Compactly supported real scalar potentials realizing the Hardy uncertainty endpoint for Schrödinger evolutions

Abstract

At the critical Hardy Gaussian weight for the Schrödinger equation in one space dimension on $[0,1]$, the known nonzero scalar example in the weighted $L^2$ class carries a complex-valued potential. Cassano and Fanelli observed that the existence of a real-valued scalar endpoint example was open, and produced examples with real electric and magnetic potentials only after introducing a magnetic potential. We construct a nonzero smooth solution of $i\partial_t u+\partial_x^2 u=Vu$ on $\mathbb{R}\times[0,1]$ such that $e^{x^2/4}u(\cdot,0),e^{x^2/4}u(\cdot,1)\in L^2(\mathbb{R})$ and the potential is bounded, smooth, real-valued, and purely scalar and is supported in one fixed compact spatial interval for all times. This compact-support endpoint example is the main result. We also record the explicit rational-tail realization underlying the construction. The main results of this paper were obtained by the multi-agent system Eureka and have subsequently been verified by the authors.