26,135 research outputs found
Quasi-local energy for cosmological models
First we briefly review our covariant Hamiltonian approach to quasi-local
energy, noting that the Hamiltonian-boundary-term quasi-local energy
expressions depend on the chosen boundary conditions and reference
configuration. Then we present the quasi-local energy values resulting from the
formalism applied to homogeneous Bianchi cosmologies. Finally we consider the
quasi-local energies of the FRW cosmologies. Our results do not agree with
certain widely accepted quasi-local criteria.Comment: Contributed to International Symposium on Cosmology and Particle
Astrophysics (CosPA 2006), Taipei, Taiwan, 15-17 Nov 200
Quasilocal Center-of-Mass for Teleparallel Gravity
Asymptotically flat gravitating systems have 10 conserved quantities, which
lack proper local densities. It has been hoped that the teleparallel equivalent
of Einstein's GR (TEGR, aka GR) could solve this gravitational
energy-momentum localization problem. Meanwhile a new idea: quasilocal
quantities, has come into favor. The earlier quasilocal investigations focused
on energy-momentum. Recently we considered quasilocal angular momentum for the
teleparallel theory and found that the popular expression (unlike our
``covariant-symplectic'' one) gives the correct result only in a certain frame.
We now report that the center-of-mass moment, which has largely been neglected,
gives an even stronger requirement. We found (independent of the frame gauge)
that our ``covariant symplectic'' Hamiltonian-boundary-term quasilocal
expression succeeds for all the quasilocal quantities, while the usual
expression cannot give the desired center-of-mass moment. We also conclude,
contrary to hopes, that the teleparallel formulation appears to have no
advantage over GR with regard to localization.Comment: 12 pages, to appear in the proceedings of the 10th Marcel Grossman
meeting (Rio de Janeiro, 2003
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