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arxiv: 2606.29780 · v1 · pith:E6ETVF5Bnew · submitted 2026-06-29 · 🌀 gr-qc

Optical Appearances of Accreting Ellis-Bronnikov Wormholes Observed from Both Sides of Throats

Yu-Hao Cui , Kai Lin , Sen Guo , Yu Liang , Tong Liu This is my paper

Pith reviewed 2026-06-30 05:37 UTC · model grok-4.3

classification 🌀 gr-qc
keywords Ellis-Bronnikov wormholeoptical appearanceaccretion diskray tracingEvent Horizon Telescopewormhole throatgeodesic equationsynthetic images
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The pith

Ellis-Bronnikov wormholes with small n can mimic EHT images when viewed from one side of the throat.

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

The paper uses ray-tracing to compute how light travels through the Ellis-Bronnikov wormhole spacetime when material is accreting on the throat. It shows that the usual equality between photon impact parameter and aiming distance breaks when the observer and the disk sit on opposite sides. For optically thick flows the apparent size grows and brightness drops as the free parameter n increases; for thin flows the image from one side looks like an inverted version of the image from the other side, and higher-order light reaches the observer. The simulations indicate that only small-n cases seen from the positive radial side produce shadow-like features that resemble current Event Horizon Telescope pictures, while large-n cases or negative-side views do not.

Core claim

Solving the geodesic equation in the Ellis-Bronnikov metric yields a relation between impact parameter and aiming distance that is unequal when observer and accretion disk lie on opposite sides of the throat. Ray-tracing then produces synthetic images for both optically thick and thin disks. Larger n increases apparent size while decreasing brightness in the thick case. In the thin case the direct image does not occult higher-order images, so emission from regions close to the throat reaches the observer; the overall pattern is an internal-external inversion of the opposite-side view. The resulting images show that small-n wormholes observed from the R+ side can reproduce EHT-like features t

What carries the argument

Ray-tracing of null geodesics in the Ellis-Bronnikov metric parameterized by n, applied separately to optically thick and optically thin accretion flows viewed from each side of the throat.

If this is right

  • Larger n enlarges the apparent size of the wormhole while lowering its surface brightness under optically thick accretion.
  • Optically thin flows transmit higher-order images without occultation, exposing emission from near the throat.
  • Views from the R- side produce images that cannot match current EHT data for any n.
  • Only the combination of small n and an R+ observer yields partial agreement with observed black-hole shadows.

Where Pith is reading between the lines

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

  • Higher-resolution future arrays could search for the predicted image inversion as a positive signature of a wormhole throat.
  • The same ray-tracing pipeline could be rerun on other traversable wormhole metrics to test whether mimicry of EHT data is generic or specific to the Ellis-Bronnikov form.
  • If independent observations constrain the accretion flow geometry, the allowed range of n could be narrowed without new telescope time.

Load-bearing premise

The Ellis-Bronnikov metric with free parameter n together with the specific optically thick and thin accretion distributions used here match the actual spacetime and matter around any real wormhole candidate.

What would settle it

A direct side-by-side comparison of the small-n R+ simulated images against existing EHT maps of M87* or Sgr A*; clear mismatches in shadow diameter, ring brightness profile, or absence of inversion features would rule out the claimed mimicry.

Figures

Figures reproduced from arXiv: 2606.29780 by Kai Lin, Sen Guo, Tong Liu, Yu-Hao Cui, Yu Liang.

