Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Black Hole Solutions in String Theory   We present two-parameter solutions of the low-energy four-dimensional
heterotic string which in the extremal limit reduce to supersymmetric monopole,
string and domain wall solutions. The effective scalar coupling to the Maxwell
field, $e^{-\alpha \phi} F_{\mu\nu} F^{\mu\nu}$, gives rise to a new string
black hole with $\alpha = \sqrt{3}$, in contrast to the pure dilaton black hole
solution which has $\alpha=1$. Implications of string/fivebrane duality in
$D=10$ to four-dimensional dualities are discussed.

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The categories of this paper are: physics
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The categories of this paper are: bayes-an
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The categories of this paper are: gr-qc
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The categories of this paper are: atom-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: nucl-ex
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The categories of this paper are: econ
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The categories of this paper are: solv-int
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The categories of this paper are: comp-gas
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The categories of this paper are: mtrl-th
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The categories of this paper are: plasm-ph
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The categories of this paper are: math
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The categories of this paper are: nlin
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The categories of this paper are: q-alg
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The categories of this paper are: supr-con
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The categories of this paper are: funct-an