REVIEW 3 major objections 3 minor 69 references
Effect of Magnetic Field on the Accretion Phase of Population III Star Formation
T0 review · 3 major / 3 minor · reviewed 2026-08-07 · deepseek-v4-flash
Pith's one-line read The central claim is that any non-zero magnetic field, no matter how weak, converts Population III disk fragmentation into a single massive protostar.
desk verdict A well-run sweep showing even 10^-20 G seed fields suppress fragmentation and merge to one Pop III protostar — but the blanket 'single star' claim rests on turbulence-free initial conditions that the paper's own caveats concede. 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 mechanism is a self-regulating feedback loop between magnetic amplification and angular momentum transport. When the field has not been amplified, magnetic torque is weak, a rotating disk forms, and the disk's differential rotation winds up and amplifies the field; once the field is strong, magnetic torque transports angular momentum outward, the gas falls inward without rotation, and the field stops amplifying, returning the system to the first state. The chaotic orbital and spin motions of multiple protostars give the loop an early boost, producing rapid amplification at densities above about $10^{13}\,\mathrm{cm}^{-3}$ shortly after the first protostar forms. The numerical setup supports the loop by resolving the region around the protostar at 0.23 au cell width without sink cells, so magnetic flux is not removed when gas is accreted, and by using a stiff equation of state above $10^{16}\,\mathrm{cm}^{-3}$ to represent the protostar.
What would settle it
Run the same collapse with an imposed turbulent velocity field, say a supersonic Kolmogorov spectrum, while holding $B_0 = 10^{-18}\,\mathrm{G}$; if after 1000 years two or more protostars remain separated by more than about 500 au and continue to accrete, the single-star conclusion fails.
Extended reading notes
Core claim
The paper's central claim is that the initial magnetic field strength only matters through whether it is zero or nonzero. For field strengths from $B_0 = 10^{-20}\,\mathrm{G}$ to $B_0 = 10^{-4}\,\mathrm{G}$, the same sequence repeats: the disk fragments shortly after the first protostar forms, the orbital and spin motions of the fragments stretch and amplify the magnetic field, and once amplified the magnetic torque removes angular momentum, drives the fragments inward, and merges them into a single star. After the merger the field keeps amplifying through differential rotation and saturates with plasma $\beta$ around $10^{-2}$ to $10^{-4}$, inflating the disk vertically and suppressing all further fragmentation. The exception is the strongest model, B04 at $10^{-4}\,\mathrm{G}$, where interchange instability leaks magnetic flux, forms ring-like structures, and triggers a second round of fragmentation. The zero-field model, by contrast, retains numerous protostars, with the most massive reaching about 200 solar masses. The authors state this directly: 'In all models except for the extremely strong magnetic field model B04, the fragments eventually merged into a single massive star. Therefore, as long as the minihalo is magnetized, a single Population III star will form.'
Load-bearing premise
The load-bearing premise is that starting from a perfectly uniform magnetic field aligned with the rotation axis and no turbulence represents a realistic enough primordial minihalo, because with turbulence the density peaks can form protostars far apart that may survive without merging.
Editorial extensions
If this is right
- For any non-zero seed field, even $B_0 = 10^{-20}\,\mathrm{G}$, a primordial minihalo ends with one massive protostar rather than a mini cluster; the zero-field control is the only model that keeps many protostars.
- Under realistic weak primordial fields, rotation-supported disks and magnetically driven outflows should be rare, since the parameter windows that produce them (around $B_0 = 10^{-10}\,\mathrm{G}$ and $B_0 \gtrsim 10^{-5}\,\mathrm{G}$) are narrow.
- The circumstellar structure around a Population III protostar should be a vertically inflated, magnetically supported thick disk with a global spiral pattern, not a thin Keplerian disk.
- Final stellar masses are set partly by magnetic braking: accretion rates in magnetized runs are lower by a factor of about 2 to 4 than in the zero-field run, giving masses of roughly 60 to 120 solar masses after 1300 years.
- At the opposite extreme, very strong fields trigger interchange instability and late-stage fragmentation, so the single-star rule has a strong-field boundary somewhere between magnetic-to-gravitational energy ratios 0.23 and 1.1.
