REVIEW 3 major objections 6 minor 42 references
Positive solutions to fractional $p$-Laplacian Choquard equation on lattice graphs
T0 review · 3 major / 6 minor · reviewed 2026-08-06 · deepseek-v4-flash
Pith's one-line read Under mild growth conditions and a coercive potential, the fractional p-Laplacian Choquard equation on Z^d has a strictly positive solution; adding a monotonicity condition gives a positive ground state.
desk verdict Plausible first combination of fractional p-Laplacian and Choquard on lattice graphs, but the (PS)_c proof rests on a false convexity inequality. 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 object carrying the argument is the energy functional $J_{s,p}(u)=\frac{1}{p}\int(|\nabla^s u|^p + h(x)|u|^p)\,d\mu - \frac{1}{2}\int (R_\alpha * F(u))F(u)\,d\mu$ on the fractional Sobolev space $H^{s,p}$, the completion of compactly supported functions in the norm $(\int(|\nabla^s u|^p + h(x)|u|^p)\,d\mu)^{1/p}$. Three tools make the variational proof work: the compact embedding $H^{s,p}\hookrightarrow\ell^q$ for every $q\ge p$, imported from the fractional Sobolev framework for locally finite graphs; the discrete Hardy-Littlewood-Sobolev inequality controlling the convolution term; and a convexity inequality for the fractional $p$-Laplacian that converts weak convergence into strong convergence in the compactness step. The positivity mechanism is the truncation $\tilde{f}(t)=0$ for $t<0$, with a lemma showing that any nontrivial weak solution of the truncated equation is strictly positive.
What would settle it
Find a bounded sequence in $H^{s,p}$ for a coercive potential $h$ that escapes to infinity and has no strongly convergent subsequence in $\ell^q$ for some $q\ge p$; such a sequence would falsify the compact embedding lemma and collapse the compactness argument behind Theorems 1.1 and 1.2.
Extended reading notes
Core claim
The central claim is that the equation $(-\Delta)_p^s u + h(x)|u|^{p-2}u = (R_\alpha * F(u))f(u)$ on $\mathbb{Z}^d$ has a strictly positive solution whenever the potential $h$ is bounded below by $h_0>0$ and tends to infinity as $|x|\to\infty$, and $f$ satisfies the stated growth and superlinearity conditions; if in addition the ratio defining (f4) is strictly increasing in $t$, a positive ground state solution exists. The proof constructs the energy functional on the weighted fractional Sobolev space $H^{s,p}$, shows it has mountain-pass geometry and satisfies the compactness condition via the compact embedding $H^{s,p}\hookrightarrow\ell^q$, then uses the Nehari manifold to select a minimizer. Positivity is obtained by truncating $f$ to vanish for negative arguments; a weak solution of the truncated equation is shown to satisfy $u>0$ everywhere on $\mathbb{Z}^d$.
Load-bearing premise
The argument rests on the fractional Sobolev framework of an unpublished preprint, specifically the compact embedding $H^{s,p}$ into $\ell^q$ and a convexity inequality for the fractional $p$-Laplacian, plus the discrete Hardy-Littlewood-Sobolev inequality; if those tools fail for the integer lattice, the existence theorems do not follow.
Editorial extensions
If this is right
- For every integer lattice $\mathbb{Z}^d$ with any $s\in(0,1)$, $p\ge 2$, and $\alpha\in(0,d)$, the equation admits a strictly positive solution under hypotheses (h1), (h2), (f1)-(f3).
- When (f4) is added, that solution is a ground state: it minimizes $J_{s,p}$ over the Nehari manifold and hence among all nontrivial weak solutions.
- The critical value produced by the mountain-pass theorem is positive, so the solution obtained is genuinely nonzero.
- The compactness tools used are stated for locally finite graphs, so the existence mechanism is not tied to the specific geometry of $\mathbb{Z}^d$ and can be expected to transfer to other coercive lattice graphs.
