Prescriptions for measuring and transporting local angular momenta in general relativity

Understand

For observers in curved spacetimes, elements of the dual space of the set of linearized Poincar\'e transformations from an observer's tangent space to itself can be naturally interpreted as local linear and angular momenta.

• We present an operational procedure by which observers can measure such quantities using only information about the spacetime curvature at their location.
• When applied by observers near spacelike or null infinity in stationary, vacuum, asymptotically flat spacetimes, there is a sense in which the procedure yields the well-defined linear and angular momenta of the spacetime.
• We also describe a general method by which observers can transport local linear and angular momenta from one point to another, which improves previous prescriptions.