99-62 Panayotis Panayotaros
Nekhoroshev stability of non-linear normal modes near an elliptic fixed point of a Hamiltonian system with symmetry (85K, TeX) Feb 22, 99
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Abstract. We consider Hamiltonian systems of resonantly coupled harmonic oscillators with a physically motivated $U(1)$ symmetry, and identify a class of small amplitude periodic orbits (the non-linear normal modes) of approximating systems. We show that under some additional conditions on the quartic part of the Birkhoff normal form Hamiltonian that are in many cases weaker than integrability and convexity, the non-linear normal modes are Nekhoroshev stable.

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