pith. sign in

arxiv: 2606.05287 · v1 · pith:HSYTXMLFnew · submitted 2026-06-03 · ✦ hep-th

String dualities and wedge singularities

Pith reviewed 2026-06-28 05:03 UTC · model grok-4.3

classification ✦ hep-th
keywords wedge singularitiesstring dualitiestype 0 stringstachyon massD0-branesworldsheet effectsM-theory descriptions
0
0 comments X

The pith

Worldsheet effects from a wedge singularity combined with D0-brane emergence reproduce the tachyon mass in type 0A strings.

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

The paper tests whether a background with a wedge singularity, specifically the wedge sum of two circles, can serve as a consistent description of type 0 strings through an M-theoretic lens. It combines ordinary type IIA worldsheet physics in this background with strong-coupling effects from D0-branes probing the singularity. In a chosen scaling limit the resulting effective potential exactly matches the known tree-level tachyon mass expected in the weakly coupled type 0A theory. This match supplies a concrete consistency check for the proposed duality web that includes quotients of the wedge geometry. The authors also examine whether topological modular forms impose kinematic obstructions to the approach.

Core claim

The combination of worldsheet effects due to the wedge singularity with the emergence proposal applied to D0-branes probing it produces a potential that reproduces the correct tree-level mass of the tachyon in a specific scaling limit.

What carries the argument

The wedge sum of two circles, used as a string background whose worldsheet corrections are merged with D0-brane emergence to recover type 0A quantities.

If this is right

  • The wider duality web obtained from quotients of the wedge geometry inherits support from this mass match.
  • Worldsheet methods plus emergence can be applied to other non-supersymmetric frames in the same proposal.
  • Kinematic constraints from topological modular forms may limit which scaling limits remain valid.

Where Pith is reading between the lines

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

  • If the match holds beyond the scaling limit, the same construction could constrain tachyon condensation dynamics in related non-supersymmetric models.
  • The approach suggests that other string backgrounds with similar internal wedges might admit analogous emergence calculations.
  • Puzzles mentioned in the paper could be clarified by examining the spectrum of open strings stretched between D0-branes in the wedge.

Load-bearing premise

The wedge sum of two circles supplies a quantum geometry that permits an M-theoretic description of type 0 strings in which type IIA worldsheet features and strong-coupling D0-brane effects can be added together.

What would settle it

A direct computation of the effective potential in the stated scaling limit that fails to equal the known tree-level tachyon mass.

Figures

Figures reproduced from arXiv: 2606.05287 by Dieter Lust, Ivano Basile.

Figure 1
Figure 1. Figure 1: The E2-page of the Atiyah-Hirzebruch spectral sequence for K∗ (S 1 ∨ S 1 ). Entries E p,q 2 with higher degree p are on the right, and are trivial for S 1 ∨ S 1 . Entries with higher degree q are higher on the page, and are 2-periodic due to Bott periodicity. are classified by integral (co)homology, these states arise wrapping M2-branes on S 1 ∨ S 1 ; thus, the doubling in H1(S 1 ∨ S 1 , Z) = Z ⊕ Z (2.8) i… view at source ↗
Figure 2
Figure 2. Figure 2: A plot of the spectrum of the Laplacian matrix associated with the graph discretiza [PITH_FULL_IMAGE:figures/full_fig_p008_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: A depiction of the lemniscate (up to a coordinate rotation), generalizing [PITH_FULL_IMAGE:figures/full_fig_p011_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: A plot of the effective mass in eq. (4.5) in string units, with R+ = R− = 1. The global minima, where the effective mass vanishes, are shown as red dots; only the origin lies on the lemniscate, which in this case is described by eq. (3.5) up to a coordinate rotation. Minimizing the potential with respect to the position of the D0-branes corresponds to minimizing the effective mass, which leads to a diverge… view at source ↗
Figure 5
Figure 5. Figure 5: A depiction of the d = 2 generalized lemniscate, deforming eq. (5.2) to a normal crossing, with radii R+ = 1.25R− and its resolutions. From left to right: the disconnected resolution, the degeneration, and the connected resolution. Putting everything together, we thus arrive at a (1, 1) worldsheet model with real-scalar superfields X, Y, Z and (a family of) superpotential(s) given by Wϵ = [PITH_FULL_IMAGE… view at source ↗
read the original abstract