Reading between the lines
- Adding turbulence to the initial cloud may break the single-star conclusion: the paper notes that turbulent fragmentation can form protostars at separated locations whose interactions are too weak to amplify the field, allowing multiple stars to survive without merging.
- A direct numerical test would hold $B_0$ fixed and add a supersonic turbulent velocity spectrum; mapping how the fragment count and merger rate change with turbulent Mach number would tell whether 'magnetized means single' survives in realistic minihalos.
- The narrow disk/outflow window implies that observational or cosmological-model searches for Population III signatures should not assume Keplerian disks; funnel accretion through magnetic torque may favor one massive star per halo, which in turn affects predictions for supermassive black hole seed formation.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. This paper presents 3D ideal MHD simulations of Population III star formation in a minihalo, varying the initial uniform magnetic field strength from 10^-20 G to 10^-4 G in addition to a zero-field control. The simulations use a nested grid with maximum resolution 0.23 au, no sink cells, a barotropic EOS with a stiff protostellar core, and are run for 1000-1400 yr after first protostar formation. The main result is that in all magnetized models except the strongest (B04), disk fragmentation occurs early but the fragments merge into a single massive protostar, after which no further fragmentation occurs; the magnetic field is amplified to ~1 kG and forms a thick, magnetically inflated disk with a global spiral pattern. In contrast, the zero-field model produces persistent multiple stars with a ~200 M_sun primary. The paper concludes that any seed magnetic field, regardless of strength, leads to a single Population III star, with disks and outflows appearing only in a narrow parameter range.
Significance. The paper provides a systematic parameter study spanning 18 orders of magnitude in initial magnetic field strength, which is valuable for the Population III star formation community. The numerical setup is careful: the Jeans length is resolved with at least 8 cells, the finest cell width is 0.23 au, and the avoidance of sink cells preserves magnetic flux, a known issue in MHD simulations. The control model reproduces the expected vigorous fragmentation in the unmagnetized case, lending credibility to the method. The finding that the magnetic field saturates at plasma beta ~10^-3 across a wide range of initial strengths, and that weak fields lead to a magnetically inflated disk rather than a rotation-supported disk, are notable. However, the headline conclusion that any magnetized minihalo forms a single star is derived from strongly idealized initial conditions (uniform field, no turbulence), and the paper's own caveats in Section 4.2 directly limit this claim. The secure result is that magnetic fields suppress, but do not eliminate, fragmentation in quiescent, non-turbulent clouds.
major comments (3)
- [Abstract and Section 5] The claim that 'as long as the minihalo is magnetized, a single Population III star will form' (Section 5) is not supported by the simulations as stated. The models assume a perfectly uniform, rotation-aligned magnetic field and zero initial turbulence (Section 2). The paper itself concedes in Section 4.2 that strong turbulence can produce multiple density peaks throughout the cloud and that 'strong turbulence may prevent the merging of fragments, potentially resulting in the survival of multiple protostars in spatially separated regions.' Since turbulent minihalos are likely the realistic case (as discussed in Section 4.1 with reference to Sharda et al. 2021 and Sadanari et al. 2024), the conclusion must be restricted to the quiescent, non-turbulent regime explored in this study. The abstract and summary should be revised to avoid overgeneralization, and the 'single Population III star' statement should be explicitly conditional on the initial conditions.
- [Sections 2 and 4.2] The use of a barotropic equation of state (EOS) may systematically underestimate fragmentation, as the authors themselves note by citing Prole et al. (2024) in Section 2. Because the central result is the suppression of fragmentation leading to a single star, a thermal treatment that yields more fragments could alter the conclusion. The paper provides no sensitivity test with a more detailed EOS or chemistry. This is a load-bearing caveat that should be addressed either by additional simulations or by substantially qualifying the claims about the number of stars, particularly in the abstract and Section 5.
- [Sections 3.1 and 5] The statement that 'no further fragmentation occurs' after the merger is based on runs of only 1000-1400 yr after first protostar formation. The accretion phase of a Population III star is expected to last much longer (typically 10^4-10^5 yr), and disk fragmentation can be episodic. A 1000 yr interval, while long compared to the local orbital time, does not rule out later fragmentation events. The conclusion should be phrased as 'no fragmentation within the simulated time span' rather than as a definitive property of the accretion phase.
minor comments (3)
- [Section 5] The phrase 'In all models except for the extremely strong magnetic field model B04' is ambiguous because model B00 (zero magnetic field) does not result in a single star and is not mentioned in that sentence. Please specify 'in all magnetized models' to avoid confusion with the zero-field control.
