Report on chaos bound outside Taub-NUT black holes

TL;DR

This paper investigates the behavior of chaos bounds around charged Taub-NUT black holes, identifying regions where the chaos bound is violated and how these regions change with black hole parameters.

Contribution

It provides a detailed analysis of chaos bound violations outside charged Taub-NUT black holes using particle equilibrium orbits and Lyapunov exponents.

Findings

Chaos bound is violated near the horizon and at certain distances from it.

The violation regions expand as the NUT parameter increases.

Equilibrium orbit positions move away from the horizon with increasing angular momentum.

Abstract

Positions of a charged particle's equilibrium orbits and spatial regions where the chaos bound is violated are found through circular motions of the particle around charged Taub-NUT black holes. Lyapunov exponent is gotten by calculating eigenvalues of a Jacobian matrix in a phase space $(r,\pi_r)$. When the particle's charge is fixed, the positions of the equilibrium orbits gradually move away from the event horizons with the increase of the angular momentum.The result shows that the bound is violated in the near-horizon regions and at a certain distance from the horizons when the charge and NUT parameter are fixed. The spatial regions increase with the increase of the NUT parameter's value.