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REVIEW 3 major objections 5 minor 49 references

An effective light-front wave function built from holographic QCD yields pion gravitational form factors A(Q^{2}) and D(Q^{2}) that match lattice results.

Reviewed by Pith at T0; open to challenge. T0 means a machine referee read the full paper against a public rubric. the ladder, T0–T4 →

T0 review · grok-4.5

2026-07-10 19:33 UTC pith:4DK4RNOJ

load-bearing objection Useful phenomenological GFF calculation for the pion; the new piece is an ad-hoc f(x)=x(1-x) that regularizes D and improves A, with parameters tuned to the same lattice set used for comparison. the 3 major comments →

arxiv 2607.07305 v1 pith:4DK4RNOJ submitted 2026-07-08 hep-ph

Gravitational form factors of the pion in light-front holographic QCD

classification hep-ph
keywords gravitational form factorspionlight-front QCDholographic QCDD-termlight-front wave functionenergy-momentum tensor
verification ladder T0 review T1 audit T2 compute T3 formal T4 reserved

The pith

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

The paper asks how energy, momentum and stress are distributed inside the pion—the lightest quark-antiquark bound state. It answers by combining light-front QCD, where those distributions appear as overlaps of light-front wave functions, with holographic QCD, which supplies a five-dimensional pion wave function that already encodes confinement. The authors’ central move is to multiply the conformal holographic wave function by a simple factor x(1−x). That factor restores the correct endpoint behaviour of the pion’s parton distribution and the exchange symmetry between the two quarks, producing an effective light-front wave function that can be used for both form factors. With this input they compute A(Q^{2}) and D(Q^{2}) in three different holographic backgrounds and obtain curves that sit close to existing lattice data at pion mass 0.17 GeV. They also extract the associated mass and mechanical radii. The calculation therefore supplies a compact phenomenological bridge between holographic wave functions and the mechanical structure of the pion, and shows that the same construction works across several common holographic models.

Core claim

An effective light-front wave function of the form ψ(x,z) ∝ √[x(1−x)] φ(z)/√z · x(1−x), where φ(z) is the five-dimensional holographic pion wave function, yields gravitational form factors A(Q^{2}) and D(Q^{2}) whose shapes and normalisations agree with lattice QCD at mπ = 0.17 GeV (χ^{2}/dof ≈ 0.4 for A and ≈ 0.94 for D) in three distinct holographic models, while the original conformal wave function either diverges or fits the data more poorly.

What carries the argument

The effective light-front wave function (Eq. 39 with f(x) = x(1−x)). It converts the five-dimensional holographic mode into a two-body light-front amplitude that can be inserted into the standard light-front overlap integrals for A(Q^{2}) and D(Q^{2}), simultaneously enforcing energy-momentum conservation, endpoint asymptotics and quark–antiquark symmetry.

Load-bearing premise

The multiplicative factor x(1−x) that turns the conformal holographic wave function into a non-conformal effective wave function is chosen by hand to match known asymptotics and symmetry; it is not derived from the light-front Hamiltonian or the holographic action.

What would settle it

A lattice or experimental determination of A(Q^{2}) and D(Q^{2}) at the same pion mass that systematically lies outside the narrow band produced by the three holographic models once the single free scale of each model is fixed by A(Q^{2} ≈ 0.07 GeV^{2}) = 0.96.

Watch this falsifier — get emailed when new claim-graph text bears on it.

If this is right

  • The same effective wave function can be used to compute other pion observables (electromagnetic form factor, GPD moments, pressure and shear distributions) without introducing new free functions.
  • The mild mass dependence found for both A and D near the physical point suggests that mechanical radii extracted at mπ ≈ 0.17 GeV already approximate the physical values.
  • Because three different holographic backgrounds give nearly identical form factors, the results are largely independent of the precise infrared cutoff chosen in the dual gravity theory.
  • The construction supplies a practical route to gravitational form factors of other light mesons once their five-dimensional holographic wave functions are known.

