$\beta$-function formalism for inflationary models with a non minimal
  coupling with gravity
  We discuss the introduction of a non minimal coupling between the inflaton
and gravity in terms of the recently proposed $\beta$-function formalism for
inflation\cite{Binetruy:2014zya}. Via a field redefinition we reduce to the
case of minimally coupled theories. The universal attractor at strong coupling
has a simple explanation in terms of the new field. Generalizations are
discussed and the possibility of evading the universal attractor is shown.
