Global methods of the calculus of variations and the infinite dimensional critical point theory of Ljusternik and Schnirelmann are applied to give results on the existence of so-called critical values and essential critical values. The case of continuous, not necessarily differentiable functionals is considered and studied introducing a suitable variant of the Palais-Smale condition.
Cite this article
Berardino Sciunzi, On the Three “Essential” Critical Values Theorem. Z. Anal. Anwend. 20 (2001), no. 3, pp. 553–563DOI 10.4171/ZAA/1030