Статьи журнала - Пространство, время и фундаментальные взаимодействия
Все статьи: 344
Nonlocal extension of relativistic non-equilibrium thermostatics
Статья научная
Based on the formalism of nonlocal extension of the Israel-Stewart causal thermodynamics [1] on the one hand, and on the formalism of the extended thermostatics [2] on the other hand, we propose the new model of nonlocal relativistic non-equilibrium thermostatics for description of the static spherically symmetric stellar systems. This nonlocal formalism operates with the pair of orthogonal four-vectors: one of them is the standard unit timelike medium velocity four-vector, the second one is the unit spacelike director. We derived the extended equation describing the profile of the non-equilibrium pressure, which can be indicated as the static analog of the Burgers equation known in classical rheology.
Бесплатно
On Weyl-Dirac gravitation theory and its development
Статья научная
Models of conformal gravitation that contain Lagrangians, which are linear on scalar curvature and with nonminimal connection with the scalar field, are discussed in this report. Theory of Weyl-Dirac gravitation has been reported in detail. A new version of conformal Lagrangian with two scalar fields is proposed, in which the Weyl vector is replaced with the vector which is transformed as a Weyl vector, but is not contained in Weyl connection. Weyl integrable space is the space of such model. The problem of describing a conformal stage in the evolution of the Universe on the basis of Friedmann metrics is considered within Weyl-Dirac gravitation theory with nonminimum connection with the real scalar field. Conformal invariant solutions for the scale factor are presented. It is demonstrated that quantum corrections to the trace of energy-momentum tensor are partially compensated by gauging the Dirac function, which results in the Lagrangian of the General Relativity theory.
Бесплатно
On conserved quantities for a moving black hole in TEGR
Статья научная
In the framework of the Teleparallel Equivalent of General Relativity (TEGR), where the field variables are tetrad components, mass and momentum for a moving (uniformly with respect to distant observers) Schwarzschild black hole (SBH) are constructed. A formalism developed by the authors earlier for constructing conserved quantities in TEGR, where currents and superpotentials are covariant with respect both to coordinate transformations and to local Lorentz rotations of tetrads is applied. This advantage has been reached by introducing inertial spin connection (ISC) and using the Noether theorem with preservation of a displacement vector in final expressions. A set of pairs (tetrad and related ISC) connected by smooth transformations we call as a “gauge”, it is the equivalence class. The quantity ISC is an external one, therefore we define it with making the use of the introduced by us generalized “turning off gravity” principle. But, even this a reasonable principle leads to different values of ISCs for the same tetrad that leads to different results. Here, on the example of the moving SBH we 1) demonstrate advantages of our fully covariant formalism, 2) study the ambiguity in definition of ISC as well. In calculations, we the use analogies with a moving mater ball in Minkowski space only in the “static gauge”. Expected mass and momentum have been obtained. Next we compare “static gauge” and “moving gauge”. It was found that they coincide. In the result, in the case of a moving SBH aforementioned ambiguity is absent because in both the cases the same mass and momentum are obtained.
Бесплатно
On the detection of high-frequency relic gravitational waves
Статья научная
The specificity of the spectrum of relic gravitational waves formed at the inflationary and post-inflationary stages of the evolution of the early universe is considered for cosmological models based on modified theories of gravity and Einstein gravity. The possibility of detecting high-frequency relic gravitational waves by using the process of converting gravitons into photons in a constant and alternating magnetic field is considered. The sensitivity of detectors of this type is compared with the sensitivity of other existing and prospective detectors of high-frequency gravitational waves. Based on the analysis of the sensitivity assessment of various types of high-frequency gravitational wave detectors, a conclusion is made about the prospects for direct verification of cosmological inflation models using gravitational-wave antennas.
Бесплатно
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.
Бесплатно
On the temporal problem in quantum cosmology
Статья научная
The time problem in quantum cosmology has been considered in the framework of quantum geometrodynamics. Although time is not present in quantum cosmology explicitly, it emerges in classical cosmology. The classical world proves to be programmed on the quantum level.
Бесплатно
Статья научная
In this paper we present the results of a theoretical study of the trajectories of massive particles in the K¨ottler metric in view of the cosmological constant Λ. For both negative and positive signs of Λ a classification of trajectories is proposed, with entries based on different solutions of the trajectory equation, obtained by the expansion of the corresponding algebraic curve in Puiseux series. We also provide some specific types of trajectories which correspond to different values of the cosmological constant. In the case of negative values of the cosmological constant its upper limit is estimated from the galaxy rotation curves.
Бесплатно
Oscillating scalar fields as dark matter
Статья научная
The work considers oscillating scalar fields acting as cold dark matter in the expanding Universe. This behavior is inherent for both real and complex fields, and besides, the complex field reproduces the properties of cold dark matter even if the energy density per particle exceeds its mass.
