Horizon structure of rotating Bardeen black hole and particle acceleration

TL;DR

This paper explores the horizon structure, ergosphere, and particle acceleration in a rotating Bardeen black hole, revealing how magnetic charge influences extremality, ergosphere size, and the potential for high-energy particle collisions.

Contribution

It provides a detailed analysis of the horizon and ergosphere structure of rotating Bardeen black holes and demonstrates their capability to act as particle accelerators with arbitrarily high collision energies.

Findings

Extremal rotation parameter decreases with magnetic charge g.

Ergosphere becomes thicker as g increases.

Center-of-mass energy can be arbitrarily high near extremal black holes.

Abstract

We investigate the horizon structure and ergosphere in a rotating Bardeen regular black hole, which has an additional parameter ($g$) due to magnetic charge, apart from mass ($M$) and rotation parameter ($a$). Interestingly, for each value of parameter $g$, there exist a critical rotation parameter ($a=a_{E}$), which corresponds to an extremal black hole with degenerate horizons, while for $a<a_{E}$ describes a non-extremal black hole with two horizons, and no black hole for $a>a_{E}$. We find that the extremal value $a_E$ is also influenced by the parameter $g$ and so is the ergosphere. While the value of $a_E$ remarkably decreases when compared with the Kerr black hole, the ergosphere becomes more thick with increase in $g$. We also study collision of two equal mass particle near the horizon of this black hole, and explicitly bring out the effect of parameter $g$. The center-of-mass energy ($E_{CM}$) not only depends on rotation parameter $a$, but also on parameter $g$. It is demonstrated that the $E_{CM}$ could be arbitrary high in the extremal cases when one of the colliding particle has critical angular momentum, thereby suggesting that the rotating Bardeen regular black hole can act as a particle accelerator.