Reading between the lines
- Testing (f4) on pure power nonlinearities $f(t)=t^{q-1}$ would show exactly which powers $q$ admit the ground-state conclusion; this check is left implicit in the paper.
- The same mountain-pass construction should work on other locally finite graphs with a coercive potential and the same kernel growth, provided the discrete Hardy-Littlewood-Sobolev inequality and the convexity inequality hold; this is an extension, not a paper claim.
- Because every nontrivial solution is shown to be strictly positive, the method cannot generate sign-changing or nodal solutions; a different minimax scheme would be needed for those.
- A finite-box numerical experiment on $\mathbb{Z}^d$ with periodic boundary conditions could test whether approximate mountain-pass solutions remain positive and whether their ground-state energy converges as the box grows.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper studies the fractional p-Laplacian Choquard equation (-Δ)_p^s u + h(x)|u|^{p-2}u = (R_α * F(u)) f(u) on the lattice graph Z^d, with s∈(0,1), p≥2, α∈(0,d). Under growth and decay assumptions on the potential h and the nonlinearity f, Theorem 1.1 asserts existence of a strictly positive solution via the mountain-pass theorem, and Theorem 1.2 asserts existence of a positive ground state solution via the Nehari manifold method. The arguments are standard variational ones: compact embedding of the fractional Sobolev space H^{s,p} into ℓ^q, the discrete Hardy-Littlewood-Sobolev inequality, verification of the (PS)_c condition, mountain-pass geometry, Nehari minimization, and a positivity argument for nonnegative weak solutions.
Significance. If the gaps identified below are repaired, the paper would provide a reasonable first extension of Choquard-type existence results to the discrete fractional p-Laplacian setting on lattice graphs. The variational structure is appropriate, the assumptions are explicit, and the two main theorems give concrete existence statements with a clear separation between the mountain-pass result and the Nehari ground-state result. The main mathematical content is a direct adaptation of known continuous counterparts, so the novelty is moderate; the paper does not ship machine-checked proofs or parameter-free derivations, but the proof strategy is standard and, after correction, likely sound.
major comments (3)
- [Section 3, Lemma 3.2] The displayed inequality after "By Lemma 15 in [39]" is false as written. The proof claims ∥u_n−u∥_{H^{s,p}}^p ≤ 2^{p−2}p(Term1+Term2), where Term1 and Term2 are the two inner-product expressions just defined. For the monotone operator A(w)=(−Δ)_p^s w + h|w|^{p−2}w, the correct convexity inequality is ∥u_n−u∥^p ≤ C⟨A(u_n)−A(u), u_n−u⟩ = C(Term1−Term2). A concrete counterexample to the printed form is obtained for p=2, h≡1, taking u=3φ and u_n=φ, where φ is the indicator function of a finite set S in Z^d. Then ∥u_n−u∥_{H^{s,p}}^2 = 4∥φ∥_{H^1}^2 > 0, while Term1+Term2 = ⟨A(φ)+A(3φ), φ−3φ⟩ = −8∥φ∥_{H^1}^2, so the right-hand side is negative. The intended conclusion ∥u_n−u∥→0 still follows if the sign is corrected, because both Term1 and Term2 have already been shown to be o(1). The author must correct the sign and either prove the needed inequality or give the exact statement of Lemma 15 of [39], which is currently an unpublished preprint.
- [Section 4, Lemma 4.4] The sentence "by Lemma 4.1, we have ∥u_n∥_{H^{s,p}} ≥ η > 0, which implies that u_0 ≠ 0" is not justified by the cited lemma. A bounded sequence in a Banach space can have norms bounded below and still converge weakly to zero, so the implication requires an additional argument. In this setting it can be obtained from the Nehari relation: since u_n ∈ M_{s,p}, ∥u_n∥_{H^{s,p}}^p = ∫(R_α*F(u_n^+))f(u_n^+)u_n^+ ≤ C(∥u_n∥_p^p + ∥u_n∥_p^τ), while Lemma 4.1 gives ∥u_n∥_{H^{s,p}} ≥ η; these inequalities force ∥u_n∥_p ≥ c>0, and then the strong convergence u_n→u_0 in ℓ^p from Lemma 2.7 yields u_0≠0. This step is load-bearing for the Nehari minimization, so the proof should be completed explicitly.
