ABSTRACT
Critical point theory is one of the important methods of solving nonlinear problems. The method can be applied if one wishes to solve the Euler-Lagrange system corresponding to a C 1 functional G on a Banach space E. If the functional is semibounded one can attempt to find an extremum. Otherwise one is required to search for local critical points. Several techniques have been developed for finding such points, or at least Palais-Smale sequences. These are sequences satisfying G ( u k ) → c , G ′ ( u k ) → 0. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780203744369/d9858e60-9246-4876-bb34-38e3d28ecc5f/content/eq1935.tif"/>
