The two-field regime of natural inflation

Ana Achúcarro, Vicente Atal, Masahiro Kawasaki, Fuminobu Takahashi

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)


The simplest two-field completion of natural inflation has a regime in which both fields are active and in which its predictions are within the Planck 1-σ confidence contour. We show this for the original model of natural inflation, in which inflation is achieved through the explicit breaking of a U(1) symmetry. We consider the case in which the mass coming from explicit breaking of this symmetry is comparable to that from spontaneous breaking, which we show is consistent with a hierarchy between the corresponding energy scales. While both masses are comparable when the observable modes left the horizon, the mass hierarchy is restored in the last e-foldings of inflation, rendering the predictions consistent with the isocurvature bounds. For completeness, we also study the predictions for the case in which there is a large hierarchy of masses and an initial period of inflation driven by the (heavy) radial field.

Original languageEnglish
Article number044
JournalJournal of Cosmology and Astroparticle Physics
Issue number12
Publication statusPublished - 2015 Dec 22


  • axions
  • ination
  • physics of the early universe

ASJC Scopus subject areas

  • Astronomy and Astrophysics


Dive into the research topics of 'The two-field regime of natural inflation'. Together they form a unique fingerprint.

Cite this