Results on Normal Forms for FPU Chains
Henrici, Andreas ; Kappeler, Thomas
In: Communications in Mathematical Physics, 2008, vol. 278, no. 1, p. 145-177
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- In this paper we prove, among other results, that near the equilibirum position, any periodic FPU chain with an odd number N of particles admits a Birkhoff normal form up to order 4, whereas any periodic FPU chain with N even admits a resonant normal form up to order 4. This resonant normal form of order 4 turns out to be completely integrable. Further, for N odd, we obtain an explicit formula of the Hessian of its Hamiltonian at the fixed point