Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Does the Schwarzschild black hole really exist?   We use the Kruskal time coordinate T to define the initial time. By this way,
it naturally divides the stable study into one connected with the two regions:
the white-hole-connected region and the black-hole-connected region. The union
of the two regions covers the Schwarzschild space-time (r>2m). We also obtain
the very reasonable conclusion: the white-hole-connected region is instable;
whereas the black-hole-connected region is stable. If we take the instability
with caution and seriousness, it might be not unreasonable to regard that the
Schwarzschild black hole might be instable too.

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The categories of this paper are: nucl-th
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The categories of this paper are: alg-geom
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The categories of this paper are: acc-phys
36
The categories of this paper are: cmp-lg
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The categories of this paper are: quant-ph
1
The categories of this paper are: cs
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The categories of this paper are: supr-con
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The categories of this paper are: solv-int
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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: comp-gas
0
The categories of this paper are: hep-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: chem-ph
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The categories of this paper are: funct-an
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The categories of this paper are: econ