Nonlinear Neumann problems driven by a nonhomogeneous differential operator

We study a nonlinear parametric Neumann problem driven by a nonhomogeneous quasilinear elliptic differential operator div(a(x, del u)), a special case of which is the p-Laplacian. The reaction term is a nonlinearity function f which exhibits (p-1)-subcritical growth. By using variational methods, we prove a multiplicity result on the existence of weak solutions for such problems. An explicit example of an application is also presented