Статьи журнала - Пространство, время и фундаментальные взаимодействия
Все статьи: 344
Exact solutions in cosmological models with non-minimal coupling of scalar field and torsion
Статья научная
Cosmological inflation models with scalar field based on teleparallel gravity with non-minimal coupling of scalar field and torsion are considered. Solution type obtained in this paper is justified for any Hubble parameter and scalar field evolution. Also, the model with scalar field potenital (𝜑) = 𝑚2 2 𝜑𝑛, relating to chaotic inflation with massive scalar field, is verified by modern restrictions on values of cosmological perturbations parameters.
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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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Extragalactic TEV photons and the zero-point vibration spectrum limit
Статья научная
There are observations indicating a possible anomalous transparency of intergalactic space (filled with infrared background light) for extragalactic gamma-rays of very high energy (> 100 GeV). The anomaly is usually associated with effects of some new physics. However, another explanation is possible - as a manifestation relating to a cut-off of the zero-point vibration spectrum. It is assumed that this boundary 𝑈ZV is isotropic in the reference frame, where the cosmic microwave background (CMB) radiation is isotropic, and an estimate is obtained: 𝑈ZV ≈ 7.4TeV. It is noted that the presence of a boundary also leads to an increased beta decay time of accelerated particles with the Lorentz factor > 50 (in the CMB rest frame; in addition to the usual (𝛽)). It is widely believed that the ZV-spectrum continues up to the Planck energy (in natural units, the gravitational constant is related to the square of the Planck length). There is, however, a 5D variant of the Absolute Parallelism theory (AP), free from singularities of solutions, where a large characteristic length appears, which determines the thickness of expanding spherical 𝑆3 shell (a cosmological solution as the longitudinal wave along the radius) in co-moving co-ordinates. Newton’s Law ~ 1/𝑟2 is replaced by 1/𝑟 at distances exceeding 𝐿, and the Planck length (a composite parameter) “arises” from when switching to the conventional energy-momentum scale (where the energy of a photon is its angular frequency). The theory features are briefly exposed - description of 15 polarizations (degrees of freedom), the energymomentum tensor (in prolonged 4th order equations), topological charges and quasi-charges of localized field configurations.
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Falsification of gravity theories from the form of dark spots on black hole images
Статья научная
Visual images of supermassive black holes M87* and SgrA* have been successfully registered recently by the international collaboration Event Horizon Telescope. This registration opens the unique possibility for verification (or falsification) of modified gravity theories in the strong filed limit when gravitational field is dominated over astrophysical factors. This verification is crucially important for physical interpretation of astrophysical and cosmological observations of the Universe and for understanding the physical origin of enigmatic dark matter and dark energy. The accuracy of Event Horizon Telescope is sufficient for demonstration of the quantitative agreement of the obtained dark spot images of both black holes with the General Relativity prediction. In particular, the forms of dark spots on the Event Horizon Telescope images correspond to the fast black hole rotation of the supermassive black holes M87* and SgrA*. Meantime, the Event Horizon Telescope accuracy is insufficient for the verification of the modified gravity theories. In the observable future this verification would be possible in realization of the international project of the Space Observatory Millimetron, which angular resolution in few orders of magnitude exceeds the corresponding one of the Event Horizon Telescope.
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Статья научная
The paper presents a some specific method of the gravitational frequency shift measurement for communication radio signals between the spacecraft and ground tracking stations. It is based on the maximum likelihood algorithm and utilizes the Cram´er-Rao bound to estimate the accuracy of signal parameter determination. It is carried out with the bank of data obtained during the “Radioastron” mission. Attention is concentrated at a compensation of the relativistic Doppler effect and frequency noises of the standards used in the experiment
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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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Generalization of the C3 matching procedure
Статья научная
To handle the case in which discontinuities are present along the matching hypersurface, in this work, we present a generalization of the 𝐶3 matching procedure discussed in previous works. It demands that a solution of Einstein’s equations also describe the matching hypersurface.
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Generalized Kaluza-Klein models with Gauss-Bonnet lagrangians
Статья научная
The five-dimensional generalization of Einstein’s theory of gravitation proposed first by Th. Kaluza (1921) and improved a few years later by O. Klein (1926) has led to the Kaluza-Klein model incorporating electromagnetism and gravitation, and a variant of the Brans-Dicke theory of gravity, containing a scalar field interacting with metric tensor field. However, neither of these models did use the possibilities offered by the enlargement of the Einstein-Hilbert variational principle via including the Gauss-Bonnet invariant, which in 5 dimensions is no more a pure divergence, and modifies substantially the equations of motion of the theory. After recalling the basics of the Kaluza-Klein model, including the non-abelian case. we give a short review of multi-dimensional cosmological models with scalar fields generated by gauge fields defined on the structural group, including the generalized lagrangian containing the Gauss-Bonnet term 𝑅𝐴𝐵𝐶𝐷𝑅𝐴𝐵𝐶𝐷-4𝑅𝐴𝐵𝑅𝐴𝐵+𝑅2. Then we turn our attention back to the 5-dimensional Kaluza-Klein model, without scalar field and neglecting gravity, but with variational principle enriched by the Gauss-Bonnet term, This leads, in the Minkowskian space-time, to an interesting variant of non-linear Electrodynamics. After discussing the modified Maxwell’s equations, we show how a toroidal soliton can be constructed, and show that it displays the most essential features of Dirac’s electron: electric charge, magnetic moment, and spin. It also predicts the particle-anti particle symmetry.
