Anisotropic Singular Neumann Equations with Unbalanced Growth

We consider a nonlinear parametric Neumann problem driven by the anisotropic (p, q)-Laplacian and a reaction which exhibits the combined effects of a singular term and of a parametric superlinear perturbation. We are looking for positive solutions. Using a combination of topological and variational tools together with suitable truncation and comparison techniques, we prove a bifurcation-type result describing the set of positive solutions as the positive parameter λ varies. We also show the existence of minimal positive solutions $u_{\lambda }^{*}$ and determine the monotonicity and continuity properties of the map $\lambda \mapsto u_{\lambda }^{*}$ .