REVIEW 3 major objections 5 minor 2 cited by
Quasinormal Modes of Schwarzschild Black Holes in the Dehnen-(1, 4, 5/2) Type Dark Matter Halos
T0 review · 3 major / 5 minor · reviewed 2026-08-07 · deepseek-v4-flash
Pith's one-line read Dark matter halos systematically lower the quasinormal-mode frequencies of Schwarzschild black holes and lengthen their damping time, while preserving stability.
desk verdict The M87* parameter scan is fine but the effective potentials in Eqs. (12) and (23) don't follow from the metric, so the reported QNM frequencies are not those of the SBHD spacetime. read the letter →
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
The reading
What carries the argument
The load-bearing objects are the effective potentials $V(r)$ in the tortoise-coordinate wave equation $d^2\psi/dr_*^2 + (\omega^2 - V)\psi = 0$, where $dr_*/dr = 1/f(r)$. For the SBHD metric, the paper writes Eq. (12) for scalar perturbations, Eq. (13) for electromagnetic perturbations, and Eq. (23) for axial gravitational perturbations; each is built from the metric function $f(r) = 1 - 2M/r - 32\pi\rho_s r_s^3 \sqrt{(r+r_s)/(r_s^2 r)}/r$ multiplied by a field-dependent bracket. These potentials feed the sixth-order WKB formula (25) and the light-cone finite-difference scheme (28), with complex frequencies extracted from the time-domain signal by the Prony method. The trend they encode—peak height decreasing as $\rho_s$ or $r_s$ grows—is what produces the paper's physical conclusions.
What would settle it
Take the metric (2), substitute the scalar and electromagnetic ansätze into Eqs. (8) and (9), and carry out the axial Regge-Wheeler reduction by hand or symbolically; if the resulting potentials differ from Eqs. (12), (13), and (23) in any dark-matter term, recompute the quasinormal-mode frequencies from the corrected potentials and compare with the paper's Table II. A second independent check is a direct full numerical evolution of the perturbation equations with no WKB approximation, to see whether the ringing frequency matches the quoted real part.
Extended reading notes
Core claim
The paper's central claim is that adding a Dehnen-(1,4,5/2) dark matter halo to a Schwarzschild black hole changes the quasinormal-mode spectrum monotonically: for fixed angular number $l=2$, increasing either the halo central density $\rho_s$ or the scale radius $r_s$ lowers the maximum of the effective potential $V(r)$ for scalar, electromagnetic, and axial gravitational perturbations. Consequently the real part of the quasinormal-mode frequency decreases, the wave oscillation slows down, and the imaginary part stays negative but moves closer to zero, meaning the perturbation damps more slowly; the black hole is stable. The paper also finds that both parameter sets consistent with the 3$\sigma$ M87* shadow-radius window enlarge the event-horizon and photon-sphere radii compared with the Schwarzschild case. The WKB and time-domain/Prony methods agree, which the paper presents as evidence that the quoted complex frequencies are consistent across approximation schemes.
Load-bearing premise
The calculations assume that the effective potentials in Eqs. (12) and (23) are the correct reductions of the Klein-Gordon, Maxwell, and Regge-Wheeler equations for the SBHD metric in Eq. (2); if those reductions are wrong, the computed frequencies describe a different spacetime or different perturbation channel.
Editorial extensions
If this is right
- Ringdown templates for supermassive black holes in Dehnen-type halos must use lower real frequencies and longer damping times than vacuum Schwarzschild templates.
- The allowed $(\rho_s, r_s)$ region from the M87* shadow radius maps to a predicted band of quasinormal-mode frequencies, so a future ringdown measurement could test the halo parameters independently.
- The negative imaginary part in all three perturbation channels means the Dehnen halo does not introduce an instability in scalar, electromagnetic, or axial gravitational perturbations for the studied parameters.
- The agreement between the WKB and time-domain/Prony methods indicates that the reported frequencies are not an artifact of one numerical scheme.
