Tensor spectra templates for axion-gauge fields dynamics during inflation

Abstract

SU(2) gauge fields can generate large gravitational waves during inflation, if they are coupled to an axion which can be either the inflaton or a spectator field. The shape of the produced tensor power spectrum h depends on the form of the axion potential. We derive analytic expressions and provide general templates for h for various types of the spectator axion potential. Furthermore, we explore the detectability of the oscillatory feature, which is present in h in the case of an axion monodromy model, by possible future CMB B-mode polarization observations.