Two-dimensional invariant tori in the neighborhood of an elliptic equilibrium of Hamiltonian systems
Hamiltonian systems in \(\mathbb{R}^{2n}\) are shown to possess, in the neighbourhood of an elliptic equilibrium, either a four-dimensional invariant disc or an invariant Cantor set with a positive \((n+2)\)-dimensional Lebesgue measure. The assumptions are related to small divisors conditions.
scientific article; zbMATH DE number 5601629