M. Degiovanni
Some basic tools of critical point theory

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MSC:
58E05 Abstract critical point theory (Morse theory, Ljusternik-Schnirelman (Lyusternik-Shnirel'man) theory, etc.)
35J65 Nonlinear boundary value problems for linear elliptic PDE; boundary value problems for nonlinear elliptic PDE
Abstract: The basic tools of abstract critical point theory, namely pseudo-gradient vector fields, deformation theorems, linking theorems, are presented. The continuity, differentiability and compactness of the Nemytskij operator between Lebesgue spaces and Sobolev spaces is also studied.
Keywords: critical point theory, deformation theorems, linking theorems, Nemytskij operator