Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Type I vacuum solutions with aligned Papapetrou fields: an intrinsic
  characterization   We show that Petrov type I vacuum solutions admitting a Killing vector whose
Papapetrou field is aligned with a principal bivector of the Weyl tensor are
the Kasner and Taub metrics, their counterpart with timelike orbits and their
associated windmill-like solutions, as well as the Petrov homogeneous vacuum
solution. We recover all these metrics by using an integration method based on
an invariant classification which allows us to characterize every solution. In
this way we obtain an intrinsic and explicit algorithm to identify them.

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The categories of this paper are: supr-con
4
The categories of this paper are: cond-mat
2
The categories of this paper are: math
14
The categories of this paper are: math-ph
7
The categories of this paper are: hep-th
12
The categories of this paper are: nucl-th
10
The categories of this paper are: q-bio
25
The categories of this paper are: patt-sol
33
The categories of this paper are: plasm-ph
9
The categories of this paper are: nlin
17
The categories of this paper are: q-fin
0
The categories of this paper are: hep-ph
1
The categories of this paper are: cs
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The categories of this paper are: atom-ph
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The categories of this paper are: q-alg
18
The categories of this paper are: econ