Abstract:
I will discuss two applications of Effective Filed Theory in the context of gravity. One is an EFT that allows us to parametrize what extensions of GR can be tested with gravitational wave observations. The most general action not involving additional degrees of freedom corresponds to adding to the GR Lagrangian operators constructed out of powers of the Riemann tensor, suppressed by a scale comparable to the curvature of the observed merging binaries. I will explain why the presence of these operators is not ruled by other GR tests, and the resulting observational signature. Then, I will pass to the early universe, and construct the most general theory of inflationary fluctuations when time-translations and supersymmetry are spontaneously broken. The non-linear realization of these invariances allows us to define a complete SUGRA multiplet containing the graviton, the gravitino, the Goldstone of time translations and the Goldstino, with no auxiliary fields. This allows us to write a remarkably-simple general Lagrangian for the fluctuations, and study its observational consequences.