- [Sections 2 and 3] Two load-bearing results are taken from the unpublished preprint [39]: the compact embedding H^{s,p}↪ℓ^q for q≥p (Lemma 2.7) and the convexity inequality used in Lemma 3.2. Because [39] is not publicly available in a peer-reviewed venue and because the quotation of the latter inequality is demonstrably wrong as written, the paper is not self-contained at its critical point. The author should either prove these results (the convexity inequality is a short standard argument from the monotonicity of t↦|t|^{p−2}t) or reproduce the precise statements and provide a verifiable reference. This is necessary for the (PS)_c condition and hence for Theorem 1.1.
minor comments (6)
- [Section 4, Lemma 4.3] The statement "for any u ∈ H^{s,p}\{0}, there exists a unique t_u > 0 such that t_u u ∈ M_{s,p}" is false after the reduction f(t)=0 for t<0: if u≤0 and u≠0, then u^+=0, so J_{s,p}(tu) = (t^p/p)∥u∥^p has no maximum on (0,∞). The lemma should be restricted to u with u^+≠0; the later applications in Lemma 4.4 and Lemma 4.5 only require that case, since u_0∈M_{s,p} implies u_0^+≠0.
- [Section 2, Lemma 2.9] In the proof of strict positivity, the assertion "we have (−Δ)_p^s u(x_0)=0" is not immediate and needs a short justification: since u≥0 and u(x_0)=0 is a minimum, the left-hand side is nonpositive, while the right-hand side of the equation is nonnegative, so both must vanish.
- [Section 2, paragraph before Lemma 2.5] The displayed definition of R_α contains a stray expression "2π (d_j/ℓ_j) → k_j, ℓ_j = 0,1,...,d_j−1, as d_j → ∞" that is not defined or used and appears to be a leftover from a discretization argument; it should be removed or clarified.
- [Section 2, Lemma 2.8] The proof of Lemma 2.8 uses the notation u_0 for the weak limit, while the statement of the lemma uses u; this is confusing and should be made consistent.
- [Throughout] There are several typos and formatting issues, including "p-Laplacain" in the introduction, "forth inequality" instead of "fourth inequality" in the proof of Lemma 3.1(i), and missing diacritics in "Hölder" and "Laplacian" in some places. These should be corrected in a revision.
- [References] Reference [39] is an arXiv preprint; if it has been accepted for publication by the time of revision, the citation should be updated. The same applies to other arXiv-only references that may have appeared in journals.
Circularity Check
No significant circularity: the existence proofs are a standard variational argument whose cited background lemmas are independent of the target theorems.
full rationale
The paper's derivation chain is a conventional mountain-pass / Nehari-manifold argument. The target results, Theorems 1.1 and 1.2, are not built from fitted parameters, hidden definitions of the conclusion, or a self-citation chain that forces the answer. The reduction to f(t)=0 for t<0 and the use of u+ are standard truncation arguments, not a restatement of the desired positivity conclusion; Lemma 2.9 then genuinely derives strict positivity from the equation. The compact embedding (Lemma 2.7) and the convexity inequality used in Lemma 3.2 are cited from the prior work [39] by Zhang, Lin and Yang, which is not authored by the present author and is not shown to contain the target result. The discrete HLS inequality is cited to standard sources, including one self-cited paper, but it is an external classical inequality. The one omitted proof, Lemma 2.6, is attributed to the author's own [33, Lemma 2.5]; this is a minor self-citation and the lemma is a routine consequence of (f3), so it is not load-bearing in the sense of making the main claim equivalent to its input. The possible sign error in the displayed use of Lemma 15 in [39] noted by the skeptic is a correctness risk, not a circularity: a false or misquoted external lemma would invalidate the proof, but it would not make the theorem an input of the argument. Therefore, no circular step can be exhibited from the paper's own equations, and the derivation is self-contained modulo independently stated background results. Score 0 is appropriate because there is no definitional identity, fitted-input-as-prediction, or self-citation chain carrying the central claim.