Where Pith is reading between the lines

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

  • The success of a single multiplicative factor suggests that endpoint suppression, rather than detailed transverse dynamics, is the dominant correction needed to go from conformal holography to realistic light-front wave functions for the pion.
  • If higher Fock components remain small, the same framework could be extended to the kaon or to excited pion states with only minor changes to the five-dimensional mass term.
  • The large mechanical radius relative to the mass radius implies that the pressure distribution inside the pion is more extended than the energy density—a pattern that could be tested once lattice data at several Q^{2} become available for both form factors simultaneously.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit.

Referee Report

3 major / 5 minor

Summary. The manuscript constructs an effective light-front wave function for the pion by combining the five-dimensional holographic wave function φ(z) with a multiplicative factor f(x)=x(1-x), then inserts it into the standard light-front overlap formulas for the gravitational form factors A(Q^{2}) and D(Q^{2}). Three holographic backgrounds (soft-wall, deformed metric, and a modified warp-factor model) are used to generate φ(z); parameters are fixed to the pion mass and one lattice point A(0.07 GeV^{2})=0.96. The resulting curves are compared with lattice QCD data at m_π=0.17 GeV, yielding χ^{2}/dof ≈ 0.4 for A and ≈ 0.94 for D, and radii r_A ≈ 0.37 fm, r_D ≈ 0.94 fm are extracted. The authors present this agreement as nontrivial support for the phenomenological model.

Significance. Gravitational form factors encode the mechanical structure of hadrons and remain difficult to access experimentally; a controlled phenomenological bridge between holographic QCD and light-front overlaps is therefore of genuine interest. The paper’s strengths are the explicit comparison of three holographic models, the reporting of χ^{2}/dof, the demonstration that the original conformal wave function renders D divergent while the modified one does not, and the extraction of both mass and mechanical radii. If the construction can be shown to be robust under reasonable variations of the regulator f(x), the work would supply a useful, computationally inexpensive tool for exploring pion GFFs and related observables.

major comments (3)
  1. Section III, Eqs. (38)–(42): the factor f(x)=x(1-x) is introduced by hand after the conformal identification (37) fails for confining backgrounds. The only constraints cited are endpoint PDF asymptotics ∼(1-x)^{2} and x↔1-x symmetry. These leave a continuous family of admissible functions (e.g. [x(1-x)]^α with α≥1). No sensitivity study is performed. Because the same lattice point used to fix the holographic parameters also enters the χ^{2} comparison, and because f is precisely the regulator that renders the previously divergent D finite, the claim of “nontrivial support” for the model is not yet established. At minimum the authors must recompute A and D for at least two other members of the family and show that the lattice agreement survives.
  2. Section IV and the paragraph preceding Eq. (40): all three models are tuned to the identical lattice datum A(Q^{2}=0.07 GeV^{2})=0.96 (and, for model 3, to m_π). The subsequent curves for both A(Q^{2}) and D(Q^{2}) are then declared to agree with the same lattice set. While parameter fixing is common, the paper should quantify how much of the reported χ^{2}/dof is already guaranteed by this single-point constraint versus genuine dynamical prediction, especially for the D-term which was divergent without f.
  3. Section II, Eqs. (11)–(12) and the restriction to n=2: only the valence Fock component is retained. The authors note this limitation in the conclusions, yet the central claim that the construction supplies a viable phenomenological model for the full GFFs rests on this truncation. A brief estimate of the expected size of higher-Fock contributions (or a statement that they are absorbed into the effective f) is needed before the lattice agreement can be interpreted as support for the model rather than a successful two-body fit.
minor comments (5)
  1. Section IV, caption of Fig. 4 and surrounding text: the phrase “The blue curve The blue curve” is duplicated; clean up the prose.
  2. Equation (20) and the sentence after Eq. (8): the paper states that D(0)=-1 is imposed as a chiral-limit constraint, yet the numerical curves appear to emerge from the overlap integrals. Clarify whether D(0) is an output or an input normalization.
  3. Figures 2–5: lattice error bars are not visible on the red crosses; either enlarge them or state that they are smaller than the symbol size.
  4. References: several arXiv numbers and journal citations appear with future dates (2026); verify and correct the bibliographic data.
  5. Section III, after Eq. (41): the asymptotic argument that forces f(x) o1-x is phrased as “we find that f(x) o1-x”; a short explicit expansion of the integrand would make the logic transparent.

