Some remarks on critical point theory for nondifferentiable functionals

In this paper we study the existence of critical points of nondifferentiable functionals J of the kind with A (x,z) a Carathéodory function bounded between positive constant and with bounded derivative respect to the variable z, and F (x,z) is the primitive of a (Carathéodory) nonlinearity f (x,z) satisfying suitable hipotheses. Since J is just differentible along bounded directions, a suitable compactness condition is introduced. Its connection with coercivity is discussed. In addition, the case of concave-convex nonlinearities f (x,z), unbounded coefficients A (x,z) and related problems are also studied. Received December 19, 1997