R. de la Llave, A. Gonz\'alez, \'A. Jorba, J. Villanueva
KAM theory without action-angle variables
(635K, postscript)
ABSTRACT. Given a torus approximately invariant under a symplectic map,
we find sufficient conditions for the existence of a true invariant
torus close to the given one.
We do not assume either that we are working on action-angle variables
nor that the map is close to integrable.
The proposed method is also useful to compute numericaly invariant
tori for symplectic maps. Analogous results are also true for vector fileds.