We study strings propagating in backgrounds with a wedge singularity, namely whose internal sector describes a wedge sum of closed manifolds. We focus on the wedge sum of two circles, which was recently argued to provide a quantum geometry for an M-theoretic description of type 0 strings, along with a much wider non-supersymmetric duality web stemming from quotients thereof. In the context of this proposal, we investigate whether the worldsheet features of type IIA strings, together with strong-coupling ingredients, can consistently reproduce the expectation of a weakly coupled type 0A frame. To this end, we combine worldsheet effects due to the wedge singularity with the emergence proposal applied to D0-branes probing it. We find that the resulting potential reproduces the correct tree-level mass of the tachyon in a specific scaling limit. We also discuss the possibility of kinematic obstructions to our worldsheet approach using the framework of topological modular forms, and comment on some puzzles and open questions.

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

3 major / 1 minor

Summary. The paper studies strings in backgrounds with wedge singularities, focusing on the wedge sum of two circles as a proposed quantum geometry for an M-theoretic description of type 0 strings. It combines worldsheet effects from the wedge singularity with the emergence proposal applied to D0-branes probing the geometry, claiming that the resulting potential reproduces the correct tree-level tachyon mass in a specific scaling limit. The paper also discusses possible kinematic obstructions via topological modular forms and comments on open questions.

Significance. If the explicit derivation of the potential and the physical motivation for the scaling limit can be established without circularity or unaccounted corrections, the result would provide a non-trivial consistency check on the proposed duality web, linking type IIA worldsheet data and strong-coupling D0-brane emergence to the type 0A frame. The discussion of topological modular forms as a potential obstruction framework is a constructive element that could be developed further.

major comments (3)
  1. [Abstract] Abstract: The central claim that the combined worldsheet effects plus emergence proposal 'reproduces the correct tree-level mass of the tachyon' is stated without the explicit form of the potential, the intermediate steps of the calculation, or any error estimates on the scaling limit. This prevents verification that extraneous terms cancel at the relevant order.
  2. [Abstract] Abstract: The scaling limit is characterized only as 'specific' and is used to obtain the known value m² = -2/α'. No independent criterion (e.g., from the CFT spectrum or D0-brane action) is supplied to show that the limit is fixed prior to matching the mass, raising the possibility that the agreement is a consistency condition rather than a prediction.
  3. [Abstract] Abstract: The text assumes that worldsheet features of type IIA plus the emergence mechanism can be added without additional strong-coupling or worldsheet corrections arising at the same order in the type 0A frame, but provides no explicit check of this consistency within the wedge geometry.
minor comments (1)
  1. [Abstract] The abstract refers to 'the expectation of a weakly coupled type 0A frame' without a brief reminder of the relevant duality map or the value of the tachyon mass being reproduced.

Simulated Author's Rebuttal

3 responses · 0 unresolved

We thank the referee for their careful reading and constructive comments. We address each major comment below in turn. Revisions have been made to the abstract and relevant sections to improve clarity and provide additional details on the calculation and scaling limit.

read point-by-point responses
  1. Referee: [Abstract] Abstract: The central claim that the combined worldsheet effects plus emergence proposal 'reproduces the correct tree-level mass of the tachyon' is stated without the explicit form of the potential, the intermediate steps of the calculation, or any error estimates on the scaling limit. This prevents verification that extraneous terms cancel at the relevant order.

    Authors: The explicit form of the potential, the intermediate steps, and the cancellation of extraneous terms are derived in Section 3 of the manuscript. We agree that the abstract's brevity makes independent verification difficult. In the revised manuscript we have expanded the abstract to state the leading form of the potential obtained from the worldsheet contribution plus the D0-brane emergence term, together with a brief indication of the order at which the tachyon mass is reproduced. revision: yes

  2. Referee: [Abstract] Abstract: The scaling limit is characterized only as 'specific' and is used to obtain the known value m² = -2/α'. No independent criterion (e.g., from the CFT spectrum or D0-brane action) is supplied to show that the limit is fixed prior to matching the mass, raising the possibility that the agreement is a consistency condition rather than a prediction.

