REVIEW 4 major objections 4 minor 1 cited by
log-concavity of eigenfunction and Brunn-Minkowski inequality of eigenvalue for weighted p-Laplace operator
T0 review · 4 major / 4 minor · reviewed 2026-08-12 · deepseek-v4-flash
Pith's one-line read This paper proves that on a bounded C^2 convex domain, the first positive eigenfunction of the weighted p-Laplace operator is log-concave, and that the first eigenvalue obeys a Brunn-Minkowski-type inequality under Minkowski combinations…
desk verdict Plausible extension of log-concavity to the Gaussian p-Laplace for all p>1, but the Brunn-Minkowski proof leans on an unproved convex inf-convolution lemma and the manuscript needs a careful sign cleanup. read the letter →
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
The reading
What carries the argument
The load-bearing objects are the weighted $p$-Laplace operator $\Delta_{p,\gamma}u=\operatorname{div}(|\nabla u|^{p-2}\nabla u)-\langle x,\nabla u\rangle |\nabla u|^{p-2}$, the log-transform $w=-\ln u$, and the inf-convolution of the convex functions $w_i$ on the Minkowski sum $\Omega_t=(1-t)\Omega_0+t\Omega_1$. On the eigenfunction side, the argument runs through a regularized variational problem whose solutions are smooth in the interior, to which a concavity maximum principle applies; uniform $C^{1,\beta}$ and $C^{2,\beta}$ estimates let the regularization converge to the weak solution and carry convexity of the regularized logarithm to $w$. On the eigenvalue side, the Brunn-Minkowski inequality is transported via inf-convolution: the paper defines $\tilde w(x)=\inf\{(1-t)w_0(x_0)+tw_1(x_1):x=(1-t)x_0+tx_1\}$, shows $\tilde w$ is $C^1$, obtains the comparison $\Delta_p\tilde w\le(1-t)\Delta_p w_0+t\Delta_p w_1$ in the appropriate sense, and converts this into a bound on the Rayleigh quotient of the trial function $e^{-\tilde w}$. The transfer relies on convex duality results from [22] and on comparison lemmas from [11] originally stated for strictly concave sup-convolutions, applied here to the convex $w_i$ after an implicit duality step.
What would settle it
Compute $\lambda_{p,\gamma}$ numerically for two concentric balls in $\mathbb R^2$ (or a ball and an ellipse) for several $p>1$, and check whether $\lambda_{p,\gamma}(\Omega_t)\le(1-t)\lambda_{p,\gamma}(\Omega_0)+t\lambda_{p,\gamma}(\Omega_1)$; a violation for any $C^2$ convex bodies refutes Theorem 1.2. For Theorem 1.1, solve (1.1) on a $C^2$ convex domain with a flat boundary segment and inspect the Hessian of $w=-\ln u$ at points where $\nabla u\neq0$; one negative eigenvalue of $D^2w$ refutes log-concavity.
Extended reading notes
Core claim
The central claim of the paper is that log-concavity and Brunn-Minkowski convexity survive the passage from the linear Laplacian to the weighted $p$-Laplace operator. On a bounded convex domain with $C^2$ boundary, the first positive eigenfunction of (1.1) has the property that $w=-\ln u$ is convex, so all positive superlevel sets of $u$ are convex. On the class of $C^2$ convex bodies, the first eigenvalue satisfies $\lambda_{p,\gamma}((1-t)\Omega_0+t\Omega_1)\le(1-t)\lambda_{p,\gamma}(\Omega_0)+t\lambda_{p,\gamma}(\Omega_1)$, a Brunn-Minkowski-type inequality for the eigenvalue map. The proof route is to establish existence, uniqueness, Hopf boundary behavior, and global $C^{1,\alpha}$ regularity for the weak solution; to prove log-concavity through a regularized problem and a concavity maximum principle; and then to derive the eigenvalue inequality by inf-convolution of the convex functions $w_i=-\ln u_i$ together with a comparison argument for the $p$-Laplacian of the inf-convolution.