Figure 1
Figure 1. Figure 1: FIG. 1. Radial distributions of [PITH_FULL_IMAGE:figures/full_fig_p003_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: shows the distribution of the effective potential of the EB wormhole with different n. We can see from the figure that the effective potential has a unique peak. As n increases, the peak of the effective potential gradually n = 2 n = 3 n = 4 -5 0 5 10 15 20 0.000 0.005 0.010 0.015 0.020 0.025 Veff(r) FIG. 2. Radial distributions of Veff (r) with different values of n. The red dashed line represents the rad… view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3. Seven kinds of unbound trajectories of photons com [PITH_FULL_IMAGE:figures/full_fig_p004_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4. The unbound trajectory of photons in EB wormhole( [PITH_FULL_IMAGE:figures/full_fig_p005_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: FIG. 5. The trajectory of particles around Schwarzschild and EB wormhole( [PITH_FULL_IMAGE:figures/full_fig_p006_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: FIG. 6. The schematic diagram of ray-tracing [63]. [PITH_FULL_IMAGE:figures/full_fig_p006_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: FIG. 7. The direct image (solid line) and secondary image (dashed line) when the observer and the accretion disk are located [PITH_FULL_IMAGE:figures/full_fig_p007_7.png] view at source ↗
Figure 8
Figure 8. Figure 8: FIG. 8. The direct image (solid line) and secondary image (dashed line) when the observer and the accretion disk are located [PITH_FULL_IMAGE:figures/full_fig_p008_8.png] view at source ↗
Figure 9
Figure 9. Figure 9: FIG. 9. Observational images of Schwarzschild black Holes and EB wormholes under optically thick accretion when the observer [PITH_FULL_IMAGE:figures/full_fig_p010_9.png] view at source ↗
Figure 10
Figure 10. Figure 10: FIG. 10. Cross-sectional profile of the data in Fig. 9 along [PITH_FULL_IMAGE:figures/full_fig_p011_10.png] view at source ↗
Figure 11
Figure 11. Figure 11: FIG. 11. Observational images of Schwarzschild black Holes and EB wormholes under optically thick accretion when the [PITH_FULL_IMAGE:figures/full_fig_p012_11.png] view at source ↗
Figure 12
Figure 12. Figure 12: FIG. 12. Cross-sectional profile of the data in Fig. 11 along [PITH_FULL_IMAGE:figures/full_fig_p013_12.png] view at source ↗
Figure 13
Figure 13. Figure 13: FIG. 13. Observational radiation flux (left) and optical images (right) of EB wormholes in optically thin accretion from the [PITH_FULL_IMAGE:figures/full_fig_p014_13.png] view at source ↗
Figure 14
Figure 14. Figure 14: FIG. 14. Observational radiation flux (left) and optical images (right) of EB wormholes in optically thin accretion from the [PITH_FULL_IMAGE:figures/full_fig_p015_14.png] view at source ↗
read the original abstract

This study investigates the optical appearance of the Ellis-Bronnikov wormhole as viewed from both sides of its throat, under conditions of optically thick and thin accretion. By solving the geodesic equation, we derive the relationship between the impact parameter and the aiming distance of photons, and found that if the observer and the accretion disk are located on both sides of the throat, these two quantities are not equal. The optical image of the wormhole observed from the other side of the throat is obtained through the ray-tracing method. For optically thick accretion, increases in the parameter $n$ lead to an increase in the apparent size of the wormhole but a decrease in its brightness. For optically thin accretion, the image is similar to the internal and external inversion of the image observed from the other side. Furthermore, for optically thin accretion flows, the direct image does not block the emission from higher-order images, allowing radiation emitted from regions much closer to the event horizon to reach the observer. Our simulation results show that when the observer is on the $\mathcal{R}^+$ side, EB wormholes with small $n$ can mimic the images taken by the EHT to some extent, while wormholes with large $n$ or with the observer on the $\mathcal{R}^-$ side can be ruled out.

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 manuscript numerically integrates null geodesics in the Ellis-Bronnikov wormhole spacetime (parameter n) and performs ray-tracing for both optically thick and optically thin accretion flows. It reports that the impact parameter and aiming distance differ when the observer and disk lie on opposite sides of the throat, that increasing n enlarges the apparent size while dimming the image for thick flows, and that thin-flow images exhibit internal-external inversion. The central claim is that small-n wormholes viewed from the R+ side can reproduce EHT images to some extent, whereas large-n cases or observations from the R- side are ruled out.

