Faculty of Physics
M.V. Lomonosov Moscow State University

# Issue 5, 2017

Astronomy, astrophysics, and cosmology

## Large reheating temperature from a small field inflation on brane

### M. Ferricha-Alami$^{1,2,4}$, Z. Mounzi$^{1,2}$, M. Naciri$^{3,4}$, M. Bennai$^{1,4}$, H. Chakir$^{2,4}$

Moscow University Physics Bulletin 2017. N 5.

We focus on the behaviours of small field of an arctangent potential form, in Randall--Sundrum II braneworld. We found that the inflation observables ( n_{s}, r, and ((dn_{s})/(dln k)) ) depend only on the e-folding number N. From the power perturbation value P_{R}(k) given by the latest observational measurements, we evaluate the values of brane tension λ and the energy scale V₀, and we have shown that the various inflationary perturbation parameters are widely consistent with the recent Planck data for a suitable choice of value of the number N. Concerning the reheating phase, we found a large value of the temperature T_{re}∼5×10¹⁴GeV.

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Physics of nuclei and elementary particles

## Modelisation and Distribution of neutron flux in Radium-Beryllium source (226Ra-Be)

### A. Didi, A. Dadouch, O. Jai

Moscow University Physics Bulletin 2017. N 5.

Abstract: Using the Monte Carlo N-Particle code (MCNP-6), to analyze the thermal, epithermal and fast neutron fluxes, of 3 millicuries of Radium-Beryllium, for determine the qualitative and quantitative of many materials, using method of neutron activation analysis, Radium-Beryllium neutron source is established to practical work and research in nuclear field. The main objective of this work was to enable us harness the profile flux of Radium-Beryllium irradiation, this theoretical study permits to discuss the design of the optimal irradiation and performance for increased the facility research and education of nuclear physics.

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## Monte Carlo simulation of thermal neutron flux of Americium Beryllium source is used in neutron activation analysis

### A. Didi, A. Dadouch, M. Bencheikh, J. Tajmouati, O. Jai

Moscow University Physics Bulletin 2017. N 5.

Abstract: The neutron activation analysis is a method of exclusively elemental analysis. Its implementation of irradiates the sample which can be analyzed by a high neutron flux, this method is widely used in developed countries with nuclear reactors or accelerators of particle. The purpose of this study is to develop a prototype to increase the neutron flux such as americium-beryllium and have the opportunity to produce radioisotopes. Americium-Beryllium is a mobile source of neutron activity of 20 curie, and gives a thermal neutron flux of (1.8 ± 0.0007) × 106 n/cm²s when using water as moderator, when using the paraffin, the thermal neutron flux increases to (2.2 ± 0.0008) × 106 n/cm²s, in the case of adding two solid beryllium barriers, the distance between them is 24 cm, parallel and symmetrical about the source, the thermal flux is increased to (2.5 ± 0.0008) × 106 n/cm²s and in the case of multi-source (5 sources), with-out barriers, increases to (1,09 ± 0.0008) × 107 n/cm²s with a rate of increase equal to 4,3 and with the both barriers flux increased to (1,22 ± 0,0008) × 107 n/cm²s. Keywords: MCNP-6, ANN, Am-Be source, Paraffin , ENDF, PGNAA

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Theoretical and mathematical physics

## The exponential parameterization of the neutrino mixing matrix as SU(3) group element and the account for new experimental data

### K. Zhukovsky

Moscow University Physics Bulletin 2017. N 5.

The exponential form of the Pontecorvo-Maki-Nakagawa-Sakata mixing matrix for neutrino is considered in the context of the fundamental representation of the SU(3) group. The logarithm of the mixing matrix is obtained. Based on the most recent experimental data on neutrino mixing, the exact values of the entries of the exponential matrix are calculated. The exact values for its real and imaginary parts are determined, respectively in charge of the mixing without CP violation and of the pure CP violation effect. The hypothesis of complementarity for quarks and neutrinos is confirmed. The factorization of the exponential mixing matrix, which allows the separation of the mixing and of the CP violation itself in the form of the product of the rotations around real and imaginary axes is demonstrated.

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## The effect of a negative particle velocity in a soliton gas within the Korteweg-de Vries-type equations

### E.G. Shurgalina$^1$, E.N. Pelinovsky$^{1,2}$, K.A. Gorshkov$^1$

Moscow University Physics Bulletin 2017. N 5.

