DBI in the sky: Non-Gaussianity from inflation with a speed limit

Abstract

We analyze the spectrum of density perturbations generated in models of the recently discovered ``D-cceleration'' mechanism of inflation. In this scenario, strong coupling quantum field theoretic effects sum to provide a Dirac-Born-Infeld--like action for the inflaton. We show that the model has a strict lower bound on the non-Gaussianity of the cosmic microwave background radiation power spectrum at an observable level, and is thus falsifiable. This, in particular, observationally distinguishes this mechanism from traditional slow-roll inflation generated by weakly interacting scalar fields. The model also favors a large observable tensor component to the cosmic microwave background radiation spectrum.