Персона: Рубин, Сергей Георгиевич
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Институт ядерной физики и технологий
Цель ИЯФиТ и стратегия развития - создание и развитие научно-образовательного центра мирового уровня в области ядерной физики и технологий, радиационного материаловедения, физики элементарных частиц, астрофизики и космофизики.
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Руководитель научной группы "Гравитация и космология"
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Рубин
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Сергей Георгиевич
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32 results
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Теперь показываю 1 - 10 из 32
- ПубликацияТолько метаданныеSelf-tuning inflation(2022) Petriakova, P.; Rubin, S. G.; Рубин, Сергей ГеоргиевичWe develop an inflationary model without small parameters on the basis of multidimensional f(R) gravity with a minimally coupled scalar field. The model is described by two stages of space expansion. The first one begins at energy scales about the D-dimensional Planck mass and ends with the de Sitter metric of our space and the maximally symmetric extra dimensions. In the following, the quantum fluctuations produce a wide set of inhomogeneous extra metrics in causally disconnected regions quickly generated in the de Sitter space. We find a specific extra space metric that leads to the effective Starobinsky model that fits the observational data. © 2022, The Author(s).
- ПубликацияТолько метаданныеFormation of Primordial Black Hole Clusters from Phase Transitions in the Early Universe(2019) Nikulin, V. V.; Rubin, S. G.; Kirillov, A. A.; Khromykh, L. A.; Никулин, Валерий Владимирович; Рубин, Сергей Георгиевич; Кириллов, Александр Александрович© 2019, Allerton Press, Inc. A new model of the formation of primordial black holes (PBHs) is considered. The PBH generation mechanism is based on the collapse of massive walls formed in a scalar field during second-order phase transitions caused by quantum fluctuations during inflation. An essential feature of the mechanism is the formation of primordial black holes in the form of clusters. An analytical spectrum of PBH masses is obtained. We also demonstrate the possibility of forming the clusters with a total mass of ∼ 10 5 –10 8 M ☉ , ∼ 1 pc in size, and ∼ 10 11 in number, which corresponds to the observational data on the number of galaxies in the visible region of the Universe. The prospect for the use of the proposed approach as a new scenario of the formation of galactic nuclei in the early Universe is shown.
- ПубликацияТолько метаданныеOn Mass Spectra of Primordial Black Holes(2021) Kirillov, A. A.; Rubin, S. G.; Кириллов, Александр Александрович; Рубин, Сергей ГеоргиевичCopyright © 2021 Kirillov and Rubin.Evidence for the primordial black holes (PBH) presence in the early Universe renews permanently. New limits on their mass spectrum challenge existing models of PBH formation. One of the known models is based on the closed walls collapse after the inflationary epoch. Its intrinsic feature is the multiple production of small mass PBH which might contradict observations in the nearest future. We show that the mechanism of walls collapse can be applied to produce substantially different PBH mass spectra if one takes into account the classical motion of scalar fields together with their quantum fluctuations at the inflationary stage. Analytical formulas have been developed that contain both quantum and classical contributions.
- ПубликацияТолько метаданныеUnveiling the early universe: Axion-like particles and their role in primordial structure formation(2024) Rubin, S. G.; Рубин, Сергей Георгиевич
- ПубликацияТолько метаданныеSix-dimensional cosmological models with conformal extensions(2026) Muller, D.; Rubin, S. G.; Shapiro, I. L.; Toporensky, A.; Рубин, Сергей Георгиевич
- ПубликацияТолько метаданныеCompact extra dimensions as the source of primordial black holes(2022) Nikulin, V. V.; Krasnov, M. A.; Rubin, S. G.; Никулин, Валерий Владимирович; Краснов, Максим Александрович; Рубин, Сергей ГеоргиевичThis article discusses a model of primordial black hole (PBH) formation at the reheating stage. These small/massive black holes appear due to the specific properties of the compact extra dimensions. The latter gives rise to the low energy model, containing an effective scalar field potential capable of domain wall production. Formed during inflation, these walls are quite dense, meaning they collapse soon after inflation ends. Discussion of the model is framed by the scope of multidimensional f ( R )-gravity. We study the possibility of the pure gravitational formation of primordial black holes (PBHs). Interpreting the scalar curvature of compact extra space R n as an effective scalar field in an Einstein framework and consider effective scalar-field theory that might potentially be capable of producing domain walls with a certain choice of parameters. Hence, we demonstrate that f ( R )-gravity contains a mechanism for PBH formation. The study assumed that cosmological inflation is an external process, which satisfied all the cosmological constraints on our mechanism.
