In this paper we construct and approximate breathers in the DNLS model
starting from the continuous limit: such periodic solutions are obtained as
perturbations of the ground state of the NLS model in $H^1(\RR^n)$, with
$n=1,2$. In both the dimensions we recover the Sievers-Takeno (ST) and the Page
(P) modes; furthermore, in $\RR^2$ also the two hybrid (H) modes are
constructed. The proof is based on the interpolation of the lattice using the
Finite Element Method (FEM).
In this paper we construct and approximate breathers in the DNLS model
starting from the continuous limit: such periodic solutions are obtained as
perturbations of the ground state of the NLS model in $H^1(\RR^n)$, with
$n=1,2$. In both the dimensions we recover the Sievers-Takeno (ST) and the Page
(P) modes; furthermore, in $\RR^2$ also the two hybrid (H) modes are
constructed. The proof is based on the interpolation of the lattice using the
Finite Element Method (FEM).
In this paper we study small amplitude solutions of nonlinear Klein Gordon
equations with a potential. Under smoothness and decay assumptions on the
potential and a genericity assumption on the nonlinearity, we prove that all
small amplitude initial data with finite energy give rise to solutions
asymptotically free. In the case where the linear system has at most one bound
state the result was already proved by Soffer and Weinstein: we obtain here a
result valid in the case of an arbitrary number of possibly degenerate bound
states.