Gravity, and the puzzle regarding its energy, can be understood from a gauge theory perspective. Gravity, i.e., dynamical s-pacetime geometry, can be considered as a local gauge theory of the symmetry group of Minkowski spacetime: the Poincare group. The dynamical potentials of the Poincare gauge theory of gravity are the frame and the metric-compatible connection. The spacetime geometry has in general both curvature and torsion. Einstein's general relativity theory is a special case. Both local gauge freedom and energy are clarified via the Hamiltonian formulation. We have developed a covariant Hamiltonian formulation. The Hamiltonian boundary term gives covariant expressions for the quasi-local energy, momentum and angular momentum. A key feature is the necessity to choose on the boundary a non-dynamic reference. With a best matched reference one gets good quasi-local energy-momentum and angular momentum values.
|Title of host publication||Memorial Volume for Yi-shi Duan|
|Publisher||World Scientific Publishing Co. Pte Ltd|
|Number of pages||20|
|State||Published - 5 Jan 2018|