Global Cauchy problems for the nonlocal (derivative) NLS in $E^s_\sigma$

TL;DR

This paper proves global existence and uniqueness of solutions for the nonlocal (derivative) nonlinear Schrödinger equation in certain super-critical function spaces, without smallness conditions on initial data, under specific support conditions.

Contribution

It establishes the first global well-posedness results for the nonlocal (derivative) NLS in super-critical spaces $E^s_\sigma$ with Fourier support restrictions.

Findings

Global existence and uniqueness of solutions in $E^s_\sigma$

No smallness condition needed for initial data

Solutions exist for initial data with Fourier support in $(0, \infty)$

Abstract

We consider the Cauchy problem for the (derivative) nonlocal NLS in super-critical function spaces $E^s_\sigma$ for which the norms are defined by $$ \|f\|_{E^s_\sigma} = \|\langle\xi\rangle^\sigma 2^{s|\xi|}\hat{f}(\xi)\|_{L^2}, \ s<0, \ \sigma \in \mathbb{R}. $$ Any Sobolev space $H^{r}$ is a subspace of $E^s_\sigma$, i.e., $H^r \subset E^s_\sigma$ for any $ r,\sigma \in \mathbb{R}$ and $s<0$. Let $s<0$ and $\sigma>-1/2$ ($\sigma >0$) for the nonlocal NLS (for the nonlocal derivative NLS). We show the global existence and uniqueness of the solutions if the initial data belong to $E^s_\sigma$ and their Fourier transforms are supported in $(0, \infty)$, the smallness conditions on the initial data in $E^s_\sigma$ are not required for the global solutions.