Gravitation and Cosmology最新文献

The basic concepts of an alternative theory of Non-Inflationary Cosmology established by the author, in this paper are applied as astrophysical mechanisms for creation of a theoretical model in favor of a unique galaxy with reverse rotating two discs. Based mainly on the phenomenon of the galactic local explosion/implosion phenomenon with its direct applications, this primary model is more extended, aiming at the consideration of the possibility of a binary system of supermassive black holes in the core of such galaxy. This prediction is necessary for enlightening the unusual behavior of this galaxy, moreover, for the disclosure of gravitational radiation of this theoretical model, initiating creation of a unique program for the prospective observations/detection of similar galaxies. Revealed by the theory of Non-Inflationary Cosmology original state of matter in the state of Bose condensate inside a galactic supermassive black hole is able to reveal macroscopic quantum gravity phenomena.

Generalizations of the Einstein gravitational and Maxwell electromagnetic field equations are studied, which are based on Weyl’s principle of scale invariance and contain Weyl’s vector field with four components. In these generalizations, the results obtained in our earlier publication (Grav. Cosmol. 25, 237–242 (2019)) are used and substantially developed. The Weyl field is regarded as a weak one, which gives small corrections to the Einstein and Maxwell field equations but could play an important role in cosmological processes. The considered equations are examined for an arbitrary system of particles interacting by means of gravitational and electromagnetic forces. The conditions of consistency of these equations are studied, which result in four second-order differential equations for four components of Weyl’s vector. The proposed system of field equations is applied to a homogeneous and isotropic vacuum, and a nonsingular cosmological solution is obtained. This solution is applied to describe the influence of the Weyl field on propagating electromagnetic waves and moving free particles in vacuum. Cosmological aspects of the obtained results are discussed.

We consider the initial conditions for inflation in the nonminimal kinetic coupling theory. If inflation is driven solely by the kinetic term with no potential, the resulting number of e-folds depends only on the initial velocity of the scalar field, (dot{phi}). We write down the expression for the number of e-folds explicitly, and show that for physically reasonable values of the coupling constant, we can get 60 e-folds only for an exponentially big initial (dot{phi}). When the scalar field potential is taken into account, a double inflation scenario arises, where the first inflation is kinetic term driven, while the second one is potential term driven. In this case, we need not a very large (dot{phi}) to start with for 60 e-folds, on the other hand, some initial conditions lead to a physically inadmissible eternal inflation. We show numerically that in the measure used in the present paper only a smaller part of initial conditions leads to eternal inflation for reasonable values of the coupling constant.

Recent developments on Bell’s experiments demonstrate that entanglement could indeed eliminate the gap between classical and quantum physics. At the same time, it is difficult for a classical theory to include a particular feature like entanglement without compromising the theory’s smooth working on a four-dimensional scale geometry. A unified theory should reconsider this difficulty. On the other hand, pregeometry holds the assumption of a noncommutative space where the Requardt-Roy model seems to be a promising one. From the ordinary five-dimensional approach, first initiated by Kaluza and Klein, a toy model is proposed to show an insignificant description of gravity at Planck’s scale physics. It is found that the classical nature of quantum correlations is fine-tuned within the geometry of space-time in four dimensions. Such a nature can be better understood by studying the pregeometric effects of gravity in five dimensions. A combined description is found, sufficient to explain the fundamental difficulties of a discrete space-time manifold in both theories.

We review the hypothesis on the existence of gravitational magnetic monopoles (H-poles for short) defined by analogy with Dirac’s hypothesis on magnetic monopoles in electrodynamics. These hypothetic dual particles violate the equivalence principle and are accelerated by a gravitational field. We propose an expression for the gravitational force exerted upon an H-pole. According to GR, ordinary matter (which we call E-poles) follows geodesics in a background metric (g_{munu}). The dual H-poles follows geodesics in an effective metric (hat{g}_{munu}).

We apply the method of osculating orbits in the Schwarzschild–Droste space-time using the relativistic orbital evolution equations for a perturbed extreme mass ratio inspiral (EMRI) by an outer supermassive black hole. The latter supposedly lies in the orbital plane, so that the orbital elements related to inclination and ascending node do not play a role. Our approach encompasses both strong and weak gravity fields. For calculating the gravitational waveforms of perturbed EMRIs through the Regge–Wheeler–Zerilli wave equations, we apply the second-order source-free integration method. Designed for integration in the time domain, our algorithm consists of a finite difference scheme that discretizes the space-time into a grid cell ((t,r^{*})), whereas the discontinuity of the gravity field at the world line of the particle is dealt with jump conditions on the wave function and its derivatives.

A self-consistent explanation of the approximately flat three-dimensional space is one of the major conceptual issues of any cosmological model, determining its viability and competitiveness among the various theoretical proposals. In particular, just the inability to resolve the problem of flatness was one of the reasons to reject the old “pre-inflationary” cosmological model and to change it by the inflationary scenario. Here, we briefly recall how the three-dimensional flatness can or cannot be explained in the various models of the early Universe and discuss in detail the case of uncertainty-mediated inflation, which was suggested in our previous paper [7]. As follows from our analysis, the approximately flat 3D space in the last-mentioned model can really be formed “dynamically,” starting from generic initial conditions. Taking into account that this model also well resolves the causality problems in the early Universe [8], the uncertainty-mediated inflation might be a reasonable alternative to other inflationary scenarios.

To find out precise criteria of double-ring structure formation in galaxies, we have studied the problem of gravitational instability of the corresponding structure oscillation modes in the background of a previously described compound disk model [1, 2, 3] with an exact nonlinear law of nonstationarity. Nonstationary analogs have been derived for the dispersion equations for these structure oscillation modes of the model, and the results of their analysis are discussed. A comparative analysis has been carried out for the instability increments of ringlike oscillation modes, aimed at determining the dependence of their characteristic manifestation times on the physical parameters of the model.

General relativity does not prohibit the existence of space-times that describe a time travel. Consideration of such spaces gives rise to a lot of questions and paradoxes, among which there are thermodynamic ones. This paper considers two situations that describe a time travel, and explains why their existence does not mean that time machines are prohibited.

We solve the Klein–Gordon oscillator equation in the five-dimensional cosmic string space-time background with a uniform magnetic field and quantum flux in the presence of a non-electromagnetic (or scalar) potential in the Kaluza–Klein theory, and observe a gravitational analogue of the Aharonov–Bohm qeffect. We see that the energy eigenvalues and the eigenfunction depends on the global parameters characterizing the space-time. Also, a quantum effect is observed due to the dependence of the magnetic field on the quantum numbers of the system.