Tensor Modes in Pure Natural Inflation

Abstract

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.

6 pages, 6 figures; v2: journal version

References in corpus (2)

• $\theta$ dependence of 4D $SU(N)$ gauge theories in the large-$N$ limit
• Pure Natural Inflation

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