On the physical interpretation of asymptotically flat gravitational fields |
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Authors: | Carlos Kozameh Ezra T Newman Gilberto Silva-Ortigoza |
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Institution: | (1) FaMaF, University of Cordoba, Cordoba, Argentina;(2) Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260, USA;(3) Facultad de Ciencias Físico Matemáticas, de la Universidad Autónoma de Puebla, Apartado Postal 1152, 72001 Puebla, Mexico |
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Abstract: | A problem in general relativity is how to extract physical information from solutions to the Einstein equations. Most often
information is found from special conditions, e.g., special vector fields, symmetries or approximate symmetries. Our concern
is with asymptotically flat space–times with approximate symmetry: the BMS group. For these spaces the Bondi four-momentum
vector and its evolution, found at infinity, describes the total energy–momentum and the energy–momentum radiated. By generalizing
the simple idea of the transformation of (electromagnetic) dipoles under a translation, we define (analogous to center of
charge) the center of mass for asymptotically flat Einstein–Maxwell fields. This gives kinematical meaning to the Bondi four-momentum,
i.e., the four-momentum and its evolution which is described in terms of a center of mass position vector, its velocity and
spin-vector. From dynamical arguments, a unique (for our approximation) total angular momentum and evolution equation in the
form of a conservation law is found.
Third Award in the 2008 Essay Competition of the Gravity Research Foundation. |
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Keywords: | Asymptotically flat space-times |
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