Scattering amplitudes of perturbative gravity in Minkowski space suffer from well-known infrared (IR) divergences.
Nevertheless, as was shown by Weinberg in a seminal paper, these IR divergencies take on a universal form such that gravity amplitudes factorize into IR-finite and IR-divergent parts. Over the course of the last decade, close connections have been uncovered between the IR behavior of scattering amplitudes of perturbative gravity and the symmetries of asymptotically flat spacetimes. These symmetries are given by the BMS group, consisting of supertranslations and superrotations.
In a similar vein, I will show in this talk that the above mentioned IR divergent contribution can be calculated from an effective action for the Goldstone bosons of broken supertranslations. Moreover, this action can be motivated starting from a well-defined variational principle of Einstein gravity near spatial infinity.
