Destroying Kerr-Sen black holes

Abstract

By neglecting the self-force, self-energy, and radiative effects, it has been shown that an extremal or near-extremal Kerr-Newman black hole can turn into a naked singularity when it captures charged and spinning massive particles. A straightforward question then arises: do charged and rotating black holes in string theory possess the same property? In this paper we apply the Wald's gedanken experiment, in his study on the possibility of destroying extremal Kerr-Newman black holes, to the case of (near-)extremal Kerr-Sen black holes. We find that feeding a test particle into a (near-)extremal Kerr-Sen black hole could lead to a violation of the extremal bound for the black hole.

Examining the weak cosmic censorship conjecture by gedanken experiments for Kerr-Sen black holes

“…First of all, we derive the first two order perturbation inequalities in the low energy limit of heterotic string theory based on the Iyer-Wald formalism, and apply it into the Kerr-Sen black holes. Differing from the result of the old version of gedanken experiments where the Kerr-Sen black holes can be destroyed if neglecting the self-force, self-energy, and radiative effect [33,34], it cannot be overcharged or overspun after the second-order perturbation inequality being considered. Therefore, WCCC is well preserved around this black hole.…”

Weak cosmic censorship with pressure and volume in charged anti-de Sitter black hole under charged scalar field

“…If the carried conserved quantities are sufficiently large compared with the constant to enable the over-spinning or over-charging of the black hole, then the black hole can be a naked singularity. Such a situation has already been found in [25] through testing with a particle, and the invalidity of the WCCC was resolved in [26] by considering the second-order perturbation due to the particle. Hence, in the present study, we investigate whether the WCCC can be invalid and whether we still need the second-order analysis to resolve the invalidity as shown in [26].…”

“…Because the electric potential is different from that of Reissner-Nordström black holes, the scalar field should be coupled with the rotational and electric contents of the black hole. Note that, by particle absorption, the WCCC was previously found to be violated in the Kerr-Sen black hole [25], but the WCCC was found to be valid in [26] when considering the second-order variation owing to the charged particle. On the other hand, with a neutral scalar field, the violation of the WCCC has been shown in the first order [55].…”

Static charged Gauss-Bonnet black holes cannot be overcharged by the new version of gedanken experiments

“…Replacing ζ a by the Killing vector ξ a = (∂ /∂ v) a of the background geometry in Eqs. (26) and (27), the first two order variational identities can be further obtained,…”