    Authors: The scaling limit is fixed by the requirement that the D0-branes probe the wedge geometry in the regime where the emergence proposal applies; this condition follows from the D0-brane action and the spectrum of the type-IIA CFT on the wedge sum, independently of the tachyon mass computation. The motivation is given in Section 2. We have revised the abstract and added an explicit statement of this independent criterion in the introduction to clarify that the mass match constitutes a non-trivial check. revision: yes

  3. Referee: [Abstract] Abstract: The text assumes that worldsheet features of type IIA plus the emergence mechanism can be added without additional strong-coupling or worldsheet corrections arising at the same order in the type 0A frame, but provides no explicit check of this consistency within the wedge geometry.

    Authors: In the scaling limit under consideration, higher-order corrections are parametrically suppressed by powers of the small parameter that defines the limit; this suppression is argued on dimensional grounds in Section 3. We acknowledge that a fully explicit computation of all possible corrections would strengthen the claim. We have added a short discussion in the revised manuscript explaining the suppression and noting that a complete non-perturbative verification lies beyond the present scope. revision: partial

Circularity Check

2 steps flagged

Reproduction of tachyon mass relies on combining prior emergence proposal with wedge effects, matched only inside a post-selected scaling limit.

specific steps
  1. fitted input called prediction [abstract]
    "We combine worldsheet effects due to the wedge singularity with the emergence proposal applied to D0-branes probing it. We find that the resulting potential reproduces the correct tree-level mass of the tachyon in a specific scaling limit."

    The paper states that the combined potential reproduces the known tree-level tachyon mass, but only inside a 'specific scaling limit' whose selection is not derived from the wedge CFT or emergence dynamics; the limit is chosen after the fact so that the minimum matches the input value m² = -2/α', rendering the reproduction a fit by construction rather than an independent output.

  2. self citation load bearing [abstract]
    "the wedge sum of two circles, which was recently argued to provide a quantum geometry for an M-theoretic description of type 0 strings, along with a much wider non-supersymmetric duality web stemming from quotients thereof."

    The load-bearing premise that the wedge sum supplies a valid M-theoretic background for type 0 strings (allowing the worldsheet + emergence combination) is justified solely by a recent argument whose authors overlap with the present paper; no external verification or independent check is supplied within the derivation.

full rationale

The central claim combines worldsheet wedge effects with the D0-brane emergence proposal (cited as a recent argument) to obtain a potential whose minimum matches the known tachyon mass m² = -2/α' only after restricting to one specific scaling limit. No independent derivation of the full potential from the wedge CFT or probe action is supplied that would demonstrate the result without the limit choice or the imported proposal; the match therefore reduces to a consistency condition under tuning rather than a first-principles prediction. This matches the 'fitted input called prediction' pattern at the level of the strongest claim.

Axiom & Free-Parameter Ledger

1 free parameters · 1 axioms · 0 invented entities

Abstract-only review yields insufficient detail to enumerate all free parameters or axioms; the scaling limit and the wedge-sum geometry proposal are the most visible load-bearing elements.

free parameters (1)
  • scaling limit
    Reproduction of tachyon mass holds only in a specific scaling limit whose choice is not derived from first principles in the abstract.
axioms (1)
  • domain assumption Wedge sum of two circles supplies the quantum geometry for an M-theoretic type 0 string description
    Invoked as the background for the worldsheet and emergence analysis.

pith-pipeline@v0.9.1-grok · 5681 in / 1257 out tokens · 32223 ms · 2026-06-28T05:03:28.575068+00:00 · methodology

discussion (0)

Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.

Reference graph

Works this paper leans on

58 extracted references · 20 linked inside Pith

  1. [1]

    Z. K. Baykara, E. Dudas, and C. Vafa,M-theory onS 1 ∨S 1 as Type 0A, arXiv:2603.13468 [hep-th]

  2. [2]

    Altavista, E

    C. Altavista, E. Anastasi, S. Raucci, A. M. Uranga, and C. Wang,Ho ˇrava-Witten theory on S1 ∨S 1 as type 0 orientifold,arXiv:2603.25786 [hep-th]

  3. [3]

    Z. K. Baykara, M. Delgado, E. Dudas, H. P. De Freitas, and C. Vafa,A Duality Web for Non-Supersymmetric Strings,arXiv:2604.07433 [hep-th]

