Dynamics of charged particles and magnetic dipoles around magnetized quasi-Schwarzschild black holes

TL;DR

This paper explores how deviations from Schwarzschild black holes and external magnetic fields can mimic the spin of Kerr black holes, analyzing charged particle and magnetic dipole dynamics to identify degeneracies in orbital properties.

Contribution

It demonstrates that spacetime deviation parameters and magnetic fields can replicate Kerr black hole spin effects, especially in rapidly rotating cases, through detailed particle and dipole motion analysis.

Findings

Deviation parameter mimics Kerr spin up to a/M ≈ 0.5 without magnetic field.

Combined magnetic field and deviation parameter mimic spin up to a/M ≈ 0.93.

Degeneracy in ISCO radius occurs for certain deviation parameters and magnetic couplings.

Abstract

In the present paper, we have investigated the motion of charged particles together with magnetic dipoles to determine how well the spacetime deviation parameter $\epsilon$ and external uniform magnetic field can mimic the spin of a rotating Kerr black hole. Investigation of charged particle motion has shown that the deviation parameter $\epsilon$ in the absence of external magnetic fields can mimic the rotation parameter of Kerr spacetime up to $a/M \approx0.5$. The combination of external magnetic field and deviation parameter can do even a better job mimicking the rotation parameter up to $a/M\simeq0.93$, which corresponds to the rapidly rotating case. Study of the dynamics of magnetic dipoles around quasi-Schwarzschild black holes in the external magnetic field has shown that there are degeneracy values of ISCO radius of test particles at $\epsilon_{cr}>\epsilon\geq 0.35$ which may lead to two different values of the innermost stable circular orbit (ISCO) radius. When the deviation parameter is in the range of $\epsilon \in (-1,\ 1)$, it can mimic the spin of a rotating Kerr black hole in the range $a/M \in (0.0537, \ 0.3952)$ for magnetic dipoles with values of magnetic coupling parameter $\beta \in [-0.25,\ 0.25]$ in corotating orbits.