Non-trivial Extension of Starobinsky Inflation
  We consider a non-canonic field in the context of Starobinsky inflation. We
work in Einstein-frame. In this frame, the gravitational part of the action is
equivalent to the Hilbert-Einstein action, plus a scalar field called scalaron.
  We investigate a model with a heavy scalaron trapped at the effective
potential minimum, where its fluctuations are negligible. To be more explicit,
we consider a Dirac-Born-Infeld (DBI) field, which is usually considered within
the brane inflation context, as the non-canonic field. Although, the DBI field
governs inflation through implicit dependence on Scalaron the boost factor, and
other quantities are different from the standard DBI model. For appropriate
parameters, this model is consistent with the Planck results.