Reading between the lines
- An implication the paper leaves implicit is that the same pipeline can map other Dehnen indices and higher overtones, producing a catalog that would let observers distinguish halo profiles by their ringdown alone.
- The negative correlation between $\rho_s$ and $r_s$ under the shadow constraint suggests that ringdown data, which the paper shows respond to both parameters in the same direction, may not cleanly break the degeneracy by itself; combining ringdown with lensing or photon-sphere measurements could.
- A natural extension is to compute polar gravitational perturbations, which the paper does not treat, and check whether the effective-potential lowering and stability results persist in that channel.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript studies quasinormal modes (QNMs) of a Schwarzschild-like black hole in a Dehnen-(1,4,5/2) dark matter halo. Using the M87* shadow-radius constraint, two sets of halo parameters (rho_s, r_s) are chosen. The authors derive effective potentials for scalar, electromagnetic, and axial gravitational perturbations, compute QNM frequencies with a sixth-order WKB method and a time-domain Prony method, and report that increasing rho_s or r_s lowers the peak of the effective potential and the real part of the QNM frequency, while the imaginary part decreases in magnitude, implying stability. Table II lists QNM frequencies for several multipole numbers.
Significance. If valid, the paper would provide a systematic catalogue of QNM frequencies for this dark-matter model and a possible connection to EHT shadow observations. The use of two independent numerical methods for cross-checking and the explicit parameter constraints from shadow data are strengths. However, the central results depend on effective potentials that are incorrectly derived: the scalar potential in Eq. (12) differs from the exact Klein-Gordon potential for metric (2) by a factor of order 30 at the adopted parameters, and the axial potential raises similar concerns. The quantitative conclusions are therefore not established by the calculations presented.
major comments (3)
- [II.B, Eq. (12)] The scalar effective potential is not the Klein-Gordon potential for metric (2). For a massless scalar in a static spherically symmetric metric, the potential is V(r) = f(r)[l(l+1)/r^2 + f'(r)/r]. Inserting f(r) from Eq. (2) and simplifying the dark-matter term H(r) = 32*pi*rho_s*r_s^3*r^(-1)*sqrt((r+r_s)/(r_s^2*r)) gives a correction f'/r = 16*pi*rho_s*r_s^2*(2r+3r_s)/(r^(7/2)*(r+r_s)^(1/2)). Equation (12) instead contains 16*pi*rho_s*r_s^3/(r^(7/2)*(r+r_s)^(1/2)). The ratio of the correct to printed correction at the paper's own parameter values (r ~ 3, r_s = 0.2) is (2r+3r_s)/r_s ~ 33, so this is not a typesetting artifact. Since Eq. (12) is the direct input to the WKB and Prony calculations, the frequencies reported in Figs. 5-7 and Table II are not quasinormal frequencies of the SBHD spacetime described by Eq. (2).
- [II.C, Eqs. (21)-(23)] The axial gravitational derivation is internally inconsistent. Equation (21), with the tortoise coordinate defined by dr_* = dr/f(r), does not reduce to a one-dimensional wave equation: after substituting psi = f(r) h1/r and Q = r*psi, the term (f/r) d/dr[f d(r*psi)/dr] produces a second derivative with respect to r_* whose coefficient is f^4/r (or f^5/r for Q), rather than unity, so Eq. (21) is not the standard Regge-Wheeler master equation for this metric. Consequently Eq. (23) does not follow from Eq. (21). The dark-matter term in Eq. (23), after simplification, is -48*pi*rho_s*r_s^3/(r^(7/2)*(r+r_s)^(1/2)), which is not the correct f'- or f''-dependent correction to the Regge-Wheeler potential for a general static spherical metric such as (2). The axial gravitational QNM results in Figs. 5-7 and Table II are therefore unsupported.
