Production and backreaction of massive fermions during axion inflation
  with non-Abelian gauge fields
  We study the production and backreaction of massive vector-like fermions in
the background of a classical SU(2) gauge field during axion-driven inflation.
We demonstrate all ultraviolet divergences due to the interactions with the
fermions can be absorbed by renormalization of the axion wavefunction and the
gauge coupling. The effects of the fermion-axion interaction vanish in the
massless limit as required by symmetry. For very massive fermions, contact
interactions are induced between the axion, the gauge field and the
gravitational field. In this massive limit, we find the usual axion-gauge field
interactions are induced, however, in addition we observe the appearance of
axion self-interactions, as well as kinetic braiding of the axion with the
Einstein tensor. These new axion derivative interactions present intriguing
opportunities for model building and phenomenology.
