A topological approach to the existence and multiplicity of positive solutions of \((p, q)\)-Laplacian systems (Q889506)

In this paper, the authors prove some fixed point results in a general framework, i.e. for non-linear operators in Banach spaces satisfying a Harnack-type inequality. Such a construction is then employed to derive, as particular cases of the theory, some existence and non-existence results for a \(p\)-Laplacian system. These results are a generalization to the case of systems of equations of those contained in [\textit{R. Precup}, J. Fixed Point Theory Appl. 12, No. 1--2, 193--206 (2012; Zbl 1277.47070)] for \(p\)-Laplace equations.