Circularity Check

2 steps flagged

Holographic scales are fixed to one lattice A point (plus mπ) before A(Q²)/D(Q²) curves are compared to the same lattice set; the enabling f(x)=x(1-x) is an acknowledged hand-chosen ansatz, not a derived uniqueness.

specific steps
  1. fitted input called prediction [Section IV, parameter fixing paragraph and comparison to lattice (Figs. 2–3, χ² statements)]
    "The parameter c0 = 0.46 GeV^{2} in model 1 … and the parameter c1 = -0.19 GeV^{2} in model 2 … are both determined by the lattice data point Aπ(Q^{2} = 0.07 GeV^{2}) = 0.96 (the first lattice data point). Model 3 has two parameters, k1 = 0.235 GeV and k2 = 3.763, which are determined by mπ = 0.17 GeV and the same lattice data point … The χ^{2}/dof values for models 1, 2, and 3 are 0.40, 0.37, and 0.37, respectively … These results indicate good agreement between the models and the lattice data and demonstrate that our adopted form of the light-front wave function provides a better description"

    Each model’s free scale(s) are fixed by the identical lattice A point that later enters the χ^{2} sum and the visual comparison. The value of A at that single point is therefore reproduced by construction; the overall magnitude of the fall-off of A (and, through the shared wave-function normalization, of D) is partially tuned to the same data set whose agreement is then advertised as independent support.

  2. other [Section III, Eqs. (38)–(42) and surrounding text; also Introduction “imposing … D(0)=-1”]
    "when we consider a background with confinement, Equation (37) no longer holds, and we instead assume it takes the form ψ(x,z)= au…f(x,z) au… we set f(x,z)=f(x) au… we choose the form of f(x): f(x)=x(1-x). au… Although our assumption in Equation (42) is consistent with some physical features, it is not rigorously derived but serves as an effective model. au… By imposing the fundamental constraints A(0)=1 au… and D(0)=-1 (chiral limit), we obtain the complete A(Q^{2}) and D(Q^{2})"

    The conformal identification produces a wave function that makes the D integral diverge; the multiplicative f that renders D finite is introduced by hand and fixed to one convenient member of a larger family consistent with the stated endpoint and symmetry constraints. D(0) is additionally set to the external chiral value -1. Both choices are load-bearing for the numerical D curve that is then compared with lattice, yet they are inputs rather than outputs of the holographic or light-front dynamics.

full rationale

The derivation is not closed by definition: the light-front overlap formulas (16)/(20) are independent, the five-dimensional φ(z) comes from solving the holographic Schrödinger equation in three different backgrounds, and D(Q²) is never used in the fit. Fitting one or two parameters to mπ and a single A lattice point, then obtaining acceptable χ² on the remaining A points plus the entire D curve, is ordinary phenomenology rather than a tautology. The paper itself flags that f(x) is effective, not first-principles. The only mild circularity is that the comparison dataset supplies the fit point whose agreement is then counted in the χ² and in the claim of “nontrivial support,” and that D(0)=-1 is imposed by hand as a chiral-limit constraint. Self-citations (model 3, earlier Deng-Hou papers) are present but not load-bearing, since models 1 and 2 give essentially identical results. Score 4 reflects partial engineering of the agreement without the central claim reducing to an identity.

Axiom & Free-Parameter Ledger

4 free parameters · 5 axioms · 1 invented entities

The central claim rests on standard light-front and holographic machinery plus one ad-hoc multiplicative factor and a handful of parameters fitted to lattice data. No new dynamical principle is introduced; the ledger therefore consists mainly of domain assumptions and free parameters that absorb non-perturbative physics.

