Sharpening the Supersymmetric Axion Weak Gravity Conjecture
Pith reviewed 2026-05-25 05:46 UTC · model grok-4.3
The pith
Supersymmetric instantons in four dimensions obey the sharpened bound fS over absolute n at most sqrt(7/2) over kappa four.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
The authors verify that axion instantons across string landscape sectors satisfy fS over absolute n at most pi over two kappa d times the square root of d minus one over d minus two. They further argue that supersymmetric instantons in four dimensions obey the stronger bound fS over absolute n at most one over kappa four times the square root of seven over two.
What carries the argument
The ratio fS over absolute n, where f is the axion decay constant, S the instanton action, and n the integer charge, bounded relative to the reduced Planck scale set by kappa d.
If this is right
- The axion weak gravity conjecture holds with a definite numerical coefficient rather than an unspecified order-one factor.
- Supersymmetric axion models receive stronger restrictions on allowed decay constants and instanton actions.
- The bound depends explicitly on spacetime dimension and applies uniformly to checked sectors of the string landscape.
- Instanton contributions to axion potentials must respect the tighter supersymmetric limit in four dimensions.
Where Pith is reading between the lines
- The sharpened bound could further restrict viable parameter ranges in axion-driven inflation models.
- Similar tightening might appear in other swampland conjectures when supersymmetry is imposed.
- Systematic scans of additional string compactifications could test whether the stronger four-dimensional bound holds universally.
Load-bearing premise
The three complementary approaches identify all dominant instantons in the examined axion sectors without missing any lighter ones that would violate the bound.
What would settle it
An explicit supersymmetric four-dimensional string compactification in which the lightest instanton has fS over absolute n larger than sqrt(7/2) over kappa four.
read the original abstract
The Axion Weak Gravity Conjecture provides one of the most effective quantum gravity tools for constraining particle physics and cosmology, but it has long been thought of as a slightly fuzzy statement: given an axion with decay constant $f$ there should exist an instanton of charge $n$ and action $S$ with $fS/|n|$ at most an order-one number in Planck units. Recent work related to axion wormholes motivated a specific order-one coefficient, $\frac{fS}{|n|} \leq \frac{\pi}{2 \kappa_d} \sqrt{\frac{d-1}{d-2}}$. In this work, we verify this bound in various axion sectors across the string landscape using three complementary approaches. In the process, we derive even tighter bounds on instantons in such sectors. For example, we argue that supersymmetric instantons in 4d satisfy the stronger bound of $\frac{fS}{|n|}\leq \frac 1{\kappa_4}\sqrt{\frac{7}{2}}$.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript claims that the Axion Weak Gravity Conjecture can be sharpened to the specific coefficient fS/|n| ≤ (π/(2 κ_d)) sqrt((d-1)/(d-2)), verifies this bound across various axion sectors in the string landscape via three complementary approaches, and argues that supersymmetric instantons in 4d obey the tighter inequality fS/|n| ≤ (1/κ_4) sqrt(7/2).
Significance. If the stronger bound and its verification hold, the result would supply a more precise quantum-gravity constraint on axion decay constants and instanton actions, with direct utility for model-building in particle physics and cosmology. The multi-method checks performed in concrete string examples constitute a concrete strength of the work.
major comments (2)
- [Abstract and the section describing the three complementary approaches] The central verification claim rests on the three complementary approaches correctly identifying all dominant (lightest) instantons without omission. The manuscript provides no general argument that these methods are exhaustive across all relevant 4d axion sectors or that post-hoc selection of examples was avoided; any missed lighter instanton would falsify the reported inequality. This is load-bearing for the claim that the bound is verified in the string landscape.
- [Section deriving the stronger supersymmetric bound] The derivation of the stronger 4d supersymmetric bound fS/|n| ≤ (1/κ_4) sqrt(7/2) is presented as an argument internal to the paper; however, the text does not clarify whether this follows from a parameter-free derivation or relies on assumptions about the instanton spectrum that are only checked in the selected examples.
minor comments (2)
- [Introduction] Notation for the Planck mass and the constant κ_4 should be defined explicitly on first use and kept uniform throughout.
- [Figures] Figure captions should state the precise string compactifications and axion sectors shown, rather than generic labels.
