How attractive is the isotropic attractor solution of axion-SU(2)
  inflation?
  The key to the phenomenological success of inflation models with axion and
SU(2) gauge fields is the isotropic background of the SU(2) field. Previous
studies showed that this isotropic background is an attractor solution during
inflation starting from anisotropic (Bianchi Type I) spacetime; however, not
all possible initial anisotropic parameter space was explored. In this paper,
we explore more generic initial conditions without assuming the initial
slow-roll dynamics. We find some initial anisotropic parameter space which does
not lead to the isotropic background, but to violation of slow-roll conditions,
terminating inflation prematurely. The basin of attraction increases when we
introduce another scalar field acting as inflaton and make the axion-SU(2)
system a spectator sector. Therefore, the spectator axion-SU(2) model is
phenomenologically more attractive.
