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arxiv: 1906.10730 · v1 · pith:PGVA2TJFnew · submitted 2019-06-25 · 🧮 math.AP

The Nehari manifold for indefinite Kirchhoff problem with Caffarelli-Kohn-Nirenberg type critical growth

Pith reviewed 2026-05-25 16:09 UTC · model grok-4.3

classification 🧮 math.AP
keywords Nehari manifoldKirchhoff problemCaffarelli-Kohn-Nirenbergcritical growthindefinite functionalpositive solutionsnonlocal elliptic equation
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The pith

At least two positive solutions exist for suitable parameters in an indefinite nonlocal Kirchhoff problem with critical growth.

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

This paper considers a Kirchhoff-type nonlocal elliptic equation in R^N with a sign-changing potential and a critical nonlinear term of Caffarelli-Kohn-Nirenberg type. It applies the method of constrained minimization on the Nehari manifold to prove that at least two positive solutions exist when the parameters λ and μ are chosen in appropriate ranges. The approach addresses the challenges posed by the nonlocal term, the indefinite nature of the linear part, and the critical growth by verifying the geometry of the Nehari manifold and the Palais-Smale condition. A reader would care because multiplicity results for such problems are useful in understanding the behavior of nonlocal models.

Core claim

Using constrained minimization on the Nehari manifold associated with the energy functional, the authors establish the existence of at least two positive solutions to the problem for suitable positive values of the parameters λ and μ.

What carries the argument

The Nehari manifold, the set of functions u where the derivative of the functional in the direction of u vanishes, on which minimization yields critical points of the original functional.

Load-bearing premise

The specific choice of the critical exponent p together with the range 0 ≤ a < b < a+1 < N/2 ensures that the embeddings and Palais-Smale conditions hold for the functional.

What would settle it

A concrete counterexample where, for λ and μ in the claimed suitable range, the constrained minimization on the Nehari manifold produces at most one positive solution would falsify the multiplicity result.

read the original abstract

In this paper we study the following class of nonlocal {problems} involving Caffarelli-Kohn-Nirenberg type critical growth \begin{align*} L(u)&-\lambda h(x)|x|^{-2(1+a)}u=\mu f(x)|u|^{q-2}u+|x|^{-pb}|u|^{p-2}u\;\; \text{in } \mathbb R^N, \end{align*} where $h(x)\geq 0$, $f(x)$ is a continuous function which may change sign, $\lambda, \mu$ are positive real parameters and $1<q<2$, $4< p=2N/[N+2(b-a)-2]$, $0\leq a<b<a+1<N/2$, $N\geq 3$. Here $$ L(u)=-M\left(\int_{\mathbb R^N} |x|^{-2a}|\nabla u|^2dx\right)\mathrm {div}(|x|^{-2a}\nabla u) $$ and the function $M:\mathbb R^+\cup \{0\} \to\mathbb R^+$ is exactly as in the Kirchhoff model, given by $M(t)=\alpha+\beta t$, $\alpha, \beta>0$. Using the idea {of the constrained minimization on} Nehari manifold we show the existence of at least two positive solutions for suitable choices of $\lambda$ and $\mu$.

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

1 major / 1 minor

Summary. The manuscript studies a nonlocal Kirchhoff-type problem with an indefinite linear term and Caffarelli-Kohn-Nirenberg critical growth. It claims to prove the existence of at least two positive solutions via constrained minimization on the Nehari manifold N = {u ≠ 0 : ⟨I'(u), u⟩ = 0} for suitable positive parameters λ and μ, under the restrictions 0 ≤ a < b < a + 1 < N/2, 1 < q < 2, and p = 2N/[N + 2(b - a) - 2] with M(t) = α + βt.