- [III.B, Figs. 5-7 and Table II] Because the effective potentials in Eqs. (12) and (23) are not derived correctly from metric (2), the central trend claim — that larger rho_s or r_s lowers the QNM frequency and increases damping time — is not established by these computations. The geodesic effective potential in Fig. 2 does decrease with rho_s, but the QNM potential involves f'(r) and f''(r), and with the correct f'(r) from Eq. (2) the correction term has a different magnitude and r-dependence. No calculation is given to show that the claimed monotonic decrease of the real frequency survives with the correct potentials; the conclusion in Section IV therefore rests on the erroneous potentials.
minor comments (5)
- [Eqs. (2), (4), (7), (12), (23)] The notation r2s, r3s, and expressions such as r2sr are hard to read; please use proper superscripts and parentheses, e.g., r_s^2 r, r_s^3, and clarify every occurrence.
- [Fig. 2] The vertical axis in Fig. 2 is labeled V(r) although the text refers to the effective potential U(r); the labeling should be consistent throughout the figure and caption.
- [Table I] The table lists b_ph values but does not define b_ph in the caption; state explicitly that b_ph is the shadow radius in units of M, consistent with the text in Section II.A.
- [Section III.B] The phrase 'the shapes overlap very well' should be 'the symbols overlap very well'; also, the legend in Fig. 7 should be clarified so that the reader can identify which color corresponds to scalar, electromagnetic, and axial gravitational fields.
- [Section IV] The conclusion that the black hole 'remains stable under perturbations' is inferred only from the fundamental mode for a few multipoles; this does not constitute a proof of stability and should be phrased with appropriate caution.
Circularity Check
No circularity: the QNM frequencies are computed from independently cited metric and perturbative potentials, with halo parameters fitted to shadow data rather than to the target QNM trend.
full rationale
The derivation chain is self-contained in the relevant sense. The paper imports the SBHD metric from the external reference [33], fixes halo parameters using M87* shadow-radius data via the geodesic equation, derives effective potentials from the Klein-Gordon, Maxwell, and Regge-Wheeler equations, and then computes quasinormal-mode frequencies with sixth-order WKB and time-domain/Prony methods. Nothing in the QNM computation is fitted to the claimed trend that larger rho_s or r_s lowers frequencies and prolongs damping; that trend emerges only after solving the wave equations. The halo parameter fit to shadow data is an input to the QNM calculation, not a reuse of its output. The authors' own prior works [24, 25] are cited only as general context and do not carry the derivation. The possible algebraic mismatch between the metric (2) and the dark-matter terms in Eqs. (12) and (23), raised as a correctness concern, would mean the computed frequencies do not describe the SBHD spacetime, but that is a derivation error or correctness issue, not an instance of a prediction reducing to its inputs by construction. Therefore no circular step is present.
Assumptions & free parameters
free parameters (2)
- Dark matter central density ρ_s =
0.01, 0.03, 0.05 (with r_s = 0.2); 0.01 (with r_s = 0.15, 0.3, 0.45)
- Dark matter core radius r_s =
0.15, 0.3, 0.45 (with ρ_s = 0.01); 0.2 (with ρ_s = 0.01, 0.03, 0.05)
assumptions (4)
- domain assumption The metric in Eq. (2) is a valid solution for a Schwarzschild black hole embedded in a Dehnen-(1,4,5/2) dark matter halo.
- domain assumption The 3σ shadow radius interval for M87*, 2.546M to 7.846M, from Ref. [37], is a valid constraint on the halo parameters ρ_s and r_s.
- standard math Standard perturbation equations for massless scalar, electromagnetic, and axial gravitational fields in a static spherical background, including the Regge-Wheeler gauge, apply to this metric.
- domain assumption The sixth-order WKB approximation is sufficiently accurate for the modes considered, including l=0 and l=1.