- [Figure 5] The axis label 'plsma βp' is a typo for 'plasma βp'. Also, the title on the first page contains 'F ormation' with an unintended space, likely a formatting artifact.
- [Section 3.3.2] The protostar identification procedure uses a 5 au radius, and the text states that if two protostars are within 5 au they are counted as one. Given that the primary conclusion concerns whether a single star forms, it would be helpful to quantify how often this situation occurs in the magnetized models, even if it is stated to be rare.
Circularity Check
No circular derivation: the single-star outcome is emergent from MHD simulations with no fitted parameters, and the self-citations are motivational or methodological rather than load-bearing.
full rationale
The paper's central claim, that any non-zero magnetic field leads to a single massive Population III star, is an emergent outcome of the reported simulations, not a quantity fitted to data or defined in terms of the conclusion. Across models B20 through B02, fragmentation, magnetic amplification, merger, and the absence of later fragmentation are presented as time-evolving simulation results (Figures 3, 12, 16). No parameter is calibrated to produce the merger; the outcome follows from the MHD equations with stated initial conditions. The self-citations to Hirano & Machida (2022) and Hirano et al. (2023) describe the amplification mechanism, but the same mechanism is independently reproduced in the present runs, e.g., in Figure 5, where the magnetic field is shown to amplify after protostar formation to B ~ 10^2-10^3 G with plasma beta ~ 10^-2 to 10^-4. The use of the barotropic EOS from Higuchi et al. (2018) and the stiff EOS from Machida & Nakamura (2015) are methodological inputs, not predictions derived from the paper's own conclusions. The statement in Section 5, 'as long as the minihalo is magnetized, a single Population III star will form,' is an extrapolation beyond the turbulence-free initial conditions, but the paper explicitly acknowledges this limitation in Section 4.2: 'strong turbulence may prevent the merging of fragments, potentially resulting in the survival of multiple protostars in spatially separated regions.' That is a caveat about the realism of the setup, not a circular step. There is no equation in which a predicted quantity equals a fitted input by construction, and no invoked uniqueness theorem or prior result that forces the conclusion. Therefore the appropriate circularity score is 0.
Assumptions & free parameters
free parameters (4)
- Initial magnetic field strength B0 =
10^-20 to 10^-4 G plus zero-field control
- Stiff EOS threshold density n_ps = 10^16 cm^-3 =
10^16 cm^-3
- Protostar identification radius of 5 au =
5 au
- Outflow detection threshold vz > 1 km/s =
1 km/s
assumptions (5)
- domain assumption Ideal MHD holds throughout the accretion phase; magnetic dissipation is negligible on star and disk scales.
- domain assumption The barotropic EOS of Higuchi et al. 2018 (model I0ZPM100) adequately represents the thermal state of collapsing primordial gas.
- domain assumption A Bonnor-Ebert sphere with rigid rotation, beta = 0.02, no turbulence, and a uniform aligned magnetic field is a representative initial condition for a primordial star-forming minihalo.
- domain assumption A protostar can be represented as gas with a stiff EOS above 10^16 cm^-3, and sink cells must be avoided.
- standard math The standard MHD equations with gravitational softening and divergence cleaning are solved faithfully by the nested grid code.
