GUT-scale inflation with sizeable tensor modes
  A sizeable tensor-to-scalar ratio, such as recently claimed by BICEP2, would
imply a scale of inflation at the typical scale of supersymmetric grand
unification. This could be an accident, or strong support for supersymmetric
theories. Models of F-term hybrid inflation naturally connect the GUT scale
with the inflationary scale, but they also predict the tensor-to-scalar ratio
to be unmeasurably small. In this work we analyze a general UV embedding of
F-term hybrid inflation into a supergravity theory with a general Kahler
potential. The CMB observables are generated during the early phase of
inflation, at large inflaton values, where the potential is dominated by
Planck-suppressed operators. Tuning the leading higher-order terms can give an
inflaton potential with sizeable tensor fluctuations and a field excursion
which is still sub-Planckian but close to the Planck scale, as expected from
the Lyth bound.
