Faculty of Physics
M.V.Lomonosov Moscow State University
Physics of nuclei and elementary particles

## Neutrino electromagnetic properties as a window to new physics

### A. I. Studenikin$^1$, K. A. Kuzakov$^2$

Moscow University Physics Bulletin 2020. N 5.

An overview of the problem of neutrino electromagnetic properties along with a contribution of the neutrino physics research group at Lomonosov Moscow State University to the investigation of this problem is presented.

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Biophysics and medical physics

## Self-organized criticality in the auto-wave model of speciation

### A. Y. Garaeva$^1$, A. E. Sidorova$^1$, N. T. Levashova$^2$, V. A. Tverdislov$^1$

Moscow University Physics Bulletin 2020. N 5.

Self-organized criticality is considered as a threshold stage of auto-wave self-organization in the evolutionary process. In the suggested model, self-organized criticality is defined as a set of threshold parameters of the auto-wave system of equations and, therefore, associated with the formation of a qualitatively new biological structure - a new species. To construct an auto-wave model of speciation at the population level, the experimental data published in scientific literature for estimating the mutation rate for groups of mice and unicellular eukaryotes were used. This modelling approach demonstrates agreement with available experimental data on the process of fixation of recessive mutations: the presence of three stages of mutation fixation (accumulation of phenotypic differences, threshold level of mutation rate and elimination of mutation carriers) and the maximum mutation rate when the MMR complex and the polymerase δ proofreading activity are disabled. A percolation model of mutations with a delay in the mutation rate is used to analyze the dynamics of mutant population size in generations. The results obtained show an exact correspondence between the application of auto-wave and percolation models of mutation fixation for calculation and analysis of dynamics of mutation process rate and number of mutation carriers.

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Physics of nuclei and elementary particles

## NEW APPROACH TO MAKE CYLINDRICAL PACKAGING PRODUCTS IN ROTATION AROUND THEIR FIXED AXIS DURING IRRADIATION IN THE MONTE CARLO SIMULATION

### A. Aknouch$^1$, Y. Elouardi$^4$, M. Mouhib$^5$, R. Sebihi$^2$, A. Didi$^3$, a. A. Choukri$^1$

Moscow University Physics Bulletin 2020. N 5.

This article, presents an approach to make the cylindrical packaging products in rotation around their xed axis, in the Monte Carlo simulation during irradiation. This approach will solve the rotating plats around its xed axis problem in the simulation so can be used to improve the dose uniformity and predict the irradiated products packaging form, taking into account its density and its position in the irradiation cell, to save time and the high costs of the experiments. This study has released at Moroccan gamma irradiation station. We have used the MCNPX code to simulate this approach. The validation has been done by an experiment measurement using sugar as a product and alanine dosimeters for dosimetric calculation.

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## Estimates of the sensitivity of muon radiography detectors to voids in the ground

### V. I. Galkin$^1$, A. K. Managadze$^2$

Moscow University Physics Bulletin 2020. N 5.

The results of model calculations of test experiments on muon radiography for several configurations of voids in the ground and various positions of muon detectors are presented. The sensitivity of the method for the cases considered is estimated. The calculation forms the basis of the quantitative analysis of the muon radiography data, it can be used for planning of the future experiments.

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## Role of the shell structure in the formation of surface tension in atomic nuclei

### N. G. Goncharova

Moscow University Physics Bulletin 2020. N 5.

Coefficients of surface tension for even-even nuclei were estimated using its dependence of nuclear rigidity. The values of nuclear rigidity were obtained owing its connection to mean squared deformations. The influence of neutron and proton subshells on the surface tension was investigated. The connection of surface tension’ values with nuclear deformation were revealed.

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Engineering physics

## Comparative study between Geant4, MCNP6 and experimental results against gamma radiation comes from a cobalt-60 source

### Y. El ouardi$^1$, A. Dadouch$^1$, A. Aknouch$^2$, M. Mouhib, A. MAGHNOUJ$^1$, A. Didi$^4$

Moscow University Physics Bulletin 2020. N 5.

The simulation codes based on the monte Carlo method are sophisticated averages and have become essential for dosimetry and radiation protection calculations close to the installations that handle radioactive sources. However, before starting to exploit these codes, they must be validated. The aim of this work is to validate two from the Monte Carlo simulation codes most used currently in the world , GEANT4 and MCNP6, for future use in dosimetry and radiation protection requirements in the BOukhalef Ionization Station (SIBO)/ Tangier, Morocco which manipulates a radioactive source of cobalt-60. The validation method is based on a comparison between the simulated results and those obtained by a Fricke system. The codes are well validated, indeed the simulation and experimental results were in good agreement.