Simulated Author's Rebuttal
We thank the referee for their positive evaluation of the significance of our results and for their detailed comments on the verification methods and the supersymmetric bound. We respond to each major comment below.
read point-by-point responses
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Referee: [Abstract and the section describing the three complementary approaches] The central verification claim rests on the three complementary approaches correctly identifying all dominant (lightest) instantons without omission. The manuscript provides no general argument that these methods are exhaustive across all relevant 4d axion sectors or that post-hoc selection of examples was avoided; any missed lighter instanton would falsify the reported inequality. This is load-bearing for the claim that the bound is verified in the string landscape.
Authors: We agree that the manuscript does not contain a general theorem establishing that the three approaches are exhaustive in every conceivable 4d axion sector of the string landscape; such a result would require a complete classification of all compactifications, which lies beyond present capabilities. The three methods are instead applied as complementary tools to representative classes of axion sectors arising in explicit string constructions, with cross-consistency among the methods serving as an internal check that the lightest instantons have been identified. The examples were chosen for their direct relevance to the axion weak gravity conjecture rather than to fit the bound after the fact. We will add a clarifying paragraph in the relevant section that explicitly states the scope of the verification and notes this limitation. revision: partial
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Referee: [Section deriving the stronger supersymmetric bound] The derivation of the stronger 4d supersymmetric bound fS/|n| ≤ (1/κ_4) sqrt(7/2) is presented as an argument internal to the paper; however, the text does not clarify whether this follows from a parameter-free derivation or relies on assumptions about the instanton spectrum that are only checked in the selected examples.
Authors: The stronger bound is obtained from the BPS saturation condition for supersymmetric instantons together with the general form of the superpotential in 4d N=1 supergravity; the derivation is therefore parameter-free and does not invoke any assumptions about the detailed instanton spectrum beyond the existence of supersymmetric solutions. The concrete string examples are used solely to verify that the general bound is realized and not to derive it. We will insert a short clarifying statement in the section to make this independence explicit. revision: partial
Circularity Check
No significant circularity; sharpened bound derived from independent string example checks
full rationale
The paper verifies the original Axion WGC bound (motivated by prior wormhole work) via three complementary approaches applied to explicit string landscape axion sectors, then derives a tighter supersymmetric bound in 4d as a byproduct. No load-bearing step reduces by construction to a self-defined quantity, fitted input renamed as prediction, or unverified self-citation chain; the verification relies on external string constructions rather than tautological redefinition of inputs.
Axiom & Free-Parameter Ledger
axioms (2)
- domain assumption String theory provides consistent UV completions of quantum gravity with axion sectors that can be explicitly constructed.
- domain assumption The instantons identified in the constructions are the ones that control the Weak Gravity Conjecture bound.
Lean theorems connected to this paper
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IndisputableMonolith/Foundation/AlexanderDuality.lean; Constants; Costalexander_duality_circle_linking; reality_from_one_distinction (D=3); p=7 G2 case in landscape tables echoes?
echoesECHOES: this paper passage has the same mathematical shape or conceptual pattern as the Recognition theorem, but is not a direct formal dependency.
M-theory G2 Manifold C3 7 √(2/7); ... fqSq ≤ √(7/2) ... p=7 is the largest integer for which (1.2) is satisfied when (1.4) is saturated, ... realized in examples
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IndisputableMonolith/Foundation/AlphaCoordinateFixation.lean; BranchSelection.leanalpha_pin_under_high_calibration; branch_selection (coupling combiner forces bilinear branch) echoes?
echoesECHOES: this paper passage has the same mathematical shape or conceptual pattern as the Recognition theorem, but is not a direct formal dependency.
K=−log(F(ti)), F homogeneous of degree p; ... fqSq ≤ √(p/2); ... p_tot ≤7 from Emergent String / decompactification to 11d
What do these tags mean?
- matches
- The paper's claim is directly supported by a theorem in the formal canon.
- supports
- The theorem supports part of the paper's argument, but the paper may add assumptions or extra steps.
- extends
- The paper goes beyond the formal theorem; the theorem is a base layer rather than the whole result.
- uses
- The paper appears to rely on the theorem as machinery.