Cite this review
Pith. "Pith review of Quasinormal Modes of Schwarzschild Black Holes in the Dehnen-(1, 4, 5/2) Type Dark Matter Halos." pith.science (2026). https://pith.science/paper/7KLKDGL2
@misc{pith2026250515540,
author = {Pith},
title = {Pith review of: Quasinormal Modes of Schwarzschild Black Holes in the Dehnen-(1, 4, 5/2) Type Dark Matter Halos},
year = {2026},
howpublished = {\url{https://pith.science/paper/7KLKDGL2}},
note = {Machine review of arXiv:2505.15540}
}
abstract
The Dehnen - type dark matter density distribution model is mainly used for dwarf galaxies. In recent years, researchers have speculated that black holes may exist in this dark matter model and have given the black hole metric solutions. On this basis, this paper conducts a systematic study on the quasinormal modes of a Schwarzschild black hole in a Dehnen - (1,4, 5/2) dark matter halo, revealing the influences of dark matter distribution and perturbation field types on the black hole's quasinormal modes.The research uses the shadow radius data of the M87$^{\ast}$ black hole. Through the geodesic equation, two sets of dark matter halo parameter values of $\rho_{\rm s}$ and $r_{\rm s}$ are determined, and the specific numerical values of the black hole's event horizon radius, photon sphere radius, and shadow radius under the corresponding conditions are obtained. The wave equations and effective potentials of the black hole under the perturbations of the scalar field, electromagnetic field, and axial gravitational were analyzed. It was found that the larger the values of $\rho_{\rm s}$ or $r_{\rm s}$, the smaller the peak value of the effective potential, and the wave function oscillation slows down with a lower frequency. The black hole remains stable under perturbations. These studies provide relevant data for the quasinormal modes of the Schwarzschild black hole in the Dehnen-(1,4, 5/2) type dark matter halo. They also offer crucial evidence for understanding the interaction mechanism between the black hole and the dark matter halo.
Figures
Figures from the paper (4 more)
Forward citations
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Reference graph
Works this paper leans on
-
[1]
A. Allahyari, M. Khodadi, S. Vagnozzi and D. F. Mota, JCAP 02, 003 (2020) doi:10.1088/1475- 7516/2020/02/003 [arXiv:1912.08231 [gr-qc]]
arXiv 2020
- [2]
-
[3]
T. P. Sotiriou and S. Y. Zhou, Phys. Rev. D 90, 124063 (2014) doi:10.1103/PhysRevD.90.124063 [arXiv:1408.1698 [gr-qc]]
arXiv 2014
-
[4]
N. Tsukamoto, Phys. Rev. D 97, no.6, 064021 (2018) doi:10.1103/PhysRevD.97.064021 [arXiv:1708.07427 [gr- qc]]
arXiv 2018
-
[5]
S. W. Wei, Y. X. Liu and R. B. Mann, Phys. Rev. Lett. 129, no.19, 191101 (2022) doi:10.1103/PhysRevLett.129.191101 [arXiv:2208.01932 [gr-qc]]
arXiv 2022
-
[6]
K. Schwarzschild, Sitzungsber. Preuss. Akad. Wiss. Berlin (Math. Phys. ) 1916, 189-196 (1916) [arXiv:physics/9905030 [physics]]
