The asymptotic behaviour of the Hawking energy along null asymptotically flat hypersurfaces

In this work we obtain the limit of the Hawking energy of a large class of foliations along general null hypersurfaces Ω satisfying a weak notion of asymptotic flatness. The foliations are not required to be either geodesic or approaching large spheres at infinity. The limit is obtained in terms of a reference background geodesic foliation approaching large spheres and a positive function, constant along the null generators on Ω, which describes the relation between the two foliations at infinity. The integrand in the limit expression has interesting covariance and invariance properties with respect to change of background foliation. The standard result that the Hawking energy tends to the Bondi energy under suitable circumstances is recovered in this framework. (paper)