Phenomenology of a pseudo-scalar inflaton: Naturally large nongaussianity

Neil Barnaby, Ryo Namba, Marco Peloso

Research output: Contribution to journalArticlepeer-review

142 Scopus citations


Many controlled realizations of chaotic inflation employ pseudo-scalar axions. Pseudo-scalars φ are naturally coupled to gauge fields through cφF. In the presence of this coupling, gauge field quanta are copiously produced by the rolling inflaton. The produced gauge quanta, in turn, source inflaton fluctuations via inverse decay. These new cosmological perturbations add incoherently with the "vacuum" perturbations, and are highly nongaussian. This provides a natural mechanism to generate large nongaussianity in single or multi field slow-roll inflation. The resulting phenomenological signatures are highly distinctive: large nongaussianity of (nearly) equilateral shape, in addition to detectably large values of both the scalar spectral tilt and tensor-to-scalar ratio (both being typical of large field inflation). The WMAP bound on nongaussianity implies that the coupling c of the pseudo-scalar inflaton to any gauge field must be smaller than about 102M p-1.

Original languageEnglish (US)
Article number009
JournalJournal of Cosmology and Astroparticle Physics
Issue number4
StatePublished - Apr 1 2011


  • axions
  • inflation
  • non-gaussianity

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