MPEJ Volume 8, No. 1, 13 pp.
Received: Feb 13, 2002. Accepted: Feb 21, 2002.

Bambusi D., Gaeta G.:
On persistence of invariant tori and a theorem by Nekhoroshev

ABSTRACT: We give a proof of a theorem by N.N. Nekhoroshev concerning
Hamiltonian systems with $n$ degrees of freedom and $s$ integrals of
motion in involution, where $1 \leq s \leq n$.  Such a theorem ensures
persistence of $s$-dimensional invariant tori under suitable
nondegeneracy conditions generalizing Poincar\'e's condition on the
Floquet multipliers.


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