Stationary untrapped boundary conditions in general relativity

Abstract

A class of boundary conditions for canonical general relativity are proposed and studied at the quasi-local level. It is shown that for untrapped or marginal surfaces, fixing the area element on the 2-surface (rather than the induced 2-metric) and the angular momentum surface density is enough to have a functionally differentiable Hamiltonian, thus providing definition of conserved quantities for the quasi-local regions. If on the boundary the evolution vector normal to the 2-surface is chosen to be proportional to the dual expansion vector, we obtain a generalization of the Hawking energy associated with a generalized Kodama vector. This vector plays the role for the stationary untrapped boundary conditions which the stationary Killing vector plays for stationary black holes. When the dual expansion vector is null, the boundary conditions reduce to the ones given by the non-expanding horizons and the null trapping horizons.

11 pages, improved discussion section, a reference added, accepted for publication in Classical and Quantum Gravity

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Cited by in corpus (6)

• The region with trapped surfaces in spherical symmetry, its core, and their boundaries
• Dynamical Surface Gravity in Spherically Symmetric Black Hole Formation
• Optimal Choices of Reference for Quasi-local Energy
• Quasi-Local Energy Flux of Spacetime Perturbation
• Evolving black hole horizons in General Relativity and alternative gravity
• Energy and angular momentum in strong gravitating systems