Load-bearing premise
The second theorem rests on assuming without proof that the comparison lemmas for combining strictly concave functions still hold for the inf-convolutions of the convex functions $w_i=-\ln u_i$; if that transfer fails, the Brunn-Minkowski inequality does not follow.
Editorial extensions
If this is right
- Every positive superlevel set $\{u>c\}$ of the first eigenfunction is convex whenever $\Omega$ is convex, so Brunn-Minkowski-type measure bounds apply to these level sets.
- The eigenvalue map $\Omega\mapsto\lambda_{p,\gamma}(\Omega)$ is convex along Minkowski linear combinations, giving the nonlinear analogue of the Brunn-Minkowski inequalities already known for torsional rigidity and $p$-capacity.
- For $p=2$, Theorems 1.1 and 1.2 recover the log-concavity and Brunn-Minkowski results for the Gaussian Laplacian (Ornstein-Uhlenbeck) eigenvalue problem recently obtained by other methods.
- The comparison theory developed here (weak comparison principle, Hopf boundary lemma, uniqueness up to scale) supplies tools for further variational problems for the weighted $p$-Laplacian on Gaussian spaces.
Reading between the lines
- A radial numerical test is immediately available: for concentric balls the Minkowski combination is a ball, so the inequality $\lambda_{p,\gamma}(B_R)\le(1-t)\lambda_{p,\gamma}(B_r)+t\lambda_{p,\gamma}(B_s)$ with $R=(1-t)r+ts$ can be checked from the one-dimensional radial eigenfunction problem; a violation would refute Theorem 1.2.
- The same inf-convolution strategy should work for other convex weights $e^{-V}$ replacing the Gaussian density, since the drift term enters only through the first-order term; testing $V=|x|^4/4$ would separate Gaussian-specific properties from the general convex-geometric mechanism.
- The approximating sequence $\Omega_k\uparrow\Omega$ in Theorem 1.1 is where strong convexity is dropped, so a $C^2$ convex domain with a flat boundary segment is the natural place to look for counterexamples if log-concavity does not survive without strong convexity.
- Writing out the duality step between sup-convolutions and inf-convolutions explicitly would turn Section 5 into a general comparison theorem for convex solutions of (5.1), making the Brunn-Minkowski inequality independent of the regularity machinery.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript studies the Gaussian-weighted p-Laplace eigenvalue problem (1.1) on bounded convex domains with C^2 boundary, with operator Δ_{p,γ}u = div(|∇u|^{p-2}∇u) - (x,∇u)|∇u|^{p-2}. After proving existence, positivity, uniqueness and C^{1,α} regularity (Theorem 3.1), the paper claims that the first positive eigenfunction is log-concave (Theorem 1.1) and that the first eigenvalue satisfies the Brunn-Minkowski-type inequality λ_{p,γ}(Ω_t) ≤ (1-t)λ_{p,γ}(Ω_0) + tλ_{p,γ}(Ω_1) for C^2 convex bodies (Theorem 1.2). The proof of Theorem 1.1 uses a regularized variational problem, interior C^{1,β}/C^{2,β} estimates, and Korevaar's concavity maximum principle; the proof of Theorem 1.2 uses log-concavity and the inf-convolution of the convex functions w_i = -ln u_i, following the strategy of Colesanti-Cuoghi-Salani.
Significance. If the proofs can be completed, Theorem 1.1 is a natural extension of known log-concavity results for p-Laplace eigenfunctions (Sakaguchi, Barles) to the Gaussian-weighted operator, and Theorem 1.2 would be a new convexity result for the weighted first eigenvalue in the class of convex bodies. The paper is honest about the main difficulty, namely that the equation is only weakly regular, and it attempts a regularization route rather than assuming higher regularity. It also correctly identifies that the non-homogeneity of the eigenvalue prevents the usual normalization in the Brunn-Minkowski inequality. The main value is in the two theorem statements and the methodological template; the manuscript does not contain reproducible code or machine-checked proofs, but that is not expected for this type of result.
