Long Time Dynamics for Generalized Korteweg–de Vries and Benjamin–Ono Equations

Abstract

We provide an accurate description of the long time dynamics of the solutions of the generalized Korteweg-De Vries (gKdV) and Benjamin-Ono (gBO) equations on the one dimension torus, without external parameters, and that are issued from almost any (in probability and in density) small and smooth initial data. We stress out that these two equations have unbounded nonlinearities. In particular, we prove a long-time stability result in Sobolev norm: given a large constant r and a sufficiently small parameter $\epsilon$, for generic initial datum u(0) of size $\epsilon$, we control the Sobolev norm of the solution u(t) for times of order $\epsilon$^{--r}. These results are obtained by putting the system in rational normal form : we conjugate, up to some high order remainder terms, the vector fields of these equations to integrable ones on large open sets surrounding the origin in high Sobolev regularity.