Assumptions & free parameters
assumptions (4)
- domain assumption Discrete Hardy-Littlewood-Sobolev inequality for the kernel R_α on Z^d
- domain assumption Fractional Sobolev space framework on Z^d: reflexivity of W^{s,p}, compact embedding Hs,p into ℓ^q, integration by parts formula, and the convexity inequality of Lemma 15 of [39]
- domain assumption The Green's function R_α has the stated Fourier representation and decays like |x-y|^{-(d-α)}
- standard math Standard mountain-pass theorem and Nehari manifold method in reflexive Banach spaces
Cite this review
Pith. "Pith review of Positive solutions to fractional $p$-Laplacian Choquard equation on lattice graphs." pith.science (2026). https://pith.science/paper/EDIQ7IID
@misc{pith2026250722552,
author = {Pith},
title = {Pith review of: Positive solutions to fractional $p$-Laplacian Choquard equation on lattice graphs},
year = {2026},
howpublished = {\url{https://pith.science/paper/EDIQ7IID}},
note = {Machine review of arXiv:2507.22552}
}
abstract
In this paper, we study the fractional $p$-Laplacian Choquard equation $$ (-\Delta)_{p}^{s} u+h(x)|u|^{p-2} u=\left(R_{\alpha} *F(u)\right)f(u) $$ on lattice graphs $\mathbb{Z}^d$, where $s\in(0,1)$, $ p\geq 2$, $\alpha \in(0, d)$ and $R_\alpha$ represents the Green's function of the discrete fractional Laplacian that behaves as the Riesz potential. Under suitable assumptions on the potential function $h$, we first prove the existence of a strictly positive solution by the mountain-pass theorem for the nonlinearity $f$ satisfying some growth conditions. Moreover, if we add some monotonicity condition, we establish the existence of a positive ground state solution by the method of Nehari manifold.
Reference graph
Works this paper leans on
-
[39]
Fractional Sobolev spaces and fractional $p$-Laplace equations on locally finite graphs
M. Zhang, Y. Lin and Y. Yang, Fractional Sobolev spaces and fractional p-Laplace equations on locally finite graphs. arXiv:2506.07694
- [1]
- [2]
-
[3]
M. Ghimenti, J. Van Schaftingen, Nodal solutions for the Choquard equation. J. Funct. Anal. 271 (2016), 107-135
work page 2016
-
[4]
A. Grigor’yan, Y. Lin and Y. Yang, Existence of positive solutions to some nonlinear equations on locally finite graphs. Sci. China Math. 60 (2017) 1311-1324
work page 2017
-
[5]
L. Guo, T. Hu, Existence and asymptotic behavior of the least energy solutions for fractional Choquard equations with potential well. Math. Methods Appl. Sci. 41 (2018), no. 3, 1145-1161
work page 2018
-
[6]
F. Han, L. Wang, Positive solutions to discrete harmonic functions in unbounded cylinders. J. Korean Math. Soc. 61 (2024), no. 2, 377-393
2024
-
[7]
B. Hua, R. Li and L. Wang, A class of semilinear elliptic equations on groups of polynomial. J. Differential Equations 363 (2023) 327-349
work page 2023
Show all 42 references
-
[8]
R. Li, L. Wang, The existence and convergence of solutions for the nonlinear Choquard equations on groups of polynomial growth. arXiv: 2208.00236
-
[9]
Li, The existence of positive ground state solutions for the Choquard type equation on groups of polynomial growth
R. Li, The existence of positive ground state solutions for the Choquard type equation on groups of polynomial growth. Discrete Contin. Dyn. Syst. 45 (2025), no. 2, 665-685
2025
-
[10]
Lizama, L
