On a $p$-superlinear Neumann $p$-Laplacian equation

Abstract

We consider a nonlinear Neumann problem, driven by the $p$-Laplacian, and with a nonlinearity which exhibits a $p$-superlinear growth near infinity, but does not necessarily satisfy the Ambrosetti-Rabinowitz condition. Using variational methods based on critical point theory, together with suitable truncation techniques and Morse theory, we show that the problem has at least three nontrivial solutions, of which two have a fixed sign (one positive and the other negative).