Boundary Value Problems 
Volume 2006 (2006), Article ID 64543, 13 pages
doi:10.1155/BVP/2006/64543

Maximum principles for a class of nonlinear second-order elliptic boundary value problems in divergence form

Cristian Enache

 Department of Mathematics and Computer Science, Ovidius University, Constanta 900 527, Romania
Received 22 January 2006; Accepted 26 March 2006

Abstract

For a class of nonlinear elliptic boundary value problems in divergence form, we construct some general elliptic inequalities for appropriate combinations of u(x) and |∇u|2, where u(x) are the solutions of our problems. From these inequalities, we derive, using Hopf's maximum principles, some maximum principles for the appropriate combinations of u(x) and |∇u|2, and we list a few examples of problems to which these maximum principles may be applied.