INTEGRABLE HAMILTONIAN-SYSTEMS;
LOWER-DIMENSIONAL TORI;
INVARIANT TORI;
KAM THEOREM;
D O I:
10.1007/s00030-016-0425-7
中图分类号:
O29 [应用数学];
学科分类号:
070104 ;
摘要:
We consider a system of rotators subject to a small quasi periodic forcing. We require the forcing to be analytic and satisfy a time reversibility property and we assume its frequency vector to be Bryuno. Then we prove that, without imposing any non-degeneracy condition on the forcing, there exists at least one quasi-periodic solution with the same frequency vector as the forcing. The result can be interpreted as a theorem of persistence of lower-dimensional tori of arbitrary codimension in degenerate cases.