The dynamics of charged particles and magnetic dipoles around magnetized quasi-Schwarzschild black holes.

Abstract

Annotation: Since the theory of general relativity is a classical theory, it is not without problems. One of the main problems is singularity. Singularities occur at the centers of black holes or in cosmological models, resulting in infinite values. For example, in cosmology, at the initial point, there is infinite curvature, infinite density, and infinite temperature. This implies that cosmological singularity is present in the theory of general relativity. From an astrophysical perspective, singularity also exists at the center of black holes. When calculating the Kretschmann scalar, the curvature at the center tends to infinity. However, the presence of infinity indicates problems in physics and shows that the theory of general relativity cannot be applied universally. There are various solutions for describing black holes mathematically within the framework of general relativity and alternative theories of gravity. These solutions can be studied by examining how test particles behave around black holes. If a magnetic field is assumed to exist around a black hole and particles are considered to have electric charge or magnetic properties, studying such processes is essential for testing theories of gravity, particularly for understanding the nature of black holes. This research involves studying the electromagnetic fields around axially symmetric black holes located in external magnetic fields and analyzing the changes in the effective potentials of charged and test particles during their motion, as well as examining this in the context of the Kerr-Taub-NUT metric.

Objective: To study the solutions of black holes under quasi-Schwarzschild and conformal gravity conditions by analyzing the motion of particles around black holes.

Methodology and methods: The mathematical apparatus of macroscopic electrodynamics within the framework of general relativity; analytical and numerical methods for solving the equations of motion for particles and fields. Studying the impact of space-time parameters involved in the solutions on the motion of particles; evaluating how these solutions differ from those in general relativity and their ability to exhibit effects; assessing the contribution of the presence of an external magnetic field to the problem.

Novelty of the results: For the first time, the motion of particles around black holes under quasi-Schwarzschild and conformal gravity conditions with an external magnetic field has been studied, and the degree to which these solutions differ from those in general relativity has been analyzed. The influence of the external electromagnetic field on these effects has been evaluated for the first time for the considered solutions. The deformation parameter of the quasi-Schwarzschild solution has been assessed in terms of how well it substitutes the spin parameter of the Kerr solution in general relativity, both with and without an external magnetic field.

Introduction: Despite attempts to detect neutron stars, the gravitational interactions at the center of the Milky Way have led to the presence of an ultra-massive black hole, Sagittarius A*, which is observed as processed radio emissions. One reason for the absence of pulsars around Sgr A* could be the propagation of radio waves in the plasma environment surrounding the black hole, while another could be the effect of the magnetic field between the dipole moment of a neutron star and the magnetic field generated by the magnetic charge or electric current of the central black hole. The stable orbital and chaotic motion of neutral particles, the dynamics of charged particles around static and rotating black holes, and their quasi-harmonic oscillations in asynchronous uniform external magnetic fields and the plasma magnetosphere encompass various black holes. The Lyapunov method, in particular, can be used to demonstrate the difference between regular and chaotic orbits. Moreover, minor system effects and gravitational influences lead to the reduction of chaotic motion.