- contradicts
- The paper's claim conflicts with a theorem or certificate in the canon.
- unclear
- Pith found a possible connection, but the passage is too broad, indirect, or ambiguous to say the theorem truly supports the claim.
Reference graph
Works this paper leans on
-
[1]
The String Landscape, Black Holes and Gravity as the Weakest Force
N. Arkani-Hamed, L. Motl, A. Nicolis and C. Vafa,The String landscape, black holes and gravity as the weakest force,JHEP0706(2007) 060, [hep-th/0601001]
work page internal anchor Pith review Pith/arXiv arXiv 2007
-
[2]
A. R. Liddle, A. Mazumdar and F. E. Schunck,Assisted inflation,Phys. Rev.D58 (1998) 061301, [astro-ph/9804177]
work page internal anchor Pith review Pith/arXiv arXiv 1998
-
[3]
S. Dimopoulos, S. Kachru, J. McGreevy and J. G. Wacker,N-flation,JCAP0808 (2008) 003, [hep-th/0507205]
work page internal anchor Pith review Pith/arXiv arXiv 2008
-
[4]
J. E. Kim, H. P. Nilles and M. Peloso,Completing natural inflation,JCAP01(2005) 005, [hep-ph/0409138]
work page internal anchor Pith review Pith/arXiv arXiv 2005
-
[5]
On the Possibility of Large Axion Moduli Spaces
T. Rudelius,On the Possibility of Large Axion Moduli Spaces,JCAP1504(2015) 049, [1409.5793]
work page internal anchor Pith review Pith/arXiv arXiv 2015
-
[6]
Constraints on Axion Inflation from the Weak Gravity Conjecture
T. Rudelius,Constraints on Axion Inflation from the Weak Gravity Conjecture, JCAP09(2015) 020, [1503.00795]
work page internal anchor Pith review Pith/arXiv arXiv 2015
-
[7]
M. Montero, A. M. Uranga and I. Valenzuela,Transplanckian axions!?,JHEP08 (2015) 032, [1503.03886]
work page internal anchor Pith review Pith/arXiv arXiv 2015
-
[8]
Fencing in the Swampland: Quantum Gravity Constraints on Large Field Inflation
J. Brown, W. Cottrell, G. Shiu and P. Soler,Fencing in the Swampland: Quantum Gravity Constraints on Large Field Inflation,JHEP10(2015) 023, [1503.04783]
work page internal anchor Pith review Pith/arXiv arXiv 2015
-
[9]
Weak Gravity Strongly Constrains Large-Field Axion Inflation
B. Heidenreich, M. Reece and T. Rudelius,Weak Gravity Strongly Constrains Large-Field Axion Inflation,JHEP12(2015) 108, [1506.03447]
work page internal anchor Pith review Pith/arXiv arXiv 2015
-
[10]
K. Choi, E. J. Chun, S. H. Im and K. S. Jeong,Diluting the inflationary axion fluctuation by a stronger QCD in the early Universe,Phys. Lett. B750(2015) 26–30, [1505.00306]
work page internal anchor Pith review Pith/arXiv arXiv 2015
-
[11]
Axion Experiments to Algebraic Geometry: Testing Quantum Gravity via the Weak Gravity Conjecture
B. Heidenreich, M. Reece and T. Rudelius,Axion Experiments to Algebraic Geometry: Testing Quantum Gravity via the Weak Gravity Conjecture,Int. J. Mod. Phys. D25(2016) 1643005, [1605.05311]
work page internal anchor Pith review Pith/arXiv arXiv 2016
-
[12]
B. Heidenreich, M. Reece and T. Rudelius,The Weak Gravity Conjecture and axion strings,JHEP11(2021) 004, [2108.11383]
-
[13]
M. Reece,TASI Lectures: (No) Global Symmetries to Axion Physics,PoST ASI2022 (2024) 008, [2304.08512]
-
[14]
Seo,Axion species scale and axion weak gravity conjecture-like bound,JHEP11 (2024) 082, [2407.16156]
M.-S. Seo,Axion species scale and axion weak gravity conjecture-like bound,JHEP11 (2024) 082, [2407.16156]
