Some versions of the Strong Maximum Principal for elliptic integral functionals

Abstract

The Strong Maximum Principle (SMP) is a well-known property, which can be recognized as a kind of uniqueness result for solutions of Partial Differential Equations. Through the necessary conditions of optimality it is applicable to minimizers in some classes of variational problems as well. The work is devoted to various versions of SMP in such variational setting, which hold also if the respective Euler-Lagrange equations are no longer valid. We prove variational SMP for some types of integral functionals in the traditional sense as well as obtain an extension of this principle, which can be seen as an extremal property of a series of specific functions.