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arxiv: 2602.00518 · v1 · pith:FRB6HTUEnew · submitted 2026-01-31 · 🌀 gr-qc

Charged Superradiant Instability of Spherically Symmetric Regular Black Holes in de Sitter Spacetime: Time- and Frequency-Domain Analysis

Pith reviewed 2026-05-21 13:54 UTC · model grok-4.3

classification 🌀 gr-qc
keywords superradiant instabilityregular black holesde Sitter spacetimecharged scalar perturbationsnonlinear electrodynamicsABG metrictime-domain evolutionfrequency-domain analysis
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The pith

de Sitter horizon triggers instability in regular black holes

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

This paper examines how massless charged scalar fields behave around Ayón-Beato-García black holes in de Sitter space. It demonstrates that these regular black holes suffer superradiant instability only in the monopole mode, thanks to the cosmological horizon acting as a confining wall. The growth rate of the instability varies with the cosmological constant, scalar charge, and black hole charge, showing peaks at intermediate values and monotonic increase with charge. This contrasts with the stability of the same black holes in flat spacetime and with the behavior of Reissner-Nordström-de Sitter black holes.

Core claim

Spherically symmetric regular black holes in de Sitter spacetime, described by the Ayón-Beato-García metric from nonlinear electrodynamics, exhibit charged superradiant instability under massless scalar perturbations exclusively for the ℓ=0 mode. The cosmological horizon provides the essential confining boundary that enables the instability, which does not occur in the asymptotically flat limit.

What carries the argument

The ABG-dS metric from nonlinear electrodynamics, whose modified electrostatic potential governs the superradiant condition and produces distinct instability features relative to linear electrodynamics.

If this is right

  • The instability growth rate reaches a maximum at intermediate values of the cosmological constant and scalar charge.
  • The growth rate increases monotonically with increasing black hole charge Q.
  • Only the spherically symmetric ℓ=0 mode is unstable; higher angular modes remain stable.
  • ABG-dS black holes display different instability characteristics from Reissner-Nordström-de Sitter black holes because of the modified electrostatic potential from nonlinear electrodynamics.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The cosmological horizon appears to be the decisive ingredient that turns a stable flat-space configuration into an unstable one for regular black holes.
  • These instabilities may affect the long-term evolution of black holes embedded in expanding cosmologies, potentially sourcing scalar radiation or gravitational-wave signals.
  • Similar analyses for massive scalars or rotating regular black holes could uncover additional instability windows.

Load-bearing premise

The background is fixed as the exact ABG-dS metric from nonlinear electrodynamics while scalar perturbations stay linear, massless, and without back-reaction on the geometry.

What would settle it

A frequency-domain computation or time-domain simulation that finds the imaginary part of the quasinormal frequency negative for every value of Λ, q, and Q in the ℓ=0 sector would falsify the instability.

Figures

Figures reproduced from arXiv: 2602.00518 by Haowei Chen, Hengyu Xu, Shao-Jun Zhang, Yizhi Zhan.

Figure 1
Figure 1. Figure 1: FIG. 1 [PITH_FULL_IMAGE:figures/full_fig_p004_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2 [PITH_FULL_IMAGE:figures/full_fig_p006_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3 [PITH_FULL_IMAGE:figures/full_fig_p006_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4 [PITH_FULL_IMAGE:figures/full_fig_p007_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: FIG. 5 [PITH_FULL_IMAGE:figures/full_fig_p009_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: FIG. 6 [PITH_FULL_IMAGE:figures/full_fig_p010_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: FIG. 7 [PITH_FULL_IMAGE:figures/full_fig_p010_7.png] view at source ↗
read the original abstract

We investigate the superradiant instability of Ay\'on-Beato-Garc\'ia-de Sitter (ABG-dS) black holes under massless charged scalar perturbations using both time-domain evolutions and frequency-domain computations. We show that the instability occurs only for the spherically symmetric mode with $\ell=0$, whereas asymptotically flat ABG black holes remain stable in the massless limit, which underscores the essential role of the cosmological horizon in providing a confining boundary. We further study the dependence of the growth rate on the cosmological constant $\Lambda$, the scalar charge $q$, and the black hole charge $Q$, finding that it reaches a maximum at intermediate values of $\Lambda$ and $q$ and increases monotonically with $Q$. Compared with Reissner-Nordstr\"om-de Sitter black holes, ABG-dS black holes exhibit distinct instability characteristics due to the modified electrostatic potential induced by nonlinear electrodynamics.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 2 minor

Summary. The paper investigates charged superradiant instability of Ayón-Beato-García-de Sitter (ABG-dS) regular black holes under massless charged scalar perturbations. Using both time-domain evolutions and frequency-domain quasinormal-mode computations, the authors report that the instability occurs exclusively for the spherically symmetric ℓ=0 mode, while asymptotically flat ABG black holes remain stable in the massless limit. They further examine the dependence of the growth rate on the cosmological constant Λ, scalar charge q, and black-hole charge Q, finding a maximum at intermediate values of Λ and q with monotonic increase in Q, and note distinct characteristics relative to Reissner-Nordström-de Sitter black holes arising from the modified electrostatic potential of nonlinear electrodynamics. The cosmological horizon is identified as providing the essential confining boundary.

