A strongly nonlinear Neumann problem at resonance with restrictions on the nonlinearity just in one direction

Abstract

Using topological degree techniques, we state and prove new sufficient conditions for the existence of a solution of the Neumann boundary value problem $$ (|x'|^{p-2} x')' +f(t, x)+ h(t, x) =0, \quad x'(0) = x'(1)=0, $$ when $h$ is bounded, $f$ satisfies a one-sided growth condition, $f + h$ some sign condition, and the solutions of some associated homogeneous problem are not oscillatory. A generalization of Lyapunov inequality is proved for a $p$-Laplacian equation. Similar results are given for the periodic problem.