Scale-dependent gravitational waves from a rolling axion

Ryo Namba, Marco Peloso, Maresuke Shiraishi, Lorenzo Sorbo, Caner Unal

Research output: Contribution to journalArticlepeer-review

120 Scopus citations


We consider a model in which a pseudo-scalar field σ rolls for some e-folds during inflation, sourcing one helicity of a gauge field. These fields are only gravitationally coupled to the inflaton, and therefore produce scalar and tensor primordial perturbations only through gravitational interactions. These sourced signals are localized on modes that exit the horizon while the roll of σ is significant. We focus our study on cases in which the model can simultaneously produce (i) a large gravitational wave signal, resulting in observable B-modes of the CMB polarizations, and (ii) sufficiently small scalar perturbations, so to be in agreement with the current limits from temperature anisotropies. Different choices of parameters can instead lead to a localized and visible departure from gaussianity in the scalar sector, either at CMB or LSS scales.

Original languageEnglish
Article number041
JournalJournal of Cosmology and Astroparticle Physics
Issue number1
StatePublished - 22 Jan 2016
Externally publishedYes


  • cosmological perturbation theory
  • ination
  • primordial gravitational waves (theory)

ASJC Scopus subject areas

  • Astronomy and Astrophysics


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