Пространство, время и фундаментальные взаимодействия @stfi
Статьи журнала - Пространство, время и фундаментальные взаимодействия
Все статьи: 387
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.
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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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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.
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Solitons in the Skyrme—Faddeev chiral model and quantum mechanics
Статья научная
We consider the essence of the well-known discussion between Bohr and Einstein (1935) which concerned the completeness of quantum mechanics. If one followed Bohr, then the wave function would give the probability description of an individual particle. However, Einstein considered the wave function as an instrument for describing the statistical ensemble of identical particles-solitons. On the other hand, Wiener found the special α-representation of quantum mechanics for which the wave function appeared to be an element of the random Hilbert space with the normal dispersion. This fact proves the equivalence of Bohr and Einstein positions, the central limiting theorem being taken into account. Moreover, we show that within the scope of the Skyrme–Faddeev chiral model particles can be considered as self-gravitating solitons. Therefore, we infer that for island systems with the plane asymptotic space-time quantum mechanics ensues from Einstein gravity equations.
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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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Spinor field in cosmology with Lyra’s geometry: Bianchi type-I model
Статья научная
Within the scope of a Bianchi type-I cosmological model with Lyra’s geometry we study the role of a nonlinear spinor field in the evolution of Universe. Earlier we have considered the nonlinear spinor field in different anisotropic and isotropic cosmological models and it was found that the presence of nontrivial non-diagonal components of energy-momentum tensor of spinor field leads to some severe restrictions on both space-time geometry and spinor field. In this study we have found that though the restrictions remain in place, the introduction of Lyra's geometry plays significant role in the evolution of Universe due to the fact that invariants of spinor field depends on the parameter of Lyra's geometry.
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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.
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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.
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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.
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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.
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The algebrodynamics: in search of the ultimate algebraic “world” structure
Статья научная
Principles of the so-called algebrodynamical approach to the construction of a unified field theory are presented, together with realization of the approach on the base of the linear algebra of complex quaternions. Then we discuss possible realizations of the algebrodynamics on a manifold equipped with the structure of a Lie group or its specific generalizations - algebraic structures (AS) defined by a single operation subject to a single relation containing three or four elements (analogous to the associativity requirement for a Lie group). Defined in such a way the so-called invariant AS turns out to be equivalent to a Lie group but allows thus for a non-canonical introduction of the latter which makes use of a single defining relation. The two more types of remarkable AS, the so-called automorphic and universal ones, are proposed for the role of the “World AS” and preliminary examined. Fundamental physical fields 𝐹(𝑥) are considered as nontrivial mappings of the elements of AS corresponding, in particular, to the multiplication of any element by itself, 𝐹(𝑥) = · 𝑥.
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The analysis of coupled gravitational and electromagnetic waves
Статья научная
A method for studying gravitational waves coupled with an electromagnetic field in the Fabry-Perot resonators by detecting free transverse gravitational waves in the surrounding space is considered. Internal solutions of the gravitational field equations describing bound gravitational waves and a method for calculating the characteristics of free gravitational waves are presented. Estimates of the source and detector parameters for implementing experiments of this type were also presented.
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The analytical description of the Earth's ring current proton flux for the pitch angle of 90 degrees
Статья научная
As mathematical model is offered the ordinary differential equation for the analytical description of a perpendicular differential flux of the charged particles in the Earth’s magnetosphere which depends on time and several parameters (the McIlwain parameter, the magnetic local time or geomagnetic eastern longitude, the geomagnetic activity index, parameter of the charged particle pitch angle distribution or the pitch angle distribution anisotropy index but is taken for the pitch angle of 90 degrees at = 0, the average parameter of the charged particle pitch angle distribution on an interval of time of calculation, the lifetime due to wave-particle interactions). Under the certain geophysical conditions and on a time interval approximately no more than three hours (when a geomagnetic activity index = const) or on a greater time interval, when ≈ const, the equation is solved analytically. The simple analytical solution is received which depends on time and several parameters...
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The coming back of the Proca field
Статья научная
A new version of the old Weyl’s unified field theory based on a strict application of the principle of gauge invariance leads to the appearance of a massive vector field, which has an entirely geometric nature and can be interpreted, under some conditions, as the Proca field. We investigate some possible consequences of the presence of this field in the modern astrophysical scenario.
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The field-theoretic approach in general relativity and other metric theories. A review
Статья обзорная
The representation of General Relativity (GR) and other metric theories of gravity in field-theoretic form on a background is reviewed. The gravitational field potential (metric perturbation) and other physical fields are propagated in an auxiliary background spacetime, which may be curved and may lack symmetries. Such a reformulation of a metric theory is exact and generally equivalent to its initial formulation in the standard geometrical form. The formalism is Lagrangian-based, in that the equations for the propagating fields are obtained by varying the related Lagrangian, as are the background field equations. A new sketch of how to include spinor fields is included. Conserved quantities are obtained by applying the Noether theorem to the Lagrangian as well. Conserved currents are expressed through divergences of antisymmetric tensor densities (superpotentials), connecting local perturbations with quasi-local conserved quantities. The gauge dependence due to the background metric is studied, reflecting the so-called non-localizability of gravitational energy in exact mathematical expressions formally, an infinity of localized energy distributions that, combined with the material energy, satisfy the continuity equation...
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The impossibility of the existence of Majorana spinors as physical particles
Статья научная
Majorana spinors play an important role in modern physical theories. Most of the neutrino mass generation mechanisms are based on the presence of the Majorana mass term in the Lagrangian. In particular, the seesaw mechanism of neutrino mass generation. Majorana solutions of the Dirac equation exist. However, we have proven that Majorana spinor mass term of the Lagrangian is equal to zero. We have proven that Majorana solutions have zero energy and momentum for both the massive and massless cases. This means that Majorana spinors cannot correspond to physically existing particles.
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The influence of the kinetic scalar of torsion on the cosmological solutions of F(T) gravity
Статья научная
This work considers power-law inflation within the modified teleparallel gravity with higher-derivative torsion terms of the kind F(T,(∇T)2). The Hubble parameter is expressed as H=m/t, where m>1. The equations of cosmological dynamics are analyzed for private values of ω(T) with the following choice of the function F: F=T+ω(T)∇μT∇μT. It is shown that the energy and pressure of the dark sector, arising due to higher derivatives, weaken over large times. At the early stage of the Universe's evolution, they support power-law inflation, and the dependence of the potential V(ϕ) on the scalar field ϕ is justified from a physical point of view.
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The scale invariant vacuum paradigm: main results plus the current BBNS progress
Статья научная
We summarize the main results within the Scale Invariant Vacuum (SIV) paradigm as related to the Weyl Integrable Geometry (WIG) as an extension to the standard Einstein General Relativity (EGR). After a short sketch of the mathematical framework, the main results until 2023 [1] are highlighted in relation to: the inflation within the SIV [2], the growth of the density fluctuations [3], the application of the SIV to scale-invariant dynamics of galaxies, MOND, dark matter, and the dwarf spheroidals [4], and the most recent results on the BBNS light-elements’ abundances within the SIV [5].
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