Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Unoriented D-brane instantons   We give a pedagogical introduction to D-brane instanton effects in vacuum
configurations with open and unoriented strings. We focus on quiver gauge
theories for unoriented D-branes at orbifold singularities and describe in some
detail the Z_3 case, where both `gauge' and `exotic' instantons can generate
non-perturbative super potentials, and the Z_5 case, where supersymmetry
breaking may arise from the combined effect of `gauge' instantons and a FI
D-term.

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The categories of this paper are: math-ph
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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: econ
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The categories of this paper are: bayes-an
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The categories of this paper are: nucl-ex
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The categories of this paper are: ao-sci
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The categories of this paper are: dg-ga
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The categories of this paper are: hep-ex
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The categories of this paper are: nlin
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The categories of this paper are: chao-dyn
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The categories of this paper are: nucl-th
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The categories of this paper are: cs
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The categories of this paper are: mtrl-th
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The categories of this paper are: chem-ph
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The categories of this paper are: plasm-ph