Electron. J. Differential Equations, Vol. 2026 (2026), No. 84, pp. 1-17.

Critical Grushin-Choquard problems with concave and superlinear perturbations

Shengbing Deng, Yichen Ling

Abstract:
Let \(m,n\geq1\), \(\gamma>0\), and \(N_\gamma=m+(1+\gamma)n >2\). Let \(\Omega\subset\mathbb R^m\times\mathbb R^n\) be a bounded smooth domain intersecting \(\{0\}\times\mathbb R^n\). We study the boundary-value problem $$\displaylines{ -\Delta_\gamma u=\lambda g(z,u)+\Big(\int_\Omega \dfrac{|u(w)|^p}{d(z-w)^\mu}\,dw\Big) |u|^{p-2}u \quad \text{in }\Omega,\cr u=0 \quad \text{on }\partial\Omega, }$$ where \(z=(x,y)\), \(\Delta_\gamma=\Delta_x+(1+\gamma)^2|x|^{2\gamma}\Delta_y\), \(d(z)=(|x|^{2(1+\gamma)}+|y|^2)^{1/[2(1+\gamma)]}\), \(0 < \mu< N_\gamma\), and \(p=(2N_\gamma-\mu)/(N_\gamma-2)\). We use a nonlocal Brezis-Lieb splitting and variational methods to prove compactness below the critical energy. For \(1< q< 2\) and small \(\lambda >0\), the problem with \(g(z,u)=|u|^{q-2}u\) has a nontrivial nonnegative local minimizer of negative energy. A second nontrivial nonnegative solution is obtained under a quantitative concentration condition. We verify this condition in an explicit range of \(q\) under a whole-space extremal and decay assumption. For \(2< q< 2^*_\gamma=2N_\gamma/(N_\gamma-2)\) and large \(\lambda\), there is a nontrivial nonnegative mountain-pass solution whose energy and norm tend to zero as \(\lambda\to\infty\). The large-parameter existence result extends to general subcritical Caratheodory nonlinearities satisfying the stated growth and superlinearity assumptions.

Submitted September 21, 2026. Published October 23, 2026.
Math Subject Classifications: 35J70, 35H20, 35A15, 35B33, 35B38.
Key Words: Grushin operator; Choquard equation; concave perturbation; Hardy-Littlewood-Sobolev critical exponent; superlinear perturbation.
DOI: 10.58997/ejde.2026.84

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Shengbing Deng
School of Mathematics and Statistics
Southwest University
Chongqing 400715, China
email: shbdeng@swu.edu.cn
Yichen Ling
School of Mathematics and Statistics
Southwest University
Chongqing 400715, China
email: yichen_ling01@163.com

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