Håkan Hedenmalm: Heisenberg's uncertainty principle in the sense of Beurling

Abstract: In the posthumous material after Beurling, a result
in the spirit of Hardy's uncertainty principle was found.
It then transpired that Hörmander had retained a copy of Beurling's
original proof, from his time at Princeton. Here, we present a
completely different proof of Beurling's theorem, which is based on
symmetry and Liouville's theorem.