On reference frames in spacetime and gravitational energy in freely falling frames

Understand

We consider the interpretation of tetrad fields as reference frames in spacetime.

• Reference frames may be characterized by an antisymmetric acceleration tensor, whose components are identified as the inertial accelerations of the frame (the translational acceleration and the frequency of rotation of the frame).
• This tensor is closely related to gravitoelectromagnetic field quantities.
• We construct the set of tetrad fields adapted to observers that are in free fall in the Schwarzschild spacetime, and show that the gravitational energy-momentum constructed out of this set of tetrad fields, in the framework of the teleparallel equivalent of general relatrivity, vanishes.