Large Tensor-to-Scalar Ratio in Small-Field Inflation

Understand

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.