http://arxiv.org/abs/1711.10490
We study tensor modes in pure natural inflation (arXiv:1706.08522), a recently-proposed inflationary model in which an axionic inflaton couples to pure Yang-Mills gauge fields. We find that the tensor-to-scalar ratio r is naturally bounded from below. This bound originates from the finiteness of the number of metastable branches of vacua in pure Yang-Mills theories. Details of the model can be probed by future cosmic microwave background experiments and improved lattice gauge theory calculations of the theta-angle dependence of the vacuum energy.
Y. Nomura and M. Yamazaki
Thu, 30 Nov 17
26/77
Comments: 6 pages, 6 figures