Significance. If the details hold, the work applies standard Nehari-manifold techniques to a nonlocal setting with weighted critical nonlinearity and an indefinite term, which may be of interest for multiplicity results in variational PDEs. The parameter restrictions are chosen to secure the required embeddings and manifold geometry, but the significance hinges on whether the second critical level remains below the compactness threshold.

major comments (1)
  1. [Abstract and the section establishing the second critical point on N] The range 0 ≤ a < b < a + 1 < N/2 and the exact choice of p are invoked to obtain continuous embedding into the weighted space and to set up the geometry of N, but no explicit argument is given showing that the second minimax value on N lies strictly below (1/N) times the best constant in the CKN embedding (adjusted for the weights). With the Kirchhoff quartic term and the indefinite λ-term present, this control is load-bearing for the Palais-Smale condition at the second critical point; without it the second solution on N may not be recovered.
minor comments (1)
  1. [Abstract] The abstract states that f(x) may change sign but does not clarify how the sign-changing behavior interacts with the choice of μ in the existence intervals.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for the careful reading of our manuscript and for highlighting this important point regarding the control of the second critical level. We address the comment below.

read point-by-point responses
  1. Referee: [Abstract and the section establishing the second critical point on N] The range 0 ≤ a < b < a + 1 < N/2 and the exact choice of p are invoked to obtain continuous embedding into the weighted space and to set up the geometry of N, but no explicit argument is given showing that the second minimax value on N lies strictly below (1/N) times the best constant in the CKN embedding (adjusted for the weights). With the Kirchhoff quartic term and the indefinite λ-term present, this control is load-bearing for the Palais-Smale condition at the second critical point; without it the second solution on N may not be recovered.

    Authors: We agree that an explicit argument establishing c_2 < (1/N) S_{a,b} (with S_{a,b} the best constant in the weighted CKN embedding) is necessary to rigorously verify the Palais-Smale condition at the second critical level, especially given the presence of the quartic Kirchhoff term and the indefinite linear term. While the geometry of the Nehari manifold N and the existence of two distinct points u_1, u_2 on N for small λ, μ are established in Section 3 using the given restrictions on a, b, p and the form M(t) = α + βt, the strict inequality for the second minimax value is used implicitly via the smallness of λ and μ but not spelled out in detail. In the revised manuscript we will insert a new lemma immediately after the definition of c_2 that provides the required estimate: by choosing λ and μ sufficiently small (depending on α, β, N, a, b), one obtains c_2 < (1/N) S_{a,b} by comparing with the unperturbed functional and using the continuity of the embedding H^{1,2}_a(ℝ^N) ↪ L^p(|x|^{-pb} dx). This will confirm that the second solution is recovered via the constrained minimization. Revision will be made accordingly. revision: yes

Circularity Check

0 steps flagged

No significant circularity; standard variational methods on new functional

full rationale

The derivation applies the established Nehari manifold constrained minimization technique to the energy functional associated with the given nonlocal Kirchhoff equation under the stated parameter ranges for a, b, p, q, λ, μ. These ranges are external assumptions chosen to guarantee continuous embeddings into weighted Sobolev spaces and the geometry needed for the manifold (global minimizer plus second critical point via fibering or mountain-pass). No equation or existence claim reduces by definition to its own inputs, no fitted parameter is relabeled as a prediction, and no load-bearing step rests on a self-citation chain. The result is obtained by direct application of known tools to the new problem, making the paper self-contained against external benchmarks.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The proof relies on standard functional-analytic facts (Sobolev embeddings, concentration-compactness) that hold under the given parameter ranges; no new entities are introduced and no parameters are fitted to data.

axioms (1)
  • domain assumption The functional satisfies the required geometry and Palais-Smale condition on the Nehari manifold when p equals the stated critical exponent and the parameter ranges hold.
    This is the key structural assumption that allows the minimization argument to go through; it is invoked implicitly when the authors restrict to the Nehari manifold.

pith-pipeline@v0.9.0 · 5810 in / 1195 out tokens · 105222 ms · 2026-05-25T16:09:11.333718+00:00 · methodology

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Works this paper leans on

22 extracted references · 22 canonical work pages

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