Primordial gravitational waves from axion-gauge fields dynamics

Emanuela Dimastrogiovanni, Matteo Fasiello, Tomohiro Fujita

Research output: Contribution to journalArticlepeer-review

96 Citations (Scopus)


Inspired by the chromo-natural inflation model of Adshead&Wyman, we reshape its scalar content to relax the tension with current observational bounds. Besides an inflaton, the setup includes a spectator sector in which an axion and SU(2) gauge fields are coupled via a Chern-Simons-type term. The result is a viable theory endowed with an alternative production mechanism for gravitational waves during inflation. The gravitational wave signal sourced by the spectator fields can be much larger than the contribution from standard vacuum fluctuations, it is distinguishable from the latter on the basis of its chirality and, depending on the theory parameters values, also its tilt. This production process breaks the well-known relation between the tensor-to-scalar ratio and the energy scale of inflation. As a result, even if the Hubble rate is itself too small for the vacuum to generate a tensor amplitude detectable by upcoming experiments, this model still supports observable gravitational waves.

Original languageEnglish
Article number019
JournalJournal of Cosmology and Astroparticle Physics
Issue number1
Publication statusPublished - 2017 Jan 11
Externally publishedYes


  • Axions
  • Gravitational waves / theory
  • Gravitational waves and CMBR polarization
  • Inflation

ASJC Scopus subject areas

  • Astronomy and Astrophysics


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