Статьи журнала - Пространство, время и фундаментальные взаимодействия
Все статьи: 247
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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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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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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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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Dynamo-optically active media: new aspects of the Minkowski-Abraham controversy
Статья научная
Based on the covariant variation formalism, two versions of the symmetric effective stress-energy tensor of the electromagnetic field in a dynamo-optically active relativistic media are reconstructed in the framework of the tetrad and aether paradigms, respectively. We show that the energy density scalars and pressure tensors coincide for both versions of the stress-energy tensors, however, the corresponding energy flux four-vectors happen to be different in general case. This mathematical fact adds new arguments into the 100-year-long discussion, which is called Minkowski-Abraham controversy and is connected with the correct definition of the electromagnetic energy flux in a continuous media. We consider three examples: first, the axionically active vacuum; second, the spatially isotropic moving dielectric medium; third, the dynamo-optically active medium. We discuss possible applications of the elaborated formalism.
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Exact solutions in Friedmann cosmology with scalar fields
Статья научная
The method of exact analysis of cosmological dynamics at the early inflation stage of the evolution of the Friedman Universe, which is determined by the dynamics of the scalar field for the case of minimal and nonminimalinteraction of the field and curvature is considered in this work. The basis of the method is to reduce theequations of dynamics to the same form for all models. The proposed approach allows us to compare modelsbased on the different theories of gravity.
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Exact solutions in modified gravity theories
Статья научная
In this paper, we have reviewed the limitations in the General Relativity theory and the requirement for geometrical dark energy models. Actions for different geometrical dark energy models have been discussed. Specifically, two matter geometry coupling models within the Einstein-Hilbert action have been investigated. The basic equations leading to the discussion of the dynamical aspects of the Universe are derived and some examples of obtaining exact solutions in these two models are discussed.
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Статья научная
The problem reduction of an evolution modelling of the open Universe for conformally flat space-time metric in Fock’s form to an equivalent problem of a particle movement with an unit mass in a force field is demonstrated. The exact cosmological models filled with a substance and radiation in an approximation of the perfect fluid are found since the Friedman solution by means an introduction of set "mechanical" potentials.In the article the possibility of deriving from the Einstein equations exact cosmological solutions for the open Universe by reduction to the equivalent problem of a mass particle motion in the force field is considered. The cosmological model is filled by substance in an approximation of the perfect fluid with nonzero pressure, generally speaking. The metric of 4D space-time is taken in the Fock form as the metric conformal to the Minkowski metric. This metric has the dependence on one variable. A square of the variable is product of advanced and retarded times.The using of mechanical interpretation of the gravitation equations leads to a possibility of consideration of various mechanics force fields with the subsequent physical interpretation of the found exact cosmological solutions.First of all a movement of a free particle with an unit mass (a mechanical force equals to zero) is considered,i.e. the particle moves on inertia. The fourth degree of discovered law of movement is a conformal factor of the cosmological metric which is conformally flat. This case corresponds to the exact cosmological solution without pressure, coinciding with known the Friedman solution for the open Universe.After that the force field leading to uniformly decelerated motion of a particle is considered. The force potential is taken in the form of linear function. The tangent of a slope angle of the function curve coincides with particle acceleration. Such research leads to the exact cosmological solution asymptotically describing both an incoherent dust, and the ultrarelativistic substance which may be interpreted as an equilibrium radiation.Further a square-law function without a linear term and a constant value is taken as a force potential. Such potential can be interpreted as potential of the free oscillator. The solution of corresponding equation of motion is written down in the form of a cosine function with some initial phase related to the ratio between parameters which define dust-like and ultrarelativistic substance. This conclusion becomes obvious after concidering asymptotic behaviour of pressure and energy density. Besides, the series expansion of a root of the fourth degree from a conformal factor asymptoticly coincides with the law of uniformly decelerated motion in previous case that indicates its particular character.
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Extended relativistic non-equilibrium thermostatics of stellar structures with radiation pressure
Статья научная
We establish the extended formalism for description of the static spherically symmetric relativistic non-equilibrium stellar systems in the formation of which the radiation pressure plays the key role. The main concept of this extended formalism inherits the ideas, on which the Israel-Stewart causal thermodynamics is based, but now the unit spacelike four-vector, indicated by the term director, is exploited in addition to the unit timelike medium velocity four-vector. An application of the extended formalism is considered; we analyze the profiles of the non-equilibrium pressure and temperature as the functions of guiding parameters introduced phenomenologically.
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Friedmann cosmological model with nonlinear scalar field
Статья научная
This paper is a translation of work Ivanov G.G "Friedmann cosmological model with nonlinear scalar field" of 1981 [1].
