Effect of noncircularity on the dynamic behaviors of particles in a disformal rotating black-hole spacetime

TL;DR

This paper explores how noncircularity in disformal rotating black-hole spacetimes affects particle dynamics, revealing that the deformation parameter's sign influences whether particle motion is regular or chaotic, thus enriching understanding of black-hole physics.

Contribution

It introduces analysis of particle motion in disformal Kerr black holes, highlighting the impact of noncircularity and deformation parameter on dynamic behaviors, which was not previously studied.

Findings

Particle motion depends on the sign of the deformation parameter.

Positive deformation parameter leads to regular, orderly motion.

Negative deformation parameter causes transitions between chaotic and regular motion.

Abstract

A disformal rotating black-hole solution is a black-hole solution in quadratic degenerate higher-order scalar-tensor theories. It breaks the circular condition of spacetime different from the case of the usual Kerr spacetime. This study investigated the dynamic behaviors of the motion of timelike particles in such disformal black-hole spacetime with an extra deformation parameter. Results showed that the characteristics of the particle's motion depend on the sign of the deformation parameter. For the positive deformation parameter, the motion is regular and orderly. For the negative one, as the deformation parameter changes, the motion of the particles undergoes a series of transitions between the chaotic motion and the regular motion and falls into the horizon or escapes to spatial infinity. This means that the dynamic behavior of timelike particles in the disformal Kerr black-hole spacetime with noncircularity becomes richer than that in the usual Kerr black-hole case.