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Theoretical and mathematical physics

## {Existence of Boundary-Layer Stationary Solution to Reaction-Diffusion Equation With Singularly Pertrubed Neumann Boundary Condition

### N. N. Nefedov, N. N. Deryugina

Moscow University Physics Bulletin 2020. N 5.

We consider an initial-boundary value problem for a reaction-diffusion equation with a singularly perturbed Neumann boundary condition in a closed, simply connected two-dimensional domain. From a physical point of view, the problem describes processes with an intensive flow through the boundary of a given area. The existence of a stationary solution is proved, the asymptotic is built, and the Lyapunov stability conditions are established. The asymptotics of the solution are constructed using the classical Vasilieva algorithm using the Lusternik-Vishik method. The proof of the existence and stability of the solution is carried out using the asymptotic method of differential inequalities

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## Non-Gibbs distribution in the Ising model

### P. K. Ilin, G. V. Koval, A. M. Savchenko

Moscow University Physics Bulletin 2020. N 5.

This work is in line with new approaches connected with receiving and researching of non- Gibbs equilibrium distributions. In this work based on Ising's model there is obtained a new equilibrium distribution for the case of a thermostat which is proportional to the system. It is also shown that the equilibrium distribution deviates strongly from Gibbs when the thermostat is smaller or commensurate with the dedicated system and committed to Gibbs in the limit of a large thermostat.

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## Spectral decomposition of solution of problem of generation galactic magnetic fields in no-z approximation

### E. A. Mikhailov

Moscow University Physics Bulletin 2020. N 5.

Nowadays one of the most popular models of generation of magnetic fields of galaxies is the no-$z$ approximation in galactic dynamo. It allows us to reduce the problem of generation of the magnetic field to solution of system of two equations for components laying in the galaxy disc plane. Usually solution of such problems is done numerically. Moreover, for some cases this system of equations gives us an opportunity of analytical solution, which makes possible to answer some important principle questions. In this work we give a spectral decomposition of the solution of corresponding problem, defining critical values of the dynamo number for different modes of solution.

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## General harmonic solution in dilaton electrodynamics: exact expression for the fields and generalized Lorentz force

### O. V. Kechkin$^{1,2}$, P. A. Mosharev$^{3,4}$

Moscow University Physics Bulletin 2020. N 5.

An exact expression is found for the harmonic fields of Maxwell electrodynamics with dilaton in terms of elliptic Jacobi functions and elliptic Legendre integrals. The case of the сentrally-symmetric fields is considered indvidually and effective charges of all three types are calculated. An expression for the generalized Lorentz force acting on a point electrically charged particle in these fields is presented.

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## Physical limitations of the efficiency of high power multibeam klystrons

### R. V. Egorov$^1$, V. L. Savvin$^1$, B. V. Prokofiev$^2$, A. V. Konnov$^2$

Moscow University Physics Bulletin 2020. N 5.

The necessity of three-dimensional modeling of the motion of a multibeam electron flow in high-power multibeam klystrons for the implementation of high efficiency values (70% and higher) is discussed. Previously, in the framework of one-dimensional and two-dimensional models, interaction efficiency calculations were performed only for one partial beam, and the value of the output microwave power was determined by formally multiplying the received power by the number of partial beams. The efficiency of multibeam klystrons calculated in this way is higher than the experimentally measured one, usually by 10-15% of the absolute value. It is known that an increase in the number of partial beams and a transversely developed configuration of ring cavities ("oversized"-cavity), as a rule, lead to an increase in the inhomogeneity of the distribution of the microwave field along the drift tubes of the ring cavity. The "oversized "-cavity generates a difference in the phases of microwave fields (phase incursions). The article shows that the energy selection even from identical electron bunches of a multibeam flow depends on the location of the partial span drift tibe relative to the energy output. It is known that the use of the BAC-method of electron grouping can increase the efficiency of klystrons. The results of 3D modeling of the interaction of a multibeam electron stream in an output ring cavity of a BAC-klystron with an output pulse power of 6 MW presented in this article allowed us to quantify the effect of phase waves. Based on 3D modeling of electron beam motion, it is shown that the phase difference of microwave fields in the output cavity significantly reduces the interaction efficiency and, consequently, the efficiency of multibeam klystrons. Thus, the phase delay of the waves excited in different span drift tubes of the gap of the "oversized" ring output cavity is one of the physical reasons for limiting the efficiency of multibeam klystrons.

