A higher (even spacetime) dimensional generalization of the Bondi energy has
recently been proposed by gr-qc/0304054 within the framework of conformal
infinity and Hamiltonian formalizm. The gauge condition employed in
gr-qc/0304054 to derive the Bondi energy expression is, however, peculiar in
the sense that cross-sections of null infinity specified by that gauge are
anisotropic and in fact non-compact. For this reason, that gauge is difficult
to use for explicit computations of the Bondi energy in general, asymptotically
flat radiative spacetimes. Also it is not clear, under that gauge condition,
whether apparent difference between the expressions of higher dimensional Bondi
energy and the 4-dimensional one is due to the choice of gauges or
qualitatively different nature of higher dimensional gravity from 4-dimensional
gravity. In this paper, we consider instead, Gaussian null conformal gauge as
one of more natural gauge conditions that admit a global specification of
background structure with compact, spherical cross-sections of null infinity.
Accordingly, we modify the previous definition of higher dimensional news
tensor so that it becomes well-defined in the Gaussian null conformal gauge and
derive, for vacuum solutions, the expression for the Bondi energy-momentum in
the new gauge choice, which takes a universal form in arbitrary (even
spacetime) dimensions greater than or equal to four.Comment: 23 pages, no figures, references are added, minor corrections,
numerous minor revisions, to appear in Class. Quantum Gra