Multiplicity of solutions for semilinear Robin problems involving sign-changing nonlinearities

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Main Authors: Tapia, José Carmona, Aparicio, Antonio J. Martínez, Martínez-Aparicio, Pedro J.
Format: Preprint
Published: 2025
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author Tapia, José Carmona
Aparicio, Antonio J. Martínez
Martínez-Aparicio, Pedro J.
author_facet Tapia, José Carmona
Aparicio, Antonio J. Martínez
Martínez-Aparicio, Pedro J.
contents In this article, we investigate the existence and multiplicity of solutions to the Robin problem \begin{equation*} \begin{cases} -Δu = λf(u) & \text{in } Ω, \frac{\partial u}{\partial ν} + γu=0 & \text{on } \partialΩ, \end{cases} \end{equation*} where $Ω\subset \mathbb{R}^N$ ($N\geq 1$) is a smooth bounded domain, and $λ, γ>0$. Our main assumption is that $f\colon \mathbb{R}\to \mathbb{R}$ is a locally Lipschitz function, possibly sign-changing, such that $f(s)>0$ for every $s\in (α,β)$, where $0<α<β$ are two zeros of $f$. Without any further conditions, we establish the existence of two nonnegative solutions whose maximum lies in $(α,β)$ for sufficiently large $λ$. Moreover, we analyse the limiting behaviour of the solution set of this Robin problem, showing that it degenerates into that of the associated Neumann problem as $γ\to 0$ and into that of the associated Dirichlet problem as $γ\to\infty$.
format Preprint
id arxiv_https___arxiv_org_abs_2511_22733
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Multiplicity of solutions for semilinear Robin problems involving sign-changing nonlinearities
Tapia, José Carmona
Aparicio, Antonio J. Martínez
Martínez-Aparicio, Pedro J.
Analysis of PDEs
35B09, 35B40, 35J61
In this article, we investigate the existence and multiplicity of solutions to the Robin problem \begin{equation*} \begin{cases} -Δu = λf(u) & \text{in } Ω, \frac{\partial u}{\partial ν} + γu=0 & \text{on } \partialΩ, \end{cases} \end{equation*} where $Ω\subset \mathbb{R}^N$ ($N\geq 1$) is a smooth bounded domain, and $λ, γ>0$. Our main assumption is that $f\colon \mathbb{R}\to \mathbb{R}$ is a locally Lipschitz function, possibly sign-changing, such that $f(s)>0$ for every $s\in (α,β)$, where $0<α<β$ are two zeros of $f$. Without any further conditions, we establish the existence of two nonnegative solutions whose maximum lies in $(α,β)$ for sufficiently large $λ$. Moreover, we analyse the limiting behaviour of the solution set of this Robin problem, showing that it degenerates into that of the associated Neumann problem as $γ\to 0$ and into that of the associated Dirichlet problem as $γ\to\infty$.
title Multiplicity of solutions for semilinear Robin problems involving sign-changing nonlinearities
topic Analysis of PDEs
35B09, 35B40, 35J61
url https://arxiv.org/abs/2511.22733