Z_2-symmetric critical point theorems for non-differentiable functions

Abstract

In this paper, some minmax theorems for even and C1 functionals established by Ghoussoub are extended to the case of functionals that are the sum of a locally Lipschitz continuous, even term and a convex, proper, lower semi-continuous, even function. A class of non-smooth functionals admitting an unbounded sequence of critical values is also pointed out. © 2008 Glasgow Mathematical Journal Trust.