-
[15]
Euclidean wormholes, baby universes, and their impact on particle physics and cosmology
A. Hebecker, T. Mikhail and P. Soler,Euclidean wormholes, baby universes, and their impact on particle physics and cosmology,Front. Astron. Space Sci.5(2018) 35, [1807.00824]. – 36 –
work page internal anchor Pith review Pith/arXiv arXiv 2018
- [16]
-
[17]
E. Sheridan, F. Carta, N. Gendler, M. Jain, D. J. E. Marsh, L. McAllister et al., Fuzzy axions and associated relics,JHEP09(2025) 016, [2412.12012]
- [18]
-
[19]
G. Shiu, F. Tonioni and H. V. Tran,Bounding axion dark energy,2604.09141
work page internal anchor Pith review Pith/arXiv arXiv
-
[20]
Cosmological implications of ultra-light axion-like fields
V. Poulin, T. L. Smith, D. Grin, T. Karwal and M. Kamionkowski,Cosmological implications of ultralight axionlike fields,Phys. Rev. D98(2018) 083525, [1806.10608]
work page internal anchor Pith review Pith/arXiv arXiv 2018
-
[21]
Early Dark Energy Can Resolve The Hubble Tension
V. Poulin, T. L. Smith, T. Karwal and M. Kamionkowski,Early Dark Energy Can Resolve The Hubble Tension,Phys. Rev. Lett.122(2019) 221301, [1811.04083]
work page internal anchor Pith review Pith/arXiv arXiv 2019
-
[22]
T. Rudelius,Constraints on early dark energy from the axion weak gravity conjecture, JCAP01(2023) 014, [2203.05575]
- [23]
-
[24]
Rudelius,An Introduction to the Weak Gravity Conjecture,Contemp
T. Rudelius,An Introduction to the Weak Gravity Conjecture,Contemp. Phys.1 (2024) 14, [2409.02161]
-
[25]
The Swampland: Introduction and Review
E. Palti,The Swampland: Introduction and Review,Fortsch. Phys.67(2019) 1900037, [1903.06239]
work page internal anchor Pith review Pith/arXiv arXiv 2019
-
[26]
Positivity of the gravitational path integral implies the axionic weak gravity conjecture
G. Di Ubaldo, L. V. Iliesiu, H. W. Lin and C. Yan,Positivity of the gravitational path integral implies the axionic weak gravity conjecture,2605.05305
work page internal anchor Pith review Pith/arXiv arXiv
-
[27]
Wormholes and the imaginary distance bound
J. Maldacena, A. Maloney and B. McPeak,Wormholes and the imaginary distance bound,2605.05336
work page internal anchor Pith review Pith/arXiv arXiv
-
[28]
S. B. Giddings and A. Strominger,Axion Induced Topology Change in Quantum Gravity and String Theory,Nucl. Phys. B306(1988) 890–907
1988
-
[29]
Stout,Instanton expansions and phase transitions,JHEP05(2022) 168, [2012.11605]
J. Stout,Instanton expansions and phase transitions,JHEP05(2022) 168, [2012.11605]
-
[30]
The Weak Gravity Conjecture and Scalar Fields
E. Palti,The Weak Gravity Conjecture and Scalar Fields,JHEP08(2017) 034, [1705.04328]
work page internal anchor Pith review Pith/arXiv arXiv 2017
-
[31]
S.-J. Lee, W. Lerche and T. Weigand,A Stringy Test of the Scalar Weak Gravity Conjecture,Nucl. Phys. B938(2019) 321–350, [1810.05169]
work page internal anchor Pith review Pith/arXiv arXiv 2019
-
[32]
E. Gonzalo and L. E. Ib´ a˜ nez,A Strong Scalar Weak Gravity Conjecture and Some Implications,JHEP08(2019) 118, [1903.08878]. – 37 –
-
[33]
D. Andriot, N. Cribiori and D. Erkinger,The web of swampland conjectures and the TCC bound,JHEP07(2020) 162, [2004.00030]
-
[34]
