Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Note on ingoing coordinates for binary black holes   In a previous paper, a binary black hole four-metric was presented in a
post-Newtonian corotating coordinate system valid only up to the holes'
apparent horizons. In this paper, I define an ingoing coordinate transformation
that extends this corotating coordinate system through the holes' horizons and
into their interiors. The motivation for using ingoing coordinates is that
numerical simulations of black holes require the computational grid to extend
inside the horizons. The coordinate transformation presented here makes the
binary black hole four-metric suitable as a source of initial data for
numerical simulations.

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The categories of this paper are: stat
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The categories of this paper are: hep-th
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The categories of this paper are: cs
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The categories of this paper are: hep-lat
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The categories of this paper are: eess
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The categories of this paper are: math
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The categories of this paper are: bayes-an
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The categories of this paper are: nlin
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The categories of this paper are: chem-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: q-fin
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The categories of this paper are: quant-ph
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The categories of this paper are: hep-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: nucl-th
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The categories of this paper are: mtrl-th