Almost sure well-posedness and scattering of the 3D cubic nonlinear Schr\"odinger equation

TL;DR

This paper establishes almost sure local and global well-posedness and scattering results for the 3D cubic defocusing nonlinear Schrödinger equation with low regularity random initial data, extending previous deterministic results.

Contribution

It proves the first almost sure large data global well-posedness and scattering for the 3D cubic NLS with low regularity radial data, lowering the derivative order needed.

Findings

Almost sure local well-posedness for s in [1/6, 1/2)

Global well-posedness and scattering for s in (17/40, 1/2)

Control of energy increment with derivative on linear flow

Abstract

We study the random data problem for 3D, defocusing, cubic nonlinear Schr\"odinger equation in $H_x^s(\mathbb{R}^3)$ with $s<\frac 12$. First, we prove that the almost sure local well-posedness holds when $\frac{1}{6}\leqslant s<\frac 12$ in the sense that the Duhamel term belongs to $H_x^{1/2}(\mathbb{R}^3)$. Furthermore, we prove that the global well-posedness and scattering hold for randomized, radial, large data $f\in H_x^{s}(\mathbb{R}^3)$ when $\frac{17}{40}< s<\frac 12$. The key ingredient is to control the energy increment including the terms where the first order derivative acts on the linear flow, and our argument can lower down the order of derivative more than $\frac12$. To our best knowledge, this is the first almost sure large data global result for this model.