Significance. If the modeling assumptions hold, the work supplies concrete, side-dependent image predictions that could help observationally constrain or exclude a class of traversable wormholes against existing EHT data. The explicit treatment of both sides of the throat and the distinction between thick and thin flows are useful additions to the literature on exotic compact-object shadows.

major comments (2)
  1. [Results and Discussion (accretion modeling)] The mimicry and exclusion conclusions rest entirely on one specific choice of optically thick and optically thin accretion density-velocity-emissivity profiles. No comparison to alternative standard models (e.g., RIAF or thin-disk prescriptions) is shown; a change in these profiles can alter apparent size, brightness, and higher-order image visibility enough to modify the qualitative assessment that small-n R+ cases mimic EHT data.
  2. [Methods (geodesic integration and ray-tracing)] No numerical details, convergence tests, error estimates, or validation against known limits (e.g., Schwarzschild or Ellis wormhole n=0) are supplied for the geodesic integrator or ray-tracing code. Without these, it is impossible to assess whether the reported impact-parameter relations and image features are numerically reliable.
minor comments (2)
  1. [Introduction] Define the R+ and R- sides and the parameter n explicitly in the introduction rather than only in the abstract.
  2. [Metric section] Add a brief statement of the coordinate ranges and asymptotic flatness conditions used for the metric.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the constructive feedback on our manuscript. We address each major comment below and outline the revisions we will make.

read point-by-point responses

  1. Referee: [Results and Discussion (accretion modeling)] The mimicry and exclusion conclusions rest entirely on one specific choice of optically thick and optically thin accretion density-velocity-emissivity profiles. No comparison to alternative standard models (e.g., RIAF or thin-disk prescriptions) is shown; a change in these profiles can alter apparent size, brightness, and higher-order image visibility enough to modify the qualitative assessment that small-n R+ cases mimic EHT data.

    Authors: The specific density-velocity-emissivity profiles adopted are standard choices from the compact-object imaging literature. The central geometric results—the inequality between impact parameter and aiming distance across the throat, the enlargement of apparent size with n for thick flows, and the internal-external inversion for thin flows—originate from the null geodesic structure of the Ellis-Bronnikov metric and are therefore independent of the emissivity details. Nevertheless, we agree that quantitative brightness contrasts and the precise visibility of higher-order images could shift under different prescriptions. In the revised manuscript we will add a short robustness subsection that (i) states the adopted profiles explicitly, (ii) notes the profile-independent nature of the side-dependent and inversion features, and (iii) presents one additional thin-disk calculation to illustrate that the qualitative exclusion of large-n and R−-side cases remains unchanged. revision: partial

  2. Referee: [Methods (geodesic integration and ray-tracing)] No numerical details, convergence tests, error estimates, or validation against known limits (e.g., Schwarzschild or Ellis wormhole n=0) are supplied for the geodesic integrator or ray-tracing code. Without these, it is impossible to assess whether the reported impact-parameter relations and image features are numerically reliable.

    Authors: We accept this criticism. The revised manuscript will contain a new Methods subsection that specifies the numerical integrator (fourth-order Runge-Kutta with adaptive step-size control), the termination criteria, and the error tolerance employed. We will also report convergence tests under successive step-size reductions and validation benchmarks: recovery of the Schwarzschild photon-sphere radius and critical impact parameter in the appropriate limit, together with the known n=0 Ellis-wormhole shadow size. These additions will allow readers to assess the numerical reliability of the reported impact-parameter relations and images. revision: yes

Circularity Check

0 steps flagged

No circularity: results from direct geodesic integration and ray-tracing

full rationale

The paper solves the geodesic equation to relate impact parameter and aiming distance, then applies ray-tracing to generate images under specified optically thick/thin accretion flows in the Ellis-Bronnikov metric. No parameters are fitted to EHT data and then relabeled as predictions; the mimicry statements are direct outputs of the numerical computation for chosen n values and flow profiles. No self-citations appear as load-bearing premises, and the metric plus flow assumptions are stated inputs rather than derived from the target images. The derivation chain is therefore self-contained against external benchmarks.

Axiom & Free-Parameter Ledger

1 free parameters · 2 axioms · 0 invented entities

The central claim rests on the standard Ellis-Bronnikov metric (a known solution in GR) and standard geodesic ray-tracing; the only free parameter introduced is n, which is varied numerically rather than derived.

free parameters (1)
  • n
    Metric parameter controlling wormhole shape and optical appearance; its values are scanned in simulations to produce different image sizes and brightnesses.
axioms (2)
  • domain assumption The Ellis-Bronnikov metric describes a traversable wormhole spacetime.
    Invoked as the background geometry for all geodesic calculations.
  • standard math Null geodesics govern photon trajectories in the spacetime.
    Fundamental assumption of general relativity used to derive impact-parameter relations.

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discussion (0)

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Reference graph

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