Gravitation and Cosmology最新文献

The task of discovering the effect of gravitational waves (GWs) from high-eccentricity relativistic binary star systems (RBSS) on the vertical electric field strength in the Earth’s atmosphere near-ground layer ((E_{z})) at higher multiples of the RBSS rotation frequencies in the infralow frequency scale has been successfully solved using a signal eigenvectors’ and components’ analyzer (eigenoscope). The monitoring data at four spatially separated (E_{z}) observation stations has been used. An approach to multifrequency RBSS monitoring has been formed.

We use a single-mode squeezed thermal vacuum state formalism and examine the nature of a massive homogeneous scalar field minimally coupled to gravity in the framework of semiclassical gravity in a Bianchi type-I universe. We have obtained an estimate leading solution to the semiclassical Einstein equation for the Bianchi type-I universe showing that each scale factor in its respective direction obeys (t^{2/3}) power-law expansion. The mechanism of nonclassical thermal cosmological particle production is also analyzed in the Bianchi type-I universe.

Asymptotically exact solutions are obtained for a spherically symmetric field with the Higgs potential generated by a point scalar charge, and a method for numerical integration of the scalar field equation with the Higgs potential of a point charge is proposed. Examples of numerical modeling of the scalar field equation for a single charge are given. With the help of the solution obtained, solutions to the relativistic equations of motion of a scalar charge in an external scalar field of the Higgs type of a singular scalar source are found, and some unique properties of the scalar interaction between particles are revealed.

It is known that spatial curvature can stabilize extra dimensions in Lovelock gravity. In the present paper, we study stability of the stabilization solutions in 3rd order Lovelock gravity. We show that in the case of negative spatial curvature of extra-dimensional space, the stabilization solution is always stable. On the contrary, for positive spatial curvature, the stability depends on the coupling constant values.

We consider the metric of an axially symmetric rotating black hole. We do not specify the concrete form of a metric and rely on its behavior near the horizon only. Typically, it is characterized (in the coordinates that generalize the Boyer–Lindquist ones) by two integers (p) and (q) that enter asymptotic expansions of the time and radial metric coefficients in the main approximation. For given (p) and (q) we find a general form for which the metric is regular, and how the expansions of the metric coefficients look like. We compare two types of requirement: (i) boundedness of curvature invariants, (ii) boundedness of separate components of the curvature tensor in a freely falling frame. Analysis is done for nonextremal, extremal and ultraextremal horizons separately.

The author investigates the general Lie algebra of operators of coordinates, momenta, and Lorentz group generators, which can be used in quantum gravity, theories with a generalized uncertainty principle, double and triple relativity and theories with noncommutative space-time and momentum spaces. The structure constants of this algebra depend on the constants (c) and (h) as well as additional constants with dimensions of action ((H)), length ((L)), and mass ((M)). In the limiting case of infinite (H), (L), and (M), the algebra goes into that of operators of canonical quantum theory in Minkowski space-time. Some representations of this algebra and equations for generalized fields depending on additional fundamental physical constants are given.

We study the nonrelativistic Schrödinger wave equation under the influence of a quantum flux field with an interaction potential in the background of a pointlike global monopole (PGM). In fact, we consider an inverse quadratic Yukawa plus inverse square potential and derive the radial equation employing the Greene–Aldrich approximation scheme in the centrifugal term. We determine the approximate eigenvalue solution using the parametric Nikiforov–Uvarov method and analyze the result. Afterwards, we derive the radial wave equation using the same potential employing a power series expansion method in the exponential potential and solve it analytically. We show that the energy eigenvalues are shifted by the topological defects of a pointlike global monopole as compared to the flat space result. In addition, we see that the energy eigenvalues depend on the quantum flux field that shows an analogue to the Aharonov–Bohm effect.

This study is an investigation of exact cosmological models in modified (f(R,L_{m})) gravity with observational constraints, where (R) is the Ricci scalar, and (L_{m}) is the matter Lagrangian for a perfect fluid. We have obtained the field equations using a flat FLRW metric with matter Lagrangian (L_{m}=-p) and (f(R,L_{m})=R/2+alpha L_{m}^{n}-beta), where (alpha), (beta), (n) are positive parameters. We have solved the field equations for the scale factor (a(t)) with the equation of state (EoS) (p=omegarho), where (p) is the isotropic pressure and (rho) is the energy density. We have obtained the scale factor (a(t)=k_{0}[sinh(k_{1}t+k_{2})]^{[2(n+omega-nomega]/[3n(1+omega)]}), where (k_{1}=frac{sqrt{3beta}}{2}frac{n(1+omega)}{n+omega-nomega}), and (k_{0}), (k_{2}) are integration constants. Using this scale factor, we have analyzed various cosmological parameters ({H_{0},q_{0},j_{0},s_{0},t_{0}}) with observational constraints by applying the (chi^{2}) test with four observational datasets (H(z)), Union 2.1, JLA and Bined datasets. Also, we have analyzed the Om diagnostic parameter.

Equations of motion of spinning density for extended objects and tthe corresponding deviation equations are derived. The problem of motion for a variable mass of a spinning extended object is obtained. Spinning fluids may be considered as a special case to express the motion of spinning density for extended objects. Meanwhile, the spinning density tensor can be expressed in terms of the tetrad formalism of general relativity to be regarded as a gauge theory of gravity. The equations of spinning and spinning deviation density tensors have been derived using a specific type of Bazanski Lagrangian.

We demonstrate a new anisotropic solution to the Einstein field equations in Finch–Skea space-time. The physical features of a stellar configuration have been studied in previous investigations. We create a model that meets all physical plausibility conditions for a variety of stars and plot graphs for 4U 1820-30.