Ultra slow-roll G-inflation
  The conventional slow-roll approximation is broken in the so-called "ultra
slow-roll" models of inflation, for which the inflaton potential is exactly (or
extremely) flat. The interesting nature of (canonical) ultra slow-roll
inflation is that the curvature perturbation grows on superhorizon scales, but
has a scale-invariant power spectrum. We study the ultra slow-roll inflationary
dynamics in the presence of non-canonical kinetic terms of the scalar field,
namely ultra slow-roll G-inflation. We compute the evolution of the curvature
perturbation and show that the primordial power spectrum follows a broken power
law with an oscillation feature. It is demonstrated that this could explain the
lack of large-scale power in the cosmic microwave background temperature
anisotropies. We also point out that the violation of the null energy condition
is prohibited in ultra slow-roll G-inflation and hence a blue tensor tilt is
impossible as long as inflation is driven by the potential. This statement is,
however, not true if the energy density is dominated by the kinetic energy of
the scalar field.
