A Super-Exponential Decaying Property of Odd-Dimensional Wave Scattered   by an Obstacle
  We examine an inverse backscattering property of wave motion imposed by an obstacle. We show that if the wave propagator decays super-exponentially along the back-scattered geodesics, then the involved scatterer must be trivial. In particular, if the fundamental solution decays super-exponentially some time after t=0, it vanishes for all time. We use finite speed of propagation in this article. 
Lung-Hui Chen
math.FA