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arxiv: 2605.05352 · v1 · submitted 2026-05-06 · 🌀 gr-qc · astro-ph.GA· hep-ph· physics.space-ph

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Perturbations in the parametrized wormhole spacetime and their related quasinormal modes

Sayan Chakrabarti, Shauvik Biswas

Authors on Pith no claims yet

Pith reviewed 2026-05-08 15:41 UTC · model grok-4.3

classification 🌀 gr-qc astro-ph.GAhep-phphysics.space-ph
keywords wormholesquasinormal modeselectromagnetic perturbationsparametrized spacetimesgalactic wormholesshadow constraintstransfer matrix methodringdown signals
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The pith

A parametrized model of galactic wormholes constrained by Sgr A* shadow data shows that quasinormal mode damping rates vary with compactness while oscillation frequencies remain stable.

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

The paper develops a parametrized description of static spherically symmetric wormholes using far-field coefficients and near-throat continued-fraction expansions to capture both asymptotic and strong-field geometry. It applies the framework first to isolated Damour-Solodukhin and braneworld wormholes, then extends it to a galactic version embedded in a Hernquist dark matter halo. Observational bounds from the shadow of Sgr A* are used to restrict the allowed range of galactic compactness and deformation parameters. Within this range, the transfer matrix method yields fundamental quasinormal frequencies for electromagnetic perturbations, with time-domain analysis of the ringdown signals. The results indicate that damping rates respond more strongly to changes in galactic compactness than the oscillation frequencies do, providing a systematic connection between the geometric parametrization and the dynamical response of horizonless objects.

Core claim

Using the Bronnikov-Konoplya-Pappas parametrization, the metric functions of Damour-Solodukhin and braneworld wormholes together with their galactic extensions are expressed in a compactified radial coordinate; far-field terms govern post-Newtonian behaviour while the near-throat continued-fraction expansion describes the strong-field region. After identifying the range of validity for isolated wormholes and noting convergence limits for non-polynomial functions, the galactic Damour-Solodukhin case is constrained by Sgr A* shadow observations to produce an observationally viable metric. Within the resulting parameter space, transfer-matrix calculations of the fundamental electromagnetic qu<f

What carries the argument

The Bronnikov-Konoplya-Pappas parametrization, which decomposes the metric into far-field coefficients controlling asymptotic structure and a near-throat continued-fraction expansion that encodes the strong-field geometry near the wormhole throat.

If this is right

  • Shadow observations can directly constrain the galactic compactness and deformation parameters of parametrized wormhole spacetimes.
  • The damping rate of quasinormal modes supplies a dynamical probe of galactic compactness that is more responsive than the oscillation frequency.
  • The framework supplies a systematic link between geometric parametrization, shadow data, and the time-domain ringdown signals of horizonless objects.
  • Spectral shifts in the ringdown remain small inside the observationally allowed region, preserving consistency with current data while permitting future tests.

Where Pith is reading between the lines

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

  • Similar parametrizations could be applied to other classes of horizonless compact objects to test whether the same damping sensitivity appears.
  • Future gravitational-wave detectors might resolve the small spectral shifts and thereby distinguish galactic wormhole models from black-hole templates.
  • The approach could be extended to rotating wormhole metrics or to different dark-matter halo profiles to broaden the range of testable configurations.
  • Constraints from gravitational lensing or orbital dynamics around galactic centers could be combined with the shadow bounds to tighten the allowed parameter space further.

Load-bearing premise

The Bronnikov-Konoplya-Pappas parametrization accurately represents the chosen Damour-Solodukhin and braneworld wormhole metrics, including their galactic extensions, despite limitations that non-polynomial metric functions can impose on convergence of the near-throat expansion.

What would settle it

A measurement of the fundamental quasinormal mode damping rate for electromagnetic perturbations around Sgr A* or an analogous compact object that shows no variation with galactic compactness within the shadow-allowed parameter range would contradict the reported sensitivity.

Figures

Figures reproduced from arXiv: 2605.05352 by Sayan Chakrabarti, Shauvik Biswas.