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H-spaces (H41,G) of type {41}: projective-group properties
Статья научная
In this paper we study five-dimensional ℎ-spaces (𝐻41, 𝑔) of type {41} [4]. Necessary and sufficient conditions for (𝐻41, 𝑔) to be a space of constant curvature are found. The general solution of the Eisnhart equation in ℎ-space (𝐻41, 𝑔) of non-constant curvature is determined. We establish conditions for the existence of a non-homothetic projective motion in (𝐻41, 𝑔) and describe the structure of a non-homothetic projective Lie algebra in ℎ-space (𝐻41, 𝑔) of type {41}.
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Статья обзорная
В данной статье представлен обзор работы III летней международной молодежной школы «Гравитация, космология и астрофизика», посвященной памяти академика РАН В.И. Пустовойта.
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Non-vanishing cosmological constant effect in super-Poincare-invariant universe
Статья научная
In [1] we defined the Minkowski superspace 𝑆𝑀(4, 4|𝜆, 𝜇) as the invariant of the Poincare supergroup of supertransformations, which is a solution of Killing superequations. In the present paper we use formulae of super-Riemannian geometry developed by V. P. Akulov and D. V. Volkov [2] for calculating a superconnection and a supercurvature of Minkowski superspace.We show that the curvature of the Minkowski superspace does not vanish, and the Minkowski supermetric is the solution of the Einstein superequations, so the eight-dimensional curved super-Poincare invariant superuniverse 𝑆𝑀(4, 4|𝜆, 𝜇) is supported by purely fermionic stress-energy supertensor with two free real parameters 𝜆, 𝜇, and, moreover, it has non-vanishing cosmological constant Λ = 12/(𝜆2-𝜇2) defined by these parameters that could mean a new look at the cosmological constant problem
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On the gravitational waves coupled with electromagnetic waves
Статья научная
A description is made of the process of excitation of coupled longitudinal-transverse gravitational waves during the propagation of a strong electromagnetic wave in a vacuum and when a standing electromagnetic wave exists in the Fabry-Perot resonator. It is shown that such waves lead to the appearance of transverse gravitational waves in empty space. It was established that two standing high-frequency electromagnetic waves in a Fabry-Perot resonator with close frequencies cause the appearance of a low-frequency transverse gravitational wave in empty space.
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Relativistic nonlinear axion magnetohydrodynamics
Статья научная
The new nonlinear axionically extended version of the general relativistic magnetohydrodynamics is formulated. The self-consistent formalism of this theory is based on the introduction into the Lagrangian of the new unified scalar invariant, which is quadratic in the Maxwell tensor, and contains two periodic functions of the pseudoscalar (axion) field. The constructed unified invariant and the elaborated nonlinear theory as a whole, are invariant with respect to two symmetries: first, the discrete symmetry associated with the properties of the axion field; second, the Jackson’s SO(2) type symmetry intrinsic for the electromagnetism. The subsystem of the master equations, which describes the velocity four-vector of the hydrodynamic flow, is constructed in the framework of Eckart’s theory of viscous heat-conducting fluid. The axionically extended nonlinear Faraday, Gauss and Ampere equations are supplemented by the ansatz about the large electric conductivity of the medium, which is usually associated with vanishing of the electric field. We have suggested two essentially new nonlinear models, in the framework of which the anomalous electric conductivity is being compensated by the appropriate behavior of the finite pseudoscalar (axion) field, providing the electric field in the magnetohydrodynamic flow to be finite (either to be proportional to the magnetic field, or to the angular velocity of the medium rotation).
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Статья научная
His paper examines the structure of the Dirac equation and gives a new treatment of the Dirac equation in 1+1 spacetime.
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Статья научная
The SU(N)-symmetric generalization of the model of the electromagnetically active dynamic aether is formulated. This generalization is based on the introduction of a Yang-Mills gauge field instead of the Maxwell field, and of a SU(N)-multiplet of vector fields instead of the standard single vector field. In the framework of the second order version of the effective field theory this generalization includes three constitutive tensors, which are the SU(N) extensions of the tensors appeared in the Einstein-Maxwell-aether theory; we reconstructed the full-format set of these constitutive tensors. The total self-consistent system of master equations for the gauge, vector and gravitational fields is obtained by the variation procedure. The general model of the SU(N)-symmetric dynamic aether is reduced to the extended Einstein-Yang-Mills-aether model by the ansatz about spontaneous color polarization of the vector fields. In fact, this ansatz requires the vector fields, which form the SU(N) multiplet, to become parallel in the group (color) space due to a phase transition, and a new selected direction in the group space to appear, thus converting it into the anisotropic color space.
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Spherical symmetric solutions of F(R) gravity with a kinetic curvature scalar
Статья научная
We consider modified 𝑓(𝑅) gravity with a kinetic curvature scalar as a chiral self-gravitating model in a spherically symmetric spacetime. Most attention devoted to finding solutions for special case of scaling transformation when modified gravity transforms to Einstein frame from Jordan one. We proposed the method of determination of kinetic function for given scalar field dependence on space coordinate. New classes of solutions are found for special choice of 𝑓(𝑅) function.
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