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## Method for determining aircraft speed from acoustic measurements on the ground

### S. V. Drozdov, S. P. Dragan, A. V. Bogomolov, A. E. Suleymanov

Moscow University Physics Bulletin 2020. N 5.

The results of determining the ground speed of an aircraft from measurements of noise parameters on the ground, including sound levels, sound pressure levels and Doppler frequency shift of the spectral components of equal sound pressure levels, are presented. It is shown that determining the speed from the maximum values of the sound level or sound pressure level measured at different points leads to a large error (more than 200%). The error in determining the aircraft speed, by measuring the Doppler frequency shift of the spectral components of equal sound pressure levels at one point on the ground, was less than 10%. To reduce the error in determining the speed of an aircraft, it is necessary to take into account the influence of interference from the direct and reflected sound waves from the earth's surface, as well as changes in the speed of sound propagation of the aircraft depending on the flight altitude. When measuring at three points, this method will correctly determine the ground speed and spatial position of aircraft, thereby filling in the gaps in the initial data necessary, in particular, for calculating the sanitary protection zones of airfields operating aircraft with unknown noise characteristics.

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## Effect of argon ion irradiation parameters on the photoluminescence spectrum of porous silicon

### A. V. Kozemiako$^1$, A. P. Evseev$^{1,2}$, Yu. M. Spivak$^3$, E. N. Muratova$^3$, Yu. V. Balakshin$^{2,4}$, A. V. Nazarov$^2$, A. A. Shemukhin$^{2,4}$, V. S. Chernysh$^{1,2}$

Moscow University Physics Bulletin 2020. N 5.

Porous silicon was irradiated Ar+ ions with energies of 100 and 200 keV and fluences from 10$^{12}$ cm$^{-2}$ to 3·10$^{13}$ cm$^{-2}$. The effect of ion irradiation at different fluences and energies of incident particles on the photoluminescence spectrum of porous silicon is studied. It was shown that ion irradiation leads to a shift in the photoluminescence maximum, which increases with increasing energy. An increase in the radiation dose leads to a decrease in the intensity of photoluminescence, without affecting the size of the maximum shift. The main mechanisms of photoluminescence in porous silicon are discussed.

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Optics and spectroscopy. Laser physics

## Selective Stimulation in Laser-induced Synthesis of Silver Nanoparticles in Nanoporous Glass

### V. G. Arakcheev$^{1,2}$, A. N. Bekin$^{1,2}$, N. V. Minaev$^3$, V. B. Morozov$^{1,2}$, A. O. Rybaltovsky$^4$

Moscow University Physics Bulletin 2020. N 5.

Laser-induced synthesis of metal nanoparticles by supercritical deposition method provides a wide range of opportunities for different strategies. It is shown here, on example of silver nanoparticles in the Vycor glass, that irradiation at the wavelength of the plasmon resonance inspires prevailing synthesis of the target group. The selective impact implemented leads to appearance of a well-defined two-peak structure in the extinction spectrum, pointing to that the mass fraction of the minor group of the particles significantly grows. The results obtained clearly demonstrate that the use of plasmon properties of the nanoparticles allows tuning of properties of the synthesized ensemble in a targeted manner.

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## Spectroscopic Detection of Critical Compression of Carbon Dioxide Confined in Nanoporous Aerogel by Coherent Anti-Stokes Raman Spectroscopy

### V. G. Arakcheev$^{1,2}$, A. N. Bekin$^{1,2}$, V. B. Morozov$^{1,2}$

Moscow University Physics Bulletin 2020. N 5.

Density of carbon dioxide confined to silica aerogel at near-critical temperatures is investigated by spectroscopy of coherent anti-Stokes Raman scattering. Density is determined by Raman shift of 1388 cm$^{-1}$ vibrational band at isochoric heating from subcritical temperature 25.2$^{\circ}$C tu supercritical 31.95$^{\circ}$C. It is found that the density of carbon dioxide increases in the vicinity of the critical temperature, exceeding the average value in the cell by ~15–20%.

