin$^1$, S.G. Yudin$^2$

Moscow University Physics Bulletin 1999. 54. N 5. P. 34

The influence of polar Langmuir-Blodgett films on the recharge of slow silicon surface states in a vacuum and in atmospheric water vapor has been studied. The deposition of a copolymer film has been shown to decrease silicon surface heterogeneity. The forms of kinetic dependence of the recharge of slow states have been analyzed. The results obtained are interpreted in terms of the electron-vibrational model of slow charge relaxation on the semiconductor surface.

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## Effect of dielectric environment on exciton spectrum of silicon quantum fibers

### M.G. Lisachenko, V.Yu. Timoshenko

Moscow University Physics Bulletin 1999. 54. N 5. P. 39

The problem of an exciton in a silicon quantium fiber $2\div4$ nm in diameter with permittivity $\varepsilon_i$ on a medium with permittivity $\varepsilon_e$ has been solved numerically. It was found that, if $\varepsilon_e<\varepsilon_i$ the exciton radius was smaller and the binding energy higher than for $\varepsilon_e=\varepsilon_i$. Conversely, with $\varepsilon_e>\varepsilon_i$, the exciton radius increased, while the binding energy sharply decreased. This explains the experimental data on dielectric quenching of exciton luminescence of porous silicon.

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## Dielectric relaxation m vinylidene fluoride/trifluorethylene copolymer doped with rhodamine 6G

### A.G. Chaplygin, I.A. Malyshkina, N.D. Gavrilova, K.A. Verkhovskaya

Moscow University Physics Bulletin 1999. 54. N 5. P. 45

The authors have investigated the dynamic dielectric properties of a vinylidene fluoride/trifluorethylene copolymer (70 mol.% and 30 mo!.%, respectively) in the presence of 6G rhodamine polar dopant (0, 0.2, 0.6, 1, and 1.5 wt.%). The measurements were made by the bridge method in the 80-300 K temperature range at frequencies of from 20 Hz to 20 kHz. The dielectric constant was found to depend nonmonotonically on the concentration of the dopant that may be due to the polar nature of rhodamine 6G. It was found that the presence of the dopant and its concentration affect the mobility of chain segments in the amorphous phase and the conduction mechanism in the copolymer.

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## Influence of s-d-scattering on quantum size effect in conductivity of ferromagnetic metal thin films

### A.V. Vedyayev, O.A. Kotel'nikova, N.G. Pugach

Moscow University Physics Bulletin 1999. 54. N 5. P. 50

The conductivity of a thin metal film for the $s$-$d$-exchange model has been calculated in the context of Kubo's formalism using the Green function method. Due account is taken of the dependence of conduction electron scattering amplitude on the film thickness resulting from the quantum size effect, and the probability for $s$-electrons to be scattered into the split $d$-zone. Conductivity has been described by an oscillating function of the film thickness with periods that correspond to the Fermi momenta of $d$-electrons.

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## The nature of spin-glass phase in semiconducting spin glasses of the $x$CuCr$_2$Se$_4$-$(1-x)$Cu$_{0,5}$Me$_{0,5}$Cr$_2$Se$_4$ (Me${}={}$In, Ga) system

### A.I. Abramovich, L.I. Koroleva

Moscow University Physics Bulletin 1999. 54. N 5. P. 55

The dependence of magnetoresistance $\Delta\rho/\rho$ on the square of magnetization $\sigma^2$ in strong magnetic fields has be studied for the $x$CuCr$_2$Se$_4$-$(1-x)$Cu$_{0,5}$Me$_{0,5}$Cr$_2$Se$_4$ (Me${}={}$In, Ga) system. Both in spin glasses and in the reciprocal spin glass, the slope of the $(\Delta\rho/\rho)(\sigma^2)$ dependences was shown to change at freezing temperature $T_f$ suggesting that at $T=T_f$, the spin system experienced substantial rearrangement, that is, underwent a thermodynamic phase transition. The spin-glass phase in the reciprocal spin glass was shown to consist of spins of separate Cr$^{3+}$ ions, whereas spin glasses contained not only these ions but also interacting ferromagnetic clusters.

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## Nonequilibrium oscillating-type phase transformations in a Pd-Er alloy relaxing after saturation with hydrogen

### V.M. Avdyukhina, A.A. Katsnelson, G.P. Revkevich

Moscow University Physics Bulletin 1999. 54. N 5. P. 61

Oscillating changes have been found in the volume content of phases and in the difference in erbium atoms density in these phases in a Pd-Er alloy following its saturation with hydrogen. A model has been suggested according to which this phenomenon is associated with the competition between the ascending and gradient diffusion processes in the nonequilibrium medium. The nonequilibrium character of the medium is due to the presence of hydrogen-enriched defect-metal complexes.

