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Бисноватый-Коган, Геннадий Семенович

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Институт лазерных и плазменных технологий

Стратегическая цель Института ЛаПлаз – стать ведущей научной школой и ядром развития инноваций по лазерным, плазменным, радиационным и ускорительным технологиям, с уникальными образовательными программами, востребованными на российском и мировом рынке образовательных услуг.

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Бисноватый-Коган

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Геннадий Семенович

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Теперь показываю 1 - 10 из 36

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Eliminating the Hubble Tension in the Presence of the Interconnection between Dark Energy and Matter in the Modern Universe
(2023) Bisnovatyi-Kogan, G. S.; Nikishin, A. M.; Бисноватый-Коган, Геннадий Семенович
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Thermodiffusion Unipolar Electric Generator
(2024) Bisnovatyi-Kogan,G.S.; Glushikhina,M.V.; Бисноватый-Коган, Геннадий Семенович
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3D numerical study of an anisotropic heat transfer in outer layers of magnetized neutron stars
(2019) Kondratyev, I. A.; Moiseenko, S. G.; Glushikhina, M. V.; Bisnovatyi-Kogan, G. S.; Бисноватый-Коган, Геннадий Семенович
© Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0).Periodic changes in a thermal soft X-ray flux of a rotating neutron star indicate a non-uniform distribution of the surface temperature. A possible cause of this phenomenon is a suppression of the heat flux across the magnetic field lines in a crust and an envelope of magnetized neutron stars. In this paper we study three-dimensional effects, associated with non-axisymmetric magnetic fields in neutron stars. We calculate the surface temperature distribution by solving numerically a three dimensional heat transfer equation in a magnetized neutron star crust. We adopt an anisotropic (tensorial) electron thermal conductivity coefficient, which is derived as an analytical solution of the Boltzmann equation with a Chapman-Enskog method. To calculate the surface temperature distribution, we construct a local one-dimensional plane-parallel model ("Ts-Tb"-relationship) of a magnetized neutron star envelope. We then use it as an outer boundary condition for the three-dimensional problem in the crust to find the self-consistent solution. To study possible observational manifestations from anisotropic temperature distributions we calculate light curves with a composite black-body model. Our calculations show, that a non-axisymmetric magnetic field distribution can lead to the irregular non-sinusoidal shape of a pulse profile as well as in some cases a significant amplification of pulsations of the thermal flux in comparison to the pure-dipolar magnetic field configurations.
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Black hole shadow as a standard ruler in cosmology
(2020) Tsupko, O. Y.; Fan, Z.; Bisnovatyi-Kogan, G. S.; Бисноватый-Коган, Геннадий Семенович
© 2020 IOP Publishing Ltd.Advancements in the black hole shadow observations may allow us not only to investigate physics in the strong gravity regime, but also to use them in cosmological studies. In this paper, we propose to use the shadow of supermassive black holes as a standard ruler for cosmological applications assuming the black hole mass can be determined independently. First, observations at low redshift distances can be used to constrain the Hubble constant independently. Secondly, the angular size of shadows of high redshift black holes is increased due to cosmic expansion and may also be reachable with future observations. This would allow us to probe the cosmic expansion history for the redshift range elusive to other distance measurements. Additionally, shadow can be used to estimate the mass of black holes at high redshift, assuming that cosmology is known.
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Approximate Analytic Model of the Boundary Layer Arround a Low Magnetic Field Neutron Star at the Disk Accretion
(2025) Bisnovatyi-Kogan, G. S.; Бисноватый-Коган, Геннадий Семенович
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Stellar Critical Parameters in the Uniform Density Approximation
(2025) Bisnovatyi-Kogan, G. S.; Patraman, E. A.; Бисноватый-Коган, Геннадий Семенович
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Strong Shock in a Uniform Expanding Universe. Approximate and Exact Solutions of Self-Similar Equations
(2019) Panafidina, S. A.; Bisnovatyi-Kogan, G. S.; Бисноватый-Коган, Геннадий Семенович
