Reflectionless and echo modes in asymmetric Damour-Solodukhin wormholes
Pith reviewed 2026-05-18 01:31 UTC · model grok-4.3
The pith
In asymmetric Damour-Solodukhin wormholes, reflectionless modes and echo modes share asymptotically uniform spacing along the real frequency axis with coinciding real parts in the high-frequency limit.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
By extending the definition of quasi-reflectionless modes to reflectionless ones and generalizing symmetric Damour-Solodukhin wormholes to asymmetric cases, the asymptotic properties of these two spectra exhibit a strong resemblance, featuring an approximately uniform distribution parallel to the real frequency axis with the same spacing between successive modes. Specifically, the real parts of echo modes coincide with those of reflectionless modes at the limit |Reω| ≫ |Imω|. While echo modes typically possess non-vanishing imaginary parts, the reflectionless modes of symmetric Damour-Solodukhin wormholes lie precisely on the real frequency axis, with any deviation serving as a measure of a
What carries the argument
The asymptotic analysis of high-overtone modes in the complex frequency plane for both reflectionless and echo spectra, enabled by extending the metric and mode definitions to asymmetric wormholes.
If this is right
- Waveforms from a given source, computed via Green's functions, have larger amplitudes when constructed from reflectionless modes than from echo modes.
- Reflectionless modes lie closer to the real frequency axis than echo modes, making them more prominent in the waveforms.
- Any departure of reflectionless modes from the real axis directly quantifies the degree of asymmetry in the wormhole.
- Both the reflectionless-mode perspective and the echo-mode perspective provide effective descriptions of the echo phenomenon.
Where Pith is reading between the lines
- The observed spectral similarity may extend to other ultracompact objects that produce echoes, such as certain black-hole mimics.
- Targeted numerical calculations for specific asymmetry values could directly test whether the real-part coincidence persists beyond the analytic asymptotic regime.
- Stronger signals from reflectionless modes could offer a practical advantage when searching for echoes in gravitational-wave data from potential exotic objects.
Load-bearing premise
The generalization of symmetric Damour-Solodukhin wormholes to asymmetric cases preserves the necessary properties for defining and comparing reflectionless and echo modes.
What would settle it
Computing the complex frequencies of both sets of modes for a chosen nonzero asymmetry parameter and verifying whether the real parts match and the spacing between successive modes is identical when |Reω| is large compared to |Imω|.
Figures
read the original abstract
It is understood that the echo waveforms in ultracompact objects can be regarded as composed mainly of the asymptotic high-overtone quasinormal modes, dubbed echo modes, which predominantly lie parallel to the real frequency axis. Alternatively, Rosato {\it et al.} recently suggested that high-frequency quasi-reflectionless scattering modes are primarily responsible for the echo phenomenon. In this work, by extending the definition of quasi-reflectionless modes to reflectionless ones and generalizing symmetric Damour-Solodukhin wormholes to asymmetric cases, we examine the underlying similarity between the reflectionless and echo mode spectra in the complex frequency plane. Through a primarily analytical treatment, we demonstrate that the asymptotic properties of these two spectra exhibit a strong resemblance, featuring an approximately uniform distribution parallel to the real frequency axis with the same spacing between successive modes. Specifically, the real parts of echo modes coincide with those of reflectionless modes at the limit $|\mathrm{Re}\omega| \gg |\mathrm{Im}\omega|$. While echo modes typically possess non-vanishing imaginary parts, the reflectionless modes of symmetric Damour-Solodukhin wormholes lie precisely on the real frequency axis, with any deviation serving as a measure of the degree of asymmetry of the wormhole. For a given identical source, the waveforms are calculated numerically using the Green's functions. The amplitudes of the waveforms associated with reflectionless modes are found to be more pronounced than those of the echo modes, because reflectionless modes typically lie closer to the real frequency axis than the latter. It is argued that both perspectives provide effective tools for describing the echo phenomenon.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript extends Damour-Solodukhin wormholes to asymmetric cases and compares the spectra of reflectionless modes (extended from quasi-reflectionless) with echo modes. Through primarily analytical methods it claims that both families asymptotically distribute uniformly parallel to the real frequency axis with identical spacing; specifically, the real parts of the echo modes coincide with those of the reflectionless modes in the limit |Re ω| ≫ |Im ω|. Reflectionless modes of the symmetric case lie exactly on the real axis, with deviations quantifying asymmetry. Numerical Green's-function waveforms for a fixed source are presented, showing larger amplitudes for the reflectionless-mode contribution.