arXiv 1916
-
[7]
K. Akiyama et al. [Event Horizon Telescope], Astro- phys. J. Lett. 875, no.1, L4 (2019) doi:10.3847/2041- 8213/ab0e85 [arXiv:1906.11241 [astro-ph.GA]]
arXiv 2019
-
[8]
K. Akiyama et al. [Event Horizon Telescope], Astro- phys. J. Lett. 930, no.2, L12 (2022) doi:10.3847/2041- 8213/ac6674 [arXiv:2311.08680 [astro-ph.HE]]
arXiv 2022
Show all 44 references
-
[9]
R. M. Shannon, V. Ravi, L. T. Lentati, P. D. Lasky, G. Hobbs, M. Kerr, R. N. Manchester, W. A. Coles, Y. Levin and M. Bailes, et al. Science 349, no.6255, 1522-1525 (2015) doi:10.1126/science.aab1910 [arXiv:1509.07320 [astro-ph.CO]]
2015 arXiv
-
[10]
Adam et al
R. Adam et al. [Planck], Astron. Astrophys. 594, A10 (2016) doi:10.1051/0004-6361/201525967 [arXiv:1502.01588 [astro-ph.CO]]
2016 arXiv
-
[11]
A. M. Green and B. J. Kavanagh, J. Phys. G 48, no.4, 043001 (2021) doi:10.1088/1361-6471/abc534 [arXiv:2007.10722 [astro-ph.CO]]
2021 arXiv
-
[12]
Clesse and J
S. Clesse and J. Garc ´ ıa-Bellido, Phys. Dark Univ. 15, 142-147 (2017) doi:10.1016/j.dark.2016.10.002 [arXiv:1603.05234 [astro-ph.CO]]
2017 arXiv
-
[13]
Andersson and H
N. Andersson and H. Onozawa, Phys. Rev. D 54, 7470- 7475 (1996) doi:10.1103/PhysRevD.54.7470 [arXiv:gr- qc/9607054 [gr-qc]]
1996
-
[14]
H. P. Nollert, Phys. Rev. D 47, 5253-5258 (1993) doi:10.1103/PhysRevD.47.5253
1993 doi
-
[15]
Nomura and D
K. Nomura and D. Yoshida, Phys. Rev. D 105, no.4, 044006 (2022) doi:10.1103/PhysRevD.105.044006 [arXiv:2111.06273 [gr-qc]]
2022 arXiv
-
[16]
Momennia and S
M. Momennia and S. H. Hendi, Eur. Phys. J. C 80, no.6, 505 (2020) doi:10.1140/epjc/s10052-020-8051-2 [arXiv:1910.00428 [gr-qc]]
2020 arXiv
-
[17]
Sollom, A
I. Sollom, A. Challinor and M. P. Hobson, Phys. Rev. D 79, 123521 (2009) doi:10.1103/PhysRevD.79.123521 [arXiv:0903.5257 [astro-ph.CO]]
2009 arXiv
-
[18]
Komatsu et al
E. Komatsu et al. [WMAP], Astrophys. J. Suppl. 192, 18 (2011) doi:10.1088/0067-0049/192/2/18 [arXiv:1001.4538 [astro-ph.CO]]
2011 arXiv
-
[19]
M. Viel, J. Lesgourgues, M. G. Haehnelt, S. Matar- rese and A. Riotto, Phys. Rev. D 71, 063534 (2005) doi:10.1103/PhysRevD.71.063534 [arXiv:astro- ph/0501562 [astro-ph]]
2005
-
[20]
Boyanovsky, Phys
D. Boyanovsky, Phys. Rev. D 83, 103504 (2011) doi:10.1103/PhysRevD.83.103504 [arXiv:1011.2217 [astro-ph.CO]]
2011 arXiv
-
[21]
Panotopoulos and I
G. Panotopoulos and I. Lopes, Phys. Rev. D 96, no.2, 023002 (2017) doi:10.1103/PhysRevD.96.023002 [arXiv:1706.07272 [gr-qc]]
2017 arXiv
-
[22]
Berezhiani, B
L. Berezhiani, B. Famaey and J. Khoury, JCAP 09, 021 (2018) doi:10.1088/1475-7516/2018/09/021 [arXiv:1711.05748 [astro-ph.CO]]
2018 arXiv
-
[23]
Z. Xu, X. Hou, X. Gong and J. Wang, JCAP 09, 038 (2018) doi:10.1088/1475-7516/2018/09/038 [arXiv:1803.00767 [gr-qc]]
2018 arXiv
-
[24]
