Singularities for solutions to time dependent Schr\"odingier equations   with sub-quadratic potential
  In this article, we determine the wave front sets of solutions to time dependent Schr\"odinger equations with a sub-quadratic potential by using the representation of the Schr\"dingier evolution operator via wave packet transform (short time Fourier transform). 
Keiichi Kato and Shingo Ito
math.AP math-ph math.MP