Large Tensor-to-Scalar Ratio in Small-Field Inflation
  We show that density perturbations seeded by the inflaton can be suppressed
when having additional light degrees of freedom contributing to the production
of perturbations. The inflaton fluctuations affect the light field dynamics by
modulating the length of the inflationary period, hence produce additional
density perturbations in the post-inflationary era. Such perturbations can
cancel those generated during inflation as both originate from the same
inflaton fluctuations. This allows production of large gravitational waves from
small-field inflation, which is normally forbidden by the Lyth bound on the
inflaton field excursion. We also find that the field bound is taken over by
the light scalar when the inflaton-induced perturbations are suppressed, thus
present a generalized form of the Lyth bound that applies to the total field
space.
