The Existence of Full Dimensional KAM tori for Nonlinear Schr\"odinger equation

TL;DR

This paper proves the existence of full-dimensional KAM tori for a 1D nonlinear Schrödinger equation with convolution potential, demonstrating a slower decay rate of the invariant torus radius, thus extending previous results.

Contribution

It establishes the existence of full-dimensional KAM tori with a slower decay rate for the radius, improving upon Bourgain's earlier results.

Findings

Existence of full-dimensional KAM tori for the nonlinear Schrödinger equation.

The radius of invariant tori decays as e^{-ln^{σ}|n|} with σ>2.

Extension of previous results by Bourgain on KAM tori.

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).