Speaker
Description
I will discuss the construction of a boundary energy-momentum tensors for asymptotically flat spacetimes in 3 and 4 bulk spacetime dimensions. This is achieved by endowing future null infinity with the most general allowed Carrollian geometry and varying the on-shall gravitational action with respect to the Carrollian data. In particular, this requires us to develop a holographic renormalisation procedure for asymptotically flat spacetimes, which reveals that, in 4d, the shear is part of the boundary data on par with the Carrollian structure. The resulting energy-momentum-news complex obtained by variation obey a diffeomorphism Ward identity that is equivalent to the Bondi mass and angular momentum loss equations, while local Carroll boosts are anomalous in both 3 and 4 dimensions.
