Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Ill-posedness of a double null free evolution scheme for black hole
  spacetimes   We suggest that ``free evolution'' integration schemes for the Einstein
equations (that do not enforce constraints) may contain exponentially growing
modes that render them useless in numerical integrations of black hole
spacetimes, independently of how the equations are differenced. As an example
we consider the evolution of Schwarzschild and Reissner-Nordstr\"om spacetimes
in double null coordinates.

31
The categories of this paper are: ao-sci
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The categories of this paper are: alg-geom
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The categories of this paper are: q-alg
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The categories of this paper are: chao-dyn
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The categories of this paper are: cmp-lg
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The categories of this paper are: solv-int
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The categories of this paper are: nucl-ex
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The categories of this paper are: acc-phys
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The categories of this paper are: supr-con
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The categories of this paper are: math
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The categories of this paper are: cond-mat
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The categories of this paper are: hep-ex
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The categories of this paper are: chem-ph
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The categories of this paper are: q-bio
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The categories of this paper are: physics
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The categories of this paper are: q-fin