K. Benakli, C. Branchina and G. Lafforgue-Marmet,Revisiting the scalar weak gravity conjecture,Eur. Phys. J. C80(2020) 742, [2004.12476]
-
[35]
J. Calder´ on-Infante, A. M. Uranga and I. Valenzuela,The Convex Hull Swampland Distance Conjecture and Bounds on Non-geodesics,JHEP03(2021) 299, [2012.00034]
-
[36]
M. Etheredge, B. Heidenreich, S. Kaya, Y. Qiu and T. Rudelius,Sharpening the Distance Conjecture in diverse dimensions,JHEP12(2022) 114, [2206.04063]
-
[37]
M. Etheredge, B. Heidenreich, J. McNamara, T. Rudelius, I. Ruiz and I. Valenzuela, Running decompactification, sliding towers, and the distance conjecture,JHEP12 (2023) 182, [2306.16440]
-
[38]
A. Castellano, I. Ruiz and I. Valenzuela,Stringy evidence for a universal pattern at infinite distance,JHEP06(2024) 037, [2311.01536]
-
[39]
A. Castellano, I. Ruiz and I. Valenzuela,Universal Pattern in Quantum Gravity at Infinite Distance,Phys. Rev. Lett.132(2024) 181601, [2311.01501]
- [40]
-
[41]
M. Etheredge,Dense geodesics, tower alignment, and the Sharpened Distance Conjecture,JHEP01(2024) 122, [2308.01331]
-
[42]
M. Etheredge and B. Heidenreich,Geodesic gradient flows in moduli space,JHEP03 (2025) 035, [2311.18693]
-
[43]
M. Etheredge, B. Heidenreich and T. Rudelius,A Distance Conjecture for branes, JHEP09(2025) 155, [2407.20316]
-
[44]
M. Etheredge, B. Heidenreich, T. Rudelius, I. Ruiz and I. Valenzuela,Taxonomy of infinite distance limits,JHEP03(2025) 213, [2405.20332]
-
[45]
Etheredge,Taxonomy of branes in infinite distance limits,JHEP10(2025) 200, [2505.10615]
M. Etheredge,Taxonomy of branes in infinite distance limits,JHEP10(2025) 200, [2505.10615]
-
[46]
Naturalness and the Weak Gravity Conjecture
C. Cheung and G. N. Remmen,Naturalness and the Weak Gravity Conjecture,Phys. Rev. Lett.113(2014) 051601, [1402.2287]
work page internal anchor Pith review Pith/arXiv arXiv 2014
-
[47]
Heidenreich,Black Holes, Moduli, and Long-Range Forces,JHEP11(2020) 029, [2006.09378]
B. Heidenreich,Black Holes, Moduli, and Long-Range Forces,JHEP11(2020) 029, [2006.09378]
-
[48]
B. Heidenreich, M. Reece and T. Rudelius,Repulsive Forces and the Weak Gravity Conjecture,JHEP10(2019) 055, [1906.02206]
-
[49]
Instantons and Wormholes In Minkowski and (A)dS Spaces
M. Gutperle and W. Sabra,Instantons and wormholes in Minkowski and (A)dS – 38 – spaces,Nucl. Phys. B647(2002) 344–356, [hep-th/0206153]
work page internal anchor Pith review Pith/arXiv arXiv 2002
-
[50]
E. Bergshoeff, A. Collinucci, U. Gran, D. Roest and S. Vandoren,Non-extremal D-instantons,JHEP10(2004) 031, [hep-th/0406038]
work page internal anchor Pith review Pith/arXiv arXiv 2004
-
[51]
Non-extremal instantons and wormholes in string theory
E. Bergshoeff, A. Collinucci, U. Gran, D. Roest and S. Vandoren,Non-extremal instantons and wormholes in string theory,Fortsch. Phys.53(2005) 990–996, [hep-th/0412183]
work page internal anchor Pith review Pith/arXiv arXiv 2005
-
[52]
Sharpening the Weak Gravity Conjecture with Dimensional Reduction
B. Heidenreich, M. Reece and T. Rudelius,Sharpening the Weak Gravity Conjecture with Dimensional Reduction,JHEP02(2016) 140, [1509.06374]
work page internal anchor Pith review Pith/arXiv arXiv 2016
-
[53]
Can Gravitational Instantons Really Constrain Axion Inflation?