free parameters (4)
  • c0 (soft-wall dilaton strength, model 1) = 0.46 GeV^{2}
    Fixed to the lattice point A(Q^{2}=0.07 GeV^{2})=0.96; value 0.46 GeV^{2}.
  • c1 (deformed-metric dilaton, model 2) = −0.19 GeV^{2}
    Fixed to the same lattice point; value −0.19 GeV^{2}.
  • k1, k2 (warp-factor parameters, model 3) = k1=0.235 GeV, k2=3.763
    Fixed simultaneously to mπ=0.17 GeV and the lattice A point; values 0.235 GeV and 3.763.
  • functional form f(x)=x(1−x) = x(1−x)
    Chosen by hand to enforce PDF endpoint behavior and x↔1−x symmetry; not derived from dynamics.
axioms (5)
  • domain assumption Gravitational form factors are given by the light-front overlap integrals (11)–(12) of the two-body LFWF.
    Standard LFQCD result used throughout §II; higher Fock components are neglected without quantitative estimate.
  • domain assumption The holographic coordinate z is identified with the light-front impact parameter ζ.
    Core LFHQCD dictionary invoked to equate Eqs. (16) and (35).
  • domain assumption In the chiral limit D(0)=−1.
    Taken from chiral perturbation theory and free-scalar results; imposed as a boundary condition.
  • ad hoc to paper The multiplicative factor f(x) may be taken independent of z and equal to x(1−x).
    Stated in §III after Eq. (38); motivated by asymptotics and symmetry but not derived from the action or Hamiltonian.
  • domain assumption Soft-wall or deformed AdS metrics with quadratic dilaton capture QCD confinement for the pion ground state.
    Standard bottom-up holographic assumption used to generate φ(z).
invented entities (1)
  • effective light-front wave function ψ(x,z) = (1/√(2π)) √[x(1−x)] φ(z)/√z · f(x) with f(x)=x(1−x) no independent evidence
    purpose: To extend the conformal holographic wave function to a non-conformal setting that yields finite D(Q^{2}) and improved A(Q^{2}).
    The factor f(x) is introduced by hand; no independent experimental or lattice handle is given outside the GFF fits themselves.

pith-pipeline@v1.1.0-grok45 · 19220 in / 3323 out tokens · 37297 ms · 2026-07-10T19:33:18.924388+00:00 · methodology

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read the original abstract

Understanding the internal structure of the pion-particularly the energy-momentum distributions of quarks and gluons and the internal mechanical properties encoded in its gravitational form factors-is a fundamental challenge in quantum chromodynamics (QCD). In this work, we study the gravitational form factors using light-front QCD (LFQCD), combined with the holographic QCD. Our main innovation is the introduction of an effective light-front wave function, with its five-dimensional component obtained from holographic QCD, which is then employed, within the light-front QCD framework, to calculate the pion's gravitational form factors $A(Q^2)$ and $D(Q^2)$ as well as its radius. Our computed pion gravitational form factors show good agreement with lattice QCD results, providing nontrivial support for the viability of our phenomenological model.

Figures

Figures reproduced from arXiv: 2607.07305 by Defu Hou, Jiali Deng, Xiaolong Wang, Yang Zhou.

Figure 1
Figure 1. Figure 1: FIG. 1 [PITH_FULL_IMAGE:figures/full_fig_p005_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2 [PITH_FULL_IMAGE:figures/full_fig_p006_2.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4 [PITH_FULL_IMAGE:figures/full_fig_p006_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: FIG. 5 [PITH_FULL_IMAGE:figures/full_fig_p006_5.png] view at source ↗

discussion (0)

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Reference graph

Works this paper leans on

49 extracted references · 49 canonical work pages · 44 internal anchors

  1. [1]

    Revisiting the mechanical properties of the nucleon

    C. Lorcé, H. Moutarde, and A. P. Trawiński, Revisiting the mechanical properties of the nucleon, Eur. Phys. J. C 79, 89 (2019) , arXiv:1810.09837 [hep-ph]

  2. [2]

    M. V. Polyakov and P. Schweitzer, Forces inside hadrons: pressure, surface tension, mechanical radius, and all that, Int. J. Mod. Phys. A 33, 1830025 (2018) , arXiv:1805.06596 [hep-ph]

  3. [3]

    Ji and C

    X. Ji and C. Yang, A journey of seeking pressure and forces in the nucleon, Nucl. Phys. B 1024, 117342 (2026) , arXiv:2508.16727 [hep-ph]

