R e v i e w s

Astronomy, astrophysics, and cosmology

Moscow University Physics Bulletin 2019. N 4.

This paper analyzes the main ideas of the formation of celestial bodies in accretion and protoplanetary disks. The mechanisms of the radial and orbital migration of celestial bodies are considered. According to the results of modeling the formation of small bodies and the growth of their sizes and masses occurs at stable libration points of orbital resonances. The appearance of a single “embryo” in protoplanetary rings is explained as a result of the action of the 1/1 orbital resonance mechanism. Using the model of wave perturbations of the dust shells of protostars and the model of orbital resonance, a general model of the formation and growth of the “embryos” of planets for disks with masses less than 0.1MS was constructed.

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Physics of nuclei and elementary particles

Moscow University Physics Bulletin 2019. N 4.

Influence of nucleon structure on single tensor-deuteron and double beam-vector-deuteron analyzing powers in the elastic electron-deuteron scattering process is investigated. We report numerical results for the tensor-deuteron ($T_{20}$, $T_{21}$, and $T_{22}$), and beam-vector-deuteron ($T_{10}$ and $T_{11}$) analyzing powers as functions of the four-momentum transfer square $Q^2$ and the electron scattering angle in the laboratory frame $\theta_e$. This is made possible with the advent of recent polarization measurements with polarized electron beams and/or polarized deuteron targets at MIT-Bates, JLab, NIKHEF, VEPP-2, and VEPP-3. We found that the predicted results for $T_{21}$, $T_{22}$, $T_{10}$, and $T_{11}$ are sensitive to the nucleon electromagnetic form factors. On the contrary, the $T_{20}$ analyzing power is found to be almost independent on the actual nucleon form factors. The predicted analyzing powers are compared with the available experimental data and a satisfactory agreement is obtained.

Show AbstractMoscow University Physics Bulletin 2019. N 4.

Polarized response functions for beam and target polarization in the elastic electron-deuteron scattering process are investigated. We report numerical results for all the non-vanishing polarized response functions as functions of the four-momentum transfer square $Q^2$. The sensitivity of the predicted results to the nucleon form factors is investigated. For the neutron and proton form factors, the standard dipole fit, the modified dipole fit 1, the modified dipole fit 2, and the relativistic harmonic oscillator model are used. In addition, the dependence of the results on the deuteron wave functions obtained from different modern $NN$ potentials is studied. For this purpose, the realistic and high-precision Argonne $v18$, chiral N$^3$LO, Nijmegen-I, and CD-Bonn $NN$ potentials are used. We found that all the non-vanishing polarized response functions are sensitive to the choices of nucleon form factors, whereas they are slightly dependent on the $NN$ potential model adopted for the deuteron wave function. The results for all polarized response functions using the relativistic harmonic oscillator model for the nucleon form factors are found to be very small in comparison to the results of other models.

Show AbstractMoscow University Physics Bulletin 2019. N 4.

Proton therapy is an advanced radiotherapy technique that delivers a high dose to the tumor, while at the same time sparing the surrounding healthy tissue. This benefit lies in the physical and radiological properties of the protons, such as excellent ballistic accuracy, the combination of low lateral beam dispersion and localized depth-of-depth deposition, which gives proton therapy a high degree of accuracy. The order of a millimeter in the delivery of the dose. However, secondary radiation, mainly neutrons, and gammas, is created by the nuclear interactions that the protons produced in the patient. These secondary neutrons lead to undesirable doses deposited to healthy tissues located at a distance from the target volume, the consequence of which could be an increase in the risk of developing second cancers in treated patients and in particular in children. The objective of this work is to determine the depth doses and the distribution of secondary radiation produced during the penetration of a proton beam of energy of 200 MeV and 250 MeV by the Monte Carlo method into a Phantom of water.

Show AbstractMoscow University Physics Bulletin 2019. N 4.

The motion of an electron in the experiment of Witteborn and Fairbank is considered. It is shown that only when using weakly relativistic or relativistic electrons the gravitational force acting on an electron is not compensated by the Barnhill-Schiff force, and the acceleration acquired by this electron in the gravitational field of the Earth is proportional to the ratio of its passive gravitational mass to the inert mass. Therefore, to measure this ratio it is necessary to carry out experiments with relativistic or weakly relativistic electrons.

Show AbstractAstronomy, astrophysics, and cosmology

Moscow University Physics Bulletin 2019. N 4.

This paper discusses the form of energy called the brane tension λ that can effect in the reheating phase after inflation. In this regard, we study an inflationary model with a tree level potential in the framework of braneworld Randall--Sundrum type II model to investigate the reheating epoch. We have computed and discussed the reheating temperature of the universe following inflation for several choices parameters of the scalar potential parameters. And we have found that the reheating temperature an upper limit that lies in the range 10⁹∼10¹⁰GeV.

Show AbstractTheoretical and mathematical physics

Moscow University Physics Bulletin 2019. N 4.

The analytical expression for the field of the molecular dipole momentum in an arbitrary point in the surrounding space is obtained. This expression permits to calculate values of inducting dipole moments of molecules in a three molecular nanocluster. The considered nanocluster formed from molecules one of which has a permanent dipole moment. The obtained results can be generalized for nanoclusters consisting of more than three molecules.

