Multiplicity of positive solutions for a gradient type cooperative/competitive elliptic system

Abstract

We study the existence of positive solutions for gradient type cooperative, competitive elliptic systems, which depends on real parameters λ, μ. Our analysis is purely variational and depends on finer estimates with respect to the Nehari sets, in fact, we determine the extremal parameter λ* (μ) for which the Nehari set is a manifold and hence standard variational techniques can be applied. We also discuss the cases where the Nehari set is not a manifold.