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

## Theory of classical gravitational field

### A.A. Logunov

Moscow University Physics Bulletin 2005. 60. N 1. P. 1

Basic postulates of the relativistic gravitation theory and its predictions with respect to the collapse and evolution of the Universe are briefly described.

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## Formation and propagation of steep transition layers in parabolic problems

### V.F. Butuzov$^1$, N.N. Nefedov$^1$, K.R. Schneider$^2$

Moscow University Physics Bulletin 2005. 60. N 1. P. 8

The formation of a solution with steep transition layer to a singularly perturbed parabolic equation is considered. The possible scenarios for the behavior of transition layers in time are described.

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## A new model of high-temperature superconductivity

### V.P. Maslov

Moscow University Physics Bulletin 2005. 60. N 1. P. 15

In contrast to the other works by the present author on high-temperature superconductivity, in this paper an exactly solvable problem is analyzed in detail and an elementary asymptotic leading to superconductivity is obtained. In the model suggested, a phase transition of "zero order" is observed, i.e., a free-energy jump occurs at the point where heat capacity goes to infinity. This work uses an analogy with the BCS (Bardeen—Cooper—SchriefFer) theory—short-range attraction of electrons of approximately the same energy. The temperature at which superconductivity occurs depends on the relation between the magnitude of attraction and the distance between bands. An example is presented to demonstrate that by reducing the distance between the bands at an attraction of about 0.01 eV, one can achieve phase transition at t°~100 K.

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Optics and spectroscopy

## Dynamics of polarization-controlled holographic recording in azo-containing polymer films

### E.A. Baklanova, D.V. Uraev, V.I. Shmal'gauzen

Moscow University Physics Bulletin 2005. 60. N 1. P. 24

A model of the interaction between elliptically polarized light and a film sample of an azo-containing polymer is analyzed. The mechanisms of optical writing and storing polarization holograms of different type are discussed. The results of an experimental study of the polarization characteristics of azo-polymer films are presented.

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## Erbium-doped silicon nanocrystal structures and their possible applications in light-emitting optoelectronic devices

### O.A. Shalygina, D.M. Zhigunov, M.G. Lisachenko, S.A. Teterukov, D.A. Sapun, V.Yu. Timoshenko, P.K. Kashkarov

Moscow University Physics Bulletin 2005. 60. N 1. P. 32

Studies into the photoluminescence properties of silicon nanocrystal ensembles prior to and after their doping with erbium show that the optical excitation energy of the nanocrystals is practically completely transferred to the Er$^{3+}$ ions that subsequently emit light at a wavelength of 1.5 fxm, intense optical pumping causing population inversion in the ions. The possibility of using the structures under study in lasers and optical amplifiers integrated with the silicon technology is discussed.

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Solid state physics

## Magnetooptic iron garnet films with high domain wall velocity

### V.V. Randoshkin, N.V. Vasil'eva, N.N. Sysoev

Moscow University Physics Bulletin 2005. 60. N 1. P. 44

The results of investigations into the domain wall dynamics in bismuthsubstituted single-crystal iron garnet (Bi-SCIG) films with the dimensionless damping parameter a ranging from $\ll$ 0.1 to $\geq$ 10 and different magnetic anisotropy are discussed. The agreement and discrepancy between theory and experiment are explained.

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## Magnetorefractive effect in nanocomposites

### V.S. Gushchin$^1$, E.A. Gan'shina$^1$, A.A. Kozlov$^1$, I.V. Bykov$^2$

Moscow University Physics Bulletin 2005. 60. N 1. P. 57

In the wavelength range of 1.5—20 μm optical reflection and the evenmagnetization magnetorefractive effect (MRE) were studied in the nanocomposites: ferromagnet (Co, Fe, CoFe, CoFeZr)-dielectric matrix (А1$_2$О$_3$, SiC$_2$, ТiO$_2$, MgF) that possess tunnel magnetoresistance of compositions near the percolation threshold. Dispersion of these effects depending on the polarization, angle of light incidence and applied magnetic field were investigated. It was shown that extreme values of MRE corresponded to minimal optical reflection and reached levels dozens of times greater than the traditional Kerr effects. Experimental data indicate that this effect is the result of spin-dependent tunneling of conduction electrons at optical frequencies.

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## New type of high-performance terahertz radiation detectors

### B.A. Akimov, N.B. Brandt, L.I. Ryabova, D.R. Khokhlov

Moscow University Physics Bulletin 2005. 60. N 1. P. 76

The properties of lead-telluride based doped semiconductors, which can be used to build high-performance terahertz radiation detectors are discussed. It is shown that these properties make it possible to build radiation detectors whose parameters are much better than those of the existing analogs.

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Geophysics

## Geomagnetic field and global geophysical processes

### V.I. Trukhin

Moscow University Physics Bulletin 2005. 60. N 1. P. 83

The basic properties of a geomagnetic field and problems of the use of different geomagnetic field models in studying global geophysical processes are considered. The application of paleomagnetic methods to investigation of the tectonics of lithospheric plates is taken. The available models of a geomagnetic field, a paleomagnetic field model and the means of making this model approach the actual field are discussed. Much attention is given to the problem of self-reversal of rock magnetization which is a mechanism of reverse rock magnetization alternative to geomagnetic field inversion. Ways of providing better geophysical interpretations of paleomagnetic data are discussed.

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