Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Anomalous Fermion Production in Gravitational Collapse   The Dirac equation is solved in the Einstein-Yang-Mills background found by
Bartnik and McKinnon. We find a normalizable zero-energy fermion mode in the
$s$-wave sector. As shown recently, their solution corresponds to a
gravitational sphaleron which mediates transitions between topologically
distinct vacua. Since the Bartnik-McKinnon solution is unstable, it will either
collapse to form a black hole or radiate away its energy. In either case, as
the Chern-Simons number of the configuration changes, there will be an
accompanying anomalous change in fermion number.

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The categories of this paper are: chem-ph
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The categories of this paper are: ao-sci
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The categories of this paper are: acc-phys
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The categories of this paper are: chao-dyn
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The categories of this paper are: hep-ex
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The categories of this paper are: dg-ga
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The categories of this paper are: stat
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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: plasm-ph
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The categories of this paper are: patt-sol
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The categories of this paper are: solv-int
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The categories of this paper are: cmp-lg
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The categories of this paper are: hep-lat
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The categories of this paper are: math-ph
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The categories of this paper are: nucl-th