The DBI action, higher-derivative supergravity, and flattening inflaton potentials

In string theory compactifications it is common to find an effective lagrangian for the scalar fields with a non-canonical kinetic term. we study the effective action of the scalar position moduli of type ii dp-branes. in many instances the kinetic terms are in fact modified by a term proportional to the scalar potential itself. this can be linked to the appearance of higher-dimensional supersymmetric operators correcting the kähler potential. we identify the supersymmetric dimension-eight operators describing the α′ corrections captured by the d-brane dirac-born-infeld action. our analysis then allows an embedding of the d-brane moduli effective action into an $$ mathcal{n}=1 $$ supergravity formulation. the effects of the potential-dependent kinetic terms be very important if one of the scalars is the inflaton, since they lead to a flattening of the scalar potential. we analyze this flattening effect in detail and compute its impact on the cmb observables for single-field inflation with monomial potentials.