On the theoretical side, the available inflationary models may be also evaluated with respect to their “cost”, ie. against what one gets from a given model in relation to what one puts in! Our approach does not introduce new fields, beyond those already present in gravity and supergravity. We also exploit (super)gravity interactions only,ie. do not introduce new interactions, in order to describe inflation. Before going into details, let me address two common prejudices and objections. The higher-order curvature terms are usually expected to be relevant near the spacetime curvature singularities. It is also quite possible that some higher-derivative gravity, subject to suitable constraints, could be the effective.
