Evolution of Non-linear Fluctuations in Preheating after Inflation
  We investigate the evolution of the non-linear long wavelength fluctuations during preheating after inflation. By using the separate universe approach, the temporal evolution of the power spectrum of the scalar fields and the curvature variable is obtained numerically. We found that the amplitude of the large scale fluctuations is suppressed after non-linear evolution during preheating. 
Yasusada Nambu and Yohei Araki