Energy-Momentum (Quasi-)Localization for Gravitating Systems

Traditional approaches to energy-momentum localization led to reference framedependent pseudotensors. The more modern idea is quasilocal energy-momentum. Wetake a Hamiltonian approach. The Hamiltonian boundary term gives not only thequasilocal values but also boundary conditions via the Hamiltonian variationboundary principle. Selecting a Hamiltonian boundary term involves severalchoices. We found that superpotentials can serve as Hamiltonian boundary terms,consequently pseudotensors are actually quasilocal and legitimate. VariousHamiltonian boundary term quasilocal expressions are considered including somefamous pseudotensors, M{\o}ller's tetrad-teleparallel ``tensor'', Chen'scovariant expressions, the expressions of Katz & coworkers, the expression ofBrown & York, and some spinor expressions. We emphasize the need foridentifying criteria for a good choice