Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Evaluating quasilocal energy and solving optimal embedding equation at
  null infinity   We study the limit of quasilocal energy defined in [7] and [8] for a family
of spacelike 2-surfaces approaching null infinity of an asymptotically flat
spacetime. It is shown that Lorentzian symmetry is recovered and an
energy-momentum 4-vector is obtained. In particular, the result is consistent
with the Bondi-Sachs energy-momentum at a retarded time. The quasilocal mass in
[7] and [8] is defined by minimizing quasilocal energy among admissible
isometric embeddings and observers. The solvability of the Euler-Lagrange
equation for this variational problem is also discussed in both the
asymptotically flat and asymptotically null cases. Assuming analyticity, the
equation can be solved and the solution is locally minimizing in all orders. In
particular, this produces an optimal reference hypersurface in the Minkowski
space for the spatial or null exterior region of an asymptotically flat
spacetime.

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The categories of this paper are: hep-ph
34
The categories of this paper are: chem-ph
25
The categories of this paper are: patt-sol
6
The categories of this paper are: astro-ph
20
The categories of this paper are: acc-phys
15
The categories of this paper are: nucl-ex
23
The categories of this paper are: solv-int
27
The categories of this paper are: comp-gas
21
The categories of this paper are: adap-org
16
The categories of this paper are: stat
32
The categories of this paper are: atom-ph
29
The categories of this paper are: funct-an
11
The categories of this paper are: hep-lat
18
The categories of this paper are: econ
24
The categories of this paper are: dg-ga
13
The categories of this paper are: quant-ph