Kerr Geodesics Following the Axis of Symmetry

TL;DR

This paper derives general expressions for the acceleration of particles along the Kerr black hole's axis, revealing a repulsive gravitational region that may influence jet formation.

Contribution

It provides new analytical expressions for Kerr geodesics along the axis and explores the physical implications of repulsive gravity near black holes.

Findings

Existence of a repulsive gravitational region near the black hole

Analytical expressions for particle acceleration along the axis

Potential role in extragalactic jet production

Abstract

We present here the general expressions for the acceleration of massive test particles along the symmetry axis of the Kerr metric, and then study the main properties of this acceleration in different regions of the spacetime. In particular, we show that there exists a region near the black hole in which the gravitational field is repulsive. We provide possible physical interpretations about the role of this effect in terms of the different conserved parameters. The studies of these geodesics are important not only to understand better the structure of the Kerr spacetime but also to its use as a possible mechanism for the production of extragalactic jets. Our results are obtained with the help of expressing the geodesics of the Kerr spacetime in terms of the Weyl coordinates.