Multiple positive solutions for semilinear elliptic systems with nonlinear boundary condition

We consider the semilinear elliptic system { −∆u+m1(x)u = fu(x, u, v) x ∈ Ω, −∆v +m2(x)v = fv(x, u, v) x ∈ Ω, with the boundary conditions ∂u ∂n = λg(x, u) and ∂v ∂n = μh(x, v), where Ω ⊂ RN is a bounded smooth domain, λ, μ > 0 and the functions f , g, h, m1 and m2 satisfy some suitable conditions. Using the fibering map and by extracting the Palais-Smale sequences in the Nehari manifold, we prove that the above system has at least two distinct positive solutions when the pair (λ, μ) belongs to a certain subset of R2.