Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Can the local stress-energy conservation laws be derived solely from
  field equations?   According to a recent suggestion [1], the energy--momentum tensor for
gravitating fields can be computed through a suitable rearrangement of the
matter field equations, without relying on the variational definition. We show
that the property observed by Accioly et al. in [1] is the consequence of a
general identity, which follows from the covariance of the matter Lagrangian in
much the same way as (generalized) Bianchi identities follow from the
covariance of the purely gravitational Lagrangian. However, we also show that
only in particular cases can this identity be used to obtain the actual form of
the stress-energy tensor, while in general the method leads to ambiguities and
possibly to wrong results. Moreover, in nontrivial cases the computations turn
out to be more difficult than the standard variational technique.

32
The categories of this paper are: atom-ph
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The categories of this paper are: plasm-ph
18
The categories of this paper are: econ
1
The categories of this paper are: cs
7
The categories of this paper are: hep-th
22
The categories of this paper are: chao-dyn
4
The categories of this paper are: cond-mat
13
The categories of this paper are: quant-ph
28
The categories of this paper are: alg-geom
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The categories of this paper are: eess
11
The categories of this paper are: hep-lat
12
The categories of this paper are: nucl-th
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The categories of this paper are: comp-gas
31
The categories of this paper are: ao-sci
9
The categories of this paper are: nlin
26
The categories of this paper are: bayes-an