Figure 1
Figure 1. Figure 1: FIG. 1: Comparison of the time-time component of the parametrized metric with that of exact metric components in case of the view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2: Schematic representation of the wormhole double bump potential view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3 view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4 view at source ↗
Figure 5
Figure 5. Figure 5: FIG. 5: Ringdown waveform of the parametrized Damour-Solodukhin wormhole under electromagnetic perturbation ( view at source ↗
Figure 6
Figure 6. Figure 6: FIG. 6: Ringdown waveform of parametrized braneworld wormhole under electromagnetic perturbation ( view at source ↗
Figure 7
Figure 7. Figure 7: FIG. 7: Comparison of view at source ↗
Figure 8
Figure 8. Figure 8: FIG. 8: Comparison of view at source ↗
Figure 9
Figure 9. Figure 9: FIG. 9: Plot of real (left panel) and imaginary (right panel) part of fundamental quasi normal frequencies with view at source ↗
Figure 10
Figure 10. Figure 10: FIG. 10: Ringdown waveform of parametrized galactic Damour-Solodukhin wormhole for two sets of galactic parameter with view at source ↗
Figure 11
Figure 11. Figure 11: FIG. 11: This figure compares the primary signal for the galactic wormhole with that of the fictitious metric obtained by setting view at source ↗
read the original abstract

We study electromagnetic perturbations and the associated quasinormal modes (QNMs) of parametrized static, spherically symmetric wormhole spacetimes, focusing on Damour-Solodukhin and braneworld geometries as well as their galactic extensions. Using the Bronnikov-Konoplya-Pappas parametrization, we express the metric functions in terms of a compactified radial coordinate and characterize the spacetime through far-field and near-throat parameters. The far-field coefficients govern the asymptotic structure and post-Newtonian behaviour, while the near-throat continued-fraction expansion captures the strong-field geometry near the throat. We first apply the parametrization to isolated wormholes and identify its range of validity, showing that non-polynomial metric functions can limit the convergence of the near-throat expansion and hence the accuracy of a truncated representation. We then extend the framework to a galactic Damour-Solodukhin wormhole embedded in a Hernquist dark matter halo. Imposing observational bounds from the shadow of Sgr A$^*$, we constrain the galactic compactness and deformation parameters and obtain an observationally viable parametrized metric. Within the allowed parameter space, we compute the fundamental QNM frequencies using the transfer matrix method and analyze the corresponding time-domain ringdown signals. We find that the damping rate is more sensitive to galactic compactness, whereas the oscillation frequency remains comparatively stable. Although the spectral shifts are small within the shadow-allowed region, the framework provides a systematic link between geometric parametrization, shadow constraints, and dynamical response. Our results establish an observationally consistent parametrized description of wormhole perturbations for strong-field tests of horizonless compact objects.

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

1 major / 0 minor

Summary. The manuscript develops a parametrized description of static spherically symmetric wormhole spacetimes (Damour-Solodukhin and braneworld) using the Bronnikov-Konoplya-Pappas (BKP) formalism, which separates far-field coefficients from a near-throat continued-fraction expansion. It extends the framework to galactic embeddings via a Hernquist dark-matter halo, imposes constraints from the Sgr A* shadow, and computes fundamental electromagnetic QNMs with the transfer-matrix method. Within the shadow-allowed parameter region the authors report that the damping rate is more sensitive to galactic compactness while the oscillation frequency remains comparatively stable, thereby linking geometric parametrization, observational bounds, and ringdown dynamics.

Significance. If the BKP truncation faithfully reproduces the target metrics inside the shadow window, the work supplies a concrete, observationally anchored pipeline from parametrized strong-field geometry to dynamical signatures. The explicit treatment of the parametrization's range of validity, the use of the transfer-matrix technique for QNMs, and the separation of galactic-compactness effects from deformation-parameter effects are genuine strengths that could be useful for future strong-field tests of horizonless objects.

