The EFT of inflation (an EFT for the Goldstone of spontaneously broken time translations) is used to map from inflation through the formation of Large Scale Structures to the present day. Comparison of the power spectrum and inflationary parameters to data then fixes the EFT coefficients, and shows consistent agreement.

While the EFT of inflation has the advantage that it doesn't commit to a particular covariant realization (i.e. time translation could be broken by a fermion, or a vector, etc.), this leads to the drawback that the background is `hard-wired' into the quadratic part of the action, and therefore the EFT coefficients measured on one background (e.g. near a star) have little bearing on those measured on another background (e.g. during inflation). This paper extrapolates from inflation through LSS using the same set of coefficients in order to compare with data - and find reasonable agreement. This suggests that the EFT coefficients do not change too radically throughout the Universe's evolution, which is good news for the EFT of inflation.

The 3-point amplitudes on `sandwich' plane wave backgrounds are calculated in gravity, and shown to obey a double copy relation with gluons on a gauge field plane wave. The gravitational memory effect also double copies.

This extends the double copy relation between Yang-Mills and gravity to curved spacetime---one should consider Yang-Mills perturbations about a non-trivial gauge field profile (on flat spacetime) in order to reproduce graviton amplitudes on a curved spacetime background.