Natural Inflation, Planck Scale Physics and Oscillating Primordial   Spectrum
  In the ``natural inflation'' model, the inflaton potential is periodic. We show that Planck scale physics may induce corrections to the inflaton potential, which is also periodic with a greater frequency. Such high frequency corrections produce oscillating features in the primordial fluctuation power spectrum, which are not entirely excluded by the current observations and may be detectable in high precision data of cosmic microwave background (CMB) anisotropy and large scale structure (LSS) observations. 
Xiulian Wang, Bo Feng, Mingzhe Li, Xue-Lei Chen, and Xinmin Zhang