Motions of spinning particles and chaos bound in Reissner-Nordstr\"om spacetime

TL;DR

This paper investigates the motion of spinning particles around Reissner-Nordström black holes to determine if the chaos bound can be violated, finding violations occur under specific spin and charge conditions.

Contribution

It demonstrates that the chaos bound can be violated in the spinor field of Reissner-Nordström black holes when particles have sufficiently large spin or charge.

Findings

Violations occur when particle spin exceeds a threshold.

Anti-aligned spin and angular momentum increase exponent values.

Large angular momentum charged particles also violate the chaos bound.

Abstract

Previous research showed that the chaos bound proposed in \cite{MSS} can be violated under specific conditions within the scalar fields surrounding black holes. In this paper, we explore motions of spinning particles orbiting a Reissner-Nordstr\"om black hole and examine whether this bound is violated in the spinor field of this black hole. For the neutral particle, when its spin magnitude surpasses a specific threshold, the value of the exponent exceeds the surface gravity, resulting in a violation of the bound. Given a fixed total angular momentum of the particle, when its spin direction is anti-aligned with the angular momentum direction, the exponent value is greater than that when the two directions are aligned. For the charged particle, taking into account the influence of the electromagnetic force, we find that for relatively large angular momenta, although the electromagnetic force does not change the trend of the exponent's variation with respect to spin and angular momentum, and only modifies its values, it still leads to the violation. Therefore, the chaos bound violations are observed in the spinor field.