Unifying attractor and non-attractor models of inflation under a single soft theorem

Understand

We study the generation of local non-Gaussianity in models of canonical single field inflation when their backgrounds are either attractor or non-attractor.

• We show that the invariance of inflation under space-time diffeomorphisms can be exploited to make powerful statements about the squeezed limit of the primordial bispectrum of curvature perturbations, valid to all orders in slow roll parameters.
• In particular, by neglecting departures from the adiabatic evolution of long-wavelength modes (for instance, produced in sharp transitions between slow-roll and ultra slow-roll phases), we derive a general expression for the bispectrum's squeezed limit in co-moving coordinates.
• This result consists in the standard Maldacena's consistency relation (proportional to the spectral index of the power spectrum) plus additional terms containing time derivatives of the power spectrum.