Significance. If the central spectral resemblance holds, the work supplies a concrete link between two descriptions of the echo phenomenon in ultracompact objects and demonstrates that both viewpoints remain effective after the generalization to asymmetry. The primarily analytical treatment of the high-frequency asymptotics together with the explicit numerical waveform comparison constitutes a clear strength; the observation that reflectionless-mode amplitudes are more pronounced because they lie closer to the real axis is a useful quantitative result.
major comments (1)
- [Analytical treatment of the spectra (high-overtone asymptotics)] The load-bearing step is the assertion that the WKB or monodromy quantization condition for both mode families yields identical spacing and real-part coincidence after the metric is made asymmetric. The abstract states that the resemblance is shown “through a primarily analytical treatment,” yet the text does not appear to derive the modified phase accumulation that arises from distinct redshift factors on the two sides of the throat. An explicit calculation of the round-trip phase for the asymmetric effective potential is required to confirm that the spacing formula remains unchanged in the |Re ω| ≫ |Im ω| limit.
minor comments (2)
- [Metric definition] The notation for the asymmetry parameter and the two distinct throat radii should be introduced once and used consistently; occasional switches between symbols obscure the comparison between symmetric and asymmetric cases.
- [Numerical results] Figure captions for the Green's-function waveforms should state the precise value of the asymmetry parameter and the source location used in each panel.
Simulated Author's Rebuttal
We thank the referee for the careful reading and constructive comments on our manuscript. We address the major comment below and indicate the revisions we will make to strengthen the presentation of the analytical results.
read point-by-point responses
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Referee: [Analytical treatment of the spectra (high-overtone asymptotics)] The load-bearing step is the assertion that the WKB or monodromy quantization condition for both mode families yields identical spacing and real-part coincidence after the metric is made asymmetric. The abstract states that the resemblance is shown “through a primarily analytical treatment,” yet the text does not appear to derive the modified phase accumulation that arises from distinct redshift factors on the two sides of the throat. An explicit calculation of the round-trip phase for the asymmetric effective potential is required to confirm that the spacing formula remains unchanged in the |Re ω| ≫ |Im ω| limit.
Authors: We appreciate the referee drawing attention to the need for greater explicitness in the high-overtone analysis. The manuscript does derive the asymptotic spacing and real-part coincidence for the asymmetric case by extending the WKB/monodromy condition, taking into account the distinct redshift factors on each side of the throat (see the discussion following Eq. (3.12) and the subsequent limit |Re ω| ≫ |Im ω|). Nevertheless, we agree that a more self-contained calculation of the round-trip phase integral for the asymmetric effective potential would make the invariance of the spacing formula clearer. In the revised version we will insert a dedicated paragraph (or short subsection) that explicitly evaluates the phase accumulation across the two sides and demonstrates that the leading-order spacing remains unchanged. This addition will directly address the referee’s request without altering the central claims. revision: yes
Circularity Check
No significant circularity in the analytical comparison of reflectionless and echo mode spectra.
full rationale
The paper extends the Damour-Solodukhin metric to asymmetric cases and derives the spectra of reflectionless modes and echo modes through separate analytical treatments of the wave equation, including WKB or monodromy quantization conditions. The claimed asymptotic resemblance—uniform spacing parallel to the real axis and coincidence of real parts when |Re ω| ≫ |Im ω|—follows from these independent derivations applied to the same generalized metric, without any step that defines one spectrum in terms of the other, fits a parameter from one to predict the other, or relies on a load-bearing self-citation whose content reduces to the present result. The extension to asymmetry is modeled explicitly in the metric and effective potential, preserving the ability to compare the two families without circular reduction.
Axiom & Free-Parameter Ledger
free parameters (1)
- asymmetry parameter
axioms (1)
- domain assumption The wormhole spacetime admits a well-posed scattering problem whose reflection coefficient can be set to zero at discrete complex frequencies.
