Existence and multiplicity of $a$-harmonic solutions for a Steklov problem with variable exponents

Résumé

Using variational methods, we prove in a different cases the existence and multiplicity of $a$-harmonic solutions for the following elleptic problem:\begin{equation*}\begin{gathered}div(a(x, \nabla u))=0, \quad \text{in }\Omega, \\a(x, \nabla u).\nu=f(x,u), \quad \text{on } \partial\Omega,\end{gathered}\end{equation*} where $\Omega\subset\mathbb{R}^N(N \geq 2)$ is a bounded domain ofsmooth boundary $\partial\Omega$ and $\nu$ is the outward normalvector on $\partial\Omega$. $f: \partial\Omega\times \mathbb{R} \rightarrow \mathbb{R},$ $a: \overline{\Omega}\times \mathbb{R}^{N} \rightarrow\mathbb{R}^{N},$ are fulfilling appropriate conditions.