Пространство, время и фундаментальные взаимодействия @stfi
Статьи журнала - Пространство, время и фундаментальные взаимодействия
Все статьи: 380
Статья обзорная
В данной статье представлен обзор работы 4-ой Международной зимней школы-семинара по гравитации, космологии и астрофизике "Петровские чтения-2018" и мероприятий, приуроченных к 70-летию академика А.А. Старобинского.
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A moving black hole in TEGR as a moving matter ball
Статья научная
Possibilities of the covariant with respect to both coordinate and local Lorentz transformations formalism developed earlier in the framework of Teleparallel Equivalent of General Relativity (TEGR) are studied. The formalism is applied to a solution for a moving with constant velocity (with respect to distant static observers) Schwarzschild black hole. Coordinate and Lorentz invariant global conserved mass and momentum are constructed. The acceptable results are obtained in spite of the solution under consideration has no, at least, Killing vectors of space displacements. Calculations are quite analogous to calculating the mass and momentum of a moving matter ball in Minkowski space, and this analogy is used essentially.
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About leptons in space-time film theory
Статья научная
In the present work, we continue the investigation of the problem for finding the toroidal soliton solutions of space-time film equation, which can represent the charged leptons. The quasi-cylindrical complex toroidal coordinate system with rotation is introduced and the appropriate equation of space-time film is obtained. We propose the way for finding the solutions in the form of formal series in negative powers of the radius of the toroidal ring. The initial approximation for this method is discussed.
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Статья научная
Based on the G¨odel spacetime platform we consider an example of exact solution to the master equations of the extended Einstein-Maxwell-aether-axion model. This exact solution describes a specific configuration of the unit vector field, associated with the velocity of the dynamic aether, of the axion field in the equilibrium state, of the electric field orthogonal to the axis of the Universe rotation, and of the dust cloud. The main feature of the solution is that the axion, vector and electric fields of this configuration turn out to be hidden from the point of view of the structure of the gravitational field of the rotating Universe.
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Статья научная
An anisotropic cosmological model with a gauge field, presented by spatially homogeneous SU(2)- symmetric Yang–Mills potentials, is considered. Bianchi-I model with axial symmetry is analyzed; a new exact solution, which describes the early Universe on the stage of domination of the gauge field of the magneto-electric type, is obtained.
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Anisotropic cosmological models of Bianchi type I, V, IX in Horndeski gravity theory
Статья научная
In this work we analyze behavior of anisotropy in cosmological models of Bianchi type I, V, IX in Horndeski gravity theory. Deriving background equations from Horndeski action, we obtain generalized system. Further, we numerically analyze solutions of diverse scalar-tensor gravity theories within Horndeski theory framework, considering the anisotropy on early and late stage of universe evolution.
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Application of the Abel equation to cosmological models with and without phantoms
Статья научная
The article is dedicated to a novel approach to the phantom cosmologies with scalar fields: a reduction of the Friedman-Robertson-Walker-Lemˆiatre system of equations to a single first-order O.D.E. called the Abel equation of the 1-st kind. In particular, we demonstrate how the phantomization of a classical cosmological model changes the structure of the Abel equation. In addition, we apply the proposed method to a construction of a number of exact phantom solutions.
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Application of the Schrodinger equation in exact scalar field cosmology
Статья научная
We propose a new method of exact solutions construction for scalar field cosmology based on representation of the Einstein-Friedmann dynamic equations as Schr¨odinger-like one. This representation allows one to compare the solutions of quantum-mechanical and cosmological problems. On the other hand, this approach makes it possible to use the well-known form-invariant transformations of the Schr¨odinger equation to generate exact cosmological solutions. As an example of the application of this method, the use of the Darboux transformations in scalar field cosmology is considered. On the other hand, the presented methods make it possible to generalize the obtained solutions to multi-field cosmological models.
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Статья научная
In the framework of axionically extended Einstein-Maxwell-aether theory we study the structure of the electromagnetic field allowed by the anisotropic cosmological spacetime platforms associated with the Bianchi models. These models guarantee that the aether velocity possesses the shear, and we focus on its role in the evolution of the axion-photon systems. In this short note we discuss the extended master equations obtained under the assumption that the square of the shear tensor is included in the potential of the axion field.
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Статья научная
We consider dynamics of the quartet of interacting cosmic substrata, which includes the dynamic aether, presented by the unit timelike vector field, the axionic dark matter, described by the pseudoscalar field, the spinor field associated with fermion particles, and the gravity field. The extended set of master equations is derived based on the idea that the potential of the axion field to be the function of seven arguments. The first one is, standardly, the pseudoscalar field; the second and third arguments are the fundamental spinor invariant and pseudoinvariant; the fourth and fifth ones are the aether-axion cross-invariants and cross-pseudoinvariants; the sixth argument is the expansion scalar, and the seventh one is the square of tensor of the shear of the aether flow. The complete set of Master equations is derived and prepared for analysis.
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Black hole image in Heisenberg-Euler electrodynamics
Статья научная
In this paper we use a geodesic method for constructing a black hole shadow. It’s based on numerical integration of geodesic equations by the 5th order Dormand-Prince method. We construct an image of charged black hole shadow in the framework of Heisenberg-Euler electrodynamics and perform a comparative analysis of this image with a similar image in the classical case of Maxwell electrodynamics
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Black holes and the nature of the event horizon
Статья научная
The problem of the event horizon in relativistic gravity is discussed. Singular solutions in general relativity are well known. The Schwarschild metric of a spherical mass is singular at zero (𝑟 = 0) and at the event horizon (𝑟 = 𝑟𝑔). Both features reflect the existence of the phenomenon of collapse in general relativity for compact masses exceeding 3𝑀⊙. A material particle crossing the event horizon falls into a central singularity according to the classical theory of general relativity. In the quantum theory of gravity, there may be no central singularity. The physics of the event horizon is currently being refined. A promising technique is the study of gravitational waves (GW) accompanying the merger of binary black holes at the ringdown stage. GW observations of quasinormal modes of the newly formed super dense remnant will help clarify the physics of the event horizon.
