Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the energy content of electromagnetic and gravitational plane waves
  through super-energy tensors   The energy content of (exact) electromagnetic and gravitational plane waves
is studied in terms of super-energy tensors (the Bel, Bel-Robinson and the
--less familiar-- Chevreton tensors) and natural observers. Starting from the
case of single waves, the more interesting situation of colliding waves is then
discussed, where the nonlinearities of the Einstein's theory play an important
role. The causality properties of the super-momentum four vectors associated
with each of these tensors are also investigated when passing from the
single-wave regions to the interaction region.

26
The categories of this paper are: bayes-an
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The categories of this paper are: solv-int
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The categories of this paper are: patt-sol
11
The categories of this paper are: hep-lat
8
The categories of this paper are: hep-ex
34
The categories of this paper are: chem-ph
0
The categories of this paper are: hep-ph
13
The categories of this paper are: quant-ph
27
The categories of this paper are: comp-gas
21
The categories of this paper are: adap-org
10
The categories of this paper are: q-bio
28
The categories of this paper are: alg-geom
31
The categories of this paper are: ao-sci
7
The categories of this paper are: hep-th
29
The categories of this paper are: funct-an
22
The categories of this paper are: chao-dyn