Global bifurcations of critical orbits of \(G\)-invariant strongly indefinite functionals (Q629301)

The authors define the degree for a special type of \(G\)-invariant strongly indefinite functionals of the class \(C^1\) acting from the separable Hilbert representation of the compact Lie group \(G\). Using this degree, they investigate the set of critical orbits of such functionals, especially the existence of a global bifurcation. The abstract Rabinowitz-type theorem formulated in the first part allows later to study bifurcations of weak solutions for a concrete differential problem, namely, the non-cooperative system of elliptic equations.