C. Lizama, L. Roncal, H¨ older-Lebesgue regularity and almost periodicity for semidiscrete equations with a fractional Laplacian. Discrete Contin. Dyn. Syst. Ser. A 38(3) (2018) 1365-1403
2018
-
[11]
Liang, S
S. Liang, S. Shi and V. Thin Nguyen, Multiplicity and concentration properties for fractional Choquard equations with exponential growth. J. Geom. Anal. 34 (2024), no. 12, Paper No. 367, 35 pp
2024
-
[12]
Y. Lin, Y. Yang, Calculus of variations on locally finite graphs. Rev. Mat. Complut. 35 (2022) 791-813
2022
-
[13]
Liu, The positive solution for the nonlinear p-Laplacian Choquard equation on lattice graphs
Y. Liu, The positive solution for the nonlinear p-Laplacian Choquard equation on lattice graphs. J. Fixed Point Theory Appl. 27 (2025), no. 2, Paper No. 36, 17 pp
2025
-
[14]
Y. Liu, M. Zhang, Existence of solutions for nonlinear biharmonic Choquard equations on weighted lattice graphs. J. Math. Anal. Appl. 534 (2024), no. 2, Paper No. 128079, 18 pp
2024
-
[15]
Y. Liu, M. Zhang, The ground state solutions to a class of biharmonic Choquard equations on weighted lattice graphs. Bull. Iranian Math. Soc. 50 (2024), no. 1, Paper No. 12, 17 pp
2024
-
[16]
L¨ u, Existence and concentration of solutions for a nonlinear Choquard equation
D. L¨ u, Existence and concentration of solutions for a nonlinear Choquard equation. Mediterr. J. Math. 12 (2015), no. 3, 839-850
2015
-
[17]
L. Ma, Z. Zhang, Symmetry of positive solutions for Choquard equations with fractional p-Laplacian. Nonlinear Anal. 182 (2019), 248-262
2019
-
[18]
Michelitsch, B
T. Michelitsch, B. Collet, A. Riascos, A. Nowakowski and F. Nicolleau, Recurrence of random walks with long-range steps generated by fractional Laplacian matrices on regular networks and simple cubic lattices. J. Phys. A 50 (2017), no. 50, 505004, 29 pp
2017
-
[19]
Moroz, J
V. Moroz, J. Van Schaftingen, Ground states of nonlinear Choquard equations: existence, qualitative properties and decay asymptotics. J. Funct. Anal. 265 (2013), 153-184
2013
-
[20]
Moroz, J
V. Moroz, J. Van Schaftingen, Existence of groundstates for a class of nonlinear Choquard equations. Trans. Amer. Math. Soc. 367 (2015), 6557-6579
2015
-
[21]
M. Ri, Y. Li, Ground state solution for fractional p-Choquard equations with upper critical exponent. J. Math. Anal. Appl. 534 (2024), no. 1, Paper No. 128073, 15 pp
2024
-
[22]
Sakuma, Infinitely many solutions for p-fractional Choquard type equations involving general nonlocal nonlinear- ities with critical growth via the concentration compactness method
M. Sakuma, Infinitely many solutions for p-fractional Choquard type equations involving general nonlocal nonlinear- ities with critical growth via the concentration compactness method. J. Differential Equations 383 (2024), 163-189
2024
-
[23]
Shang, Existence and concentration of positive solutions for a p-fractional Choquard equation
X. Shang, Existence and concentration of positive solutions for a p-fractional Choquard equation. AIMS Math. 6 (2021), no. 11, 12929-12951
2021
-
[24]
M. Shao, Y. Yang and L. Zhao, Sobolev spaces on locally finite graphs. Proc. Amer. Math. Soc. 153 (2025), no. 2, 693-708
2025
-
[25]
Wang, Eigenvalue estimates for the fractional Laplacian on lattice subgraphs
J. Wang, Eigenvalue estimates for the fractional Laplacian on lattice subgraphs. arXiv: 2303.15766
-
[26]
Wang, The ground state solutions to discrete nonlinear Choquard equations with Hardy weights