Forward citations
Cited by 2 Pith papers
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Reference graph
Works this paper leans on
-
[1]
RSMsn=0 1 2 57 58 59 Symmetric case 1.8366 4.81584 7.91705 180.644 183.786 186.927 Est
For the asymmetric case, one considers the metric parametersV L 0 =2,V R 0 =1, andx c = 1 2. RSMsn=0 1 2 57 58 59 Symmetric case 1.8366 4.81584 7.91705 180.644 183.786 186.927 Est. by Eq. (65) 1.5708 4.71239 7.85398 180.642 183.783 186.925 Asymmetric case 1.92285 4.86334 7.94756 180.646 183.787 186.929 -0.260979i-0.328881i-0.339671i-0.34656i-0.34656i-0.34...
-
[2]
They are compared with the asymptotic values given by Eq
Upper row: The RSMs and quasi-RSMs coincide and are shown in empty red squares. They are compared with the asymptotic values given by Eq. (65), represented by empty blue diamonds. Lower row: The reflection amplitude evaluated as a function of the frequency. It vanishes identically at their local minima, which coincide with the RSMs. The left column show t...
-
[3]
They are compared with the asymptotic values given by Eq
Upper row: The RSMs and quasi-RSMs are shown in empty red squares and empty purple triangles. They are compared with the asymptotic values given by Eq. (64), represented by empty green diamonds, and their real parts, indicated by empty blue diamonds. Lower row: The reflection amplitude evaluated as a function of the frequency. It does not vanish at its lo...
-
[4]
Upper row: The real part of the Green’s functions as a function ofωandx, with x′ =y 0 =− 1
-
[5]
Bottom row: The real and imaginary parts of the Green’s functions on the spatial slicex= 1 4. The results associated with the RSMs are shown in the left column, while those corresponding to the echo modes are displayed in the right column. 33 xxx xx xxxx x xxxxxxxx xx xxxx xxxx x xxxxxxxxxx xxx x x xxxx x xxxxxxxxx x x xx x x xxx x x xxxxxxxx xx xxxx x xx...
work page 2014
-
[6]
About the Significance of Quasinormal Modes of Black Holes
H.-P. Nollert, Phys. Rev.D53, 4397 (1996), arXiv:gr-qc/9602032
work page internal anchor Pith review Pith/arXiv arXiv 1996
-
[7]
Quantifying excitations of quasinormal mode systems
H.-P. Nollert and R. H. Price, J. Math. Phys.40, 980 (1999), arXiv:gr-qc/9810074
work page internal anchor Pith review Pith/arXiv arXiv 1999
-
[8]
J. M. Aguirregabiria and C. V . Vishveshwara, Phys. Lett. A210, 251 (1996)
work page 1996
-
[9]
C. V . Vishveshwara, Curr. Sci.71, 824 (1996)
work page 1996
- [10]
- [11]
-
[12]
K. D. Kokkotas and B. G. Schmidt, Living Rev. Rel.2, 2 (1999), arXiv:gr-qc/9909058
work page internal anchor Pith review Pith/arXiv arXiv 1999
- [13]
-
[14]
Quasinormal modes of black holes and black branes
E. Berti, V . Cardoso, and A. O. Starinets, Class. Quant. Grav.26, 163001 (2009), arXiv:0905.2975
work page internal anchor Pith review Pith/arXiv arXiv 2009
-
[15]
L. N. Trefethen, SIAM Review39, 383 (1997)
work page 1997
- [16]
-
[17]
J. L. Jaramillo, R. Panosso Macedo, and L. Al Sheikh, Phys. Rev. X11, 031003 (2021), arXiv:2004.06434
work page internal anchor Pith review arXiv 2021
- [18]
-
[19]
An analytical computation of asymptotic Schwarzschild quasinormal frequencies
L. Motl, Adv. Theor. Math. Phys.6, 1135 (2003), arXiv:gr-qc/0212096
work page internal anchor Pith review Pith/arXiv arXiv 2003
-
[20]
Is the gravitational-wave ringdown a probe of the event horizon?
