2010/11/30 by Neil Barnaby, Marco Peloso · 2 citations
Physics and Astronomy · #hep-ph #astro-ph.CO #hep-th
paper · pdf · doi:10.1103/physrevlett.106.181301
published as Phys.Rev.Lett.106:181301,2011 · 4 pages, 2 figures. V2: One approximation improved, resulting in stronger observational constraints. Physical results unchanged. References added
arxiv created 2010/12/14 · arxiv updated 2011/05/12
The inflationary paradigm has enjoyed phenomenological success, however, a compelling particle physics realization is still lacking. The key obstruction is that the requirement of a suitably flat scalar potential is sensitive to Ultra-Violet (UV) physics. Axions are among the best-motivated inflaton candidates, since the flatness of their potential is naturally protected by a shift symmetry. We re-consider the cosmological perturbations in axion inflation, consistently accounting for the coupling to gauge fields ϕF F, which is generically present in these models. This coupling leads to production of gauge quanta, which provide a new source of inflaton fluctuations, δϕ. For an axion decay constant < 10-2 Mp, this effect typically dominates over the standard fluctuations from the vacuum, and saturates the current observational bounds on nongaussianity of the CMB anisotropies. Since sub-Planckian values of the decay constant are typical for concrete realizations that admit a UV completion (such as N-flation and axion monodromy), we conclude that large nongaussianity is easily obtained in very minimal and natural realizations of inflation.