Bound on Lyapunov exponent in Einstein-Maxwell-Dilaton-Axion black holes

TL;DR

This study explores how the angular momentum of a charged particle affects the Lyapunov exponent near Einstein-Maxwell-Dilaton-Axion black holes, revealing conditions under which the chaos bound is violated.

Contribution

It identifies specific conditions and parameter ranges where the Lyapunov exponent bound is violated in the vicinity of these black holes, considering rotation and extremality.

Findings

Violations occur with large rotation parameters and opposite rotation directions.

Spatial regions outside extremal black holes show larger violations.

Near-horizon violations depend on rotation directions, not angular momentum.

Abstract

In this paper, we investigate the influence of the angular momentum of a charged particle around non-extremal and extremal Einstein-Maxwell-Dilaton-Axion black holes on the Lyapunov exponent. The angular momentum's ranges and spatial regions where the bound of the exponent is violated are found for certain values of the rotation parameter and dilatonic constant of the black holes. This violation always exists when the rotation parameter is large enough and the rotation directions of the particle is opposite to those of the black holes. The spatial regions outside the extermal black hole for the violation is relatively large. In the near-horizon regions of the extremal black holes, the violation depends on the rotation directions of the black holes and particle, and does not depend on the value of the angular momentum.