L. Wang, The ground state solutions to discrete nonlinear Choquard equations with Hardy weights. Bull. Iranian Math. Soc. 49 (2023), no. 3, Paper No. 30, 29 pp
2023
-
[27]
Wang, The ground state solutions of discrete nonlinear Schr¨ odinger equations with Hardy weights
L. Wang, The ground state solutions of discrete nonlinear Schr¨ odinger equations with Hardy weights. Mediterr. J. Math. 21 (2024), no. 3, Paper No.78
2024
-
[28]
Wang, Solutions to discrete nonlinear Kirchhoff-Choquard equations
L. Wang, Solutions to discrete nonlinear Kirchhoff-Choquard equations. Bull. Malays. Math. Sci. Soc. 47 (2024), no. 5, Paper No. 138
2024
-
[29]
Wang, A class of p-Laplacian equations on lattice graphs
L. Wang, A class of p-Laplacian equations on lattice graphs. Acta Math. Sin. (Engl. Ser.) 41 (2025), no. 5, 1418-1430
2025
-
[30]
Wang, Sign-changing solutions to discrete nonlinear logarithmic Kirchhoff equations
L. Wang, Sign-changing solutions to discrete nonlinear logarithmic Kirchhoff equations. J. Geom. Anal. 35 (2025), no. 9, Paper No. 274
2025
-
[31]
Wang, Solutions to discrete fractional Schr¨ odinger equations
L. Wang, Solutions to discrete fractional Schr¨ odinger equations. Bull. Iranian Math. Soc. 51 (2025), no. 4, Paper No. 49. 16
2025
-
[32]
Wang, Solutions to discrete nonlinear Kirchhoff-Choquard equations with power nonlinearity
L. Wang, Solutions to discrete nonlinear Kirchhoff-Choquard equations with power nonlinearity. J Elliptic Parabol Equ (2025). https://doi.org/10.1007/s41808-025-00363-2
2025 doi
-
[33]
Wang, p-Laplacian equations with general Choquard nonlinearity on lattice graphs
L. Wang, p-Laplacian equations with general Choquard nonlinearity on lattice graphs. arXiv:2408.10584
-
[34]
J. Wang, Y. Zhu and K. Wang, Existence and asymptotical behavior of the ground state solution for the Choquard equation on lattice graphs. Electron. Res. Arch. 31 (2023), no. 2, 812-839
2023
-
[35]
J. Yang, H. Chen, Semiclassical states for fractional Choquard equations with a potential well. Math. Methods Appl. Sci. 48 (2025), no. 12, 12292-12308
2025
-
[36]
Z. Yang, F. Zhao, Multiplicity and concentration behaviour of solutions for a fractional Choquard equation with critical growth. Adv. Nonlinear Anal. 10 (2021), no. 1, 732-774
2021
-
[37]
Y. Yang, L. Zhao, Normalized solutions for nonlinear Schr¨ odinger equations on graphs. J. Math. Anal. Appl. 536 (2024), no. 1, Paper No. 128173, 17 pp
2024
-
[38]
Zhang, Y
M. Zhang, Y. Lin and Y. Yang, Fractional Laplace operator and related Schr¨ odinger equations on locally finite graphs. arXiv:2408.02902
-
[40]
Zhang, X
X. Zhang, X. Sun, S. Liang and V. Thin Nguyen, Existence and concentration of solutions to a Choquard equation involving fractional p-Laplace via penalization method. J. Geom. Anal. 34 (2024), no. 3, Paper No. 90, 59 pp
2024
-
[41]
Zhang, S
W. Zhang, S. Yuan and L. Wen, Existence and concentration of ground-states for fractional Choquard equation with indefinite potential. Adv. Nonlinear Anal. 11 (2022), no. 1, 1552-1578
2022
-
[42]
S. Zhao, Y. Yu, Sign-changing solutions for a fractional Choquard equation with power nonlinearity. Nonlinear Anal. 221 (2022), Paper No. 112917, 18 pp. Email address: wanglidan@ujs.edu.cn Lidan W ang: School of Mathematical Sciences, Jiangsu University, Zhenjiang 212013, Peop...
2022
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