Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Vacuum spacetimes with an isometry   In vacuum space-times the exterior derivative of a Killing vector field is a
two-form that satisfies Maxwell equations without electromagnetic sources.
Using the algebraic structure of this two-form we have set up a new formalism
for the study of vacuum space-times with an isometry.

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The categories of this paper are: hep-th
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The categories of this paper are: eess
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The categories of this paper are: chao-dyn
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The categories of this paper are: physics
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The categories of this paper are: adap-org
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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-fin
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The categories of this paper are: acc-phys
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The categories of this paper are: quant-ph
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The categories of this paper are: cond-mat
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The categories of this paper are: ao-sci
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The categories of this paper are: q-alg
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The categories of this paper are: comp-gas
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The categories of this paper are: q-bio
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The categories of this paper are: bayes-an