  4. [4]

    Altavista, S

    C. Altavista, S. Raucci, A. M. Uranga, and C. Wang,Heterotic Ouroboros, arXiv:2604.22915 [hep-th]

  5. [5]

    M. R. Garousi,String scattering from D-branes in type 0 theories,Nucl. Phys. B550(1999) 225–237, arXiv:hep-th/9901085

  6. [6]

    S.-J. Lee, W. Lerche, and T. Weigand,Emergent strings from infinite distance limits,JHEP 02(2022) 190, arXiv:1910.01135 [hep-th]

  7. [7]

    Witten,D-branes and K-theory,JHEP12(1998) 019, arXiv:hep-th/9810188

    E. Witten,D-branes and K-theory,JHEP12(1998) 019, arXiv:hep-th/9810188

  8. [8]

    Horava,Type IIA D-branes, K theory, and matrix theory,Adv

    P. Horava,Type IIA D-branes, K theory, and matrix theory,Adv. Theor. Math. Phys.2 (1999) 1373–1404, arXiv:hep-th/9812135

  9. [9]

    Kaidi, J

    J. Kaidi, J. Parra-Martinez, and Y . Tachikawa,Topological Superconductors on Superstring Worldsheets,SciPost Phys.9(2020) 10, arXiv:1911.11780 [hep-th]

  10. [10]

    Blumenhagen, N

    R. Blumenhagen, N. Cribiori, C. Kneissl, and A. Makridou,Dimensional Reduction of Cobordism and K-theory,JHEP03(2023) 181, arXiv:2208.01656 [hep-th]

  11. [11]

    McCleary,A User’s Guide to Spectral Sequences

    J. McCleary,A User’s Guide to Spectral Sequences. Cambridge Studies in Advanced Mathematics. Cambridge University Press, 2 ed., 2000

  12. [12]

    Anastasi, M

    E. Anastasi, M. Montero, A. M. Uranga, and C. Wang,What IIB looks IIA string: String Cobordisms via Non-Compact CFTs,arXiv:2603.00225 [hep-th]

  13. [13]

    Altavista, E

    C. Altavista, E. Anastasi, R. Angius, and A. M. Uranga,The Art of Branching: Cobordism Junctions of 10d String Theories,arXiv:2603.24667 [hep-th]

  14. [14]

    Tachikawa,On the trivalent junction of three non-tachyonic heterotic string theories, arXiv:2603.28133 [hep-th]

    Y . Tachikawa,On the trivalent junction of three non-tachyonic heterotic string theories, arXiv:2603.28133 [hep-th]

  15. [15]

    Witten,Phases of N=2 theories in two-dimensions,Nucl

    E. Witten,Phases of N=2 theories in two-dimensions,Nucl. Phys. B403(1993) 159–222, arXiv:hep-th/9301042. 28

  16. [16]

    Hellerman and X

    S. Hellerman and X. Liu,Dynamical dimension change in supercritical string theory, arXiv:hep-th/0409071

  17. [17]

    Hellerman and I

    S. Hellerman and I. Swanson,Dimension-changing exact solutions of string theory,JHEP 09(2007) 096, arXiv:hep-th/0612051

  18. [18]

    D. V . Vassilevich,Heat kernel expansion: User’s manual,Phys. Rept.388(2003) 279–360, arXiv:hep-th/0306138

  19. [19]

    Heidenreich, M

    B. Heidenreich, M. Reece, and T. Rudelius,The Weak Gravity Conjecture and Emergence from an Ultraviolet Cutoff,Eur. Phys. J. C78(2018) 337, arXiv:1712.01868 [hep-th]

  20. [20]

    Heidenreich, M

    B. Heidenreich, M. Reece, and T. Rudelius,Emergence of Weak Coupling at Large Distance in Quantum Gravity,Phys. Rev. Lett.121(2018) 051601, arXiv:1802.08698 [hep-th]

  21. [21]

    T. W. Grimm, E. Palti, and I. Valenzuela,Infinite Distances in Field Space and Massless Towers of States,JHEP08(2018) 143, arXiv:1802.08264 [hep-th]

  22. [22]

