A Search for an N=2 Inflaton Potential
  We consider N=2 supergravity theories that have the same spectrum as the R+R^2 supergravity, as predicted from the off-shell counting of degrees of freedom. These theories describe standard N=2 supergravity coupled to one or two long massive vector multiplets. The central charge is not gauged in these models and they have a Minkowski vacuum with N=2 unbroken supersymmetry. The gauge symmetry, being non-compact, is always broken. $\alpha$-deformed inflaton potentials are obtained, in the case of a single massive vector multiplet, with $\alpha=1/3$ and $2/3$. The $\alpha=1$ potential (i.e. the Starobinsky potential) is also obtained, but only at the prize of having a single massive vector and a residual unbroken gauge symmetry. The inflaton corresponds to one of the Cartan fields of the non-compact quaternionic-K{\"a}hler cosets. 
Anna Ceresole, Gianguido Dall'Agata, Sergio Ferrara, Mario Trigiante   and Antoine Van Proeyen
hep-th gr-qc