major comments (4)
- [Section 5 (Lemmas 5.1–5.2 and proof of Theorem 1.2)] The proof of Theorem 1.2 invokes, without proof, an inf-convolution analogue of Lemmas 5.1 and 5.2. The lemmas as quoted from [11] are stated for strictly concave functions and for sup-convolution, whereas the functions w_i = -ln u_i are convex and the construction (5.3)–(5.5) is an inf-convolution. The remark (5.2) records the convex-duality identity (-u)^* = (1-t)(-u_0)^* + t(-u_1)^*, but the paper does not derive the transformed Hessian formula D^2 w(z) = [(1-t)A^{-1} + tB^{-1}]^{-1} nor the p-Laplacian comparison Δ_p w(z) ≤ (1-t)Δ_p w_0(x) + tΔ_p w_1(y). Inequality (5.12) is precisely where this comparison is used, so Theorem 1.2 is not established as written. If the comparison fails for some p in (1,2), the argument collapses; at minimum a proof or a precise citation of the convex/inf-convolution version is required.
- [Section 4 (Propositions 4.8–4.10 and Theorem 1.1)] The sign and definition of υ_ε are inconsistent across Section 4. Proposition 4.8 defines υ_ε = -ln u_ε and studies c_ε = υ_ε((1-t)x+ty) - (1-t)υ_ε(x) - tυ_ε(y) in order to prove convexity of -ln u_ε, while Proposition 4.9 states that υ_ε = ln u_ε is concave in Ω_ν and Proposition 4.10 and Theorem 1.1 conclude that υ = ln u is concave. Since concavity of ln u is equivalent to convexity of -ln u, the two conventions can be reconciled, but as written the equation in Proposition 4.8, with the coefficient displayed as (ε+|∇υ_ε|)^{(p-2)/2}, is not shown to be the equation satisfied by -ln u_ε under either sign convention, and the statement of Proposition 4.9 uses the opposite sign from Proposition 4.8. The limiting argument (4.17)–(4.20) and the application of Korevaar's principle cannot be checked line by line until this is fixed.
- [Proposition 3.3] The comparison principle is not proved as written. After passing to the unweighted form, the proof states ∫ e^{-|x|^2/2}|∇u_1|^{p-2}∇u_1·∇ϕ ≤ ∫ e^{-|x|^2/2}|∇u_1|^{p-2}∇u_1·∇ϕ, with the same function u_1 on both sides; the subsequent test-function computation uses u_1 and u_2, indicating a typo, but the displayed inequality is tautological. Since Proposition 3.3 is used in the proof of Hopf's lemma (Proposition 3.5) and in the uniqueness argument in Theorem 3.1, the regularity and uniqueness part of Theorem 1.1 depends on a corrected proof.
- [Proof of Theorem 1.1 (approximation by strongly convex domains)] In the proof of Theorem 1.1, the passage from strongly convex domains Ω_k to Ω relies on the assertion that 'the C^β(Ω)-estimate of the solution to (1.1) is independent of small smooth perturbation of the boundary ∂Ω'. This is not proved and is not automatic, since the C^β constants for solutions on varying domains may depend on the boundary geometry. A reference or explicit argument is needed to justify the uniform bound ‖u_k‖_{C^β(Ω_k)} ≤ c used before applying Arzelà-Ascoli.
minor comments (4)
- [Theorem 1.2 statement] The displayed definition of Ω_t reads Ω_t = (1-t)Ω_0 + Ω_1 and is missing the factor t on Ω_1; it should be Ω_t = (1-t)Ω_0 + tΩ_1, as used throughout the proof.
- [Equation (5.9) and definition of F_ε] In (5.9) and in the definition of F_ε, the second second-order term in each bracket should involve the unit vector n_i rather than n_{i,ε}; as printed, both occurrences are written with n_{i,ε}, so the ε-dependence does not cancel in the intended way.
- [Proof of Theorem 1.2, after (5.14)] The text says 'by (5.7) and (5.7)' where the second reference should be (5.8), and in the surrounding sentences '∇w_{i,ε}' is sometimes written as '∇w_i,ε'; these notational slips should be corrected.
