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

Theoretical and mathematical physics

Moscow University Physics Bulletin 1993. **48**. N 4. P. 1

Within the framework of special relativity theory, based on the geometrization principle, fundamental equations are derived for gravitational field, which necessarily involve the graviton mass. According to these equations, a homogeneous and isotropic Universe develops cyclically and can only be "planar". The existence of a large "latent" mass of substance in this Universe is predicted. The theory excludes the existence of "black holes".

Show AbstractMoscow University Physics Bulletin 1993. **48**. N 4. P. 15

A standard sine mapping of a circle which effectively describes the transition from quasi-periodic motion to chaos in nonlinear systems is considered. For some parameter values corresponding to the chaotic dynamics of this mapping invariant distributions are calculated. It is shown that certain parametric actions on the mapping of a circle being in a chaotic mode result in suppression of chaos, that is, in parametric destochastization.

Show AbstractAtomic and nuclear physics

Moscow University Physics Bulletin 1993. **48**. N 4. P. 23

The energy spectra of photoneutrons generated in the $(\gamma, xn)$ reaction on medium and heavy nuclei in the region of dipole giant resonance were analyzed. The analysis was carried out within tl1e framework of the generalized model of multipole giant resonance decay using the formalism of statistical multistep compound processes and allowing for the yield multiplicity. The nucleons were explicitly separated into two types (neutrons and protons). The emission of two neutrons was correctly taken into account. The results of calculations of photoneutron spectra for the nuclei $^{115}In (E_{\gamma}^{max} = 28 MeV)$, $^{181}Та (E_{\gamma}^{max} = 19 MeV)$, and $^{209}Bi (E_{\gamma}^{max} =20 MeV)$ are presented and compared with experiment.

Show AbstractRadiophysics

Moscow University Physics Bulletin 1993. **48**. N 4. P. 27

This paper considers characteristics of a resonance bolometer which is an infrared radiation detector depending for its operation on measuring the temperature dependence of parameters of a reactive element connected into a high-Q oscillatory circuit. The optimal pumping and heat removal conditions are determined with consideration for thermal feedback. The voltage-power sensitivity and noise are measured for microwave-pumped bolometers with active elements (cryogenic dielectric resonators made of potassium tantalate and strontium titanate) included in their circuits.

Show AbstractMoscow University Physics Bulletin 1993. **48**. N 4. P. 33

The interaction of an electron beam with the field of the electrodynamic system of a relativistic carcinotron is analyzed in a linear approximation. Consideration is given not only to the interaction of the electron flux with the field of the (-1 )th space harmonic of a backward wave, but also to the field of the 0th space harmonic of a forward wave. The presence of this wave is due to the carcinotron design, where the microwave energy is taken out towards the electron collector. The effect of interaction with the forward wave on the starting conditions of the oscillator is demonstrated by an example of a concrete mock-up of a relativistic backward-wave tube.

Show AbstractMoscow University Physics Bulletin 1993. **48**. N 4. P. 38

The minimal noise factor of a solid-state gravitational antenna with an arbitrary displacement pickup has been calculated on the basis of electromechanical transformation theory for a realistic model of external effects. A physically achievable algorithm for output signal processing is discussed.

Show AbstractOptics and spectroscopy

Moscow University Physics Bulletin 1993. **48**. N 4. P. 44

Applicability of the Kramers-Kronig relations to the problem of unambiguous reproduction of the amplitude reflection coefficient from the energy reflection coefficient for a layered medium is considered. Examples of nonuniqueness of the solution are given. The conditions necessary for the existence of a one-to-one correspondence between the amplitude and phase of the amplitude reflection coefficient (the conditions for unambiguous reproduction of the amplitude reflection coeffident from the energy one) are determined.

Show AbstractMoscow University Physics Bulletin 1993. **48**. N 4. P. 51

A theoretical model is developed that describes generation of solid-state lasers with intraresonator transformation of radiation into the second harmonic in crystals with type II wave synchronism. Regions of existence of stationary and nonstationary generation modes are studied.

Show AbstractAcoustics and molecular physics

Moscow University Physics Bulletin 1993. **48**. N 4. P. 60

The results of experiments are discussed in which a nonlinear evolution of acoustic pulses was observed under specially chosen conditions, where the effect of diffraction was practically ruled out. Acoustic pulses were generated by an optoacoustic method, which enables one to obtain short powerful pulses of predictable shape. The pulses were picked up by a hydrophone based on a polyvinylidene fluoride film. At high peak pressures the evolution of an almost triangular profile with a clearly pronounced discontinuous front was observed. The pulse amplitude decreased in inverse proportion to the root of the distance to the radiator. The experimental results are in good agreement with the classical theory of such waves.