Бесплатно
Physical basis of sensitivity of the Earth’s electromagnetic field to gravitation
Статья научная
Components of the Earth’s electric field vertical strength which are spectrally localized at the multiplied rotation frequencies of relativistic binary star systems, have significant amplitude and sharper spectral localization than at the other frequencies, have been discovered at the experimental material of multy-year time series of the Earth’s electric field strength in the infralow frequency band using eigenoscopy (second mixed moments eigenvectors’ amplitude spectra analysis at finite analysis span).
Бесплатно
Quasi-de Sitter solution in F(T, (T )2) teleparallel gravity
Статья научная
This paper considers the relevance of the quasi-de Sitter solution for the modified 𝐹(𝑇, (∇𝑇)2) teleparallel theory of gravity. The Hubble parameter is represented in the form: = 𝐻* + 𝜖𝑒-𝐵𝑡, where 𝐻*,𝐵 - 𝑐𝑜𝑛𝑠𝑡. The cosmological equations of the model with a perfect fluid are written for the following choice of function 𝐹: = 𝐴𝑇𝑛+𝜔(𝑇)∇𝜇𝑇∇𝜇𝑇. The evolution of matter density perturbations in the absence of pressure perturbations is considered.
Бесплатно
Статья научная
Optical coatings play a crucial role in interferometric detectors of gravitational waves. A short up-to-date review of related research lines and results is proposed, including new methods and results from the Author’s resarch group.
Бесплатно
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).
Бесплатно
Статья научная
His paper examines the structure of the Dirac equation and gives a new treatment of the Dirac equation in 1+1 spacetime.
Бесплатно
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.
Бесплатно
Semiclassical description of the electromagnetic radiation by accelerated charged distributions
Статья научная
We review our recent results on the electromagnetic radiation produced by charge distributions in the framework of a semiclassical approach. In this approach, currents, generating the radiation are considered classically, while the quantum nature of the radiation is kept exactly. Pertinent quantities to the radiation problem are calculated with the aid of transition probabilities, whose quantum states of the electromagnetic field have well-defined number of photons and are solutions of the corresponding Schro¨dinger’s equation. We summarize the calculation of the total energy and and rates radiated by point charges accelerated by electromagnetic fields and compare our results with those obtained in classical electrodynamics.
Бесплатно
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.
Бесплатно
Spins of supermassive black holes
Статья научная
Shapes of black hole images, viewed by a distant observer, depend on the distribution of emitting matter around black holes. There are two distinctive astrophysical cases: (1) Luminous stationary background behind the black hole (emission of photons outside the photon spheres). In this case the dark classical black hole shadow is viewed, which is a capture photon cross-section in the black hole gravitational field. (2) Luminous accretion inflow near the black hole event horizon (emission of photons inside the photon spheres). In this case the dark event horizon shadow is viewed, which is a lensed image of the event horizon globe. The existence of hot accreting matter in the vicinity of black hole event horizons is predicted by the Blandford-Znajek mechanism. The basic feature of this mechanism is the existing of electric current embracing the black hole and heating the accretion disk very near the black hole event horizon providing the main contribution to the black hole luminosity. We used the numerically calculated sizes of dark spots in the EHT images of supermassive black holes SgrA* and M87* for inferring their spins, 0.65 0.75, respectively.
Бесплатно
Статья научная
In recent studies linear perturbations of a static and spherically symmetric background of neutron stars have been considered in full Horndesky’s theory, the propagation speeds of perturbations were derived and the stability conditions were obtained. In the present paper we applied this general stability conditions to the study of the neutron stars stability in theory of gravity with the scalar-derivative coupling of the Einstein tensor and the scalar field with the standard kinetic term and the cosmological constant. It was shown that there are stable stellar configurations in a wide class of model parameters ℓ and for which all squared speeds of perturbations, 𝑐2 , 𝑐2 Ω, 𝑐2 3, 𝑐2 Ω± and are positive.
Бесплатно
Standard-dimensional transformation systems for special relativity
Статья научная
We introduce a comprehensive framework comprising standard and dimensional reference frames. We suggest a theory composed of three interconnected transformation systems. The standard-dimensional transformation system is combined with a dimensional-dimensional transformation system corresponding to the typical Lorentz- Einstein transformation and the standard-standard system. The velocity at which the dimensional frame moves plays a crucial role so that the Maxwell spherical wave equation remains invariant and the transition of the wave-nature to particle-nature of light becomes subject to the transformation system.The consistency of the proposed standard-dimensional transformation systems can also be examined in implications. We drove the mass and energy equations of a free particle and found that the particle’s velocity and that of the moving frame are essential. We also conclude that the Schrodinger equation remains invariant under the proposed transformation. Further implications to the phenomena challenging special relativity could be carried out elsewhere.
Бесплатно
The Dirac equation and a fermionic algebra
Статья научная
This paper examines the structure of the Dirac equation and gives a new treatment of the Dirac equation in 1+1 spacetime.
Бесплатно
