A dynamical Amrein-Berthier uncertainty principle

Abstract

Given a selfadjoint magnetic Schr\"odinger operator \begin{equation*} H = ( i \partial + A(x) )^2 + V(x) \end{equation*} on $L^{2}(\mathbb{R}^n)$, with $V(x)$ strictly subquadratic and $A(x)$ strictly sublinear, we prove that the flow $u(t)=e^{-itH}u(0)$ satisfies an Amrein--Berthier type inequality \begin{equation*} \|u(t)\|_{L^{2}}\lesssim_{E,F,T,A,V} \|u(0)\|_{L^{2}(E^{c})} + \|u(T)\|_{L^{2}(F^{c})}, \qquad 0\le t\le T \end{equation*} for all compact sets $E,F \subset \mathbb{R}^{n}$. In particular, if both $u(0)$ and $u(T)$ are compactly supported, then $u$ vanishes identically. Under different assumptions on the operator, which allow for time--dependent coefficients, the result extends to sets $E,F$ of finite measure. We also consider a few variants for Schr\"{o}dinger operators with singular coefficients, metaplectic operators, and we include applications to control theory.