In this paper, we compare brane inflation models with the Planck data and the pre-Planck data (which combines WMAP, ACT, SPT, BAO and H0 data). The Planck data prefer a spectral index less than unity at more than 5\sigma confidence level, and a running of the spectral index at around 2\sigma confidence level. We find that the KKLMMT model can survive at the level of 2\sigma only if the parameter β (the conformal coupling between the Hubble parameter and the inflaton) is less than O(10−3), which indicates a certain level of fine-tuning. The IR DBI model can provide a slightly larger negative running of spectral index and red tilt, but in order to be consistent with the non-Gaussianity constraints from Planck, its parameter also needs fine-tuning at some level.
Cite
@article{arxiv.1303.6244,
title = {Confronting brane inflation with Planck and pre-Planck data},
author = {Yin-Zhe Ma and Qing-Guo Huang and Xin Zhang},
journal= {arXiv preprint arXiv:1303.6244},
year = {2013}
}