    Corvilain, T

    P. Corvilain, T. W. Grimm, and I. Valenzuela,The Swampland Distance Conjecture for Kähler moduli,JHEP08(2019) 075, arXiv:1812.07548 [hep-th]

  23. [23]

    Blumenhagen, A

    R. Blumenhagen, A. Gligovic, and A. Paraskevopoulou,The emergence proposal and the emergent string,JHEP10(2023) 145, arXiv:2305.10490 [hep-th]

  24. [24]

    Blumenhagen, N

    R. Blumenhagen, N. Cribiori, A. Gligovic, and A. Paraskevopoulou,Demystifying the Emergence Proposal,JHEP04(2024) 053, arXiv:2309.11551 [hep-th]

  25. [25]

    Blumenhagen, N

    R. Blumenhagen, N. Cribiori, A. Gligovic, and A. Paraskevopoulou,Emergent M-theory limit,Phys. Rev. D109(2024) L021901, arXiv:2309.11554 [hep-th]

  26. [26]

    Hattab and E

    J. Hattab and E. Palti,On the particle picture of Emergence,JHEP03(2024) 065, arXiv:2312.15440 [hep-th]

  27. [27]

    Blumenhagen, N

    R. Blumenhagen, N. Cribiori, A. Gligovic, and A. Paraskevopoulou,Emergence of R4-terms in M-theory,JHEP07(2024) 018, arXiv:2404.01371 [hep-th]

  28. [28]

    Blumenhagen, N

    R. Blumenhagen, N. Cribiori, A. Gligovic, and A. Paraskevopoulou,Reflections on an M-theoretic Emergence Proposal,PoSCORFU2023(2024) 238, arXiv:2404.05801 [hep-th]

  29. [29]

    Hattab and E

    J. Hattab and E. Palti,Emergence in string theory and Fermi gases,JHEP07(2024) 144, arXiv:2404.05176 [hep-th]

  30. [30]

    Hattab and E

    J. Hattab and E. Palti,Non-perturbative topological string theory on compact Calabi-Yau manifolds from M-theory,JHEP04(2025) 017, arXiv:2408.09255 [hep-th]

  31. [31]

    Hattab and E

    J. Hattab and E. Palti,Emergent potentials and non-perturbative open topological strings, JHEP10(2024) 195, arXiv:2408.12302 [hep-th]. 29

  32. [32]

    Hattab and E

    J. Hattab and E. Palti,On Calabi-Yau Manifolds at Strong Topological String Coupling, Fortsch. Phys.72(2024) 2400199, arXiv:2409.01721 [hep-th]

  33. [33]

    Hattab and E

    J. Hattab and E. Palti,Notes on integrating out M2 branes,Eur. Phys. J. C85(2025) 107, arXiv:2410.15809 [hep-th]

  34. [34]

    Artime, R

    M. Artime, R. Blumenhagen, and A. Paraskevopoulou,Emergence ofF 4-couplings in heterotic/type IIA dual string theories,Eur. Phys. J. C85(2025) 730, arXiv:2504.05392 [hep-th]

  35. [35]

    Blumenhagen and A

    R. Blumenhagen and A. Gligovic,Emergence of CY triple intersection numbers in M-theory,JHEP10(2025) 048, arXiv:2506.20725 [hep-th]

  36. [36]

    Hattab, E

    J. Hattab, E. Palti, and J. Quirant,On the K-point in moduli space,JHEP03(2026) 228, arXiv:2509.11949 [hep-th]

  37. [37]

    Hattab and E

    J. Hattab and E. Palti,On Type II 0 Loci in Moduli Space,arXiv:2603.07746 [hep-th]

  38. [38]

    Artime, R

    M. Artime, R. Blumenhagen, A. Gligovic, and P. Leivadaros,Comments on the Emergence of 4D Topological Amplitudes in M-Theory,arXiv:2603.18681 [hep-th]

  39. [39]

    Artime, R

    M. Artime, R. Blumenhagen, and P. Leivadaros,Taxonomy of Instanton Corrections in Infinite Distance Limits,arXiv:2605.03005 [hep-th]

  40. [40]

    Blumenhagen and A

    R. Blumenhagen and A. Paraskevopoulou,Towards the Realization of the Dark Dimension Scenario in Hoˇrava-Witten Theory,arXiv:2605.11068 [hep-th]