major comments (1)
  1. Abstract and the section on the range of validity of the parametrization: the manuscript correctly notes that non-polynomial metric functions restrict convergence of the near-throat continued-fraction expansion. The galactic Damour-Solodukhin + Hernquist extension introduces additional non-polynomial terms; it is therefore necessary to demonstrate (e.g., by direct comparison of the truncated BKP metric with the exact target metric near the throat, or by reporting the size of the omitted continued-fraction coefficients) that the truncation error remains small for the specific parameter values allowed by the Sgr A* shadow. Without such a check the reported sensitivity of the damping rate to galactic compactness cannot be unambiguously attributed to the intended spacetime rather than to an approximation artifact.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for the careful reading of our manuscript and for the constructive major comment. We agree that an explicit check of the truncation error is required for the galactic extensions and will incorporate the requested verification in the revised version.

read point-by-point responses

  1. Referee: Abstract and the section on the range of validity of the parametrization: the manuscript correctly notes that non-polynomial metric functions restrict convergence of the near-throat continued-fraction expansion. The galactic Damour-Solodukhin + Hernquist extension introduces additional non-polynomial terms; it is therefore necessary to demonstrate (e.g., by direct comparison of the truncated BKP metric with the exact target metric near the throat, or by reporting the size of the omitted continued-fraction coefficients) that the truncation error remains small for the specific parameter values allowed by the Sgr A* shadow. Without such a check the reported sensitivity of the damping rate to galactic compactness cannot be unambiguously attributed to the intended spacetime rather than to an approximation artifact.

    Authors: We agree with the referee that while the range of validity was examined for the isolated wormhole cases, an explicit demonstration is needed for the galactic Damour-Solodukhin + Hernquist models inside the Sgr A* shadow window. In the revised manuscript we will add a dedicated subsection (or appendix) that (i) directly compares the truncated BKP metric functions with the exact target metric near the throat for representative shadow-allowed values of galactic compactness and deformation parameters, and (ii) reports the numerical size of the first few omitted continued-fraction coefficients. This will quantify the truncation error and confirm that the reported sensitivity of the QNM damping rate to galactic compactness arises from the underlying spacetime rather than from the approximation. revision: yes

Circularity Check

0 steps flagged

No circularity: QNMs computed numerically from externally constrained parametrized metric

full rationale

The derivation applies the external BKP parametrization to Damour-Solodukhin and braneworld metrics (with galactic extensions), imposes independent shadow bounds from Sgr A* to fix compactness and deformation parameters, and then evaluates fundamental QNMs via the transfer-matrix method on the resulting metric functions. None of the reported frequencies or damping rates are obtained by algebraic rearrangement of the input metric coefficients or by a self-citation chain; the transfer-matrix step is a distinct numerical procedure whose output is not forced to equal any fitted input by construction. The paper explicitly notes the convergence limitation for non-polynomial functions, but this is a validity caveat rather than a circular reduction. The central claim therefore remains self-contained against external benchmarks.

Axiom & Free-Parameter Ledger

4 free parameters · 3 axioms · 0 invented entities

The central claim rests on the validity of the BKP parametrization for the chosen wormhole metrics, the applicability of the transfer matrix method to electromagnetic perturbations, and the Hernquist halo model for the galactic environment; no new entities are postulated.

free parameters (4)
  • far-field coefficients
    Control asymptotic structure and post-Newtonian behaviour; introduced via the BKP parametrization
  • near-throat continued-fraction coefficients
    Capture strong-field geometry near the throat; truncated expansion used in the framework
  • galactic compactness parameter
    Constrained by Sgr A* shadow bounds for the embedded wormhole
  • deformation parameters
    Shape parameters for Damour-Solodukhin and braneworld models
axioms (3)
  • domain assumption The spacetime is static and spherically symmetric
    Assumed for all wormhole geometries studied in the paper
  • domain assumption Electromagnetic perturbations obey the wave equation on the given background metric
    Basis for applying the transfer matrix method to obtain QNMs
  • ad hoc to paper The Bronnikov-Konoplya-Pappas parametrization provides a usable representation of the metric functions
    Central framework choice, with explicit caveat on convergence for non-polynomial cases

pith-pipeline@v0.9.0 · 5610 in / 1785 out tokens · 56222 ms · 2026-05-08T15:41:08.139486+00:00 · methodology

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Reference graph

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