Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Neighbourhoods of Isolated Horizons and their stationarity   A distinguished (invariant) Bondi-like coordinate system is defined in the
spacetime neighbourhood of a non-expanding horizon of arbitrary dimension via
geometry invariants of the horizon. With its use, the radial expansion of a
spacetime metric about the horizon is provided and the free data needed to
specify it up to given order are determined in spacetime dimension $4$. For the
case of an electro-vacuum horizon in $4$-dimensional spacetime the necessary
and sufficient conditions for the existence of a Killing field at its
neighbourhood are identified as differential conditions on the horizon data and
data on null surface transversal to the horizon.

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The categories of this paper are: chao-dyn
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The categories of this paper are: supr-con
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The categories of this paper are: atom-ph
3
The categories of this paper are: physics
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The categories of this paper are: patt-sol
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The categories of this paper are: adap-org
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The categories of this paper are: stat
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The categories of this paper are: math-ph
4
The categories of this paper are: cond-mat
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The categories of this paper are: bayes-an
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The categories of this paper are: nucl-ex
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The categories of this paper are: astro-ph
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The categories of this paper are: chem-ph
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The categories of this paper are: q-fin
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The categories of this paper are: plasm-ph
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The categories of this paper are: hep-lat