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Geophysics

## Transformation of ocean stratification structure resulting from underwater earthquake

### M.A. Nosov, S.N. Skachko

Moscow University Physics Bulletin 1999. 54. N 5. P. 66

Turbulent energy and turbulent heat transfer balance equations are used for evaluating the possibility of vertical temperature profile transformation resulting from an underwater earthquake.

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Theoretical and mathematical physics

## Method of modeling potentials for Schr$\stackrel{..}{o}$dinger equation

### V.N. Sidorenko

Moscow University Physics Bulletin 1999. 54. N 5. P. 73

A method of modeling potentials is discussed for constructing the energy spectrum of the Schr$\stackrel{..}{o}$dinger equation in quasiclassical framework. The idea of the method consists in constructing a modeling potential, which is simpler than the original potential not necessarily being locally close to the latter, but with the same global structure of the spectrum.

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## Schr$\stackrel{..}{o}$dinger equation for an oscillator. A spectral problem

### A.S. Vshivtsev, V.A. Vshivtsev, A.V. Tatarintsev, A.R. Frenkin

Moscow University Physics Bulletin 1999. 54. N 5. P. 76

A procedure for finding the spectrum of the one-dimensional Schr$\stackrel{..}{o}$dinger equation for a linear oscillator and a phase-shift oscillator has been suggested. The procedure is related to examination of the analytical properties of the Laplace images of wave functions.

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Atomic and nuclear physics

## Experimental investigations into the structure of polarized bremsstrahlung of relativistic electrons in polycrystalline aluminum

### S.V. Blazhevich$^1$, V.K. Grishin$^2$, O.S. Ishkhanov$^2$, N.N. Nasonov$^1$, V.P. Petukhov$^2$, V.I. Shvedunov$^2$

Moscow University Physics Bulletin 1999. 54. N 5. P. 79

We have investigated experimentally the influence of collective effects on the structure of the polarized bremsstrahlung of relativistic electrons in a polycrystalline aluminum film. The experiment was conducted using an electron accelerator with electron energy of 2.4 Mev built at the Research Institute of Nuclear Physics attached to Moscow State University. The peaked structure of polarized bremsstrahlung observed for the first time agrees with the theoretical predictions.

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Solid state physics

## Violation of the Mooij rule in ferromagnetic composites Co$_x$(CuO)$_{100-x}$ and Co$_x$(Al$_2$O$_3$)$_{100-x}$

### A.B. Granovsky$^1$, V.A. Kovalev$^1$, H.R. Khan$^2$, V.N. Prudnikov$^1$, M.V. Prudnikova$^1$

Moscow University Physics Bulletin 1999. 54. N 5. P. 83

It is demonstrated that the Mooij rule is violated for the composites Co$_x$(CuO)$_{100-x}$ and Co$_x$(Al$_2$O$_3$)$_{100-x}$ with $x>40$ (%), namely, the resistance of these systems does not tend to saturation, as their temperature increases and reaches $300\div7000$ μ$\Omega\cdot$cm, which is many imeslthe value of $\rho^*\approx150$ μ$\Omega\cdot$cm, with the temperature resistance coefficient remaining positive. The violation of the Mooij rule is associated with an important role played by intergranular contacts in the resistance growth.

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## Phase transitions in thin layers of solid solutions К$_x$Na$_{1-x}$NO$_2$

### T.M. Hammad$^1$, A.A. Al-Tauyan$^1$, B.A. Strukov$^2$

Moscow University Physics Bulletin 1999. 54. N 5. P. 86

Thin layers of the К$_x$Na$_{1-x}$NO$_2$ system have been obtained from a melt using special techniques. It is shown that a ferroelectric phase transition disappears when the content of К$^+$ ions reaches $x=0,1$. The dielectric constant, pyroelectric current and conductivity diminish with an increase of $x$. These data demonstrate that phase transition temperature goes down when the concentration of impurity grows. A phase diagram of the system under consideration has been plotted.

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Astronomy

## Stability of triangular libration points in a nonlinear approximation in spatial restricted photogravitational elliptic three-body problem

### A.Yu. Kochetkova

Moscow University Physics Bulletin 1999. 54. N 5. P. 90

The stability regions of triangular libration points in a restricted photogravitational elliptic three-body problem have been first investigated in a nonlinear approximation.

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