D. Liu, Y. Yang, S. Wu, Y. Xing, Z. Xu and Z. W. Long, Phys. Rev. D 104, no.10, 104042 (2021) doi:10.1103/PhysRevD.104.104042 [arXiv:2104.04332 [gr-qc]]
2021 arXiv
-
[25]
Y. Yang, D. Liu, A. ¨Ovg¨ un, G. Lambiase and Z. W. Long, Eur. Phys. J. C 84, no.1, 63 (2024) doi:10.1140/epjc/s10052-024-12412-6 [arXiv:2308.05544 [gr-qc]]
2024 arXiv
-
[26]
Bertone and T
G. Bertone and T. Tait, M.P., Nature562, no.7725, 51-56 (2018) doi:10.1038/s41586-018-0542-z [arXiv:1810.01668 [astro-ph.CO]]
2018 arXiv
-
[27]
Hochberg, E
Y. Hochberg, E. Kuflik, H. Murayama, T. Volansky and J. G. Wacker, Phys. Rev. Lett. 115, no.2, 021301 (2015) doi:10.1103/PhysRevLett.115.021301 [arXiv:1411.3727 [hep-ph]]
2015 arXiv
-
[28]
Dehnen, Mon
W. Dehnen, Mon. Not. Roy. Astron. Soc. 265, 250 (1993)
1993
-
[29]
R. C. Pantig and A. ¨Ovg¨ un, JCAP08, no.08, 056 (2022) doi:10.1088/1475-7516/2022/08/056 [arXiv:2202.07404 [astro-ph.GA]]
2022 arXiv
-
[30]
M. M. Gohain, P. Phukon and K. Bhuyan, Phys. Dark Univ. 46, 101683 (2024) doi:10.1016/j.dark.2024.101683 [arXiv:2407.02872 [gr-qc]]. 10
2024
-
[31]
A. Ali, N. U. Molla, S. G. Ghosh, A. Ramasamya and U. Debnath, Phys. Dark Univ. 48, 101859 (2025) doi:10.1016/j.dark.2025.101859
2025
-
[32]
Xamidov, U
T. Xamidov, U. Uktamov, S. Shaymatov and B. Ahmedov, Phys. Dark Univ. 47, 101805 (2025) doi:10.1016/j.dark.2024.101805
2025
-
[33]
Al-Badawi and S
A. Al-Badawi and S. Shaymatov, Commun. Theor. Phys. 77, no.3, 035402 (2025) doi:10.1088/1572-9494/ad89b2 [arXiv:2412.20037 [gr-qc]]
2025 arXiv
-
[34]
Al-Badawi, S
A. Al-Badawi, S. Shaymatov and Y. Sekhmani, JCAP 02, 014 (2025) doi:10.1088/1475-7516/2025/02/014 [arXiv:2411.01145 [gr-qc]]
2025 arXiv
-
[35]
Hosseinifar, S
F. Hosseinifar, S. Mamedov, F. Studniˇ cka and H. Has- sanabadi, [arXiv:2503.03260 [gr-qc]]
-
[36]
Alloqulov, T
M. Alloqulov, T. Xamidov, S. Shaymatov and B. Ahme- dov, [arXiv:2504.05236 [gr-qc]]
-
[37]
R. C. Pantig, Phys. Dark Univ. 45, 101550 (2024) doi:10.1016/j.dark.2024.101550 [arXiv:2405.07531 [gr- qc]]
2024
-
[38]
Kobayashi, H
T. Kobayashi, H. Motohashi and T. Suyama, Phys. Rev. D 85, 084025 (2012) [erratum: Phys. Rev. D 96, no.10, 109903 (2017)] doi:10.1103/PhysRevD.85.084025 [arXiv:1202.4893 [gr-qc]]
2012 arXiv
-
[39]
K. D. Kokkotas and B. G. Schmidt, Living Rev. Rel. 2, 2 (1999) doi:10.12942/lrr-1999-2 [arXiv:gr-qc/9909058 [gr-qc]]
1999 arXiv
-
[40]
Regge and J
T. Regge and J. A. Wheeler, Phys. Rev. 108, 1063-1069 (1957) doi:10.1103/PhysRev.108.1063
1957 doi
-
[41]
R. A. Konoplya, Phys. Rev. D 68, 024018 (2003) doi:10.1103/PhysRevD.68.024018 [arXiv:gr-qc/0303052 [gr-qc]]
2003 arXiv
- [42]
-
[43]
Gundlach, R
C. Gundlach, R. H. Price and J. Pullin, Phys. Rev. D 49, 883-889 (1994) doi:10.1103/PhysRevD.49.883 [arXiv:gr- qc/9307009 [gr-qc]]
1994
- [44]
Reviewed August 7, 2026 · model on record in the stance chip above.
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