In this short overview I present some recent results about the KAM theory for multidimensional partial differential equations (PDEs) trying to avoid technicalities. In particular I will not state a precise KAM theorem but I will focus on the dynamical consequences for the PDEs: the existence and the stability (or not) of quasi periodic in time solutions. Concretely, I present the complete study of the nonlinear beam equation on the -dimensional torus recently obtained in collaboration with H. Eliasson and S. Kuksin. When we are able to construct explicit examples where the quasi periodic solutions are linearly unstable, a new feature in Hamiltonian PDEs that could complement recent results in weak turbulence theory.
@article{JEDP_2014____A4_0, author = {Gr\'ebert, Beno\^\i t}, title = {Recent results on KAM for multidimensional PDEs}, journal = {Journ\'ees \'equations aux d\'eriv\'ees partielles}, year = {2014}, pages = {1-12}, doi = {10.5802/jedp.107}, language = {en}, url = {http://dml.mathdoc.fr/item/JEDP_2014____A4_0} }
Grébert, Benoît. Recent results on KAM for multidimensional PDEs. Journées équations aux dérivées partielles, (2014), pp. 1-12. doi : 10.5802/jedp.107. http://gdmltest.u-ga.fr/item/JEDP_2014____A4_0/
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