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

## Dilepton production in deep inelastic lepton-proton scattering: effect of interference of heavy majorana neutrinos

### A. Ali$^1$, A.V. Borisov$^2$, D.V. Zhuridov$^2$

Moscow University Physics Bulletin 2005. 60. N 2. P. 1

A cross section of the deep inelastic production of lepton pairs $e^+p\to\bar{\nu}_e\ell^+\ell'^+X$ ($\ell,\ell'=e,\mu,\tau$) with nonconservation of the lepton number due to exchange of heavy Majorana neutrinos is calculated. The contribution of two neutrino mass states is considered, and the effect of their interference is studied. The results are extended to the case of a larger number of neutrinos. The possibilities of observation of the above process at future lepton—proton supercolliders are discussed.

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## Scenario of a constantly pulsating universe

### Yu.M. Loskutov

Moscow University Physics Bulletin 2005. 60. N 2. P. 6

It is shown that in certain physical conditions the complete system of gravitation equations leads to a scenario of the periodically pulsating Universe between states with maximal $\sim10^{66}$ g/sm$^3$ and minimal $\sim 5\cdot 10^{-30}$ g/sm$^3$ ) energy density of matter. The total energy density of all the matter in the Universe is always equal to zero. In Riemannian space, the evolution of the Universe amounts to constant alteration of its stages of "expansion" and "contraction". The period of each stage is estimated at (15-16)X10$^9$ years. "Acceleration" in the last third of an "expansion" stage is positive and increases with time. The temperature regime in such a universe is also investigated. Within the framework of the proposed concept, an explanation of the cosmological red shift is given. Finally, a theoretical explanation is given for the observed effect of the non-Faraday cosmological rotation of the polarization plane of the electromagnetic radiation emitted by distant radio galaxies.

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## Color ferromagnetism in the $SU(2)$ model of field theory at finite temperatures

### V.Ch. Zhukovskii$^1$, О.V. Tarasov$^1$, D. Ebert$^2$

Moscow University Physics Bulletin 2005. 60. N 2. P. 18

A possibility of color ferromagnetism in QCD with the $SU(2)$ group is investigated. A phase transition between this state and the color superconducting state is considered. The influence of finite temperature effects on this phase transition is analyzed.

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## Nature of instability in a system with two coupled branches in the oscillation spectrum near the opacity band

### I.N. Kartashov, M.V. Kuzelev

Moscow University Physics Bulletin 2005. 60. N 2. P. 29

The problem of instability development within a system with two coupled waves near the opacity band is considered. In this case the system is shown to be absolutely unstable. The instability development increments are found.

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Optics and spectroscopy

## Optical harmonics generation in porous semiconductor nanostructures

### L.A. Golovan', P.K. Kashkarov, V.Yu. Timoshenko, A.M. Zheltikov

Moscow University Physics Bulletin 2005. 60. N 2. P. 36

Ways of increasing the efficiency of optical harmonics generation in porous silicon and gallium phosphide nanostructures formed via electrochemical etching of crystalline semiconductors are studied. Among the ways of increasing the efficiency of nonlinear-optical interactions are phase matching in anisotropically nanostructured semiconductors, fabricating one-dimensional photon crystals, and increasing the local field strength, including the case of light scattering in macroporous semiconductors.

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## Two-frequency undulator and harmonic generation by an ultrarelativistic electron

### К.V. Zhukovskii, V.V. Mikhailin

Moscow University Physics Bulletin 2005. 60. N 2. P. 50

Investigation and analysis of the radiation spectrum of a relativistic electron moving in the magnetic field of a two-frequency undulator, oscillating in two orthogonal planes, are carried out. The spectral properties of the radiation emitted in the undulator with integer-multiple spatial periods Eire discussed.

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Solid state physics

## Electrons forming the superconducting current

### N.B. Brandt, G.A. Mironova, V.V. Rzhevskii

Moscow University Physics Bulletin 2005. 60. N 2. P. 59

The relationships between the density of elementary excitations and the total number of electrons in different temperature intervals for normal and superconducting states of the London superconductors are considered. It is shown that the fundamentally different Drude—Lorentz and Lifshits conduction models can be combined if the effective density of superconducting electrons is introduced.

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## Gyromagnetic ratio in garnet ferrite Tm$_3$(Fe,Ga)$_5$O$_{12}$

### V.V. Randoshkin, A.V. Spazhakin, N.N. Sysoev, V.A. Bazilenko

Moscow University Physics Bulletin 2005. 60. N 2. P. 65

The concentration and temperature dependences of the effective gyromagnetic ratio in garnet ferrite Tm$_3$[Fe$_{2-x}$Ga$_x$](Fe$_{3-y}$Ga$_y$)O$_{12}$ have been calculated. In the calculations the molecular field theory and the Kittel formula for the effective gyromagnetic ratio have been used.

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Geophysics

## Model of rock magnetization self-reversal phenomenon

### N.S. Bezaeva, Т.V. Matveeva, V.I. Trukhin

Moscow University Physics Bulletin 2005. 60. N 2. P. 70

The fundamental geophysical problem of rock magnetization self-reversal, i. е., the phenomenon of rock magnetization antiparallel to a magnetizing field is considered. A physical model of magnetization self-reversal and computer implementation of this model are presented. Modeling results are in good qualitative agreement with experimental data.

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Astronomy

## Gravitational microlensing: new possibilities for astronomic observations

### A.M. Cherepashchuk

Moscow University Physics Bulletin 2005. 60. N 2. P. 74

Gravitational microlensing is associated with curvature of light rays from a background far star in a gravitational field of a nearer object which results in a characteristic variability of the stellar brightness whose duration is about 1-1000 days. Observations of gravitational microlensing effects through simultaneous registration of the brightness of millions of stars of the Large and Small Magellanic Clouds as well as of the bulge of our Galaxy have been extensively made by a number of research teams in the recent decade. Several hundreds of microlensing phenomena have already been discovered. Since the microlensing effect duration is proportional to the square root of the gravitational lens mass, the masses of dark bodies in the Galaxy have been measured: they are on the average in the range of 0.15—0.90 solar mass. In three cases the mass of dark bodies was found to be equal to about six solar masses which suggests that they are single black holes. By specific features of the gravitational microlensing effects a dark object—gravitational lens—can be identified as a "wormhole" which may exist in accordance with predictions of the Einstein theory of relativity. At present astronomers conduct an active search for "wormholes" using gravitational microlensing effects.

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