Multiple positive solutions for a class of p-Laplacian Neumann problems without growth conditions

Abstract

For $1<p<\infty$, we consider the following problem $$-{\Delta }_{p}u=f(u),u>0\text{ in }\Omega ,{\partial }_{\nu }u=0\text{ on }\partial \Omega ,$$ where $\Omega \subset {\mathbb{R}}^N$ is either a ball or an annulus. The nonlinearity $f$ is possibly supercritical in the sense of Sobolev embeddings; in particular our assumptions allow to include the prototype nonlinearity $f(s)=-s^{p-1}+s^{q-1}$ for every $q>p$. We use the shooting method to get existence and multiplicity of non-constant radial solutions. With the same technique, we also detect the oscillatory behavior of the solutions around the constant solution $u\equiv 1$. In particular, we prove a conjecture proposed in [D. Bonheure, B. Noris, T. Weth, {\it Ann. Inst. H. Poincaré Anal. Non Lináire} vol. 29, pp. 573-588 (2012)], that is to say, if $p=2$ and $f^{\prime }(1)>{\lambda }_{k+1}^{rad}$, there exists a radial solution of the problem having exactly $k$ intersections with $u\equiv 1$ for a large class of nonlinearities.

22 pages, 4 figures