invented entities (2)
-
Magnetically inflated thick disk (pseudodisk supported by magnetic pressure)
-
Interchange instability as the cause of the B04 ring fragmentation
Cite this review
Pith. "Pith review of Effect of Magnetic Field on the Accretion Phase of Population III Star Formation." pith.science (2026). https://pith.science/paper/J43BNPOI
@misc{pith2026250521110,
author = {Pith},
title = {Pith review of: Effect of Magnetic Field on the Accretion Phase of Population III Star Formation},
year = {2026},
howpublished = {\url{https://pith.science/paper/J43BNPOI}},
note = {Machine review of arXiv:2505.21110}
}
abstract
We examine the impact of the magnetic field on Population III star formation by varying the magnetic field strength. We perform simulations with magnetic field strengths ranging from $10^{-20}$ G to $10^{-4}$ G, in addition to a model without a magnetic field. The simulations are run for $>1000-1400$ yr after the first protostar forms. In weak-field models, the surrounding disk fragments, forming multiple protostars, and the magnetic field is amplified by the orbital motion and rotation of these protostars. In the model without a magnetic field, frequent fragmentation occurs, and the most massive protostar reaches $\sim200 M_\odot$. However, in models with a magnetic field, once the magnetic field is amplified, the protostars merge to form a single massive protostar, and no further fragmentation occurs except in the model with the strongest magnetic field. Even after the formation of the single protostar, the magnetic field continues to amplify, leading to the formation of a thick disk supported by magnetic pressure and a global spiral pattern. In models with moderate or strong magnetic fields, a rotating disk can form, but fragmentation does not occur, and a strong magnetic field drives an outflow. However, the range of parameters for both disk formation and outflow driving is very narrow, making their appearance under realistic conditions unlikely. Given the weak magnetic field in the early universe, Population III stars are expected to form as single stars, surrounded by a thick disk with a spiral pattern. Thus, the magnetic field, regardless of its strength, plays a crucial role in Population III star formation.
Figures
Figures from the paper (17 more)
Reference graph
Works this paper leans on
-
[1]
2014, in Protostars and Planets VI, ed
Andr \'e , P., Di Francesco , J., Ward-Thompson , D., et al. 2014, in Protostars and Planets VI, ed. H. Beuther , R. S. Klessen , C. P. Dullemond , & T. Henning , 27--51, 10.2458/azu_uapress_9780816531240-ch002
-
[2]
2004, , 70, 123003, 10.1103/PhysRevD.70.123003
Banerjee , R., & Jedamzik , K. 2004, , 70, 123003, 10.1103/PhysRevD.70.123003
-
[3]
Basu , S., Sharkawi , M., & Machida , M. N. 2024, , 964, 116, 10.3847/1538-4357/ad1bf3
-
[4]
Beuther , H., Schilke , P., Sridharan , T. K., et al. 2002, , 383, 892, 10.1051/0004-6361:20011808
-
[5]
Clark , P. C., Glover , S. C. O., Klessen , R. S., & Bromm , V. 2011, , 727, 110, 10.1088/0004-637X/727/2/110
-
[6]
Crutcher , R. M. 1999, , 520, 706, 10.1086/307483
doi:10.1086/307483 1999
-
[7]
M., Wandelt , B., Heiles , C., Falgarone , E., & Troland , T
Crutcher , R. M., Wandelt , B., Heiles , C., Falgarone , E., & Troland , T. H. 2010, , 725, 466, 10.1088/0004-637X/725/1/466
-
[8]