- ПубликацияТолько метаданныеCosmological baryon/lepton asymmetry in terms of Kaluza-Klein extra dimensions(2021) Nikulin, V. V.; Rubin, S. G.; Никулин, Валерий Владимирович; Рубин, Сергей Георгиевич© 2021 World Scientific Publishing Company.In this paper, we discuss the mechanism for generating the lepton/baryon number and its subsequent conservation based on extra-dimensional evolution. The internal angular momentum of extra space is related to the lepton/baryon charge. Extra space metric is assumed to be initially asymmetric. Symmetries appear during inflation due to an increase in entropy. Using the multidimensional field toy model, we show that internal angular momentum can accumulate in fermions, which could explain the lepton/baryon asymmetry of the universe.
- ПубликацияТолько метаданныеHot Primordial Regions with Anomalous Hydrogenless Chemical Composition(2022) Belotskiy, K. M.; El Kasmi, M. M.; Rubin, S. G.; Solovyov, M. L.; Белоцкий, Константин Михайлович; Рубин, Сергей Георгиевич; Соловьев, Максим ЛеонидовичWe study primordial nucleosynthesis in hypothetical hot regions that could be formed by the primordial density inhomogeneities. It is shown that the regions that survived up to the present times acquire an abnormally high metallicity. This conclusion holds in a wide range of initial parameters of such regions. We considered the thermonuclear reaction rates and estimated abundances of deuterium and helium-3 and -4 inside these areas. It has been established that all baryons tend to form helium-4, which is the thermonuclear link in the chain of formation of heavier elements. © 2022 by the authors.
- ПубликацияТолько метаданныеLooking at the NANOGrav signal through the anthropic window of axionlike particles(2021) Sakharov, A. S.; Eroshenko, Y. N.; Rubin, S. G.; Рубин, Сергей ГеоргиевичWe explore the inflationary dynamics leading to formation of closed domain walls in course of evolution of an axion like particle (ALP) field whose Peccci-Quinn-like phase transition occurred well before inflationary epoch. Evolving after inflation, the domain walls may leave their imprint in stochastic gravitational waves background, in the frequency range accessible for the pulsar timing array measurements. We derive the characteristic strain power spectrum produced by the distribution of the closed domain walls and relate it with the recently reported NANOGrav signal excess. We found that the slope of the frequency dependence of the characteristic strain spectrum generated by the domain walls is very well centered inside the range of the slopes in the signal reported by the NANOGray. Analyzing the inflationary dynamic of the ALP field, in consistency with the isocurvature constraint, we reveal those combinations of the parameters where the signal from the inflationary induced ALPs domain walls could saturate the amplitude of the NANOGrav excess. The evolution of big enough closed domain walls may end up in wormholes with the walls escaping into baby universes. We study the conditions when closed walls escape into baby universes and could leave a detectable imprint in the stochastic gravitational waves background.
- ПубликацияТолько метаданныеEvolution of sub-spaces at high and low energies(2019) Popov, A. A.; Rubin, S. G.; Рубин, Сергей Георгиевич© 2019, The Author(s).The evolution of sub-spaces in the framework of gravity with higher derivatives is studied. Numerical solutions to exact differential equations are found. It is shown that the initial conditions play crucial role in the space dynamic. Appropriate metrics describing an expanding and a stationary sub-space shed light on the well-known question: why our 3-dim space is large but an extra space is small and stable (if exists)? It is assumed that the values of parameters at high energies strongly depend on uncontrolled quantum corrections and, hence, are not equal to their values at low energies. Therefore, there is no way to trace solutions throughout the energy range, and we restrict ourselves to the sub-Planckian and the inflationary energies.