R e g u l a r p a p e r s

Theoretical and mathematical physics

Moscow University Physics Bulletin 1996. **1996**. N 5. P. 1

А gauge model of а superstring that has а property of self-similarity has been proposed. Equations for the function of state and the Hamiltonian operator have been oЬtained Ьу means of а regular representation of the group of motion of а spinor manifold and its Lie algebra. А self-consistent boundary-value problem for eigenvalues ofthe constructed Hamiltonian operator has been solved. Energy levels corresponding to а relative mass spectrum of charged leptons е±, μ±, т± have been found. А possiЫe reason for the existence of three generations of elementary fermions has been discovered.

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Two new mathematical formulations of the proЬlem of thermoelectric cooling have been considered in the framework of а known thermodynamic model of the Peltier effect. The solution algorithms of these formulations have been realized in computer programs. The results of а mathematical experiment have been presented.

Show AbstractMoscow University Physics Bulletin 1996. **1996**. N 5. P. 10

The proЬlem of synthesizing circular dielectric waveguides is stated as typically ill-conditioned and solved Ьу applying the Tychonoffregularization method. The functionals have been constructed and а working algorithm for solving а wide range of problems of designing fiber-optic communication lines according to the preset operation cliaracteristics has been suggested. Examples of synthesized profiles of dielectric waveguides have also been given.

Show AbstractMoscow University Physics Bulletin 1996. **1996**. N 5. P. 15

Methods of detection and estimation of parameters of а localized new growth in soft tissues Ьу means ofpressure field measurements on its surface in а static case are considered. А minimax method of estimation of heterogeneity parameters in soft tissues is proposed. The analysis of maximum possiЬilities for detecting and estimating the heterogeneity parameters at measurements of pressure on the sample surface is carried out. The analysis of the information content measurements for the estimation of localized inclusion parameters is carried out. The validity of the metl10ds proposed is demonstrated bу а numerical experiment.

Show AbstractMoscow University Physics Bulletin 1996. **1996**. N 5. P. 22

А new approach to the use of asymptotic methods in statistical thermodynamics of systems with short-range potentials the repulsive part of which is similar to the potential of nonrigid spheres has been suggested. For such systems, an equation of state has been obtained, which describes stable and metastable phases with an accuracy of computer experiments.

Show AbstractRadiophysics

Moscow University Physics Bulletin 1996. **1996**. N 5. P. 27

The changes in the mutual synchronization domains for the case of fractional-multiple relationship of oscillation frequencies of the self-excited system {SES) have been investigated bу computer simulation methods. А system consisting of two oscillators coupled through а resonant circuit, in which the harmonics differing in number coincide in frequency, has been considered. The ranges of the parameters have been determined for this system, at which there exists а synchronous frequency stabilization mode. The relation has been estaЪlished between the frequency characteristics of the passive part of the SES, the composition of the oscillator spectra, and the synchronization bandwidth.

Show AbstractMoscow University Physics Bulletin 1996. **1996**. N 5. P. 32

А strong possiЬility of detecting а classical signal with unknown parameters in the quantum noise of an optical displacement tranducer is considered for the case of an optimally synthesized compensator of excessive interferences which are typical for parametric three-frequency systems.

Show AbstractMoscow University Physics Bulletin 1996. N 5.

The interaction of а plane shock wave with а region of gas-dynamic inhomogeneities in а flow has been studied Ьу numerical techniques and experimentally. In the experiments, а shock wave propagated in а turbulent flow region. The numerical modeling was based on the Euler and Boltzmann equations. The qualitative data have been oЬtained on the modification of the shock wave shape and other effects that accompany this process. It has been shown experimentally that the shock wave thickness increases when it propagates in the turbulent region. The calculated and experimental fluctuation gains behind the wave front agree witl1 each other.

Show AbstractOptics and spectroscopy

Moscow University Physics Bulletin 1996. **1996**. N 5. P. 37

The problem of suppressing stimulated Raman scattering (SRS) in а plasma under the conditions of laser thermonuclear fusion is discussed. А method of SRS suppression, based on а rapid frequency modulation of pumping radiation, has been proposed.

Show AbstractSolid state physics

Moscow University Physics Bulletin 1996. **1996**. N 5. P. 50

The present paper describes the results of the first experiments on the study of thermophysical characteristics of the impurity-helium solid phase {IHSP} which is formed upon condensation in superfluid helium of а gas-phase helium stream containing the impurity studied. The results oЪtained made it possiЪle to evaluate the thermal diffusivity, thermal conductivity and heat capacity of samples of the neon IHSP in а temperature range of 2.2-3 К. It appeared that the values obtained are close Ьу an order of magnitude, to those oЪtained for liquid helium Hel.