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## The influence of the asymmetry of the geometry of a core-shell particle on a substrate on the optical characteristics accounting for a spatial dispersion

### Yu. A. Eremin$^1$, A. G. Sveshnikov$^2$

Moscow University Physics Bulletin 2020. N 5.

The problem of excitation of a core-shell particle located on a transparent substrate by a field of an evanescent electromagnetic wave is considered. A particle consists of a dielectric core with a metal nanoplasmonic shell in which spatial dispersion occurs. Based on the Discrete Sources Method, a model is constructed that takes into account the influence of nonlocality in a metal on the optical scattering characteristics. The effect of the asymmetry of the particle geometry on the optical characteristics of the near field is investigated. It was found that the asymmetry of the particle geometry significantly affects of the intensity enhancement, as well as the absorption cross-section.

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Astronomy, astrophysics, and cosmology

## Determination of the orbit of unknown ultra-small spacecraft based on the circular perturbed motion model and Doppler frequency shift measurements

### A. A. Spiridonov, A. G. Kezik, V. A. Saechnikov, V. E. Cherny, D. V. Ushakov

Moscow University Physics Bulletin 2020. N 5.

In this work, the determination of the orbit of an unknown ultra-small spacecraft based on Doppler measurements of the frequency of the telemetric signal in several orbits with a limited number of data on one pass is studied. The reception and processing of telemetry radio signals was carried out by the ground station of the Belarusian State University in the amateur radio frequency range of 435-445 MHz with an interval of 6 minutes, two to three packets per flight with time intervals between telemetry receptions on adjacent turns in the range from 94 to 102 minutes. In the model of perturbed circular motion, the radio signals of a small satellite were processed and the parameters of its orbit were determined. Based on a probabilistic estimate of the elevation angle and Doppler frequency shift of an unknown ultra-small spacecraft from 10 and 20 measurements, a set of orbital parameters (T, i, u, Omega) is determined for the estimated time of receiving telemetry signals. For antenna systems, the dynamics of changes in elevation angle, azimuth and Doppler frequency shift of telemetry radio signals for the next flights of an ultra-small spacecraft are predicted. Based on the obtained parameters, the University Ground Station successfully received and decoded telemetry packets of an unknown ultra-small spacecraft. Using the NORAD database of orbital parameters, the Chinese nanosatellite of the Cubesat (6U) LUOJIA-1 01 format (number 43485 in the NORAD system) was identified. The absolute errors in the prediction of altitude and azimuth did not exceed 3o, and the absolute error in determining the Doppler frequency shift did not exceed 250 Hz, which is sufficient for the successful reception of telemetric radio signals and their decoding.

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## Entropy of a gravitating body

### A. V. Belinsky, M. H. Shulman

Moscow University Physics Bulletin 2020. N 5.

In the beginning of 1970’s, a group of cosmologists made the revolutionary breakthrough in understanding of the Black Holes thermodynamics. Using Hawking’s result about non-decreasing of absolute event horizon, Bekenstein identified Black Hole’s entropy with the surface area of this horizon. Later, Hawking himself proved that Black Hole has to radiate like an absolutely black body having corresponding temperature. Until today, many physicists perceive the Black Hole’s thermodynamics (including their colossal entropy value) as phenomenon that has not any analogy with usual objects of thermodynamics. In this paper we show that it is not the case; that a gradual transit from usual objects to black holes is possible. Particularly, the known “Bekenstein bound” really presents the upper limit for the gravitating object entropy

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Physics of Earth, atmosphere, and hydrosphere

## On the effect of the choice of a nodal plane on the estimation of tsunami energy

### M. A. Nosov$^{1,2}$, S. V. Kolesov$^{1,2}$, A. V. Bolshakova$^1$, G. N. Nurislamova$^{1,2}$

Moscow University Physics Bulletin 2020. N 5.

Making use of data on focal mechanism solutions of the Bulletin of the International Seismological Centre (ISC), the influence of the choice of the nodal plane on the estimate of the potential energy of the initial elevation in the tsunami source is studied. It is shown that for most seismic events the energy estimate weakly depends on the choice of the nodal plane. But in some rare cases, energy estimates can differ significantly - up to one order of magnitude. As a rule, such significant differences are peculiar to strong shallow earthquakes, i.e., precisely to those seismic events that are capable of effectively generating tsunami waves. It is established that in all cases when the ratio of the rupture length to the depth of the earthquake is small, the choice between nodal planes practically does not affect the energy estimate.

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