Dapp , W. B., Basu , S., & Kunz , M. W. 2012, , 541, A35, 10.1051/0004-6361/201117876
Show all 69 references
-
[9]
2002, Journal of Computational Physics, 175, 645, 10.1006/jcph.2001.6961
Dedner , A., Kemm , F., Kr \"o ner , D., et al. 2002, Journal of Computational Physics, 175, 645, 10.1006/jcph.2001.6961
2002
-
[10]
2011, , 741, 93, 10.1088/0004-637X/741/2/93
Doi , K., & Susa , H. 2011, , 741, 93, 10.1088/0004-637X/741/2/93
2011 doi
-
[11]
Federrath , C., Sur , S., Schleicher , D. R. G., Banerjee , R., & Klessen , R. S. 2011, , 731, 62, 10.1088/0004-637X/731/1/62
2011 doi
-
[12]
Gaches , B. A. L., Tan , J. C., Rosen , A. L., & Kuiper , R. 2024, , 692, A219, 10.1051/0004-6361/202451842
2024 doi
-
[13]
H., Bromm , V., Clark , P
Greif , T. H., Bromm , V., Clark , P. C., et al. 2012, , 424, 399, 10.1111/j.1365-2966.2012.21212.x
2012
-
[14]
2024, , 962, 158, 10.3847/1538-4357/ad2066
Higashi , S., Susa , H., Federrath , C., & Chiaki , G. 2024, , 962, 158, 10.3847/1538-4357/ad2066
2024 doi
-
[15]
N., & Susa , H
Higuchi , K., Machida , M. N., & Susa , H. 2018, , 475, 3331, 10.1093/mnras/sty046
2018 doi
- [16]
-
[17]
2017, , 470, 898, 10.1093/mnras/stx1220
Hirano , S., & Bromm , V. 2017, , 470, 898, 10.1093/mnras/stx1220
2017 doi
-
[18]
Hirano , S., & Machida , M. N. 2022, , 935, L16, 10.3847/2041-8213/ac85e0
2022 doi
-
[19]
N., & Basu , S
Hirano , S., Machida , M. N., & Basu , S. 2021, , 917, 34, 10.3847/1538-4357/ac0913
2021 doi
- [20]
-
[21]
Hirano , S., Tsukamoto , Y., Basu , S., & Machida , M. N. 2020, , 898, 118, 10.3847/1538-4357/ab9f9d
2020 doi
-
[22]
2012, , 543, A128, 10.1051/0004-6361/201118730
Joos , M., Hennebelle , P., & Ciardi , A. 2012, , 543, A128, 10.1051/0004-6361/201118730
2012 doi
-
[23]
S., & Glover , S
Klessen , R. S., & Glover , S. C. O. 2023, , 61, 65, 10.1146/annurev-astro-071221-053453
2023 doi
-
[24]
2003, , 67, 043505, 10.1103/PhysRevD.67.043505
Langer , M., Puget , J.-L., & Aghanim , N. 2003, , 67, 043505, 10.1103/PhysRevD.67.043505
2003 doi
-
[25]
2020, , 641, A112, 10.1051/0004-6361/202038174
Lebreuilly , U., Commer c on , B., & Laibe , G. 2020, , 641, A112, 10.1051/0004-6361/202038174
2020 doi
- [26]
- [27]
- [28]
- [29]
- [30]
-
[31]
N., Higuchi , K., & Okuzumi , S
Machida , M. N., Higuchi , K., & Okuzumi , S. 2018, , 473, 3080, 10.1093/mnras/stx2589
2018 doi
-
[32]
N., & Hosokawa , T
Machida , M. N., & Hosokawa , T. 2013, , 431, 1719, 10.1093/mnras/stt291
2013 doi
-
[33]
N., Inutsuka , S.-i., & Matsumoto , T
Machida , M. N., Inutsuka , S.-i., & Matsumoto , T. 2008 a , , 676, 1088, 10.1086/528364
2008 doi
-
[36]
N., Matsumoto , T., Tomisaka , K., & Hanawa , T
Machida , M. N., Matsumoto , T., Tomisaka , K., & Hanawa , T. 2005, , 362, 369, 10.1111/j.1365-2966.2005.09297.x
2005
-
[37]
N., & Nakamura , T
Machida , M. N., & Nakamura , T. 2015, , 448, 1405, 10.1093/mnras/stu2633
2015 doi
-
[38]
N., Omukai , K., Matsumoto , T., & Inutsuka , S.-i
Machida , M. N., Omukai , K., Matsumoto , T., & Inutsuka , S.-i. 2006, , 647, L1, 10.1086/507326
2006 doi
- [39]
-
[40]
N., Tomisaka , K., & Matsumoto , T
Machida , M. N., Tomisaka , K., & Matsumoto , T. 2004, , 348, L1, 10.1111/j.1365-2966.2004.07402.x
2004
- [41]
- [42]
- [43]
-
[44]
Mouschovias , T. C. 1976, , 207, 141, 10.1086/154478
1976 doi
-
[45]
2002, , 573, 199, 10.1086/340587
Nakano , T., Nishi , R., & Umebayashi , T. 2002, , 573, 199, 10.1086/340587