Significance. If the numerical results hold, the work demonstrates the essential role of the cosmological horizon in triggering charged superradiant instabilities on regular black-hole backgrounds in de Sitter spacetime, a feature absent in the asymptotically flat case. The dual time- and frequency-domain approach supplies cross-validation, and the explicit parameter scans (maximum growth at intermediate Λ and q, monotonic rise with Q) together with the direct contrast to RN-dS supply concrete, falsifiable predictions. The use of an exact nonlinear-electrodynamics metric rather than an approximate one strengthens the analysis.

major comments (2)
  1. [§4] §4 (time-domain section): the reported growth rates for the ℓ=0 mode rely on direct numerical evolution, yet the manuscript provides no explicit convergence tests, grid-resolution studies, or error estimates on the extracted imaginary parts of the frequencies; these are load-bearing for the central claim that only ℓ=0 is unstable.
  2. [§5] §5 (frequency-domain section): the effective potential for the charged scalar is modified by the nonlinear-electrodynamics term; the manuscript should show explicitly how this modification alters the superradiant condition relative to the RN-dS case (e.g., via a direct comparison of the potential barriers or the critical q/Q ratio).
minor comments (2)
  1. [Abstract] The abstract and introduction use “ABG-dS” without first spelling out the full name on its initial occurrence; this should be corrected for clarity.
  2. [Results] Figure captions for the growth-rate plots should state the precise values of the fixed parameters (e.g., Q=0.5, q=0.3) rather than referring only to “intermediate values.”

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the careful reading of our manuscript and the constructive comments. We address each major comment below and will incorporate the suggested improvements in the revised version.

read point-by-point responses
  1. Referee: [§4] §4 (time-domain section): the reported growth rates for the ℓ=0 mode rely on direct numerical evolution, yet the manuscript provides no explicit convergence tests, grid-resolution studies, or error estimates on the extracted imaginary parts of the frequencies; these are load-bearing for the central claim that only ℓ=0 is unstable.

    Authors: We agree that explicit convergence tests, grid-resolution studies, and error estimates are necessary to substantiate the numerical results, particularly given their importance to the claim that instability is restricted to the ℓ=0 mode. In the revised manuscript we will add a new subsection to §4 presenting convergence tests under successive grid refinements, resolution studies, and quantitative error estimates on the extracted imaginary parts of the frequencies. revision: yes

  2. Referee: [§5] §5 (frequency-domain section): the effective potential for the charged scalar is modified by the nonlinear-electrodynamics term; the manuscript should show explicitly how this modification alters the superradiant condition relative to the RN-dS case (e.g., via a direct comparison of the potential barriers or the critical q/Q ratio).

    Authors: We concur that a direct, explicit comparison would clarify how the nonlinear-electrodynamics modification of the electrostatic potential changes the superradiant condition relative to the RN-dS case. In the revised manuscript we will include, in §5, a side-by-side plot of the effective potentials for ABG-dS and RN-dS together with a discussion of the resulting shifts in the critical q/Q ratio and the location of the potential barrier. revision: yes

Circularity Check

0 steps flagged

No significant circularity detected

full rationale

The paper's central results on superradiant instability for ℓ=0 modes in ABG-dS spacetime are obtained via direct numerical time-domain evolution of the perturbation equations and frequency-domain quasinormal-mode computations on the exact background metric. These methods solve the linear wave equation without fitting parameters to the target growth rates, without self-referential definitions of the instability criterion, and without load-bearing reliance on prior self-citations that presuppose the present conclusions. The contrast with the asymptotically flat limit follows from the same numerical procedure applied to the Λ=0 case, and the reported parameter dependencies (growth rate vs. Λ, q, Q) are outputs of the computation rather than inputs. The derivation chain is therefore self-contained against external benchmarks.

Axiom & Free-Parameter Ledger

3 free parameters · 2 axioms · 0 invented entities

The analysis rests on the standard Einstein equations coupled to nonlinear electrodynamics for the background metric and on the linear wave equation for a massless charged scalar field; no new entities are postulated.

free parameters (3)
  • Black-hole charge Q
    Physical parameter of the ABG-dS solution that is varied to study instability growth.
  • Cosmological constant Λ
    Parameter controlling the size of the cosmological horizon; varied to locate the maximum growth rate.
  • Scalar charge q
    Charge of the perturbing field; varied to locate the maximum growth rate.
axioms (2)
  • domain assumption The Ayón-Beato-García-de Sitter metric satisfies the Einstein equations sourced by nonlinear electrodynamics.
    Provides the fixed background spacetime on which perturbations are evolved.
  • domain assumption Scalar perturbations remain linear and massless with no back-reaction.
    Justifies the use of the linear wave equation on the fixed metric.

pith-pipeline@v0.9.0 · 5711 in / 1507 out tokens · 51934 ms · 2026-05-21T13:54:47.838246+00:00 · methodology

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