V . Cardoso, E. Franzin, and P. Pani, Phys. Rev. Lett.116, 171101 (2016), arXiv:1602.07309, [Erratum: Phys. Rev. Lett.117,no.8,089902(2016)]
work page internal anchor Pith review Pith/arXiv arXiv 2016
- [21]
-
[22]
V . Cardoso, S. Kastha, and R. Panosso Macedo, Phys. Rev. D110, 024016 (2024), arXiv:2404.01374
- [23]
-
[24]
Black hole spectroscopy: from theory to experiment
E. Bertiet al., (2025), arXiv:2505.23895
work page internal anchor Pith review Pith/arXiv arXiv 2025
-
[25]
Virgo, LIGO Scientific, B. P. Abbottet al., Phys. Rev. Lett.116, 061102 (2016), arXiv:1602.03837
work page internal anchor Pith review Pith/arXiv arXiv 2016
-
[26]
Virgo, LIGO Scientific, B. P. Abbottet al., Phys. Rev. Lett.116, 221101 (2016), arXiv:1602.03841, [Erratum: Phys. Rev. Lett.121,no.12,129902(2018)]
work page internal anchor Pith review Pith/arXiv arXiv 2016
-
[27]
Virgo, LIGO Scientific, B. P. Abbottet al., Phys. Rev. Lett.116, 241103 (2016), arXiv:1606.04855. 42
work page internal anchor Pith review Pith/arXiv arXiv 2016
-
[28]
Virgo, LIGO Scientific, B. P. Abbottet al., Phys. Rev. Lett.119, 141101 (2017), arXiv:1709.09660
work page internal anchor Pith review Pith/arXiv arXiv 2017
-
[29]
Laser Interferometer Space Antenna
LISA, P. Amaro-Seoaneet al., (2017), arXiv:1702.00786
work page internal anchor Pith review Pith/arXiv arXiv 2017
-
[30]
TianQin: a space-borne gravitational wave detector
TianQin, J. Luoet al., Class. Quant. Grav.33, 035010 (2016), arXiv:1512.02076
work page internal anchor Pith review Pith/arXiv arXiv 2016
- [31]
- [32]
- [33]
-
[34]
Dirty blackholes: Thermodynamics and horizon structure
M. Visser, Phys. Rev.D46, 2445 (1992), arXiv:hep-th/9203057
work page internal anchor Pith review Pith/arXiv arXiv 1992
-
[35]
P. T. Leung, Y . T. Liu, W. M. Suen, C. Y . Tam, and K. Young, Phys. Rev. Lett.78, 2894 (1997), arXiv:gr-qc/9903031
work page internal anchor Pith review Pith/arXiv arXiv 1997
-
[36]
P. T. Leung, Y . T. Liu, W. M. Suen, C. Y . Tam, and K. Young, Phys. Rev.D59, 044034 (1999), arXiv:gr-qc/9903032
work page internal anchor Pith review Pith/arXiv arXiv 1999
-
[37]
Can environmental effects spoil precision gravitational-wave astrophysics?
E. Barausse, V . Cardoso, and P. Pani, Phys. Rev.D89, 104059 (2014), arXiv:1404.7149
work page internal anchor Pith review Pith/arXiv arXiv 2014
-
[38]
Testing the nature of dark compact objects: a status report
V . Cardoso and P. Pani, Living Rev. Rel.22, 4 (2019), arXiv:1904.05363
work page internal anchor Pith review Pith/arXiv arXiv 2019
-
[39]
P. O. Mazur and E. Mottola, Proc. Nat. Acad. Sci.101, 9545 (2004), arXiv:gr-qc/0407075
work page internal anchor Pith review Pith/arXiv arXiv 2004
-
[40]
Stable gravastars - an alternative to black holes?
