Classification of threshold dynamics for the focusing mass-critical inhomogeneous NLS

Abstract

We study the focusing mass-critical inhomogeneous nonlinear Schrödinger equation $i{\partial }_{t}u+\Delta u+|x{|}^{-b}|u{|}^{\frac{4-2b}{d}}u=0$ in dimensions $d\ge 3$. For $\frac{1}{2}<b<\min \{2,d/2\}$, we prove that every forward-global $H^1$ solution with mass equal to that of the ground state $Q$ either scatters forward or coincides with $e^{it}Q$, up to phase rotation and scaling. As a consequence, every solution with nonradial $H^1$ initial data at the ground-state mass must be global and scatter in both time directions. For $0<b\le \frac{1}{2}$, analogous rigidity and scattering results hold under an additional finite-variance assumption. The key new ingredients in our proof are a nonradial incoming/outgoing decomposition and exterior frequency-decay estimates, which yield the kinetic-energy localization needed for a localized virial argument.