Research Article
Sign-Changing and Extremal Constant-Sign Solutions of Nonlinear Elliptic Neumann Boundary Value Problems
Institut für Mathematik, Technische Universität Berlin, Straße des 17. Juni 136, 10623 Berlin, Germany
Boundary Value Problems 2010, 2010:139126 doi:10.1155/2010/139126
Published: 6 July 2010Abstract
Our aim is the study of a class of nonlinear elliptic problems under Neumann conditions
involving the 
-Laplacian. We prove the existence of at least three nontrivial solutions, which means
that we get two extremal constant-sign solutions and one sign-changing solution by
using truncation techniques and comparison principles for nonlinear elliptic differential
inequalities. We also apply the properties of the Fu
ik spectrum of the 
-Laplacian and, in particular, we make use of variational and topological tools, for
example, critical point theory, Mountain-Pass Theorem, and the Second Deformation
Lemma.