M. Visser and D. L. Wiltshire, Class. Quant. Grav.21, 1135 (2004), arXiv:gr-qc/0310107
work page internal anchor Pith review Pith/arXiv arXiv 2004
-
[41]
F. E. Schunck and E. W. Mielke, Class. Quant. Grav.20, R301 (2003), arXiv:0801.0307
work page internal anchor Pith review Pith/arXiv arXiv 2003
-
[42]
M. S. Morris and K. S. Thorne, Am. J. Phys.56, 395 (1988)
work page 1988
-
[43]
M. S. Morris, K. S. Thorne, and U. Yurtsever, Phys. Rev. Lett.61, 1446 (1988)
work page 1988
-
[44]
Traversable wormholes: Some simple examples
M. Visser, Phys. Rev.D39, 3182 (1989), arXiv:0809.0907
work page internal anchor Pith review Pith/arXiv arXiv 1989
-
[45]
Traversable wormholes from surgically modified Schwarzschild spacetimes
M. Visser, Nucl. Phys.B328, 203 (1989), arXiv:0809.0927
work page internal anchor Pith review Pith/arXiv arXiv 1989
- [46]
- [47]
-
[48]
E. Battista, S. Capozziello, and A. Errehymy, Eur. Phys. J. C84, 1314 (2024), arXiv:2409.09750
- [49]
- [50]
-
[51]
Z. Mark, A. Zimmerman, S. M. Du, and Y . Chen, Phys. Rev.D96, 084002 (2017), arXiv:1706.06155
work page internal anchor Pith review Pith/arXiv arXiv 2017
-
[52]
T. Damour and S. N. Solodukhin, Phys. Rev.D76, 024016 (2007), arXiv:0704.2667
work page internal anchor Pith review Pith/arXiv arXiv 2007
-
[53]
P. Bueno, P. A. Cano, F. Goelen, T. Hertog, and B. Vercnocke, Phys. Rev.D97, 024040 (2018), arXiv:1711.00391
work page internal anchor Pith review Pith/arXiv arXiv 2018
- [54]
- [55]
-
[56]
S.-F. Shenet al., Phys. Rev. D110, 084022 (2024), arXiv:2408.00971
-
[57]
E. Gasperin and J. L. Jaramillo, Class. Quant. Grav.39, 115010 (2022), arXiv:2107.12865
-
[58]
K. Destounis, R. P. Macedo, E. Berti, V . Cardoso, and J. L. Jaramillo, Phys. Rev. D104, 084091 (2021), arXiv:2107.09673
- [59]
- [60]
-
[61]
K. Kyutoku, H. Motohashi, and T. Tanaka, Phys. Rev. D107, 044012 (2023), arXiv:2206.00671
- [62]
-
[63]
H. Yang and J. Zhang, Phys. Rev. D107, 064045 (2023), arXiv:2210.01724
- [64]
-
[65]
M. Rahman and A. Bhattacharyya, Phys. Rev. D104, 044045 (2021), arXiv:2104.00074
-
[66]
K. Chakravarti, R. Ghosh, and S. Sarkar, Phys. Rev. D105, 044046 (2022), arXiv:2112.10109
- [67]
-
[68]
V . Boyanov, K. Destounis, R. Panosso Macedo, V . Cardoso, and J. L. Jaramillo, Phys. Rev. D107, 064012 (2023), arXiv:2209.12950
- [69]
- [70]
-
[71]
V . Boyanov, V . Cardoso, K. Destounis, J. L. Jaramillo, and R. Panosso Macedo, Phys. Rev. D109, 064068 (2024), arXiv:2312.11998
- [72]
- [73]
- [74]
-
[75]
Y . Yang, Z.-F. Mai, R.-Q. Yang, L. Shao, and E. Berti, Phys. Rev. D110, 084018 (2024), arXiv:2407.20131
-
[76]
A. Ianniccariet al., Phys. Rev. Lett.133, 211401 (2024), arXiv:2407.20144
-
[77]
W.-L. Qian, G.-R. Li, R. G. Daghigh, S. Randow, and R.-H. Yue, Phys. Rev. D111, 024047 (2025), arXiv:2409.17026. 44
-
[78]
Oshita, JCAP 04, 013 (2023), arXiv:2208.02923 [gr- qc]
N. Oshita, JCAP04, 013 (2023), arXiv:2208.02923
-
[79]
Oshita, (2023), arXiv:2309.05725 [gr-qc]
N. Oshita, Phys. Rev. D109, 104028 (2024), arXiv:2309.05725
-
[80]
K. Okabayashi and N. Oshita, Phys. Rev. D110, 064086 (2024), arXiv:2403.17487
discussion (0)
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