Motion of spinning particles around black hole in a dark matter halo

TL;DR

This paper studies how dark matter halos influence the motion of spinning particles around black holes, revealing significant changes in orbital characteristics compared to black holes without dark matter.

Contribution

It provides the first detailed analysis of spinning particle dynamics around a black hole immersed in a Hernquist dark matter distribution using the Mathison-Papapetrou-Dixon framework.

Findings

Dark matter halos alter orbital eccentricity and energy of spinning particles.

The innermost stable circular orbit moves closer to the black hole in the presence of dark matter.

Dark matter significantly affects the properties of marginally bound and periodic orbits.

Abstract

The motion of a rapidly rotating object in curved spacetime is affected by the spin-curvature force, an effect captured in the motion of spinning test particles. Recently, Cardoso et al.~[Phys. Rev. D 105, L061501 (2022)] found an exact solution describing a black hole immersed in a Hernquist distribution of dark matter. In this work, we investigate the motion of spinning particles around this black hole. We use the Mathison-Papapetrou-Dixon equation and the Tulczyjew spin-supplementary condition to calculate the effective potential, four-momentum, and four-velocity of the spinning particle. The equatorial motion of spinning test particles and the properties of the marginally bound orbits, innermost stable circular orbits, and periodic orbits are further studied. We find that the existence of dark matter halos can significantly change the orbital eccentricity, energy, and the marginally bound orbits, innermost stable circular orbits, and periodic orbits parameters of spinning test particles. Compared to the Schwarzschild black hole, dark matter halos bring the marginally bound orbit and innermost stable circular orbit of a spinning test particle closer to the event horizon. These results could help us understand the properties of black holes in dark matter halos.