We study the production of observable primordial local non-Gaussianity in two opposite regimes of canonical single field inflation : attractor ( standard single field slow-roll inflation ) and non attractor ( ultra slow-roll inflation ) .
In the attractor regime , the standard derivation of the bispectrum ’ s squeezed limit using co-moving coordinates gives the well known Maldacena ’ s consistency relation f _ { NL } = 5 ( 1 - n _ { s } ) / 12 .
On the other hand , in the non-attractor regime , the squeezed limit offers a substantial violation of this relation given by f _ { NL } = 5 / 2 .
In this work we argue that , independently of whether inflation is attractor or non-attractor , the size of the observable primordial local non-Gaussianity is predicted to be f _ { NL } ^ { obs } = 0 ( a result that was already understood to hold in the case of attractor models ) .
To show this , we follow the use of the so-called Conformal Fermi Coordinates ( CFC ) , recently introduced in the literature .
These coordinates parametrize the local environment of inertial observers in a perturbed FRW spacetime , allowing one to identify and compute gauge invariant quantities , such as n -point correlation functions .
Concretely , we find that during inflation , after all the modes have exited the horizon , the squeezed limit of the 3 -point correlation function of curvature perturbations vanishes in the CFC frame , regardless of the inflationary regime .
We argue that such a cancellation should persist after inflation ends .