2002 doi
-
[46]
2021, , 508, 6176, 10.1093/mnras/stab2999
Park , J., Ricotti , M., & Sugimura , K. 2021, , 508, 6176, 10.1093/mnras/stab2999
2021 doi
-
[47]
R., Clark , P
Prole , L. R., Clark , P. C., Klessen , R. S., & Glover , S. C. O. 2022 a , , 510, 4019, 10.1093/mnras/stab3697
2022 doi
-
[48]
R., Clark , P
Prole , L. R., Clark , P. C., Klessen , R. S., Glover , S. C. O., & Pakmor , R. 2022 b , , 516, 2223, 10.1093/mnras/stac2327
2022 doi
-
[49]
R., Clark , P
Prole , L. R., Clark , P. C., Priestley , F. D., Glover , S. C. O., & Regan , J. A. 2024, The Open Journal of Astrophysics, 7, 4, 10.21105/astro.2310.10730
2024 arXiv
- [50]
-
[51]
2025, , 980, L38, 10.3847/2041-8213/adaf94
Ryu , T., Sills , A., Pakmor , R., de Mink , S., & Mathieu , R. 2025, , 980, L38, 10.3847/2041-8213/adaf94
2025 doi
-
[52]
E., Omukai , K., Sugimura , K., Matsumoto , T., & Tomida , K
Sadanari , K. E., Omukai , K., Sugimura , K., Matsumoto , T., & Tomida , K. 2024, , 76, 823, 10.1093/pasj/psae051
2024 doi
-
[53]
2012, , 754, 99, 10.1088/0004-637X/754/2/99
Schober , J., Schleicher , D., Federrath , C., et al. 2012, , 754, 99, 10.1088/0004-637X/754/2/99
2012 doi
- [54]
-
[55]
Sharda , P., Federrath , C., & Krumholz , M. R. 2020, , 497, 336, 10.1093/mnras/staa1926
2020 doi
-
[56]
R., & Schleicher , D
Sharda , P., Federrath , C., Krumholz , M. R., & Schleicher , D. R. G. 2021, , 503, 2014, 10.1093/mnras/stab531
2021 doi
- [57]
- [58]
-
[59]
J., Glover , S
Smith , R. J., Glover , S. C. O., Clark , P. C., Greif , T., & Klessen , R. S. 2011, , 414, 3633, 10.1111/j.1365-2966.2011.18659.x
2011
-
[60]
2013, , 433, 1094, 10.1093/mnras/stt789
Stacy , A., & Bromm , V. 2013, , 433, 1094, 10.1093/mnras/stt789
2013 doi
-
[61]
F., Lee , A
Stacy , A., McKee , C. F., Lee , A. T., Klein , R. I., & Li , P. S. 2022, , 511, 5042, 10.1093/mnras/stac372
2022 doi
-
[62]
2020, , 892, L14, 10.3847/2041-8213/ab7d37
Sugimura , K., Matsumoto , T., Hosokawa , T., Hirano , S., & Omukai , K. 2020, , 892, L14, 10.3847/2041-8213/ab7d37
2020 doi
- [63]
-
[64]
2019, , 877, 99, 10.3847/1538-4357/ab1b6f
Susa , H. 2019, , 877, 99, 10.3847/1538-4357/ab1b6f
2019 doi
- [65]
-
[66]
Takasao , S., Tomida , K., Iwasaki , K., & Suzuki , T. K. 2022, , 941, 73, 10.3847/1538-4357/ac9eb1
2022 doi
-
[67]
2023, , 956, L16, 10.3847/2041-8213/acfca9
Tokuda , K., Fukaya , N., Tachihara , K., et al. 2023, , 956, L16, 10.3847/2041-8213/acfca9
2023 doi
-
[68]
2024, , 965, 99, 10.3847/1538-4357/ad2f9a
Tokuda , K., Harada , N., Omura , M., et al. 2024, , 965, 99, 10.3847/1538-4357/ad2f9a
2024 doi
-
[69]
2023, in Astronomical Society of the Pacific Conference Series, Vol
Tsukamoto , Y., Maury , A., Commercon , B., et al. 2023, in Astronomical Society of the Pacific Conference Series, Vol. 534, Protostars and Planets VII, ed. S. Inutsuka , Y. Aikawa , T. Muto , K. Tomida , & M. Tamura , 317, 10.48550/arXiv.2209.13765
-
[70]
J., Oishi , J
Turk , M. J., Oishi , J. S., Abel , T., & Bryan , G. L. 2012, , 745, 154, 10.1088/0004-637X/745/2/154
2012 doi
-
[71]
2018, , 615, A5, 10.1051/0004-6361/201732075
Vaytet , N., Commer c on , B., Masson , J., Gonz \'a lez , M., & Chabrier , G. 2018, , 615, A5, 10.1051/0004-6361/201732075
2018 doi
Reviewed August 7, 2026 · model on record in the stance chip above.
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