Multiple solutions for some symmetric supercritical problems

Abstract

The aim of this paper is investigating the existence of one or more critical points of a family of functionals which generalizes the model problem \[ \bar J(u)\ =\ \frac1p\ \int_\Omega \bar A(x,u)|\nabla u|^p dx - \int_\Omega G(x,u) dx \] in the Banach space $X = W^{1,p}_0(\Omega)\cap L^\infty(\Omega)$, where $\Omega \subset {\mathbb R}^N$ is an open bounded domain, $1 < p < N$ and the real terms $\bar A(x,t)$ and $G(x,t)$ are $C^1$ Carath\'eodory functions on $\Omega \times {\mathbb R}$. We prove that, even if the coefficient $\bar A(x,t)$ makes the variational approach more difficult, if it satisfies ``good'' growth assumptions then at least one critical point exists also when the nonlinear term $G(x,t)$ has a suitable supercritical growth. Moreover, if the functional is even, it has infinitely many critical levels. The proof, which exploits the interaction between two different norms on $X$, is based on a weak version of the Cerami-Palais-Smale condition and a suitable intersection lemma which allow us to use a Mountain Pass Theorem.