Gravitational Rutherford scattering and Keplerian orbits for electrically charged bodies in heterotic string theory

Properties of the motion of electrically charged particles in the background of the Gibbons–Maeda–Garfinkle–Horowitz–Strominger black hole is presented in this paper. Radial and angular motions are studied analytically for different values of the fundamental parameter. Therefore, gravitational Rutherford scattering and Keplerian orbits are analyzed in detail. Finally, this paper complements previous work by Fernando for null geodesics (Phys Rev D 85:024033, 2012), Olivares and Villanueva (Eur Phys J C 73:2659, 2013) and Blaga (Automat Comp Appl Math 22:41–48, 2013; Serb Astron 190:41, 2015) for time-like geodesics.     

Gravitational field of radiating charged systems: Petrov type II twist-free metrics

The problem of finding certain algebraically special solutions of the Einstein-Maxwell equations with radiation is investigated using the formalism of Newman and Penrose.     

Gravitational collapse of charged scalar fields

In order to study the gravitational collapse of charged matter we analyze the simple model of an self-gravitating massless scalar field coupled to the electromagnetic field in spherical symmetry. The evolution equations for the Maxwell–Klein–Gordon sector are derived in the \(3+1\) formalism, and coupled to gravity by means of the stress–energy tensor of these fields. To solve consistently the full system we employ a generalized Baumgarte–Shapiro–Shibata–Nakamura formulation of General Relativity that is adapted to spherical symmetry. We consider two sets of initial data that represent a time symmetric spherical thick shell of charged scalar field, and differ by the fact that one set has zero global electrical charge while the other has non-zero global charge. For compact enough initial shells we find that the configuration doesn’t disperse and approaches a final state corresponding to a sub-extremal Reissner–Nördstrom black hole with \(|Q| . By increasing the fundamental charge of the scalar field \(q\) we find that the final black hole tends to become more and more neutral. Our results support the cosmic censorship conjecture for the case of charged matter.     

Thermodiffusion motion of electrically charged nanoparticles

The present work deals with experimental studies to examine the theoretical model of thermodiffusion of electrically charged nanoparticles. Three different ionic magnetic colloid samples have been synthesized and profoundly analyzed. The theoretical model is a classical one, based on the calculation of the temperature and the electric potential distribution around nanoparticles. The discrepancy between experimental data and theory turns out not to exceed 20%. We focus on applying different approximations between calculated electrical double layer in the theoretical model and experimental determination of the surface charge density of colloidal particles. We assume this is the main reason for obtained discrepancy.     

Gravitational potential in fractional space

In this paper the gravitational potential with β-th order fractional mass distribution was obtained in α dimensionally fractional space. We show that the fractional gravitational universal constant G _α is given by , where G is the usual gravitational universal constant and the dimensionality of the space is α > 2.      

Metric of a rotating radiating charged mass in a de Sitter space

A new exact solution of the Einstein-Maxwell equations is presented for a rotating radiating charge mass in a de Sitter cosmological background. This solution is shown to encompass previous results by various authors.     

Gravitational multisolitons in two space dimensions

Two classes of regular solutions of five-dimensional general relativity, depending only on two space coordinates, and fulfilling boundary conditions appropriate to gravity theory in two space dimensions, are obtained. The solutions of the first class have a Euclidean spatial topology, while the solutions of the second class have two spatial end points connected byk wormholes.     

Gravitational and electromagnetic fields of a charged tachyon

An axially symmetric exact solution of the Einstein-Maxwell equations is obtained and is interpreted to give the gravitational and electromagnetic fields of a charged tachyon. Switching off the charge parameter yields the solution for the uncharged tachyon which was earlier obtained by Vaidya. The null surfaces for the charged tachyon are discussed.     

Gravitational decoupled charged anisotropic solutions in modified Gauss-Bonnet gravity

This paper is devoted to the study of charged anisotropic exact solutions for spherical geometry in the context of modified Gauss-Bonnet gravity using the gravitational decoupling technique. We take Krori-Barua solution in the presence of charge for a spherically symmetric self-gravitating system and extend it to obtain two anisotropic solutions through some constraints. We study the stability as well as the physical viability criterion of the resulting solutions using anisotropy, squared speed of sound parameter and energy bounds. Both models turn out to be physically viable and stable as they fulfill the required energy conditions and stability criterion. We conclude that the stability of both anisotropic solutions increases with a decrease in charge.     

也谈均匀带电细圆环的电场分布

用Mathematica研究均匀带电细圆环的电场的空间分布,准确地绘制出电场强度量值的分布图和电场方向的分布图,并纠正了最近文献中一幅场强量值分布图的失误.     

Gravitational radiation in asymptotic de Sitter space

A solution of the gravitational field equations is found by using an axially symmetric metric which is asymptotically a de Sitter space metric. We use the general approach of Bondi, van der Burg, and Metzner as applied to the asymptotic flat-space case and search for the necessary conditions for gravitational radiation in asymptotic de Sitter space. We find that the character of the gravitational radiation, if it exists at all, is considerably different from that obtained in the case of asymptotic flat space.     

Exact solution for the gravitational field of a charged,magnetized, spinning mass

A family of solutions of the Einstein-Maxwell field equations is presented, corresponding to the exterior of stationaryaxisymmetric sources with charge, mass, angular momentum, and magnetic dipole moment. The Riemann tensor vanishes asymptotically for each member of the family; some solutions are asymptotically flat and some have NUT-like behavior asymptotically. For the asymptotically flat solutions, the gyromagnetic ratio may vary from zero to one. The corresponding value for the Kerr-Newman solution is one. A method for generating infinite chains of families of solutions of the Einstein-Maxwell equations is described.     

Stability of a charged drop of a viscous electrically conducting liquid in a viscous electrically conducting medium

A dispersion relation is derived for capillary oscillations of a charged electrically conducting viscous drop in an electrically conducting viscous medium. It is shown that aperiodic instability of the charged interface between the two media can arise in this system, with a growth rate that depends qualitatively differently on the ratio of their conductivities in different ranges of values of this ratio. In a certain range of conductivity ratios the drop undergoes oscillatory instability. Zh. Tekh. Fiz. 69, 34–42 (October 1999)     

Gravitational collapse of a charged and radiating fluid ball in the diffusion limit

The collapse of a charged and radiating ball in the diffusion limit is studied using a method reported by Herrera and collaborators. The interior solution is matched with the exterior Reissner-Nordström-Vaidya metric to obtain a system of differential equations at the surface of the distribution, which can be integrated numerically for some set of initial data. For one model, the profiles of the physical variables are obtained at any piece of the material in terms of Schwarzschild-like coordinates.     

Effective dynamics of an electrically charged string with a current

Equations of motion for an electrically charged string with a current in an external electromagnetic field with regard to the first correction due to the self-action are derived. It is shown that the reparameterization invariance of the free action of the string imposes constraints on the possible form of the current. The effective equations of motion are obtained for an absolutely elastic charged string in the form of a ring (circle). Equations for the external electromagnetic fields that admit stationary states of such a ring are derived. Solutions to the effective equations of motion of an absolutely elastic charged ring in the absence of external fields as well as in an external uniform magnetic field are obtained. In the latter case, the frequency at which one can observe radiation emitted by the ring is evaluated. A model of an absolutely nonstretchable charged string with a current is proposed. The effective equations of motion are derived within this model, and a class of solutions to these equations is found.