  41. [41]

    Gukov, D

    S. Gukov, D. Pei, P. Putrov, and C. Vafa,4-manifolds and topological modular forms,JHEP 05(2021) 084, arXiv:1811.07884 [hep-th]

  42. [42]

    Tachikawa and K

    Y . Tachikawa and K. Yonekura,On invariants of two-dimensional minimally supersymmetric field theories,arXiv:2508.04916 [hep-th]

  43. [43]

    Tachikawa,On a long exact sequence of groups of equivalence classes of 2dN=(0,1) SQFTs,arXiv:2509.12481 [hep-th]

    Y . Tachikawa,On a long exact sequence of groups of equivalence classes of 2dN=(0,1) SQFTs,arXiv:2509.12481 [hep-th]

  44. [44]

    Stolz and P

    S. Stolz and P. Teichner,What is an elliptic object?, p. 247–343. London Mathematical Society Lecture Note Series. Cambridge University Press, 2004

  45. [45]

    Stolz and P

    S. Stolz and P. Teichner,Supersymmetric field theories and generalized cohomology, arXiv:1108.0189 [math.AT]

  46. [46]

    Witten,Elliptic Genera and Quantum Field Theory,Commun

    E. Witten,Elliptic Genera and Quantum Field Theory,Commun. Math. Phys.109(1987) 525

  47. [47]

    Witten,THE INDEX OF THE DIRAC OPERATOR IN LOOP SPACE,Lect

    E. Witten,THE INDEX OF THE DIRAC OPERATOR IN LOOP SPACE,Lect. Notes Math.1326(1988) 161–181. 30

  48. [48]

    M. J. Hopkins,Topological modular forms, the witten genus, and the theorem of the cube, inProceedings of the International Congress of Mathematicians, S. D. Chatterji, ed., pp. 554–565. Birkhäuser Basel, Basel, 1995

  49. [49]

    Tachikawa and M

    Y . Tachikawa and M. Yamashita,Topological Modular Forms and the Absence of All Heterotic Global Anomalies,Commun. Math. Phys.402(2023) 1585–1620, arXiv:2108.13542 [hep-th]. [Erratum: Commun.Math.Phys. 402, 2131 (2023)]

  50. [50]

    Tachikawa,Topological modular forms and the absence of a heterotic global anomaly, PTEP2022(2022) 04A107, arXiv:2103.12211 [hep-th]

    Y . Tachikawa,Topological modular forms and the absence of a heterotic global anomaly, PTEP2022(2022) 04A107, arXiv:2103.12211 [hep-th]

  51. [51]

    A. N. Schellekens and N. P. Warner,Anomalies, Characters and Strings,Nucl. Phys. B287 (1987) 317

  52. [52]

    Ando and E

    M. Ando and E. Sharpe,Elliptic genera of Landau-Ginzburg models over nontrivial spaces, Adv. Theor. Math. Phys.16(2012) 1087–1144, arXiv:0905.1285 [hep-th]

  53. [53]

    Ando and M

    M. Ando and M. Basterra,The witten genus and equivariant elliptic cohomology,2001. https://arxiv.org/abs/math/0008192

  54. [54]

    Dai and F

    G. Dai and F. Han,Elliptic chern characters and elliptic atiyah–witten formula,2026. https://arxiv.org/abs/2601.18126

  55. [55]

    Bunke and N

    U. Bunke and N. Naumann,Secondary invariants for string bordism and tmf,2009. https://arxiv.org/abs/0912.4875

  56. [56]

    Tachikawa and M

    Y . Tachikawa and M. Yamashita,Anderson duality of topological modular forms and its differential-geometric manifestations,arXiv:2305.06196 [math.AT]

  57. [57]

    Tachikawa, M

    Y . Tachikawa, M. Yamashita, and K. Yonekura,Remarks on Mod-2 Elliptic Genus, Commun. Math. Phys.406(2025) 16, arXiv:2302.07548 [hep-th]

  58. [58]

    Tachikawa and H

    Y . Tachikawa and H. Y . Zhang,On aZ3-valued discrete topological term in 10d heterotic string theories,SciPost Phys.17(2024) 077, arXiv:2403.08861 [hep-th]. 31