| Contents |
| In the limit of small coupling in the nearest neighbour interaction,
and small $\ell^2$ norm, an extensive resonant normal form for the
Klein-Gordon finite chain is constructed. It turns out to be a generalized
discrete nonlinear Schr\"odinger (GdNLS) model, characterized by all
neighbours couplings, both in the linear and nonlinear terms, with
exponential decay of the coefficients with the distance between
sites. Long time stability of true or approximated small amplitude
Breathers can be obtained using variational arguments. |
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