  4. [4]

    M. V. Polyakov, Generalized parton distributions and strong forces inside nucleons and nuclei, Phys. Lett. B 555, 57 (2003) , arXiv:hep-ph/0210165

  5. [5]

    Generalized Parton Distributions in the valence region from Deeply Virtual Compton Scattering

    M. Guidal, H. Moutarde, and M. Vanderhaeghen, Gen- eralized Parton Distributions in the valence region from Deeply Virtual Compton Scattering, Rept. Prog. Phys. 76, 066202 (2013) , arXiv:1303.6600 [hep-ph]

  6. [6]

    S. J. Brodsky, D. S. Hwang, B.-Q. Ma, and I. Schmidt, Light cone representation of the spin and orbital angular momentum of relativistic composite systems, Nucl. Phys. B 593, 311 (2001) , arXiv:hep-th/0003082

  7. [7]

    X. Cao, Y. Li, and J. P. Vary, Forces inside a strongly- coupled scalar nucleon, Phys. Rev. D 108, 056026 (2023) , arXiv:2308.06812 [hep-ph]

  8. [8]

    J. M. Maldacena, The Large N limit of superconformal field theories and supergravity, Adv. Theor. Math. Phys. 2, 231 (1998) , arXiv:hep-th/9711200

  9. [9]

    Anti De Sitter Space And Holography

    E. Witten, Anti de Sitter space and holography, Adv. Theor. Math. Phys. 2, 253 (1998), arXiv:hep-th/9802150

  10. [10]

    AdS/CFT Duality User Guide

    M. Natsuume, AdS/CFT Duality User Guide , Vol. 903 (2015) arXiv:1409.3575 [hep-th]

  11. [11]

    Hard Scattering and Gauge/String Duality

    J. Polchinski and M. J. Strassler, Hard scattering and gauge / string duality, Phys. Rev. Lett. 88, 031601 (2002), arXiv:hep-th/0109174

  12. [12]

    Gauge/string duality and scalar glueball mass ratios

    H. Boschi-Filho and N. R. F. Braga, Gauge / string duality and scalar glueball mass ratios, JHEP 05, 009 , arXiv:hep-th/0212207

  13. [13]

    Deng and D

    J. Deng and D. Hou, Exploring nucleon structure and the proton mass problem through holographic qcd, Phys. Rev. D 114, 026013 (2026)

  14. [14]

    Linear Confinement and AdS/QCD

    A. Karch, E. Katz, D. T. Son, and M. A. Stephanov, Linear confinement and AdS/QCD, Phys. Rev. D 74, 015005 (2006) , arXiv:hep-ph/0602229

  15. [15]

    S. J. Brodsky, G. F. de Teramond, H. G. Dosch, and J. Erlich, Light-Front Holographic QCD and Emerging Confinement, Phys. Rept. 584, 1 (2015), arXiv:1407.8131 [hep-ph]

  16. [16]

    Z.-R. Zhu, M. Sun, R. Zhou, Z. Ma, and J. Han, Heavy quarkonium spectral function in the spinning black hole background, Eur. Phys. J. C 84, 1252 (2024) , arXiv:2406.19661 [hep-ph]

  17. [17]

    Proton Structure Functions from an AdS/QCD model with a deformed background

    E. Folco Capossoli, M. A. Martín Contreras, D. Li, A. Vega, and H. Boschi-Filho, Proton structure functions from an AdS/QCD model with a deformed background, Phys. Rev. D 102, 086004 (2020) , arXiv:2007.09283 [hep- ph]

  18. [18]

    X. Chen, B. Yu, P.-C. Chu, and X.-h. Li, Studying the potential of QQq at finite temperature in a holo- graphic model *, Chin. Phys. C 46, 073102 (2022) , arXiv:2112.06234 [hep-ph]

  19. [19]

    The nucleon structure from an AdS/QCD model in the Veneziano limit

    J. Deng and D. Hou, Nucleon structure from an AdS/QCD model in the Veneziano limit, Phys. Rev. D 112, 036011 (2025) , arXiv:2502.00771 [nucl-th]