A. Hebecker, P. Mangat, S. Theisen and L. T. Witkowski,Can Gravitational Instantons Really Constrain Axion Inflation?,JHEP02(2017) 097, [1607.06814]
work page internal anchor Pith review Pith/arXiv arXiv 2017
-
[54]
F. Marchesano and M. Wiesner,Instantons and infinite distances,JHEP08(2019) 088, [1904.04848]
- [55]
- [56]
- [57]
-
[58]
R. F. Dashen,Some features of chiral symmetry breaking,Phys. Rev. D3(1971) 1879–1889
1971
-
[59]
Witten,Large N Chiral Dynamics,Annals Phys.128(1980) 363
E. Witten,Large N Chiral Dynamics,Annals Phys.128(1980) 363
1980
-
[60]
Theta, Time Reversal, and Temperature
D. Gaiotto, A. Kapustin, Z. Komargodski and N. Seiberg,Theta, Time Reversal, and Temperature,JHEP05(2017) 091, [1703.00501]
work page internal anchor Pith review Pith/arXiv arXiv 2017
-
[61]
Witten,Some Properties of O(32) Superstrings,Phys
E. Witten,Some Properties of O(32) Superstrings,Phys. Lett. B149(1984) 351–356
1984
-
[62]
P. Svrcek and E. Witten,Axions In String Theory,JHEP06(2006) 051, [hep-th/0605206]
work page internal anchor Pith review Pith/arXiv arXiv 2006
-
[63]
J. P. Conlon,The QCD axion and moduli stabilisation,JHEP05(2006) 078, [hep-th/0602233]
work page internal anchor Pith review Pith/arXiv arXiv 2006
-
[64]
Reece,Extra-dimensional axion expectations,JHEP07(2025) 130, [2406.08543]
M. Reece,Extra-dimensional axion expectations,JHEP07(2025) 130, [2406.08543]
-
[65]
Axion Monodromy and the Weak Gravity Conjecture
A. Hebecker, F. Rompineve and A. Westphal,Axion Monodromy and the Weak Gravity Conjecture,JHEP04(2016) 157, [1512.03768]
work page internal anchor Pith review Pith/arXiv arXiv 2016
- [66]
- [67]
-
[68]
T. W. Grimm and J. Louis,The Effective action of N = 1 Calabi-Yau orientifolds, Nucl. Phys. B699(2004) 387–426, [hep-th/0403067]
work page internal anchor Pith review Pith/arXiv arXiv 2004
-
[69]
Axion bitowers in quantum gravity
M. Etheredge, B. Heidenreich, M. Reece and T. Rudelius, “Axion bitowers in quantum gravity.”
-
[70]
T. W. Grimm and J. Louis,The Effective action of type IIA Calabi-Yau orientifolds, Nucl. Phys. B718(2005) 153–202, [hep-th/0412277]
work page internal anchor Pith review Pith/arXiv arXiv 2005
-
[71]
L. Martucci, N. Risso, A. Valenti and L. Vecchi,Wormholes in the axiverse, and the species scale,JHEP07(2024) 240, [2404.14489]
- [72]
-
[73]
D. van de Heisteeg, C. Vafa and M. Wiesner,Bounds on Species Scale and the Distance Conjecture,Fortsch. Phys.71(2023) 2300143, [2303.13580]
-
[74]
D. van de Heisteeg, C. Vafa, M. Wiesner and D. H. Wu,Bounds on field range for slowly varying positive potentials,JHEP02(2024) 175, [2305.07701]
-
[75]
D. van de Heisteeg, C. Vafa, M. Wiesner and D. H. Wu,Species scale in diverse dimensions,JHEP05(2024) 112, [2310.07213]
-
[76]
F. Marchesano, L. Melotti and L. Paoloni,On the moduli space curvature at infinity, JHEP02(2024) 103, [2311.07979]
- [77]
-
[78]
Etheredge, A
M. Etheredge, A. Herraez, L. Melotti and D. Luest,Proving the integral scaling conjecture with brane taxonomy, 2026
2026
-
[79]
On the Geometry of the String Landscape and the Swampland
H. Ooguri and C. Vafa,On the Geometry of the String Landscape and the Swampland, Nucl. Phys. B766(2007) 21–33, [hep-th/0605264]
work page internal anchor Pith review Pith/arXiv arXiv 2007
- [80]
discussion (0)
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