Show AbstractMoscow University Physics Bulletin 1996. N 5.

The electrical conductance of structures based on Sn02 films doped with Cu and Ni has been measured in the temperature range of 100 to 300 К. Doping has been found to increase the resistance R. ln weakly doped filrns, the activation energy of conductance coincided with the ionization energy of oxygen vacancy Еа ~ 130 MeV. The influence of contacts on the shape of cur1·ent-voltage characteristics of the structures has been determined.

Show AbstractMoscow University Physics Bulletin 1996. **1996**. N 5. P. 61

А Mossbauer study has been carried out of the process of low-temperature crystallization of cristobalite under hydrothermal conditions from а gel of the composition Si02 + 0.3 mass percent 57 Fе2 0з. It has been shown that in the original gel the paramagnetic Fe3+ ions are in the form of а diluted impurity in the diamagnetic matrix, with а spin-lattice relaxation oftheir magnetic moments being observed. At the beginning of the synthesis process the iron atoms are reduced to а divalent higl1-spin state with а sixfold oxygen coordination, and then, when cristobalite is formed, there occur the reverse oxidation and the formation of magnetically ordered Fe2 0 3 particles with sizes of 80 А< d < 300 А. No entry of iron atoms into tetrahedral positions of the structure has been observed.

Show AbstractB r i e f r e p o r t s

Theoretical and mathematical physics

Moscow University Physics Bulletin 1996. **1996**. N 5. P. 66

The interaction between positively charged hydrogen ions and а metal surface is studied bу the method of analysis of the structure of the metal electron gas in the presence of а proton. Calculations were performed within the framework of the theory of many-particle density functionals. The energy characteristics of the interaction between а hydrogen ion and the surface and the spatial distribution of the electron gas in the system "metal-adatom" have been calculated.

Show AbstractRadiophysics

Moscow University Physics Bulletin 1996. **1996**. N 5. P. 70

The present work is concerned with the study of the effect of propagation of signals in waveguides filled with а medium of cublc nonlinearity at а frequency extending outside the band. А numerical modeling has shown that а powerful wave shifts the critical frequency of the waveguide. As а result, а tunneling of one or several slow solitons that do not coincide in frequency with the exciting signal is observed.

Show AbstractSolid state physics

Moscow University Physics Bulletin 1996. **1996**. N 5. P. 74

The effect of а Fermi level displacement caused when substituting tin for antimony in submetallic ferromagnetic NiMnSЪ1-:r:Sn:r: alloys on sнperfine fields and magnetic moments was studied. The conclusion has been made that superfine fields and local magnetic moments are determined Ьу а partieular atomic environment of а given ion rather than Ьу generalized physical characteristics such as the position of the Fermi level, the lattice parameter, and the Curie temperature.

Show AbstractMoscow University Physics Bulletin 1996. **1996**. N 5. P. 77

А structure corresponding to free exciton states with n = 1, 2, 3 has been detected in zinc diarsenide. The state with n = 3 is observed up to а temperature of 10 К, with n = 2, up to 110 К, and with n = 1, up to 300 К. The exciton binding energy has been determined (17.5 meV).

Show AbstractMoscow University Physics Bulletin 1996. **1996**. N 5. P. 80

It is found that in the range of low-temperature transformation of magnetite (Tt = 100-120 К), the spontaneous magnetization decreases sharply, whereas the susceptiЬility of the paraprocess increases. At the same t ime, the technical magnetization characteristics ( the coercive force and the susceptiЬility measured in а weak field) reach extreme values in this domain. This suggests that the lowtemperature transformation in magnetite is а special kind of magnetic phase transition.

Show AbstractMoscow University Physics Bulletin 1996. **1996**. N 5. P. 83

The existence of а strong short-range order has Ъееn discovered using the method of diffuse scattering of X-rays in the high-temperature face-centered cublc (FCC) phase of the Mn-21 at. % Ga alloy, its parameters have bееn evaluated, and the characteristic temperature (0п = 200°С) has bееn determined. The elastic constants used for calculating the modulating functions of the dimensional effect have Ъееn calculated with the aid of the model potential technique. The short-range order parameters ai for the first four coordination spheres appeared to bе -0.16, 0.23, 0.12, and -0.24, respectively.

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