Trajectories with suppressed tensor-to-scalar ratio in Aligned Natural Inflation

Marco Peloso, Caner Unal

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34 Scopus citations


In Aligned Natural Inflation, an alignment between different potential terms produces an inflaton excursion greater than the axion scales in the potential. We show that, starting from a general potential of two axions with two aligned potential terms, the effective theory for the resulting light direction is characterized by four parameters: an effective potential scale, an effective axion constant, and two extra parameters (related to ratios of the axion scales and the potential scales in the 2-field theory). For all choices of these extra parameters, the model can support inflation along valleys (in the 2-field space) that end in minima of the potential. This leads to a phenomenology similar to that of single field Natural Inflation. For a significant range of the extra two parameters, the model possesses also higher altitude inflationary trajectories passing through saddle points of the 2-field potential, and disconnected from any minimum. These plateaus end when the heavier direction becomes unstable, and therefore all of inflation takes place close to the saddle point, where - due to the higher altitude - the potential is flatter (smaller parameter). As a consequence, a tensor-to-scalar ratio r = O (10-4 - 10-2) can be easily achieved in the allowed ns region, well within the latest 1 σ CMB contours.

Original languageEnglish (US)
Article number040
JournalJournal of Cosmology and Astroparticle Physics
Issue number6
StatePublished - Jun 1 2015

Bibliographical note

Publisher Copyright:
© 2015 IOP Publishing Ltd and Sissa Medialab srl.


  • axions
  • ination


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