Multiple solutions for a sinh-Gordon equation with a concave term
摘要
We use three different techniques to show the existence of positive solutions for the sinh-Gordon equation with a concave term, namely −Δυ = λυq + sinh(α υm) in some bounded domain Ω with υ = 0 on ∂Ω, where λ, α, m > 0 and 0 < q < 1. By means of a topological fixed point method we get a solution υ even though Ω has dimension bigger than two and m > 1. For two-dimensional domains and 0 < m ≤ 2, another solution u0 is a consequence of a Galerkin convergence scheme. In our third approach, for m = 2, we use variational methods together with critical level estimates applied to an energy functional shifted by u0, allowing us to find a function w such that u0 + w is a true second solution.