Rescuing Quartic and Natural Inflation in the Palatini Formalism
  When considered in the Palatini formalism, the Starobinsky model does not
provide us with a mechanism for inflation due to the absence of a propagating
scalar degree of freedom. By (non)--minimally coupling scalar fields to the
Starobinsky model in the Palatini formalism we can in principle describe the
inflationary epoch. In this article, we focus on the minimally coupled quartic
and natural inflation models. Both theories are excluded in their simplest
realization since they predict values for the inflationary observables that are
outside the limits set by the Planck data. However, with the addition of the
$R^2$ term and the use of the Palatini formalism, we show that these models can
be rendered viable.
