Composition Operators on Sobolev Spaces and Neumann Eigenvalues

Abstract

In this paper we discuss applications of the geometric theory of composition operators on Sobolev spaces to the spectral theory of non-linear elliptic operators. Lower estimates of the first non-trivial Neumann eigenvalues of the p-Laplace operator in cusp domains $$\Omega \subset \mathbb R^n$$ , $$n\ge 2$$ , are given.