Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Exact Gravitational Shock Wave Solution of Higher Order Theories   We find an {\it exact} pp--gravitational wave solution of the fourth order
gravity field equations. Outside the (delta--like) source this {\it not} a
vacuum solution of General Relativity. It represents the contribution of the
massive, $m=(-\beta)^{-1/2}$, spin--two field associated to the Ricci squared
term in the gravitational Lagrangian. The fourth order terms tend to make
milder the singularity of the curvature at the point where the particle is
located. We generalize this analysis to $D$--dimensions, extended sources, and
higher than fourth order theories. We also briefly discuss the scattering of
fields by this kind of plane gravitational waves.

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The categories of this paper are: comp-gas
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The categories of this paper are: patt-sol
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The categories of this paper are: funct-an
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The categories of this paper are: chem-ph
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The categories of this paper are: plasm-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: math
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The categories of this paper are: supr-con
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The categories of this paper are: stat
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The categories of this paper are: hep-ex
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The categories of this paper are: math-ph
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The categories of this paper are: q-fin
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The categories of this paper are: ao-sci
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The categories of this paper are: econ
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The categories of this paper are: adap-org
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The categories of this paper are: solv-int