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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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Hyperbolic-logarithmic model of nonlinear electrodynamics
Статья научная
In this paper we consider a new model of nonlinear electrodynamics - "Hyperbolic-logarithmic". This model contain a three parameters and describe by following Lagrangian: ℒ = -ℱ - 𝛽 𝑎𝑟𝑡ℎ(𝛽ℱ) - 2𝛽 [ln(1 + 𝛽ℱ) + ln(1-𝛽ℱ)], where ℱ = 1 4𝐹𝑖𝑘𝐹𝑖𝑘. We show, that in this model dual symmetry is broken. Also we proved that the electric field of a point-like charge becomes non-singular in this framework, static electric energy of this charge is finite. We calculate a theory parameters values guided by electron parameters and Abraham - Lorentz idea about a pure electromagnetic nature of electron mass. We find the canonical and symmetrical Belifante energy momentum tensors.
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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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Inflationary models based on generalized exact cosmological solutions
Статья научная
This paper proposes a method for constructing an unlimited number of exact solutions to the equations of cosmological dynamics for the case of Einstein gravity and the teleparallel equivalent of general relativity. The exact cosmological solutions obtained within the framework of this approach imply complex types of evolution of the scalar field and the dynamics of the expansion of the universe. As an example, solutions to the equations of cosmological dynamics in the form of series are considered, each term of which and the entire series are exact solutions. It is shown that with a certain choice of parameters, the solutions obtained correspond to the correct dynamics of the expansion of the universe at various stages of its evolution
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Interacting spinor and electromagnetic fields in cosmology
Статья научная
Within the scope of a Bianchi type-I (BI) cosmological model we study the interacting system of spinor and electromagnetic fields. The corresponding system of Maxwell, Dirac and Einstein equations are obtained and solved. It was found that under such generalization nonlinear and massive spinor field can exist in a general BI space-time and give rise to different type of solutions depending on the choice of nonlinear and interacting terms.
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Investigation of the chiral cosmological model of f(R, oR) gravity
Статья научная
We study modified f (R, OR) gravity which can be reduced to the chiral cosmological model of the special type. Various types of cosmological solutions are considered based on exact analytical solutions, the slow-roll approximation, the superpotential method, the inclusion of additional material fields and reduction multi-field model to single-field one as well. Thus, this paper presents topical methods for analyzing cosmological models based on an effective multi-field interpretation of the proposed modified gravity.
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Lie differential geometry Aufbau of the atoms and molecules
Статья научная
In previous PIRT conferences I have reported on a differential geometry structural make-up of the standard model of the elementary particles and the periodic system of the atoms following Marius Sophus Lie’s Ph.D. dissertation Over en Classe Geometriske Transformationer at Christiana (now Oslo) University in 1871. This thesis essentially describes Nature at the infinitesimal level it appears as by “a transition from a point to a straight line as element” both mathematically and materially of a coherent differential constitution. Under nucleosynthetic conditions its partial derivative square wave steps “of length equal to zero” goes into a space- filling modular “curve-net” formation. In the first generation, from the 10-15 meter size of the Nucleon radius, this is a bi-layer wave-packet accumulation of palindromic Bohr Aufbau configuration, whose repeated application like in an oriental tiling or carpet first outlines its pattern in the periodic table over the more than 10,000 times larger extension of the atom cross-section area. When an integral surface layer is covered by a full excursion of the knot returning to the origin, the train continues by moving upward the Nucleon shaft to a new facet of the crystal which retains the shape of its infinitesimal module and so can self-assemble into a polymeric nanostructure cluster of itself or molecular combinations with other atoms exactly and extensively as specified in established chemical formulas. This is here exemplified by some basic and more advanced organic compounds including the proteinogenic amino acids and DNA.
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Motion in the gravitational field of a black hole in a synchronous coordinate system
Статья научная
Motion of a test body, or a particle, in the gravitational field of a black hole bordering dark matter is considered. The static gravitational field of extremely compressed matter is determined by solving the Einstein and Klein- Gordon equations in the synchronous coordinate system. An extremely compressed state of matter in the form of a condensate of a quantum Bose liquid is energetically more favorable than a degenerate Fermi gas. An important difference from the Schwarzschild and Kerr black holes is the absence of a singularity in the center. In a regular gravitational field, depending on the impact parameter, there are trajectories leading through the “event horizon” into the black hole, and not just passing by. At zero temperature, depending on the pair interaction of bosons, the condensate consists of components of a superfluid and an ordinary (non-superfluid) quantum liquid. The problem of the motion of a test body inside a black hole is solved analytically in the limiting case when, against the background of dominant gravity, friction with the non-superfluid component of the Bose condensate can be neglected.
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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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Статья научная
Based on the concept of the dynamic aether emergence as a result of spontaneous polarization of the color aether, we consider the SU(2) symmetric theory of interaction of the gauge and axion fields in the framework of anisotropic cosmological model of the Bianchi-I type. We focus on the analysis of the non-Abelian analog of the U(1) symmetric model of axionically induced generation of the electric field in a magnetized medium.
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