Cosmic Censorship Conjecture in Kerr-Sen Black Hole

TL;DR

This paper investigates the cosmic censorship conjecture in Kerr-Sen black holes, showing that while violations can appear in certain approximations, a more complete analysis confirms the horizon's stability, aligning with thermodynamic laws.

Contribution

It demonstrates that the apparent violations of cosmic censorship in Kerr-Sen black holes are resolved when considering adiabatic processes, confirming horizon stability.

Findings

Violations occur at first and second order approximations for angular momentum and charge.

Adiabatic processes restore the stability of the black hole horizon.

Results are consistent with the third law of thermodynamics.

Abstract

The validity of the cosmic censorship conjecture for the Kerr-Sen black hole, which is a solution to the low-energy effective field theory for four-dimensional heterotic string theory, is investigated using charged particle absorption. When the black hole absorbs the particle, the charge on it changes owing to the conserved quantities of the particle. Changes in the black hole are constrained to the equation for the motion of the particle and are consistent with the laws of thermodynamics. Particle absorption increases the mass of the Kerr-Sen black hole to more than that of the absorbed charges such as angular momentum and electric charge; hence, the black hole cannot be overcharged. In the near-extremal black hole, we observe a violation of the cosmic censorship conjecture for the angular momentum in the first order of expansion and the electric charge in the second order. However, considering an adiabatic process carrying the conserved quantities as those of the black hole, we prove the stability of the black hole horizon. Thus, we resolve the violation. This is consistent with the third law of thermodynamics.