Show AbstractSolid state physics

Moscow University Physics Bulletin 1993. **48**. N 4. P. 66

The earlier introduced representation of characteristic solutions of the Takagi equations in the two-ray dynamic diffraction is further developed by the authors. It is shown that this approach is physically adequate to the concept of a dynamically self-consistent system of fields in a crystal. Within the framework of this approach, equations are derived for characteristic solutions in a perfect and in a one-dimensionally distorted crystal. It is demonstrated that the system of Takagi equations involving a local accommodation function is singled out in the consideration of diffraction by one-dimensionally distorted crystals. Based on the notion of characteristic solutions of the Takagi equations, a model of a crystal with random one-dimensional distortion field is considered and the statistical averaging of the equations for characteristic solutions is carried out.

Show AbstractMoscow University Physics Bulletin 1993. **48**. N 4. P. 71

Tl1e structural and magnetic parameters of Ni films obtained from a discharge with oscillating electrons are shown to depend on the energy of $Кr^+$ ions bombarding the film in the course of deposition. The shape of the energy dependence is explained by several factors, including the presence of discrete ionization regions in the discharge, the elastic and inelastic interactions of $Кr^+$ ions with the film surface, the ratio of fluxes of Ni atoms and $Кr^+$ ions in the two discharge regimes studied, and the difference in the character of ion interaction with the fee and hep phases of nickel.

Show AbstractMoscow University Physics Bulletin 1993. **48**. N 4. P. 76

It has been shown by the technique of X-ray diffuse scattering that in the AlCu (0.5 at.%) alloy immediately after its preparation there is inhomogeneous short-range order.

Show AbstractMoscow University Physics Bulletin 1993. **48**. N 4. P. 80

A new modulation method was suggested to determine short lifetimes $(\ge10^{-8} с)$ of minority charge carriers in the base region of solar cells. The method is based on compensation for the alternating photocurrent by an additional current source. Data obtained for single-crystal silicon solar cells irradiated by a fluence of electrons (below $10^{16} см^{-2}$) with 1 MeV energy are presented.

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

Theoretical and mathematical physics

Moscow University Physics Bulletin 1993. **48**. N 4. P. 85

The total cross section of the process $\gamma e\to eWW$ at energies up to 2 TeV has been calculated. The contributions to the process come from the three- and fourboson vertices ($\gamma WW$, $ZWW$, $\gamma \gamma WW$ and $\gamma ZWW$). The large magnitude of the cross section suggests that this will be one of the most interesting processes in studying the structure of the electroweak sector of the Standard Model using the linear colliders that are now being designed.

Show AbstractAcoustics and molecular physics

Moscow University Physics Bulletin 1993. **48**. N 4. P. 88

The process of focusing of acoustic pulses is investigated theoretically and experimentally. The analysis is carried out in the parabolic approximation. It is shown that the pulse profile at an arbitrary point of a Gaussian beam can be found using Green's function. The calculation of the acoustic field is performed for different focusing conditions. The numerical results are in good agreement with the experimental data. The proposed approach makes it possible to calculate pulse acoustic fields sufficiently accurately and take account of the effects of focusing and diffraction.

Show AbstractMoscow University Physics Bulletin 1993. **48**. N 4. P. 92

The problem of one-frequency matching of complex impedances with the help of an acoustic lumped-parameter matching system is considered. The solution is illustrated by calculations of matching systems for hydroacoustic transducers of small wave size. The properties of matching systems and the possibilities of their optimization are discussed.

Show AbstractGeophysics

Moscow University Physics Bulletin 1993. **48**. N 4. P. 95

A numerical method is used to study the possibility and efficiency of tsunami generation. by an underwater landslide. The effect of the rate and travel distance of the landslide on characteristics of the wave it generates is considered at slope angles within 0-0.06 rad corresponding to actual slopes of the sea floor. It is shown that the dependence of the energy and amplitudes of the waves on the rate of the landslide are of resonance nature, and that the position of the resonance region depends on the landslide travel distance both for a horizontal and a sloping sea floor.

Show AbstractSolid state physics

Moscow University Physics Bulletin 1993. **48**. N 4. P. 98

A phononless contribution to low-temperature alternating-current conductivity for a model with a diagonal disorder is calculated with consideration for quantum correlation of the levels. It is shown that a band corresponding to resonance transitions between neighboring-localized states can appear in the IR absorption spectra of organic semiconductors.

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