Talk detail

Participant	Nester, James M
Institution	Dept of Physics, National Central University - No. 300, Jhongda Rd. - Jhongli - Taoyuan County - Taiwan

Session	ST3	Accepted	Yes	Order	4	Time	16:30 - 17:10
Talk	Oral abstract	Title	On the effective equivalence of the Einstein-Cartan, GR, and teleparallel theories
Co-authors	Lau Loi So
Abstract	Alternatives to Riemannian spacetime include Riemann-Cartan and teleparallel. Respective theories are GR, Einstein-Cartan (EC) and TEGR, the so-called “teleparallel equivalent of GR”. We first note that the dynamical field equations of GR with any source can be represented in terms of any other connection. Extending an argument re the “effective equivalence” between GR and the Einstein-Cartan theory, we construct the TEGR source action which is equivalent to a given GR one. The procedure thus identifies the “effectively equivalent” coupling in the action for all sources (including spinors) between the EC, GR and TEGR formulations. The same physical dynamics can be represented in any of the three geometries. Which is the real “physical” geometry? Minimal coupling could give an answer.

Session	GT3	Accepted	Yes	Order	1	Time	14:00
Talk	Oral abstract	Title	A reference for our covariant Hamiltonian boundary term
Co-authors	C.-M. Chen, J.-L. Liu
Abstract	Our covariant Hamiltonian for dynamic geometry generates the evolution of a spatial region along a vector field. It includes a boundary term which determines both the value of the Hamiltonian and the boundary conditions. The value gives the quasi-local quantities: energy-momentum, angular-momentum/center-of-mass. The boundary term depends not only on the dynamical variables but also on their reference values, the latter determine the ground state (having vanishing quasi-local quantities). For our preferred boundary term for Einstein's GR we propose using 4D isometric matching and extremizing the energy to determine the ``best matched'' reference metric and connection values.