Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Photon rockets and the Robinson-Trautman geometries   We point out the relation between the photon rocket spacetimes and the
Robinson Trautman geometries. This allows a discussion of the issues related to
the distinction between the gravitational and matter energy radiation that
appear in these metrics in a more geometrical way, taking full advantage of
their asymptotic properties at null infinity to separate the Weyl and Ricci
radiations, and to clearly establish their gravitational energy content. We
also give the exact solution for the generalized photon rockets.

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The categories of this paper are: nlin
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The categories of this paper are: solv-int
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The categories of this paper are: astro-ph
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The categories of this paper are: math-ph
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The categories of this paper are: econ
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The categories of this paper are: q-bio
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The categories of this paper are: q-fin
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The categories of this paper are: patt-sol
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The categories of this paper are: ao-sci
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The categories of this paper are: comp-gas
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The categories of this paper are: alg-geom
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The categories of this paper are: cond-mat
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The categories of this paper are: nucl-th
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The categories of this paper are: hep-lat
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The categories of this paper are: math
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The categories of this paper are: hep-th