BMS algebra as an extension of the Poincar\'e symmetry in light-cone gravity

Abstract

We analyze possible local extensions of the Poincar\'e symmetry in light-cone gravity in four dimensions. We use a formalism where we represent the algebra on the two physical degrees of freedom, one with helicity $2$ and the other with helicity $-2$. The representation is non-linearly realized and one of the light-cone momenta is the Hamiltonian, which is hence a non-linear generator of the algebra. We find that this can be locally realized and the Poincar\'e algebra extended to the BMS symmetry without any reference to asymptotic limits.