D. Bambusi, M. Berti, E. Magistrelli
Degenerate KAM theory for partial differential equations.
(551K, pdf)
ABSTRACT. This paper deals with degenerate KAM theory for lower
dimensional elliptic tori of infinite dimensional Hamiltonian systems,
depending on one parameter only. We assume that the linear frequencies
are analytic functions of the parameter, satisfy a weak non degeneracy
condition of R ssmann type and an asymptotic behavior. An application
to nonlinear wave equations is given.