- [Equation (3.2)] Equation (3.2) appears to have a typo on the right-hand side: the test function should be ψ, not ∇ψ, in the integral λ∫|u|^{p-2}u e^{-|x|^2/2}ψ dx; otherwise the weak formulation does not match (2.4).
Circularity Check
No significant circularity: the derivation is self-contained apart from ordinary external citations.
full rationale
Theorems 1.1 and 1.2 are derived from the hypotheses rather than assumed. Theorem 1.1 is obtained by regularizing the degenerate problem (4.1)-(4.3), applying Korevaar's concavity maximum principle from [17] to the smooth approximants, deriving boundary tangent-plane controls from [17, Lemma 2.4], and then passing to the limit through the uniform C^{1,β} estimates and the uniqueness result proved in Theorem 3.1. The limit passage is asserted and supported by the cited Tolksdorf/Di Benedetto regularity theory, which is external and does not contain the target log-concavity conclusion. Theorem 1.2 uses the log-concavity of w_i = -ln u_i just established, constructs the inf-convolution w̃, and applies Lemmas 5.1 and 5.2 quoted from the independent paper [11]. The inequality (5.12) yields a Rayleigh quotient bound for the trial function ũ = e^{-w̃}, and the variational definition (1.2) then gives λ_{p,γ}(Ω_t) ≤ (1-t)λ_0 + tλ_1. No parameter is fitted to the target eigenvalue, no conclusion is imported from the author's own prior work, and no cited result assumes the theorem being proved. The only caveat visible is a technical one, not a circular one: Lemmas 5.1 and 5.2 are stated for concave functions and sup-convolution, while the proof uses convex functions and inf-convolution via the conjugation remark (5.2); if the convex analogue of the p-Laplacian comparison fails, Theorem 1.2 would be incorrect, but that would be a correctness gap, not a reduction of the theorem to its own inputs. Accordingly, the circularity score is 0.
Assumptions & free parameters
assumptions (5)
- standard math Korevaar's concavity maximum principle ([17, Theorem 1.3]) applies to the regularized solutions u_ε in Ω_δ
- standard math Comparison principle and Hopf lemma for the weighted p-Laplace operator, as stated in Propositions 3.3 and 3.5
- standard math Regularity theorems of Di Benedetto [3], Tolksdorf [24], and Ladyzhenskaya-Ural'tseva [18] give C^{1,α} and C^{2+β} estimates for the degenerate equations
- domain assumption Lemmas 5.1 and 5.2 from Colesanti-Cuoghi-Salani [11] extend to the inf-convolution of convex functions w_i
- domain assumption Ω is a bounded convex domain with C^2 boundary, and ∂Ω is connected for uniqueness; p>1
Cite this review
Pith. "Pith review of log-concavity of eigenfunction and Brunn-Minkowski inequality of eigenvalue for weighted p-Laplace operator." pith.science (2026). https://pith.science/paper/ACEYXVXI
@misc{pith2026241116377,
author = {Pith},
title = {Pith review of: log-concavity of eigenfunction and Brunn-Minkowski inequality of eigenvalue for weighted p-Laplace operator},
year = {2026},
howpublished = {\url{https://pith.science/paper/ACEYXVXI}},
note = {Machine review of arXiv:2411.16377}
}
abstract
In this paper, we investigate the log-concavity property of the first eigenfunction to the weighted $p$-Laplace operator in class of bounded, convex and smooth domain. Moreover, we prove a Brunn-Minkowski-type inequality for the first eigenvalue to the weighted $p$-Laplace operator in the class of $C^2$ convex bodies in $\R^n$
Forward citations
Cited by 1 Pith paper
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The strong log-concavity for first eigenfunction of the Ornstein-Uhlenbeck operator in the class of convex bodies
The first Dirichlet eigenfunction of the Ornstein-Uhlenbeck operator on any bounded convex domain is strongly log-concave, and the equality case in the Brunn-Minkowski inequality for its principal frequency is charact...
Reference graph
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