BMS Group at Spatial Infinity: the Hamiltonian (ADM) approach

Understand

New boundary conditions for asymptotically flat spacetimes are given at spatial infinity.

• These boundary conditions are invariant under the BMS group, which acts non trivially.
• The boundary conditions fulfill all standard consistency requirements: (i) they make the symplectic form finite; (ii) they contain the Schwarzchild solution, the Kerr solution and their Poincar\'e transforms, (iii) they make the Hamiltonian generators of the asymptotic symmetries integrable and well-defined (finite).
• The boundary conditions differ from the ones given earlier in the literature in the choice of the parity conditions.