 But in this case, a coordinate-free definition of the divergence is used which incorporates the covariant derivative

where formula_20 is the Christoffel symbol which is the gravitational force field.Consequently, if formula_21 is any Killing vector field, then the conservation law associated with the symmetry generated by the Killing vector field may be expressed as

The integral form of this is

In special relativity, the stress–energy tensor contains information about the energy and momentum densities of a given system, in addition to the momentum and energy flux densities.Given a Lagrangian Density formula_24 that is a function of a set of fields formula_25 and their derivatives, but explicitly not of any of the spacetime coordinates, we can construct the tensor by looking at the total derivative with respect to one of the generalized coordinates of the system.