The effect of changing a defect’s moving direction in soliton lattices, described by the integrable equations of Korteweg – de Vries equation – type (KdV and mKdV) is studied. Manifestation of this effect is possible as the result of negative phase shift of small soliton in the moment of nonlinear interaction with large solitons as it was already mentioned in [Kuznetsov, Mikhailov, 1975 [1]] within the KdV equation. In recent paper [Carbone et al., 2016 [2]] the expression for the mean soliton velocity in a “cold” KdV-soliton gas through the kinetic theory was found from where this effect follows but did not mentioned. In the present letter we will show that the effect of negative velocity is the same for both equations (KdV and mKdV), and it can be found from the simple kinematic assumption without applying the kinetic theory. Averaged dynamics of the “smallest” soliton (defect) in a soliton gas, consisting of solitons with random amplitudes is investigated. The averaged criterion of velocity sign change, confirmed by numerical solution within the KdV and mKdV equations, is obtained.

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## Intermitteny of vector fields and random number generators

### A.O. Kalinin$^1$, D.D. Sokoloff$^{1,3}$, V. N. Tutubalin$^2$

Moscow University Physics Bulletin 2017. N 5.

We consider how successful are natural random number generators reproduce intermittency arising in vectorial field transport in random media. As a most promising one a random number generator based on financial statistics is suggested. We demonstrate however that even this generation fails to reproduce intermittency while C++ generator successfully solves the problem. We discuss perspectives to use shell models of turbulence as a desired generator.

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## Neutrino oscillations in homogeneous moving medium

### A. E. Lobanov, A. V. Chukhnova

Moscow University Physics Bulletin 2017. N 5.

The quasi-classical equation describing both flavor neutrino oscillations and its spin rotation in dense matter is obtained in the framework of the quantum field theory. The solution of this equation for homogeneous medium is found. The probabilities of the spin-flavor transitions in unpolarized moving matter are calculated in the two-flavor model. We show that, if the medium is at rest the neutrino helicity is conserved and the flavor transition probabilities are equal to those obtained with the help of the phenomenological approach.

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Condensed matter physics

## Investigation of the charge distribution in small cluster ions Ar13+ and Ar19+

### J.G. Korobova, A.E. Ieshkin, V.S. Chernysh

Moscow University Physics Bulletin 2017. N 5.

Atomic and charge structures of small clusters and cluster ions consisted of 13 and 19 argon atoms are studied from the first principals. We revealed that for considered clusters, icosahedral atomic structure is more energetically preferable. Our calculations showed that when one electron is removed from the cluster, the excess electrical charge distributes mainly on the surface of the formed cluster ion.

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## Single-electron transistor with island formed by several dopant phosphorus atoms

### S. A. Dagesyan$^1$, V. V. Shorokhov$^1$, D. A. Presnov$^{1,2}$, E. S. Soldatov$^1$, A. S. Trifonov$^{1,2}$, V. A. Krupenin$^1$, O. V. Snigirev$^1$

Moscow University Physics Bulletin 2017. N 5.

Here we present the results of the experimental study of the electron transport through the individual phosphorus dopants implanted into the silicon crystal. We developed the original technique for the single-electron transistor fabrication from silicon-on-insulator material with an island formed by single phosphorus atoms. The proposed method is based on well known CMOS compatible technological processes which are standard in semiconductor electronics and may be used in the most research groups. The large Coulomb blockade energy value of the investigated single-electron transistor ($n\approx 20$ meV) allows one to register single-electron effects in wide temperature range up to 77 K. We measured and analyzed stability diagrams of fabricated experimental structures. We demonstrated the single-electron transistor with controllable electron transport through 2 – 3 phosphorus dopants only.

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Chemical physics, physical kinetics, and plasma physics

## The simulation of shock wave propagation in the argon plasma discharge positive column

### A.K. Sukhov

Moscow University Physics Bulletin 2017. N 5.

Computer simulation of shock wave propagation in plasma of positive column discharge in argon was performed. One-dimensional model of gas-discharge plasma was used, comprising the continuity equation for electron and ion component of plasma, and the equations of electrostatics, taking into account the initial and boundary conditions. Distributions of plasma parameters in the shock wave were obtained; the influence of shock wave intensity was evaluated. Simulation results with experimental data were compared.

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Biophysics and medical physics

## Hydrodynamic interaction of blood cells with micro-rough surfaces in shear flow

### A.V. Belyaev

Moscow University Physics Bulletin 2017. N 5.

In this paper we address hydrodynamic interactions of individual red blood cells (erythrocytes) with micro-rough surfaces in a shear flow of a viscous fluid with help of computer simulations. We study the influence of the microrelief on the dynamics of cell movement. It has been shown that periodic microrelief with typical length scale comparable with the size of an erythrocyte, may cause an increase of the repulsive hydrodynamic force directed outwards the micro-rough wall. The results can be used in the design of microfluidic devices intended to operate with whole blood samples.

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