We give a full analysis of the conservation along null surfaces of generalized energy and supermomenta, for gravitational systems enclosed by a finite boundary. In particular, we interpret the conservation equations in a canonical manner, revealing a notion of symplectic potential and a boundary current intrinsic to null surfaces. This generalizes similar analyses done at asymptotic infinity or on horizons.

• Received 23 February 2018

DOI:https://doi.org/10.1103/PhysRevD.97.124029