Invariant conserved currents for gravity

Abstract

We develop a general approach, based on the Lagrange-Noether machinery, to the definition of invariant conserved currents for gravity theories with general coordinate and local Lorentz symmetries. In this framework, every vector field \xi on spacetime generates, in any dimension n, for any Lagrangian of gravitational plus matter fields and for any (minimal or nonminimal) type of interaction, a current J[\xi] with the following properties: (1) the current (n-1)-form J[\xi] is constructed from the Lagrangian and the generalized field momenta, (2) it is conserved, d J[\xi] = 0, when the field equations are satisfied, (3) J[\xi]= d\Pi[\xi] "on shell", (4) the current J[\xi], the superpotential \Pi[\xi], and the charge Q[\xi] = \int J[\xi] are invariant under diffeomorphisms and the local Lorentz group. We present a compact derivation of the Noether currents associated with diffeomorphisms and apply the general method to compute the total energy and angular momentum of exact solutions in several physically interesting gravitational models.