Wave front set for solutions to Schrodinger equations with time-dependent variable coefficients

In this paper, we determine the C-infinity type wave front sets of the solutions to the Schrodinger equations with time-dependent variable coefficients and potentials by using the wave packet transform. We introduce the infinite sum and estimate the perturb terms of the flat Laplacian on flat plane, which cannot be estimated by the method in Kato-Ito.