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Bouncing cosmology in modified theories of gravity
Статья научная
In this study, we describe a 𝑓(𝑅) gravity theory-based bouncing cosmological model of the universe. The flat FLRW space-time were used to determine the model’s dynamical behaviour. At the bouncing epoch, the geometrical parameters exhibit singularity behaviour. The parameters of the scale factor have a significant impact on the bouncing behaviour.
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Chiral cosmological model of F(R,R) gravity
Статья научная
We study the modified gravity 𝑓(𝑅,□𝑅), which can be reduced to a chiral cosmological model of a particular type with scalar field observers 𝜒, 𝜑, 𝜙. The method of studying the chiral cosmological model was used for the 𝑓(𝑅, (∇𝑅)2) models, but was first used by Naruko for the more general 𝑓(𝑅) Gracing model. In this paper, equations for chiral fields and the Einstein-Friedmann equations in the Friedmann-Robertson-Walker metric are presented. Note that the solutions for this chosen model are based on a special choice of one of the chiral fields: = - √ 3/2 ln 2. Solutions are considered in the case of reducing the model to a one-field model: two chiral fields of the model depend linearly on the third one. The obtained solutions are of interest, since quantum corrections must also be taken into account in the analysis.
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Construction of chiral cosmological models unifying inflation and primordial black hole formation
Статья научная
We propose the method for construction of 𝐹(𝑅, 𝜉) gravity model, unifying inflation and primordial black hole formation. The proposed models are based on the Starobinsky + 𝑅2 inflationary model, so, the function 𝐹(𝑅, 𝜉) is a quadratic polynomial of the Ricci scalar 𝑅, is a scalar field. We show that the potential of the corresponding two-field chiral cosmological model in the Einstein frame can be always found in terms of the elementary functions. The special choice of the function 𝐹(𝑅, 𝜉) allows us to get such a generalization of the hybrid inflation that can describe both inflation, and the primordial black hole formation.
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Cosmological models based on scalar-torsion gravity
Статья научная
Cosmological models based on teleparallel gravity with a non-minimal coupling between the scalar field and torsion (scalar-torsion gravity) are considered in the context of their comparison with the case of Einstein gravity (GR) and the teleparallel equivalent of general relativity (TEGR). A classification of cosmological inflationary models is proposed based on the type of dependence of the tensor-scalar ratio on the spectral index of scalar perturbations. The difference between inflationary models based on scalar-torsion gravity and models based on GR and TEGR is shown in the context of their verification using observational data based on this dependence.
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Cosmological solutions of a chiral self-gravitating model of F(R, (R)2,R) gravity
Статья научная
We study modified 𝑓(𝑅, (∇𝑅)2,□𝑅) gravity and show in detail how it can be reduced to Einstein gravity with a few scalar fields and then represented in the form of chiral self-gravitating model of the special type. In further investigation of the model we focus on cosmology and looking for solutions of the dynamic equations of chiral fields and the Einstein-Friedman equations in the Friedman-Robertson-Walker space-time. Exact solutions of the considered model for zero and constant potential are found. Between them power law solution corresponded to equation of state for stiff matter, de Sitter solution, trigonometric and hyperbolic expansion solution. Various type of chiral fields evolution support listed above solutions.
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Could the Barrow Universe be an antidote for cosmological singularites?
Статья научная
The article is dedicated to the Many Interacting Worlds (MIW) quantization approach, initially proposed by M. Hall, D.-A. Deckert and H. Wiseman in [1], as it is applied to the old problem of emergent cosmological singularities. We begin by discussing the history of de Broglie–Bohm theory and its evolution into the MIW formalism, followed by the direct application of MIW approach to Friedman cosmology in the model of Many Interacting Universes (MIU). After that we recall John D. Barrow's idea about the physical nature of zero solutions a(t)=˙a=0 for the Friedman equations and surmise the necessity for including such solutions into the framework of MIU. This works like a charm, as it directly leads to the Theorem 1 which, under some physically sensible assumptions, prohibits the remaining Friedman cosmological solutions from reaching zeroes, thereby preventing the formation of cosmological singularities. In conclusion we discuss some exact solutions to illustrate the aforementioned Theorem.
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Cамодействие скалярного заряда в заряженной экстремальной анти-дилатонной кротовой норе
Статья научная
Вычислена сила самодействия скалярного заряда в пространство-времени экстремальной заряженной анти-дилатонной кротовой норы. Предполагается, что скалярный заряд является источником безмассо- вого скалярного поля, минимально связанного с кривизной пространства-времени.
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Статья научная
The various stages of the universe evolution are considered for the case of Einstein gravity based on exact solutions of the equations of cosmological dynamics for one Hubble parameter in various regimes with a scalar field and different matter fields. It is shown that the obtained solutions correspond to the correct change of the stages of the universe evolution. It is also shown that the proposed model corresponds to observational constraints on the values of the parameters of cosmological perturbations. The physical interpretation of the scalar field is also discussed in the context of its fundamental and effective treatment.
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