  20. [20]

    D. A. Pefkou, D. C. Hackett, and P. E. Shanahan, Gluon gravitational structure of hadrons of different spin, Phys. Rev. D 105, 054509 (2022) , arXiv:2107.10368 [hep-lat]

  21. [21]

    D. C. Hackett, P. R. Oare, D. A. Pefkou, and P. E. Shanahan, Gravitational form factors of the pion from lattice QCD, Phys. Rev. D 108, 114504 (2023) , arXiv:2307.11707 [hep-lat]

  22. [22]

    Gravitational form factors of light mesons

    A. Freese and I. C. Cloët, Gravitational form factors of light mesons, Phys. Rev. C 100, 015201 (2019) , [Erra- tum: Phys.Rev.C 105, 059901 (2022)], arXiv:1903.09222 [nucl-th]

  23. [23]

    S. J. Brodsky and G. F. de Teramond, Light-Front Dy- namics and AdS/QCD Correspondence: Gravitational Form Factors of Composite Hadrons, Phys. Rev. D 78, 025032 (2008) , arXiv:0804.0452 [hep-ph]

  24. [24]

    A. F. Krutov and V. E. Troitsky, Pion gravitational form factors in a relativistic theory of composite particles, Phys. Rev. D 103, 014029 (2021) , arXiv:2010.11640 [hep- ph]

  25. [25]

    Gluon Gravitational Form Factors at Large Momentum Transfer

    X.-B. Tong, J.-P. Ma, and F. Yuan, Gluon gravitational form factors at large momentum transfer, Phys. Lett. B 823, 136751 (2021) , arXiv:2101.02395 [hep-ph]

  26. [26]

    Z. Xing, M. Ding, and L. Chang, Glimpse into the pion gravitational form factor, Phys. Rev. D 107, L031502 (2023), arXiv:2211.06635 [hep-ph]

  27. [27]

    W.-Y. Liu, E. Shuryak, and I. Zahed, Pion gravitational form factors in the QCD instanton vacuum. II, Phys. Rev. D 110, 054022 (2024) , arXiv:2405.16269 [hep-ph]

  28. [28]

    Gravitational form factors of pion from top-down holographic QCD

    D. Fujii, A. Iwanaka, and M. Tanaka, Gravitational form factors of pion from top-down holographic QCD, Phys. Rev. D 110, L091501 (2024) , arXiv:2407.21113 [hep-ph]

  29. [29]

    Gravitational form factors of pion in a nonlocal quark model

    V. Voronin, Gravitational form Factors of Pion in a Nonlocal Quark Model, Phys. Part. Nucl. Lett. 23, 147 (2026), arXiv:2507.06025 [hep-ph]

  30. [30]

    S. J. Brodsky and G. F. de Téramond, Light-front hadron dynamics and AdS/CFT correspondence, Phys. Lett. B 582, 211 (2004) , arXiv:hep-th/0310227

  31. [31]

    H. G. Dosch, G. F. de Téramond, T. Liu, R. S. Sufian, S. J. Brodsky, and A. Deur (HLFHS), To- wards a single scale-dependent Pomeron in holographic light-front QCD, Phys. Rev. D 105, 034029 (2022) , arXiv:2201.09813 [hep-ph]

  32. [32]

    S. J. Brodsky and G. F. de Teramond, Hadronic spectra and light-front wavefunctions in holographic QCD, Phys. Rev. Lett. 96, 201601 (2006) , arXiv:hep-ph/0602252. 9

  33. [33]

    S. J. Brodsky, H.-C. Pauli, and S. S. Pinsky, Quan- tum chromodynamics and other field theories on the light cone, Phys. Rept. 301, 299 (1998) , arXiv:hep- ph/9705477

  34. [34]

    P. A. M. Dirac, Forms of Relativistic Dynamics, Rev. Mod. Phys. 21, 392 (1949)

  35. [35]

    J. F. Donoghue and H. Leutwyler, Energy and momen- tum in chiral theories, Z. Phys. C 52, 343 (1991)

  36. [36]

