Energy extraction-driven instability and horizon formation in Kerr-Newman naked singularities and their limiting cases

TL;DR

This paper analyzes how energy extraction mechanisms in Kerr-Newman spacetimes influence the stability and potential horizon formation of naked singularities, revealing that continuous extraction can drive these objects toward extremality over cosmic timescales.

Contribution

It provides a unified analysis of rotational and electromagnetic energy extraction in various spacetimes and demonstrates how these processes can induce instability and horizon formation in naked singularities.

Findings

Electromagnetic interactions extend negative energy regions, increasing extraction efficiency.

Continuous energy extraction can evolve naked singularities toward extremality.

Long-term evolution timescale is approximately 10^9 years.

Abstract

Energy extraction from compact objects has been a central topic in general relativity since the introduction of the Penrose process. In this work we present a unified analysis of rotational and electromagnetic energy extraction in Kerr, Reissner-Nordstrom, and Kerr-Newman spacetimes. Using particle energetics and the irreducible mass formalism, we compare the efficiencies of these mechanisms and examine their consequences for horizonless objects. While purely rotational extraction in Kerr spacetime is fundamentally limited by geometric constraints, electromagnetic interactions enlarge the region of negative energy orbits through an effective ergoregion, allowing significantly higher efficiencies. In Kerr-Newman geometry, the combined effect of rotation and charge further enhances the extractable energy. We then study the long-term evolution of over-extremal cases under continuous extraction. By deriving coupled evolution equations for the mass, spin, and charge parameters, we show that continuous extraction can gradually drive a naked singularity toward the extremal bound. For astrophysically realistic luminosities, the characteristic evolution timescale is of order about 10^9 years. These results suggest that energy extraction provides an energetic indication of instability in Reissner-Nordstrom, Kerr, and Kerr-Newman naked singularities and may lead to horizon formation as a long-term stabilizing outcome.