A Multiple Step-like Spectrum of Primordial Perturbation
  We show that if the inflaton effective potential has multiple discontinuous points in its first derivative, the spectrum of primordial perturbation will be multiple step-like. We give a general analysis by applying a simple model. In principle, as long as the height of step is low enough, the result of spectrum will be consistent with observations. 
Jie Liu, Yun-Song Piao
hep-th gr-qc