Evolution of Braneworld Kerr-Newman Naked Singularities

TL;DR

This paper investigates how braneworld Kerr-Newman naked singularities evolve under matter accretion, revealing conditions for their transformation into black holes or other exotic states, with implications for energy extraction and gravitational physics.

Contribution

It introduces a detailed analysis of the evolution of braneworld Kerr-Newman naked singularities considering tidal charge variations, highlighting new outcomes like unlimited energy extraction and toroidal matter structures.

Findings

Counter-rotating accretion converts naked singularities into extreme black holes.

Corotating accretion can lead to unlimited energy extraction for certain tidal charges.

Different tidal charge regimes result in diverse end states, including transcendental and toroidal structures.

Abstract

We study evolution of the braneworld Kerr--Newman (K-N) naked singularities, namely their mass $M$ , spin $a$, and tidal charge $b$ characterizing the role of the bulk space, due to matter in-falling from Keplerian accretion disk. We construct the evolution in two limiting cases applied to the tidal charge. In the first case we assume $b$ = const during the evolution, in the second one we assume that the dimensionless tidal charge $\beta \equiv b/M^2$ = const. For positive values of the tidal charge the evolution is equivalent to the case of the standard K-N naked singularity under accretion of electrically neutral matter. We demonstrate that counter-rotating accretion always converts a K-N naked singularity into an extreme K-N black hole and that the corotating accretion leads to variety of outcomes. The conversion to an extreme K-N black hole is possible for naked singularity with dimensionless tidal charge $\beta < 0.25$, and $\beta \in (0.25, 1)$ with sufficiently low spin. In other cases the accretion ends in a transcendental state. For $0.25 < \beta < 1$ this is a mining unstable K-N naked singularity enabling formally unlimited energy extraction from the naked singularity. In the case of $\beta > 1$, the corotating accretion creates unlimited torodial structure of mater orbiting the naked singularity. Both non-standard outcomes of the corotating accretion imply a transcendence of such naked singularity due to nonlinear gravitational effects.