Show AbstractMoscow University Physics Bulletin 2019. N 4.

The behavior of atomic hydrogen in a half-space with the third type (or Robin) boundary condition for the electronic wavefunction is considered. It is shown that for certain parameters of the boundary condition, the effective potential of such an atom as a function of the distance between the nucleus and the boundary has a pronounced minimum at finite distances, which corresponds to the effect of the atom "soaring" over the plane. For the general case of Robin boundary conditions, both the results of variational estimates based on the choice of special trial functions and the results of numerical calculations are given. For particular cases of Dirichlet and Neumann, the research is carried out by analytical methods.

Show AbstractOptics and spectroscopy. Laser physics

Moscow University Physics Bulletin 2019. N 4.

The photoluminescence of two types of heterostructural silicon solar cells with different passivation of crystalline silicon layer was investigated. The contributions of various processes to the photoluminescence of the samples were revealed by measuring the photoluminescence at low temperatures. The possibility to estimate the dopant concentration in crystalline silicon for solar cells based on a heterojunction amorphous silicon/crystalline silicon from photoluminescence spectra has been shown. A correlation between the photoluminescence kinetics of heterostructural silicon solar cells and the efficiency of their phototransformation was established. An effective method to determine the surface passivation quality in crystalline silicon solar cells based on a heterojunction amorphous silicon/crystalline silicon is proposed.

Show AbstractMoscow University Physics Bulletin 2019. N 4.

We investigate reflection of electromagnetic wave from the structure consisted from 2 or 3 non-absorbing layers placed on the absorbing semi-infinite base. As a falling wave we take flat wave with linearly changing amplitude and specified filling in frequency. We figured out the conditions for the parameters of the layers, which provide complete congruence of falling wave with changing amplitude with base. We investigated influence of the small variations of parameters of layers to the effect of complete congruence.

Show AbstractMoscow University Physics Bulletin 2019. N 4.

The interference of two dispersed laser speckle fields with a large spectrum width is investigated by numerical simulation. Local small-scale disturbances of interference fringes accompanied by a sharp drop in the contrast of the interference pattern are found. It is shown that these perturbations occur in the regions of the large phase gradient and the small module of the mutual coherence function of the overlapping interfering fields. The analytical description of small-scale disturbances is given and the probability of their occurrence is estimated

Show AbstractCondensed matter physics

Moscow University Physics Bulletin 2019. N 4.

Result of investigation with the self-learning kinetic Monte Carlo method of processes, occurring during the formation of the Pt/Cu(111) surface alloy, is presented. A model is proposed that takes into account the jumps of dimers during the formation of a heterogeneous alloy on the (111) surface. The role of dimers diffusion at temperature close to room temperature is investigated. Relative number of dimer jumps at the most significant stages of the Pt/Cu(111) alloy formation is calculated.

Show AbstractMoscow University Physics Bulletin 2019. N 4.

Dielectric spectroscopy method was used to study dielectric properties and conductivity of superprotonic single crystals (Kx(NH4)1-x)3H(SO4)2 (x=0.19, 0.27, 0.43) in the frequency range 0.1 Hz – 10 МHz and the temperature interval 223 – 353 K. The analysis of experimental data have been carried out using the formalisms of AC conductivity and electric modulus. The room temperature values of DC conductivity of studied crystals obtained from solid solutions was about ~ 10-5 (S/cm) which corresponds to the conductivity values of initial compounds at high temperatures. The comparable values of the activation energy of both DC conductivity and modulus spectrum suggest that protons are involved not only in the conductivity, but also in the process of electric relaxation. Modulus analysis had indicated the temperature independent distribution of relaxation times and the non-Debye behavior in these materials. The temperature dependence of DC conductivity exhibits three (for x=0.19 and 0.27) and two (for x=0.43) temperature intervals with different activation energies, which indicates the presence of structural transitions causing a change in the mechanism of proton transport.

Show AbstractBiophysics and medical physics

Moscow University Physics Bulletin 2019. N 4.

Platelets play a key role in homeostasis and hemostasis. To study the functions of platelets, various models are built that allow to select the most significant parameters regulating the formation of blood clots, blockage of blood vessels. This study examines ellipsoid cells which interact with the substrate surface through the formation of ligand-receptor bonds. The movement of a platelet at a constant speed, directed perpendicular to the surface, and under the action of a constant force, also directed perpendicularly to the surface, is considered. The effect of platelet form during this interaction is investigated. In case of movement under the action of a constant force, threshold forces were obtained, which determine two possible states: the separation of a platelet or its retention at the surface.

Show AbstractPhysics of Earth, atmosphere, and hydrosphere

Moscow University Physics Bulletin 2019. N 4.

The features of determining the phase velocities of sea waves due to the presence of dominant wave harmonics and the difference in the spreading functions of free wave and harmonics are analyzed. It is shown that the phase spectrum in the field of sea waves changes nonlinearly with increasing distance between the points for which it is calculated. As a consequence, phase velocity estimates are a function of distance. It is shown that deviations of phase velocity estimates from the linear theory depend on the stage of wave field development.

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