Electron. J. Differential Equations, Vol. 2026 (2026), No. 83, pp. 1-17.

Existence of infinitely many solutions for nonlinear Poisson-Poisson elliptic systems

Raul Nina-Mollisaca, Julio Huayta-Centeno, Mauricio Sepulveda-Cortes, Octavio Vera-Villagran

Abstract:
We study a nonlinear Poisson-Poisson system in a bounded domain \(\Omega\subset\mathbb{R}^N\), \(N\geq 3\), whose reduced form is the nonlocal elliptic equation \(-\Delta u+\lambda(-\Delta)^{-1}u=|u|^{p-2}u\). We assume that \(\lambda\in(-\lambda_1(\Omega)^2,\infty)\), where \(\lambda_1(\Omega)\) denotes the first Dirichlet eigenvalue of \(-\Delta\) in \(\Omega\), and that the exponent is subcritical, \(2< p< 2^*=2N/(N-2)\). We first show that, throughout this coercive range, the quadratic part of the associated energy functional defines a norm equivalent to the standard norm of \(H_0^1(\Omega)\). We then establish the Palais-Smale condition on the Nehari manifold and use the Krasnosel'skii genus to prove the existence of infinitely many pairs of nontrivial weak solutions. More precisely, there exists a sequence of solutions \((u_k,\phi_{u_k})\) such that \(\|u_k\|_\lambda^2\to\infty\). A three-dimensional finite element experiment illustrates two distinct discrete solutions, one of which changes sign.

Submitted August 4, 2026. Published October 22, 2026.
Math Subject Classifications: 35J47, 35J60, 35A15, 58E05, 65N30.
Key Words: Nonlinear elliptic system; inverse Laplacian; nonlocal elliptic equation; Nehari manifold; Krasnosel'skii genus; infinitely many solutions; finite element method.
DOI: 10.58997/ejde.2026.83

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Raul Nina Mollisaca
Departamento de Matemática y Estadística
Universidad Nacional Jorge Basadre Grohmann
Tacna, Perú
email: raninamo@unjbg.edu.pe
Julio Huayta-Centeno
Departamento de Educación de Matemática y Computación
Universidad Nacional Jorge Basadre Grohmann
Tacna, Perú
email: jhuaytac@unjbg.edu.pe
Mauricio Sepúlveda-Cortés
Departamento de IngenierĂ­a Matemática and CI2MA
Universidad de Concepción
Concepción, Chile
email: maursepu@udec.cl
Octavio Vera-Villagrán
Departamento de Matemática
Universidad de Tarapacá
Av. 18 de Septiembre 2222, Arica, Chile
email: opverav@academicos.uta.cl

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