The Existence of Full Dimensional KAM tori for Nonlinear Schrödinger equation (2103.14777v1)

Abstract: In this paper, we will prove the existence of full dimensional tori for 1-dimensional nonlinear Schr\"odinger equation with periodic boundary conditions \begin{equation*}\label{L1} \mathbf{i}u_t-u_{xx}+V*u+\epsilon|u|^4u=0,\hspace{12pt}x\in\mathbb{T}, \end{equation*} where $V*$ is the convolution potential. Here the radius of the invariant torus satisfies a slower decay, i.e. \begin{equation*}\label{031601} I_n\sim e^{- \ln^{\sigma}|n|},\qquad \mbox{as}\ |n|\rightarrow\infty, \end{equation*} for any $\sigma>2$, which improves the result given by Bourgain (J. Funct. Anal. 229 (2005), no.1, 62-94).