Online First version
https://doi.org/10.7494/OpMath.202509181
Opuscula Mathematica
Radial solutions for a Neumann elliptic system with quadratic growth in the gradient
Filomena Cianciaruso
Paolamaria Pietramala
Abstract. We prove the existence of multiple positive solutions for elliptic systems with linear boundary conditions of Neumann type. We suppose that the nonlinearities grow quadratically with respect to gradient. A key step is to obtain a priori bound on the derivatives by using a Gronwall-type inequality. Our approach is topological and relies on the fixed point index.
Keywords: elliptic system, annular domain, radial solution, fixed point index, linear Neumann boundary conditions, Gronwall inequality.
Mathematics Subject Classification: 35B07, 34B18, 35J57, 47H10.
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- Filomena Cianciaruso
https://orcid.org/0000-0002-3522-1765- University of Calabria, Department of Mathematics and Computer Sciences, 87036 Rende, Cosenza, Italy
- Paolamaria Pietramala (corresponding author)
https://orcid.org/0000-0002-7435-9767- University of Calabria, Department of Mathematics and Computer Sciences, 87036 Rende, Cosenza, Italy
- Communicated by Marek Galewski.
- Received: 2025-06-30.
- Revised: 2025-09-11.
- Accepted: 2025-09-18.
- Published online: 2026-03-18.