© 2019, Pleiades Publishing, Ltd. Self-similar solution is obtained for propagation of a strong shock, in a flat expanding dusty Friedman universe. Approximate analytic solution was obtained earlier, using relation between self-similar variables, equivalent to the exact energy conservation integral, which was obtained by L.I. Sedov for the strong explosion in the static uniform medium. Here, numerical integration of self-similar equation is performed, providing an exact solution of the problem, which is rather close to the approximate analytic one. The differences between these solutions are most apparent in the vicinity of the shock. For a polytropic equation of state, self-similar solutions exist in a more narrow interval of the adiabatic power than in the static case.
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Free electron gas and electron-positron pair equilibrium in a magnetic field
(2021) Kondratyev, I. A.; Bisnovatyi-Kogan, G. S.; Бисноватый-Коган, Геннадий Семенович
© 2021 Uspekhi Fizicheskikh Nauk. All rights reserved.The thermodynamic properties of electron gas under the extreme conditions of high temperature, high matter density, and/or a strong magnetic field largely determine the beha-vior of matter in upper layers of neutron stars and accretion columns of magnetized neutron stars in binary systems. A strong magnetic field in these objects makes the motion of electrons across the field essentially quantum. The possible electron degeneracy and relativism of electrons are also important. When studying accretion onto a magnetar in a binary system, the intensive generation of electron-positron pairs in the quantizing magnetic field should also be taken into account. We consider in detail the thermody namic properties of a gas of free electrons in strong magnetic fields, taking into account their relativism and degeneracy, as well as the equilibrium creation of electron-positron pairs in a high-temperature plasma in the presence of a quantizing magnetic field.
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Cosmological model with interconnection between dark energy and matter
(2021) Bisnovatyi-Kogan, G. S.; Бисноватый-Коган, Геннадий Семенович
© 2021 by the authors. Licensee MDPI, Basel, Switzerland.It is accepted in the present cosmology model that the scalar field, which is responsible for the inflation stage in the early universe, transforms completely into matter, and the accelerated universe expansion is presently governed by dark energy (DE), whose origin is not connected with the inflationary scalar field. We suppose here that dark matter (DM) has a common origin with a small variable component of dark energy (DEV). We suggest that DE may presently have two components, one of which is the Einstein constant Λ, and another, smaller component DEV (ΛV) comes from the remnants of the scalar field responsible for inflation, which gave birth to the origin of presently existing matter. In this note we consider only the stages of the universe expansion after recombination, z≃1100, when DM was the most abundant component of the matter, therefore we suggest for simplicity that a connection exists between DM and DEV so that the ratio of their densities remains constant over all the stages after recombination, ρDM=αρDEV, with a constant α. One of the problems revealed recently in cosmology is a so-called Hubble tension (HT), which is the difference between values of the present Hubble constant, measured by observation of the universe at redshift z≲1, and by observations of a distant universe with CMB fluctuations originated at z∼1100. In this paper we suggest that this discrepancy may be explained by deviation of the cosmological expansion from a standard Lambda-CDM model of a flat universe, due to the action of an additional variable component DEV. Taking into account the influence of DEV on the universe’s expansion, we find the value of α that could remove the HT problem. In order to maintain the almost constant DEV/DM energy density ratio during the time interval at z<1100, we suggest the existence of a wide mass DM particle distribution.
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Spectral Distortions in CMB by the Bulk Comptonization Due to Zeldovich Pancakes
(2019) Bisnovatyi-Kogan, G. S.; Бисноватый-Коган, Геннадий Семенович
If the large scale structure of the Universe was created, even partially, via Zeldovich pancakes, than the fluctuations of the CMB radiation should be formed due to bulk comptonization of black body spectrum on the contracting pancake. Approximate formulae for the CMB energy spectrum after bulk comptonization are obtained. The difference between comptonized energy spectra of the CMB due to thermal and bulk comptonozation may be estimated by comparison of the plots for the spectra in these two cases.