    W.-Y. Liu, E. Shuryak, C. Weiss, and I. Zahed, Pion gravitational form factors in the QCD instanton vacuum. I, Phys. Rev. D 110, 054021 (2024) , arXiv:2405.14026 [hep-ph]

  37. [37]

    Particle seismology: mechanical and gravitational properties from parton-hadron duality

    E. Ruiz Arriola and W. Broniowski, Particle seismology: mechanical and gravitational properties from parton- hadron duality, in 65. Jubilee Cracow School of Theo- retical Physics: Fundamental Interactions – 65 years of the Cracow School (2026) arXiv:2604.26537 [hep-ph]

  38. [38]

    S. J. Brodsky and G. F. de Teramond, Light-Front Dy- namics and AdS/QCD Correspondence: The Pion Form Factor in the Space- and Time-Like Regions, Phys. Rev. D 77, 056007 (2008) , arXiv:0707.3859 [hep-ph]

  39. [39]

    G. F. de Teramond, H. G. Dosch, and S. J. Brod- sky, Kinematical and Dynamical Aspects of Higher-Spin Bound-State Equations in Holographic QCD, Phys. Rev. D 87, 075005 (2013) , arXiv:1301.1651 [hep-ph]

  40. [40]

    Generalized Parton Distributions at x->1

    F. Yuan, Generalized parton distributions at x — > 1, Phys. Rev. D 69, 051501 (2004) , arXiv:hep-ph/0311288

  41. [41]

    S. J. Brodsky and F. Yuan, Single transverse-spin asym- metries at large-x, Phys. Rev. D 74, 094018 (2006) , arXiv:hep-ph/0610236

  42. [42]

    M. B. Hecht, C. D. Roberts, and S. M. Schmidt, Valence quark distributions in the pion, Phys. Rev. C 63, 025213 (2001), arXiv:nucl-th/0008049

  43. [43]

    Soft-Gluon Resummation and the Valence Parton Distribution Function of the Pion

    M. Aicher, A. Schafer, and W. Vogelsang, Soft-gluon resummation and the valence parton distribution func- tion of the pion, Phys. Rev. Lett. 105, 252003 (2010) , arXiv:1009.2481 [hep-ph]

  44. [44]

    Basic features of the pion valence-quark distribution function

    L. Chang, C. Mezrag, H. Moutarde, C. D. Roberts, J. Rodríguez-Quintero, and P. C. Tandy, Basic features of the pion valence-quark distribution function, Phys. Lett. B 737, 23 (2014) , arXiv:1406.5450 [nucl-th]

  45. [45]

    C. Chen, L. Chang, C. D. Roberts, S. Wan, and H.- S. Zong, Valence-quark distribution functions in the kaon and pion, Phys. Rev. D 93, 074021 (2016) , arXiv:1602.01502 [nucl-th]

  46. [46]

    Light and heavy mesons in a soft-wall holographic approach

    T. Branz, T. Gutsche, V. E. Lyubovitskij, I. Schmidt, and A. Vega, Light and heavy mesons in a soft-wall holographic approach, Phys. Rev. D 82, 074022 (2010) , arXiv:1008.0268 [hep-ph]

  47. [47]

    Hadronic Spectra from Deformed AdS Backgrounds

    E. Folco Capossoli, M. A. Martín Contreras, D. Li, A. Vega, and H. Boschi-Filho, Hadronic spectra from deformed AdS backgrounds, Chin. Phys. C 44, 064104 (2020), arXiv:1903.06269 [hep-ph]

  48. [48]

    J. Deng, D. Hou, X. Wang, and Y. Zhou, Pion structure in Holographic QCD (2026), arXiv:2606.05583 [hep-ph]

  49. [49]

    Hadron tomography by generalized distribution amplitudes in pion-pair production process $\gamma^* \gamma \rightarrow \pi^0 \pi^0 $ and gravitational form factors for pion

    S. Kumano, Q.-T. Song, and O. V. Teryaev, Hadron to- mography by generalized distribution amplitudes in pion- pair production process γ∗γ → π0π0 and gravitational form factors for pion, Phys. Rev. D 97, 014020 (2018) , arXiv:1711.08088 [hep-ph]