58Exx Variational problems in infinite-dimensional spaces

58E05  Abstract critical point theory (Morse theory,
               Ljusternik-Schnirelman (Lyusternik-Shnirelman)
               theory, etc.)
58E07  Abstract bifurcation theory
58E09  Group-invariant bifurcation theory
58E10  Applications to the theory of geodesics (problems in one
               independent variable)
58E11  Critical metrics
58E12  Applications to minimal surfaces (problems in two
               independent variables)
58E15  Application to extremal problems in several variables;
               Yang-Mills functionals, See also {81T13}, etc.
58E17  Pareto optimality, etc., applications to economics
58E20  Harmonic maps
58E25  Applications to control theory (optimal and nonoptimal)
58E30  Variational principles
58E35  Variational inequalities (global problems)
58E40  Group actions
58E50  Applications
58E99  None of the above but in this section